Optical Properties of Electronic Materials: Fundamentals and Characterization
Light interacts with materials in a variety of ways; this chapter focuses on refraction and absorption. Refraction is characterized by a materialʼs refractive index. We discuss some of the most useful models for the frequency dependence of the refractive
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3. Optical Properties of Electronic Materials: Fundamentals and Characterization
Optical Prope
3.1
Optical Constants ................................. 3.1.1 Refractive Index and Extinction Coefficient .......... 3.1.2 Kramers–Kronig Relations ..........
47 47 49
3.2
3.3
3.4
Refractive Index .................................. 3.2.1 Cauchy Dispersion Equation........ 3.2.2 Sellmeier Dispersion Equation .... 3.2.3 Gladstone–Dale Formula............ 3.2.4 Wemple–Di Dominico Dispersion Relation ................................... 3.2.5 Group Index (N ) ........................
50 50 51 51
Optical Absorption ............................... 3.3.1 Lattice or Reststrahlen Absorption and Infrared Reflection .............. 3.3.2 Free Carrier Absorption (FCA) ....... 3.3.3 Band-to-Band or Fundamental Absorption........ 3.3.4 Exciton Absorption .................... 3.3.5 Impurity Absorption .................. 3.3.6 Effects of External Fields ............
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54 55 57 63 66 69
Thin Film Optics................................... 3.4.1 Swanepoel’s Analysis of Optical Transmission Spectra ... 3.4.2 Ellipsometry .............................
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Optical 3.5.1 3.5.2 3.5.3
Materials ................................. Abbe Number or Constringence ... Optical Materials ....................... Optical Glasses ..........................
74 74 74 76
References ..................................................
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3.5
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3.1 Optical Constants The changes that light undergoes upon interacting with a particular substance are known as the optical properties of that substance. These optical properties are influenced by the macroscopic and microscopic properties of the substance, such as the nature of its surface and its electronic structure. Since it is usually far easier to detect the way a substance modifies light than to investigate its macroscopic and microscopic properties directly, the optical properties of a substance are often used to probe other properties of the material. There are many optical properties, including the most well known: reflection, refraction, transmission and absorption. Many of these optical properties are associated with important optical constants, such as the refractive index and the extinc-
tion coefficient. In this section we review these optical constants, such as the refractive index and the extinction coefficient. Books by Adachi [3.1], Fox [3.2] and Simmons and Porter [3.3] are highly recommended. In addition, Adachi also discusses the optical properties of III–V compounds in this handbook.
3.1.1 Refractive Index and Extinction Coefficient The refractive index n of an optical or dielectric medium is the ratio of the velocity of light c in vacuum to its velocity v in the medium; n = c/v. Using this and Maxwell’s equations, one obtains the well-known
Part A 3
Light interacts with materials in a variety of ways; this chapter focuses on refraction and absorption. Refraction is characterized by a material’s refractive index. We discuss some of the most useful models for the frequency
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