Go With the Flow: Novel Diode-Pumped Alkali Laser Achieves First Light

  • Published
  • By Mary Rodriguez
  • Directed Energy
KIRTLAND AIR FORCE BASE, New Mexico --  Air Force Research Laboratory's achievement of "first light" lasing from a new type of diode-pumped alkali laser --namely, a flowing DPAL, or FDPAL--marks a significant first step in the direction of high-power laser systems exhibiting the thermal management characteristics needed for future military applications. The lab's successfully designed, developed, and demonstrated FDPAL configuration enables the thermal management system to be decoupled from the lasing cavity--which, in turn, improves the capacity to remove excess heat from the system without sacrificing performance.

DPALs, which themselves represent a relatively new class of lasers, are essentially gas lasers that leverage the advantages of both gaseous gain media and solid-state pump sources. Early DPAL demonstrations relied on the use of gain media in static cell configurations, an approach that effectively limits the amount of heat deposited into a system before thermal effects begin to degrade performance. By incorporating flow technology into the standard DPAL design, AFRL's FDPAL innovation achieves the same effect: removing heat from the gain medium and thereby improving overall beam quality.

Though gas/chemical and solid-state lasers offer a powerful range of capabilities, each variety has its shortcomings. For instance, because gas lasers depend on a chemical reaction to excite their gain medium for lasing, they come with a chemical storage requirement and the burden of the accompanying logistics trail. DPALs (including AFRL's FDPAL) address this issue by accomplishing their lasing via electrically driven diode pumps--a plus traditionally associated with solid-state laser sources. Meanwhile, solid-state lasers have problems with thermal management--specifically, with heat buildup that, by detrimentally affecting the lasing medium, ultimately degrades beam quality. The recently demonstrated FDPAL overcomes this problem by means of its built-in flowing medium, which carries surplus heat away and thereby produces better beam quality.