Development and implementation of a configurable quadrant photodetector

Position sensitive detectors (PSDs), used in high-end biotechnology, are based on optical sensors built over quadrant photodetectors and active pixel sensors. These devices are intended to measure slight movements of a laser spot. Quadrant photodetectors (QD) are, by far, the best approach in terms of resolution and noise, but require complex and expensive micropositioning machinery to perform sensor alignment with the incoming laser spot. Active pixel sensors (APS) are more versatile devices that can virtually align with the spot by means of device configuration. However, due to its intrinsic digital nature, the SNR and resolutions are degraded in APS. In this article, a new type of device called configurable quadrant photodetector (CQD) is presented. It combines the analog operation of the QD with the configurability of the APS, by means of combining photodetector elements with analog switches in a matrix-shaped architecture. A prototype has been designed, fabricated, and tested, and its electrical characterisation is presented.