Out-of-plane motion of 260-nm thick guided-mode resonant grating filter controlled by four micro-thermal actuators

We fabricate a wavelength-selective variable-reflection filter driven by four bimorph actuators to realize out-of-plane motion in parallel. The actuators are designed using a simple calculation model for controlling position of the filter anywhere within air gap fabricated in between the filter and silicon substrate. In order to keep a 260-nm thick filter flat, the filter and actuators are stabilized by torsion bars each with a width and length of 3 and 10 μm, respectively. Displacement, flatness and surface roughness of the fabricated filter are measured. As a result, 10.1 μm of the displacement is obtained at 24.7 mW input power using a 70-μm length actuator. Besides, the filter with a flat surface and roughness of 0.08 μm is obtained. Reflectivity of the filter consisting of 800-nm period grating is also measured.