Reflective metamaterial polarizer enabled by solid-immersion Lloyd's mirror interference lithography

Abstract

Metamaterials with induced form birefringence arising from orderly arrangements of subwavelength structures can realize effective refractive indices that do not exist in nature. Using lithographically-defined thin film or multilayered metasurfaces, such form birefringence can be used for polarization and phase control in thin-film elements. In this work, the authors experimentally demonstrate a highly birefringent omnidirectional broadband reflective metamaterial polarizer (RMP), fabricated using a solid-immersion Lloyd's mirror interference lithography (SILMIL) technique. This technique can create 55 nm half-pitch gratings, up to 200 nm tall, using single 405 nm exposures. Angle-resolved reflection spectra of SILMIL-fabricated subwavelength dual-silver grating RMPs exhibit excellent omnidirectionality over a broad spectral bandwidth in the optical range. The behavior and mechanism of the double-layer RMP has been analyzed with finite-difference time domain and rigorous coupled wave analysis simulations, showing coupling between excited surface plasmon polaritons and multiple Fabry–Perot resonances. Furthermore, the authors propose via simulation that by switching from a dielectric resonator to a metallic resonator, the SILMIL technique can be used to fabricate dual-layer thin-film metamaterials that have the capability of phase retardation control, providing a new scheme for reflective thin-film waveplates.