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Prospects for using ZnSe polycrystals synthesized by the chemical vapor deposition (CVD) method for the development of Faraday isolators for high-power radiation at a wavelength of 1076 nm are investigated. A Faraday isolator was built by a conventional scheme for room temperature operation. No thermally induced depolarization was observed in the device for the laser power range up to 1270 W, which is the main limiting factor for powerful isolators. It was demonstrated experimentally that thermally induced depolarization is not expected at powers up to 2.5 kW.

Two multi-pass optical schemes of a disk laser amplifier have been proposed. Different variants of both the schemes with the smallest amount of optical elements and a lens in the active element taken into account have been calculated. For 64 passes of radiation through the active element, the average power of ∼50  W with ∼10% optical-to-optical efficiency in a pulse-periodic regime with a repetition rate of 10 kHz and a pulse duration of 2 ns was obtained at the amplifier output. The small signal gain amounted to 200.

Thermally induced depolarization of radiation introduced by a system of two optical elements separated by a quartz rotator has been analyzed. The conditions of full compensation of thermally induced depolarization for two nonidentical optical elements have been found. The model experiment has demonstrated that full compensation in two optical elements of different materials is possible without a quartz rotator between them.

The influence of paramagnetic magnetization of magneto-optical elements on the characteristics of Faraday isolators is studied. The theoretical estimates confirmed by the experiment indicate that this effect should be taken into consideration, particularly when designing large-aperture and cryogenic Faraday isolators.

Faraday isolators play a key role in the operation of large-scale gravitational-wave detectors. Second-generation gravitational-wave interferometers such as the Advanced Laser Interferometer Gravitational-Wave Observatory (LIGO) and Advanced Virgo will use high-average-power cw lasers (up to 200 W) requiring specially designed Faraday isolators that are immune to the effects resulting from the laser beam absorption–degraded isolation ratio, thermal lensing, and thermally induced beam steering. In this paper, we present a comprehensive study of Faraday isolators designed specifically for high-performance operation in high-power gravitational-wave interferometers.

A cryogenic Faraday isolator with disc-shaped magneto-optical element is described. Depolarization of laser radiation caused by transverse inhomogeneity of Verdet constant has been measured for the first time. The decrease of the thermally induced effects caused by heat removal from the face-end of the magneto-optical element of terbium gallium garnet with sapphire and aluminum-yttrium garnet discs is investigated. Characteristics of the cryogenic Faraday isolator at high laser power above 1 kW have been investigated experimentally and the possibility of its use at power as high as 6 kW is demonstrated. The reduction of thermo-optical constants Q and P by a factor of 5.7 and 6.8, respectively, with cooling from 300 K to 80 K has been measured for TGG crystal.

We analyzed a number of optical media, such as GGG, Nd:YAG, Yb:YAG, fused silica, CaF_2, Yb:CaF_2, and CdMnTe, that have not been used, to our knowledge, in the cryogenic Faraday isolator (FI) before. The temperature dependence of the Verdet constant and thermo-optical constants was experimentally investigated for λ=1.07?μm. We calculated the magneto-optical figure-of-merit and assessed the feasibility of using FI media with multikilowatt average laser power.

Two Nd:YLF lasers with a pulse duration of about 2 ns have been synchronized. The duration and synchronization of two laser pulses are provided by two pairs of Pockels cells with synchronized voltage pulses. One of the Pockels cells in the first pair ensures Q switching, and the other cuts out a 2 ns pulse from the giant 20 ns pulse. In the second pair, one of the cells, driven by a two-step voltage pulse, forms a giant pulse synchronized with the pulse of the first laser, and the other cell cuts a short pulse out of it. The proposed scheme allows a rather simple and reliable synchronization of two Q-switched lasers with a jitter of 150 ps.

We present a novel, to the best of our knowledge, method for measuring the intensity profile of far-IR beams. The method is based on the measurements of nonstationary variation in optical thickness of a fused-silica plate heated by the studied radiation. The optical thickness is observed by means of a reflecting interferometer. Purpose-made experimental setup allows one to measure beams with an aperture of up to 60 mm with a spatial resolution of 1 mm. The accessibility of the utilized technologies and the possibility to easily increase the aperture are the major advantages of this approach. The probable area of application for the method is measurements of beams produced by powerful industrial far-IR lasers.

An optical system that comprises two devices for remote measurements, a broadband optical interferometer and a scanning Hartmann sensor, is described. The results of simultaneous measurements with both devices and the results of numerical modeling of sample surface heating are presented.

Different ways of varying the output pulse duration in laser schemes comprising a powerful master oscillator, a multipass amplifier, and a stimulated Brillouin scattering (SBS) mirror are suggested and realized experimentally. Conditions are determined at which introduction of losses between a SBS mirror and an amplifier allow variation of the output pulse duration without any significant decrease in energy. The use of two different SBS media (SnCl4and freon) allows construction of a laser where the output pulse duration is varied between 6 and 40 ns and the energy loss is no more than 30. © 2000 Society of Photo-Optical Instrumentation Engineers.