Fabrication-tolerant Δκ directional coupler switch using annealing in proton exchange

Abstract

A fabrication-tolerant Δκ directional coupler switch was fabricated in z-cut LiNbO 3 substrate by the annealed proton exchange method. In order to improve fabrication tolerance of the device, the metal mask was used for selective proton exchange as a self-aligned electrode, and the desired overlap of electrode and waveguide mode was accomplished by annealing process. Performing successive annealing of the device, at each annealing step the width mode size of the waveguide, the switching voltage of the device, and the crosstalk of two output waveguides were measured. The voltage-length product of the device is 28 Vmm at the wavelength of 633 nm and the crosstalk is smaller than -20 dB.