Integrated-optic wavelength demultiplexer on lithium niobate by double proton exchange

Abstract

An integrated-optic wavelength demultiplexer produced by double proton exchange on z-cut lithium niobate is demonstrated. The mode sorting effect and waveguide dispersion characteristics are utilized to demultiplex the optical fields at the wavelengths 980 nm and 1550 nm. The opposite waveguide dispersion in the two output waveguides can be obtained by designing the aspect ratio of the waveguide structure and the refractive index profile of the waveguide. The design parameters include the waveguide width, the proton-exchange time, the annealing time, and the depth of the second proton-exchanged layer. The semivectorial finite difference method is utilized to calculate the effective index of the guided mode in the output waveguide in order to obtain the required waveguide dispersion for wavelength demultiplexing. In the experiment, the effects of waveguide width, branching angle, and depth of the second proton-exchanged layer on the device performance are discussed.