THE EFFECT OF THE GROUP PROPAGATION OF WAVES ON THE SPECTRAL BEHAVIOROF A MULTILAYER AR COATING

As the monitoring wavelength detected by an optical monitor (photomete r) is inevitably of a considerable spectral width, it should be travel ling as a group of waves rather than a monochromatic wave. In addition , the photometer is influenced simultaneously by the waves' combined e ffect. The phases of the disturbance of different wavelengths travelli ng with the group velocity are in good agreement. Therefore, the phase thickness(es) of the monitored layer(s) should be modulated by the gr oup factor. The effect of the new thickness(es) is investigated and th e close correlation between theoretically predicted and experimental r esults is presented. (C) 1998 Elsevier Science Ltd. All rights reserve d.