Progress in experimental studies into the beam parameter product of GaAs-based high-power diode lasers
Experimental studies into the limits to beam parameter product (BPP) in high-power diode lasers are summarized. Monolithically grating-stabilized lasers confirm the presence of a well-defined series of guided modes, rather than filaments. A series of custom tests shows that thermal lensing and current spreading dominate the bias-dependent variation in BPP. The bias-independent BPP is 30-50% of the total, most likely partly originates from gain-guiding. Longitudinal temperature variation along the resonator further degrades the bias-independent background. Lateral current blocking reduces current-spreading and leads to smaller bias-dependent BPP. Thermal engineering via changes to epitaxial layers and bar layout also improves bias-dependent BPP.
Paul Crump (Senior Member, IEEE) received the B.A. (Hons.) degree in natural science (physics) from Oxford University, Oxford, U.K., and the doctoral degree in physics from Nottingham University, Nottingham, U.K., in 1992 and 1996, respectively. His thesis dealt with experimental studies of 2D electrical transport effects in semiconductor heterostructures. From 1996 to 2001, he was with Agilent Technologies Corporation, Ipswich, U.K., where he helped develop high-performance single-mode InP-based laser diodes. In 2001, he joined nLight Photonics Corporation, Vancouver, WA, USA, where he helped develop high-power, high-efficiency GaAs, and InP-based broad-area diode lasers and bars. In 2007, he joined the Ferdinand-Braun-Institut gGmbH, Leibniz-Institut für Höchst-frequenztechnik, Berlin, Germany, where he leads the High-Power Diode Laser Lab, that develops high performance broad-area diode lasers.