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Sample records for liquid crystal photonic

  1. Liquid crystal orientation control in photonic liquid crystal fibers

    NASA Astrophysics Data System (ADS)

    Chychlowski, M. S.; Nowinowski-Kruszelnicki, E.; Woliński, T. R.

    2011-05-01

    Similarly to liquid crystal displays technology in photonic liquid crystal fibers (PLCFs) a molecular orientation control is a crucial issue that influences proper operation of PLCF-based devices. The paper presents two distinct configurations: planar and radial escaped orientation of the LC molecules inside capillaries as well as methods of their application to photonic liquid crystal fibers. Possibilities of LC orientation control influence both: attenuation and transmitting spectra of the PLCF The orienting method is based on creation of an additional orienting layer on the inner surface of the capillary or air hole of the photonic liquid crystal fiber. Aligning materials used in the experiment are commercially available polyimides SE1211 and SE130 which induce liquid crystal homeotropic and planar anchoring conditions. The orienting layer increase an order parameter of the liquid crystal improving propagation properties and stability of photonic liquid crystal fiber-based devices.

  2. Liquid crystal applications in photonics

    NASA Astrophysics Data System (ADS)

    Chigrinov, Vladimir G.

    2009-02-01

    Liquid crystal (LC) devices for Photonics applications is a hot topic of research. Such elements begin to appear in Photonics market. Passive elements for fiber optical communication systems (DWDM components) based on LC cells can successfully compete with the other elements used for the purpose, such as micro electromechanical (MEM), thermo-optical, opto-mechanical or acousto-optical devices. We have already successfully fabricated certain prototypes of the optical switches based on various electrooptic modes in ferroelectric and nematic LC materials. The electrooptical modes used for the purpose included the light polarization rotation, voltage controllable diffraction and fast switching of the LC refractive index. Use of photo-alignment technique pioneered by us makes it possible to develop new LC fiber components. Almost all the criteria of perfect LC alignment are met in case of azo-dye layers. We have already used azo-dye materials to align LC in superthin photonic holes, curved and 3D surfaces and as cladding layers in microring silicon based resonators. We have already used the photoaligning materials to align LC mixtures in small cavities, such as the holes and tubes of photonic crystals, having size of 1 μm and less and obtained excellent LC orientation inside the tubes by photoalignment. The prototypes of new LC efficient Photonics devices, such as optically rewritable LC waveguides and voltage controllable diffraction gratings are envisaged. The polarization controllers, polarization rotators, variable optical attenuators and other passive LC optical elements for fiber communication networks are under way.

  3. Tunable liquid crystal photonic devices

    NASA Astrophysics Data System (ADS)

    Fan, Yun-Hsing

    2005-07-01

    Liquid crystal (LC)-based adaptive optics are important for information processing, optical interconnections, photonics, integrated optics, and optical communications due to their tunable optical properties. In this dissertation, we describe novel liquid crystal photonic devices. In Chap. 3, we demonstrate a novel electrically tunable-efficiency Fresnel lens which is devised for the first time using nanoscale PDLC. The tunable Fresnel lens is very desirable to eliminate the need of external spatial light modulator. The nanoscale LC devices are polarization independent and exhibit a fast response time. Because of the small droplet sizes, the operating voltage is higher than 100 Vrms. To lower the driving voltage, in Chap. 2 and Chap. 3, we have investigated tunable Fresnel lens using polymer-network liquid crystal (PNLC) and phase-separated composite film (PSCOF). The operating voltage is below 12 Vrms. The PNLC and PSCOF devices are polarization dependent. To overcome this shortcoming, stacking two cells with orthogonal alignment directions is a possibility. Using PNLC, we also demonstrated LC blazed grating. The diffraction efficiency of these devices is continuously controlled by the electric field. We also develop a system with continuously tunable focal length. A conventional mechanical zooming system is bulky and power hungry. In Chap. 4, we developed an electrically tunable-focus flat LC spherical lens and microlens array. A huge tunable range from 0.6 m to infinity is achieved by the applied voltage. In Chap. 5, we describe a LC microlens array whose focal length can be switched from positive to negative by the applied voltage. The fast response time feature of our LC microlens array will be very helpful in developing 3-D animated images. In Chap. 6, we demonstrate polymer network liquid crystals for switchable polarizers and optical shutters. The use of dual-frequency liquid crystal and special driving scheme leads to a sub-millisecond response time. In

  4. Cholesteric liquid crystal photonic crystal lasers and photonic devices

    NASA Astrophysics Data System (ADS)

    Zhou, Ying

    This dissertation discusses cholesteric liquid crystals (CLCs) and polymers based photonic devices including one-dimensional (1D) photonic crystal lasers and broadband circular polarizers. CLCs showing unique self-organized chiral structures have been widely used in bistable displays, flexible displays, and reflectors. However, the photonic band gap they exhibit opens a new way for generating laser light at the photonic band edge (PBE) or inside the band gap. When doped with an emissive laser dye, cholesteric liquid crystals provide distributed feedback so that mirrorless lasing is hence possible. Due to the limited surface anchoring, the thickness of gain medium and feedback length is tens of micrometers. Therefore lasing efficiency is quite limited and laser beam is highly divergent. To meet the challenges, we demonstrated several new methods to enhance the laser emission while reducing the beam divergence from a cholesteric liquid crystal laser. Enhanced laser emission is demonstrated by incorporating a single external CLC reflector as a polarization conserved reflector. Because the distributed feedback from the active layer is polarization selective, a CLC reflector preserves the original polarization of the reflected light and a further stimulated amplification ensues. As a result of virtually doubled feedback length, the output is dramatically enhanced in the same circular polarization state. Meanwhile, the laser beam divergence is dramatically reduced due to the increased cavity length from micrometer to millimeter scale. Enhanced laser emission is also demonstrated by the in-cell metallic reflector because the active layer is pumped twice. Unlike a CLC reflector, the output from a mirror-reflected CLC laser is linearly polarized as a result of coherent superposition of two orthogonal circular polarization states. The output linear polarization direction can be well controlled and fine tuned by varying the operating temperature and cell gap. Enhanced laser

  5. Liquid crystal devices for photonics applications

    NASA Astrophysics Data System (ADS)

    Chigrinov, Vladimir G.

    2007-11-01

    Liquid crystal (LC) devices for Photonics applications is a hot topic of research. Such elements begin to appear in Photonics market. Passive elements for fiber optical communication systems (DWDM components) based on LC cells can successfully compete with the other elements used for the purpose, such as micro electromechanical (MEM), thermo-optical, opto-mechanical or acousto-optical devices. Application of nematic and ferroelectric LC for high speed communication systems, producing elements that are extremely fast, stable, durable, of low loss, operable over a wide temperature range, and that require small operating voltages and extremely low power consumption. The known LC applications in fiber optics enable to produce switches, filters, attenuators, equalizers, polarization controllers, phase emulators and other fiber optical components. Good robustness due to the absence of moving parts and compatibility with VLSI technology, excellent parameters in a large photonic wavelength range, whereas the complexity of the design and the cost of the device are equivalent to regular passive matrix LC displays makes LC fiber optical devices very attractive for mass production. We have already successfully fabricated certain prototypes of the optical switches based on ferroelectric and nematic LC materials. The electrooptical modes used for the purpose included the light polarization rotation, voltage controllable diffraction and fast switching of the LC refractive index. We used the powerful software to optimize the LC modulation characteristics. Use of photo-alignment technique pioneered by us makes it possible to develop new LC fiber components. Almost all the criteria of perfect LC alignment are met in case of azo-dye layers. We have already used azo-dye materials to align LC in superthin photonic holes, curved and 3D surfaces and as cladding layers in microring silicon based resonators. The prototypes of new LC efficient Photonics devices are envisaged. Controllable

  6. High birefringence liquid crystals for photonic applications

    NASA Astrophysics Data System (ADS)

    Gauza, S.; Wen, C. H.; Wu, S. T.; Dabrowski, R.; Hsu, C. S.; Catanescu, C. O.; Chien, L. C.

    2005-09-01

    High birefringence liquid crystals (LCs) play an important role for laser beam steering, tunable-focus lens, reflective display, cholesteric LC laser, infrared dynamic scene projector, and telecom variable optical attenuator applications. We have developed some high birefringence compounds and eutectic mixtures with birefringence in the 0.4-0.7 range. For some photonic devices where response time is critical, we have also developed high birefringence dual-frequency LC mixtures. The cross-over frequency is around 5-10 kHz. Using such a dual-frequency LC mixture, sub-millisecond response time is achieved.

  7. Thermal tunability of photonic bandgaps in liquid crystal filled polymer photonic crystal fiber

    NASA Astrophysics Data System (ADS)

    Wang, Doudou; Chen, Guoxiang; Wang, Lili

    2016-05-01

    A highly tunable bandgap-guiding polymer photonic crystal fiber is designed by infiltrating the cladding air holes with liquid crystal 5CB. Structural parameter dependence and thermal tunability of the photonic bandgaps, mode properties and confinement losses of the designed fiber are investigated. Bandgaps red shift as the temperature goes up. Average thermal tuning sensitivity of 30.9 nm/°C and 20.6 nm/°C is achieved around room temperature for the first and second photonic bandgap, respectively. Our results provide theoretical references for applications of polymer photonic crystal fiber in sensing and tunable fiber-optic devices.

  8. Photonics of liquid-crystal structures: A review

    SciTech Connect

    Palto, S. P. Blinov, L. M.; Barnik, M. I.; Lazarev, V. V.; Umanskii, B. A.; Shtykov, N. M.

    2011-07-15

    The original results of studies of the electro-optical and laser effects which have been performed at the Laboratory of Liquid Crystals of the Institute of Crystallography, Russian Academy of Sciences, over the last few years are reviewed. Cholesteric liquid crystals as vivid representatives of photonic structures and their behavior in an electric field are considered in detail. The formation of higher harmonics in the periodic distribution of the director field in a helical liquid crystal structure and, correspondingly, the new (anharmonic) mode of electro-optical effects are discussed. Another group of studies is devoted to bistable light switching by an electric field in chiral nematics. Polarization diffraction gratings controlled by an electric field are also considered. The results of studies devoted to microlasers on various photonic structures with cholesteric and nematic liquid crystals are considered in detail. Particular attention is given to the new regime: leaky-mode lasing. Designs of liquid crystal light amplifiers and their polarization, field, and spectral characteristics are considered in the last section.

  9. Controllable light diffraction in woodpile photonic crystals filled with liquid crystal

    SciTech Connect

    Ho, Chih-Hua; Zeng, Hao; Wiersma, Diederik S.; Cheng, Yu-Chieh; Maigyte, Lina; Trull, Jose; Cojocaru, Crina; Staliunas, Kestutis

    2015-01-12

    An approach to switching between different patterns of light beams transmitted through the woodpile photonic crystals filled with liquid crystals is proposed. The phase transition between the nematic and isotropic liquid crystal states leads to an observable variation of the spatial pattern transmitted through the photonic structure. The transmission profiles in the nematic phase also show polarization sensibility due to refractive index dependence on the field polarization. The experimental results are consistent with a numerical calculation by Finite Difference Time Domain method.

  10. Thermally Driven Photonic Actuator Based on Silica Opal Photonic Crystal with Liquid Crystal Elastomer.

    PubMed

    Xing, Huihui; Li, Jun; Shi, Yang; Guo, Jinbao; Wei, Jie

    2016-04-13

    We have developed a novel thermoresponsive photonic actuator based on three-dimensional SiO2 opal photonic crystals (PCs) together with liquid crystal elastomers (LCEs). In the process of fabrication of such a photonic actuator, the LCE precursor is infiltrated into the SiO2 opal PC followed by UV light-induced photopolymerization, thereby forming the SiO2 opal PC/LCE composite film with a bilayer structure. We find that this bilayer composite film simultaneously exhibits actuation behavior as well as the photonic band gap (PBG) response to external temperature variation. When the SiO2 opal PC/LCE composite film is heated, it exhibits a considerable bending deformation, and its PBG shifts to a shorter wavelength at the same time. In addition, this actuation is quite fast, reversible, and highly repeatable. The thermoresponsive behavior of the SiO2 opal PC/LCE composite films mainly derives from the thermal-driven change of nematic order of the LCE layer which leads to the asymmetric shrinkage/expansion of the bilayer structure. These results will be of interest in designing optical actuator systems for environment-temperature detection. PMID:26996608

  11. Thermally Driven Photonic Actuator Based on Silica Opal Photonic Crystal with Liquid Crystal Elastomer.

    PubMed

    Xing, Huihui; Li, Jun; Shi, Yang; Guo, Jinbao; Wei, Jie

    2016-04-13

    We have developed a novel thermoresponsive photonic actuator based on three-dimensional SiO2 opal photonic crystals (PCs) together with liquid crystal elastomers (LCEs). In the process of fabrication of such a photonic actuator, the LCE precursor is infiltrated into the SiO2 opal PC followed by UV light-induced photopolymerization, thereby forming the SiO2 opal PC/LCE composite film with a bilayer structure. We find that this bilayer composite film simultaneously exhibits actuation behavior as well as the photonic band gap (PBG) response to external temperature variation. When the SiO2 opal PC/LCE composite film is heated, it exhibits a considerable bending deformation, and its PBG shifts to a shorter wavelength at the same time. In addition, this actuation is quite fast, reversible, and highly repeatable. The thermoresponsive behavior of the SiO2 opal PC/LCE composite films mainly derives from the thermal-driven change of nematic order of the LCE layer which leads to the asymmetric shrinkage/expansion of the bilayer structure. These results will be of interest in designing optical actuator systems for environment-temperature detection.

