Free carrier absorption-assisted photodetection using a waveguide-integrated bolometer with flat spectral response for integrated optical sensors

We experimentally demonstrate the free-carrier absorption (FCA)-assisted photodetection using a waveguide-integrated bolometer on the silicon-on-insulator (SOI) platform at the near-infrared range (1520-1620 nm). A heavily-doped silicon (n + Si) plays a role as an efficient light absorption medium, which exploits the mechanism of FCA in Si. For the thermal-to-electrical conversion, a bolometric material of TiOx/Ti/TiOx tri-layer film is integrated onto the n + Si. It offers a sensitivity of -26.75 %/mW with a highly flat spectral response. In addition, a clear on/off bolometric response with the 1 kHz-modulated optical signal was obtained with the rise and fall times of 24.2 μs and 29.2 μs, respectively, which is enough for diverse sensing applications.