This PDF file contains the front matter associated with SPIE Proceedings Volume 9162, including the Title Page, Copyright information, Table of Contents, Authors, Introduction, and Conference Committee listing.

We describe a quasi-normal mode (QNM) theory of light-matter interactions in nanoplasmonics. We first use a QNM expansion technique to obtain the photon Green function and compute the enhanced spontaneous emission rate from a quantum dot as a function of frequency; these QNM calculations show excellent agreement with full dipole finite-difference time-domain simulations and we also obtain a rigorous definition of the generalized effective mode volume for the localized surface plasmon mode. Using the examples of a single gold nanorod and a gold dimer of identical nanorods, we demonstrate why the Purcell factor is not the correct metric for describing enhancement spontaneous emission for dipole emitters away from the field antinode position, and we also show how the dimer structure can be used as an efficient single photon source. Exploiting a quantum master equation approach in combination with the QNM Green function theory, we shown examples of the Mollow triplet spectrum from a field-excited quantum dot in the vicinity of the gold nanorod and we discuss how to include Ohmic losses and quasistatic coupling in a fully analytic way. Finally, we show how to exploit the QNM theory to solve the “local field problem” for a finite-size photon emitter embedded inside a lossy metal nanorod.

We have developed a self-consistent electromagnetic theory of the link between light-matter interactions and optical resonances in three-dimensional nanoresonators. The theory that relies on the concept of quasinormal modes with complex frequencies is capable of accurately handling any photonic or plasmonic resonator with strong radiation leakage, absorption and material dispersion. We first provide a simple iterative method to calculate and normalize quasinormal modes that may be implemented with any numerical tool. We then use the modal formalism to derive a modal expansion of the imaginary part of the Green tensor. This modal representation provides a powerful tool to calculate and understand light-matter interactions in complex photonic or plasmonic systems. In particular, we analyze the degree of spatial coherence in nanoantennas made of metallic nanorods.

Generating strong interactions between single quanta of light and matter is central to quantum information science, and a key component of quantum computers and long-distance quantum networks. In quantum information processing, these interactions are required to create elementary logic operations (quantum gates) between stationary matter quantum bits (qubits) and photonic qubits that can be transmitted over long distances. Efficient quantum gates between photonic and matter qubits are a crucial enabler for a broad range of applications that include robust quantum networks, nondestructive quantum measurements, and strong photon-photon interactions. So far these qubit-photon gates have been achieved using single atoms and at microwave frequencies in circuit QED systems. Their implementation with solidstate quantum emitters, however, has remained a difficult challenge. We demonstrate that the qubit state of a photon can be controlled by a single solid-state qubit composed of a quantum dot (QD) strongly coupled to an optical nanocavity. We show that the QD acts as a coherently controllable qubit system that conditionally flips the polarization of a photon reflected from the cavity mode on picosecond timescales. This operation implements a controlled NOT (cNOT) logic gate between the QD and the incident photon, which is a universal quantum operation that can serve as a general light-matter interface for remote entanglements and quantum computations. Our results represent an important step towards an all solid-state implementation of quantum networks and quantum computers, and provide a versatile approach for controlling and probing interactions between a photon and a single quantum emitter on ultra-fast timescales.

We demonstrate a novel process for selective binding of single semiconductor core-shell quantum dots (QDs) to transparent all-dielectric (glass) substrates with nanoscale resolution. This is accomplished by defining a mask via electron-beam lithography (EBL) followed by functionalization of only the exposed areas of the substrate with a heterobifunctional linker, while applying a binding inhibitor to all other areas. Single QD blinking is clearly observed for several QD functionalized sites. Our approach is compatible with standard two-step EBL nanofabrication schemes and it does not rely on the presence of metals, making it suitable for coupling QDs to all-dielectric nanoresonators.

