Semiconductor laser has the advantages of small size, light weight, high electro-optical conversion efficiency, high reliability and long life. It has important applications in the fields of industrial processing, biomedicine and national defense. In 1962, American scientists successfully developed the first Generation GaAs homogeneous structure injection semiconductor laser. In 1963, Alferov and others of the Yofei Institute of Physics of the former Soviet Academy of Sciences announced the successful development of a double heterojunction semiconductor laser. After the 1980s, due to the introduction of energy band engineering theory, at the same time The emergence of new crystal epitaxial material growth processes [such as molecular beam epitaxy (MBE) and metal organic chemical vapor deposition (MOCVD), etc.], quantum well lasers are on the stage of history, greatly improving device performance and achieving high power output.
High-power semiconductor lasers are mainly divided into two structures: single tube and Bar strip. The single tube structure mostly adopts the design of wide strip and large optical cavity, and increases the gain area to achieve high power output and reduce the catastrophic damage of the cavity surface; Bar strip structure It is a parallel linear array of multiple single-tube lasers, multiple lasers work at the same time, and then combine beams and other means to achieve high-power laser output. The original high-power semiconductor lasers are mainly used for pumping solid-state lasers and fiber lasers, with a waveband of 808nm. And 980nm. With the maturity of near-infrared band high-power semiconductor laser unit technology and the reduction of cost, the performance of all-solid-state lasers and fiber lasers based on them has been continuously improved.The output power of single-tube continuous wave (CW) The 8.1W of the decade reached the level of 29.5W, the bar CW output power reached the level of 1010W, and the pulse output power reached the level of 2800W, which greatly promoted the application process of laser technology in the processing field. The cost of semiconductor lasers as a pump source accounts for the total solid-state laser 1/3~1/2 of the cost, which accounts for 1/2~2/3 of fiber lasers. Therefore, the rapid development of fiber lasers and all-solid-state lasers has contributed to the development of high-power semiconductor lasers.
With the continuous improvement of the performance of semiconductor lasers and the continuous reduction of costs, its application range has become wider and wider. How to achieve high-power semiconductor lasers has always been the forefront and hotspot of research. To achieve high-power semiconductor laser chips, t is necessary to start from The three aspects of material, structure and cavity surface protection are considered:
1) Material technology. It can start from two aspects: increasing gain and preventing oxidation. Corresponding technologies include strained quantum well technology and aluminum-free quantum well technology. 2) Structural technology. In order to prevent the chip from burning out at high output power, asymmetrical is usually used Waveguide technology and wide waveguide large optical cavity technology. 3) Cavity surface protection technology. In order to prevent catastrophic optical mirror damage (COMD), the main technologies include non-absorbent cavity surface technology, cavity surface passivation technology and coating technology. With various industries The development of laser diodes, whether used as a pump source or directly applied,has put forward further demands on semiconductor laser light sources. In the case of higher power requirements, in order to maintain high beam quality, laser beam combination must be performed. Semiconductor laser beam combination Beam technology mainly includes: conventional beam combining (TBC), dense wavelength combining (DWDM) technology, spectral combining (SBC) technology, coherent beam combining (CBC) technology, etc.