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 Title
 OPTICAL SOLITONS IN PERIODIC STRUCTURES.
 Creator

Makris, Konstantinos, Christodoulides, Demetrios, University of Central Florida
 Abstract / Description

By nature discrete solitons represent selftrapped wavepackets in nonlinear periodic structures and result from the interplay between lattice diffraction (or dispersion) and material nonlinearity. In optics, this class of selflocalized states has been successfully observed in both oneand twodimensional nonlinear waveguide arrays. In recent years such lattice structures have been implemented or induced in a variety of material systems including those with cubic (Kerr), quadratic,...
Show moreBy nature discrete solitons represent selftrapped wavepackets in nonlinear periodic structures and result from the interplay between lattice diffraction (or dispersion) and material nonlinearity. In optics, this class of selflocalized states has been successfully observed in both oneand twodimensional nonlinear waveguide arrays. In recent years such lattice structures have been implemented or induced in a variety of material systems including those with cubic (Kerr), quadratic, photorefractive, and liquidcrystal nonlinearities. In all cases the underlying periodicity or discreteness leads to new families of optical solitons that have no counterpart whatsoever in continuous systems. In the first part of this dissertation, a theoretical investigation of linear and nonlinear optical wave propagation in semiinfinite waveguide arrays is presented. In particular, the properties and the stability of surface solitons at the edge of Kerr (AlGaAs) and quadratic (LiNbO3) lattices are examined. Heterostructures of two dissimilar semiinfinite arrays are also considered. The existence of hybrid solitons in these latter types of structures is demonstrated. Rabitype optical transitions in zmodulated waveguide arrays are theoretically demonstrated. The corresponding coupled mode equations, that govern the energy oscillations between two different transmission bands, are derived. The results are compared with direct beam propagation simulations and are found to be in excellent agreement with coupled mode theory formulations. In the second part of this thesis, the concept of paritytimesymmetry is introduced in the context of optics. More specifically, periodic potentials associated with PTsymmetric Hamiltonians are numerically explored. These new optical structures are found to exhibit surprising characteristics. These include the possibility of abrupt phase transitions, band merging, nonorthogonality, nonreciprocity, double refraction, secondary emissions, as well as power oscillations. Even though gain/loss is present in this class of periodic potentials, the propagation eigenvalues are entirely real. This is a direct outcome of the PTsymmetry. Finally, discrete solitons in PTsymmetric optical lattices are examined in detail.
Show less  Date Issued
 2008
 Identifier
 CFE0002013, ucf:47610
 Format
 Document (PDF)
 PURL
 http://purl.flvc.org/ucf/fd/CFE0002013
 Title
 OPTICAL WAVE PROPAGATION IN DISCRETE WAVEGUIDE ARRAYS.
 Creator

Hudock, Jared, Christodoulides, Demetrios, University of Central Florida
 Abstract / Description

The propagation dynamics of light in optical waveguide arrays is characteristic of that encountered in discrete systems. As a result, it is possible to engineer the diffraction properties of such structures, which leads to the ability to control the flow of light in ways that are impossible in continuous media. In this work, a detailed theoretical investigation of both linear and nonlinear optical wave propagation in one and twodimensional waveguide lattices is presented. The ability to...
Show moreThe propagation dynamics of light in optical waveguide arrays is characteristic of that encountered in discrete systems. As a result, it is possible to engineer the diffraction properties of such structures, which leads to the ability to control the flow of light in ways that are impossible in continuous media. In this work, a detailed theoretical investigation of both linear and nonlinear optical wave propagation in one and twodimensional waveguide lattices is presented. The ability to completely overcome the effects of discrete diffraction through the mutual trapping of two orthogonally polarized coherent beams interacting in Kerr nonlinear arrays of birefringent waveguides is discussed. The existence and stability of such highly localized vector discrete solitons is analyzed and compared to similar scenarios in a single birefringent waveguide. This mutual trapping is also shown to occur within the first few waveguides of a semiinfinite array leading to the existence of vector discrete surface waves. Interfaces between two detuned semiinfinite waveguide arrays or waveguide array heterojunctions and their possible applications are also considered. It is shown that the detuning between the two arrays shifts the dispersion relation of one array with respect to the other. Consequently, these systems provide spatial filtering functions that may prove useful in future alloptical networks. In addition by exploiting the unique diffraction properties of discrete arrays, diffraction compensation can be achieved in a way analogous to dispersion compensation in dispersion managed optical fiber systems. Finally, it is demonstrated that both the linear (diffraction) and nonlinear dynamics of twodimensional waveguide arrays are significantly more complex and considerably more versatile than their onedimensional counterparts. As is the case in onedimensional arrays, the discrete diffraction properties of these twodimensional lattices can be effectively altered depending on the propagation Bloch kvector within the first Brillouin zone. In general, this diffraction behavior is anisotropic and as a result, allows the existence of a new class of discrete elliptic solitons in the nonlinear regime. Moreover, such arrays support twodimensional vector soliton states, and their existence and stability are also thoroughly explored in this work.
Show less  Date Issued
 2005
 Identifier
 CFE0000833, ucf:46687
 Format
 Document (PDF)
 PURL
 http://purl.flvc.org/ucf/fd/CFE0000833
 Title
 ELECTROMAGNETIC PROPAGATION ANOMALIES IN WAVEGUIDING STRUCTURES AND SCATTERING SYSTEMS.
 Creator

Salandrino, Alessandro, Christodoulides, Demetrios, University of Central Florida
 Abstract / Description

The effects related to diffraction and interference are ubiquitous in phenomena involving electromagnetic wave propagation, and are accurately predicted and described within the framework of classical electrodynamics. In the vast majority of the cases the qualitative features of the evolution of a propagating wave can be inferred even without detailed calculations. A field distribution will spread upon propagation, will accumulate phase along the direction of power flow, will exert mechanical...
Show moreThe effects related to diffraction and interference are ubiquitous in phenomena involving electromagnetic wave propagation, and are accurately predicted and described within the framework of classical electrodynamics. In the vast majority of the cases the qualitative features of the evolution of a propagating wave can be inferred even without detailed calculations. A field distribution will spread upon propagation, will accumulate phase along the direction of power flow, will exert mechanical forces upon scattering objects in the direction of propagation etc. When such predictions fail, counterintuitive effects and new functionalities can be engineered. In this work a series of exceptional cases under different degrees of field confinement have been isolated. In such instances the electromagnetic behavior significantly deviates from conventional cases. In particular, considering structures with monodimensional field confinement, the only possible class of diffraction free surface waves has been introduced. Again within the context of surface waves the mechanism of Enhanced Evanescent Tunneling (EET) has been proposed, which allows a net power flow to be sustained by evanescent fields only with applications to subdiffraction imaging. Increasing the degree of field confinement, a unique class of fully dielectric waveguide arrays able to support negative effective index modes has been theoretically demonstrated. Finally the optomechanical consequences of such effective negative index environments have been studied, highlighting counterintuitive properties. Instrumental to these findings was the introduction of a general theory of optical forces in terms of vector spherical harmonics.
Show less  Date Issued
 2011
 Identifier
 CFE0003930, ucf:48691
 Format
 Document (PDF)
 PURL
 http://purl.flvc.org/ucf/fd/CFE0003930
 Title
 OPTICAL NONLINEAR INTERACTIONS IN DIELECTRIC NANOSUSPENSIONS.
 Creator

