Polarization-independent electro-optically tuned add/drop multiplexers in LiNbO3 utilizing strain optic effect

Abstract

Polarization-independent Ti:LiNbO3 2 x 2 optical add/drop multiplexers for the 1550 nm wavelength regime are fabricated. The device consists of two input waveguides, two polarization splitters, two polarization conversion/electro-optic tuning waveguide sections, and two output waveguides. The single mode channel waveguides for both transverse electric (TE) and transverse magnetic (TM) polarizations are fabricated on a x-cut Ti:LiNbO3 substrate by Ti diffusion. Spectral section is based on phase-matched polarization conversion due to static shear-strain induced by a thick SiO2 grating overlay film. An applied voltage tunes the device by changing the waveguide birefringence, hence the optical wavelength at which most efficient polarization conversion occurs. Tuning rate of 0.094 nm/V with a maximum range of 16.44 nm has been obtained. The nearest side-lobe is about 8.2 dB. The full-width at half maximum (FWHM) is 3.72 nm.