Single mode 660 nm master-oscillator power-amplifier with 500 mW optical output power

Red-emitting lasers with longitudinal and lateral single mode emission are currently required for non-destructive spectroscopy methods based on quantum mechanical effects (e.g. MID-IR quantum-OCT). So far, the size of currently used solid state lasers prevents effective miniaturization, which is required for successful out-of-the lab usage. To address this challenge the FBH developed specialized ridge waveguide lasers (RWL) near 660 nm with an integrated fourth order distributed Bragg reflector (DBR) surface grating, requiring only a single epitaxy step. The DBR-RWLs feature a diffraction limited output beam with a stabilized emission linewidth below 10 MHz. An optical output power of more than 50 mW and lifetimes of more than 10,000 h at 20 mW could be demonstrated. Furthermore, we used tapered diode amplifiers (TPA) to boost the optical output power to more than 500 mW in an all-semiconductor master-oscillator power-amplifier (MOPA) configuration. The TPA has a total length of 2.5 mm and was mounted p-side-down on structured CVD-diamonds, allowing optimal cooling and separate currents for the RW and taper sections. The MOPA setup did not degrade the linewidth properties. The side mode suppression rate exceeds 40 dB. However, the spatial beam quality in the slow axis degraded somewhat to an M-1/e2(2) of 1.8 (M-4 sigma(2) = 3.1). As a next step we are working towards miniaturization of the MOPA setup to about matchbox size to make it a suitable candidate for a pump source in a portable MID-IR quantum-OCT scanner system.