Integrated photonic materials for the mid-infrared

While silicon photonic integrated circuits for the near-infrared (IR) telecommunication band have attracted great research interest in the past decade, recent advances offer opportunities to extend the operational wavelength to the mid-IR (2.5-20 mu m) for free space communications, sensing, environmental monitoring and much more. In this study, we will comprehensively review the current status of materials available for mid-IR waveguides and waveguide integrated photodetectors, with a few application oriented examples to illustrate the technological importance and significant growth opportunity for integrated photonics in the mid-IR regime. However, this wavelength regime also presents new material design and fabrication challenges. Therefore, we will discuss the critical issues prior to commercialization and will briefly summarize the outlook on future research topics along with opportunities

Subwavelength integrated photonics

In the late nineteenth century, Heinrich Hertz demonstrated that the electromagnetic properties of materials are intimately related to their structure at the subwavelength scale by using wire grids with centimetre spacing to manipulate metre-long radio waves. More recently, the availability of nanometre-scale fabrication techniques has inspired scientists to investigate subwavelength-structured metamaterials with engineered optical properties at much shorter wavelengths, in the infrared and visible regions of the spectrum. Here we review how optical metamaterials are expected to enhance the performance of the next generation of integrated photonic devices, and explore some of the challenges encountered in the transition from concept demonstration to viable technology