Lawrence Livermore National Laboratory

The Directed Energy Program provides laser systems design, engineering and production for specific applications and missions, experimentally validated first-principles understanding of weapon lethality and vulnerability, and evaluation and prediction of the emergence of potential threats.

The program is developing “electric” laser systems that will enable the tactical and strategic laser missions of the 21st century. In the last 15 years, LLNL’s technological advances and innovations in scaled, semiconductor diode-laser pump arrays and large-aperture transparent ceramic gain slabs have made possible much more efficient and less massive all-electric laser systems with power levels and beam characteristics suitable to a wide variety of defense applications.

Diode-Pumped Alkali Laser: A New Combination

Since the advent of lasers more than four decades ago, solid-state and gas lasers have followed largely divergent development paths. Gas lasers are based primarily on direct electrical discharge for pumping (energizing), while solid-state lasers are pumped by flashlamps and semiconductor diode laser arrays.

Resonance-Transition Alkali Laser
The first demonstration of a resonance-transition alkali laser using rubidium vapor occurred at LLNL in the winter of 2002.

The alkali-vapor laser’s intrinsically high efficiency and its compatibility with today’s commercially available diode arrays enable fast-track development paths to tactical systems, with mass-to-power ratios that far exceed what is possible with today’s other laser systems.

Building on alkali-vapor laser research done by Z. Konefal, NIF & Photon Science engineers and scientists recently developed a new class of laser that combines features of both gas and solid-state lasers, based on diode excitation of atomic alkali vapors. The defining features of the diode-pumped alkali laser (DPAL) are its ability to be incoherently pumped and its compatibility with diode arrays having several-nanometer-wide spectral emissions. These characteristics distinguish DPALs from previous demonstrations of alkali-based lasers that used narrow-band, coherent pumping to demonstrate lasing.

LLNL’s extensive laser modeling capability, anchored to experimental laboratory demonstrations, supports extreme power scaling with good efficiency and beam quality. LLNL is the world leader in the development of this new class of laser; the first demonstration took place at LLNL in 2002, and it has been followed by many other demonstrations and developments.

Solid-State Heat-Capacity Laser

LLNL developed a high-average-power diode-pumped, solid-state heat-capacity laser (SSHCL) suitable for use in military weapons. Potential military applications of such a system include the targeting and destruction of short-range rockets, guided missiles, artillery and mortar fire, unmanned aerial vehicles and improvised explosive devices, or IEDs.

In 2006, a major accomplishment was achieved when the SSHCL produced 67 kilowatts of power—a 50-percent increase in the world-record-setting power level attained the previous year. This class of power demonstrates that tabletop-sized solid-state lasers have come of age and can fulfill the performance requirements for their use in tactical weapon applications.

Solid-state Heat Capacity Laser


Additionally, improvements to the SSHCL’s laser optics, both in material selection and geometric architecture, have greatly enhanced temperature profile uniformity throughout the lasing cavity, yielding a beam quality 2 times the diffraction limit for 5 seconds of run time in an unstable resonator. Beam quality control is integral to LLNL’s laser system development, and results like these portend the use of directed-energy weapons on the battlefield where they can effect “speed-of-light” engagement in compact, mobile packages.