High-power, spectrally stabilized, near-diffraction-limited 970 nm laser light source based on truncated-tapered semiconductor optical amplifiers with low confinement factors

Published in:
Semicond. Sci. Technol., vol. 27, no. 015010 (2012).
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Abstract:
High-power spectrally single-moded coherent emission with high beam quality is demonstrated using a master-oscillator (MO) power-amplifier (PA) system. The MO is a single-moded distributed Bragg reflector ridge-waveguide (DBR-RW) laser and the PA is a semiconductor amplifier with a truncated-tapered gain region. The spectrum of the DBR-RW is found to be preserved, with >40 dB of noise suppression. Peak output powers from the PA of >50 W (250 µs, 100 Hz) are demonstrated for laser designs with conventional confinement factors in the active region, Γ = 1%, but only with substantial degradation in the beam quality (M² at 1/e² level of >30). The use of alternative designs with low confinement (Γ = 0.4%) reduces the gain and hence peak power, but dramatically improves the beam quality (M² at 1/e² level of ~3), enabling ~11 W emission into a diffraction-limited central lobe, with temperature and current invariant central wavelength and a spectral width of ~40 pm.

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