High-speed and high-resolution interrogation of a silicon photonic microdisk sensor based on microwave photonic filtering

High-speed and high-resolution interrogation of a silicon photonic microdisk sensor based on microwave photonic filtering and advanced signal processing is proposed and experimentally demonstrated. An integrated microdisk resonator (MDR) with a high Q factor is used as a sensor which is interrogated by incorporating the MDR into a microwave photonic filter (MPF) consisting of a laser source, a phase modulator (PM), the MDR, and a photodetector (PD), with the central frequency of the MPF being a function of the resonant wavelength of the MDR. A broadband linearly chirped microwave waveform (LCMW) is applied to the input of the MPF to generate a filtered microwave waveform. By measuring the temporal location of the filtered microwave waveform, the sensing information is revealed. To increase the signal-to-noise ratio (SNR) of the filtered microwave waveform, a phase-only filter (POF) realized based on the LCMW is correlated with the filtered microwave waveform, to generate a compressed pulse, which is filtered using a Hamming window to remove the noise and recorrelated with the POF to recover the filtered microwave waveform. Since the SNR is significantly increased, the interrogation accuracy is improved. The use of the proposed sensor for temperature and refractive index (RI) sensing is performed. The experimental results show that the sensor has a sensitivity of 76.8 pm/°C and a resolution of 0.234 °C as a temperature sensor, and a sensitivity of 33.28 nm/RIU and a resolution of 1.32 × 10^-3 RIU as an RI sensor. The interrogation speed is as high as 100 kHz.