ElGanainy, Ramy, Christodoulides, Demetrios, University of Central Florida
 Abstract / Description

This work is divided into two main parts. In the first part (chapters 27) we consider the nonlinear response of nanoparticle colloidal systems. Starting from the NernstPlanck and Smoluchowski equations, we demonstrate that in these arrangements the underlying nonlinearities as well as the nonlinear Rayleigh losses depend exponentially on optical intensity. Two different nonlinear regimes are identified depending on the refractive index contrast of the nanoparticles involved and the...
Show moreThis work is divided into two main parts. In the first part (chapters 27) we consider the nonlinear response of nanoparticle colloidal systems. Starting from the NernstPlanck and Smoluchowski equations, we demonstrate that in these arrangements the underlying nonlinearities as well as the nonlinear Rayleigh losses depend exponentially on optical intensity. Two different nonlinear regimes are identified depending on the refractive index contrast of the nanoparticles involved and the interesting prospect of selfinduced transparency is demonstrated. Soliton stability is systematically analyzed for both 1D and 2D configurations and their propagation dynamics in the presence of Rayleigh losses is examined. We also investigate the modulation instability of plane waves and the transverse instabilities of soliton stripe beams propagating in nonlinear nanosuspensions. We show that in these systems, the process of modulational instability depends on the boundary conditions. On the other hand, the transverse instability of soliton stripes can exhibit new features as a result of 1D collapse caused by the exponential nonlinearity. Manybody effects on the systems' nonlinear response are also examined. Mayer cluster expansions are used in order to investigate particleparticle interactions. We show that the optical nonlinearity of these nanosuspensions can range anywhere from exponential to polynomial depending on the initial concentration and the chemistry of the electrolyte solution. The consequence of these interparticle interactions on the soliton dynamics and their stability properties are also studied. The second part deals with linear and nonlinear properties of optical nanowires and the coupled mode formalism of paritytime (PT) symmetric waveguides. Dispersion properties of AlGaAs nanowires are studied and it is shown that the group velocity dispersion in such waveguides can be negative, thus enabling temporal solitons. We have also studied power flow in nanowaveguides and we have shown that under certain conditions, optical pulses propagating in such structures will exhibit power circulations. Finally PT symmetric waveguides were investigated and a suitable coupled mode theory to describe these systems was developed.
Show less  Date Issued
 2009
 Identifier
 CFE0002847, ucf:48538
 Format
 Document (PDF)
 PURL
 http://purl.flvc.org/ucf/fd/CFE0002847
 Title
 ACCELERATING OPTICAL AIRY BEAMS.
 Creator

Siviloglou, Georgios, CHRISTODOULIDES, DEMETRIOS, University of Central Florida
 Abstract / Description

Over the years, nonspreading or nondiffracting wave configurations have been systematically investigated in optics. Perhaps the best known example of a diffractionfree optical wave is the socalled Bessel beam, first suggested and observed by Durnin et al. This work sparked considerable theoretical and experimental activity and paved the way toward the discovery of other interesting nondiffracting solutions. In 1979 Berry and Balazs made an important observation within the context of...
Show moreOver the years, nonspreading or nondiffracting wave configurations have been systematically investigated in optics. Perhaps the best known example of a diffractionfree optical wave is the socalled Bessel beam, first suggested and observed by Durnin et al. This work sparked considerable theoretical and experimental activity and paved the way toward the discovery of other interesting nondiffracting solutions. In 1979 Berry and Balazs made an important observation within the context of quantum mechanics: they theoretically demonstrated that the SchrÃƒÂ¶dinger equation describing a free particle can exhibit a nonspreading Airy wavepacket solution. This work remained largely unnoticed in the literaturepartly because such wavepackets cannot be readily synthesized in quantum mechanics. In this dissertation we investigate both theoretically and experimentally the acceleration dynamics of nonspreading optical Airy beams in both one and twodimensional configurations. We show that this class of finite energy waves can retain their intensity features over several diffraction lengths. The possibility of other physical realizations involving spatiotemporal Airy wavepackets is also considered. As demonstrated in our experiments, these Airy beams can exhibit unusual features such as the ability to remain quasidiffractionfree over long distances while their intensity features tend to freely accelerate during propagation. We have demonstrated experimentally that optical Airy beams propagating in free space can perform ballistic dynamics akin to those of projectiles moving under the action of gravity. The parabolic trajectories of these beams as well as the motion of their center of gravity were observed in good agreement with theory. Another remarkable property of optical Airy beams is their resilience in amplitude and phase perturbations. We show that this class of waves tends to reform during propagation in spite of the severity of the imposed perturbations. In all occasions the reconstruction of these beams is interpreted through their internal transverse power flow. The robustness of these optical beams in scattering and turbulent environments was also studied. The experimental observation of selftrapped Airy beams in unbiased nonlinear photorefractive media is also reported. This new class of nonlocal selflocalized beams owes its existence to carrier diffusion effects as opposed to selffocusing. These finite energy Airy states exhibit a highly asymmetric intensity profile that is determined by the inherent properties of the nonlinear crystal. In addition, these wavepackets selfbend during propagation at an acceleration rate that is independent of the thermal energy associated with twowave mixing diffusion photorefractive nonlinearity.
Show less  Date Issued
 2010
 Identifier
 CFE0003193, ucf:48569
 Format
 Document (PDF)
 PURL
 http://purl.flvc.org/ucf/fd/CFE0003193
 Title
 NonHermitian Optics.
 Creator

Ulhassan, Absar, Christodoulides, Demetrios, Khajavikhan, Mercedeh, Likamwa, Patrick, Kaup, David, University of Central Florida
 Abstract / Description

