9 December 2014 Experimental demonstration of adaptive fiber-optics collimator based on flexible hinges
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Beam combining (BC) of fiber lasers based on master oscillator power amplifier (MOPA) configuration has been considered as a promising way to achieve high power laser output. In recent years, it has been demonstrated that tip-tilt phase errors impact the combining effect seriously, especially the beam quality in coherent beam combining even if all the beamlets are phase-locked. Adaptive fiber-optics collimator (AFOC) is an effective way to compensate the tip-tilt aberrations in fiber laser systems. As the piezoelectric bimorph actuators used in the AFOCs of traditional type provide very weak force (0.1~1N level), they can only actuate the naked fiber. So the application of traditional AFOCs in high power level is limited by the structure. When the output power is scaled up-to several kW, a coreless end cap is usually spliced on the output side as the end of fiber. Because of the end cap, the expansion of the beam reduces the extractable fluence and avoids fiber facet damage. Then the AFOCs that can be used in high-power situations become the direction of research and development. In this paper, a new structure of AFOC based on flexible hinges is presented for the first time to our knowledge. It utilizes two piezoelectric stacks actuators for X-Y displacement of the fiber end cap placed in the focal planes of the collimating lens. Also the new type of AFOC based on flexible hinges has been developed and demonstrated experimentally. The thrust of zero displacement of the piezoelectric stacks actuators is 330 N. The maximum tip/tilt deviation angle of the collimated beam is 180μrad in X direction and 150 μrad in Y direction for a chosen focal length of 0.05m. The first resonance-frequency of this device is about 700 Hz and the bandwidth of this device is 500Hz. This work provides a reference for beam combing and beam pointing controlling in high power conditions.
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Dong Zhi, Yan-xing Ma, Lei Si, Xiao-lin Wang, Pu Zhou, "Experimental demonstration of adaptive fiber-optics collimator based on flexible hinges", Proc. SPIE 9294, International Symposium on Optoelectronic Technology and Application 2014: Development and Application of High Power Lasers, 92940E (9 December 2014); doi: 10.1117/12.2072865; https://doi.org/10.1117/12.2072865

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