Dual‐Wavelength Polarization Multiplexed Single‐Layer Metalens for Ultracompact STED Microscopy

Abstract High‐resolution imaging techniques have revolutionized the observation and analysis of features or structures across various disciplines, including nanotechnology, material science, and biomedical imaging. Stimulated emission depletion (STED) microscopy is a groundbreaking super‐resolution imaging approach that overcomes the diffraction limit of traditional microscopy techniques, enabling visualization of nanoscale sub‐cellular characteristics with remarkable resolution and precision. However, the requirement of precise alignment of multiple laser beams, the use of complex and bulky optical system, and high operational costs make the system challenging, difficult to maintain and less accessible. Development of high‐performance, ultracompact, lightweight optics is thus necessary to realize a robust, efficient and accessible high‐resolution optical system. Here, a single‐layer dual‐wavelength polarization multiplexed metalens that shapes the depletion beam and achieves achromatic focusing of the excitation and depletion beams in orthogonal polarization states at the focal plane for STED microscopy is proposed. The optical performance of the metalens at the focal plane is characterized, and the achievable resolution is numerically calculated. Leveraging the benefits of planar and ultracompact architecture, high integrability, the proposed metasurface‐based approach establishes a stable single‐beam STED microscopy system that can democratize super‐resolution imaging, therefore expanding accessibility and applicability across various scientific domains.