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The energy transfer from Sm3+ and Eu3+ due to dipole–dipole interaction, variation in emission intensity of Sm3+ and Eu3+ peaks with varying concentration of Eu3+ and thermal stability of 2Sm3+, 2.5Eu3+ and 2Sm3+/2.5Eu3+ co-doped CaTiO3 phosphors.

The present work focuses on studying the effect of Dy doping on the structural and optical properties of SnO2 nanoparticles. We prepared the pure and Dy3+ (1, 2, 3 and 4 at %) doped SnO2 nanoparticles sample using the co-precipitation method. Three different techniques XRD, UV– Vis & FTIR spectroscopy, have been used to characterize the prepared sample. X- Ray diffraction was used to determine the crystal structure and crystallite size of the prepared sample. Structural analysis by XRD confirms the substitution of Dy3+ atoms on the sites of the host matrix (SnO2). Tetragonal rutile structure is formed by pure and Dy- doped at different concentrations. UV–VIS spectroscopy was used to study the optical properties of the sample. Optical study shows that the prepared sample is highly transparent and absorption increases with Dy doping concentration due to the increase of defect state. The band gap of the sample was found to decrease with increasing Dy concentration, this is due to defect level formation below the conduction band. FTIR spectroscopy determines the molecular geometry, inter and intermolecular interaction and type of functional group present in the prepared sample.

In this paper, we report synthesis of pure SrMoO4, Sm3+ (1 at%–5 at%) doped SrMoO4 and Bi3+ (1 at%–3 at%) co-doped in 4 at% Sm3+ doped SrMoO4 (SrMoO4:4Sm3+) phosphors by solution combustion method. The X-ray diffraction (XRD) analysis reveals the tetragonal phase of all samples, also Bi3+ co-doping supports crystallite size growth and reduces lattice strain. Absorption analysis of Sm3+ doped SrMoO4 ascertains a decrease in band gap and Bi3+ co-doping confirms the emergence of an absorbance peak at around 308 nm attributed to Bi3+ energy levels. Photoluminescence (PL) analysis ascertains an increase in emission peaks for Sm3+ doped SrMoO4 up to 4% concentration, which are attributed to an electron transition from 4G5/2 to 6HJ (J = 5/2, 7/2, 9/2, and 11/2) energy levels of Sm3+ ions. We have explained the effects of Bi3+ co-doping on the luminescence of Sm3+ doped SrMoO4. The reduced microstrain and increased crystallinity of the phosphors as a result of Bi3+ co-doping and their correlation with the luminescence of Sm3+ ions are discussed.

We propose a highly efficient, low-cost metamaterial absorber of nickel (Ni) metal-based cone-shaped resonators with a silicon dioxide dielectric layer (SiO2). The proposed absorber exhibits an average absorption of 97% for the transverse magnetic (TM) and transverse electric (TE) modes over the visible region which is simulated by CST software. The nickel-metal impedance coincides with the impedance of free space and makes the proposed design an effective broadband absorber in the visible region. The average absorption with different incidence angles obtains over 90% and shows the polarization angles' independence. The average absorption spectra are also examined for the absorber with different noble metals. In addition, short-circuit current densities (Jsc) are calculated at different incidence angles for both modes under a global air mass of 1.5 (AM1.5). We have also plotted the J–V curve to obtain the values of the open-circuit voltage (Voc), Fill Factor, and conversion efficiency (η), whose values are 0.563V, 81.86%, and 11.68%, respectively. The proposed metamaterial absorber can be utilized to develop more reliable, highly efficient, cost-effective, and maximum-power extraction photovoltaic systems.

We present the consequences of different Fibonacci quasiperiodic sequences on the sensing performance of a one-dimensional (1D) photonic crystal (PC) based sensor to detect the blood plasma and cancer cells. We demonstrate that the sensitivity and figure of merit (FOM) of the sensor can be modulated, respectively, from 427.5 nm/RIU to 530 nm/RIU and from 162.5 RIU− 1 to 2983.33 RIU− 1 by utilizing the pertinent sensor structures with Fibonacci generation and structural parameters for the analyte refractive index from 1.31 to 1.41. We have also shown that the operational sensing wavelengths and sensitivity can be changed significantly by introducing the different Fibonacci sequences in the proposed sensor. The sensing peaks separation, FWHM, and sensitivity can also be tuned by changing the analyte and PC stacked layers' thicknesses. We also introduce the sensing performances for the Blood plasma and Cancer cells detection using the proposed Fibonacci quasiperiodic PC sensor. We observe that the maximum sensitivities and FOM of the proposed sensor are 552.5 nm/RIU and 2986.93 RIU− 1 for cancer cells and 553.55 nm/RIU and 2214.21 RIU− 1 for blood plasma, respectively. The proposed structure reveals the tunable sensing performances and stimulates the fabrication interest.