Hyperuniform disordered solids are a new class of designer photonic materials with large isotropic band gaps comparable to those found in photonic crystals. The hyperuniform disordered materials are statistically isotropic and possess a controllable constrained randomness. We have employed their unique properties to introduce novel architectures for optical cavities that achieve an ultimate isotropic confinement of radiation, and waveguides with arbitrary bending angles. Our experiments demonstrate low-loss waveguiding in submicron scale Si-based hyperuniform structures operating at infrared wavelengths and open the way for the realization of highly flexible, disorder-insensitive optical micro-circuit platforms.

Photonic crystals may support the propagation of surface waves, provided that they are properly terminated. An additional grating like-layer may facilitate the coupling of the surface waves to outgoing propagating waves leading to enhanced transmission and directionality of the beam. This work investigates and demonstrates how the proper design of the grating layer provides control over the beam shape and emission angle. We also demonstrate both experimentally and theoretically, that a single bilayer dielectric structure allows for the collimation and enhanced transmission of a Gaussian incident beam, while a system of multiple cascading bilayers can sustain the beam for large propagation distances.

We provide a brief report on our recent work on dielectric and metallic colloidal nanosuspensions with negative polarizability where we observed robust propagation of self-trapped light over a long distance. Our results open up new opportunities in developing soft-matter systems with tunable optical nonlinearities.

Up-conversion (UC) generally refers to any nonlinear optical process that facilitates the conversion of low energy radiation into higher energy emission. Typically achieved in materials incorporating rare-earth ions, exploiting their rich density of available electronic state transitions, non-parametric UC systems are often placed in categories including excited state absorption, photon avalanche and energy transfer. The latter, energy transfer up-conversion achieves nonlinear excitation of chromophores as a consequence of non-radiative resonance energy transfer (RET) events, through coupling with neighboring sensitizer ions. Being susceptible to the local electromagnetic environment, the mechanism of RET is known to be influenced by surrounding matter, underscoring the importance of similar channels for media control within UC materials. By developing the principles of two-center UC, a fully quantized representation of local electronic structure and electrodynamics is extended through the introduction of a mediator species – a vicinal, nonabsorbing chromophore. This theory underpins a new application of the medium-modified energy transfer theory to three-center UC. The present report then considers an alternative up-conversion mechanism in which pairs of identical donors transfer energy to the acceptor species, promoting two-photon excitation and shorter wavelength emission. The mechanism for this three-center system proves to be significantly influenced by a fourth, essentially passive chromophore. Investigations of the influence of this mediator, in improving or inhibiting RET, determine parameters that can be modified to improve the UC efficiency. The results provide insight into factors that might assist the optimization of laser active media, and the improvement of optical characteristics in designer materials.

Nanophotonic techniques can enable numerous novel and exciting phenomena. However, in order to make use of these opportunities for many applications of interest (e.g. energy, or displays), one has to have the ability to implement nanophotonic structures over large scales. In this talk, I will present some of our recent theoretical and experimental progress in exploring these opportunities.

I will discuss the optical properties and possible applications of graphene in photonics and plasmonics. I will review the basics of the single particle and collective excitations of graphene, discuss the mechanisms of photocurrent generation in graphene and the design and characteristics of graphene-based photodetectors. I will show that the coupling of light to localized graphene plasmons provides an excellent way of enhancing the strength of graphene-light interaction. Plasmon excitations in graphene micro- and nano-structures and their use in graphene devices in the infrared and terahertz ranges of the EM spectrum will be discussed. The interactions of graphene plasmons with intrinsic graphene and substrate phonons and their implications will also be analyzed.

We review the optical properties of carbon nanotubes (CNTs) and graphene and describe how those properties have been used for the implementation of various nonlinear fiber optic applications. Early studies on the optical properties of CNTs in the late 90s revealed that these materials exhibit high third order susceptibility and a broadband saturable absorption with a sub-picosecond response time. Recent discovery of similar nonlinear optical properties in graphene attracts much attention in this field. Such ultrafast, highly nonlinear optical response means that they can be employed for noise suppression and for the mode-locking of fiber lasers, and in addition, their high third order nonlinearity holds great promise for the implementation of various other nonlinear fiber optic devices such as wavelength converters based on four wave mixing. In this paper, we will discuss the various methods that have been considered thus far for the integration of CNTs and graphene in optical systems and highlight the advantages and limitations of using the saturable absorption of CNTs and graphene for the passive mode-locking of fiber lasers, and the current status of CNT and graphene saturable absorbers in the state of art fiber laser technologies.

