This PDF file contains the front matter associated with SPIE Proceedings Volume 10345, including the Title Page, Copyright information, Table of Contents, and Conference Committee listing.

Plasmonic interconnects as well as metasurfaces manipulating the phase and amplitude of reflected and/or transmitted light, have attracted significant attention in the fields of planar optics and on-chip nanophotonics. The application space of plasmonics has recently been expanded by new materials classes including transparent conducting oxides (TCOs) and refractory transition metal nitrides (TMNs). These materials offer superior thermal stability, robustness, tailorability and CMOS compatibility, thus outperforming the conventional plasmonic components (e.g. gold and silver) in application-specific requirements. Here, we discuss recent progress in the areas of plasmonic interconnects, modulators and metasurfaces realized using TMNs and TCOs. Ultrafast nonlinear responses near the epsilon near zero (ENZ) region have been recently demonstrated for Al doped zinc oxide (AZO) (TCO). This has spurred the development of ultrafast, on-chip modulators with TCOs as an active material. Building from on our previous work on LRSPP waveguides with ultrathin Titanium Nitride (TiN) (5.5mm propagation length) and Zirconium Nitride (ZrN), we will report solid-state hybrid mode waveguides using TiN as well as a modulator based on this waveguide which provides all-optical tunability, low optical losses at the telecommunication window, and CMOS-compatibility. Successful integration of these alternative plasmonic components into the phase gradient metasurfaces platform without loss of performance have also been demonstrated. A metasurface employing ZrN brick antennas shows the photonic spin Hall Effect (PSHE), by reflecting the two circular polarizations in different directions. In another device, a metasurface based on nanostructures of Ga doped ZnO (TCO), functioning as a quarter-wave plate, have been realized.

A single waveguide laser with two separately addressed sections is fabricated using selective area intermixing of InGaAsP multiple quantum well grown on InP substrate. The selective intermixing of quantum wells is achieved by capping the two sections with PECVD grown silicon nitride and silicon dioxide respectively followed by rapid thermal annealing the device at 750°C for 30s prior to the fabrication of the quantum well laser. The fabricated device is capable of producing laser emission that can be tuned continuously from 1523 nm to 1556 nm by applying separate electrical currents into each 400 μm long section.

Ultrafast optical microscopy is an important tool
 for examining fundamental phenomena in semiconductor
 nanowires with high temporal and spatial resolution. Here, we used this technique to study carrier dynamics in single
GaN/InGaN core−shell nonpolar multiple quantum well
 nanowires. We find that intraband carrier−carrier scattering is
 the main channel governing carrier capture, while subsequent
 carrier relaxation is dominated by three-carrier Auger
 recombination at higher densities and bimolecular recombina
tion at lower densities. The Auger constants in these nanowires are approximately 2 orders of magnitude lower than in planar InGaN multiple quantum wells, highlighting their potential for future light-emitting devices.

There is an increasing demand for high performance long wave infrared (LWIR) detectors with multispectral capability. Meta-materials and antenna based concepts offer some interesting solutions to win the signal to noise ratio and provide enhanced functionality at the pixel level. The long wave infrared region is appealing due to the low metallic loss, large penetration depth of the localized field and the larger feature sizes compared to the visible region. I will discuss approaches to realize multispectral detectors with examples of double metal meta-material design combined with Type II superlattice absorbers (collaboration with Padilla group at Duke University).

We consider gold plasmonic nanorods in the infrared domain. Such elements are very anisotropic and only polarizable along their longer dimension. Varying the nanorod length from 150 to 500 nm changes the resonant frequency of the element, which allows us to tune the phase-shift provided to an incident plane wave which electric field is parallel to the long axis. On the contrary, the nanorod is transparent to an incoming plane wave with a polarization perpendicular to its main axis. In order to provide a 0 to 2pi phase shift, we chose to work in reflection with metasurfaces made of elements with random positions and orientation. We emphasize that the length of each nanorod is not random, but strongly depends on the position of the element. It is chosen accordingly so that the reflected phase shift follows a parabolic law. The focusing efficiency strongly depends on the density of nanorods but also of the dimensionality and of the symmetry of the metasurface. Using full wave simulations, we design ordered and random metalens and compare their characteristics. Unfortunately, simulating 2D large area metasurface is numerically challenging. Hence, we extract the transmission matrix parameters for single elements from our FDTD simulation, and model the metasurface as an array of two level atom scatterers Finally, we present an experimental realization of such random metalens. The latter is made with conventional top-down fabrication techniques and e-beam lithography. We will show that the resulting lens focus light on diffraction limited focal spots for the two polarizations.

