Research On The Technology Of High-power Laser Coupling Into Optical Fiber

It is desirable in many industrial applications to employ a flexible fiber optic beamdelivery (FOBD) system, which can achieve3D processing through integration of highpower into the robot and deliver energy from laser source to remote work stations. The mostimportant performance parameters in the FOBD system are efficiency and output beamquality. However, it will lead to fiber failure in term of the fiber transmission of high powerlaser if there exists leakage of beam into outside the core resulting from the incouplingmisalignment. Besides that, high power density projected on the entrance surface may alsocause surface damage. Therefore proper design of coupling method to raise the ceiling powerloss that the fiber can bear and protect the entrance surface is instrumental to fiber couplingtechnique under high power.In this thesis, the principle and the frequently used methods of fiber coupling are firstlyillustrated. Different factors are considered in the analysis of the efficiency of fiber deliverysystem, while the numerical relationship between the power loss and the incouplingmisalignment is obtained through the ray tracing simulation using a ZEMAX model of fibercoupling. For the influencing factors of fiber failure caused by power leakage into claddingand end surface damage, which limit the maximum power transmitted through silica fiber,the principle of a fiber connector design with a quartz block provided onto the fiber endsurface to reduce the power density on it and the mode stripping technique aimed ateliminating the power leakage into the fiber cladding are researched. The mode strippingtechnique is simulated by a ZEMAX model to define the length of mode stripper under theconditions of different beam deviations and the defocus of fiber end. To study thetransmission characteristics of large core multi-mode fiber, the beam quality degradationcaused by fiber bending and the incident condition are discussed, and the relationshipbetween the incident condition and the profile of output spot is simulated.At last, an experimental investigation of fiber coupling of high power disk laser ispresented, from which the fiber output with efficiency larger than94%and power equals to708W is acquired and the simulated conclusion of fiber transmission characteristics isproved.