Optical interference pattern

An experimental method based on the theories for rainbow phenomena has been applied to the measurement of droplet size and velocity and to the detection of non-sphericity.[7] In this method, a comparison between two droplet diameters is deduced from two different optical interference patterns observed in a rainbow that is created by a droplet scattering laser light. Once a rainbow pattern is... 

The thickness of thin film layers separated by uniform, parallel interfaces can be determined from optical interference patterns that result. These measurements can be made from about 400 nm out through the visible spectrum and on into the near-infrared (NIR) region. Since film thickness measurements rely not on the absolnte magnitude of the reflected light, but on the variation of that signal with wavelength, the choice of nnits is less important. Typically %R is used, but in some cases raw intensity is also satisfactory. We will treat thickness determinations in more detail in the applications section of this chapter. 

Figure 1 Phase relationship between the optical interference pattern and the space-charge field. For liquid crystals, this example illustrates mobile anions migrating into the nulls of the interference pattern. The application of an applied electric field Ej is usually required to observe a phase-shifted photorefractive grating.

A great deal of recent interest is related to the Doppler capabilities of OCT for resolving blood flow [92,93], In principle, there is no reason why OCT or photorefractive imaging cannot perform similarly in this regard. The similar capabilities are a result of the fact that both techniques require an optical interference pattern to be created between two overlapping beams whose path lengths lie within the coherence length of the laser. The only difference between... 

Other interesting applications for organic photorefractives result from the phase shift between the original optical interference pattern and the holographic refractive index modulation. The phase shift is unique to photorefractive materials and allows... 

Values for the extension ratios, estimated by Kramer and colleagues [36, 42] and also by Ward and co-workers [18, 22] from analysis of optical interference patterns, compare reasonably well with estimates of the network extensibility from small-angle neutron scattering data [36] or stress-optical measurements [43]. It was therefore proposed that the criterion for craze failure, and hence crack propagation via a craze, is to assume that the entangled strands crossing the section of the craze at the crack tip break due to the development of the critical stress at the crack tip cTfaii,... 

Interference, constructive When radiation from two sources interact such that the amplitudes add together to produce an intense signal. Example The white band in optical interference patterns. 

Holographic polymer dispersed liquid crystals (H-PDLCs) are obtained by photopolymerisation of a hquid crystal-prepolymer mixture in the interference field of two or more laser beams [14,15]. This induces phase separation in which hquid crystalline material predominantly congregates in dark regions of the optical interference pattern [16,17]. As a result, holographic gratings with extremely high refractive-index contrast are formed. In addition, the diffraction efficiency of these gratings is electrically switchable the apphcation of an electric field results in reorientation of the nematic director field within... 

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