Research On The Characteristic Of The Force Exerted On A Particle In The Optical Vortex

Optical tweezers has been widely used in biology and medicine. Optical tweezers can manipulate several tens of nanometers to tens of microns particles. With the technology development, optical tweezers have been becoming a powerful tool in biotechnology and micro-manipulation filed. However the traditional optical tweezers have great limitations, for example, it can only capture high refractive index particles but can not capture the low refractive index particles, and particles may be damaged due to heat absorption in the focusing area. Different from traditional optical tweezers, the optical vortex can overcome the above shortcoming. Optical vortex tweezers not only can capture particles in high-focus area, but also can capture the low refractive index particles.This paper studies the force of particles in the high order Bessel beam, and derives force expression exerting to a particle according to the high Bessel beam light field. The relationship among the optical wavelength, particle radius, waist radius, refractive index and axial force are discussed. In accordance with simulated results, the stability of the captured particles is discussed in bound conditions. The results showed that the smaller the wavelength of beam , the greater the axial force and the better the stability of captured particles. The refractive index is more greater potential wells is much deeper and capturing particles is more easy. The waist radius affects the axial force greatly. With the waist radius increasing, the axial force become larger quickly. Because of wavelength of beam, particle refractive index, particle radius and waist radius of beam have significant effects to the axial force, choosing a suitable experimental parameters has an important significance on the stability of trapping particles. Through the comparing on high-order Bessel beam and the zero-order Bessel beam descripe that vortex optical field can binde particles more stable.This thesis is consisted of five chapters. The first chapter describes the history of optical tweezers, background and status of international research. The second chapter presents an overview of basic principles. The third chapter presents the force analysis in Gaussian beams. The fourth chapter analyse a particle in the vortex optical field. The fifth chapter study the angular momentum of optical vortices and research progress of optical vortex.