The project aims at the research of diffractive optical elements for widely-tunable high-power fiber lasers. High power fiber lasers are highly demanded by industry because of high average power and excellent beam quality. We will investigate diffraction elements etched by a focused ion beam directly into the facets of optical fibers. These gratings will serve as antireflection coatings or as output mirrors of fiber lasers. We will also investigate wavelength selective elements based on shallow leaky mode resonant diffraction gratings. The diffractive elements will be optimized numerically to achieve either reguired reflectivity, polarization properties and bandwidth for the fiber facets or high diffraction efficiency, high wavelength selectivity and high suppression of unwanted diffraction orders for the wavelength selective elements. The diffractive optical elements will be tested in the widely-tunable thulium-doped fiber lasers for 2000 nm band, where they are supposed to increase the quality of laser resonators.
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