Switchable Cascade Raman Lasing in a Tellurite Glass Microresonator

Abstract

Light transformations based on stimulated Raman scattering in microresonators with whispering gallery modes have tremendous potential for implementing compact, widely tunable, low-threshold coherent light sources attractive for applications. Search for new microlaser materials is of great interest since they may extend laser capabilities and offer new regimes of controllable Raman-assisted generation. We obtained Raman lasing in a 30 μm microsphere made of tellurite glass with huge Raman gain and ultrabroad bandwidth providing switchable light conversion with maximum frequency shift over 27 THz for the first cascade. We attained different steady-state regimes, including switchable and simultaneous generation at 1.73 and 1.8 μm with a pump at 1.55 μm as well as at 1.77, 1.85, and 2.01 μm with a pump at 1.57 μm. We analytically explained the nontrivial dynamics with mode competition due to direct and cascade stimulated Raman scattering, confirming the coexistence of different interacting modes and their controllable switching with a change in the pump parameters. To the best of our knowledge, this work is the first demonstration of Raman lasing in tellurite glass microresonators.