Professor Marian Florescu

We explore the dynamics of $N$ coupled atoms to a generic bosonic reservoir under specific system symmetries. In the regime of multiple atoms coupled to a single reservoir with identical couplings, we identify remarkable effects, notably that the initial configuration of the atomic excited state amplitudes strongly impacts the dynamics of the system and can even fully sever the system from its environment. Additionally, we find that steady state amplitudes of the excited states become independent of the choice of the reservoir. The framework introduced is applied to a structured photonic reservoir associated with a photonic crystal, where we show it reproduces previous theoretical and experimental results and it predicts superradiant behaviour within the single-excitation regime.

We introduce novel architecture for cavity design in an isotropic disordered photonic band gap material. We demonstrate that point-like defects can support localized modes with different symmetries and multiple resonant frequencies, useful for various applications.

Photonic crystal cavities enable the realization of high Q-factor and low mode-volume resonators, with typical architectures consisting of a thin suspended periodically-patterned layer to maximize confinement of light by strong index guiding. We investigate a heterostructure-based approach comprising a high refractive index core and lower refractive index cladding layers. Whilst confinement typically decreases with decreasing index contrast between the core and cladding layers, we show that, counter-intuitively, due to the confinement provided by the photonic band structure in the cladding layers, it becomes possible to achieve Q-factors $>10^4$ with only a small refractive index contrast. This opens up new opportunities for implementing high Q-factor cavities in conventional semiconductor heterostructures, with direct applications to the design of electrically-pumped nano-cavity lasers using conventional fabrication approaches.

The transmission of information as optical signals encoded on light waves traveling through optical fibers and optical networks is increasingly moving to shorter and shorter distance scales. In the near future, optical networking is poised to supersede conventional transmission over electric wires and electronic networks for computer-to-computer communications, chip-to-chip communications, and even on-chip communications. The ever-increasing demand for faster and more reliable devices to process the optical signals offers new opportunities in developing all-optical signal processing systems (systems in which one optical signal controls another, thereby adding "intelligence" to the optical networks). All-optical switches, two-state and many-state all-optical memories, all-optical limiters, all-optical discriminators and all-optical transistors are only a few of the many devices proposed during the last two decades. The "all-optical" label is commonly used to distinguish the devices that do not involve dissipative electronic transport and require essentially no electrical communication of information. The all-optical transistor action was first observed in the context of optical bistability [1] and consists in a strong differential gain regime, in which, for small variations in the input intensity, the output intensity has a very strong variation. This analog operation is for all-optical input what transistor action is for electrical inputs.

We investigate the general features of thermal emission and absorption of radiation in photonic crystals. The light-matter interaction is strongly affected by the presence of the three-dimensional photonic crystal and the alteration of the photonic density of states can be used to suppress or enhance the thermal emissivity and absorptivity of the dielectric structure. Our analysis shows that the thermal response of the system depends on both the elementary absorbers/emitters and the photonic reservoir characteristics. In particular, we demonstrate that, depending on the system configuration, the thermal emission may exceed the free-space radiative energy density given by Planck's law. This modification of the Planck's law is achieved without altering the optical properties of the absorber/emitter medium, which remain consistent with the usual definition of a frequency and angle dependent grey-body. We also evaluate the rate of spontaneous emission, stimulated emission and absorption for thermally driven two-level atomic systems in a photonic crystal, and introduce effective A and B coefficients for the case of a photonic crystal. © 2005 OSA/FIO.

Hyperuniform geometries feature correlated disordered topologies which follow from a tailored k-space design. Here we study gold plasmonic hyperuniform metasurfaces and we report evidence of the effectiveness of k-space engineering on both light scattering and light emission experiments. The metasurfaces possess interesting directional emission properties which are revealed by momentum spectroscopy as diffraction and fluorescence emission rings at size-specific k-vectors. The opening of these rotational-symmetric patterns scales with the hyperuniform correlation length parameter as predicted via the spectral function method.

To-date, despite remarkable applications in optoelectronics and tremendous amount of theoretical, computational and experimental efforts, there is no technological pathway enabling the fabrication of 3D photonic band gaps in the visible range. The resolution of advanced 3D printing technology does not allow to fabricate such materials and the current silica-based nanofabrication approaches do not permit the structuring of the desired optical material. Materials based on colloidal self-assembly of polymer spheres open 3D complete band gaps in the infrared range, but, owing to their critical index, not in the visible range. More complex systems, based on oriented tetrahedrons, are still prospected. Here we show, numerically, that FCC foams (Kepler structure) open a 3D complete band gap with a critical index of 2.80, thus compatible with the use of rutile TiO2. We produce monodisperse solid Kepler foams including thousands of pores, down to 10 um, and present a technological pathway, based on standard technologies, enabling the downsizing of such foams down to 400 nm, a size enabling the opening of a complete band gap centered at 500 nm.

Phys. Rev. B 95, 094120 (2017) We demonstrate the existence of large phononic band gaps in designed hyperuniform (isotropic) disordered two-dimensional (2D) phononic structures of Pb cylinders in epoxy matrix. The phononic band gaps in hyperuniform disordered phononic structures are comparable to band gaps of similar periodic structures, for both out-of-plane and in-plane polarizations. A large number of localized modes is identified near the band edges, as well as, diffusive transmission throughout the rest of the frequency spectrum. Very high-Q cavity modes for both out-of-plane and in-plane polarizations are formed by selectively removing a single cylinder out of the structure. Efficient waveguiding with almost 100% transmission trough waveguide structures with arbitrary bends is also presented. We expand our results to thin three-dimensional layers of such structures and demonstrate effective band gaps related to the respective 2D band gaps. Moreover, the drop in the Q factor for the three-dimensional structures is not more than three orders of magnitude compared to the 2D ones.

