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Detector Johnson-noise-limited operation of InSb photovoltaic detectors has previously been reported. Typically, a cooled, dual JFET is used to amplify the signal before passage to subsequent amplification electronics. Most configurations employ an arrangement in which the cooled JFET's and feedback resistors are packaged and cooled separately from the detector element. This can result in large amounts of pickup noise from the observatory environment. With the advent of higher quality InSb photodiodes the ultimate NEP's possible depend more upon the investigator's ability to shield the detector and initial amplification stage from outside sources than on detector properties. In this paper we describe InSb detector-hybrid configurations in which the detectors, dual JFET dies, and feedback resistors are mounted closely together in the same hybrid flatpack. This allows complete shielding of detector and initial-stage amplification electronics. With typical 0.25 mm and 0.5 mm detectors and RoA products near 5 x 106 Ω-cm2, theoretical-limit NEP's of approximately 5 x 10-16 W/(Hz)1/2 at 77 K are obtained.© (1982) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only. |
