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Proceedings Paper

Coherent fiber coupling of laser diodes
Author(s): Lars C. Berger; Uwe Brauch; Adolf Giesen; Helmut Huegel; Hans Opower; Michael Schubert; Klaus Wittig
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Paper Abstract

Laser diodes with diffraction-limited beam quality offer high power densities of the order of 107 - 108 W/cm2, but are limited in output power to some watts. Scaling to higher powers has to be realized by superposition of a number of laser diodes. Coherent superposition allows us to further increase the power density in the far field. This is realized by injection locking of three slave laser diodes (Toshiba TOLD) 9140, 20 mW, 690 nm) by one master laser diode (TOLD 9140) and superpositioning of the three slaves lasers by a lens array. The feedback of the slaves into the master is suppressed by two Faraday isolators. For superpositioning the light of the slaves while maintaining the high beam quality, the light of each diode is coupled into an optical single-mode fiber. Phase shifts due to mechanical or thermal disturbances of the single-mode fibers for frequencies up to 1 kHz are compensated by a single-mode optical fiber piezoceramic phase modulator and an electronic control circuit. A phase stability with a maximum phase error smaller than 6 degrees is kept over an hour. The power-density distribution in the focal plane of the focusing lens shows a peak power 2.6 times that of the incoherent superposition and a modulation corresponding to the Fourier transform of the nearfield distribution of the lens array.

Paper Details

Date Published: 12 April 1996
PDF: 8 pages
Proc. SPIE 2682, Laser Diodes and Applications II, (12 April 1996); doi: 10.1117/12.237672
Show Author Affiliations
Lars C. Berger, Institut fur Technische Physik/DLR (Germany)
Uwe Brauch, Institut fur Technische Physik/DLR (Germany)
Adolf Giesen, Univ. Stuttgart (Germany)
Helmut Huegel, Univ. Stuttgart (Germany)
Hans Opower, Instutut fur Technische Physik/DLR (Germany)
Michael Schubert, Instutut fur Technische Physik/DLR (Germany)
Klaus Wittig, Univ. Stuttgart (Germany)


Published in SPIE Proceedings Vol. 2682:
Laser Diodes and Applications II
Kurt J. Linden; Prasad R. Akkapeddi, Editor(s)

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