Optical nonreciprocity using light shifts

Hot atoms have been demonstrated to be a promising platform for the manipulation of optical fields. However, the thermal motion of atoms results in the broadening of spectral lines, which is accompanied by a reduction in the light-atom interaction. In this study we propose a nonreciprocal optical system that significantly enhances the strength of the light-atom interaction by unidirectionally compensating for the broadening associated with two-photon processes, employing inhomogeneous light shifts in a $\mathrm{\ensuremath{\Lambda}}$ system. Utilizing the density matrix formalism, we provide a detailed description of the dynamics and examine the nonreciprocity in two distinct detuned regions. In the far-detuned region, a room-temperature nonreciprocity with an isolation of $37.3\phantom{\rule{0.28em}{0ex}}\mathrm{dB}$ and a transmission of 0.99 can be achieved. Furthermore, in the near-resonance region, the ultrabroad bandwidth of the nonreciprocal window can reach gigahertz. Our findings pave the way for the realization of high-performance optical nonreciprocity and present opportunities for applications in integrated optics and quantum networks.