Second order NLO properties including SHG arise from the second order NLO susceptibility x tensor in the relationship for the bulk polarization, P, such that (2-3) [Pg.298]

Non-linear second-order optical properties such as second harmonic generation (SHG) and the linear electrooptic effect are due to the non-linear susceptibility in the relation between the polarization and the applied electric field. SHG involves the [Pg.465]

The states /m and fn could be anj state in the molecule, so the full molecular second order SHG polarization, Pshg must be represented as the sum of all possible microscopic three-wave scattering events(1) [Pg.687]

Apart from SHG and THG, Eq. (3) also reveals a second-order DC contribution (optical rectification) and the optical Kerr effect (i.e., the dependence of the term at the original frequency upon the light intensity / CX Eg ). A similar expression can be derived for the macroscopic polarization. Other NLO effects can be described utilizing different frequencies and/or static "(0) or magnetic B(0) fields (see Table 1). [Pg.3418]

The 1/33=0 result implies that it is difficult to produce an axial second-order polarization with an optical field parallel to the myosin/actin filaments and that the radiated SHG are contributed mainly from d =dacx and dis=dxzx- Note that the non-zero d i and dis suggest the chirahty in myosin/actin filaments inside a myofibril. This suggestion comphes with a previous conjecture, which states that the nonlinear optical properties in several biological materials (e.g. collagen matrix and muscle) are induced or enhanced by the chirality in their structure [68,69]. [Pg.39]

The susceptibility tensors measure the macroscopic compliance of the electrons. Since the second order polarization is a second rank tensor, SHG is zero in a centrosymmetric or randomly oriented system. To make the material capable of SHG, the NLO dopants must be oriented noncentrosymmetricaly in the polymer matrix (2-3). When modeling the poled, doped films using a free gas approximation, the poled second order susceptibilities are given by (2.19) [Pg.298]

Optical frequency up-conversion, or second harmonic generation (SHG), in nanostructured surfaces can be also considered as a kind of field enhance-menf [61]. In general, SHG efficiency is proportional to the square of nonlinear polarization ha (x [P (2

Turning to the investigation of the anisotropy of second-order nonlinearity, one must be cautious of evaluation of the magnitude of X zxx Performed as just described by simply rotating the plane of polarization of the laser beam. We tried this operation and saw a drastic decrease in I2<0. However, this may merely reflect the smaller magnitude of lQ in this SHG process. In this case [Pg.123]

The general condition of second-order NLO effects involves the interaction of two distinct waves of frequencies coi and C02 in an NLO material. In this case, polarization occurs at sum (coi + C02) and difference (coi — C02) frequencies. This electronic polarization will therefore reemit radiation at these frequencies, with contributions that depend on x , which is itself frequency-dependent. The combination of frequencies is called sum (or difference) frequency generation (SFG). SHG is a special case of SFG, in which the two frequencies are equal. [Pg.674]

Nonlinear optics deals with physical systems described by Maxwell equations with an nonlinear polarization vector. One of the best known nonlinear optical processes is the second-harmonic generation (SHG) of light. In this section we consider a well-known set of equations describing generation of the second harmonic of light in a medium with second-order nonlinear susceptibility %(2 The classical approach of this section is extended to a quantum case in Section IV. [Pg.358]

Because the second harmonic response is sensitive to the polarizability of the interface, it is sensitive to the adsorption and desorption of surface species and is capable of quantifying surface species concentrations. Furthermore, SHG can be used to quantify surface order and determine surface symmetry by measuring the anisotropic polarization dependence of the second harmonic response. SHG can also be used to determine important molecular-level and electrochemical quantities such as molecular orientation and surface charge density. [Pg.501]

For certain macroscopic nonlinear parameters the tensor notation can be simplified due to the intrinsic symmetry of the experiment, e.g., second-harmonic generation and the linear electro-optic effect. Let us first consider SHG. The second-order contribution to the polarization is given by Eq. (9). [Pg.3420]

See also in sourсe #XX -- [ Pg.2 ]

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