Optical Properties of Single-Crystal Germanium in the THz Range

Optics and Spectroscopy - The transmission of intrinsic, antimony-doped, and gallium-doped Ge single crystals in the THz spectral range have been experimentally investigated. It is shown that the...     

Dependence of growth of the phases of multiphase binary systems on the diffusion parameters

A mathematical model of the diffusion interaction of a binary system with several phases on the equilibrium phase diagram is presented. The theoretical and calculated dependences of the layer thickness of each phase in the multiphase diffusion zone on the isothermal annealing time and the ratio of the diffusion parameters in the neighboring phases with an unlimited supply of both components were constructed. The phase formation and growth in the diffusion zone during “reactive” diffusion corresponds to the equilibrium state diagram for two components, and the order of their appearance in the diffusion zone depends only on the ratio of the diffusion parameters in the phases themselves and on the duration of the incubation periods. The dependence of phase appearance on the incubation periods, annealing time, and difference in the movement rates of the components across the interface boundaries was obtained. An example of the application of the model for processing the experimental data on phase growth in a two-component three-phase system was given.     

Two-Photon Absorption of Nonchain HF Laser Radiation in Germanium Single Crystals

Some results of experimental and numerical studies on the transmission of a nonchain high-frequency (HF) laser beam through germanium (Ge) single crystals of differing thickness and specific resistance are presented. Based on the experimental data for the HF(DF) lasing spectrum, the coefficient of two-photon absorption in germanium has been estimated as K₂ = 55 ± 10 cm/GW at λ = 2.8 μm. The results are in good agreement with theory. The developed experimental data-processing software has enabled the numerical study of the transmission of a high-power beam with λ = 2.6–3 μm through Ge at any laser-pulse-impact moment. It has been shown that thin germanium coatings can efficiently smoothen the distribution of energy over the beam aperture for high-power laser radiation with λ = 2.6–4 μm.     

Nonlinear absorption of non-chain HF laser radiation in germanium

The transmission of high-power HF(DF) laser radiation through Ge single crystals of different quality has been experimentally and numerically investigated. Based on the experimental data for the lasing spectrum, the two-photon absorption coefficient in Ge is estimated to be K₂ =55±10 cmGW?1 at λ=2.8μm. The transmission dynamics of high-power radiation with λ=2.6?3 μm through germanium crystals is numerically simulated.     

Fundamental absorption of calcium,magnesium, and lithium fluorides in the range of 8–12 μm

The fundamental absorption of calcium, magnesium, and lithium fluorides in the range of 8–12 μm has been studied experimentally by the spectrophotometric method. The known and experimentally obtained values of the absorption coefficients of these materials have been analyzed. It has been shown that the values experimentally measured in the range of 8–12 μm obey the Uhrbach rule and the multiphoton absorption determines the long-wavelength transmission cutoff of pure optical materials. The results presented make it possible to suggest that plates made of LiF and CaF₂ crystals and of optical ceramics based on MgF₂ can be used to fabricate calibrated radiation attenuators in the spectral range of 8–12 μm.     

Effect of absorbing microinhomogeneities on optical damage to Alkali-Halide crystals

Micropores up to 30?C100 ??m in size (bulk density ??10⁵ cm^?3) are obtained in NaCl, KCl, KBr, and RbI via the effect of a pulse of a CO₂ laser with power density 10⁶?C10⁷ W cm^?2 up to 5 ??s long. When a pore appears, plasma formation is initiated. The average temperature is ??5500 K and the pressure is ??10⁴ kg cm^?2. The dependence of the average weight of the material removed from the pore on the energy of the crystal lattice is found. Pore formation occurs mainly via the effect of the radiation pulse, due to evaporation at the absorption wave front (velocity, 5 m s^?1) and plastic deformation. The annealing kinetics of micropores and the effect of the ionizing radiation on the bulk pore formation in NaCl crystals are investigated.     

On the Transparency of Alkali-Halide Crystal in the Terahertz Spectral Range

Optics and Spectroscopy - The transmission of THz (to 3000 μm) radiation by alkali halide single crystals of sodium chloride (NaCl), potassium chloride (KCl), potassium bromide (KBr), and...     

Monitoring the Optical Surface Purity of Components by an Ellipsometric Method

Journal of Applied Spectroscopy - The possibility of monitoring the chemical purity of the surface of optical components by an ellipsometric method is analyzed. The rationale for the possible...     

Preparation of Anion Exchanger for High-Efficiency Purification of Halogen-substituted Hydrocarbon Solvents Used To Clean Metal Optics

Phenomenon of rising sorption capacity of AV-17-8 anion exchanger upon an increase in its humidity due to the superequivalent absorption of Cl^– ions was revealed and substantiated. The purification of halogensubstituted hydrocarbon solvents to remove acids under dynamic conditions by the ion-exchange method and the dynamics of sorption by anion exchangers of halogen-substituted solvents from model solutions were studied. It was shown that AV-17-8 anion exchanger is stable in halogen-substituted solvents and, when present in the OH–form, raises their stability against destruction, and the equilibrium sorption capacity of the anion exchanger is 2–3 times its exchange capacity.     

Thermooptical processes in the window of a high-power gas laser

Optics and Spectroscopy - We have developed a mathematical model of thermomechanical and thermooptical processes that proceed in the output window of a continuous gas laser of a multikilowatt...