In this article, simulation of surface plasmon resonance (SPR) based Al-doped ZnO (AZO) coated long-range low refractive index detections in infrared range sensor by the finite element method (FEM) is presented. Plasmonic material Al-doped ZnO used for SPR condition in the desired range. The effect of thickness of the AZO layers on resonance wavelength, confinement loss, and sensitivity of the proposed sensor has been examined for different analyte refractive index. These parameters do not change with AZO layers width variation. We have optimized coated AZO layer thickness 90 nm and width 124.70 µm in our work. The proposed infrared sensor has achieved refractive index sensitivity 2000-16000 nm/RIU and resolution 5.00x10-5 - 6.25x10-6 RIU for refractive index of analyte range from 1.23 to 1.37. The proposed sensor is useful for detection of low refractive index organic chemical, biomedical, liquid foods and may be used other analyte sensing applications.

In this paper, we present a detailed study on surface plasmon resonance (SPR)-based D-shaped single-mode optical fiber sensor for the range of refractive index (RI) 1.33–1.42 sensing using the finite element method (FEM). Gold (Au), silver (Ag), and copper (Cu) metal layers have used separately to investigate the performance of proposed sensor employed with SPR conditions. Average and maximum sensitivity of the sensor increases with the thicknesses of the metal layer. We observe the higher sensitivity for the Au layer in comparison to Ag and Cu layers. Sensor with Au layer with 50 nm thickness shows the average sensitivity of 5855 nm/RIU with maximum sensitivity of 15,200 nm/RIU and resolution 1.780 × 10−5 RIU. The figure of merit (FOM) has also investigated for such sensor. The sensing performance of the sensor sequentially decreases with Ag and Cu layers. The proposed optical fiber sensors with high sensing performance can be utilized as RI sensors for different chemical and biological sensing.

In this article we report design, mathematical formulation, simulation and fabrication of fiber optic flow sensor using fiber Bragg gratings (FBG) mounted on a cantilever-based transducer support. Design, fabrication and material parameters are optimized in a way that the sensor is operational even at higher flow velocities and finds potentially capable of determining flow rate in rocket fuel tanks for space applications. The reported cantilever supported FBG flow sensor based on simulation results has shown sensitivity to flow rates ranging from 0.1 m/s to as high as 10 m/s flow velocities with varied fuels ranging from liquid hydrogen with density 70.99 kg/m3 to Dinitrogen tetroxide with density 1110 kg/m3. Effect of flow rate is simulated and experimented by placing different weights on the disc and the wavelength shift corresponding to the weights from the designed sensor are recorded. It is observed that the experimental results matched with simulation results to around 50-60%. Flow sensor fabricated is thermally, electrically stable and with its minimal weight finds its extensive use in space applications.

The research in developing a single ingredient phosphor for white-light emission is progressively increasing. It is well known that the

The aim of present study was to investigate the association of the ENPP1 (K121Q) gene polymorphism with DKD in eastern Uttar Pradesh population. A total of 162 DKD and 155 apparently healthy controls were enrolled and K121Q polymorphism was determined by PCR-RFLP followed by sequencing. It was observed that genotype KQ was more frequent in patients than controls and allelic frequencies of Q allele were higher in DKD (Q 21.3%) than control (Q 15.81%). It depicted that Q allele may be associated with DKD patient and has more risk in eastern UP population. The study indicated a significant association of KQ polymorphism of the ENPP1 gene with DKD in the eastern Uttar Pradesh population.

Metamaterials (MTMs) have various applications like plasmonic sensors, light trapping, light detector, color imaging, real invisible clock, magnetic resonance imaging, thermal imaging, solar cells, etc. We have used CST software to simulate four nano-rings-based broadband MTM absorbers in this paper. The simulated structure consists of three layers in the form of a metal-dielectric-metal that exhibit a good impedance near unity with plasmonic resonance characteristics. Tungsten (W) is chosen as the metal and silicon dioxide (SiO2)as the dielectric. The designed structure exhibits an average absorption of 98.19% at the applied wavelength and also exhibits broadband absorption with almost perfect absorption. The physical dimensions, as well as the design of the proposed absorber, have been studied parametrically. Absorber performance has been investigated for transverse electric (TE) and transverse magnetic (TM) modes at wide angles up to 50°, which may be helpful for solar thermo-photovoltaic (STPV) and solar power harvesting device applications. For solar cell applications, we have calculated numerical values of short circuit current density (Jsc) and efficiency (η).

