Optical diffraction phenomena around the edges of photodetectors: A simplified method for metrological applications

An optical method for simultaneous generation and detection of diffraction of light around the edges of photodetectors is reported in this paper along with its application for vibration sensing. The method makes use of an innovative illumination of light beam in which the laser light is made to incident at the interface between the active and opaque regions of a photodetector. Diffraction and induced interference occur together at the sensing area of the photodetector. The same photodetector responds to the dynamic intensity variations corresponding to the diffraction induced interference pattern and concurrently generates a dynamic electrical output. Comparing to the established diffraction techniques employing edges, the proposed method is simple to implement and extends the measurement applications. The experimental results obtained here verify the efficacy of the proposed method indicating its suitability for a novel class of sensors to be employed in practical circumstances.