Artificially engineered metamaterials consisting of nanocomposites (i.e. metal- dielectric) elements in the form of metallic split ring resonators (SRRs), parallel wires or slabs can provide unique optical responses at high frequencies that not available in naturally existing materials. A variety of metamaterials have been used in many important applications such as superlenses, tunable mirrors and negative index materials. Decreasing the size of the magnetic resonators is critical if strong magnetic response is desired at optical and near- infrared frequencies. However, this scaling breaks down at high frequencies causing saturation in the magnetic response. In this study, we present a transmission line theory with models the magnetic response of pair of metallic nanostripes separated by a dielectric material. The predicted by the model magnetic susceptibility χ_𝑚 and magnetic resonance frequency (MRF) are compared to exact numerical simulations showing excellent agreement. Parametric study of the MRF dependence on the resonator’s sizes show a clear saturation for small resonators

We show the fabrication of a novel optofluidic chip that uses a a network of nanochannels optimized for the transport of DNA-stretched molecules. The molecules can move through the nanochannels in the femto-liter per second. The nanochannels are optically accessible via a transparent cover of pyrex, allowing fluorescence microscopy imaging of the travelling molecules. The nanochannels are surrounded by photonic crystal structures to enhance the emission of the fluorescent light. The photonic crystal structures provide an enhancement up to 2.5 times in the light emitted by fluorescent molecules in motion inside the nanochannels which increases to around 250 when normalized to the area of the nanochannels emitting fluorescence. The results may help to the detection of fluorescent molecules (like marked-DNA) in series by speeding it or allowing the use of less sophisticated equipment.

In this invited talk I will review our research activity on near-field Anapole nanolasers. Anapoles are radiationless light states that do not possess far field emission. Thanks to their unique nature, these states enable a new concept of laser source, whose emission is totally confined in the near field. We will discuss applications of this concept for ultra-fast (100 fs), mode-locking pulse generation in integrated optical structures with GaAs semiconductors.

Nanoplasmonic stopped-light lasing is a recently established principle [1] that not only opens the door to ultrafast cavity-free nanolasing, ultra-thin lasing sufaces exploiting van Hove singularities [2] and cavity-free quantum-electrodynamics but also provides an entry point to quantum gain in quantum plasmonics. We show that engineered singularities in the density of optical states realised in a metal-dielectric-metal nano-waveguide structure lead to a stopped-light feedback mechanism that is the basis for the dynamics of the observed cavity-free photonic and surface-plasmon polariton nanolasing. The condensed surface plasmon polaritons are characterised by ultrafast spatio-temporally oscillating amplified surface-plasmon polaritons on ultrafast timescales <5 femtoseconds and with spatial periods on the nanoscale <100 nm. [1] T. Pickering, J. M. Hamm, A. F. Page. S. Wuestner and O. Hess, “Cavity-free plasmonic nanolasing enabled by dispersionless stopped light”, Nature Communications 5, 4972 (2014). [2] J. M. Hamm and O. Hess, “Two Two-Dimensional Materials Are Better Than One”, Science 340, 1298 (2014) [3] S. Wuestner, T. Pickering, J. M. Hamm, A. F. Page, A. Pusch and O. Hess, “Ultrafast dynamics of nanoplasmonic stopped-light lasing”, Faraday Discuss., 178, 397 (2015).

We demonstrate novel plasmon resonator geometries consisting of ultra-smooth metal surfaces that support surface plasmon polariton modes exhibiting record-high quality factors in the visible frequency range. The resonators are utilized to achieve record narrow-linewidth, low-threshold surface-plasmon-polariton lasing at optical frequencies, as well as exhibit high figure-of-merit sensing. The lasing threshold of the plasmon-laser was further minimized by leveraging grating-coupled plasmons to pump the lasing-plasmons with strong spatial overlap and minimum perturbation. The results predict potential applications in small-volume optical sensing or energy-efficient coherent on-chip optical sources.

Metal-clad nanolasers with high spontaneous emission factors (β) represent a class of ultra-compact light emitters with applications in fiber-optic communications, hybrid and all optical computing, imaging and sensing. In-depth studies on both the coherence and dynamical properties of these emitters are necessary before practical applications can be realized. However, the coherence characterization of a high-β nanolaser using the conventional measurement of output light intensity versus input pump intensity (L-L curve) is inherently difficult due to the diminishing kink in the measurement curve. We conducted the second order intensity correlation measurement, or g²(τ) - a more definitive method to confirm coherence - on a high-β metallo-dielectric nanolaser under nanosecond optical pulse pumping. Our result indicates that full coherence is achieved at three times the threshold conventionally defined by the kink in the L-L curve. Additionally, we observed that the g²(τ) peak width shrinks below and broadens above threshold. Rate-equation analyses reveal that the above-threshold broadening is due to the delayed threshold phenomenon, providing the first observation of dynamical hysteresis in a nanolaser. We propose that this dynamical phenomenon can be exploited to determine the lasing regimes of a unity-β nanolaser, whose threshold is inherently ambiguous and difficult to observe.

