Research On Beam Quality Control Of High Power Red Semiconductor Laser

Semiconductor laser is a widely used laser light source because of its advantages such as large output power,high conversion efficiency,good reliability,long service life,small device size,wide wavelength coverage and so on.However,due to the structure of the semiconductor laser,the light emitted by the device is different in the vertical direction and the horizontal direction,and the beam quality is very different,so that the beam waist position does not coincide,and there is astigmatism.At present,improving the output power of the device and ensuring the beam quality of the device has become a research hotspot and a difficult point in the semiconductor laser industry.High output power and high beam quality are often contradictory.At high currents,the device can achieve higher output power.However,at high currents,the uneven distribution of carriers and currents inside the device will increase,causing the device.The refractive index of the internal material changes unevenly,which leads to the far field diffusion and divergence angle of the device,which seriously affects the quality of the output beam.Therefore,we introduce asymmetric optical waveguides and partition electrodes into conventional semiconductor lasers.The experimental results show that the structure improves the beam quality of the device while ensuring the output power of the device,and also reduces the dependence of the lateral far-field divergence angle on the current.The semiconductor laser design process we designed is relatively simple and the production cost is low,which is very suitable for mass production,and also lays a good foundation for the design of high power and high beam quality red semiconductor laser.This thesis mainly studies the theory,design,process preparation and device performance of high power and high beam quality red semiconductor lasers.The main contents and innovations are as follows:(1)Using the principle of effective refractive index approximation of the material,the waveguide equation and the carrier diffusion equation inside the red semiconductorlaser are solved,and the expression of the lateral light field mode is obtained.Then the device compares and analyzes the distribution of the light field of the fundamental mode and the higher-order mode,summarizes the conditions and principles of the high-order mode lasing,and obtains the scheme of optimizing the lateral beam quality.(2)In order to improve the beam quality of the device,a large cavity structure is adopted in the direction of the vertical PN junction;in the size of the waveguide layer,the P region is thinner overall and the N region is thicker,and the asymmetric design can reduce the inside of the device.Absorption of the light field,thereby reducing losses;etching the ridge waveguide in a direction laterally parallel to the PN junction to limit the light field of the device.At the same time,the dry etching process is optimized to precisely control the depth and angle of the etching to ensure the reliability of the process flow of the device.(3)Using Lastip,comsol and other software to simulate the current applied to the device,the carrier of the active region and the temperature distribution inside the device.According to the simulation results and theoretical analysis,the partition electrode structure is proposed.The addition of this structure greatly improves the beam quality of conventional red semiconductor lasers,and the lateral far-field slow-axis divergence angle of the device is below 10°,and the range of variation with current is also smaller.