Abstracts

• Timothy J. Atherton, Tufts University:

  Hyperpolarizabilities of Exotic Potentials

  All known Hamiltonians appear to obey fundamental limits on the hyperpolarizabilities. Potentials that give a nonlinear response close to these limits have been found through numerical searches, and give some insight into molecular design. A long standing question is whether more exotic potentials can come closer, or even violate, these limits. This work considers non-Hermitian but PT-symmetric potentials as candidates and examines their nonlinear response. While these Hamiltonians are pathological, they provide important insights into the nature of the limits.

• Ivan Biaggio, Lehigh University:

  Spectroscopy of the Third-Order Polarizability via Degenerate Four-Wave Mixing, and the Exceptional Two-Photon Absorption of Some Small Molecules

  The first part of the talk presents a method for semi-automatic measurement of the complex-valued spectrum of the third-order polarizability using degenerate four-wave mixing. The second part of the talk discusses the nonlinear optical spectrum of some donor-acceptor substituted small molecules and their large two-photon absorption to the lowest excited state when compared to the fundamental limit, the size of the molecules, and established two-photon absorbers like AF-50.

• Chris Burke, Tufts University:

  Searching for potentials which optimize the second hyperpolarizability with multiple non-interacting electrons

  The existence of fundamental limits on the intrinsic molecular second hyperpolarizability has motivated a body of research studying the features of molecular potentials which are important for approaching this limit. In one previous study, a molecule was modeled using a one-dimensional piecewise-linear potential, and the second hyperpolarizability was optimized with respect to the shape of the potential, revealing important features. Here I present an extension of this work to potentials containing multiple non-interacting elections.

• Jacquiline M. Cole, Cambridge University:

  Classifying local pi-conjugation effects in organic nonlinear optical materials

  A new method is proposed by which local pi-conjugation effects can be indexed beyond immediate bond neighbors. Thus, the influence of intramolecular charge transfer is fully characterized, surpassing the pI-contribution confines of bond length alternation theory. Case studies of representative organic NLO materials will demonstrate the use of the methodology, and its ability to identify local hotspots of ICT structure. The talk concludes with prospecting the use of this classification toward high throughout materials discovery of new NLO chromophores.

• Sheng Ting Hung, University of Leuven:

  Molecular symmetry as a constraint preventing the many-state catastrophe of fundamental limits of the first hyperpolarizability

  The calculation of the fundamental limits of hyperpolarizabilities posits that when a quantum system is at the fundamental limit, only three energy states contribute to hyperpolarizabilities. Allowing more states to contribute leads to divergence of the intrinsic hyperpolarizability at the limit of an infinite number of states. We discuss the effects of degeneracy and symmetry on the fundamental limits of the first hyperpolarizability.

• Mark G. Kuzyk, Washington State University:

  Fundamental Limits of Device Figures of Merit

  An electro-optic modulator requires a large second-order nonlinear susceptibility; but, large nonlinearity is often accompanied by larger optical loss, potentially rendering a material unsuitable. This work describes how device figures-of-merit, which account for this type of interdependence, can be optimized from first principles.

• Alexander Lou, Northwestern University:

  Exceptional Nonlinear Optical Response in Twisted Chromophores

  Steric constraints in twisted intramolecular charge transfer (TICT) chromophores dictate a unique electronic structure, which gives rise to very large second order NLO response that approaches the fundamental limit. Both the synthesis and theoretical description of TICT chromophores has proven to be a challenging task. We have used experimental and computational results to describe the origin of large NLO response and to guide the design of several generations of TICT chromophores.

• Rick Lytel, Washington State University & First Degree Innovation:

  Optimization of Optical Nonlinearities Using Quantum Graph Models

  Quantum graph models are applied to nonlinear optics to show how a single, short side-chain, placed judiciously on a linear structure, can generate a large phase disruption of critical eigenfunctions along the structure, producing large changes in the transition moments which leads to large intrinsic nonlinearities

• Sean Mossman, Washington State University:

  The Role of the Continuum in Static Nonlinear Optics

  Nonlinear optical responses of molecules are typically done as a sum over a finite set of states. We show that the continuum plays a significant role in limiting the nonlinear response for singular potentials and discuss methods for including this effect.

