Conference Series, The 3rd International Photonics and OptoElectronics Meeting (POEM2010), Wuhan, China, 276, pp. 012140, 2011. Analysis of an optimized lateral effect sensing detector with low-nonlinearity S Olyaee 1,2 , A Bidrang 2 , M Izadpanah 2 1 Head of Nano-Photonics and Optoelectronics Research Laboratory (NORLab), S_Olyaee@srttu.edu 2 Faculty of Electrical and Computer Engineering, Shahid Rajaee Teacher Training University (SRTTU),Iran Abstract- In this paper, current time delay mode has been compared to the voltage difference mode in the lateral effect position sensing detectors. Several advantageous features unique to the current time delay mode are: more linear response, independent position from magnitude and frequency, background illumination-independent response, and no need to signal normalization. Also, the comparison between current time delay and voltage difference modes in several lateral effect position sensing detectors (LEPSDs) has been studied. Key words: Lateral effect position sensing detectors, voltage delay, time delay, range finding. 1. Introduction Position-sensing detectors are known as simple photodiodes capable of detecting centroid of light beam position. There is an important feature for PSDs due to no need to have contact with specimen being inspected. Position information is calculated from photo-current signal magnitude by these detectors. For designing these detectors with high resolution, the most effective method is to create Schottky barrier with surface diffusion method [1]. When an optical spot incidents on the detector surface, electric charge is generated proportional to the light intensity at the collision region. Electric charge passes from resistive layer and collected as the light current by electrodes. It's divided between two terminals with an inverse relation to the distance of optical spot from electrodes. Applying full reverse bias to LEP, the thickness of depletion region increases, diffusion current decreases to zero and surface regeneration is avoided. To achieve best performance quality, the photodiode should be able to absorb maximum photons in it's depletion region. It means photons should not be absorbed anywhere except depletion region before passing it. So, when a p-n junction is illuminated by the optical spot, little energy is saved in space charge region. Under reverse bias, this light energy will move horizontally to the electrodes mounted next to the junction. This phenomenon is called" lateral effect" presented by Schottky in 1930, but has not been noticed much. In 1959, Walmark used this theory practically. He designed a device including a