题　目：Optical Properties of Lamella Multilayer Gratings in the Soft X-Ray Region
报告人：Dr. Igor Kozhevnikov
时　间：11月25日（周一），下午6:00
地　点：物理馆512会议室

报告摘要:
Multilayer mirrors are widely used as dispersive elements in the soft-x-ray (SXR) region. Typically, such mirrors have a spectral resolution E/ΔE in the range of 20 to 200 and a peak reflectivity of several tens of percent. High absorption of SXR in any material limits the number of bi-layers that can effectively contribute to the reflection of the incident beam and therefore limits the ultimate resolution. By fabricating a grating structure in the multilayer mirror, the penetration depth of SXR can be increased such that more bi-layers contribute to the reflection and a higher resolution can be obtained. Multilayer mirrors equipped with such a grating structure are referred to as Lamellar Multilayer Gratings (LMG).
Using the rigorous coupled waves approach (CWA), it is derived that for small lamellar widths only the zeroth diffraction order needs to be considered for LMG performance calculations, referred to as the single-order regime. In this regime, LMG performance can be calculated by assuming a conventional multilayer mirror with decreased density, which significantly simplifies the calculations. Novel analytic criteria for the design of LMGs are derived from the CWA and it is shown that the resolution of an LMG operating in the single-order regime is not limited by absorption as in conventional multilayer mirrors. It is also shown that the peak reflectivity of an LMG can then still be as high as that of a conventional multilayer mirror. Experimental results on LMG fabrication and measurements are shortly discussed as well.

个人简介：
M.S. in physics: Moscow State University in 1980.
Ph.D. in physics: Lebedev Physical Institute, Moscow in 1987. Thesis title: "Theory of reflective elements for the soft X-ray region".
1982 - 1985: post graduate student at the Lebedev Physical Institute, Moscow, Russia.
1985 - 2004: Junior Research Scientist, Research Scientist, and Senior Research Scientist at the Lebedev Physical Institute, Moscow, Russia.
2004 – present: Senior Research Scientist and Leading Research Scientist at the Institute of Crystallography, Moscow, Russia.

A wide experience in the collaboration with research groups in Russia and abroad (France, The Netherlands, Germany, Italy, and China).