In this paper, we have presented a new design of a metamaterial perfect absorber (MPA) consisting of three layers of metal-dielectric-metal in which the top layer is considered of special kind square patches at different places in a unit cell. This MPA exhibits wideband, wide-angle, and polarization-independent absorption performance in the visible region. This structure originates the plasmonic resonance which is responsible for the perfect absorption in the optical region. Under a specific condition, this simulated absorber structure exhibits an extremely high broadband absorption between 591.54 nm to 704.40 nm wavelength range with near-unity absorption, and a single peak observed at 385.33 nm with absorption 94.16%. We extracted the impedance of the absorber and matched it with free space, and also demonstrated the effective permittivity and permeability. Moreover, the parametric study of the resonators, dielectric layer, and multi-band topology has also been investigated. The polarization-insensitive-based metamaterial may be utilized to improve the efficiency of different devices in the visible range. Furthermore, we have calculated the absorption of the proposed MPA under the solar radiation (AM1.5) for different structural parameters. The proposed absorber greatly enhances the conversion efficiency which is highly useful for solar cells. We also determined the short circuit current density of this absorber for different thicknesses of the GaAs layer. Al metal patches at meta-surface provide nearly similar performance in comparison with other costly metals. Therefore, the proposed structure with cheaper Al metal may be used for different devices as the perfect absorber.

A photovoltaic cell requires the perfect absorption of solar energy which can be converted into electrical energy. We present a simulative work on gallium arsenide (GaAs) based absorber, which provides a broad absorbance in the wavelength regime 200-1000 nm. This absorber has the simplest design of a square resonator built up over tungsten metal. This metal provides high thermal stability due to the high melting point. We found that the proposed MPA is insensitive to the incident angle. Moreover, we have shown the impedance matching of absorber with free space, absorbance with different incident angles, the effect of thickness of resonator, and comparison with the various dielectric spacers.

In this paper, Dy3+/Sm3+ co-doped CaMoO4 compounds were synthesized successfully via the auto-combustion method. The tetragonal crystal structure of the phosphors is confirmed by structural study. The vibrational modes are examined by infrared spectroscopy. It has been observed that 4% Dy3+ doped CaMoO4 phosphor shows maximum luminescence intensity. Further, Sm3+ ions are co-doped in 4% Dy3+ doped CaMoO4 for improving their luminescence properties. The Photoluminescence study illustrates energy transfer between [MoO4]-2 groups and Dy3+/Sm3+ ions, under 296 nm excitation. The Dy3+ doped CaMoO4 phosphors emit two sharp peaks at 484 nm (4F9/2→6H15/2) and 574 nm (4F9/2→6H13/2). Further, with Sm3+ co-doping in 4% Dy3+ doped CaMoO4 phosphor, another distinctive emission peak is observed at 647 nm, which is attributed to 4G5/2→6H9/2 electric dipole transition of Sm3+ ion. The Dy3+/Sm3+ co-doped CaMoO4 phosphor gives overall white light emission. For 3% Sm3+ co-doped CaMoO4:4Dy3+ phosphor, white light is obtained with the CCT value of 4439 K. Hence, the prepared phosphor might be used in white lighting diode applications.

In this paper, a photonic crystal fiber (PCF) sensor based on surface plasmon resonance is proposed for refractive index (RI) sensing with improved sensitivity and resolution. In this design, solid core PCF with three layers of holes is used. Instead of a coating metal layer, we have used two metal wires at both sides of the outside layer of fiber to originate surface plasmon resonance for detection of RI of analyte effectively. Design and analyses have been performed by a Full vectorial finite element method (FV-FEM). Metals Cu, Au, and Ag have been used as plasmonic materials that exhibit higher wavelength sensitivity 7300 nm/RIU, 6200 nm/RIU, and 6100 nm/RIU, respectively. For Cu metal, we observe maximum amplitude sensitivity 597 RIU−1 with higher resolution 1.36 × 10–5 RIU for refractive index of range 1.31–1.36. However, the average sensitivity for Cu, Au, and Ag are 4320 nm/RIU, 4275 nm/RIU, and 3950 nm/RIU, respectively. The effect of air holes along with metal wires for sensitivity is also investigated. In results, copper has provided better sensitivity as well as resolution for a long-range analyte for this proposed RI sensor.

This paper presents a report on the correlation between structural, morphological, and luminescence properties of a series of Sm3+ (1–7 mol %) doped and Li+ (0.5–3 mol %) co-doped Bi2O3 nano-sheets synthesized via co-precipitation method. The X-ray diffraction (XRD) study ascertains monoclinic phase of the prepared samples. Average crystallite size and strain values have been estimated using Debye-Scherrer and Williamson-Hall methods, which exhibits an improved crystalline nature and reduced strain upon Li+ co-doping. X-ray photoelectron spectroscopy (XPS) has been carried out to explore the chemical composition and oxidation state of the elements present in the sample surface. The UV–Vis spectroscopy has been implemented to investigate the band gap of the samples. A slight increment is observed in the band gap upon doping as well as co-doping. An excitation wavelength of 481 nm has been used to explicate the photoluminescence (PL) emission studies over the range of 540–740 nm. Two-fold enhancement in the emission intensity of the Li+ co-doped samples has been recorded as compared to the Sm3+ doped Bi2O3 samples which make them worthy to be served as exquisite candidates to realize efficient warm white light emitting diodes (wLEDs).