Hyperuniform disordered photonic materials have recently been shown to display large, complete photonic band gaps and isotropic optical properties, and are emerging as strong candidates for a plethora of optoelectronic applications, making them competitive with many of their periodic and quasiperiodic counterparts. In this work, high quality factor optical cavities in hyperuniform disordered architectures are fabricated through semiconductor slabs and experimentally addressed by scanning near-field optical microscopy. The wide range of confined cavity modes that we detect arise from carefully designed local modifications of the dielectric structure. Previous works on hyperuniform disordered photonic systems have previously identified several Anderson localized states spectrally located at the PBG edges with relatively high quality factors. In this work, by engineering the structural parameters of the cavity, we achieve an experimental quality factor of order 6000 (higher than the one of the Anderson states) and we demonstrate that three types of localized modes of different nature coexist within a small area and in a relatively narrow spectral window of the disordered correlated system. Their compatibility with general boundary constraints, in contrast with ordered architectures that suffer strict layout constraints imposed by photonic crystals' axes orientation, makes optical cavities in disordered hyperuniform patterns a flexible optical insulator platform for planar optical circuits. Comment: 9 pages, 5 figures

In photonic crystals, the propagation of light is governed by their photonic band structure, an ensemble of propagating states grouped into bands, separated by photonic band gaps. Due to discrete symmetries in spatially strictly periodic dielectric structures their photonic band structure is intrinsically anisotropic. However, for many applications, such as manufacturing artificial structural color materials or developing photonic computing devices, but also for the fundamental understanding of light-matter interactions, it is of major interest to seek materials with long range nonperiodic dielectric structures which allow the formation of isotropic photonic band gaps. Here, we report the first ever 3D isotropic photonic band gap for an optimized disordered stealthy hyperuniform structure for microwaves. The transmission spectra are directly compared to a diamond pattern and an amorphous structure with similar node density. The band structure is measured experimentally for all three microwave structures, manufactured by 3D laser printing for metamaterials with refractive index up to n=2.1⁠. Results agree well with finite-difference-time-domain numerical investigations and a priori calculations of the band gap for the hyperuniform structure: the diamond structure shows gaps but being anisotropic as expected, the stealthy hyperuniform pattern shows an isotropic gap of very similar magnitude, while the amorphous structure does not show a gap at all. Since they are more easily manufactured, prototyping centimeter scaled microwave structures may help optimizing structures in the technologically very interesting region of infrared.

In photonic crystals the propagation of light is governed by their photonic band structure, an ensemble of propagating states grouped into bands, separated by photonic band gaps. Due to discrete symmetries in spatially strictly periodic dielectric structures their photonic band structure is intrinsically anisotropic. However, for many applications, such as manufacturing artificial structural color materials or developing photonic computing devices, but also for the fundamental understanding of light-matter interactions, it is of major interest to seek materials with long range non-periodic dielectric structures which allow the formation of {\it isotropic} photonic band gaps. Here, we report the first ever 3D isotropic photonic band gap for an optimized disordered stealthy hyperuniform structure for microwaves. The transmission spectra are directly compared to a diamond pattern and an amorphous structure with similar node density. The band structure is measured experimentally for all three microwave structures, manufactured by 3D-Laser-printing for meta-materials with refractive index up to $n=2.1$. Results agree well with finite-difference-time-domain numerical investigations and a priori calculations of the band-gap for the hyperuniform structure: the diamond structure shows gaps but being anisotropic as expected, the stealthy hyperuniform pattern shows an isotropic gap of very similar magnitude, while the amorphous structure does not show a gap at all. The centimeter scaled microwave structures may serve as prototypes for micrometer scaled structures with bandgaps in the technologically very interesting region of infrared (IR).

Hyperuniform disordered photonic materials offer a novel setting for the study of electromagnetic wave propagation in disordered media. They have been shown to have large and complete photonic band gaps in two-dimensions, which have proved useful for arbitrarily shaped waveguides, enhanced solar absorption, and high-Q optical cavities. Investigation of one-dimensional stealthy hyperuniform disordered (SHD) photonic structures remains sparse. Therefore, further exploration is owed to the propagation of electromagnetic waves in one-dimensional SHD photonic structures, and to the geometric properties of the SHD patterns underlying them. In this work, we have generated one-dimensional SHD point patterns using a potential minimisation technique. Through plane-wave expansion simulation of one-dimensional SHD photonic structures, we found that the formation of photonic band gaps requires inclusion of a softcore repulsion term in the potential used to generate the SHD patterns. This repulsion set a minimum displacement between adjacent points and enables the prevention of overlapping scattering elements in the SHD photonic structure. This is in contrast to the case of two-dimensional SHD photonic structures in which large photonic band gaps are present in the absence of a softcore repulsion. With the introduction of a softcore repulsion, we were able to observe examples of photonic band gaps of 21.6% in one-dimensional SHD photonic structures based on Silicon and air. However, the mechanism behind band gap formation is thought to be the onset of medium to long range order. Finally, we present preliminary study of the localisation of electromagnetic waves in one-dimensional SHD photonic structures using both inverse participation ratio and level spacing statistics approaches.

Waveguides and electromagnetic cavities fabricated in hyperuniform disordered materials with complete photonic bandgaps are provided. Devices comprising electromagnetic cavities fabricated in hyperuniform disordered materials with complete photonic bandgaps are provided. Devices comprising waveguides fabricated in hyperuniform disordered materials with complete photonic bandgaps are provided. The devices include electromagnetic splitters, filters, and sensors.

We develop a recurrent neural network framework to model the non-Markovian dynamics exhibited by two-level atoms interacting with the radiation reservoir of a photonic crystal. Despite the strong non-Markovianity of the atomic dynamics induced by the rapid spectral variation in photonic density of states of the photonic reservoir, our recurrent neural network approach is able to capture precise details in the atomic evolution, including the fractional steady-state atomic population inversion and spectral splitting of the atomic transition. We demonstrate the robustness of the recurrent neural network setup against reduced data sets and its effectiveness to deal with systems of increased complexity.

Efficient and high-speed photodetection in the NIR is essential in several applications such as LiDAR and imaging. Silicon is an established choice as the base material for absorbing and converting photons to charge carriers. However, its high absorption length in the NIR imposes a trade-off between the absorption efficiency and detection bandwidth. Here, the rigorous coupled-wave analysis method together with the particle swarm optimization algorithm has been employed to optimize photonic crystal slab architectures with hexagonal symmetry to achieve efficient coupling of incoming pulses of light to the guided modes of the silicon photodetector. Our optimal design yields an ultra-efficient compact photodetector with more than 80% average absorption in the wavelength range 700 – 900 nm. Furthermore, considering scatterers of arbitrarily shaped polygonal cross-section, augments significantly the landscape in the optimization parameter space and results in further enhancement of the absorption efficiency. Our results show that introducing different length scales in the texturing leads to efficient broadband absorption in the compact device.

