Optical Aperture Gating for Single-pixel and Imaging LIDAR Systems

One of the key limitations in optical band underwater imaging and communications systems is the excessive attenuation and scattering light experiences in traversing the intervening media. Strong attenuation fuels the demand for high transmitter energy and high sensitivity (photon counting) detectors. Strong backscatter can temporarily blind or damage highly sensitive detectors, undermining the systems ability to sense (or communicate) over both short and long distances. In principle, the “backscatter problem” can be mitigated by employing high dynamic range detectors (i.e. a detector that is responsive to both high and low levels of photons). This requirement is often at odds with the sensitivity requirement of detecting a few photons/nanosecond. One potential solution is use a fast optical switch (or attenuator) in front of the detector to gate out the undesired near-field backscatter. Current technology cannot address all of the needs, such as polarization insensitivity, large aperture, and wide acceptance angle. Areté Associates has devised an elegant solution to this problem that promises to meet the demanding requirements in a compact, low power consumption open-architecture module. This program will result in the development of a stand-alone, polarization insensitive, fast optical attenuator module (10-100 ns) capable of achieving an off-on contrast of -30 dB over large physical (> 1 cm2) and angular (> +/- 10 degrees) apertures and with low insertion loss (< 2 dB).