Tunable Autler–Townes Splitting in Optical Fiber

Based on the theory of quantum optics, an analogue of the Autler-Townes splitting (ATS) system is realized by coupling a Fabry-Pérot (FP) microcavity and a long-period fiber grating via the photonic tunneling effect. The stationary equations of the intracavity field amplitudes indicate that the splitting modes can be tuned by controlling the resonance frequency of the device. We demonstrated the feasibility of this theoretical result by adjusting the microcavity mirror offset Δx in the experiments. Both the theoretical analysis and the experimental results show that the transmission spectrum is remarkably adjustable due to the tunable ATS effect. The splitting modes of the developed device allow for an extra degree of freedom to respond to the sensing signal, which is important for ultra-sensitive sensing. The refractive index is accurately adjustable, providing for potential phase matching applications. In addition, the device can serve as either an ATS system or an FP cavity.