  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.
