Electromagnetically-induced focusing

The theoretical basis for electromagnetically-induced focusing (EIF), which is caused by spatial variations-in the coupling laser strength in an electromagnetically-induced transparency (EIT) experiment, is studied in detail. Using a numerical model it is shown that radial changes in both absorption and refractive index are important in predicting the probe beam's propagation conditions. Detailed calculations of the focusing and defocusing during EIF under various conditions are presented and compared with appropriate experiments. Diffraction like patterns are predicted for, and observed on, a probe beam after propagation through a smaller EIT aperture.