Global ETD Search
Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
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Showing 1 to 20 of 72 for “"Two photon absorption"”.
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THz transceiver/two-photon absorption autocorrelator
Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2002.
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One and two photon absorption of atoms and ions
One and two-photon photoabsorption of atoms and ions is the primary focus of this study, with special emphasis on photoabsorption in a laser-produced strontium plasma. The dual laser plasma (DLP) technique has been employed to carry out these studies and adapted to include an optical parametric …
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On the theory of polarization-dependent two-photon absorption
… of an atom or molecule with more than one photon. The simplest; such multiphoton interaction is two-photon absorption by an atom. In this thesis, I develop a model of polarization-dependent two-photon absorption (PDTPA) as a generalization of the present scalar models of two-photon …
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Two-photon absorption and nonlinear polariton effects in organic crystals
<p>Two-photon excitation (TPE) and second harmonic generation (SHG) have been studied in phenanthrene crystals at low temperatures (2 to 6K) in order to investigate mechanisms of two-photon absorption (TPA), the relationship between TPE and SHG, and polariton effects. The transition studied is of …
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Two-photon absorption in bulk semiconductors and quantum well structures and its applications
… to provide a study and possible applications of two-photon absorption (2PA), in direct-gap semiconductors and quantum-well (QW) semiconductor structures. One application uses extremely nondegenerate (END) 2PA, for mid-infrared (mid-IR) detection in uncooled semiconductors. The use of END, where …
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Large Two-photon Absorption of Highly Conjugated Porphyrin Arrays and Their in vivo Applications
<p>Two-photon excited fluorescence microscopy (TPM) has become a standard biological imaging tool due to its simplicity and versatility. The fundamental contrast mechanism is derived from fluorescence of intrinsic or extrinsic markers via simultaneous two-photon absorption which provides inherent …
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All-optical processing for terabit/s wavelength division multiplexed systems using two-photon absorption in a semiconductor micro-cavity
… To implement these high-speed optical networks operating at individual channel rates above 100 Gb/s, all-optical processing techniques are necessary. A novel approach based on two photon absorption nonlinearity within a resonance cavity enhanced structure is explored within this thesis. …
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Ultrafast nonlinear optical properties of passive and active semiconductor devices
… reflectors are studied. The limits imposed by two photon absorption and free-carrier absorption on the gain and output powers of an InGaAsP/InP slab-coupled optical waveguide amplifier with a confinement factor of [gamma] = 0.5% are determined. The two-photon absorption coefficient and the …
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Enhancing the Third-Order Nonlinear Optical Properties of Porphyrins and Molecular Wires
… 10-l8 m2 V(sup>-2 at 1500 nm (6700 cm-1) due to two-photon absorption by free carriers (electrons). Ultrafast electron relaxation was also observed. The ~100 fs lifetime of this process could reflect electron scattering in the conduction band. This DFWM method was also used to investigate the …
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Photoassociation of krypton and fluorine collision pairs
… Kr}$ $\leq$ 1000 Torr and 1 Torr of F$\sb2$. Two-photon absorption of Kr/F$\sb2$ mixtures was also observed over the wavelength range 220 nm $\leq$ $\lambda$ $\leq$ 250 nm. The mechanism of the two-photon absorption is determined to be photodissociation of F$\sb2$ followed by photoassociation …
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Nonlinear Applications using Silicon Nanophotonic Wires
… 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 …
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Alkali-rare gas photodissociation lasers: applications to laser physics and atom-atom interactions
… has been investigated experimentally, as have two-photon absorption processes in atomic Rb and Cs.
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The optical cubic susceptibility dispersion of some transparent thin films.
… that case tunable Third-Harmonic-Generation and Two-Photon-Absorption measurements both agreed with the result of a Near-Infrared-Three-Wave-Mixing measurement. In the case of β-carotene and polythiophenes the four level model also fits the Third-Harmonic-Generation data well. In the previously …
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Development of ultrashort pulse fiber lasers for optical communication utilizing semiconductor devices
… measurements. The relative contributions of absorption bleaching and induced absorption are studied as a function of fluence and wavelength. The impact of induced absorption on the stability of continuous-wave mode-locking is considered theoretically. Picosecond pulses are produced from an …
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Quantum noise propagation in nonlinear optical media
… forward Brillouin scattering (GAWBS), and two-photon absorption are incorporated into the model, which is linearized and solved for the continuous-wave case. The model successfully predicts several interactions between nonlinearity, dispersion, and noise. It is shown that low levels of …
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Photophysics of Organic Probes and their Applications in Bioimaging & Photodynamic Therapy
… have been regarded as attractive tools in biophotonics. With the progress of ultrafast laser sources, two-photon absorption (2PA), in which a molecule absorbs two photons simultaneously, has opened possibilities of using it for various applications. Two-photon fluorescence microscopy (2PFM), …
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Časově rozlišená laserová spektroskopie nanomateriálů
… measure the nonlinear refractive index and the two-photon absorption coefficient. In theoretical part we describe the influence the quality of laser beam, quality and thickness of the sample on measurements. There are numerical simulations of the measurements influenced by these parameters. This …
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MULTIPHOTON ABSORPTION IN MONOLAYER TRANSITION METAL DICHALCOGENIDES
Identifying light absorption mechanisms in nanoscale materials, which are more efficient than those observed in bulk semiconductors, are of paramount importance to next-generation, infrared photo-detection. In this thesis, degenerate two-photon absorption (2PA) and three-photon absorption (3PA) …
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Characterization of third order nonlinearities in TiO₂ waveguides at 1550 nm
… wavelengths. Titanium dioxide does not support two-photon absorption at 1550 nm, has a high refractive index, and a relatively low loss, which allows for high-index-contrast waveguides. The TiO₂ waveguides studied for this thesis were single-mode, with dimensions 200nm x 900nm, deposited on …
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Optical Processes in Krypton and Krypton(2)fluoride: Absolute Cross-Sections for Multiphoton Ionization of Krypton (1S(0)), Photoionization of Metastable Atomic and Molecular States of Krypton, Andabsorption of Krypton(2)fluoride (4-Doublet-Gamma)
A microwave absorption apparatus has been used to measure a cross section for the three-photon, resonantly-enhanced ionization of Kr(('1)S(,0)) at 193 nm. The presence of a two-photon resonance with the Kr 6p 3/2 (,2) level enabled the generation of large electron densities and a measurement of the …
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