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In a present study our purpose is to enhance the efficiency of third generation CZTS solar cell. We present a hydrothermal process for the synthesis of Cu 2 ZnSnS 4 (CZTS) nanocrystals straightforward inorganic salts of Cu(II), Zn(II), and Sn(II) and using thiourea as a precursor dissolved in 40 ml deionized water, stir for 3 h and heated at 210 °C. Because of its low cost, non-toxic components, perfect direct band gap as an absorber layer, and higher absorption coefficient, the semiconductor Cu 2 ZnSnS 4 (CZTS) material has attracted significant technological interest in the photovoltaic sector. At 210 °C, kieserite-structured CZTS nanocrystals were created. Wet chemical co-precipitation was used to create Ti 3 C 2 doped CZTS nanocrystals. The CZTS nanocrystals have an optical indirect band gap of 1.47 eV extracted from UV–visible spectra, which is ideal for photovoltaic packages in keeping with the absorption spectrum. XRD peaks of both CZTS and Ti 3 C 2 are quite close to one another, and the results of these peaks are closely matched with relevant prior research. The FTIR spectra do not shows any broad band at any point but having short band at 2120 cm−1. A broad PL band from CZTS was recently found at roughly 490 nm. Successful chemical synthesis of CZTS nanostructures demonstrate the production of affordable, eco-friendly and less toxic nanomaterials that may be used in future solar equipment. • Cu 2 ZnSnS 4 /Ti 3 C 2 were prepared by hydrothermal method. • Cu 2 ZnSnS 4 composites were synthesized by varying concentration of Ti 3 C 2. • Cu 2 ZnSnS 4 (95 %) and Ti 3 C 2 (5 %) exhibited enhanced absorption coefficient and reduced band gap of Cu 2 ZnSnS 4 material. • Cu 2 ZnSnS 4 (95 %) and Ti 3 C 2 (5 %) exhibit high efficiency in solar cell. [ABSTRACT FROM AUTHOR]

Low-cost, flexible broadband photodetectors fabricated from two-dimensional transition metal chalcogenides have garnered attention because of their excellent absorption coefficient and photoconductivity. Likewise, vertical heterojunctions fabricated from two two-dimensional (2D) transition metal chalcogenides (TMCs) also have drawn major curiosity lately owing to their superior optical performance. This work reports a p-p type II vertical Van der Waal's heterojunction structure by depositing thin film of NiS over SnS on a flexible paper substrate. Morphological and structural characterization confirms presence of a rhombohedral β-NiS crystal structure along with traces of Ni(OH) 2 on orthorhombic SnS nanoparticles. The device fabrication method made use of the inexpensive, clean room free SILAR (Successive Ionic Layer Adsorption and Reaction) technique. A purposeful modification of narrow bandgap property of NiS is done by depositing it in an alkaline environment. The fabricated device records optical responsivity of 0.92 mA/W under UV illumination, 5.32 mA/W under Visible illumination, and 0.8 mA/W under NIR illumination. A maximum EQE of 1.3 % is observed along with superior response times of 0.114 s (UV),0.103 s (Visible) and 1.34 s (NIR). The acquired photo response is due to superior absorption property of NiS in UV region and SnS in the visible and NIR region. The difference in fermi level between two materials causes efficient separation of the charge carriers that results in junctional electric field upon light illumination. The device underwent flexibility testing and shown exceptional resistance to bending force making it suitable for numerous applications like wearable healthcare monitoring, security purposes and flexible image sensors. [Display omitted] • This work introduces a broadband photodetector using type II vertical Van der Waal's heterojunction fabricated from 2D-photoresponsive Transition metal chalcogenides. • The device is fabricated on cellulose paper using Successive Ionic Layer Adsorption and Reaction(SILAR)technique having remarkable responsivities in UV, visible, NIR region along with superior response times of 0.114 s,0.103 s and 1.34 s and high photostability up to 1050 bending cycles. • A modification of narrow bandgap property of NiS is done by depositing it in an alkaline environment which makes it suitable for broadband photodetection applications. [ABSTRACT FROM AUTHOR]

Compared with the traditional slow evaporation solution technique to grow KAP crystals, we have improved a set of Rapid Growth Technology of Continuous Filtration System based on existing research conditions. KAP crystals were grown by program-controlled solution cooling method. A KAP crystal with a size of 220 mm × 170 mm × 45 mm and a weight of 1934.9 g was successfully grown, which is the largest KAP crystal reported so far. The optical studies such as transmittance, absorption coefficient, optical energy band gap, photoluminescence, and Z-scan of the crystal show that the crystal is more excellent than the traditional slow evaporation solution technique. Compared with the traditional slow evaporation solution technique to grow KAP crystals, we have improved a set of Rapid Growth Technology of Continuous Filtration System based on existing research conditions. KAP crystals were grown by program-controlled solution cooling method. A KAP crystal with a size of 220 mm × 170 mm × 45 mm and a weight of 1934.9 g was successfully grown, which is the largest KAP crystal reported so far. The optical studies such as transmittance, absorption coefficient, optical energy band gap, and photoluminescence of the crystal show that the crystal is more excellent than the traditional slow evaporation solution technique. [ABSTRACT FROM AUTHOR]

The coefficients of nonlinear absorption and nonlinear refraction of the quaternary barium chalcogenide crystal BaGa 2 GeSe 6 at a wavelength corresponding to half the band gap, as well as their dependence on the pulse repetition rate and peak on-axis irradiance, were measured for the first time. The third-order nonlinear optical properties were studied using the single-beam Z-scan technique. An Nd: YLF laser at 1.053 μm with a pulse duration of approximately 5.2 ns was used as a radiation source. In addition, a thermal Z-scan was carried out to investigate thermal lensing in the BaGa 2 GeSe 6 crystal, employing a continuous wave Nd: YAG laser at 1064 nm. These studies represent an important step in comprehending the nonlinear optical properties of barium chalcogenide crystals and their behavior at different pulse intensities. The results might be significant for the modelling and design of mid-infrared optical systems. • Nonlinear absorption and refraction of BaGa 2 GeSe 6 (BGGSe) crystal were investigated experimentally through the application of the single-beam Z-scan technique. • The pulse repetition rate significantly influenced both nonlinear absorption and nonlinear refraction. • The impacts of the Kerr term, electrostriction, and thermal effects on the third-order nonlinearity were evaluated and measured. [ABSTRACT FROM AUTHOR]

Samples of borosilicate glasses reinforced with various moles of MoO 3 with general chemical formula (52-X)B 2 O 3 +13SiO 2 +19.75BaO+ 0.25Sm 2 O 3 +15Na 2 O+XMoO 3 : (0.0 (BSMO-0.0) ≤ X ≤ 10.0 (BSMO-10.0) mol%) were prepared using the melt-quenching technique. The physical, optical absorption, electronic transitions, and linear/nonlinear optical properties as well as γ-ray absorption capacity has been investigated. Density (ρ) of the BSMO-X glasses enhanced from 2.83 g cm−3 to 3.16 g cm−3. Molar volume (V m) gradually decreased from 29.81 cm3/mol to 29.10 cm3/mol as MoO 3 concentration increased from 0.0 to 10.0 mol% in the glass network. The BSMO-X glass samples exhibit absorption peaks at wavelengths of 402, 476, 936, 1072, 1227, 1368, 1469, 1527, and 1944 nm which associated with the electronic transitions originating from the lowest energy state (6H 5/2) to 6P 3/2 , 4I 11/2 , 6F 11/2 , 6F 9/2 , 6F 7/2 , 6F 5/2 , 6F 3/2 , 6H 15/2 and 6H 13/2 states, respectively. The indirect optical energy gap (E g) changed from 3.15 eV to 2.82 eV, while the linear refractive index (n o) increased from 2.37 to 2.44. Mass- (MAC) and linear- (LAC) absorption coefficients increased as MoO 3 content increased in the glass network. The BSMO-10.0 possessed the lowest values of half-value (HVL) layer among all investigated samples. The BSMO-X glasses achieve higher capability in radiation shielding than some standard concrete and glasses. • B 2 O 3 +SiO 2 +BaO + Sm 2 O 3 +Na 2 O + MoO 3 glasses have been successfully fabricated. • Physical properties of the BSMO-X glasses have been studied. • Optical characteristics of the BSMO -X glasses have been investigated. • Radiation shielding capacity of the BSMO-X glasses has been examined. • Glasses can be used as alternative materials for optical and radiation protection applications. [ABSTRACT FROM AUTHOR]

The ultrafast optical nonlinearity of an azonaphthalene derivative, hydroxy naphthol blue (HNB) disodium salt, is investigated using transient absorption spectra (TAS) and Z-scan technique. Reverse saturable absorption (RSA) is observed within the resonant absorption band, which is usually dominated by ground-state bleaching (GSB) and stimulated emission (SE) in most organic compounds. This observation indicates a remarkably strong excited-state absorption (ESA) in HNB. Global analysis of TAS suggests an ultrafast conversion from saturable absorption (SA) to RSA, which is assigned to the internal conversion from locally excited (LE) state to the first singlet (S 1) state. Further Z-scan study verifies the above results and reveals another intensity-depend SA-RSA transition, indicating increased S 1 population under strong laser irradiation. The calculated value of third-order nonlinear absorption coefficient at 650 nm, 190 fs is determined as 1.23 × 10−12 m/W. These studies demonstrate significant potential of azonaphthalene in ultrafast laser protection if further modulation of excited-state absorption can be achieved. • The ultrafast optical nonlinearity of HNB is studied by TAS and Z-scan. • RSA in resonant absorption region is observed due to extremely strong ESA on first excited state. • Mechanism of intensity-depend SA-RSA transition is investigated. [ABSTRACT FROM AUTHOR]

