Improving Photodetector Performance by Means of Microoptics Concentrators

Abstract

We discuss the benefits of using microoptics concentration arrays in connection with image (or pixellated) photodetectors, in terms of: 1) recovery of area fill-factor; 2) reduction of equivalent dark-current; 3) mitigate dead-time issues; and 4) improved dynamic range. As an example of application, we describe the fill-factor recovery in connection to an array of 32$\, \times \,$32 6-$\mu$m diameter, 50-$\mu$m pitch, single photon avalanche detector (SPAD). We use a 32$\, \times \,$32 array of microlenses, fabricated by polymer casting in a photoresist replica mold. We demonstrate, for the first time to the best of our knowledge, an increase by a factor ${\times}25$ of the effective spectral sensitivity of the final device. The lens array itself allows a ${\times}35$ recovery, and projected improvements in excess of ${\times}50$ appear feasible.

© 2011 IEEE