Raman Effect in Non-Raman Lasers

This chapter investigates the impact of nuclear vibrations in active materials characterized by strong electron-phonon coupling on the amplification properties of conventional lasers. Traditionally, this effect is regarded as negligible, even in active media with pronounced electron-phonon interaction. However, our study reveals that active mediums with significant Raman cross sections may lead to unconventional laser behavior. The presence of robust electron-phonon coupling introduces novel regimes of laser dynamics, potentially transforming a laser into a coherent optical phonon generator. The analysis of the system operation above the conventional lasing threshold unveils the emergence of a new pump rate threshold, which arises above a critical value of the Fröhlich constant. Beyond this second threshold, depending on system parameters, the system may exhibit joint self-oscillations of coherent phonons in the gain medium and photons in a cavity or even chaotic behavior. Furthermore, we identify a range of Fröhlich constant and pump rate values where multiple stable dynamical regimes coexist. In such cases, the laser’s dynamics are uniquely determined by the initial conditions.