Abstract: Integrated optics on silicon gives the opportunity to obtain microsystems for optical communications or sensor applications on one silicon chip. In all types of applications it is necessary to connect the waveguides to the photodetectors to transform the optical signal in an electrical signal. We have designed an opto-FET with a special structure that allow the optical coupling to a waveguide. A 3-D model was developed for the system: opto-FET-coupler-waveguide. The model takes into account two effects of the incident illumination: the variation of channel conductivity due to the carrier generation; the variation of channel depth due to the photovoltaic effect across the channel-gate junction. Also we studied the channel depth variation along the channel length (due to the potential variation) and along the channel width (due to the exponential decrease of optical power). The most important conclusion of the model is: in case of leaky-wave coupling of the opto-FET to a waveguide, the dependence of the photocurrent on optical power is practically linear, while in the case of uniform illumination it is logarithmic. The model was verified on a circuit integrated on silicon. !19
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