We demonstrate that hyperuniform disordered structures support electromagnetic states with very different transport properties, ranging from Bloch-like modes to diffusive states with characteristic time scales almost two-orders of magnitude larger.

We devise a new technique to enhance transmission of quantum information through linear optical quantum information processors. The idea is based on applying the Quantum Zeno effect to the process of photon absorption. By frequently monitoring the presence of the photon through a QND (quantum non-demolition) measurement the absorption is suppressed. Quantum information is encoded in the polarization degrees of freedom and is therefore not affected by the measurement. Some implementations of the QND measurement are proposed.

High quality opal-like photonic crystals containing graphene are fabricated using evaporation-driven self-assembly of soft polymer colloids. A miniscule amount of pristine graphene within a colloidal crystal lattice results in the formation of colloidal crystals with a strong angle-dependent structural color and a stop band that can be reversibly shifted across the visible spectrum. The crystals can be mechanically deformed or can reversibly change color as a function of their temperature, hence their sensitive mechanochromic and thermochromic response make them attractive candidates for a wide range of visual sensing applications. In particular, we show that the crystals are excellent candidates for visual strain sensors or integrated time-temperature indicators which act over large temperature windows. Given the versatility of these crystals, this method represents a simple, inexpensive and scalable approach to produce multifunctional graphene infused synthetic opals and opens up exciting applications for novel solution-processable nanomaterial based photonics.

We investigate the general features of thermal emission and absorption of radiation in photonic crystals. The light-matter interaction is strongly affected by the presence of the three-dimensional photonic crystal and the alteration of the photonic density of states can be used to suppress or enhance the thermal emissivity and absorptivity of the dielectric structure. Our analysis shows that the thermal response of the system depends on both the elementary absorbers/emitters and the photonic reservoir characteristics. In particular, we demonstrate that, depending on the system configuration, the thermal emission may exceed the free-space radiative energy density given by Planck's law. This modification of the Planck's law is achieved without altering the optical properties of the absorber/emitter medium, which remain consistent with the usual definition of a frequency and angle dependent grey-body. We also evaluate the rate of spontaneous emission, stimulated emission and absorption for thermally driven two-level atomic systems in a photonic crystal, and introduce effective A and B coefficients for the case of a photonic crystal. © 2005 OSA/FIO.

The quality factor, Q, of photonic resonators permeates most figures of merit in applications that rely on cavity-enhanced light–matter interaction such as all-optical information processing, high-resolution sensing, or ultralow-threshold lasing. As a consequence, large-scale efforts have been devoted to understanding and efficiently computing and optimizing the Q of optical resonators in the design stage. This has generated large know-how on the relation between physical quantities of the cavity, e.g., Q, and controllable parameters, e.g., hole positions, for engineered cavities in gaped photonic crystals. However, such a correspondence is much less intuitive in the case of modes in disordered photonic media, e.g., Anderson-localized modes. Here, we demonstrate that the theoretical framework of quasinormal modes (QNMs), a non-Hermitian perturbation theory for shifting material boundaries, and a finite-element complex eigensolver provide an ideal toolbox for the automated shape optimization of Q of a single photonic mode in both ordered and disordered environments. We benchmark the non-Hermitian perturbation formula and employ it to optimize the Q-factor of a photonic mode relative to the position of vertically etched holes in a dielectric slab for two different settings: first, for the fundamental mode of L3 cavities with various footprints, demonstrating that the approach simultaneously takes in-plane and out-of-plane losses into account and leads to minor modal structure modifications; and second, for an Anderson-localized mode with an initial Q of 200, which evolves into a completely different mode, displaying a threefold reduction in the mode volume, a different overall spatial location, and, notably, a 3 order of magnitude increase in Q.

We report the first experimental demonstration of guiding, bending and power-splitting of light in 2D disordered photonic bandgap materials at infrared wavelengths, along curved paths, around sharp bends of arbitrary angles, and through Y-shape junctions. © 2013 Optical Society of America.

Hyperuniform disordered photonic materials have recently been shown to display large, complete photonic band gaps and isotropic optical properties, and are emerging as strong candidates for a plethora of optoelectronic applications, making them competitive with many of their periodic and quasiperiodic counterparts. In this work, high quality factor optical cavities in hyperuniform disordered architectures are fabricated through semiconductor slabs and experimentally addressed by scanning near-field optical microscopy. The wide range of confined cavity modes that we detect arise from carefully designed local modifications of the dielectric structure. Previous works on hyperuniform disordered photonic systems have previously identified several Anderson localized states spectrally located at the PBG edges with relatively high quality factors. In this work, by engineering the structural parameters of the cavity, we achieve an experimental quality factor of order 6000 (higher than the one of the Anderson states) and we demonstrate that three types of localized modes of different nature coexist within a small area and in a relatively narrow spectral window of the disordered correlated system. Their compatibility with general boundary constraints, in contrast with ordered architectures that suffer strict layout constraints imposed by photonic crystals' axes orientation, makes optical cavities in disordered hyperuniform patterns a flexible optical insulator platform for planar optical circuits.

Hyperuniform disordered photonic structures are a peculiar category of disordered photonic heterostructures located between random structures and ordered photonic crystals. These materials, thanks to the presence of a photonic bandgap, exhibit the advantages of random and ordered structures since they have been shown to support in a small spatial footprint a high density of Anderson-localized modes, which naturally occur at the bandgap edges with peculiar features like relatively high Q/V ratios. Different localization behaviors have been recently reported in hyperuniform disordered luminescent materials, with a well-established and widely studied design, based on disordered networks. Here, we explore an alternative design, based on circular holes of different sizes hyperuniformely distributed, that we investigate theoretically and experimentally by means of scanning near-field optical microscopy. We report that the spectral features of hyperuniform disordered networks can also be extended to a different design, which, in turn, displays pseudo-photonic bandgaps and light localization. The ability of generating different kinds of hyperuniform disordered photonic systems that share the same theoretical and experimental optical features can largely extend practical potentialities and integration in many optoelectronic applications.

