Ya. K. Skasyrsky

Study of a 2-J pulsed Fe:ZnSe 4-μm laser

We report the results of a study of a pulsed Fe:ZnSe laser for temperatures ranging from 85 to 295 K. With a free-running Er:YAG laser, operating at 2.94 μm, as a pump source, a maximum output energy of 2.1 J at 85 K was produced at a wavelength of 4.1 μm. The optical-to-optical efficiency of the laser was 35% at maximum energy while the maximum absorbed energy slope efficiency was as high as 51%. By operating at 245 K (a temperature which can be easily reached using thermoelectric coolers) we achieved 1.3 J of output energy from an Fe:ZnSe laser, with a slope efficiency of 29% (23% optical-to-optical efficiency). The maximum output energy reached 42 mJ at room temperature (295 K). The temperature dependence of the lifetime of the 5T2 energy level of Fe2+ in ZnSe was studied in the 275–365 K temperature range. The activation energy for nonradiative relaxation was found to be 2235 cm−1.

3 J pulsed Fe:ZnS laser tunable from 3.44 to 4.19 μm

We report the laser properties of Fe:ZnS in the temperature range from 85 to 186 K. Under pumping by a pulsed free-running 2.94 μm Er:YAG laser, a maximum output energy of 3.25 J at 85 K was produced with 27% optical-to-optical efficiency. The output wavelength was observed to tune with temperatures from 3.60 μm at 85 K to 3.78 μm at 186 K. As the temperature was increased, the absorbed energy slope efficiency decreased from 42.4% at 85 K down to 2.5% at 183 K. With a CaF2 prism, the Fe:ZnS laser could be tuned from 3.44 to 4.19 μm at 85 K.

E-Beam Longitudinally Pumped Laser Based on ZnCdSe/ZnSe MQW Structure Grown by MBE on ZnSe(001) Substrate

Electron beam longitudinally pumped laser based on 15 ZnCdSe/ZnSe QW periodic-gain structure grown by molecular beam epitaxy on ZnSe(001) substrate was studied. An output power of 0.3 W was achieved. The laser wavelength was in 518-536 nm range, being at the short wavelength side of the QW emission line at low excitation level. Such unusual feature was explained by the participation of excited QW levels in the creation of the optical gain.

2.92 µm Cr2+:CdSe single crystal laser pumped by a repetitively pulsed Tm3+:Lu2O3 ceramics laser at 2.066 µm

A laser oscillator based on Cr2+:CdSe single crystal pumped by 2.066 µm radiation of a Tm3+:Lu2O3 ceramic laser was created and investigated. Repetitively pulsed oscillations at a wavelength of 2.92 µm with a bandwidth of 80 nm were demonstrated. The output power was up to 350 mW at 10 kHz repetition rate with a pulse duration of ~200 ns in the good-quality beam.

Layer structure of Zn1−xCdxSe films grown by vapor-phase epitaxy from metal-organic compounds on Cd0.92Zn0.08S(0001) substrates

The structure of Zn1−xCdxSe films, which were grown by vapor-phase epitaxy from metal-organic compounds on a Cd0.92Zn0.08S(0001) substrate, was investigated by X-ray diffractometry. For both cubic and hexagonal phases, asymmetric reflections were selected. These reflections make it possible not only to reliably determine the presence of these phases in the film, but also to estimate the dimensions of coherent X-ray scattering regions and (or) variation in the lattice parameters in the intergrowth plane. The ZnSe films preferentially consist of twinned interlayers of the cubic phase, 200–250 Å thick, and with a low content of the hexagonal phase. In contrast, the hexagonal phase with a small number of cubic interlayers predominates in CdSe films. The thickness of the interlayers of the cubic phase in Zn1−xCdxSe decreases, whereas the concentration of the hexagonal phase increases for low x values with an approximately identical development of both phases for x=0.15–0.20.

MBE Growth of II–VI Epilayers and QW Structures on Hexagonal ZnCdS and CdSSe Substrates

ZnTe, ZnSe layers and ZnCdTe/ZnTe, ZnCdSe/ZnSe quantum well structures were grown on hexagonal Zn 0.05 Cd 0.95 S(0001) and CdS 0.85 Se 0.15 (1120) by molecular beam epitaxy and studied by cathodoluminescence (CL), photoreflection, and X-ray diffraction. The structures grown on the (1120) substrates had rough surface while the structures grown on the (0001) substrate were mirror-like. All structures were cubic. In the ZnSe based structures, the (111) and (110) lattice directions of epilayers coincided with the (0001) and (1120) directions of CdZnS(0001) substrate, respectively. High mismatching leaded to a lattice relaxation of these epilayers by introduction of misfit dislocations. This was the reason of low CL intensity. In spite of higher mismatching, the ZnTe based epilayers grown on (0001) substrates had more perfect lattice structure and more intense CL than ZnSe based epilayers. Cubic lattice of ZnTe was found to be rotated approximately by 15° around the (111) direction coincided with the (0001) direction of the (0001) substrate. It was proposed that a geometrical lattice matching took place at epitaxy of ZnTe on the CdZnS(0001).

2.92 μm Cr 2+ :CdSe single crystal laser pumped by repetitively-pulsed Tm 3+ :Lu 2 O 3 ceramics lasers

Laser oscillator based on Cr²⁺:CdSe single crystal pumped by radiation of Tm³⁺:Lu₂O₃-ceramic laser was created and investigated. Repetitively-pulsed oscillations at the wavelength of 2.92 μm with bandwidth of 80 nm were demonstrated. The output power was up to 3W at 15-30 kHz repetition rate with the pulse duration of ~40-300 ns in the good-quality beam.

Efficient 10-J pulsed Fe:ZnSe laser at 4100 nm

Energies of over 10 J and efficiencies of over 44% have been demonstrated in single-shot operation of liquid nitrogen cooled single-crystalline Fe:ZnSe laser at 4100-nm wavelength.

Study of the formation of a microrelief on ZnSe- and CdSe-crystal surfaces ablated by excimer KrF-laser radiaton

One-dimensional gratings with a period of are formed on the surfaces of CdSe and ZnSe crystals ablated by two interfering radiation beams of a nanosecond excimer KrF laser. Investigated are the dependences of the shape and depth of gratings on the energy density under irradiation by a single pulse, and on the number of pulses at a given energy density. The maximum grating depth is estimated as of the period. By forming a one-dimensional grating with a period of and a depth of on the CdSe-crystal surface, this surface becomes antireflective at a wavelength of . The surface reflectivity is reduced by 88 %. A possibility of forming two-dimensional gratings having periods of 1 and is demonstrated.