Second harmonic generation intensities

The integral over t is the convolution of the intensities of the two laser pulses at time separation r. This function is identical to the noncollinear second-harmonic-generation intensity autocorrelation of the laser pulses,... 

The large values reported for squaraines indicate that noncentrosymmetric crystals or films of these dyes should be capable of efficient second harmonic generation (SHG). A new class of chiral D -A-D squaraines 37-44 obtained by 1,2-substitution of squaric acid showed second harmonic generation intensities of up to 64 times that of urea (Table 3) in the powder form [124,125]. X-ray crystal analysis indicated that two hydrogen bonds between adjacent mol-... 

Figure 9.31. Second-harmonic generation intensity profiles as a function of the applied electric field for four input/output polarization combinations, i.e., p-p [p-in/ /3-out), s-p, p-s, and s-s at normal incidence in the optical geometry shown at the top of the figure [94].

Non-linear optical interactions occur in materials with high optical intensities and have been used to produce coherent light over a wide range of frequencies from the far infra-red to the ultra-violet. The three wave mixing process is of particular interest as it can be used for optical parametric amplification and optical second harmonic generation (SHG) and occurs in non-centrosymmetric materials. 

The symmetry of the LB films was determined by polarized ultraviolet-visible (UV-Vis) absorption spectroscopy, optical rotation, and second-harmonic generation. All studies showed that the constructed LB films are anisotropic in the plane of the film and that the symmetry of the film is C2 with the twofold rotation axis perpendicular to the film plane. For example, when the SH intensity is plotted as a function of the azimuthal rotation angle (rotation around an axis perpendicular to the plane of the film), the twofold symmetry becomes evident (Figure 9.23). Isotropic films generate an SH signal independent of the azimuthal rotation angle. On the other hand, the LB... 

Electric discharge ozone generator, 77 798 Electric-field-induced second harmonic generation (EFISH), 20 515 Electric field intensity, exponents of dimensions, 8 585t Electric field perturbations, 74 616 Electric fields... 

Second harmonic generation (SHG) is one of the most intensively studied nonlinear optical effects that have ever been combined with near-held scanning optical microscopy (Shen et al. 2000 Zayats and Sandoghdar 2000 Zayats and Sandoghdar 2001 Takahashi and Zayats 2002). SHG, which is an even-order nonlinear process, is forbidden in centrosymmetric media under the dipole approximation (Shen 1984). Non-centrosymmetric molecules and lattices are allowed to exhibit SHG light. The second-order nonlinear polarization for SHG (T shg) is given in a scalar form by... 

For the second task second harmonic generation by quartz has been proposed. The first procedure is to determine the relative intensity of SH compared with etalon, where the ratio of SH intensities is used for sorting. In the second procedure the laser source is working with a very high repetition rate and the number of pulses with SH intensity above a certain level is used as the separation criterion. Sorting using non-linear optics may be very effective, because... 

Optical second harmonic generation (SHG), which stems from the conversion of two photons of frequency to to a single photon of frequency 2(o, is an inherently surface-sensitive technique. Whereas no optical second harmonic wave is generated in the centrosymmetric bulk of a liquid, molecules participating in the asymmetry of the interface between two liquids (noncentrosymmetric environ-ment) contribute to SHG. Since the square root of SHG signal intensity, is proportional to the number N (per unit area), the molecular orientation (I) and the second order nonlinear polarizability of the SHG active species at the interface... 

The same equations, albeit with damping and coherent external driving field, were studied by Drummond et al. [104] as a particular case of sub/second-harmonic generation. They proved that below a critical pump intensity, the system can reach a stable state (field of constant amplitude). However, beyond the critical intensity, the steady state is unstable. They predicted the existence of various instabilities as well as both first- and second-order phase transition-like behavior. For certain sets of parameters they found an amplitude self-modula-tion of the second harmonic and of the fundamental field in the cavity as well as new bifurcation solutions. Mandel and Erneux [105] constructed explicitly and analytically new time-periodic solutions and proved their stability in the vicinity of the transition points. 

A number of special optical techniques such as the study of second harmonic generation by irradiation of non-centrosymmetric systems by high intensity laser light will be discussed in relation to particular materials and problems. However, one optical technique having a general applicability, namely ellipsometry, must be discussed here. It is one of the best techniques available to determine the thickness of a thin organic film. Such determinations are important as they allow one to have an independent check on the number of layers deposited, given that the thickness of one layer has been determined by X-ray diffraction. 

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