An elliptical Talbot interferometer for fiber Bragg grating fabrication

A simple and easily aligned two-mirror interferometer for fabricating Bragg gratings in optical bulk materials, waveguides, and fibers is presented. The interferometer consists of a simple phase mask splitting element and two dielectric mirrors optimized for maximum reflectance at an incident angle of 45 deg. By choosing a suitable optical configuration the half-period of the phase mask is patterned on the interference plane, while a wide range of periodicities can be inscribed by adjusting the relative angles between the interferometer folding mirrors. The operation of the interferometer is demonstrated for grating inscription in Ge-doped optical fibers, using 213 nm, 150 ps Nd:YAG radiation.