Showing papers on "Photonic crystal published in 2009"
TL;DR: It is demonstrated that, like their electronic counterparts, electromagnetic CESs can travel in only one direction and are very robust against scattering from disorder; it is found that even large metallic scatterers placed in the path of the propagating edge modes do not induce reflections.
Abstract: One of the most striking phenomena in condensed-matter physics is the quantum Hall effect, which arises in two-dimensional electron systems subject to a large magnetic field applied perpendicular to the plane in which the electrons reside. In such circumstances, current is carried by electrons along the edges of the system, in so-called chiral edge states (CESs). These are states that, as a consequence of nontrivial topological properties of the bulk electronic band structure, have a unique directionality and are robust against scattering from disorder. Recently, it was theoretically predicted that electromagnetic analogues of such electronic edge states could be observed in photonic crystals, which are materials having refractive-index variations with a periodicity comparable to the wavelength of the light passing through them. Here we report the experimental realization and observation of such electromagnetic CESs in a magneto-optical photonic crystal fabricated in the microwave regime. We demonstrate that, like their electronic counterparts, electromagnetic CESs can travel in only one direction and are very robust against scattering from disorder; we find that even large metallic scatterers placed in the path of the propagating edge modes do not induce reflections. These modes may enable the production of new classes of electromagnetic device and experiments that would be impossible using conventional reciprocal photonic states alone. Furthermore, our experimental demonstration and study of photonic CESs provides strong support for the generalization and application of topological band theories to classical and bosonic systems, and may lead to the realization and observation of topological phenomena in a generally much more controlled and customizable fashion than is typically possible with electronic systems.
2,383 citations
TL;DR: In this paper, the authors presented the design and experimental realization of strongly coupled optical and mechanical modes in a planar, periodic nanostructure on a silicon chip, where 200-Terahertz photons are co-localized with mechanical modes of Gigahertz frequency and 100-femtogram mass.
Abstract: Structured, periodic optical materials can be used to form photonic crystals capable of dispersing, routing, and trapping light A similar phenomena in periodic elastic structures can be used to manipulate mechanical vibrations Here we present the design and experimental realization of strongly coupled optical and mechanical modes in a planar, periodic nanostructure on a silicon chip 200-Terahertz photons are co-localized with mechanical modes of Gigahertz frequency and 100-femtogram mass The effective coupling length, which describes the strength of the photon-phonon interaction, is as small as 29 microns, which, together with minute oscillator mass, allows all-optical actuation and transduction of nanomechanical motion with near quantum-limited sensitivity Optomechanical crystals have many potential applications, from RF-over-optical communication to the study of quantum effects in mesoscopic mechanical systems
901 citations
TL;DR: In this paper, a silicon-organic hybrid slot waveguide with a strong optical nonlinearity is demonstrated to perform ultrafast all-optical demultiplexing of high-bit-rate data streams.
Abstract: Integrated optical circuits based on silicon-on-insulator technology are likely to become the mainstay of the photonics industry. Over recent years an impressive range of silicon-on-insulator devices has been realized, including waveguides1,2, filters3,4 and photonic-crystal devices5. However, silicon-based all-optical switching is still challenging owing to the slow dynamics of two-photon generated free carriers. Here we show that silicon–organic hybrid integration overcomes such intrinsic limitations by combining the best of two worlds, using mature CMOS processing to fabricate the waveguide, and molecular beam deposition to cover it with organic molecules that efficiently mediate all-optical interaction without introducing significant absorption. We fabricate a 4-mm-long silicon–organic hybrid waveguide with a record nonlinearity coefficient of γ ≈ 1 × 105 W−1 km−1 and perform all-optical demultiplexing of 170.8 Gb s−1 to 42.7 Gb s−1. This is—to the best of our knowledge—the fastest silicon photonic optical signal processing demonstrated. A silicon–organic hybrid slot waveguide with a strong optical nonlinearity is demonstrated to perform ultrafast all-optical demultiplexing of high-bit-rate data streams. The approach could form the basis of compact high-speed optical processing units for future communication networks.
821 citations
TL;DR: Measurements of an optical system consisting of a pair of specially patterned nanoscale beams in which optical and mechanical energies are simultaneously localized to a cubic-micron-scale volume and for which large per-photon optical gradient forces are realized enable the exploration of cavity optomechanical regimes.
