Evaluation and optimization of NIR HgCdTe avalanche photodiode arrays for adaptive optics and interferometry

摘要

The performance of the current high speed near infrared HgCdTe sensors operating in fringe trackers, wavefront sensorsand tip-tilt sensors is severely limited by the noise of the silicon readout interface circuit (ROIC), even if state-of-the- artCMOS designs are used. A major improvement can only be achieved by the amplification of the photoelectron signaldirectly at the point of absorption by means of avalanche gain inside the infrared pixel. Unlike silicon, HgCdTe offersnoiseless avalanche gain. This has been verified with the LPE grown 320x256 pixel λsubc/sub=2.5 μm HgCdTe eAPD arraysfrom SELEX both on a prototype ROIC called SWALLOW and on a newly developed ROIC, specifically designed forAO applications, called SAPHIRA. The novel features of the new SAPHIRA ROIC, which has 32 parallel video channelsoperating at 5 MHz, will be described, together with the new high speed NGC data acquisition system. Performanceresults will be discussed for both ROICs. The LPE material on the SWALLOW prototype was excellent and allowedoperation at an APD gain as high as 33. Unfortunately, the LPE material of the first devices on the SAPHIRA ROIC suffersfrom problems which are now understood. However, due to the excellent performance of the SAPHIRA ROIC evenwith the limitations of present HgCdTe material, it is possible with simple double correlated sampling to detect test patternswith signal levels of 1 electron. An outlook will be given on further developments of heterojunctions grown byMOVPE, which eventually may replace eAPD arrays grown by LPE.© (2012) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.