Micro-integrated dual-wavelength ridge-waveguide master oscillator power amplifier with an optical output power of 0.5 W at 785 nm

Abstract

A micro-integrated diode laser based dual-wavelength master oscillator power amplifier (MOPA) at 785 nm is presented. The device is realized on a 5 x 25 mm2 micro-optical bench and consists of a Y-branch distributed Bragg reflector ridge waveguide (RW) diode laser as MO with a front facet reflectivity of 30%, micro-cylindrical lenses for beam shaping and a tilted RW amplifier as PA. This approach allows power scaling of 785 nm dual-wavelength diode lasers that have already been applied for Raman spectroscopy and terahertz frequency generation. The optical concept is designed to reduce unwanted optical feedback to the MO and avoids integrating an optical isolator, which was used in a previous tabletop configuration. 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 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.