Coherent Combining Of Five Coupled Fiber Laser Arrays

Compared with gas laser and the whole solid-state laser of diode pumping, high power fiber laser has notable predominance in efficiency, cubage, refrigeration, quality of beam of light and so on. Fiber laser has many potential applications in versatile fields. To attain high power fiber laser, it is necessary to develope the technology of coherent combination of fiber lasers. The effective means is fiber laser arrays.In this paper, coherent beam combining of two fiber lasers by use of a fused fiber coupler has been obtained and studied. A large portion of the output power was transferred to the port with less loss. Stable addition efficiency as high as 95% was achieved. The differences of the output power of the two fiber lasers worked independently and the dispersion of their wavelengths have great effects on the addition efficiency. The output power from the loss port arrived at the least level when the two fiber lasers operated at the equal power level. Adjust the central wavelength of one FBG by changing the temperature at which the FBG worked, the wavelength of the corresponding laser would be shifted. In the experiment it can be discovered that the coherent combined output was failed when the gap between the wavelengths of the two fiber laser was too large. Under this condition, the two lasers worked independently and had no influence on each other. The output spectra have two peaks. Decreasing the gap gradually, the output power from the crushed port was reducing and the power from the output port was increasing. Finally, the high efficient coherent combination was achieved.The coherent combining arrays of five fiber lasers was also achieved with a 1×5 tree fiber coupler which consists of three 50:50 fiber couplers and one 20:80 fiber coupler. The coherent addition efficiency was up to 83.3% calculated from the data. Although the output power fluctuated, the maximal relative value was under 3.8%. The coherent combining output spectra with different number of fiber lasers were measured.The coherent combination of coupled fiber laser arrays is novelty, simple and has high coherent addition efficiency without active control. It has been demonstrated that the configuration is easy to achieve coherent addition of fiber lasers.