Holographic Techniques

By the HTOF technique, an interference pattern from two ps or ns laser pulses creates a sinusoidal distribution of carriers. Under the influence of an applied field, the carriers separate. As the charge separation proceeds, a space-charge field is created that can be probed with a cw laser through the electrooptic effect. The space-charge field reaches a maximum when the carriers have drifted to a position of anticoincidence with the immobile distribution of carriers of opposite polarity. Further drift causes a decrease of the space-charge field until coincidence is reached again. The diffraction efficiency versus time shows oscillatory behavior. From the time tmax that corresponds to the first maximum, the mobility can be derived from the relationship 

The major advantages of the HTOF technique are that it is not subject to trapping constraints nor the restrictions concerning the absorption depth of conventional photocurrent transient measurements. The principal limitation is that it is limited to photorefractive materials. Malliaras et al. (1995) used the HTOF method to measure mobilities of ternary mixtures of poly(N-vinylcarbazole), 2.4.7-trinitro-9-fluorenone, and 4-(hexyloxy)nitrobenzene. Results obtained by the HTOF method were in good agreement with those obtained by conventional photocurrent transient measurements. 

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This expression is the main tool used in describing diffraction effects associated with Fourier optics. Holographic techniques and effects can, likewise, be approached similarly by describing first the plane wave case which can then be generalized to address more complex distribution problems by using the same superposition principle. 

With holographic techniques, the ceramic piece is imaged by coherent light or sound waves before and after it is stressed slightly. The holo-... 

Yule et. al. [76] suggest these holographic techniques offer no significant advantage over the relatively simple two-dimensional spark photography technique for measuring particles in sprays. Tyler [77] has reassessed the application of Fraunhofer holography to particle size determination. 

To overcome the above limitations, we employ double-exposure holographic interferometry [110]. Holographic techniques have the crucial advantage of storing the full field image of the sample before and after irradiation, thereby permitting spatially resolved characterization of the induced effects over the full sample. The technique is applied to the study of polymeric systems, either in the form of plates or mainly in the form of films cast on transparent substrates. 

Spatial coherence e.g., remote sensing, range finding and many holographic techniques. 

Barbarisi, M.J., B.R. Chishohn, and P.J. Kisatsky, Evaluation of the Adhesive Bonding Process Used in Helicopter Manufacture—Part 4. Nondestructive Inspection of Adhesive Bonds Using Holographic Techniques, Picatinny Arsenal Technical Report 4419, AD 765 455, October 1972. 

We meet this case in technics. For instance, in an optical microscope, lenses fulfil the direct and inverse Fourier transforms the light is focused by a condenser onto the object, then diffracted, then collected by an objective, and finally the image is taken by a video camera and seen on a screen. The form of the object is seen as an intensity pattern that is a flat distribution of the optical density, because the phases of the waves forming the image are lost. A holographic technique, which always uses an interference of scattered rays with a reference beam having a known phase, allows the restoration of a volume image of the object. 

In the present chapter, we describe a holographic technique to generate these kinds of optical fields by incorporating sp>atial filtering techniques. The resulting optical fields can be diffraction free beams and/or dark hollow beams. The spatial filtering is implemented by controlling the kind of illumination which allows us to add or avoid, in the diffraction field some spatial frequencies. 

In this chapter we have described a simple method using holographic techniques in order to generate a variety of diffraction free beams and dark hollow beams. A fundamental part of the study consists in the generation of the boundary condition for the optical field characterized by a transmittance function. This is obtained by interfering two zero order Bessel beams. However, our model can be easily extended to other kind of diffracting free beams. 

Schieber JD, Venerus DC, Bush K, Balasubramanian V, Smoukov S (2004) Measurement of anisotropic energy transport in flowing polymers using a holographic technique. Proc Nat Acad Sci 101 13142-13146... 

Several techniques (fast camera, image converter, schlleren, and ombroscoplc records) have been used to record the main phenomena in water and surface motion. The free surface motion details have been observed with more precision by holographic techniques, which appeared very suitable for the description of the first phenomena and particularly the water jets in the air and the cavitation in the water. 

The free surface motion of water-air Interface accelerated by the impact of a shock Impulse generated by an explosive has been observed by means of holographic technique. The results of the analysis of the holograms allowed us to confirm and to clarify the role of cavitation phenomena, which ... 

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