First order optical nonlinearities χ2χ2 for organic nanofibers from functionalized para-phenylenes

Optical frequency doubling is demonstrated from nanoscaled, parallely oriented needle-like organic aggregates (‘nanofibers’) that have been grown on mica surfaces from unsymmetrically functionalized para  -quaterphenylene organic molecules. Wavelength dependent absolute values of the first order non-linear susceptibility, χzzz(2), are measured for nanofibers from six differently functionalized molecules. These quantitative measurements are enabled by combining relative second-harmonic intensity measurements with reference to a quartz crystal with morphological information on the individual nanoaggregates gathered from atomic force microscopy images. Values up to that of KDP(d36)KDP(d36) are found for nanofibers from specific functionalized molecules.