Single-longitudinal-mode lasing based on enhanced scattering in eccentric-hole microstructured optical fiber resonators

In this paper, we propose a dual-core eccentric-hole fiber (DCEHF) microresonator to achieve single-longitudinal-mode (SLM) laser emission based on enhanced pump light field induced by scattering effect of the two fiber cores. The directional dependences of the scattered pump field distribution on incident angle as well as overlap integrals between scattered pump light fields and WGMs have been theoretical investigated, and the calculation results show that when the incident angle of the pump light is close to 180°, significant discrepancies would occur in the overlap integrals between WGMs and the scattered field. And consequently, specific mode having the largest overlap integral would outperform through the mode competition process to excite SLM lasing. We have experimentally obtained SLM lasing emission when the DCEHF-based microresonator is rotated by 206°, which is in good accordance with our calculation results. Additionally, experimental observation of the output laser spectrum shows that the proposed fiber microcavity supports highly stable SLM laser emission. The proposed microresonator based on DCEHFs possesses several desirable merits such as compact size, good laser stability, single-mode operation, and good compatibility with existent fiber-optic systems, which make it a good candidate for applications as functional photonic device in future micro-optics systems.