Vladimir E. Rogalin

Mechanisms of surface relief formation on bulk polycrystalline oxygen-free copper samples under single and multiple UV nanosecond laser pulses (355 nm, 10 ns) in air are investigated. The laser spot size ∼100 μm is several times larger than the average size ∼40 μm of crystal grains. Incident fluences are limited by ∼1 J/cm2 to avoid melting of copper. Confocal laser microscopy, scanning electron microscopy, and transmission electron microscopy are utilized to reveal the deformation processes leading to surface relief development. It is found that irradiation uncovers the grain boundaries on the exposed surface. Dislocation subboundaries and packets of nanoscale plates of deformation twins near the grain boundaries are observed in a subsurface layer of 20–100 nm thick. According to our theoretical analysis and simulations, the observed surface modification is caused by nonuniform plastic deformation of crystallites induced by nonmelting laser heating. Continuum modeling of such heating shows that the shockwave effects are negligible since the generated acoustic waves have a pressure of less than 100 atm. We demonstrate that the solid copper goes to the plastic deformation regime if the temperature rise exceeds ∼250 °C. Atomistic simulation of polycrystals reveals anisotropy of grain deformation and asynchronous plastic response due to their different stiffnesses depending on lattice orientation, as well as the residual stresses and growth of surface roughness after each heating–cooling cycle. The obtained results are important for understanding the physical mechanisms of surface degradation of copper mirrors under laser induced thermocycling.

Germanium (Ge) is a system-forming material of IR photonics for the atmospheric transparency window of 8–14 µm. For optics of the 3–5 µm range, more widespread silicon (Si), which has phonon absorption bands in the long-wave region, is predominantly used. A technology for growing Ge single crystals has been developed, allowing the production of precision optical parts up to 500 mm in diameter. Ge is used primarily for the production of transparent optical parts for thermal imaging devices in the 8–14 µm range. In addition, germanium components are widely used in a large number of optical devices where such properties as mechanical strength, good thermal properties, and climatic resistance are required. A very important area of application of germanium is nonlinear optics, primarily acousto-optics. The influence of doping impurities and temperature on the absorption of IR radiation in germanium is considered in detail. The properties of germanium photodetectors are reported, primarily on the effect of photon drag of holes. Optical properties in the THz range are considered. The features of optical properties for all five stable isotopes of germanium are studied. The isotopic shift of absorption bands in the IR region, caused by phonon phenomena, which was discovered by the authors for the first time, is considered.

Germanium (Ge) is a system-forming material of IR photonics for the atmospheric transparency window of 8 – 14 µm. For optics of the 3 – 5 µm range, more widespread silicon (Si), which has phonon absorption bands in the long-wave region, is predominantly used. A technology for growing Ge single crystals has been developed, allowing the production of precision optical parts up to 500 mm in diameter. Ge is used primarily for the production of transparent optical parts for thermal imaging devices in the 8 – 14 µm range. In addition, germanium components are widely used in a large number of optical devices where such properties as mechanical strength, good thermal properties and climatic resistance are required. A very important area of application of germanium is nonlinear optics, primarily acousto-optics. The influence of doping impurities and temperature on the absorption of IR radiation in germanium is considered in detail. The properties of germanium photodetectors are reported, primarily on the effect of photon drag of holes. Optical properties in the THz range are considered. The features of optical properties for all five stable isotopes of germanium are studied. The isotopic shift of absorption bands in the IR region, caused by phonon phenomena, which was discovered by the authors for the first time, is considered.

A review analysis of the problematic aspects of creating high-power nanosecond frequency-pulse solid-state lasers for use in various technological fields, including the electronics industry, has been carried out. Considered installations with various pumping methods (lamp and diode) in the frequency (about 100 Hz) of generation in the micron region of the infrared range. The possibilities of increasing the energy potential of influencing pulses in master oscillator-amplifier circuits, including two-pass amplification, are analyzed. Discussed possibilities and prospects for the use of lasers with active elements (AEs) on glass, as well as the synthesis of large-sized garnet single crystals with an admixture of rare earth elements and opticalceramics for the production of AEs.

The prethreshold processes on the surface of copper and its alloys are investigated. In the absence of obvious traces of melting, while preserving the metal in a condensed state, under a nanosecond ultraviolet laser radiation energy density of 0.1–1.0 J/cm², manifestations of high-temperature plastic deformation were observed. These are sliding and cracking along grain boundaries, within which crystallographic slipping was observed. A microprotrusion was formed on the surface of the irradiated zone, which was outwardly similar the distribution of laser radiation in the spot. The height of the microprotrusion reached 1 μm, and sometimes even more. An increase in the number of impacting impulses led to the accumulation of damage. The data obtained are in many ways similar to the acoustoplastic, electroplastic, and magnetoplastic effects. By analogy, we consider it possible to call the discovered effect optoplastic.

A review analysis of the problematic aspects of creating high-power nanosecond frequency-pulse solid-state lasers for use in various technological fields, including the electronics industry, has been carried out. Considered installations with various pumping methods (lamp and diode) in the frequency (about 100 Hz) of generation in the micron region of the infrared range. The possibilities of increasing the energy potential of influencing pulses in master oscillator-amplifier circuits, including two-pass amplification, are analyzed. Discussed possibilities and prospects for the use of lasers with active elements (AEs) on glass, as well as the synthesis of large-sized garnet single crystals with an admixture of rare earth elements and optical ceramics for the production of AEs.

Представлена современная приборная база и методики измерений оптически прозрачных материалов в широком спектральном диапазоне – ​от ультрафиолетового до терагерцевого. Особое внимание уделено терагерцевому диапазону – ​сравнительно новому направлению оптики, находящемуся на стыке с радиофизикой.

For the first time, in a single experiment, the dependence of the position of the phonon absorption peaks in the IR spectrum (range 11–40 μm) for all five stable monoisotopic germanium single crystals was studied. The dependence obtained can be used to study the mass composition of germanium of various isotopic purity.