Experimental Demonstration of Coherent Combining With Tip/Tilt Control Based on Adaptive Space-to-Fiber Laser Beam Coupling
A novel approach of tip/tilt control through optimizing laser beam coupling efficiencies from space to polarization-maintaining-fibers with stochastic parallel gradient descent (SPGD) algorithm for coherent beam combining (CBC) applications is proposed and demonstrated experimentally usin...
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| Main Authors: | , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
IEEE
2017-01-01
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| Series: | IEEE Photonics Journal |
| Subjects: | |
| Online Access: | https://ieeexplore.ieee.org/document/7891900/ |
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| Summary: | A novel approach of tip/tilt control through optimizing laser beam coupling efficiencies from space to polarization-maintaining-fibers with stochastic parallel gradient descent (SPGD) algorithm for coherent beam combining (CBC) applications is proposed and demonstrated experimentally using a seven-element adaptive fiber-optics collimator (AFOC) array for the first time to the best of our knowledge. Compared with the normal target-in-the-loop SPGD method with just a single cost function, the tip/tilt control here is independent of the phase-locking control and parallel for each cell of the AFOC array. Such characteristic gives the AFOC array capacities of real-time correction of fast-changing turbulence induced tip/tilt-type phase errors. Piezoelectric-ceramic-ring fiber-optic phase compensator and AFOC are developed to correct the piston- and tip/tilt-type aberrations, respectively. The power-in-the-bucket (PIB) metric is used for phase-locking. Parallel tip/tilt control is implemented via maximizing the received power in each subaperture with fixed two-channel SPGD control. The average of normalized coupling efficiencies of seven AFOCs increases from 0.76 without tip/tilt control to 0.94 under control. In CBC, the PIB metric increases by 4.6 times, and the phase residual error is less than <italic>λ</italic>/15. |
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| ISSN: | 1943-0655 |