Disordered photonic nanostructures have attracted tremendous interest in the past three decades, not only due to the fascinating and complex physics of light transport in random media, but also for peculiar functionalities in a wealth of interesting applications. Recently, the interest in dielectric disordered systems has received new inputs by exploiting the role of long-range correlation within scatterer configurations. Hyperuniform photonic materials, that share features of photonic crystals and random systems, constitute the archetype of systems where light transport can be tailored from diffusive transport to a regime dominated by light localization due to the presence of photonic band gap. Here, advantage is taken of the combination of the hyperuniform disordered (HuD) design in slab photonics, the use of embedded quantum dots for feeding the HuD resonances, and near-field hyperspectral imaging with sub-wavelength resolution in the optical range to explore the transition from localization to diffusive transport. It is shown, theoretically and experimentally, that photonic HuD systems support resonances ranging from strongly localized modes to extended modes. It is demonstrated that Anderson-like modes with high Q/V are created, with small footprint, intrinsically reproducible and resilient to fabrication-induced disorder, paving the way for a novel photonic platform for quantum applications.

The quality factor, Q, of photonic resonators permeates most figures of merit in applications that rely on cavity-enhanced light–matter interaction such as all-optical information processing, high-resolution sensing, or ultralow-threshold lasing. As a consequence, large-scale efforts have been devoted to understanding and efficiently computing and optimizing the Q of optical resonators in the design stage. This has generated large know-how on the relation between physical quantities of the cavity, e.g., Q, and controllable parameters, e.g., hole positions, for engineered cavities in gaped photonic crystals. However, such a correspondence is much less intuitive in the case of modes in disordered photonic media, e.g., Anderson-localized modes. Here, we demonstrate that the theoretical framework of quasinormal modes (QNMs), a non-Hermitian perturbation theory for shifting material boundaries, and a finite-element complex eigensolver provide an ideal toolbox for the automated shape optimization of Q of a single photonic mode in both ordered and disordered environments. We benchmark the non-Hermitian perturbation formula and employ it to optimize the Q-factor of a photonic mode relative to the position of vertically etched holes in a dielectric slab for two different settings: first, for the fundamental mode of L3 cavities with various footprints, demonstrating that the approach simultaneously takes in-plane and out-of-plane losses into account and leads to minor modal structure modifications; and second, for an Anderson-localized mode with an initial Q of 200, which evolves into a completely different mode, displaying a threefold reduction in the mode volume, a different overall spatial location, and, notably, a 3 order of magnitude increase in Q.

We present designs of 2D, isotropic, disordered, photonic materials of arbitrary size with complete band gaps blocking all directions and polarizations. The designs with the largest band gaps are obtained by a constrained optimization method that starts from a hyperuniform disordered point pattern, an array of points whose number variance within a spherical sampling window grows more slowly than the volume. We argue that hyperuniformity, combined with uniform local topology and short-range geometric order, can explain how complete photonic band gaps are possible without long-range translational order. We note the ramifications for electronic and phononic band gaps in disordered materials.

We investigate the possibility to selectively reflect certain wavelengths while maintaining the optical properties on other spectral ranges. This is of particular interest for transparent materials, which for specific applications may require high reflectivity at pre-determined frequencies. Although there exist currently techniques such as coatings to produce selective reflection, this work focuses on new approaches for mass production of polyethylene sheets which incorporate either additives or surface patterning for selective reflection between 8 to 13 mu m. Typical additives used to produce a greenhouse effect in plastics include particles such as clays, silica or hydroxide materials. However, the absorption of thermal radiation is less efficient than the decrease of emissivity as it can be compared with the inclusion of Lambertian materials. Photonic band gap engineering by the periodic structuring of metamaterials is known in nature for producing the vivid bright colors in certain organisms via strong wavelength-selective reflection. Research to artificially engineer such structures has mainly focused on wavelengths in the visible and near infrared. However few studies to date have been carried out to investigate the properties of metastructures in the mid infrared range even though the patterning of microstructure is easier to achieve. We present preliminary results on the diffuse reflectivity using FDTD simulations and analyze the technical feasibility of these approaches.

The porosity and inhomogeneity of 3D printed polymer samples were examined using terahertz time-domain spectroscopy, and the effects of 3D printer settings were analysed. A set of PETG samples were 3D printed by systematically varying the printer parameters, including layer thickness, nozzle diameter, filament (line) thickness, extrusion, and printing pattern. Their effective refractive indices and loss coefficients were measured and compared with those of solid PETG. Porosity was calculated from the refractive index. A diffraction feature was observed in the loss spectrum of all 3D printed samples and was used as an indication of inhomogeneity. A “sweet spot” of printer settings was found, where porosity and inhomogeneity were minimised.

Typical supercell approaches used to investigate the electronic properties of GaAs(1−x)Bi(x) produce highly accurate, but folded, band structures. Using a highly optimized algorithm, we unfold the band structure to an approximate $E____left(____mathbf{k}____right)$ relation associated with an effective Brillouin zone. The dispersion relations we generate correlate strongly with experimental results, confirming that a regime of band gap energy greater than the spin–orbit-splitting energy is reached at around 10% bismuth fraction. We also demonstrate the effectiveness of the unfolding algorithm throughout the Brillouin zone (BZ), which is key to enabling transition rate calculations, such as Auger recombination rates. Finally, we show the effect of disorder on the effective masses and identify approximate values for the effective mass of the conduction band and valence bands for bismuth concentrations from 0–12%.

Using finite-difference-time-domain and band-structure simulations, we demonstrate efficient confinement of TE-polarized radiation and high-Q optical-cavities and low-loss waveguides in planar hyperuniform-disordered (HUD) architectures based on a design strategy that has potential to be a general purpose platform for optical microcircuits. © OSA 2015.

We introduce designs for high-Q photonic cavities in slab architectures in hyperuniform disordered solids displaying isotropic band gaps. Despite their disordered character, hyperuniform disordered structures have the ability to tightly confine the transverse electric-polarized radiation in slab configurations that are readily fabricable. The architectures are based on carefully designed local modifications of otherwise unperturbed hyperuniform dielectric structures. We identify a wide range of confined cavity modes, which can be classified according to their approximate symmetry (monopole, dipole, quadrupole, etc.) of the confined electromagnetic wave pattern. We demonstrate that quality factors Q>109 can be achieved for purely two-dimensional structures, and that for three-dimensional finite-height photonic slabs, quality factors Q>20000 can be maintained.

We introduce novel planar hyperuniform-disordered (HUD) architectures as potential general-purpose platform for optical microcircuits. Efficient confinement of TE-polarized radiation and high-Q optical-cavities and low-loss waveguides is demonstrated using finite difference-time-domain and band-structure simulations. © 2015 Optical Society of America.

