Continuous-wave laser performance of Nd:LuVO4 crystal operating at 1.34 microm

The Use of Diatoms in the Synthesis of New 3D Micro-Nanostructured Composites (SiO2/CaCO3/Corg/NdVO4NPs and SiO2/CaO/Corg/NdVO4NPs) Exhibiting an Intense Anti-Stokes Photoluminescence

New 3D micro-nanostructured composite materials have been synthesised. These materials comprise SiO2/CaCO3/Corg/NdVO4NPs and SiO2/CaO/Corg/NdVO4NPs, exhibiting strong upconversion luminescence. The synthesis was accomplished by metabolically doping diatom cells with neodymium and vanadium. Subsequently, the biomass of these doped diatoms was subjected to pyrolysis at 800 °C. The morphology, structure, and physicochemical properties of the doped diatom biomass as well as dried (SiO2/CaCO3/Corg/NdVO4NPs) and pyrolysed (SiO2/CaO/Corg/NdVO4NPs) samples were characterised using scanning electron microscopy (SEM), scanning transmission electron microscopy (STEM), energy dispersive X-ray spectroscopy (EDX), X-ray powder diffraction (XRD), thermal analysis (TG), and fluorescence spectroscopy (FS). Studies have shown that the surface of diatom shells is covered with trigonal prismatic nanocrystallites (nanoparticles) of NdVO4 with dimensions of 30-40 nm, forming the crystallite clusters in the form of single-layer irregular flakes. The synthesised composites produced intense anti-Stokes fluorescent emission in the visible region under xenon lamp excitation in the near-infrared (λex = 800 nm) at room temperature in an ambient atmosphere. Such materials could be attractive for applications in solar spectrum conversion, optical sensing, biosensors, or photocatalysts.

Optical Crystals for 1.3 μm All-Solid-State Passively Q-Switched Laser

In recent years, optical crystals for 1.3 μm all-solid-state passively Q-switched lasers have been widely studied due to their eye-safe band, atmospheric transmission characteristics, compactness, and low cost. They are widely used in the fields of high-precision laser radar, biomedical applications, and fine processing. In this review, we focus on three types of optical crystals used as the 1.3 μm laser gain media: neodymium-doped vanadate (Nd:YVO4, Nd:GdVO4, Nd:LuVO4, neodymium-doped aluminum-containing garnet (Nd:YAG, Nd:LuAG), and neodymium-doped gallium-containing garnet (Nd:GGG, Nd:GAGG, Nd:LGGG). In addition, other crystals such as Nd:KGW, Nd:YAP, Nd:YLF, and Nd:LLF are also discussed. First, we introduce the properties of the abovementioned 1.3 μm laser crystals. Then, the recent advances in domestic and foreign research on these optical crystals are summarized. Finally, the future challenges and development trend of 1.3 μm laser crystals are proposed. We believe this review will provide a comprehensive understanding of the optical crystals for 1.3 μm all-solid-state passively Q-switched lasers.

Symmetry of the Optical Phonons in LuVO4: A Raman Study

A thorough analysis of the first-order vibrational spectrum of LuVO4 is presented by using polarized micro-Raman spectroscopy with special focus on the phonon modes with the weakest intensity and occasional controversial assignment. Group-theory analysis is carried out to demonstrate the determination of numbers and symmetries of the Raman active modes. Crystal- and correlation-field splitting effects in the vibrational spectrum of LuVO4 are discussed. Under conditions adjusted to minimize the birefringence effects we recorded, in each main scattering configuration, a series of Raman spectra in different sample orientations achieved by rotating the sample around the incident laser beam. The dependence of the Raman intensity on the rotational angle allowed us to identify the correct symmetry of the phonons with exceptionally weak scattering cross-section. A complete assignment of all twelve first-order Raman active phonons of LuVO4 is thus obtained.

7.6 W 1342 nm passively mode-locked picosecond composite Nd:YVO4/YVO4 laser with a semiconductor saturable absorber mirror

A high average power 1342 nm passively CW mode-locked picoseconds (ps) composite Nd:YVO4 laser was demonstrated with a semiconductor saturable absorber mirror (SESAM). The oscillator cavity was carefully designed to optimize the laser beam radii in the crystal and on the SESAM. The combination of composite bonded laser crystal, direct pumping, and dual end-pumped configuration was adopted to reduce the thermal effect and produce high output power with high beam quality. A maximum average output power of 7.63 W was obtained with a repetition rate of 77 MHz and a pulse duration of 24.2 ps under an absorbed pump power of 38.6 W, corresponding to an optical-optical efficiency of 19.7% and a slope efficiency of 25.9%, respectively. The beam quality factor M(2) was measured to be 1.49.

Controllable synthesis and size-dependent upconversion luminescence properties of Lu2O3:Yb3+/Er3+ nanospheres

Lu₂O₃:Yb³⁺/Er³⁺ nanospheres with various sizes have been synthesized by the soft chemistry coprecipitation route and these samples have shown size-dependent UCL property under 980 nm excitation.

