Learning by Research

Thesis Title: Optical cryocooler design and demonstration for space applications

The goal of this thesis is the design and development of an optical cryo-cooler for space applications such as earth or universe observation satellites. The cooling of the optical sensors located at the satellites focal plane is a key point in order to attain weaker and weaker electrical noise levels and hence improve their performances in terms of image quality. In that context, Air Liquide (who offers coolers for the leading actors of the european space industry such as the ESA and the CNES) partners with the Néel Institute to research a new cryo-cooler technology using the principles of laser cooling in solids.
This type of cooling is based on Anti-Stokes shift observed in rare earth ions (Ytterbium) doped crystals. During the interaction process, a photon is absorbed by the crystal along with a small quantity of thermal energy (phonon) and re-emitted as a fluorescence photon at higher energy. A laser tuned to the crystal’s excitation frequency causes the material’s cooling, as long as the laser-crystal interaction is maximized inside an optical cavity and the fluorescence photons are evacuated out of the crystal. Recent publications on the subject shows that this technology is promising, allowing to attain cryogenic temperatures of about 100K with a compact design, no vibrations and reduced cost.

Key Words: Laser, Cryogenics, Rare earths, Space, Optics,Crystals

Doctoral School:  ED of Physics
Research Laboratory: Institut Néel (CNRS)
Thesis Supervision: Gilles NOGUE and Arnaud GARDELEIN

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