2022, Miah, M. Jarez, Boni, Anisuzzaman, Arslan, Seval, Martin, Dominik, Casa, Pietro Della, Crump, Paul

GaAs-based, highly-efficient, kW-class, 1-cm laser bars with high peak power P opt and improved beam quality in quasi-continuous-wave mode are presented. The use of an extreme-triple-asymmetric (ETAS) epitaxial layer structure diminishes power saturation of high-power bars at high driving current. The resulting ETAS bars with 4 mm cavity produce a record 1.9 kW peak power, limited by available current supply, with a maximum power conversion efficiency η E = 67% at T HS = 25 °C heat-sink temperature. Both P opt and η E have been increased further by operating the bars at T HS = −70 °C. Sub-zero operation raises the P opt to 2.3 kW and the maximum η E to 74%. A second configuration of ETAS bars with optimized lateral layout is further realized to obtain narrow lateral beam divergence θ up to 2 kA driving current, without sacrificing P opt and η E . A 2–3° lower θ (95% power level) is observed over a wide operating range at room temperature. A high degree of polarization is also maintained across the whole operatingrange.

2020, Boni, Anisuzzaman, Wünsche, Hans-Jürgen, Wenzel, Hans, Crump, Paul

Electrons and holes injected into a semiconductor heterostructure containing quantum wellsare captured with a finite time. We show theoretically that this very fact can cause a considerableexcess contribution to the series resistivity and this is one of the main limiting factors to higherefficiency for GaAs based high-power lasers. The theory combines a standard microscopic-basedmodel for the capture-escape processes in the quantum well with a drift-diffusion description ofcurrent flow outside the quantum well. Simulations of five GaAs-based devices differing in theirAl-content reveal the root-cause of the unexpected and until now unexplained increase of theseries resistance with decreasing heat sink temperature measured recently. The finite capturetime results in resistances in excess of the bulk layer resistances (decreasing with increasingtemperature) from 1 mΩ up to 30 mΩ in good agreement with experiment.