# Switching between positive and negative group delay of the optical pulse refection from layer structures with a Graphene sheet

## TL;DR

This study demonstrates how the reflection of optical pulses from layered structures with graphene can be tuned between positive and negative group delays by adjusting graphene's properties, enabling advanced control of pulse propagation.

## Contribution

It introduces two mechanisms—resonances and surface plasmon excitations—for tunable control of optical pulse delays in graphene-layered systems, advancing optical device design.

## Key findings

- Reflected group delays can be tuned from positive to negative.
- Tuning Fermi energy and temperature controls delay properties.
- Mechanisms involve resonances and surface plasmon excitations.

## Abstract

In this paper, we investigate the propagation of the light pulse reflected from the layer system with a graphene layer. We show a tunable transition between positive and negative group delay of the optical pulse reflection in such a layered system controlled by the properties of the graphene layer, and reveal two mechanisms to control the propagation properties of the light reflected from such systems. It is demonstrated that the reflected group delays are greatly tunable from positive and negative values in both mechanisms of resonances and the excitations of the surface plasmon resonances, which are adjusted by tuning the Fermi energy and temperature of the graphene layer. Our results are helpful to control the pulse propagations and are useful for design of graphene-based optical devices.