Tunnelling metal-semiconductor contact optically pumped mixer

The results of an investigation into the use of heavily doped tunnelling metal-semiconductor contacts as optically pumped mixers are presented. The electrical and optoelectronic characteristics of the contacts are determined, and these characteristics are used in optically pumped mixer models to obtain predictions of the performance of the devices. Conversion losses as low as 10 dB are predicted with 500 mu A average photocurrent. Experimental measurements have confirmed the accuracy of the mixer models, and conversion losses of less than 18 dB have been measured with 120 mu A average photocurrent. Analysis of the behaviour of the devices has suggested that optically pumped mixers could compete effectively with photodiode-mixer combinations in terms of noise performance, and could simplify systems substantially. This would make them attractive in systems in which an optically distributed local-oscillator or reference signal was desired.<>