Diffractive optics

The analysis of siUcon carbide involves identification, chemical analysis, and physical testing. For identification, x-ray diffraction, optical microscopy, and electron microscopy are used (136). Refinement of x-ray data by Rietveld analysis allows more precise deterrnination of polytype levels (137). 

The apparatuses used for the studies of both ammonia synthesis emd hydrodesulfurization were almost identical, consisting of a UHV chamber pumped by both ion and oil diffusion pumps to base pressures of 1 x10 " Torr. Each chamber was equipped with Low Energy Electron Diffraction optics used to determine the orientation of the surfaces and to ascertain that the surfaces were indeed well-ordered. The LEED optics doubled as retarding field analyzers used for Auger Electron Spectroscopy. In addition, each chamber was equipped with a UTI 100C quadrupole mass spectrometer used for analysis of background gases and for Thermal Desorption Spectroscopy studies. 

In the course of his studies of the dyeing process, he became deeply interested in the structure of natural fibers, and most of his efforts were directed toward this new field of research, with the help of able associates, among them R. Brill, M. Dunkel, G. von Susich, and E. Valkd. His investigation of various aspects of the problem utilized physical means (for example, x-ray diffraction, optical properties, and viscosity) and the purely chemical approach. A young scientist, H. Mark, who later became an authority in the field of high polymers, was appointed head of the physical chemistry laboratory. 

Figure 2.8. Scanning electron microscopy (SEM) photomicrographs of (a) a micro-diffractive optical element mold fabricated by a focused ion beam (FIB) and (b) the transferred optical element on a sol-gel film. [Reprinted with permission from Ref. 98.]... 

The minerals of the solid tailings and evaporites were assessed qualitatively with X-ray diffraction, optical, and scanning electron microscopy. 

Finally we remark that proper alignment of all diffractive-optic beam corrditioners normally reqrrires that they be adjusted with a common dispersion plane. This is defirred as the plane corrtaining the incident and diffracted beam (and therefore also the rrormals of the diffracting plane) for any given reflection. If the dispersion planes are rrot parallel then some intensity will be lost from the restriction this causes to the angular acceptance in the plane perpendicular to the dispersion plane. 

Table 2.6 Comparison of the Diffraction, Optical and Mechanical Properties of the Six Asbestos Minerals... 

Another important optical phenomena that relies on light interference and diffraction is holography, the process by which holograms (interference patterns) are produced. Whilst holograms are best known for the reproduction of near perfect 3D images of an object in the graphic arts, they also find apphcations in newer areas such as laser eye protection, LCDs, diffractive optical elements, optical processing... 

Diffractive Optics-Based Four-Wave Mixing with Heterodyne Detection... 

FIG U RE 1.10 Schematic representation of the experimental setnp for diffractive optics-hased fonr-wave mixing with heterodyne detection. (From Ogilvie, J. P., Plazanet, M., Dadusc, G., and Miller, R. J. D. 2002. J. Phys. Chem. 109 10460-67. With permission)... 

Dadusc, G., Ogilvie, J. R, Schulenberg, R, Marvet, U., and Miller, R. J. D. 2001. Diffractive optics-based heterodyne-detected four-wave mixing signals of protein motion From protein quakes to ligand escape for myoglobin. Proc. Nat. Acad. Sci. USA 98 6110-6115. 

The optical scheme of holographic lithography is schematically illustrated in Fig. 4. The beam of the same laser system as used for DLW recording passes through a diffractive optical element (DOE), where it is spht into a set of diverging multiple beamlets by diffraction. The set of beamlets is subsequently colhmated by a lens, and passed through the transmission mask, which selects... 

The simple picture of two interfering rays can be a great help in visualizing what is happening in an acoustic microscope as it is defocused (Quate 1980), and for many intuitive purposes this is quite sufficient. For analytical purposes more substantial theory is needed, and this can be derived both from diffraction optics and from a more rigorous development of ray theory. The simple ray model is vindicated both by the more detailed theoretical models presented in this chapter, and also by quantitative measurements based on them, which will be described in Chapter 8. 

Figure 4 Crossing of ultrashort pulses, (a) The pancake effect is illustrated for two crossed 40 fs pulses with 200 pm spot sizes. These two pulses, which travel from left to right, would have been produced from a single pulse with a beamsplitter. The spatial extent of the overlap area is seen to be only a fraction of the incident beam s spatial extent, (b) Pulses split with diffractive optics and recombined with a two-lens telescope overlap over the entire spatial extent of the beam profile. (Adapted from Ref. 14.)...

The use of diffractive optics for generation of the two excitation pulses results in fixed interference pattern maxima and minima at the sample,... 

Fixed spatial phase in the grating pattern also facilitates experiments with multiple excitation pulses (20). A second, delayed pulse incident on the diffractive optic is split in the same manner as the first and results in a second excitation pattern with the same peak and null positions. Thus, multiple excitation gratings, delayed temporally and shifted spatially if desired, can be used for excitation of phonon-polaritons whose coherent superposition is well controlled. A preliminary experiment of this type has been reported (21). 

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