The Key Technology Research Of High-precision And Low-defect Fabrication For Silicon Reflectors

In infrared high-power laser systems,mono-crystalline silicon reflectors are widely used,and the reflectors need to achieve high-precision,high-stability beam transmission under high-power laser irradiation for a long time.Both the accuracy of components and the laser load capacity are extremely high demanded.With the continuous development of high-energy laser technology,the performance of existing mono-crystalline silicon components has been unable to support the further improvement of system output power and performance,which has become a technical shortcoming.The high-energy laser system requires reflector performance in systems,namely precision and laser load capacity.The pursuit of full-frequency spatial error restrain and reduction of laser energy absorption rate both depend on fabrication quality.However,at present,fabricaton technology inherits from traditional optical processing,and it is difficult to achieve both precision and laser load capability.It is necessary to carry out research on manufacturing methods and processes,and innovative manufacturing techniques are combined with application characteristics.This desertation chooses the high-energy laser system as the background and focus on the high-level manufacturing of mono-crystalline silicon reflectors.It deeply studies the absorption characteristics of various types of energy absorbing precursors and reveals the correlation between the absorption precursors,processing quality,and laser load capacity.Further study of precursor restrain strategies,the introduction of advanced optical manufacturing technology to improve the processing accuracy,inhibit the absorption of precursors,the formation of a parabolic,cylindrical joint manufacturing process,and ultimately achieve the typical components of high precision,low defect,low absorption level manufacturing.The specific research includes the following aspects:(1)Analysis of fabrication requirements for high-energy laser components.For the dual index requirements of high-power laser applications on accuracy and laser load capacity,the mechanism for enhancing the performance of components,the relationship between decoupling system performance,component performance.The physical mechanism are studied,and the factors that drive the energy absorption of components are divided into surface extrinsic chemistry.Structural,surface/sub-surface processing defect,and medium-to-high-frequency errors are three types of absorption precursors.Control key process indicators to suppress all types of precursors.The relationship between microscopic and nanoscopic component surface features,process indicators and macroscopic component performance was studied.The mechanism of the improvement of the component performance and the key processing index are indicated.The evaluation method of the component absorption performance based on the measurement of the precursor characteristics is proposed to lay a theoretical foundation for low absorption manufacturing.(2)Study on the method of inhibiting the absorption of precursors.Monocrystalline silicon is a typical hard-brittle material which is easy to produce processing defects on the surface.In this paper,an immersion polishing method is proposed,the principle of interface energy level is innovatively used,and coarse particles are separated from the polished area with nano-abrasive material.Thereby,surface processing defects can be suppressed.After polishing,the nano-structure defects on the single crystal silicon subsurface were studied to study the infrared absorption characteristics and reveal the essential composition.From the perspectives of suppressing the subsurface precursor,improving the quality of the subsequent coating and reducing the absorption,ion etching is used as a post-treatment process.(3)Coupling research on medium-high frequency error and laser load capacity.Based on the existing process routes,the generation mechanism and frequency band characteristics of high-frequency errors in different processes are studied;the energy absorption theory of the existing medium-to-high frequency errors is optimized,the relevant spatial frequency bands affecting the absorption are determined,and innovation utilizes medium-high frequency errors for energy absorption levels.Perform semiquantitative predictions.The traditional smoothing process can not suppress the highfrequency errors in the cylinder.This paper adopts the isotropy polishing plate translation and smoothing process to achieve the restrain of the IF error on the non-rotary symmetry plane.Based on the nano-delineation experiment,the single abrasive is analyzed.In this way,processing quality of component is improved from two dimensions: machining accuracy and energy absorption.(4)Research on high-quality component processing combined process processing.The process of immersive smoothing,ion beam modification and post-processing are used to optimize the defect restrain strategy and to develop monocrystalline silicon substrates.Compared with the traditional process,the advantages of the combined process in improving the accuracy and reducing the absorption,and the good adaptability on the paraboloid and cylindrical elements are verified.Full-frequency sub-nano-accurate manufacturing is realized on small-diameter planar components.Full-band error convergence and absorption precursor restrain are realized on large-aperture planar,parabolic,and cylindrical component and high-precision,low-absorption and high-energy laser monocrystalline silicon is processed Component substrate.