Nonlinear Dielectric Polarization in Optical Media
TL;DR: The physical mechanisms which can produce second-order dielectric polarization are discussed on the basis of a simple extension of the theory of dispersion in ionic crystals in this paper.
Abstract: The physical mechanisms which can produce second-order dielectric polarization are discussed on the basis of a simple extension of the theory of dispersion in ionic crystals. Four distinct mechanisms are described, three of which are related to the anharmonicity, second-order moment, and Raman scattering of the lattice. These mechanisms are strongly frequency dependent, since they involve ionic motions with resonant frequencies lower than the light frequency. The other mechanism is related to electronic processes of higher frequency than the light, and, therefore, is essentially flat in the range of the frequencies of optical masers. Since this range lies an order of magnitude higher than the ionic resonances, the fourth mechanism may be the dominant one. On the other hand, a consideration of the linear electro-optic effect shows that the lattice is strongly involved in this effect, and, therefore, may be very much less linear than the electrons. It is shown that the question of the mechanism involved in the second harmonic generation of light from strong laser beams may be settled by experiments which test the symmetry of the effect. The electronic mechanism is subject to further symmetry requirements beyond those for piezoelectric coefficients. In many cases, this would greatly reduce the number of independent constants describing the effect. In particular, for quartz and KDP there would be a single constant.
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TL;DR: In this article, an experimental technique using powders is described which permits the rapid classification of materials according to the magnitude of nonlinear optical coefficients relative to a crystalline quartz standard and the existence or absence of phase matching direction(s) for second-harmonic generation.
Abstract: An experimental technique using powders is described which permits the rapid classification of materials according to(a) magnitude of nonlinear optical coefficients relative to a crystalline quartz standard and(b) existence or absence of phase matching direction(s) for second‐harmonic generation.Results are presented for a large number of inorganic and organic substances including single‐crystal data on phase‐matched second‐harmonic generation in HIO3, KNbO3, PbTiO3, LiClO4·3H2O, and CO(NH2)2. Iodic acid (HIO3) has a nonlinear coefficient d14∼1.5×d31 LiNbO3. Since it is readily grown from water solution and does not exhibit optical damage effects, this material should be useful for nonlinear device applications.
5,070 citations
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TL;DR: In this method, non-linear susceptibility tensors are introduced which relate the induced dipole moment to a power series expansion in field strengths and the various experimental observations are described and interpreted in terms of this formalism.
Abstract: Recent advances in the field of nonlinear optical phenomena are reviewed with particular empphasis placed on such topics as parametric oscillation self-focusing and trapping of laser beams, and stimulated Raman, Rayleigh, and Brillouin scattering. The optical frequency radiation is treated classically in terms of the amplitudes and phases of the electromagnetic fields. The interactions of light waves in a mterial are then formulated in terms of Maxwell's equations and the electric dipole approximation. In this method, non-linear susceptibility tensors are introdueed which relate the induced dipole moment to a power series expansion in field strengths. The tensor nature and the frequency dependence of the nonlinearity coefficients are considered. The various experimental, observations are described and interpreted in terms of this formalism.
3,893 citations
TL;DR: In this article, a theoretical study on the optimization of second harmonic generation (SHG) and parametric generation (PG) by a laser beam in a uniaxial nonlinear crystal is presented.
Abstract: A theoretical study is presented on the optimization of second harmonic generation (SHG) and parametric generation (PG) by a laser beam in a uniaxial nonlinear crystal. Numerically computed curves show the dependence of the SHG power, and the reciprocal of the PG threshold power, on the parameter l/b, where l is the optical path length in the crystal and b is the confocal parameter (determined by the focal length of the focusing lens and the minimum radius of the laser beam, assumed to be in the TEM00 mode of an optical resonator). The calculations take full account of diffraction and double refraction. In the absence of double refraction, the optimum focusing condition is found to be l/b=2.84. For PG the optimization of the crystal length l is also discussed, and curves are given showing the dependence of the threshold on l for the case in which signal and idler have the same losses. It is shown that the computed functions are also relevant to the mixing of two Gaussian beams and to parametric amplificat...
1,700 citations
TL;DR: Second-harmonic imaging microscopy (SHIM) on a laser-scanning system proves, therefore, to be a powerful and unique tool for high-resolution, high-contrast, three-dimensional studies of live cell and tissue architecture.
936 citations
TL;DR: Coherent anti-Stokes Raman scattering (CARS) microscopy permits vibrational imaging with high-sensitivity, high speed, and three-dimensional spatial resolution as discussed by the authors, and the development of multiplex CARS microspectroscopy, which allows high-speed characterization of microscopic samples.
Abstract: Coherent anti-Stokes Raman scattering (CARS) microscopy permits vibrational imaging with high-sensitivity, high speed, and three-dimensional spatial resolution. We review recent advances in CARS microscopy, including experimental design, theoretical understanding of contrast mechanisms, and applications to chemical and biological systems. We also review the development of multiplex CARS microspectroscopy, which allows high-speed characterization of microscopic samples, and CARS correlation spectroscopy, which probes fast diffusion dynamics with vibrational selectivity.
921 citations