Title: High Dynamic Range UV to SWIR Photon Counting Sensor for PEM-based imaging polarimeters
Presenting Author: Jeffrey Beck
Organization: Leonardo DRS
Co-Author(s): Jeff Beck, Billy Sullivan, Russel Austen – Leonardo DRS;
Bruce Hancock, David Diner, Michael Hoenk – Jet Propulsion Laboratory;
Darren Carpenter – Analog Digital Integrated Circuits Inc

Abstract:
An advanced multispectral photoelastic modulator (PEM) based polarimetric imaging sensor, being developed at the Jet Propulsion Laboratory, requires a high dynamic range detector with photon counting sensitivity in the UV to SWIR wavelength range. We report results from an on-going effort to develop a detector approach based on the MWIR cutoff HgCdTe linear mode (LM) electron avalanche photodiode (e-APD) that is being provided by Leonardo DRS, Electro-Optical Infrared Systems. The MWIR HgCdTe LM APD exhibits good quantum efficiency and single photon sensitivity from 360 nm to 4400 nm. Linear mode APD gains of greater than 1000 with an excess noise factor of 1.25 and gain normalized dark current levels of less than 20 k electrons/s are routinely achieved in these detectors at an operating temperature of 80 K. Single photon counting demodulation of a low level, time varying, polarimetric, 650 nm , signal was successfully demonstrated using a 2x8 APD focal plane array. Time varying counts per bin data from 600 to 2200 were recorded and fit to produce the polarization parameters I, Q, U, δo and phase offset. A maximum linear photon counting rate of 10 MHz was determined that is limited by the bandwidth of the preamp which sets the width of the single photon pulse output. Additional dynamic range in the maximum count rate can be achieved by increasing the preamp bandwidth, however, not enough to achieve the full dynamic range desired. We will show a digital pixel approach for the readout integrated circuit (ROIC) that we are pursuing to extend the dynamic range to accommodate larger signal levels.