| Summary: | 碩士 === 國立成功大學 === 微電子工程研究所 === 105 === This thesis studies on the cladding-pump technique to pump the ytterbium-doped fiber with a 915-nm multimode laser diode as a pumping source to generate 976-nm laser which is under the all-fiber system. We found that the Yb-doped fiber is difficult to laser at 976-nm in the cladding-pump system. Therefore, our main purpose is that etching the Yb-doped fiber by HF to decrease the diameter so that increasing the intensity of pump source and reducing the laser threshold. After that, we improved the quality of etching and optimized the pump efficiency to increase the laser efficiency. We found that the transmission of the SMF-130V etching by HF 24.5% was above 75%. The transmission of the SMF-130V etching by HF 30% is less than 20%, Presumably the slope of taper etching by HF 30% is larger, so that most of the light refract out of the fiber. We make different lengths of taper and compare their transmissions. We confirm that the smoother the taper’s slope become, the higher the transmission is. Next, the material of gain fiber is the phosphate glass, so that the etching rate between the Yb-doped fiber and SMF-130V is different. According to this result, we change the position of the taper from DCF 20/125 to Yb-doped fiber. Because of the different etching rate, the original etching method would result in the difference in diameter at the connection point of two fibers. It leads to low transmission. Changing the position of the taper can solve this problem. In the condition without TEC to reduce the loss of mode-field mismatch, we successfully increased the laser efficiency from the original 5.1% to 8.2%, the threshold decreased from 2.9W to 1.9W, and the maximum measured power from 223.8W to 320.5W.
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