A Photonic Local Oscillator for an SIS Mixer in the 100 GHz Band

We have developed a waveguide-mounted photomixer in the 75-115 GHz band with a unitraveling carrier photodiode which is optically-pumped by two 1.55-gm lasers. We have successfully demonstrated to produce an output power of ,2 rnW at 100 GHz with an input laser power of -400 mW. An SIS mixer has been pumped by the photomixer as a local oscillator. It is found that in this configuration the photomixer can provide a sufficient local oscillator power required for optimum operation of the SIS mixer in the frequency band from 85 to 110 GHz. We have carried out similar experiment using a Gunn-diode local oscillator source and carefully compared the receiver noise temperature of the SIS mixer with those pumped by the photomixer. It is found that the receiver noise temperatures of the SIS mixer pumped by the photomixer is a little higher than those pumped by the Gunn oscillator.