From the viewpoint of quantum mechanics, a system must always be Hermitian since all its corresponding eigenvalues must be real. In contrast, the eigenvalues of open systemsunrestrained because of either decay or amplificationcan be in general complex. Not so long ago, a certain class of nonHermitian Hamiltonians was discovered that could have a completely real eigenvalue spectrum. This special class of Hamiltonians was found to respect the property of commutation with the paritytime (PT)...
Show moreFrom the viewpoint of quantum mechanics, a system must always be Hermitian since all its corresponding eigenvalues must be real. In contrast, the eigenvalues of open systemsunrestrained because of either decay or amplificationcan be in general complex. Not so long ago, a certain class of nonHermitian Hamiltonians was discovered that could have a completely real eigenvalue spectrum. This special class of Hamiltonians was found to respect the property of commutation with the paritytime (PT) operator. Translated into optics, this implies a balance between regions exhibiting gain and loss. Traditionally, loss has been perceived as a foe in optics and something that needs to be avoided at all costs. As we will show, when used in conjunction with gain, the presence of loss can lead to a host of counterintuitive outcomes in such nonHermitian configurations that would have been otherwise unattainable in standard arrangements. We will study PT symmetric phase transitions in various optical settings that include semiconductor microrings and coupled fiber cavities, and show how they can allow modeselectivity in lasers. One of the key outcomes of this effort was the realization of higher order degeneracies in a threecavity laser configuration that can exhibit ordersofmagnitude larger sensitivity to external perturbations. We will also consider systems that display nonlinear effects such as gain saturation, thus allowing novel phase transitions. Some interesting properties associated with degeneracies in nonHermitian settings will be investigated as well. Such degeneracies, called exceptional points (EPs), are much more drastic compared to standard degeneracies of eigenvalues because the corresponding eigenvectors also coalesce, which in turn reduces the dimensionality of the phase space. We will show that dynamic parameter contours enclosing or close to EPs can lead to a robust chiral mode conversion process () something that can be potentially used to realize omnipolarizing optical devices.
Show less  Date Issued
 2018
 Identifier
 CFE0007259, ucf:52182
 Format
 Document (PDF)
 PURL
 http://purl.flvc.org/ucf/fd/CFE0007259
 Title
 Analysis and Design of NonHermitian Optical Systems.
 Creator

Kazemi Jahromi, Ali, Abouraddy, Ayman, Christodoulides, Demetrios, Likamwa, Patrick, Chini, Michael, University of Central Florida
 Abstract / Description

From a very general perspective, optical devices can be viewed as constructions based on the spatial engineering of the optical index of refraction. Sculpting the real part of the refractive index produces the wide variety of known passive optical devices, such as waveguides, resonators, gratings, among a plethora of other possibilities for managing the transport of light. Less attention has been directed to engineering the imaginary part of the refractive index () that is responsible for...
Show moreFrom a very general perspective, optical devices can be viewed as constructions based on the spatial engineering of the optical index of refraction. Sculpting the real part of the refractive index produces the wide variety of known passive optical devices, such as waveguides, resonators, gratings, among a plethora of other possibilities for managing the transport of light. Less attention has been directed to engineering the imaginary part of the refractive index () that is responsible for optical gain and absorption () in conjunction with the real part of the refractive index. Optical gain is the building block of amplifiers and lasers, while optical absorption is exploited in photovoltaic devices, photodetectors, and as dopants in lasing media. Recently, the field of nonHermitian photonics has emerged in which the new opportunities afforded by the spatial engineering of the optical gain and loss in an optical device are being exploited. Indeed, the judicious design of such active devices can result in counterintuitive physical effects, new optical functionalities that enable unexpected applications, and enhanced performance of existing devices.In this work, we have theoretically and experimentally demonstrated four different nonHermitian arrangements exhibiting novel nontrivial features. First, we show that the direction of energy flow can be controlled inside an active cavity by tuning the optical gain. Reversing the direction of the energy flow within the cavity () such that Poynting's vector points backwards towards the source () takes place when the cavity gain exceeds a certain threshold value, which we have named 'Poynting's threshold'. To realize this effect, we have employed a fiberbased arrangement that allows for unambiguous determining of the direction of the energy flow within the cavity. Second, we have studied the implication of Poynting's threshold with respect to spectral reflection from an active cavity. Surprisingly, the reflection at Poynting's threshold becomes spectrally flat and is guaranteed to attain unity reflectivity while maintaining nonzero transmission. In other words, at Poynting's threshold, the cavity becomes a 'transparent perfect mirror'. We have realized this effect in an onchip active waveguide device and in an opticalfiberbased system. Third, we have examined a paritytime (PT) symmetric fiberbased cavity consisting of two coupled subcavities, one of which contains gain and the other loss. In contrast to all previous onchip PTsymmetric microdevices, the exotic features of such a system may be expected to vanish when the length of the cavity is extremely large (exceeding 1 km in our experiments) due to the strong fluctuations in the optical phase. Nevertheless, we have found that some of the central features of such a system survive; e.g., lossinduced enhancement of lasing power is still observable. Finally, we have demonstrated () for the first time () the interferometric perfect absorption of light in a weakly absorbing (erbiumdoped) fiber system. Additionally, we verified that this coherent effect is the most efficient configuration with respect to utilizing the absorbing species in the medium.
Show less  Date Issued
 2018
 Identifier
 CFE0007206, ucf:52271
 Format
 Document (PDF)
 PURL
 http://purl.flvc.org/ucf/fd/CFE0007206
 Title
 Thirdorder optical nonlinearities for integrated microwave photonics applications.
 Creator

Malinowski, Marcin, Fathpour, Sasan, Delfyett, Peter, Christodoulides, Demetrios, Lyakh, Arkadiy, University of Central Florida
 Abstract / Description

The field of integrated photonics aims at compressing large and environmentallysensitive opticalsystems to micronsized circuits that can be massproduced through existing semiconductor fabrication facilities. The integration of optical components on single chips is pivotal to the realizationof miniature systems with high degree of complexity. Such novel photonic chips find abundant applications in optical communication, spectroscopy and signal processing. This work concentrateson...
Show moreThe field of integrated photonics aims at compressing large and environmentallysensitive opticalsystems to micronsized circuits that can be massproduced through existing semiconductor fabrication facilities. The integration of optical components on single chips is pivotal to the realizationof miniature systems with high degree of complexity. Such novel photonic chips find abundant applications in optical communication, spectroscopy and signal processing. This work concentrateson harnessing nonlinear phenomena to this avail.The first part of this dissertation discusses, both from component and system level, the developmentof a frequency comb source with a semiconductor modelocked laser at its heart. New nonlinear devices for supercontinuum and secondharmonic generations are developed and their performance isassessed inside the system. Theoretical analysis of a hybrid approach with synchronouslypumpedKerr cavity is also provided. The second part of the dissertation investigates stimulated Brillouinscattering (SBS) in integrated photonics. A fullytensorial opensource numerical tool is developedto study SBS in optical waveguides composed of crystalline materials, particularly silicon. SBS isdemonstrated in an allsilicon optical platform.
Show less  Date Issued
 2019
 Identifier
 CFE0007674, ucf:52497
 Format
 Document (PDF)
 PURL
 http://purl.flvc.org/ucf/fd/CFE0007674
 Title
 NonHermitian and SpaceTime Mode Management.
 Creator

