Light matter interaction in the nanoscale is one of the most exciting topics in nanooptics. In this thesis novel nanoparticles that exhibit both plasmon resonance in the visible and phonon resonance in the mid-infrared spectral regions are studied in the nearfield. Nanoparticles composed of silica, silica capped gold, and gold are imaged with high resolution using apertureless near-field scanning optical microscopy (ANSOM) in the visible (λ = 633 nm) and mid-infrared (λ = 9.2-10.7 µm) frequencies. In the visible wavelength, high resolution subsurface imaging and particle detection based on difference in index of refraction is demonstrated. Strong optical contrast between the silica and the silica capped gold nanoparticles is observed in the visible wavelength primarily due to the plasmon resonance of the embedded gold core, this effect is absent in the infrared frequencies and as a result the contrast between the silica and silica capped gold nanoparticles is reduced. In the infrared, because of the phonon resonance of silica, spectroscopic resolved imaging and differentiation of the silica and silica capped particles is made possible. The phase spectra shows contrast at frequencies near the phonon resonance of silica and the frequencies further away from resonance, even in the silica capped gold nanoparticles which have a thin silica coating layer. Experimental results are guided by dielectric function model calculations, which includes the vertical composition of the nanoparticles in the extended dipole approximation.
|Commitee:||Abate, Yohannes, Gredig, Thomas, Kwon, Chuhee|
|School:||California State University, Long Beach|
|Department:||Physics and Astronomy|
|School Location:||United States -- California|
|Source:||MAI 51/03M(E), Masters Abstracts International|
|Subjects:||Solid State Physics, Condensed matter physics|
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