24 October 2012 Mode-hop-free tuning of a semiconductor laser with a chirped grating in a simple extended cavity
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Proceedings Volume 8412, Photonics North 2012; 84121Q (2012) https://doi.org/10.1117/12.2000548
Event: Photonics North 2012, 2012, Montréal, Canada
Abstract
Among the multiple techniques proposed to obtain continuous tuning of a laser, many involve a wavelength selective element that needs to be rotated in order to select the output wavelength. Such methods usually require more optical components than the technique proposed in this paper. Our group uses the line spacing variation in a custom-engineered chirped grating to achieve a mode-hop free modification of the output wavelength of a semiconductor laser by a simple translation of the grating. The useful beam out-coupled through the 0th-order is propagating in a constant direction for any tuned wavelength. The variation in the line space also induces a focal effect in the axis perpendicular to the grooves; it is exploited to compensate a part of the beam divergence in the external cavity. Moreover, a transverse focal effect from the holographic grating is introduced for improved reinjection in the laser chip. With this simple configuration, it has been possible to obtain a continuous tuning of a semiconductor laser over 10 nm at an average wavelength close to 1540 nm. The output power of such a laser was near 8 mW and quite stable over all the tuning range. Fine adjustments are still made to obtain a greater tuning range.
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Denis Panneton, Gilles Fortin, Nathalie McCarthy, "Mode-hop-free tuning of a semiconductor laser with a chirped grating in a simple extended cavity", Proc. SPIE 8412, Photonics North 2012, 84121Q (24 October 2012); doi: 10.1117/12.2000548; https://doi.org/10.1117/12.2000548
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