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 proces...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 directionindependent 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.展开更多
基金supported by National Natural Science Foundation of China(Grant Nos.62475209,62022066,12074306 and 92365107)the National Key R&D Program of China(Grant No.2019YFA0308700)+2 种基金Qinchuangyuan“Scientist+Engineer”Team Construction of Shaanxi Province(Grant No.2024QCY-KXJ-178)Key Scientific and Technological Innovation Team of Shaanxi Province(2021TD-56)the Program for Innovative Talents and Teams in Jiangsu(Grant No.JSSCTD202138).
文摘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 directionindependent 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.
