Browsing by Author "Chen, Jim Jui-Kai"

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Bubble generation and molecular crystallization at solution surface by intense continuous-wave laser irradiation
(2018-08-01)
Chen, Jim Jui-Kai
;
Yuyama, Ken-ichi
;
Sugiyama, Teruki
;
Masuhara, Hiroshi
;
應用化學系
We demonstrate bubble generation outside the focus induced by irradiating a focused 1064 nm continuous-wave laser beam into the surface of water and L-phenylalanine H2O solutions. In the former case of water, bubbles stay at positions distant from the focus during the irradiation, and their size and location are controllable by the laser power. In the latter solution, bubbles move outward toward the surrounding area, and subsequently crystallization takes place at the focus. We discuss these behaviors from the viewpoints of the temperature elevation accompanying the decrease in air solubility as well as the optical trapping of L-phenylalanine clusters giving a single crystal. (C) 2018 The Japan Society of Applied Physics
Femtosecond laser trapping, assembling, and ejection dynamics of dielectric nanoparticles in solution
(2018-01-01)
Masuhara, Hiroshi
;
Chen, Jim Jui-Kai
;
Chiang, Wei-Yi
;
Usman, Anwar
;
Sugiyama, Teruki
We elucidated femtosecond laser trapping dynamics of Rayleigh particles by modifying the surface property of nanoparticles and changing the viscosity. Through bright field, dark field and backscattering images, we monitored ejection behavior of nanoparticles which takes place in the direction perpendicular to laser polarization and switched from one side to the other. For very hydrophobic nanoparticle, we succeeded in observing directly a transient assembly and confirmed that its formation is responsible to the directional ejection. Also the trapping dynamics was compared for femtosecond and continuous-wave lasers in highly viscous solvent, which gives a new viewpoint for understanding femtosecond laser trapping mechanism.
Formation Mechanism and Fluorescence Characterization of a Transient Assembly of Nanoparticles Generated by Femtosecond Laser Trapping
(2019-11-14)
Chiang, Wei-Yi
;
Chen, Jim Jui-Kai
;
Usman, Anwar
;
Kudo, Tetsuhiro
;
Xia, Kangwei
Femtosecond (fs) laser trapping of dielectric nanoparticles displays a unique trapping and directional ejection phenomenon, which is never observed in continuous-wave (cw) laser trapping. We studied the fs laser trapping and considered its dynamics and mechanism in terms of gathering, association, and ejection of nanoparticles. By tuning solution viscosity through adding ethylene glycol, the trapping behavior by fs and cw lasers are examined and compared with each other. The viscous solution slows down the diffusional and rotational movement of nanoparticles and increases the chance of nanoparticle assembly in the trapping site, which eventually leads to the novel ejection. We took advantage of fluorescence measurement to confirm the formation of the nanoparticle assembly during fs laser trapping. A red emission irregularly appeared in the fluorescence supports the transient assembly formation in the molecular level.
In situ reflection imaging and microspectroscopic study on three-dimensional crystal growth of L-phenylalanine under laser trapping
(2019-11-01)
Chen, Jim Jui-Kai
;
Yuyama, Ken-ichi
;
Sugiyama, Teruki
;
Masuhara, Hiroshi
;
交大名義發表
We investigate growth behavior of an L-phenylalanine crystal formed by laser trapping with the use of reflection imaging and microspectroscopy. Optical reflection micrographs show colored images of the crystal due to constructive interference of incident white light. The color distribution on the crystal is dynamically changed under laser trapping, which is in addition to enlargement of the crystal plane area. The temporal change in the crystal thickness is examined by measuring reflection spectra of the crystal. We discuss the three-dimensional crystal growth under laser trapping by comprehensively considering the changes in crystal thickness and crystal plane area. (C) 2019 The Japan Society of Applied Physics