Abstract
The resputtering of gold films from nano-holes defined in a sacrificial PMMA mask, which was made by electron beam lithography, was carried out with a dry plasma etching tool in order to form well-like structures with a high aspect ratio (height/width ≈ 3–4) at the rims of the nano-holes. The extraordinary transmission through the patterns of such nano-wells was investigated experimentally and numerically. By doing numerical simulations of 50-nm and 100-nm diameter polystyrene beads in water and air, we show the potential of such patterns for self-induced back-action (SIBA) trapping. The best trapping conditions were found to be a trapping force of 2 pN/W/μm2 (numerical result) exerted on a 50-nm diameter bead in water. The simulations were based on the analytical Lorentz force model.
Highlights
IntroductionOptical trapping is a fundamental experimental technique for physics and biology, which allows to precisely control and position micrometer-sized objects such as dielectric parts for nanoassembly, and biomaterials such as cells and bacteria, through the use of gradient forces, which originate from the interaction with a focused laser beam [1]
Optical trapping is a fundamental experimental technique for physics and biology, which allows to precisely control and position micrometer-sized objects such as dielectric parts for nanoassembly, and biomaterials such as cells and bacteria, through the use of gradient forces, which originate from the interaction with a focused laser beam [1].Nano-focusing and light control, which are possible with metallic plasmonic structures, are very attractive to engineer optical traps, in order to accurately position and manipulate objects down to the nanometer-scale [2]
The resputtering of gold films from nano-holes defined in a sacrificial PMMA mask, which was made by electron beam lithography, was carried out with a dry plasma etching tool in order to form well-like structures with a high aspect ratio at the rims of the nano-holes
Summary
Optical trapping is a fundamental experimental technique for physics and biology, which allows to precisely control and position micrometer-sized objects such as dielectric parts for nanoassembly, and biomaterials such as cells and bacteria, through the use of gradient forces, which originate from the interaction with a focused laser beam [1]. We explore experimentally and numerically whether extraordinary transmission [16] can be controlled in terms of intensity and spectral width using such 3D nano-well patterns, and we show the suitability of the fabricated structures for SIBA trapping. For the calculation of transmitted and reflected power by the substrate, the domain was changed to a plane-wave illumination from the bottom, modifying the lateral domain boundaries to periodic boundary conditions (PBC) to avoid diffraction of the plane wave from the borders In this case, the reflected and transmitted power were measured by two power monitors, placed at either end of the domain, to gather evidence of extraordinary transmission. Each simulation took about 1 hour on a 16-node cluster with 256 total cores
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