White‐Light Generation through Nonlinear Optical Response of 1,3,5,7‐Tetraphenyladamantane: Amorphous versus Crystalline States

Abstract

The development of advanced nonlinear media as well as active optical materials for light conversion applications is an ongoing process. [1,2] Aims include improved conversion efficiencies, brilliance, i.e., beam quality, and accessible target wavelengths. Light-converting materials for white-light generation are of particular interest, e.g., for white light-emitting diodes (LEDs) and their applications. Here, phosphors offer great efficiency even at low driving power densities and huge spectral versatility across the visible spectrum. [3][4][5][6] The virtually perfect Lambertian angular emission pattern of such functionalized LEDs is highly desirable in applications such as backlights in displays, while others require low-étendue sources with limited angular spread. [7,8] Laser-driven phosphors in automotive headlights are a recent, prominent example where a small laser spot is exploited to achieve a virtual point source and tailorThe vast optical nonlinearity of 1,3,5,7-tetraphenyladamantane (AdPh 4 ) enables efficient frequency conversion. The observed spectrum depends heavily on the material's habitus. In particular, it shows nonlinear white-light generation when its powder form is irradiated in the near-infrared, similar to an analogous organotin sulfide cluster [(PhSn) 4 S 6 ]. In contrast, single crystals of AdPh 4 exclusively exhibit narrow-band second-harmonic generation, i.e., discrete conversion within the crystal, rather than spectrally broadband white-light emission. This shows that crystallinity restricts the nonlinear response to the symmetryallowed higher-harmonics, in this case the even-numbered, second harmonic, and inhibits the quasi-continuum white-light emission. Using the diamondoidbased material significantly enhances compatibility with conventional production techniques using photorefractive polymers and is thus an important step towards the fabrication of all-integrated white-light emitting devices.

Amorphous Molecular Materials for Directed Supercontinuum Generation

“…Indeed, single-crystals of compound 17 showed SHG, while an amorphous sample generated white light (Figure 9, left). [13] Inspection of the power dependence of the WLG in 17 demonstrated that lower laser power shifts the spectrum to lower energies, as also found for 1. Furthermore, a weak SHG signal is detected at low pump energies (Figure 9, right).…”

“…Habitus [a] Optical response Remarks [(StySn) 4 S 6 ] (1) [8] a WLG Sty = styryl [(PhSn) 4 S 6 ] (2) [12] a WLG [(MeSn) 4 S 6 ] (3) [12] a SHG [(NpSn) 4 S 6 ] (4) [12] a SHG Beginning order, π stacking [(BnSn) 4 S 6 ] (5) [10] c SHG [(R 1 Sn) 4 S 6 ] (6) [10] a WLG R 1 = (CH 2 ) 2 À (C 6 H 4 )CO 2 Et [(η 1 -CpSn) 4 S 6 ] (7) [10] a WLG [(CySn) 4 S 6 ] (8) [10] a WLG [(PhSn) 4 Se 6 ] (9) [10] a WLG [(BnSn) 4 Se 6 ] (10) [10] c WLG Melts upon irradiation [(R 1 Sn) 4 Se 6 ] (11) [10] a WLG R 1 = (CH 2 ) 2 À (C 6 H 4 )CO 2 Et [(η 1 -CpSn) 4 Se 6 ] (12) [10] a WLG [(CySn) 4 Se 6 ] (13) [10] a WLG [(PhGe) 4 S 6 ] (14) [12] a WLG [(PhSi) 4 S 6 ] (15) [9] c SHG [(NpSi) 4 S 6 ] (16) [9] c None Decomposition 1,3,5,7-Tetraphenyl-adamantane (17) [13] a WLG Nearly insoluble material [34] c SHG [{(Me 3 P) 3 AuSn}(PhSn) 3 S 6 ] (18) [11] c WLG Amorphization upon laser irradiation [{(Et 3 P) 3 AgSn}(PhSn) 3 S 6 ] (19) [11] c WLG Amorphization upon laser irradiation [{(Me 3 P) 3 CuSn}(PhSn) 3 S 6 ] (20) [11] c None WLG hindered by re-absorption…”

Current advances in tin cluster chemistry

“…5). 83 Further studies showed that this effect seems to be specic to adamantane-type organotetrel clusters and to organic adamantanes, 84 given that the samples are amorphous and possess cyclic organic substituents. 85,86 This represents the current state of knowledge, as the exact mechanism for this process is still unknown and under investigation.…”

Generating large starting configurations for molecular Reverse Monte Carlo modelling of an unique non-linear optical amorphous solid

“…Recently, a new class of materials has been synthesized which exhibits unique non-linear optical properties. Some of these substances convert infrared light from a commercially available low-cost low-power laser diode into brilliant white light, thereby maintaining the favourable coherent emission characteristics of the laser [1][2][3][4][5]. This so-called supercontinuum generation was so far only possible if expensive high-power pulsed laser sources were used, and was therefore mainly restricted to academic applications [6][7][8].…”