Sub-wavelength imaging at optical frequencies using canalization regime

摘要

Imaging with sub-wavelength resolution using a lens formed by periodicmetal-dielectric layered structure is demonstrated. The lens operates incanalization regime as a transmission device and it does not involve negativerefraction and amplification of evanescent modes. The thickness of the lenshave to be an integer number of half-wavelengths and can be made as large asrequired for ceratin applications, in contrast to the other sub-wavelengthlenses formed by metallic slabs which have to be much smaller than thewavelength. Resolution of $\lambda/20$ at 600 nm wavelength is confirmed bynumerical simulation for a 300 nm thick structure formed by a periodic stack of10 nm layers of glass with $\epsilon=2$ and 5 nm layers of metal-dielectriccomposite with $\epsilon=-1$. Resolution of $\lambda/60$ is predicted for astructure with same thickness, period and operating frequency, but formed by7.76 nm layers of silicon with $\epsilon=15$ and 7.24 nm layers of silver with$\epsilon=-14$.