Active phase locking of fiber amplifiers using sine-cosine single-frequency dithering technique.

The sine-cosine single-frequency dithering technique for active phase locking of fiber amplifiers is presented for the first time to our knowledge. It has twice the phase control speed as the single-frequency dithering technique. Detailed theoretical development has been presented and the relevant experiment has been done. In the experiment, nine 10 W level fiber amplifiers are tiled into 3×3 array and the total output power is about 100 W. The sine-cosine single-frequency dithering algorithm is run on a signal processor based on a field-programmable gate array for phase control on the fiber amplifiers. When the phase control system is in a closed loop, the fringe contrast of far-field intensity pattern is improved by more than 90% from 21% in an open loop, and the residual phase error is less than λ/20.

[1]  T. R. O’Meara,et al.  The multidither principle in adaptive optics , 1977 .

[2]  Vincent Benham,et al.  First experimental demonstration of phase locking of optical fiber arrays by RF phase modulation , 2004, SPIE Optics + Photonics.

[3]  Mikhail A. Vorontsov,et al.  Adaptive phase-locked fiber array with wavefront phase tip-tilt compensation using piezoelectric fiber positioners , 2007, SPIE Optical Engineering + Applications.

[4]  Pu Zhou,et al.  Coherent Beam Combining of Fiber Amplifiers Using Stochastic Parallel Gradient Descent Algorithm and Its Application , 2009, IEEE Journal of Selected Topics in Quantum Electronics.

[5]  Chunte A. Lu,et al.  First experimental demonstration of self-synchronous phase locking of an optical array. , 2006, Optics express.

[6]  J. Hou,et al.  Coherent combining technology of master oscillator power amplifier fiber arrays. , 2008, Optics express.

[7]  Mikhail A. Vorontsov,et al.  Phase-locking of tiled fiber array using SPGD feedback controller , 2005, SPIE Optics + Photonics.

[8]  Y. Jaouen,et al.  Beam Shaping of Single-Mode and Multimode Fiber Amplifier Arrays for Propagation Through Atmospheric Turbulence , 2009, IEEE Journal of Selected Topics in Quantum Electronics.

[9]  Pu Zhou,et al.  Coherent beam combination with single frequency dithering technique. , 2010, Optics letters.

[10]  T. Shay,et al.  Theory of electronically phased coherent beam combination without a reference beam. , 2006, Optics express.

[11]  Mark E. Weber,et al.  8-W coherently phased 4-element fiber array , 2003, SPIE LASE.