Amorphous Molecular Materials for Directed Supercontinuum Generation

Abstract

Molecular compounds of the general formula [(RT) 4 E 6 ] (R = organic or organometallic substituent; T = C, Si, Ge, Sn; E = CH 2 , S, Se), hence adamantane derivatives and inorganic-organic hybrid compounds based on a heteroadamantane structure exhibit a non-linear optical response upon radiation with a continuous-wave near-infrared laser. The effect depends on the compounds' habitus, which itself depends on the elemental composition of the cluster core, and on the nature of the organic substituents. A combination of these parameters that cause the material to be intrinsically amorphous leads to supercontinuum generation and thus to the emission of a broad spectrum, potentially appearing as white light. Notably, the emission essentially retains the driving laser's directionality. For crystalline samples, second harmonic generation is observed instead, which points to a close relationship of the optical properties and the intermolecular order. Variation of R, T, and E allows further fine-tuning of the emitted spectra. We present all studies made in regards to these effects and our overarching conclusions derived from them.

White Light Generating Molecular Materials: Correlation Between the Amorphous/Crystalline Structure and Nonlinear Optical Properties

“…[18] [(PhSn) 4 S 6 ] shows white-light emission observable by the bare eye for an excitation at 980 nm (1.265 eV). [8,9,13] The spectral data are shown scaled with the photometric eye sensitivity in Figure 5b) for better visualization. This corroborated the previous attributions of WLG to purely amorphous nature of the compounds as prerequisite.…”

“…The initial observation consequently triggered studies of various adamantane-type clusters featuring different inorganic or organic core atoms and organic substituents with respect to their nonlinear optical properties. [8][9][10][11][12] The white-light generating (WLG) mechanism has tentatively been attributed to the presence of electron-rich organic substituents, their interaction with the driving electromagnetic field, and the absence of any long-range structural order in these materials. [13] The true microscopic nature of the process, however, remains undecided as well as any correlation with the arrangement of the clusters within the materials since their amorphous/crystalline structure on the relevant length scales remain unclear itself.…”

“…The immense application potential for such light sources is widespread. The initial observation consequently triggered studies of various adamantane‐type clusters featuring different inorganic or organic core atoms and organic substituents with respect to their nonlinear optical properties [8–12] . The white‐light generating (WLG) mechanism has tentatively been attributed to the presence of electron‐rich organic substituents, their interaction with the driving electromagnetic field, and the absence of any long‐range structural order in these materials [13] .…”

Regioselective Synthesis of meta‐Tetraaryl‐Substituted Adamantane Derivatives and Evaluation of Their White Light Emission

“…understood WLG mechanism, these findings will help us develop a better working hypothesis for this remarkable effect that is described in detail elsewhere. [28] In brief, we currently assume that WLG depends on the compounds' habitus and on the nature of the substituents. Obtaining amorphous materials thereby is key for supercontinuum generation and thus the emission of a broad light spectrum.…”

Nonlinear optical response of ferroelectric oxides: first-principles calculations within the time-domain and the frequency-domain

“…They range from, e.g., well established frequency converters [5] to exciting novel approaches for white light generation [6][7][8][9][10][11][12], which is currently understood as a combination of several nonlinear optical effects of different order [13,14]. The demand for a theoretical description of nonlinear effects and the accurate calculation of the related susceptibilities has grown parallel to the employment of nonlinear optical materials in different devices.…”