ZnSe-based Faraday isolator for high-power mid-IR lasers
É. A. Mironov, Oleg Palashov, Ilya Snetkov, Stanislav Balabanov
Abstract
Abstract High-power Faraday isolators (FIs) for mid-IR radiation are of great practical importance, since they expand the capabilities of constructing optical schemes of solid state mid-IR lasers, which have progressed significantly in recent years. Isolators for high-power radiation with a wavelength of 1.5–2 µ m are especially important for the solid-state lasers in order to cover the entire mid-IR range. We developed the FI for high-power mid-IR radiation based on CVD-ZnSe polycrystals and studied its characteristics. The isolation of radiation with a wavelength of 1940 nm was demonstrated. No thermally induced depolarization effects were observed for radiation with a wavelength of 1940 nm up to 20 W. For studying the limitations of the isolator in terms of operating power, experiments with more powerful radiation at a wavelength of 1075 nm were performed. Estimates show the possibility of isolating radiation with a power of up to 200 W with the isolation ratio of the device of ∼25 dB. Ways to improve the device are discussed. The level of cold depolarization can be reduced, by annealing the magneto-optical elements. The device can be compactified by using a different optical isolation scheme and a different organization of the magnetic system. This path will also allow compensating thermally induced depolarization and, according to the estimates, will ensure the isolation of mid-IR radiation of a kilowatt power level.