High power, high efficiency semiconductor diode lasers are used as the primary pump source in virtually all new solid state and fiber laser systems. In many cases, the output power scalability of the full system is limited by the pump diode performance (power, spatial brightness, and/or spectral brightness). Over the past decade, research and development in the commercial sector has resulted in significant improvements increase in each of these areas. Both diode laser power and spatial brightness are thermally-limited, and addressing each requires addressing the waste heat flux in the device. Improved power conversion efficiency at the operating point provides a straightforward path to reducing the waste heat flux, yet diode lasers are not much more efficient today than they were ten years ago. Newer advanced epitaxial design techniques, however, have enabled longer cavity lengths while maintaining high efficiency. This approach reduces the total heat flux which enables greater power extraction at equivalent junction temperature and reduces the magnitude of the thermal lens responsible for brightness loss. Improvements in spectral brightness have been made by wavelength locking through the use of external gratings. This work reviews the principal technical challenges and recent advancements in the development of high power, high efficiency semiconductor lasers for pumping and direct use applications.
This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.
Dr. Paul O. Leisher is a Senior Engineer with the Laser Systems Engineering and Operation Division at Lawrence Livermore National Laboratory (LLNL) in Livermore, California. Prior to joining LLNL, Dr. Leisher served as Associate Professor of Physics and Optical Engineering at Rose-Hulman Institute of Technology (Terre Haute, Indiana) and as the Manager of Advanced Technology at nLight Corporation (Vancouver, Washington). He received a B.S. degree in electrical engineering from Bradley University (Peoria, Illinois) in 2002, and a M.S. and Ph.D. in electrical and computer engineering from the University of Illinois at Urbana-Champaign in 2004 and 2007, respectively. Dr. Leisher’s research interests include the design, fabrication, characterization, and analysis of high power semiconductor lasers and other photonic devices. He has authored over 200 technical journal articles and conference presentations and served as the principal investigator on 48 funded research projects. Dr. Leisher is a senior member of both SPIE and IEEE.
Note: Graduate students who are nearing completion of their Ph.D. and interested in post-doctoral opportunities at LLNL in the areas of high power laser systems, semiconductor lasers, and optics are encouraged to attend. Dr. Leisher will meet with interested students to discuss current openings and take resumes after the seminar. Some positions may require U.S. citizenship and the ability to obtain a security clearance.