Polarization-Independent and Optical-Damage-Insensitive LiNbO₃ Interferometric Waveguide Modulator

Abstract

A polarization-independent Mach-Zehnder interferometric light modulator consisting of z -propagation Ti-indiffused waveguides is fabricated on an x -cut LiNbO 3 substrate in which electrically induced phase shifts are nearly identical for TE and TM modes. The optimum Ti-film thickness for making the modulator is determined by measurements on the electrooptic property of the waveguides. Using the modulator we have achieved an extinction ratio of ∼17 dB with a 14.5 V drive voltage for both modes and low sensitivity to optical damage at a wavelength of 633 nm.