Photonic crystal mirrors: Fundamental components for integrated photonic crystal optical MEMS

Two-dimensional photonic-crystal (PC) slabs consist of a periodic lattice of air holes introduced into a dielectric layer such as polysilicon. We can control the optical spectra of 2-D PC slabs by adjusting their geometries such as hole radius or shape, pitch, and the slab thickness. By doing this, we can implement a broadband mirror on a single dielectric membrane, which achieves 100% reflectivity. High reflectivity, structural compactness, and design flexibility make such a broadband dielectric 2-D PC mirror a very attractive component for optical MEMS devices such as tunable filters, position sensors, and scanners.;The optical spectra of 2-D PC mirrors can be further improved by controlling their surface quality. Hydrogen anneal is a standard way of reducing the roughness of etched silicon surfaces. We show that silicon migration due to hydrogen anneal can be used to improve the optical spectra of PC mirrors by smoothing the rough interfaces and increasing the uniformity of PC holes. In particular, we apply hydrogen anneal on a 2-D PC mirror that was processed on silicon substrates by isotropic silicon etching. As a result, the reflectivity of the 2-D PC mirror increases and its polarization dependence decreases.;We demonstrate that 2-D PC mirrors have attractive properties as micro-mirrors for MEMS. The surface quality control brings improvements to their optical properties, implying a brighter future for integrated PC MEMS devices with high performance.;A broadband dielectric 2-D PC mirror has higher reflectivity than metal mirrors at optical communication wavelengths because of its low material loss. In addition, it has been theoretically shown that a broadband dielectric 2-D PC mirror implemented in a single dielectric membrane can achieve reflectivity higher than that of Distributed Bragg Reflector (DBR) mirrors, which consist of several pairs of dielectric layers. This high reflectivity results from guided resonance modes of the PC mirror. We develop a fabrication process for a broadband PC mirror, which can be easily integrated with fabrication processes for MEMS devices. The fabricated PC mirror achieves reflectivity higher than 90% around 1550 nm. It has small polarization and moderate angular dependences.