| Optical trap is a kind of micromanipulation technique, which useslaser beams’ mechanical effects to accelerate, trap and rotate microparticles. Single beam gradient force trap is known as the so-called‘Optical Tweezer’, which was created by Bell Labs scientist ArthurAshkin in1986. Since its creation, optical tweezer has been commonlyused in biomedical science, chemistry, physics, micromachining andmany other fields. Theoretical and experimental researches related tooptical tweezer have been coming out in an unending flow, which makesthis technique greatly and rapidly develop.In this thesis, the main contents consist of the following aspects: Thefirst chapter introduces the fundamental theories and models related toresearch of optical trap. Internal and external status of theoretical andexperimental research is also presented. The second chapter specificallypresents the Ray Optics Model and gives related formulas and calculationexamples. The third chapter, based on ROM, presents the effect of truncation parameter and numerical aperture on trapping forces when aGaussian beam is used to trap micro particles. The fourth chapter presentsthe effect of truncation parameter and radial mode number ofLaguerre-Gausssian beams of different polarizations on trapping forceswhen the incident power is a constant value. Summary and outlook aregiven in the fifth chapter.The innovations of this thesis rest in: Firstly, based on ROM, effect oftruncation parameter and numerical aperture on trapping forces isdiscussed when the incident beam is a Gaussian beam. Results show thatone can change the truncation parameter to maximize the trapping forces.Secondly, ROM is used to study the effect of polarizations on trappingforce when a high-order Laguerre-Gaussian beam is used. And the resultshows that changing truncation parameter can generate dark light spotsthat can trap particles with smaller refraction index than the medium. |
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