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Characterization of a coherently coupled 2x2 W fiber amplifier array

Nowack, Rolf/R. and Bähnisch, Ralf/R. and Mahnke, Peter/P. and Speiser, Jochen/J. and Giesen, Adolf (2009) Characterization of a coherently coupled 2x2 W fiber amplifier array. Proceedings of the SPIE, Proc. of SPIE Vol. 7195. Society of Photo-Optical Instrumentation Engineers (SPIE).

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Experimental investigations concerning the operation characteristics of a coherent fiber laser MOPA array are presented. The experimental set up consists of a single frequency fiber coupled 35 mW DBR diode laser at 1063 nm as master oscillator and two polarization maintaining two stage 2 W Yb doped commercial fiber amplifiers. Phase control is accomplished by fiber coupled acousto-optic frequency shifters prior to the amplifiers and an opto-electric phase locked loop operating at 100 MHz. Phase measurement at the amplifier output is achieved by a combination of a free space and fiberoptic interferometer in combination with RF photodiodes. A heterodyne signal of the amplifier output signal is generated with respect to a reference signal derived from the master oscillator and works as input signal for the phase control. Phase coupling of the array is demonstrated and the degree of coherence is determined from the contrast of the far field diffraction pattern of the output beam as well as from analysis of the RF photodiode signals. The characteristics of the phase control and phase stability are investigated and residual phase disturbances resulting from thermal and acoustic effects as well as depolarization are identified. Achievable beam quality as a function of fill factor is compared to theoretical computations. Finally, perspectives concerning a coherent 4x15 W MOPA array with three stage amplifying systems are outlined.

Document Type:Proceedings
Title:Characterization of a coherently coupled 2x2 W fiber amplifier array
AuthorsInstitution or Email of Authors
Bähnisch, Ralf/R.UNSPECIFIED
Speiser, Jochen/J.UNSPECIFIED
Volume:Proc. of SPIE Vol. 7195
Number of Pages:10
Gapontsev, DenisUNSPECIFIED
Tankala, KanishkaUNSPECIFIED
Publisher:Society of Photo-Optical Instrumentation Engineers (SPIE)
Series Name:Proceedings of the SPIE
Keywords:Fiber amplifier array, fiber laser MOPA array, coherent coupling, phase coupling, phsed array
HGF - Research field:Aeronautics, Space and Transport (old)
HGF - Program:Aeronautics
HGF - Program Themes:Aircraft Research
DLR - Research area:Aeronautics
DLR - Program:L AR - Aircraft Research
DLR - Research theme (Project):L - Laser Research and Technology
Location: Stuttgart
Institutes and Institutions:Institute of Technical Physics
Deposited By: Rolf Nowack
Deposited On:20 Jul 2009 21:52
Last Modified:27 Apr 2010 13:39

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