Light field mode

Single-mode operation of the waveguides is identified from near-field mode patterns (NFPs). The light intensity of an NFP has a Gaussian distribution with the strongest intensity located at the core center. This waveguide shows single-mode behavior at 1.3 pm. 

Here, in accord with Eq. (2.9), we have added an extra phase, (j>k, to each plane wave field mode in Eq. (12.15), representing the phase shifts accumulated by the light in the k mode as it travels from the source to the sample. f... 

Xia and coworkers have demonstrated that the polarization of light plays an important role for nanoparticles with anisotropic shapes, especially with tmncated comers [77]. Optical dark-field mode imaging was employed to identify individual silver nanocubes deposited on silicon substrate as shown in Fig. 15.10a. Raman spectra were collected from the nanocubes, which were oriented in different directions with respect to the laser polarization. Subsequent SEM imaging of the same cubes enabled the authors to directly correlate the orientation of the nanocubes with respect to the light polarization and the SERS enhancement factor. They observed dramatic variation in SERS intensity when the nanocubes were oriented at different angles relative to the polarization of excitation laser as shown in Fig. 15.10b. SERS spectra of 1,4-benzenedithiol adsorbed on Ag nanocubes oriented in different directions showed different intensities with respect to the light polarization direction. The individual nanocubes with sharp comers were the most... 

Phase contrast is a useful technique for specimens such as polymers that have little inherent contrast in the bright-field mode. In the technique, a phase change due to light diffraction by an object is converted to an amplitude change. This conversion is based on interference... 

The visibility of the interference pattern of the intensity correlations provides a means of testing for quantum correlations between two light fields. Mandel et al. [18] have measured the visibility in the interference of signal and idler modes simultaneously generated in the process of degenerate parametric downconver-sion, and observed a visibility of about 75%, that is a clear violation of the upper bound of 50% allowed by classical correlations. Richter [19] has extended the analysis of the visibility into the third-order correlation function and also found significant differences in the visibility of the interference pattern of the classical and quantum fields. 

Figure 3 Micrographs offresh control bread crumb in the bright field mode (a) and after an aging period of 7 din the polarized light mode (b). Amylose-rich regions (AM) and amylopectin-rich regions (AP) are pointed out...

The basic equation used is the same as eq. (3), but with different expression of E(t). The complex amplitude of the light field in a multi-mode model as shown in Fig. 4 is expressed as... 

Figure 13. Three states of a cholesteric phase change device operated in light scattering mode. The grandjean texture (a) and homeotropic field-on state (b) are optically clear the focal-conic state (c) represents an alternative field-off state, which is optically scattering.

In the previous section we discussed light and matter at equilibrium in a two-level quantum system. For the remainder of this section we will be interested in light and matter which are not at equilibrium. In particular, laser light is completely different from the thennal radiation described at the end of the previous section. In the first place, only one, or a small number of states of the field are occupied, in contrast with the Planck distribution of occupation numbers in thennal radiation. Second, the field state can have a precise phase-, in thennal radiation this phase is assumed to be random. If multiple field states are occupied in a laser they can have a precise phase relationship, something which is achieved in lasers by a teclmique called mode-locking Multiple frequencies with a precise phase relation give rise to laser pulses in time. Nanosecond experiments... 

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