Frequency-space few-photon diode effect

We study coherent few-photon transport in a dissipative nonlinear cavity coupled to a 1D waveguide, deriving analytical solutions that reveal how cavity dissipation regulates the few-photon diode effect. Key findings show that under Γ/κ = 1 (Γ: waveguide-cavity coupling, κ: dissipation) and γ₁ = 0Γ (coupling rate for right propagating photons): (1) for single photons, left incidence yields perfect transmission while right incidence causes complete dissipative absorption, thereby forming an efficient single-photon diode; (2) for two photons under single-photon resonance, left incidence allows unimpeded transmission whereas right incidence results in near-total dissipation (>99%) and leaving only a faint bound state, maintaining strong diode characteristics despite minimal transmission. The condition Γ/κ = 1 optimizes directional suppression via cavity dissipation, providing a theoretical foundation for quantum diode devices in integrated quantum optics and information processing.