This article explores the dynamics of many-body atomic systems symmetrically coupled to Lorentzian photonic cavity systems. Our study reveals interesting dynamical characteristics, including non-zero steady states, super-radiant decay, enhanced energy transfer, and the ability to modulate oscillations in the atomic system by tuning environmental degrees of freedom. We also analyze a configuration consisting of a three-atom chain embedded in a photonic cavity. Similarly, we find a strong enhancement of the energy transfer rate between the two ends of the chain and identified specific initial conditions that lead to significantly reduced dissipation between the two atoms at the end of the chain. Another configuration of interest consists of two symmetrical detuned reservoirs with respect to the atomic system. In the single atom case, we show that it is possible to enhance the decay rate of the system by modulating its reservoir detuning. In contrast, in the many-atom case, this results in dynamics akin to the on-resonant cavity. Finally, we examine the validity of the rotating wave approximation through a direct comparison against the numerically exact hierarchical equations of motion. We find good agreement in the weak coupling regime, while in the intermediate coupling regime, we identify qualitative similarities, but the rotating wave approximation becomes less reliable. In the moderate coupling regime, we find deviations of the steady states due to the formation of mixed photon-atom states.

Dataset accompanying the "Quantum memory effects in atomic ensembles coupled to photonic cavities" publication.

We report the first experimental demonstration of photonic bandgaps (PBGs) in 2D hyperuniform disordered materials and show that is possible to obtain isotropic, disordered, photonic materials of arbitrary size with complete PBGs. (C)2010 Optical Society of America

In this article we propose to build a (semi-)deterministic photon gun by modifying the spontaneous decay in a photonic band-gap material. We show that such a device allows for deterministic and unidirectional single-photon emission with a repetition rate of the order of 100 kHz. We describe a specific realization of the 1D band-gap model by means of a 3D photonic-crystal heterostructure and the feasability of implementing such a device using Er3+ ions that produce single photons at the telecommunication wavelength of 1.55,m, important for many applications.

Many optically active systems possess spatially asymmetric electron orbitals. These generate permanent dipole moments, which can be stronger than the corresponding transition dipole moments, significantly affecting the system dynamics and creating polarised Fock states of light. We derive a master equation for these systems by employing an optical polaron transformation that captures the photon mode polarisation induced by the permanent dipoles. This provides an intuitive framework to explore their influence on the system dynamics and emission spectrum. We find that permanent dipoles introduce multiple-photon processes and a photon sideband which causes substantial modifications to single-photon transition dipole processes. In the presence of an external drive, permanent dipoles lead to an additional process that we show can be exploited to optimise the decoherence and transition rates. We derive the emission spectrum of the system, highlighting experimentally detectable signatures of optical polarons, and measurements that can identify the parameters in the system Hamiltonian, the magnitude of the differences in the permanent dipoles, and the steady-state populations of the system.

Hyperuniform geometries feature correlated disordered topologies which follow from a tailored k-space design. Here, we study gold plasmonic hyperuniform disordered surfaces and, by momentum spectroscopy, we report evidence of k-space engineering on both light scattering and light emission. Even if the structures lack a well-defined periodicity, emission and scattering are directional in ring-shaped patterns. The opening of these rotational-symmetric patterns scales with the hyperuniform correlation length parameter as predicted via the spectral function method.

We report the first experimental demonstration of guiding, bending, filtering, and splitting of EM wave in 2D disordered PBG materials, along arbitrarily curved paths, around sharp bends of arbitrary angles, and through Y shape junctions. © 2012 OSA.

Photonic crystal cavities enable the realization of high Q-factor and low mode-volume resonators, with typical architectures consisting of a thin suspended periodically patterned layer to maximize confinement of light by strong index guiding. We investigate a heterostructure-based approach comprising a high refractive index core and lower refractive index cladding layers. While confinement typically decreases with decreasing index contrast between the core and cladding layers, we show that, counterintuitively, due to the confinement provided by the photonic band structure in the cladding layers, it becomes possible to achieve Q factors > 10 4 with only a small refractive index contrast. This opens up opportunities for implementing high-Q factor cavities in conventional semiconductor heterostructures, with direct applications to the design of electrically pumped nanocavity lasers using conventional fabrication approaches.

Many optically active systems possess spatially asymmetric electron orbitals. These generate permanent dipole moments, which can be stronger than the corresponding transition dipole moments, significantly affecting the system dynamics and creating polarized Fock states of light. We derive a master equation for these systems with an externally applied driving field by employing an optical polaron transformation that captures the photon mode polarization induced by the permanent dipoles. This provides an intuitive framework to explore their influence on the system dynamics and emission spectrum. We find that permanent dipoles introduce multiple-photon processes and a photon sideband, which causes substantial modifications to single-photon transition dipole processes. In the presence of an external drive, permanent dipoles lead to an additional process that we show can be exploited to control the decoherence and transition rates. We derive the emission spectrum of the system, highlighting experimentally detectable signatures of optical polarons, and measurements that can identify the parameters in the system Hamiltonian, the magnitude of the differences in the permanent dipoles, and the steady-state populations of the system.

We introduce novel planar hyperuniform-disordered (HUD) architectures as potential general-purpose platform for optical microcircuits. Efficient confinement of TE-polarized radiation and high-Q optical-cavities and low-loss waveguides is demonstrated using finite difference-time-domain and band-structure simulations. © 2015 Optical Society of America.

Hyperuniform disordered photonic structures/solids (HUDS) are a new class of photonic solids, which display large, isotropic photonic band gaps (PBG) comparable in size to the ones found in photonic crystals (PC). The existence of large band gaps in HUDS contradicts the long-standing intuition that Bragg scattering and long- range translational order is required in PBG formation, and demonstrates that interactions between Mie-like local resonances and multiple scattering can induce on their own PBGs. HUDS combine advantages of both isotropy due to disorder (absence of long range two-point correlations) and controlled scattering properties from uniform local topology due to hyperuniformity (constrained disorder). In this paper we review the photonic properties of HUDS including the origin of PBGs and potential applications. We address technologically realisable designs of HUDS including localisation of light in point-defect-like optical cavities and the guiding of light in free-form PC waveguide analogues. We show that HUDS are a promising general-purpose design platform for integrated optical micro-circuitry, including active devices such as optical microcavity lasers and modulators.

