SBIR/STTR Award attributes
LADAR (laser detection and ranging) is an enabling technology for remote sensing, enabling 3D target recognition, detection through obscurants, and monitoring and mapping a scene. A new generation of avalanche photodetectors is needed to align with recent advances in 2 μm fiber laser technology. At this wavelength, lasers are eye safe, atmospheric transmission is good, and long-distance objects can be detected and tracked. Current LADAR systems use a high performance but expensive detector technology with mercury-cadmium-telluride (MCT, HgCdTe1) that has low yield and high non-uniformity. SK Infrared LLC (SKIR) and The Ohio State University (OSU) are teaming together to develop a LADAR sensing solution using InAs APDs. During the Phase I effort, the industry and academic team built on its existing collaboration with AFRL Sensors Directorate, AFRL/RY (Drs. Reyner/Raab/ Woods) to identify a customer in the Air Force Life Cycle Management program executive office (PEO). At the end of the proposed Phase II, we will deliver a small format, high sensitivity array for laboratory testing for AF applications. These linear mode detectors have the ability to not only detect just a few photons in an active mode, but also to perform grayscale imaging in passive mode. The combination of these two capabilities enables higher degrees of detection, recognition, and identification. Unlike traditional PN junction detectors that do not have a selectable internal gain, APDs have multiplication gain resulting from impact ionization of carriers. In an APD, the primary carriers give rise to secondary electron-hole pairs that in turn can multiply. This leads to an avalanche effect and increases the current. There are several key engineering questions that need to be addressed in order to transition this advancement in science to a real technology that can be deployed by the AF. Some of the research questions that need to be addressed are: 1. What are the fundamental limits of the photon sensitivity in terms of noise equivalent photons? 2. Can the InAs APDs operate at 150-200 K? What are the bulk dark current mechanisms that contribute to noise in these diodes? An increase in the Top will lead to huge advantage in terms of reduction of size, weight, and power (SWaP) of a LADAR system 3. How can we suppress the surface leakage current when the pixel size is shrunk from 260 μm in diameter to < 100 μm? Can we develop a dry-etching process to delineate the pixels since the wet etching is not manufacturable and scalable? 4. Can we develop a process to transition from a front-side illuminated single element detector in a university laboratory environment to a back-side illuminated array geometry that lends itself to integration with the LADAR system? The defense LADAR market shows significant potential for Air Force ISR systems. The proposed technology will match a new generation of 2 μm lasers for LADAR illumination for ISR.
