Fig. 1. Pump diode pulse energy levels of HEC-DPSSL installations, sorted by pump wavelength. Solid symbols: systems proven or under construction. Empty symbols: systems at design level.

Fig. 2. Illustration of Jenoptik’s 940 nm laser diode bar portfolio. For a given technology, the output power is linear with chip size. The New Generation (NG) QCW bars increase output power from 300 to 500 W at the fixed resonator length of 1.5 mm.

Fig. 3. 808 nm QCW laser diode: output power-versus-current characteristic and efficiency.

Fig. 4. Life testing of 808 nm 500 W QCW bar in constant current mode. The bars are mounted on microchannel heatsinks with $T_{c}=25\,^{\circ }\text{C}$, ${\it\tau}=300~{\rm\mu}\text{s}$, $f=100$ Hz.

Fig. 5. 880 nm QCW laser diode: light output power-versus-current characteristic and wall-plug efficiency.

Fig. 6. Reliability testing of the 880 nm QCW laser diode in constant current mode, mounted on microchannel heatsinks. $T_{c}=25\,^{\circ }\text{C}$, ${\it\tau}=300~{\rm\mu}\text{s}$, $f=100~\text{Hz}$.

Fig. 7. Power–voltage–current characteristics of 940 nm laser bars with 75% filling factor and 1.5 mm resonator length. ${\it\tau}=1~\text{ms}$, $f=60~\text{Hz}$, 6% duty cycle, $T_{c}=25\,^{\circ }\text{C}$.

Fig. 8. Comparison of epitaxial structures for kW-class laser bars. The NG structure used in the 500 W bars is compared to structure C. ${\it\tau}=1~\text{ms}$, $f=10~\text{Hz}$, $T_{c}=25\,^{\circ }\text{C}$.

Fig. 9. Wall-plug efficiency of 940 nm laser bars based on the NG epitaxial structure optimized structure C.

Fig. 10. Photograph of JenLas^®QCW Cool laser diode stack with 8 laser bars spaced at 1.7 mm pitch.

Fig. 11. Cross-section of actively cooled QCW stack on mount with illustration of the water passage.

Fig. 12. Transient thermal behaviour of the passively cooled QCW stack, showing the thermal impedance $Z_{\mathit{th}}(t)$ of one laser bar. The CW operating temperature is attained after 3 s.

Fig. 13. Temperature gradient in pulsed operation of the QCW stack with power dissipation of 1 W per bar during ${\it\tau}=300~{\rm\mu}\text{s}$. The solid lines denote the exact temporal evolution. The dashed lines show the product of $R_{\mathit{th}}$ and the duty cycle.

Fig. 14. Pump power densities achieved with commercially available laser diodes. Squares: JENOPTIK, circles: NGCEO ARR179P6000HDS and Quantel QD-Q5912-B.

Fig. 15. Electro-optical data of a passively cooled QCW stack with eight laser bars emitting at 880 nm, ${\it\tau}=300~{\rm\mu}\text{s}$, bar-to-bar pitch 1.7 mm, duty cycle (d.c.) varied between 1% and 10%. (The step in efficiency at 450 A is a measurement artefact.)

Fig. 16. Worldwide production capacities for GaAs LEDs and laser bars. InGaAlP (red) LED production capacity from Ref. [22]. LIFE and HiPER one-time demands from Table 1, assuming 220 bars per $4^{\prime \prime }$ wafer.

Fig. 17. Functionalities of a diode laser pump.

Fig. 18. Utilization aspects of standardization at different levels.