Induced transparency by interference or polarization.

Wang, Changqing; Jiang, Xuefeng; Sweeney, William R; Hsu, Chia Wei; Liu, Yiming; Zhao, Guangming; Peng, Bo; Zhang, Mengzhen et al. · Proc Natl Acad Sci U S A · 2021

basic_science · Level V

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Abstract

Polarization of optical fields is a crucial degree of freedom in the all-optical analogue of electromagnetically induced transparency (EIT). However, the physical origins of EIT and polarization-induced phenomena have not been well distinguished, which can lead to confusion in associated applications such as slow light and optical/quantum storage. Here we study the polarization effects in various optical EIT systems. We find that a polarization mismatch between whispering gallery modes in two indirectly coupled resonators can induce a narrow transparency window in the transmission spectrum resembling the EIT lineshape. However, such polarization-induced transparency (PIT) is distinct from EIT: It originates from strong polarization rotation effects and shows a unidirectional feature. The coexistence of PIT and EIT provides additional routes for the manipulation of light flow in optical resonator systems.