Double polarization active Y junctions in the L band, based on Ti:LiNbO3 lithium niobate waveguides: polarization and contrast performances

Double polarization electro-optic beam combiners based on a Ti:diffusion lithium niobate waveguide have been developed for mid-infrared applications. A monochromatic rejection ratio of up to 33 dB at lambda = 3.39 mu m was obtained, as well as wideband fringes showing low dispersion. In a first part, studying the fringe contrast as a function of waveguide width, we found a compromise among transmission, signal-to-noise ratio, and fringe contrast, depending on the single-mode behavior of the waveguides. We will show that both polarizations are guided, and at least 70% and 90% contrast is achieved, respectively, in TE and TM with a 400 nm wideband light centered at 3.39 mu m. After choosing the optimal combiner and designing the electrodes, we studied the electro-optic response of the device, using a monochromatic source and scanning the fringe, by external as well as internal modulation, in order to determine the rejection ratio and the voltage needed to cover half a fringe (V-pi) voltage for both TE and TM polarizations. (C) 2012 Optical Society of America