The effect of copper doping of ZnSe:Fe crystals on the kinetics of luminescence of iron ions is investigated in this work. It has been discovered that doping with copper leads to a sharp decrease in the radiative recombination of iron ions at a temperature of 77 K. The obtained results are explained based on the model of nonradiative relaxation of iron ions due to Auger recombination with the participation of electrons in the conduction band.

The generation characteristics of a laser with a Fe:CdTe single crystal grown by a modified vertical gradient freeze method and subjected to high-temperature treatment as an active element have been studied. The possibility of efficient pumping using Fe:ZnSe or deuterium fluoride laser has been demonstrated. The broadband generation in the range of 5.3-6.0 $\mu \mathrm{m}$ with a maximum energy of up to 0.35 J per pulse has been obtained.

The work is devoted to the study of the second-harmonic generation (SHG) process as a result of random quasi-phase-matching of thulium laser radiation in ZnSe polycrystals. A linear dependence of the SHG efficiency on the nonlinear medium length has been observed in the experiment. The efficiencies of SHG in ZnSe polycrystals with average grain sizes from 35[Formula: see text][Formula: see text]m to 380[Formula: see text][Formula: see text]m were compared. The obtained results are in good agreement with the theory in the case of a Gaussian grain size distribution.

The diffusion of iron impurities in zinc selenide (ZnSe) during hot isostatic pressing (HIP) in the temperature range T = 1000-1300 degrees C and pressures P = 100-190 MPa has been investigated. The iron concentration and its distribution over the sample volume with a step from 20 to 50 mu m was determined by IR spectroscopy in combination with an IR microscope. The diffusion coefficients of Fe in ZnSe at various temperatures and pressures were determined. The diffusion coefficients of Fe in ZnSe at P = 100 MPa and T = 1000 degrees C were (5.3 +/- 0.6) x10-(10) cm(2)/s, T = 1300 degrees C were (9.4 +/- 0.9)x10(-9) cm(2)/s. It is shown that the temperature dependences are described by the Arrhenius equation, and the isostatic pressure does not affect the value of the diffusion coefficients.

Iron-doped cadmium sulfide films (Fe-CdS) were produced by spray pyrolysis using iron nitrate, chloride and sulfate as iron precursors. Based on experimental analysis data and thermodynamic calculations, it was found that the composition, uniformity and surface morphology of the films significantly depend on the nature of the iron precursor. It has been found that all synthesized Fe-CdS films can be used as master alloys for the manufacture of Fe:ZnSe laser elements.

The record value of the output energy of Fe:CdTe laser, as well as the slope and total efficiency in terms of absorbed energy of 350 mJ, 57% and 42%, respectively, were obtained at the room temperature of the active element. An Fe:CdTe single crystal was pumped by a nonchain electric discharge deuterium fluoride laser operated in the spectral range of 3.6–4.06 μ m. The pump pulse full duration at half maximum was 220 ns. The output energy of the Fe:CdTe laser was limited by the development of transverse parasitic oscillations for pump spot diameters on the crystal surface of more than 11 mm. A laser with a non-selective cavity generated in the ranges of 5.5–6.0 μ m and 5.3–5.5 μ m at the output mirror reflectances of 53% and 21%, respectively.

The operation at room temperature of a single-crystal Fe:CdTe laser excited by a nonchain electric-discharge DF laser was studied. The output energy of 29 mJ was obtained with a slope efficiency in terms of absorbed energy of 30%. The development of transverse parasitic oscillation at large pump spot sizes on the crystal surface limited the laser output energy. The laser with a nonselective cavity operated in the range of 5.3–5.9 μ m; the total width of the generation spectrum was about 600 nm. Comparison of the Fe:CdTe generation spectra, obtained by pumping the crystal with DF and Fe:ZnSe lasers, confirmed the shift of the generation spectrum to the long wavelength region with increasing pump wavelengths. The maximum generation wavelength of the Fe:CdTe laser with a nonselective resonator excited by the Fe:ZnSe laser was 6.02 μ m with a total width of the generation spectrum of about 370 nm. Ways are discussed for further increasing the room-temperature output energy of a Fe:CdTe laser.

