Breakthroughs in Photonics 2014: Relaxed Total Internal Reflection

TL;DR

This paper discusses the concept of relaxed total internal reflection, enabling better light confinement in photonic devices through engineered anisotropic media, overcoming diffraction limits without metals.

Contribution

Introduction of relaxed total internal reflection using anisotropic media to improve nanoscale light confinement in photonics.

Findings

Enhanced light confinement in dielectric media.

Comparison with plasmonic and photonic crystal waveguides.

Potential for integration in nanoelectronics and nanophotonics.

Abstract

Total internal reflection (TIR) is a ubiquitous phenomenon used in photonic devices ranging from waveguides and resonators to lasers and optical sensors. Controlling this phenomenon and light confinement are keys to the future integration of nanoelectronics and nanophotonics on the same silicon platform. We introduced the concept of relaxed total internal reflection in 2014 to control evanescent waves generated during TIR. These unchecked evanescent waves are the fundamental reason photonic devices are inevitably diffraction-limited and cannot be miniaturized. Our key design concept is the engineered anisotropy of the medium into which the evanescent wave extends thus allowing for skin depth engineering without any metallic components. In this article, we give an overview of our approach and compare it to key classes of photonic devices such as plasmonic waveguides, photonic crystal waveguides and slot waveguides. We show how our work can overcome a long standing issue in photonics nanoscale light confinement with fully transparent dielectric media.