Nanophotonic coatings and structures provide an attractive approach for enhancing light-matter interactions in advanced photovoltaics. A little-discussed aspect of many photonic architectures is the presence of strong anisotropies in the electromagnetic field enhancements. These anisotropies are of particular importance in relation to nanostructured materials that possess intrinsic structure-dependent optical anisotropies. In this talk, we describe a novel class of momentum-resolved spectroscopies that provide new insight into structure-dependent optical properties of thin-film material and discuss approaches to exploit these effects in photovoltaic devices that incorporated nanophotonic enhancements. Specifically, we use Fourier imaging techniques to measure or control the momentum distribution of in-coming or out-going light rays respectively. These techniques are applied to test-case organic photovoltaic materials that can be deposited with distinct morphologies depending on processing conditions. Using momentum-resolved photoluminescence, we determine the morphology-dependent orientation of transmission and absorption dipoles. We subsequently demonstrate the use of momentum-resolved reflectometry to perform “model-free” measurements of optical constants. The approach provides precise and accurate optical constants with quantified error estimates, obviating the complications associated with highly model-dependent, multi-parameter spectral fitting procedures used in ellipsometry. We conclude by describing ongoing efforts to exploit optical anisotropies to enhance light absorption in nanostructured photovoltaics.

We show that nanophotonic device performance scales non-monotonically with critical length. Such scaling can be synergistic with the atomistic-scale of 2D materials. The naturally-low modal overlap factor can be engineered to approach 1% for electric in-plane field polarization waveguides, i.e. slot-waveguides. Moreover, we show that a polaritonic mode character (i.e. plasmonic) improves the modulator performance by about 10x due to (i), a lower contact resistance from synergistic use of one contact, and (ii) the higher modal group index. As an example we discuss our demonstration of the 1st sub-1Volt electro-optic modulator based on 2D material plasmonic hybrid integration on Silicon.

The functionalization of graphene can enhance the optoelectronic properties of graphene, allowing the creation of highly sensitive broadband photodetectors. Presently, the role played by defects, induced by the functionalization of graphene, on the performance of graphene photodetectors is not well understood. Here, we investigate the optoelectronic properties of van der Waals heterostructures comprising of graphene and a functionalized partner, formed by pristine and fluorinated graphene. We find that the electrical properties of graphene are preserved upon formation of the heterostructure. A negligible charge transfer is observed across the interface between the two materials which limits the performance of the photodetector due to the vertical separation of the two materials.

Light absorption in conducting materials produces heating of their conduction electrons, followed by relaxation into phonons within picoseconds, and subsequent diffusion into the surrounding media over longer timescales. This conventional picture of optical heating is supplemented by radiative cooling, which typically takes place at an even lower pace, only becoming relevant for structures held in vacuum or under extreme thermal isolation. Here, we reveal an ultrafast radiative cooling regime between neighboring plasmon-supporting graphene nanostructures in which noncontact heat transfer becomes a dominant channel. We predict that more than 50% of the electronic heat energy deposited on a graphene disk can be transferred to a neighboring nanoisland within a femtosecond timescale. This phenomenon is facilitated by the combination of low electronic heat capacity and large plasmonic field concentration in doped graphene. Similar effects should occur in other van der Waals materials, thus opening an unexplored avenue toward efficient heat management.

The purpose of this study is to investigate the electrical properties of graphene transparent conductive film under visible light irradiation. Sample in the study is chemical vapor deposition (CVD) growth graphene on the surface of copper foils and then transferred to the SiO2 substrate. Three monochromatic visible lights with wavelength of 635nm, 520nm and 450nm representing red (R), green (G) and blue (B) lights are used as irradiation sources. Results show that the graphene resistances increase slowly under light irradiation with all the three different wavelengths, while decrease slowly after the light is switched off. Light irradiation with higher power density will induce larger relative resistance change. When graphene is irradiated at the same density, blue light irradiation may result in the largest resistance change.

Coherent control of nonlinear and ultrafast plasmon-polariton mediated interactions has attracted wide attention for its potential for enhancing functionality in nano-scale photonic devices and applications. Contemporary research in ultrafast and nonlinear plasmonics primarily utilizes noble metals, such as gold and silver, as material platforms because of their high performance both in linear and nonlinear optical properties. Unfortunately, noble metals possess numerous drawbacks including low melting points, chemical instabilities, and an incompatibility with standard CMOS processing techniques, all of which hamper their incorporation into functional plasmonic devices. Here we investigate the mid-infrared ultrafast and nonlinear properties of the alternative plasmonic material, aluminum-doped zinc oxide (AZO). By performing time-resolved pump-probe spectroscopy, we observe an unprecedentedly large and ultrafast (sub-picosecond) response in AZO thin films for both intra- and inter-band pumping frequencies. These two nonlinearities arise from distinct electron excitation dynamics and, as such, can be controlled simultaneously and independently to provide a novel method of dynamic tunability. We demonstrate this phenomenon with two-color excitation and find our AZO films exhibit a THz modulation bandwidth. We also probed the nonlinear response of AZO films at the epsilon-near-zero (ENZ) frequency and observed a dramatic increase in the Kerr nonlinearity with an induced refractive index change on the order of unity. In summary, our ultrafast and nonlinear studies strongly support AZO as an alternative plasmonic material with qualities pertinent to the development and realization of practical plasmonic technologies.

