Detector noise induced by ultra-fast laser

Irradiation of a photodetector by very short laser pulses was presented as a technique that can remotely alter detector's performance [1]. Recent experimental data demonstrated that energy of femto-second laser pulse transforms almost entirely into thermal energy. Thermal energy may inflict long-lasted changes in the detector that based on lattice structural changes or disorder [2], and semiconductor compound heats up. Those changes may result in detector's responsivity change - to induce a spectral shift that may prevent detection at specific wavelengths and in overall noise increase. Both phenomena may contribute into ultimately non-compensated losses in detectivity. Effect completely reversible if energy level is below energy threshold for melting E th -therefore integrity of the photodetector is protected during the alteration. In the paper we demonstrate that much longer laser pulses can be used to inflict similar effects in photo- detectors. Laser pulse can be arranged in such a way that combination of energy per pulse, repetition rate, pulse dwell time and duty cycle will not destroy detector or generate signal, but just inflict responsivity shift and noise variance increase. Technique of noise generation by ultra-fast laser is described and analyzed in details with respect to newly presented experimental data.