Resonant Cavity Enhanced Photo-Diodes for LWIR Communications

LWIR is well suited for free space communications because of its atmospheric window and low scattering by dust, precipitation, and fog. Due to recent developments of QCLs, the technology is poised to provide the high speed LWIR transmitter for such a free space communication system. However, a corresponding advance in LWIR detectors for the high-speed receiver is needed. The specifics of the LWIR detector requirements are: 8-12 m wavelength response, GHz bandwidths, and D*=1013 Jones. Wavelength and bandwidth requirements are already met by existing detectors, however present detectors are 100 away from meeting the D* requirement. Meeting the needed D* requires a 104improvements in both dark and background current. Phase I of this program successfully demonstrated a detector breakthrough, that can accomplish the 100 x improvement in D* using an advanced type of resonant cavity-enhanced photodiode (RCE-PD). In Phase II the RCE-PD design will be optimized, and a receiver module operating at 9.3 m will be fabricated and tested. The detector will be matched with a 9.3 m QCL developed by our partner, Pranalytica for high bandwidth (~ GHz) operation. The resulting paired QCL/RCE-PD will be field and range tested to determine performance for LWIR free space communications.