Plasmonic laser antennas and related devices and their nearfield optics applications
By: by Ertugrul Cubukcu
Published: 2008
Language: eng
Number of pages: 106
Description: In the first part of this thesis, we present our results on plasmonic laser antennas and related devices. Localized surface plasmon resonances of gold nanorod antennas resting on a silica glass substrate were modeled by finite difference time domain simulations. Plasmonic laser antennas based on the coupled nanorod antenna design were fabricated by focused ion beam lithography on the facet of a semiconductor laser diode operating at a wavelength of 830 nm. An optical spot size of few tens of nanometers was measured by apertureless near-field optical microscope. We have extended our plasmonic antenna work into mid-infrared wavelengths by implementing resonant nanorod and bowtie antennas on the facets of various quantum cascade lasers. Experiments show that this mid-infrared device can provide an optical intensity confinement 70 times higher than that would be achieved with diffraction limited optics. Near-field intensities ∼1 GW/cm 2 were estimated for both near-infrared and mid-infrared plasmonic antennas. A fiber device that takes advantage of plasmonic resonances of gold nanorod arrays providing a high density of optical "hot spots" is proposed. Results of a systematic theoretical and experimental study of the reflection spectra of these arrays fabricated on a silica glass substrate are also presented.

In the second part, we introduce a new aperture-type near-field scanning optical microscopy (NSOM) imaging concept that relies on specially designed large-area aperture geometries having sharp corners. Unlike in conventional NSOM, the spatial resolution of this near-field imaging modality is not determined by the size of the aperture, but rather by the sharpness of the corners of the large aperture. In the third part, we present the polarization dependent resonant surface enhanced Raman scattering from aligned single wall carbon nanotubes induced by the transverse near-field components of periodic and quasiperiodic arrays of nanodisk optical antennas fabricated on them. Confocal Raman microscopy images show G-band surface enhanced Raman scattering in the proximity of the gold nanoantennas from nanotubes for laser polarization normal to the nanotubes, which is normally suppressed in carbon nanotubes due to the "antenna effect".
Notes: "June 2008."

Thesis (Ph.D., School of Engineering and Applied Sciences)--Harvard University, 2008.

Includes bibliographical references.