Li Changbiao, Yuan Jiaqi, He Ruidong, Yu Jiawei, Zhang Yanpeng, Xiao Min, Xia Keyu, Zhang Zhaoyang
Key Laboratory for Physical Electronics and Devices of the Ministry of Education & Shaanxi Key Lab of Information Photonic Technique, School of Electronic Science and Engineering, Faculty of Electronic and Information Engineering, Xi'an Jiaotong University, Xi'an, 710049, China.
Department of Physics, University of Arkansas, Fayetteville, AR, 72701, USA.
Light Sci Appl. 2025 May 19;14(1):200. doi: 10.1038/s41377-025-01844-8.
Mediated by the interactions with quantum vacuum fields, a probe laser field propagating in a nonlinear optical medium can generate new pair of light fields over a broad spectral range via spontaneous parametric process. Such process is inherently independent of the incident direction of light and reciprocal thus far, due to the direction-independent field-vacuum interactions. In this work, we experimentally demonstrate within sodium atomic vapors that such spontaneous parametric process can be nonreciprocal by unidirectionally coupling it to another pumped four-wave mixing process. Thanks to the broad bandwidth of the spontaneous parametric process, in combination with the Doppler and power-induced broadening of atomic energy levels, we achieve optical isolation with isolation ratio >25 dB over a bandwidth larger than 100 GHz. Considering that both spontaneous parametric processes and the pumped four-wave mixing have been realized in diverse solid photonic platforms, the demonstrated concept can motivate further explorations in the design of integrated magnetic-free broadband optical nonreciprocity via the interactions between nonlinear optical processes.
在与量子真空场的相互作用介导下，在非线性光学介质中传播的探测激光场可通过自发参量过程在很宽的光谱范围内产生新的光场对。由于场 - 真空相互作用与方向无关，到目前为止，这种过程本质上与光的入射方向无关且具有互易性。在这项工作中，我们在钠原子蒸气中通过实验证明，通过将这种自发参量过程单向耦合到另一个泵浦四波混频过程，可以使其具有非互易性。由于自发参量过程的宽带宽，结合原子能级的多普勒和功率诱导展宽，我们在大于100 GHz的带宽上实现了隔离比>25 dB的光学隔离。考虑到自发参量过程和泵浦四波混频都已在各种固体光子平台中实现，所展示的概念可以推动通过非线性光学过程之间的相互作用来设计集成无磁宽带光学非互易性的进一步探索。
