Molecular Scale Imaging with a Multilayer Superlens
- PDF / 221,046 Bytes
- 7 Pages / 612 x 792 pts (letter) Page_size
- 12 Downloads / 192 Views
0919-J04-07
Molecular Scale Imaging with a Multilayer Superlens Pratik Chaturvedi, and Nicholas X. Fang Mechanical & Industrial Engineering, Univ. of Illinois at Urbana-Champaign, 158 Mechanical Engineering Building, MC-244, 1206 W. Green St., Urbana, IL, 61801
ABSTRACT It has been experimentally demonstrated that a single layer of silver functions as a “superlens” [Fang et al, Science 308, 534 (2005)], providing image resolution much better than the diffraction limit. Resolution as high as 60 nanometer (λ/6) half-pitch was achieved. In this paper, we explore the possibility of further refining the image resolution using a “multilayer superlens” design. With optimized design of silver-alumina multilayer superlens, our numerical simulations show a feasibility of resolving 15nm features, about 1/26th of the illumination wavelength. We present preliminary experimental results targeted towards achieving the molecular scale imaging resolution. The development of potential low-loss and high resolution superlens opens the door to exciting applications in nanoscale optical metrology and nanomanufacturing.
INTRODUCTION The resolution of optical images has been historically constrained by the wavelength of light, a well known behavior which is termed as the diffraction limit. This is because conventional optical imaging is only capable of focusing the propagating components from the source. The evanescent components which carry the subwavelength information exponentially decay in a medium with positive permittivity (ε), and positive permeability (µ) and hence, are lost before making it to the image plane. Recent theory [1] suggested a thin negative index film should function as a superlens, providing image detail with resolution beyond the diffraction limit. This planar slab of negative index film, termed as “superlens”, derives its super-resolution capability from the amplification of evanescent waves via the excitation of surface plasmons. Artificially designed negative index materials (also known as metamaterials) have demonstrated promising effects of beam bending [2] and refocusing [3] at microwave frequencies. Yet, achieving negative permeability at optical frequencies is difficult, thus making superlensing extremely challenging. Fortunately, in the electrostatic near field limit, the electric and magnetic responses of materials are decoupled [1]. Thus, for transverse magnetic (TM) polarization, having only negative permittivity suffices for near field superlensing effect. This makes metals like silver natural candidates for superlens at optical frequencies. It has been demonstrated experimentally [4] that a silver superlens allows to resolve features well below the working wavelength. Resolution as high as 60 nanometer (λ/6) half-pitch has been achieved. In this paper, we explore the possibility of further refining the image resolution using a multilayer superlens [5]. Using a transfer matrix scheme [6], our numerical calculations show an ultimate imaging resolution of λ/26. This is made possible using alternating s
Data Loading...