• Javier Perez-Moreno, Skidmore College:

  Beyond simple scaling: Finding the best molecular paradigms for nonlinear optics

  Simple scaling must be taken into account in order to eliminate the size effects when we evaluate the efficiency of a molecule with nonlinear optical properties. This allows us to classify the performance of molecular classes in three categories: sub-scaling, nominal scaling, or super-scaling; and to determine the best molecular paradigms that can be scaled up through the synthesis of larger homologues.

• Joseph Perry, Georgia Tech:

  Processable organic materials with large figures-of-merit for all-optical signal processing

  Molecular design strategies to achieve nonlinear optical properties suitable for all-optical signal processing based on substitution of polymethines with rigid, bulky groups will be discussed. Polymethines exhibit a negative real part of the third order susceptibility that can be useful in the compensation of self phase modulation in optical fibers.

• Rolfe G. Petschek, Case Western Reserve University:

  Quantum Bounds on Hyperpolarizability for Multiple Electrons and Constraints on FerroElectricity

  I will present two lines of research.Ê First, I will discuss numerical experiments to find upper limits on the second order hyperpolarizability of non-interacting electrons confined to move along a line.Ê Electrons with very strong attractive interactions can achieve a hyperpolarizability about 30% below the proven quantum limit.Ê Non-interacting electrons may provide more realistic limits on "real" electrons which repel each other.Ê Second, I will discuss how new ferromagnetic fluids with (only) orientational order suggest strong constraints the possibility of making fluids that have (only) orientational ferroelectric suggested order for practical non-linear optical materials.

• Meghana Rawal, Nanoviricides, Inc.:

  Breaking Linear Conjugation in Second Order NLO Chromophores, Allowed or Disallowed?

  Organic second order non-linear optical chromophores typically consist of linearly conjugated donor/acceptor architecture. Theoretically, the donor and acceptor must be connected electronically to allow for large transition dipole moments and obtain molecules with large nonlinearities. This work discusses cross-conjugated bridge structures that while breaking true conjugation, still allow for hyperpolarizabilities comparable to linearly conjugated systems.

• Kenneth D. Singer, Case Western Reserve University:

  Cavity Effects in Organic Molecular Materials

  The coupling between cavity modes and excitons is an area of extensive research. Ultrastrong coupling has recently been observed in organic molecular materials with known large optical nonlinearities. We describe our recent results related to coupling between pairs coupled cavities in the ultrastrong limit, reflecting the breakdown of the rotating wave approximation. In addition, we show how strong material-cavity coupling can be applied to the design of efficient photovoltaic devices. Prospects for cavity QED in organic nonlinear optics will be described.

• Volker Sorger, George Washington University:

  Nanophotonic scaling laws & light-matter enhanced optoelectronic devices

  Over the last decade, on-chip integrated opto-electronic circuits such as the silicon and III-V platforms showed great potential for big-data bandwidth applications. However, while the photonic device performance is steadily increasing, the inherently weak light-matter-interactions sets fundamental limits to critical performance metrics such as footprint (i.e. integration density), speed (i.e. bandwidth), and drive power. The objective of this talk is to show ultimate device limitations while highlighting recent advances and solutions to overcome them for two key devices at the nanoscale; a case will be made on EO modulators.

• Eric Van Stryland, CREOL, The College of Optics and Photonics:

  Nondegenerate Nonlinearities and 3-level models

  Two-photon absorption, 2PA, in semiconductors is enhanced by orders of magnitude due to intermediate-state resonance enhancement, ISRE. Much smaller enhancement is seen in organic dyes, but quasi 3-level models work well to describe the 2PA spectra and nonlinear refractive dispersion.