Application of 1.55 μm photomixers as local oscillators & noise sources at millimetre wavelengths

Ultrafast commercial photodiodes have been incorporated into mm-wave waveguide mounts. A method of rapidly characterizing the frequency response of these photomixers using spontaneous-spontaneous beating of light from an erbium doped fibre amplifier (EDFA) is described. The combination of photomixer and EDFA forms a bright, single mode, continuum source suitable for spectroscopy. Results show that the available power is significantly greater than that from a mercury arc lamp. A new photomixer design, featuring a combined probe and filter structure, impedance matched over the W-band to both the coplanar output line on the photodiode chip and to reduced height milled waveguide, is also presented.