Leaky-mode resonant gratings on a fibre facet

Numerical investigation shows that an optimised leaky-mode resonant diffraction gratings fabricated in ${Ta}_2{O}_5$ layer deposited on the facet of an optical fibre can have a modal reflectance peak of more than 95%, 3 dB spectral bandwidth of about 50 nm and polarization extinction ratio of almost 18 dB. The grating is intended to be employed as a high-reflectance, wavelength- and polarization-dependent mirror in a fibre laser. We compare results of 2D and 3D modelling, investigate influence of grating parameters on spectral shape of modal reflectance and discuss fabrication tolerances.