The reverse saturable absorption (RSA) and optical limiting (OL) mechanisms of polyaniline (PANI) and fullerene doped PANI (PANI-C60) solutions were investigated by open-aperture z-scan studies, using a nanosecond pulsed Nd:YAG laser operating at 532 nm wavelength as the excitation source. The nonlinear absorption coefficient (β), OL threshold, and imaginary part of nonlinear susceptibility ( χ i (3) ) of PANI and PANI-C60 solutions were determined for three different laser input pulse energies and are found to be in the order of 10−9 cm/W, 106 W/cm2, and 10−10 esu respectively. The results showed enhanced OL efficiency for the PANI-C60 solution, making it a promising candidate for applications in optoelectronics and optical limiting. The transmission electron microscope (TEM) images revealed the uniform distribution of C60 of particle size in the range of 5–10 nm in the PANI matrix. The composite formation of PANI-C60 was confirmed by Fourier transform infrared spectroscopy (FTIR). The presence of C60 and its charge transfer complex (CTC) formation with PANI are responsible for the enhanced OL efficiency. The linear refractive index values were measured using UV–Visible absorption spectra and compared with the theoretical values. The investigation of the OL mechanism and the calculation of its associated NLO parameters for PANI and PANI-C60 solutions are reported for the first time. [Display omitted] • The NLO absorption mechanism of PANI and PANI-C60 composite was examined in this study. • The β , OL threshold, and χ i (3) of PANI and PANI-C60 composite were determined for three laser input pulse energies. • The findings revealed that PANI-C60 composite had better nonlinear absorption and OL properties than PANI. • Investigation of OL mechanism and calculation of NLO parameters for PANI and PANI-C60 solutions in the first time. • The results imply, PANI-C60 composites are considered to be promising materials in OL and optoelectronic devices. [ABSTRACT FROM AUTHOR]

LiH 3 (SeO 3) 2 ferroelectric crystal exposed to UV light radiation has been found to demonstrate specific photoelectric properties with the significant protonic conductivity outweighed the bulk photovoltaic effect (BPVE). It was shown that the protonic conductivity can be mostly compensated by several cycles of reversal of the applied electric field. As a result, a noticeable photovoltaic response was detected along all main crystallographic directions. The largest power conversion efficiency was observed at the measurements performed along the ferroelectric direction. Its value was found to be increased with excitation light energy approaching the crystal bandgap width. While remaining well below the bandgap of 5.12 eV, the 285 nm and 365 nm excitations can be still considered favorable to study the photoelectric response due to the spread of the photocarrier generation process over the entire volume of the sample. In this case, the broadening of the absorption edge due to the pronounced exciton-phonon interaction, characteristic of the ferroics with hydrogen bonds, is proposed as the dominant mechanism. The higher values of the PV effect parameters observed under the influence of UV light illumination with the wavelength of 285 nm in comparison with 365 nm were explained by a higher value of the corresponding absorption coefficient. The obtained results open the way for investigations of the bulk photovoltaic effect in the ferroics with hydrogen bonds including those with an absorption edge located in the UV region of spectrum. • LiH 3 (SeO 3)2 ferroelectric crystal reveals the bulk photovoltaic effect under UV light radiation. • The bulk photovoltaic effect is observed under the exciting light with a subthreshold value of energy in respect to the bandgap width. • The protonic conductivity overlaps with the bulk photovoltaic effect in LiH 3 (SeO 3) 2 ferroelectric crystal. • The largest value of the power conversion efficiency was detected along the ferroelectric direction. [ABSTRACT FROM AUTHOR]

The 2.1 μm laser, characterized by high absorption coefficients in the atmospheric window, is important in remote sensing and medical treatment. In pulsed operation, Ho3+ and Tm3+ solid-state lasers have a higher gain than Raman lasers, semiconductor lasers, optical parametric oscillators, fiber lasers, and several other methods. In recent years, there has been research on solid-state laser systems doped with Ho3+ and Tm3+, as well as the development of host-doped Ho3+ and Tm3+. The principles of generating a 2.1 μm laser with singly doped Ho3+, singly doped Tm3+, and co-doped Ho3+ and Tm3+ systems are described. The advantages and disadvantages of the three methods are discussed in detail below. The single-doped Ho3+ laser can produce a high-energy laser, while the doped Tm3+ and co-doped Ho3+ and Tm3+ systems have a simple structure. The properties of the host materials determine the upper limits of the laser parameters achievable in the system. This study summarizes the physicochemical properties of different host materials as well as the unique advantages of their output in the 2.1 μm band. In recent years, there has been research on solid-state laser systems doped with Ho3+ and Tm3+, as well as the development of host-doped Ho3+ and Tm3+. • The research on solid-state laser systems doped Ho3+, Tm3+ are introduced. • The development of host doped Ho3+, Tm3+ is exhibited. • The principles of 2.1 μm laser generation by doped Ho3+, doped Tm3+, and Ho3+, Tm3+ co-doped ion systems are described. • The challenges and prospects for the 2.1 μm laser generated by doping Ho3+ and Tm3+ solid-state are presented. • Summarizes the important applications of 2.1 μm laser in recent years. [ABSTRACT FROM AUTHOR]

Chromium trioxide-doped borosilicate glass with composition xNa 2 O-(90-x) B 2 O 3 + 1CrO 3 + 9SiO 2 ; x = 20, 30, 40, 50, and 60 mol% was produced following the melt quenching method. The presence of Cr6+ and Cr3+ states caused the appearance of absorption bands at 315–327 nm and 427–451 nm, respectively, which overlapped with the absorption edge and masked the optical bandgaps. Detailed deconvolution processes were applied to their optical absorption coefficient spectra to obtain the fundamental edge and optical bandgaps. The remarkable observations are a decrease in Cr3+ peaks and an increase in Cr6+ peaks with the addition of Na 2 O to the present glass. The areas under the Cr3+ and Cr6+ peaks were used to calculate the redox ratio. The decreased values of the redox ratio reflect the increase in the oxidized states (Cr6+) and the decrease in the reduced states (Cr3+) with increasing Na 2 O in the glass system. The optical bandgap exhibits a decreasing behavior with increasing Na 2 O contents due to the increase in optical basicity and polarizability with increasing Na 2 O content. Additionally, the metallization criterion values changed from 0.373 to 0.341 with more Na 2 O additives. This behavior reflects the tendency toward metal behavior. Moreover, the values of optical basicity increased from 0.573 to 0.877, and the values of polarizability increased from 1.522 to 2.106 as Na 2 O contents increased from 20 mol% to 60 mol%. These reduced values of E g and increased optical basicity and polarizability increase the nonlinear parameters of the present glasses. These obtained results propose the use of the present glasses in several fields, such as optical switching, computing, data storage, etc. Deconvolution process applied to the optical absorption coefficient spectra for BSCrNa60 glass samples as a representative figure. [Display omitted] • The presence of Cr6+ and Cr6+ states confirmed by the absorption bands at 315–327 nm and 427–451 nm respectively. • A decrease in Cr3+ peaks and an increase in Cr6+ peaks with the addition of Na 2 O to the present glass. • The optical bandgaps exhibit a decreasing behavior with increasing Na 2 O contents. • The optical basicity and polarizability exhibit increasing behaviors with increasing Na 2 O contents. • The decreased values of the redox ratio reflect the increase in the oxidized states (Cr6+) with increasing Na 2 O contents. [ABSTRACT FROM AUTHOR]

Inorganic materials are intensively probed for their non-linear optical properties for optoelectronic applications; the synthesis of Ni 0.5 Zn (0.5-x) Mn x Fe 2 O 4 nanoparticles for x = 0.15,0.25,0.4,0.5 by co-precipitation method and its structural, morphological, vibrational and third order non-linear optical characterization is reported in this work. The prepared samples belong to a cubic spinel structure with a 15–30 nm crystallite size with a bandgap ranging from 1.6 eV to 2eV. The samples show reverse saturable absorption with a coefficient of the order of 10−10 m/W, a positive nonlinear refraction, and significant optical limiting characteristics. The nonlinear optical response is co-related with linear optical properties. [Display omitted] • Centrosymmetric spinel cubic system shows substantial third- order nonlinear optical (NLO) response. • Third-order nonlinear optical parameters and optical limiting response of Ni 0.5 Zn (0.5-x) Mn x Fe 2 O 4 nanoparticles were studied using z scan. • Pump laser of wavelength 532 nm and 7 ns pulse width. • Simultaneous presence of nonlinear absorption (NLA) and refraction (NLR). • Optical power limiting onset above a fluence of 12 J/cm2. [ABSTRACT FROM AUTHOR]

