High-power broadly tunable grating-coupled external cavity laser in green region

A broadly tunable grating-coupled external cavity laser system in the green region is demonstrated by employing a commercially available broad-area green laser diode. A simple Littrow-type external cavity configuration was adopted, and two gratings with different diffraction efficiencies were used as the light feedback elements. When a grating with the first-order diffraction efficiency of 50% and the zeroth-order diffraction efficiency of 31% was used, a tuning bandwidth of 11.0 nm with an output power near 400 mW was achieved. When a grating with the first-order diffraction efficiency of 10% and the zeroth-order diffraction efficiency of 78% was used, a tuning bandwidth of 5.0 nm with an output power near 750 mW was achieved. Meanwhile, the spectral linewidth was narrowed significantly down to 0.08-0.18 nm from the free-running linewidth of 2.81 nm due to the external mode selection effect. Such high-power broadly tunable green EC lasers are important for second harmonic generation.