At T = 25°C and 20 mW pump power, diffraction limited laser emission with 0.5 W optical output power and beam propagation parameters of 1.3 (M24σ) are obtained. At both emission wavelengths of 784.6 nm and 785.2 nm, spectral bandwidths below 0.02 nm at full width at half maximum and side mode suppression ratios of 30 dB are measured. A negligible wavelength shift of < 0.02 nm/A between threshold and maximum power corresponds to a temperature rise during operation of only 0.3 K. This indicates a low thermal influence from the PA to the MO and allows a free choice of excitation power for applications. Compared to previously reported free-running Y-branch diode lasers, the MOPA does not show lateral spatial tilts between the two far field intensity distributions at both wavelengths.
This compact MOPA allows addressing applications such as shifted excitation Raman difference spectroscopy under in-situ conditions and confocal Raman microscopy without the need of a spectral recalibration during the measurements. In addition, simultaneous dual-wavelength operation also enables terahertz frequency generation.