Dissertation/Thesis Abstract

Phase-Shifting Interferometry for Near-Field Optical Microscopy and Nanoparticle Detection
by Deutsch, Bradley M., Ph.D., University of Rochester, 2011, 186; 3498230
Abstract (Summary)

Two systems capable of investigating linear scattering from nanoscopic systems are developed. The first is a Scanning Near-field Optical Microscope (SNOM), which is used to image near fields of optical antennas in the near-infrared (NIR) and visible regimes. The second is a scalable apparatus for detection and characterization of nanoparticles in solution, for which sensitivity to 30 nanometer particles with a bandwidth of > 1 kilohertz is demonstrated.

In SNOM, a sharp probe is scanned in the near field of an illuminated sample to create an image with resolution far exceeding the diffraction limit. Optical antennas are of interest as a SNOM sample because of their potential applications in energy harvesting, microscopy and light emission. The physics of optical antennas is not well understood, and near-field imaging is an important step in their design and development. The home-built SNOM presented in this thesis is one of the first to operate in the visible spectrum, where optical antennas are applicable. It uses phase-shifting interferometry to decouple amplitude and phase of scattered fields. The instrument is used to investigate near-field coupling of nanoparticles, and to image simple optical antennas fabricated with focused ion-beam lithography.

It has also been demonstrated that interferometric detection with elastic light scattering is a viable method for detection and characterization of nanoparticles in solution, which has applications in manufacturing, environmental monitoring, biodefense and medical research. Such methods have shortcomings, including small throughput and difficulty of scaling the apparatus to small sizes. The latter makes it impractical to use the device in the field or clinic. Therefore, a homebuilt dual-phase particle detection apparatus is presented, which makes two orthogonal interferometric measurements to decouple amplitude and phase of fields scattered from nanoparticles, and uses no active optical elements or lock-in detection. Benchmark sensitivity to 30nm particles with detection bandwidth > 1kHz is shown.

Indexing (document details)
Advisor: Novotny, Lukas
Commitee: Bigelow, Nick, Brown, Thomas, Donaldson, William, Hillenbrand, Rainer, Novotny, Lukas, Vamivakas, Nick
School: University of Rochester
Department: Hajim School of Engineering and Applied Sciences
School Location: United States -- New York
Source: DAI-B 73/07(E), Dissertation Abstracts International
Subjects: Nanoscience, Optics
Keywords: Interferometry, Nano optics, Nanoparticle detection, Nsom, Phase-shifting, Snom
Publication Number: 3498230
ISBN: 978-1-267-20620-6
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