ApplOpt91b

ApplOpt91b - Attenuated-total-reflection technique for the...

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Attenuated-total-reflection technique for the determination of optical constants L. E. Regalado, R. Machorro and J. M. Siqueiros In a glass-metal-dielectric system, it is normally impossible to determine simultaneously the complex dielectric constant, the thickness of the metal, and the corresponding parameters of a dielectric overlayer. We propose the use of the pseudo-Brewster or Abeles angle as an additional parameter to characterize simultaneously a dielectric thin-film overcoating and the metal surface parameters. We use a Kretschmann attenuated-total-reflection configuration. An admittance diagram is used to illustrate graphically the role of an absentee layer at this angle. A study of the limitations of the method is also presented. 1. Introduction Attenuated total reflection (ATR) has been shown to be a powerful tool for optical characterization of metal surfaces. 1 The effect of a double interface 2 and the modification of surface electromagnetic waves by a thin layer 3 have also been studied with this technique. The detection of the ATR signal may be photometric or ellipsometric 4 ; the experimental parameters ob- tained by this technique give enough information for the optical characterization of the active medium sur- face under study. 5 However, it is impossible to deter- mine simultaneously the complex dielectric constant, the thickness of the metal, and the corresponding pa- rameters of a dielectric overlayer. We propose here the use of the pseudo-Brewster or Abeles angle 6 as a source of extra information to characterize dielectric thin-film overcoatings and the metal surface parame- ters in a Kretschmann ATR configuration. We also study the limitations of ATR. II. Theory In the ATR technique the Abeles angle is an experi- mental parameter observed at angles below the critical angle 0, inside the prism and corresponds to zero re- flection at the film-air interface for p polarization. L. E. Regalado is with Centro de Investigacion en Fisica, Universi- dad de Sonora, Apartado Postal 5-088, 83190 Hermosillo, Sonora, Mexico. The other authors are with Instituto de Fisica, Universidad Nacional Aut6noma de Mexico, Apartado Postal 2681, 22800 Ense- nada, B.C., Mexico. Received 13 November 1989. 0003-6935/91/223176-05$05.00/0. © 1991 Optical Society of America. In the following discussion we use subscripts m andf for the metal and dielectric layers, respectively; sub- scripts g and 0 for the prism (glass) and the air proper- ties, respectively; and p for p polarization. Optical excitation by a prism coupler of the surface electromagnetic waves in metal surfaces and interfaces has been reviewed extensively. 7 In a classical experi- ment, a metal film is deposited upon the hypotenuse of a right-angle prism. This is called the Kretschmann
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This note was uploaded on 03/15/2011 for the course FISICA 101 taught by Professor Chavez during the Spring '11 term at ASU.

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ApplOpt91b - Attenuated-total-reflection technique for the...

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