Computational reconstruction on-chip spectrometer based on reconfigurable silicon photonic filters

<sec>Spectroscopic analysis technique is an indispensable tool in many disciplines such as biomedical research, materials science, and remote sensing. Traditional benchtop spectrometers have several drawbacks; bulky, complex, and expensive, making them ineffective for emerging applications such as wearable health monitoring and Lab-on-Chip systems. Compared with bulky desktop spectrometers, integrated chip-level spectrometers find many applications in portable health monitoring, environmental sensing, and other scenarios. We design an on-chip spectrometer based on a silicon photonics platform. The device consists of a silicon photonic filter with a reconfigurable transmission spectrum.</sec><sec>By changing the transmission spectrum of the filter, the multiple and diverse sampling of the input spectrum can be obtained. Using an artificial neural network algorithm, the incident spectrum is reconstructed from the sampled signals. The reconfigurable silicon photonic filter is composed of intercoupled Mach-Zehnder interferometer and micro-ring resonator. The introduction of thermal-optic phase shifter facilitates the reconstruction of the transmission spectrum of filter. Through this approach, a response function encompassing diverse features of broad and narrow spectra can be obtained from a single reconfigurable filter, eliminating the need for a filter array and significantly reducing the footprint of the spectrometer.</sec><sec> Simulation results demonstrate that the designed device can achieve continuous and sparse spectrum reconstruction in a wavelength range of 1500–1600 nm, with a resolution of approximately 0.2 nm. On a test set composed of synthetic spectra, the calculated average RMSE for the reconstructed spectra is 0.0075, with an average relative error of 0.0174. Owing to the reconfigurable nature of the silicon photonic filter, this device exhibits the ability to flexibly adjust the number of sampling channels, thus enabling users to configure the chip according to specific application scenarios. This device possesses significant potential applications such as in wearable optical sensors and portable spectrometers.</sec>