21 Aug 2002
A highly efficient quantum dot laser emits almost 12 W in quasi-continuous-wave mode.
Researchers in Germany have fabricated a quantum dot (QD) laser that emits almost 11.7 W in "quasi" continuous-wave (CW) mode. In normal CW mode, the maximum power is 4.7 W.
These are the highest reported powers of QD lasers, and the first time that one has breached the 10 W level (Electronics Letters 38 883).
Dieter Bimberg and colleagues at the Technical University of Berlin made the device, which consisted of six layers of quantum dots stacked on top of each other to form the gain medium.
The laser was based on a gallium arsenide waveguide and indium gallium arsenide dots, and it emitted light at 1135 nm. With the output power set to 1.5 W, it had a lifetime of over 3000 hours at room temperature.
QD lasers have a variety of advantages over conventional diode lasers based on double-heterostructure and quantum well (QW) structures. These include narrower-linewidth emission, higher efficiency and reduced temperature effects.
The Berlin team's laser eventually failed due to catastrophic optical mirror damage when the optical power density reached 19.5 MW cm-2. The team says that this damage limit could be increased to 30 MW cm-2 using a special mounting technique and temperature stabilization of the chip.
Michael Hatcher is technology editor of Opto and Laser Europe magazine.