Nye, Nicholas, Christodoulides, Demetrios, Khajavikhan, Mercedeh, Abouraddy, Ayman, Kaup, David, University of Central Florida
 Abstract / Description

In the last few years, optics has witnessed the emergence of two fields namely metasurfaces and paritytime (PT) symmetry. Optical metasurfaces are engineered structures that provide unique responses to electromagnetic waves, absent in natural materials. On the other hand, PT symmetry has emerged from quantum mechanics, when a new class of nonHermitian Hamiltonian quantum systems was shown to have real eigenvalues. In this work, we demonstrate how PTsymmetric diffractive structures are...
Show moreIn the last few years, optics has witnessed the emergence of two fields namely metasurfaces and paritytime (PT) symmetry. Optical metasurfaces are engineered structures that provide unique responses to electromagnetic waves, absent in natural materials. On the other hand, PT symmetry has emerged from quantum mechanics, when a new class of nonHermitian Hamiltonian quantum systems was shown to have real eigenvalues. In this work, we demonstrate how PTsymmetric diffractive structures are capable of eliminating diffraction orders in specific directions, while maintaining/enhancing the remaining orders. In the second part of this work, we emphasize on supersymmetry (SUSY) and its applications in optics. Even though the full ramification of SUSY in highenergy physics is still a matter of debate that awaits experimental validation, supersymmetric techniques have already found their way into lowenergy physics. In this work, we apply certain isospectral techniques in order to achieve single mode lasing in multielement waveguide systems, where multimode chaotic emission is expected. In the third part of this dissertation, we emphasize on dynamically reconfigurable nanoparticle platforms. By exploiting the dielectrophoresis effect, we demonstrate how controllable lasing can be achieved in random photonic arrangements. Although this work focuses on the case of controlling random lasers, we expect that the proposed nanoparticle architecture can incorporate heterogeneous materials of a wide range of optical functionalities, including gain, scattering, plasmonic resonance, and nonlinearity. In the last part of the dissertation, we demonstrate the capability of synthesizing spacetime (ST) wave packets, based on new propagationinvariant elementary solutions of the wave equation identified through a complexification of the spatial and temporal degrees of freedom. By establishing the connection between ST propagationinvariant pulses and tiltedpulsefront pulses, a path is opened to exploiting the unique attributes of such wave packets both in nonlinear and quantum optics.
Show less  Date Issued
 2019
 Identifier
 CFE0007896, ucf:52780
 Format
 Document (PDF)
 PURL
 http://purl.flvc.org/ucf/fd/CFE0007896
 Title
 NonReciprocal Wave Transmission in Integrated Waveguide Array Isolators.
 Creator

Ho, Yat, Likamwa, Patrick, Christodoulides, Demetrios, Vanstryland, Eric, Kaup, David, University of Central Florida
 Abstract / Description

Nonreciprocal wave transmission is a phenomenon witnessed in certain photonic devices when the wave propagation dynamics through the device along one direction differs greatly from the dynamics along the counterpropagating direction. Specifically, it refers to significant power transfer occurring in one direction, and greatly reduced power transfer in the opposite direction. The resulting effect is to isolate the directionality of wave propagation, allowing transmission to occur along one...
Show moreNonreciprocal wave transmission is a phenomenon witnessed in certain photonic devices when the wave propagation dynamics through the device along one direction differs greatly from the dynamics along the counterpropagating direction. Specifically, it refers to significant power transfer occurring in one direction, and greatly reduced power transfer in the opposite direction. The resulting effect is to isolate the directionality of wave propagation, allowing transmission to occur along one direction only.Given the popularity of photonic integrated circuits (PIC), in which all the optical components are fabricated on the same chip so that the entire optical system can be made more compact, it is desirable to have an easily integrated optical isolator. Common freespace optical isolator designs, which rely on the Faraday effect, are limited by the availability of suitable magnetic materials. This research proposes a novel integrated optical isolator based on an array of closely spaced, identical waveguides. Because of the nonlinear optical properties of the material, this device exploits the differing behaviors of such an array when illuminated with either a high power or a low power beam to achieve nonreciprocal wave transmission in the forwards and backwards directions, respectively. The switching can be controlled electrooptically via an integrated gain section which provides optical amplification before the input to the array. The design, fabrication, characterization and testing of this optical isolator are covered in this dissertation. We study the switching dynamics of this device and present its optimum operating conditions. ?
Show less  Date Issued
 2012
 Identifier
 CFE0004305, ucf:49495
 Format
 Document (PDF)
 PURL
 http://purl.flvc.org/ucf/fd/CFE0004305
 Title
 Paritytime and supersymmetry in optics.
 Creator

Miri, Mohammad, Christodoulides, Demetrios, Abouraddy, Ayman, Likamwa, Patrick, Choudhury, Sudipto, University of Central Florida
 Abstract / Description

Symmetry plays a crucial role in exploring the laws of nature. By exploiting some of the underlying analogies between the mathematical formalism of quantum mechanics and that of electrodynamics, in this dissertation we show that optics can provide a fertile ground for studying, observing, and utilizing some of the peculiar symmetries that are currently out of reach in other areas of physics. In particular, in this work, we investigate two important classes of symmetries, paritytime symmetry ...
Show moreSymmetry plays a crucial role in exploring the laws of nature. By exploiting some of the underlying analogies between the mathematical formalism of quantum mechanics and that of electrodynamics, in this dissertation we show that optics can provide a fertile ground for studying, observing, and utilizing some of the peculiar symmetries that are currently out of reach in other areas of physics. In particular, in this work, we investigate two important classes of symmetries, paritytime symmetry (PT) and supersymmetry (SUSY), within the context of classical optics. The presence of PT symmetry can lead to entirely real spectra in nonHermitian systems. In optics, PTsymmetric structures involving balanced regions of gain and loss exhibit intriguing properties which are otherwise unattainable in traditional Hermitian systems. We show that selective PT symmetry breaking offers a new method for achieving single mode operation in laser cavities. Other interesting phenomena also arise in connection with PT periodic structures. Along these lines, we introduce a new class of optical lattices, the so called mesh lattices. Such arrays provide an ideal platform for observing a range of PTrelated phenomena. We show that defect sates and solitons exist in such periodic environments exhibiting unusual behavior. We also investigate the scattering properties of PTsymmetric particles and we show that such structures can deflect light in a controllable manner. In the second part of this dissertation, we introduce the concept of supersymmetric optics. In this regard, we show that any optical structure can be paired with a superpartner with similar guided wave and scattering properties. As a result, the guided mode spectra of these optical waveguide systems can be judiciously engineered so as to realize new families of mode filters and mode division multiplexers and demultiplexers. We also present the first experimental demonstration of light dynamics in SUSY ladders of photonic lattices. In addition a new type of transformation optics based on supersymmetry is also explored. Finally, using the SUSY formalism in nonHermitian settings, we identify more general families of complex optical potentials with real spectra.
Show less  Date Issued
 2014
 Identifier
 CFE0005844, ucf:50915
 Format
 Document (PDF)
 PURL
 http://purl.flvc.org/ucf/fd/CFE0005844
 Title
 Techniques for characterization of third order optical nonlinearities.
 Creator

