Operational regimes of lasers based on gain media with a large Raman scattering cross-section

TL;DR

This paper explores new operational regimes of lasers using gain media with large Raman scattering cross-sections, revealing conditions for stable, joint phonon-photon oscillations or chaos influenced by electron-phonon coupling.

Contribution

It introduces a theoretical analysis of laser regimes in media with strong electron-phonon coupling, identifying a critical Fr"ohlich constant and multiple stable dynamical states.

Findings

Below a critical Fr"ohlich constant, only conventional laser operation occurs.

Above the critical value, new regimes including joint phonon-photon oscillations or chaos emerge.

Multiple stable dynamical regimes depend on initial conditions and system parameters.

Abstract

We report on unusual regimes of operation of a laser with a gain medium with a large Raman scattering cross-section, which is often inherent in new types of gain media such as colloidal and epitaxial quantum dots and perovskite materials. These media are characterized by a strong electron-phonon coupling. Using the Fr\"ohlich Hamiltonian to describe the electron-phonon coupling in such media, we analyze the operation of the system above the lasing threshold. We show that below a critical value of the Fr\"ohlich constant, the laser can only operate in the conventional regime: namely, there are coherent cavity photons but no coherent phonons. Above the critical value, a new pump rate threshold appears. Above this threshold, either joint self-oscillations of coherent phonons in the gain medium and photons in a cavity or a chaotic regime are established. We also find a range of the values of the Fr\"ohlich constant, the pump rate, and the resonator eigenfrequency, in which more than one dynamical regime of the system is stable. In this case the laser dynamics is determined by the initial values of the resonator field, the active medium polarization, the population inversion, and phonon amplitude.