Abstract

The lateral, focal, and angular shifts associated with fields incident on dielectric interfaces can be significant in applications involving guided waves and beams. For incidence angles θ that are close to the critical angle of total reflection θ_c, the conventional expressions for those shifts fail because their values become infinitely large as θ→θ_c, which is inconsistent with experimental evidence. For the lateral shift, Horowitz and Tamir have derived¹ a formula that remains finite around θ_c and approaches asymptotically the conventional result for θ away from θ_c. We have obtained expressions that are valid around θ_c also for the focal and angular shifts. These results have been derived for Gaussian beams with normal or parallel polarization, and they hold also for incident beams that are either convergent or divergent. The new results approach asymptotically the conventional expressions for θ far from θ_c but they predict finite values for both the focal and angular shifts for θ around θ_c. As expected, we have ascertained that these shifts are most pronounced near θ_c, in which case their magnitudes are strongly dependent on the beamwidth/wavelength ratio, which is assumed large.

© 1985 Optical Society of America