The Recoil Regime: A New Domain of Laser Cooling
Abstract
We have begun exploration of the domain of laser cooling where the ratio of the recoil frequency ωr to the natural width γ no longer satisfies ω_r/γ≡\varepsilon<<1. For polarization gradient cooling (lin⊥lin in our case) on the J=1arrow2 transition 2 ^3Sarrow2 ^3P of metastable He, the 1-D cooling limit is ≈25 hbarω_r, whereas the smaller Doppler limit is 7 hbarγ/20≈13 hbarω_r. In the usual cases of laser cooling, the Doppler limit is much larger (≈25× larger for ^85Rb where \varepsilon≈1/1600). For this transition in He, \varepsilon≈1/40, still small compared with unity, but large enough to produce this unusual circumstance. In combination with our calculations, we have found that the lin⊥lin cooling helps the Doppler cooling instead of the other way around. The steady-state presence of atoms in velocity space outside the linear region of the damping force results in velocity distributions with quite non-Gaussian shapes. We are beginning experiments on the 2 ^3Sarrow3 ^3P transition of He* at λ=389 nm, where \varepsilon≈1/5 to push further into this unexplored, recoil-dominated domain.
- Publication:
-
APS April Meeting Abstracts
- Pub Date:
- April 1997
- Bibcode:
- 1997APS..APR.D1580W