Optical Cooling of RF systems using an All Optical Fiber Approach

We propose an all-fiber approach to heat removal from devices such as high-power RF amplifiers. In our approach, the cooling fiber segment, the pump fiber laser, and the optical fiber used for photon waste removal are all integrated into a single fiber configuration. NP Photonics' high efficiency thulium-doped fiber lasers are used to pump high purity thulium-doped glass fibers, which provide the cooling action on the affixed heat source. Our system has several key advantages compared to conventional bulk glass systems. Its cooling power benefits from high optical confinement in the thulium-doped fiber core. Second, heat removal and waste photon piping into the fiber occur in the same location (the cooling fiber segment), increasing the fraction of heat that can be dumped at a remote location. Fiber Bragg gratings, which are transparent to the waste photons and thus minimize fluorescence reabsorption, will be used for enhancing pump absorption. In Phase I, cooling fibers are based on germanate host glass, but in Phase II other host glasses such as ZBLAN and telluride can also be investigated. Theoretical modeling of optical cooling in our cooling fiber and thermal modeling of the entire fiber cooler will be performed in parallel with the experiments.