Room-temperature optical non-reciprocity in a Doppler-broadened medium.

Here, we present an experimental demonstration of a true room-temperature magnetic-free non-reciprocity in a Doppler-broadened medium. By applying an additional pump field, the absorption of the forward probe field is significantly enhanced due to the canceling of the Doppler shifts; in contrast, the backward one is weakened due to the optical pumping process. In the experiment, we achieved a forward isolation of 11.47 dB and a backward transmission of 0.94 at 25 °C. This approach has potential applications in integrated optics and quantum information processing.