Abstract: The dynamic back-action caused by electromagnetic forces (radiation pressure) in optical and microwave cavities is of growing interest. Back-action cooling, for example, is being pursued as a means of achieving the quantum ground state of macroscopic mechanical oscillators. Work in the optical domain has revolved around millimetre- or micrometre-scale structures using the radiation pressure force. By comparison, in microwave devices, low-loss superconducting structures have been used for gradient-force-mediated coupling to a nanomechanical oscillator of picogram mass. Here we describe measurements of an optical system consisting of a pair of specially patterned nanoscale beams in which optical and mechanical energies are simultaneously localized to a cubic-micron-scale volume, and for which large per-photon optical gradient forces are realized. The resulting scale of the per-photon force and the mass of the structure enable the exploration of cavity optomechanical regimes in which, for example, the mechanical rigidity of the structure is dominantly provided by the internal light field itself. In addition to precision measurement and sensitive force detection, nano-optomechanics may find application in reconfigurable and tunable photonic systems, light-based radio-frequency communication and the generation of giant optical nonlinearities for wavelength conversion and optical buffering.
749 citations
TL;DR: In this article, a photonic-crystal structure for superior optical mode control was proposed for blue light-emitting diodes with a light extraction efficiency of 73% using InGaN-GaN devices.
Abstract: Blue light-emitting diodes with a light extraction efficiency of 73% are reported. The InGaN–GaN devices use a photonic-crystal structure for superior optical mode control; their performance has been characterized experimentally and modelled theoretically.
716 citations
TL;DR: In this article, a maskless high-resolution patterning of structural colours is demonstrated using a new material called "M-Ink" which is tunable by magnetically changing the periodicity of the nanostructure and fixable by photochemically immobilizing those structures in a polymer network.
Abstract: Many creatures in nature, such as butterflies and peacocks, display unique brilliant colours, known as ‘structural colours’, which result from the interaction of light with periodic nanostructures on their surfaces. Mimicking such nanostructures found in nature, however, requires state-of-the-art nanofabrication techniques that are slow, expensive and not scalable. Herein, we demonstrate high-resolution patterning of multiple structural colours within seconds, based on successive tuning and fixing of colour using a single material along with a maskless lithography system. We have invented a material called ‘M-Ink’, the colour of which is tunable by magnetically changing the periodicity of the nanostructure and fixable by photochemically immobilizing those structures in a polymer network. We also demonstrate a flexible photonic crystal for the realization of structural colour printing. The simple, controllable and scalable structural colour printing scheme presented may have a significant impact on colour production for general consumer goods. Maskless high-resolution patterning of structural colours is demonstrated using a new material called ‘M-Ink’. The period of the material is patterned magnetically and a photochemical process immobilizes the structure in a polymer network.
606 citations
TL;DR: In this paper, the use of slow light for enhancing a nonlinear optical process in a two-dimensional silicon photonic-crystal waveguide is demonstrated, highlighting yet another functionality of silicon photonics chips.
Abstract: Slow light has attracted significant interest recently as a potential solution for optical delay lines and time-domain optical signal processing1,2. Perhaps even more significant is the possibility of dramatically enhancing nonlinear optical effects3,4 due to the spatial compression of optical energy5,6,7. Two-dimensional silicon photonic-crystal waveguides have proven to be a powerful platform for realizing slow light, being compatible with on-chip integration and offering wide-bandwidth and dispersion-free propagation2. Here, we report the slow-light enhancement of a nonlinear optical process in a two-dimensional silicon photonic-crystal waveguide. We observe visible third-harmonic-generation at a wavelength of 520 nm with only a few watts of peak power, and demonstrate strong third-harmonic-generation enhancement due to the reduced group velocity of the near-infrared pump signal. This demonstrates yet another unexpected nonlinear function realized in a CMOS-compatible silicon waveguide. The use of slow light for enhancing a nonlinear optical process in a two-dimensional silicon photonic-crystal waveguide is demonstrated. More specifically, green emission by third-harmonic generation is obtained, highlighting yet another functionality of silicon photonics chips.
548 citations
TL;DR: The theoretical investigation shows that the present hybrid plasmonic waveguide with a metal cap on a silicon-on-insulator rib (or slab) has a low loss and consequently a relatively long propagation distance.
