Physics and Applications of Microstructured Photonic Materials

The field of photonics has advanced tremendously recently through the development of micro and nanostructured photonic materials. An important class of such materials is represented by photonic band gap (PBG) materials that present frequency ranges over which the electromagnetic light propagation is prohibited for all directions and polarizations. These materials are the optical analogues of semiconductors. Due to their unique ability to mold the flow of light and to control the light-matter interaction, PBG materials lead to a broad new frontier both in basic science and technology. An important part of our research is aimed at developing a theoretical understanding of these materials and at the identification and design of novel functionalities. Directions of research include photonic band gap formation in disordered and quasiperiodic photonic structures, physics and applications of thermal radiation control in photonic crystals and quantum optics and all-information processing in photonic band gap architectures.

Quantum Optics in Structured Photonic Reservoirs

The engineered electromagnetic vacuum associated with microstructured photonic materials is characterized by photonic density of states exhibiting discontinuous changes as a function of frequency and by highly anisotropic electromagnetic field distribution. As a result, the conventional quantum optical formalism can not be applied to describe the light-matter interaction in these materials, and new theories are needed.

In this context, we are interested in developing generalized theoretical frameworks for open quantum systems to accurately describe the quantum optical phenomena in frequency-dependent photonic reservoirs.

Linear Optical Quantum Information Processing in Photonic Nanostructures

It was demonstrated that efficient quantum computing can be implemented using only single-photon sources, passive linear optical elements, and detectors. Optical approaches to quantum computation benefit from the lack of decoherence of photons and the relative ease with which photons may be manipulated. In this context, my research concentrates on the implementation of highly efficient single-photon sources and quantum memory devices in nanostructured photonic materials.

Nanoelectronics and Spintronics

Experimental progress over the past two decades has made available electronic systems with an effectively reduced spatial dimensionality. The ability to create and manipulate charge and spin populations in low-dimensional quantum systems has generated a wide class of spin electronic (spintronics) applications. Our research in this area deals with the electronic and spins properties of quantum dots and their relevance for technological applications.

Designer disordered materials with large complete photonic band gaps

Marian Florescu, Salvatore Torquato, and Paul Steinhardt, "Designer disordered materials with large complete photonic band gaps",, Proceedings of the National Academy of Sciences 106, 20658 (2009).

Until recently, the only materials known to have sizeable complete photonic band gaps were photonic crystals, periodic structures, and it was generally assumed that long-range periodic order was instrumental in the PBG formation. We have discovered a new class of materials with large complete band gaps, namely, hyperuniform non-crystallographic  micro-structures. This class of materials characterized by suppressed density fluctuations (hyperuniformity) includes highly-isotropic, translationally-disordered structures. Due to their distinctive optical and structural properties, non-crystallographic PBG materials are expected to facilitate unprecedented capabilities for controlling light, such as waveguiding with arbitrary bending angle and highly-efficient isotropic emission, with great impact for information processing, energy harvesting, sensing, and lighting applications.

High-Q optical cavities in hyperuniform disordered materials

Timothy Amoah and Marian Florescu, "High-Q optical cavities in hyperuniform disordered materials",, Physical Review B, Rapid Communications 91, 020201(R) (2015); editors suggestion.

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>10^9 can be achieved for purely two-dimensional structures, and that for three-dimensional finite-height photonic slabs, quality factors Q>20,000 can be maintained.

Isotropic band gaps and freeform waveguides observed in hyperuniform disordered photonic solids

Weining Man, Marian Florescu, Eric Paul Williamson, Yingquan He, Seyed Reza Hashemizad, Brian YC Leung, Devin Robert Liner, Salvatore Torquato, Paul M Chaikin, Paul J Steinhardt, "Isotropic band gaps and freeform waveguides observed in hyperuniform disordered photonic solids",, Proceedings of the National Academy of Sciences 110, 15886 (2013).

Recently, disordered photonic media and random textured surfaces have attracted increasing attention as strong light diffusers with broadband and wide-angle properties. We report the experimental realization of an isotropic complete photonic band gap (PBG) in a 2D disordered dielectric structure. This structure is designed by a constrained optimization method, which combines advantages of both isotropy due to disorder and controlled scattering properties due to low-density fluctuations (hyperuniformity) and uniform local topology. Our experiments use a modular design composed of Al2O3 walls and cylinders arranged in a hyperuniform disordered network. We observe a complete PBG in the microwave region, in good agreement with theoretical simulations, and show that the intrinsic isotropy of this unique class of PBG materials enables remarkable design freedom, including the realization of waveguides with arbitrary bending angles impossible in photonic crystals. This experimental verification of a complete PBG and realization of functional defects in this unique class of materials demonstrate their potential as building blocks for precise manipulation of photons in planar optical microcircuits and has implications for disordered acoustic and electronic band gap materials.

