Extended 9.7  nm tuning range in a MOPA system with a tunable dual grating Y-branch laser

In this Letter, we present a tunable Y-branch hybrid master oscillator power amplifier (MOPA) with 5.5 W output power, emitting between 973.7 and 983.4 nm. The MO is a monolithic Y-branch distributed Bragg reflector (DBR) diode laser, which is collimated and coupled into a tapered amplifier using cylindrical microlenses in a compact 25  mm×25  mm conduction cooled laser package. The wavelength spacing between the two laser branches is 2.2 nm. Each branch can be electrically tuned by up to 7.5 nm of quasi-continuous wavelength tuning, which in combination covers up to 9.7 nm of spectral range. Over this range, an output power variation of 0.5% and 0.2% is observed for the left and right arms, respectively, while maintaining a spectral width of less than 17 pm. In addition, the MOPA system can be operated as a dual-wavelength system by operating both branches simultaneously. The presented device is suitable for nonlinear frequency conversion applications.