Metallic nanorods array for magnified subwavelength imaging (Presentation Recording)

Earlier, our group proposed a lens made of metallic nanorods, stacked in 3D arrays tapered in a conical shape. This nanolens could theoretically realize super-resolution color imaging in the visible range. The image could be magnified and transferred through metallic nanorods array. Lithography or self-assembly are common ways to fabricate such nanostructured devices. However, to precisely arrange nanorods is challenging due to the limitations to scale down components, and to increase accuracy of assembling particles in large area. Here we experimentally demonstrated 2D nanolens with long chains of metallic nanorods placed at tapered angles in a fan-like shape to magnify images. In the fabrication, we chemically synthesized gold nanorods coated with CTAB surfactant to ensure a 10 nm gap between the rods for the resonance control of nanolens. And we prepared trenches patterned by FIB lithography on a PMMA coated glass substrate. The different hydrophobicity of PMMA and CTAB coats enabled to optimize capillary force in gold nanorod solution and selectively assemble nanorods into hydrophilic trenches. Finally, we obtained 2D nanolens after lift-off of the PMMA layer. We numerically estimated the resonance property of nanorods chain and found a broad peak in the visible range located at a wavelength of 727 nm. The broadness of this peak (~178 nm) confirms that a broad range of wavelength can be resonant with this structure. This phenomenon was also confirmed experimentally by optical measurements. These results show that the combination of lithography and self-assembly has the potential to realize plasmonic nanolens.