  The characteristics of an imaging system formed by a left-handed material
(LHM) slab of finite length are studied, and the influence of the finite length
of the slab on the image quality is analyzed. Unusual phenomena such as surface
bright spots and negative energy stream at the image side are observed and
explained as the cavity effects of surface plasmons excited by the evanescent
components of the incident field. For a thin LHM slab, the cavity effects are
found rather sensitive to the length of the slab, and the bright spots on the
bottom surface of the slab may stretch to the image plane and degrade the image
quality.