Ferdinandus, Manuel, Hagan, David, Vanstryland, Eric, Christodoulides, Demetrios, Hernandez, Florencio, University of Central Florida
 Abstract / Description

This dissertation describes the development of novel techniques for characterization of nonlinear properties of materials. The dissertation is divided into two parts, a background and theory section and a technique development section.In the background and theory section we explain the origins of the nonlinear optical response of materials across many different spatial and temporal scales. The mechanisms that we are most interested in are the electronic nuclear and reorientational responses,...
Show moreThis dissertation describes the development of novel techniques for characterization of nonlinear properties of materials. The dissertation is divided into two parts, a background and theory section and a technique development section.In the background and theory section we explain the origins of the nonlinear optical response of materials across many different spatial and temporal scales. The mechanisms that we are most interested in are the electronic nuclear and reorientational responses, which occur on the range of subfemtosecond to several picoseconds. The electronic mechanism is due to the electrons of a material experiencing a nonparabolic potential well due a strong electric field and occurs on the subfemtosecond timescale. The nuclear or vibrational effect results from the motion of the nuclei of the atoms and typically occurs on the order of a few hundred femtoseconds. Finally the reorientational nonlinearity is due to the alignment of the molecule to the electric field, which alters the polarizability of the molecule and typically occurs on the scale of a few picoseconds. There are other mechanisms can induce nonlinear optical effects such as thermal effects and electrostriction, but these effects typically occur on much larger timescales than we are interested in, and hence will not be a major focus of this dissertation.In the nonlinear characterization techniques section, we describe previous research into the field of nonlinear optical characterization techniques, describing the techniques used to characterize the nonlinear properties of materials, their applications and limitations. We will trace the development of two recently developed techniques for nonlinear spectroscopy ? the Dual Arm ZScan and the Beam Deflection techniques. The Dual Arm ZScan technique is an enhancement of the standard ZScan technique that allows for the measurement of small nonlinear signals in the presence of large background signals. This technique allows for the measurement of materials under certain conditions not previously measureable using the standard ZScan technique, such materials with low damage thresholds, poor solubility and thin films.In addition to the Dual Arm ZScan, we have developed a new method for characterizing nonlinear refraction, the Beam Deflection technique, which is a variation of the photothermal beam deflection technique previously used to measure very weak absorption signals. This technique offers relative ease of use, the ability to measure the absolute magnitude and sign of both the real and imaginary parts of ?^((3)) simultaneously with high sensitivity. We fully develop the theory for materials with instantaneous and noninstantaneous nonlinearities, with nonlinear absorption and group velocity mismatch. We also demonstrate the power of this technique to separate the isotropic and reorientational contributions of liquids by examining the temporal response and polarization dependences.Lastly, we summarize our conclusions and describe two promising future research directions that would benefit from the Dual Arm ZScan and Beam Deflection techniques.
Show less  Date Issued
 2013
 Identifier
 CFE0005164, ucf:50709
 Format
 Document (PDF)
 PURL
 http://purl.flvc.org/ucf/fd/CFE0005164
 Title
 OPTICAL PROPAGATION OF SELFSUSTAINING WAVEFRONTS AND NONLINEAR DYNAMICS IN PARABOLIC MULTIMODE FIBERS.
 Creator

Mills, Matthew, Christodoulides, Demetrios, Hagan, David, Dogariu, Aristide, Kaup, David, University of Central Florida
 Abstract / Description

The aim of this thesis is to introduce my work which has generally been focused on opticalwavefronts that have the unusual property of resisting commonplace phenomena such as diffraction and dispersion. Interestingly, these special beams are found both in linear and nonlinear situations. For example, in the linear regime, localized spatiotemporal waves which resemble the spherical harmonic symmetries of the hydrogen quantum orbitals can simultaneously negotiate both diffractive and...
Show moreThe aim of this thesis is to introduce my work which has generally been focused on opticalwavefronts that have the unusual property of resisting commonplace phenomena such as diffraction and dispersion. Interestingly, these special beams are found both in linear and nonlinear situations. For example, in the linear regime, localized spatiotemporal waves which resemble the spherical harmonic symmetries of the hydrogen quantum orbitals can simultaneously negotiate both diffractive and dispersiveeffects. In the nonlinear regime, dressed optical filaments can be arranged to propagate multiphoton produced plasma channels orders of magnitude longer than expected.The first portion of this dissertation will begin by surveying the history of diffractionfree beamsand introducing some of their mathematical treatments. Interjected throughout this discussion will be several relevant concepts which I explored during my first years a CREOL. The discussion will then be steered into a detailed account of diffraction/dispersion free wavefronts which display hydrogenlike symmetries. The second segment of the document will cover the highly nonlinear process of optical filamentation. This chapter will almost entirely investigate the idea of the dressed filament, an entity which allows for substantial prolongation of this light string. I will then conclude by delving into the topicof supercontinuum generation in parabolic multimode fibers which, in the upcoming years, has great potential of becoming important in optics.
Show less  Date Issued
 2015
 Identifier
 CFE0005977, ucf:50767
 Format
 Document (PDF)
 PURL
 http://purl.flvc.org/ucf/fd/CFE0005977
 Title
 Photon Statistics in Disordered Lattices.
 Creator

Kondakci, Hasan, Saleh, Bahaa, Abouraddy, Ayman, Christodoulides, Demetrios, Mucciolo, Eduardo, University of Central Florida
 Abstract / Description

