V. V. Badikov

Broadly tunable compact continuous-wave Cr 2+ :ZnS laser

We report the development of a continuous-wave, room-temperature Cr(2+) ZnS laser that is compact and tunable over 700 nm. The laser is pumped by a diode-pumped Er-fiber laser and generates 0.7 W of linearly polarized radiation at 2.35microm , at up to 40% slope efficiency. Cr(2+) ZnS directly diode-pumped at 1.6microm yields polarized radiation that is tunable over 400 nm at up to 25 mW of output power. A comparison of Cr(2+) ZnS with Cr ZnSe (70 mW, 350 nm) in a similar setup is given. As opposed to Cr ZnSe, the Cr ZnS laser is intrinsically polarized. Finally, we observe sensitization of the output radiation by a few milliwatts of the visible (470-500-nm) and near-infrared (740-770-nm) radiation.

Erbium fiber laser–pumped continuous-wave microchip Cr 2+ :ZnS and Cr 2+ :ZnSe lasers

Efficient continuous-wave (cw) lasing of Cr(2+):ZnS and Cr(2+):ZnSe crystals in external hemispherical cavities and in a microchip configuration under Er-fiber-laser pumping at room temperature are reported. The key result is what is believed to be the first successful demonstration of cw Cr(2+):ZnS and Cr(2+):ZnSe microchip lasers with maximum output powers of 63 and 100 mW at 2320 and 2520 nm, with slope efficiencies of 53% and 20%, respectively.

3.9–4.8 μm gain-switched lasing of Fe:ZnSe at room temperature

We report a room temperature Fe:ZnSe laser in gain-switched operation and tuning over the 3.9 - 4.8microm spectral range. Mid-IR emission of Fe2+:ZnSe was studied under three regimes of excitation: ordinary optical (2.92mum) excitation of 5T2 excited state of Fe2+; excitation via 5E level of Cr co-dopant (1.56mum); and excitation via photo-ionization transition of Fe2+ (0.532mum). The energy transfer from Cr2+ (5E level) to Fe2+ (5T2 level) under 1.56microm wavelength excitation was observed and resulted in simultaneous RT emission of Fe:Cr:ZnSe crystal over ultra-broadband spectral range of 2- 3 and 3.5-5mum. We also report the observation of mid-IR emission at 3.5- 5mum induced by 2+->3+->2+ ionization transitions of the iron ions in Fe:ZnSe.

Optical properties of lithium indium selenide

Conditions of growth of LiInS2 and LiInSe2 crystals with high optical quality are studied. Data on the dispersion of refractive indices in red-phase LiInSe2 crystals are presented. Possible nonlinear three-frequency processes in LiInS2 and LiInSe2 crystals used for SHG and OPO are analyzed. Potentials of these crystals for application in OPO devices are shown.

Optical properties of thallium mercury iodide

We investigated the growth conditions and obtained Tl4HgI6 nonlinear crystals of red and black phases. We also measured the dispersion of the black-phase crystal refractive indices and analyzed possible nonlinear three-frequency processes.

Phase-matching and femtosecond difference-frequency generation in the quaternary semiconductor AgGaGe5Se12.

We present data on the linear (transmission, index of refraction) and nonlinear (second-order susceptibility) optical properties of the quaternary semiconductor AgGaGe5Se12 with orthorhombic symmetry--a solid solution in the AgxGaxGe1-xSe2 system with x = 0.17. The nonlinear coefficients are estimated from phase-matched second-harmonic generation near 3 microm. After numerical analysis of the phase-matching configurations for three-wave nonlinear interactions, the first experimental results on difference-frequency mixing, producing tunable (4-7.5-microm) femtosecond pulses at a 1-kHz repetition rate, are described. The pulses of only five optical cycles (FWHM = 84 fs) are generated near 5 microm with energy of 0.5 microJ. Because of its higher damage threshold, larger birefringence and bandgap, and greater variety of phase-matching schemes, AgGaGe5Se12 could become an alternative to AgGaS2 and AgGaSe2, more widely used in high-power and specific applications.

Laser performance of Cr2+-doped ZnS

Laser properties and spectroscopic characterization of diffusion doped Cr2+: ZnS crystals synthesized by chemical transport reaction from gas phase are reported. Lasing was realized with a threshold of 170 uJ and slope efficiency of 9.5 % with respect to the 1.5607 um pump energy, in a hemispherical cavity. Low doped samples (3-4 cm-1 at 1.7 um) of 1.7 mm thickness were utilized. The 1.5607 um excitation was realized with a D2 Raman cell pumped in a backscattering geometry by the 1.064 um radiation of the single frequency Nd:YAG laser. Maximum output energy reached 100 uJ. Lasing in the hemispherical cavity was achieved with output couplers R=80 % and 90 % at 2.36 um and radius of curvature 20 cm. Absorption cross section was estimated from spectroscopic measurements and was in a good agreement with saturation data (0.80x10-18 cm2) calculated with the modified Frantz-Nodvik equation for a four level slow absorber. Findlay Clay losses were found to be about 14%. Selective cavity experiments were performed in a hemispherical cavity with a CaF2 prism as the dispersive element. A tuning range of 2.05-2.40 um was realized, limited by the spectral range of the output coupler of the selective laser cavity.

Spectroscopic characterization and laser performance of diffusion doped Cr2+:ZnS

Spectroscopic, saturation, and laser properties of diffusion doped Cr2+:ZnS crystals synthesized by chemical reaction from gas phase are reported. Lasing was realized with a threshold of 170 µJ and slope efficiency of 9.5% with respect to the 1.5607 µm pump energy, in a hemispherical cavity. Maximum output energy reached 100 µJ. A tuning range of 2.05-2.40 µm was realized, limited by the spectral range of the output coupler of the selective hemispherical laser cavity. Selective cavity experiments used a CaF2 prism as the dispersive element. Findlay Clay losses were found to be about 14%. Absorption cross section (0.80×l0−18 cm2) was estimated from spectroscopic measurements and was in good agreement with saturation data, calculated with the modified Frantz-Nodvik equation for a four level slow absorber.

Preparation and Structure of AgGa1 – xInxSe2 Single Crystals

AgGa1 – xInxSe2 single crystals grown by the Bridgman–Stockbarger method, using presynthesized charges with x = 0.27, 0.335, and 0.375 are studied by x-ray diffraction (phase analysis, determination of lattice parameters, structure refinement of powdered crystals by the Rietveld profile analysis method, and single-crystal structural analysis). The results suggest that the crystals may contain Se and Ag vacancies. The polarity of the crystals is found to depend on their composition.

Nonlinear Optical Properties of Defect Tetrahedral Crystals HgGa 2 S 4 and AgGaGeS 4 and Mixed Chalcopyrite Crystal Cd (0.4) Hg (0.6) Ga 2 S 4

Growth and nonlinear optical properties of defect tetrahedral crystals HgGa 2 S 4 and AgGaGeS 4 and mixed chalcopyrite crystal Cd (0.4) Hg (0.6) Ga 2 S 4 have been reported. Sellmeier coefficients have also been developed from the measured refractive indices of these crystals. Nonlinear optical laser device application has also been explored.