Ultrafast response (∼2.2 ps) of ion-irradiated InGaAs photoconductive switch at 1.55 μm

A 2.2 ps full-width-at-half-maximum impulse response is measured for ion-irradiated InGaAs photoconductive switches triggered by ultrashort 1.55 μm laser pulses. Correspondingly, the −3 dB bandwidth is estimated to be ∼120 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 0.6×105 Ω/square. The photoconductive switch responsivity is found to exhibit a nonlinear dependence with optical power. The results are qualitatively interpreted.