A technology for obtaining high-quality single-crystal active elements for a Fe:CdTe laser was described, which includes growing a single crystal from a melt using a modified vertical gradient freeze method followed by high -temperature treatment to remove free charge carriers. The room-temperature lasing and luminescence charac-teristics of a Fe:CdTe single crystal with a Fe2+ ions concentration of 6.1 x 1018 cm-3 were studied. The upper laser level lifetime, the output energy and a slope efficiency with respect to absorbed energy of the Fe:CdTe laser excited by the Fe:ZnSe laser were 340 ns, 13.5 mJ and 32%, respectively. The lasing spectrum of the Fe:CdTe laser with a nonselective cavity was located within the range 5.63-6.02 mu m. It was noted the possibility to control the lasing spectrum by changing the pump laser spectrum (shifting the Fe:ZnSe laser spectrum to the short-or long-wavelength region by changing the quality factor of the cavity). Ways are discussed for further increasing the output energy of a Fe:CdTe laser at room temperature of the active element, in particular, by using a non -chain electric-discharge DF laser for pumping.

The current study is dedicated to measuring the laser-induced damage threshold of chemical vapor-deposited ZnSe and ZnSe:Cr flat optical elements, which were subjected to chemical–mechanical polishing and polishing using magnetorheological fluids. Research was carried out using a Q-switched 1064 nm Nd:YAG laser with 12-ns pulse duration at a repetition rate of 5 Hz. It was shown that as a result of the magnetorheological finishing, the surface roughness is significantly reduced and the damage threshold for the surfaces of chalcogenide optical elements is significantly increased.

A technique was presented for obtaining laser media based on polycrystalline zinc selenide doped with iron from spray pyrolysis deposited films in the solid-phase diffusion process. The effect of the ligature film composition and the high-temperature treatment conditions on the lasing characteristics of Fe:(In):ZnSe active elements was investigated. Lasing with an energy of 100 mJ at a differential absorbed energy efficiency of 42% was obtained on 20 mm disk Fe:ZnSe element pumped by a pulsed electric-discharge HF laser.

In this Letter, a multi-pass amplifier based on polycrystalline Fe:ZnSe element grown by the chemical vapor deposition (CVD) method and doped through diffusion technique is realized with output energy of more than 3 mJ at 4.5 mu m. The crystal used in the experiment has external doping layers with peak Fe ions concentration of (1-2).1019 m(-3) located on the surface and Fe ions diffusion depth of hundreds of microns. The crystal demonstrates small-signal gain per pass of 5.7 (corresponding to effective gain of 7.1 cm(-1) taking into account 8 mm total length of the crystal) for short pump pulse (40-ns) under the optimal pump fluence of around 0.8 J/cm(2) and upper-level lifetime of 670 +/- 10 ns under moderate cooling to 7-8 degrees C, which makes such a crystal very attractive for mid-IR femtosecond multi-pass amplifiers and generators. Moreover, properties of the polycrystalline Fe:ZnSe elements grown by CVD and doped through diffusion and CVD methods with higher Fe ions concentration are also studied at different temperatures and compared with a single crystal element.

The paper discusses the results of experimental studies of the Fe 2+ :ZnSe and Fe 2+ :ZnS lasers based on polycrystalline bulk active elements created using solid-state diffusion bonding of pre-alloyed CVD-ZnSe(S) plates and hot isostatic pressing method.