Propagation of coherent waves through disordered media, whether optical, acoustic, or radio waves, results in a spatially redistributed random intensity pattern known as speckle  a statistical phenomenon. The subject of this dissertation is the statistics of monochromatic coherent light traversing disordered photonic lattices and its dependence on the disorder class, the level of disorder and the excitation configuration at the input. Throughout the dissertation, two disorder classes are...
Show morePropagation of coherent waves through disordered media, whether optical, acoustic, or radio waves, results in a spatially redistributed random intensity pattern known as speckle  a statistical phenomenon. The subject of this dissertation is the statistics of monochromatic coherent light traversing disordered photonic lattices and its dependence on the disorder class, the level of disorder and the excitation configuration at the input. Throughout the dissertation, two disorder classes are considered, namely, diagonal and offdiagonal disorders. The latter exhibits disorderimmune chiral symmetry  the appearance of the eigenmodes in skewsymmetric pairs and the corresponding eigenvalues in opposite signs. When a disordered photonic lattice, an array of evanescently coupled waveguides, is illuminated with an extended coherent optical field, discrete speckle develops. Numerical simulations and analytical modeling reveal that discrete speckle shows a set of surprising features, that are qualitatively indistinguishable in both disorder classes. First, the fingerprint of transverse Anderson localization  associated with disordered lattices, is exhibited in the narrowing of the spatial coherence function. Second, the transverse coherence length (or speckle grain size) freezes upon propagation. Third, the axial coherence depth is independent of the axial position, thereby resulting in a coherence voxel of fixed volume independently of position.When a single lattice site is coherently excited, I discovered that a thermalization gap emerges for light propagating in disordered lattices endowed with disorderimmune chiral symmetry. In these systems, the span of subthermal photon statistics is inaccessible to the input coherent light, which  once the steady state is reached  always emerges with superthermal statistics no matter how small the disorder level. An independent constraint of the input field for the chiral symmetry to be activated and the gap to be observed is formulated. This unique feature enables a new form of photonstatistics interferometry: by exciting two lattice sites with a variable relative phase, as in a traditional twopath interferometer, the excitationsymmetry of the chiral mode pairs is judiciously broken and interferometric control over the photon statistics is exercised, spanning subthermal and superthermal regimes. By considering an ensemble of disorder realizations, this phenomenon is demonstrated experimentally: a deterministic tuning of the intensity fluctuations while the mean intensity remains constant.Finally, I examined the statistics of the emerging light in two different lattice topologies: linear and ring lattices. I showed that the topology dictates the light statistics in the offdiagonal case: for evensited ring and linear lattices, the electromagnetic field evolves into a single quadrature component, so that the field takes discrete phase values and is noncircular in the complex plane. As a consequence, the statistics become superthermal. For oddsited ring lattices, the field becomes random in both quadratures resulting in subthermal statistics. However, this effect is suppressed due to the transverse localization of light in lattices with high disorder. In the diagonal case, the lattice topology does not play a role and the transmitted field always acquires random components in both quadratures, hence the phase distribution is uniform in the steady state.
Show less  Date Issued
 2015
 Identifier
 CFE0005968, ucf:50786
 Format
 Document (PDF)
 PURL
 http://purl.flvc.org/ucf/fd/CFE0005968
 Title
 Optical Parity Time Metasurface Structures.
 Creator

El Halawany, Ahmed, Christodoulides, Demetrios, Rahman, Talat, Peale, Robert, Likamwa, Patrick, University of Central Florida
 Abstract / Description

In the last few years, optics has witnessed the emergence of two fields namely metasurfaces and paritytime (PT) symmetry. Optical metasurfaces are engineered structures that provide unique responses to electromagnetic waves, absent in natural materials. Optical metasurfaces are known for their reduced dimensionality i.e. subwavelength and consequently lower losses are anticipated. The other paradigm is the PT symmetric materials, also known as photonic synthetic matter. PT symmetry has...
Show moreIn the last few years, optics has witnessed the emergence of two fields namely metasurfaces and paritytime (PT) symmetry. Optical metasurfaces are engineered structures that provide unique responses to electromagnetic waves, absent in natural materials. Optical metasurfaces are known for their reduced dimensionality i.e. subwavelength and consequently lower losses are anticipated. The other paradigm is the PT symmetric materials, also known as photonic synthetic matter. PT symmetry has emerged from quantum mechanics when a new class of nonHermitian Hamiltonian quantum systems was highlighted to have real eigenvalues, hence eradicating Hermiticity of the Hamiltonian as an essential condition to the existence of real eigenvalues.The first half of the thesis is focused on the experimental and numerical realization of PT symmetric metasurfaces. A systematic methodology is developed to implement this class of metasurfaces in both onedimensional and twodimensional geometries. In two dimensional systems, PT symmetry can be established by employing either Hlike diffractive elements or diatomic oblique Bravais lattices. It is shown that the passive PT symmetric metasurfaces can be utilized to appropriately engineer the resulting farfield characteristics. Such PTsymmetric structures are capable of eliminating diffraction orders in specific directions, while maintaining or even enhancing the remaining orders. Later, it is shown a first ever attempt of PT metasurface fabricated on a flexible polymer (polyimide) substrate. The studied PT metasurface exhibits the ability to direct light, i.e. Poynting vector in a desired direction. Herein, the light scattered from the fabricated device in the undesired direction is attenuated by at least an order of magnitude. The proposed PT symmetric metasurface is essentially diatomic Honeycomb Bravais lattice, where both the passive and lossy elements exist side by side on each site separated by 50 nm. The unidirectionality of the studied metasurface is not limited to a single wavelength, on the contrary, it is observed to be effective on the entire visible band (400 () 600 nm). The PT symmetric meatsurface is also fabricated on a high strength substrate; sapphire (Al2O3). An excellent agreement between the experimental and numerical (COMSOL) results is found for both substrates. Customized modifications to the current design can open avenues to study the unidirectionality of metasurfaces to different optical bands, for example IR.The second part of the thesis deals with the theoretical modeling of the dynamics of an electron that gets trapped by means of decoherence and quantum interference in the central quantum dot (QD) of a semiconductor nanoring (NR) made of five QDs, between 100 and 300 K. The electron's dynamics is described by a master equation with a Hamiltonian based on the tightbinding model, taking into account electron()LO phonon interaction. Based on this configuration, the probability to trap an electron with no decoherence is almost 27%. In contrast, the probability to trap an electron with decoherence is 70% at 100 K, 63% at 200 K and 58% at 300 K. Our model provides a novel method of trapping an electron at room temperature.This setup is then used to propose a theoretical model for an electrically driven single photon source operating at high temperatures. It is shown that the decoherence, which is usually the main obstacle for operating single photon sources at high temperatures, ensures an efficient operation of the presented electrically driven single photon source at high temperatures. The singlephoton source is driven by a single electron source attached to a heterostructure semiconductor nanoring. The electron's dynamics in the nanoring and the subsequent recombination with the hole is described by the generalized master equation with a Hamiltonian based on tightbinding model, taking into account the electronLO phonon interaction. As a result of decoherence, an almost 100% single photon emission with a strong antibunching behavior i.e. g(2)(0) (<)(<) 1 at high temperature up to 300 K is achieved.
Show less  Date Issued
 2016
 Identifier
 CFE0006454, ucf:51421
 Format
 Document (PDF)
 PURL
 http://purl.flvc.org/ucf/fd/CFE0006454
 Title
 Coupling of Laser Beams for Filament Propagation.
 Creator

