Enhanced optical confinement of dye-doped dielectric nanoparticles using a picosecond-pulsed near-infrared laser

Kittiravechote, Aungtinee; Chiang, Wei-Yi; Usman, Anwar; Liau, Ian; Masuhara, Hiroshi

doi:10.1088/1612-2011/11/7/076001

Cited by 6 publications

(12 citation statements)

References 29 publications

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“…We note that the conne-ment efficiency of undoped nanoparticles increases linearly with the laser power. 21 As the connement efficient of the enhancement factor was dened as the ratio of the scattering intensity determined on doped nanobeads relative to that on undoped nanobeads of the same dimension, an increase of the enhancement factor with the laser power indicates that nonlinear optical interaction plays a dominant role for the enhanced optical connement of doped-505 and doped-543. Conforming to the result displayed in Fig.…”

Section: Discussionmentioning

confidence: 99%

“…[20][21][22][23][24][25] In particular, we employed a picosecond (ps)-pulsed NIR laser to trap doped dielectric nanobeads with the half-wavelength of the laser falling within the absorption band of the dopant. Distinct from most preceding work that addressed mainly the stiffness of the optical trap, we concerned particularly the enhanced ability to conne nanobeads near the laser focus.…”

Section: -19mentioning

confidence: 99%

“…21 Briey, a pulsed laser (1064 nm, FWHM 7 ps, 76 MHz; PicoTran, High-Q Laser), or a cw laser (1064 nm; DPSSL, Changchun New Industries), was employed for optical trapping. The laser beam was rst expanded and collimated using a telescope, directed to the back port of the microscope, and then focused with an objective lens (60X, NA 0.95; PlanApo; Nikon).…”

Section: Optical Setupmentioning

confidence: 99%

“…As describe, we have veried the generation of twophoton uorescence on exciting the doped nanobead with the 1064 nm pulsed laser. 21 This result indicates that two-photon resonance between the optical eld of the laser and the dopant was fullled.…”

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confidence: 94%

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Enhanced optical confinement of dielectric nanoparticles by two-photon resonance transition

et al. 2017

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Despite a tremendous success in the optical manipulation of microscopic particles, it remains a challenge to manipulate nanoparticles especially as the polarizability of the particles is small. With a picosecond-pulsed near-infrared laser, we demonstrated recently that the confinement of dye-doped polystyrene nanobeads is significantly enhanced relative to bare nanobeads of the same dimension. We attributed the enhancement to an additional term of the refractive index, which results from two-photon resonance between the dopant and the optical field. The optical confinement is profoundly enhanced as the half-wavelength of the laser falls either on the red side, or slightly away from the blue side, of the absorption band of the dopant. In contrast, the ability to confine the nanobeads is significantly diminished as the half-wavelength of the laser locates either at the peak, or on the blue side, of the absorption band. We suggest that the dispersively shaped polarizability of the dopant near the resonance is responsible to the distinctive spectral dependence of the optical confinement of nanobeads. This work advances our understanding of the underlying mechanism of the enhanced optical confinement of doped nanoparticles with a nearinfrared pulsed laser, and might facilitate future research that benefits from effective sorting of selected nanoparticles beyond the limitations of previous approaches. IntroductionOptical trapping of microscopic objects with a focused continuous wave (cw) laser beam is a mainstream tool to manipulate microscopic particles in solutions. Despite its widespread applications in physical, 1,2 materials, 3 and life 4-6 sciences, effective trapping of particles in the nanometre scale has been demonstrated only with limited success. 7,8In comparison with metallic nanoparticles comprising gold 9,10 or silver 11,12 the polarizability of dielectric nanoparticles of a comparable dimension is much smaller. As a result, optical manipulation of dielectric nanoparticles remains challenging. 13Towards this end, numerous strategies have been attempted aiming either to decrease the pushing (scattering, absorption and temporal) force, or to increase the trapping (gradient) force.14-19 For instance, a near-infrared (NIR) pulsed laser was employed as a trapping laser to minimize the scattering and absorption forces; 14 the temporal force was further decreased with a laser of a long pulse-width.15 On the other hand, the trapping force can be increased by maximizing the gradient of the optical eld; this is achieved mainly by (i) using a high numerical-aperture (NA) objective lens, (ii) creating a large optical eld in the near eld, 14 or (iii) utilizing the intense optical eld associated with a ultrashort pulsed laser. 16Distinct from these approaches, it is possible to boost the gradient force by increasing the real part of the polarizability through optical resonance. This idea has been demonstrated on trapping doped dielectric nanoparticles, whose effective polarizability is increased as a result of opt...

