Improving Photodetector Performance by Means of Microoptics Concentrators

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 × 32 6-μm diameter, 50-μm pitch, single photon avalanche detector (SPAD). We use a 32 × 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 × 25 of the effective spectral sensitivity of the final device. The lens array itself allows a × 35 recovery, and projected improvements in excess of × 50 appear feasible.