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In this work, we present the operation of a femtosecond-laser-written diode-pumped visible waveguide laser based on praseodymium-doped lithium lutetium fluoride. The refractive index modification induced by the femtosecond laser in the crystal exhibits an anisotropic behavior, thus enabling the fabrication of different types of waveguides from single-track structures to stress-induced waveguides and depressed cladding structures. All the waveguides were characterized by realizing transmission measurements and the waveguide design was optimized to obtain extremely low propagation losses, equal to 0.12 d B / c m. Lasing has been achieved at 604 n m and 721 n m from different waveguides. In addition, stable continuous-wave lasing at 698 n m has been obtained in a depressed cladding waveguide. This wavelength corresponds to the one needed for the transition of the atomic clock based on the neutral strontium atom. In the end, we report the observation of laser emission at 645 n m from a depressed cladding waveguide. [ABSTRACT FROM AUTHOR]

• Lead telluride quantum dots (PbTe QDs) were used as a novel saturable absorber (SA). • A high-power Pr:YLF ultrashort pulse laser using PbTe QDs SA was obtained. • PbTe QDs provide new ideas for the development of visible ultrashort pulse lasers. High-quality lead telluride quantum dots (PbTe QDs) are prepared by a top-down liquid phase exfoliation (LPE) method successfully and used as a novel saturable absorber (SA) to first realize a picosecond continuous-wave mode-locked (CWML) red laser with a Pr:YLF crystal. The nonlinear optical saturable characteristic of the PbTe QDs SA is measured by applying a double-channel synchronous detection technique. Further, a picosecond CWML Pr:YLF laser with a highest average output power of 115 mW is obtained, corresponding to a pulse energy of 1.5 nJ and a peak power of 24.2 W. These findings indicate that high-quality PbTe QDs SA is an effective optical modulator, demonstrating its application prospects in the field of visible ultrafast photonics. [ABSTRACT FROM AUTHOR]

• 570.3-nm CW yellow self-frequency doubling laser realized 8.7 W output power. • The maximum slope efficiency of the continuous wave yellow laser is 34.6 %. • A high power yellow laser was realized in a monolithic cavity with an oscillator length of 6 mm. • This study provides an avenue for developing high-efficiency CW yellow laser. Although yellow laser is applied in diverse fields, the development of yellow laser technology faces challenges due to the scarcity of suitable materials that efficiently emit light at this specific wavelength range. In this study, a continuous-wave yellow laser with high output power and efficiency operating at 570.3 nm using a Yb: YCa 4 O(BO 3) 3 (Yb: YCOB) crystal in a monolithic cavity, with an oscillator length of 6 mm through the integration of multiphonon-electron coupling and self-frequency doubling. To characterize its multiphonon-electron coupling effect, we examined the temperature distribution in the laser crystal and temperature-dependent phase-matching conditions. The maximum output power of the yellow laser was 8.7 W, which is two-fold higher than that of semiconductor diode lasers and nearly 20-fold higher compared with that of diode-pumped yellow lasers in Tb3+/Dy3+-doped crystals. This study provides a compact yellow coherent source for power-scaling and promising applications in modern equipment and promotes a novel paradigm in electron–phonon-coupling related optics and photonics. [ABSTRACT FROM AUTHOR]

High quality crystals with composition of Ca 0.95 Tb 0.05 F 2.05 and Ca 0.85 Tb 0.05 Yb 0.1 F 2.15 were grown by Bridgman-Stockbarger technique. Yb3+ ions were used as a sensitizer for Tb3+ ions. Optical properties were measured, including the absorption spectrum, emission spectrum, and fluorescence decay curves. Judd-Ofelt theory was used to analyze the spectroscopic parameters. Fluorescence branch ratio, transition probability, radiative and fluorescence lifetimes, and quantum efficiency were determined. The emission cross section of Tb3+ ions in Tb:CaF 2 and Tb/Yb:CaF 2 crystals for the green emission at 544 nm, corresponding to the transitions of 5D 4 →7F 5 were calculated to be 4.61 × 10−22 cm2 and 4.60 × 10−22 cm2, respectively. Our experiments have shown that doping with Yb3+ ions does not significantly affect the spectral properties of Tb3+ ions in CaF 2 crystal. Quadratic dependence of the emission intensity of Tb3+ ion in Tb/Yb:CaF 2 crystal on the intensity of a diode laser at 955 nm proved that the excitation of Tb3+ ion occurs due to the cooperative process of transferring the excitation from two Yb3+ ions to one neighboring Tb3+ ion. The Tb/Yb:CaF 2 crystal can be considered as a promising up-converting medium for creating diode-pumped visible phosphorus and active laser media. • Spectral properties of Tb3+ ions are not affected by Yb3+ in Ca 0.85 Tb 0.05 Yb 0.1 F 2.15 crystal. • Ga–As diode laser effectively excites Tb3+ ions in Tb/Yb:CaF 2 crystal due to cooperative up-conversion process • Tb/Yb:CaF 2 crystal is promising for creating diode-pumped visible phosphorus and active laser media. [ABSTRACT FROM AUTHOR]

In this work we report a thermal stress test executed on high efficiency diode pumped waveguide lasers based on Pr:LiLuF 4. Numerical simulations have been performed to estimate the core temperature. We demonstrated that no modifications in the output power, 275 mW at 604 nm and 310 mW at 721 nm, and in the bulk-level slope efficiency, 40% at 604 nm and 50% at 721 nm, have been observed with an estimated core temperature of 70 °C. We also executed stability measurements of the free running laser in thermally severe conditions, demonstrating output power fluctuations of mechanical origin as low as 10% of the peak value. • Direct femtosecond-laser-writing allows the fabrication of waveguides in dielectrics. • Praseodymium-based lasers can be used as metrological or medical-oriented sources. • Praseodymium-based waveguide lasers can be passively dissipated without power loss. • Passively-cooled devices play a key role in aerospace-oriented lightweight systems. [ABSTRACT FROM AUTHOR]

We demonstrated a mode-locked fiber laser oscillator using nonlinear polarization rotation as a saturable absorption system. The fiber laser generates mode-locked pulses by adjusting four waveplates. A single-clad Pr ^3+ -doped single mode fluoride fiber with a 425 mW threshold pump power serves as the foundation for the ring cavity, which operates in the dissipative soliton resonance regime. The radio frequency signal-to-noise ratio of the pulses at 634.9 nm is 60 dB, maximum output power of 5.5 mW, and repetition rate of 34.5 MHz. These findings provide a foundation for the advancement of photonic applications in the visible spectrum.