The presence of lattice distortion and defects in a composition leads towards a significant change in the optical, magnetic and electrical properties of the host material. In the present work, we have investigated the role of Li concentrations (0.25–1.0%) on structural property of Tb (1%) doped zinc oxide nanoparticles. A small concentration of terbium (1%) has been used to get minimum lattice distortion in the original structure of ZnO. To reduce the possible large lattice deformation on doping of Tb ion we have co-doped the material with Li. The crystalline nature of the sample has been confirmed by the XRD, Raman and FTIR studies of the material. The variation of bond length and lattice disorder in ZnO lattice due to the substitution of Tb and Li were studied from the EXAFS analysis at Zn K edge and Tb L3 edge. Interestingly, the study also shows that disorder decreases due to co-doping of Li in the considered system. Moreover, the oxidation states of all the elements present in the prepared samples were ascertained the XANES analysis. The morphology and particle size are calculated by TEM characterization. This work mainly emphasises on the structural property of synthesized compositions using these analyses. The study will also be helpful in exploring the change in optical, magnetic and electrical properties of the doped ZnO nanoparticles.

We have investigated the influence of different lithium concentrations (0.25–1.0%) on Eu(1%) doped zinc oxide nanoparticles synthesized by sol gel method. The results of XRD, TEM, EDS, FTIR and Raman analysis authenticate the crystalline structure and incorporation of europium and lithium in hexagonal crystal structure of zinc oxide without any impurity phase. The XPS spectra of lithium confirm the existence of Li substitutional and Li interstitial. The local structure has been investigated by X-ray absorption spectroscopy analysis. The results ascertain oxidation state of elements in samples. The variation in bond length observed by EXAFS fitting supports XPS data and indicates the presence of dopant in the host. The position of Li plays an important role in defect mediated ferromagnetism of zinc oxide. The photoluminescence study demonstrates the enhancement in europium related peak for small lithium concentration. We found that the ferromagnetism in zinc oxide reduces after europium doping, while incorporation of lithium (0.5–1.0%) in europium doped zinc oxide significantly enhances the ferromagnetic property of zinc oxide. Li substitutions contribute to ferromagnetic property of zinc oxide by stabilizing Zn vacancy and other magnetic defects. The existence of enhanced luminescence coupled with RTFM makes this material suitable for optoelectronics devices.

In this paper, both sides flat photonic crystal fiber-based surface plasmon resonance (PCF-SPR) sensor has been proposed. In this external sensing mechanism based sensor, we have used gold as plasmonic material with an adhesive TiO2 layer over it, enhancing the interaction between analyte channel and gold metal. Using the wavelength interrogation and amplitude interrogation method, the maximum wavelength and amplitude sensitivities are obtained 22,800 nm/RIU and 947 RIU−1, respectively, for analyte range 1.30–1.40 with a maximum wavelength resolution of 4.38 × 10−6. With Full-width half maxima (FWHM) around 45 nm, the sensor provides a high figure of merit (FOM) 507 RIU−1. The proposed sensor can be fabricated from newly available technologies such as the sol-gel method, stack and draw method for several practical applications in the bio-medical field, bio-chemical field to provide higher and accurate sensing results. The presented sensor has also played a vital role in cancer cell detection with higher sensing performance.

We have investigated the photonic bandgap characteristics in one-dimensional (1-D) exponential graded photonic crystals (GPCs) in the microwave region. Proposed 1-D GPC structures are the stacked of the exponential graded index layers. In an exponential graded index layer, the refractive index between the boundaries of the layer modulates in an exponential fashion in terms of the layer's depth. We observe that the number of photonic bands increases with an increase in the graded layer's thicknesses. When the graded layer's thicknesses are proportional to one-quarter of the optical wavelength relative to the mean refractive index, observed photonic bands increase with an integral multiple of λ0/4 (λ0 represents the optical wavelength of the selected frequency). The bandwidth of photonic band gaps can be tuned with the modulations of the initial and final refractive index of the graded layer. Therefore, the desirable photonic bands can be controlled and achieved in a selected frequency range by choosing the GPC structure's convenient parameters. This work will facilitate the design of filters and multi-channel filters and provide more design freedom for other photonic devices. This work may also provide the basis for understanding the effect of exponentially graded material on photonic band gap characteristics in 1-D GPCs.

