arXiv subjects

J. E. Sipe

Publications and source records attributed to J. E. Sipe.

At least 73 records · Page 4Linked to original sources

arXiv2018

Jerk current: A novel bulk photovoltaic effect

We investigate a physical divergence of the third order polarization susceptibility representing a photoinduced current in biased crystalline insulators. This current grows quadratically with illumination time in the absence of momentum relaxation and saturation; we refer to it as the \textit{jerk current}. Two contributions to the current are identified. The first is a hydrodynamic acceleration of optically injected carriers by the static electric field, and the second is the change in the carrier injection rate in the presence of the static electric field. The jerk current can have a component perpendicular to the static field, a feature not captured by standard hydrodynamic descriptions of carriers in electric fields. We suggest an experiment to detect the jerk current and some of its interesting features.

cond-mat.mes-hall↗

arXiv2018

Nonlinear optics of graphene and other 2D materials in layered structures

We present a theoretical framework for nonlinear optics of graphene and other 2D materials in layered structures. We derive a key equation to find the effective electric field and the sheet current density in the 2D material for given incident light beams. Our approach takes into account the effect of the surrounding environment and characterizes its contribution as a structure factor. We apply our approach to two experimental setups, and discuss the structure factors for several nonlinear optical processes including second harmonic generation, third harmonic generation, and parametric frequency conversion. Our systematic study gives a strict extraction method for the nonlinear coefficients, and provides new insights in how layered structures influence the nonlinear signal observed from 2D materials.

physics.optics↗

arXiv2018

Scalable squeezed light source for continuous variable quantum sampling

We propose a novel squeezed light source capable of meeting the stringent requirements of continuous variable quantum sampling. Using the effective $χ_2$ interaction induced by a strong driving beam in the presence of the $χ_3$ response in an integrated microresonator, our device is compatible with established nanophotonic fabrication platforms. With typical realistic parameters, squeezed states with a mean photon number of 10 or higher can be generated in a single consistent temporal mode at repetition rates in excess of 100MHz. Over 15dB of squeezing is achievable in existing ultra-low loss platforms.

quant-ph↗

arXiv2018

A full vectorial mapping of nanophotonic light fields

Light is a union of electric and magnetic fields, and nowhere is their complex relationship more evident than in the near fields of nanophotonic structures. There, complicated electric and magnetic fields varying over subwavelength scales are generally present, leading to photonic phenomena such as extraordinary optical momentum, super-chiral fields, and a complex spatial evolution of optical singularities. An understanding of such phenomena requires nanoscale measurements of the complete optical field vector. However, while it was recently demonstrated that near-field scanning optical microscopy is sensitive to the complete electromagnetic field, a separation of the different components required a priori knowledge of the sample. Here we introduce a robust algorithm that can disentangle all six electric and magnetic field components from a single near-field measurement, without any numerical modeling of the structure. As examples, we unravel the fields of two prototypical nanophotonic structures: a photonic crystal waveguide and a plasmonic nanowire. These results pave the way to new studies of complex photonic phenomena at the nanoscale, and for the design of structures that optimize the optical behavior that they exhibit.

physics.optics↗

arXiv2018

The optical properties of dibenzoterrylene

Dibenzoterrylene (DBT) has garnered interest as a potential single photon source (SPS). To have a better grasp of any possible limitations of using DBT for this application, a better understanding of its optical properties is needed. We use a configuration interaction (CI) strategy to calculate the many body wavefunctions of DBT, and we use these wavefunctions to calculate its optical properties. We calculate the linear absorption spectrum and the spatial distributions of electrons involved in several bright transitions. We also calculate the two-photon absorption spectrum of DBT and show that there are several excited states that are bright due to two-photon absorption. Except at high photon energies, we predict that there are no competing optical processes regarding the use of DBT as a SPS. Our calculations provide details of the optical properties of DBT that are interesting in general, and useful for considering optical applications of DBT.

cond-mat.mtrl-sci↗

arXiv2017

Generation of path-encoded Greenberger-Horne-Zeilinger states

We study the generation of Greenberger-Horne-Zeilinger (GHZ) states of three path-encoded photons. Inspired by the seminal work of Bouwmeester et al. [1] on polarization-entangled GHZ states, we find a corresponding path representation for the photon states of an optical circuit, identify the elements required for the state generation, and propose a possible implementation of our strategy. Besides the practical advantage of employing an integrated system that can be fabricated with proven lithographic techniques, our example suggests that it is possible to enhance the generation efficiency by using microring resonators.

quant-ph↗

arXiv2017

Gate tunable third-order nonlinear optical response of massless Dirac fermions in graphene

