We calculate the time required for a broad light pulse to traverse a plate bounded by dissimilar media. If the three media are transparent, then the peak velocity is a periodic function of the thickness of the plate, the period being equal to a half-wavelength in the plate. The minimum and maximum speeds depend on the optical constants of the three media; however, their geometric average is the group velocity in the slab medium. In the presence of small absorption the minimum (maximum) speed increases (decreases) linearly with thickness. We also discuss situations of experimental interest, including that of a thin metallic film on a glass substrate, in which case the oscillations of the transit velocity are strongly attenuated.
© 1991 Optical Society of America
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