2-amino 6-methyl pyridinium adipate adipic acid (2A6MPAA) crystallized with a strong optical third order nonlinearity. This crystal was created using the standard slow evaporation solution growth method. The features of the produced crystals were analyzed using a variety of characterization methods. The structure of the crystal was established using the single crystal X-ray diffraction (SXRD) method. Powder X-ray diffraction (PXRD) was used to validate the crystallinity of 2-amino 6-methyl pyridinium adipate adipic acid. The compounds' numerous functional groups were confirmed by the use of FTIR analysis. Adipic acid crystal with 2-amino- 6-methyl pyridinium adipate has a decreased UV cut-off wavelength and a high optical transmittance over the whole visible range, according to studies employing UV–Vis spectrometers. The developed 2A6MPAA crystal's third order susceptibility, nonlinear refraction, and nonlinear absorption coefficient were assessed using the Z-scan technique. Additionally, this publication concentrated on theoretical investigations of a crystal's traditional nucleation dynamics. Vickers microhardness analysis was utilised to conclusively evaluate the mechanical stability of the growing crystal, and the Hays-Kendall technique proved effective in explaining the proportional stability model (PSRM) and the indentation size effect (ISE). For the as-grown 2A6MPAA crystal, the piezoelectric coefficients (d 33) were additionally premediated. [Display omitted] • Slow evaporation solution growth technique was used to grow a novel organic 2A6MPAA crystal. • The grown crystal has a great degree of transparency. • The hardness number rises when the load is increased. • Compared to other organic materials, 2A6MPAA has better relative third-order nonlinearity. [ABSTRACT FROM AUTHOR]

This research paper investigated the change of optical and structural properties resulting from depositing and thermally induced diffusing of Ag layer into Ge 20 Se 50 S 30 film. The thermally evaporated bilayer Ag/Ge 20 Se 50 S 30 film was subjected to 200 °C thermal annealing, which resulted in diffusing the top Ag layer in the bottom Ge 20 Se 50 S 30 layer. XRD illustrated that all films were amorphous. Additionally, the presence of component elements in the prepared films was verified by energy-dispersive X-ray analysis (EDX). The linear and nonlinear optical parameters of the Ge 20 Se 50 S 30 , as-prepared and annealed Ag/Ge 20 Se 50 S 30 films were evaluated by fitting the transmittance T (λ) measured at a wavelength range of 200–2500 nm based on Swanepoel's method. The indirect optical bandgap was decreased by 0.41 eV due to Ag deposition onto Ge 20 Se 50 S 30 film. The thermal diffusion of Ag increased the optical bandgap by 0.15 eV with decreasing the disorder proved by Urbach energy values. Using Wemple–DiDomenico and Sellmeier models, the analysis of the refractive index's dispersion were conducted. Furthermore, nonlinear properties (NLO), including third-order nonlinear susceptibility (χ (3)) , nonlinear refractive index (n 2) , as well as nonlinear absorption coefficient (β c) were calculated using semi-empirical relations. • The effect of annealing on the structural and optical properties of Ag/Ge 20 Se 50 S 30 bilayer thin films was studied. • The normal dispersion behavior of the refractive index was analyzed by the Wemple-DiDomenico and Sellmeier models. • The non-linear optical properties were estimated using semi-empirical relations. [ABSTRACT FROM AUTHOR]

Density Functional Theory (DFT) calculations were conducted to explore the electronic, optical, and photovoltaic properties of the NaBiS 2 compound with orthorhombic structure, aiming to evaluate its potential for ferroelectric-photovoltaic applications in solar cells. Exchange and correlation electronic effects were approximated using Tran and Blaha's modified Becke-Johnson potential in its semiconductor variance form. The compound was found to have a direct band gap of 1.2 eV, with an absorption coefficient exceeding 105 cm−1 for photon energies higher than 2.2 eV. The material exhibits a pronounced optical anisotropy. Optical absorption in the visible range is primarily caused by electron transitions from the S 2p x,y to the Bi 2p x,y states. Photoconversion efficiency (PHCE) under sunlight reaches a maximum of 20% for a film thickness of approximately 5 μm. This efficiency surpasses that of the MAPbI 3 perovskite compound, a ferroelectric-photovoltaic material with the highest experimental power conversion efficiency (PCE) to date, by 4%. These findings, combined with previously published estimates of ferroelectric polarization and the mobility of charge carriers, uncover the unexplored potential of the orthorhombic NaBiS 2 compound to be employed in photovoltaic and solar-cell devices. • The ferroelectric orthorhombic phase of the NaBiS 2 was studied by DFT. • Bandgap is found to be 1.2 eV, fitting into the ideal range for solar-cell materials. • Absorption coefficient is found to be > 105 cm−1 for photon energies >2.2 eV. • Photoconversion efficiency reaches 20%, 4% higher than that of the MAPbI3 perovskite. • Results indicate a high power conversion efficiency of the material. [ABSTRACT FROM AUTHOR]

Poly(Vinyl)Chloride (PVC) films modified by Sr x ZnO nanoparticles (NPs) were prepared by a simple casting method utilizing its solution in tetrahydrofuran (THF). The PVC films contained 5 wt% of Sr x ZnO NPs. Sr x ZnO particles with 0.00, 0.025, 0.05, 0.075 and 0.1 Sr-doping levels were synthesized by the sol-gel method associated with a hydrothermal process. The PVC/Sr x ZnO films were characterized by XRD, FTIR, Raman, SEM, UV–Visible and PL spectroscopy. XRD analysis demonstrated that Sr x ZnO into PVC matric are well crystallized in the hexagonal ZnO structure with wurtzite phase, while PVC is in an amorphous state. The particle sizes of Sr x ZnO vary in the range of 17–31 nm in agreement with the Sr levels. The ATR and Raman spectroscopy verified the existence of a Zn–O bond related to the wurtzite phase. The SEM cross-section views of the films revealed the bulk nature as well as the thicknesses. Strong emission at 733 nm is observed from the PL analysis, associated with Sr content in the PVC/Sr x ZnO films. Reflectivity, transmittance, and absorption coefficient confirmed the contribution of the physics developed by Sr x ZnO NPs into the PVC matrix. Urback energies are Sr-level dependent, as a consequence of defects tailoring. Optical transitions (directly and indirectly allowed) decrease in some cases by close to 1 eV indicating a transition of PVC to a semi-crystalline material. Other optical properties including linear and nonlinear characteristics promoted PVC/Sr x ZnO as a serious candidate for antireflective coating, and a new generation of photovoltaic cells. [Display omitted] • Poly(Vinyl)Chloride (PVC) films modified by Sr x ZnO nanoparticles (NPs) were prepared. • Strong emission at 733 nm is observed from the PL analysis. • Optical properties including linear and nonlinear characteristics are improved. • PVC/Sr x ZnO films are a serious candidate for antireflective coating. [ABSTRACT FROM AUTHOR]

The photovoltaic use of iodoplumbates perovskites is limited because of lead toxicity and its instability. An alternative is the iodobismuthate compounds. In this work, the microscopically optical properties of two iodobismuthate compounds, (C 28 H 40 N 4) (Bi 4 I 18) and (C 6 H 8 N) (BiI 5) , are obtained using first principles. To relate these properties to the structure and to analyze the effect of the iodine linker atoms in these compounds, we split the absorption coefficients into an exact many-specie expansion. The results indicate that the optical gap and the optical properties are determined by the anionic fragment of these compounds. The presence of iodine linker atoms results in a reduction in the energy gap and a larger absorption near the gap. • The electronic and optical properties are obtained using first-principles. • The optical properties are split into different atomic species contributions. • The effect of iodine linker atoms on the optical properties is analyzed. • The exchange of lead by Bi is evaluated. [ABSTRACT FROM AUTHOR]

In order to realize effective optical limiting (OL), it is necessary to utilize materials that exhibit distinct traits, such as a large and rapid nonlinear optical response, high photothermal stability, and cost-effectiveness. In the present study, the nonlinear optical (NLO) response of methyl orange (MO) is modified by inducing conformational and structural changes through appropriate modification of pH conditions. The NLO properties of MO under two different pH conditions were investigated via the z-scan technique under 7 nanoseconds excitation in the visible region (532 nm). From z-scan results, the nonlinear absorption coefficient of pristine MO and protonated-MO (P-MO) was estimated. Compared to MO, the nonlinear absorption coefficient of P-MO increased by 3.6 times, and it can be attributed to the redistribution of energy levels of MO, which favored resonant absorption in the system. Molecular energy shift and the corresponding apparent red shift in the absorption spectrum of MO are confirmed from both experimental and theoretical analysis. The mechanism behind the nonlinear absorption (NLA) and OL activity of MO is found to be effective two-photon absorption. The closed aperture (CA) z-scan data reveal a negative nonlinear refraction response of MO and P-MO. These findings suggest an efficient way to tune the NLO response of MO through protonation, and this method readily applies to numerous nonlinear optical applications, including but not limited to OL. [Display omitted] • The NLO properties of the methyl orange (MO) are modified by protonation. • Z-scan technique at 532 nm with 7 ns pulses measures NLO properties. • Protonated MO has better nonlinear absorption and optical limiting than MO. • Effective two-photon absorption is the mechanism behind NLA and OL activity. • MO and P-MO exhibit negative nonlinear refraction. [ABSTRACT FROM AUTHOR]

