Versatile and Efficient Dual-Range Frequency Shifts by Intracavity Epsilon-Near-Zero Nanolayers

We experimentally demonstrate for the first time, the efficient input-dependent dual-range frequency shifts of 279.73 GHz and 3.63 THz in a mode-locked fiber laser with an intracavity epsilon-near-zero element. Real-time observation reveals that the presented frequency shifts are non-adiabatic processes, unlike the reported extracavity settings.