Alfalight laser hits 65% wallplug efficiency
The US company Alfalight has made a laser diode that operates at 65% wallplug efficiency.
Producing 3W of optical output at around 970nm, the device s structure has been improved in a number of ways to reach the 65% figure.
According to the Wisconsin-based company, a "dramatic" improvement in overall efficiency was achieved by improving the internal injection efficiency through strain adjustments to the quantum well barriers.
In addition, the doping profile of the laser s separate confinement heterostructure layer has been modified, leading to a reduction in the device s overall built-in voltage.
Alfalight has been working on the device improvements under DARPA s super-high efficiency diodes (SHEDS) program, which also includes US-based companies nLight Photonics and JDS Uniphase, as well as a number of academic institutions.
JDS Uniphase has itself developed a 64%-efficient laser diode, using an asymmetric waveguide configuration. It is also looking into the effects of different quantum well designs and interface bandgap engineering.
Meanwhile, nLight engineers are looking at epitaxial growth of mirrors on laser facets with large optical cavities.
DARPA has set its contractors the target of making a 480W diode stack operate at 80% wallplug efficiency by the end of the 3-year project in September 2006, a feat that will likely require some radical approaches to device design.
Alfalight is hoping to further improve efficiency by reducing threshold losses. Two of the approaches the company is considering are to use quantum-dot-based gain media, and to grow quantum wells on (110)-oriented GaAs wafers.
Additional reporting by Jacqueline Hewett.