The visible light spectrum attracts vast interest in photodetector applications and takes an integral part in image sensing and communication. Ternary chalcopyrite, such as CuGaS 2 can be used for visible light detection owing to its higher light absorption coefficient and wider bandgap. This work presents pristine and Nickel-doped CuGaS 2 (0.5, 1.0, 1.5 wt. %) thin film photodetectors prepared by the low-cost Chemical Spray Pyrolysis technique. Structural analysis confirms the formation of the pure CuGaS 2 phase and the evidence of Ni inclusion inside the lattice. The optical bandgap of the Ni-doped CGS thin films was reduced compared with pristine CuGaS 2 , leading to higher absorption in the visible region. The interaction of photons with CuGaS 2 and its photoconductive mechanism is probed through photoresponse studies. The responsivity and detectivity were calculated for all the photodetectors under constant bias (1V) and power density (4 mW/cm2). All the devices show excellent photoresponse despite having a higher photosensitive area of 1 cm2 and a very low bias for operation. Particularly, 0.5 wt. % Ni-doped CGS photodetector device showed higher responsivity and detectivity of 1.6 μAW−1 and 19.6 × 106 Jones respectively than others. The admirable optical and electrical properties due to Ni doping played a crucial role in this superior performance. Hence, our investigation suggests Ni-doped CuGaS 2 thin films can be employed in the fabrication of thin film photodetector devices. [Display omitted] • Deposition of phase pure CuGaS 2 thin films by spray pyrolysis. • Interpreting the impact of Ni substitution in the CuGaS 2 crystal lattice. • Tuning of the optical bandgap via doping. • Improvement in electrical properties lead to enhanced photocurrent. • Good photoresponse of prepared films under visible light illumination. [ABSTRACT FROM AUTHOR]

The effects of introducing some amount of KNO 3 into the raw materials on preparation of fluorophosphate glass are investigated in terms of UV–vis transmittance, absorption coefficient and change of refractive index. As the content of KNO 3 reaches 50%, the UV absorption coefficient of the optimized fluorophosphate glass reaches the minimum due to absence of microcrystals in the produced glass. The Schott's Sellmeier dispersion formula and Ghosh's two-polar wavelength-dependent Sellmeier equation were both used to calculate dispersion constants of the optimized fluorophosphate glass. The optimized fluorophosphate glass maintains special characteristics of negative temperature coefficient of refractive index and near-zero thermo-optical coefficient. The lower absorption both in UV and near-infrared (NIR) helps to improve its laser-induced damage resistance. The athermal fluorophosphate glass shows great potential for compensation of thermal-induced distortion in high-power solid-state lasers and high-resolution optical systems. • Introduction of KNO 3 into the investigated fluorophosphate glass batch helps to prevent formation of microcrystals and thus reduced the scattering loss of the prepared glass, resulting in higher UV transmission and improved resistance to 1 laser irradiation. The optimized fluorophosphate glass has negative thermo-optical coefficient and low near-infrared loss, which show potential as thermal distortion compensation in high-power near-infrared lasers (for example 1 μm solid lasers and 1.3 μm oxy-iodine laser) and high-resolution optical systems. [ABSTRACT FROM AUTHOR]

Chemically inert and van der Waal-structured tin-disulfide (SnS 2) has become a potential candidate for optoelectronics due to its ultra-sensitivity and high performance resulting from high light absorption coefficient and thickness-dependent electrical properties. We report the facile synthesis of SnS 2 Terrazzo-like structure using the CVD technique. A highly responsive MSM SnS 2 -based device is designed to detect optical radiation ranging from 300 to 800 nm. The fabricated device exhibits excellent responsivity (external quantum efficiency) of 2240 mAW−1 (522%) under 532 nm wavelengths for a 5 μW optical signal. The other merits, like detectivity and noise equivalent power, are 1.4 × 1010 Jones and 2.6 × 10−12 WHz−1/2, respectively, with a linear dynamic range (LDR) of ∼41 dB. The low LDR plays a vital role in evaluating light intensity from the corresponding generated photocurrent. The weak optical signal detection capability of SnS 2 -based photodetector paves the way for its application in astronomy, communication systems, and biomedical imaging. [Display omitted] • Facile synthesis of SnS 2 -Terrazzo-like structures. • Fabrication of visible photodetector which exhibits excellent responsivity (2240 mAW−1) & EQE (522%) for low optical signals (5 μW) of 532 nm. • Detectivity (1.4 × 1010 Jones) and noise equivalent power (2.6 × 10−12 WHz−1/2) with linear dynamic range of ∼41 dB is observed. [ABSTRACT FROM AUTHOR]

GdVO 4 single crystals doped with different concentration of Nd (0.6, 0.8, 1.0 and 1.2 at.%) were grown by optical floating zone method. The absorption coefficient measured for two orthogonal polarization of light is different due to anisotropic structure in both the direction. The line strength and Judd-Ofelt parameters evaluated from the recorded absorption spectra are also dependent on the polarization of the incident light. Further, the spectroscopic quality factor was estimated by Judd Ofelt parameters and found to be maximum for 0.8 at.% Nd doped GdVO 4 crystals. The emission study shows that photoluminescence (PL) intensity at 1062 (lasing wavelength), 1069 and 1081 nm increases with the doping concentration of Nd up to 0.8 at.% and beyond that the PL intensity at all emission wavelengths decreases. The emission cross-section with excitation at 808 nm was estimated by Judd Ofelt theory for the 4F 3/2 → 4I 11/2 transition and it was found to be independent of doping of Nd in GdVO 4. The measured fluorescence life-time of Nd:GdVO 4 samples is ∼100, 101, 92 and 93 μs corresponding to the doping concentration of 0.6, 0.8, 1.0 and 1.2 at.% of Nd respectively. The measured fluorescence life-time exhibits the maximum value for 0.8 at.% of Nd doping. The decrease in the PL intensity as well as fluorescence life-time for higher doping concentration is because of quenching due to ion-to-ion interaction in the crystal. All the spectroscopic investigation presented here suggest that the optimum concentration of Nd ion in GdVO 4 single crystals is 0.8 at.%, at which the best lasing performance can be obtained. • Single crystals of Nd:GdVO 4 (Nd: 0.6, 0.8, 1.0, 1.2 at.%) were grown by OFZ method. • PL intensity at 1062 nm increases with the doping concentration of Nd up to 0.8 at.%. • The spectroscopic quality factor & fluorescence life time is maximum for 0.8 at.% Nd. • Emission cross-section is independent doping concentration of Nd ion. • Study suggests that the optimum concentration of Nd ion for best lasing is 0.8 at.%. [ABSTRACT FROM AUTHOR]

Laser-induced damage of magneto-optical (MO) materials is a key factor that limits the application of optical isolators in high-power laser systems. In order to investigate parameters that affecting laser-induced damage thresholds (LIDT) of MO garnet films grown by liquid-phase epitaxial (LPE) method, YIG, (LuBi) 3 Fe 5 O 12 and (BiTm) 3 (GaFe) 5 O 12 single crystal films with small lattice mismatch were prepared in this study. The transmittance, optical absorption coefficient, crystal structures, surface quality and laser-induced damage thresholds (LIDT) of the prepared three kinds of MO films were investigated. Microstructure analysis shows that single crystal garnet films grown by LPE method have high surface and crystal quality. Laser-induced damage tests (@1064 nm, 11 ns) pointed out that LIDT of YIG, (LuBi) 3 Fe 5 O 12 and (BiTm) 3 (GaFe) 5 O 12 films are 6.41 ± 0.18 J/cm2, 6.32 ± 0.25 J/cm2 and 4.11 ± 0.27 J/cm2, respectively, and intrinsic optical absorption coefficient of single crystal garnet films plays a decisive role in their laser-induced damage. • Single crystal garnet films with small lattice mismatch and high quality were prepared in this study. • Intrinsic optical absorption of garnet films plays a decisive role in their laser-induced damage. • Laser-induced damage of garnet films is accompanied by generating and releasing thermal stress. • LIDT of single crystal garnet films can be controlled by appropriate ions-substitution. [ABSTRACT FROM AUTHOR]

The temperature of the ZnTe detection crystal in a THz time-domain system was tuned continuously from 300 K to 1.5 K to minimize phonon absorption, thus enhance its detectivity. The THz peak amplitude was observed to increase more than 10 times. To explain this phenomenon, the THz transmission spectra of the ZnTe crystal at different temperatures were also measured, and the refractive index and absorption coefficient of the crystal were extracted. The experiments and theoretic analysis reveal that the significant detectivity enhancement is due to the reduced absorption of the THz field and phase matching change in the detection crystal with temperature decreasing, which makes the ZnTe crystal suitable for integrating with cryogenic applications. • A twelve-fold enhancement of the THz signal amplitude was observed when the ZnTe crystal was cooled from 300 K to 1.5 K. • THz detection sensitivity was calculated based on extracted refractive indices and absorption coefficients. • The significant enhancement is relevant to the suppressed phonon absorption. [ABSTRACT FROM AUTHOR]

