Production of Single Crystalline Seeds of Organic Nonlinear Optical Materials via Laser Ablation

Abstract

Production of single crystal seeds of organic nonlinear optical materials (4-dimethylamino-N-methly-4-stilbazolium tosylate, DAST) by laser ablation was demonstrated. Here, laser ablation of DAST crystals in a supersaturated solution was induced with focused laser pulses, which resulted in the generation of crystal seeds that grew independently from the original (mother) crystal. We found that the seed crystals showed single crystallinity with nonlinear optical properties (terahertz wave generation), indicating that laser irradiation did not deteriorate the quality of the seed crystals. Systematic screening of laser parameters showed that the number of seed crystals tends to increase with laser energy and pulse duration. High-speed imaging of the microseeding dynamics revealed that the generation of seed crystals could be attributed to not only primary effects of laser ablation (e.g., melting, vaporization, and mechanical disruption via photoexcitation of crystals) but also secondary effects such as mechanical stimuli due to laser-induced cavitation bubbles. This laser ablation method is expected to be used as a practical tool for the precise spatial control of the microseeding of various functional materials.

Spatiotemporal Control of Polymorphic Phase Transition of Glycine Crystals by Three-Dimensional Femtosecond Laser Ablation Processing

“…For instance, our group has succeeded in triggering crystal nucleation of various organic/biological materials including proteins and pharmaceutical compounds by the focused femtosecond laser irradiation into supercooled/supersaturated liquids, which can produce well-localized stimuli (e.g., cavitation bubbles and shockwave) to crystal nucleation. − We also recently reported that ice crystal nucleation could be induced with a single laser pulse, which enables us to monitor the spatiotemporal dynamics of ice crystallization with micrometers and microseconds resolution . In addition, we also demonstrated in situ observation of subsequent crystal growth dynamics from dislocations, cracks, and fragments of crystals that were induced via femtosecond laser ablation of crystals. − Notably, various analytical methods (e.g., X-ray diffraction analysis, terahertz wave measurement) confirmed that the quality of crystals did not deteriorate after femtosecond laser ablation, probably because of its thermal-less processing feature. − Considering these fine applications of ultrashort laser ablation to crystallization control, ultrashort laser ablation is expected to be utilized as a spatiotemporal trigger for phase transition.…”

“…Since laser irradiation can provide various external perturbations (e.g., chemical bond cleavage, mechanical torque, local melting/sublimination) to crystals depending on laser parameters such as wavelength and pulse duration, we believe future systematic studies will contribute to further precise selective polymorphic control. We foresee that the combination of the laser-induced polymorphic phase transition technique with laser-induced nucleation − and growth − techniques can expand the horizon of the spatiotemporal control of various crystallization phenomena.…”