Coherent fiber coupling of laser diodes

Lars C. Berger; Uwe Brauch; Adolf Giesen; Helmut Huegel; Hans Opower; Michael Schubert; Klaus Wittig

doi:10.1117/12.237672

12 April 1996 Coherent fiber coupling of laser diodes

Lars C. Berger, Uwe Brauch, Adolf Giesen, Helmut Huegel, Hans Opower, Michael Schubert, Klaus Wittig

Proceedings Volume 2682, Laser Diodes and Applications II; (1996) https://doi.org/10.1117/12.237672
Event: Photonics West '96, 1996, San Jose, CA, United States

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.

Citation Download Citation

Lars C. Berger, Uwe Brauch, Adolf Giesen, Helmut Huegel, Hans Opower, Michael Schubert, and Klaus Wittig "Coherent fiber coupling of laser diodes", Proc. SPIE 2682, Laser Diodes and Applications II, (12 April 1996); https://doi.org/10.1117/12.237672

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