We describe a practical implementation of a semi-deterministic photon gun based on the stimulated Raman adiabatic passage pumping and the nonlinear tuning of the photonic density of states in a photonic band-gap material. We show that this device allows deterministic and unidirectional production of single photons with a high repetition rate of the order of 100 kHz. We also discuss specific 3D photonic microstructure architectures in which our model can be realized and the feasibility of implementing such a device using Er 3+ ions that produce single photons at the telecommunication wavelength of 1.55 microns

We explore the ability of hyperuniform disordered structures to enhance light absorption in thin-film solar cells architectures and perform full electromagnetic wave simulations that unveil light trapping techniques capable to attain large absorption enhancements up 85% over the visible spectrum. We predicate this enhancement to the interplay between two key physical phenomena: ultimate control over the light diffraction via a hyperuniformly-patterned surface layer which results in a highly efficient coupling of light to the quasi-guided modes of the absorbing silicon film and a concomitant minimisation of the reflection losses atop of the solar absorber. Our experimental results further validate this approach, showcasing an impressive 65% enhancement in solar light absorption in a freely suspended 1-μm c-Si membrane across the spectral range from 400 to 1050nm. We also explore applications of hyperuniform disordered architectures to high-efficiency solar-thermal absorbers.

We employ a recently introduced class of artificial structurally-disordered phononic structures that exhibit large and robust elastic frequency band gaps for efficient phonon guiding. Phononic crystals are periodic structures that prohibit the propagation of elastic waves through destructive interference and exhibit large band gaps and ballistic propagation of elastic waves in the permitted frequency ranges. In contrast, random-structured materials do not exhibit band gaps and favour localization or diffusive propagation. Here, we use structures with correlated disorder constructed from the so-called stealthy hyperuniform disordered point patterns, which can smoothly vary from completely random to periodic (full order) by adjusting a single parameter. Such amorphous-like structures exhibit large band gaps (comparable to the periodic ones), both ballistic-like and diffusive propagation of elastic waves, and a large number of localized modes near the band edges. The presence of large elastic band gaps allows the creation of waveguides in hyperuniform materials, and we analyse various waveguide architectures displaying nearly 100% transmission in the GHz regime. Such phononic-circuit architectures are expected to have a direct impact on integrated micro-electro-mechanical filters and modulators for wireless communications and acousto-optical sensing applications.

Hyperuniform geometries feature correlated disordered topologies which follow from a tailored k-space design. Here, we study gold plasmonic hyperuniform disordered surfaces and, by momentum spectroscopy, we report evidence of kspace engineering on both light scattering and light emission. Even if the structures lack a well-defined periodicity, emission and scattering are directional in ring-shaped patterns. The opening of these rotational-symmetric patterns scales with the hyperuniform correlation length parameter as predicted via the spectral function method.

Using finite-difference-time-domain and band-structure simulations, we demonstrate efficient confinement of TE-polarized radiation and high-Q optical-cavities and low-loss waveguides in planar hyperuniform-disordered (HUD) architectures based on a design strategy that has potential to be a general purpose platform for optical microcircuits. © OSA 2015.

  Conference Title: 2014 Optical Fiber Communications Conference and Exhibition (OFC) Conference Start Date: 2014, March 9 Conference End Date: 2014, March 13 Conference Location: San Francisco, CA, USA We report preliminary results for silicon waveguides and devices in hyperuniform disordered photonic solids. Temperature sensitivity of resonant defects is more than 500 times lower than that of the standard silicon microring resonators. [PUBLICATION ABSTRACT]

We introduce novel planar hyperuniform-disordered (HUD) architectures as potential general-purpose platform for optical microcircuits. Efficient confinement of TE-polarized radiation and high-Q optical-cavities and low-loss waveguides is demonstrated using finite difference-time-domain and band-structure simulations. © 2015 Optical Society of America.

Waveguides and electromagnetic cavities fabricated in hypemniform disordered materials with complete photonic bandgaps are provided. Devices comprising electromagnetic cavities fabricated in hypemniform disordered materials with complete photonic bandgaps are provided. Devices comprising waveguides fabricated in hypemniform disordered materials with complete photonic bandgaps are provided. The devices include electromagnetic splitters, filters, and sensors.

We report preliminary results for silicon waveguides and devices in hyperuniform disordered photonic solids. Temperature sensitivity of resonant defects is more than 500 times lower than that of the standard silicon microring resonators. © 2013 Optical Society of America.

Coherent control of optical waves by scattering from 2D plasmonic surfaces is a very active field with the goal of wavefront shaping an incoming light beam via nanostructured surfaces. Here we report gold hyperuniform surfaces fabricated by electron beam lithography and designed to interact with visible radiation. We observe omnidirectional light diffraction in the far-field indicating successful k-space design with rotational symmetry, and spontaneous emission directional control of near-field coupled emitters.

We report experimental and simulation results for silicon waveguides and resonant cavities in hyperuniform disordered photonic solids. Our results demonstrate the ability of disordered photonic bandgap materials to serve as a platform for silicon photonics.

We introduce novel architecture for cavity design in an isotropic disordered photonic band gap material. We demonstrate that point-like defects can support localized modes with different symmetries and multiple resonant frequencies, useful for various applications.

Solid foams with micrometric pores are used in different fields (filtering, 3D cell culture, etc.), but today, controlling their foam geometry at the pore level, their internal structure, and the monodispersity, along with their mechanical properties, is still a challenge. Existing attempts to create such foams suffer either from slow speed or size limitations (above 80 μm). In this work, by using a temperature-regulated microfluidic process, 3D solid foams with highly monodisperse open pores (PDI lower than 5%), with sizes ranging from 5 to 400 μm and stiffnesses spanning 2 orders of magnitude, are created for the first time. These features open the way for exciting applications, in cell culture, filtering, optics, etc. Here, the focus is set on photonics. Numerically, these foams are shown to open a 3D complete photonic bandgap, with a critical index of 2.80, thus compatible with the use of rutile TiO2. In the field of photonics, such structures represent the first physically realizable self-assembled FCC (face-centered cubic) structure that possesses this functionality.

