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Academic Commons Search Resultsen-usChip-scale Photonic Devices for Light-matter Interactions and Quantum Information Processing
http://academiccommons.columbia.edu/catalog/ac:143058
Gao, Jiehttp://hdl.handle.net/10022/AC:P:12160Tue, 10 Jan 2012 00:00:00 +0000Chip-scale photonic devices such as microdisks, photonic crystal cavities and slow-light photonic crystal waveguides possess strong light localization and long photon lifetime, which will significantly enhance the light-matter interactions and can be used to implement new functionalities for both classical and quantum information processing, optical computation and optical communication in integrated nanophotonic circuits. This thesis will focus on three topics about light matter interactions and quantum information processing with chip-scale photonic devices, including 1) Design and characterization of asymmetric resonate cavity with radiation directionality and air-slot photonic crystal cavity with ultrasmall effective mode volume, 2) Exciton-photon interactions between quantum dots and photonic crystal devices and non-classical photon source from a single quantum dot, and 3) Quantum controlled phase gate and phase switching based on quantum dots and photonic crystal waveguide. The first topic is engineered control of radiation directionality and effective mode volume for optical mode in chip-scale silicon micro-/nano-cavities. High quality factor (Q), subwavelength mode volume (V) and controllable radiation directionality are the major properties for optical cavities designs. In Chapter 2, asymmetric resonant cavities with rational caustics are proposed and interior whispering gallery modes in monolithic silicon mesoscopic microcavities are experimentally demonstrated. These microcavities possess unique robustness of cavity quality factor against roughness Rayleigh scattering. In Chapter 3, air-slot mode-gap photonic crystal cavities with quality factor of 10^4 and effective mode volume ~ 0.02 cubic wavelengths are experimentally demonstrated. The origin of the high Q air-slot cavity mode is the mode-gap effect from the slotted photonic crystal waveguide mode with negative dispersion. The second topic is exciton-photon coupling between quantum dots and twodimensional photonic crystal nanocavities and waveguide localized modes, including Purcell effect in weak coupling regime and vacuum Rabi splitting in strong coupling regime. In Chapter 4, micro-photoluminescence measurements of PbS quantum dots coupled to air-slot mode-gap photonic crystal cavities with potentially high qualify factor and small effective mode volume are presented. Purcell factor due to ultrahigh Q/V ratios are critical for applications in non-classical photon sources, cavity QED, nonlinear optics and sensing. In Chapter 5, the observation of subpoisson photon statistics from a single InAs quantum dot emission is presented from both continuous wave and pulsed Hanbury Brown and Twiss measurement. Furthermore, strong coupling between single quantum dot exciton line and photonic crystal waveguide localized mode is demonstrated experimentally and theoretically analyzed with master equations, which can be used as a great implementation platform for realizing future solid-state quantum computation. The third topic is quantum controlled phase gate and phase switching operations based on quantum dots and photonic crystal slow-light waveguide. In Chapter 6, we propose a scheme to realize controlled phase gate between two single photons through a single quantum dot embedded in a photonic crystal waveguide. Enhanced Purcell factor and large Î² factor lead to high gate fidelity over broadband frequencies compared to cavity-assisted system. The excellent physical integration of this photonic crystal waveguide system provides tremendous potential for large-scale quantum information processing. In Chapter 7, dipole induced transparency can be achieved in a system which consists of two quantum dots properly located in silicon photonic crystal waveguide. Furthermore, we describe how this effect can be useful for designing full Ï€ phase switching in a hetero-photonic crystal waveguide structure just by a small amount of photons.Optics, Nanosciencejg2499Applied Physics and Applied Mathematics, Center for Integrated Science and Engineering, Electrical Engineering, Mechanical EngineeringDissertationsNonlinear Applications using Silicon Nanophotonic Wires
http://academiccommons.columbia.edu/catalog/ac:132924
Liu, Xiaopinghttp://hdl.handle.net/10022/AC:P:10443Thu, 26 May 2011 00:00:00 +0000This thesis is concerned with an emerging set of nonlinear-optical applications using silicon nanophotonic "wires" fabricated on a silicon-on-insulator photonic chip. These deeply scaled silicon nanophotonic wires are capable of confining the telecom and mid-infrared (mid-IR) light tightly into an optical-modal area ~ 0.1 μm2. The tight optical confinement leads to many advantageous physical properties including enhanced effective nonlinearity, flexible control of waveguide dispersion, and short free-carrier lifetime. All these advantages make silicon nanophotonic wires an ideal platform for a variety of nonlinear applications. The first part of my thesis study is focused on nonlinear applications in the telecom bands. In Chapter 3, I study the frequency dependence of optical nonlinearity in silicon nanophotonic wires, and its influence on the propagation of ultra-short optical pulses in such wires. I show that silicon nanophotonic wires possess a remarkably large characteristic time associated with the self-steepening effect and optical-shock formation. In Chapter 4, I present an experimental demonstration of an ultrafast cross-phase-modulation-based wavelength-conversion (XPM-WC) technique for telecom RZ-OOK data. I also investigate the effect of pump-probe detuning on the efficacy of this XPM-WC technique. In Chapter 5, I show a (primarily) numerical study of a method for dispersion-engineering of silicon nanophotonic wires using a conformal thin-silicon-nitride dielectric film deposited around the silicon wire core. My simulation results show that this approach may be used to achieve the dispersion characteristics required for broadband phase-matched four-wave-mixing processes, while simultaneously maintaining strong modal confinement within the silicon core for high effective nonlinearity. The second part of my thesis is devoted to investigations of nonlinear applications in mid-IR spectral region, in which nonlinear optical loss due to parasitic two-photon absorption can be significantly reduced and therefore a large nonlinear figure of merit can be achieved in order to facilitate efficient nonlinear processes. In Chapter 6, I present an experimental demonstration of a mid-IR-silicon-nanophotonic-wire optical parametric amplifier with 25.4 dB on-chip gain. This gain achieved with only a 4-mm-long silicon nanophotonic wire is sufficient enough to overcome all the insertion loss, resulting in 13 dB net off-chip amplification. In addition, I show, on the same waveguide, efficient generation of 4 orders of cascaded FWM products enabled by the large on-chip gain. In Chapter 7, I report a comprehensive study of the propagation characteristics of a picosecond pulse through a 4-mm-long silicon nanophotonic wire with normal dispersion with excitation wavelengths crossing the mid-infrared two-photon absorption edge at λ = 2200 nm. Significant reduction in nonlinear loss due to two-photon absorption is demonstrated as the excitation wavelengths approach 2200 nm. Self-phase modulation at high input power is also observed. Analysis of experimental data and comparison with numerical simulations illustrates that the two-photon absorption coefficient obtained from nanophotonic wire measurements is in reasonable agreement with prior measurements of bulk silicon crystals, and that bulk silicon values of the nonlinear refractive index can be confidently incorporated in the modeling of pulse propagation in deeply-scaled waveguide structures. In Chapter 8, I investigate a higher-order phase matching technique utilizing the 4th-order dispersion term for realizing a broadband or discrete band parametric process in silicon nanophotonic wires. I demonstrate experimentally, on a silicon nanophotonic wire designed to exhibit a desired 2nd-order and 4th-order dispersion, broadband/discrete-band modulation instability and 50 dB Raman assisted parametric gain.Optics, Nanotechnologyxl2165Applied Physics and Applied Mathematics, Center for Integrated Science and Engineering, Electrical EngineeringDissertations