Lawrence Livermore National Laboratory



Robert Deri

Overview

Improved performance of diode-pumped high-power lasers is achieved by operating diode pumps at the highest practical output power while maintaining efficiency. Recent efforts by diode manufacturers to continue improving output power have failed because the primary method used to scale power—lengthening the cavity—now exhibits a corresponding decrease in power conversion efficiency, likely due to longitudinal nonuniformities in photon density, carrier density, and carrier lifetime, which result in nonuniform current densities (current crowding) that limit the ability to scale power efficiently through longer cavities.

Our study produced the first experimental confirmation of current crowding and demonstrated feasibility of current profile tailoring techniques using a segmented diode to control this effect. However, for the diodes studied, the increase in efficiency was small. Additional research is required to confirm that 1) current crowding is the primary reason for limiting cavity length scaling, and 2) the studied control techniques, using segmented diodes, can result in relevant increases in diode output power and efficiency.

Impact on Mission

Our study enhances Lawrence Livermore National Laboratory's core competencies in laser and optical science and technology. Improving the Laboratory's capabilities in diode-pumped high-power lasers advances multiple Livermore mission areas.