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Section: Discussionmentioning

confidence: 99%

Section: -19mentioning

confidence: 99%

Section: Optical Setupmentioning

confidence: 99%

mentioning

confidence: 94%

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Enhanced optical confinement of dielectric nanoparticles by two-photon resonance transition

et al. 2017

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“…The objects are attracted at the focal spot where the electromagnetic interaction potential is deeper than the surroundings. Recently beyond the conventional optical trapping, locally enhanced light field around plasmonic metal nanostructures [2][3][4][5][6], and pico-and femto-second laser pulses [7][8][9][10][11][12][13] are utilized for the optical trapping studies.…”

Section: Introductionmentioning

confidence: 99%

Resonance optical trapping of individual dye-doped polystyrene particles with blue- and red-detuned lasers

2017

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We demonstrate resonance optical trapping of individual dye-doped polystyrene particles with blue- and red-detuned lasers whose energy are higher and lower compared to electronic transition of the dye molecules, respectively. Through the measurement on how long individual particles are trapped at the focus, we here show that immobilization time of dye-doped particles becomes longer than that of bare ones. We directly confirm that the immobilization time of dye-doped particles trapped by the blue-detuned laser becomes longer than that by the red-detuned one. These findings are well interpreted by our previous theoretical proposal based on nonlinear optical response under intense laser field. It is discussed that the present result is an important step toward efficient and selective manipulation of molecules, quantum dots, nanoparticles, and various nanomaterials based on their quantum mechanical properties.

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Nanoparticle Assembling Dynamics Induced by Pulsed Optical Force

Chen

Chiang

Kudo

et al. 2021

The Chemical Record

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Femtosecond (fs) laser trapping dynamics is summarized for silica, hydrophobically modified silica, and polystyrene nanoparticles (NPs) in aqueous solution, highlighting their distinct optical trapping dynamics under CW laser. Mutually repulsive silica nanoparticles are tightly confined under fs laser compared to CW laser trapping and, upon increasing laser power, they are ejected from the focus as an assembly. Hydrophobically modified silica and polystyrene (PS) NPs are sequentially ejected just like a stream or ablated, giving bubbles. The ejection and bubbling take place with the direction perpendicular to laser polarization and its direction is randomly switched from one to the other. These characteristic features are interpreted from the viewpoint of single assembly formation of NPs at an asymmetric position in the optical potential. Temporal change in optical forces map is prepared for a single PS NP by calculating scattering, gradient, and temporal forces. The relative contribution of the forces changes with the volume increase of the assembly and, when the pushing force along the trapping pulse propagation overcome the gradient in the focal plane, the assembly undergoes the ejection. Further fs multiphoton absorption is induced for the larger assembly leading to bubble generation. The assembling, ejection, and bubbling dynamics of NPs are characteristic features of pulsed optical force and are considered as a new platform for developing new material fabrication method.

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Enhanced optical confinement of dye-doped dielectric nanoparticles using a picosecond-pulsed near-infrared laser

Cited by 6 publications

References 29 publications

Enhanced optical confinement of dielectric nanoparticles by two-photon resonance transition

Enhanced optical confinement of dielectric nanoparticles by two-photon resonance transition

Resonance optical trapping of individual dye-doped polystyrene particles with blue- and red-detuned lasers

Nanoparticle Assembling Dynamics Induced by Pulsed Optical Force

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