Enhanced, Site-Specific Loading
We have shown enhanced, site-specific loading of optical lattices.
The light-shift of an atomic level in the presence of an laser field is given by
where alpha_0 is the static polarizability and alpha_2 is the tensor
polarizability. Q is a matrix which determines the coupling of
levels, and will be discussed further. The polarizabilities
can be obtained from the dipole
polarizabilites of an atom in an orientated field from the following formulae:
where alpha_xx is the dipole polarizability for an atom in a laser field
polarized along x and similarly for the others.
An s state is spherically symmetric
and so alpha_2 is now 0. The light-shift equation is now
For Rb, the polarizability of the ground state (5s1/2
) at 10.6
with the first line being in the commonly quoted atomic units and the second in
SI units. For a laser power of 50 W focussed down to 70 microns this would
correspond to a ground state trap depth of approximately 0.5 mK, or 10 MHz.
For the excited p state we must
consider the tensor polarizability. The graph below shows the static and tensor
polarizabilities for the states we consider.
to be continued ...