Research On Optical Field Modulation And Its Application In Optofluidic Chips

Optofluidic chip is a chip platform that integrates micro-optics and incorporates microfluidic technology on which operations such as reagent mixing and particle sorting can be performed,providing a basis for handling micro-samples.The structural tunability of optofluidic chips offers new technical approaches to optical field modulation,while the integration of microfluidics and optics simultaneously offers the possibility of miniaturisation,low cost and high precision control of traditional optical devices.The advantages of the optofluidic chip have led to its rapid development in recent years.However,the high integration of the chip brings with it difficult problems in optics such as optical focusing and beam shaping.At the same time,how to separate and extract target particles from a large number of similar micro and nano particles and achieve accurate control of single particle needs to be strengthened.This thesis introduces the technique of surface plasmon resonance and fibre optical tweezers to the optofluidic chip,focusing on its modulation of the optical field and the resulting trap,sorting and movement of particles.The main works in this thesis are as follows:(1)A light field modulation method based on bowtie nanostructures is discussed,and particle sorting is proposed using the properties of nano bowtie arrays and nanoparticle resonances.In this thesis,the optical properties of single solid and gold nanobowties with hollow cavity are compared and analyzed,and the influence of hollow cavity structural parameters on plasmon resonance wavelength is discussed.Nano bowties with specific resonance wavelengths encoded are sequentially arranged to produce hot spots that act as optical traps.The linear repetitive structure of three separately addressable traps forms a ’nano-sorter’,and by sequentially activating adjacent traps,the nano bowtie array enables the sorting of particles.The feasibility of this method is demonstrated by simulating and designing the sorting of three gold nanobipyramidal particles.(2)A quadrangular lens chip based on fibre optical tweezers is proposed and the movement of the trapped particles is investigated through optical field modulation.This chip improves on the axial lens forming a Bessel beam by the synergy of optical and fluid forces to form a multi-optical tweezer potential well.The effect of the top angle of the quadrangular lens and the refractive index of the salt solution between the injection end of the Gaussian beam and the quadrangular lens on the distribution of the light field is analysed using a time-domain finite difference method(FDTD),and the trapping properties and transfer properties of the quadrangular lens chip on the particles are also analysed.It is demonstrated that a quadrangular lens chip based on fibre optical tweezers enables the trap and transfer of nanoscale to micrometre particles.