  12. Tunable complete photonic band gap in anisotropic photonic crystal slabs with non-circular air holes using liquid crystals

    NASA Astrophysics Data System (ADS)

    Fathollahi Khalkhali, T.; Bananej, A.

    2016-06-01

    In this study, we analyze the tunability of complete photonic band gap of square and triangular photonic crystal slabs composed of square and hexagonal air holes in anisotropic tellurium background with SiO2 as cladding material. The non-circular holes are infiltrated with liquid crystal. Using the supercell method based on plane wave expansion, we study the variation of complete band gap by changing the optical axis orientation of liquid crystal. Our numerical results show that noticeable tunability of complete photonic band gap can be obtained in both square and triangular structures with non-circular holes.

  13. Dispersion properties of transverse anisotropic liquid crystal core photonic crystal fibers

    NASA Astrophysics Data System (ADS)

    Karasawa, Naoki

    2016-04-01

    The dispersion properties of liquid crystal core photonic crystal fibers for different core diameters have been calculated by a full vectorial finite difference method. In calculations, air holes are assumed to be arranged in a regular hexagonal array in fused silica and a central hole is filled with liquid crystal to create a core. In this study, three types of transverse anisotropic configurations, where liquid crystal molecules are oriented in a transverse plane, and a planar configuration, where liquid crystal molecules are oriented in a propagation direction, are considered. The large changes of the dispersion properties are found when the orientation of the liquid crystal molecules is changed from a planar configuration to a uniform configuration, where all molecules are oriented in the same direction in a transverse plane. Since the orientation of liquid crystal molecules may be controlled by applying an electric field, it could be utilized for various applications including the spectral control of supercontinuum generation.

  14. Holographic polymer-dispersed liquid crystal Bragg grating integrated inside a solid core photonic crystal fiber.

    PubMed

    Zito, Gianluigi; Pissadakis, Stavros

    2013-09-01

    A polymer/liquid crystal-based fiber Bragg grating (PLC-FBG) is fabricated with visible two-beam holography by photo-induced modulation of a prepolymer/liquid crystal solution infiltrated into the hollow channels of a solid core photonic crystal fiber (PCF). The fabrication process and effects related to the photonic bandgap guidance into the infiltrated PCF, and characterization of the PLC-FBG, are discussed. Experimental data presented here demonstrate that the liquid crystal inclusions of the PLC-FBG lead to high thermal and bending sensitivities. The microscopic behavior of the polymer/liquid crystal phase separation inside the PCF capillaries is examined using scanning electron microscopy, and is discussed further. PMID:23988927

  15. Wavefront sensing using a liquid-filled photonic crystal fiber.

    PubMed

    Valente, Denise; Rativa, Diego; Vohnsen, Brian

    2015-05-18

    A novel wavefront sensor based on a microstructural array of waveguides is proposed. The method is based on the sensitivity in light-coupling efficiency to the wavefront gradient present at the entrance aperture of each waveguide in an array, and hence the amount of incident light that couples is influenced by wavefront aberrations. The concept is illustrated with wavefront measurements that have been performed using a liquid-filled photonic crystal fiber (LF-PCF) working as a coherent fiber bundle. The pros and cons of the LF-PCF based sensor are discussed. PMID:26074553

  16. Reconfigurable Photonic Capsules Containing Cholesteric Liquid Crystals with Planar Alignment.

    PubMed

    Lee, Sang Seok; Kim, Su Kyung; Won, Jong Chan; Kim, Yun Ho; Kim, Shin-Hyun

    2015-12-01

    Cholesteric liquid crystals (CLCs) reflect selected wavelengths of light owing to their periodic helical structures. The encapsulation of CLCs leads to photonic devices that can be easily processed and might be used as stand-alone microsensors. However, when CLCs are enclosed by polymeric membranes, they usually lose their planar alignment, leading to a deterioration of the optical performance. A microfluidics approach was employed to integrate an ultrathin alignment layer into microcapsules to separate the CLC core and the elastomeric solid membrane using triple-emulsion drops as the templates. The thinness of the alignment layer provides high lubrication resistance, preserving the layer integrity during elastic deformation of the membrane. The CLCs in the microcapsules can thus maintain their planar alignment, rendering the shape and optical properties highly reconfigurable.

  17. Electrically tunable zero dispersion wavelengths in photonic crystal fibers filled with a dual frequency addressable liquid crystal

    NASA Astrophysics Data System (ADS)

    Wahle, Markus; Kitzerow, Heinz-Siegfried

    2015-11-01

    We present a liquid crystal (LC) infiltrated photonic crystal fiber, which enables the electrical tuning of the position of zero dispersion wavelengths (ZDWs). A dual frequency addressable liquid crystal is aligned perpendicular on the inclusion walls of a photonic crystal fiber, which results in an escaped radial director field. The orientation of the LC is controlled by applying an external electric field. Due to the high index of the liquid crystal the fiber guides light by the photonic band gap effect. Multiple ZDWs exist in the visible and near infrared. The positions of the ZDWs can be either blue or red shifted depending on the frequency of the applied voltage.

  18. Electrically tunable zero dispersion wavelengths in photonic crystal fibers filled with a dual frequency addressable liquid crystal

    SciTech Connect

    Wahle, Markus Kitzerow, Heinz-Siegfried

    2015-11-16

    We present a liquid crystal (LC) infiltrated photonic crystal fiber, which enables the electrical tuning of the position of zero dispersion wavelengths (ZDWs). A dual frequency addressable liquid crystal is aligned perpendicular on the inclusion walls of a photonic crystal fiber, which results in an escaped radial director field. The orientation of the LC is controlled by applying an external electric field. Due to the high index of the liquid crystal the fiber guides light by the photonic band gap effect. Multiple ZDWs exist in the visible and near infrared. The positions of the ZDWs can be either blue or red shifted depending on the frequency of the applied voltage.

  19. Angular dependences of the luminescence and density of photon states in a chiral liquid crystal

    SciTech Connect

    Umanskii, B A; Blinov, L M; Palto, S P

    2013-11-30

    Luminescence spectra of a laser dye-doped chiral liquid crystal have been studied in a wide range of angles (up to 60°) to the axis of its helical structure using a semicylindrical quartz prism, which made it possible to observe the shift and evolution of the photonic band gap in response to changes in angle. Using measured spectra and numerical simulation, we calculated the spectral distributions of the density of photon states in such a cholesteric crystal for polarised and unpolarised light, which characterise its structure as that of a chiral one-dimensional photonic crystal. (optics of liquid crystals)

  20. Room Temperature Single-Photon Source: Single-Dye Molecule Fluorescence in Liquid Crystal Host

    SciTech Connect

    Lukishova, S.G.; Schmid, A.W.; McNamara, A.J.; Boyd, R.W.; Stroud, C.R.Jr.

    2003-12-31

    OAK-(B204)We report on new approaches toward an implementation of an efficient, room temperature, deterministically polarized, single-photon source (SPS) on demand-a key hardware element for quantum information and quantum communication. Operation of a room temperature SPS is demonstrated via photon antibunching in the fluorescence from single terrylene-dye molecules embedded in a cholesteric liquid crystal host. Using oxygen-depleted liquid crystal hosts, dye-bleaching was avoided over the course of more than 1 h of continuous 532-nm excitation. Liquid crystal hosts (including liquid crystal oligomers/polymers) permit further increase of the efficiency of the source: (1) by aligning the dye molecules along a direction preferable for the maximum excitation efficiency; (2) by tuning a one-dimensional (1-D) photonic-band-gap microcavity of planar-aligned cholesteric (chiral nematic) liquid crystal layer to the dye fluorescence band.

  1. Photochemical switching behavior of azofunctionalized polymer liquid crystal/SiO{sub 2} composite photonic crystal

    SciTech Connect

    Moritsugu, M.; Kim, S. N.; Ogata, T.; Nonaka, T.; Kurihara, S.; Kubo, S.; Segawa, H.; Sato, O.

    2006-10-09

    A photochemically tunable photonic crystal was prepared by infiltrating azopolymer liquid crystal in a SiO{sub 2} inverse opal structure. The SiO{sub 2} inverse opal film obtained reflected a light corresponding to the periodicity as well as the refractive indices of the inverse opal structure. Linearly polarized light irradiation shifted the reflection band to longer wavelength more than 15 nm. This is caused by the formation of anisotropic molecular orientation of the azopolymer. The switched state was stable in the dark, and the reversible switching of the reflection band can be achieved by the linearly and circularly polarized light irradiations.

  2. Magnetic-field tunable defect modes in a photonic-crystal/liquid-crystal cell.

    PubMed

    Zyryanov, Victor Ya; Myslivets, Sergey A; Gunyakov, Vladimir A; Parshin, Alexander M; Arkhipkin, Vasily G; Shabanov, Vasily F; Lee, Wei

    2010-01-18

    Light transmission spectrum of a multilayer photonic crystal with a central liquid-crystal defect layer placed between crossed polarizers has been studied. Transmittance was varied due to the magnetically induced reorientation of the nematic director from homeotropic to planar alignment. Two notable effects were observed for this scheme: the spectral shift of defect modes corresponding to the extraordinary light wave and its superposition with the ordinary one. As a result, the optical cell allows controlling the intensity of interfering defect modes by applied magnetic field. PMID:20173953

  3. A nano-patterned photonic crystal laser with a dye-doped liquid crystal

    NASA Astrophysics Data System (ADS)

    Ko, Doo-Hyun; Morris, Stephen M.; Lorenz, Alexander; Castles, Flynn; Butt, Haider; Gardiner, Damian J.; Qasim, Malik M.; Wallikewitz, Bodo; Hands, Philip J. W.; Wilkinson, Timothy D.; Amaratunga, Gehan A. J.; Coles, Harry J.; Friend, Richard H.

    2013-07-01

    Covering a nano-patterned titanium dioxide photonic crystal (PC) within a well-oriented film of dye-doped liquid crystal (LC), a distributed feedback laser is constructed whereby the emission characteristics can be manipulated in-situ using an electric field. This hybrid organic-inorganic structure permits simultaneous selectivity of both the beam pattern and laser wavelength by electrical addressing of the LC director. In addition, laser emission is obtained both in the plane and normal to the PC. Along with experimental data, a theoretical model is presented that is based upon an approximate calculation of the band structure of this birefringent, tuneable laser device.

  4. Dye-doped cholesteric-liquid-crystal room-temperature single-photon source

    SciTech Connect

    Lukishova, S.G.; Schmid, A.W.; Supranowitz, C.M.; Lippa, N.; McNamara, A.J.; Boyd, R.W.; Stroud, Jr., C.R.

    2004-06-15

    Fluorescence antibunching from single terrylene molecules embedded in a cholesteric-liquid-crystal host is used to demonstrate operation of a room-temperature single-photon source. One-dimensional (1-D) photonic-band-gap microcavities in planar-aligned cholesteric liquid crystals with band gaps from visible to near-infrared spectral regions are fabricated. Liquid-crystal hosts (including liquid crystal oligomers and polymers) increase the source efficiency, firstly, by aligning the dye molecules along the direction preferable for maximum excitation efficiency (deterministic molecular alignment provides deterministically polarized output photons), secondly, by tuning the 1-D photonic-band-gap microcavity to the dye fluorescence band and thirdly, by protecting the dye molecules from quenchers, such as oxygen.

  5. Single-Photon Source for Quantum Information Based on Single Dye Molecule Fluorescence in Liquid Crystal Host

    SciTech Connect

    Lukishova, S.G.; Knox, R.P.; Freivald, P.; McNamara, A.; Boyd, R.W.; Stroud, Jr., C.R.; Schmid, A.W.; Marshall, K.L.

