Research On Lateral Beam Quality Control Of Loss Tailoring Microstructure Diode Laser

After more than half a century of development,the epitaxial growth and process preparation technology of semiconductor lasers are very mature.Semiconductor lasers are widely used in industrial production or as pump sources of other lasers because of their small size,lightweight,high reliability,all solid-state,long life-time,high optic-electric conversion efficiency and direct modulation.In recent years,with the development of new technology and the increasing demand for laser light sources,the output power and beam quality of the device are required to be higher.Because of the limitation of high-order modes,thermal lens effect and other nonlinear phenomena on the beam quality of traditional broad-area semiconductor lasers,the poor lateral beam quality can not fully meet the requirements of many application fields,which is very detrimental to the development of broad-area semiconductor laser devices.Although beam shaping and combining technology can achieve great brightness,the manufacturing cost and system volume will increase significantly,and the reliability and energy efficiency of the system will also decrease.Therefore,it is of great significance to improve the beam quality of the semiconductor laser itself.In this thesis,the loss tailoring method was proposed to improve the lateral beam quality of semiconductor laser.The investigation contents and achievements were as follows:(1)Characteristics of the mode distribution in the broad-area semiconductor laser were studied by finite element method,the related simulations were carried out by using the simulation software FDTD Solutions and MODE Solutions.Through the detailed analysis of the distribution of different modes,the loss tailoring method was proposed to improve the output beam quality by etching microstructure on the broad-area waveguide.(2)A distributed loss tailoring laser based on super-large optical cavity(SLOC)epitaxial structure with a cavity length of 1.5 mm and a strip width of 100 ?m was fabricated.The circle microstructure was introduced into the peak position of the high-order modes,which increased the loss and threshold of the high-order mode and improved the far-field divergence angle of the device.The feasibility of this improved method is verified.(3)An edge loss tailoring semiconductor laser based on sawtooth(ST)microstructure was designed and fabricated.The cavity length was 1.5 mm and the strip width was 100 ?m.The performance of the device is analyzed by measuring the relevant parameters.Compared with the standard device,the lateral beam quality of the ST laser is improved by 41.6%,and the dependence of beam parameter product(BPP)on current was greatly reduced.The beam quality of the device was stable,which was of great significance for practical applications.(4)By combining the arrow loss tailoring microstructure with the trench structure,a composite loss tailoring microstructure semiconductor laser(AT laser)was proposed.The device is fabricated and analyzed.The beam quality and output power were improved by 58.5% and 21% respectively.The dependence of far-field divergence angle on current was reduced,and the size of near-field beam waist was significantly reduced.The suppression of high-order mode and carrier diffusion was realized,which greatly reduces the lateral carrier accumulation effect and made the brightness of the laser increased nearly twice.(5)High-performance AT lasers were fabricated,and their related indicators were measured.The feasibility of microstructure laser in the practical application was proved.