Guangzong Xiao, Tengfang Kuang, Wei Xiong, Xiang Han, Hui Luo
Efficiently loading particle into optical trap in air is always a challenge, especially for the small enclosed trapping chamber. We propose and demonstrate a novel particle-loading method by optimally selecting the vibration mode of the PZT system. The forces exerted on the particle and its dynamic characteristics in the loading process are investigated. The minimum detachment velocity and the optimal capturable detachment velocity ranges are defined and discussed. We point out that the optimal vibration mode should be selected to ensure that the minimum detachment velocity is tiny lower than minimum capturable detachment velocity. Then the detachment velocity can be enhanced into the optimal capturable detachment velocity range through changing the actuating voltage for the selected vibration mode. Our experiment prove that the method can achieve controllable and highly efficient particle loading into the optical trap in air.
DOI
Showing posts with label Optics & Laser Technology. Show all posts
Showing posts with label Optics & Laser Technology. Show all posts
Thursday, February 27, 2020
Radiation forces of hypergeometric-Gaussian type-II beams acting on a Rayleigh dielectric sphere
Gui Jin, Lirong Bian, Li Huang, Bin Tang
We drive the analytical expressions for the propagation of hypergeometric-Gaussian typed-II (HyGG-II) beam passing through a paraxial ABCD optical system. The radiation forces of a strongly focused HyGG-II beam exerting on a Rayleigh dielectric sphere are theoretically and numerically investigated under the dipole approximation. The influences of optical parameters on the radiation forces are also discussed in detail. The results demonstrate that the HyGG-II beams can hold the micro particles with both high and low refractive index. Finally, we analyze the necessary conditions for stably trapping the particle.
DOI
We drive the analytical expressions for the propagation of hypergeometric-Gaussian typed-II (HyGG-II) beam passing through a paraxial ABCD optical system. The radiation forces of a strongly focused HyGG-II beam exerting on a Rayleigh dielectric sphere are theoretically and numerically investigated under the dipole approximation. The influences of optical parameters on the radiation forces are also discussed in detail. The results demonstrate that the HyGG-II beams can hold the micro particles with both high and low refractive index. Finally, we analyze the necessary conditions for stably trapping the particle.
DOI
Friday, February 21, 2020
Tunable emission and optical trapping of upconverting LiYF4:Yb,Er nanocrystal
L. Anbharasi, E. A. Bhanu Rekha, V. R. Rahul, Basudev Roy, M. Gunaseelan, S. Yamini, Venkata N.K.B. Adusumalli, Debashrita Sarkar, Venkataramanan Mahalingam, J. Senthilselvana
Present work investigates about hydrothermally prepared LiYF4:Yb,Er nanocrystals with novel tunable emission and optical trapping results. Optical trapping effect of LiYF4:Yb,Er upconversion nanocrystal under 980 nm diode laser interaction is reported and a single nanoparticle trapping is demonstrated. Optical trapping force of 10.8 fN is exerted on LiYF4:Yb,Er upconversion nanocrystal of size ~238 nm at laser power 50 mW and the result is in agreement with the reported values. At 980 nm excitation, tunable green to red upconversion emission is achieved by calcination. It depends on orthorhombic and tetragonal phases that confirmed by XRD. The nanocrystals calcined at 450 and 600 °C resulted in a decay time of 26 and 19 µs respectively and the upconversion emission mechanism is explained. FESEM and HRTEM examinations showed the hydrothermally synthesized nanocrystals are in trapezohedral, pyramidal, bi-pyramidal and tetragonal morphologies. The differential scanning calorimetry revealed the tetragonal phase formation temperature is lower at 450 °C compared to the reported value of 750 °C. The UV–VIS-NIR spectra of LiYF4:Yb,Er showed high absorption at 380, 480, 520 and 660 nm due to Er3+ ion and the broad absorption from 900 to 1000 nm centered at 980 nm is owing to Yb3+ ion. The crystalline phase, morphology, upconversion emission and optical trapping behaviors of LiYF4:Yb,Er nanocrystal are explained elaborately.
DOI
Present work investigates about hydrothermally prepared LiYF4:Yb,Er nanocrystals with novel tunable emission and optical trapping results. Optical trapping effect of LiYF4:Yb,Er upconversion nanocrystal under 980 nm diode laser interaction is reported and a single nanoparticle trapping is demonstrated. Optical trapping force of 10.8 fN is exerted on LiYF4:Yb,Er upconversion nanocrystal of size ~238 nm at laser power 50 mW and the result is in agreement with the reported values. At 980 nm excitation, tunable green to red upconversion emission is achieved by calcination. It depends on orthorhombic and tetragonal phases that confirmed by XRD. The nanocrystals calcined at 450 and 600 °C resulted in a decay time of 26 and 19 µs respectively and the upconversion emission mechanism is explained. FESEM and HRTEM examinations showed the hydrothermally synthesized nanocrystals are in trapezohedral, pyramidal, bi-pyramidal and tetragonal morphologies. The differential scanning calorimetry revealed the tetragonal phase formation temperature is lower at 450 °C compared to the reported value of 750 °C. The UV–VIS-NIR spectra of LiYF4:Yb,Er showed high absorption at 380, 480, 520 and 660 nm due to Er3+ ion and the broad absorption from 900 to 1000 nm centered at 980 nm is owing to Yb3+ ion. The crystalline phase, morphology, upconversion emission and optical trapping behaviors of LiYF4:Yb,Er nanocrystal are explained elaborately.
DOI
Friday, August 2, 2019
Numerical design of a plasmonic nano-tweezer for realizing high optical gradient force
Khalil Mokri, Mohammad Hazhir Mozaffari
Plasmonic tweezers are recently being considered as a promising optical trapping tool because of their absolute advantages over conventional optical tweezing systems. In this article, by exploiting a gold nano-bowtie and a gold nano-ring, we theoretically propose a novel combined nano-tweezing structure that reaps the benefits of both nano-bowtie and nano-ring plasmonic tweezers. Simulations show that the gradient force has increased more than 30 times in the new proposed structure as compared with that in the nano-bowtie structure. Moreover, the designed tweezer can potentially exert trapping force as strong as 3.23 nNW−1 on a suspended bioparticle with a radius of 10 nm.
DOI
Plasmonic tweezers are recently being considered as a promising optical trapping tool because of their absolute advantages over conventional optical tweezing systems. In this article, by exploiting a gold nano-bowtie and a gold nano-ring, we theoretically propose a novel combined nano-tweezing structure that reaps the benefits of both nano-bowtie and nano-ring plasmonic tweezers. Simulations show that the gradient force has increased more than 30 times in the new proposed structure as compared with that in the nano-bowtie structure. Moreover, the designed tweezer can potentially exert trapping force as strong as 3.23 nNW−1 on a suspended bioparticle with a radius of 10 nm.
DOI
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