Impulse response of a picosecond photodetector directly from power spectrum measurement

A technique for determining the ps impulse response of a photodetector from the observed power spectrum is developed analytically and demonstrated for the case of a very-high-speed high-efficiency GaAlAs/GaAs PIN photodiode with integral SMA-type electrical connector, subjected to 3-ps pulses from a mode-locked dye laser. The technique employs the Hurwitz factor commonly used in the analysis of electrical networks and in the synthesis of filters. In the sample measurement, a rise time of 19 ps and a fall time of 38 ps are determined. The need for electrooptic sampling devices with ps resolution to verify the present method is indicated.