Abstract: A hybrid plasmonic waveguide with a metal cap on a silicon-on-insulator rib (or slab) is presented. There is a low-index material nano-layer between the Si layer and the metal layer. The field enhancement in the nano-layer provides a nano-scale confinement of the optical field (e.g., 50nm × 5nm) when operates at the optical wavelength λ = 1550nm. The theoretical investigation also shows that the present hybrid plasmonic waveguide has a low loss and consequently a relatively long propagation distance (on the order of several tens of λ).
523 citations
TL;DR: In this paper, the authors investigated the design, fabrication, and experimental characterization of high quality factor photonic crystal nanobeam cavities in silicon using a five-hole tapered one-dimensional photonic mirror and precise control of the cavity length.
Abstract: We investigate the design, fabrication, and experimental characterization of high quality factor photonic crystal nanobeam cavities in silicon. Using a five-hole tapered one-dimensional photonic crystal mirror and precise control of the cavity length, we designed cavities with theoretical quality factors as high as 1.4×107. By detecting the cross-polarized resonantly scattered light from a normally incident laser beam, we measure a quality factor of nearly 7.5×105. The effect of cavity size on mode frequency and quality factor was simulated and then verified experimentally.
509 citations
TL;DR: A self-assembly principle is demonstrated that is capable of organizing a diverse set of colloidal particles into highly reproducible, rotationally symmetric arrangements.
Abstract: The assembly of complex structures out of simple colloidal building blocks is of practical interest for building materials with unique optical properties (for example photonic crystals and DNA biosensors) and is of fundamental importance in improving our understanding of self-assembly processes occurring on molecular to macroscopic length scales. Here we demonstrate a self-assembly principle that is capable of organizing a diverse set of colloidal particles into highly reproducible, rotationally symmetric arrangements. The structures are assembled using the magnetostatic interaction between effectively diamagnetic and paramagnetic particles within a magnetized ferrofluid. The resulting multipolar geometries resemble electrostatic charge configurations such as axial quadrupoles ('Saturn rings'), axial octupoles ('flowers'), linear quadrupoles (poles) and mixed multipole arrangements ('two tone'), which represent just a few examples of the type of structure that can be built using this technique.
419 citations
TL;DR: The majority of previously reported phononic crystal devices have been constructed by hand, assembling scattering inclusions in a viscoelastic medium, predominantly air, water or epoxy, resulting in large structures limited to frequencies below 1 MHz as mentioned in this paper.
Abstract: Phononic crystals are the acoustic wave analogue of photonic crystals. Here a periodic array of scattering inclusions located in a homogeneous host material forbids certain ranges of acoustic frequencies from existence within the crystal, thus creating what are known as acoustic bandgaps. The majority of previously reported phononic crystal devices have been constructed by hand, assembling scattering inclusions in a viscoelastic medium, predominantly air, water or epoxy, resulting in large structures limited to frequencies below 1 MHz. Recently, phononic crystals and devices have been scaled to VHF (30–300 MHz) frequencies and beyond by utilizing microfabrication and micromachining technologies. This paper reviews recent developments in the area of micro-phononic crystals including design techniques, material considerations, microfabrication processes, characterization methods and reported device structures. Micro-phononic crystal devices realized in low-loss solid materials are emphasized along with their potential application in radio frequency communications and acoustic imaging for medical ultrasound and nondestructive testing. The reported advances in batch micro-phononic crystal fabrication and simplified testing promise not only the deployment of phononic crystals in a number of commercial applications but also greater experimentation on a wide variety of phononic crystal structures.
TL;DR: Two-photon polymerization is a 3D nanoscale manufacturing tool that offers great potential for rapid prototyping and the manufacture of photonic devices, tissue scaffolds and biomechanical parts.
Abstract: Two-photon polymerization is a 3D nanoscale manufacturing tool that offers great potential for rapid prototyping and the manufacture of photonic devices, tissue scaffolds and biomechanical parts.
TL;DR: First observations of deterministic phase- and resonance-controlled all-optical electromagnetically induced transparency in multiple coupled photonic crystal cavities are reported.
