The term "supercontinuum generation" describes an extreme spectral broadening of an originally monochromatic light beam upon propagating through a nonlinear medium, [8,10] as an alternative to the conventional generation of white light by means of inorganic phosphors or inorganic as well as organic semiconductors. [14][15][16] The broad spectrum obtained may cover the entire visible spectral range; in these cases, the observed emission resembles white light and the process is therefore referred to as WLG. The physical mechanisms underlying supercontinuum generation can be diverseand can also occur as a combination of nonlinear optical effects, like self-phase and cross-phase modulation, four-wave mixing, or solitonic phenomena. [17][18][19][20] While in most cases pulsed-laser sources are required for such processes, WLG upon irradiation of a material with a near-infrared continuous-wave (NIR CW) laser of significantly lower costs (by a factor of ≈10 3 …10 4 as compared to the pulsed lasers) has been reported for (doped) oxides or oxidic hybrid compounds, for complexes of rare-earth metals, and for carbon-based solids. [1] Given the complexity of the processes, different compounds exhibiting WLG can show the extreme nonlinear effects owing to different reasons or different combinations of mechanisms, which in many cases have not yet been fully elucidated to date.The development of efficient and high-brilliance white-light sources is an essential contribution to innovative emission technologies. Materials exhibiting strong nonlinear optical properties, in particular second-harmonic generation (SHG) or white-light generation (WLG), have therefore been investigated with great activity in recent times. While many new approaches have been reported until now, the processability of the compounds remains a challenge. Here, a new class of materials, denoted as "cluster-glass", which do not only show superior white-light emission properties upon irradiation by an inexpensive continuous-wave infrared laser diode, but can be easily accommodated in size and shape by formation of robust glassy solids, is introduced. The cluster-glass materials are fabricated by mild heating from crystalline powders of adamantane-type clusters exhibiting a quaternary, inorganic-organic hybrid cluster core [(PhSi)(CH 2 ) 3 (PhSn)E 3 ] (E = S, Se, Te). The process is fully reversible and preserves the integrity of the clusters in the glass, as proven by solution spectroscopy and recrystallization. Theoretical studies corroborate the importance of the quaternary nature of the cluster cores for the observed structural and optical phenomena. Thanks to these findings, high-brilliance white-light sources can be synthesized in form of stable, robust glass of any shape, which ultimately renders them suitable for everyday's applications.

A class of adamantane-like molecular materials attracts attention because they exhibit an extreme non-linear optical response and emit a broad white-light spectrum after illumination with a continuous-wave infrared laser source. According to recent studies, not only the nature of the cluster molecules, but also the macroscopic structure of the materials determines their non-linear optical properties. Here we present a systematic study of cluster dimers of the compounds AdR 4 and [(RT) 4 S 6 ] (T = Si, Ge, Sn) with R = methyl, phenyl or 1-naphthyl to gain fundamental knowledge about the interactions in the materials. For all compounds, a similar type of dimer structures with a staggered arrangement of substituents was determined as the energetically most favorable configuration. The binding energy between the dimers, determined by including London dispersion interactions, increases with the size of the core and the substituents.The cluster interactions can be classified as substituent-substituent-dominated (small cores, large substituents) or core-core-dominated (large cores, small substituents).Among various possible dimer conformers, those with small core-core distances are energetically preferred. Trimer and tetramer clusters display similar trends regarding the minimal core-core distances and binding energies. The much lower energy barrier determined for the rotation of substituents as compared to the rotation of the cluster dimers past each other indicates that the rotation of substituents more easily leads to different conformers in the material. Thus, understanding the interaction of the cluster dimers allows an initial assessment of the interactions in the materials.

The strong sensitivity of plasmonic excitations on nanostructures to their environment is studied, going to the ultimate limit of single atomic chains. As a first step, we investigated how metallicity in self-assembled arrays of Au chains on Si(557) is modified by the simplest possible adsorbate, namely, atomic hydrogen. Both experimental studies and ab initio simulations were carried out combining plasmon spectroscopy with atomistic first-principles density functional calculations (DFT). While metallicity, in general, is only distorted by H-induced disorder, we also observed band gap opening in the measured plasmon dispersion at large momenta, k ∥, that limits the plasmonic excitation to an energy of 0.43 eV in the presence of H. In the long-wavelength limit, disorder leads to plasmonic standing wave formation on short sections of wires and finite excitation energies for k ∥ → 0. DFT shows that Si surface bands strongly hybridize with those of Au so that H adsorption on the energetically most favorable sites at the Si step edge and the restatom chain not only causes a significant shift of bands but also strongly changes the character of hybridization. Together with H-induced changes in band order, this causes band gap opening and reduced overlap of wave functions. These mechanisms were identified as the main reasons for plasmon localization. Interestingly, although the whole electronic system is modified by H adsorption, there is no direct interaction between H and the Au chains.

Sustainable efficient light emitters based solely on elements-of-hope are needed to replace current compounds based on less-abundant materials. Functionalized diamondoids are a potential solution for this challenge, as a prototypical example offers efficient, octave-spanning emission across the visible spectrum in their single-crystalline form. Its large quantum efficiency increases towards higher-than-ambient temperatures to beyond 7%. The stability beyond 200 °C renders such functionalized diamondoids as sustainable phosphors for LED applications. Detailed structural and theoretical investigations suggest a crucial role of exciton states accompanied by structural modifications (self-trapped excitons) in the emission process.

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