No-Vibration Agile Cryogenic Optical Refrigerator

Optical refrigeration is currently the only all-solid-state cryocooling technology that has been demonstrated. Optical cryocoolers are devices that use laser light to cool small crystal or glass cooling elements. The cooling element absorbs the laser light and reradiates it at higher energy, an example of anti-Stokes luminescence. The difference between the energy of the outgoing and incoming light comes from the thermal energy of the cooling element, which in turn becomes colder. Currently, the most successful cooling element is Yb:YLF, which PI Richard Epstein and his colleagues have cooled from room temperature to 155 K with about 2% efficiency, an important step toward revolutionizing cryogenic systems for sensor applications. Entitled No-Vibration Agile Cryogentic Optical Refrigerator, this proposal directly addresses the continued development of the key concepts necessary to transition this scientific breakthrough into NSSA sensor applications in line with the objectives of topic 50b. ThermoDynamic Films (TDF), in collaboration with the University of New Mexico (UNM), proposes to develop and test critical concepts leading to the incorporation of optical cryocoolers into space systems. Validation of innovative prototype optical cryocoolers in this Phase I program will provide the foundation for a Phase II program producing completely functional prototype systems. TDF and UNM will establish the optical and thermal design configurations necessary for the lowest achievable temperature and the highest cooling power. These include design and implementation of a thermal link as well as an investigation of erbium-based coolers for potential high power scaling Additionally, the team will measure the scaling behavior of ytterbium-doped yttrium lithium fluoride (Yb:YLF) optical cryocooling crystals to verify that the available materials do, in fact, cool as predicted at the high laser intensities.