Optical Cooling of RF systems

This Phase II Proposal is for the development of an all-fiber based approach to optical cooling for RF systems: a high power, high efficiency Tm+3-doped fiber laser (Lambda from 1.9 microns to ~ 2 microns) is used to pump Tm+3-doped glass fibers, which provide the cooling action on the affixed heat source. One of the main advantages of this approach is that the waste (heat) photons can in principle be piped substantial distances and expelled wherever the system designer wishes. The cooling fibers for Phase II have much less impurities and background losses compared to the glasses used in Phase I. These features of the new glasses will greatly reduce the parasitic heat in the cooling fiber. Fiber structures with multiple cores will be designed and fabricated to increase significantly both pump absorption and net cooling power. The broad wavelength operation of Tm-doped fiber lasers will be utilized for optimization of cooling processes such as pump wavelength dependence. Tm-doped fiber lasers with different lasing wavelengths will be built for that purpose. Optimization of losses in the system, in particular the scattering loss in the fiber system, will be investigated both experimentally and theoretically. Furthermore, multiple fibers/lasers will also be investigated to achieve maximum cooling power and cooling efficiency in the system.