Cavity-Induced Optical Nonreciprocity Based on Degenerate Two-Level Atoms

• Published in: Nanomaterials (Basel, Switzerland) Vol. 14; no. 15; p. 1236
• Main Authors: Qi, Chuan-Zhao, Zheng, Jia-Rui, Tong, Yuan-Hang, Li, Ruo-Nan, Wang, Dan, Huang, Liang-Hui, Zhou, Hai-Tao
• Format: Journal Article
• Language: English
• Published: Switzerland MDPI AG 01.08.2024
• Subjects: Configurations; Coupling; degenerate two-level system; Doppler effect; Lasers; Light; Light scattering; Nuclear excitation; optical nonreciprocity; Optical properties; Optics; single-dark-state peak; strong coupling; China; degenerate two-level system; single-dark-state peak; strong coupling; optical nonreciprocity
• ISSN: 2079-4991; 2079-4991
• DOI: 10.3390/nano14151236

We developed and experimentally realized a scheme of optical nonreciprocity (ONR) by using degenerate two-level atoms embedded in an optical ring cavity. For the degenerate transition Fg = 4 ↔ Fe = 3, we first studied the cavity-transmission property in different coupling field configurations and verified that under the strong-coupling regime, the single-dark-state peak formed by electromagnetically induced transparency (EIT) showed ONR. The stable ground-state Zeeman coherence for Λ-chains involved in the degenerate two-level system was found to be important in the formation of intracavity EIT. However, different from the three-level atom–cavity system, in the degenerate two-level system, the ONR effect based on intracavity EIT occurred only at a low probe intensity, because the cavity–atom coupling strength was weakened in the counter-propagating probe and coupling field configuration. Furthermore, ONR transmission with a high contrast and linewidth-narrowing was experimentally demonstrated.