Third-order optical nonlinearity experimental techniques

A variety of experimental techniques have been used to obtain information about the third-order optical nonlinearities and optical power limiting behavior of materials. This section includes descriptions of those techniques that have been used or have potential use with organometallics. For an excellent source of information about other techniques, the interested reader is directed to Ref. 6. 

The term nonlinear optical property refers to an optical property, which can be modified by exposing the material to intense light irradiation. In this section, we focus on the cascaded first- (/ 1 ) and third-order ( / ) susceptibilities describing nonlinear absorption (ESA and 2PA) and nonlinear refraction (n2) processes. Z-scan, pump-probe, and two-photon upconverted fluorescence techniques are among the most used experimental methods for determining optical nonlinearities. 

This review covers the theoretical background and some of the practical aspects of nonlinear optics, including a description of the origins of third-order nonlinearities, systems of units that are encountered, experimental techniques that have been used or may be used to probe the third-order NLO properties of organometallic complexes, and computational methods that have or could be used to calculate third-order NLO properties. Subsequent sections collect comprehensive data of organometallic complexes in tables categorized by complex type and discussions of the results of third-order NLO measurements and calculations performed on organometallic... 

As the local electric field in the particles is enhanced at the SPR, the metal nonlinear optical response can be amplified as compared to the bulk solid one. Moreover, the intrinsic nonlinear properties of metals may themselves be modified by effects linked with electronic confinement. These interesting features have led an increasing number of people to devote their research to the study of nonlinear optical properties of nanocomposite media for about two decades. Tire third-order nonlinear response known as optical Kerr effect have been particularly investigated, both theoretically and experimentally. It results in the linear variation of both the refraction index and the absorption coefficient as a function of light intensity. These effects are usually measured by techniques employing pulsed lasers. 

Because of their large optical nonlinearities and good mechanical, chemical, thermal, and optical stability, organic nonlinear materials are among the leading practical materials for device applications [2]. A number of experimental techniques have been proposed to obtain information about the dispersion, the sign, and the contributions of both the real and imaginary parts of the nonlinear optical response. In this chapter, we will explore the methods most widely used to characterize the third-order nonlinear coefficient and introduce some of the more recent results. 

One of our major contributions to the experimental techniques used in nonlinear spectroscopy has been the wide-ranging use of diffractive optics. Simple period gratings have been used in third-order resonant [22,72,73] and nonresonant... 

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