High-quality copper-graphene holds great potential for applications in electronics, but fabricating these hybrid structures in a cost-effective route remains challenging. Herein, we propose a one-step writing process for manufacturing copper-doped graphene hybrid structure using low-cost visible laser. The ionic precursor coated on the surface of polymeric substrate not only acts as a copper source for doping, but also can promote near-surface graphenization of the polymer as proved in this study. The interaction between copper and graphene during this in-situ laser processing has been in-deep discussed to reveal the formation mechanism of the hybrid structure. The obtained hybrid structure shows excellent performance that can assemble high-performance devices, such as the in-plane supercapacitor we demonstrated. This study presents a low-cost, rapid, and efficient strategy for structuring the composites to meet the demands for high-performance structures in booming electronics. [Display omitted] • A one-step laser writing route for manufacturing Cu-doped graphene composites on a flexible substrate was proposed. • The in-situ formed Cu-rich component during processing can improve the quality of visible lase induced graphene. • The mechanism of structural evolution was revealed, and the application of the composites in energy storage were demonstrated. [ABSTRACT FROM AUTHOR]

We report on the generation of few-ns pulses with kW peak power in the red and orange spectral range obtained from a passively Q-switched Pr3+:YLF laser. A compact resonator and thorough investigation of the Co:MgAl2O4 saturable absorber’s initial transmission enables peak powers in excess of 1.1 kW at pulse durations of 2.4 ns and 5.3 ns at 640 nm and 607 nm, respectively. These are the shortest pulse durations among any Q-switched Pr3+ laser and make this system a suitable front-end for efficient frequency doubling into the ultraviolet range. [ABSTRACT FROM AUTHOR]

Effects of P-codoping on X-ray/450 nm LD induced photodarkening in Dy3+ doped silica glass and fiber were investigated to develop a visible fiber laser. P and Dy concentrations in Dy-P-doped silica glass were optimized to reduce Rayleigh scattering. It was found in optimized glass that X-ray-induced photodarkening can be well suppressed by P co-doping. 450 nm LD pumped laser oscillation was firstly observed in the fiber using optimized glass. The slope efficiency is 4.2% which is lower than those in Dyâ€"Al-and Dyâ€"Alâ€"Ge-doped fibers previously reported. Contrary to the results of X-ray-induced PD, 450 nm LD-induced photodarkening easily occurred. [ABSTRACT FROM AUTHOR]

Here we developed a novel wavelength-switchable visible continuous-wave (CW) Pr3+:YLF laser around 670 nm. In single-wavelength laser operations, the maximum output powers of 2.60 W, 1.26 W, and 0.21 W, the maximum slope efficiencies of 34.7%, 27.3%, and 12.3% were achieved with good beam qualities (M2 < 1.6) at 670.4 nm, 674.2 nm, and 678.9 nm, respectively. Record-high output power (2.6 W) and record-high slope efficiency (34.7%) were achieved for the Pr3+:YLF laser operation at 670.4 nm. This is also the first demonstration of longer-wavelength peaks beyond 670 nm in the 3P1→3F3 transition of Pr3+:YLF. In multi-wavelength laser operations, the dual-wavelength lasings, including 670.1/674.8 nm, 670.1/679.1 nm, and 675.0/679.4 nm, were obtained by fine adjustment of one/two etalons within the cavity. Furthermore, the triple-wavelength lasings, e.g. 672.2/674.2/678.6 nm and 670.4/674.8/679.4 nm, were successfully demonstrated. Moreover, both the first-order vortex lasers (LG0+1 and LG0-1 modes) at 670.4 nm were obtained by off-axis pumping.

Graphene-based materials present unique properties for electrochemical applications, and laser-induced conversion of polyimide to graphene is an emerging route to obtain a high-quality material for sensing. Herein we present compact and low-cost equipment constructed from an open-source 3D printer at which a 3.5-W visible (449 nm) laser was adapted to fabricate laser-induced graphene (LIG) electrodes from commercial polyimide, which resulted in electron transfer kinetic (k0) of 5.6 × 10−3 cm s−1 and reproducibility calculated by relative standard deviation (RSD < 5%) from cyclic voltammograms of [Fe(CN)6]3−/4− using 5 different electrodes. LIG electrodes enabled the simultaneous voltammetric determination of uric acid (+ 0.1 V vs. pseudo-reference) and nitrite (+ 0.4 V vs pseudo-reference), with limit of detection (LOD) values of 0.07 and 0.27 µmol L−1, respectively. Amperometric measurements for the detection of H2O2 (applying + 0.0 V vs. Ag|AgCl|KCl(sat.)) after Prussian blue (PB) modification and ciprofloxacin (applying + 1.2 V vs. Ag|AgCl|KCl(sat.)) were performed under flow conditions, which confirmed the high stability of LIG and LIG-PB surfaces. The LOD values were 1.0 and 0.2 µmol L−1 for H2O2 and ciprofloxacin, respectively. The RSD values (< 12%) obtained for the analysis using three different electrodes attested the precision of LIG electrodes manufactured in two designs. No sample matrix effects on the determination of ciprofloxacin in milk samples were observed (recoveries between 84 and 96%). The equipment can be built with less than $300 and each LIG electrode costs less than $0.01. [ABSTRACT FROM AUTHOR]

