| 1. |
- Bresolí-Obach, Roger, et al.
(författare)
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Resonantly Enhanced Optical Trapping of Single Dye-Doped Particles at an Interface
- 2021
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Ingår i: ACS Photonics. - : American Chemical Society (ACS). - 2330-4022. ; 8:6, s. 1832-1839
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Tidskriftsartikel (refereegranskat)abstract
- The optical resonance between an absorbing particle and the trapping laser can enhance the radiation force exerted on micro/nanoscale objects. However, the exact mechanism behind this resonance is still elusive. To unravel the phenomenon, we studied the resonance between a single dye-doped polystyrene particle and a 1064 nm trapping laser under specifically designed optical conditions. The dye-doped particle was trapped at a water-glass interface while simultaneously being excited by a 488 nm widefield laser. In contrast with former reports (â 10-35% trapping stiffness enhancement), we obtained an unprecedented 4-fold trapping stiffness enhancement due to resonant excitation. When we photobleached the embedded dyes as a control, the trapping stiffness enhancement was no longer observed. Based on nonlinear resonant radiation force theory and the experimental data obtained with a three-dimensional multiplane microscope, we propose that the widefield laser excites the dye to S1 and the trapping laser induces a simultaneous ultrafast S1-S2-S1 cyclic transition, resonantly enhancing the induced dye polarization and, consequently, the radiation force. The elucidation of the optical resonance effect is expected to ultimately enable single molecule manipulation in solution at room temperature.
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| 2. |
- Kudo, Tetsuhiro, et al.
(författare)
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Gaining control on optical force by the stimulated-emission resonance effect
- 2023
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Ingår i: Chemical Science. - 2041-6520. ; 14:37, s. 10087-10095
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Tidskriftsartikel (refereegranskat)abstract
- The resonance between an electronic transition of a micro/nanoscale object and an incident photon flux can modify the radiation force exerted on that object, especially at an interface. It has been theoretically proposed that a non-linear stimulated emission process can also induce an optical force, however its direction will be opposite to conventional photon scattering/absorption processes. In this work, we experimentally and theoretically demonstrate that a stimulated emission process can induce a repulsive pulling optical force on a single trapped dye-doped particle. Moreover, we successfully integrate both attractive pushing (excited state absorption) and repulsive pulling (stimulated emission) resonance forces to control the overall exerted optical force on an object, validating the proposed non-linear optical resonance theory. Indeed, the results presented here will enable the optical manipulation of the exerted optical force with exquisite control and ultimately enable single particle manipulation.
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| 3. |
- LOUIS, BORIS, et al.
(författare)
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Fast-tracking of single emitters in large volumes with nanometer precision
- 2020
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Ingår i: Optics Express. - 1094-4087. ; 28:19, s. 28656-28671
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Tidskriftsartikel (refereegranskat)abstract
- Multifocal plane microscopy allows for capturing images at different focal planes simultaneously. Using a proprietary prism which splits the emitted light into paths of different lengths, images at 8 different focal depths were obtained, covering a volume of 50x50x4 μm3. The position of single emitters was retrieved using a phasor-based approach across the different imaging planes, with better than 10 nm precision in the axial direction. We validated the accuracy of this approach by tracking fluorescent beads in 3D to calculate water viscosity. The fast acquisition rate (>100 fps) also enabled us to follow the capturing of 0.2 μm fluorescent beads into an optical trap.
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| 4. |
- Louis, Boris, et al.
(författare)
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Unravelling 3D Dynamics and Hydrodynamics during Incorporation of Dielectric Particles to an Optical Trapping Site
- 2023
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Ingår i: ACS Nano. - : American Chemical Society (ACS). - 1936-0851 .- 1936-086X. ; 17:4, s. 3797-3808
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Tidskriftsartikel (refereegranskat)abstract
- Mapping of the spatial and temporal motion of particles inside an optical field is critical for understanding and further improvement of the 3D spatio-temporal control over their optical trapping dynamics. However, it is not trivial to capture the 3D motion, and most imaging systems only capture a 2D projection of the 3D motion, in which the information about the axial movement is not directly available. In this work, we resolve the 3D incorporation trajectories of 200 nm fluorescent polystyrene particles in an optical trapping site under different optical experimental conditions using a recently developed widefield multiplane microscope (imaging volume of 50 × 50 × 4 μm3). The particles are gathered at the focus following some preferential 3D channels that show a shallow cone distribution. We demonstrate that the radial and the axial flow speed components depend on the axial distance from the focus, which is directly related to the scattering/gradient optical forces. While particle velocities and trajectories are mainly determined by the trapping laser profile, they cannot be completely explained without considering collective effects resulting from hydrodynamic forces.
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| 5. |
- Lu, Jia Syun, et al.
(författare)
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Optical Force-Induced Dynamics of Assembling, Rearrangement, and Three-Dimensional Pistol-like Ejection of Microparticles at the Solution Surface
- 2020
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Ingår i: Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 124:49, s. 27107-27117
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Tidskriftsartikel (refereegranskat)abstract
- Optical trapping and assembling dynamics of polystyrene microparticles (MPs) of 1 μm in diameter are studied at its solution-air surface using a widefield microscope. Upon switching on the intense 1064 nm laser, the MPs are gathered, forming a single concentric circle (CC)-like assembly larger than the focus. It consists of a few tens of MPs, and the central part of the assembly shows structural color, which indicates that the assembly is also growing in the axial direction. The MPs are dynamically fluctuating in the assembly, and some of them are ejected when newly coming MPs collide with the CC-like assembly from the bulk solution. The MPs speedily leaving the assembly are aligned in a linear manner, which we refer to as "pistol-like ejection". The three-dimensional (3D) dynamics was elucidated by changing laser power, MP concentration, and surface chemical property. It is directly observed that the trapping laser was scattered radially from the CC-like assembly, and the ejection was induced along the scattered laser path. This pistol-like ejection is stochastically repeated upon the collision. After prolonged irradiation, the assembly rearranges to a hexagonal close packing (HCP)-like assembly, in which no pistol-like ejection was observed. We note that our observation is a characteristic of the solution surface and were never observed in bulk solution. We conclude that the kinetically driven assembly formation gives rise to a CC-like structure that is metastable and shows the pistol-like ejection phenomenon. Later, the assembly rearranges to a thermodynamically stable HCP-like assembly. The assembling, pistol-like ejection, and its rearrangement are all driven by optical force, which is common for optical trapping-induced molecular crystallization and optically evolved assembling and swarming of gold nanoparticles.
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