Abstract
Optical spot position sensing performance of a silicon APD-QD (Avalanche Photo-Diode Quadrant Detector) is presented. The APD-QD is useful for measuring low power laser or optical beam spot position, since the detector is more sensitive than a photo-diode-QD. We measured the cross talk between cells as well as fundamental charactaristics which are required for position sensing. Signal-to-noise ratio and noise equivalent power (NEP) are calculated using results of the nose spectral density measurement. The effects of the cooled APD-QD at 77K are also presented.
