Apparatus for generating an optical interference pattern

Apparatus for writing a grating on a waveguide, comprising:

• a) a block of light transmissive material, said block including:
• i) a surface for receiving a plurality of optical beams for propagation through said block;
• ii) a reflective element for reflecting optical energy in a first one of the optical beams to produce a reflected beam such that the reflected beam is directed to exit said block and continue propagating toward the waveguide and intersect a second one of the optical beams outside of said block.

Method for writing a grating on a waveguide, comprising:

• a) directing a plurality of optical beams toward a first surface of a block of light transmissive material for propagation through said block;
• and
• b) while a first one of the optical beams is propagating through said block of light transmissive material, reflecting optical energy from the first one of the optical beams to produce a reflected beam that also propagates through said block and is directed to exit said block and continue propagating toward the waveguide and intersect a second one of the optical beams outside of said block.

Apparatus for writing a grating on a waveguide, said apparatus comprising a block of light transmissive material, said block including first and second reflective elements integrated to said block, said first and second reflective elements being located one with respect to the other such that when first and second optical beams that propagate through said block of light transmissive material impinge upon the first and second reflective elements, respectively, the first and second optical beams are directed to exit said block of light transmissive material toward the waveguide and intersect each other outside said block of light transmissive material.