Raman laser cooling of solids

A new approach is proposed for 3-D laser cooling of solids. Stimulated Raman scattering on a narrowband electronic transition is used in conjunction with 1-photon optical pumping on a broadband transition to provide a mechanism that cools all the vibrational modes of solids while conserving energy and momentum, photon by photon. The individual steps in the 2-photon Raman process are 4f–5d and 5d–4f transitions which are electric-dipole-allowed (broadband) transitions that form a Λ-system. By contrast, the 2-photon transition between the 4f states of the rare earth ion is narrowband. By considering examples of Ce3+ ions in Y3Al5O12 and CeF3, elevated transition rates are predicted to offer substantial improvement over anti-Stokes fluorescence cooling when all 1-photon detunings exceed their corresponding Stokes shifts.