Direct Writing of Quasi-Sinusoidal and Blazed Surface Relief Optical Transmission Gratings in Bi12GeO20, Er: LiNbO3 and Er: Fe: LiNbO3 Crystals by Nitrogen Ion Microbeams of 5 MeV and 10.5 MeV Energy

High diffraction efficiency optical transmission gratings with quasi-sinusoidal and saw-tooth surface relief profiles were fabricated in Bi₁₂GeO₂₀, Er: LiNbO₃ and Er: Fe: LiNbO₃ crystals by ion beam implantation. The gratings were directly written by nitrogen ion microbeams at energies of 5 MeV and 10.5 MeV. The finest grating constant was 4 μm. Grating constants for the majority of the gratings were 16 μm. The highest amplitudes of the gratings reached 1600 nm. The highest first-order diffraction efficiency obtained in a sinusoidal grating was 25%, close to the theoretical maximum of 33%. The highest first-order diffraction efficiency of a blazed grating was also 25%, without Littrow optimization. Such gratings can be incorporated into integrated optical biosensors.