Ultrafast response (similar to 2.2 ps) of ion-irradiated InGaAs photoconductive switch at 1.55 mu m

A 2.2 ps full-width-at-half-maximum impulse response is measured for ion-irradiated InGaAs photoconductive switches triggered by ultrashort 1.55 mum laser pulses. Correspondingly, the -3 dB bandwidth is estimated to be similar to120 GHz. Measurements of the electrical signals delivered by photoconductive switches are performed using an electro-optic sampling technique. As is shown, the ion irradiation reduces the carrier lifetime to less than 1 ps. The sheet resistance is 0.6x10(5) Omega/square. The photoconductive switch responsivity is found to exhibit a nonlinear dependence with optical power. The results are qualitatively interpreted. (C) 2003 American Institute of Physics.