arXiv subjects

Mark G. Kuzyk

Publications and source records attributed to Mark G. Kuzyk.

At least 37 records · Page 2Linked to original sources

arXiv2016

Applying universal scaling laws to identify the best molecular design paradigms for second-order nonlinear optics

We apply scaling and the theory of the fundamental limits of the second-order molecular susceptibility to identify material classes with ultralarge nonlinear-optical response. Size effects are removed by normalizing all nonlinearities to get intrinsic values so that the scaling behavior of a series of molecular homologues can be determined. Several new figures of merit are proposed that quantify the desirable properties for molecules that can be designed by adding a sequence of repeat units, and used in the assessment of the data. Three molecular classes are found. They are characterized by sub-scaling, nominal scaling, or super-scaling. Super-scaling homologues most efficiently take advantage of increased size. We apply our approach to data currently available in the literature to identify the best super-scaling molecular paradigms with the aim of identifying desirable traits of new materials.

physics.optics↗

arXiv2015

Spectroscopic studies of the mechanism of reversible photodegradation of 1-substituted aminoanthraquinone-doped polymers

The mechanism of reversible photodegradation of 1-substituted aminoanthraquinones doped into poly(methyl methacrylate) and polystyrene is investigated. Time-dependent density functional theory is employed to predict the transition energies and corresponding oscillator strengths of the proposed reversibly- and irreversibly-damaged dye species. Ultraviolet-visible and Fourier transform infrared (FTIR) spectroscopy are used to characterize which species are present. FTIR spectroscopy indicates that both dye and polymer undergo reversible photodegradation when irradiated with a visible laser. These findings suggest that photodegradation of 1-substituted aminoanthraquinones doped in polymers originates from interactions between dyes and photoinduced thermally-degraded polymers, and the metastable product may recover or further degrade irreversibly.

physics.chem-ph↗

arXiv2015

Wavelength dependence of reversible photodegradation of disperse orange 11 dye-doped PMMA thin films

Using transmittance imaging microscopy we measure the wavelength dependence of reversible photodegradation in disperse orange 11 (DO11) dye-doped (poly)methyl-methacrylate (PMMA). The reversible and irreversible inverse quantum efficiencies (IQEs) are found to be constant over the spectral region investigated, with the average reversible IQE being $\overline{B}_α= 8.70 (\pm 0.38)\times 10^5$ and the average irreversible IQE being $\overline{B}_ε= 1.396 (\pm 0.031)\times 10^8$. The large difference between the IQEs is hypothesized to be due to the reversible decay channel being a direct decay mechanism of the dye, while the irreversible decay channel is an indirect mechanism, with the dye first absorbing light, then heating the surrounding environment causing polymer chain scission and cross linking. Additionally, the DO11/PMMA's irreversible IQE is found to be among the largest of those reported for organic dyes, implying that the system is highly photostable. We also find that the recovery rate is independent of wavelength, with a value of $\overlineβ=3.88(\pm 0.47) \times 10^{-3}$ min$^{-1}$. These results are consistent with the correlated chromophore domain model of reversible photodegradation.

physics.optics↗

arXiv2015

Phase disruption as a new design paradigm for optimizing the nonlinear-optical response

The intrinsic optical nonlinearities of quasi-one dimensional structures, including conjugated chain polymers and nanowires, are shown to be dramatically enhanced by the judicious placement of a side group or wire of sufficiently short length to create a large phase disruption in the dominant eigenfunctions along the main path of probability current. Phase disruption is proposed as a new general principle for the design of molecules, nanowires and any quasi-1D quantum system with large intrinsic response and does not require charge donors-acceptors at the ends.

physics.optics↗

arXiv2015

Optimization of eigenstates and spectra for quasi-linear nonlinear optical systems

Quasi-one-dimensional quantum structures with spectra scaling faster than the square of the eigenmode number (superscaling) can generate intrinsic, off-resonant optical nonlinearities near the fundamental physical limits, independent of the details of the potential energy along the structure. The scaling of spectra is determined by the topology of the structure, while the magnitudes of the transition moments are set by the geometry of the structure. This paper presents a comprehensive study of the geometrical optimization of superscaling quasi-one-dimensional structures and provides heuristics for designing molecules to maximize intrinsic response. A main result is that designers of conjugated structures should attach short side groups at least a third of the way along the bridge, not near its end as is conventionally done. A second result is that once a side group is properly placed, additional side groups do not further enhance the response.