We present several approaches for orders-of-magnitude enhancement of optical nonlinearities in specially engineered nanostructures containing graphene and other 2D materials and illustrate how they apply to second- and third-harmonic generation in such 2D-3D photonic heteromaterials. Applications to active photonic devices, such as nonlinear optical gratings, are discussed as well.

Graphene exhibits a remarkably high intrinsic nonlinearity that can be pushed even further when the optical frequency is tuned to the plasmon resonances of the material. Atomistic simulations provide an accurate description of these phenomena, although their computational cost is prohibitive for large graphene nanostructures. In the weak-field, cw regime, an alternative formalism consists in relying on classical electromagnetism, using the local nonlinear conductivities extracted from perturbative models of extended graphene. We show that both of these approaches are in excellent agreement for sufficiently-large structures (10s of nm in lateral size) when describing second- and third-harmonic generation, as well as the Kerr nonlinearity. Additionally, we exploit an eigenmode decomposition of the optical field in the classical formalism to obtain analytical expressions for the plasmon-driven response of graphene ribbons and finite islands, in excellent agreement with atomistic calculations. In contrast to the instantaneous nonlinear response, where input and output fields maintain relative coherences, a delayed nonlinearity also takes place as a consequence of the strong dependence of the graphene response on the temperature of its conduction electrons. Here we show that transient plasmons arising from the elevated electronic temperature in graphene upon ultrafast optical pumping can produce strong modulations of the optical absorption. Our nonperturbative time-domain simulations indicate that the strong incoherent nonlinearity associated with plasmons in doped graphene nanostructures can be used for all-optical switching in nonlinear optical devices.

With advances in the technology, high-density on-chip electrical interconnects are not able to meet current technology demands due to inherent RC limitation. Silicon photonics is an emerging technology with the prospects of electronics and photonics integration on a chip, which can improve system performance and open up numerous design opportunities. The potential of optical interconnects have been investigated immensely for compact design, strong light confinement, high bandwidth, low crosstalk, low loss propagation, in the design of high density, next generation on-chip systems. Plasmonics is considered to be the most promising candidate for the miniaturization of photonic components, which can provide subwavelength confinement by coupling electromagnetic energy to electron oscillations at metallic-dielectric interface leading to localized electromagnetic field. Graphene, an allotrope of carbon with unique optoelectronic properties and silicon compatibility has prompted intense research in graphene based electrical and optical applications, ranging from the terahertz to the visible spectral region. It has been shown as a promising candidate in planar photonic circuit design, paving the way for realistic applications. This paper analyzes the mode characteristics i.e. effective mode index, propagation distance, and field distribution of graphene integrated plasmonic waveguide architectures. The transmission through the waveguide is directly affected by location and tunability of graphene refractive index. To enhance graphene interaction with light, it is placed at the maximal electric field to increase absorption through graphene for the design of compact electro-absorption modulator. The simulation results show agreement with the analytical models.

The use of photonics in computing is a hot topic of interest, driven by the need for ever-increasing speed along with reduced power consumption. In existing computing architectures, photonic data storage would dramatically improve the performance by reducing latencies associated with electrical memories. At the same time, the rise of ‘big data’ and ‘deep learning’ is driving the quest for non-von Neumann and brain-inspired computing paradigms. To succeed in both aspects, we have demonstrated non-volatile multi-level photonic memory avoiding the von Neumann bottleneck in the existing computing paradigm and a photonic synapse resembling the biological synapses for brain-inspired computing using phase-change materials (Ge₂Sb₂Te₅).

Chalcogenides are materials that substantially consist of sulphur, selenium, and tellurium. Their dielectric properties can be tuned by thermally induced structural phase transitions, photostructural transitions, and dissolution of metal dopants. We have designed active photonic structures using a range of `tuneable' chalcogenides. The resonant frequency of plasmonic structures was tuned over a 100 nm band in the visible, metal-chalcogenidemetal structures provide tuning of over a band of 0.5 μm in the mid-infrared, and hyperbolic metamaterials incorporating chalcogenides provide a means to alter the radiative decay rate of uorescent photons.

We consider the design of nanostructured materials for thermal homeostasis, or the ability to maintain a temperature within a fixed range despite externally varying heat input. Our design uses nano- and microstructured phase-change materials to achieve a sharp change in thermal emission at a particular phase-transition temperature. We use electromagnetic simulations to calculate the thermal infrared absorption spectra for metal and insulator phases of the phase-change material. The results indicate a large increase in thermal emission at the phase transition. We then use numerical simulations of the heat equation to show that the sharp change in emission results in thermal homeostasis. For a varying external heat source, the material experiences much smaller temperature fluctuations than an unstructured or bulk material.

