Optical responsive surfaces

The linear and nonlinear optical responses for this problem are defined by e, 2, e and respectively, as indicated in figure Bl.5.5. In order to detemiine the nonlinear radiation, we need to introduce appropriate pump radiation fields E(m ) and (co2)- If these pump beams are well-collimated, they will give rise to well-collimated radiation emitted tlirough the surface nonlmear response. Because the nonlinear response is present only in a thin layer, phase matching [37] considerations are unimportant and nonlinear emission will be present in both transmitted and reflected directions. 

If we consider the optical response of a molecular monolayer of increasing surface density, the fomi of equation B 1.5.43 is justified in the limit of relatively low density where local-field interactions between the adsorbed species may be neglected. It is difficult to produce any rule for the range of validity of this approximation, as it depends strongly on the system under study, as well as on the desired level of accuracy for the measurement. The relevant corrections, which may be viewed as analogous to the Clausius-Mossotti corrections in linear optics, have been the... 

Figure 14.7. Left Solution-processed quantum dot structure of InP nanoparticles (black dots) in a Ti02 nanoparticle array (open circles). The QDs could sensitize an optical response similar to the dye in a Gratzel cell. Right A schematic of very small QDs (balls) bonded to a controlling surfactant that is bonded to a surface specific element, such as a TCO surface.

These studies demonstrate how the nonlinear optical response from the surface can provide both a qualitative and quantitative probe of chemisorption. 

The surface sensitivity is ensured by detecting the decay products of the photoabsorption process instead of the direct optical response of the medium (transmission, reflection). In particular one can measure the photoelectrons, Au r electrons, secondary electrons, fluorescence photons, photodesorbed ions and neutrals which are ejected as a consequence of the relaxation of the system after the photoionization event. No matter which detection mode is chosen, the observable of the experiment is the interference processes of the primary photoelectron with the backscattered amplitude. 

D. A. Micha, A. Santana, and A. Salam. Nonlinear optical response and yield in the femtosecond photodesorption of CO from the Cu(001) surface a density matrix treatment. J. Chem. Phys., vvv ppp, 2002. to appear. 

III. Surface-Exciton Photodynamics and Intrinsic Relaxation Mechanisms A. The Optical Response of the Surface Exciton... 

The optical response of a monomolecular layer consists of scattered waves at the frequency of the incident wave. Since the surface model is a perfect infinite layer, the scattered waves are reflected and transmitted plane waves. In the case of a 3D crystal, we have defined (Section I.B.2) a dielectric permittivity tensor providing a complete description of the optical response of the 3D crystal. This approach, which embodies the concept of propagation of dressed photons in the 3D matter space, cannot be applied in the 2D matter system, since the photons continue propagating in the 3D space. Therefore, the problem of the 2D exciton must be tackled directly from the general theory of the matter-radiation interaction presented in Section I. 

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