    2006-08-18

    This paper describes a new application for liquid crystals: quantum information technology. A deterministically polarized single-photon source that efficiently produces photons exhibiting antibunching is a pivotal hardware element in absolutely secure quantum communication. Planar-aligned nematic liquid crystal hosts deterministically align the single dye molecules which produce deterministically polarized single (antibunched) photons. In addition, 1-D photonic bandgap cholesteric liquid crystals will increase single-photon source efficiency. The experiments and challenges in the observation of deterministically polarized fluorescence from single dye molecules in planar-aligned glassy nematic-liquid-crystal oligomer as well as photon antibunching in glassy cholesteric oligomer are described for the first time.

  6. Density of photonic states in cholesteric liquid crystals

    NASA Astrophysics Data System (ADS)

    Dolganov, P. V.

    2015-04-01

    Density of photonic states ρ (ω ) , group vg, and phase vph velocity of light, and the dispersion relation between wave vector k , and frequency ω (k ) were determined in a cholesteric photonic crystal. A highly sensitive method (measurement of rotation of the plane of polarization of light) was used to determine ρ (ω ) in samples of different quality. In high-quality samples a drastic increase in ρ (ω ) near the boundaries of the stop band and oscillations related to Pendellösung beatings are observed. In low-quality samples photonic properties are strongly modified. The maximal value of ρ (ω ) is substantially smaller, and density of photonic states increases near the selective reflection band without oscillations in ρ (ω ) . Peculiarities of ρ (ω ) , vg, and ω (k ) are discussed. Comparison of the experimental results with theory was performed.

  7. One-dimensional photonic crystals containing memory-enabling liquid-crystal defect layers

    NASA Astrophysics Data System (ADS)

    Wu, Po-Chang; Lee, Wei

    2013-09-01

    Incorporating liquid crystal (LC) as a defect layer in a photonic crystal (PC) leads to the electrically tunable optical spectrum in defect modes within the photonic band gap. While the LC defect layer has bi- or multi-stable states, the profile of defect modes in each stable state can be preserved permanently without applied voltage, indicating a feature of low power consumption for photonic applications. In this paper, we report on our recent development of optical and spectral properties of multilayer PC structures containing various types of memory-enabling LC (ME-LC), including a bistable chiral-tilted homeotropic nematic (BHN), a bistable chiral-splay nematic (BCSN), a bistable dual-frequency cholesteric LC (DFCLC), a tristable polymer-stabilized cholesteric texture (PSCT), and a tristable smectic-A liquid crystal as a defect layer. The defect modes of the PC/ME-LC cell can be switched to not only the voltage-sustained states but the memory states. As a result, PC/ME-LC cells reveal several features such as the wavelength tunability, transmission tunability and optical bistability or tristability of defect modes that are of potential for realizing tunable and memorable optical devices such as low-power-consumption multichannel filters, light shutters or electrically controllable intensity modulators with green concept.

  8. Synthesis of Two-Photon Materials and Two-Photon Liquid Crystals

    NASA Technical Reports Server (NTRS)

    Subramaniam, Girija

    2001-01-01

    The duration of the grant was interrupted by two major accidents that the PI met with-- an auto accident in Pasadena, CA during her second summer at JPL which took almost eight months for recovery and a second accident during Fall 2000 that left her in crutches for the entire semester. Further, the time released agreed by the University was not given in a timely fashion. The candidate has been given post-grant expire time off. In spite of all these problems, the PI synthesized a number of new two-photon materials and studied the structure-activity correlation to arrive at the best-optimized structure. The PI's design proved to be one of the best in the sense that these materials has a hitherto unreported two-photon absorption cross section. Many materials based on PI's design was later made by the NASA colleague. This is Phase 1. Phase II of this grant is to orate liquid crystalline nature into this potentially useful materials and is currently in progress. Recent observations of nano- and pico-second response time of homeotropically aligned liquid crystals suggest their inherent potentials to act as laser hardening materials, i.e., as protective devices against short laser pulses. The objective of the current project is to exploit this potential by the synthesis of liquid crystals with high optical nonlinearity and optimizing their performance. The PI is trying structural variations to bring in liquid crystalline nature without losing the high two-photon cross section. Both Phase I and Phase II led to many invited presentations and publications in reputed journals like 'Science' and 'Molecular Crystals'. The list of presentations and reprints are enclosed. Another important and satisfying outcome of this grant is the opportunity that this grant offered to the budding undergraduate scientists to get involved in a visible research of international importance. All the students had a chance to learn a lot during research, had the opportunity to present their work at

  9. High-Q silicon-on-insulator slot photonic crystal cavity infiltrated by a liquid

    SciTech Connect

    Caër, Charles; Le Roux, Xavier; Cassan, Eric

    2013-12-16

    We report the experimental realization of a high-Q slot photonic crystal cavity in Silicon-On-Insulator (SOI) configuration infiltrated by a liquid. Loaded Q-factor of 23 000 is measured at telecom wavelength. The intrinsic quality factor inferred from the transmission spectrum is higher than 200 000, which represents a record value for slot photonic crystal cavities on SOI, whereas the maximum of intensity of the cavity is roughly equal to 20% of the light transmitted in the waveguide. This result makes filled slot photonic crystal cavities very promising for silicon-based light emission and ultrafast nonlinear optics.

  10. Light-induced deformation in a liquid crystal elastomer photonic crystal

    NASA Astrophysics Data System (ADS)

    Krishnan, D.; Johnson, H. T.

    2014-01-01

    Elastomer materials can undergo large, reversible elastic deformation, and offer novel possibilities for coupled optomechanical behavior when light itself is used to induce that deformation. This phenomenology is especially interesting to consider when photonic bandstructure effects and mechanical instabilities are present over the same length scales. Here we investigate a novel, coupled optomechanical material behavior whereby complex deformation, with the potential to occur cyclically, occurs in a soft photonic crystal structure due to a mechanical instability, as a result of constant, uniform illumination by normally incident light. We suppose that the base material for the structure is a material that responds to light by undergoing a microstructural change. Such a behavior is observed, for example, in a liquid crystal elastomer containing azobenzene moieties attached to the liquid crystal main-chains (Finkelmann et al., 2001) transformational strain generated by the effect of localized light energy on the isomerization of the azobenzene moieties can be calculated from an order-parameter based model (Hogan et al., 2002). Under uniform exposure to constant illumination, the interaction between the light, the material, and the deforming structure lead to a complex, reversible deformation sequence. We analyze the electromagnetic energy distribution inside this photonic crystal structure by solving Maxwells equations for the electromagnetic problem of light transmittance using finite element analysis. First, upon contraction of the structure due to isomerization in the uniformly illuminated material, the photonic bandstructure shifts, thereby significantly reducing the average illumination of material within the structure. The locally reduced illumination allows for a relaxation of the strain in some parts of the structure, due to the reversible isomerization at room temperature. Then, as a result of this relaxation, the structure is subjected to uniaxial stress

  11. Single-photon experiments with liquid crystals for quantum science and quantum engineering applications

    NASA Astrophysics Data System (ADS)

    Lukishova, Svetlana G.; Liapis, Andreas C.; Bissell, Luke J.; Gehring, George M.; Winkler, Justin M.; Boyd, Robert W.

    2015-03-01

    We present here our results on using liquid crystals in experiments with nonclassical light sources: (1) single-photon sources exhibiting antibunching (separation of all photons in time), which are key components for secure quantum communication systems, and (2) entangled photon source with photons exhibiting quantum interference in a Hong-Ou- Mandel interferometer. In the first part, cholesteric liquid crystal hosts were used to create definite circular polarization of antibunched photons emitted by nanocrystal quantum dots. If the photon has unknown polarization, filtering it through a polarizer to produce the desired polarization for quantum key distribution with bits based on polarization states of photons will reduce by half the efficiency of a quantum cryptography system. In the first part, we also provide our results on observation of a circular polarized microcavity resonance in nanocrystal quantum dot fluorescence in a 1-D chiral photonic bandgap cholesteric liquid crystal microcavity. In the second part of this paper with indistinguishable, time-entangled photons, we demonstrate our experimental results on simulating quantum-mechanical barrier tunnelling phenomena. A Hong-Ou-Mandel dip (quantum interference effect) is shifted when a phase change was introduced on the way of one of entangled photons in pair (one arm of the interferometer) by inserting in this arm an electrically controlled planar-aligned nematic liquid crystal layer between two prisms in the conditions close to a frustrated total internal reflection. By applying different AC-voltages to the planar-aligned nematic layer and changing its refractive index, we can obtain various conditions for incident photon propagation - from total reflection to total transmission. Measuring changes of tunnelling times of photon through this structure with femtosecond resolution permitted us to answer some unresolved questions in quantum-mechanical barrier tunnelling phenomena.

  12. Versatile alignment layer method for new types of liquid crystal photonic devices

    SciTech Connect

    Finnemeyer, V.; Bryant, D.; Lu, L.; Bos, P.; Reich, R.; Clark, H.; Berry, S.; Bozler, C.; Yaroshchuk, O.

    2015-07-21

    Liquid crystal photonic devices are becoming increasingly popular. These devices often present a challenge when it comes to creating a robust alignment layer in pre-assembled cells. In this paper, we describe a method of infusing a dye into a microcavity to produce an effective photo-definable alignment layer. However, previous research on such alignment layers has shown that they have limited stability, particularly against subsequent light exposure. As such, we further describe a method of utilizing a pre-polymer, infused into the microcavity along with the liquid crystal, to provide photostability. We demonstrate that the polymer layer, formed under ultraviolet irradiation of liquid crystal cells, has been effectively localized to a thin region near the substrate surface and provides a significant improvement in the photostability of the liquid crystal alignment. This versatile alignment layer method, capable of being utilized in devices from the described microcavities to displays, offers significant promise for new photonics applications.

  13. Tunable pattern transitions in a liquid-crystal-monomer mixture using two-photon polymerization.

    PubMed

    Jisha, Chandroth P; Hsu, Kuei-Chu; Lin, Yuanyao; Lin, Ja-Hon; Jeng, Chien-Chung; Lee, Ray-Kuang

    2012-12-01

    Through two-photon lithographic processes, we report experimentally and numerically a series of photoinduced tunable polymerization patterns in shapes from straight channel, serpentine curve, to periodic grating when an ultrashort femtosecond laser pulse directly writes in a liquid-crystal-monomer mixture along a line for different scanning speeds. Laser beams with polarization perpendicular to the direction of writing and the alignment of liquid crystals, produce snake-shaped patterns at an intermediate scan rate. PMID:23202094

  14. Tunable narrow-bandpass filter based on an asymmetric photonic bandgap structure with a dual-mode liquid crystal.

    PubMed

    Wang, Hsiao-Tsung; Timofeev, Ivan V; Chang, Kai; Zyryanov, Victor Ya; Lee, Wei

    2014-06-16

    A one-dimensional asymmetric photonic crystal with dual-frequency liquid crystal as a central defect layer was demonstrated. Such asymmetric structure was characterized by the dramatic increase in intensity of the electric field of light localized at the overlapped photonic bandgap edges, thereby enhancing the observed transmittance of the spectral windows originating from the defect layer. The defect layer was made of a dual-mode liquid crystal that exhibited not only electrical tunability and switchability but also optical bistability. Consequently, tunable and bistable defect modes can be realized in the photonic structure. This asymmetric photonic crystal structure is promising and should be further explored for photonic device applications.

  15. Tunable narrow-bandpass filter based on an asymmetric photonic bandgap structure with a dual-mode liquid crystal.

    PubMed

    Wang, Hsiao-Tsung; Timofeev, Ivan V; Chang, Kai; Zyryanov, Victor Ya; Lee, Wei

    2014-06-16

    A one-dimensional asymmetric photonic crystal with dual-frequency liquid crystal as a central defect layer was demonstrated. Such asymmetric structure was characterized by the dramatic increase in intensity of the electric field of light localized at the overlapped photonic bandgap edges, thereby enhancing the observed transmittance of the spectral windows originating from the defect layer. The defect layer was made of a dual-mode liquid crystal that exhibited not only electrical tunability and switchability but also optical bistability. Consequently, tunable and bistable defect modes can be realized in the photonic structure. This asymmetric photonic crystal structure is promising and should be further explored for photonic device applications. PMID:24977602

  16. Modulation of defect modes intensity by controlled light scattering in photonic crystal with liquid crystal domain structure

    NASA Astrophysics Data System (ADS)

    Gunyakov, V. A.; Krakhalev, M. N.; Zyryanov, V. Ya.; Shabanov, V. F.; Loiko, V. A.

