Yury M. Andreev

SHG phase matching in GaSe and mixed GaSe 1-x S x , x≤0.412, crystals at room temperature

The optical properties of p-type GaSe and mixed GaSe(1-x)S(x), x=0.04, 0.023, 0.090, 0.133, 0.175, 0.216, 0.256, 0.362, 0.369, and 0.412, crystals were studied to reveal the potentials for phase matching and frequency conversion. Comparative experiment on Er3+:YSGG and CO2 laser SHG at identical experimental conditions is carried out at room temperature. Any change in polytype structure of GaSe1(1-x)S(x) was not found.

Wide-tunable, high-energy AgGaS 2 optical parametric oscillator

Nanosecond AgGaS(2) type-I singly resonant optical parametric oscillator pumped by a Q-switched 1.064 mum Nd:YAG laser is demonstrated experimentally. Continuously tunable 2.6-5.3 mum radiation and output pulse energy up to 0.6 mJ at 4 mum are achieved in a single-stage conversion process. The analysis of pump threshold is investigated both theoretically and experimentally.

Limiting pump intensity for sulfur-doped gallium selenide crystals

High optical quality undoped and sulfur-doped gallium selenide crystals were grown from melts by the modified vertical Bridgman method. Detailed study of the damage produced under femtosecond pulse exposure has shown that evaluation of the damage threshold by visual control is unfounded. Black matter spots produced on crystal surfaces do not noticeably decrease either its transparency or its frequency conversion efficiency as opposed to real damage identified as caked well-cohesive gallium structures. For the first time it was demonstrated that optimally sulfur-doped gallium selenide crystal possesses the highest resistivity to optical emission (about four times higher in comparison with undoped gallium selenide).

Absorption anisotropy in sulfur doped gallium selenide crystals studied by THz-TDS

Abstract: Top optical quality nonlinear gallium selenide crystals doped with different sulfur concentrations (1.1, 2.5, 5, 7, 11 mass%) are grown by modified Bridgman method. Physical origins of inaccuracy in the measurement of THz o- and e-wave absorption spectra by THz-TDS are identified. Dominant absorption for o-wave is established for all crystal compositions. Frequency independent absorption within 0.3-2 THz is demonstrated. Phonon mode transformation is studied in detail. Phonon absorption peak for e-wave centered at 1.1 THz is recorded for the first time. It is shown that e-wave THz generation is preferable in GaSe:S (2.5-5 mass%) crystal.

Model and experimental investigation of frequency conversion in AgGaGexS2(1 + x) (x = 0, 1) crystals

Analysis of available and developed data on phase matching in AgGaGexS2(1 + x) (x = 0, 1) crystals is carried out. Nanosecond AgGaS2 type I optical parametric oscillator with a continuously tunable range 2.65–5.29 µm is demonstrated pumped by a Q-switched Nd : YAG laser. An output pulse energy of up to 0.56 mJ at 4 µm is recorded. Phase matching of second harmonic generation in both crystals is represented. Best sets of Sellmeier equations for two crystals are determined.

Optimal doping of GaSe with isovalent elements

The сentimeter-sized GaSe crystals doped with 0.01, 0.05, 0.1, 0.2, 0.5, 1, 2 at.% of Al and 0.025, 0.1, 0.5, 1,2 at. % of Er have been grown by the modified Bridgman method with heat field rotation. The crystals have been studied in comparison with GaSe crystals doped with 0.1, 0.5, 1, 2, 3, 5, 7, 10.2 wt.% of S, 0.01, 0.1, 0.5, 1, 2, 3, 5 wt.% of In and 0.01, 0.1, 0.5, 1, 2 wt. % of Te grown by the conventional Bridgman method. The distribution coefficient of Al in the grown GaSe:Al (≥0.1 at.%) crystals has been estimated to be ∼8⋅10-3 and it is within the range of 10-2-10-3 in Er-doped crystals. For the first time, the optimal doping levels have been estimated for Al and Er in GaSe as 0.01- 0.05 at.% for Al and ~ 0.5 wt.% for Er, respectively.

GaSe 1−x S x crystals for teraherz frequency range

GaSe1−xSx single crystals has been grown by Bridgman-Stockbarger technique. Structural quality has been evaluated with TEM observation. Terahertz time-domain spectroscopy has been applied for measurements of the frequency-dependent optical constant of doped GaSe crystals as a function of s-content.

SHG in γ-Ga2S3 powder

We report results on comparative study of SHG in powder of promising nonlinear γ-Ga2S3 crystal. Digallium trisulfide powders with particle size from 20 μm to 500 μm were tested in comparison with powders of well-known LBO, BBO, KABO, KDP, and LN crystals under the pumping by 7 ns 1064 Nd:YAG laser. Laser-induced damage threshold of different powder fractions were determined. The γ-Ga2S3 shown high damage threshold and large SHG intensity: 56 times to that in LBO powder, 15 in BBO, 50 in KABO, 67 in KDP, and 3 in LN (for particle size: 20–50 μm), that renders it amongst the most promising crystal for frequency conversion of high-intense nanosecond radiation of near-IR lasers by optical rectification technique.

Perspective Material and Applications of Uncooled Metal Bolometers

A new method is proposed to compare the sensitivity of uncooled metal bolometers. This method allows us to conduct a comparative analysis for the sensitivity of uncooled bolometers with metal and metal alloy resistive elements. The experiments showed a twofold superiority in the sensitivity of the TiNi alloy-based bolometer with a resistive element less than 10 Ω in resistance over the identical bolometers based on technologically applicable metals due to improved electrophysical properties. The Ti50.5Ni49.5 bolometer developed to measure the total solar radiation has a higher sensitivity, a higher measuring efficiency, a smaller weight, and size compared with a serial CMP-11 pyranometer, as well as the best environmental protection. The highly sensitive uncooled metal bolometers are shown to be used as an integral part of the optical absorption gas analyzer to provide the control of background mercury vapors in the atmosphere.

Physical origins of double peak phase matching in GaSe

Double peak phase matching was recorded during experimental study of parametric frequency converters based on GaSe, its solid solutions crystals like GaSe1-xSx and ZnGeP2. Its physical origins are identified as presence of twin, large difference between cut and PM angles, self-heating effect at appropriate conditions, mismatched second (Φ) phase matching angle and microdefects.