Heterodyne Experiments from Millimeter Wave to Optical Frequencies Using GaAs MESFETs Above fT*

Response of GaAs FETs in mm-wave and optical heterodyne experiments has been obtained at frequencies above the frequency of unity current gain, f_T. In the mixing of two visible lasers, beat frequencies as high as 300 GHz have been observed. These high IFs were down converted to microwave frequencies by radiatively coupling mm-wave local oscillators into the gate region.