Abstract

Optical heterodyning is an established technique for the generation of microwave signals. Multichannel optical heterodyning using an integrated optics power-splitter device is studied with the intent of introducing different phase shifts in each individual channel. An optical heterodyne interferometer is set up in the laboratory with a He-Ne laser source. A 100-MHz TeO₂ Bragg cell for frequency shifting is in one arm, and an integrated optics 1-8 power splitter consisting of Ti-diffused waveguides in a LiNbO₃ crystal is in the second arm. The cross section of each waveguide channel is 2 × 3 µm, with a 50-µm interchannel separation. The reference beam coming from the Bragg cell is focused into a line image using a cylindrical lens to overlap the image of the output of more than one waveguide channel. The optical signals are carried by a fiber optic array to Si PIN photodiode fiber optic receivers that feed into rf amplifiers. The heterodyned signals are analyzed on a spectrum analyzer. At present, an electronic rf phase shifter is used to introduce phase shift in one of the detector outputs. Optical phase shifting based on photorefractive and electrorefractive effects will be carried out next, and the source will be changed to an infrared laser diode. Multichannel optical heterodyning with different phase information has use in optical control of phased-array antennas and in contactless testing of MMIC circuits.

© 1989 Optical Society of America