Centimeter-scale suspended photonic crystal mirrors

Demand for lightweight, highly reflective and mechanically compliant mirrors for optics experiments has seen a significant surge. In this aspect, photonic crystal (PhC) membranes are ideal alternatives to conventional mirrors, as they provide high reflectivity with only a single suspended layer of patterned dielectric material. However, due to limitations in nanofabrication, these devices are usually not wider than 300 $\mu$m. Here we experimentally demonstrate suspended PhC mirrors spanning areas up to 10$\times$10 mm. We overcome limitations imposed by the size of the PhC and measure reflectivities greater than 90% on 56 nm thick mirrors at a wavelength of 1550 nm -- an unrivaled performance compared to PhC mirrors with micro scale diameters. These structures bridge the gap between nano scale technologies and macroscopic optical elements.