Pulse propagation through a dispersive intracavity medium

TL;DR

This paper presents a theoretical method to analyze pulse propagation inside a dispersive intracavity medium, revealing superluminal effects and interference phenomena crucial for high-bandwidth data buffering.

Contribution

It introduces a novel approach to model pulse behavior inside a cavity with a dispersive medium, overcoming limitations of transfer function methods.

Findings

Pulse propagates superluminally inside the cavity.

Interference patterns form immediately after pulse entry.

No delay or distortion for vanishing group index.

Abstract

In this paper, we study theoretically the behavior of a pulse as it propagates through an intracavity fast-light medium. The method of using a transfer function to determine a pulse after it passes through a cavity is well known. However, this approach cannot be used to determine the behavior of the pulse inside the cavity. To circumvent this constraint, we use an approach that starts by finding a self-consistent solution for a monochromatic field of infinite spatial and temporal extents, and determine its amplitudes before, inside, and after the cavity. We then construct a Gaussian input pulse by adding a set of these waves, properly phased and weighted, to represent a moving pulse before the cavity. Adding these waves at various time intervals then yields the complete spatial profile everywhere, including before, inside and after the cavity. We first confirm the prediction of this model by analyzing the behavior of a pulse passing through an empty cavity, and comparing the prediction of the output with the one produced by the transfer function method. We then apply the technique to a cavity containing a fast-light medium. The resulting model allows us to visualize the behavior of the pulse as it propagates superluminally inside the cavity, and interferes with itself through multiple bounces. For a vanishing group index, an interference pattern is formed immediately after the pulse enters the cavity, with an output pulse emerging with no time delay or distortion. The results obtained here illustrates the physical mechanism behind pulse propagation through a white light cavity, a process we have proposed earlier for realizing a high bandwidth, long delay data buffering system