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Description
This thesis summarizes the research work carried out on design, modeling and simulation of semiconductor nanophotonic devices. The research includes design of nanowire (NW) lasers, modeling of active plasmonic waveguides, design of plasmonic nano-lasers, and design of all-semiconductor plasmonic systems. For the NW part, a comparative study of electrical injection in the longitudinal p-i-n and coaxial p-n core-shell NWs was performed. It is found that high density carriers can be efficiently injected into and confined in the core-shell structure. The required bias voltage and doping concentrations in the core-shell structure are smaller than those in the longitudinal p-i-n structure. A new device structure with core-shell configuration at the p and n contact regions for electrically driven single NW laser was proposed. Through a comprehensive design trade-off between threshold gain and threshold voltage, room temperature lasing has been proved in the laser with low threshold current and large output efficiency. For the plasmonic part, the propagation of surface plasmon polariton (SPP) in a metal-semiconductor-metal structure where semiconductor is highly excited to have an optical gain was investigated. It is shown that near the resonance the SPP mode experiences an unexpected giant modal gain that is 1000 times of the material gain in the semiconductor and the corresponding confinement factor is as high as 105. The physical origin of the giant modal gain is the slowing down of the average energy propagation in the structure. Secondly, SPP modes lasing in a metal-insulator-semiconductor multi-layer structure was investigated. It is shown that the lasing threshold can be reduced by structural optimization. A specific design example was optimized using AlGaAs/GaAs/AlGaAs single quantum well sandwiched between silver layers. This cavity has a physical volume of 1.5×10-4 λ03 which is the smallest nanolaser reported so far. Finally, the all-semiconductor based plasmonics was studied. It is found that InAs is superior to other common semiconductors for plasmonic application in mid-infrared range. A plasmonic system made of InAs, GaSb and AlSb layers, consisting of a plasmonic source, waveguide and detector was proposed. This on-chip integrated system is realizable in a single epitaxial growth process.
ContributorsLi, Debin (Author) / Ning, Cun-Zheng (Thesis advisor) / Zhang, Yong-Hang (Committee member) / Balanis, Constantine A (Committee member) / Yu, Hongbin (Committee member) / Arizona State University (Publisher)
Created2012
Description
To detect and resolve sub-wavelength features at optical frequencies, beyond the diffraction limit, requires sensors that interact with the electromagnetic near-field of those features. Most instruments operating in this modality scan a single detector element across the surface under inspection because the scattered signals from a multiplicity of such elements would end up interfering with each other. However, an alternative massively parallelized configuration, consisting of a remotely interrogating array of dipoles, capable of interrogating multiple adjacent areas of the surface at the same time, was proposed in 2002.
In the present work a remotely interrogating slot antenna inside a 60nm silver slab is designed which increases the signal to noise ratio of the original system. The antenna is tuned to resonance at 600nm range by taking advantage of the plasmon resonance properties of the metal’s negative permittivity and judicious shaping of the slot element. Full-physics simulations show the capability of detecting an 8nm particle using red light illumination. The sensitivity to the λ/78 particle is attained by detecting the change induced on the antenna’s far field signature by the proximate particle, a change that is 15dB greater than the scattering signature of the particle by itself.
To verify the capabilities of this technology in a readily accessible experimental environment, a radiofrequency scale model is designed using a meta-material to mimic the optical properties of silver in the 2GHz to 5GHz range. Various approaches to the replication of the metal’s behavior are explored in a trade-off between fidelity to the metal’s natural plasmon response, desired bandwidth of the demonstration, and
ii
manufacturability of the meta-material. The simulation and experimental results successfully verify the capability of the proposed near-field sensor in sub-wavelength detection and imaging not only as a proof of concept for optical frequencies but also as a potential imaging device for radio frequencies.
In the present work a remotely interrogating slot antenna inside a 60nm silver slab is designed which increases the signal to noise ratio of the original system. The antenna is tuned to resonance at 600nm range by taking advantage of the plasmon resonance properties of the metal’s negative permittivity and judicious shaping of the slot element. Full-physics simulations show the capability of detecting an 8nm particle using red light illumination. The sensitivity to the λ/78 particle is attained by detecting the change induced on the antenna’s far field signature by the proximate particle, a change that is 15dB greater than the scattering signature of the particle by itself.
To verify the capabilities of this technology in a readily accessible experimental environment, a radiofrequency scale model is designed using a meta-material to mimic the optical properties of silver in the 2GHz to 5GHz range. Various approaches to the replication of the metal’s behavior are explored in a trade-off between fidelity to the metal’s natural plasmon response, desired bandwidth of the demonstration, and
ii
manufacturability of the meta-material. The simulation and experimental results successfully verify the capability of the proposed near-field sensor in sub-wavelength detection and imaging not only as a proof of concept for optical frequencies but also as a potential imaging device for radio frequencies.
