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Dynamic Broadband Chiral Response in Mid-infrared via Hybrid Phase-Change Metasurfaces



Author(s)

Yujie Zhang

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DOI:10.17265/2161-6213/2025.1-3.004

Department of Physics, China Jiliang University, Hangzhou 310018, China

Chirality is a widespread physical phenomenon in nature, but natural materials often exhibit weak chiroptical responses. Recent advances have used chiral metasurfaces to enhance these responses, with applications in holographic imaging, chiral molecule detection, and circularly polarized lasers. However, most chiral metasurfaces exhibit strong chiroptical responses only at fixed wavelengths, which limits their suitability for wavelength-tunable optical devices. We address this by designing a silicon-GST (silicon-Ge₂Sb₂Te₅) hybrid metasurface with asymmetric cross-shaped units that support multi-wavelength resonances, achieving broadband and dynamically tunable CD (circular dichroism). In the amorphous phase, GST enables CD > 0.7 in the range of 2,137 nm to 2,657 nm, with a PER (polarization extinction ratio) up to 38 dB. Upon transition to the crystalline phase, CD enhances with a redshift, and the sign of CD reverses. This enables dynamic wavelength tuning of broadband CD via the phase transition of GST.

Chirality, CD, metasurface, GST.