All-optical modulators are likely to play an important role in future chip-scale information processing systems. In this work, through simulations, we investigate the potential of a recently reported vanadium dioxide (VO₂) embedded silicon waveguide structure for ultrafast all-optical signal modulation. With a VO₂ length of only 200 nm, finite-differencetime- domain simulations suggest broadband (200 nm) operation with a modulation greater than 12 dB and an insertion loss of less than 3 dB. Predicted performance metrics, including modulation speed, modulation depth, optical bandwidth, insertion loss, device footprint, and energy consumption of the proposed Si-VO₂ all-optical modulator are benchmarked against those of current state-of-the-art all-optical modulators with in-plane optical excitation.

Using time- and angle-resolved hemispherical elastic light scattering technique we reveal complex pathways of photoinduced nonlinear optical dynamics in VO₂, V₂O₃ and V₃O₅ thin films. The structural dynamics was monitored by using an ultrafast diffraction conoscopy technique. The evolution of phases in these correlated oxides is substantially different and significantly depends on optical excitation, temperature and size of grains and domains. Strong optical nonlinearity along with its complex transient dynamics makes vanadium oxides attractive for high-contrast all-optical switches, high-speed optical data storage and holographic devices. The characteristic time of optical nonlinearity can be tuned from several femtoseconds to picoseconds by altering the excitation fluence and size of grains and domains. Additional control of ultrafast phase transition dynamics can be achieved by photoacoustical generation of strain waves. Depending on material morphology and level of optical excitation, the optical signal shows coherent oscillations caused by photoacoustic wave at picosecond and nanosecond time scales. Complex nonlinear dynamics of correlated vanadium oxides can provide a way for precise tuning of transient optical and electronic properties in photonic devices.

The unique light-matter interaction in metamaterials, a type of artificial medium in which the geometrical features of subunits dominate their optical responses, have been utilized to achieve exotic material properties that are rare or nonexistent in natural materials. Furthermore, to extend their behaviors, active materials have been introduced into metamaterial systems to advance tunability, switchability and nonlinearity. Nevertheless, practical examples of versatile photonic metamaterials remain exceedingly rare for two main reasons. On the one hand, in sharp contrast to the broad material options available at lower frequencies, it is less common to find active media in the optical regime that can provide pronounced dielectric property changes under external stimuli, such as electric and magnetic fields. Vanadium dioxide (VO₂), offering a large refractive index variation over a broad frequency range due to its near room temperature insulator-to-metal transition (IMT), has been favored in recent studies on tunable metamaterials. On the other hand, it turns out that regulating responses of hybrid metamaterials to external forces in an integrated manner is not a straightforward task. Recently, metamaterial-enabled devices (i.e., metadevices) with ‘self-sufficient’ or ‘self-contained’ electrical and optical properties have enabled complex functionalities. Here, we present a design methodology along with the associated experimental validation of a VO₂ thin film integrated optical metamaterial absorber as a hybrid photonic platform for electrically driven multifunctional control, including reflectance switching, a rewritable memory process and manageable localized camouflage. The nanoengineered topologically continuous metal structure simultaneously supports the optical resonance and electrical functionality that actuates the phase transition in VO₂ through the process of Joule heating. This work provides a universal approach to creating self-sufficient and highly-versatile nanophotonic systems.

In the nonlinear optics regime, photonic devices that have topologically nontrivial photonic bandstructures are predicted to support a novel class of "topological solitons", which inherit exotic features of linear topological edge states such as unidirectional edge propagation. We present a detailed theoretical study of the conditions under which topological solitons can arise, and how they can be used to implement nonlinear optical isolators. Such isolators can achieve large isolation ratios, while being robust to lattice defects. Our results are based on theoretical analysis backed by numerical simulations of coupled-waveguide lattice and ring resonator lattice structures.

We demonstrate that the distorted Kagome lattice formed by two-dimensional(2d) array of dielectric rods embedded in air exhibits a new class of topological states characterized by a topological invariant number in Pauli vector space. The Kagome lattice can be considered as a 2d analogue of the Su-Schrieffer–Heeger (SSH) model, which displays a phase transition by detuning the relative amplitudes of the inter-cell and intra-cell hopping terms. The phase transition is accompanied by the opening of a complete band gap in the Brillouin zone, which may host topological edge states on either the truncated end of the lattice or at the domain walls between topological nontrivial and trivial domains. To further reveal the connection between the bulk invariance and edge states, polarizations of shrunken and expanded effects are calculated. Our first-principles simulations based on finite element method (FEM) are used to design the lattice and confirm the analytic prediction.

Defining elements with reconfigurable input-output characteristics is of importance to achieve flexible circuitry where light can be manipulated and routed using external control signals. We have developed an experimental approach for shaping of the transmission function of multimode silicon photonic waveguides by projecting a pattern of local nonlinear perturbations induced by an ultrafast laser pulse. Making use of the degrees of freedom offered by a spatial light modulator, the technique offers a new approach for studying light transport, for controlling its flow on ultrafast time scale, and for programming functions on a photonic chip.

We discuss novel electromagnetic effects in topological metamaterial and in complex birefringent meta material. In particular, we discuss the creation of novel topology using meta-material geometry., We also discuss three-dimensional meta-materials with balanced gain and loss for the purpose of achieving arbitrary control of a pair of polarization states.

