Advanced circular dichroism measurements with coherent circular polarization switching in dual-comb spectroscopy

We propose a novel method for measuring circular dichroism (CD) using polarization-modulated dual-comb spectroscopy (PM-DCS). This method utilizes two tightly phase-locked optical frequency combs to realize rapid and precise polarization modulation, eliminating the need for mechanical polarization modulators, and achieves high-speed, high-precision control of the polarization states. The experimental results demonstrated successful polarization switching between left- and right-circularly polarized light, enabling accurate detection of the CD spectra. Moreover, this method supports customizable polarization switching, realizing applications such as simultaneous circular-linear dichroism measurements. Our findings offer a pathway for high-sensitivity, broadband, and dynamic polarization measurements, extending applications in the analysis of chiral materials, particularly in the fields of chemistry, biology, materials science, and device characterization, where the ability to perform real-time high-sensitivity measurements is essential.