We show by a combination of spectrally resolved fluorescence and atomic force microscopy that individual, single crystalline, needlelike aggregates of hexaphenyl molecules with submicron cross-sectional dimensions act as optical waveguides (“nanofibers”) in the blue spectral range. The nanofibers are formed via laser-supported, dipole-assisted self-assembly on single crystalline mica substrates. This method allows us to modify the morphology of individual aggregates as well as their mutual distances and the overall orientation of needle arrays. An analytical theory describes quantitatively the waveguiding behavior. From measurements of the damping of propagating 425-nm light the imaginary part of the dielectric function of individual nanoscaled organic aggregates is determined.

Laser-supported, dipole-assisted self-assembly results in blue-light guiding nanostructures, namely single-crystalline nanofibers of hexaphenyl molecules. The nanofibers are up to 1 mm long, extremely well-aligned to each other and their cross sections can be tuned to span the range from nonguiding to guiding single optical modes at λ=425.5 nm. An analytical theory for such organic waveguides can reproduce quantitatively the experimentally observed behavior. From the measured damping of propagating, vibrationally dressed excitons the imaginary part of the dielectric function of isolated nanoscaled organic aggregates is determined.

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The rigorous theory of normal electromagnetic modes of a cylindrical nanowire of finite length is developed. The exact integral equation which determines the solution of Maxwell’s equations obeying the boundary conditions at the whole nanowire surface is derived. The nanowire normal (Fabry-Pérot) modes are defined as nontrivial solutions of the source-free equation. The approach is considered in more detail for elongated nanowires whose length is much larger than their diameter. The resonance condition obtained for a single-mode nanowire resembles the formula for the Fabry-Pérot resonator if one introduces an effective wavelength-dependent phase shift which can be determined from the calculation of the nanowire response function.