physics.optics↗

arXiv2014

Optimum topology of quasi-one dimensional nonlinear optical quantum systems

We determine the optimum topology of quasi-one dimensional nonlinear optical structures using generalized quantum graph models. Quantum graphs are relational graphs endowed with a metric and a multiparticle Hamiltonian acting on the edges, and have a long application history in aromatic compounds, mesoscopic and artificial materials, and quantum chaos. Quantum graphs have recently emerged as models of quasi-one dimensional electron motion for simulating quantum-confined nonlinear optical systems. This paper derives the nonlinear optical properties of quantum graphs containing the basic star vertex and compares their responses across topological and geometrical classes. We show that such graphs have exactly the right topological properties to generate energy spectra required to achieve large, intrinsic optical nonlinearities. The graphs have the exquisite geometrical sensitivity required to tune wave function overlap in a way that optimizes the transition moments. We show that this class of graphs consistently produces intrinsic optical nonlinearities near the fundamental limits. We discuss the application of the models to the prediction and development of new nonlinear optical structures.

quant-ph↗

arXiv2014

A Heuristic Approach for Treating Pathologies of Truncated Sum Rules in Limit Theory of Nonlinear Susceptibilities

The Thomas Kuhn Reich sum rules and the sum-over-states (SOS) expression for the hyperpolarizabilities are truncated when calculating the fundamental limits of nonlinear susceptibilities. Truncation of the SOS expression can lead to an accurate approximation of the first and second hyperpolarizabilities due to energy denominators, which can make the truncated series converge to within 10% of the full series after only a few excited states are included in the sum. The terms in the sum rule series, however, are weighted by the state energies, so convergence of the series requires that the position matrix elements scale at most in inverse proportion to the square root of the energy. Even if the convergence condition is met, serious pathologies arise, including self inconsistent sum rules and equations that contradict reality. As a result, using the truncated sum rules alone leads to pathologies that make any rigorous calculations impossible, let alone yielding even good approximations. This paper discusses conditions under which pathologies can be swept under the rug and how the theory of limits, when properly culled and extrapolated using heuristic arguments, can lead to a semi-rigorous theory that successfully predicts the behavior of all known quantum systems, both when tested against exact calculations or measurements of broad classes of molecules.

physics.optics↗

arXiv2014

Mechanisms of the refractive index change in DO11/PMMA due to photodegradation

Using a white light interferometric microscope (WLIM) we measure the photodamage induced change in the complex index of refraction of disperse orange 11 (DO11) dye-doped (poly)methyl-methacrylate. We find that the change in the imaginary part of the refractive index is consistent with previous measurements of photodamage-induced absorbance change. Additionally, we find that the change in the real refractive index can be separated into a component due to damage to the dye molecules and a component due to irreversible damage to the polymer.

physics.optics↗

arXiv2013

The effect of pump depletion on reversible photodegradation

We model the effect of pump depletion on reversible photodegradation using the extended domain model[Anderson and Kuzyk, arXiv:1309.5176v1, 2013] and the Beer-Lambert law. We find that neglecting pump absorption in the analysis of the linear optical transmittance leads to an underestimate of the degree and rate of photodegradation. The model is used to accurately measure the molecular absorbance cross sections of the three species involved in photodegradation of disperse orange 11 dye in (poly)methyl-methacralate polymer (DO11/PMMA). Finally we find that the processing history of a dye-doped polymer affects reversible photodegradation, with polymerized monomer solutions of DO11 being more photostable than those prepared from solvent evaporated dye-polymer solutions.

physics.optics↗

arXiv2013

A White Light Interferometric Microscope for Measuring Dose-Dependent Reversible Photodegradation

