Multi-Parameter Control of Optical Bistability–Multistability Switching in a Four-Level N-Type Atomic System via Quantum Interference

Abstract

Abstract This work presents a theoretical study of optical bistability (OB) and multistability (OM) in a four-level N-type atomic system embedded in a unidirectional ring cavity, with particular attention to the role of quantum interference (QI) between decay channels. Going beyond earlier reports that focused on single-parameter or cavity-based control without considering quantum interference or multistability, we develop a unified framework investigating how the cooperative parameter C, probe and control field detunings (Δ₂, Δ₃), non-radiative decay rates (γ₀, γ₀₀), quantum interference (P), pump/control Rabi frequencies (Ω₁, Ω₂), and relative phase (φ) collectively govern OB and OM thresholds. Systematic analysis reveals that increasing C broadens hysteresis loops and raises thresholds, thereby enhancing switching stability, while quantum interference significantly lowers the OB threshold, enabling bistability at lower input intensities. Non-radiative decay rates γ₀ and γ₀₀, pump/control Rabi frequencies, and the relative phase φ further provide flexible switching between bistable and multistable regimes. Notably, we demonstrate that OB ↔ OM transitions can be induced through multiple independent pathways beyond phase control alone—including tuning of the cooperative parameter, non-radiative decay rates, and pump/control field intensities—extending the phase-driven switching mechanism established in earlier N-type studies to a broader, multi-parameter control framework. Furthermore, probe and control field detunings (Δ₂, Δ₃) enable dynamic tuning of the system's dispersive and absorptive properties, offering additional control over threshold behavior. These results identify practical routes for designing reconfigurable optical memory, quantum information processors, and all-optical switching devices with enhanced controllability.