The surface-wave scattering processes responsible, in part, for the optical glory have never been compared with theoretical predictions. Here, THz impulse ranging is used to measure the time domain impulse response of spherical targets with sufficiently high temporal resolution to permit the surface-wave contribution to the total impulse response to be isolated. The first direct experimental comparison for the surface wave with Mie theory as well as the surface-wave approximation of van de Hulst is performed. Interference of the surface waves from a dielectric sphere is shown to lead to the frequency and angular intensity dependence of the THz glory.

• Received 24 June 1997

DOI:https://doi.org/10.1103/PhysRevLett.80.269