Optimizing Charge-Coupled Devices For Red And Near-Infrared Observations

Abstract
Methods to improve the red and near-IR quantum efficiency (QE) of CCDs are discussed. The effects of thinning, antireflection (AR) coating, and mounting CCDs for use in astronomical observations at wavelengths greater than 700 nm are presented. Thinning CCDs to inside their epitaxy and backside illuminating them increases their QE over thick devices even in the far red, due to the absence of frontside absorption and reflection losses. AR coatings decrease the backside reflection loss and greatly reduce the amplitudes of interference fringes. Mounting CCDs on a substrate eliminates surface warpage which improves the user's ability to correct for instrumental and background signatures. Some of these optimization techniques are demonstrated using the Photometrics PM512 CCD made by Ford Aerospace.