TiOx/Ti/TiOx Tri-Layer Film-Based Waveguide Bolometric Detector for On-Chip Si Photonic Sensor

In this article, we experimentally demonstrate an on-chip optical power monitoring at the near-infrared spectral region (1520–1600 nm) using the waveguide bolometric detector with a TiO_x/Ti/TiO_x tri-layer film based on the silicon-on-insulator (SOI) platform. For the incident light absorption causing a heat generation, a heavily doped ( ${n}^{+}$ ) Si waveguide is introduced to utilize the mechanism of free-carrier absorption (FCA), and a metal (Au) strip is deposited onto the ${n}^{+}$ Si waveguide to further enhance the light absorption. A bolometric material of TiO_x/Ti/TiO_x tri-layer film is integrated for the thermal-to-electrical conversion. As a result, it exhibits superior performances, which are the temperature coefficient of resistance (TCR) of −2.296%/K and the maximum sensitivity of −46.45%/mW with a low wavelength-dependency. In addition, a rapid response time is obtained with the rise/fall time of $24.6 ~\mu \text{s}/29.8 ~\mu \text{s}$ , which is enough for a variety of optical sensing applications. This work demonstrates the waveguide-based bolometric photodetection using the FCA effect, for the first time to our knowledge, which can also be simply extended for the operation wavelength range to the mid-infrared (MIR) spectral region for bio/chemical sensing applications.