In this article we explore the dynamics of many-body atomic systems symmetrically coupled to a single Lorentzian photonic cavity. Our study reveals interesting dynamical characteristics including non-zero steady states, superradiant decay, enhanced energy transfer and the ability to modulate oscillations in the atomic system by tuning environmental degrees of freedom. We also analyse a configuration consisting of a three-atom chain embedded in a photonic cavity. Similarly, we find a strong enhancement of the energy transfer rate between the two ends of the chain and identified specific initial conditions that lead to significantly reduced dissipation between the two atoms at the end of the chain. Another configuration of interest consists of two symmetrical detuned reservoirs with respect to the atomic system. In the single-atom case, we show that it is possible to enhance the decay rate of the system by modulating its reservoir detuning, while in the many-atom case, this results in dynamics akin to the on-resonant cavity. Finally, we examine the validity of rotating wave approximation through a direct comparison against the numerically exact hierarchical equations of motion approach. We find good agreement in the weak coupling regime while in the intermediate coupling regime, we identify qualitative similarities, but the rotating wave approximation becomes less reliable. In the moderate coupling regime, we find deviation of the steady states due to the formation of mixed photon atom states.

In this article we employ a model open quantum system consisting of two-level atomic systems coupled to Lorentzian photonic cavities, as an instantiation of a quantum physical reservoir computer. We then deployed the quantum reservoir computing approach to an archetypal machine learning problem of image recognition. We contrast the effectiveness of the quantum physical reservoir computer against a conventional approach using neural network of the similar architecture with the quantum physical reservoir computer layer removed. Remarkably, as the data set size is increased the quantum physical reservoir computer quickly starts out perform the conventional neural network. Furthermore, quantum physical reservoir computer provides superior effectiveness against number of training epochs at a set data set size and outperformed the neural network approach at every epoch number sampled. Finally, we have deployed the quantum physical reservoir computer approach to explore the quantum problem associated with the dynamics of open quantum systems in which an atomic system ensemble interacts with a structured photonic reservoir associated with a photonic band gap material. Our results demonstrate that the quantum physical reservoir computer is equally effective in generating useful representations for quantum problems, even with limited training data size.

In this article, we explore the dynamical decoherence of the chromophores within a green fluorescent protein when coupled to a finite-temperature dielectric environment. Such systems are of significant interest due to their anomalously long coherence lifetimes compared to other biomolecules. We work within the spin-boson model and employ the Hierarchical Equations of Motion formalism which allows for the accounting of the full non-perturbative and non-Markovian characteristics of the system dynamics. We analyse the level coherence of independent green fluorescent protein chromophores and the energy transfer dynamics in homo-dimer green fluorescent proteins, focusing on the effect of dielectric relaxation on the timescales of these systems. Using the Fluctuation-Dissipation theorem, we generate spectral densities from local electric susceptibility generated from Poisson's equation and employ a Debye dielectric model for the solvent environment. For different system architectures, we identify a number of very striking features in the dynamics of the chromophore induced by the dielectric relaxation of the environment, resulting in strong memory effects that extend the coherence lifetime of the system. Remarkably, the complex architecture of the green fluorescent protein, which includes a cavity-like structure around the atomic system, is well suited to preserving the coherences in the homo-dimer system. The system dynamics generate a dynamical correlation between the coherent energy transfer between its sub-systems and the entropy production, which can lead to transient reductions in entropy, a unique feature of the non-Markovian nature of the system-environment interaction.

We report experimental and simulation results for low-loss wave-guiding in Si-based hyperuniform disordered photonic bandgap materials at infrared wavelengths. These results pave the way for deploying disordered photonic solids in integrated photonic circuits. © 2014 Optical Society of America.

We describe a practical implementation of a semi-deterministic photon gun based on the stimulated Raman adiabatic passage pumping and the nonlinear tuning of the photonic density of states in a photonic band-gap material. We show that this device allows deterministic and unidirectional production of single photons with a high repetition rate of the order of 100 kHz. We also discuss specific 3D photonic microstructure architectures in which our model can be realized and the feasibility of implementing such a device using Er ions that produce single photons at the telecommunication wavelength of 1.55 μ m. © 2006 Elsevier B.V. All rights reserved.

We introduce a hyperuniform-disordered platform for the realization of near-infrared photonic devices on a silicon-on-insulator platform, demonstrating the functionality of these structures in a fexible silicon photonics integrated circuit platform unconstrained by crystalline symmetries. The designs proposed advantageously leverage the large, complete, and isotropic photonic band gaps provided by hyperuniform disordered structures. An integrated design for a compact, sub-volt, sub-fJ/ bit, hyperuniform-clad, electrically controlled resonant optical modulator suitable for fabrication in the silicon photonics ecosystem is presented along with simulation results. We also report results for passive device elements, including waveguides and resonators, which are seamlessly integrated with conventional silicon-on-insulator strip waveguides and vertical couplers. We show that the hyperuniform-disordered platform enables improved compactness, enhanced energy efciency, and better temperature stability compared to the silicon photonics devices based on rib and strip waveguides.

We explore the dynamics of $N$ coupled atoms to a generic bosonic reservoir under specific system symmetries. In the regime of multiple atoms coupled to a single reservoir with identical couplings, we identify remarkable effects, notably that the initial configuration of the atomic excited state amplitudes strongly impacts the dynamics of the system and can even fully sever the system from its environment. Additionally, we find that steady state amplitudes of the excited states become independent of the choice of the reservoir. The framework introduced is applied to a structured photonic reservoir associated with a photonic crystal, where we show it reproduces previous theoretical and experimental results and it predicts superradiant behaviour within the single-excitation regime.

When fabricating photonic crystals from suspensions in volatile liquids using the horizontal deposition method, the conventional approach is to evaporate slowly to increase the time for particles to settle in an ordered, periodic close-packed structure. Here, we show that the greatest ordering of 10 nm aqueous gold nanoparticles (AuNPs) in a template of larger spherical polymer particles (mean diameter of 338 nm) is achieved with very fast water evaporation rates obtained with near-infrared radiative heating. Fabrication of arrays over areas of a few cm2 takes only seven minutes. The assembly process requires that the evaporation rate is fast relative to the particles’ Brownian diffusion. Then a two-dimensional colloidal crystal forms at the falling surface, which acts as a sieve through which the AuNPs pass, according to our Langevin dynamics computer simulations. With sufficiently fast evaporation rates, we create a hybrid structure consisting of a two-dimensional AuNP nanoarray (or “nanogrid”) on top of a three-dimensional polymer opal. The process is simple, fast and one-step. The interplay between the optical response of the plasmonic Au nanoarray and the microstructuring of the photonic opal results in unusual optical spectra with two extinction peaks, which are analyzed via finite-difference time-domain method simulations. Comparison between experimental and modelling results reveals a strong interplay of plasmonic modes and collective photonic effects, including the formation of a high-order stop band and slow-light enhanced plasmonic absorption. The structures, and hence their optical signatures, are tuned by adjusting the evaporation rate via the infrared power density.

