Focal shift is inevitable in conventional lens systems due to the Fresnel number and angular aperture. In this Letter, we demonstrate that there is no focal shift when a paraxial Gaussian beam passes through a left-handed material slab lens without absorption or gain. However, the effect is exhibited in the presence of absorption or gain, and becomes larger as the absorption or gain increases. When the absorption is equal to the gain, the phenomenon of the focal shift caused by the gain is more obvious. In addition, the field distribution is not affected by the absorption or gain and always remains Gaussian both in internal and external focus planes.
Focal shift is inevitable in conventional lens systems due to the Fresnel number and angular aperture. In this Letter, we demonstrate that there is no focal shift when a paraxial Gaussian beam passes through a left-handed material slab lens without absorption or gain. However, the effect is exhibited in the presence of absorption or gain, and becomes larger as the absorption or gain increases. When the absorption is equal to the gain, the phenomenon of the focal shift caused by the gain is more obvious. In addition, the field distribution is not affected by the absorption or gain and always remains Gaussian both in internal and external focus planes.
ZHANG Kang-Kang;LUO Hai-Lu;WEN Shuang-Chun. Focal Shift of Paraxial Gaussian Beams in a Left-Handed Material Slab Lens[J]. 中国物理快报, 2010, 27(7): 77801-077801.
ZHANG Kang-Kang, LUO Hai-Lu, WEN Shuang-Chun. Focal Shift of Paraxial Gaussian Beams in a Left-Handed Material Slab Lens. Chin. Phys. Lett., 2010, 27(7): 77801-077801.
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2010, Vol. 27 