In this paper, we report the synthesis of pure ZnO and plasmonic Ag–ZnO nanocomposites by a facile precipitation method. X-ray diffraction analysis is done for the investigation of phase purity of the synthesized samples. The crystallite size and lattice strain of the samples are obtained by Debye-Scherrer and Williamson–Hall analysis. The UV–Vis absorption spectra of the Ag–ZnO nanocomposites reveal an increased optical absorption in the UV region, which suggests that Ag–ZnO nanocomposite can be used as a UV detector. Furthermore, I–V characteristics of the samples have been measured in an applied bias range of -2V–2V under dark and UV illumination (λ = 365 nm). A significant increase in the photocurrent and a three-fold enhancement in the responsivity values in 13.7 wt % Ag–ZnO nanocomposite as compared to the bare ZnO are attributed to the localized surface plasmon resonance phenomena and strain reduction.

In this paper, we have explored the photoluminescence properties of rare-earth free Zn(3-x)Bix(VO4)2 (x = 0, 0.01, 0.03, 0.05) phosphors, synthesized by solution combustion method. The Rietveld refinement confirms that the prepared phosphors have an orthorhombic phase. The Bi3+ doping in the host supports the crystallite growth and reduction of microstrain. The absorption study ascertains the shift in the absorption edge with Bi3+ doping. The lowering of Urbach energy with Bi3+ doping in the host confirms the improvement of crystallinity. The prepared phosphors have near-Ultraviolet (UV) excitation of 350 nm, which reduces visible light reabsorption. The host has broadband emission centered on 540 nm and is enhanced by the factor of 11 after 1% doping of Bi3+ ions. The emission enhancement is attributed to the improved crystallinity and reduced microstrain. Thus, Bi3+ doped Zn3(VO4)2 phosphor can be used as a greenish-white emission source for optical devices.

Theoretical analysis of dye-sensitized solar cell integrated with photonic crystals based on coupled coherent and geometrical optics formalism has presented. The effect of structural parameters, such as thickness of layer, number of unit cells and light incident angle on the optical properties and photo-current magnification for the proposed photonic crystal based dye-sensitized solar cell have studied. The angular response of the cell in terms of light harvesting efficiency and cumulative photo-generation rate has also analysed. A strategy has presented to enhance the performance of the cell under oblique incidence. The effect of number of photonic crystal unit cells has also analysed in view of percentage enhancement in cumulative photo-generation rate. This work provides new insight into the design and tailoring of the photonic crystals to enhance the light harvesting efficiency in the solar cells.

A spiral shaped plastic optical fiber (POF) has been constructed and applied for sensing of the refractive index of a sucrose solution. The sensing mechanism is based on evanescent wave interaction between the light travelling within the fiber and the medium surrounding it. Difference in output voltage is observed as the concentration of sucrose solution is varied from 10% to 50%, demonstrating a uniform relation among them. By varying the pitch of the spiral shape and applying strain to the same, the sensitivity of the POF is refined. This spiral-shaped POF sensor is comparatively easy to fabricate, has low cost of operation, and provides real-time sensing-based data.

The analysis of band structure of one-dimensional (1-D) photonic crystal containing dispersive and non-linear dispersive materials has been presented. The band spectra for the different combination of photonic crystals have been calculated by the well-known plane wave expansion method. The effect of the dispersive and non-linear materials on the band structures has been determined. The third-order nonlinearity has been considered in the non-linear material, and Lorentz–Drude model has been taken for dispersive material. The band gaps of considered photonic crystal are affected by the nonlinearity in the presence of dispersive material like gold. We have observed that the normalized frequency difference between photonic bands decreases on increasing intensity of input beam. This work may be useful in optical switching devices.

We have investigated the consequences of cobalt (Co) incorporation with different doping concentrations (0, 2, 4 and 6 %) on structural, optical and magnetic properties of ZnO nanoparticles. The results of X-ray diffraction spectra (XRD), transmission electron microscopy (TEM), selected area electron diffraction (SAED) pattern of single particle, energy-dispersive X-ray spectroscopy (EDS) and Fourier transform infrared (FT-IR) authenticate the substitution of cobalt and hexagonal crystal structure without any secondary phase formation of all the samples under investigation. The ultraviolet–visible (UV–Vis) absorption study indicates that increase in Co concentration improves the visible region absorption (550–700 nm). The absorption edge of Co-doped ZnO shifts towards visible region with increase in Co concentration. The band gap of samples shows a red shift with increase in Co percentage. The photoluminescence (PL) study of the samples indicates that Co doping shifts the intense peak position of ZnO from violet to blue colour. The weak emission peak at 572 nm is also observed in all the samples. The emission is represented by chromaticity diagram. The room temperature magnetic properties have been studied using vibrating sample magnetometer (VSM). The room temperature magnetisation curve shows that an increase in Co concentration increases the linear behaviour of M–H loop. The magnetic susceptibility results indicate that all the samples have Curie–Weiss behaviour. The coercive field (Hc) and the remanence magnetisation (Mr) increase with Co doping concentration. Fig. M–H curve of pure and cobalt-doped ZnO nanoparticles at 300 K. Inset (a) shows absorption spectra, and inset (b) shows the emission spectra of Zn1−x Co x O nanoparticles.

