Tapered high-power, high-brightness diode lasers: Design and performance

The development of high-power, high-brightness tapered diode lasers and laser amplifiers is reported in this review. Experimental and theoretical work is described that aims to improve the beam quality of these devices at output power levels well above 1W. Special emphasis is laid on the dependence of the beam quality on the design of the epitaxial layer structure. For tapered diode lasers as well as for tapered laser amplifiers, the introduction of layer structures with a reduced modal gain leads to an improvement in beam quality by an order of magnitude. At output power levels of 2W and CW operation beam-quality parameters of $M2 = 2$ are achieved. The corresponding far-field widths are near the diffraction limit. Furthermore, a tunable diode-laser system is presented that consists of a tapered amplifier chip and a diffraction grating in an external cavity. This high-power high-brightness diode-laser system provides a nar row-bandwidth emission spectrum together with a wide-range tunability.