Patent ID: 8828624
Filing Date: 2014-09-09
Classification: G02B,G03F,G03H

Abstract:
1. A method for recording multiple volume Bragg gratings (VBGs) in a body of photo thermo-refractive material comprising the steps of: energizing a laser, thereby emitting a light beam along a light path, intercepting the light beam by an upstream mirror pivotal about an axis, which extends transversely to the light path, thereby providing a desired optical distance between the laser and a phase mask which is located upstream from the body; intercepting the reflected light beam by a beam expander configured with two spaced apart mirrors upstream from the phase mask and displacing the two spaced apart mirrors relative to one another thereby adjusting a spot size of the light beam to a desired spot size; exposing a phase mask to the light beam, the light beam being coherent, thereby irradiating the body of photo thermo-refractive material by the reflected light beam through the phase mask so as to form a plurality of spaced apart VBGs in the body at a desired depth corresponding to the desired spot size and; wherein the laser, upsteam mirror and beam expander are operative to move while the phase mask is stationary.