Discrete nonplanar reflections from an ultrashort pulse written volume Bragg grating.

In this Letter, we present a direct writing technique for two-dimensional periodic volume Bragg gratings (VBGs) in fused silica based on the phase mask technology, ultrashort laser pulses, and three-beam interference. An algorithm to predict the grating pattern and its diffraction behavior under collimated, spectral broad illumination is developed. The predicted data are in good agreement with the measurements.