Research On Key Technology Of Absorbance Modulated Laser Direct Writing

Optical super-resolution technology is widely used in the fields of optical processing,detection and imaging.And optical super-resolution lithography is the practice of optical super-resolution in the field of photolithography.In many super-resolution lithography technologies,super-resolution lithography based on the absorbance modulation of photochromic materials is a kind of non-contact lithography technology by far field light modulating near-field light,and has the advantages of simple control and high contrast.But the technology can only produce simple patterns,and is difficult to improve single point resolution.We have innovatively combined the technology with laser direct writing system to form an absorbance modulated laser direct writing system,and successfully wrote super-resolution straight lines.In spite of this,there is still a lack of deep research on the laser direct writing technology based on photochromic materials.Based on this,the main purpose of this paper is not to produce super-resolution straight line,but as a supplement,to study its theoretical basis and some key technologies.The mechanism of laser direct writing based on photochromic material is absorbance modulation effect.It regulates the absorbance of media to the writing light by modulating light intensity,thus modulating the transmitted light intensity.The photochromic material has two molecular structures that are obviously different in absorption spectrum.When irradiated by the writing light,the material will transform from one structure to another,while the confining light can reverse the transformation,and the two effects compete with each other.As the effect of the confining light is much stronger,the written linewidth is effectively compressed when the dynamic equilibrium is reached.In this paper,the microcosmic process of the effect is analyzed,and a mathematical model of the whole process of absorbance modulated laser direct writing is established.The photochromic layer and photoresisit layer constitute the composite layers used in the system,and their related characteristics have a great influence on the direct writing progress.In this paper,the chemical properties of photochromic materials and photoresists are studied.Based on the analysis of the difficulties encountered in their selection,the criterion for choosing two kinds of materials is put forward.At the same time,composite layers containing metanil yellow's PMMA film and PVA film are produced and tested for their compatibility and independent characteristics step by step.Considering the existence of vortex laser in our absorbance modulated laser direct writing system,we propose a technical scheme of focus detection using vortex laser shearing interferometry.Optical vortex beam has a dark hollow structure in its intensity distribution,its shearing interference pattern contains a pair of forks pointing to the opposite directions which is very sensitive to defocus.With the help of the focusing scheme of vortex laser,the degree and direction of defocus can be obtained simultaneously within one frame of interference image,providing a new idea for the focus of a non-imaging optical system.In conclusion,absorbance modulated laser direct writing is an excellent combination of absorbance modulation and laser direct writing.As long as we study it deeply and put it into practical production and application,the prospect is definitely bright.