Office of Technology Transfer – University of Michigan

Raman Laser Cooling of Solids

Technology #5073

Cooling temperatures of solid-state electronics

The working temperature of solid-state electronics, including optical detectors and lasers, can significantly affect their operation and stability. High sensitivity IR detectors, for example, must be cooled to minimize the noise associated with carriers being thermally excited to the conduction band. This can be difficult to achieve in locations where conventional cooling methods like liquid nitrogen are unfeasible. For instance, space-based missile detectors, where sensitivity is paramount, are limited by the noise generated by the heat of operation. Laser cooling presents an attractive means of breaking the thermo-electric temperature barrier responsible for this noise. However, unlike the relative ease of optically cooling gases, in obtaining Bose-Einstein condensation (BEC), laser cooling of solids is formidable. The present method, anti-Stokes fluorescence (ASF), has limitations on its efficiency, rate and minimum achievable temperature that have inhibited commercialization.

Improved optical cooling method

A University of Michigan scientist has developed a concept for optically cooling solids that has the potential of becoming a competitive alternative to conventional methods. Based on phonon annihilation, initial conservative estimates yield efficiencies greater than 10% and temperatures as low as 50 mK, analogous to the Doppler limit in gas cooling. It shows an exponential cooling improvement over ASF at cryogenic temperatures and single pass efficiencies far greater than ASF with an enhancement cavity. With these advantages, this optical cooling method could see use in a wide range of applications.

Applications

  • Optical detection
  • Gravity wave detection
  • Lasers
  • Frequency standards

Advantages

  • 10% efficiency
  • 50 mK temperature potential
  • Exponential cooling improvement over ASF at cryogenic temperatures