Application of a self-organizing photorefractive filter to the expansion of the single-mode operation range of tunable extended-cavity semiconductor lasers

Commercial 1.55-?m extended-cavity semiconductor lasers provide single-mode operation that can be continuously tuned over a range larger than 100 nm without mode hopping. But, such performances require delicate factory adjustments and a high mechanical stability of the external cavity. Furthermore, at high emission power, the tuning range is limited to smaller values because of annoying multimode operations. Previously, we showed that the alignment constraints can be relaxed by use of an intracavity photorefractive filter. Here, we present new results obtained using a crystal with low absorption and high photorefractive gain. We demonstrate that, without inducing excessive additional loss, single-mode emission is preserved at output power higher than the maximum power obtained in the absence of crystal, in the full tuning range of the laser.