  We report on the observation of enhanced microwave transmission through
quasi-periodic hole arrays in metal films. The fraction of transmitted light
reaches 50% in a self-standing metal film and approaches 90% when the film is
sandwiched between thin dielectric slabs, while the holes occupy only 10% of
the sample area. The maximum transmission is accompanied by zero phase change,
rendering the film almost 'invisible' over a wide frequency range. The
extraordinary transmission phenomenon is interpreted in terms of resonances in
the self-consistent interaction between holes, which are represented by
effective electric and magnetic dipoles.
