1. Optical Properties of Materials
재료의 전자기적 성질
Part II.
Optical Properties of Materials

2. The Optical Constants 7 Goethe (1749-1832): “Treatise on Color”
Color is not an absolute property of matter (such as the resistivity), but requires a living being for its perception and description.
If the color blue is removed from the spectrum, then blue, violet, and green are missing and red and yellow remain.” Thin gold films are bluish-green when viewed in transmission. These colors are missing in reflection. Consequently, gold appears reddish-yellow.

3. 7.1 Introduction
THz

4. 7.2 Index of Refraction, n Index of refraction: Dispersion:
optically thin
Index of refraction:
the refraction is caused by the different velocities, c,
of the light in the two media
optically dense
Dispersion:
The magnitude of the refractive index depends on the wavelength of the incident light which we called dispersion.

5. 7.3 Damping Constant, k Electromagnetic Wave Equation
Metals damp the intensity of light in a relatively short distance. Thus, an additional materials constant is needed to characterize the optical properties of metals.
Electromagnetic Wave Equation
Trial Solution
Complex index of refraction,
Set
where, k is called the damping constant

6. For insulators (s=0), :complex index of refraction
Absorption
:complex index of refraction
:complex dielectric constant
Maxwell relation
For insulators (s=0),

7. Damped amplitude
Undamped wave

8. 7.4 Characteristic Penetration Depth, W, and Absorbance,
Damping Term
Characteristic penetration depth
The inversion of W is sometimes called the (exponential) attenuation or the absorbance, a.
Inversion of W :
It is related to the energy loss

9. 7.5 Reflectivity, R, and Transmittance, T
: Transmissivity
N is generally a complex quantity,
By definition R has to remain real. Thus, the modulus of R becomes
(Beer equation)

10. (1)
(2)

11. 7.6 Hagen-Rubens Relation
Find out the relationship between reflectivity and conductivity.
For small frequencies (i.e., u<1013 s-1), in the IR region, with e~ 10
Hagen-Rubens Equation
(neglecting 2n+1<<2n2)
Set, s=s0
States that in the infrared region, metals with large electrical conductivity are good reflectors
(DC conductivity)
(only valid at frequencies below 1013 s-1, or wavelengths larger than 30 mm)

12. In the case of no conductivity:
Summary:
In the case of no conductivity:
When there is a conductivity:
Hagen-Rubens equation