In this talk, we will review our recent progress towards the concept, design and realization of magnet-free non-reciprocal photonic devices and arrays of them with strong topological protection, aimed at realizing reconfigurable, broadband isolators and circulators. We will discuss our approaches to design topological photonic metasurfaces based on spatio-temporal modulation, nonlinearities, and/or opto-mechanical interactions, and discuss our vision towards new transport phenomena for light, and new nanophotonic devices with enhanced non-reciprocal properties.

We study transport of time-bin entangled photon pairs in a 2D topological photonic system of coupled ring resonators. We show that the transport through edge bands preserves temporal correlations of input photons. Furthermore, edge transport is robust against system disorder and only marginally affects the temporal correlations of photons. In contrast, transport through bulk band leads to unwanted bunching/anti-bunching of photons and the probability of bunching/anti-bunching increases with increasing disorder. Finally, we discuss our experimentally efforts to demonstrate the robustness of edge states for quantum transport.

We present our work on photonic crystal membrane devices exploiting Fano resonance between a line-defect waveguide and a side coupled nanocavity. Experimental demonstration of fast and compact all-optical switches for wavelength-conversion is reported. It is shown how the use of an asymmetric structure in combination with cavity-enhanced nonlinearity can be used to realize non-reciprocal transmission at ultra-low power and with large bandwidth. A novel type of laser structure, denoted a Fano laser, is discussed in which one of the mirrors is based on a Fano resonance. Finally, the design, fabrication and characterization of grating couplers for efficient light coupling in and out of the indium phosphide photonic crystal platform is discussed.

We introduce non-parity-time-symmetric plasmonic waveguide-cavity systems, consisting of resonators with unbalanced gain and loss side-coupled to a waveguide. We show that the design parameters of such systems can be tuned to obtain exceptional points, and realize unidirectional reflectionless light propagation. We then propose a compact perfect absorber unit cell, based on unidirectional reflectionlessness at exceptional points. We show that with proper design, light can propagate into the perfect absorber unit cell with reflection close to zero in a broad wavelength range. By cascading multiple unit cell structures, near total light absorption can be achieved in a wide range of frequencies.

Greatly enhanced high-speed modulation performance has been recently predicted in numerical calculations for a novel injection-locking scheme involving a distributed Bragg reflector master laser monolithically integrated with a unidirectional whistle-geometry semiconductor microring laser. Operation of these devices relies on the assumption of large difference between modal losses experienced by counterpropagating modes. In this work, we confirm the unidirectionality of the whistle-geometry configuration through rigorous three-dimensional finite-difference timedomain (FDTD) simulation by showing a strong asymmetry in photon lifetimes between the two counterpropagating modes. We also show that similar asymmetry occurs in three-port couplers, whose structure resembles the coupling section of whistle-geometry lasers. We explain why these results do not violate the Helmholtz reciprocity principle.

In recent years, non-Hermitian degeneracies, also known as exceptional points (EPs), have emerged as a new paradigm for engineering the response of optical systems. Among many different non-conservative photonic configurations, parity-time (PT) symmetric arrangements are of particular interest since they provide an excellent platform to explore the physics of exceptional points. In this talk, I will present some of the work in our group, where the intriguing properties of exceptional points that are arising in judiciously designed parity-time-symmetric systems are utilized to address two of the long standing challenges in the field of integrated photonics: enforcing single mode lasing in intrinsically multimode cavities, and enhancing sensitivity of micro-resonators.