Engineering of multi-channel photonic band gap sensing consequences has been demonstrated in hyperbolic graded index materials embedded one-dimensional (1-D) photonic crystal (PC) in the frequency 150–850 THz region. The multi-channel photonic band gap sensing properties have been investigated by taking into account the reflection and photonic band gap (PBG) spectra of the proposed PC structures. For quarter-wave stacking, we obtain single optical reflection band for band region 646.8 – 434.3 THz with the constituted normal layer refractive index 1.5. Band regions and bandwidths of the single PBG channel can be modulated by changing the refractive index of the constituted normal layer and grading parameter of the hyperbolic graded layer. The number of photonic bands increases with increasing the layer thickness of the GPC structures and leads to work as multi-channel PBG sensors. The operation frequency of the multi-channel PBG sensors can also be tuned by changing the constituted normal layer and grading parameter of the hyperbolic graded layer. These properties lead to design the tunable multi-channel optical sensors/filters engineering. Moreover, the demonstration of the reflection phase shift, group velocity, group delay, and electric field distributions shows the effect of hyperbolic graded index materials on the propagation of light in 1-D PCs. With the engineering of tunable PBGs and structure controllability, hyperbolic graded index materials embedded 1-D PCs provide a promising way to fabricate tunable optical reflectors and multi-channel optical sensors/filters for future optical devices.

Phosphors doped with rare-earth elements have been extensively employed as white light emitting diodes (wLEDs). Red component is essential in realizing the warm white light efficiently. In this work, we report enhancement in red luminescence of Eu doped phosphor by transition metal doping. Here, a series of Eu3+ doped CaMoO4 and Mn+2/Eu3+ co-doped samples are synthesized successfully by facile auto combustion method. Structural and optical analyses of all samples are studied. UV–Vis analysis of Eu3+ doped CaMoO4 samples ascertains the red-shift in the absorption peak and peak broadening in Mn+2/Eu3+ co-doped CaMoO4. PL study shows an increase in the intensity of emission peaks at 610–630 nm and at 702–711 nm wavelength range up to 4 at % Eu3+ doped CaMoO4, which indicates effective energy transfer from Mo–O charge transfer band to 5D0 level of Eu3+. Luminescence intensity is further increased by Mn+2/Eu3+ co-doping in CaMoO4. For 0.3% at Mn+2 co-doping in CaMoO4:4Eu3+, it is observed that upon 290 nm excitation there is a decrease in the emission broadband around 425 nm–575 nm and increase in intensities of peaks at 612 nm, 615 nm, 654 nm, and 702 nm. Therefore, it is concluded that with proper tuning of Mn+2/Eu3+ doping in CaMoO4, prepared phosphor might have potential application in the fields of lighting and display.

Functional Prussian blue nanoparticles (PBN) is invented as photo-Fenton catalyst and conferred inexpensive, eco-friendly and more effective photodegradation approach to treat the dyestuff Rhodamine B using natural solar light. The photo-Fenton catalyst with four different crystallite size of functional PBN as PBN1, PBN2, PBN3 and PBN4 between 53 to 13 nm were fabricated by chemical reduction method using 2-(3,4-Epoxycyclohexyl)ethyltrimethoxysilane (EETMSi) and Cyclohexanone. EETMSi precisely control the morphology and crystallite size of the catalyst. The as-synthesized photo-Fenton catalysts were characterized by XRD, FTIR, EDX, DLS, HR-TEM, UV/Vis spectroscopy, XPS and BET techniques. Functional PBN/H2O2 combination presented a very promising approach for complete RhB degradation in the acidic condition via N-de-ethylation under solar light irradiation. RhB photodegradation efficiency has been evaluated under different condition to understand the influential role of different parameters; catalyst concentration, H2O2 concentration, size of catalyst and pH. The Kinetic rate constant for RhB photodegradation is found in the order of; (PBN4/H2O2) > (PBN3/H2O2) > (PBN2/H2O2) > (PBN1/H2O2) > (H2O2). The kinetics of the degradation process is found to obey Langmuir-Hinshelwood rate law and approved Pseudo-first order kinetics. The investigation also assessed the quicker (1.5 min) and more effective photodegradation approach for 100% removal of RhB justifying most efficient inexpensive photocatalyst compared to other reported methods. Similarly, the concurrently generated reactive oxygen species (ROS) was detected by EPR technique. The catalyst can be recovered even after five times of repetition. Further Analytical methods LC/MS and COD analysis were utilized to identify the degraded end product and extent of mineralization.