The recent renaissance in pulsed lasers operating in the visible spectral region has been driven by their significant applications in a wide range of fields such as display technology, medicine, microscopy, material processing, and scientific research. Low-dimensional nanomaterials as saturable absorbers are exploited to create strong nonlinear saturable absorption for pulse generation at visible wavelengths due to their absorption peaks located in visible spectral region. Here we provide a detailed overview of visible-wavelength pulsed lasers based on low-dimensional nanomaterials, covering the optical properties and various integration strategies of these nanomaterials saturable absorbers, and their performance from solid-state as well as fiber pulsed lasers in the visible spectral range. This emerging application domain will undoubtedly lead to the rapid development of visible pulsed lasers.

The concentration of smoke in an environment can cause obvious interference to visible light intensity imaging, and it is a non-negligible factor in the polarized imaging of ground-based targets. Smoke particles cause severe scattering of photon intensity, resulting in polarization. In this case, low-visibility targets can be effectively identified by detecting the polarization dimension of targets. However, the polarization transmission of smoke in an environment is unclear, and the theoretical simulation lacks experimental reliability verification. To study this problem, this study constructs a polarization transmission model in a smoke environment and simulates and analyzes the scattering of visible polarized light at 450, 532, and 671 nm under different smoke densities. The optical thickness is determined to establish a reliable connection between the simulation and the external field long optical path test and verify the transmission of polarized light. Results show that the method has a 60% confidence in the polarization transmission model. With the increase in optical thickness, the degree of polarization (DOP) of the three wavelengths in the visible light band decreases, and the DOP of each polarized light decreases. No obvious difference is found between the DOPs of circularly polarized light at 450 nm and linearly polarized light. The DOP of circularly polarized light at 532 nm is 1–5% higher than that of linearly polarized light, 1–10% higher than that of the outdoor test, 1–5% higher than that of circularly polarized light at 671 nm, and 2–15% higher than that of the outdoor test. Therefore, the shorter the wavelength in the visible band, the higher the DOP. With the increase in wavelength, the polarization characteristics of circularly polarized light are gradually better than those of linearly polarized light.

In this work, we present the operation of a femtosecond-laser-written diode-pumped visible waveguide laser based on praseodymium-doped lithium lutetium fluoride. The refractive index modification induced by the femtosecond laser in the crystal exhibits an anisotropic behavior, thus enabling the fabrication of different types of waveguides from single-track structures to stress-induced waveguides and depressed cladding structures. All the waveguides were characterized by realizing transmission measurements and the waveguide design was optimized to obtain extremely low propagation losses, equal to 0.12 dB/cm. Lasing has been achieved at 604 nm and 721 nm from different waveguides. In addition, stable continuous-wave lasing at 698 nm has been obtained in a depressed cladding waveguide. This wavelength corresponds to the one needed for the transition of the atomic clock based on the neutral strontium atom. In the end, we report the observation of laser emission at 645 nm from a depressed cladding waveguide.

We present the first demonstration of visible laser oscillation in the Dy3+-doped silica fiber pumped by a 451 nm InGaN laser diode. It was found that Ge-co-doping plays the following important roles of laser oscillation: (1) to reduce the Rayleigh scattering loss, (2) to suppress the X-ray-induced and pump-induced photodarkening (PD), and (3) to increase lasing slope efficiency. In a fiber with 0.46 wt% Dy, 1.8 wt% Ge, and 0.54 wt% Al, the slope efficiency is 22.0% at 582.5 nm, and the maximum output power is 18.4 mW. [ABSTRACT FROM AUTHOR]

Sm3 + -doped YAG and Y3SCAI4O12 single crystal fibers were successfully grown by the micro-pulling-down (r-PD) technique. X-ray diffraction test shows that the crystals are cubic phase structure, the lattice constants of Sm ： YAG and Sm：Y3ScAl4O12 single crystal fibers are calculated to be a = 1. 199 3 nm and a = 1. 200 0 nm, respectively. The Raman spectra, absorption spectra, fluorescence spectra and fluorescence lifetimes of the crystal fibers were measured at room temperature. The strong absorption band centered at 405 nm matches well the InGaN/GaN laser diode pumping. Under 404 nm excitation, the emission transition of 4G5/2--6H7/2 peaked at 618 nm appears to be strongest, and the fluorescence lifetime of the 4G5 2 level of Sm3 + -doped YAG and Y3ScAl4O12 single crystal fibers are determined to be 1. 86 ms and 1. 83 ms, respectively. The experimental data shows that Sm：YAG and Sm： Y3 ScAl4 O12 single crystal fibers are potential laser media in the red-orange wavelength range. [ABSTRACT FROM AUTHOR]

This study aims to use the method of laser reflection from the surface of strawberry fruits to classify different strawberry defects to facilitate the process of sorting the fruits during the handling process. The study was conducted on exposing the strawberry fruits (festival variety) to laser radiation with wavelengths of 543.5 and 632.8 nm, after dividing the fruits into six groups according to strawberry defects, to measure the amounts of reflected radiation and generated electricity. The results obtained were follows: a) For the physical and chemical properties of strawberry fruits: It was found that there is no dispersion in height, width, length, volume, weight, total soluble solids (Brix) and the pH value of the fruits. Their variance values indicate that there is stability of the physical and chemical characteristics in this variety of strawberries., b) The results of the T-test showed that there was a significant difference between the light density reflected or the amount of generating electricity from the surface of standard strawberry fruits and the surface of defective strawberry fruits at every defect (mold, insects, green end, white shoulder, green), in the case of using different levels of the laser beam with a wavelength of 543.5 or 632.8 nm. Then, the amount of reflected radiation or the amount of electrical energy generated could be used to separate the affected fruits from the healthy ones, c) The results of the One Way Anova analysis showed that there was a statistically significant correlation between the light density reflected from strawberry fruits (as a result of using laser beams at 543.5 or 632.8 nm wavelengths) and the amount of electricity generated on the surface of the photovoltaic cells, d) It was possible to use laser reflection light or the amount of generating electricity to classify and sort strawberry fruits according to its defects. [ABSTRACT FROM AUTHOR]

