a much smaller GH shift than the case of the plane-wave incidence. As the half-width of the Gaussian beam increases, the magnitude of the lateral shift of the reflected beam increases and approaches the value for the plane-wave incidence. The reflectance for plane waves takes a dip at $\theta = 62.33^\circ$ and the maximum of $\delta_r$ occurs at the reflectance dip.

In figure 5(b), we show the normalized half-width of the reflected beam, $W_r / W$, as a function of the incident angle for each half-width of the incident Gaussian beam. We find that the half-width of the reflected beam at the reflectance dip is substantially larger than that of the incident Gaussian beam. The relative distortion of the reflected beam profile is larger for narrower beams and does not disappear at $\theta_i\approx 62.33^\circ$ as the beam width $W$ increases.

![\[fig6\] (a) Backward normalized GH shift of the reflected beam versus incident angle for several different values of $W$ when $x_m=0.08638$. (b) Normalized half-width of the reflected beam versus incident angle for the same values of $x_m$ and $W$ as in (a).](fig6){width="8.5cm"}

In figure 6(a), we plot $\delta_r$ as a function of the incident angle for different values of $W$, 