Journal
OPTICS COMMUNICATIONS
Volume 495, Issue -, Pages -Publisher
ELSEVIER
DOI: 10.1016/j.optcom.2021.127071
Keywords
Laser trapping; Ultrafast nonlinear optics; thermal-optical nonlinearity
Categories
Funding
- National Natural Science Foundation of China [11774055, 12074066]
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This study investigates optical forces on Rayleigh particles using high-repetition-rate femtosecond-pulsed Gaussian beams, considering Kerr nonlinearity and thermal-optical nonlinearity simultaneously. It successfully achieves stable trapping of slightly low-refractive-index particles and studies the influence of thermal-optical nonlinearity on trapping high-refractive-index particles. The work opens up the possibility of trapping low refractive-index particles beyond the linear optics regime and provides theoretical support for tapping nonlinear optical particles in femtosecond optical tweezers.
In femtosecond-pulsed optical tweezers, the high peak intensity of each laser pulse results in the instantaneous trapping of a particle, while the high-repetition-rate ensures the repetitive trapping of a particle by pulse trains. Therefore, the high peak intensity and high-repetition-rate inevitably lead to the third-order optical nonlinearity and the thermal-optical nonlinearity, respectively. Herein, we investigate the optical forces on the Rayleigh particle using a high-repetition-rate femtosecond-pulsed Gaussian beam when the Kerr nonlinearity and thermal-optical nonlinearity are considered simultaneously. With the help of thermally induced nonlinearity of the surrounding medium to change the relative refractive index of particles, the three-dimensional stable trapping of slightly low-refractive-index particles is realized by the use of high-repetition-rate femtosecondpulsed Gaussian beams. Besides, we study the influence of thermal-optical nonlinearity on optical trapping of high-refractive-index particles. It is shown that the trapping stiffness increases nonlinearly with the increase of power due to the thermal-optical nonlinearity. This work opens up the possibility of trapping the low refractive-index beyond the linear optics regime, successfully explains the reported experimental observations, and provides the theoretical support for tapping nonlinear optical particles in femtosecond optical tweezers.
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