Frozen Mode Regime in an Optical Waveguide With Distributed Bragg Reflector

TL;DR

This paper introduces a glide symmetric optical waveguide with a stationary inflection point that creates a frozen mode with zero group velocity, enhancing light-matter interaction for various optical applications.

Contribution

It demonstrates the formation of a stationary inflection point in a glide symmetric waveguide using chirped Bragg reflectors and coupling, advancing frozen mode regime understanding.

Findings

Existence of SIP confirmed via dispersion flatness and eigenvector coalescence.

Quality factor and group delay grow cubically with cavity length.

Frozen mode regime benefits optical delay, sensing, and lasing applications.

Abstract

We introduce a glide symmetric optical waveguide exhibiting a stationary inflection point (SIP) in the Bloch wavenumber dispersion relation. An SIP is a third order exceptional point of degeneracy (EPD) where three Bloch eigenmodes coalesce to form a so-called frozen mode with vanishing group velocity and diverging amplitude. We show that the incorporation of chirped distributed Bragg reflectors and distributed coupling between waveguides in the periodic structure facilitates the SIP formation and greatly enhances the characteristics of the frozen mode regime. We confirm the existence of an SIP in two ways: by observing the flatness of the dispersion diagram and also by using a coalescence parameter describing the separation of the three eigenvectors collapsing on each other. We find that in the absence of losses, both the quality factor and the group delay at the SIP grow with the cubic power of the cavity length. The frozen mode regime can be very attractive for light amplification and lasing, in optical delay lines, sensors, and modulators.