NOISE-ANALYSIS FOR POSITION-SENSITIVE DETECTORS

A study of the different noise sources in a position sensitive detecto r (PSD)-transimpedance amplifier (TIA) sensing system is presented and the dominant noise sources are identified, The effect of these noise sources on the position detection capability of the sensing system is analyzed, An expression derived for the position resolution of the pha se method of position detection reveals the position resolution depend s inversely on the modulation frequency of the light source and the sq uare of the amplitude of the currents flowing through the metal electr odes, and is dependent on the position of the incident light beam, Sim ulation results show that the best achievable position resolution is a t the center of the PSD and becomes worse as one moves away from the c enter toward the edges, Compared to the 4 nm/root Hz position resoluti on that is achievable using the amplitude method of position detection , the phase method of position detection provides a resolution of 9 nm /root Hz and 6 nm/root Hz corresponding to a modulation frequency of 5 0 kHz and 70 kHz respectively.