We present the structuring of different graded-index materials in the form of one-dimensional (1D) photonic crystals (PCs) for highly efficient light trapping and controlling photonic devices in terms of tuned and controlled photonic bandgap (PBG) performance. We consider hyperbolic, exponential, and linear refractive index variation in the graded-index layer. We systematically study the influence of structural and grading parameters on the bandgap performance for two different graded photonic crystal (GPC) structures formed by stacking different graded-index layers. Compared with conventional PCs, the GPC bandgaps can be changed and tuned by the refractive index profile of the graded-index layer. We show that the number of bandgaps increases with the graded-index layer thickness and the bandgap frequencies can be tuned by the grading profiles. We observe the sequential increment in bandwidth for the complete PBGs in the GPC structures with linear, exponential, and hyperbolic graded-index materials. We also study the influence of the stacking pattern and grading profiles on the bandgap, phase shift, group velocity, delay time, and field distribution. The proposed GPC configurations facilitate the design of reflectors, multi-channel filters, detectors, and other photonic devices. The study may also provide the basis of understanding of the influence of graded-index materials on the PBG characteristics in the GPCs.

We present an innovative platform for photonic crystal fiber (PCF) based refractive index (RI) sensor for the detection of analytes. Our PCF operating on the principle of a single mode is spliced with multi-mode fiber on both sides. This PCF contains an empty core, surrounded by elliptical plasma dielectric rods suspended in solid microstructured cladding for different pump signals over the extended range of E + S + C + L + U communication bands. The empty core of this photonic device is injected with analytes leading to generation of an evanescent field. The doping of boron is subjected to significantly diminish the upgraded refractive index of silica which ingresses special capabilities that endow an outstanding potential to PCF for the profoundly intense pulse laser. We present structure with over the extended E-band (1360-1460 nm) ultra-flat anomalous dispersion below −50 ps/nm/km and over the ultra-long U-band (1625–1675 nm) flat near zero anomalous dispersion with high birefringence dedicated to sensing application over the entire communication band. Our designed PCF shows better performance for both high contribution and asymmetric shape of plasma dielectric rods and is strongly sensitive to the refractive index of analytes injected in the core of the PCF.

Tunable temperature dependent terahertz photonic band gaps (PBGs) in one-dimensional (1-D) photonic crystal composed of alternating layers of graded index and semiconductor materials are demonstrated. Results show the influence of temperature, geometrical parameters, grading profile and material damping factor on the PBGs. Number of PBG increases with increasing the layer thickness and their bandwidth can be tuned with external temperature and grading parameters. Lower order band gap is more sensitive to the temperature which shows increasing trend with temperature, and higher order PBGs can also be tuned by controlling the external temperature. Band edges of PBGs are shifted toward higher frequency side with increasing the temperature. Results show that the operational frequencies of PBGs are unaffected when loss involved. This work enables to design tunable Temperature dependent terahertz photonic devices such as reflectors, sensors and filters etc.Tunable temperature dependent terahertz photonic band gaps (PBGs) in one-dimensional (1-D) photonic crystal composed of alternating layers of graded index and semiconductor materials are demonstrated. Results show the influence of temperature, geometrical parameters, grading profile and material damping factor on the PBGs. Number of PBG increases with increasing the layer thickness and their bandwidth can be tuned with external temperature and grading parameters. Lower order band gap is more sensitive to the temperature which shows increasing trend with temperature, and higher order PBGs can also be tuned by controlling the external temperature. Band edges of PBGs are shifted toward higher frequency side with increasing the temperature. Results show that the operational frequencies of PBGs are unaffected when loss involved. This work enables to design tunable Temperature dependent terahertz photonic devices such as reflectors, sensors and filters etc.

