Transmission Modulation of Micro Retarder Using Out-of-Plane Thermally-Driven Au Nanograting

Abstract

A reconfigurable transmittance modulation device for Au nanograting retarder that consisted of out-of-plane thermally-driven grating was designed, fabricated, and demonstrated. In this study, an Au nanograting that is known to exhibit giant birefringence was constituted by integrating MEMS thermal actuators. The thermally-driven grating was made of Au/SiO₂ bimorph beams that period and slit width are 800 nm and 400 nm, respectively. The device is fabricated on a glass substrate with embedded Si as a sacrificial layer. The gap between the grating and the substrate is changed by applying driving current, and transmittance was changed affected by Fabry-Pérot interference. Transmittance peak wavelength for TE polarization was shifted up to 40 nm keeping the retardation of the Au nanograting. A calculation model of transmittance applying multilayer interference was proposed and demonstrated its effectiveness in TE polarization. By optimizing the design dimensions of the Au nanograting, it is expected to realize a microscale waveplate capable of transmittance modulation.