| Diode laser arrays have many advantages. For example, high optical conversion efficiency, small size, high reliability and long life, etc. It has important applications in industrial processing, biomedical, communicationand pumper so on. However, due to its unique waveguide structures, high power diode laser arrays have drawbacks of poor beam quality, which restrict its further applications. After a lot of researches, it is proved that the spectral beam combination technology with external-cavity feedback is an effective method to improve the beam quality of LDA and can get outputs beam which is near the diffraction limit. Compared with coherent combination technology, spectral beam combination technology can get more large power output and can be controlled and realized more easily. So diode laser arrays spectral beam combination technology is one of the research hotspots in recent years. Therefore, a series theoretical and experimental research about diode laser arrays spectral beam combination technology have been studied in this paper, the main research works are as follows:First of all, the fundamental of diffraction gratings and diode laser arrays spectral beam combination technology is analyzed, then, the expression of theoretical spectra line width in LDA spectral beam combination is derived. And some researched have been done on the structure of LDA spectral beam combination.Finally, the main way to increase the output power of LDA spectral beam combination is presented, which include the improvement of the output power of single light-emitting unit, the improvement of the efficiency of LDA spectral beam combination and the improvement of the number of light-emitting unit in spectral beam combination. It is pointed that the improvement of the number of light-emitting unit in spectral beam combination is the key factor to increase the output power of LDA spectral beam combination.Then, the existing matters of the beam combination along the slow axis of each emitter in the traditional spectral beam combining structure are analyzed and summarized, which include the influence of BTS smile effect and the limitations of selecting slow axis light collimating lens. At the same time, improvement is made in the traditional spectral beam combination structure by adding beam shaping element, namely BTS. The slow axis light distribution becomes horizontal distribution. It overcomes the above drawbacks. Then a verification experiment is done by using the 980 nm standard BTS. The laser output is obtained, whose spectral line-width is 7.7nm and maximum power is 70 W, which is M2 of 1.28(BPP=0.4mm*mrad) in horizontal and M2 of 11.2(BPP=3.5mm*mrad) in vertical. Based on the analysis and discussion of the results, the validity of this improvement structure is confirmed.At last, on the basis of the summing up the spectral beam combining existing structures, the function of the transformer lens is analyzed. The system’s optical path of the traditional structure is too long, which is unfavorable to spectral beam combining.So a new structure is designed that the functions of focusing and collimation of the transformer lens in the traditional spectral beam combining systems can be achieved by two optical lenses. Then a verification experiment is done. The beam quality with output power of 49.42 W and electro-optic conversion efficiency of 42.7% is achieved. M2 of 1.29(BPP=0.4 mm*mrad) in horizontal and M2 of 11.6(BPP=3.6 mm*mrad) in vertical are obtained. The beam quality of the output is close to that of a single emitter of the array in both directions. Through the analysis and discussion of the experiment results, it is confirmed the new structure is useful for the LDA spectral beam combination. |
PDF Full Text Request