Polarization‐Independent Dichroic Beam Splitter Using All‐Dielectric Metasurface at Near‐Infrared Wavelength

ABSTRACT

In the modern era, metasurfaces have gained significant attention for their potential in light manipulation, including focusing, bending, blocking, and wavefront control, as well as designing ultra‐thin optical components. Metasurfaces comprising high‐index dielectric nanostructures have emerged as an inevitable platform for high‐performance flat optical devices. Among these, a dichroic beam splitter is a crucial optical component that selectively reflects and transmits light based on the wavelength, enabling precise control over beam routing. In this work, we demonstrate a polarization‐ and angle‐tolerant metasurface‐based dichroic beam splitter that operates as a harmonic separator, efficiently separating the fundamental wavelength (1560 nm) and its second harmonic (780 nm) wavelength. Using a 2D array of gallium phosphide (GaP) cylindrical nanostructures, the proposed device exhibits high transmission at 1560 nm while simultaneously achieving near‐unity reflection at 780 nm over a bandwidth of approximately 168 nm. This device finds application in fluorescence microscopy, multispectral imaging and advanced laser systems due to its precise spectral selectivity in the near‐infrared regime. Beyond these applications, our result highlights a versatile design route to compact dichroic beam splitters that can replace conventional bulky optical devices, with promising prospects for on‐chip photonics and portable optical elements.