This presentation is concerned with nanophotonic structures, especially with arrays of asymmetric split-ring resonator (ASRR) structures, that may be exploited in a variety of sensing applications. These applications include bio-medical sensing, organic material sensing more generally - and environmental sensing. Specific attention has been paid to the identification of molecules of interest via their bond-resonance spectral signatures.

Photonic crystals are widely known for their light-trapping capabilities. This is often associated with the occurrence of a photonic band gap or other suppression in the electromagnetic density of states [1-3]. This enables guiding of light on an optical micro-chip and unprecedented forms of strong-coupling between light and matter. In the past, practical applications of these effects have focused on information technology. More recently, an important opportunity has emerged in the area of energy technology. This arises from lighttrapping in the higher bands of a photonic crystal, where the electromagnetic density of states is enhanced rather than suppressed [4]. This enables unprecedented strong absorption of sunlight in materials with weak intrinsic absorption [4-15]. We apply this to solar cells based in silicon [5-9, 11, 13, 14], GaAs [12], dye-sensitized TiO2 [10] and low-bandgap polymers [15].

In this communication, we present the potentialities offered by 2D photonic crystals to trap and absorb photons in thin silicon layers. We will specifically focus on the impact of the photonic crystal unit cells symmetry, and the possibility to increase light absorption and generated photocurrent using multi-periodic and pseudo-disordered photonic nanostructures.

Multi-dielectric thin films are usually studied as waveguiding structures with low absorption effect because of the low imaginary part of the refractive index. However, when properly designed, we demonstrated that multi-dielectric stacks can sustain large optical fields. We briefly present here our design method leading the fabrication of such multi-dielectric stacks, which can be optimized for arbitrary wavelengths, indices or polarizations. We then report on our experimental character-ization in near and far field, using a photon scanning tunneling microscope and scattering optical setup, respectively. This investigation may find applications for ultra-sensitive optical sensors or integrated light sources to mention a few.

Solar cell science and technology is changing. New efficiency records have been set. Alta Devices has reached 28.8% efficiency in a thin film single-junction cell at 1-sun, and 30.8% efficiency in a thin-film dual junction cell at 1-sun. Counter-intuitively, efficient external fluorescence is a necessity for approaching the ultimate limits. A great Solar Cell also needs to be a great Light Emitting Diode. Why would a solar cell, intended to absorb light, benefit from emitting light? Although it is tempting to equate light emission with loss, paradoxically, light emission actually improves the open-circuit voltage, and the efficiency. The single-crystal thin film technology that achieved these high efficiencies, is created by epitaxial liftoff, and can be produced at cost well below the other less efficient thin film solar technologies. The path is now open to a 30% efficient photovoltaic technology that can be produced at low cost.

In this presentation, it will be shown that the plasmonic absorption of a graphene sheet can be enhanced and perturbed in controllable ways by controlling the thickness and permittivity of the supporting substrate. We will show the results of recent experiments where 25% absorption is achieved in the plasmonic modes of a graphene sheet by carefully selecting the properties of an underlying silicon nitride substrate. We also demonstrate how additional absorption pathways can be created by modifying the surrounding dielectric environment to have optical resonances that can couple to the graphene plasmons.

The resonant plasmonic properties of metallic nanostructures depend strongly on charge carrier density. Stemming from this dependence, we report a theoretical framework and provided experimental evidence for a ‘plasmoelectric effect’, a newly described mechanism for generating electrochemical potentials in plasmonic nanostructures. Systematic electrical and optical characterization of Au nano-hole arrays shows that the magnitude and sign of the plasmoelectric potential depends on the frequency difference between the plasmon resonance and incident narrowband radiation. Our findings guide the development of solid-state power conversion devices based on the plasmoelectric effect, as our samples generate electrochemical potentials 1000x larger than comparable thermocouples.

