Research On Key Technology Of High Order Surface Grating DFB Semiconductor Laser

Distributed feedback(DFB)semiconductor laser is widely used because of its narrow spectral linewidth and good stability.Fabricating the grating in the surface of epitaxial wafer can avoid the secondary epitaxy technology,which can reduce the production cost and cycle of DFB semiconductor lasers.However,the spectral linewidth and wavelength stability features of surface grating DFB semiconductor lasers are relatively poor at present.In order to explore the influence of high-order surface grating on the performance of DFB semiconductor laser,the optical feedback characteristics of surface grating and the fabrication technology of high-order surface grating semiconductor laser devices were studied theoretically and technically in this thesis,The specific research contents include:(1)Starting with the theoretical analysis,the basic working principle of DFB semiconductor laser was analyzed.Based on the coupled mode theory and perturbation theory,the coupling characteristics of the optical field of the grating were analyzed theoretically.The influence of the grating structural parameters on the coupling coefficient was discussed.The epitaxial structure of 1.06 μm DFB semiconductor laser was designed and optimized.The optical feedback characteristics and loss of the high-order ridge-surface grating were simulated and analyzed.(2)The fabrication process of ridge-surface grating DFB semiconductor laser device based on holographic exposure technology was proposed.A ridge-surface grating DFB semiconductor laser with a grating period of 1.29 μm was fabricated.Driven by a continuous current of 0.6 A,the output central wavelength of the laser device was 1066.3nm,and the output laser had a 3d B spectral linewidth of 0.2 nm.The output power of 29 m W was obtained at 0.8A.(3)A fabrication process of high-order ridge-surface grating DFB semiconductor laser device based on buried metal mask was proposed.The ridge-surface grating etching was achieved with the aid of buried metal mask,the contradiction between grating technology and ridged waveguide technology was solved.Based on the proposed fabrication process,a high-order ridge-surface grating DFB semiconductor laser with grating period of 4.68 μm was fabricated.The output power of the laser device was 33 m W and the 3 d B spectral linewidth was 40 pm at a continuous current of 0.4 A.(4)The theoretical model of the structure of the laterally coupled asymmetric grating was established and analyzed.It was pointed out that the laterally coupled asymmetric grating can achieve a more uniform photons distribution in the resonant cavity by reducing the effectiveness of optical field coupling,which effectively avoided the spatial hole burning effect and was beneficial to obtain narrow linewidth laser.Two kinds of high order laterally coupled DFB semiconductor lasers have been fabricated experimentally,Compared with high-order laterally coupled symmetric grating DFB semiconductor laser,which output power was 46 m W at 0.6 A and the 3d B spectral linewidth was 70 pm at 0.4 A.Under the same test conditions,the output power of high-order laterally coupled asymmetric grating DFB semiconductor laser is 71 m W,increased by 54%,the 3 d B spectrum linewidth was reduced to 49 pm.In addition,laterally coupled asymmetric grating structure can also reduce the dependence of coupling coefficient on grating parameters,which is beneficial to reduce the difficulty of grating fabrication.