Research On Ultra Precision Mechanical Cleavage Of Cavity Mirror Of GaAs Based Semiconductor Laser

As one of the four new inventions of the 20 th century,the semiconductor laser has the characteristics of low threshold current density,good temperature characteristics,high power density,high electro-optical conversion efficiency,small size,and lightweight.Among them,GaAs-based high-power semiconductor lasers have good application prospects in industrial processing,laser processing,optical fiber communication,unmanned driving and other fields.As a key part of the high-power semiconductor lasers,a mirror-like facet quality as well as exact parallel facets are very significant contributors to good reflective properties and the long term operational reliability of the lasers.As a novel technology for high-power semiconductor lasers with broad area mirror facets,mechanical cleavage technology has received extensive attention.However,there are still a lot of technical gaps to be filled at this stage.How to realize a high-efficiency and ultra-precision cleavage technology for semiconductor materials is not only a key technical problem in semiconductor lasers and related industries.Therefore,the research on ultra-precision mechanical cleavage of cavity mirror of GaAs-based semiconductor lasers will carried out,using the combination of theoretical calculation and modeling,multi-scale simulation analysis and process experiment.The main research contents and results can be summarized as follows:Firstly,according to Hooke’s law and Euler angle,the distribution of the twodimensional and three-dimensional mechanical properties,including Young’s modulus,Poisson’s ratio and shear modules,of GaAs crystals with the crystal orientation was calculated.The vickers hardness and average fracture toughness of GaAs crystals were studied based on the indentation experiments.On this basis,combining the Boussinesq stress field,Cerruti stress field and sliding bubble field stress field,ascribing stress field model suitable for GaAs crystals was established,which lays the foundation for the subsequent simulation analysis of the GaAs crystal cleavage process.Secondly,the multi-scale simulation research of GaAs crystal cleavage process is carried out.At the macroscopic level,the GaAs crystal constitutive model parameters obtained above were integrated into the ABAQUS software,and the influence of scribing depth and scribing speed on the scribing load was analyzed.At the microscopic level,a molecular dynamics model was established to analyze the different crystal.In addition,it also explores the mechanism of the influence of different process parameters on the damage degree of the material surface and sub-surface during the processing process.The results show that the [011] crystal orientation on the GaAs(100)crystal plane is the preferred scribing orientation,and the scribing depth will significantly affect the damage degree of the material.The obtained simulation results can provide the necessary theoretical basis for the process experiment research.Subsequently,the scratching capability index(SCI)was proposed,and there is a good correlation between the SCI and the cleavage plane quality,which can effectively predict the cleavage plane quality.A number of experiments were carried out for the GaAs(100)crystal plane.The results showed that the maximum damage width and scribe width on the workpiece surface in the [011] crystal direction were smaller than the [100] crystal direction,and the scribing quality along this crystal direction was better.Furthermore,subsurface crack configurations of scribed grooves were made via FIB.The research on how to inhibit the damage of the cleavage plane played a key role.To obtain a broad area mirror facet,an improved scribing method,dot scribing,was provided.The experimental results showed that scribing along the <110> direction using the dot scribing method is beneficial for reducing the maximum damage width of GaAs.The dot scribing method can significantly reduce energy consumption during the cleavage of GaAs,and the energy saving ratios exceed 70%.Then,a series of cleavage experiments were designed according to the Taguchi method for analyzing the main effects of three parameters.The achieved optimal combination of parameters are scribing load of 10 g,scribing speed of 20 mm/s and scribing length of 0.6 mm.The undamaged length and surface roughness of cleaved planes can reach 11.77 mm and0.43 nm,respectively.The above research results have significantly improved the existing processing efficiency,while the key technical factors of the obtained cleavage plane have reached the current international mainstream level.Meanwhile,these results could also guide actual production and manufacturing field of the mirror facet of GaAs-based highpower laser bars.