Multiphoton polymerization

The latter case involves the infiltration of a colloidal crystal with a pho-topolymerizable monomer or a photoinitiator. Selective polymerization of the monomer in the focus of a confocal microscope via multiphoton polymerization renders a protected environment for the colloidal material. The unpolymerized monomer can be removed with the conservation of the engraved defect [139,140]. 

Dong, X.Z., Zhao, Z.S., and Duan, X.M. (2008) Improving spatial resolution and reducing aspect ratio in multiphoton polymerization nanofabrication. 

Bhawalkar JD, He GS, Prasad PN (1996) Nonlinear multiphoton processes in organic and polymeric materials. Rep Prog Phys 59 1041-1070... 

One strategy is to fabricate a template structure using polymeric material (thus, using the same chemistry as described in Sects. 5.2 and 5.3) and back-fill or coat this structure with inorganic materials. For example, surface modification, followed by electroless deposition of Ag [217-219] or Cu [220], or by chemical reduction of Au solutions by surface functionalities [220], has been used to obtain metallized structures, while infiltration of polymeric photonic bandgap-type structures with Ti(0 Pr)4 solution, followed by hydrolysis and calcination, has been used to obtain highly refractive inverted Xi02 structures [221]. Au has also been deposited onto multiphoton-patterned matrices of biomaterials [194]. 

In addition to using imaging as a technique to obtain spatially and temporally patterned chemical data from a sample, one can also pattern chemical reactions in space and time using similar methods. Figure 2.18 demonstrates an example in which multiphoton scanning with ultrafast laser pulses was used to polymerize a photoresist resin with about 120 nm spatial resolution in three dimensions. 

Wong KL, Law GL, Kwok WM, Wong WT, Phillips DL. Simultaneous observation of green multiphoton upconversion and red and blue NLO process from polymeric terbium(III)complexes. Angew Chem Int Ed 2005 44 3436. 

This article introduces the field of nonlinear optics and the electronic nonlinear optical (NLO) response of polymers and pol5mier composites. Both second- and third-order NLO phenomena are included, with primary emphasis on harmonic generation, the intensity-dependent refractive index, and nonlinear (multiphoton) absorption effects. The beginning sections introduce the phenomena and explain how the order of the nonlinearity can be understood from a series expansion of the polarization in powers of the electric-field. In addition to listing the variety of nonlinear optical phenomena and some applications, some of the advantages of polymeric materials for NLO applications are also surveyed. 

The laser-induced breakdown is not necessarily related to the multiphoton absorption process [145] while photopolymerization depends on it strictly [24, 25]. Therefore, measures could be taken to increase the quantum yield of polymerization, and therefore the dynamic power range. A simple and effective method is choosing laser wavelength so that radicals are produced more efficiently. It was experimentally observed [127] that the two-... 

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