An optical isolator with a low insertion loss and high isolation is desirable for quantum networks and modern optical communication. Here, we realize an optical isolator with the far-off resonant Raman process in a thermal $\Lambda$-type atomic system. The experimental results show a high isolation, ultra-low insertion loss, and widely tunable frequency simultaneously. The maximum isolation is more than 30 dB with 0.07 dB insertion loss. And, the frequency of the isolation can be tuned continuously over 1.2 GHz. This high-performance magnetic-free optical isolator offers opportunities for applications in integrated optics and quantum networks.

中文翻译：

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具有广泛可调频率的低插入损耗光隔离器

具有低插入损耗和高隔离度的光隔离器是量子网络和现代光通信所需要的。在这里，我们实现了在热中具有遥远的共振拉曼过程的光隔离器$\Lambda$型原子系统。实验结果表明，它具有很高的隔离度，极低的插入损耗和可同时广泛调节的频率。最大隔离度超过30 dB，插入损耗为0.07 dB。并且，隔离的频率可以在1.2 GHz范围内连续调整。这种高性能的无磁光隔离器为集成光学和量子网络中的应用提供了机会。