Characterization of a 1×32 element metal-semiconductor-metal optoelectronic mixer array for FM/cw LADAR

We characterize a 1×32 element metal-semiconductor-metal photodetector (MSM-PD) array utilized for optoelectronic mixing in an incoherent, amplitude-modulated laser detection and ranging (LADAR) system. The MSM-PDs that make up the one-dimensional array internally detect and down-convert light signals that are amplitude modulated at ultrahigh frequency (UHF). Range information is contained in the low-frequency mixing product derived by mixing a reference UHF chirp with a detected, time-delayed UHF chirp. When utilized in the LADAR system, the MSM-PDs eliminate the need for wideband transimpedance amplifiers in the LADAR receiver. This, in turn, reduces both the cost and complexity of the system. The breadboard LADAR architecture and components are described, and fundamental measurements and imagery taken from the LADAR, using these unique MSM-PDs, are also presented.