    2016-07-01

    A method to modulate the defect modes intensity in a multilayer photonic crystal with a nematic liquid crystal layer arranged midmost has been proposed. The various electrohydrodynamic domain structures (Williams domains, oblique rolls and grid pattern) were formed in the nematic layer under the action of ac electric field. The domains cause a polarization-sensitive light scattering which leads to an anisotropic reduction of the defect modes intensity. Thus by varying the applied voltage, we can tune gradually the transmittance spectrum of photonic crystal. In addition, the spectrum strongly depends on the light polarization direction above threshold voltage.

  17. Dispersion engineering in nonlinear soft glass photonic crystal fibers infiltrated with liquids.

    PubMed

    Pniewski, Jacek; Stefaniuk, Tomasz; Van, Hieu Le; Long, Van Cao; Van, Lanh Chu; Kasztelanic, Rafał; Stępniewski, Grzegorz; Ramaniuk, Aleksandr; Trippenbach, Marek; Buczyński, Ryszard

    2016-07-01

    We present a numerical study of the dispersion characteristic modification of nonlinear photonic crystal fibers infiltrated with liquids. A photonic crystal fiber based on the soft glass PBG-08, infiltrated with 17 different organic solvents, is proposed. The glass has a light transmission window in the visible-mid-IR range of 0.4-5 μm and has a higher refractive index than fused silica, which provides high contrast between the fiber structure and the liquids. A fiber with air holes is designed and then developed in the stack-and-draw process. Analyzing SEM images of the real fiber, we calculate numerically the refractive index, effective mode area, and dispersion of the fundamental mode for the case when the air holes are filled with liquids. The influence of the liquids on the fiber properties is discussed. Numerical simulations of supercontinuum generation for the fiber with air holes only and infiltrated with toluene are presented. PMID:27409187

  18. Ultra-high tunable liquid crystal-plasmonic photonic crystal fiber polarization filter.

    PubMed

    Hameed, Mohamed Farhat O; Heikal, A M; Younis, B M; Abdelrazzak, Maher; Obayya, S S A

    2015-03-23

    A novel ultra-high tunable photonic crystal fiber (PCF) polarization filter is proposed and analyzed using finite element method. The suggested design has a central hole infiltrated with a nematic liquid crystal (NLC) that offers high tunability with temperature and external electric field. Moreover, the PCF is selectively filled with metal wires into cladding air holes. Results show that the resonance losses and wavelengths are different in x and y polarized directions depending on the rotation angle φ of the NLC. The reported filter of compact device length 0.5 mm can achieve 600 dB / cm resonance losses at φ = 90° for x-polarized mode at communication wavelength of 1300 mm with low losses of 0.00751 dB / cm for y-polarized mode. However, resonance losses of 157.71 dB / cm at φ = 0° can be achieved for y-polarized mode at the same wavelength with low losses of 0.092 dB / cm for x-polarized mode.

  19. Electro-optical device based on photonic structure with a dual-frequency cholesteric liquid crystal.

    PubMed

    Hsiao, Yu-Cheng; Wu, Chong-Yin; Chen, Chih-Heng; Zyryanov, Victor Ya; Lee, Wei

    2011-07-15

    An electrically tunable and polarizer-free photonic device is developed using a one-dimensional photonic crystal (PC) infiltrated with dual-frequency cholesteric liquid crystal (DFCLC) as a defect layer. The PC/DFCLC hybrid cell allows the employment of various frequency-modulated voltage pulses to regulate defect modes and switch between stable states. This device possesses many alluring features such as rapid bistable switching, intensity tunability, and wavelength tunability in the defect modes, and it requires no polarizers. It can be used as a filter, fast-speed shutter, or light-intensity modulator.

  20. Electro-optical device based on photonic structure with a dual-frequency cholesteric liquid crystal

    NASA Astrophysics Data System (ADS)

    Hsiao, Yu-Cheng; Wu, Chong-Yin; Chen, Chih-Heng; Zyryanov, Victor Ya.; Lee, Wei

    2011-07-01

    An electrically tunable and polarizer-free photonic device is developed using a one-dimensional photonic crystal (PC) infiltrated with dual-frequency cholesteric liquid crystal (DFCLC) as a defect layer. The PC/DFCLC hybrid cell allows the employment of various frequency-modulated voltage pulses to regulate defect modes and switch between stable states. This device possesses many alluring features such as rapid bistable switching, intensity tunability, and wavelength tunability in the defect modes, and it requires no polarizers. It can be used as a filter, fast-speed shutter, or light-intensity modulator.

  1. Electro-optical device based on photonic structure with a dual-frequency cholesteric liquid crystal.

    PubMed

    Hsiao, Yu-Cheng; Wu, Chong-Yin; Chen, Chih-Heng; Zyryanov, Victor Ya; Lee, Wei

    2011-07-15

    An electrically tunable and polarizer-free photonic device is developed using a one-dimensional photonic crystal (PC) infiltrated with dual-frequency cholesteric liquid crystal (DFCLC) as a defect layer. The PC/DFCLC hybrid cell allows the employment of various frequency-modulated voltage pulses to regulate defect modes and switch between stable states. This device possesses many alluring features such as rapid bistable switching, intensity tunability, and wavelength tunability in the defect modes, and it requires no polarizers. It can be used as a filter, fast-speed shutter, or light-intensity modulator. PMID:21765491

  2. Nematic and blue phase liquid crystals for temperature stabilization and active optical tuning of silicon photonic devices (Presentation Recording)

    NASA Astrophysics Data System (ADS)

    Ptasinski, Joanna N.; Khoo, Iam Choon; Fainman, Yeshaiahu

    2015-10-01

    We describe the underlying theories and experimental demonstrations of passive temperature stabilization of silicon photonic devices clad in nematic liquid crystal mixtures, and active optical tuning of silicon photonic resonant structures combined with dye-doped nematic and blue phase liquid crystals. We show how modifications to the resonator device geometry allow for not only enhanced tuning of the resonator response, but also aid in achieving complete athermal operations of silicon photonic circuits. [Ref.: I.C. Khoo, "DC-field-assisted grating formation and nonlinear diffractions in methyl-red dye-doped blue phase liquid crystals," Opt. Lett. 40, 60-63 (2015); J. Ptasinski, I.C. Khoo, and Y. Fainman, "Enhanced optical tuning of modified-geometry resonators clad in blue phase liquid crystals," Opt. Lett. 39, 5435-5438 (2014); J. Ptasinski, I.C. Khoo, and Y. Fainman, "Passive Temperature Stabilization of Silicon Photonic Devices Using Liquid Crystals," Materials 7(3), 2229-2241 (2014)].

  3. Optically Generated Reconfigurable Photonic Structures of Elastic Quasiparticles in Frustrated Cholesteric Liquid Crystals

    SciTech Connect

    Smalyukh,, I. I.; Kaputa, D.; Kachynski, A. V.; Kuzmin, A. N.; Ackerman, P. J.; Twombly, C. W.; Lee, T.; Trivedi, R. P.; Prasad, P. N.

    2012-03-26

    We describe laser-induced two-dimensional periodic photonic structures formed by localized particle-like excitations in an untwisted confined cholesteric liquid crystal. The individual particle-like excitations (dubbed 'Torons') contain three-dimensional twist of the liquid crystal director matched to the uniform background director field by topological point defects. Using both single-beam-steering and holographic pattern generation approaches, the periodic crystal lattices are tailored by tuning their periodicity, reorienting their crystallographic axes, and introducing defects. Moreover, these lattices can be dynamically reconfigurable: generated, modified, erased and then recreated, depending on the needs of a particular photonic application. This robust control is performed by tightly focused laser beams of power 10-100 mW and by low-frequency electric fields at voltages {approx}10 V applied to the transparent electrodes.

  4. Theoretical design of a liquid-core photonic crystal fiber for supercontinuum generation.

    PubMed

    Zhang, Rui; Teipel, Jörn; Giessen, Harald

    2006-07-24

    We have numerically studied a hollow-core photonic crystal fiber, with its core filled with highly nonlinear liquids such as carbon disulfide and nitrobenzene. Calculations show that the fiber has an extremely high nonlinear parameter gamma on the order of 2.4/W/m at 1.55 mum. The group velocity dispersion of this fiber exhibits an anomalous region in the near-infrared, and its zero-dispersion wavelength is around 1.55 mum. This leads to potentially significant improvements and a large bandwidth in supercontinuum generation. The spectral properties of the supercontinuum generation in liquid-core photonic crystal fibers are simulated by solving the generalized nonlinear Schrödinger equation. The results demonstrate that the liquid-core PCF is capable to generate dramatically broadened supercontinua in a range from 700 nm to more than 2500 nm when pumping at 1.55 mum with subpicosecond pulses. PMID:19516862

  5. Theoretical design of a liquid-core photonic crystal fiber for supercontinuum generation

    NASA Astrophysics Data System (ADS)

    Zhang, Rui; Teipel, Jörn; Giessen, Harald

    2006-07-01

    We have numerically studied a hollow-core photonic crystal fiber, with its core filled with highly nonlinear liquids such as carbon disulfide and nitrobenzene. Calculations show that the fiber has an extremely high nonlinear parameter γ on the order of 2.4/W/m at 1.55 μm. The group velocity dispersion of this fiber exhibits an anomalous region in the near-infrared, and its zero-dispersion wavelength is around 1.55 μm. This leads to potentially significant improvements and a large bandwidth in supercontinuum generation. The spectral properties of the supercontinuum generation in liquid-core photonic crystal fibers are simulated by solving the generalized nonlinear Schrödinger equation. The results demonstrate that the liquid-core PCF is capable to generate dramatically broadened supercontinua in a range from 700 nm to more than 2500 nm when pumping at 1.55 μm with subpicosecond pulses.

  6. Enhancing the sensitivity of liquid refractive index sensor based on slow light photonic crystal waveguide

    NASA Astrophysics Data System (ADS)

    Zhao, Yong; Huang, He; Wang, Qi

    2011-05-01

    This paper designed a high sensitivity refractive index sensor based on two-dimensional square-lattice slow light photonic crystal waveguide. This structure based on Mach-Zehnder interferometer (MZI) which can be widely used in measuring the refractive index of liquid. The resolution of this sample structure can reach 7×10-7 RIU. This kind of sensor can be integrated with electronic systems to measure the refractive index of gas or fluid.

  7. Dielectric measurements of nanoliter liquids with a photonic crystal resonator at terahertz frequencies

    NASA Astrophysics Data System (ADS)

    Hanham, S. M.; Watts, C.; Otter, W. J.; Lucyszyn, S.; Klein, N.

    2015-07-01

    We present a highly sensitive technique for determining the complex permittivity of nanoliter liquid samples in the terahertz band based on a photonic crystal resonator and microcapillary. Liquids are characterized by using a capillary tube to introduce a ˜4 nl liquid sample into the electromagnetic field of a resonant mode confined by an L3 resonant cavity in a high-resistivity silicon photonic crystal slab. Monitoring the perturbation of the resonant frequency and unloaded Q-factor of the resonant mode at 100 GHz and ˜5800, respectively, allows a sample's permittivity to be calculated. An analytical model describing the system response based on perturbation theory and quasi-static analysis of the electric field within the capillary is also presented and found to agree well with FEM simulations and experimental measurements of ethanol-water mixtures of various concentrations for low to moderate loss tangents of the liquid samples. We demonstrate the utility of this approach by measuring the complex permittivity of several bioliquids, including suspensions of red and white blood cells. These results represent a step towards a lab-on-a-chip device for the analysis of extremely small quantities of biological, toxic, explosive, and other liquid types at terahertz frequencies.

  8. Dielectric measurements of nanoliter liquids with a photonic crystal resonator at terahertz frequencies

    SciTech Connect

    Hanham, S. M. Watts, C.; Klein, N.; Otter, W. J.; Lucyszyn, S.

    2015-07-20

    We present a highly sensitive technique for determining the complex permittivity of nanoliter liquid samples in the terahertz band based on a photonic crystal resonator and microcapillary. Liquids are characterized by using a capillary tube to introduce a ∼4 nl liquid sample into the electromagnetic field of a resonant mode confined by an L3 resonant cavity in a high-resistivity silicon photonic crystal slab. Monitoring the perturbation of the resonant frequency and unloaded Q-factor of the resonant mode at 100 GHz and ∼5800, respectively, allows a sample's permittivity to be calculated. An analytical model describing the system response based on perturbation theory and quasi-static analysis of the electric field within the capillary is also presented and found to agree well with FEM simulations and experimental measurements of ethanol-water mixtures of various concentrations for low to moderate loss tangents of the liquid samples. We demonstrate the utility of this approach by measuring the complex permittivity of several bioliquids, including suspensions of red and white blood cells. These results represent a step towards a lab-on-a-chip device for the analysis of extremely small quantities of biological, toxic, explosive, and other liquid types at terahertz frequencies.