This work proposes a facile approach to fabricate a dual-core hollow waveguide based on two common and low-cost raw materials, namely polytetrafluoroethylene (PTFE) tube and ultraviolet (UV) gel. A silica glass tube is nested inside a heat-shrinkable PTFE tube. After heat treatment at 350 °C, the PTFE tube shrinks and then transforms into the low-index polymer on the outside of the silica tube. The PTFE-coated silica glass tubing is filled with UV gel followed by inserting a typical Ag/AgI mid-infrared (IR) hollow optical fiber. The UV gel is cured by UV radiation, forming a solid low-index layer between the PTFE-coated silica glass tubing and the Ag/AgI hollow optical fiber. A visible laser beam can be transmitted at a loss of 0.4 dB/m through the silica annulus between the low-index PTFE and UV gel layer. A 10.6-μm-wavelength CO2 laser beam is delivered through the Ag/AgI hollow optical fiber (core size 530 μm) and the transmission loss goes up from 1.63 to 3.22 dB/m as the bending angle increases from 0° to 90°. [ABSTRACT FROM AUTHOR]

We demonstrate a discretely tunable multiwavelength visible laser through second harmonic generation (SHG) and sum frequency generation (SFG) of multiorder Stokes lasers generated from an external Raman laser oscillator. The Raman laser oscillator, driven by a 1064 nm laser with an energy of 120 mJ, is based on a cascade of Ba(NO3)2 and two axial orthogonal KGd(WO4)2 crystals. Through adjusting the angle of the SHG/SFG crystal, we obtain 16 visible wavelengths with a wide range from 579.5–658.4 nm. In addition, we investigate the output energy and conversion efficiency of the resulting laser with various phase-matching angles. We show that the maximum energy of the visible laser is 8.87 mJ with five wavelengths, and the corresponding total conversion efficiency is 7.4%. These experimental results demonstrate a practical and effective method of generating a discretely tunable multiwavelength visible laser. [ABSTRACT FROM AUTHOR]

We successfully demonstrate a blue diode-pumped green single-wavelength self-Q-switched Ho3+:ZrF4-BaF2-LaF3-AlF3-NaF (Ho:ZBLAN) all-fiber laser emitting at ∼550 nm. Such a green laser, being a very simple device, consists of a 15-cm-long Ho:ZBLAN fiber and a pair of fiber input/output mirrors. The Ho:ZBLAN fiber not only acts as a gain medium but also works as a saturable absorber (SA). The modulation mechanism is induced by the ground-state reabsorption effect in an ineffectively pumped section of the active fiber. Stable Q-switching pulses are characterized by a 889 ns of minimum pulse duration and a 264 nJ of maximum energy pulse at a repetition rate of 67.25 kHz. We believe that this work could provide an appreciable alternative for next generation of pulsed green laser source, which finds the applications in the medical diagnosis, optical imaging, and industrial manufacturing. [ABSTRACT FROM AUTHOR]

Lasing and spectroscopic properties of an LiY0.3Lu0.7F4:Pr3+ crystal grown by the Bridgman–Stockbarger method were investigated in detail. Absorption and luminescence spectra were recorded using polarized light. Lifetimes of excited states 3PJ were determined. Absorption and emission transition intensities were calculated according to f–f-transition intensity theory taking into account interconfiguration interaction. Stimulated emission transverse cross sections were determined using the Füchtbauer–Ladenburg method. Pumping by an InGaN laser diode produced continuous-wave laser generation at 522.6 nm (3P1 → 3H5) in Pr-doped mixed fluoride crystals with a maximum output power of 0.38 W and a slope efficiency of 19%. [ABSTRACT FROM AUTHOR]

• The optimization of the pump focusing system yields excellent mode matching. • The slope efficiency of the CW fundamental-frequency laser at 522 nm is 59.12%. • 261-nm CW deep ultraviolet laser is realized based on intracavity frequency doubling. • The optical–optical conversion efficiency of the deep ultraviolet laser is 33.4%. • This study provides an avenue for developing high-efficiency deep ultraviolet laser. High-power continuous-wave (CW) deep ultraviolet lasers attract growing research interest in the field of optoelectronics. Herein, we perform a CW deep ultraviolet laser at 261 nm by the intracavity frequency doubling of a single-blue-laser-diode-pumped Pr3+:LiYF 4 (Pr:YLF) laser. The excellent mode matching between the pump and fundamental-frequency laser beams is realized by optimizing the pump focusing and laser resonator systems. On that basis, the maximum CW fundamental-frequency laser obtained is 1.41 W at 522 nm, corresponding to a slope efficiency of 59.12%. Moreover, a deep ultraviolet laser is further demonstrated at 261 nm using a β -BaB 2 O 4 (BBO) frequency-doubling crystal, yielding a maximum output power of 1.17 W and an optical–optical conversion efficiency of 33.4% with respect to the pump power. Such a result is the highest optical–optical conversion efficiency of the CW DUV lasers from Pr3+-doped crystals, to the best of our knowledge. The finding in this work manifests the development potential of all-solid-state deep ultraviolet lasers and provides a feasible avenue for achieving high-efficiency deep ultraviolet laser output. [ABSTRACT FROM AUTHOR]

