Optical properties, non linear

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. 

Such efforts have met with limited success, and the reason usually advanced is our lack of understanding of the frequency dependence of molecular NLO properties. In classical electromagnetism, we refer to properties that depend on the frequency of radiation as dispersive and we say that (for example) dispersion is responsible for a rainbow. The blue colour of the sky is a dispersion effect, as is the red sky at night and morning. There is more to it than that, and you might like to read a more advanced text (Hinchliffe and Munn, 1985). 

We have seen above how to calculate polarizabilities and hyperpolarizabilities for statie electric fields. I will consider a simple oscillating electric field 

I should mention the convention that in electromagnetic studies we write oscillating fields as (e.g.) E = Eq expfjujf) rather than E = Eq cos(ju)f). There is nothing sinister in this—it just makes the maths simpler. A laboratory electric field is the real part of E = Eq exp(jujr), and so we have to remember to take the real part of any result before comparison with experiment. 

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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. 

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

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... 

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. 

Finally, some liquid-crystalline elastomers exhibit interesting photonic effects [200,201]. Of particular importance are non-linear optical properties. These involve interactions of light with the elastomer in a way that some of the characteristics of the incident light change, specifically its phase or frequency (including frequency doubling or frequency mixing) [202,203]. 

Metal complexes as dyes for optical data storage and electrochromic materials (R.J. Mortimer, N.M. Rowley) Non-linear optical properties of metal complexes (B. Coe)... 

Another example of recent work is the demonstration of non linear optical properties of Cu nanoparticles in an ITO matrix.62 This is an example of a structure that can be obtained fully by solution processing. Coupled with this is the observation of enhanced surface plasmons in some nanoparticles, which potentially produces tailorable, non linear optical properties.63 This effect can... 

Ferrocenes as Materials Displaying Non-linear Optical Properties. One of the most recent applications of ferrocene molecules exploits their non-linear optical properties. Firstly, however, we must describe the concept of ffffnon-linear optical properties.67,68... 

The non-linear optical properties of a material are evaluated by measuring (using techniques from the field of physics) its molecular hyperpolarizability coefficient (3. 

There are many organic and inorganic materials available which exhibit significant non-linear optical properties. In the present context, however, we underline that ferrocene derivatives were the first organo-metallic materials observed possessing non-linear optical properties. In fact, in 1987 it was reported that ci s-ferrocenyl-2-(4-nitrophenyl)ethylene has a 62-fold greater efficiency than urea in generating the second harmonic, Scheme 13.71... 

Measurement of non-linear optical properties [580] also provides a means for characterizing size-quantized semiconductor particles. Third-order optical non-linearity of size-quantized semiconductor particles has been discussed in terms of resonant and non-resonant contributions [11]. Resonant non-linearity is expected to increase with decreasing particle size and increasing absorption coefficients. 

Particles in the nanometer-size regime necessarily have large surface-to-volume ratios approximately one-third of the atoms are located on the surfaces of 40 A CdS particles, for example. Furthermore, colloid chemical preparations typically result in the development of surface imperfections and in the incorporation of adventitious or deliberately added dopants. Such surface defects act as electron and/or hole traps and, thus, substantially modify the optical and electro-optical properties of nanosized semiconductor particles. Altered photostabilities [595], fluorescence [579, 594, 596, 597], and non-linear optical properties [11, 598-600] are manifestations of the surface effects in colloidal semiconductors. 

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