Optical reflection response of dye-aggregate films in the absorption bands

摘要

Optical reflection properties of strongly absorbing dye-aggregate films are discussed with respect to spectroscopic experiments and numerical calculations based on classical wave optics. The dye-aggregate films exhibit enhanced reflection in the wavelengths of the absorption bands and exhibit reflection spectra analogous in profile to the absorption spectra. Although film thickness is much smaller than the wavelength of light, the simple simulations based on a dielectric model reproduced well the essential features of the reflection spectra. The macroscopic analysis, which involved using a complex refractive index, indicates that the enhanced reflection can be expressed by increasing the extinction coefficient with respect to absorption. The spectrally distinct behaviors of reflection at low absorption on wavelengths on either side of the absorption bands are attributed to the changing refractive index with an anomalous dispersion due to the absorption bands. (c) 2006 Optical Society of America.