We study the focusing of two-dimensional (2D) electromagnetic waves th
rough a plane interface. Starting from the exact solution for the tran
smitted field due to an arbitrary three-dimensional (3D) incident wave
, we derive solutions for focused 3D waves in the Kirchhoff approximat
ion. Then we construct corresponding solutions for focused 2D electrom
agnetic waves and study in detail the focusing properties of a TM fiel
d numerically and analytically.