Fiber Loop Laser Stabilized by Fano Resonance in Metallic Grating Coupled Resonator

A compact fiber loop laser is developed based on Fano resonance in sub-wavelength metallic grating coupled whispering gallery mode (WGM) resonator. The laser utilizes the erbium-doped fiber amplifier as the gain medium, and the metallic grating coupled WGM resonator serves as a narrow linewidth filter to stabilize the lasing performance. The new sub-wavelength metallic grating coupler enables single-port configuration and is optimized to provide maximum reflected peak resonance as the feedback. A linear increase in output power and a redshift of the lasing wavelength are also observed with increasing input power. Furthermore, four-wave mixing up to the second order is observed with the current configuration. Such structure opens up the possibility of simple, compact, low power-threshold multi-wavelength lasers, and the realization of microresonator-based frequency combs.