Abstract
Abstract Optical pulling forces exerted on small particles can be achieved by tailoring the properties of the electromagnetic field, the particles themselves, or the surrounding environment. However, the nonlinear optical effect of the surrounding environment has been largely neglected. Herein, we report the optical pulling forces on a Rayleigh particle immersed in a nonlinear optical liquid using high-repetition-rate femtosecond laser pulses. The analytic expression of time-averaged optical forces allows us to better understand the underlying mechanism of the particle transportation. It is shown that the two-photon absorption of the surrounding liquid gives rise to a negative radiation force. Transversely confined Rayleigh particles can be continuously dragged towards the light source during a pulling process.
Highlights
In the past 40 years, an optical tweezers technique has experienced impressive progress for trapping and manipulating small objects in air [1], in vacuum [2, 3], in liquid [4, 5], in solid [6, 7], or at interfaces [8–10], taking advantages of the optical forces produced by a tightly focused continuous-wave laser beam [4, 5]
We studied the time-averaged optical forces exerted on a Rayleigh particle immersed in nonlinear optical solvent using high-repetition-rate ultrafast laser α2m(10–11 m/W) × 10–38 C·m2/V α2m(10–11 m/W) × 10–39 C·m2/V
We investigated the characteristics of the three-dimensional optical forces for Si3N4 nanoparticles immersed in CS2 at different excitation wavelengths
Summary
In the past 40 years, an optical tweezers technique has experienced impressive progress for trapping and manipulating small objects in air [1], in vacuum [2, 3], in liquid [4, 5], in solid [6, 7], or at interfaces [8–10], taking advantages of the optical forces produced by a tightly focused continuous-wave laser beam [4, 5]. This technique has become a very important tool in various disciplines, including optics [5], quantum physics [2], biological science [6, 11], and chemistry [12]. We report the theoretical investigation of optical pulling forces on a dielectric Rayleigh particle immersed in nonlinear optical liquids (e.g. carbon disulfide) arising from focused femtosecond laser pulses. Under the excitation of ultrafast laser pulses, the time-averaged optical force acting on the Rayleigh particle (R λ) is [51]:
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