Direct measurement of the composite Goos-Hänchen shift of an optical beam.

We experimentally study the Goos-Hänchen shift of a focused Gaussian optical beam in the critical region of incidence. We directly measure the beam's shift evaluated from the displacement of the location of the beam's intensity peak and its centroid by a novel image analysis method. We verify that the evaluation method has a dramatic impact on the physics of beam shift phenomena. The influence of wavelength, beam waist, and propagation distance on the beam shift is studied. Our experimental results confirm recent theoretical predictions about the composite Goos-Hänchen shift, including the observation of negative shifts of the beam's intensity peak.