Materials with massless Dirac fermions can possess exceptionally strong and widely tunable optical nonlinearities. Experiments on graphene monolayer have indeed found very large third-order nonlinear responses, but the reported variation of the nonlinear optical coefficient by orders of magnitude is not yet understood. A large part of the difficulty is the lack of information on how doping or chemical potential affects the different nonlinear optical processes. Here we report the first experimental study, in corroboration with theory, on third harmonic generation (THG) and four-wave mixing (FWM) in graphene that has its chemical potential tuned by ion-gel gating. THG was seen to have enhanced by ~30 times when pristine graphene was heavily doped, while difference-frequency FWM appeared just the opposite. The latter was found to have a strong divergence toward degenerate FWM in undoped graphene, leading to a giant third-order nonlinearity. These truly amazing characteristics of graphene come from the possibility to gate-control the chemical potential, which selectively switches on and off one- and multi-photon resonant transitions that coherently contribute to the optical nonlinearity, and therefore can be utilized to develop graphene-based nonlinear optoelectronic devices.

cond-mat.mes-hall↗

arXiv2017

The role of impurities on the optical properties of rectangular graphene flakes

We study rectangular graphene flakes using mean field states as the basis for a configuration interaction calculation, which allows us to analyze the low lying electronic excited states including electron correlations beyond the mean field level. We find that the lowest energy transition is polarized along the long axis of the flake, but the charge distributions involved in these transitions are invariably localized on the zigzag edges. We also investigate the impact of both short and long range impurity potentials on the optical properties of these systems. We predict that even a weak impurity localized at a zigzag edge of the flake can have a significant -- and often dramatic -- effect on its optical properties. This is in contrast to impurities localized at armchair edges or central regions of the flake, for which we predict almost no change to the optical properties of the flake even with strong impurity potentials.

cond-mat.mtrl-sci↗

arXiv2017

Coherent control of current injection in zigzag graphene nanoribbons

We present Fermi's golden rule calculations of the optical carrier injection and the coherent control of current injection in graphene nanoribbons with zigzag geometry, using an envelope function approach. This system possesses strongly localized states (flat bands) with a large joint density of states at low photon energies; for ribbons with widths above a few tens of nanometers, this system also posses large number of (non-flat) states with maxima and minima close to the Fermi level. Consequently, even with small dopings the occupation of these localized states can be significantly altered. In this work, we calculate the relevant quantities for coherent control at different chemical potentials, showing the sensitivity of this system to the occupation of the edge states. We consider coherent control scenarios arising from the interference of one-photon absorption at $2\hbarω$ with two-photon absorption at $\hbarω$, and those arising from the interference of one-photon absorption at $\hbarω$ with stimulated electronic Raman scattering (virtual absorption at $2\hbarω$ followed by emission at $\hbarω$). Although at large photon energies these processes follow an energy-dependence similar to that of 2D graphene, the zigzag nanoribbons exhibit a richer structure at low photon energies, arising from divergences of the joint density of states and from resonant absorption processes, which can be strongly modified by doping. As a figure of merit for the injected carrier currents, we calculate the resulting swarm velocities. Finally, we provide estimates for the limits of validity of our model.

cond-mat.mtrl-sci↗

arXiv2017

An effective model for the electronic and optical properties of stanene

The existence of several 2D materials with heavy atoms in their composition has been recently demonstrated. The electronic and optical properties of these materials can be accurately computed with numerically intensive density functional theory methods. However, it is desirable to have simple effective models that can accurately describe these properties at low energies. Here we present an effective model for stanene that is reliable for electronic and optical properties for photon energies up to 1.1 eV. For this material, we find that a quadratic model with respect to the lattice momentum is the best suited for calculations based on the bandstructure, even with respect to band warping. We also find that splitting the two spin-z subsectors is a good approximation, which indicates that the lattice buckling can be neglected in calculations based on the bandstructure. We illustrate the applicability of the model by computing the linear optical injection rates of carrier and spin densities in stanene. Our calculations indicate that an incident circularly polarized optical field only excites electrons with spin that matches its helicity.

cond-mat.mtrl-sci↗

arXiv2017

A Green function method to study thin diffraction gratings

The anomalous features in diffraction patterns first observed by Wood over a century ago have been the subject of many investigations, both experimental and theoretical. The sharp, narrow structures - and the large resonances with which they are sometimes associated - arise in numerous studies in optics and photonics. In this paper we present an analytical method to study diffracted fields of optically thin gratings that highlights the nonanalyticities associated with the anomalies. Using this approach we can immediately derive diffracted fields for any polarization in a compact notation. While our equations are approximate, they fully respect energy conservation in the electromagnetic field, and describe the large exchanges of energy between incident and diffracted fields that can arise even for thin gratings.

