Lasing oscillation condition and group delay control in gain-assisted plasmon-induced transparency

TL;DR

This paper investigates a gain-assisted plasmonic waveguide with detuned resonators, revealing conditions for lasing oscillation and demonstrating enhanced group delay, high transmittance, and narrow linewidth in the amplification regime.

Contribution

It analytically derives the lasing oscillation condition and explores group delay control in gain-assisted plasmonic systems, highlighting advantages over passive and loss-compensated cases.

Findings

Lasing oscillation coefficient varies quadratically with frequency detuning.

Amplification regime achieves large group delay and high transmittance.

Narrow linewidth is maintained in the amplification regime.

Abstract

A gain-assisted plasmonic waveguide with two detuned resonators is investigated in the plasmon-induced transparency window. Phase map is employed to study power transmittance and group delay for varying gain coefficients and frequency detunings of the two resonators. The gain coefficient for lasing oscillation condition is analytically shown to vary quadratically with the frequency detuning. In the amplification regime below the lasing threshold, the spectrum implies not only large group delay, but also high transmittance and narrow linewidth. This is in contrast to those in the loss-compensation regime and the passive case in which there always exists a trade-off between the linewidth and the peak transmittance.