• Continuous-wavelength laser operation has been achieved with the maximum output power of 47 mW and the initial slope efficiency of 4.4% on 0.6Pr,1.2Gd:SrF 2 single-crystal. • The first report about the CW laser output on Pr-doped SrF 2 crystal in orange region related to 3P 0 -3H 6 transition. • The bandwidth of absorption and emission is found to be 11 nm and 8 nm, respectively, which is the highest one among as-reported crystals. The study of Pr3+ ion doped visible light laser crystals with wide spectral luminescence characteristics is of great significance for the exploration of new ultrafast laser materials in the future. Orange laser source at 605.98 nm corresponding to 3H 4 → 1D 2 optical transition of the Pr3+ ions in Pr:Y 2 SiO 5 crystal is very crucial for quantum information experiments, which was only provided by dye laser in previos experiments. Although optical parametric oscillators (OPOs) or frequency doubling may be utilized in these years, high-power laser diodes are not yet accessible at this wavelength, and neither have appropriate output powers nor frequency stability. In this work, Pr:SrF 2 and Pr,Gd:SrF 2 single crystals were grown by TGT method and the spectroscopic investigation was carried out systematically. By co-doping Gd3+ ions into Pr:SrF 2 single crystal, the intensity of orange emission at about 606 nm is strengthened while the red emission is suppressed. The first demonstration of all-solid-state continuous-wave orange laser at this specific wavelength was first reported in Pr3+ doped SrF 2 crystal, to the best of our knowledge. Moreover, by using an un-doped YAG etalon for wavelength tuning, the orange emission of Pr,Gd:SrF 2 laser showed certain wavelength tunability, which indicates Pr,Gd:SrF 2 crystal could be promising for generation of ultrashort pulse laser in visible region. [ABSTRACT FROM AUTHOR]

We demonstrate a discretely tunable multiwavelength visible laser through second harmonic generation (SHG) and sum frequency generation (SFG) of multiorder Stokes lasers generated from an external Raman laser oscillator. The Raman laser oscillator, driven by a 1064 nm laser with an energy of 120 mJ, is based on a cascade of Ba(NO3)2 and two axial orthogonal KGd(WO4)2 crystals. Through adjusting the angle of the SHG/SFG crystal, we obtain 16 visible wavelengths with a wide range from 579.5–658.4 nm. In addition, we investigate the output energy and conversion efficiency of the resulting laser with various phase-matching angles. We show that the maximum energy of the visible laser is 8.87 mJ with five wavelengths, and the corresponding total conversion efficiency is 7.4%. These experimental results demonstrate a practical and effective method of generating a discretely tunable multiwavelength visible laser.

This letter reports the fabrication of a high quality gate oxide for metal–oxide–semiconductor field-effect transistors using a continuous-wave blue laser. A thin Zr metal layer was inserted between the dielectric and substrate to increase laser absorption and reduce the interface layer. A simulation of laser irradiation showed that the metal layer insertion induces a significant increase in temperature during laser annealing compared with the dielectric without a metal layer. The laser annealed capacitor with a 1-nm-thick Zr metal layer showed superior electrical characteristics, such as high capacitance, low leakage current, low fixed charge density, and low interface state density. Based on these results and the economic advantage of blue laser diodes, this technique can be a solution for low temperature processes, such as monolithic 3-dimensional integration, where low temperature processes are required. [ABSTRACT FROM AUTHOR]

The main objectives of this work are to conduct experiments and measurements for the optical, electrical, physical and chemical properties of strawberry fruits. Strawberry was classified into three grades according to the varieties of strawberry (Festival, Fortona and Red Marline Strawberry). The strawberry fruits were exposed to visible laser to determine optical and electrical signal reflections of strawberry. The samples were classified into six kinds of defects of strawberry according to codex specification of strawberry. It was found that the high value of physical properties was Fortona variety while the low value was Festival variety, but the physical properties of Red Marlin variety intermediately between values of fortona and festival variety. It was found that mass increased also gradually with volume. The density of strawberry fruits increased by the increase of the mass of fruit. Also, the high value of chemical properties Brix value was Festival variety (7.5), while the Brix low value of Red Marlin variety (6.78), but the chemical properties Brix of Fortona variety (7.14) intermediately between values of Festival and Red Marlin variety. The electric signal high values were from control samples (standard) while the low values were from green tip defect for Festival, Fortona and Red Marlin varies of strawberry defects. It was found that, the values of electrical signals were gradually decreased for control (standard, mold, insect green tip, white shoulder and green of strawberry defects). It was noticed that the high values of reflection intensities were from control samples (standard) while the low values were from green tip defect for festival, fortona and red marlin varies of strawberry defects. Thus, the values of reflection intensities were gradually decreased for the control (standard, mold, insect, green tip, white shoulder and green of strawberry defects. [ABSTRACT FROM AUTHOR]

Abstract Pr3+-doped LaMgAl 11 O 19 (LMA) crystals have been successfully grown by the Czochralski method with different concentrations ranging from 0.5 to 10.0 mol%. Crystalline quality and the phonon energy were determined by X-ray diffraction and Raman measurements. Spectroscopic parameters based on absorption spectra were systematically calculated using the modified Judd-Ofelt theory. The fluorescence results indicate a large dependence on the factor of doping concentration. The 3P 0 →3F 2 transition red laser channel has the largest emission cross section at 10.7 × 10−20 cm2 for 5.0 mol% Pr:LMA. The fluorescence lifetime of the 3P 0 energy level is determined to be 32.6 μs at room temperature with a quantum efficiency of 82.9% for a 5.0 mol% Pr3+-doped sample. The overall spectral properties confirm that Pr:LMA is a promising candidate for visible laser operation. Graphical abstract Image 1 Highlights • LaMgAl 11 O 19 crystals doped with 0.5–10.0 mol% Pr3+ were grown by Czochralski method. • Pr:LMA has good crystalline quality and low phonon energy as visible laser medium. • Spectroscopic properties were systematically analyzed by modified Judd-Ofelt theory. • Pr:LMA exhibits comparable spectral properties with those prominent oxide crystals. [ABSTRACT FROM AUTHOR]