Terahertz time-domain spectroscopy has been used to measure the temperature-dependent absorption coefficients and refractive indices of different polymers in 0.2–1.8 THz spectral frequency. The coefficients of temperature-dependent Sellmeier equation for all these polymers have also been evaluated by statistical fitting the measured data, which will be helpful for the evaluation of dispersion properties of the material. Additionally, the thermo-optic coefficients have been evaluated to be the range of − 1.230 × 10 − 4 to − 2.50 × 10 − 4 K−1 for 298–373 K. This data would be helpful for the applications of polymers as THz-waveguide and other temperature sensitive devices. These results provide a temperature-dependent database of optical properties of different polymers for their efficient utilization in THz technology. Image 1 • Study of the temperature-dependent optical properties of different polymers in 0.2–1.8 THz spectral-frequency range. • THz time-domain spectroscopy is a non-contact and damage free technique for the characterization of different materials. • Measurement of temperature-dependent Sellmeier and thermo-optic coefficients as well as refractive index. • Measured refractive indices indicate a prominent decrease w.r.t temperature in 298–373 K range. [ABSTRACT FROM AUTHOR]

Optical properties of a spherical quantum dot (QD) with an on-center hydrogenic impurity in the external static magnetic field are studied. Energies and wavefunctions of the impurity electron are calculated using the Lagrange mesh method. Expressions for the optical absorption coefficients (ACs), refractive index changes (RICs) and group index (GI) are derived with the help of the density matrix formalism for a two-level system, and analyzed from the theoretical point of view. The behavior of ACs, RICs and GI with respect to the incident photon energy is examined, as well as their dependence on the magnetic field strength, laser intensity and relaxation time. It is observed that all of these parameters strongly affect the studied properties of the QD. • The Hamiltonian eigenproblem of the spherical quantum dot with H impurity is solved by using the Lagrange mesh method. • The effect of the magnetic field and QD radius on ACs, RICs and GI is studied. • The influence of the laser intensity and relaxation time on ACs, RICs and GI is also investigated. • Graphically illustrated the possibility of subluminal and superluminal propagation of laser light. [ABSTRACT FROM AUTHOR]

Abstract This paper demonstrates the appropriateness of the Spectroscopic Ellipsometry (SE), a non destructive optical characterization technique in analyzing the optical properties of a few layers of reduced graphene oxide (RGO) in NIR-UV-Vis range of spectrum. The paper discusses the study of the optical properties of RGO sample prepared by exposing GO to natural sunlight. The Drude-Lorentz model is used to extract the optical constants of RGO from the ellipsometric measurement. This paper investigates how the optical parameters change due to the variations in the degree of reduction along with the presence of defects on RGO sheets. The result reveals that the refractive index (n) and the extinction coefficient (k) increase, with the increase in the level of reduction. The effect of the variations in structural defects and the presence of functional groups on the absorption coefficient are studied. The paper also discusses the sensitivity of ellipsometry in analyzing the variations in the dielectric constant due to presence of the residual oxygen moieties. Such detailed optical characterization of RGO samples has great potential application in deciding the best suitable reduction technique for developing specific optical device. Highlights • Graphene is an interesting material with excellent properties and wide possible applications. • In this paper we have explored the optical properties of the reduced graphene oxides by Spectroscopic Ellipsometry. • Studies are performed to understand the impact of oxygen functionalities and the presence of the structural defects on the optical properties of graphene as well. • The study investigates how the optical parameters vary based on the degree of reduction in RGO sample reduced using natural sunlight. • The synthesis proved to be an eco-friendly and cost effective method for synthesizing bulk amount of RGO. • The optical properties of NSRGO sample are comparable to CVD prepared graphene which finds applications in photovoltaics and optoelectronics. [ABSTRACT FROM AUTHOR]

Lanthanide ions (Yb, Er) doped cerium oxide (CeO 2) and yttrium oxide (Y 2 O 3) upconverter nanoparticles were prepared by sol-gel synthesis technique. And the upconverter nanoparticles (CeO 2 : Yb, Er and Y 2 O 3 : Yb, Er) were made us heterostructure with MoS 2 by hydrothermal synthesis. XRD confirms the formation of cubic phase of CeO 2 , cubic phase of Y 2 O 3 , hexagonal phase of MoS 2 and their coexistence in heterostructures. Further, the observation of characteristic Raman peaks between 400 and 700 cm−1 (Raman modes of CeO 2 , Y 2 O 3) and 300–400 cm−1 (Raman modes of MoS 2) assured the formation of heterostructures. FESEM exposes that in heterostructures nanospheres (CeO 2 : Yb, Er) and nanospindle (Y 2 O 3 : Yb, Er) were dispersed on MoS 2 nanoplatelets. Furthermore, when forming the heterostructure with MoS 2 , the diameter of the CeO 2 nanosphere got increased (90 nm) whereas, the length of the Y 2 O 3 nanospindle was decreased (166 nm). The maximum absorption band occurred at UV region due to the charge transition from O2− to Ce ion or Y ion for CeO 2 (340 nm) and Y 2 O 3 (274 nm) respectively. Both upconverters exhibits interesting luminescence behaviour with green emission (537 nm, 588 nm), blue emission (497 nm) and red emission (621 nm). Nonlinear absorption induced optical limiting action were examined by open aperture Z-scan technique using nanosecond pulse laser. All the prepared nanoparticles exhibit a reverse saturable absorption pattern ascribed due to sequential two photon absorption. Among, all the samples, MoS 2 –CeO 2 : Yb, Er and MoS 2 –Y 2 O 3 : Yb, Er heterostructure possess a high nonlinear absorption coefficient (16.76 × 10−10 m/W, 13.61 × 10−10 m/W) and low limiting threshold (0.33 × 1012 W/m2, 0.51 × 1012 W/m2) due to the strong inter-band collision between of MoS 2 and upconverters. The absorption of high number of photons and low limiting threshold behaviour make MoS 2 –CeO 2 : Yb, Er and MoS 2 –Y 2 O 3 : Yb, Er heterostructures as potential candidate for the fabrication of optical limiter based laser safety devices. • Upconverter nanoparticles (CeO 2 : Yb, Er and Y 2 O 3 : Yb, Er) were made us heterostructure with MoS 2 by hydrothermal synthesis. • Absorption band occurred at UV region due to the charge transition from O2− to Ce or Y for CeO 2 and Y 2 O 3 respectively. • FESEM exposes the formation of nanosphere (CeO 2), nanospindle (Y 2 O 3) and nanoplatelet (MoS 2) morphology in heterostructures. • The intensity dependence of nonlinear absorption coefficient declare the sequential 2PA process. [ABSTRACT FROM AUTHOR]

The electron transport layer (ETL) plays an important role in the performance and stability enhancement of perovskite solar cells (PSCs). Zinc oxide is considered a cost-effective and low-temperature processed ETL for PSCs, which offers decent mobility. However, the interface reaction occurs via a reaction of zinc oxide with the organic-inorganic metal hybrid halide perovskite absorber, which results in the degradation of the PSCs. To overcome this issue, metal doping was carried out. However, metal doping causes a reduction in the transmittance of the zinc oxide ETL layer because of high absorption. Thus, the overall performance of the PSCs was reduced due to the lessening of the photogenerated current. In this regard metal co-doping (Mn and Co) was done to improve the electrical as well as electronic properties. Furthermore, the influence of Mn doping on the structural, optical, and photoluminescence properties of Mn x Co 0.015 Zn 1-x O (x = 0, 0.002, 0.008, and 0.012) hexagonal nanosheets was investigated. X-ray diffraction results revealed that the inter-planar spacing, cell parameters, unit cell volume, lattice strain, and dislocation density were maximum for the Mn content of 0.2%. The acquired values of the optical band gap (E g) are 3.39, 3.52, 3.58, and 3.18 eV for x = 0, 0.2%, 0.8%, and 1.2%, respectively. The corresponding absorption coefficient is reduced with increasing Mn content. The obtained refractive indices are 1.437, 1.402, 1.428, and 1.426 for x = 0, 0.2, 0.8, and 1.2%, respectively. The above results confirm that the Mn x Co 0.015 Zn 1-x O with x = 0.8% provides the lowest absorption and the highest value of bandgap. Thus, it can be the most suitable ETL for high-performance PSCs. The simulation results reveal that via applying MCZO ETL, the efficiency can be achieved over 23%. • New ZnO-based compounds (Mn x Co 0.015 Zn 1-x O) were synthesized via the Co-doping of Mn and Co into ZnO. • Influence of Mn doping in Co–ZnO (CZO) was investigated on some of the properties of ZnO. • Highest values of cell parameters were obtained for Mn doping of 0.2%. • The value of the absorption coefficient was reduced with increasing Mn content. • All the samples offer a refractive index value of less than 1.5. [ABSTRACT FROM AUTHOR]

We reported the broadband optical nonlinearity of indium tin oxide (ITO) films with different thickness in the near-infrared spectrum region. The maximum nonlinear response is obtained at its epsilon-near-zero (ENZ) wavelength, and the measured maximum nonlinear refractive index n 2 and nonlinear absorption coefficient β at the ENZ wavelength are 47 times and 28 times larger than the corresponding values at the 1000 nm wavelength, respectively. Meanwhile, a large modulation depth of 9.8% hinted that the ITO has good nonlinear modulation characteristics. In addition, the numerical simulation analysis illustrates the large nonlinear enhancement effect of ITO films, which is attributed to the significant enhancement of electric field due to the ENZ conditions. Our results highlight that ITO is a competitive nonlinear material and has great potential applications in the field of nonlinear optics and all-optical modulators. • The ENZ properties of three thicknesses ITO were characterized. • The broadband nonlinear optical response of ITO were studied. • The large optical nonlinearity of ITO enhanced by ENZ effect were analyzed. • The nonlinear modulation characteristics of ITO were investigate. [ABSTRACT FROM AUTHOR]

