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The Design And Fabrication Of Waveguide Beam Splitter Based On Metal-dielectric-semiconductor Hybrid Structure

Posted on:2016-04-11Degree:MasterType:Thesis
Country:ChinaCandidate:Y Y LiFull Text:PDF
GTID:2348330473966397Subject:Physics
Abstract/Summary:PDF Full Text Request
Miniaturization of optical components or devices is necessary in developing integrated photonic circuit, which has led to the great advances in developing various compact optical elements such as nanolasers, optical switching and filter recently. Beam splitter is another key element for photonic circuits and is commonly used in many kinds of optical systems for optical information processing, optical computing, holography, and metrology. Surface plasmons(SPs), a coherent oscillation of the surface conduction electrons excited by electromagnetic radiation, which has series of special optical properties, such as sub-wavelength confinement of light, electromagnetic enhancement and polarization sensitivity.For these particular properties of SPs, low dimensional noble metal nanostructures, such as nanoparticles, nanowires and nanofilms, have enabled a vast array of applications, including surface-enhanced spectroscopies, biological and chemical sensing, and optical information processing.However, because of the large intrinsic ohmic damping of the metal, transferring optical information by SPs only is not a ideal choice. Fortunately, low-dimensional semiconductor nanostructures are emerging as promising building blocks in assembling compact optical elements for their unique optical properties and promising potential applications in nano/microscalphotonic devices. Especially, one-dimensional(1D) structured nanowires and nanoribbons, synthesized through chemical vapor deposition(CVD) route can offer an excellent platform for tight confining and guiding light at sub-wavelength scale due to their single-crystal structure, high refractive index, and large optical nonlinearity. Utilizing the strong electromagnetic coupling between the optical waveguide in the 1D semiconductor nanostructures and low dimensional noble metal nanostructures to induce SPs may give rise to abundant optical properties and even create a new path to invent better-performance optical elements. Some kinds of optical device based on h ybrid nanostructures that combined with low-dimensional semiconductor nanostructures and metal particles has been investigated and do own more advantages for all kinds of photonic applications. Here, we first designed and fabricated a novel sandwich-like nanostructure, which composed by Au nanodisk array covered on a Cd S nanoribbon, with a thin film of Hf O2 as the intermediate dielectric layer. Optical waveguide in the nanoribbon can be modulated by the Au nanodisk array for the electromagnetic coupling between metal nanodisk and optical waveguide in the nano ribbon.Firtsly, through a CVD route, high-quality Cd S nanoribbons were synthesized. Then these synthesized nanoribbons were dispersed onto a pre-cleaned Si/ Si O2(200 nm) substrate which was lithographically patterned with markers. After dispersion, a 15 nm thick Hf O2 dielectric cladding was deposited on the dispersed nanoribbons through atomic layer deposition(ALD) and 50 nm thick Au nanodisk arrays were attached on some pre-selected nanoribbons by EBL(JOEL, JSM-6510) using a standard liftoff procedure. It is interesting to note that compared to Cd S nanoribbon without Au nanodisk array attached, under locally excitation with focused 488 nm laser, the light emitted at the terminal end of the ribbon is split into several independent light spots dramatically, and the number of light spots is dominated by the structure parameter of this hybrid nanostructure.Secondly, a series of numerical simulation work basing on the finite element method were carried out and the calculated results demonstrate that the light propagating in the nanoribbon is trapped by the Au nanodisks, leading to the collective oscillations of free electrons. For the scattering loss and inherent ohmic damping of the metal, much of the absorbed energy is dissipated in these Au nanodisks. It's reasonable to believe that the propagating light through the areas covered by Au nanodisks is interacted with these metal arrays. This kind of nanostructure can separate the propagating light into several optical beams and guiding the split multiple beams along channels between the adjacent Au nanodisks at sub-wavelength scale. Meanwhile, due to the effect of multi-beam interference as the split beams traveling through the blank region between the nanodisks and the terminal end of the Cd S ribbon, emission at the terminal end of nanoribbon output as several light spots. The simulated results confirm to the experimental phenomenon very well.
Keywords/Search Tags:surface plasmons, semiconductor, optical waveguide, integrated photonic circuit, numerical simulation
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