Nonreciprocal light propagation in coupled microcavities system beyond weak-excitation approximation

Area of Science:

• Quantum optics
• Nonlinear optics
• Cavity optomechanics

Background:

• Nonreciprocal light propagation is essential for optical isolators and circulators.
• Quantum emitters coupled to optical cavities offer a platform for enhanced light-matter interactions.
• Parity-time (PT) symmetry in coupled systems provides unique pathways for controlling light propagation.

Purpose of the Study:

• To propose and theoretically investigate a scheme for achieving non-lossy nonreciprocal light propagation.
• To explore the role of enhanced optical nonlinearity in PT-symmetric coupled cavity systems.
• To demonstrate the tunability of nonreciprocal light propagation direction.

Main Methods:

• Theoretical modeling of a two-level quantum emitter coupled to two coupled optical microcavities.
• Analysis of a parity-time (PT) symmetric system comprising active and passive cavities.
• Investigation beyond the weak-excitation approximation to capture enhanced optical nonlinearity.
• Numerical simulations to analyze light propagation characteristics, isolation ratios, and effects of optical bistability.

Main Results:

• Achieved non-lossy nonreciprocal light propagation with a high isolation ratio in a PT-symmetric coupled cavity system.
• Demonstrated that cavity gain significantly enhances optical nonlinearity, enabling strong nonreciprocity.
• Showed that nonreciprocal light propagation is robust against optical bistability-induced field intensity fluctuations.
• Confirmed the ability to switch the direction of nonreciprocal light propagation by adjusting system parameters.

Conclusions:

• The proposed scheme offers a promising route for realizing high-performance optical isolators and circulators.
• Enhanced optical nonlinearity in PT-symmetric systems is a key mechanism for achieving efficient nonreciprocity.
• The tunability of nonreciprocal propagation direction provides flexibility for integrated photonic applications.