Comparison with third harmonic generation

Written by an international panel of experts, this volume begins with a comparison of nonlinear optical spectroscopy and x-ray crystallography. The text examines the use of multiphoton fluorescence to study chemical phenomena in the skin, the use of nonlinear optics to enhance traditional optical spectroscopy, and the multimodal approach, which incorporates several spectroscopic techniques in one instrument. Later chapters explore Raman microscopy, third-harmonic generation microscopy, and nonlinear Raman microspectroscopy. The text explores the promise of beam shaping and the use of a broadband laser pulse generated through continuum generation and an optical pulse shaper. 

Initial third harmonic generation (THG) experiments carried out at a fixed pump frequency (1.17 eV) were consistent with this prediction x 3(o co,(o,(o) for trans- CY was found to be 15-20 times larger than for the cA-(CH), isomer [223-225]. However, since there are 3u> and 2to resonances in the perturbation expansion for x (3w w,w,a)) which have been observed in experimental studies of rra i-(CH)j, the proof of a symmetry specific mechanism requires comparison of x (3(o (o,ci),o)) for cis- and trans-(CVi) over a broad range of pump frequencies for hv < Eg. 

As one can see, the limit values for the condensed and uncondensed polyfulvenes are similar. In comparison with other polymers (represented in the two previous sections) these values are small, indicating unlikely use of these polymers as chromophores for generating the second and third harmonics. 

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