Research On Effect Of Laser Beam Coherent Combination

Some initial research of the laser beam coherent combination (or called coherent addition technology) based on laser diode-pumped laser has been done. A theoretical model of multi-beam laser coherent combining is established on the bases of coherent theories. Based on the theoretical model, influences of the number of lasers, arrangement of laser array, line width of laser spectrum on the coherent combination effect are studied respectively. The results show that, under the ideal conditions, the total amplitude and light intensity of N beams coherernt combining are N times and N2 times higher than the single respectively, the resultant main peak is more narrow and energy is more concentrative with the increasing quantity of laser beam; the smaller the beam spacing is, the better the coherence combination effect will be. By analyzing the shape of main peak intensity which is got at the same distance of far-field with different beam spacing, and the rule about the peak intensity changed when spot gets to stable state, the influence on coherent combination system is much less when beams are arranged in a square, which is an ideal arrangement relatively in the three (square, cross, line). From this conclusion, the better symmetry of laser beams are arranged, the better the coherent combination result is obtained. When achieve better coherent combination, the narrower the line width of laser spectrum is, the longer the optical path difference will be. That is to say, with phase control, the longer the adjustable phase-related distance is, the easier a better coherent combination result will obtain. Transformate formulas properly which come from models in references, when obtained coherent combination in the Michelson laser cavity, the relationship between the number of lasers and combination efficiency of coherent combination, the line width of the laser spectrum and combination efficiency of coherent combination are analysed respectively. When the number of lasers which take part in coherent combination over a certain value, the larger the number is, the lower the combination efficient will be; the wider the line width of laser spectrum is, the more obvious the improvement of combination efficiency will be.