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

Abstract The vast optical nonlinearity of 1,3,5,7‐tetraphenyladamantane (AdPh₄) 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)₄S₆]. In contrast, single crystals of AdPh₄ 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 symmetry‐allowed higher‐harmonics, in this case the even‐numbered, second harmonic, and inhibits the quasi‐continuum white‐light emission. Using the diamondoid‐based 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.