The third-order nonlinear optical properties for aqueous solution of methyl blue are explored by the Z -scan method with 800 nm fs radiation. The magnitudes and signs of the nonlinear refractive index n 2 , the nonlinear absorption coefficient β , and the third-order nonlinear optical susceptibility χ (3) are determined at four different concentrations. The β and n 2 values are found to be in the order of 10−13 m/W and 10−20 m2/W, respectively. All the calculated nonlinear optical parameters are linearly proportional to the sample concentration in the studied range. The open aperture Z -scan of methyl blue exhibits reverse saturable absorption, and the closed aperture transmittance reveals the self-defocusing effect and the negative refraction nonlinearity. Our results indicate that methyl blue may be a promising candidate for photonic applications. • The third-order nonlinear absorption and refractive coefficients of methyl blue were measured. • The effect of concentration on the optical nonlinearities was elucidated. • Femtosecond Z -scan technique was applied to investigate the third-order nonlinear optical properties. [ABSTRACT FROM AUTHOR]

The saturable absorbers play key role in passively Q-switched lasers, and Cr4+-doped crystals present attractive advantages for Yb:YAG lasers. At present the major problem is the low doping concentration of Cr4+ and the effective way to promote Cr3+→Cr4+ conversion. From this view, we introduce divalent additives Ca2+ and Mg2+ as charge compensators to ensure the charge state of Cr4+ in the tervalence environment of Yb:YAG. The results reveal that this method can promote Cr3+→Cr4+ conversion effectively and an optimal CaO/MgO ratio is 1:4. The corresponding Cr 0.01at.% ,Yb 5at.% :YAG single crystals present enhanced absorption coefficients and fluorescence intensity at 941 nm and 1030 nm, and decreased fluorescence lifetimes and decay curves than Yb:YAG. The thermal expansion coefficient and laser damage threshold of Cr,Yb:YAG single crystal are approaching the YAG host material. The results show that Cr,Yb:YAG crystal has good potential for self-Q-switched monolithic solid-state lasers. • The Cr 0.01at.% ,Yb 5at.% :YAG single crystals of different CaO/MgO ratios as charge compensators by the Czochralski method. • The Ca2+ and Mg2+ can effectively force Cr3+ convert to Cr4+, and an optimal CaO/MgO ratio of 1:4 can obtain the highest concentration of Cr4+. • The increase of the concentration of Cr4+ can enhance the absorption coefficients of Cr,Yb:YAG single crystals at 941 nm and 1030 nm. • The thermal expansion coefficient and laser damage threshold of Cr,Yb:YAG single crystal are identified as 8.68 × 10−6/°C and 100 ± 5 J/cm2 respectively, which are approaching the values of YAG host material. [ABSTRACT FROM AUTHOR]

Environmentally friendly quantum dots (QDs) with high two-photon absorption coefficients in the near-infrared region are important for nonlinear optics (NLO) applications. In this work, CuLaSe 2 and ZnCuLaSe 2 QD are successfully synthesized and characterized using UV–Vis, Photoluminescence and HRTEM analysis. Next, the third-order NLO properties of these materials are studied using the femtosecond Z-scan method. The samples showed efficient nonlinear responses. The nonlinear absorption coefficient (β), the nonlinear refractive index (n 2) and the third-order nonlinear susceptibility (χ (3) ) values for all samples are deduced and discussed in detail. The results reported here pave the way towards building CuLaSe 2 and ZnCuLaSe 2 QDs-based nonlinear photoelectric devices operating in the near-infrared field. • CuLaSe 2 and ZnCuLaSe 2 QD are successfully synthesized and characterized. • Third-order NLO properties of CuLaSe 2 and ZnCuLaSe 2 QDs have been investigated using femtosecond Z-scan analysis for the first time. • The third-order optical properties of CuLaSe 2 QDs are far better than that of ZnCuLaSe 2 QDs. • The extrapolated values of β, n 2 and χ (3) are found to be on the order of 10−11 cm/W, 10−16 cm2/W and 10−14 esu, respectively. • The results suggest that ZnCuLaSe 2 and CuLaSe 2 QDs can be potential candidates for future applications in NLO. [ABSTRACT FROM AUTHOR]

Particle size and surface trap effects on the third-order nonlinear optical (NLO) properties of CsPbCl 3 and CsPbBr 3 perovskite quantum dots (PQD) have been investigated using a femtosecond (fs) z-scan experiment. Firstly, optical, morphological, and structural characterizations of the synthesized PQDs were performed using linear absorption and photoluminescence (PL) spectra, XRD, and TEM methods. Next, NLO properties of CsPbCl 3 and CsPbBr 3 PQDs were studied at the operating wavelength of 800 nm and 3.564 × 1011 W/cm2 laser intensity. The nonlinear absorption coefficient (β), the nonlinear refraction coefficient (γ), and the third-order susceptibilities (χ (3) ) values for both sample types were calculated to be on the order of 10−11 m/W, 10−17 m2/W, and 10−11 esu, respectively. The effects of particle size and surface trap sites on the nonlinear properties of the PQDs were studied thoroughly. γ , χ (3) , and the unitless nonlinear figure of merits (FOM) parameters were realized to be proportional to the particle size for both types of materials. In addition, these parameters were improved by decreasing the surface trap sites in the PQDs. These results strongly indicate the significant potential of CsPbCl 3 and CsPbBr 3 PQDs for numerous nonlinear applications. • CsPbCl 3 and CsPbBr 3 PQD have shown promising nonlinear optical performances. • The particle size of the material, the electrons and holes trapped on the surface of the PQDs. • NLO properties of PQDs have been studied 3.564 × 1011 W/cm2 intensity per pulse. • The nonlinear parameters obtained are compatible with the used laser intensity. [ABSTRACT FROM AUTHOR]

Metal-doped CdTe has become a heated topic in recent years due to its ultrafast nonlinear optical properties. Herein, Ag-CdTe thin films with different doping amount (1W, 3W and 5W) and pure CdTe thin films were fabricated on quartz substrates by magnetron sputtering. The effects of Ag doping on the morphology, optical band gap and nonlinear optical properties of the thin films were systematically investigated. The nonlinear optical properties were investigated by femtosecond(fs) Z-scan technique under 800 nm. The results indicated that the Ag-CdTe thin films exhibit good nonlinear optical properties in the near-infrared region due to free carrier absorption and two-photon absorption. The results showed that the dopant content and the variation of the incident laser energy can control the RSA intensity, the nonlinear absorption coefficient, and the nonlinear refractive index of Ag-CdTe thin films. These results can provide new support for their applications in the field of nonlinear optoelectronic devices. • This study sheds new light on the preparation of CdTe thin films. • This research makes outstanding contributions to the field of nonlinear optics and provides new ideas in the field of metal-doped semiconductors. • Therefore, this study demonstrates through experiments and a series of test characterizations that Ag doping can improve the third-order nonlinear optical properties of CdTe thin films. [ABSTRACT FROM AUTHOR]

The influence of band-gap on the non-linear absorption mechanism in nickel oxide nanoparticles synthesized by the chemical precipitation method was investigated. The NiO nanoparticles with different optical band-gaps were prepared by varying the calcination temperature from 200 to 400°C. The open aperture Z-scan technique estimated the two-photon absorption coefficients (2PA) and two-photon absorption cross-sections (σ 2 P A ) of NiO nanoparticles at an excitation of 532 nm. The 2PA coefficient has undergone an increase with a reduction in the band-gap. The 2PA coefficient, 2PA cross-section and optical limiting threshold were estimated to be 41.77 cm/GW, 1.93 × 106 GM and 157.91 MW/cm2, respectively. The significant 2PA coefficient and 2PA cross-section values suggest that the NiO nanoparticles could be a promising material for developing optical limiting devices with a relatively low threshold value. All the inferences were validated with structural, elemental and stoichiometric analysis. • The structural and optical properties of nickel oxide nanoparticles synthesized by different calcination temperatures have been studied. • This paper investigates the effect of the band gap on the nonlinear absorption coefficient and cross-section of nickel oxide nanoparticles at 532 nm. • The nonlinear absorption coefficient is obtained to be 41.77 cm/GW. • The nonlinear absorption cross-section is estimated in the range of 106 GM, which is higher than that of other semiconductors reported. • This low limiting threshold value makes the nickel oxide nanoparticles suitable for optical limiters at this wavelength. [ABSTRACT FROM AUTHOR]

This paper presents a new method for computations of the optical absorption coefficient spectra from the normalized photoacoustic amplitude spectra of thin semiconductor samples deposited on the optically transparent and thermally thick substrates. This method was tested on CuIn(Te 0.7 Se 0.3 ) 2 thin films. From the normalized photoacoustic amplitude spectra, the optical absorption coefficient spectra were computed with the new formula as also with the numerical iterative method. From these spectra, the value of the energy gap of the thin film material and the type of the optical transitions were determined. From the experimental optical transmission spectra, the optical absorption coefficient spectra were computed too, and compared with the optical absorption coefficient spectra obtained from photoacoustic spectra. [ABSTRACT FROM AUTHOR]