An all-solid-state blue laser at 430nm generated by intracavity sum-frequency mixing of a Nd: YAG laser emitting at 1319nm and a Pr:YLF laser at 639.5nm is presented. The continuous output power of 430nm is over 190mW which is the highest laser power emitting at this wavelength according to current report. The Nd: YAG and Pr:YLF crystal was pumped by a 5.9W 808nm and a 3.0W 444nm laser diode respectively. The optical-to-optical conversion efficiency is 2.1%. [ABSTRACT FROM AUTHOR]

Tb 3+ -doped YAlO 3 (YAP) single crystal was grown by Czochralski (Cz) method. Based on the polarized absorption spectra, the spectroscopic parameters were calculated to be Ω 2 = 3.49 × 10 −20 cm 2 , Ω 4 = 5.87 × 10 −20 cm 2 and Ω 6 = 2.55 × 10 −20 cm 2 , and then the spontaneous transition rate, fluorescent branching ratio and radiative lifetime of 5 D 4 multiplet were obtained. The yellow emission cross sections of 5 D 4 → 7 F 4 transition were calculated to be 1.72 × 10 −22 cm 2 , 2.73 × 10 −22 cm 2 and 2.65 × 10 −22 cm 2 for a, b and c polarization, respectively. The fluorescence lifetime of the 5 D 4 multiplet was fitted to be 1.72 ms. All the data indicate that Tb:YAP crystal is a promising candidate for yellow laser operation. [ABSTRACT FROM AUTHOR]

Optical spectroscopic properties of Dy 3+ ions in Dy:CaYAlO 4 single crystals were investigated, aiming at evaluating the potential for visible laser applications. The crystals were grown by the Czochralski technique in reducing atmosphere in order to circumvent the color-center formation in this host material. Chemical compositions of the as-grown crystals were determined by electron probe micro-analysis. Absorption and emission spectra were recorded in the visible and near infrared spectral range at room temperature. Experimental oscillator strengths derived from the ground-state absorption transitions were used to fit the electrostatic, spin-orbit coupling as well as Judd-Ofelt intensity parameters. The theoretical electric dipole as well as magnetic dipole oscillator strengths, fluorescence branching ratios, and radiative lifetime were calculated in the framework of Judd-Ofelt theory. Experimental and calculated results showed that the yellow 4 F 9/2 → 6 H 13/2 transition features the largest branching ratio and emission cross-sections under 453-nm excitation. Fluorescence decay profiles were recorded to analyze the fluorescence lifetime of the 4 F 9/2 level. Anisotropy of magnetic-dipole transitions was observed in the spectroscopic study and discussed in detail. [ABSTRACT FROM AUTHOR]

We report bidirectional red-light passively Q-switched all-fiber lasers based on a ring-cavity configuration using single-wall carbon nanotubes (SWNTs) as saturable absorber (SA). By manipulating the cavity design and intra-cavity polarization state, two sets of output pulses with different features could be achieved from the clockwise (C.W.) and counterclockwise (C.C.W.) directions, respectively. In the C.W. direction, the lasers generate the wavelength of 635.4 nm, the pulse trains with minimum pulse duration of 1.35 μs (1.51 μs) and the repetition rate ranging from 65.2 to 143 kHz (67.8 to 96.5 kHz). In the C.C.W. direction, the lasers, also emitting at 635.4 nm, deliver the pulse trains with minimum pulse duration of 0.81 μs (3.59 μs), as well as the repetition rate range of 57.5–98.2 kHz (37.2–58.9 kHz). This is, to the best of our knowledge, the first demonstration of bidirectional red-light passively Q -switched all-fiber ring lasers based on SWNT-SA. [ABSTRACT FROM AUTHOR]

Optical spectroscopic characterization of Ba 3 Tb(PO 4 ) 3 single crystals grown by the Czochralski technique was performed in order to evaluate the potential for visible laser application. Powder X-ray diffraction patterns at different temperatures were recorded to calculate the thermal expansion for temperatures between 298 and 1073 K. Refractive indices in the visible spectral region were determined and fitted into a Sellmeier equation. Absorption spectra were measured in the UV and visible range to obtain the ground-state absorption cross-sections, which were used for a Judd-Ofelt analysis. Electrostatic and spin-orbit interaction parameters were fitted, allowing for more precise Judd-Ofelt calculations. The Judd-Ofelt intensity parameters were calculated and employed to study the radiative transition probabilities, branching ratios and radiative lifetime associated to the potential upper laser level 5 D 4 . The fluorescence spectrum shows several lines in the visible range, which can be assigned to 5 D 4 → 7 F J ( J = 6,5,4,3,2,1,0 ) transitions of Tb 3+ . These data enabled the determination of the branching ratio of the transitions from the 5 D 4 excited state. The stimulated emission cross-section of the 5 D 4 → 7 F 5 transition was found to be 5.9 × 10 −22 cm 2 at a wavelength of 549.6 nm by using the Füchtbauer-Ladenburg equation. Fluorescence decay curves were recorded to obtain the fluorescence lifetime. The resulting value of 3.17 ms is in reasonable agreement with the theoretical value of 3.54 ms pointing towards a high radiative quantum efficiency of 90% despite a high doping ion density of 3.5 × 10 21 cm −3 and revealing the low effect of detrimental inter-ionic processes in Tb 3+ . [ABSTRACT FROM AUTHOR]

