Plasma effects in silicon detectors and the Two Photon Absorption Transient Current Technique

Two Photon Absorption-Transient Current Technique (TPA-TCT) is a new pulsed laser method for high resolution mapping of the electric field in solid state particle detectors. As it uses strongly focused ultrashort infrared laser pulses in the femtosecond regime, plasma effects need to be contended with. Plasma Effects are responsible for the increase of the current pulse duration, measured as response of the detector to the laser pulse. Based on a mathematical model originated from the analyses of plasma effects during ion detection with silicon semiconductor detectors, we determine the charge collection time increase due to plasma effects. The model is verified with data obtained from TPA-TCT experiments in silicon PIN diodes. The agreement between model and experiment enables to predict the maximum admissible laser pulse energy to avoid plasma effects.