Fig. 5: RS band enhanced birefringence in α-MoO₃.

a Schematic of depolarization experiment, (b) reflectance of sample S2 for different analyzer values ϕ_a when polarizer is set to ϕ_i = 45°, the black curve is the simulated intensity for ϕ_a = −45°. c Simulated polarization ellipse characteristics, ellipticity (r) and polarization ellipse major axis angle (ψ). d Simulated polarization ellipse of reflected beam at ω = 727 cm⁻¹ which represents circularly polarized light. The purple dot represents an example of the |E| value from the reflected polarization ellipse at ω = 727 cm⁻¹ used for obtaining the black simulation curve in panel b. e Spectral polarization ellipse major axis angle (ψ) versus Ge thickness (t_Ge) and (f) spectral quarter-wave plate action quality factor (Q_circ) versus t_Ge, with α-MoO₃ thickness t_MO = 0.95 μm and incident angle θ = 25° and ϕ_i  = 45°. g ψ versus t_MO and (h) Q_circ versus t_MO, with t_Ge = 0.42 μm and θ = 25° and ϕ_i = 45°. The white dots in panels f and h are the experiment data points representing the circularly polarized reflected beam in panel d.