Abstract: We report first observations of deterministic phase- and resonance-controlled all-optical electromagnetically induced transparency in multiple coupled photonic crystal cavities. The full-range tuning of coherently coupled cavity-cavity phase and resonances allow observations of transparency resonance in dark states with lifetimes longer than incoherently summed individual cavities. Supported by theoretical analyses, our multipump beam approach allows arbitrary control in two and three coupled cavities, while the standing-wave wavelength-scale photon localization allows direct scalability for chip-scale optical pulse trapping and coupled-cavity QED.
TL;DR: In this paper, a review of the optical nonlinearities of liquid crystals is presented, and a thorough review of a wide range of nonlinear optical processes and phenomena enabled by these unique properties.
TL;DR: By demonstrating a general technique to implement reflecting or absorbing boundaries, this work produces evidence that whispering-gallery-like modes or true photonic-crystal states can be alternatively excited and provides a solution for the quasi-total lack of directionality typical of THz semiconductor lasers based on metal–metal waveguides.
Abstract: Semiconductor lasers based on two-dimensional photonic crystals generally rely on an optically pumped central area, surrounded by un-pumped, and therefore absorbing, regions. This ideal configuration is lost when photonic-crystal lasers are electrically pumped, which is practically more attractive as an external laser source is not required. In this case, in order to avoid lateral spreading of the electrical current, the device active area must be physically defined by appropriate semiconductor processing. This creates an abrupt change in the complex dielectric constant at the device boundaries, especially in the case of lasers operating in the far-infrared, where the large emission wavelengths impose device thicknesses of several micrometres. Here we show that such abrupt boundary conditions can dramatically influence the operation of electrically pumped photonic-crystal lasers. By demonstrating a general technique to implement reflecting or absorbing boundaries, we produce evidence that whispering-gallery-like modes or true photonic-crystal states can be alternatively excited. We illustrate the power of this technique by fabricating photonic-crystal terahertz (THz) semiconductor lasers, where the photonic crystal is implemented via the sole patterning of the device top metallization. Single-mode laser action is obtained in the 2.55-2.88 THz range, and the emission far field exhibits a small angular divergence, thus providing a solution for the quasi-total lack of directionality typical of THz semiconductor lasers based on metal-metal waveguides.
TL;DR: In this paper, the photonic crystal waveguides and cavities supporting resonant modes in air were fabricated for the detection of refractive index changes in a given analyte with high sensitivity because of the large overlap between the optical mode and the analyte.
Abstract: We fabricated slotted photonic crystal waveguides and cavities supporting resonant modes in air. Their peculiar geometry enables the detection of refractive index changes in a given analyte with high sensitivity because of the large overlap between the optical mode and the analyte. This yields a high figure of merit for the sensitivity of the device and we are able to report values of S=Δλ/Δn over 1500. By applying a photonic crystal heterostructure to the slotted geometry, we are able to create high quality-factor cavities essential for realizing low detection limits up to Q=50 000.
TL;DR: In this paper, light scattering from high-Q planar photonic crystal nanocavities can display Fano-like resonances corresponding to the excitation of localized cavity modes.
Abstract: The authors show that light scattering from high-Q planar photonic crystal nanocavities can display Fano-like resonances corresponding to the excitation of localized cavity modes. By changing the scattering conditions, we are able to tune the observed lineshapes from strongly asymmetric and dispersivelike resonances to symmetric Lorentzians. Results are interpreted according to the Fano model of quantum interference between two coupled scattering channels. Combined measurements and line shape analysis on a series of silicon L3 nanocavities as a function of nearby hole displacement demonstrate that Q factors as high as 1.1×105 can be directly measured in these structures. Furthermore, a comparison with theoretically calculated Q factors allows to extract the rms deviation of hole radii due to weak disorder of the photonic lattice.
TL;DR: In this article, the authors review rare-earth-doped chalcogenide fiber for mid-and long-wave IR lasers, and highly nonlinear chalgogenide fibers and photonic crystal fiber for wavelength conversion in the mid and longwave IR.
