Non-linear-optics

5 Non-linear Optics. - Gopalan et looked at experimental charge density to study the effect of the noncentric crystal field on the molecular properties of organic NLO materials. Although extensive lists of BCP properties and Laplacian 

The previous paragraphs have been concerned with linear optical properties. Throughout the long history of optics, and indeed until relatively recently, it was thought that all optical media were linear. The assumption of linearity of the optical medium has far-reaching consequences  

The invention of the laser in 1960 allowed to examine the behavior of light in optical materials at higher intensities than previously possible. Many of the experiments carried out made it clear that optical media do in fact exhibit nonlinear behavior, as exemplified by the following observations  

The properties of a dielectric medium through which an electromagnetic (optical) wave propagates are completely described by the relation between the polarization density vector P(r, t) and the electric-field vector E r, t). It was suggested that P(r, t) could be regarded as the output of a system whose input was E(r, t). The mathematical relation between the vector functions P(r, t) and E(r, t) defines the system and is governed by the characteristics of the medium. The medium is said to be nonlinear if this relation is nonlinear. 

In the previous section the effects of a d.c. bias field on optical properties were discussed. The effects arise because the bias field is sufficiently strong ( 106 Y m ) to significantly disturb the structure of an anisotropic crystal such as LiNb03, a 

Field strengths as high as this, if applied statically or at low frequency, are strong enough to detach electrons from atoms or ions and cause breakdown. As a component of light the peak fields persist for only very short times ( 10 15 s) and so do not cause breakdown. 

Because the susceptibilities are tensors, for the linear dependence we have 

In the literature relating to second harmonic generation d-coefficients are sometimes used rather than vs when, employing a contracted notation (jk = s (1,2,. . ., 6)) 

If laser light of sufficient intensity is propagating through an optically nonlinear material, and the time dependence of the electric vector component of the electromagnetic field is given by E = E0 sin(cot), then from Eq. (8.35), the polarization is given by 

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Mukamel S 1995 Prf/rc/p/es of Non-linear Optical Spectroscopy (New York Oxford University Press)... 

A good introduction to the use of coherent optical teclmiques and their use to probe molecular spectra. Shen Y R 1984 The Principles of Non-linear Optics (New York Wiley)... 

McGlip J F 1990 Epioptics linear and non-linear optical spectroscopy of surfaces and interfaces J. Phys. Condens Matter 2 7985-8006... 

Furtlier details of PDLCs can be found in tire excellent monograph by Drzaic [121]. A review of tire non-linear optical properties of PDLCs has also been presented [1241. 

R. A. Haim and D. Bloor, eds.. Organic Materials for Non-linear Optics II, Royal Society of Chemistry, Cambridge, UK, 1991. 

Optics Electrochromic displays, optical filters (windows with adjustable transparency), materials with non-linear optical properties... 

Unlike linear optical effects such as absorption, reflection, and scattering, second order non-linear optical effects are inherently specific for surfaces and interfaces. These effects, namely second harmonic generation (SHG) and sum frequency generation (SFG), are dipole-forbidden in the bulk of centrosymmetric media. In the investigation of isotropic phases such as liquids, gases, and amorphous solids, in particular, signals arise exclusively from the surface or interface region, where the symmetry is disrupted. Non-linear optics are applicable in-situ without the need for a vacuum, and the time response is rapid. 

A concise survey of where the broad domain of optical information processing had got to a few years ago is in a book issued by the European Commission (Kotte et al. 1989), while a good overview of non-linear optical materials is by Bloor (1994). 

There is a growing interest in the non-linear optical (NLO) properties of organic materials. Organic and polymeric materials with large non-linear optical coefficients can be used in principle in optoelectronic and photonic devices, and a great deal of research effort has been expended in efforts to design new compounds with optimal NLO properties. 

Tantalum and niobium are added, in the form of carbides, to cemented carbide compositions used in the production of cutting tools. Pure oxides are widely used in the optical industiy as additives and deposits, and in organic synthesis processes as catalysts and promoters [12, 13]. Binary and more complex oxide compounds based on tantalum and niobium form a huge family of ferroelectric materials that have high Curie temperatures, high dielectric permittivity, and piezoelectric, pyroelectric and non-linear optical properties [14-17]. Compounds of this class are used in the production of energy transformers, quantum electronics, piezoelectrics, acoustics, and so on. Two of... 

Spontaneous polarization and non-linear optical effect in niobium and tantalum fluoride compounds... 

The index of refraction in a non-linear optical material can be written ... 

A.J. Hceger, D. Moses, M. Sinclair, Semiconducting polymers fast response non-linear optical materials, Synth. Met., 1986. 15, 95. 

The benzannulation reaction of ethynylferrocene 120 with the diterpenoid chromium alkoxycarbene 119 leads to novel diterpenoid ferrocenyl quinones 121 which, due to their electron-transfer properties, are regarded as potential candidates for non-linear optical materials [71] (Scheme 52). 

Wudl F, Ikenoue Y, Patil AO in Ulrich D, Prassad PN (eds) Non-linear Optical and Electroactive Polymers, Plenum Press, New York, in press... 

The present study demonstrates that the analytic calculation of hyperpolarizability dispersion coefficients provides an efficient alternative to the pointwise calculation of dispersion curves. The dispersion coefficients provide additional insight into non-linear optical properties and are transferable between the various optical processes, also to processes not investigated here as for example the ac-Kerr effect or coherent anti-Stokes Raman scattering (CARS), which depend on two independent laser frequencies and would be expensive to study with calculations ex-plictly frequency-dependent calculations. 

The unique features of chalcogenide glasses (Chap. 6), such as quasi-stability, photoconductivity, infrared transparency, non-linear optical properties, and ionic... 

The first part of this paper responds to the first two problems through the calculation of the polarizability of CO (1). In this work, we bring our contribution to the three formal challenges enumerated by Ratner (2) in the special issue of Int. J. Quant. Chem. devoted to the understanding and calculation of the non linear optical response of molecules ... 

In a previous work [1,2], we were interested in the calculation of second order hyperpolarizabilities of eonjugated systems including substituted benzenes, pyridine N-oxydes and vinyl oligomers, in relation with non linear optical activity [3]. We showed that MNDO ealeulations were in good agreement with SCF ab initio results obtained using a double zeta basis set plus polarization and diffuse orbitals. 

J.M. Andre, C. Barbier, V.P. Bodart and J. Delhalle, Non linear optical properties of organic molecules and crystals. Vol. 2, D.S. Chemla and J. Zyss Ed. 

Kohei Uosaki received his B.Eng. and M.Eng. degrees from Osaka University and his Ph.D. in Physical Chemistry from flinders University of South Australia. He vas a Research Chemist at Mitsubishi Petrochemical Co. Ltd. from 1971 to 1978 and a Research Officer at Inorganic Chemistry Laboratory, Oxford University, U.K. bet veen 1978 and 1980 before joining Hokkaido University in 1980 as Assistant Professor in the Department of Chemistry. He vas promoted to Associate Professor in 1981 and Professor in 1990. He is also a Principal Investigator of International Center for Materials Nanoarchitectonics (MANA) Satellite, National Institute for Materials Science (NIMS) since 2008. His scientific interests include photoelectrochemistry of semiconductor electrodes, surface electrochemistry of single crystalline metal electrodes, electrocatalysis, modification of solid surfaces by molecular layers, and non-linear optical spectroscopy at interfaces. 

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