Optimizing Vertical and Lateral Waveguides of kW-Class Laser Bars for Higher Peak Power, Efficiency and Lateral Beam Quality

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.