Student contribution: In recent years, non-Hermitian degeneracies, also known as exceptional points (EPs), have emerged as a new paradigm for engineering the response of optical systems. This class of degeneracies represents points in parameter space where the eigenvalues and their corresponding eigenvectors simultaneously coalesce [1,2]. Among the large set of non-conservative photonic systems, parity-time (PT) symmetric arrangements are of particular interest since they provide an excellent platform to study the physics and properties of non-Hermitian degeneracies [3,4]. So far, the abrupt nature of the phase transitions at EPs has led to a number of new functionalities such as loss-induced transparency [5], unidirectional invisibility [6,7], and single mode lasing [8-11]. In addition, it has been suggested that the bifurcation properties associated with second-order exceptional points can be utilized to achieve enhanced sensitivity in micro-resonator arrangements [11]. Of interest is to use even higher-order exceptional points that in principle could further amplify the effect of perturbations. While such higher-order singularities have been theoretically studied in a number of recent works [13,14], their experimental realization in the optical domain has so far remained out of reach. In this paper, for the first time, we show the emergence of third order exceptional points in ternary parity-time-symmetric coupled resonator lasers by judiciously designing the gain/loss distribution and coupling strengths following a recursive bosonic quantization procedure. Subsequently, the nature of the third order exceptional point is confirmed through the cubic root response of this ternary system to external perturbations. Our work may pave the way towards the utilization of higher order exceptional points in designing ultrasensitive photonic arrangements. References [1] W. D. Heiss, J. of Phys. A: Mathematical and Theoretical 45, 444016 (2012). [2] N. Moiseyev, Non-Hermitian Quantum Mechanics. (Cambridge University Press, 2011). [3] K. G. Makris, R. El-Ganainy, and D. N. Christodoulides, Phys. Rev. Lett. 100, 103904 (2008). [4] C. E. Rüter, K. G. Makris, R. El-Ganainy, D. N. Christodoulides, M. Segev, and D. Kip, Nat. Phys. 6, 192 (2010). [5] A. Guo et al., Phys. Rev. Lett. 103, 093902 (2009). [6] B. Peng et al., Nat. Phys. 10, 394 (2015). [7] A. Regensburger, C. Bersch, M.-A. Miri, G. Onishchukov, D. N. Christodoulides, and U. Peschel, Nature 488, 167 (2012). [7] M. Miri, P. Likamwa, D. N. Christodoulides, Opt. Lett. 37, 764 (2012) [8] H. Hodaei, M.-A. Miri, M. Heinrich, D. N. Christodoulides, and M. Khajavikhan, Science 346, 975 (2014). [9] L. Feng, Z. J. Wong, R.-M. Ma, Y. Wang, X. Zhang, Science 346, 972 (2014). [11] H. Hodaei et al., Laser & Photon. Rev. 10, 494 (2016). [12] J. Wiersig, Phys. Rev. Lett. 112, 203901 (2014). [13] G. Demange, and E.-M. Graefe, J. Phys. Math. Theor. 45, 25303 (2012). [14] M.H. Teimourpour, R. El-Ganainy, A. Eisfeld, A .Szameit, D.N. Christodoulides, Phys. Rev. A 90, 053817 (2014).

Photonic lattices composed of balanced gain and loss waveguides have attracted considerable attention due of their potential applications in optical beam engineering and image processing. These photonic lattices belong to a larger class of intriguing active metamaterials that exhibit the parity-time ( ) symmetry. Kagome lattice is a two-dimensional network of corner-sharing triangles and is often associated with geometrical frustration. In particular, the frustrated coupling between waveguide modes in a kagome array leads to a dispersionless flat band consisting of spatially localized modes. Recently, a -symmetric photonics lattice based on the kagome structure has been proposed by placing -symmetric dimers at the kagome lattice points. Each dimer corresponds to a pair of strongly coupled waveguides. With balanced arrangement of gain and loss on individual dimers, the system exhibits a -symmetric phase for finite gain/loss parameter up to a critical value. Here we discuss the linear and nonlinear optical beam propagations in this novel -symmetric kagome system. The linear beam evolution in this complex kagome waveguide array exhibits a novel oscillatory rotation of optical power along the propagation distance. Long-lived local chiral structures originating from the nearly flat bands of the kagome structure are observed when the lattice is subject to a narrow beam excitation. We further show that inclusion of Kerr-type nonlinearity leads to novel optical solitons.

Integrated quantum photonic technologies hold a great promise for application in quantum information processing. A major challenge is to integrate multiple single photon sources on a chip. Quantum dots are bright sources of high purity single photons, and photonic crystals can provide efficient photonic platforms for generating and manipulating single photons from integrated quantum dots. However, integrating multiple quantum dots with photonic crystal devices still remains as a challenging task due to the spectral randomness of the emitters. Here, we present the integration of multiple quantum dots with individual photonic crystal cavities and report quantum interference from chip-integrated multiple quantum dots. To solve the problem of spectral randomness, we introduce local engineering techniques for tuning multiple quantum dots and cavities. From integrated quantum dot devices we observe indistinguishable nature of single photons from individual quantum dots on the same chip. Therefore, our approach paves the way for large-scale quantum photonics with integrated quantum emitters.

Although the enhanced near fields produced by plasmon resonances in metal nanoparticles can enable strong local light-matter interactions, the strong dissipation of plasmon resonances would seem to be incompatible with quantum-mechanical phenomena such as entanglement. Counter to this intuition, the dissipation can in fact lead to the production of transient entanglement between the occupation states of dots coupled to a common plasmonic system. Building on previous results that showed entanglement between pairs of dots, we scale to larger systems of two, three, and more closely spaced dots. Moreover, we show that tuning the degree of coupling between each dot and the common plasmonic nanostructure enables entanglement to be created in the case where the entire system begins in its ground state and is excited by a single laser pulse. Entanglement is achieved without the need for the dots to be individually addressable, and without the need for controlled quantum gates, postselective measurements, or engineering of the dissipative environment. Through analytical solutions and numerical simulation of a model Hamiltonian based on a cavity-quantum-electrodynamics approach, we determine system configurations that maximize pairwise entanglement among the quantum dots, illustrating in principle the potential for true “quantum plasmonics.