  9. Influence of structural parameters on tunable photonic band gaps modulated by liquid crystals

    NASA Astrophysics Data System (ADS)

    Huang, Aiqin; Zheng, Jihong; Jiang, Yanmeng; Zhou, Zengjun; Tang, Pingyu; Zhuang, Songlin

    2011-10-01

    Tunable photonic crystals (PCs), which are infiltrated with nematic liquid crystals (LCs), tune photonic band gap (PBG) by rotating directors of LCs when applied with the external electrical field. Using the plane wave expansion method, we simulated the PBG structure of two-dimensional tunable PCs with a triangular lattice of circular column, square column and hexagon column, respectively. When PCs are composed of LCs and different substrate materials such as germanium (Ge) and silicon (Si), the influence of structural parameters including column shape and packing ration on PBG is discussed separately. Numerical simulations show that absolute PBG can't be found at any conditions, however large tuning range of polarized wave can be achieved by rotating directors of LCs. The simulation results provide theoretical guidance for the fabrication of field-sensitive polarizer with big tunable band range.

  10. Liquid gallium cooling of silicon crystals in high intensity photon beams (invited)

    NASA Astrophysics Data System (ADS)

    Smither, R. K.; Forster, G. A.; Bilderback, D. H.; Bedzyk, M.; Finkelstein, K.; Henderson, C.; White, J.; Berman, L. E.; Stefan, P.; Oversluizen, T.

    1989-07-01

    The high-brilliance, insertion-device-based photon beams of the next generation of synchrotron sources (Argonne's APS and Grenoble's ESRF) will deliver large thermal loads (1-10 kW) to the first optical elements. Considering the problems that present synchrotron users are experiencing with beams from recently installed insertion devices, new and improved methods of cooling these first optical elements, particularly when they are diffraction crystals, are clearly needed. A series of finite element calculations were performed to test the efficiency of new cooling geometries and various cooling fluids. The best results were obtained with liquid Ga metal flowing in channels just below the surface of the crystal. Ga was selected because of its good thermal conductivity and thermal capacity, low melting point, high boiling point, low kinetic viscosity, and very low vapor pressure. Its very low vapor pressure, even at elevated temperatures, makes it especially attractive in UHV conditions. A series of experiments were conducted at CHESS in February of 1988 that compared liquid gallium-cooled silicon diffraction crystals with water-cooled crystals. A six-pole wiggler beam was used to perform these tests on three different Si crystals, two with new cooling geometries and the one presently in use. A special high-pressure electromagnetic induction pump, recently developed at Argonne, was used to circulate the liquid gallium through the silicon crystals. In all experiments, the specially cooled crystal was used as the first crystal in a two crystal monochromator. An infrared camera was used to monitor the thermal profiles and correlated them with rocking curve measurements. A second set of cooling experiments were conducted in June of 1988 that used the intense, highly collimated beam from the newly installed ANL/CHESS undulator. Tests were performed on two new Ga-cooled Si crystals and compared with the standard water-cooled Si crystal. One of the crystals had cooling

  11. Liquid gallium cooling of silicon crystals in high intensity photon beams

    SciTech Connect

    Smither, R. K.; Forster, G. A.; Bilderback, D. H.; Bedzyk, M.; Finkelstein, K.; Henderson, C.; White, J.; Berman, L. E.; Stefan, P.; Oversluizen, T.; and others

    1989-07-01

    The high-brilliance, insertion-device-based photon beams of the next generation of synchrotron sources (Argonne's APS and Grenoble's ESRF) will deliver large thermal loads (1--10 kW) to the first optical elements. Considering the problems that present synchrotron users are experiencing with beams from recently installed insertion devices, new and improved methods of cooling these first optical elements, particularly when they are diffraction crystals, are clearly needed. A series of finite element calculations were performed to test the efficiency of new cooling geometries and various cooling fluids. The best results were obtained with liquid Ga metal flowing in channels just below the surface of the crystal. Ga was selected because of its good thermal conductivity and thermal capacity, low melting point, high boiling point, low kinetic viscosity, and very low vapor pressure. Its very low vapor pressure, even at elevated temperatures, makes it especially attractive in UHV conditions. A series of experiments were conducted at CHESS in February of 1988 that compared liquid gallium-cooled silicon diffraction crystals with water-cooled crystals. A six-pole wiggler beam was used to perform these tests on three different Si crystals, two with new cooling geometries and the one presently in use. A special high-pressure electromagnetic induction pump, recently developed at Argonne, was used to circulate the liquid gallium through the silicon crystals. In all experiments, the specially cooled crystal was used as the first crystal in a two crystal monochromator. An infrared camera was used to monitor the thermal profiles and correlated them with rocking curve measurements. A second set of cooling experiments were conducted in June of 1988 that used the intense, highly collimated beam from the newly installed ANL/CHESS undulator.

  12. Reflectance-based two-dimensional TiO2 photonic crystal liquid sensors.

    PubMed

    Huang, Yujian; Pandraud, Grégory; Sarro, Pasqualina M

    2012-08-01

    We propose and experimentally demonstrate a reflectance-based photonic crystal (PC) liquid sensor. The PC is made of two-dimensional TiO2 nanopillar arrays. Such a reflectance-based structure with large functional area not only simplifies the optical guiding but also enhances the sensor signal. A linear shift of reflectance peaks is found for liquids with refractive indices varying from 1.333 to 1.390 at wavelength near 1.5 μm. Excellent agreement between measured values and the generated reflectance model at a fixed wavelength is obtained, indicating the high potential of these PC-based liquid sensors for biological and environmental applications. PMID:22859119

  13. Liquid gallium cooling of silicon crystals in high intensity photon beam

    SciTech Connect

    Smither, R.K.; Forster, G.A.; Bilderback, D.H.; Bedzyk, M.; Finkelstein, K.; Henderson, C.; White, J.; Berman, L.E.; Stefan, P.; Oversluizen, T.

    1988-11-01

    The high-brilliance, insertion-device-based, photon beams of the next generation of synchrotron sources will deliver large thermal loads (1 kW to 10 kW) to the first optical elements. Considering the problems that present synchrotron users are experiencing with beams from recently installed insertion devices, new and improved methods of cooling these first optical elements, particularly when they are diffraction crystals, are clearly needed. A series of finite element calculations were performed to test the efficiency of new cooling geometries and new cooling fluids. The best results were obtained with liquid Ga metal flowing in channels just below the surface of the crystal. Ga was selected because of its good thermal conductivity and thermal capacity, low melting point, high boiling point, low kinetic viscosity, and very low vapor pressure. Its very low vapor pressure, even at elevated temperatures, makes it especially attractive in uhv conditions. A series of experiments were conducted at CHESS in February of 1988 that compared liquid gallium cooled silicon diffraction crystals with water cooled crystals. 2 refs., 16 figs., 1 tab.

  14. Responsive ionic liquid-polymer 2D photonic crystal gas sensors.

    PubMed

    Smith, Natasha L; Hong, Zhenmin; Asher, Sanford A

    2014-12-21

    We developed novel air-stable 2D polymerized photonic crystal (2DPC) sensing materials for visual detection of gas phase analytes such as water and ammonia by utilizing a new ionic liquid, ethylguanidine perchlorate (EGP) as the mobile phase. Because of the negligible ionic liquid vapor pressure these 2DPC sensors are indefinitely air stable and, therefore, can be used to sense atmospheric analytes. 2D arrays of ~640 nm polystyrene nanospheres were attached to the surface of crosslinked poly(hydroxyethyl methacrylate) (pHEMA)-based polymer networks dispersed in EGP. The wavelength of the bright 2D photonic crystal diffraction depends sensitively on the 2D array particle spacing. The volume phase transition response of the EGP-pHEMA system to water vapor or gaseous ammonia changes the 2DPC particle spacing, enabling the visual determination of the analyte concentration. Water absorbed by EGP increases the Flory-Huggins interaction parameter, which shrinks the polymer network and causes a blue shift in the diffracted light. Ammonia absorbed by the EGP deprotonates the pHEMA-co-acrylic acid carboxyl groups, swelling the polymer which red shifts the diffracted light.

  15. Circular dichroism of chiral photonic crystal liquid layers with enclosed defect inside

    NASA Astrophysics Data System (ADS)

    Gevorgyan, Ashot; Kocharian, Armen; Vardanyan, Gagik

    2015-03-01

    The photonic crystals of artificial and self-organizing structures with spatial periodic changes in dielectric and magnetic properties have attracted considerable interest recently due to unusual physical properties and wide practical applications. The chiral periodic structure in the scale of optical wavelength gives rise to strong and characteristic circular dichroism responses at visible wavelengths. Here we investigate photonic density, circular dichroism and peculiarities of absorption and emission spectra at various eigen polarizations in multilayered one-dimensional chiral soft matter with two layers of CLCs and an isotropic defect layer inside. The circular dichroism is defined by differences in light energy absorption A=1-(R + T) by the system (R and T are the reflection and transmission coefficients, respectively) and A s , r are the light absorptions, if the incident light has left and right circular polarizations, respectively. This problem can be solved by the modified Ambartsumian's layer addition method. The influence of absorption and gain on the circular dichroism, absorption and emission spectra is established in cholesteric liquid crystal (CLC) cell with an isotropic defect layer inside.

  16. Localised polymer networks in chiral nematic liquid crystals for high speed photonic switching

    NASA Astrophysics Data System (ADS)

    Tartan, Chloe C.; Salter, Patrick S.; Booth, Martin J.; Morris, Stephen M.; Elston, Steve J.

    2016-05-01

    Self-assembled periodic structures based upon chiral liquid crystalline materials have significant potential in the field of photonics ranging from fast-switching optoelectronic devices to low-threshold lasers. The flexoelectro-optic effect, which is observed in chiral nematic liquid crystals (LCs) when an electric field is applied perpendicular to the helical axis, has significant potential as it exhibits analogue switching in 10-100 μs. However, the major technological barrier that prohibits the commercial realisation of this electro-optic effect is the requirement of a uniform, in-plane alignment of the helix axis between glass substrates. Here, it is shown that periodic polymer structures engineered in the nematic phase of a chiral nematic LC device using direct laser writing can result in the spontaneous formation of the necessary uniform lying helix (ULH) state. Specifically, two-photon polymerization is used in conjunction with a spatial light modulator so as to correct for aberrations introduced by the bounding glass substrates enabling the polymer structures to be fabricated directly into the device. The ULH state appears to be stable in the absence of an externally applied electric field, and the optimum contrast between the bright and dark states is obtained using polymer structures that have periodicities of the order of the device thickness.

  17. Photonic liquid crystal fibers tuning by four electrode system produced with 3D printing technology

    NASA Astrophysics Data System (ADS)

    Ertman, Slawomir; Bednarska, Karolina; Czapla, Aleksandra; Woliński, Tomasz R.

    2015-09-01

    Photonic liquid crystal fiber has been intensively investigated in last few years. It has been proved that guiding properties of such fibers could be tuned with an electric field. In particular efficient tuning could be obtained if multi-electrode system allowing for dynamic change of not only intensity of the electric field, but also its direction. In this work we report a simple to build four electrode system, which is based on a precisely aligned four cylindrical microelectrodes. As an electrodes we use enameled copper wire with diameter adequate to the diameter of the fiber to be tuned. To ensure uniform and parallel alignment of the wires a special micro-profiles has been designed and then produced with filament 3D printer. The possibility of the dynamic change of the electric field direction in such scalable and cost effective electrode assembly has been experimentally confirmed.

  18. Design and optimization of photonic crystal fiber for liquid sensing applications

    NASA Astrophysics Data System (ADS)

    Arif, Md. Faizul Huq; Ahmed, Kawsar; Asaduzzaman, Sayed; Azad, Md. Abul Kalam

    2016-06-01

    This paper proposes a hexagonal photonic crystal fiber (H-PCF) structure with high relative sensitivity for liquid sensing; in which both core and cladding are microstructures. Numerical investigation is carried out by employing the full vectorial finite element method (FEM). The analysis has been done in four stages of the proposed structure. The investigation shows that the proposed structure achieves higher relative sensitivity by increasing the diameter of the innermost ring air holes in the cladding. Moreover, placing a single channel instead of using a group of tiny channels increases the relative sensitivity effectively. Investigating the effects of different parameters, the optimized structure shows significantly higher relative sensitivity with a low confinement loss.

