High-resolution, broadband reconstructive spectrometer enabled by cascaded dispersion

Measuring spectrum with high resolution and broadband synchronously, which is vital to various applications, remains challenging. Here, we introduce a cascading dispersive reconstructive spectrometer (CDRS) that integrates an acousto-optic tunable filter (AOTF) and a multimode fiber (MMF) in tandem. The time-varying AOTF divides the broad spectrum with moderate dispersion, and the disordered MMF presents a fine dispersion by wavelength-dependent speckles. Consequently, a bandwidth-to-resolution ratio of 20,000 can be achieved, with a spectral resolution of 2 pm over a 40 nm range. Experimental results indicate that, compared to traditional speckle reconstructive spectrometers (RSs), the presented scheme reduces broadband spectral reconstruction errors by one order of magnitude. The all-fiber CDRS offers notable advantages, including wide bandwidth, high resolution, and a simplified design, making it well-suited for diverse spectral measuring scenarios.