We calculate the Conduction, Heavy Hole (HH) - Split-off Hole (SO), HH (CHSH) Auger Recombination rates for GaAs(1-x)Bix alloys, which are candidates for highly efficient telecommunication devices. A ten-band, tight-binding method, including spin-orbit coupling, was performed on a 9×9×9 strained supercell in order to generate an accurate band structure to perform the calculation on. This band structure was then unfolded to give a true E-k relation. As predicted by experiment, there should be a decrease in the Auger recombination rate as the concentration of Bismuth increases ending in a suppression at greater than ∼11% Bismuth. © 2013 IEEE.

An optical structure includes a Hyperuniform Disordered Solid ("HUDS") structure, a photonic crystal waveguide, and a perforated resonant structure. The HUDS structure is formed by walled cells organized in a lattice. The photonic crystal waveguide is configured to guide an optical signal and includes an unperforated central strip extended lengthwise and three rows of circular perforations disposed on each side of the unperforated central strip. The perforated resonant structure is formed along a boundary of the photonic crystal waveguide. The perforated resonant structure is configured to be resonant at a frequency band that is a subset of a bandwidth of the optical signal. The perforated resonant structure includes an outer segment, a middle segment, and an inner segment of the circular perforations that are offset away from the unperforated central strip at a first, second, and third offset distance.

The invention provides an article of manufacture, and methods of designing and making the article. The article permits or prohibits waves of energy, especially photonic/electromagnetic energy, to propagate through it, depending on the energy band gaps built into it. The structure of the article may be reduced to a pattern of points having a hyperuniform distribution. The point-pattern may exhibit a crystalline symmetry, a quasicrystalline symmetry or may be aperiodic. In some embodiments, the point pattern exhibits no long-range order. Preferably, the point-pattern is isotropic. In all embodiments, the article has a complete, TE- and TM-optimized band-gap. The extraordinary transmission phenomena found in the disordered hyperuniform photonic structures of the invention find use in optical micro-circuitry (all-optical, electronic or thermal switching of the transmission), near-field optical probing, thermophotovoltaics, and energy-efficient incandescent sources.

Thin, flexible, and invisible solar cells will be a ubiquitous technology in the near future. Ultrathin crystalline silicon (c-Si) cells capitalize on the success of bulk silicon cells while being lightweight and mechanically flexible, but suffer from poor absorption and efficiency. Here we present a new family of surface texturing, based on correlated disordered hyperuniform patterns, capable of efficiently coupling the incident spectrum into the silicon slab optical modes. We experimentally demonstrate 66.5% solar light absorption in free-standing 1 μm c-Si layers by hyperuniform nanostructuring for the spectral range of 400 to 1050 nm. The absorption equivalent photocurrent derived from our measurements is 26.3 mA/cm2, which is far above the highest found in literature for Si of similar thickness. Considering state-of-the-art Si PV technologies, we estimate that the enhanced light trapping can result in a cell efficiency above 15%. The light absorption can potentially be increased up to 33.8 mA/cm2 by incorporating a back-reflector and improved antireflection, for which we estimate a photovoltaic efficiency above 21% for 1 μm thick Si cells.

The invention provides a composition comprising a three-dimensional amorphous trivalent network which reduces the number of modes within a particular frequency range (ωc±Δω). The invention also extends to use of the composition as a structural colouration material and a paint, dye or fabric comprising the structural colouration material. Additionally, the invention extends to use of the composition as an optical filter or as a supporting matrix configured to define at least one optical component, such as a frequency filter, light-guiding structure for a telecommunications application, an optical computer chip, an optical micro-circuit or a laser comprising the supporting matrix.

We demonstrate the existence of large phononic band gaps in designed hyperuniform (isotropic) disordered two-dimensional (2D) phononic structures of Pb cylinders in epoxy matrix. The phononic band gaps in hyperuniform disordered phononic structures are comparable to band gaps of similar periodic structures, for both out-of-plane and in-plane polarizations. A large number of localized modes is identi ed near the band edges, as well as, di usive transmission throughout the rest of the frequency spectrum. Very high-Q cavity modes for both out-of-plane and in-plane polarizations are formed by selectively removing a single cylinder out of the structure. E cient waveguiding with almost 100% transmission trough waveguide structures with arbitrary bends is also presented. We expand our results to thin three-dimensional layers of such structures and demonstrate e ective band gaps related to the respective 2D band gaps. Moreover, the drop in the Q factor for the three-dimensional structures is not more than three orders of magnitude compared to the 2D ones.

The interaction of a material with light is intimately related to its wavelength-scale structure. Simple connections between structure and optical response empower us with essential intuition to engineer complex optical functionalities. Here we develop local self-uniformity as a novel measure of a random network’s internal structural similarity, ranking networks on a continuous scale from crystalline, through glassy intermediate states, to chaotic configurations. We demonstrate that complete photonic band gap structures possess substantial local selfuniformity and validate local self-uniformity’s importance in gap formation through design of novel amorphous gyroid structures. Amorphous gyroid samples are fabricated via 3D ceramic printing and the band gaps experimentally verified. We explore also the wing-scale structuring in the butterfly Pseudolycaena marsyas and show that it possesses substantial amorphous gyroid character, demonstrating the subtle order achieved by evolutionary optimisation and the possibility of an amorphous gyroid’s self-assembly.

We report preliminary results for silicon waveguides and devices in hyperuniform disordered photonic solids. Temperature sensitivity of resonant defects is more than 500 times lower than that of the standard silicon microring resonators. © 2013 Optical Society of America.

We report preliminary results for silicon waveguides and devices in hyperuniform disordered photonic solids. Temperature sensitivity of resonant defects is more than 500 times lower than that of the standard silicon microring resonators. © 2014 OSA.

We report the first experimental demonstration of guiding, bending and power-splitting of light in 2D disordered photonic bandgap materials at infrared wavelengths, along curved paths, around sharp bends of arbitrary angles, and through Y-shape junctions. © 2013 Optical Society of America.