The diffusion of chromium impurities in zinc chalcogenides (ZnS, ZnSe) during hot isostatic pressing (HIP) in the temperature range T = 1000-1330 degrees C and pressures P = 100-190 MPa has been investigated. The chromium concentration and its distribution over the sample volume with a step from 5 to 50 mu m was determined by FTIR spectroscopy in combination with an IR microscope. The diffusion coefficients of Cr in ZnS and ZnSe at various temperatures and pressures were determined. The diffusion coefficients of Cr at 1300 degrees C were (7.0 +/- 0.3) x 10(-8) cm2/s in ZnSe and (3.4 +/- 0.4) x 10(-8) cm(2)/s in ZnS. It is shown that the temperature dependences are described by the Arrhenius equation, and the isostatic pressure does not affect the value of the diffusion coefficients.

A laser-quality anisotropic ZnS:Cr2+ element was obtained using prolonged hot isostatic pressing at high temperature. Lasing centered at a wavelength of 2.45 µm was obtained with longitudinal pumping at a wavelength of 1.94 µm. The short-cavity laser slope efficiency with respect to the absorbed power was about 78%. The lasing wavelength was continuously tuned in the range of 2.35-2.52 µm by rotating the Brewster active element around the normal to its surface.

The methods for suppressing transverse parasitic oscillation (TPO) at room temperature in Fe:ZnSe and Fe:ZnS lasers based on polycrystals doped using high-temperature diffusion have been considered. When active elements of this type are used, the development of TPO at large pump spots is due to the high dopant concentration on the surface of element end face and small length of the active medium as a whole (i.e., typical disk laser geometry). The TPO suppression methods under consideration are based on the fact that undoped Fe:ZnSe and Fe:ZnS exhibit significant absorption at the corresponding lasing wavelengths. Thus, the TPO development can be excluded by simple increase in the transverse size of active element and growth of active elements with several inner doped layers or an inner doped layer (layers) in the form of a meniscus. The problems of damage of active elements at large pump spots are discussed, and the potential of further increase in the radiation energy of Fe:ZnSe and Fe:ZnS lasers with room-temperature active elements is predicted.

It is measured the kinetics of the luminescence of Fe 2+ in ZnSe at liquid nitrogen temperature at excitation by short pulse of accelerated electrons. An explanation of the observed dependence is presented, which is based on Auger effect of quenching the excited state of the Fe 2+ ion by free electrons of the electric current in the volume of the sample.

We present a compact diode-pumped Tm:KYW laser passively Q-switched with polycrystalline Cr:ZnSe saturable absorber. The laser operates at around 1910 nm and 1940 nm and produces pulses with duration as short as 10 ns and energy up to 40 μJ.

The prospects for using multicomponent films produced by aerosol spray pyrolysis for doping bulk ZnSe crystals with optically and electrically active impurities are shown for the first time. Lasing was obtained on ZnSe:Cr active elements doped during hot isostatic pressing treatment from CrS and CdS:Cr films. The lasing efficiency with respect to the absorbed radiation energy at a wavelength of 1.94 μ m was about 54% for ZnSe:Cr doped from CrS film and 50% for ZnSe:Cr doped from CdS:Cr film, respectively. The luminescence and lasing characteristics of ZnSe:Cr active elements co-doped with Al and Na impurities were investigated. A high diffusion rate of Cr 2+ ions into polycrystalline ZnSe doping process from sulfide films was observed.

Cr2+:ZnSe polycrystalline active elements in the form of disks with one and two inner doped layers were fabricated by using solid-state diffusion bonding (SSDB) with subsequent hot isostatic pressing. A comparison of the generation properties of active elements with the same absorption and various profiles of internal doping was made using a scheme with a semi-confocal cavity and CW thulium fiber laser pumping. All test samples showed high thermal and optical resistance at a pump power density of up to 50 kW cm(-2) in room-temperature experiments that indicates the promise of using SSDB technology in high-power mid-IR lasers. The samples with two layers of internal doping demonstrated 30% higher lasing slope efficiency, than samples with one doped layer. This difference is explained by more uniform heating of the active element which was caused by increasing the volume of the sample involved in the absorption of pumping radiation.