Integrated waveguide modulator using a LiNbO3 TE&rlarr2;TM convertor for electrooptic coherence modulation of light

The authors report a wavelength independent TE-TM mode convertor used as a waveguide electrooptic modulator in a coherence modulated system. The modulation voltages thus obtained (20 V) are about 10 times lower than those previously reported in earlier coherence modulated devices. The modulator is a strip waveguide fabricated on Y-cut Z-propagation, Ti-indiffused LiNbO₃. When used in conjunction with a birefringent plate and polarizers, the modulator is shown to imprint on light a signal encoded into an optical delay greater than the source coherence length. Demonstration of the device is reported using a highly multimode laser diode at 820 nm