Subwavelength imaging at optical frequencies using a transmission device formed by a periodic layered metal-dielectric structure operating in the canalization regime

Imaging with subwavelength resolution using a periodic metal-dielectric layered structure is demonstrated. The structure operates in canalization regime as a transmission device and it does not involve negative refraction and amplification of evanescent modes. The thickness of the structure has to be an integer number of half-wavelengths and can be made as large as required for ceratin applications, in contrast to the solid metallic slabs operating with subwavelength resolution which have to be much thinner than the wavelength. Resolution of $\lambda ∕20$ at $600\mathrm{nm}$ wavelength is confirmed by numerical simulation for a $300\mathrm{nm}$ thick structure formed by a periodic stack of $10\mathrm{nm}$ layers of glass with $\epsilon =2$ and $5\mathrm{nm}$ layers of metal-dielectric composite with $\epsilon =-1$. Resolution of $\lambda ∕60$ is predicted for a structure with same thickness, period and operating frequency, but formed by $7.76\mathrm{nm}$ layers of silicon with $\epsilon =15$ and $7.24\mathrm{nm}$ layers of silver with $\epsilon =-14$.

Figure 1

Geometry of layered metal-dielectric metamaterial.

Figure 2

(Color online) Geometry of transmission device formed by a layered metal-dielectric metamaterial: (a) Perspective view, (b) side view, (c) front view, (d) small details. All dimensions are in nm.

Figure 3

(Color online) Distributions of normal to the interface component of electrical field (arbitrary units): (a) In free space, $20\mathrm{nm}$ from source, (c) at the front interface, (e) at the back interface, (g) in free space, $20\mathrm{nm}$ from back interface; and their absolute values, (b), (d), (f), (h), respectively.

Figure 4

(Color online) Isofrequency contour of layered metal-dielectric structure with ${\epsilon }_1=2$, ${\epsilon }_2=-1$, $d_1=10\mathrm{nm}$, $d_2=5\mathrm{nm}$, $d=d_1+d_2=15\mathrm{nm}$ for $\lambda =600\mathrm{nm}$. The region where the dispersion curve is flat $(\mid q_{x}d∕\pi \mid <0.5)$ is shadowed. The circle in the center represents isofrequency contour of the free space.