In this work, silicon-based plasmonic nanoantennas was realized. Using silicon instead of metals as the material of choice in building such nanoantennas is advantageous as it enables the integration of nanoantennas-based structures into integrated-optoelectronics circuits built using the standard fabrication techniques in the electronic industry. It also allows for low cost mass production of the proposed devices. Upon light incidence on an array of nanoantennas, Localized Surface Plasmon Resonance (LSPR) is generated which causes an enhancement in the localized field inside the structure and in the near field zone. The enhanced localized field is manifested as an enhancement in the absorbed as well as the scattered field. Varying the surrounding material causes variations in the wavelength of the enhancement peak as well as the enhancement level itself. Hence, sensors can be built to facilitate sensing molecules with its characteristic vibrational transitions. In this paper, dipole and bowtie silicon nanoantennas are investigated. It is found that when using silicon with high excess carrier concentrations as the material of choice, the enhancement occur in the mid-IR spectral range which is red shifted compared to the enhancement produced when using metal such as gold or silver. Working in mid-IR is advantageous for sensing applications as the characteristic vibrational transitions of the majority of bio-chemical molecules happens in the mid-IR.
This work studies the fundamental mode and dispersion relation of a slot waveguide made of intrinsic silicon as the high index region and Air as the low index region by solving the full vectorial wave equation using vectorial finite element method. The objective is to identify the effect of dynamically inducing high excess carrier concentrations in silicon on the slot mode and it dispersion. Tracking the slot mode over a range of wavelengths reveals a reduction in the slot mode effective index upon introducing high concentration of excess carriers. This can be exploited in the dynamic tuning of a silicon slot waveguide dispersion and hence the operation of any sensor based on such waveguide by dynamically generate excess carrier at runtime.
In this work a detailed analysis of the scattering cross-section of silicon Nano-particles with high number of excess carriers in the near and Mid Infrared (MIR) is provided. The effect of different radii of the nanoparticles on the resonance peaks is studied using Mie theory and verified using FDTD. The effect of the level of excess carrier generated on the scattering cross section also analyzed. The study reveals many useful characteristics for such particles which behaves as plasmonic particles in the MIR. Using this study, different particles are designed as scatters in the MIR based on specific dimensions and excess carriers level. These particles can be utilized for infrared spectroscopy of different application such as gas and biomedical sensing in the MIR.
Localized Surface Plasmon Resonance (LSPR) that occur in plasmonic nanoparticles due to interaction with electromagnetic waves at wavelengths larger than the nanoparticles themselves has been exploited in many application like solar cells, cancer treatment and spectroscopy due to the enhanced scattering and absorption cross sections that LSPR provides. Being able to control the resonance peaks of scattering in real time using light can be a valuable tool for sensing-related applications as well especially if it happens in the near and Mid-IR spectrum where most of the biological molecules can be sensed as such spectrum contains strong characteristic vibrational transitions of many important molecules . In this work presented here, we used silicon nanoparticles and increased the concentration of free excess carriers in the nanoparticles by light generation until the free carrier concentration was large enough to cause LSPR similar to what we get with nanoparticles made of Noble metals. The LSPR generated by Si nanoparticles with high concentration of free carriers caused the resonance peak to happen in near and mid IR. Depending on the level of carrier concentration which can be changed dynamically in real time, we can control the scattering resonance peak characteristics and position as shown in our work. Successful fabrication of the Silicon nanosphere is demonstrated as well.
While optical interconnects is expected in the near future to provide the most definitive answer to the current bottleneck in further scale down of the electrical interconnects in VLSI circuits by replacing electrical interconnects altogether, it is currently hindered by the fact that traditional optical interconnect would usually require waveguides that are at least an order of magnitude larger than its electrical interconnect counterpart with a separation distance of few microns to avoid undesirable coupling. Plasmonics offer a solution to the waveguide dimension problem as the guiding mechanism in plasmonic waveguide depends on the coupling between electrons and photons and allow for using waveguides with sub-wavelength dimensions on the expense of greater losses. By using silicon with high concentration of excess carriers as the material of choice, we can acquire plasmonic mode in the near and mid infrared. In this paper we use slot waveguides with both intrinsic silicon with and without high excess carrier’s materials and investigate their transmission effectiveness over 90 degree bends. For silicon with high excess carrier concentration, the modes are plasmonic and allow for excellent performance in transmission through 90 degree bends. This enables dynamic control of routing over 90 degree bends by manipulating the number of free carriers through light excitation. The fact that the slot waveguide is used makes the optical interconnect has dimensions in the same order of magnitude as current electrical interconnects dimension.
An investigation has been performed of the low order guided modes in TiN 2D hollow metallic waveguide. The
dispersion characteristics of the TiN 2D hollow metallic waveguides key guided modes are identified and analyzed.
Dispersion manipulating is proposed by changing the material of the cladding region. The dispersion analysis of 2D
plasmonic waveguide using TiN has been investigated for the first time and compared to that of silver. A study has
been conducted on the effect of varying the material on the cutoff in the modes dispersion. The effect of changing
the plasmonic material on the dispersion curve key characteristics is also identified. Finally the effect of shifting the
cutoff on the enhanced transmission phenomena is investigated.