Intrinsic refractivity, optical properties

There are two sets of quantities that are often used to describe optical properties the real and imaginary parts of the complex refractive index N = n + ik and the real and imaginary parts of the complex dielectric function (or relative permittivity) e = c + ie". These two sets of quantities are not independent either may be thought of as describing the intrinsic optical properties of matter. The relations between the two are, from (2.47) and (2.48),... 

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. 

Fig. 1 Chemical interaction mechanisms, basic components of the optical sensor instrumentation and their operation. Mechanisms direct measurement of chemical compounds that exhibit spectroscopic properties (1 A) and measurement of light originating from a chemical or a biological reaction in chemiluminescent or bioluminescent phenomena (IB) 2 optodes based on the interaction of indicators and labels with light, which are immobilized in a support and sensors that modify the intrinsic physical or chemical properties of a waveguide (refractive index, phase, etc.) as a result of the presence of the analyte (3A), a recognition element (35), an intermediate analyte (3C) or an indicator (3D)...

In this chapter we have reviewed a number of techniques used for optical characterization of organic samples, in particular those concerning the determination of complex optical constants and the dynamics of elementary photoexcitations. It has been stressed that very good optical quality samples are needed in order to obtain reliable estimates of the refractive index. In general, samples with controlled morphology, low defect and impurity concentration, and good optical quality allow more reliable photophysical studies and hence better determination of the intrinsic properties of the material. 

Size separation has been successfully demonstrated in many of microfluidic separation approaches of a continuous mode. In the field-based separation such as DEP, acoustic, and optical methods, the force acting on particles is proportional to their volume and corresponding native physical properties, including dielectric susceptibility, particle compressibility, and refractive index, respectively [10-12]. In many applications, target and non-target particles, however, exhibit similar responses to the acting force that precludes sorting particles based on intrinsic phenot> pes. On the other hand, the... 

Nonmetallic inorganic materials are widely used for optical purposes lenses, pigments, interference filters, laser hosts, luminescent coatings, displays, solar cells, fiber optics, lamp bulbs, and tubes. For optical applications use is made of the refractory index, light absorption, luminescence, and nonlinear optical behavior of materials. These are intrinsic but may depend on the concentration of impurities. Refraction index and optical absorptivity in insulators are atomic properties and are only indirectly related to the structure, but the structure affects the selection rules and the term splitting in the atomic chromophores. The coordination number determines the intensity and wavelength of absorption and... 

These examples cQso illustrate the difference in spatial resolution and contrast mechanisms between optical and infrared microscopies. While optical microscopy is capable of higher spatial resolution, its discrimination is limited to a difference in the average of a property of materials, namely refractive index, unless specially labeled to detect a property of the label. Infrared microspectroscopy derives its contrast mechanism from the intrinsic composition of the material but suffers from a poorer spatial resolution. A judicious use of the two complementary techniques is often required to achieve good characterization. While the example above illustrated the detection of differences, FTIR microspectroscopy can also be used to determine homogeneity. For example, compositional differences in a PP-PE film could not be detected between the surface and up to 500 pm into the bulk of the sample [61]. 

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