Measurement of the Quantum Efficiency of an HgCdTe Infrared Sensor Array

We measured the quantum efficiency of an H2RG HgCdTe near infrared sensor array. We determine a 2-σ lower limit of 85% for the quantum efficiency averaged over the array and over three observed wavelengths, 3.38μm , 3.9μm , and 4.5μm . The peak quantum efficiency occurs near the center of the sensor and is unity within measurement uncertainty (5%). We used a blackbody, narrowband filters, and a pinhole camera to provide a calibrated irradiance on the HgCdTe sensor H2RG-S010. We verified the methods and equipment by substituting a calibrated PbSe diode for the H2RG sensor. Accurate measurement of the quantum efficiency requires a well-calibrated system gain, the determination of which is complicated by interpixel capacitance, which correlates noise between adjacent pixels. If unaccounted for, the correlation induced by interpixel capacitance would cause the system gain and hence the quantum efficiency to be overestimated by ∼20%. We accurately measured the interpixel capacitance using the autocorrelation method of Brown et al. (2006) and by a method described in this report that uses post-readout binning. The two methods yield consistent results, but the binning method is more robust than the autocorrelation method in the presence of electromagnetic interference. The interpixel capacitance we measured for the H2RG-S010 sensor is similar to that of another epoxy-backfilled H2RG sensor tested by Brown et al. (2006). Subject headings: instrumentation: miscellaneous – telescopes – techniques: photometric – calibration JWST-STScI-001053, SM-12 Check with the JWST SOCCER Database at: http://soccer.stsci.edu/DmsProdAgile/PLMServlet To verify that this is the current version.