We have developed a white light interferometric microscope (WLIM), which can spatially resolve the change in the complex index of refraction and apply it to study reversible photodegradation of 1,4-Diamino-9,10-anthraquinone doped into (poly)methyl methacrylate. The measured change in absorbance is consistent with standard spectrometer measurements. The refractive index of a pristine sample measured with the WLIM is also found to be consistent with the spectrum found by independent means (F. Yakuphanoglu and B. Senkal, Electrical conductivity, photoconductivity, and optical properties of poly(1,4 diaminoanthraquinone) organic semiconductor for optoelectronic applications, Polym. Adv. Technol. 19, 1193 to 1198 (2008)). We report on measurements of the change in refractive index due to photodegradation, which is found to be consistent with Embaye's two population model (N. Embaye et al., Mechanisms of reversible photodegradation in disperse orange 11 dye doped in PMMA polymer, J. Chem. Phys. 129, 054504 (2008)). We show that the WLIM can be used as a powerful tool to image the complex refractive index of a planar surface and to detect changes in a material's optical properties.

physics.optics↗

arXiv2013

Generalizing the correlated chromophore domain model of reversible photodegradation to include the effects of an applied electric field

All observations of photodegradation and self healing follow the predictions of the correlated chromophore domain model. [Ramini et.al. Polym. Chem., 2013, 4, 4948.] In the present work, we generalize the domain model to describe the effects of an electric field by including induced dipole interactions between molecules in a domain by means of a self-consistent field approach. This electric field correction is added to the statistical mechanical model to calculate the distribution of domains that are central to healing. Also included in the model are the dynamics due to the formation of an irreversibly damaged species. As in previous studies, the model with a one-dimensional domain best explains all experimental data of the population as a function of time, temperature, intensity, concentration, and now applied electric field. Though the nature of a domain is yet to be determined, the fact that only one-dimensional domain models are consistent with observations suggests that they might be made of correlated dye molecules along polymer chains.

physics.optics↗

arXiv2013

The influence of an electric field on photodegradation and self healing in disperse orange 11 dye-doped PMMA thin films

The influence of an applied electric field on reversible photodegradation of disperse orange 11 (DO11) doped into PMMA is measured using digital imaging and conductivity measurements. Correlations between optical imaging, which measures photodegradation and recovery, and photoconductivity enables an association to be made between the damaged fragments and their contribution to current, thus establishing that damaged fragments are charged species, or polarizable. Hence, the decay and recovery process should be controllable with the applications of an electric field. Indeed, we find that the dye polymer system is highly sensitive to an applied electric field, which drastically affects the decay and recovery dynamics. We demonstrate accelerated recovery when one field polarity is applied during burning, and the opposite polarity is applied during recovery. This work suggests that the damage threshold can be increased through electric field conditioning; and, the results are qualitatively consistent with the domain model of Ramini[3, 4]. The observed behavior will provide useful input into better understanding the nature of the domains in the domain model, making it possible to design more robust materials using common polymers and molecular dopants.

physics.optics↗

arXiv2013

Dressed quantum graphs with optical nonlinearities approaching the fundamental limit

We dress bare quantum graphs with finite delta function potentials and calculate optical nonlinearities that are found to match the fundamental limits set by potential optimization. We show that structures whose first hyperpolarizability is near the maximum are well described by only three states, the so-called three-level Ansatz, while structures with the largest second hyperpolarizability require four states. We analyze a very large set of configurations for graphs with quasi-quadratic energy spectra and show how they exhibit better response than bare graphs through exquisite optimization of the shape of the eigenfunctions enabled by the existence of the finite potentials. We also discover an exception to the universal scaling properties of the three-level model parameters and trace it to the observation that a greater number of levels are required to satisfy the sum rules even when the three-level Ansatz is satisfied and the first hyperpolarizability is at its maximum value, as specified by potential optimization. This exception in the universal scaling properties of nonlinear optical structures at the limit is traced to the discontinuity in the gradient of the eigenfunctions at the location of the delta potential. This is the first time that dressed quantum graphs have been devised and solved for their nonlinear response, and it is the first analytical model of a confined dynamic system with a simple potential energy that achieves the fundamental limits.

quant-ph↗

arXiv2013

The paradox of the many-state catastrophe of fundamental limits and the three-state conjecture

