Measurements of the far infrared magnetotransmission of
YBa2(ZnxCu(1-x))3O(7-d) thin film (x = 0.025) deposited on a wedged MgO
substrate are reported. The application of magnetic field perpendicular to the
ab plane produces at low temperature a linear increase of transmission for
frequencies below 30 cm-1. We present a model of high frequency vortex dynamics
which qualitatively explains these results.Comment: 2 pages with 2 figures, presented on LT2