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Research Of High Power Weak-tapering Pump/signal Fiber Combiner

Posted on:2014-11-16Degree:MasterType:Thesis
Country:ChinaCandidate:L C KongFull Text:PDF
GTID:2308330479479290Subject:Optical Engineering
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As the key component in all-fiber laser, the tapered fused-bundle pump/signal combiner has been widely used in all-fiber high power laser system. In order to raise the output power of the fiber laser with master oscillation power amplifier, we proposed a new type of pump/signal combiner, namely weak tapering combiner. The weak tapering combiner allows for exceptionally low signal insertion loss for both fundamental mode and higher order mode. Therefore the temperature rise inside the weak tapering combiner is very low which means that this combiner can be used to amplify kilo watts level of signal power. The main work of this thesis is listed as below:1. Based on the scalar mode theory, we established the theoretical modal to compute the signal insertion loss. The difference between using mode field diameter method and modal overlap integral method on the simulation of combiner insertion loss is compared. We concluded that it is proper to use modal overlap integral method to compute combiner signal insertion loss.2. The signal insertion of traditional combiner and the temperature rise ratio were studied. Firstly, We investigated the signal insertion loss of a domestic 20/400 combiner numerically and proposed the phenomenon of back-floating of the cladding light. Then the insertion loss and beam quality degradation were studied through experiment. Secondly, we analyzed the reasons that lead to temperature rise inside the combiner. The result indicates that the cladding light is an important factor that leads to temperature rise and we summarized a method to control the temperature rise inside the combiner. Finally, we tested the relationship between the power of input signal light and the temperature rise. Based on the numerical analysis and experiment result, we concluded that this type of combiner cannot be used to amplify kilo watts level of signal power with few modes.3. The design of weak tapering combiner and temperature rise were investigated in this chapter. Firstly, the structure of combiner was redesigned. Then the numerical aperture and taper length were optimized through simulation analysis. Secondly the relationship between input signal power and temperature rise was studied through experiment. Compared with traditional combiner, the temperature rise ratio and the insertion loss was much lower. This proved that the weak tapering combiner can be used to amplify kilo watts level of signal power with few modes.
Keywords/Search Tags:Fiber laser, MOPA, Pump/signal combiner, Weak tapering
PDF Full Text Request
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