The calculation of the fundamental limits of nonlinear susceptibilities posits that when a quantum system has a nonlinear response at the fundamental limit, only three energy eigenstates contribute to the first and second hyperpolarizability. This is called the three-level ansatz and is the only unproven assumption in the theory of fundamental limits. All calculations that are based on direct solution of the Schrodinger equation yield intrinsic hyperpolarizabilities less than 0.709 and intrinsic second hyperpolarizabilities less than 0.6. In this work, we show that relaxing the three-level ansatz and allowing an arbitrary number of states to contribute leads to divergence of the optimized intrinsic hyperpolarizability in the limit of an infinite number of states - what we call the many-state catastrophe. This is not surprising given that the divergent systems are most likely not derivable from the Schrodinger equation, yet obey the sum rules. The sums rules are the second ingredient in limit theory, and apply also to systems with more general Hamiltonians. These exotic Hamiltonians may not model any real systems found in nature. Indeed, a class of transition moments and energies that come form the sum rules do not have a corresponding Hamiltonian that is expressible in differential form. In this work, we show that the three-level ansatz acts as a constraint that excludes many of the nonphysical Hamiltonians and prevents the intrinsic hyperpolarizability from diverging. We argue that this implies that the true fundamental limit is smaller than previously calculated. Since the three-level ansatz does not lead to the largest possible nonlinear response, contrary to its assertion, we propose the intriguing possibility that the three-level ansatz is true for any system that obeys the Schrodinger equation, yet this assertion may be unprovable.

physics.optics↗

arXiv2013

Scaling and universality in nonlinear optical quantum graphs containing star motifs

Quantum graphs have recently emerged as models of nonlinear optical, quantum confined systems with exquisite topological sensitivity and the potential for predicting structures with an intrinsic, off-resonance response approaching the fundamental limit. Loop topologies have modest responses, while bent wires have larger responses, even when the bent wire and loop geometries are identical. Topological enhancement of the nonlinear response of quantum graphs is even greater for star graphs, for which the first hyperpolarizability can exceed half the fundamental limit. In this paper, we investigate the nonlinear optical properties of quantum graphs with the star vertex topology, introduce motifs and develop new methods for computing the spectra of composite graphs. We show that this class of graphs consistently produces intrinsic optical nonlinearities near the limits predicted by potential optimization. All graphs of this type have universal behavior for the scaling of their spectra and transition moments as the nonlinearities approach the fundamental limit.

physics.optics↗

arXiv2013

The influence of geometry and topology of quantum graphs on their nonlinear-optical properties

We analyze the nonlinear optics of quasi one-dimensional quantum graphs and manipulate their topology and geometry to generate for the first time nonlinearities in a simple system approaching the fundamental limits of the first and second hyperpolarizabilities. Changes in geometry result in smooth variations of the nonlinearities. Topological changes between geometrically-similar systems cause profound changes in the nonlinear susceptibilities that include a discontinuity due to abrupt changes in the boundary conditions. This work may inform the design of new molecules or nano- scale structures for nonlinear optics and hints at the same universal behavior for quantum graph models in nonlinear optics that is observed in other systems.

physics.optics↗

arXiv2013

Experimental tests of the correlated chromophore domain model of self-healing in a dye-doped polymer

Temperature dependent photodegradation and recovery studies of Dipserse Orange 11 (DO11) dye dissolved in poly(methyl methacrylate) and polystyrene polymer hosts are used as a test of the recently proposed correlated chromophore domain model.[1] This model posits that dye molecules form domains or aggregates. The nature of aggregation or how it mediates self healing is not yet well understood. In this paper we present qualitative evidence that supports the hypothesis that the dye molecules undergo a change to a tautomer state with higher dipole moment and hydrogen bond with the amines and keto oxygens of the polymer. Groupings of such molecules in a polymer chain form what we call a domain, and interactions between molecules in a domain make them more robust to photodegradation and mediate self healing.

physics.chem-ph↗

arXiv2012

Geometry-Controlled Nonlinear Optical Response of Quantum Graphs

We study for the first time the effect of the geometry of quantum wire networks on their nonlinear optical properties and show that for some geometries, the first hyperpolarizability is largely enhanced and the second hyperpolarizability is always negative or zero. We use a one-electron model with tight transverse confinement. In the limit of infinite transverse confinement, the transverse wavefunctions drop out of the hyperpolarizabilities, but their residual effects are essential to include in the sum rules. The effects of geometry are manifested in the projections of the transition moments of each wire segment onto the 2-D lab frame. Numerical optimization of the geometry of a loop leads to hyperpolarizabilities that rival the best chromophores. We suggest that a combination of geometry and quantum-confinement effects can lead to systems with ultralarge nonlinear response.

physics.optics↗