Integrated-optic grating-scale-displacement sensor using linearly focusing grating couplers

An integrated-optic device was proposed for sensing displacement/position of a grating scale. The sensor is constructed by integrating a glass waveguide, a pair of linearly focusing grating couplers (LFGCs) and a pair of photodiodes (PDs) on a Si substrate. Two beams, radiated by the LFGCs from the sensor, overlap with each other on the grating scale. The beams diffracted by the grating scale interfere on the PDs, and the interference signals vary when the grating scale moves along its grating vector direction. The device was designed and fabricated, and the variation of output photocurrents was experimentally confirmed.<
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