Selection of parameters of position-sensitive photodetectors for measurement of lateral displacements of laser beams

Conclusions

1. Theoretical relationships have been obtained for the design and practical application of devices using position-sensitive photodetectors. 2. It has been found that for maximum sensitivity it is sufficient that the photodetector size is twice as large as the spot radius (Ã ≈ 2). It has been proved that maximum nonlinearity of the positional response is observed for small reduced dimensions of the photodetector (Ã) and is of the order of$\tilde r_o^2$ ($\tilde r_o$ being the reduced radial displacement of the spot); the minimum nonlinearity occurs for Ã>2 where it does not exceed$\tilde r_o^2 /2$. 4. The threshold displacement sensitivity has been evaluated as being of the order of several hundredths of a micrometer (for a spot radius equal to 1 cm).