Near-field Nonlinear Optics

Nonlinear optical phenomena, as well as near-field optics, provide us with super resolving capability [20]. The probability of nonlinear optical phenomena is proportional to the number of photons which participate in the phenomenon. For example, the intensity distribution of two-photon excited fluorescence corresponds to the square of the excitation light. Thus, we proposed a combination of the field... 

In this chapter, we showed the capability of near-field optical spectroscopy combined with vibrational spectroscopy and nonlinear optics for biochemical applications. The evanescent field localized at the nanoscale tip realized the extremely small light source for various spectroscopes in the near-field. Especially when the tip is made... 

Abstract Optical techniques for three-dimensional micro- and nanostructuring of transparent and photo-sensitive materials are reviewed with emphasis on methods of manipulation of the optical field, such as beam focusing, the use of ultrashort pulses, and plasmonic and near-field effects. The linear and nonlinear optical response of materials to classical optical fields as well as exploitation of the advantages of quantum lithography are discussed. 

The terms beyond odE are not linear in E they are referred to as the nonlinear polarization and give rise to nonlinear optical effects. Also note that at small fields the polarization will more nearly approximate a linear response however, with increasing field strength, nonlinear effects become more important. Since a p, y, there were few observations of NLO effects before the invention of the laser with its associated large electric fields. 

Two of the most important nonlinear optical (NLO) processess, electro-optic switching and second harmonic generation, are second order effects. As such, they occur in materials consisting of noncentrosymmetrically arranged molecular subunits whose polarizability contains a second order dependence on electric fields. Excluding the special cases of noncentrosymmetric but nonpolar crystals, which would be nearly impossible to design from first principles, the rational fabrication of an optimal material would result from the simultaneous maximization of the molecular second order coefficients (first hyperpolarizabilities, p) and the polar order parameters of the assembly of subunits. (1)... 

Gregor MJ, Biome PG, Schofer J, Ulbrich RG (1996) Probe-surface interaction in near-field optical microscopy the nonlinear bending force mechanism. Appl Phys Lett 68 307... 

Ichimura T, Hayazawa N, Hashimoto M, Inouye Y, Kawata S (2004) Application of tip-enhanced microscopy for nonlinear Raman spectroscopy. Appl Phys Lett 84 1768 Ichimura T, Hayazawa N, Hashimoto M, Inouye Y, Kawata S (2004) Tip-enhanced coherent anti-stokes raman scattering for vibrational nanoimaging. Phys Rev Lett 92 220801 Tanaka S, Maeda Y, Cai L, Tabata H, Kawai T (2001) Application of tip-enhanced microscopy for nonlinear Raman spectroscopy. Jpn J Appl Phys 40 4217 Watanabe H, Ishida Y, Hayazawa N, Inouye Y, Kawata S (2004) Tip-enhanced near-field Raman analysis of tip-pressurized adenine molecule. Phys Rev B 69 155418 Yano T, Verma P, Saito Y, Ichimura T, Kawata S (2009) Pressure-assisted tip-enhanced Raman imaging at a resolution of a few nanometres. Nature Photon 3 473 Yano T, Inouye Y, Kawata S (2006) Nanoscale uniaxial pressure effect of a carbon nanotube bundle on tip-enhanced near-field Raman spectra. Nano Lett 6 1269 Downes A, Salter D, Elfick A (2006) Heating effects in tip-enhanced optical microscopy. Opt Exp 14 5216... 

Nonlinear optical responses of molecules near fractal metal clusters are expected to be enhanced by many orders of magnitude. They are proportional to a high-order function of the local field [361], Strong enhancement of multiphoton absorption potentially exists because simultaneous absorption of n photons scales the intensity (/) to the power of n (/"). Thus, net multiphoton absorption is proportional to the average value of /" over a given volume. It can therefore approach a value that is orders of magnitude larger. 

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