Abstract: The Naval Research Laboratory (NRL) is developing chalcogenide glass fibers for applications in the mid-and long-wave IR wavelength regions from 2 to 12 mum. The chalcogen glasses (i.e., glasses based on the elements S, Se, and Te) are transparent in the IR, possess low phonon energies, are chemically durable, and can be drawn into fiber. Both conventional solid core/clad and microstructured fibers have been developed. Chalcogenide glass compositions have been developed that allow rare earth doping to enable rare-earth-doped fiber lasers in the IR. Also, highly nonlinear compositions have been developed with nonlinearities ~1000times silica that enables nonlinear wavelength conversion from the near IR to the mid-and long-wave IR. In this paper, we review rare-earth-doped chalcogenide fiber for mid-and long-wave IR lasers, and highly nonlinear chalcogenide fiber and photonic crystal fiber for wavelength conversion in the mid-and long-wave IR.
TL;DR: Comparison of the measurements and numerical simulations of the pulse propagation elucidates the contribution of the various effects that determine the output pulse shape and the waveguide transfer function.
Abstract: We report nonlinear measurements on 80microm silicon photonic crystal waveguides that are designed to support dispersionless slow light with group velocities between c/20 and c/50. By launching picoseconds pulses into the waveguides and comparing their output spectral signatures, we show how self phase modulation induced spectral broadening is enhanced due to slow light. Comparison of the measurements and numerical simulations of the pulse propagation elucidates the contribution of the various effects that determine the output pulse shape and the waveguide transfer function. In particular, both experimental and simulated results highlight the significant role of two photon absorption and free carriers in the silicon waveguides and their reinforcement in the slow light regime.
TL;DR: A display unit that has on/off bistable states by embedding the magnetochromatic microspheres in a matrix that can thermally switch between solid and liquid phases is fabricated.
Abstract: Magnetochromatic microspheres have been fabricated through instant assembly of superparamagnetic (SPM) colloidal particles inside emulsion droplets of UV curable resin followed by an immediate UV curing process to polymerize the droplets and fix the ordered structures When dispersed in the liquid droplets, superparamagnetic Fe(3)O(4)@SiO(2) core/shell particles self-organize under the balanced interaction of repulsive and attractive forces to form one-dimensional chains, each of which contains periodically arranged particles diffracting visible light and displaying field-tunable colors UV initiated polymerization of the oligomers of the resin fixes the periodic structures inside the droplet microspheres and retains the diffraction property Because the superparamagnetic chains tend to align themselves along the field direction, it is very convenient to control the orientation of such photonic microspheres and, accordingly, their diffractive colors, by changing the orientation of the crystal lattice relative to the incident light using magnetic fields The excellent stability together with the capability of fast on/off switching of the diffraction by magnetic fields makes the system suitable for applications such as color display, rewritable signage, and sensors As a simple demonstration, we have fabricated a display unit that has on/off bistable states by embedding the magnetochromatic microspheres in a matrix that can thermally switch between solid and liquid phases
TL;DR: The solar-to-electric power-conversion efficiency of dye-sensitized solar cells can be improved by integrating a mesoporous, nanoparticle-based, 1D photonic crystal as a coherent scatt... as discussed by the authors.
Abstract: The solar-to-electric power-conversion efficiency (71) of dye-sensitized solar cells can be greatly enhanced by integrating a mesoporous, nanoparticle-based, 1D photonic crystal as a coherent scatt ...
TL;DR: In this article, all solid photonic bandgap optical fiber comprising a core region and a cladding region is disclosed, which includes a background optical material having a first refractive index and elements arranged in a two-dimensional periodic structure.
Abstract: All solid photonic bandgap optical fiber comprising a core region and a cladding region is disclosed. The cladding region surrounding the core region includes a background optical material having a first refractive index and elements arranged in a two-dimensional periodic structure. In one embodiment, each of the elements comprises a center part and peripheral part having a higher refractive than the central part. In other embodiments, each element comprises a plurality of rods having a higher refractive index higher than the fist, the rods of each element arranged in a circle or polygon. Light transmission apparatus and methods of using the fiber are also disclosed.
TL;DR: In this paper, the authors demonstrate the suitability of high resolution optical lithography and dry etch processes for mass production of photonic integrated circuits, and demonstrate a propagation loss of 2.7 dB/cm for 500-nm photonic wire and an excess bending loss of 0.013 dB/90deg bend of 5mum radius.
