Design progress for higher efficiency and brightness in 1 kW diode-laser bars

We present 1 kW-emitting diode-laser bars optimized for higher conversion efficiency and smaller far-field angle Θ_95% power content), as needed, e.g., for solid-state laser pumping (wavelength λ= 940 nm). First, we review the latest high-efficiency designs, targeting reduced series resistance R_s and less power saturation and then discuss developments for high brightness via tailored chip-internal heat distribution. Recent results include conversion efficiency η of 66% and far-field width Θ _95%= 8.8° at 1 kW (thermal resistance R_th ~ 0.02 K/W), as well as 64% efficiency and 10.8° divergence at R_th ~ 0.05 K/W, equivalent to CW operation with advanced packaging.