Kepler, Daniel, Richardson, Martin, Baudelet, Matthieu, Christodoulides, Demetrios, University of Central Florida
 Abstract / Description

Laser filamentation is a nonlinear process involving highenergy, ultrashort pulses that create narrow, nondiffracting structures over many times the Raleigh length. While many of the characteristics of filaments can vary greatly depending on the physical parameters used to create them, they share several defining features: a high intensity core, a lower intensity cladding of photons that serves as an energy reservoir to the core, and spectral broadening into a supercontinuum. While there...
Show moreLaser filamentation is a nonlinear process involving highenergy, ultrashort pulses that create narrow, nondiffracting structures over many times the Raleigh length. While many of the characteristics of filaments can vary greatly depending on the physical parameters used to create them, they share several defining features: a high intensity core, a lower intensity cladding of photons that serves as an energy reservoir to the core, and spectral broadening into a supercontinuum. While there have been many studies on the creation and control of multiple filaments from one laser pulse and a few studies on the interaction of two single filaments, many fundamental questions concerning the nature of this interaction still exist.This thesis seeks to explore the correlation between ultrashort pulses involving spatial separation, temporal delay, and relative degree of polarization using an interferometric approach. Evaluating the beam profiles and spectrum that result from varying those parameters.
Show less  Date Issued
 2016
 Identifier
 CFE0006531, ucf:51374
 Format
 Document (PDF)
 PURL
 http://purl.flvc.org/ucf/fd/CFE0006531
 Title
 Buidling Lax Integrable VariableCoefficient Generalizations to Integrable PDEs and Exact Solutions to Nonlinear PDEs.
 Creator

Russo, Matthew, Choudhury, Sudipto, Moore, Brian, Schober, Constance, Christodoulides, Demetrios, University of Central Florida
 Abstract / Description

This dissertation is composed of two parts. In Part I a technique based on extended Lax Pairs isfirst considered to derive variablecoefficient generalizations of various Laxintegrable NLPDE hierarchies recently introduced in the literature. It is demonstrated that the technique yields Lax or Sintegrable nonlinear partial differential equations (PDEs) with both time and spacedependent coefficients which are thus more general than almost all cases considered earlier via other methods such...
Show moreThis dissertation is composed of two parts. In Part I a technique based on extended Lax Pairs isfirst considered to derive variablecoefficient generalizations of various Laxintegrable NLPDE hierarchies recently introduced in the literature. It is demonstrated that the technique yields Lax or Sintegrable nonlinear partial differential equations (PDEs) with both time and spacedependent coefficients which are thus more general than almost all cases considered earlier via other methods such as the Painleve Test, Bell Polynomials, and various similarity methods. However, this technique, although operationally effective, has the significant disadvantage that, for any integrable system with spatiotemporally varying coefficients, one must 'guess' a generalization of the structure of the known Lax Pair for the corresponding system with constant coefficients. Motivated by the somewhat arbitrary nature of the above procedure, we present a generalization to the well known EstabrookWahlquist prolongation technique which provides a systematic procedure for the derivation of the Lax representation. In order to obtain a nontrivial Lax representation we must impose differential constraints on the variable coefficients present in the nlpde. The resulting constraints determine a class of equations which represent generalizations to a previously known integrable constant coefficient nlpde. We demonstrate the effectiveness of this technique by deriving variablecoefficient generalizations to the nonlinear Schrodinger (NLS) equation, derivative NLS equation, PTsymmetric NLS, fifthorder KdV, and three equations in the MKdV hierarchy. In Part II of this dissertation, we introduce three types of singular manifold methods which have been successfully used in the literature to derive exact solutions to many nonlinear PDEs extending over a wide range of applications. The singular manifold methods considered are: truncated Painleve analysis, Invariant Painleve analysis, and a generalized Hirota expansion method. We then consider the KdV and KPII equations as instructive examples before using each method to derive nontrivial solutions to a microstructure PDE and two generalized PochhammerChree equations.
Show less  Date Issued
 2016
 Identifier
 CFE0006173, ucf:51144
 Format
 Document (PDF)
 PURL
 http://purl.flvc.org/ucf/fd/CFE0006173
 Title
 NonDegenerate Two Photon Gain in Bulk Gallium Arsenide.
 Creator

Turnbull, Brendan, Hagan, David, Vanstryland, Eric, Christodoulides, Demetrios, University of Central Florida
 Abstract / Description

