Goos-Hänchen Shifts at 458 nm from DUV Dichroic Laser Mirrors

We report polarization- and angle-dependent lateral beam shifts observed at 458~nm upon reflection from a deep-ultraviolet (DUV) dichroic multilayer mirror. These Goos--Hänchen (GH) shifts originate from the phase of the complex Fresnel reflection coefficient and are quantitatively reproduced using a transfer-matrix model. Simultaneous reflectance (R), transmittance (T), and GH shift measurements provide complementary constraints on the coating's amplitude and phase response. The analysis is extended to transmission, predicting analogous phase-induced lateral shifts. In frequency-doubling cavities using dichroic mirrors, these phase effects can accumulate over multiple reflections, leading to deviations from ray-optics predictions that may affect cavity mode structure and resonance conditions. Our results show a GH shift of as much as 2~ m ({≈ 4.4λ}), which, combined with RT data, enables improved characterization of the phase response of the multilayer coating. The p-polarized reflectance is minimized at a pseudo-Brewster angle of {θB ≈ 46^∘} at 458~nm, providing a natural reference point around which the GH shift is enhanced.