A silicon carbide face cooled ceramic Nd:YAG laser

The efficient extraction of heat generated during the operation of lasers continues to occupy designers of High Energy Lasers (HEL). In the case of bulk solid state lasers, the trend towards improved thermal management design has spurred the re-arrangement of the gain medium from a rod geometry configuration to a "disk" like approach. This rearrangement of the gain medium into a disk configuration maximizes the surface-area-to-volume ratio for improved heat transfer rate from heated core to heatsink surface allowing for power scaling of the solid state laser. Two forms of the face cooled laser exist; the "Thin Disk" and "Diamond Cooled" Laser. While both architectures are based on the face cooling of the gain medium through contact with a heatsink, only the diamond cooled laser requires that one heatsink surface be of high optical quality, laser finished and highly thermally conductive. The diamond cooled laser configuration has the advantage of being able to cool both gain disk surfaces while permitting lasing. The diamond cooled laser approach has been validated in the United States [1] and Israel [2] where diamond has been employed as the thermally conductive medium in small area solid state (SS) lasers. We recently demonstrated the use of SiC as a replacement for diamond in the face cooled laser [3].This work used a single wafer of SiC in pressure-contact (press contact) with 4% Nd:YAG without AR coating between SiC and Nd:YAG. Although the assembly was lased, the press contact construction introduced at least 6.6% single pass cavity losses into the laser cavity, thereby reducing the overall efficiency of the laser. In this paper, we report on improvements in lasing efficiency due to the of reduction of the Fresnel losses through the high temperature bonding of AR coated SiC to Nd:YAG. In what follows, we will present thermo-optic modeling as well the experimental and modeling results of a double SiC face cooled 4%Nd:YAG, longitudinally pumped solid state laser.