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978-3-8439-2225-8, Reihe Physik
Transformational plasmon optics
128 Seiten, Dissertation Universität Hamburg (2015), Softcover, A5
In this thesis the effective refractive index implementation of the transformational plasmon optics concept is studied experimentally, theoretically and with numerical computer simulations. Gray scale electron beam lithography is used to prepare three dimensional resist structures that generate an effective refractive index distribution for propagating surface plasmons on top of gold films. The interaction with these structures is measured phase-resolved by use of heterodyne near field scanning optical microscopy.
We prepare a dome-shaped resist structure to realize a Lüneburg lens, i.e., a lens that exhibits a focal spot at its outer perimeter, for surface plasmons that are excited by light that is incident on an adjacent grating coupler. We could clearly observe a bending of the wave fronts inside the lens as well as a weak focal spot. Thereby we could show the functionality of the transformational plasmon optics approach in the near field.
To study the interaction of a propagating surface plasmon with a gradient effective refractive index in greater detail, we prepare a wedge shaped resist structure on top of a gold film. The thickness of the resist continuously increases from zero to 250 nm over a distance of 10 µm to create an ascending effective refractive index. The resulting near field pattern of an incident plasmonic wave that is excited through attenuated total reflection is measured with phase resolution using optical heterodyne detection. Our results clearly show a tsunami like behavior for propagating surface plasmons.
Utilizing the effective refractive index approach, we present and realize the concept of an integrable, planar, surface plasmon resonance based micro spectrometer. Our conceptual device exhibits planar dimensions as tiny as 200 µm x 200 µm and is capable of determining the wavelength of incident monochromatic light with sub-nanometer resolution in the visible regime.