ContributorsMostafavi, Mahkamehossadat (Author) / Diaz, Rodolfo E (Thesis advisor) / Pan, George W (Committee member) / Aberle, James T (Committee member) / Ning, Cun-Zheng (Committee member) / Arizona State University (Publisher)
Created2016
Description
Semiconductor nanolasers, as a frontier subject has drawn a great deal of attention over the past decade. Semiconductor nanolasers are compatible with on-chip integrations towards the ultimate realization of photonic integrated circuits. However, innovative approaches are strongly required to overcome the limitation of lattice-mismatch issues. In this dissertation, two alternative approaches are employed to overcome the lattice-mismatch issues. i) By taking advantage of nanowires or nanobelts techniques, flexibility in bandgap engineering has been greatly expanded, resulting in the nanolasers with wide wavelength coverage and tunability. Simultaneous two-color lasing in green and red is firstly achieved from monolithic cadmium sulfide selenide nanosheets. The wavelength separation is up to 97 nm at room temperature, larger than the gain bandwidth of a single semiconductor material in the visible wavelength range. The strategies adopted for two-color lasers eventually leads to the realization of simultaneous red, green and blue lasing and white lasing from a single zinc cadmium sulfide selenide nanosheet with color tunability in the full visible range, making a major milestone in the ultimate solution of laser illumination and laser display. In addition, with the help of nanowire techniques, material emission has been extended to mid-infrared range, enabling lasing at ~3µm from single lead sulfide subwavelength wires at 180 K. The cavity volume of the subwavelength laser is down to 0.44 λ3 and the wavelength tuning range is over 270 nm through the thermo-optic mechanism, exhibiting considerable potentials for on-chip applications in mid-infrared wavelength ranges. ii) By taking advantage of membrane transfer techniques, heterogeneous integration of compound semiconductor and waveguide material becomes possible, enabling the successful fabrication of membrane based nano-ring lasers on a dielectric substrate. Thin membranes with total thickness of ~200nm are first released from the original growth substrate and then transferred onto a receiving substrate through a generally applicable membrane transfer method. Nano-ring arrays are then defined by photolithography with an individual radius of 750 nm and a radial thickness of 400-500 nm. As a result, single mode lasing is achieved on individual nano-ring lasers at ~980 nm with cavity volumes down to 0.24 λ3, providing a general avenue for future heterogeneous integration of nanolasers on silicon substrates.
ContributorsFan, Fan (Author) / Ning, Cun-Zheng (Thesis advisor) / Balanis, Constantine A (Committee member) / Palais, Joseph C. (Committee member) / Yu, Hongbin (Committee member) / Arizona State University (Publisher)
Created2016
Description
The energy band gap of a semiconductor material critically influences the operating wavelength of an optoelectronic device. Realization of any desired band gap, or even spatially graded band gaps, is important for applications such as lasers, light-emitting diodes (LEDs), solar cells, and detectors. Compared to thin films, nanowires offer greater flexibility for achieving a variety of alloy compositions. Furthermore, the nanowire geometry permits simultaneous incorporation of a wide range of compositions on a single substrate. Such controllable alloy composition variation can be realized either within an individual nanowire or between distinct nanowires across a substrate. This dissertation explores the control of spatial composition variation in ternary alloy nanowires. Nanowires were grown by the vapor-liquid-solid (VLS) mechanism using chemical vapor deposition (CVD). The gas-phase supersaturation was considered in order to optimize the deposition morphology. Composition and structure were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive x-ray spectroscopy (EDS), and x-ray diffraction (XRD). Optical properties were investigated through photoluminescence (PL) measurements. The chalcogenides selected as alloy endpoints were lead sulfide (PbS), cadmium sulfide (CdS), and cadmium selenide (CdSe). Three growth modes of PbS were identified, which included contributions from spontaneously generated catalyst. The resulting wires were found capable of lasing with wavelengths over 4000 nm, representing the longest known wavelength from a sub-wavelength wire. For CdxPb1-xS nanowires, it was established that the cooling process significantly affects the alloy composition and structure. Quenching was critical to retain metastable alloys with x up to 0.14, representing a new composition in nanowire form. Alternatively, gradual cooling caused phase segregation, which created heterostructures with light emission in both the visible and mid-infrared regimes. The CdSSe alloy system was fully explored for spatial composition variation. CdSxSe1-x nanowires were grown with composition variation across the substrate. Subsequent contact printing preserved the designed composition gradient and led to the demonstration of a variable wavelength photodetector device. CdSSe axial heterostructure nanowires were also achieved. The growth process involved many variables, including a deliberate and controllable change in substrate temperature. As a result, both red and green light emission was detected from single nanowires.
ContributorsNichols, Patricia (Author) / Ning, Cun-Zheng (Thesis advisor) / Carpenter, Ray (Committee member) / Bennett, Peter (Committee member) / Smith, David (Committee member) / Arizona State University (Publisher)
Created2012