Pr 3+ -doped YAlO 3 (YAP) single crystal was successfully grown by the Czochralski (Cz) method. Polarized absorption and polarized fluorescence spectra were measured at the room temperature. The spectroscopic parameters based on the polarized absorption spectra were calculated by Judd-Ofelt (J-O) theory for the first time. The fluorescence lifetime of 3 P 0 energy level was fitted to be 19.16 μs with the quantum efficiency of 95.8%. Through the analyzing of the spectroscopic properties, Pr:YAP crystal was demonstrated to be a promising candidate for solid state laser operation. [ABSTRACT FROM AUTHOR]

A novel Praseodymium-doped borate (Pr:α-BBO) laser crystal was grown successfully by using the Czochralski method. The phase structure, absorption and fluorescence lifetime, as well as blue laser diode (LD) pump performances of Pr:α-BBO were totally studied. The segregation coefficient and valence state of Pr ions in the crystals were investigated using inductively coupled plasma atomic emission spectroscopy and X-ray photoelectron spectroscopy. A 450 nm blue LD was employed to carry out a pump experiment on the Pr:α-BBO slab crystal with a doping concentration of 0.22 at.%. The main emission peaks of Pr3+ ions in the orange-red light band were found to be at 611.5 nm, 634.7 nm, and 638.3 nm. The experimental results show that the Pr:α-BBO crystal exhibits higher orange light fluorescence emission performance, with an emission peak intensity at 611 nm that is 2.1 times stronger than that at 635 nm due to the splitting of the 3P 0 →3F 2 transition (635 nm). By optimizing the Pr:α-BBO laser crystal growth process and further solid-state laser experiments, it can be expected to have broad applications in laser medicine, spectral detection, and nonlinear optical frequency conversion fields. • A novel Pr:α-BBO laser crystal was successfully grown for the first time. • The spectral properties of novel Pr:α-BBO laser crystals were studied systematically. • Blue LD pumped Pr:α-BBO laser crystals exhibit good orange fluorescence characteristics. • Important guiding significance for the development of blue light pumped visible laser. [ABSTRACT FROM AUTHOR]

In this paper, we demonstrate two-dimensional nanohole array substrates prepared using the visible laser ablation technique. We fabricated Au/polymer hybrid thin films where the Au nanoparticles were fixed onto the block copolymer substrate, which was used as the microphase-separated structure. The film was coated with a thin layer of poly(methyl acrylate), and was then irradiated with a nanosecond 532 nm pulsed laser light. The light excited the resonant plasmon absorption band of the Au nanoparticles. The nanoparticles underwent explosive vaporization via a superheated state, resulting in the formation of two-dimensional nanohole arrays on the film surface. The relevant mechanism aspects of the nanohole formation process and the relationship with laser fluence are presented. [ABSTRACT FROM AUTHOR]

Optical feedback originating from the interfaces of the periodically poled domains of a nonlinear crystal is usually blocked by a bulky optical isolator to avoid an influence on the pump source. Here, a nonlinear bulk crystal with a slanted design of the periodic poling is used to suppress the optical feedback toward the laser source. This crystal is compared with a conventionally poled crystal, in which the incident radiation propagates perpendicular to the domains. Both crystals are made of magnesium oxide doped congruent lithium niobate (PPMgO:CLN). A distributed Bragg reflector tapered diode lasers with a maximum optical power of 7.0 W at a wavelength of 1122 nm and each nonlinear crystal are employed in a single-pass setup. In comparison with the conventional crystal, the optical feedback of the crystal with slanted domains is reduced by 13.4 dB enabling a stable narrow-band operation of the pump laser source without an optical isolator. The impact of the optical feedback on the diode laser with respect to the optical output power and the spectral behavior is investigated. For the crystal with slanted domains, a frequency doubled output power up to 0.39 W at 561 nm is generated without reaching the coherence collapse regime, as observed in case of the conventional crystal. These results are promising for miniaturization of the setup without a need for a bulky optical isolator. [ABSTRACT FROM PUBLISHER]

This letter reports the low-temperature solution-based fabrication of indium oxide (In2O3) thin-film transistors (TFTs) using a visible laser-assisted urea combustion process. An In2O3 precursor solution containing a small amount of urea absorbed the photon energy from a blue laser and started the combustion of urea to form a crystallized In2O3 phase. Atomic force microscopy and X-ray diffraction showed that both laser radiation and urea combustion together are necessary to convert a dried precursor solution layer to a crystallized In2O3 phase. A TFT fabricated from the 0.2-mol% urea-added solution and laser annealed with a 250-J/cm ^\textsf 2 energy fluence exhibited superior transfer characteristics compared with the TFTs fabricated either without urea addition or with small energy fluence radiation. Based on these results and considering the price of blue laser diodes, this technique can be an economical solution for the fabrication of oxide semiconductor TFTs on flexible substrates with a low melting point. [ABSTRACT FROM PUBLISHER]

We report on passive Q-switching of diode-pumped Pr:YLF visible lasers at 721 nm, 640 nm and 607 nm using CdTe/CdS quantum dot as saturable absorber. At the three wavelengths, the maximum average output powers and the shortest pulse widths are (38.7 mW, 235 ns), (48.3 mW, 226 ns), and (39.6 mW, 295 ns), respectively. The laser results represent the best laser performance of nano-material based Q-switched \rmPr^3+ visible lasers, to the best of our knowledge. CdTe/CdS quantum dot could be very promising in generating ultrashort pulse visible lasers. [ABSTRACT FROM PUBLISHER]

