Light velocity control in monolithic microfiber bridged ring resonator

Electromagnetically-induced transparency (EIT), classically generated by the coherent interaction between light and multilevel atoms, is a cutting-edge research theme in optical memories. Unfortunately, the strict requirements of gaseous atoms and particular frequencies that obey atomic transitions pose a challenge to practical application. Here we propose an all-fiber monolithic microfiber bridged ring resonator (MBRR), and experimentally demonstrate its EIT-like effect called microfiber resonator induced transparency (MRIT). Because the MRIT is induced by destructive interference between two counter propagating modes inside the cavity, the MBRR shows excellent light velocity control ability, with both fast light and slow light up to several nanoseconds in theory. Continuous pulse delay tuning from −60  ps (fast light) to +160  ps (slow light) within one MBRR was experimentally achieved. The pulse retardation of the MBRR is one order of magnitude larger than that of previously reported microfiber resonators. The proposed MBRR with unique bridged structure features such as multi-channels, all-fiber structure, compact size, and low cost, could be applied in quantum computation, information storage, optical processing, and fiber sensing.