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Complete band gaps in two-dimensional photonic quasicrystals

Marian Florescu, Salvatore Torquato, and Paul Steinhardt, "Complete band gaps in two-dimensional photonic quasicrystals", Physical Review B 80, 155112 (2009).

In photonic crystals, the opening of the PBG is understood to be governed by the synergetic interplay between Bragg scattering resonances of the periodic dielectric array and the Mie resonances of individual dielectric scattering centers. A similar combination of scattering mechanisms is possible in photonic quasicrystals, in which the dielectric materials are arranged in a pattern with long-range quasiperiodic translational order. The photonic band gaps in quasiperiodic structures are considerably more isotropic and may open for lower dielectric contrast required. We have introduced an optimization method to design examples of photonic quasicrystals with substantial, complete photonic band gaps. The method can be applied to photonic quasicrystals with arbitrary rotational symmetry, and we illustrate it for fivefold and eightfold symmetric quasicrystals. The optimized band gaps are highly isotropic, which may offer advantages over photonic crystals for certain applications.

Unfolding the band structure of non-crystalline photonic band gap materials

Samuel Tsitrin, Eric Paul Williamson, Timothy Amoah, Geev Nahal, Ho Leung Chan, Marian Florescu, and Weining Man, "Unfolding the band structure of non-crystalline photonic band gap materials", Scientific Reports 5, 13301(R) (2015).

Non-crystalline photonic band gap (PBG) materials have received increasing attention, and sizeable PBGs have been reported in quasi-crystalline structures and, more recently, in disordered structures. Band structure calculations for periodic structures produce accurate dispersion relations, which determine group velocities, dispersion, density of states and iso-frequency surfaces, and are used to predict a wide-range of optical phenomena including light propagation, excited-state decay rates, temporal broadening or compression of ultrashort pulses and complex refraction phenomena. However, band calculations for non-periodic structures employ large super-cells of hundreds to thousands building blocks, and provide little useful information other than the PBG central frequency and width. Using stereolithography, we construct cm-scale disordered PBG materials and perform microwave transmission measurements, as well as finite-difference time-domain (FDTD) simulations. The photonic dispersion relations are reconstructed from the measured and simulated phase data. Our results demonstrate the existence of sizeable PBGs in these disordered structures and provide detailed information of the effective band diagrams, dispersion relation, iso-frequency contours, and their angular dependence. Slow light phenomena are also observed in these structures near gap frequencies. This study introduces a powerful tool to investigate photonic properties of non-crystalline structures and provides important effective dispersion information, otherwise difficult to obtain.

Experimental observation of photonic bandgaps in hyperuniform disordered materialExperimental observation of photonic bandgaps in hyperuniform disordered material

Weining Man, Marian Florescu, Kazue Matsuyama, Polin Yadak, Geev Nahal, Seyed Hashemizad, Eric Williamson, Paul Steinhardt, Salvatore Torquato, and Paul Chaikin, "Photonic band gap in isotropic hyperuniform disordered solids with low dielectric contrast",Optics Express 21, 19972 (2013).

We report the first experimental demonstration of a TE-polarization photonic band gap (PBG) in a 2D isotropic hyperuniform disordered solid (HUDS) made of dielectric media with a dielectric index contrast of 1.6:1, very low for PBG formation. The solid is composed of a connected network of dielectric walls enclosing air-filled cells. Direct comparison with photonic crystals and quasicrystals permitted us to investigate band-gap properties as a function of increasing rotational isotropy. We present results from numerical simulations proving that the PBG observed experimentally for HUDS at low index contrast has zero density of states. The PBG is associated with the energy difference between complementary resonant modes above and below the gap, with the field predominantly concentrated in the air or in the dielectric. The intrinsic isotropy of HUDS may offer unprecedented flexibilities and freedom in applications (i. e. defect architecture design) not limited by crystalline symmetries.

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Fast Assembly of Gold Nanoparticles in Large-Area 2D Nanogrids Using a One-Step, Near-Infrared Radiation-Assisted Evaporation Process

André Utgenannt, Ross Maspero, Andrea Fortini, Rebecca Turner†, Marian Florescu, Christopher Jeynes, Antonios G. Kanaras, Otto L. Muskens, Richard P. Sear, and Joseph L. Keddie, "Fast Assembly of Gold Nanoparticles in Large-Area 2D Nanogrids Using a One-Step, Near-Infrared Radiation-Assisted Evaporation Process", ACS Nano, 10 (2), 2232 (2016).

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 7 min. 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 modeling results reveals a strong interplay of plasmonic modes and collective photonic effects, including the formation of a high-order stopband 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.

Thermal radiation from finite photonic crystals

Christian Schuler, Christian Wolff, Kurt Busch, and Marian Florescu, "Thermal radiation from finite photonic crystals", Applied Physics Letters 95, 241103 (2009).