We investigate the optical properties of cadmium selenide (CdSe) crystals in a wide terahertz (THz) range from 0.2 to 6 THz by THz time-domain spectroscopy (THz-TDS) and Fourier transform infrared spectroscopy (FTIR). The refractive index, absorption coefficient and transmittance are measured and analyzed. The properties are characterized by several absorption peaks which represent the relevant phonon vibrations modes. The experimental results are in agreement with the theoretical results. The dispersion and absorption properties of CdSe crystal are analyzed in THz range. These properties indicate a good potential for THz sources and THz modulated devices. [ABSTRACT FROM AUTHOR]

The series of SiO 2 -Bi 2 O 3 -PbO-ZnO-BaO and SiO 2 -TiO 2 -Bi 2 O 3 -PbO-Na 2 O glasses were synthetized to obtain non-crystallizing materials, dedicated to fabrication of photonic crystal fibers. During composition development, the thermal properties were investigated according to the change of chemical composition. The glasses contain high concentrations of heavy metal oxides for high refractive index, large nonlinear refractive index and spectrally broad transmission window from 0.5 to 4.5 μm. Their thermal properties are optimized to enable drawing of all-solid glass photonic crystal fibers in tandem with previously designed highly nonlinear glass PBG81 based on SiO 2 -Ga 2 O 3 -Bi 2 O 3 -PbO-CdO system. This creates novel dual glass combinations for PCF fibers. We have also investigated influence of melting conditions on the final thermal and optical properties, including absorption from water contamination at around 2.8 μm. [ABSTRACT FROM AUTHOR]

Third order nonlinear optical properties of organic crystal L-threoninium P-toluenesulfonate monohydrate was investigated by 'Z-scan' technique employing two different laser sources under different intensities at 532 nm CW laser and 1064 nm pulsed laser respectively. Nonlinear absorption coefficient (α NL) and nonlinear refraction (n 2) were evaluated at six different intensities using 532 nm CW laser source and with pulsed laser source (λ = 1064 nm) by changing the pulse rate keeping intensity same. It is found that this crystal possesses positive nonlinearity and exhibit saturation absorption. • NLA coefficient (β) and NLR (n 2) of L-threoninium P-toluenesulfonate monohydrate organic single crystal using two laser sources at 532 nm and 1064 nm. • It is found that this crystal possess positive nonlinearity and exhibit saturation absorption. • The nonlinear absorption of this crystal found to be negative. • This crystal may be useful in optical switching application. [ABSTRACT FROM AUTHOR]

Polymer nanocomposites of Poly(styrene-co-methylmethacrylate) (P(St-co-MMA))/Nickel oxide (NiO) with different NiO nanoparticles wt% (0.0, 0.2, 0.4, 0.6, 0.8 and 1.0) are prepared by solution casting technique. The UV–Vis and XRD results revealed decreased direct energy band gap, increased Urbach energy and decreased crystallinity with the increased NiO nanoparticles wt%. The SEM results show the agglomeration of nanoparticles for higher concentrations of NiO nanoparticles loading. The Z - scan studies show the increased nonlinear optical (NLO) parameters viz., nonlinear absorption coefficient (β), nonlinear refractive index (n 2) and nonlinear susceptibility ( χ e f f (3)) with increased NiO nanoparticles wt%. The free volume parameters viz., free volume (V f) and fractional free volume (F v) show increasing and decreasing trends with the NiO nanoparticles concentration respectively. The effect of free volume parameters on nonlinear optical parameters such as β , n 2 and χ e f f (3) is brought out. The increased β , n 2 and χ e f f (3) is due to the increased polarization by the NiO nanoparticles in P(St-co-MMA) polymer matrix. The decreased fractional free volume (F v) with the increased NiO (wt%) indicates the increased packing density of polymeric chains of P(St-co-MMA) polymer matrix. The increased NLO parameters are attributed to the increased polarizability and packing density of polarizable groups in the P(St-co-MMA) polymer matrix. • Poly(St-co-MMA)/NiO polymer nanocomposites were prepared with different NiO nanoparticles wt% by solution casting technique. • The free volume hole size is more for 1.0 wt% of NiO nanofiller loading. • Third order nonlinear absorption and refraction increased with NiO concentration. • The microstructure dependent third order nonlinear absorption properties were explored. [ABSTRACT FROM AUTHOR]

Nanopulsed Nd: YAG green laser-induced nonlinear absorption and optical limiting properties of rGO/MnO 2 , NrGO/MnO 2 and NrGO/MnO 2 /WO 3 nanostructures were studied for the first time utilizing single beam Z-scan experiment. Initially, rGO was prepared by solar exfoliation whereas MnO 2 , WO 3 , rGO/MnO 2 , NrGO/MnO 2 and NrGO/MnO 2 /WO 3 nanostructures were synthesized by hydrothermal method. XRD was used to determine the structure and crystallite size of the materials. Carbon allotropes and functional groups of the prepared materials were studied using Raman and FT-IR spectroscopy. SEM images showed layered rGO, as well as rod-like MnO 2 and flake-like WO 3 nanostructures adorned on the top of NrGO layers. EDS analysis validated the presence of C, N, Mn, W, and O. Linear optical study manifested absorption in the UV–Visible region between 200 nm and 800 nm. The occurrence of reverse saturable absorption (RSA) was confirmed by an open aperture Z-scan technique. Compared to its pure analogs and derivatives of graphene, MnO 2 decorated NrGO had a higher two-photon absorption coefficient (8.92 × 10−11 m/W) and the lowest optical limiting (OL) threshold (3.29 × 1012 W/m2). Extensive conjugation for charge transfer in NrGO and rod-like shape, homogeneous decorating, and strong visible absorption in MnO 2 combine to provide enhanced nonlinear optical (NLO) response and has the potential use in energy stabilizers and laser safety devices in the 532 nm, 9ns laser domain. • NrGO adorned with metal oxides (Mn, W) nanostructures were prepared. • The nonlinear optical properties were examined using an Nd: YAG laser. • The observed nonlinearity was caused by two-photon absorption. • The optical limiting action of NrGO/MnO 2 is stronger than that of other compounds. [ABSTRACT FROM AUTHOR]

In this work, we study the magneto-optical absorption coefficients (MOACs) and refractive index changes (RICs) in monolayer graphene under a perpendicular magnetic field using the compact density matrix approach. The results are presented as functions of photon energy and external magnetic field. Our results show that there are three groups of the possible transitions: the intra-band, the mixed, and the inter-band transitions; in which the MOACs and the RICs appear as a series of peaks in both intra-band and inter-band transitions between the Landau levels. With an increase magnetic field, the resonant peaks give a blue-shift and reduce in their amplitudes. These results suggest a potential application of monolayer graphene in nanoscale electronic and magneto-optical devices. [ABSTRACT FROM AUTHOR]

We theoretically investigated the effects of electric field and structural parameters of the confining potential on the optical properties of a GaAs/AlGaAs double quantum dot related to the occurrence of the electromagnetically induced transparency phenomenon, using the compact density-matrix formalism and the effective mass approximation. The dependences of the absorption coefficient, refraction index and light group velocity on the Rabi frequency of the control field, intensity of the static electric field, asymmetry parameter of the potential and dot dimension are discussed in detail. It is found that electromagnetically induced transparency occurs in the system for intermediate field values and its transparency window for probe field absorption and sub- and super-luminal frequency interval of the probe field are blueshifted by the increment of the electric field strength and dot dimension but are redshifted by the augment of the asymmetry parameter of the potential. [ABSTRACT FROM AUTHOR]

THz optical properties of lithium borate (LBO) crystals were measured using time-domain spectroscopy (TDS). The LBO crystal samples were of high optical quality and were cut and polished along the 〈100〉, 〈010〉 and 〈001〉 axes. Two independent measurements were performed in order to confirm the reproducibility and consistency of results. The contradictions in the previously published data on the THz optical properties of LBO were clarified. It was shown that the birefringence order at THz frequencies is n z < n x < n y , whereas at optical frequencies it is known to be n x < n y < n z . It was seen that n z , which has the highest value in the visible, has the lowest value at THz. This is explained in terms of ionic polarizability and is consistent with the fact that the THz absorption coefficient for a wave polarized along the Z -axis is more than an order of magnitude lower than for the X and Y axes. Absorption as low as 0.2 cm −1 was found at frequencies up to 0.5 THz for a wave polarized parallel to the Z -axis. A set of new dispersion equations was designed for the entire transparency range. [ABSTRACT FROM AUTHOR]

Thermal lens in zinc selenide (ZnSe), cadmium selenide (CdSe) and zinc sulfphide (ZnS) magnetooptical media was investigated by phase-shifting interferometry. It was shown that the thermal lens in ZnSe is 10 times weaker and in ZnS and CdSe are 2 and 16 times higher than in popular magnetooptical terbium gallium garnet crystal. The focal shift and thermo-optical characteristics and of magneto-optical figure of merit were determined. The obtained values of absorption coefficient 1.1х10−4 cm−1 allowed determining a record, 4 kW maximum operating power of a ZnSe Faraday isolator. • Thermal lens in ZnS, CdSe and ZnSe was investigated by phase-shifting interferometry. • The thermo-optical characteristics and figure of merit were determined. • The Faraday isolator using ZnSe can work with laser power up to 4 kW. [ABSTRACT FROM AUTHOR]

