ThermoPix: an electronic-photonic temperature sensor array with microsecond row readout

This paper presents ThermoPix, a CMOS-compatible electronic–photonic architecture for high-spatial-resolution temperature sensing. The proposed system converts temperature-induced wavelength shifts in a photonic interferometric sensor into timing information that can be processed by CMOS circuitry. We use a valley photonic crystal Mach–Zehnder interferometer (VPC-MZI) as the sensing element, whose temperature-dependent spectral response is detected using an integrated waveguide photodetector and translated into a time-varying photocurrent. A CMOS readout circuit employing a phase-transition-material device performs threshold detection and generates a timing signal corresponding to the temperature-dependent crossing event. Circuit-level simulations yield a temperature sensitivity of 3.12 ns/K, a row readout time of 2 µs, and a circuit-level sensing power–delay product (PDP) of 0.152 fJ. The 3.33 ns timing quantization corresponds to a nominal temperature resolution of 1.07 K, while Monte Carlo analysis including process and laser wavelength variations yields a post-calibration MAE of 0.49 K and RMSE of 0.66 K. The required optical power per photonic cell is 150 nW, enabling energy-efficient array operation without requiring cooling or special environmental arrangements. We also present alternative photonic layer architectures for optical power distribution across the array. In one approach, we use different tap ratios along the row, while the other uses identical tap ratios with bidirectional excitation. The resulting average photonic cell pitches are 23.26 μm and 38.52 μm, respectively. These simulation and variation results indicate the potential of the proposed ThermoPix architecture for scalable integrated temperature sensing arrays that combine photonic sensing elements with CMOS-compatible timing-based readout.