Frankfurt 2006 – wissenschaftliches Programm
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Q: Quantenoptik und Photonik
Q 6: Halbleiterlaser
Q 6.1: Vortrag
Montag, 13. März 2006, 11:10–11:25, HIV
Improvements of the spectral properties of multimode standard laser diodes by back-coupling of light with volume holographic gratings* — •Ingo Breunig, Felix Kröger, and Karsten Buse — Physikalisches Institut, Universität Bonn, Wegelerstr. 8, 53115 Bonn
High power laser diodes in the red or near-infrared spectral range are cheap and compact light sources for various applications. Standard Fabry-Perot laser diodes unfortunately show spatial and spectral characteristics that are insufficient for several applications. A good method to improve the
spectral properties is to provide an optical feedback, e.g. by a surface grating in the Littrow or Littman configuration. In our experiments we use a fixed volume holographic grating recorded in silica glass with a maximum reflectivity of 61 % at a wavelength of 976 nm and with a bandwidth of ±0.15 nm. The beam of a standard multimode laser diode without
antireflection coating is sent back by the grating under an angle of 0o. With this feedback we observe a narrowing of the spectral linewidth by a factor of 100. Furthermore, we achieve a stabilization of the center wavelength which is better than 2 pm on a timescale of ten minutes without any active feedback. Such improvement of the spectral characteristics can be observed with but also without collimation optics, being a remarkable difference to the common methods with surface gratings. The frequency stability is unfortunately reduced in such a system. Compactness and robustness makes the direct Bragg reflection of light advantageous over the other methods.
*Financial support by the Deutsche Forschungsgemeinschaft (FOR 557), and by the Deutsche Telekom AG is greatfully acknowledged.