We report the first experimental results for optoelectronic mixing usi
ng a two-terminal edge-coupled InP/InGaAs heterojunction phototransist
or (HPT), The HPT optoelectronic mixer (OEM) exhibits a maximum of 7-d
B conversion gain relative to a 100% quantum efficient photodetector o
perated at the optical modulation frequency, We give a qualitative exp
lanation for the observed conversion gain variation with the HPT bias
voltage.