Optical Absorption and Reflection Spectra of Very Thin KI Crystal

Abstract

The very thin KI crystal has been grown from the melt inside a narrow gap of the cell composed of two quartz plates. Thickness of the crystal is determined to be about 0.2 μm from the interference fringes in the transparent region. Consequently, the transmitted light can be detected up to the absorption coefficient of 3×10⁵ cm⁻¹. From the measurements of absorption and reflection spectra, it is shown that the 2s exciton band consists of the oscillatory structures separated by about 16 meV, in contrast to the case of evaporated thin films.