Experimental Determination of Optical Constants

Measurement of refraction angles, such as the angle of minimum deviation of a prism n is obtained from Snell s law. This requires samples of high transparency (k = 0). 

Measurement of the transmittance and reflectance of a slab for light at near-normal incidence. The samples must be sufficiently transparent for measurable transmission in thin slabs, but not as transparent as required in method 1. 

Ellipsometric techniques in which amplitude ratios and phase shifts for reflected light are directly measured as opposed to the previous technique in which the phase shift is indirectly obtained. This is difficult to do over large wavelength regions because of requirements on optical elements such as polarizers and retarders. 

Measurement of reflectances for incident light of various polarization states and two oblique angles of incidence the results are analyzed with the Fresnel formulas. Large angles are required for high accuracy, and this requires large sample surfaces. 

These methods and their variations are the principal means of measuring optical constants. As noted, none of them is clearly superior in all instances 

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