We report the first experimental observation of three-dimensional light bullets, excited by femtosecond pulses in a system featuring quasi-instantaneous cubic nonlinearity and a periodic, transversally modulated refractive index. Stringent evidence of the excitation of light bullets is based on time-gated images and spectra which perfectly match our numerical simulations. Furthermore, we reveal a novel evolution mechanism forcing the light bullets to follow varying dispersion or diffraction conditions, until they leave their existence range and decay.

We experimentally investigate light propagation in a disordered two-dimensional array of mutually coupled optical fibers. In the linear case light either spreads in a diffusive manner or localizes at a few sites. For high excitation power diffusive spreading is arrested by the focusing nonlinearity, i.e., forming a discrete soliton. By contrast, fields, which are localized in the linear regime, can experience both spreading and contraction caused by the nonlinearity.

We report the first experimental observation of vortex light bullets that are discrete, spatiotemporal, solitary waves with orbital angular momentum. We analyze conditions for their existence and investigate their rich properties and dynamics. Vortex light bullets are excited in fiber arrays with spatially shaped femtosecond pulses and analyzed with a spatiotemporal cross correlator. Most importantly, we find that they have entirely new stability properties, being robust against considerable degrees of perturbation in a limited range of energies. All experimental findings are backed up by rigorous simulations, giving further insight into the rich dynamics of vortex light bullets.

In binary aluminosilicate liquids and glasses, heterogeneity on intermediate length scale is a crucial factor for optical fiber performance, determining the lower limit of optical attenuation and Rayleigh scattering, but also clustering and precipitation of optically active dopants, for example, in the fabrication of high-power laser gain media. Here, we consider the low-frequency vibrational modes of such materials for assessing structural heterogeneity on molecular scale. We determine the vibrational density of states VDoS g(ω) using low-temperature heat capacity data. From correlation with low-frequency Raman spectroscopy, we obtain the Raman coupling coefficient. Both experiments allow for the extraction of the average dynamic correlation length as a function of alumina content. We find that this value decreases from about 3.9 nm to 3.3 nm when mildly increasing the alumina content from zero (vitreous silica) to 7 mol%. At the same time, the average inter-particle distance increases slightly due to the presence of oxygen tricluster species. In accordance with Loewensteinian dynamics, this proves that mild alumina doping increases structural homogeneity on molecular scale.

The increasing fields of applications for modern optical fibers present great challenges to the material properties and the processing technology of fiber optics. This paper gives an overview of the capabilities and limitations of established vapor deposition fiber preform technologies, and discusses new techniques for improved and extended doping properties in fiber preparation. In addition, alternative fabrication technologies are discussed, such as a powder-based process (REPUSIL) and an optimized glass melting method to overcome the limits of conventional vapor deposition methods concerning the volume fabrication of rare earth (RE)-doped quartz and high silica glasses. The new preform technologies are complementary with respect to enhanced RE solubility, the adjustment of nonlinear fiber properties, and the possibility of hybrid fiber fabrication. The drawing technology is described based on the requirements of specialty fibers such as adjusted preform and fiber diameters, varying coating properties, and the microstructuring of fiber configurations as low as in the nanometer range.