Efficient optical isolator via dual-Raman process with chiral nonlinearity

A scheme for optical nonreciprocity is proposed via dual-mode Raman process in thermal atoms. We investigate a far-detuned nonlinear Raman process, with the assistance of the Doppler effect to achieve chiral optical nonlinearity. The resulting Kerr nonlinear absorption is subject to a direction-dependent Doppler shifts seen by the thermal atoms. Moreover, the inter-channel Raman interference could significantly enhance Kerr nonlinear absorption for probe field, leading to the enhancement of the optical nonreciprocity. Simulation results show that the isolation ratio could reach 41 dB and the insertion loss is about 0.16 dB, with bandwidth up to 2π ×48 MHz. Furthermore, the sensitivity of the system is investigated under different strengths of the control and Raman fields.