Refractive indices electric field effects

P( P(-o> w,0) P(0 -fa>,w) Y( - Y(-2(i) (i>,tD,0) Y(-o) (i>,0,0) Second harmonic generation (SHG) Electrooptic Pockels effect Optical rectification Third harmonic generation DC electric-field-induced SHG Intensity-dependent refractive index Optical Kerr effect Coherent anti-Stokes Raman pSHG pEOPE pOR. yTHG. EFISH oj DC-SHG. JlDRI or. yOKE. yCARS... 

Suppose the waveguide is composed of an unbounded uniform medium of refractive index i.e. effectively free space . The modal fields are then found from Maxwell s equations to be the fields of transverse electromagnetic, or TEM, waves propagating in the z-direction parallel to the waveguide axis. Thus, the propagation constant )S = n k, the longitudinal components satisfy e = h = 0, and the transverse electric and magnetic fields are related by... 

Using Equation 12.12 one obtains (AA/A — Av /v 2) = (Aao/ao). We see that precise refractive index differences measured over a reasonable range of wavelengths allow the recovery of the polarizability isotope effect (i.e. the isotope effect on the electric field induced dipole moment), provided the molar volume and its isotope effect are available. 

Non-stationary self-effects of the light beam depend on the pulse duration with respect to the time Tr of nonlinear response of the medium. When the response is instantaneous, the refractive index at the time t is defined by the value of electrical field at the same moment. If the time of a nonlinear response is finite, the nonlinear part of the refractive index satisfies the... 

Figure 3.38. Principle of the photorefractive effect By photoexcitation, charges are generated that have different mobilities, (a) The holographic irradiation intensity proHle. Due to the different diffusion and migration velocity of negative and positive charge carriers, a space-charge modulation is formed, (b) The charge density proHle. The space-charge modulation creates an electric Held that is phase shifted by 7t/2. (c) The electric field profile. The refractive index modulation follows the electric field by electrooptic response, (d) The refractive index profile.

An applied electric field can also change a material s linear susceptibility, and thus its refractive index. This effect is known as the linear electro-optic (LEO) or Pocket s effect, and it can be used to modulate light by changing the voltage applied to a second-order NLO material. The applied voltage anisotropically distorts the electron... 

Electrooptic materials. The dependence of refractive index on the electric field or the lattice polarization is referred to as the electrooptic effect ... 

Physical properties of liquid crystals are generally anisotropic (see, for example, du Jeu, 1980). The anisotropic physical properties that are relevant to display devices are refractive index, dielectric permittivity and orientational elasticity (Raynes, 1983). A nematic LC has two principal refractive indices, Un and measured parallel and perpendicular to the nematic director respectively. The birefringence An = ny — rij is positive, typically around 0.25. The anisotropy in the dielectric permittivity which is given by As = II — Sj is the driving force for most electrooptic effects in LCs. The electric contribution to the free energy contains a term that depends on the angle between the director n and the electric field E and is given by... 

The supporting medium (aqueous or organic solvents membrane-mimetic compartments) also has a profound influence on the optical and electro-optical properties of nanosized semiconductor particles. This dielectric confinement (or local field effect) originates, primarily, in the difference between the refractive indices of semiconductor particles and the surrounding medium [573, 604], In general, the refractive index of the medium is lower than that of the semiconductor particle, which enhances the local electric field adjacent to the semiconductor particle surface as compared with the incident field intensity. Dielectric confinement of semiconductor particles also manifests in altered optical and electro-optical behavior. 

Just as linear polarization leads to linear optical effects, such as refractive index and birefringence, nonlinear polarization leads to other and usually more subtle (nonlinear) effects. It is precisely these effects we hope to understand and exploit. In Figure 14, application of a symmetric field (i.e., the electric field associated with the light wave) to the anharmonic potential leads to an asymmetric polarization response. This polarization wave shows diminished maxima in one direction and accentuated... 

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