Abstract

We demonstrate a method for single-detector coherent sensing and automated coalignment of group delays in a coherently combined laser array, enabling robust coherent combining of broadband sources despite initial path mismatches exceeding the laser coherence length. The method is based on Fourier-domain filtering of the coherently combined laser beam to extract error signals, and it is equally applicable to controlling both spatial and temporal misalignments.

© 2012 Optical Society of America

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References

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  1. C. X. Yu and T. Y. Fan, in High Power Laser Handbook, H. Injeyan and G. D. Goodno, eds. (McGraw-Hill, 2011), pp. 533–571.
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2011 (4)

2010 (2)

2006 (1)

1998 (1)

1977 (1)

Beresnev, L. A.

Bourdon, P.

Breitkopf, S.

Carhart, G. W.

Daniault, L.

Druon, F.

Fan, T. Y.

C. X. Yu and T. Y. Fan, in High Power Laser Handbook, H. Injeyan and G. D. Goodno, eds. (McGraw-Hill, 2011), pp. 533–571.

Georges, P.

Goodno, G. D.

Goular, D.

Hanna, M.

Klenke, A.

Limpert, J.

Liu, J. J.

Lombard, L.

McComb, T.

McNaught, S. J.

Mottay, E.

O’Meara, T. R.

Plötner, M.

Polnau, E. E.

Rostov, A. P.

Rothenberg, J. E.

Seise, E.

Shay, T. M.

Shih, C. C.

Sivokon, V. P.

Smith, A. V.

Smith, J. J.

Thielen, P. A.

Tünnermann, A.

Vorontsov, M. A.

Weber, M. E.

Weyrauch, T.

Wickham, M. G.

Yu, C. X.

C. X. Yu and T. Y. Fan, in High Power Laser Handbook, H. Injeyan and G. D. Goodno, eds. (McGraw-Hill, 2011), pp. 533–571.

Zaouter, Y.

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Figures (7)

Fig. 1.
Fig. 1.

Principle of Fourier-domain optical filtering. (a) Spatial filter converts beam overlap or pointing errors to piston errors. (b) Spectral filter converts group-delay errors to piston errors.

Fig. 2.
Fig. 2.

Three-channel closed-loop phase-locking and group-delay-locking experimental layout.

Fig. 3.
Fig. 3.

Filtered spectra incident on the phase and delay sensors.

Fig. 4.
Fig. 4.

Measured error signals Sk (symbols) compared with Eq. (1) model predictions (solid curves).

Fig. 5.
Fig. 5.

Closed-loop group-delay control. (a) CBC power of all three channels, and (b) FS control voltages and change in group delay of one channel.

Fig. 6.
Fig. 6.

Test results for a three-channel array with a 10.5 nm FWHM MO source. (a) Input and filtered spectra at sensors, (b) measured field autocorrelation envelopes γ(τ) at each sensor, and (c) closed-loop performance.

Fig. 7.
Fig. 7.

Closed-loop performance using a hill-climbing algorithm in place of LOCSET multidither for both phase and group-delay control loops.

Equations (1)

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Sk=ikγ(τik)sin(δω·τik),

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