  19. Design and optimization of photonic crystal fiber for liquid sensing applications

    NASA Astrophysics Data System (ADS)

    Arif, Md. Faizul Huq; Ahmed, Kawsar; Asaduzzaman, Sayed; Azad, Md. Abul Kalam

    2016-09-01

    This paper proposes a hexagonal photonic crystal fiber (H-PCF) structure with high relative sensitivity for liquid sensing; in which both core and cladding are microstructures. Numerical investigation is carried out by employing the full vectorial finite element method (FEM). The analysis has been done in four stages of the proposed structure. The investigation shows that the proposed structure achieves higher relative sensitivity by increasing the diameter of the innermost ring air holes in the cladding. Moreover, placing a single channel instead of using a group of tiny channels increases the relative sensitivity effectively. Investigating the effects of different parameters, the optimized structure shows significantly higher relative sensitivity with a low confinement loss.

  20. Spectral and polarization structure of field-induced photonic bands in cholesteric liquid crystals

    NASA Astrophysics Data System (ADS)

    Palto, S. P.; Barnik, M. I.; Geivandov, A. R.; Kasyanova, I. V.; Palto, V. S.

    2015-09-01

    Transmission of planar layers of cholesteric liquid crystals is studied in pulsed electric fields perpendicular to the helix axis at normal incidence of both linearly polarized and unpolarized light. Spectral and light polarization properties of the primary photonic band and the field-induced bands up to fourth order of Bragg selective reflection are studied in detail. In our experiments we have achieved an electric field strength several times higher than the theoretical values corresponding to the critical field of full helix unwinding. However, the experiments show that despite the high strength of the electric field applied the helix does not unwind, but strongly deforms, keeping its initial spatial period. Strong helix deformation results in distinct spectral band splitting, as well as very high field-induced selective reflectance that can be applied in lasers and other optoelectronic devices. Peculiarities of inducing and splitting the bands are discussed in terms of the scattering coefficient approach. All observed effects are confirmed by numerical simulations. The simulations also show that liquid crystal surface anchoring is not the factor that prevents the helix unwinding. Thus, the currently acknowledged concept of continuous helix unwinding in the electric field should be reconsidered.

  1. Tuning quantum-dot organization in liquid crystals for robust photonic applications.

    PubMed

    Rodarte, Andrea L; Nuno, Zachary S; Cao, Blessing H; Pandolfi, Ronald J; Quint, Makiko T; Ghosh, Sayantani; Hein, Jason E; Hirst, Linda S

    2014-05-19

    Mesogenic ligands have the potential to provide control over the dispersion and stabilization of nanoparticles in liquid crystal (LC) phases. The creation of such hybrid materials is an important goal for the creation of soft tunable photonic devices, such as the LC laser. Herein, we present a comparison of isotropic and mesogenic ligands attached to the surface of CdSe (core-only) and CdSe/ZnS (core/shell) quantum dots (QDs). The mesogenic ligand's flexible arm structure enhances ligand alignment, with the local LC director promoting QD dispersion in the isotropic and nematic phases. To characterize QD dispersion on different length scales, we apply fluorescence microscopy, X-ray scattering, and scanning confocal photoluminescent imaging. These combined techniques demonstrate that the LC-modified QDs do not aggregate into the dense clusters observed for dots with simple isotropic ligands when dispersed in liquid crystal, but loosely associate in a fluid-like droplet with an average interparticle spacing >10 nm. Embedding the QDs in a cholesteric cavity, we observe comparable coupling effects to those reported for more closely packed isotropic ligands.

  2. Photonic crystal light source

    DOEpatents

    Fleming, James G.; Lin, Shawn-Yu; Bur, James A.

    2004-07-27

    A light source is provided by a photonic crystal having an enhanced photonic density-of-states over a band of frequencies and wherein at least one of the dielectric materials of the photonic crystal has a complex dielectric constant, thereby producing enhanced light emission at the band of frequencies when the photonic crystal is heated. The dielectric material can be a metal, such as tungsten. The spectral properties of the light source can be easily tuned by modification of the photonic crystal structure and materials. The photonic crystal light source can be heated electrically or other heating means. The light source can further include additional photonic crystals that exhibit enhanced light emission at a different band of frequencies to provide for color mixing. The photonic crystal light source may have applications in optical telecommunications, information displays, energy conversion, sensors, and other optical applications.

  3. A Reflective Photonic Crystal Fiber Temperature Sensor Probe Based on Infiltration with Liquid Mixtures

    PubMed Central

    Wang, Ran; Yao, Jianquan; Miao, Yinping; Lu, Ying; Xu, Degang; Luan, Nannan; Musideke, Mayilamu; Duan, Liangcheng; Hao, Congjing

    2013-01-01

    In this paper, a reflective photonic crystal fiber (PCF) sensor probe for temperature measurement has been demonstrated both theoretically and experimentally. The performance of the device depends on the intensity modulation of the optical signal by liquid mixtures infiltrated into the air holes of commercial LMA-8 PCFs. The effective mode field area and the confinement loss of the probe are both proved highly temperature-dependent based on the finite element method (FEM). The experimental results show that the reflected power exhibits a linear response with a temperature sensitivity of about 1 dB/°C. The sensor probe presents a tunable temperature sensitive range due to the concentration of the mixture components. Further research illustrates that with appropriate mixtures of liquids, the probe could be developed as a cryogenic temperature sensor. The temperature sensitivity is about 0.75 dB/°C. Such a configuration is promising for a portable, low-power and all-in-fiber device for temperature or refractive index monitoring in chemical or biosensing applications. PMID:23787726

  4. Function photonic crystals

    NASA Astrophysics Data System (ADS)

    Wu, Xiang-Yao; Zhang, Bai-Jun; Yang, Jing-Hai; Liu, Xiao-Jing; Ba, Nuo; Wu, Yi-Heng; Wang, Qing-Cai

    2011-07-01

    In this paper, we present a new kind of function photonic crystals (PCs), whose refractive index is a function of space position. Conventional PCs structure grows from two materials, A and B, with different dielectric constants εA and εB. Based on Fermat principle, we give the motion equations of light in one-dimensional, two-dimensional and three-dimensional function photonic crystals. For one-dimensional function photonic crystals, we give the dispersion relation, band gap structure and transmissivity, and compare them with conventional photonic crystals, and we find the following: (1) For the vertical and non-vertical incidence light of function photonic crystals, there are band gap structures, and for only the vertical incidence light, the conventional PCs have band gap structures. (2) By choosing various refractive index distribution functions n( z), we can obtain more wider or more narrower band gap structure than conventional photonic crystals.

  5. Liquid Crystals

    NASA Technical Reports Server (NTRS)

    1990-01-01

    Thermochromic liquid crystals, or TLCs, are a type of liquid crystals that react to changes in temperature by changing color. The Hallcrest/NASA collaboration involved development of a new way to visualize boundary layer transition in flight and in wind tunnel testing of aircraft wing and body surfaces. TLCs offered a new and potentially better method of visualizing the boundary layer transition in flight. Hallcrest provided a liquid crystal formulation technique that afforded great control over the sensitivity of the liquid crystals to varying conditions. Method is of great use to industry, government and universities for aerodynamic and hydrodynamic testing. Company's principal line is temperature indicating devices for industrial use, such as non-destructive testing and flaw detection in electric/electronic systems, medical application, such as diagnostic systems, for retail sale, such as room, refrigerator, baby bath and aquarium thermometers, and for advertising and promotion specials. Additionally, Hallcrest manufactures TLC mixtures for cosmetic applications, and liquid crystal battery tester for Duracell batteries.

  6. Liquid sensor based bio-chip for DNA analysis of cancer using photonic crystal

    NASA Astrophysics Data System (ADS)

    Patil, Harshada; Nischitha, R.; Indumathi, T. S.; Sharan, Preeta

    2015-07-01

    Silicon photonics is poised to revolutionize bio-sensing applications, specifically in medical diagnostics. The need for cost effective and reliable bio-sensors in medical applications is an ever growing and everlasting one. In this synopsis we have designed a 2-D hexagonal photonic crystal ring resonator based bio-sensor that is able to detect lung cancer from blood. Simulation and analysis has been done for normal DNA and the cancer affected DNA in blood. The intensity level of transmission spectrum has been observed. Finite Difference Time Domain (FDTD) method is used for analysis. MEEP (MIT Electromagnetic Equation Propagation) tool and RSOFT Photonic Suite CAD tool are used designing the photonic crystal sensor. The results show that for small changes in the refractive index of the input samples there is a significant shift in wavelength and amplitude. Thus the sensor is highly sensitive for change in refractive index and hence differentiating normal and cancer affected DNA.

  7. Fiber Sagnac interferometer based on a liquid-filled photonic crystal fiber for temperature sensing

    NASA Astrophysics Data System (ADS)

    Liu, Qiang; Li, Shu-Guang; Shi, Min

    2016-12-01

    A fiber Sagnac interferometer based on the square-lattice photonic crystal fiber (PCF) for temperature sensing is designed. All the air holes are assumed to be filled with temperature sensitive liquid. The temperature sensing characteristics are analyzed by finite element method (FEM). The phase birefringence B, the group birefringence Bg, and the sensitivity dependence on the operable wavelength λ are studied, and the temperature varies from 25 °C to 85 °C. The birefringence sensitive coefficient of ∂ B / ∂ T is -10-7 / ° C. The sensitivity could reach to -11.9 nm/°C (-29 750 nm/RIU) at 1.8 μm as the temperature is 25 °C. The sensitivity is also studied by the transmission spectrum, and the wavelength spacing between the resonance wavelengths at 85 °C can reach to 492 nm. The average sensitivity could reach to -7.54 nm/°C (-18 850 nm/RIU). The diameter d1 on the sensing characteristics of the temperature sensor is also analyzed. The temperature sensor shows high sensitivity and broad detecting window.

  8. Photonic crystal fiber with a dual-frequency addressable liquid crystal: behavior in the visible wavelength range.

    PubMed

    Lorenz, A; Kitzerow, H-S; Schwuchow, A; Kobelke, J; Bartelt, H

    2008-11-10

    Wave-guiding in the visible spectral range is investigated for a micro-structured crystal fiber filled with a dual-frequency addressable nematic liquid crystal mixture. The fiber exhibits a solid core surrounded by just 4 rings of cylindrical holes. Control of the liquid crystal alignment by anchoring agents permits relatively low attenuation. Samples with different anchoring conditions at the interface of the silica glass and the liquid crystal show different transmission properties and switching behavior. Polarization dependent and independent fiber optic switching is observed. Due to a dualfrequency addressing scheme, active switching to both states with enhanced and reduced transmission becomes possible for planar anchoring. Even a non-perfect fiber shows reasonable transmission and a variety of interesting effects.

  9. Photonic crystal fiber with a dual-frequency addressable liquid crystal: behavior in the visible wavelength range.

    PubMed

    Lorenz, A; Kitzerow, H-S; Schwuchow, A; Kobelke, J; Bartelt, H

    2008-11-10

    Wave-guiding in the visible spectral range is investigated for a micro-structured crystal fiber filled with a dual-frequency addressable nematic liquid crystal mixture. The fiber exhibits a solid core surrounded by just 4 rings of cylindrical holes. Control of the liquid crystal alignment by anchoring agents permits relatively low attenuation. Samples with different anchoring conditions at the interface of the silica glass and the liquid crystal show different transmission properties and switching behavior. Polarization dependent and independent fiber optic switching is observed. Due to a dualfrequency addressing scheme, active switching to both states with enhanced and reduced transmission becomes possible for planar anchoring. Even a non-perfect fiber shows reasonable transmission and a variety of interesting effects. PMID:19582031

  10. Continuously tunable devices based on electrical control of dual-frequency liquid crystal filled photonic bandgap fibers.

    PubMed

    Scolari, Lara; Alkeskjold, Thomas; Riishede, Jesper; Bjarklev, Anders; Hermann, David; Anawati, Anawati; Nielsen, Martin; Bassi, Paolo

    2005-09-19

    We present an electrically controlled photonic bandgap fiber device obtained by infiltrating the air holes of a photonic crystal fiber (PCF) with a dual-frequency liquid crystal (LC) with pre-tilted molecules. Compared to previously demonstrated devices of this kind, the main new feature of this one is its continuous tunability due to the fact that the used LC does not exhibit reverse tilt domain defects and threshold effects. Furthermore, the dual-frequency features of the LC enables electrical control of the spectral position of the bandgaps towards both shorter and longer wavelengths in the same device. We investigate the dynamics of this device and demonstrate a birefringence controller based on this principle.

  11. Continuously tunable devices based on electrical control of dual-frequency liquid crystal filled photonic bandgap fibers

    NASA Astrophysics Data System (ADS)

    Scolari, Lara; Tanggaard Alkeskjold, Thomas; Riishede, Jesper; Bjarklev, Anders; Sparre Hermann, David; Anawati, Anawati; Dybendal Nielsen, Martin; Bassi, Paolo

    2005-09-01

    We present an electrically controlled photonic bandgap fiber device obtained by infiltrating the air holes of a photonic crystal fiber (PCF) with a dual-frequency liquid crystal (LC) with pre-tilted molecules. Compared to previously demonstrated devices of this kind, the main new feature of this one is its continuous tunability due to the fact that the used LC does not exhibit reverse tilt domain defects and threshold effects. Furthermore, the dual-frequency features of the LC enables electrical control of the spectral position of the bandgaps towards both shorter and longer wavelengths in the same device. We investigate the dynamics of this device and demonstrate a birefringence controller based on this principle.

