Dispersion-engineered low-crosstalk metasurface for mid-infrared snapshot multi-spectral imaging

Infrared spectroscopy covers the "fingerprint" region of molecular vibrations, offering non-destructive detection capabilities and excellent anti-interference performance, thereby providing robust technical support for material identification and target recognition. However, conventional infrared spectral imaging systems typically rely on complex wavelength separation or time-division filtering schemes, leading to challenges such as low energy utilization efficiency, inadequate system stability, and limited integration capabilities. Here, we present a dispersion-engineered metasurface with a quadratic phase profile, which maps spectral information directly onto spatial coordinates for single-shot spatial-spectral data acquisition. Additionally, we introduce a novel, to the best of our knowledge, wavelength-dependent focal position function that achieves broadband tunable focusing across the mid-wave infrared (MWIR) range. Based on this design, we demonstrate four-band detection capability in the MWIR range (3-5 μm), achieving peak efficiencies of 28%, 52%, 61%, and 49% at four distinct pixels, with an average efficiency of 54%. The broadband-efficient focusing capability effectively suppresses spectral crosstalk, yielding a maximum isolation of 48 between the four bands. This is the first demonstration of pixel-level-multiplexed spectral detection in the mid-infrared regime, offering a promising pathway toward compact, energy-efficient, and real-time multi-spectral infrared detection technologies.