Abstract
Abstract Subwavelength structures such as subwavelength gratings (SWGs) and subwavelength metamaterials are capable of tailoring the optical properties of materials and controlling the flow of light at the nanoscale. The effective indices of the subwavelength structured strip and slab waveguides can be changed in a wide range by choosing an appropriate duty cycle or a filling factor of silicon, which provides an effective method to manipulate the optical field and achieve effective index matching for functional devices. Recent advances in nanofabrication techniques have made it possible to implement subwavelength structures in silicon strip and slab waveguides. Here we review various approaches used to design subwavelength structures and achieve exotic optical responses and discuss how these structures can be used to realize high-performance silicon photonic devices. Both one-dimensional SWG devices and two-dimensional subwavelength metamaterial devices are covered in this review, including subwavelength structure–based polarization handling devices, mode manipulation devices, and building blocks for integrated optical interconnects. Perspectives on subwavelength structured silicon photonic devices are also discussed.
Highlights
Optical waveguides are fundamental elements in integrated optics
We introduce the recent development of these three kinds of devices to illustrate how subwavelength structures can improve the performance of traditional silicon photonic devices
This article provides a comprehensive review of subwavelength structured silicon photonic devices
Summary
Optical waveguides are fundamental elements in integrated optics. Essentially, all integrated devices are built on waveguides. The high refractive index of silicon (~3.45) enables a high contrast relative to the surrounding cladding of a silicon waveguide and high confinement of the optical field These properties are desirable for achieving densely integrated photonic circuits. Powered by advanced fabrication capabilities, recent years have seen a boom in subwavelength research in 1D SWG devices and extending to twodimensional (2D) index control in waveguides. This provides more freedom in optical field manipulation in the space domain, enabling new functional devices (e.g. mode converters) or improving the performances of integrated devices.
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