Absorption induced transparency consists in a transmission peak observed in holey metal films when a molecular dye is deposited on top of it [Hutchison et al., Angew. Chem. Int. Ed. 50, 2085 (2011)]. This transmission feature appears unexpectedly close to one of the absorption energies of the molecules, hence its name. Tentative explanations pointed to strong-coupling interactions between plasmons and molecules. However, we recently demonstrated the actual mechanism behind, which takes place through a strong modification of the propagation constant of holes. We also found that absorption induced transparency occurs in single holes and it is not restricted to the optical range.

Bulk thermal emittance sources possess incoherent, isotropic, and broadband radiation spectra that vary from material to material. However, these radiation spectra can be drastically altered by modifying the geometry of the structures. In particular, several approaches have been proposed to achieve narrowband, highly directional thermal emittance based on photonic crystals, gratings, textured metal surfaces, metamaterials, and shock waves propagating through a crystal. Here we present optimized aperiodic structures for use as narrowband, highly directional thermal infrared emitters for both TE and TM polarizations. One-dimensional layered structures without texturing are preferable to more complex two- and three-dimensional structures because of the relative ease and low cost of fabrication. These aperiodic multilayer structures designed with alternating layers of silicon and silica on top of a semi-infinite tungsten substrate exhibit extremely high emittance peaked around the wavelength at which the structures are optimized. Structures were designed by a genetic optimization algorithm coupled to a transfer matrix code which computed thermal emittance. First, we investigate the properties of the genetic-algorithm optimized aperiodic structures and compare them to a previously proposed resonant cavity design. Second, we investigate a structure optimized to operate at the Wien wavelength corresponding to a near-maximum operating temperature for the materials used in the aperiodic structure. Finally, we present a structure that exhibits nearly monochromatic and highly directional emittance for both TE and TM polarizations at the frequency of one of the molecular resonances of carbon monoxide (CO); hence, the design is suitable for a detector of CO via absorption spectroscopy.

We report the observation of unusual thermal radiation at elevated temperatures (T=400-900K) from a three-dimensional metallic photonic-crystal composite that includes a micro-cavity. Upon thermal excitation by a heating element of a large heat-mass and a constant temperature (heat bath), its emissive power at resonant wavelengths exceeds a blackbody’s at nominally the same surface temperature. The possible explanations include, but are not limited to, angular concentration of light emission, slightly lower lattice-temperature for a reference blackbody and also a significant pumping of hot electrons at resonance such that our sample’s electron-temperature is higher than its latticetemperature.

The development of practical light sources based on group-IV semiconductors is a major outstanding goal of optoelectronics research, as a way to enable the continued integration of electronic and photonic functionalities on a CMOS compatible platform. However, this goal is severely complicated by the indirect energy bandgap of silicon, germanium, and related alloys. A possible solution is provided by the ability of biaxial tensile strain in Ge to lower the conduction-band edge at the direct (Γ) point relative to the L-valley minima, until at a strain of about 1.9% the fundamental bandgap becomes direct. Here we show that, by virtue of their ultrasmall thicknesses, Ge nanomembranes under externally applied mechanical stress are capable of accommodating such relatively high strain levels (up to over 2%). With this approach, we have demonstrated strong strain-enhanced Ge photoluminescence accompanied by a large strain-induced red shift in emission wavelength. A theoretical model of the emission properties of tensilely strained Ge has also been developed and applied to the measured high-strain luminescence spectra, providing evidence of population inversion. Finally, mechanically flexible photonic-crystal cavities have been developed on these nanomembranes, and used to demonstrate particularly large (20×) strain-induced enhancements in radiative efficiency, together with the observation of luminescence signatures associated with band-edge cavity modes. These results are promising for the development of group-IV semiconductor lasers for the technologically important short-wave infrared spectral region.

