Fabricating micro-Bragg reflectors in 3-D photorefractive waveguides

Bragg reflectors as small as optical waveguides can be used at the intersections of waveguides as spectral filters, beam splitters, or beam combiners. We present the concept of fabricating small Bragg reflectors in photorefractive waveguides and show the spectral selectivity of these micro-Bragg reflectors fabricated in a lithium niobate crystal. We also show that we can fabricate waveguide structures simultaneously with the micro-Bragg reflector, by using a crystal whose c-axis is directed 45 degree off the optical axis of the fabrication beam. The reflectivity of the micro-Bragg reflector was smaller than 0.01 and was not large enough for the immediate use.