Femtosecond Laser Dynamic Holographic Processing Microtube Based On Bessel Beam And Its Applications

The femtosecond laser(fs)two-photon polymerization(TPP)technology is a micro/nano processing technology that can break through the optical diffraction limit to achieve hundreds of nanometers of processing resolution.Because it can achieve true 3D processing of micro/nano structures with arbitrary shape,this technology has been widely used in micro/nano machinery,micro/nano optics,microfluidics,biosensing,cell engineering,etc.The current research hotspots based on this technology include:1.Optimizing technical parameters,such as improving resolution and processing efficiency;2.Realizing various functional applications in the field of micro/nano research based on 3D micro/nanostructure.In this thesis,we report the study on the propagation characteristics of Bessel beam,a special long-distance-non-diffraction light field,under the focus of a high numerical aperture objective lens based on the spatial light modulation(SLM)technology,and the controllable micro-ring structure processing by this focused annular light field.Moreover,its applications as cell scaffold,micro-filter,and micro-cavity in the fields of cell engineering,microfluidics,and micro/nano optics have also been studied.Traditional femtosecond laser TPP is a serial processing method in which a single fs beam is combined with a 3D positioning platform or scanning galvanometer to achieve point-by-point and layer-by-layer scanning.In this thesis,a rapid holographic dynamic processing technology with high-precision for 3D microtube structures based on the special analytical light field(Bessel beam)is proposed.In this thesis,a series of complex microtube structures are processed through holographic parameter adjustment and processing parameter optimization.The processing of variable-section microtube is difficult to be achieved by traditional photolithography.At the same time,in order to meet the needs of different threshold energies for the focal spot with different sizes,we propose an energy control scheme based on compressing the hologram phase depth to change the diffraction efficiency,and we experimentally realize smooth and variable cross-section microtube processing with diameters ranging from 3 μm to 10μm.This method has strong scalability,which can be extended from Bessel light field to any light field,from global phase compression to local phase compression.In order to demonstrate the functional applications of the micro-ring-like structures,we first realize the preparation of microtube arrays as cell scaffolds through array-type tube processing combined with the self-falling effect of the tube array during development.The culture of yeast in microtubes with different diameters is realized by siphon method and we further study the effects of 2D and 3D tubular confined microenvironments with different diameters and variable diameters on yeast division.It provides an experimental reference model for the preparation of cell scaffold structure and the realization of cell array culture.In addition,in terms of microfluidic devices,the filtration and enrichment of specific particles or cells is indispensable for some key applications in the chemical and biological fields.In this thesis,for the first time,the preparation of an integrated microfilter inside a commercial needle is achieved by this holographic processing method.Screening and filtering of particles with different diameters is realized experimentally.This method realizes the rapid programmable processing of functionalized and integrated Lab-in-a-needle devices,and provides a processing reference for the rapid process of functional devices on non-planar semi-closed base.Finally,in the field of microcavities that require high structural quality(symmetry,surface roughness,etc.),we successfully prepare polymer microcavities with a quality factor of the order of 102 by further optimizing the processing parameters.The photoluminescence(PL)spectrum of a microtube as WGM microcavity is experimentally measured.The resonance modes of different parts of the same microtube and different microtubes with the same parameter are compared and their consistency is analyzed.At the same time,experimental measurements and numerical simulation analysis are performed for the resonance modes of different microtubes with different parameters.This holographic TPP processing method provides a technical means for efficiently and flexibly preparing polymer ring microcavities,and can provide a new experimental platform for functional applications in the fields of biosensing,micro/nano optics,etc.