William Angerer - Department of Physics and Astronomy - University ...

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4.2 Measurement of Indices of Refraction and Absorption Coefficient
We measured the index of refraction and absorption coefficient for GaN over an energy
range from the VV to the IR. These measurements are essential for an accurate
determination of X~Jk(w = 2wo).
4.2.1 Experimental Techniques
We measured the real and imaginary parts of the dielectric function with the apparatus
shown in Fig. 4.5. The light source was an Oriel 450 W Xe lamp with an f/1.0 CV
enhanced lens. The spectral range of this lamp is 200-2500 nm. The wavelength was
selected by a Jarrel Ash Monospec 25 monochrometer with a 1200 grooves/mm grating.
The wavelength of the monochrometer was selected by a computer controlled
stepper motor. The light from the monochrometer was p-polarized and a fraction
was used to remove temporal fluctuations as in section 4.1.1. The sample was rotated
by a stepper motor to change the angle of incidence. By measuring transmitted
light intensity as a function of the angle of incidence, the dielectric constant can be
accurately determined.
4.2.2 Calculations of Dielectric Constants
'vVe formulate a description of the transmission of light through a multilayer film by
matrix methods [56, 59]. The technique relates the tangential electric and magnetic
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