physics.optics↗

arXiv2017

Why you should not use the electric field to quantize in nonlinear optics

We show that using the electric field as a quantization variable in nonlinear optics leads to incorrect expressions for the squeezing parameters in spontaneous parametric down-conversion and conversion rates in frequency conversion. This observation is related to the fact that if the electric field is written as a linear combination of bosonic creation and annihilation operators one cannot satisfy Maxwell's equations in a nonlinear dielectric.

quant-ph↗

arXiv2017

Thermal Light as a Mixture of Sets of Pulses: the Quasi-1D Example

The relationship between thermal light and coherent pulses is of fundamental and practical interest. We now know that thermal light cannot be represented as a statistical mixture of single pulses. In this paper we ask whether or not thermal light can be represented as a statistical mixture of sets of pulses. We consider thermal light in a one-dimensional wave-guide, and find a convex decomposition into products of orthonormal coherent states of localized, nonmonochromatic modes.

quant-ph↗

arXiv2017

Surface - lattice resonances in 2d arrays of spheres: multipolar interactions and a mode analysis

We present a multipolar model of surface - lattice resonances (SLRs) in 2d arrays of spheres including the electric dipole, magnetic dipole, and electric quadrupole moments of the spheres. We identify SLRs of dipolar and multipolar character, show the importance of non-resonant multipoles in their description, and discuss the sensitivity of SLRs to illumination conditions. We link SLRs to an excitation of modes supported by the array, and we propose a simplified model of the mode dispersion relations that explains the sensitivity of SLRs and the band gap in mode dispersion found at low frequencies. Finally we discuss the resonant features associated with a direct coupling to a mode which can occur in addition to the diffractive coupling signalled by SLRs.

physics.optics↗

arXiv2017

Truly unentangled photon pairs without spectral filtering

We demonstrate that an integrated silicon microring resonator is capable of efficiently producing photon pairs that are completely unentangled; such pairs are a key component of heralded single photon sources. A dual-channel interferometric coupling scheme can be used to independently tune the quality factors associated with the pump and signal and idler modes, yielding a biphoton wavefunction with Schmidt number arbitrarily close to unity. This will permit the generation of heralded single photon states with unit purity.

physics.optics↗

arXiv2017

Second order optical nonlinearity of graphene due to electric quadrupole and magnetic dipole effects

We present a practical scheme to separate the contributions of the electric quadrupole-like and the magnetic dipole-like effects to the forbidden second order optical nonlinear response of graphene, and give analytic expressions for the second order op- tical conductivities, calculated from the independent particle approximation, with relaxation described in a phenomenological way. We predict strong second order nonlinear effects, including second harmonic generation, photon drag, and difference fre- quency generation. We discuss in detail the controllability of these effects by tuning the chemical potential, taking advantage of the dominant role played by interband optical transitions in the response.

cond-mat.mtrl-sci↗

arXiv2017

Optical theorem for 2d magnetoelectric quadrupolar arrays

We present all the periodic Green function dyadics that enter a description of a 2d array of emitters at the level that includes the electric dipole, magnetic dipole and electric quadrupole moment of each emitter. We find a concise analytic form for the radiative contributions to the periodic Green function dyadics that give rise to radiation reaction fields, and we give the non-radiative contributions that do not affect energy balance in the form of rapidly converging series. Finally, we present an approximation scheme for evaluating periodic Green function dyadics at long wavelengths that rigorously respects energy conservation. The scheme extends the range of validity of the usual static approximation by the inclusion of a simple dynamic correction.

physics.optics↗

arXiv2016

Strong and Anisotropic Third Harmonic Generation in Monolayer and Multilayer ReS$_2$

We report observation of strong and anisotropic third harmonic generation (THG) in monolayer and multilayer ReS$_2$. The third-order nonlinear optical susceptibility of monolayer ReS$_2$, $\left| χ^{(3)} \right|$ is on the order of $10^{-18} $ m$^2$/V$^2$, which is about one order of magnitude higher than reported results for hexagonal-lattice transition metal dichalcogenides such as MoS$_2$. A similar magnitude for the third-order nonlinear optical susceptibility was also obtained for a multilayer sample. The intensity of the THG field was found to be dependent on the direction of the incident light polarization for both monolayer and multilayer samples. A point group symmetry analysis shows that such anisotropy is not expected from a perfect $1T$ lattice, and must arise from the distortions in the ReS$_2$ lattice. Our results show that THG measurements can be used to characterize lattice distortions of two-dimensional materials, and that lattice distortions are important for the nonlinear optical properties of such materials.

cond-mat.mtrl-sci↗