Applied Nanophotonics, Liquid Crystals and Biomedical Optics

The time-delay (TD) mode of operation of lateral effect position sensors (LEPSD) is investigated and compared with the voltage-difference mode. A normalized dynamic equation describing the lateral photovoltage spatial and temporal distribution is derived and solved in response to a variety of beam shapes and time modulations. The normalization of the dynamic equation allows description of the characteristics of a whole group of LEPSDs having the same ratio of series to shunt resistance. Several advantageous features unique to the TD mode are found: (1) Existence of operating frequencies where the response around the midpoint becomes perfectly linear. (2) The response becomes more linear and the dynamic range increases as the optical spot size increases. (3) The dynamic range increases with the operating frequency. (4) The TD response is not affected by the existence of background illumination. (5) No need for signal normalization.