Near field angular filtering with volume Bragg gratings in photothermorefractive glass

Abstract

Angular filtering with volume Bragg gratings in photothermorefractive glass was described. The coupled-wave theory was used to discuss the angular filtering based on Transmission Volume Bragg Gratings (TBGs). The results showed that the cutoff frequency was improved, the refractive index modulation had a greater impact on the output beam and the deviation from Bragg condition for incident beam should be less than 0.1mrad. The influence on output beam quality with TBGs parameters was analyzed. Experimental results showed that the near-field distribution of output beam through the angular filtering is better than that of the incident laser beam, and the low-frequency loss of near-field angular filtering is less than 1.8%.