Precise measurement of group refractive indices and temperature dependence of refractive index for Nd-doped yttrium orthovanadate by intracavity spontaneous mode locking

We report on a novel method based on intracavity spontaneous mode locking to precisely measure the group refractive indices and temperature dependence of refractive index of Nd:YVO(4) crystal at the wavelength of 1064 nm. All the experimental results are found to agree very well with the most recent measured values. We also confirm that the developed method is applicable to measuring the group refractive indices and the temperature dependence of the refractive indices of other vanadate crystals, as well as nonlinear crystals.

Optical properties of Nd-doped rare-earth vanadates

Rare-earth orthovanadates are being used as substitutes for traditional solid-state laser hosts, such as YAG. While the most common of these is yttrium orthovanadate, other rare-earth vanadates, such as lutetium vanadate and gadolinium vanadate, are being used for their special properties in certain applications. We report new measurements of the refractive indices and thermo-optic coefficients of these materials, which will aid in the design of laser cavities and other nonlinear optical elements.

Diode-pumped continuous-wave Nd:LuVO4 laser emitting at 1089 nm based on the 4F(3/2)-4I(11/2) transition

We present what is, to the best of our knowledge, the first diode-pumped Nd:LuVO(4) laser emitting at 1089 nm, based on the (4)F(3/2)-(4)I(11/2) transition, generally used for a 1066 nm emission. A power of 8.7 W at 1089 nm has been achieved in continuous-wave (cw) operation with a fiber-coupled laser diode emitting 18.7 W at 809 nm. Intracavity second-harmonic generation in cw mode has also been demonstrated with a power of 3.6 W at 544.5 nm by using a LiB(3)O(5) nonlinear crystal.

High-power, diode-end-pumped, multigigahertz self-mode-locked Nd:YVO4 laser at 1342 nm

We report on a high-power, diode-pumped, self-mode-locked laser at 1342 nm with the Kerr effect arising from large third-order nonlinearity of Nd:YVO(4) crystal. At the pump power of 10.2 W, the average output power of 1.2 W was generated with a repetition rate in the range of 2-6 GHz. The mode-locked pulse width can be smoothly varied from 11.5 to 37 ps by controlling the amount of spatial hole burning.

Diode-pumped passively mode-locked 1,342 nm Nd:YVO4 laser with an AlGaInAs quantum-well saturable absorber

We demonstrate what we believe to be the first use of AlGaInAs quantum wells (QWs) as a saturable absorber for a diode-pumped passively mode locked Nd:YVO(4) laser at 1342 nm. The QWs are grown on a Fe-doped InP substrate that is transparent at lasing wavelength. At an incident pump power of 13.5 W an average output power of 1.05 W with a continuous mode-locked pulse duration of 26.4 ps at a repetition rate of 152 MHz was generated.

Diode-pumped passively Q-switched and mode-locked Nd:GdVO4 laser at 1.34 microm with V:YAG saturable absorber

Using V:YAG as the saturable absorber, a diode-pumped passively Q-switched and mode-locked Nd:GdVO(4) laser at 1.34 microm is realized. Nearly 100% modulation depth of mode-locking has been achieved. The width of the mode-locked pulse is estimated to be less than 460 ps with 125 MHz repetition rate within an about 1 micros-long Q-switched pulse envelope. A maximum output power of 220 mW and Q-switched pulse energy of 10.5 microJ is obtained. Using the hyperbolic secant function methods, a fluctuation rate equation model considering the Gaussian distribution of the intracavity photon density and the population inversion in the gain medium as well as the ground-state population intensity of the saturable absorber has been proposed to describe the mode-locking process of diode-pumped Nd:GdVO(4)/V(3+):YAG laser. With the space-dependent rate equations solved numerically, the theoretical calculations reproduce the laser characteristics well.

Diode-pumped passively Q-switched Nd:LuVO4 laser at 1.34 microm with a V3+:YAG saturable absorber

We report a diode-pumped passively Q-switched Nd:LuVO4 laserat 1.34 microm using V3+:YAG as saturable absorber. The characteristics of a-cut and c-cut Nd:LuVO4 passive Q-switching operation were studied. The average output power of 1.02 W was obtained under the pump power of 12.88 W, corresponding to the optical conversion efficiency of 8% and slope efficiency of 10% in c-cut Nd:LuVO4 laser. The maximum pulse energy of 17.6 microJ and the highest peak power of 820 W were obtained at pulse width of 21 ns and pulse repetition rate of 22.4 kHz in a-cut Nd:LuVO4 laser.

Diode-pumped continuous-wave Nd:LuVO4 laser operating at 916 nm

We realized an efficient diode-pumped Nd:LuVO4 continuous-wave (CW) laser operating at 916 nm. Laser experiments with 0.5 at. % Nd-doped Nd:LuVO4 crystals of various lengths and cutting directions were also investigated. The maximum output power of 930 mW was obtained with a slope efficiency of 27.2% and an optical conversion efficiency of 20.8% at the absorbed pump power of 4.5 W. The laser experiment shows that Nd:LuVO4 crystal can be used for an efficient diode-pumped laser system.