Design And Experimental Investigation On Dual-beam Super-resolution Direct Laser Writing System

Throughout the history of science,processing technology is the key factor to the advancement of science and technology.The technological innovation in the processing field brings revolutionary impact to various areas of scientific research.Optical processing has long been a tower of strength in the processing field,and the advent of two-photon direct laser writing technology has broken through the constraint of the optical diffraction limit,and improves the processing precision to around 100 nm.The emergence of Dual-Beam Super-resolution Direct Laser Writing(DBSR-DLW)has further enhanced the capability of optical processing for the past few years,making it more promising for applications in semiconductor manufacturing,optical information storage,micro-nano fluidics and other fields.However,the research on DBSR-DLW was started late in China,and very few scientific research institutes have mastered the relevant technology in our country.In particular,the lack of relevant technology and equipment in northwest China has further exacerbated the imbalance of regional development of this field.In view of these problems,a DBSR-DLW system is designed and constructed independently in this paper,and the experimental investigation is carried out based on this system.The investigations are summarized as follows:(1)The designing and constructing of the DBSR-DLW system.The main body of the initiating laser and inhibiting laser paths of DBSR-DLW system are constructed based on femtosecond laser and visible band continuous laser source,respectively.The spatial light modulator is settled in the initiating laser path to improve the control ability of the femtosecond laser beam and the processing flexibility.By loading phase diagrams,which are obtained based on the non-iterative algorithm,the spatial light modulator could solve the key issues in dual-beam coupling.A "Z" shaped reflective structure in the main body of the initiating laser path is used to shield the zero-order beam spot and improve the light energy utilization rate of the system.The overall optical path of the system is constructed as an inverted fluorescence microscope structure.A wide-field illumination and CMOS monitoring unit is built to enable the positioning of the sub-interface and the real-time monitoring of the processing.Specific solutions are given especially for the technical difficulties of the beam coupling calibration and the processing sub-interface positioning of the system.(2)The designing and implementing of the control software for the DBSR-DLW system.The system control software is designed and developed independently based on Lab VIEW,which is enabled the effective integration of functions such as data loading,structure scale setting,exposure control,processing path planning,nano-stage control and processing monitoring.The software supports the direct import of processing data in JPG,BMP and PNG formats.The control software is simple to operate and enables automated processing of 2D and 3D structures by setting the processing parameters such as exposure time,scanning range and scanning interval,as well as the flexibility to change the processing scale of the target structure.After the greyscale and binarisation procedures,the processing points and non-processing points can be distinguished,making it possible to automatically skip the non-processing points during processing and only the expose points will be processed,thus increasing the processing efficiency of the system.The path planning of serpentine scanning allows for a significant reduction in empty stroke and further increases the system’s processing speed.Through the program interface,the movement control of the nano stage is more flexible.By presenting the processing information in the main display area of the software in real time,it is easy for the user to evaluate the entire process.At the same time,the processing progress is displayed in real time as a percentage in the system status bar,allowing the visualisation of the processing.(3)Experimental investigation of nano structure processing based on the DBSR-DLW system.The mechanism of DBSR-DLW is discussed based on the molecular dynamics model of the photopolymerization chemical reaction from the system processing principle.The photoresist for the DBSR-DLW is prepared based on the stimulated emission transition mechanism and its optical characteristics and laser sources selection are analyzed and discussed.Micro-nano structures are processed by using the prepared photoresist,which validates the performance of the DBSR-DLW system.Further experiments are carried out on the system for dual-beam direct laser writing,and the effects of initiating laser power,inhibiting laser power on the processing of polymer wires are investigated,and the wire structure with a line width of less than 100 nm is achieved.