Fabrication Investiuation Of Metal-polymer Micro-Nano Devices Based On Laser Direct Writing Technology

Metallic micro-nano devices play an important role in modern optics,and functional devices based on surface plasmonic plaritons have attracted much attentions both in fundamental research and applications in recent years.One of the key issues in the researches and applications is the efficient fabrication of the metal/dielectric composite micro-and nano-structures.The currently widely used micro-nano fabrication techniques including electron beam lithography,ion beam etching,vacuum coating,and/or vapor phase epitaxy,etc.suffer from complicated multiple processes,low yield and low tolerance,especially in the metallic material related nano structures.Laser direct writing technology,as an emerging technology in micro-nano fabrication in recent years has the advantages of high precision and high degree of freedom.How to apply it to the fabrication of metallic micro-and nano-devices and simplify the experimental process has attracted lots of attentions.In this thesis,a one-step fabrication technique of metal contained micro-and nano-structures based on two-photon absorption is experimentally demonstrated,in which the reduction of gold ions and polymerization of polymer are realized simultaneously in the mixture of gold salt and resins using a near-infrared femtosecond laser.The detailed contents of the thesis include:(1)The research background and current status of the fabrication techniques of metallic micro-nano devices are introduced.The difficulties and shortcomings of traditional micro-nano manufacturing techniques in the fabrication of metallic micro structure devices are analyzed.Laser direct writing technology and especially the reduction of metal ions and the polymerization of the resin under the conditions of two-photon absorption are emphasized,and the theoretical and simulation calculation methods used in the design of the micro structures are also introduced.(2)Fabrication technique of metal contained micro-and nano-structures based on two-photon absorption is experimentally investigated,in which experimental conditions of reduction of gold ions and polymerization of polymer under a near-infrared femtosecond laser are investigated in detail.According to the characteristics of the chemicals,HAuCl4,IP-L 780 and ethanol are selected as the metal salt,resin and solvent,and the mixture configuration process is elaborated;The effect of the concentration of golden salt on the performance of process is studied,and the effect of Rhodamine B and DETC as additional photoinitiator on the process is also conducted,respectively,and from which an optimized recipe of containing Rhodamine B is obtained;The influence of the laser power on the reduction of gold ions and polymerization process is conducted,and the polymerization thresholds of the mixture and the pure photoresist resin are found to be 45 mW and 33 mW,respectively;The thinning effect of line width caused by the increase of the polymerization threshold is observed.Finally,a low-power repeated exposure method is proposed to reduce the local burning caused by high-power laser.(3)Potential applications of metal-polymer laser direct writing is explored theoretically.Two gold-containing functional devices are designed and optimized:one is a gold-containing linear nano-grating polarizer operating in 3-5 ?m band.It is found that a TM transmission of 68%and extinction ratio of greater than 26 dB can be obtained with a volume density of gold particle 20%,grating period,height and duty ratio of 600 nm,600 nm and 0.5 respectively.Moreover,the performance is better as the volume density of gold particle is larger and the particle size is smaller.The second is a gold-containing imperfect quarter waveplate operating at 700 nm with a linear polarized incident light with an orientation angle of 45°.A quarter waveplate with a phase shift of ?/2 can be theoretically obtained with volume density of gold particle 10%,period of 280 nm,height of 1 ?m and duty ratio of 0.5,respectively.(4)In order to further demonstrate the capability of proposed fabrication method in fabricating functional gold-containing devices,a gold-containing grating sample(period of 600 nm,line width of 250nm and height of 280nm)with phase control capability at?1550nm waveband is fabricated and tested.Experimental results show the phase shifts of the transmission at 1510nm,1530nm,1550nm,and 1570nm match well with theoretical simulation results.