Research On Femtosecond Laser Fabrication Of Micro/Nano Structure And Its Anti-reflection Properties

The anti-reflection capability of the photoelectric detection system in the aerospace field is of great significance for improving the performance of equipment products.For example,the extinction performance of satellite hoods affects the attitude accuracy of star sensors,which is the key to the stable operation of satellites.The anti-reflection performance of the fairing optical window of a high-speed aircraft determines its detection range extension and dynamic performance.Traditional methods such as coating,black paint,and sandblasting are used to achieve antireflection ability.Due to the interface bonding effect and harsh service environment,there are defects such as narrow spectrum,small incident angle,high and low temperature shedding,short life,and volatilization polluting the lens,which stringent technical and tactical requirements for aerospace equipment.The realization of anti-reflection by preparing micro-nano structures on the surface of the device is the frontier of international research.Attribute to the ultra-fast and strong characteristics of femtosecond lasers,it has unique advantages in selective,non-contact,high-precision,and high-quality(small thermal effects)manufacturing of special materials and three-dimensional complex structures.It has become one of the most ideal methods for the processing of anti-reflection micro-nano structures,but there are problems including insufficient understanding of the micro-nano structure forming rules and the anti-reflection mechanism of composite micro-nano structures.It has become one of the most ideal methods for the processing of anti-reflection micro-nano structures,but there are problems including insufficient understanding of the micro-nano structure forming rules and the anti-reflection mechanism of composite micro-nano structures,lack of large-format high-quality manufacturing methods.It led to the anti-reflection performance of the micro-nano structure is not excellent,which restricts its practical application.This dissertation focuses on the design,manufacturing and simulation of the antireflective micro-nano structure on the surface of typical materials.The article reveals the evolution of the micro-nano structure of typical materials under femtosecond laser irradiation,and develops new method for manufacturing high-performance antireflective micro-nano structures.And two types of composite micro-nano structures including titanium alloy hybrid micro-nano hybrid structure and zinc sulfide microporous and nano-stripe composite structure are obtained.established a numerical simulation model of the composite micro-nano structure,and clarified the anti-reflection mechanism of the composite anti-reflection micro-nano structure.two numerical simulation model of the composite micro-nano structure established,and the anti-reflection mechanism of the composite anti-reflection micro-nano structure are clarified.The research provides theoretical and technical support for the application of anti-reflection micro-nano structures in the aerospace field,and the main innovative research contents of this paper are as follows:The anti-reflection mechanism of different scales micro-nano structures is analyzing,then the relationship between the parameters of the micro-nano structure and its anti-reflection performance is explores.Subsequent,the structural parameter limitation conditions of one-dimensional grating and two-dimensional grating subwavelength structure is studied to achieve the anti-reflection effect.And then,the subwavelength anti-reflection structure of the typical material surface is designed,and the microstructure period,minimum depth and duty cycle when the titanium alloy and zinc sulfide reach the optimal anti-reflection effect are calculated,which provides theoretical basis for subsequent simulation calculation and experimental research.A new method is proposed for the fabrication of anti-reflection micro-nano structures by femtosecond(fs)laser assisted with airflow pressure.The formation mechanism of the micro-nano structure under the synergistic effect of different air pressure and femtosecond laser parameters is revealed,and the influence of energy deposition and micro-nano structure evolution controlled by air pressure on the characteristics of the absorption spectrum is analyzed.In addition,the relationship between anti-reflection performance and structure morphology is verified by element analysis and high and low temperature tests.An ultralow average reflectance of 2.31%over the 250 nm-2300 nm spectral range is obtained,and the reflection for specific wavelengths can go below 1.5%.Finally,after 12 high and low temperature cycle tests from-40°C to 50°C(each temperature),the average reflectance of the sample only increased by 0.06%?0.27%,which show excellent environmental stability.An effective method is declared to achieve metal anti-reflective micro-nano structures by femtosecond laser irradiation parameter controlled.The morphological evolution and forming of the micro-nano hybrid anti-reflection structure on the surface of titanium alloy controlled by pulse fluence are conducted,the sample achieve an ultra-low average reflectance of 2% in the250nm-2300 nm spectral range.A numerical model of the micro-nano hybrid anti-reflective extinction structure is established,and the relationship between sub-micron fringes(period,depth,duty cycle,etc.),nano-particles(diameter,number,morphology)and reflection spectra are analyzed.Furthermore,anti-reflection mechanism of the broad spectrum and ultra-low reflectivity of the multi-scale micro-nano hybrid structure is clarified,which composed of micron optical cavity,sub-micron fringe,and nanoparticles.A method is suggested for preparing anti-reflection micro-nano structures with femtosecond laser Bessel beams of transparent media.Two types of Bessel beam optical systems with different magnification conical lenses are designed and developed.The light field distribution and micro-hole ablation characteristics under Bessel beam irradiation are studied,and the anti-reflection micro-nano structure with micro-holes and nano-stripes is obtained,of which has an average transmittance of9.7% from 5 ?m to12 ?m.Specially in the 8 ?m-12 ?m spectrum,the average transmittance increased by 12.3%,and the increase in transmittance at 11.9 nm wavelength reached 14%.A numerical model of anti-reflection micro-nano structure with micro-holes and nano-stripe obtained by high repetition frequency Bessel beam is constructed,and the relationship between two-dimensional sub-wavelength structure parameters(period,depth,etc.),nano-stripe(height,height,etc.)and the transmission and reflection spectra are established.Moreover,the broad spectrum and high antireflection mechanism of the composite micro-nano structure is reveals.