Fig. 3: Perfect zero-reflection (PZR) observed in experiment.

a–c Mappings of |S₁₁| as functions of Δ_H and Δ₂ in four cases: fixing ω₂/2π = 3.6 GHz, 4.24 GHz, 4.69 GHz, respectively. d High-resolution zoom-in image of (a). g–i Mappings of |S₂₂| as functions of Δ_H and Δ₂ in four ω₂ cases. Blues dotted curves are the fitted hybridized modes, white long dashed lines are the calculated frequencies of the ZR states. The PZR conditions are marked by arrows. j High-resolution zoom-in image of (g). e and k are the group delay τ_g mappings corresponding to (d) and (j), the PZRs emerge as singularities, where the group delay abruptly switches between negative infinity and positive infinity. f and l are the PZR spectra (|S₁₁| and |S₂₂|) at the black arrows marked fields in (d) and (j), respectively.