Browsing by Subject "Extraordinary optical transmission"

Now showing 1 - 3 of 3
  • Thumbnail Image
    Item
    Engineering metallic nanogap apertures for enhanced optical transmission
    (2016-10) Yoo, Daehan
    Physics and technology of metallic nanoapertures have been of great interest in nanophotonics. In particular, enhanced optical transmission mediated by surface plasmon waves in metallic nanoapertures has been widely studied and utilized in biochemical sensing, imaging, optical trapping, nonlinear optics, metamaterials, and optoelectronics. State-of-the-art nanotechnology enables researchers to explore optical physics in complex nanostructures. However, the high cost and tedium of conventional fabrication approaches such as photolithography, electron-beam lithography, or focused-ion-beam milling have limited the utilization of metallic nanoapertures for practical applications. This dissertation explores new approaches to enable high-throughput fabrication of sub-10-nm nanogaps and apertures in metal films. In particular, we focus on a new technique called atomic layer lithography, which turns atomic layer deposition into a lithographic patterning technique and can create ultra-small coaxial nanoapertures. The resulting nanostructures allowed us to observe extraordinary optical transmission in mid-infrared regime that originates from an intriguing physical phenomenon called the epsilon-near-zero (ENZ) condition. Subsequently, we turn this nanogap structure into a high-Q-factor plasmonic resonator, called a trench nanogap resonator, by combining a nanogap and sidewall mirrors. This structure is optimized for electrical trapping of biomolecules and concurrent optical detection, which is demonstrated experimentally via dielectrophoresis-enhanced plasmonic sensing. The fabrication technique and resulting structures demonstrated in this thesis work can facilitate practical engineering of metallic nanoapertures towards harnessing the potential of plasmonics.
  • Thumbnail Image
    Item
    Large-scale engineered metallic nanstructures for high-throughput surface plasmon resonance biosensing and surface-enhanced Raman spectroscopy
    (2012-07) Lee, Si Hoon
    Precise measurements of binding kinetics and affinity of receptor-ligand interactions play an important role in pharmaceutical development as well as basic biology. Since a new drug discovery requires tremendous amount of time and cost, the demand for a high-throughput screening as well as precise kinetics measurement has increased dramatically. Although the commercially available BIAcoreTM system has been the gold standard for label-free and real-time biosensing, it is not capable of high-throughput kinetic measurements that are required for large-scale proteomics studies. To address the critical challenges, high-throughput SPR imaging instruments based on plasmonic nanohole arrays is demonstrated in this dissertation. The key advantage of nanohole-based SPR setup is that plasmons can be excited at normal incidence, which enables simple optical alignment and high-resolution imaging. Using template stripping technology, massively parallel and highly homogenous nanohole arrays, which is the prerequisite to perform high-throughput SPR imaging, are obtained over a large area (~cm2). Linewidths of extraordinary transmission (EOT) peaks are optimized by reducing the damping losses of surface plasmon polaritons (SPPs), leading to the improved detection limits of the sensor. By combining the highly parallel microfluidics with periodic nanohole arrays, our SPR imaging spectrometer system enables high-throughput, label-free, real-time SPR biosensing, and its full-spectral imaging capability increases the dynamic range of detection. Additionally, molecular identification via surface-enhanced Raman spectroscopy (SERS) is also presented in the second portion of the dissertation. Two approaches include planar-type nanohole structures aimed for highly reproducible SERS substrates with low-cost and dynamic nanogaps pearlchains via dielectrophoresis (DEP) for the rapid and ultrasensitive molecular detection and identification.
  • Thumbnail Image
    Item
    Template-stripped plasmonic cup resonators for single-nanohole-based sensing and spectroscopy
    (2015-05) Olson, Stephen Andrew Olaf
    We have designed and tested a new plasmonic biosensor, featuring a centered nanohole in the base of a recessed metallic nanocup. This configuration enables us to perform independent plasmon-resonance-enhanced single-nanohole transmission spectroscopy on femtoliter volumes of solution. In this thesis we will demonstrate the fabrication, characterization, and application of these novel cup resonator plasmonic biosensors. Utilizing plasmonic confinement to enhance and modulate transmission through a nanohole aperture, the resulting transmission spectra can be used to determine changes in the material properties of a dielectric material located inside the sensing volume of the cup. We have determined, through measurements and simulations, the physical mechanisms causing transmission modulation through the structure. Utilizing this information, we have constructed predictive behavior models for the design and customization of these devices for specific purposes. We show that these structures are responsive to refractive index changes in their surroundings, and propose some possible application of these resonators in biological sensing roles which take advantage of their unique geometry.