• The Pr:LaF 3 crystals with different doping concentrations were grown by the Bridgman method with the dimension is about Φ20 mm × 30 mm. • The effects of Pr3+ doping concentration on the LaF 3 crystal optical properties were expounded for the first time. • The continuous-wave (cw) deep red laser were obtained with different doping concentrations of Pr:LaF 3 crystals pumped by an blue laser diode for the first time. The crystal compositions, fluorescence lifetimes, polarized absorption and emission spectra, and laser performance were measured with different doping concentrations of Pr:LaF 3 crystals. Moreover, the effects of Pr3+ doping concentration on LaF 3 crystal optical properties were expounded for the first time. The study found that high doping concentration is easy to cause cross-relaxation, which in turn leads to a decrease in the lifetime of the laser upper energy level. And then affects the output efficiency of the visible laser. The laser experiment results confirm that the maximum output power of 176 mW was obtained with Pr:LaF 3 crystal of 0.5 at.% doping concentration, which is higher than output power (71.3 mW) of 1 at.% doping concentration crystal. As we all know, this is the first report about continuous-wave (cw) laser operation with Pr:LaF 3 crystal pumped by an blue laser diode. [ABSTRACT FROM AUTHOR]

The polarization absorption spectra of Pr3+-doped GdScO 3 have been measured. Polarized emission spectra and fluorescence decay from the 3P 0 upper level have been investigated. The strongest absorption peaks are located at 448 nm for a, b and c polarization, the absorption cross sections are 1.29 × 10−20 cm2, 0.98 × 10−20 cm2 and 1.57 × 10−20 cm2, respectively. The maximum emission cross section is located at 662 nm, which is 18.55 × 10−20 cm2 (a polarization), 12.74 × 10−20 cm2 (b polarization) and 22.41 × 10−20 cm2 (c polarization), and the FWHM is 10.02 nm, 9.38 nm and 10.14 nm, respectively. The fluorescence lifetime of 3P 0 level is 12.39 μs. Those results indicated that Pr3+-doped GdScO 3 crystal grown by the Czochralski method is a potential laser medium for visible laser operation. •The spectra of Pr:GdScO 3 have been measured at room temperature. •Pr3+-doped GdScO 3 crystal is a potential laser medium for 662 nm laser. [ABSTRACT FROM AUTHOR]

The power scaling of an all-solid-state visible laser is limited by the mode-to-pump ratio related to the thermal effect based on the spatial rate equation. The mode-to-pump ratio is also known as the overlap efficiency factor (OEF). We investigated the thermal effect as a function of pump power, the waist radius of pump beams, and the waist position of pump beams and have simulated the three-dimensional distribution of the OEF as a variable of the waist position and size of pump beams. Also, it is seen that the calculated optimal OEF under a plane–concave cavity is a decreasing function of input pump power, and it is less than unity in the case of high pump power. The practical example of a Pr:YLF laser pumped by 9-W fiber-coupled laser diodes confirms our theoretical analysis. The output power instability was < ± 1. 625 % (RMS) within 1 h. In addition, by changing the cavity length to 38 mm, the output power of 607 nm is up to 103 mW with an OEF of 0.741. [ABSTRACT FROM AUTHOR]

Pr3+-doped Y3Al5O12(Pr:YAG) single crystal has been grown by the Czochralski technique. The room temperature absorption spectrum, emission spectrum, and fluorescence decay curves of Pr:YAG single crystal were studied systematically. Strong absorption peaks in the blue region corresponding to3H4→3P2,1,0 + 1I6transitions and emission peaks in the visible region originating from the3P1,3P0and1D2levels of Pr3+are observed. The emission cross-sections of four main promising laser transitions at 488, 566, 611 and 638 nm were estimated separately. Results show that Pr:YAG single crystal is an excellent candidate for all-solid-state visible laser material that can be pumped by blue laser diode. [ABSTRACT FROM AUTHOR]

Sm 3+ ion doped 20 ZnO 10Li 2 O 10Na 2 O 60P 2 O 5 glasses were prepared. The density was determined by the Archimedes method and the glasses were analyzed by using, optical absorption spectroscopy, excitation and emission luminescence studies. The Sm 3+ concentration was varied between 0 and 1 mol%. The Judd-Ofelt (J-O) parameters (Ω 2 , Ω 4 , Ω 6 ) were calculated by using the absorption data and the least square fit method. The Nephelauxetic ratio ( β ), bonding parameters (δ), spectroscopic quality factors, effective line width ( Δλ eff ), radiative transition probability ( A ) and emission cross section ( σ p ) were deduced by using the J-O parameters and emission spectra. The emission spectra showed the 4 G 5/2 → 6 H 5/2 , 4 G 5/2 → 6 H 7/2 , 4 G 5/2 → 6 H 9/2 & 4 G 5/2 → 6 H 11/2 transitions of the Sm 3+ ions in the prepared glasses. Concentration quenching behavior was also observed, which was explained by the increase number of Sm 3+ ions in the glass matrix. This was confirmed by the decrease in decay times with an increase in Sm 3+ concentration. The analysis of the concentration shows 0.75 mol % Sm 2 O 3 containing glasses can possibly be used for visible laser and fiber optic amplifier applications due to the fact that it has higher emission cross section and branching ratio values. [ABSTRACT FROM AUTHOR]

In this letter, a compact $Q$ -switched red (635.7 nm) praseodymium (Pr3+)-doped fluorozirconate fiber laser using graphene-oxide (GO) as a saturable absorber (SA) is demonstrated experimentally. Furthermore, a silica fiber end coated with a dielectric film was employed to construct the compact resonator. The laser possesses a wide range of pulse repetition rate from 64.1 to 195.3 kHz and the minimum pulse duration of 554 ns. This is the first reported passively $Q$ -switched laser, to the best of our knowledge, at visible region with a GO SA. The experimental results show that the GO can be a promising SA for visible pulsed lasers. [ABSTRACT FROM PUBLISHER]