  12. Continuously tunable devices based on electrical control of dual-frequency liquid crystal filled photonic bandgap fibers.

    PubMed

    Scolari, Lara; Alkeskjold, Thomas; Riishede, Jesper; Bjarklev, Anders; Hermann, David; Anawati, Anawati; Nielsen, Martin; Bassi, Paolo

    2005-09-19

    We present an electrically controlled photonic bandgap fiber device obtained by infiltrating the air holes of a photonic crystal fiber (PCF) with a dual-frequency liquid crystal (LC) with pre-tilted molecules. Compared to previously demonstrated devices of this kind, the main new feature of this one is its continuous tunability due to the fact that the used LC does not exhibit reverse tilt domain defects and threshold effects. Furthermore, the dual-frequency features of the LC enables electrical control of the spectral position of the bandgaps towards both shorter and longer wavelengths in the same device. We investigate the dynamics of this device and demonstrate a birefringence controller based on this principle. PMID:19498773

  13. Density of photon states in dye-doped chiral nematic liquid crystal cells in the presence of losses and gain.

    PubMed

    Mavrogordatos, Th K; Morris, S M; Castles, F; Hands, P J W; Ford, A D; Coles, H J; Wilkinson, T D

    2012-07-01

    We calculate the density of photon states (DOS) of the normal modes in dye-doped chiral nematic liquid crystal (LC) cells in the presence of various loss mechanisms. Losses and gain are incorporated into the transmission characteristics through the introduction of a small imaginary part in the dielectric constant perpendicular and along the director, for which we assume no frequency dispersion. Theoretical results are presented on the DOS in the region of the photonic band gap for a range of values of the loss coefficient and different values of the optical anisotropy. The obtained values of the DOS at the photonic band gap edges predict a reversal of the dominant modes in the structure. Our results are found to be in good agreement with the experimentally obtained excitation thresholds in chiral nematic LC lasers. The behavior of the DOS is also discussed for amplifying LC cells providing additional insight to the lasing mechanism of these structures.

  14. Dispersion in photonic crystals

    NASA Astrophysics Data System (ADS)

    Witzens, Jeremy

    2005-11-01

    Investigations on the dispersive properties of photonic crystals, modified scattering in ring-resonators, monolithic integration of vertical-cavity surface-emitting lasers and advanced data processing techniques for the finite-difference time-domain method are presented. Photonic crystals are periodic mesoscopic arrays of scatterers that modify the propagation properties of electromagnetic waves in a similar way as "natural" crystals modify the properties of electrons in solid-state physics. In this thesis photonic crystals are implemented as planar photonic crystals, i.e., optically thin semiconductor films with periodic arrays of holes etched into them, with a hole-to-hole spacing of the order of the wavelength of light in the dielectric media. Photonic crystals can feature forbidden frequency ranges (the band-gaps) in which light cannot propagate. Even though most work on photonic crystals has focused on these band-gaps for application such as confinement and guiding of light, this thesis focuses on the allowed frequency regions (the photonic bands) and investigates how the propagation of light is modified by the crystal lattice. In particular the guiding of light in bulk photonic crystals in the absence of lattice defects (the self-collimation effect) and the angular steering of light in photonic crystals (the superprism effect) are investigated. The latter is used to design a planar lightwave circuit for frequency domain demultiplexion. Difficulties such as efficient insertion of light into the crystal are resolved and previously predicted limitations on the resolution are circumvented. The demultiplexer is also fabricated and characterized. Monolithic integration of vertical-cavity surface-emitting lasers by means of resonantly enhanced grating couplers is investigated. The grating coupler is designed to bend light through a ninety-degree angle and is characterized with the finite-difference time-domain method. The vertical-cavity surface-emitting lasers are

  15. Polarization filter characters of the gold-coated and the liquid filled photonic crystal fiber based on surface plasmon resonance.

    PubMed

    Xue, Jianrong; Li, Shuguang; Xiao, Yuzhe; Qin, Wei; Xin, Xujun; Zhu, Xingping

    2013-06-01

    The polarization filter characters of a gold-coated and liquid-filled photonic crystal fiber are studied using the finite element method. Results show that the resonance strength and wavelengths are different in two polarized directions. Filling liquid of refractive index n=1.33 (purified water) in holes in longitudinal direction can increase the loss of core mode polarized in the y-direction around the resonance peak. The resonance strength is much stronger in y-polarized direction than in x-polarized direction. The resonance strength can achieve 508dB/cm in y-polarized direction at the communication wavelength of 1311nm in one of our structures. Moreover, the full width half maximum is only 20nm. Such a small number makes such photonic crystal fibers promising candidate to filter devices. A liquid filled PCF of the small hole in the fiber core is designed and we find that filling liquid increases the resonance strength peak by thirty eight percent for the y-polarized resonance point.

  16. Photonic crystal beam splitters.

    PubMed

    Chen, Chii-Chang; Chien, Hung-Da; Luan, Pi-Gang

    2004-11-20

    This work studies two-dimensional photonic crystal beam splitters with two input ports and two output ports. The beam splitter structure consists of two orthogonally crossed line defects and one point defect in square-lattice photonic crystals. The point defect is positioned at the intersection of the line defects to divide the input power into output ports. If the position and the size of the point defect are varied, the power of two output ports can be identical. The beam splitters can be used in photonic crystal Mach-Zehnder interferometers or switches. The simulation results show that a large bandwidth of the extinction ratio larger than 20 dB can be obtained while two beams are interfered in the beam splitters. This enables photonic crystal beam splitters to be used in fiber optic communication systems.

  17. Room-temperature single photon sources with definite circular and linear polarizations based on single-emitter fluorescence in liquid crystal hosts

    NASA Astrophysics Data System (ADS)

    Bissell, Luke J.; Lukishova, Svetlana G.; Schmid, Ansgar W.; Hahn, Megan A.; Evans, Chris M.; Krauss, Todd D.; Stroud, Carlos R., Jr.; Boyd, Robert W.

    2010-09-01

    Experimental results of two room-temperature, robust and efficient single-photon sources with definite circular and linear polarization using single-emitter fluorescence in cholesteric and nematic liquid crystal hosts are discussed. For single emitters, we used nanocrystal quantum dots, single color centers in nanodiamonds, and single dye molecules. Single-photon sources based on single emitters in liquid crystals are the room temperature alternatives to cryogenic single-photon sources base on semiconductor heterostructured quantum dots in microcavities prepared by molecular beam epitaxy.

  18. Photonic crystal fibers for food quality analysis

    NASA Astrophysics Data System (ADS)

    Malinin, A. V.; Zanishevskaja, A. A.; Tuchin, V. V.; Skibina, Yu. S.; Silokhin, I. Y.

    2012-06-01

    The aspects of application of the hollow core photonic crystal waveguides for spectroscopic analysis of liquid medium were considered. The possibility of using these structures for analysis of a fruit juice was evaluated. The principles of processing of photonic crystal waveguide transmission spectra, which is sensitive to quality of juice, its composition, and main component concentration, were revealed.

  19. Near-infrared imaging of liquid mixtures utilizing multi-channel photonic crystal wavelength filters.

    PubMed

    Mitsuhashi, Masahiro; Ohtera, Yasuo; Yamada, Hirohito

    2014-09-15

    We demonstrate a near-infrared (NIR) spectroscopy-based real-time imaging system of aqueous alcohol solutions (ethanol containing water). The system obtains a set of NIR images by the combination of an InGaAs area sensor and four-channel patterned photonic crystal wavelength filters. Acquired pictures were decomposed into a set of NIR images and processed by principal component analysis (PCA). According to a preliminary experiment for water/ethanol mixture samples, we confirmed that the system was capable of identifying the mixture ratio with accuracy of the order of a few percentage points at a frame rate of approximately 24 frames per second (fps). PMID:26466256

  20. Surface modes in "photonic cholesteric liquid crystal-phase plate-metal" structure.

    PubMed

    Vetrov, S Ya; Pyatnov, M V; Timofeev, I V

    2014-05-01

    The light transmission spectrum has been calculated for a "cholesteric liquid crystal-phase plate-metal" structure. It is shown that the system can have an isolated waveguide surface mode with characteristics efficiently controllable by external fields acting on the cholesteric. The degree of localization of surface modes and the transmission coefficients have been found to differ considerably for the light of different polarizations. PMID:24784092

  1. Liquid sensor based on high-Q slot photonic crystal cavity in silicon-on-insulator configuration.

    PubMed

    Caër, Charles; Serna-Otálvaro, Samuel F; Zhang, Weiwei; Le Roux, Xavier; Cassan, Eric

    2014-10-15

    We present the realization of an optical sensor based on an infiltrated high-Q slot photonic crystal cavity in a nonfreestanding membrane configuration. Successive infiltrations by liquids with refractive indices ranging from 1.345 to 1.545 yield a sensitivity S of 235 nm/RIU (refractive index unit), while the Q-factor is comprised between 8000 and 25,000, giving a sensor figure of merit up to 3700. This sensor has a detection limit of 1.25×10⁻⁵. The operation of this device on a silicon-on-insulator (SOI) substrate allows a straightforward integration in the silicon photonics platform, while providing a compliant mechanical stability. PMID:25361086

  2. Numerical simulation for optimizing mode shaping and supercontinuum flatness of liquid filled seven-core photonic crystal fibers

    NASA Astrophysics Data System (ADS)

    Tian, Liang; Wei, Li; Guoying, Feng

    2015-05-01

    A seven-core photonic crystal fiber filled with commercial index-matching liquids is designed to optimize mode shaping and supercontinuum flatness. Numerical simulation of supercontinuum generation in these liquid-filled seven-core PCFs is conducted at 25 °C. The definition of spectral flatness measure is used to quantitatively describe SC flatness. Numerical simulations are performed to study the propagation of femtosecond pulse in the liquid-filled seven-core PCFs. Results show that mode shaping and supercontinuum flatness can be easily optimized and modified using the index-matching liquids in seven-core PCF without varying the structure of the air rings around the guiding cores. Simulations also show that 50 fs pulses with a center wavelength of 1064 nm generate relatively flat SC spectra in the 25 cm-long liquid-filled PCF. A flat spectral bandwidth of 400 nm (900-1300 nm) is achieved with an applied pump power of 30 kW. The simulation results demonstrate that using index-matching liquids to fill the inner ring of the seven-core PCF optimizes mode shaping and generates flat SC spectrum in specified wavelength region. Results further demonstrate that the SC flatness increased with increasing PCF dispersion corresponding to pump wavelength, on the premise that generated enough spectrum width, when the pump worked in the normal dispersion region. Temperature barely affects the spectrum flatness, but can affect spectrum broadening.

  3. Photonic Crystal Microchip Laser

    PubMed Central

    Gailevicius, Darius; Koliadenko, Volodymyr; Purlys, Vytautas; Peckus, Martynas; Taranenko, Victor; Staliunas, Kestutis

    2016-01-01

    The microchip lasers, being very compact and efficient sources of coherent light, suffer from one serious drawback: low spatial quality of the beam strongly reducing the brightness of emitted radiation. Attempts to improve the beam quality, such as pump-beam guiding, external feedback, either strongly reduce the emission power, or drastically increase the size and complexity of the lasers. Here it is proposed that specially designed photonic crystal in the cavity of a microchip laser, can significantly improve the beam quality. Experiments show that a microchip laser, due to spatial filtering functionality of intracavity photonic crystal, improves the beam quality factor M2 reducing it by a factor of 2, and increase the brightness of radiation by a factor of 3. This comprises a new kind of laser, the “photonic crystal microchip laser”, a very compact and efficient light source emitting high spatial quality high brightness radiation. PMID:27683066

  4. Photonic Crystal Microchip Laser

    NASA Astrophysics Data System (ADS)

    Gailevicius, Darius; Koliadenko, Volodymyr; Purlys, Vytautas; Peckus, Martynas; Taranenko, Victor; Staliunas, Kestutis

    2016-09-01

    The microchip lasers, being very compact and efficient sources of coherent light, suffer from one serious drawback: low spatial quality of the beam strongly reducing the brightness of emitted radiation. Attempts to improve the beam quality, such as pump-beam guiding, external feedback, either strongly reduce the emission power, or drastically increase the size and complexity of the lasers. Here it is proposed that specially designed photonic crystal in the cavity of a microchip laser, can significantly improve the beam quality. Experiments show that a microchip laser, due to spatial filtering functionality of intracavity photonic crystal, improves the beam quality factor M2 reducing it by a factor of 2, and increase the brightness of radiation by a factor of 3. This comprises a new kind of laser, the “photonic crystal microchip laser”, a very compact and efficient light source emitting high spatial quality high brightness radiation.

