Optical Cooling of RF systems using an All Optical Fiber Approach Navy STTR FY2010.A Sol No.: Navy STTR FY2010.A Topic No.: N10A-T017 Topic Title: Optical Cooling of RF systems using an All Optical Fiber Approach Proposal No.: N10A-017-0330 Firm: NP Photonics, Inc. UA Science and Technology Park 9030 S. Rita Road, Suite #120 Tucson, Arizona 85747-9108 Contact: Dan Nguyen Phone: (520) 799-7419 Web Site: www.npphotonics.com Abstract: 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. Benefits: Using all-fiber optical cooling techniques removes the need for cooling fins and fans or liquid coolant and would be a substantial advantage in naval topside designs or in satellite or space applications. Fiber-based optical cooling or thermal management could find applications in a variety of commercial applications, such as broadcast transmitters and other concentrated radiators, or other heat limited electronic or opto-electronic devices - such as microprocessors or semiconductor receivers. One of the challenges associated with scaling-up the power output of fiber lasers toward and beyond the kW level is thermal management in the active fiber. One promising direction is optical cooling using laser sources to cool down the fiber and enabling alternate approaches for thermal dissipation strategies in high power fiber lasers. Cooling and thermal dissipation using fibers and fiber lasers would not only apply to the RF power amplifiers specifically targeted in this program, but many other electronic and opto-electronic applications where conventional proximity cooling is inconvenient or unsuitable. Return