A light-transmitting two-dimensional photodetector array using a-Si pin photodiodes and poly-Si TFT's integrated on a transparent substrate

A light-transmitting two-dimensional photodetector array (32/spl times/32 cells) using amorphous silicon (a-Si) pin photodiodes and polysilicon (poly-Si) thin film transistors (TFT's) integrated on a transparent substrate has been developed for use in a free-space optical switching network. The fabrication and the characteristics of the photodetector array are discussed. With driving circuits and sensing amplifiers, this photodetector array shows a minimum detectable power of /spl minus/25 dBm and an insertion loss of 0.4 dB for an incident optical beam with a diameter of 550 /spl mu/m. By monitoring the positions and the states of input optical beams, this photodetector array can be used to control the optical paths in photonic switching systems, such as a 1024-input-port optical concentrator.<
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