Perfect lensing using negative refractive index materials and radiationless electromagnetic interference both provides extreme subwavelength focusing by “amplifying” evanescent wave components that are usually lost. This Letter provides a relation between the achievable focus spot size, the amplification available, and the focal length. This may be considered as a revised version of Abbe’s diffraction limit for focusing systems that have evanescent wave amplification. It is useful in comparing the amplification achieved in various subwavelength focusing implementations as well as determining when it is better to use existing near-field techniques, such as simple diffraction from an aperture or slit, than to attempt complicated superfocusing.
© 2012 Optical Society of America
Original Manuscript: December 2, 2011
Manuscript Accepted: January 21, 2012
Published: February 27, 2012
Reuven Gordon, "Limits for superfocusing with finite evanescent wave amplification," Opt. Lett. 37, 912-914 (2012)