Optical Constants and Their Measurement

Abstract

R6sum6. -Nous exposons dans ses lignes gknkrales la mkthode de la fonction diklectrique et ses limites dans la description des propriktks optiques des solides, en particulier des mktaux. Nous dkcrivons aussi des methodes pour deduire cette fonction a partir des expkriences. Nous soulignons I'importance d'erreurs dkrivant de la prkparation des kchantillons plutbt que de la technique de mesure. On discute les donnkes expkrimentales pour diffkrents Clkments mktalliques.Abstract. -A description of the optical properties of solids, especially metals, in terms of a dielectric function is outlined, along with some of its limitations. Methods of deriving this function from measurements are outlined as well. Errors due to sample preparation, rather than measurement errors, are emphasized. Experimental data for several elemental metals is discussed.1. Introduction. -We review the description of the optical properties of solids in terms of a dielectric function, indicating some of the limitations to such a description. Most of the limitations to be discussed are more likely to be encountered in metals than in semiconductors or insulators, and metals are of greater interest in photoelectrochemistry, so the subsequent discussion and examples will be limited to metals. We outline briefly a microscopic model for the dielectric function which illustrates some other general properties of dielectric functions (which, however, are modelindependent). We then outline general methods for obtaining dielectric functions from experimental data, discussing experimental errors, conceptual errors, and problems with sample preparation. Several sets of data will then be examined. by while the linear response of a similarly simplifiedconductor is characterized by a conductivity a, defined 4 nIf the electric field is time-dependent, the response generally will not be instantaneous, so that we must use In crystalline media the dielectric function becomes a symmetric Cartesian tensor which can be diagonalized by a suitable choice of axes. For cubic crystals, all three diagonal components are equal and tensor notaArticle published online by EDP Sciences and available at http://dx

Optical Constant Determination in the Infrared of Uniaxially Oriented Monolayers from Transmittance and Reflectance Measurements

“…Determination of the Optical Constants of a Uniaxial Ultrathin Film. There are numerous methods to calculate the optical constants of films, mainly based on spectrophotometric or ellipsometric measurements. , In spectrophotometry, the refractive index n and the extinction coefficient k of a thin film may be calculated from transmittance T and reflectance R data, knowing the thickness d of the layer. In the previous section we have shown that R and T can be expressed in terms of n , k , d , and experimental conditions (p or s polarization, normal or oblique incidence).…”

Incorporation of macroscopic heterogeneity within a porous layer to enhance its acoustic absorptance

“…Eq. (44) shows us that ρ(ω) depends only on the 'reflected' field in the half space Ω 0 so that it is legitimate to associate it with what in optics [59] is termed the 'spectral reflectance'. We prefer to term it the (normalized) 'reflected flux'.…”