A Directional Filter Diplexer Using Optical Techniques for Millimeter to Submillimeter Wavelengths

An optical diplexer for injection of a local oscillator into a mixer, useful in the submillimeter and short millimeter range, is described. It has very low insertion loss for both the signal and local oscillator (L.O.) and high rejection of L.O. noise. Measured performance of a unit tested at 337 GHz indicates ~.2 dB loss for both inputs and 20 dB noise rejection.