Multiphoton material

The phenomenon of multiphoton dissociation finds a possible application in the separation of isotopes. For this purpose it is not only the high power of the laser that is important but the fact that it is highly monochromatic. This latter property makes it possible, in favourable circumstances, for the laser radiation to be absorbed selectively by a single isotopic molecular species. This species is then selectively dissociated resulting in isotopic enrichment both in the dissociation products and in the undissociated material. 

He GS, Tan LS, Zheng Q, Prasad PN (2008) Multiphoton absorbing materials molecular designs, characterizations, and applications. Chem Rev 108 1245-1330... 

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

Direct visualization of femtosecond filamentation is crucial to understanding the phenomenon. As the energy of a single infrared photon is much too small to effect an electronic transition, one has to take recourse to multiphoton absorption induced fluorescence to come up with a scheme to directly visualize filamentation in condensed media. One such scheme that has been successfully implemented involves the use of a crystal of barium fluoride, a material that is known to be very good scintillator [38]. 

The latest advancement in femtosecond (fs)-based micromachining technology has opened a new window of opportunity for fabrication of microdevices. Direct exposure of most solid materials (including fused silica glass) to high power fs laser pulses may lead to the ablation of a thin layer of materials at the laser focal point13. Due to the multiphoton nature of the laser-material interaction, the ablation process can be conducted on the material surface as well as within its... 

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]. 

Multiphoton microscopy has been used to initiate photopolymerization of a photoresist material in three dimensions with resolution in the hundred-nanometer range. 

MALDI MCM-41 MCR MD ME MEM MI MPM MRI MS MVA Matrix-assisted Laser Desorption/Ionization Mobile Crystalline Material-41 Multivariate Curve Resolution Molecular Dynamics Matrix-enhanced Magnetic Force Micrscopy Multivariate Image Multiphoton Microscopy Magnetic Resonance Imaging Mass Spectroscopy Multivariate Analysis... 

LeBozec and co-workers have reported nonlinear behavior in a series ofterpyri-dyl and dipicolinic acid complexes, with further studies on these complexes by Maury and co-workers [83, 84]. Their research was on new molecular materials for optoelectronics, with studies based on octupolar nonlinear optical molecules showing that molecular quadratic hyperpolarizability values were strongly influenced by the symmetry of the complexes [85]. Other studies on organic-lanthanide complexes with nonlinear optics have also reported second- and third-harmonic generation behavior with simultaneous multiphoton absorption properties [50]. Such studies have shown the importance of coordination chemistry as a versatile tool in the design of nonlinear materials. 

Gold nanoparticles have large second- and third-order nonlinear susceptibilities and are therefore a promising class of nonlinear optical materials.214 We will briefly discuss several nonlinear optical processes from metal nanoparticles, such as multiphoton luminescence, hyper-Rayleigh scattering, and multiharmonic generation. 

The chemical vapor deposition processes obtained from the laser induced multiphoton decomposition of neat organogermanes or sensitized by SFg have also been characterized for several systems. For example, the decomposition of Ge(OMe)4 leads to the formation of organoxogermanium polymers, while EtOGeMcs leads to materials rich in Ge and containing small amounts of oxygen and carbon. In the latter case, two primary processes have been proposed to be responsible for the chain reactions leading to the final products (equations 40a and 40b)... 

It was supposed that, because of a rapid intramolecular energy pooling, infrared laser multiphoton decomposition at low laser fluence usually proceeds via the energetically most favourable reaction channel [26], From the material balance of gaseous decomposition products (Fig. 2) it was inferred that there are common primary steps for both the thermal and the explosive laser-induced decomposition of (fluoromethyl)silanes. 

---