Optical intensity modulator using inverted slot line at 60 GHz

The inverted slot line (ISL) structure which has been proposed for millimeter wave LiNbO/sub 3/ optical modulator is found to be very simple in structure, and also is capable of achieving perfect velocity matching between carrier and modulating waves. This paper describes the development of a Mach-Zehnder Ti-diffused LiNbO/sub 3/ optical intensity modulator using the ISL at 60 GHz. To launch millimeter waves into the ISL structure two types of transitions have been developed successfully. In one type, a balun which is made from semirigid coaxial cable is used to feed millimeter waves into the ISL. In another type, nonradiative dielectric (NRD) waveguide, which can provide the total integration of the modulator with millimeter wave integrated circuits, is used to excite the ISL structure ensuring minimum transition losses. Optical response of 0.17 W/sup -1/ could be obtained at 60 GHz using a Mach-Zehnder interferometer with a rather poor extinction ratio of 5 dB at an optical wavelength of 0.633 /spl mu/m.