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

Area of Science:

• Quantum Optics
• Atomic Physics
• Nanophotonics

Background:

• Optical isolators are crucial for preventing back-reflection in photonic systems.
• Dynamical reciprocity poses a significant challenge for achieving effective optical isolation using traditional nonlinear optical methods.

Purpose of the Study:

• To demonstrate a novel approach for optical isolation that circumvents dynamical reciprocity.
• To realize an optical isolator and a four-port optical circulator using atomic nonlinearity at room temperature.

Main Methods:

• Utilizing the chiral cross-Kerr nonlinearity induced by the thermal motion of N-type atoms.
• Employing a weak probe field to observe directional-dependent cross-phase shift and absorption.
• Integrating the atomic medium into a Mach-Zehnder interferometer to design an optical circulator.

Main Results:

• Achieved an optical isolation ratio exceeding 30 dB with minimal insertion loss (<1 dB).
• Demonstrated a four-port optical circulator with high fidelity (>0.9) and low average insertion loss (<1.6 dB).
• Proposed a chip-compatible method for optical isolation at the single-photon level using atomic vapor in waveguides.

Conclusions:

• Chiral cross-Kerr nonlinearity in atomic systems offers a viable solution to overcome dynamical reciprocity for optical isolation.
• The proposed method is scalable for integrated photonic circuits and operates at room temperature.
• This work paves the way for advanced optical components for quantum information processing and communication.