SBIR-STTR Award

We propose an all-fiber approach to heat removal from devices such as IR and LWIR detectors and sensors. In our approach, the cooling fibersegment, the pump fiber laser, and the optical fiber used for photon waste removal are all integrated into a single fiber configuration. NPPhotonics' high efficiency fiber lasers are used to pump high purity doped glass fibers, which provide the cooling action on the affixed heatsource. Our system has several key advantages compared to conventional bulk glass systems. Its cooling power benefits from high opticalconfinement in the fiber core. Second, heat removal and waste photon piping into the fiber occur in the same location (the cooling fibersegment), increasing the fraction of heat that can be dumped at a remote location. Fiber Bragg gratings, which are transparent to the wastephotons and thus minimize fluorescence reabsorption, will be used for enhancing pump absorption. Based on NP Photonics' extensiveexperience in specialty glass and fibers, we will investigate laser cooling in Dy3+ doped glass. In Phase I, we will fabricate Dy3+-doped in bothtellurite and ZBLAN glasses. The glasses will be characterized to determine key parameters for IR fluorescent materials oriented to lasercooling using

Electro-optical infrared and long wavelength infrared detectors and sensors are increasingly important for the Chemical/Biological Defensecommunity. Solid-state optical cooler materials are in demand for replacing mechanical closed cycle coolers used in current LWIR standoffsensors to achieve cryogenic temperatures. Recent advances in optical cooling of rare-earth doped materials are pointing towards a possibleparadigm shift in vibration-less cooling systems. Optical cooling has been demonstrated experimentally in Yb3+-doped material operating at 1micron and Tm3+-doped material at 2 microns, but their cooling efficiencies are very low. Higher cooling efficiencies can be achieved frommaterials operating at 3 microns. NP Photonics will investigate laser cooling materials at 3 microns and fabricate optical fiber coolers at thiswavelength for higher efficiency. The proposed fiber cooler has seamless integration and is alignment-free, light-weight, and maintenance-free.In Phase I we fabricated Dy3+-doped glasses and studied their spectroscopic properties for laser cooling based on anti-Stokes fluorescence. Wealso completed theoretical modeling and simulation on Dy3+-doped fiber coolers and demonstrated the feasibility of optical cooling withDy3+-doped material with reduced phonon energy. In Phase II we will develop an all-optical fiber cooling system based on our expertise in 3micron fiber lasers and laser cooling.