Effect of anomalous transmittance in EUV multilayer optics

In this paper the effect of anomalous transmittance in the EUV spectral region is considered theoretically. The effect consists in a resonant enhancement of the transmittance of a periodic multilayer structure compared with that of a uniform film. The physical reason of the effect lies in the fact that the minima of the wave field intensity of a certain wavelength are placed just in the center of thin absorbing layers resulting in a resonant decrease of wave absorption. The condition of this appearance is analyzed: it is necessary the absorption coefficient (imaginary part of the dielectric constant) of two materials composing a multilayer structure to differ by a factor of 10, at least. A possibility of the use of a multilayer filter in metrology of broadband EUV sources is discussed.