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.