The present study has been carried out to investigate the effect of Co doping on structural and optical properties of Dy doped ZnO nanoparticles. We have prepared pure Zinc oxide, Dy (1%) doped ZnO and Dy (1%) doped ZnO co-doped with Co(2%) with the help of simple sol-gel combustion method. The structural analysis carried out using X-ray diffraction spectra (XRD) indicates substitution of Dy and Co at Zn site of ZnO crystal structure and hexagonal crystal structure without any secondary phase formation in all the samples. The surface morphology was analyzed by transmission electron microscopy (TEM). Absorption study indicates that Dy doping causes a small shift in band edge, while Co co-doping results significant change is absorption edge as well as introduce defect level absorption in the visible region. The band gap of samples decreases due to Dy and Co doping, which can be attributed to defect level formation below the conduction band in the system.The present study has been carried out to investigate the effect of Co doping on structural and optical properties of Dy doped ZnO nanoparticles. We have prepared pure Zinc oxide, Dy (1%) doped ZnO and Dy (1%) doped ZnO co-doped with Co(2%) with the help of simple sol-gel combustion method. The structural analysis carried out using X-ray diffraction spectra (XRD) indicates substitution of Dy and Co at Zn site of ZnO crystal structure and hexagonal crystal structure without any secondary phase formation in all the samples. The surface morphology was analyzed by transmission electron microscopy (TEM). Absorption study indicates that Dy doping causes a small shift in band edge, while Co co-doping results significant change is absorption edge as well as introduce defect level absorption in the visible region. The band gap of samples decreases due to Dy and Co doping, which can be attributed to defect level formation below the conduction band in the system.

We have investigated the photonic band gaps (PBG) and omnidirectional band gaps in one-dimensional photonic crystals made up of alternate layer of exponential graded index material and negative index material. We have considered the influence of material properties, geometrical parameters and material composition on the PBG and omnidirectional band gap. Results show that the parameters of exponential graded index material and negative index material can change the photonic and omnidirectional band structures remarkably. Number and bandwidth of PBG increases with increasing the negative index material layer thicknesses while thicknesses of graded index layer only have an effect on the bandwidth of PBGs. The bandwidth of PBG also depends on grading profile parameter of exponential graded index layers and bandwidth can be tuned with increase the value of grading profile parameter. This work can facilitate the design of filters and reflectors, and provide the basic understanding of the influence of graded ind...

In this paper, we present the investigation on the photonic localization and band gaps in quasi-periodic photonic crystals containing graded index materials using a transfer matrix method in region 150–750 THz of the electromagnetic spectrum. The graded layers have a space dispersive refractive index, which vary in a linear and exponential fashion as a function of the depth of layer. The considered quasiperiodic structures are taken in the form of Thue–Morse and Double-Periodic sequences. The grading profile in the layers affects the position of reflection dips and forbidden bands, and frequency region of the bands. We observed that vast number of forbidden band gaps and dips are developed in its reflection spectra by increasing the number of quasi-periodic generation. Moreover, we compare the total forbidden bandwidths with increasing the generation of the quasi-periodic sequences for the structures with linear and exponential graded layer. Results show that the different graded profiles with same boundary refractive index can change the position of localization modes, number of photonic bands and change the frequency region of the bands. Therefore, we can achieve suitable photonic band gaps and modes by choosing the different gradation profiles of the refractive index and generation of the quasi-periodic sequences.

We have demonstrated control of the photonic band gaps (PBGs) in 1-D photonic crystals using linear graded index material. The analysis of PBG has been done in THz region by considering photonic crystals in the form of ten periods of second, third and fourth generation of the Fibonacci sequence as unit cell. The unit cells are constituted of two kinds of layers; one is taken of linear graded index material and other of normal dielectric material. For this investigation, we used a theoretical model based on transfer matrix method. We have obtained a large number of PBGs and their bandwidths can be tuned by changing the grading profile and thicknesses of linear graded index layers. The number of PBGs increases with increase in the thicknesses of layers and their bandwidths can be controlled by the contrast of initial and final refractive index of the graded layers. In this way, we provide more design freedom for photonic devices such as reflectors, filters, optical sensors, couplers, etc.

We present the structuring of different double graded-index materials in the form of one-dimensional (1D) photonic crystals (PCs) for highly efficient light trapping and controlling photonic devices in terms of tuned and controlled photonic bandgap (PBG) performances. Considered 1D graded photonic crystal (GPC) structures are stacked of hyperbolic, exponential, and linear double graded index layers. In the graded index layers, the refractive indices vary in hyperbolic, exponential, and linear fashions as a function of the layer thickness. These configurations show that the operating frequencies and the number of PBGs can be tuned by controlling layer thickness, grading profiles, and grading parameters of the constituted graded layers. The changes in the grading profiles of the graded layers modulate the operation frequencies and also the number of PBGs. We also found that the operating frequencies and bandwidth of PBGs can be tuned by changing the values of initial and final refractive indices of the graded layer. Therefore, the desirable PBG regions and bandwidths can be achieved and controlled by selecting appropriate parameters of the systems. Results can be implemented to design tunable reflectors, multi-channel filters, sensors, and optical detectors. Also, this work may provide an understanding of the effect of different double graded-index materials on PBG characteristics in the GPCs.