We have developed a microscopic theory of thermal emission from finite-sized photonic crystals and show that the directional spectral emissivity and related quantities can be evaluated via standard bandstructure computations without any approximation. We then identify the physical mechanisms through which interfaces modify the potentially super-Planckian radiation flow inside infinite photonic crystals, such that thermal emission from finite-sized samples is consistent with the fundamental limits set by Planck's law. As an application, we further demonstrate that a judicious choice of a photonic crystal's surface termination facilitates considerable control over both the spectral and angular thermal emission properties.

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Thermal radiation in photonic crystals

Marian Florescu, Kurt Busch and Jonathan P. Dowling, "Thermal radiation in photonic crystals", Physical Review B Rapid Communications 75, 201101 (R) (2007).

We analyze the properties of thermal radiation in photonic crystals and show that the spectral energy density, the spectral intensity, and the spectral hemispherical power are only limited by the total number of available photonic states and their propagation characteristics. In addition, we show that the central quantity that determines these thermal radiation characteristics is the area of the isofrequency surfaces and not the photonic density of states as it is generally assumed. Through the presence of partial or complete photonic band gaps and the associated spectral and angular redistribution of photonic states, it is possible to obtain propagation directions along which thermal photon focusing effects appear.

Improving solar cell efficiency using photonic band-gap materials

Marian Florescu, Hwang Lee, Irina Puscasu, Martin Pralle, Lucia Florescu, David Ting and Jonathan Dowling, "Improving Solar Cell Efficiency Using Photonic Band-Gap Materials", Solar Energy Materials and Solar Cells 91, 1599 (2007).

The potential of using photonic crystal structures for realizing highly efficient and reliable solar-cell devices is presented. We show that due their ability to modify the spectral and angular characteristics of thermal radiation, photonic crystals emerge as one of the leading candidates for frequency- and angular-selective radiating elements in thermophotovoltaic devices. We show that employing photonic crystal-based angle- and frequency-selective absorbers facilitates a strong enhancement of the conversion efficiency of solar cell devices without using concentrators.

Thermal emissivity in finite 3D photonic band gap crystals

Marian Florescu, Andrew Simpson, Hwang Lee and Jonathan Dowling, "Thermal emissivity in finite 3D photonic band gap crystals",Physical Review A 72, 033821 (2005).

We study the optical properties of a finite inverted-opal photonic crystal. The light-matter interaction is strongly affected by the presence of the three-dimensional photonic crystal and the alterations of the light emission and absorption processes can be used to control the thermal emissivity and absorptivity of the dielectric structure. Our study reveals that the absorption processes cause spectral broadening and shifting of the band edge optical resonances, and determine a strong reduction of the photonic band gap spectral range. Our results also suggest that is possible to realize frequency- and angle-sensitive photonic crystal absorbers/emitters.

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Resonance fluorescence in photonic band gap waveguide architectures: Engineering the vacuum for all-optical switching

Marian Florescu and Sajeev John, "Resonance fluorescence in photonic band gap waveguide architectures: Engineering the vacuum for all-optical switching", Physical Review A 69, 053810 (2004).

We have described the spectral characteristics of the radiation scattered by two-level atoms (quantum dots) driven by a strong external field, and coupled to a photonic crystal radiation reservoir. In the presence of strong variations with the frequency of the photonic reservoir density of states, the atomic, Mollow, sideband components of the scattered intensity can be strongly modified. Consequently, a weak optical probe field experiences a substantial differential gain in response to slight variations in the intensity of an optical driving field. We have suggested that these effects may be of relevance to all-optical transistor action in photonic crystals. Using a specific photonic crystal heterostructure, we suggest that an all-optical microtransistor based on photonic crystals may operate at less than 100 nW switching threshold power.

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Photonic Band Gap Materials: Towards an all-optical micro-transistor

Sajeev John and Marian Florescu, "Photonic Band Gap Materials: Towards an all-optical micro-transistor", Journal of Optics A: Pure and Applied Optics 3, S103 (2001).

We describe all-optical transistor action in photonic bandgap (PBG) materials doped with active atoms and analyse the advantages of this system over other all-optical transistor proposals. In the presence of a PBG material, a coherent laser beam with the frequency slightly detuned from the resonant atomic transition frequency can drive a collection of two-level atoms to an almost totally inverted state, a phenomenon strictly forbidden in ordinary vacuum. By varying the laser field intensity in the neighbourhood of a threshold value, it is possible to drive the atomic system through a transition from states in which the atoms populate preferentially the ground level to almost totally inverted states. In this process, the atomic system switches from a passive medium (highly absorptive) to a active medium (highly amplifying). The large differential gain exhibited by the atomic medium is very robust with respect to nonradiative relaxation and dephasing mechanisms.

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Linear Optical Quantum Information Processing in Photonic Nanostructures

Quantum Optics in Structured Photonic Reservoirs

Lateral Quantum Dots

Copyright © 2010 Marian Florescu. All Rights Reserved.

Last updated: 2015-01-02