Advanced Detectors for Long Wave Infrared (LWIR) Communications

ABSTRACT:Using lasers as signal carriers, FSO laser communications (Laser-Com) can provide a line-of-sight, wireless, high-bandwidth, communication link between remote sites. Because of the reduced scattering, long-wavelength infrared (LWIR) 8 13 um radiation possesses significantly better all-weather transmission than the shorter wavelengths in use today. The superior transmission through common atmospheric problems such as fog, clouds, and smoke coupled with improvements in LWIR laser and modulator design makes possible reliable optical replacements for radio, microwave, and even SWIR/MWIR FSO communications links in many applications. InAs/GaSb Type-II superlattices are a developing new technology for the realization of LWIR imaging sensors that has the potential to offer a low-cost LWIR detector for next generation systems. The overall objective of this project is to develop and demonstrate fast LWIR photodetectors based on Type-II superlattices material system. This new superlattice design is expected to show high bandwidth (> 1 GHz) while maintaining the same or even higher sensitivity (D* > 10^13 Jones) as the state-of-the-art photodetector technologies. BY the end of Phase II, a LWIR FSO communication receiver will be demonstrated using our photodetector, custom-made electronics and miniaturized cooler.BENEFIT:Bandwidth is a scarce resource in many of the diverse locations the DoD operates, and satellite communications suffer from high latency and limited available bandwidth. The ability to rapidly move in and set up a free-standing communications link would significantly aid battle-field communications. The use of a point-to-point optical link instead of an RF link avoids interception of communications and reduces the probability that the source and destination of the communications link can be externally detected. The use of LWIR is especially appealing for and ad-hoc environment where being eye-safe allows for much more simple setup. The use of LWIR also makes for better immunity to smoke, fog, dust, or other interferants that would cripple a NIR system. Commercially, Free-space optical communication is a promising solution to the last mile bottleneck of data networks. A dedicated, non-shared, optical link would provide the needed security and data rates for such a situation.