Optic-frequency dielectric constant, optical

Here, and are the static (low-frequency) and optical (high-frequency) dielectric constants respectively. 

In this chapter some of the presently known optical properties of zinc oxide are reviewed. In particular, the anisotropic dielectric functions (DFs) of ZnO and related compounds from the far-infrared (FIR) to the vacuum-ultraviolet (VUV) spectral range are studied. Thereupon, many fundamental physical parameters can be derived, such as the optical phonon-mode frequencies and their broadening values, the free-charge-carrier parameters, the static and high-frequency dielectric constants, the dispersion of the indices of refraction within the band-gap region, the fundamental and above-band-gap band-to-band transition energies and their excitonic contributions. 

The electron effective mass in GaN is now reasonably well established by cyclotron resonance measurements [14-16] asm, = (0.22 0.0 l)m, and the low frequency dielectric constant (appropriately averaged spatially) e(0) = 9.5 0.2, from infrared refractive index and optic phonon energy measurements [17]. We can therefore derive a reliable value for the hydrogenic donor ionisation energy of EDH = (33.0 1.5) meV which compares well with IR absorption measurements, giving Ed = (35 1) meV [18] (see below). The discrepancy is readily explained in terms of a small chemical shift. 

Figure 17.1.9 Dependence of the real and imaginary components of the optical-frequency dielectric constant of gold on the energy of incident photons. The normal-incidence reflectivity of gold in air is shown in the inset. [From D. M. Kolb and J. D. E. McIntyre, Surf. ScL, 28, 321 (1971), with permission.]...

In analogy to the optical models for doped In203, the Drude model has been applied to undoped [187] and doped [155] tin oxide layers. In pure Sn02 films, the high frequency dielectric constant as well as the plasma frequency cOp, are strongly... 

Ice is a (leaky) dielectric and may therefore contain polarization charges from three sources making characteristic contributions to the dielectric constant. At optical frequencies, the high-frequency dielectric constant is caused by the displacement of electron clouds and of atomic nuclei from their equilibrium positions. It is temperature-independent. 

Here is the high-frequency dielectric constant, the static dielectric constant, and Lo the frequency of the longitudinal optical vibration mode. The values of P range from about 3 (GaP, ZnS, Csl, Nal), via 4(La202S), 5.6 (Y3AI5O12), to 7 (CaW04, YVO4). 

Over the past five years, a new class of electro-optic polymeric materials has evolved which provides for the first time the capability to fabricate simple and inexpensive electro-optic devices on a variety of substrates. More importantly, these materials possess optical dielectric constants (or refractive indexes) comparable to radio-frequency dielectric constants allowing for fabrication of devices in which the electric field and the optical field propagate at the same velocity. Finally, the low dielectric constant of these materials relative to inorganic ionic crys s provides for operation of devices at much higher efficiency. Although the above facts have been clear for some time, the practical applications of these materials cannot be realized until materials can be created which satisfy a host of practical requirements and until device architectures and fabrication techniques appropriate for these materials can be developed. We will describe here research directed toward both of these ends. 

Optical Conductivity Optical Dielectric Function Discussion of Conductivity and Dielectric Functions Microwave Frequency Dielectric Constant Pseudoprotonic Add Doping of Polyanihne Comparison of Doped Aniline Tetramers, Aniline Octamers, and Polyanihne Chiral Metalhc-Doped Polyanihne... 

The two dielectric constants in Eq. [6] warrant some discussion. The quantity e, which is sometimes called simply the dielectric constant (often denoted e instead of e ) is more precisely the static or zero-frequency dielectric constant. (Even more precisely, it is the scalar electric permittivity relative to that of vacuum, and is therefore dimensionless.) This quantity includes the effects of both orientational and electronic polarization. For a vertical ionization process, however, the solvent s orientational degrees of freedom are frozen, but the electron densities of individual solvent molecules can adjust on the same timescale on which the ionization process occurs. Such considerations lead to a correction involving the optical (infinite-frequency) dielectric constant, where denotes the solvent s index of refraction. 

The optical phonon energies are linked to the low- and high-frequency dielectric constants and therefore can be calculated from one another. Electromagnetic theory indicates that for any longitudinal electromagnetic wave to propagate, the dielectric function e((0) must vanish. Doing so leads to [113]... 

Fig. 29. Dielectric behavior of an ideal polar material, (a) Effect of frequen r on the static value of the dielectric constant, in relation to the dipole contribution, and on the dissipation factor and loss index as frequency is reduced the dielectric constant reaches its highest static value and the dissipation factor and loss index reach a minimum, (b) Debye curves representing a set or distribution of relaxation times, e s = Static dielectric constant e oo = high frequency dielectric constant t = dielectric relaxation time and n = optical index of refraction, m = 27zf = angular frequency. The broadened loss curve caused by multiple relaxation time is shown by the dashed curve.

Figure Bl.5.5 Schematic representation of the phenomenological model for second-order nonlinear optical effects at the interface between two centrosynnnetric media. Input waves at frequencies or and m2, witii corresponding wavevectors /Cj(co and k (o 2), are approaching the interface from medium 1. Nonlinear radiation at frequency co is emitted in directions described by the wavevectors /c Cco ) (reflected in medium 1) and /c2(k>3) (transmitted in medium 2). The linear dielectric constants of media 1, 2 and the interface are denoted by E2, and s, respectively. The figure shows the vz-plane (the plane of incidence) withz increasing from top to bottom and z = 0 defining the interface.

The dielectric constant is a measure of the ease with which charged species in a material can be displaced to form dipoles. There are four primary mechanisms of polarization in glasses (13) electronic, atomic, orientational, and interfacial polarization. Electronic polarization arises from the displacement of electron clouds and is important at optical (ultraviolet) frequencies. At optical frequencies, the dielectric constant of a glass is related to the refractive index k =. Atomic polarization occurs at infrared frequencies and involves the displacement of positive and negative ions. 

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