The purpose of this thesis is to investigate the nonlinear phenomena known as doublystimulated, nondegenerate twophoton emission (ND2PE) in Gallium Arsenide (GaAs). 2PE refers to the simultaneous emission of twophotons as electrons move from the conduction band in a direct gap semiconductor to the valence band. Following the same path for describing onephoton emission (1PE) we describe 2PE as a product of the irradiance, I, and the negative of the loss which in this case is twophoton...
Show moreThe purpose of this thesis is to investigate the nonlinear phenomena known as doublystimulated, nondegenerate twophoton emission (ND2PE) in Gallium Arsenide (GaAs). 2PE refers to the simultaneous emission of twophotons as electrons move from the conduction band in a direct gap semiconductor to the valence band. Following the same path for describing onephoton emission (1PE) we describe 2PE as a product of the irradiance, I, and the negative of the loss which in this case is twophoton absorption, ?_2, the negative coming from the population inversion. We attempt to observe 2PE by using a frequency nondegenerate pumpprobe experiment in which a third beam optically excites a 4 (&)#181;m thick GaAs sample. We use nondegenerate beams in hopes of utilizing the 3orders of magnitude enhancement seen in twophoton absorption (2PA) by going to extreme nondegeneracy (END) to enhance 2PE. GaAs is chosen due to the availability of the appropriate wavelengths, the maturity of the GaAs technology, its use in optoelectronic devices and its ability to be electrically pumped. During the experimental development we learn how to effectively etch and manipulate thin GaAs samples and model the transmission spectrum of these samples using thin film transmission matrices. We are able to match the measured transmission spectrum with the theoretical transmission spectrum. Here we etch the bulk GaAs left on the sample leaving only the 4 (&)#181;m thickness of molecular beam epitaxial grown GaAs plus additional layers of aluminum gallium arsenide (AlGaAs). These samples were grown for us by Professor Gregory Salamo of the University of Arkansas.Using the pumpprobe experiment on the 4 (&)#181;m GaAs sample, we measure the change of the 2PA due to the presence of optically excited carriers. The goal is to reduce the 2PA signal to zero and then invert the 2PA signal indicating an increase in transmission indicative of 2PE when the population is inverted. Our results show that we achieve a 45% reduction in the 2PA signal in a 4 ?m thick GaAs sample due to the excited carriers. Unfortunately, we currently cannot experimentally determine whether the reduction is strictly due to freecarrier absorption (FCA) of our pump or possibly due to a change in the twophoton absorption coefficient. We measure the transmission of various wavelengths around the bang gap of GaAs as a function of excitation wavelength and achieve a transmittance of ~80% which we attribute to possibly be one photon gain (1PG) at 880 nm. We also go to cryogenic temperatures to concentrate the carriers near the bottom of the conduction band and improve the theoretical gain coefficient for 2PE. Unfortunately, we do not observe a measurable change in 2PA with the addition of optically excited carriers. Along with FCA of our infrared pump we suspect that the difficulties in this first set of experiments are also a result or radiative recombination due to amplified spontaneous emission reducing our free carrier density along with the fact that 4 ?m is too thick for uniform excitation. We now have 1 ?m samples from Professor Gregory Salamo which we hope will give better and more definitive results.
Show less  Date Issued
 2013
 Identifier
 CFE0004762, ucf:49776
 Format
 Document (PDF)
 PURL
 http://purl.flvc.org/ucf/fd/CFE0004762
 Title
 Laser Filamentation Interaction with Materials for Spectroscopic Applications.
 Creator

Weidman, Matthew, Richardson, Martin, Schulzgen, Axel, Christodoulides, Demetrios, Sigman, Michael, University of Central Florida
 Abstract / Description

Laser filamentation is a nondiffracting propagation regime consisting of an intense core that is surrounded by an energy reservoir. For laser ablation based spectroscopy techniques such as Laser Induced Breakdown Spectroscopy (LIBS), laser filamentation enables the remote delivery of high power density laser radiation at long distances. This work has shown a quasiconstant filamentinduced mass ablation along a 35 m propagation distance. The mass ablated was sufficient for the application of...
Show moreLaser filamentation is a nondiffracting propagation regime consisting of an intense core that is surrounded by an energy reservoir. For laser ablation based spectroscopy techniques such as Laser Induced Breakdown Spectroscopy (LIBS), laser filamentation enables the remote delivery of high power density laser radiation at long distances. This work has shown a quasiconstant filamentinduced mass ablation along a 35 m propagation distance. The mass ablated was sufficient for the application of laser filamentation as a sampling tool for plasma based spectroscopy techniques. Within the scope of this study, singleshot ablation was compared with multishot ablation. The dependence of ablated mass on the number of pulses was observed to have a quasilinear dependence on the number of pulses, advantageous for applications such as spectroscopy. Sample metrology showed that both physical and optical material properties have significant effects on the filamentinduced ablation behavior. A relatively slow filamentinduced plasma expansion was observed, as compared with a focused beams. This suggests that less energy was transferred to the plasma during filamentinduced ablation. The effects of the filament core and the energy reservoir on the filamentinduced ablation and plasma formation were investigated. Goniometric measurements of the filamentinduced plasma, along with radiometric calculations, provided the number of emitted photons from a specific atomic transition and sample material.This work has advanced the understanding of the effects of single filaments on the ablation of solid materials and the understanding of filamentinduced plasma dynamics. It has laid the foundation for further quantitative studies of multiple filamentation. The implications of this work extend beyond spectroscopy and included any application of filamentation that involves the interaction with a solid material.
Show less  Date Issued
 2012
 Identifier
 CFE0004616, ucf:49940
 Format
 Document (PDF)
 PURL
 http://purl.flvc.org/ucf/fd/CFE0004616
 Title
 Multifunctional, Multimaterial Particle Fabrication Via an InFiber Fluid Instability.
 Creator

Kaufman, Joshua, Abouraddy, Ayman, Schoenfeld, Winston, Christodoulides, Demetrios, Seal, Sudipta, University of Central Florida
 Abstract / Description

Spherical micro and nanoparticles have found widespread use in many various applications from paint to cosmetics to medicine. Due to the multiplicity of desired particle material(s), structure, size range, and functionality, many approaches exist for generating such particles. Bottomup methods such as chemical synthesis have a high yield and work with a wide range of materials; however, these processes typically lead to large polydispersity and cannot produce structured particles. Topdown...
Show moreSpherical micro and nanoparticles have found widespread use in many various applications from paint to cosmetics to medicine. Due to the multiplicity of desired particle material(s), structure, size range, and functionality, many approaches exist for generating such particles. Bottomup methods such as chemical synthesis have a high yield and work with a wide range of materials; however, these processes typically lead to large polydispersity and cannot produce structured particles. Topdown approaches such as microfluidics overcome the polydispersity issue and may produce a few different structures in particles, but at lower rates and only at the microscale. A method that can efficiently produce uniformlysized, structured particles out of a variety of materials and at both the micro and nanoscales does not yet exist.Over the past few years, I have developed an infiber particle fabrication method that relies on a surface tensiondriven fluid instability, the PlateauRayleigh capillary instability (PRI). Thermal treatment of a multimaterial core/cladding fiber induces the PRI, causing the initially intact core to break up into a periodic array of uniformlysized spherical particles. During this time, I have demonstrated that this method can produce particles from both polymers and glasses, in a multiplicity of structures, and from diameters of over 1 mm down to 20 nm. Furthermore, by using a stackanddraw method, a high density of cores may be incorporated into a single fiber, making the infiber PRI approach a highly scalable process. Finally, I have shown that it is possible to add dopants to the particles to give them functionality. By structuring the particles, it is thus possible to fabricate multifunctional particles whose functionalities may be allocated arbitrarily throughout the volume of the particles.
Show less  Date Issued
 2014
 Identifier
 CFE0005357, ucf:50479
 Format
 Document (PDF)
 PURL
 http://purl.flvc.org/ucf/fd/CFE0005357