SiC-SiO2 MEMS-DBR Based Widely Tunable Optical Filters Around 1550 nm with Narrow FWHM

Ever growing optical data transmission networks and miniaturization of spectroscopic equipment demand for small, energy efficient and mass-produced optical components. Here we present distributed Bragg reflector (DBR) mirror based widely tunable optical Fabry-Perot filters comprising a novel material combination namely, silicon carbide (SiC) and silicon dioxide (SiO 2 ) layers with refractive indices of 2.46 and 1.45, respectively. The resulting refractive index step of 1, provides high reflectivites (>99.5%) with wide stopbands of more than 300 nm [1]. Hence, large wavelength tuning range and a narrow full width at half maximum (FWHM) filtered signals can be produced. Structuring the dielectric layers by surface micromachining creates a free standing movable mirror supported by four beams. Due to inherent stress created during low-temperature plasma enhanced chemical vapor depositions (PECVD) we obtain a tunable stable plane concave resonator. In the end the cross section of a filter shows a fixed bottom DBR deposited on a silicon substrate, a tunable airgap and an electrothermally actuated top MEMS DBR with a gold electrode for heating current I MEMS . On the substrate backside where the filtered signal is exiting an anti-reflection coating is deposited.