Browsing by Subject "Plasmons."

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    Design and fabrication of resonant nanoantennas on chalcogenide glasses for nonlinear photonic applications
    (2013) Duman, Hüseyin
    Optical nanoantennas are the metallic nanostructures which confine electromagnetic waves into sub-wavelength volumes at resonant conditions. They are used for various applications including biological and chemical sensing, single molecule spectroscopy, manipulation and generation of light. Combining extremely large electromagnetic field enhancement in plasmonic resonant nanoantenna with high optical nonlinearity of chalcogenide glass leads to a low-threshold broadband light generation scheme in sub-wavelength chip-scale structures. New frequency generation with ultra-low pumping power in plasmonic nanostructures allows compact on-chip light sources which can find applications in single molecule spectroscopy, optical signal processing and broadband lasers. We propose plasmonic nanoantenna chalcogenide glass systems for initiating nonlinear phenomena at low threshold. Size and shape of antennas are optimized according to linear refractive index of substrate and surrounding media for this purpose by finite difference time domain (FDTD) simulations. Resonant behaviour of antennas at their near-field and nonlinear response of optically highly nonlinear chalcogenide glasses are investigated. On resonance, strong field accumulation at the interface of the gold stripe and highly nonlinear As2Se3 glass triggers a start of the spectral broadening of incident beam accompanied by third harmonic generation at an ultra-low threshold power level of 3 W/µm2 . Moreover, we fabricate the designed structures by electron beam lithography, wet chemical techniques and optimize each fabrication step of processes by several experiments. Fabrication steps are explained and SEM images of related steps are presented.
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    ItemOpen Access
    Resonant optical nanoantennas and applications
    (2010) Kılınç, Murat Celal
    Being one of the fundamentals of electrical engineering, an antenna is a metallic shape structured to transmit or receive electromagnetic waves. Thanks to the recent advances in nano fabrication and nano imaging, metallic structures can be defined with sizes smaller to that of visible light, wavelengths of several nanometers. This opens up the possibility of the engineering of antennas working at optical wavelengths. Nanoantennas could be thought of optical wavelength equivalent of common antennas. Today physics, chemistry, material science and biology use optical nanoantennas to control light waves. Optical nanoantennas are tailored for many technological applications that include generation, manipulation and detection of light. The near field enhancement of resonant optical nanoantennas at specific wavelengths is their most promising advantage that attracts technological applications. In this thesis, we study the resonance characteristics of optical nanoantennas and investigate the governing factors by numerical calculations. We also evaluate radiated electric field from the resonating nanoantenna. Finally, we employ the resonant near field enhancement in optical nonlinear generation. The fabrication of nanoantennas with FIB milling is also explored.