Nonlinear optics basic concepts

D. L. Mills, Nonlinear Optics, Basic Concepts, Springer, Berlin, 1998. 

D.L. Mill, "Nonlinear Optics Basic concepts" 2nd ed. (Springer-Verlag, New York,... 

The tutorial begins with a description of the basic concepts of nonlinear optics and presents illustrations from simple models to account for the origin of the effects. The microscopic or molecular origin of these effects is then discussed in more detail. Following this, the relationship between molecular responses and the effects observed in bulk materials are presented and finally some of the experimental methods used to characterize these effects are described. 

BASIC CONCEPTS OF SECOND-ORDER NONLINEAR OPTICS... 

Demtrdder W 1996 Laser Spectroscopy Basic Concepts and Instrumentation 2nd edn (Beriin Springer) Levenson M D and Kano S S 1988 Introduction to Nonlinear Laser Spectroscopy Boston, MA Academic) Mukamei S 1995 Principles of Nonlinear Optical Spectroscopy Oxford Oxford University Press)... 

Figure 2 illustrates the basic concept of a typical pump-probe spectroscopy used in most ultrafast spectroscopy techniques. In its simplest form the output pulse train of an ultrafast laser is divided in two by a beam splitter. One pulse in train (called pump) first excites the sample under investigation. The second pulse train (called probe) will probe the sample with a suitable time delay with respect to the pump by introducing an optical delay in its path and some optical property (e.g., reflectivity, absorption, Raman scattering, luminescence, optical nonlinear responses) of the sample is then detected to investigate the changes produced by the pump. In most of the time-resolved pump-probe experiments, the time resolution is limited only by the pulse width of the laser or the jitter between the laser systems. 

The applicable fundamental concepts of nonlinear integrated optics for SHG were outlined decades ago and can be found in a number of review papers [6-8]. The basic theory as applied to organic materials and polymers is of course unchanged from that for dielectric materials and these papers are still very useful. Some twenty plus years ago, nonlinear integrated optical experiments started to be conducted, but mostly on inorganics and crystals. The specific field of amorphous and semi-ordered organics came when the chemical engineering of nonlinear chromophores was developed. 

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