Two-point source interferometric grating writing.

A novel grating-writing interferometer is demonstrated. This interferometer is compact, stable, and tunable well over 1000 nm and does not suffer from the inherent path-length differences that are present in other methods. It allows for high-quality gratings to be inscribed by preventing light from unwanted orders from affecting the fringe pattern. This technique is used to introduce a novel method of apodization based on removing the Fresnel end reflections in a grating. The experimental evidence proves the concept and shows that the technique is potentially useful for Bragg-grating inscription.