Ultra-compact on-chip snapshot chiral spectral imaging with dispersion-engineered chiral metalens

Abstract Chiral spectral imaging techniques, in contrast to conventional intensity imaging, can provide rich information on the multiscale chirality and spectrum of objects. However, conventional methods often require complex optical systems and multiple shots to achieve this, making the process both cumbersome and time-consuming. Here, we present an ultra-compact on-chip chiral spectral imaging (CSIM) system enabled by a dispersion-engineered chiral metalens (DECM). The meta-atoms can independently control the phase and phase dispersion of orthogonal circular polarization states through the combination of propagation and geometric phases of chiral meta-atoms. Then, the metalens generates two images on opposite sides of the image plane, corresponding to different polarization states, while images at different wavelengths are laterally separated in the focal plane. Consequently, the DECM can be integrated with a CMOS sensor, enabling the simultaneous acquisition of circular dichroism and spectral information in a single snapshot, achieving a high spectral resolution of 10 nm and an extinction ratio exceeding 6 dB. Our results represent a significant advancement toward the integration of multi-dimensional light field perception systems.