Externally Wavelength-Stabilized Single Mode Lasers with 65% Conversion Efficiency and 50 pm Spectral Width at 1 W Output

Dense wavelength beam combining (DWBC) techniques can be used to image many diode lasers into a single beam with minimal degradation of beam quality M 2 95% (at 95% power) and conversion efficiency η E . Systems based on DWBC of broad area lasers can be scaled into the many-kW class for use in material processing applications [1] . Laterally single mode diode lasers with wavelength around λ = 970 nm that use advanced waveguide designs (with lateral mode filter and extremely asymmetric vertical design) offer a path to much higher brightness [2] . Such lasers achieve high power P opt and efficiency η E in continuous wave CW ( P opt = 1 W, η E = 65%, M 2 95% < 1.1) [3] and pulsed ( P opt = 18W, 3.3 ns 10 kHz, M 2 95% < 2.2) [4] operation, whilst remaining close to the diffraction limit. When external λ-stabilization is performed via a diffractive element (grating), the operating characteristics are strongly affected by the interaction between external optical configuration and internal diode laser design, seen in P opt , η E , spectral width Δ λ 95% (at 95% power), λ -tuning range and beam stability. The λ -tuning range and Δ λ 95% for each diode laser are especially important as this limits the number of emitters that can be combined and thus the maximum achievable power via DWBC.