INCREASING THE QUANTUM EFFICIENCIES OF ADVANCED PHOTONIC IMAGERS WITH MICROLENS ARRAYS

Single-photon counting detectors or imagers such as front-illuminated single-photon avalanche diodes (SPAD) have a clear benefit in quantum efficiency when augmented with microlenses. Indeed, microlenses can be used to redirect photons initially impinging on the surrounding pixel electronics into the photosensitive surface/volume of the photosensitive device, which dramatically increases the external quantum efficiency – the effective fill-factor. We report the design, deposition, optical characterization, and reliability assessment of such microlenses for demanding applications.