Subwavelength Metamaterials: From On-Chip Devices to Free-Space Beams

Silicon-on-insulator is rapidly becoming the optical integration platform of choice for applications ranging from telecom and datacom to sensing and quantum photonics. Silicon waveguides exhibit a strong index contrast, and can be produced via mature CMOS processeses with high-resolution lithography, enabling dense optical integration. However, few materials are compatible with these processes, severely limiting the degrees of freedom for device design. Subwavelength structures overcome this limitation by enabling metamaterials with adjustable optical properties: their subwavelength periodicity suppresses diffraction, allowing light to travel through them as it would in an equivalent homogeneous yet anisotropic material [1]. These properties have been extensively exploited to create low-loss devices with very broad bandwidths and compact footprints [1].