Research Of Beam Homogenizing Technology For Diode Laser

Compared with other types of lasers,semiconductor laser have the advantages of small size,light weight,long life,low power consumption and high reliability.In addition,using low voltage and constant current power has the advantages of low power failure rate,safe use and low maintenance cost.Therefore,the application field is expanding increasingly.In some situations where laser is the core device,such as laser cutting,drilling,annealing,semiconductor manufacturing,laser medical operation,laser nuclear fusion etc,the shape and energy uniformity of laser spot affect the accuracy of laser application.However,due to the asymmetry of fast and slow axis divergence angle of semiconductor lasers,the beam quality is poor and the intensity distribution is not uniform.With its application and development,the laser beam shaping can meet the application requirements.It is of great significance and application value to obtain flat-topped spot by homogenizing the laser beam of semiconductor lasers.At present,there are few studies on laser beam homogenization for semiconductor lasers with inherent astigmatism and different divergence angles of fast and slow axes.Therefore,based on the beam characteristics of semiconductor lasers,the homogenization analysis and system design of semiconductor lasers are studied in this thesis.The main contents of this thesis are as follows:(1)four mathematical models for describing flat-topped beams are introduced.According to the requirements,one model can be selected to program and optimize lens parameters to achieve the homogenization effect.The commonly used methods for evaluating the uniformity of spot energy distribution are introduced,and the advantages and limitations of various evaluation methods are explained.The principle of microlens array for beam homogenization is introduced.The beam is segmented and finally superimposed.The tiny inhomogeneity within each sub-beam will obtain uniform spot in the process of coincidence.(2)based on the ray tracing method,the aspheric ray tracing model for beam homogenization is given.The model can obtain different homogenization effects according to the different distribution functions of light intensity.For a single emitter with only one light-emitting region,two kinds of optical systems are designed and simulated,which can shape elliptical Gauss beams into circular and square uniform flattopped spots.The effects of divergence angle,position of observation plane and rotation of collimator on the uniformity of the laser spot are analyzed.The results show that the uniformity of the laser spot is more than 90%.(3)we simulate the linear array and stacking structure of semiconductor lasers with Zemax.The square flat-top spot is obtained in the far field of the laser bar,and the uniform line spot and square uniform spot are obtained in the far field of the laser stack.The uniformity is more than 90%.