PT-symmetric optical structures represent a new generation of artificial optical systems which utilize gain and loss in a balanced fashion in order to perform a desired task. Such non-Hemitian arrangements exhibit interesting properties which are otherwise unattainable in passive Hermitian systems. As a result, since the first experimental demonstration of PT-symmetry in coupled optical configurations, there has been a flurry of activities in understanding and utilizing PT-symmetric processes in optics. Here we review recent developments in the newly emerging field of PT-symmetric optics.

We experimentally demonstrate single longitudinal mode operation in microring laser using the concept of PT symmetry. A PT-symmetric coupled resonator arrangement can considerably enhance the maximum achievable gain of single mode microring cavity. The method is broadband thus work well for inhomogenously broadened gain mediums. It doesn’t rely on any additional component to ensure its mode selective performance, and it is robust with respect to fabrication inaccuracies. This result may pave the way for a novel way of designing integrated laser sources based on PT symmetry.

We introduce a class of unidirectional lasing modes associated with the frozen mode regime of non-reciprocal slow-wave structures.¹ Such asymmetric modes can only exist in cavities with broken time-reversal and space inversion symmetries. The lasing frequency coincides with a spectral stationary inflection point of the underlying passive structure and it is virtually independent of the size of the cavity. These unidirectional lasers can be indispensable components of photonic integrated circuitry.

The dynamic manipulation of light can be achieved by the interaction of a signal pulse propagating through or reflected from a refractive index front. Both the frequency and the wave vector of the signal are changed in this case, which is generally referred to as an indirect transition. We have developed a theory to describe such transitions in integrated photonic crystal waveguides. Through indirect transitions, the following effects can be envisaged: large frequency shifts and light stopping and order of magnitude pulse compression and broadening without center frequency shift. All effects can be potentially realized with a refractive index modulation as small as 0.001. For the experimental realization, we have used slow light photonic crystal waveguides in silicon. The refractive index front was obtained by free carriers generation with a switching pulse co-propagating with the signal in the same slow light waveguide. The group velocities of the signal and the front could be varied arbitrarily by choosing the right frequencies of the signal and switching pulses. The indirect transition was unambiguously demonstrated by considering two situations: a) the front overtaking the signal and b) the signal overtaking the front. In both cases, a blue shift of the signal frequency was observed. This blue shift can only be explained by the occurrence of the expected indirect transition and not by a direct transition without wave vector variation.

The extremely large speed of light is a tremendous asset but also makes it challenging to control, store or shrink beyond its wavelength. Particularly, reducing the speed of light down to zero is of fundamental scientific interest that could usher in a host of important photonic applications, some of which are hitherto fundamentally inaccessible. These include cavity-free, low-threshold nanolasers, novel solar-cell designs for efficient harvesting of light, nanoscale quantum information processing (owing to the enhanced density of states), as well as enhanced biomolecular sensing. We shall here present nanoplasmonic-based schemes where timedependent sources excite “complex-frequency” modes in uniform (plasmonic) heterostructures, enabling complete and dispersion-free stopping of light pulses, resilient to realistic levels of dissipative, radiative and surface-roughness losses. Our theoretical and computational results demonstrate extraordinary large lightdeceleration factors (of the order of 15,000,000) in integrated nanophotonic media, comparable only to those attainable with ultracold atomic vapours or with quantum coherence effects, such as coherent population oscillations, in ruby crystals.

In this paper, the enhancement of third-harmonic generation in one-dimensional periodic grating structure with lowindex contrast, which is produced by holographic illuminated liquid crystal droplets and called polymer-dispersed liquid crystal grating, with near-infrared pumping has been demonstrated. The observed enhancement process is theoretically explained and modeled with a multi-scale perturbation analysis and split-step Fourier transform technique, respectively. We show that the third-harmonic generation has been enhanced by setting the fundamental frequency wavelength to the long-wavelength band-edge of the first photonic band-gap of this periodic structure and satisfying band-edge phasematched condition. The numerical results show that a dramatic enhancement of the third-harmonic field is observed near the long-wavelength band-edge of the second photonic band-gap. Furthermore, the conversion efficiency of thirdharmonic field of forward-propagating direction is more than of backward-propagating direction by a factor of 600.