Self-organized criticality emerges in dynamical complex systems driven out of equilibrium, and characterizes a wide range of classical phenomena in physics, geology and biology. However, for decades now, it remains a fundamental open question whether this broad property also finds a place in the quantum regime. In the talk, we shall present the first example of quantum self-organized criticality, emerging from quantum fluctuations and controlled by quantum coherence. We shall introduce a many-body quantum-coherently driven nanophotonic system where heavy photons interact in the presence of active nonlinearities. In this system, we shall show how quantum self-organized criticality emerges in an inherently new type of light localization, arising from two first-order phase transitions and being robust to dissipation, fluctuations and many-body interactions. The observed localization exhibits emergence of scale-invariant power laws and absence of finely-tuned control parameters. In analogy with the regime of quantum criticality at Tc = 0 in equilibrium static systems, we find that for our nonequilibrium dynamical system there exists a range of parameters for which the effective critical ‘temperature’ drops to zero, at which point we enter a fundamentally new regime of phase transitions – the quantum self-organized critical regime. We shall also approach the problem from a thermodynamic and information-theory perspective, deriving the multidimensional-state-vector Fokker-Planck (FP) equation for the distribution function of our problem, applying the maximum information entropy principle to make unbiased estimates on the probability distribution of microscopic states of our active nanosystem, and finally determining and analyzing the information gain and efficiency of the complex nanosystem close to its critical points.

Metasurfaces are ultra-thin patterned photonic structures that emerged recently as planar metadevices capable of reshaping and controlling incident light. They are composed of resonant subwavelength elements distributed across a flat surface. Due to the resonant scattering, each element can alter the phase, amplitude and polarization of the incoming light. Many designs and functionalities of metasurfaces suggested so far are based on plasmonic planar structures, however most of these metasurfaces demonstrate low efficiencies in transmission due to losses in their metallic components. In contrast, all-dielectric resonant nanophotonic structures avoid absorption losses, and can drastically enhance the overall efficiency, especially in the transmission regime. Here we utilize this platform to create flat optical elements such as vector beam q-plates, holograms and quantum polarization tomography devices. Holograms, in particular, showcase a potential of the metasurface platform as they rely on a complex wavefront engineering. Metasurface platform enables a new way to create highly efficient holograms with single-step patterning. Here, we design and realize experimentally greyscale meta-holograms with superior transmission properties. Another promising area for implementation of all-dielectric metasurfaces is quantum optics. We suggest and develop experimentally a new concept of quantum-polarization measurements with a single all-dielectric resonant metasurface. A metasurface enables full reconstruction of the state of entangled photon pairs based on the photon correlations with single-photon detectors. The subwavelength thin structure provides an ultimate miniaturization, scalability to a larger number of entangled photons, and gives the possibility to study the dynamics of quantum states in real-time.

In the present work, we present a metamaterial made of a periodic collection of dielectric resonators in which a quantum oscillator (denoted QO in the following) is inserted. The geometry at stake here is much more complicated than the textbook 1D cavity usually dealt with theoretically in quantum optics. We do provide a treatment essentially based on the scattering matrix non-perturbative approach, in order to investigate the various effects that could be expected to exist in such structures.The theoretical methods used are the Feshbach projection method associated with multiple scattering theory. First, the phenomenology for one scatterer with a QO inserted is presented, then the collective behavior of a finite periodic set of such scatterers is investigated and it is shown that it is possible to open and close a conduction band according to the state of the oscillators when the inserted quantum oscillators are put in the inversion regime by means of a pump field. They add gain to the system, allowing to reach the amplification regime in the vicinity of the Mie resonances of the dielectric resonators. When the transition frequency is situated at the photonic band gap edge, it creates switchable conducting modes within the bandgap.

We investigate laser energy localization in a layered photonic crystal with Kerr nonlinear response in dependence of the wave front aberrations of an incident femtosecond laser beam (which are similar to the pulse chirp). Such kind of energy localization appears due to soliton formation in certain layers of photonic crystal. Layers position, in which a soliton appear, depend on the beam wave front aberrations and the incident beam intensity essentially. It is important to emphasize that a soliton occurs in separate layers. Therefore, its width must be less than a layer thickness. Consequently, an intensity of the incident beam must be greater than its crucial value. A process of energy localization strongly depends on relation between the wave packet carrier frequency and a frequency characterizing a photonic crystal. The problem under consideration is described by a nonlinear Schrödinger equation with respect to amplitude slowly varying in time. We investigate a femtosecond beam interaction with photonic crystal numerically and analytically.

We study a self-similar mode of femtosecond pulse propagation in a medium with non-resonant TPA of laser energy and with taking into account the TOD influence. Non-resonant TPA appears due to detuning between a carrier frequency of wave packet and doubled frequency corresponding to certain energy level transition of substance atoms. This pulse propagation mode appears for a pulse with nonlinear chirp of definite form. Moreover, the pulse shape is asymmetric, as a rule. Laser pulse propagation in nonlinear medium is described by nonlinear Schrödinger equation. Using the analytical approach we derive a soliton-like pulse shape and its chirp evolution in time. Analytical results are confirmed by computer simulation, based on nonlinear Schrödinger equation. We demonstrate that the analytical results are valid at a long propagation distance.