High-order harmonic mixing with GaAs Schottky diodes

The performance of the planar type of fast planar Schottky diode is investigated for harmonic mixing with harmonic numbers from 8 to 201. The measurements indicate that, with optimum biasing and power, harmonic mixing with harmonic numbers up to approximately 80 can be achieved with good signal-to-noise ratios (SNRs). Detectable signals are observed for harmonic numbers of 201. In a test of both the nonlinear and the high-frequency performance, a beat signal between the 34th harmonic of a 74.7 GHz klystron and a laser operating at 2522 GHz is obtained. The resulting SNR is 48 dB (bandwidth of 3 kHz). Frequency roll-off effects in the diode are not detectible at 2.5 THz, which is consistent with a calculated value of 11 THz based on mask geometries. The SNR is nearly identical for either odd or even order harmonic mixing for harmonic numbers above 11. The sample diodes tested are very stable in time and are reproducible on the same die