Efficiently squeezing near infrared light into a 21nm-by-24nm nanospot

Abstract

Recent work demonstrated light transmission through deep subwavelength slits or coupling light into waveguides with deep subwavelength dimension only in one direction. In this paper, we propose an approach to squeeze light (lambda = 1550 nm) from a dielectric waveguide into a deep subwavelength spot. Vertical confinement is achieved by efficiently coupling light from a dielectric waveguide into a 20-nm metal-dielectric-metal plasmonic waveguide. The horizontal dimension of the plasmonic waveguide is then tapered into 20 nm. Numerical simulation shows that light fed from a dielectric waveguide can be squeezed into a 21 nm-by-24 nm spot with efficiency 62%.

Squeezing and expanding light without reflections via transformation optics

“…Given the size of the input beam, a compression 1 4 F  is enough, which satisfies condition 1 for no reflections. A seamless coupling can be observed in Fig.…”

“…As for its size, the squeezer can be as short as desired. Nonetheless, the necessary constitutive parameters become extreme as we reduce 1 d . A surprisingly small length below 10 μm, far below the current state of the art, is enough to achieve a set of parameters with very moderate values for the 2D and 3D cases.…”

“…The above theoretical results, enables us to design an expander that implements a completely flat reflectionless hyperlens. Following a similar approach to that of [17], we transform a little slab of length 1 d into a larger slab of length 1 d  (this can be done without affecting the reflection properties of the device, since the reflection coefficient is independent of compressions/expansions in z direction as was shown above), while expanding the fields in x direction at the same time. This transformation can be described by 11 described by the previous functions with the same value of 3 F and satisfying 13 Fn  (no coating is needed in this case).…”

“…The ability to squeeze and expand light has many applications in optics, ranging from beam collimation to nanolithography, optical data storage, imaging quality enhancing and efficient coupling to nanoscale structures [1,2]. Transformation optics offers a new way to achieve these effects, since it provides the necessary medium to force electromagnetic fields to undergo the spatial distortion introduced by a certain coordinate transformation [3,4].…”

Design and implementation of photonic metamaterials

“…Although this kind of elements arise from one of the simplest transformations (a continuous compression or expansion of space), they may lead to extremely useful applications, ranging from beam collimation to nanolithography, optical data storage, imaging quality enhancing and efficient coupling to nanoscale structures. 119,120 Squeezers and expanders correspond to transformations that are inherently discontinuous at the input or the output of the device. This kind of mappings belong to what has been termed finite embedded transformation.…”