High Power Ceramic Disk Lasers with Gradient Doping Made by Direct Ink Writing

The power output of the high power lasers used in physics research is limited by the materials available for making the gain media in the laser. Future increases in power will require new and better materials. Operation at high power creates great thermal stresses that can lead to effects such as birefringence, thermal lensing or even physical fracture damage to the host itself. Effective cooling and small temperature gradients are critical for achieving higher powers. Using disk lasers can mitigate these issues, but the achievable power is still limited by the material. The innovation in this proposed effort is to produce ceramic YAG disks with a radial gradient of dopant concentration. This will improve the beam quality by “matching” the laser and pump profiles; optimize the efficiency by minimizing the pumped area that is not extracted, and minimize the ASE losses (amplified spontaneous emission) by limiting the (unextracted) lateral gain (i.e. perpendicular to the lasing axis). The graded disk will be fabricated using a revolutionary new ceramics processing technology, the Direct Ink Write process. This will make possible the construction of a higher power, side-pumped, back-cooled solid state disk laser for accelerator applications. In Phase I, RMD, in collaboration with Lawrence Livermore National Laboratory (LLNL), will determine the feasibility of producing ceramic components with a graded dopant concentration profile that can replace the present crystalline, or even ceramic materials, now used in high power lasers. The issues addressed will include optimizing ceramic composition and dopant concentration profile by direct ink write deposition, to produce a design that minimizes temperature gradients, and thus reduces thermally induced birefringence and depolarization. By the end of Phase I we expect to have prepared and characterized sample disks containing a radial gradient in dopant content. In Phase II, RMD and LLNL will optimize the production process and build a laboratory prototype laser system. Lasers are now used in every aspect of life. High-power lasers are used for research, laser ranging, and for environmental sciences. Defense agencies also use high-power lasers for missile guiding and ranging. Industrial applications include cutting and welding. In healthcare services, high power lasers are used in areas such as eye surgery and cosmetic surgery. Laser seeded coherent X-ray sources can be used for very high resolution imaging of fundamental events in biology and physics. The ability to produce higher power will enhance research, improve security, and increase the productivity of manufacturing processes that use high power lasers.