Resonant cavities using nanostructured front mirror for efficient LT-GaAs photoconductor operating at λ=1.55 μm

We investigate optical resonant cavities using metallic mirror in order to increase the absorption in low-temperature-grown GaAs (LT-GaAs) based photoconductors operating at telecom wavelength. Two different semi-transparent front mirrors are compared: the first one is a thin gold layer whereas the second one consists of a gold periodic array. We show that the generated photocurrent is 3 times higher by using the gold grating as top mirror. A transient photoresistivity (R
_on
) around 5 Ω is achieved under 1.55 μm pulsed laser illumination. This work paves the way to efficient and reliable optoelectronics systems for GHz or THz waves sampling driven by 1.55 μm pulsed lasers.