Highly conjugated organic molecules are attractive chromophores for nonlinear optics due to their significant third-order nonlinear response near the absorption bands located in the broad spectral range from 200 to 900 nm. In this work, we report on the wavelength-dependence of one- and two-photon absorption processes in Hibiscus sabdariffa organic dye excited by femtosecond (fs) laser pulses centered at 1030 nm and 515 nm. Z-scan and transient absorption (TA) techniques have been employed to investigate the absorption and relaxation processes in the target dye. The dye is found to have a significant negative nonlinear absorption coefficient (β) of value ∼ −2.7 × 10−11 cm/W at 515 nm probing laser pulses, while it has a positive value equal to +2.1 × 10−13 cm/W when 1030 nm laser pulses were employed. The TA decay measurements using 40 fs laser pulses, centered at 515 nm wavelength, reveal that the dye exhibits a short relaxation time of ∼3 ps attributed to the involvement of the excited state proton transfer (ESPT) process in the Hibiscus dye solution. Moreover, our time-integrated fluorescence measurements revealed that no fluorescence emission could be detected. The application of ultrashort pulses of ∼40 fs duration enabled the tracking of ESPT in the Hibiscus dye, which was not detected in previous studies that employed laser pulses of picoseconds and nanoseconds duration. • Nonlinear optical response and transient absorption behaviour of aqueous Hibiscus Sabdariffa dye extract have been investigated. • The role of nonlinear absorption and nonlinear optical Kerr has been demonstrated. • The transient absorption measurements revealed an ultrashort relaxation time of 2.8 ps. • The optical nonlinearity observed in the Hibiscus dye makes it an excellent candidate for fabricating ultrafast photonics and optical devices. [ABSTRACT FROM AUTHOR]

A descriptive method for the attenuation and spatial distribution of flux of photons and fast neutrons for 20Bi 2 O 3 − xPbO − (80 − 2x) B 2 O 3 − xGeO 2 (x = 5, 10, 20 and 30 mol %) glass systems (coded as S 1 , S 2 , S 3 , S 4 respectively) were performed using PHITS code. The calculated elastic moduli, Young modulus, E M was ranged between 32.58 and 33.81 GPa, while bulk K M and shear G M moduli were in the range of 23.36–30.45 and 12.32–13.15 GPa, respectively. However longitudinal modulus L M was between 40.89 and 46.89 GPa. The spatial distribution of the transmitted photon flux showed a decrease with increasing Pb and Ge concentrations. The mass attenuation coefficients, μ m were found to be 70.755–0.042, 76.160–0.043, 83.378–0.046 and 91.895–0.047 cm2/g for S 1 , S 2 , S 3 and S 4 respectively in the energy range of 0.015–15 MeV. The Half Value Layer (HVL) and mean free path (MFP) values were registered in the order of S 4 < S 3 < S 2 < S 1. At low energy, the exposure buildup factor EBF of the glasses recorded decrease by the substitution of B 2 O 3 by PbO and GeO 2 contents. At energy 0.15 MeV, a crossed behavior was noticed. However, at high energy the inverse behavior of EBF was observed. The neutron transmitted flux percentages, at thickness 10 cm were in the range of 10.26–15.51% at all the selected energies. The linear absorption coefficients Σ T , ranged between 0.220 and 0.278 cm−1 which indicated that S4 represents the best shielding capacity among all. The overall results of this work assessed the selected glasses potential for use as gamma and fast neutron radiation shielding products. • Shielding coefficients and flux distribution in borate glass were investigated. • Distribution of transmitted flux decreased with increasing Pb concentrations. • The linear absorption coefficients Σ T were recorded. • EBF of glasses decreased by substitution of B 2 O 3 by PbO and GeO 2 contents. • The relative deviation between PHITS and XCOM database is almost <10%. [ABSTRACT FROM AUTHOR]

The inherent defect states in perovskite nanocrystals (PNCs) have been known to cause degradation in device performance. Hydrophobic polymers with long chained repeating units are frequently employed as protecting layers to passivate the perovskite surface and improve their performance and stability. Here, we report the preparation and Schottky analysis of Formamidinium lead halide PNCs incorporating polyvinylidene fluoride (PVDF) as an additive. The structural characterization of the polymerized compounds confirms the formation of PNCs with better crystallinity and larger grains. The PVDF- incorporated samples (PVDF/PNCs) showed enhanced absorption in the entire visible region along with a decrease in non-radiative recombination events confirmed from dynamic PL studies. In consequence, the PVDF/PNCs Schottky device reveals better electrical performance with higher values of rectification and ideality factor close to unity. Also, from the C–V analysis of the devices, an almost 5-fold increase in carrier concentration is observed. Additionally, the thermal stability of the polymerized PNCs samples improved owing to the interaction between the organic cation and the polymer functional group. This study provides a new design strategy for interface engineering by PVDF incorporation into PNCs that can improve device performance and stability. • Synthesis of perovskite nanomaterials. • PVDF incorporation with the perovskite via hydrogen bonding yielded larger grain sizes with better crystallinity, higher absorption coefficient in the visible range, reduced non-radiative recombination sites, and higher thermal stability. • Improved surface morphology and coverage in WITH PVDF samples, a better Schottky contact was established at the PNCs/Al interface. • A 5-fold increase in the current density of the WITH PVDF devices point out the fact that the polymer additive successfully passivates the defect states in PNCs. [ABSTRACT FROM AUTHOR]

MoS 2 /PVA polymer nanocomposites have been synthesized using In-Situ technique with varying concentrations of MoS 2 in polyvinyl alcohol (PVA). The samples of varying concentrations have been sonicated at different times. The effect of sonication time on the structural, linear and non-linear (NL) optical properties have been studied. Structural properties are investigated with the help of X-ray diffraction (XRD). The morphology of the prepared samples has been studied using Field Effect Scanning Electron Microscopy (FESEM). UV–visible (UV–vis) spectroscopy is used to study linear absorption properties. The smoothly varying absorption spectra acknowledge the presence of saturable absorption (SA) in MoS 2 /PVA nanocomposites. Photo-luminescence (PL) spectroscopy is used to investigate the emission spectra of the prepared nanocomposites with sonication. Fourier Transform Infrared (FTIR) spectroscopy depicts the presence of various physiochemical bondings within the prepared nanocomposites. NL optical properties are studied with the help of the Z-scan technique. The result confirms the occurrence of SA in the MoS 2 /PVA nanocomposites. Further, it can be seen that with rise in the concentration of MoS 2 nanoparticles within the polymer matrix, self-focusing transforms into self-defocusing. The maximum order of NL refractive index and NL absorption coefficient obtained is 10−5 cm2/W and 10−6 cm/W, respectively. In this article, we have found that the NL optical properties of MoS 2 /PVA nanocomposites can be tuned by varying concentration of MoS 2 nano-particles within the polymer matrix as well as by sonicating the particular concentration for different times. • Synthesis of MoS 2 and MoS 2 /PVA nanocomposites with different concentrations of MoS 2 nanoparticles using in-situ method. • Investigation of third order non-linearity of MoS 2 /PVA nanocomposites via Z-scan technique. • Tuning of their linear and non-linear optical properties with ultrasonication. • Occurrence of saturable absorption ensures their use in the field of optoelectronics. [ABSTRACT FROM AUTHOR]

Barium titanate ceramics synthesized employing the solid-state method were investigated for their optical properties and phase transition characteristics. X-ray diffraction method and Scanning electronic microscopy were used to reveal a typical perovskite structure. The average grain size of (Sb or Y) doped barium titanate ceramics falls considerably as the concentration of Sb 2 O 3 or Y 2 O 3 increases. XRD investigation revealed the creation of cubic crystal structure. The impact of (Sb, Y) concentration on structure, including the appearance of various tetragonal phases, grain size reduction, and microstructure development, was investigated. The cell parameters of the formed phases decrease from 4.05418 to 3.99385 and from 4.05418 to 3.98605 as the doping rate increases Ba 1-x Sb x TiO 3 and Ba 1-x Y x TiO 3 ceramics respectively,where (x = 0.00,x = 0.05, x = 0.1, x = 0.15 and x = 0.20).Crystallites sizes of Sb-doped BaTiO 3 crystals changes from 34.59 to 40.47 nm when dopant concentration is changed from 0.05 to 0.20. For Y doped BaTiO 3 crystallite change in size from 28.92 to 29.10 nm. Additionally, assessed were the absorption coefficient (α), extinction coefficient (k), and refractive index (n). When the concentration of Sb3+ or Y3+ ions is increased from 0.05 to 20%, the values of the energy bandgaps for Ba 1-x Sb x TiO 3 and Ba 1-x Y x TiO 3 increase from 3.11 to 3.17 eV and 3.07–3.14 eV, respectively. It is found that the refractive index(n) rises as wavelength rises. It has been shown that the absorption coefficient (α) increases when photon energy increases. It is found that the extinction coefficient (k) decreases with wavelength. The extinction coefficient (k) and the absorption coefficient (α) are both observed to decrease with increasing concentration for all compositions. [ABSTRACT FROM AUTHOR]