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- All Subjects: Materials Science
- All Subjects: Mean Field Approximation
- Genre: Masters Thesis
Description
The study of subwavelength behavior of light and nanoscale lasing has broad
potential applications in various forms of computation i.e. optical and quantum, as well as
in energy engineering. Although this field has been under active research, there has been
little work done on describing the behaviors of threshold and saturation. Particularly, how
the gain-molecule behavior affects the lasing behavior has yet to be investigated.
In this work, the interaction of surface-plasmon-polaritons (SPPs) and molecules is
observed in lasing. Various phenomenologies are observed related to the appearance of the
threshold and saturation regions. The lasing profile, as a visual delimiter of lasing threshold
and saturation, is introduced and used to study various parametrical dependencies of lasing,
including the number-density of molecules, the molecular thickness and the frequency
detuning between the molecular transition frequency and the SPP resonant frequency. The
molecular population distributions are studied in terminal and dynamical methods and are
found to contain unexpected and theoretically challenging properties. Using an average
dynamical analysis, the simulated spontaneous emission cascade can be clearly seen.
Finally, theoretical derivations of simple 1D strands of dipoles are presented in both
the exact and mean-field approximation, within the density matrix formalism. Some
preliminary findings are presented, detailing the observed behaviors of some simple
systems.
potential applications in various forms of computation i.e. optical and quantum, as well as
in energy engineering. Although this field has been under active research, there has been
little work done on describing the behaviors of threshold and saturation. Particularly, how
the gain-molecule behavior affects the lasing behavior has yet to be investigated.
In this work, the interaction of surface-plasmon-polaritons (SPPs) and molecules is
observed in lasing. Various phenomenologies are observed related to the appearance of the
threshold and saturation regions. The lasing profile, as a visual delimiter of lasing threshold
and saturation, is introduced and used to study various parametrical dependencies of lasing,
including the number-density of molecules, the molecular thickness and the frequency
detuning between the molecular transition frequency and the SPP resonant frequency. The
molecular population distributions are studied in terminal and dynamical methods and are
found to contain unexpected and theoretically challenging properties. Using an average
dynamical analysis, the simulated spontaneous emission cascade can be clearly seen.
Finally, theoretical derivations of simple 1D strands of dipoles are presented in both
the exact and mean-field approximation, within the density matrix formalism. Some
preliminary findings are presented, detailing the observed behaviors of some simple
systems.
ContributorsBrewer, Andre J (Author) / Sukharev, Maxim (Thesis advisor) / Rivera, Daniel E (Thesis advisor) / Menéndez, Jose (Committee member) / Arizona State University (Publisher)
Created2017
Description
Sn-based group IV materials such as Ge1-xSnx and Ge1-x-ySixSny alloys have great potential for developing Complementary Metal Oxide Semiconductor (CMOS) compatible devices on Si because of their tunable band structure and lattice constants by controlling Si and/or Sn contents. Growth of Ge1-xSnx binaries through Molecular Beam Epitaxy (MBE) started in the early 1980s, producing Ge1-xSnx epilayers with Sn concentrations varying from 0 to 100%. A Chemical Vapor Deposition (CVD) method was developed in the early 2000s for growing Ge1-xSnx alloys of device quality, by utilizing various chemical precursors. This method dominated the growth of Ge1-xSnx alloys rapidly because of the great crystal quality of Ge1-xSnx achieved. As the first practical ternary alloy completely based on group IV elements, Ge1-x-ySixSny decouples bandgap and lattice constant, becoming a prospective CMOS compatible alloy. At the same time, Ge1-x-ySixSny ternary system could serve as a thermally robust alternative to Ge1-ySny binaries given that it becomes a direct semiconductor at a Sn concentration of 6%-10%. Ge1-x-ySixSny growths by CVD is summarized in this thesis. With the Si/Sn ratio kept at ~3.7, the ternary alloy system is lattice matched to Ge, resulting a tunable direct bandgap of 0.8-1.2 eV. With Sn content higher than Si content, the ternary alloy system could have an indirect-to-direct transition, as observed for Ge1-xSnx binaries. This thesis summarizes the development of Ge1-xSnx and Ge1-x-ySixSny alloys through MBE and CVD in recent decades and introduces an innovative direct injection method for synthesizing Ge1-x-ySixSny ternary alloys with Sn contents varying from 5% to 12% and Si contents kept at 1%-2%. Grown directly on Si (100) substrates in a Gas-phase Molecular Epitaxy (GSME) reactor, both intrinsic and n-type doped Ge1-x-ySixSny with P with thicknesses of 250-760 nm have been achieved by deploying gas precursors Ge4H10, Si4H10, SnD4 and P(SiH3)3 at the unprecedented low growth temperatures of 190-220 °C. Compressive strain is reduced and crystallinity of the Ge1-x-ySixSny epilayer is improved after rapid thermal annealing (RTA) treatments. High Resolution X-ray Diffraction (HR-XRD), Rutherford Backscattering Spectrometry (RBS), cross-sectional Transmission Electron Microscope (XTEM) and Atomic Force Microscope (AFM) have been combined to characterize the structural properties of the Ge1-x-ySixSny samples, indicating good crystallinity and flat surfaces.
ContributorsHu, Ding (Author) / Kouvetakis, John (Thesis advisor) / Menéndez, Jose (Committee member) / Trovitch, Ryan (Committee member) / Arizona State University (Publisher)
Created2019