Abstract: High-index contrast silicon-on-insulator technology enables wavelength-scale compact photonic circuits. We report fabrication of photonic circuits in silicon-on-insulator using complementary metal-oxide-semiconductor processing technology. By switching from advanced optical lithography at 248 to 193 nm, combined with improved dry etching, a substantial improvement in process window, linearity, and proximity effect is achieved. With the developed fabrication process, propagation and bending loss of photonic wires were characterized. Measurements indicate a propagation loss of 2.7 dB/cm for 500-nm photonic wire and an excess bending loss of 0.013 dB/90deg bend of 5-mum radius. Through this paper, we demonstrate the suitability of high resolution optical lithography and dry etch processes for mass production of photonic integrated circuits.
TL;DR: In this paper, the authors present recent and ongoing developments on the way to functional one-dimensional photonic structures obtained from simple bottom-up techniques, which allow the incorporation of a wide range of materials into photonic structure.
Abstract: One-dimensional photonic structures, known as Bragg stacks or Bragg reflectors or Bragg mirrors, represent a well-developed subject in the field of optical science. However, because of a lack of dynamic tunability and their dependence on complex top-down techniques for their fabrication, they have received little attention from the materials science community. Herein, we present recent and ongoing developments on the way to functional one-dimensional photonic structures obtained from simple bottom-up techniques. We focus on the versatility of this new approach, which allows the incorporation of a wide range of materials into photonic structures.
TL;DR: In this article, the authors demonstrate all-optical modulation based on ultrafast optical carrier injection in a GaAs photonic crystal cavity using a degenerate pump-probe technique.
Abstract: We demonstrate all-optical modulation based on ultrafast optical carrier injection in a GaAs photonic crystal cavity using a degenerate pump-probe technique. The observations agree well with a coupled-mode model incorporating all relevant nonlinearities. The low switching energy (∼120 fJ), small energy absorption (∼10 fJ), fast on-off response (∼15 ps), limited only by carrier lifetime, and a minimum 10 dB modulation depth suggest practical all-optical switching applications at high repetition rates.
TL;DR: In this paper, a review of recent developments in self-assembly of polymer colloids into colloidal crystals, a good candidate material for photonic crystals, is presented, where the authors focus on controlling the morphology and improving the quality, as well as finding applications of the colloidal crystal.
Abstract: This article reviews recent developments in self-assembly of polymer colloids into colloidal crystals, a good candidate material for photonic crystals. Self-assembly strategy has developed as a facile and efficient method to fabricate colloidal crystals. Much research work has been focused on controlling the morphology and improving the quality, as well as finding applications of the colloidal crystals.
TL;DR: A design that increases significantly the absorption of a thin layer of absorbing material such as amorphous silicon by patterning a one-dimensional photonic crystal (1DPC) in this layer by coupling the incident light into slow Bloch modes of the 1DPC.
Abstract: We propose a design that increases significantly the absorption of a thin layer of absorbing material such as amorphous silicon. This is achieved by patterning a one-dimensional photonic crystal (1DPC) in this layer. Indeed, by coupling the incident light into slow Bloch modes of the 1DPC, we can control the photon lifetime and then, enhance the absorption integrated over the whole solar spectrum. Optimal parameters of the 1DPC maximize the integrated absorption in the wavelength range of interest, up to 45% in both S and P polarization states instead of 33% for the unpatterned, 100 nm thick amorphous silicon layer. Moreover, the absorption is tolerant with respect to fabrication errors, and remains relatively stable if the angle of incidence is changed.
TL;DR: In this article, the photonic crystal geometry is fabricated using a materials-agnostic process called PRINT wherein highly ordered arrays of nanoscale features are readily made in a single processing step over wide areas (∼4 cm2) that is scalable.
Abstract: We report organic solar cells with a photonic crystal nanostructure embossed in the photoactive bulk heterojunction layer, a topography that exhibits a 3-fold enhancement of the absorption in specific regions of the solar spectrum in part through multiple excitation resonances. The photonic crystal geometry is fabricated using a materials-agnostic process called PRINT wherein highly ordered arrays of nanoscale features are readily made in a single processing step over wide areas (∼4 cm2) that is scalable. We show efficiency improvements of ∼70% that result not only from greater absorption, but also from electrical enhancements. The methodology is generally applicable to organic solar cells and the experimental findings reported in our manuscript corroborate theoretical expectations.