Thermo-Optical Studies of Laser Ceramics.

A cycle of works on manufacturing and studying laser and magnetooptical ceramics with a focus on their thermo-optical characteristics performed by the research team is analyzed. Original results that have not been published before such as measurements of the Verdet constant in the Zr:TAG, Re:MgAl2O4, and ZnAl2O4 ceramics are also presented.

High-purity CVD-ZnSe polycrystal as a magneto-active medium for a multikilowatt Faraday isolator.

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.

High-power Faraday isolator on a uniaxial CeF3 crystal.

We have created the first high-power Faraday isolator on an anisotropic magneto-optical element (MOE). The isolator is based on one MOE of a uniaxial CeF3 crystal and ensures an isolation degree of 30 dB at a high average laser radiation power of 700 W. The limitations due to the anisotropic nature of the crystal do not impose significantly more stringent requirements, either for the beam or the MOE.

Cryogenically cooled CeF3 crystal as media for high-power magneto-optical devices.

The thermally induced depolarization and Verdet constant of CeF3 crystals-their most important characteristics-have been studied in the 79-293 K temperature range. It has been found that thermal effects reduce substantially upon cooling down to 79 K and the Verdet constant grows in inverse proportion to the temperature. It was shown that CeF3 crystals are not inferior to TGG as a medium for Faraday isolators, including cryogenic ones.

Faraday rotator based on TSAG crystal with <001> orientation.

A Faraday isolator (FI) for high-power lasers with kilowatt-level average power and 1-µm wavelength was demonstrated using a terbium scandium aluminum garnet (TSAG) with its crystal axis aligned in the <001> direction. Furthermore, no compensation scheme for thermally induced depolarization in a magnetic field was used. An isolation ratio of 35.4 dB (depolarization ratio γ of 2.9 × 10-4) was experimentally observed at a maximum laser power of 1470 W. This result for room-temperature FIs is the best reported, and provides a simple, practical solution for achieving optical isolation in high-power laser systems.

Effect of paramagnetic magnetization in Faraday isolators.

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.