Quantum mechanics

Kerr effect

Engineering

Materials science

Social psychology

Optical fiber

Reciprocity (cultural anthropology)

Laser

Insertion loss

Physics

Nonlinear system

Psychology

Waveguide

Optics

Electromagnetically induced transparency

Interferometry

Electronic engineering

Circulator

Isolator

Optical isolator

Optical circulator

Physical Review Letters

Optical nonlinearity has been widely used to try to produce optical isolators. However, this is very difficult to achieve due to dynamical reciprocity. Here, we show the use of the chiral cross-Kerr nonlinearity of atoms at room temperature to realize optical isolation, circumventing dynamical reciprocity. In our approach, the chiral cross-Kerr nonlinearity is induced by the thermal motion of N-type atoms. The resulting cross phase shift and absorption of a weak probe field are dependent on its propagation direction. This proposed optical isolator can achieve more than 30 dB of isolation ratio, with a low loss of less than 1 dB. By inserting this atomic medium in a Mach-Zehnder interferometer, we further propose a four-port optical circulator with a fidelity larger than 0.9 and an average insertion loss less than 1.6 dB. Using atomic vapor embedded in an on-chip waveguide, our method may provide chip-compatible optical isolation at the single-photon level of a probe field.

Cavity-Free Optical Isolators and Circulators Using a Chiral Cross-Kerr Nonlinearity