21 Jun Alfalight increases laser efficiency for DOD program
Project supported by Department of Defense program
MADISON, Wis.– Alfalight, Inc., a Wisconsin-based diode laser manufacturer, recently demonstrated 65 percent total power conversion efficiency in its 970 nm laser material at a conference in Albuquerque, N.M. This step toward the eventual goal of 80 percent efficiency is supported by the Defense Advanced Research Projects Agency’s Super High Efficiency Diode Sources program, located within the U.S. Department of Defense.
The program’s funding, according to DARPA spokeswoman Jan Walker, totals $6.77 million for 2004. The money is being used to help program participants develop laser diodes with breakthrough efficiency for both the government and commercial customers.
“[There are] at least six companies and universities participating in program. They have slightly different approaches … and technologies,” Walker said. “At this point, because of the type of research, it’s not clear what will work best so we’re using multiple approaches.”
SHEDS’ goals for swift diode development are 65 percent efficiency in 18 months, or May 2005, and 80 percent in 36 months. Current production diode pump lasers provide approximately 50 percent of peak “wallplug,” or electrical-to-optical power conversion efficiency.
“…for some applications, including DARPA’s interest, the efficiency improvement is so significant as to make currently unfeasible systems potentially feasible,” said ,” Robert S. Williamson III, director, Alfalight business development.
Increasing laser diode efficiency – even by 15 percent – has a dramatic effect on the amount of heat generated, Williamson added.
“…from a diode efficiency improvement of 50 percent to 65 percent the amount of heat generated is halved, from 50 percent to 80 percent the heat is one-quarter,” he said.
The lasers can be used in many fields, Williamson said. The diode-pumped Nd:YAG (Neodymium:Yttrium-Aluminum-Garnet) laser, for example, has a range of uses; from metal welding to biomedical instrumentation.
“The laser diodes we manufacture convert electrical current into multimode laser light, which then pumps a crystal, such as Nd:YAG,” Williamson said. “The Nd:YAG crystal absorbs the laser diode light and converts it to single-mode light, which is what we picture when we think of a traditional laser. Laser diode pumps are used to pump a wide variety of crystals, can be used to drive fiber amplifiers and lasers, and can be used directly for some materials processing, printing and medical applications.”
Although Alfalight is set to deliver 65 percent efficient laser bars to DARPA by March of 2005, the company acknowledges the radical approach to design it will need to take to reach the 80 percent target.
“The 65 percent milestone is achieved primarily through evolutionary design modifications to known laser structures; the challenge here is to modify the structures to achieve this high efficiency while maintaining high output power and consistent manufacturability,” Williamson said. “The 80 percent goal will require revolutionary design changes, which we are pursuing through the use of quantum-dot structures and by growing our quantum wells on an unusual crystal plane orientation (110). Both approaches hold the promise of significant improvement in efficiency.”
The SHEDS program began nine months ago.