Optical absorption coefficient wavelength dependence

Fig. 25. Wavelength dependence of the optical absorption coefficient a and the specific polar Faraday rotation F for MnSb at room temperature. (After Sawatzky and Street 1971.)...

The real part determines the refractive index, while the imaginary part measures the extent of absorption of the radiation by the molecule, i.e. the optical absorption coefficient. For visible and UV radiation, the wavelength or frequency (co) dependence of the polarisability is given by ... 

EXAMPLE 4.3 Figure 4.9(a) shows the dependence of the absorption coefficient versus the photon energy for indium arsenide, (a) Determine whether or not InAs is a direct-gap semiconductor, (b) Estimate the band-gap energy, (c) If an InAs sample of 1 mm thickness is illuminated by a laser of 1 W at a wavelength of 2 jam, determine the laser power for the beam after it passes through the sample. Only consider the loss of light by optical absorption. 

Accurate modeling is only possible by the consideration of wavelength-dependent optical and temperature-dependent thermodynamic parameters and the correct application of the thermal accommodation coefficient which is dependent on the ambient particle conditions and is described in detail elsewhere (Schulz et al., 2006 Daun et al., 2007). Moreover, Michelsen (2003) suggested the inclusion of a nonthermal photodesorption mechanism for heat and mass loss, the sublimation of multiple cluster species from the surface, and the influence of annealing on absorption, emission, and sublimation. A more general form of the energy equation including in more detail mass transfer processes has been derived recently by Hiers (2008). For practical use, Equation (1) turns out to be of sufficient physical detail. 

K4Nb60i7 crystals exhibit optical birefringence [34] and absorb in the UV region with an optical absorption edge between 320 and 330 nm. Figure 4 shows the wavelength dependences of the transmittance and absorption coefficient along the... 

We now focus on the main subject of this contribution, namely the optical Kerr effect. Depending on the material characteristics and experimental conditions - that is, on laser wavelength and power as well as on metal and matrix kinds and relative amounts - the nonlinear absorption coefficient (3 is found to be either negative or positive. The influence of each of these parameters on the nonlinear response will be examined in details in forthcoming sections. 

Fig. 24. (a) Specific magneto-optic Faraday rotation (F) and absorption coefficient (a) as function of wavelength for both normal and quenched MnBi (after Chen et al. 1973). (b) Temperature dependence of the magneto-optical Kerr rotation of a MnBi film. The quantities Kerr rotation in the saturated and remanent state, respectively (after Chen and Gondo 1964). 

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