Position-Sensitive Photoreceivers: Sensitivity and Detectable Range of Displacements of a Focused Single-Mode Laser Beam

Analysis is given to advantages and drawbacks of methods for measuring laser beam center coordinates and determining a range and amount of linear beam displacements using a quadrant photoreceiver, CCD matrix, and dividing plates. It is shown that the quadrant photoreceiver method and the dividing plate method are most sensitive to displacements of a single-mode laser beam. The minimum detected displacement limited by the shot noise of the laser beam in the photoreceiver for a beam 4 µm in diameter is 3 × 10–14 m/Hz–1/2 with a possibility of detecting linear displacements down to 0.85 µm (dividing plate method). The measurement accuracy for the 100-µm-diameter laser beam is 2.5 × 10–13 m/Hz–1/2 with a possibility of detecting linear displacements down to 13 µm (quadrant photoreceiver method). It is shown that the accuracy of the CCD matrix method is 0.01 µm with a possibility of detecting linear displacements that is limited by the CCD matrix size.