The nonlinear optical effects described in Chaps. 4 and 5 have to be characterized for a given material up to a certain level before they can be applied in photonics. The already wide range of applications in science, technology and medicine contains analytic aspects, questions of the structure of matter, reaction mechanisms on all time scales and the production of new states, phases or even of new matter. Thus two main questions are asked in nonlinear optics:


Which nonlinear optical effect is, for a given material suitable for a new laser analytic method (analytic tasks)?


Which nonlinear optical effect is most suitable for a desired photonic application (material and light modification tasks)?

Nonlinear Optical Spectroscopy

Pulse radiolysis of polystyrene and benzene in cyclohexane, chloroform and carbon tetrachloride

Picosecond pulse radiolysis studies on the formation of excited singlet states of solute molecules in several saturated hydrocarbon and ethanol solvents

Molecular mechanisms of nanosecond and femtosecond laser ablation and morphology-changing dynamics of neat liquid benzene derivatives, such as benzyl chloride and toluene, were investigated by photoacoustic measurement, nanosecond shadowgraphy, femtosecond surface light scattering imaging, and time-resolved ultraviolet−visible absorption spectroscopy Ablation thresholds of the liquids were determined by photoacoustic measurement and shadowgraphy, whereas primary processes in ablation were elucidated by time-resolved absorption spectroscopy Femtosecond surface light scattering imaging revealed how electronic excited/radical states evolved to nanometer morphological changes In nanosecond laser ablation, ablation threshold value was related to photochemical reactivity producing benzyl radical; however, no correlation between the threshold and boiling point was confirmed Indeed, a benzyl radical absorption band was clearly observed Moreover, benzyl radical concentration at the threshold was estimated qua

Nanosecond and femtosecond laser photochemistry and ablation dynamics of neat liquid benzenes

ZEP520A (1:1 copolymer of α-chloromethacrylate and α-methylstyrene, ZEON) is a main-chain scission-type positive-tone resist used for electron beam (EB) lithography and is known for its high sensitivity and high resolution. In this study, ZEP520A was irradiated using a 100 kV EB, and the decomposition mechanisms were analyzed by gel permeation chromatography, Fourier transform IR spectroscopy, NMR spectroscopy, and pulse radiolysis. Chlorines were confirmed to easily dissociate as Cl- ions (dissociative electron attachment, DEA) and ZEP520A underwent β-scission. Multiple channels could be considered for the main-chain scission, including DEA and the charge transfer complex between phenyl radical cations and Cl- ions.

https://iopscience.iop.org/article/10.1143/APEX.5.036501/pdf

S. Tagawa

Papers

Laser flash photolysis studies on excited singlet states of benzene, toluene, p-xylene, polystyrene, and poly-α-methylstyrene