Ultrahigh Resolution Reconstructive Spectrometer Using a Disordered Cavity on Thin-Film Lithium Niobate

Integrated spectrometers offer unique advantages for spectral measurements in portable devices. While reconstructive spectrometers overcome the bandwidth-to-resolution trade-off of traditional designs, they often require complex electrical control or spatial sampling. Here, we propose and demonstrate a speckle-based spectrometer on thin-film lithium niobate, utilizing single-drive logic and a single photodetector. By leveraging the random reflections of a disordered multimode waveguide grating resonant cavity in a spiral waveguide, we achieve an ultrahigh resolution of 1 pm for sparse spectra and a theoretical resolution of 6 pm within a 5 nm spectral range, while maintaining an ultralow power consumption of 7.21 μW and an energy consumption of 0.453 μJ at a scan rate of 10 Hz. Furthermore, we demonstrate high-speed spectral recognition at 100 kHz under a low-voltage drive of ±5 V using a neural network algorithm. This work presents an energy-efficient, high-speed, and ultrahigh-resolution solution for spectral analysis.