| With the development of technology, many new fields, such as free-space optical communication, phase array radar and so on demand high-power, narrow-linewidth, small-divergence coherent laser. So, recently improving high-power lasers'beam quality has been becoming a hot topic. Because of special diffractive characteristics, second-order grating distributed feedback semiconductor lasers (DFB-LD) implement mode-control and surface-emitting or end-emitting and are made into high-power and high beam quality surface-emitting distributed feedback semiconductor lasers (SEDFB-LD) and broad-area second-order distributed feedback semiconductor lasers (DFB-LD). In this thesis, structure design, theory analysis, numerical simulation and grating manufacture have been completed, which will be a valuable reference for related work.For high-power and high beam quality coherent laser, passive and positive phase-locking systems have been analysized, and then two single high-integrated phase-locking structures, called mutual injection-locking SEDFB-LD array and single chip-integrated phase-locking SEDFB-LD array by external cavity, have been designed. Besides, in order to improve transversal mode and longitudinal mode of semiconductor lasers, lateral grating and curved grating have been introduced into semiconductor lasers with new-style structures designed.Modified coupled mode theory and transport matrix model have been used to analysize second-order DFB-LD and numerical simulation of 940nm second-order DFB-LD is presented. For duty cycleσ~0.4, the photon density distribution along the cavity is relatively uniform and side-mode suppress ratio SMSR is as high as 46dB. Forσ=0.4, surface-emitting external differential quantum efficiency reach 20% and far-field divergence angle is only 0.2°(1.5 diffraction limit); forσ=0.43, end-emitting external differential quantum efficiency is as high as 40%. So, we can separately manufacture SEDFB-LD with duty cycle of 0.4 and DFB-LD with that of 0.43.After referring processing techniques of end-emitting LD and vertical cavity surface emitting laser and inserting manufacture step of second-order grating, a complete process of second-order DFB-LD has been presented. Uniform sinusoidal second-order grating with depth of 70nm in 940nm semiconductor chip has been got by holography lithography under two-beam laser interference exposing system and wet-etching for 80s in 1HCl:1H3PO4:30H2O solution, which will be the base for following manufacture of the devices. |
