Laser Cooling in Solids

Ultrafast Phenomena

Parallel to advances in laser cooling of atoms and ions in dilute gas phase, major experimental progress has recently been made in laser cooling of matter in solid and liquid phases1,2. Laser refrigeration of solids can potentially lead to the development of an all solid-state cryocooler that can be used for a variety of applications such as cooling sensors and electronics3.

Since the first observation of optical refrigeration in a solid (ytterbium-doped glass) in 1995 by Epstein, et al.1, researchers have made major strides toward achieving laser induced solid-state cryocoolers4. Ytterbium-doped glass has been cooled by more than 50 K below room temperature and has been shown to cool at 100 K3,5,6. Progress has been made toward cooling semiconductor materials although no net cooling has yet been observed due to radiation trapping7, 8.

We have recently reported the first demonstration of laser induced cooling of a thulium-doped glass -- the second solid after ytterbium-doped glass to exhibit net bulk cooling. These measurements allow us to test material scalability such as the predicted increase in cooling efficiency with decreasing pump photon energy. Moreover, unlike in ytterbium-doped systems, these results demonstrate anti-Stokes fluorescent cooling in the presence of excited-state absorption.

Follow the link below to view a set of slides presenting the general ideas and results of this cooling. This particular presentation was made as a post-deadline paper (QPD10) at the Quantum Electronics and Laser Science conference in San Francisco in May, 2000. Questions or comments are welcome -- please address Chad Hoyt at

  1. R. I. Epstein, M. I. Buchwald, B. C. Edwards, et al., Nature 377, 500 (1995)
  2. J. L. Clark and G. Rumbles, Physical Review Letters 76, 2037 (1996)
  3. B. C. Edwards, J. E. Anderson, R. I. Epstein, et al., Journal of Applied Physics 86, 6489 (1999)
  4. B. C. Edwards, M. I. Buchwald, and R. I. Epstein, Review of Scientific Instruments 69, 2050 (1998)
  5. T. R. Gosnell, Optics Letters 24, 1041 (1999)
  6. C. E. Mungan, M. I. Buchwald, B. C. Edwards, et al., Applied Physics Letters 71, 1458 (1997)
  7. H. Gauck, T. H. Gfroerer, M. J. Renn, et al., Applied Physics a-Materials Science & Processing 64, 143 (1997)
  8. E. Finkeissen, M. Potemski, P. Wyder, et al., Applied Physics Letters 75, 1258 (1999)