In this paper, measurement results of an illuminated MESFET characteristics, demonstration of the illuminated MESFET model and an investigation of physical phenomena in an illuminated MESFET are reported. From the investigation of the experimental data, a novel illuminated MESFET model was proposed and its output conductance of an illuminated MESFET was modified with a series capacitance. From this consideration, fundamental data for a design of an illuminated MMIC oscillator were obtained and it is believed to be possible to design a light-weight low-cost, high-efficient and high-speed optical-millimeter wave transducer.
