Interferometric optical profile

Compared with optical interferometric microscopes (optical profiles), it may provide unambiguous measurement of step heights, independent of reflectivity differences between materials. 

Optical techniques, in particular interferometry, may be used to measure a nonzero concentration of the reactant at the electrode. However, such measurements are restricted to (a) dilute solutions, because refraction occurs in addition to interference (B4a), and (b) solutions in which only the concentration of the reacting species varies, that is, to solutions of a single salt. If the solution contains two electrolytes with dissimilar concentration profiles in the diffusion layer, then a second independent measurement is needed to establish the reactant concentration at the electrode. Interferometric methods are considered in detail by Muller (M14). 

A. Cameron and his co-workers developed an optical interferometric method of measuring film thickness and mapping film profiles, details of which are described in Chapter 6. The method is capable of resolving thickness to better than 100 nm and does not require empirical calibration. For reasons of technique, most of the published data are for a... 

There are two different techniques that are used to measure the time profiles and optical oscillations of ultrashort pulses noncoUinear intensity correlation and interferometric autocorrelation. While the former measures the envelope of the pulse, the latter can even measure the optical oscillations within the pulse envelope. Combined with the spectral resolution, the time profiles of the different spectral components within the optical pulse spectrum can be simultaneously measured by the FROG technique. The relative phases of these spectral components are observable using the SPIDER technique (see Sect. 6.2.4). 

The laser interferometry technique is widely used for the study of the detonation wave time profile and structure due to its exceptionally good time resolution. The laser interferometry operating principle is based on the Doppler effect. The technique records the position and time dependence of the interferometric fields obtained due to the Doppler shift in wavelength of the reflected laser beam, resulting from the thin metal shim motion. The metal shim, 15-25 pm thick, is placed between the explosive charge and windows that are made of an inert optically transparent material, such as water, lithium fluoride, or polymethylmethacrylate. On the basis of the velocity of the explosive/metal shim interface as a function of time, it is possible to calculate the values of detonation parameters of the explosive (Gimenez et al., 1985, 1989 Hemsing, 1985 Leeetal., 1985). 

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