Measurement of Optical Constants in the Vacuum Ultraviolet Spectral Region

Publisher Summary The optical constants of an isotropic material are the index of refraction n and the extinction coefficient k . They are respectively the real and imaginary components of the complex index of refraction. They can be measured at a given wavelength by direct methods or inferred from the photometric or polarimetric measurements. A number of methods exist for extracting n and k from specular-reflectance measurements at both normal and oblique incidence; and for semi-infinite media and layers on substrates. This chapter discusses the most useful methods for obtaining n and k in the vacuum ultraviolet and explores the problems encountered in applying these methods. The specular reflectance of a substance at an angle of incidence Φ, measured from a normal surface, is related to the complex index of refraction by the generalized Fresnel reflection coefficients. It is noted that these equations cannot be solved explicitly for n and k . Because the equations have two unknown measurements, however, two independent measurements are necessary if a solution is to be obtained.

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