### Focusing Vacuum Fluctuations

**L.H. Ford and N.F. Svaiter**

*Physics Department*

Tufts University

Medford, MA 02155

The quantization of the electromagnetic field in the presence
of a parabolic mirror is discussed in the context of a geometric
optics approximation. We calculate the mean squared electric
field near the focal line of a parabolic cylindrical mirror. This
quantity is found to grow as an inverse power of the distance
from the focus. We give a combination of analytic and numerical
results for the mean squared field. In particular, we find that
the mean squared electric field can be either negative or positive,
depending upon the choice of parameters. The case of a negative
mean squared electric field corresponds to a repulsive Van der
Waals force on an atom near the focus, and to a region of negative
energy density. Similarly, a positive value corresponds to an
attractive force and a possibility of atom trapping in the vicinity
of the focus.