Birefringent response of graphene oxide film structurized via femtosecond laser

In-plane birefringent materials present an effective modulation of the optical properties and more degrees of freedom for the signal detection in low dimension, and thus remain a hot topic in realizing the integrated, miniature, and flexible devices for multiple applications. Here, the artificial in-plane birefringence properties have been successfully achieved on a graphene oxide film by a novel femtosecond laser lithography method, which provides a high-speed, large-area, and regular subwavelength gratings (~ 380 nm) fabrication and photoreduction. The obtained sample manifests an evident optical birefringence (~ 0.18) and anisotropic photoresponse (~ 1.21) in the visible range, both of which can be significantly modulated by either the structural morphology or the degree of oxide reduction. Based on the analysis of effective-medium theory and measurements of angle-resolved polarized Raman spectroscopy, the artificial in-plane birefringence is originated from various optical responses of the periodic subwavelength structures for the incident light with different polarization states. This technique shows great advantages for the fabrication of integrated in-plane polarization-dependent devices, which is expected to solve the problems in this field, such as the deficient selection of materials, complex design of micro/nanostructure, and inflexible processing technology.