High‐speed focus‐induced photoresponse in amorphous silicon photodetectors for optical distance measurements

The Focus‐Induced Photoresponse (FIP) enables 3D sensing capabilities by evaluating the irradiance dependent non‐linear detector response in defect‐based materials. Since this advantage is intricately associated to a slow response, the electrical bandwidth of previous FIP sensors is limited to a few kHz only. We report the FIP in amorphous silicon pin photodiodes and propose a sensor read out based on a harmonics analyses. We achieve modulation frequencies of 500 kHz and a non‐linear beat frequency detection up to at least 3.5 MHz, surpassing the bandwidth of state‐of‐the‐art architectures by at least a factor of 175. The FIP sensors further achieve signal‐to‐noise ratios of ∼50 dB, depth resolutions of at least 5.4 mm at 126 cm and a DC FIP detection limit of 1.3 µW/mm 2 .