Fig. 3: Coupling strength influence on S₂₁₍₁₂₎ and n’ measurements.

|S₂₁| spectra (first row) and |S₁₂| spectra (third row), along with the derived refractive indices n'₂₁ (second row) and n'₁₂ (fourth row), plotted in a range of 2.8 GHz <f_AC < 4.2 GHz and 40 mT <μ₀H < 80 mT. These measurements correspond to varied coupling strengths, κ/κ_c = 0.1, 0.5, 0.8, and 1.0, based on fitting to the higher and lower hybrid modes. The parameter d indicates scotch tape thickness, affecting the coupling constant κ with κ_c (at d = 0). Insets show the coupled mode for d = 3 mm in ranges of 3.3 GHz <f_AC < 3.5 GHz and 55 mT <μ₀H < 65 mT.