Next: Raman cooling
Up: Two sub-recoil cooling methods
Previous: Two sub-recoil cooling methods
-Works for He atoms
Level scheme:
Two circularly polarized laser beams resonant on transitions as shown above.
Characterize state of atom by internal quantum numbers and momentum p:
|e0,p> coupled to
and
by laser light (closed family of states, neglecting spontaneous emission)
Transition matrix element:
(
),
sign from Clebsch-Gordan coefficent (given in graph)
Non-absorbing state:
For
: Mixes with absorbing state
(state vector oscillates between
and
with frequency
, i.e. the difference in kinetic energy
)
For p=0 this is a stationary state because
, and also radiatively stable (mixture of ground states)
Absorption rate of ground state
.
Atoms with p=0 are trapped in this state indefinitely. Spontaneous emission randomizes p (recoil momentum along z-axis random variable between
and
) and gives atoms chance to fall into the p=0 trap.
is not a p-eigenstate
two peaks in momentum distribution
Next: Raman cooling
Up: Two sub-recoil cooling methods
Previous: Two sub-recoil cooling methods
Birger Bergersen
1998-12-12