Photorefractive long-period waveguide grating filter in lithium niobate strip waveguide
To fabricate a long-period waveguide grating (LPWG) filter in a simple, reliable and low-cost way, a novel LPWG scheme based on photorefractive grating is designed and theoretically analyzed in a Ti-diffused strip waveguide embedded in a Ti-diffused planar \(\hbox {LiNbO}_{3}\) waveguide. By means of effective index method and coupled-mode theory, the processing conditions of the planar and the strip waveguide have been calculated. The minimum 100% filtering length \(L=1.40\)cm and the coupling coefficient \(\kappa =112.23\,\hbox {m}^{-1}\) are obtained. The photorefractive LPWG filter can be used in coarse wavelength division multiplexing system.
filter lithium niobate photorefractive grating ti-diffusion waveguide