  5. Liquid Crystal Devices.

    ERIC Educational Resources Information Center

    Bradshaw, Madeline J.

    1983-01-01

    The nature of liquid crystals and several important liquid crystal devices are described. Ideas for practical experiments to illustrate the properties of liquid crystals and their operation in devices are also described. (Author/JN)

  6. Liquid Crystal Inquiries.

    ERIC Educational Resources Information Center

    Marroum, Renata-Maria

    1996-01-01

    Discusses the properties and classification of liquid crystals. Presents a simple experiment that illustrates the structure of liquid crystals and the differences between the various phases liquid crystals can assume. (JRH)

  7. Fluorescence-based remote irradiation sensor in liquid-filled hollow-core photonic crystal fiber

    NASA Astrophysics Data System (ADS)

    Zeltner, R.; Bykov, D. S.; Xie, S.; Euser, T. G.; Russell, P. St. J.

    2016-06-01

    We report an irradiation sensor based on a fluorescent "flying particle" that is optically trapped and propelled inside the core of a water-filled hollow-core photonic crystal fiber. When the moving particle passes through an irradiated region, its emitted fluorescence is captured by guided modes of the fiber core and so can be monitored using a filtered photodiode placed at the fiber end. The particle speed and position can be precisely monitored using in-fiber Doppler velocimetry, allowing the irradiation profile to be measured to a spatial resolution of ˜10 μm. The spectral response can be readily adjusted by appropriate choice of particle material. Using dye-doped polystyrene particles, we demonstrate detection of green (532 nm) and ultraviolet (340 nm) light.

  8. EDITORIAL: Photonic Crystal Devices

    NASA Astrophysics Data System (ADS)

    Bhattacharya, Pallab K.

    2007-05-01

    The engineering of electromagnetic modes at optical frequencies in artificial dielectric structures with periodic and random variation of the refractive index, enabling control of the radiative properties of the materials and photon localization, was first proposed independently by Yablonovitch and John in 1987. It is possible to control the flow of light in the periodic dielectric structures, known as photonic crystals (PC). As light waves scatter within the photonic crystal, destructive interference cancels out light of certain wavelengths, thereby forming a photonic bandgap, similar to the energy bandgap for electron waves in a semiconductor. Photons whose energies lie within the gap cannot propagate through the periodic structure. This property can be used to make a low-loss cavity. If a point defect, such as one or more missing periods, is introduced into the periodic structure a region is obtained within which the otherwise forbidden wavelengths can be locally trapped. This property can be used to realize photonic microcavities. Similarly, a line of defects can serve as a waveguide. While the realization of three-dimensional (3D) photonic crystals received considerable attention initially, planar two-dimensional (2D) structures are currently favoured because of their relative ease of fabrication. 2D photonic crystal structures provide most of the functionality of 3D structures. These attributes have generated worldwide research and development of sub-μm and μm size active and passive photonic devices such as single-mode and non- classical light sources, guided wave devices, resonant cavity detection, and components for optical communication. More recently, photonic crystal guided wave devices are being investigated for application in microfludic and biochemical sensing. Photonic crystal devices have been realized with bulk, quantum well and quantum dot active regions. The Cluster of articles in this issue of Journal of Physics D: Applied Physics provides a

  9. Correcting spherical aberrations in a biospecimen using a transmissive liquid crystal device in two-photon excitation laser scanning microscopy

    NASA Astrophysics Data System (ADS)

    Tanabe, Ayano; Hibi, Terumasa; Ipponjima, Sari; Matsumoto, Kenji; Yokoyama, Masafumi; Kurihara, Makoto; Hashimoto, Nobuyuki; Nemoto, Tomomi

    2015-10-01

    Two-photon excitation laser scanning microscopy has enabled the visualization of deep regions in a biospecimen. However, refractive-index mismatches in the optical path cause spherical aberrations that degrade spatial resolution and the fluorescence signal, especially during observation at deeper regions. Recently, we developed transmissive liquid-crystal devices for correcting spherical aberration without changing the basic design of the optical path in a conventional laser scanning microscope. In this study, the device was inserted in front of the objective lens and supplied with the appropriate voltage according to the observation depth. First, we evaluated the device by observing fluorescent beads in single- and two-photon excitation laser scanning microscopes. Using a 25× water-immersion objective lens with a numerical aperture of 1.1 and a sample with a refractive index of 1.38, the device recovered the spatial resolution and the fluorescence signal degraded within a depth of ±0.6 mm. Finally, we implemented the device for observation of a mouse brain slice in a two-photon excitation laser scanning microscope. An optical clearing reagent with a refractive index of 1.42 rendered the fixed mouse brain transparent. The device improved the spatial resolution and the yellow fluorescent protein signal within a depth of 0-0.54 mm.

  10. Correcting spherical aberrations in a biospecimen using a transmissive liquid crystal device in two-photon excitation laser scanning microscopy.

    PubMed

    Tanabe, Ayano; Hibi, Terumasa; Ipponjima, Sari; Matsumoto, Kenji; Yokoyama, Masafumi; Kurihara, Makoto; Hashimoto, Nobuyuki; Nemoto, Tomomi

    2015-10-01

    Two-photon excitation laser scanning microscopy has enabled the visualization of deep regions in a biospecimen. However, refractive-index mismatches in the optical path cause spherical aberrations that degrade spatial resolution and the fluorescence signal, especially during observation at deeper regions. Recently, we developed transmissive liquid-crystal devices for correcting spherical aberration without changing the basic design of the optical path in a conventional laser scanning microscope. In this study, the device was inserted in front of the objective lens and supplied with the appropriate voltage according to the observation depth. First, we evaluated the device by observing fluorescent beads in single- and two-photon excitation laser scanning microscopes. Using a 25× water-immersion objective lens with a numerical aperture of 1.1 and a sample with a refractive index of 1.38, the device recovered the spatial resolution and the fluorescence signal degraded within a depth of 0.6 mm. Finally, we implemented the device for observation of a mouse brain slice in a two-photon excitation laser scanning microscope. An optical clearing reagent with a refractive index of 1.42 rendered the fixed mouse brain transparent. The device improved the spatial resolution and the yellow fluorescent protein signal within a depth of 0-0.54 mm. PMID:26244766

  11. Correcting spherical aberrations in a biospecimen using a transmissive liquid crystal device in two-photon excitation laser scanning microscopy.

    PubMed

    Tanabe, Ayano; Hibi, Terumasa; Ipponjima, Sari; Matsumoto, Kenji; Yokoyama, Masafumi; Kurihara, Makoto; Hashimoto, Nobuyuki; Nemoto, Tomomi

    2015-10-01

    Two-photon excitation laser scanning microscopy has enabled the visualization of deep regions in a biospecimen. However, refractive-index mismatches in the optical path cause spherical aberrations that degrade spatial resolution and the fluorescence signal, especially during observation at deeper regions. Recently, we developed transmissive liquid-crystal devices for correcting spherical aberration without changing the basic design of the optical path in a conventional laser scanning microscope. In this study, the device was inserted in front of the objective lens and supplied with the appropriate voltage according to the observation depth. First, we evaluated the device by observing fluorescent beads in single- and two-photon excitation laser scanning microscopes. Using a 25× water-immersion objective lens with a numerical aperture of 1.1 and a sample with a refractive index of 1.38, the device recovered the spatial resolution and the fluorescence signal degraded within a depth of 0.6 mm. Finally, we implemented the device for observation of a mouse brain slice in a two-photon excitation laser scanning microscope. An optical clearing reagent with a refractive index of 1.42 rendered the fixed mouse brain transparent. The device improved the spatial resolution and the yellow fluorescent protein signal within a depth of 0-0.54 mm.

  12. Reversible photo-induced long-period fiber gratings in photonic liquid crystal fibers.

    PubMed

    Liou, Jia-hong; Chang, Tin-hao; Lin, Ta; Yu, Chin-ping

    2011-03-28

    A novel light-controllable long-period fiber grating (LPFG) is demonstrated by making use of a PCF infiltrated with a photoresponsive liquid crystal (LC) mixture consisting of nematic LC molecules and light-sensitive 4-methoxyazobenzene (4MAB). With the aid of the photo-induced isomerization of 4MAB, the refractive index of the LC mixture can be modulated and the periodic index perturbation along the fiber can be achieved by exposing the PCF to a blue laser through a mask. The resonance wavelength and dip depth of the LPFG can be controlled by using different blue-laser irradiation time, numbers of period, and 4MAB concentrations. In addition, the photo-induced LPFG is erasable under green-laser illumination. PMID:21451702

  13. Coexistence of positive and negative refractive index sensitivity in the liquid-core photonic crystal fiber based plasmonic sensor.

    PubMed

    Shuai, Binbin; Xia, Li; Liu, Deming

    2012-11-01

    We present and numerically characterize a liquid-core photonic crystal fiber based plasmonic sensor. The coupling properties and sensing performance are investigated by the finite element method. It is found that not only the plasmonic mode dispersion relation but also the fundamental mode dispersion relation is rather sensitive to the analyte refractive index (RI). The positive and negative RI sensitivity coexist in the proposed design. It features a positive RI sensitivity when the increment of the SPP mode effective index is larger than that of the fundamental mode, but the sensor shows a negative RI sensitivity once the increment of the fundamental mode gets larger. A maximum negative RI sensitivity of -5500nm/RIU (Refractive Index Unit) is achieved in the sensing range of 1.50-1.53. The effects of the structural parameters on the plasmonic excitations are also studied, with a view of tuning and optimizing the resonant spectrum. PMID:23187403

  14. Photonic crystal waveguide created by selective infiltration

    NASA Astrophysics Data System (ADS)

    Casas Bedoya, A.; Domachuk, P.; Grillet, C.; Monat, C.; Mägi, E. C.; Li, E.; Eggleton, B. J.

    2012-06-01

    The marriage of photonics and microfluidics ("optofluidics") uses the inherent mobility of fluids to reversibly tune photonic structures beyond traditional fabrication methods by infiltrating voids in said structures. Photonic crystals (PhCs) strongly control light on the wavelength scale and are well suited to optofluidic tuning because their periodic airhole microstructure is a natural candidate for housing liquids. The infiltration of a single row of holes in the PhC matrix modifies the effective refractive index allowing optical modes to be guided by the PhC bandgap. In this work we present the first experimental demonstration of a reconfigurable single mode W1 photonic crystal defect waveguide created by selective liquid infiltration. We modified a hexagonal silicon planar photonic crystal membrane by selectively filling a single row of air holes with ~300nm resolution, using high refractive index ionic liquid. The modification creates optical confinement in the infiltrated region and allows propagation of a single optical waveguide mode. We describe the challenges arising from the infiltration process and the liquid/solid surface interaction in the photonic crystal. We include a detailed comparison between analytic and numerical modeling and experimental results, and introduce a new approach to create an offset photonic crystal cavity by varying the nature of the selective infiltration process.

  15. Photonic crystal optical memory

    NASA Astrophysics Data System (ADS)

    Lima, A. Wirth; Sombra, A. S. B.

    2011-06-01

    After several decades pushing the technology and the development of the world, the electronics is giving space for technologies that use light. We propose and analyze an optical memory embedded in a nonlinear photonic crystal (PhC), whose system of writing and reading data is controlled by an external command signal. This optical memory is based on optical directional couplers connected to a shared optical ring. Such a device can work over the C-Band of ITU (International Telecommunication Union).

  16. Slotted Photonic Crystal Sensors

    PubMed Central

    Scullion, Mark G.; Krauss, Thomas F.; Di Falco, Andrea

    2013-01-01

    Optical biosensors are increasingly being considered for lab-on-a-chip applications due to their benefits such as small size, biocompatibility, passive behaviour and lack of the need for fluorescent labels. The light guiding mechanisms used by many of them results in poor overlap of the optical field with the target molecules, reducing the maximum sensitivity achievable. This review article presents a new platform for optical biosensors, namely slotted photonic crystals, which provide higher sensitivities due to their ability to confine, spatially and temporally, the optical mode peak within the analyte itself. Loss measurements showed values comparable to standard photonic crystals, confirming their ability to be used in real devices. A novel resonant coupler was designed, simulated, and experimentally tested, and was found to perform better than other solutions within the literature. Combining with cavities, microfluidics and biological functionalization allowed proof-of-principle demonstrations of protein binding to be carried out. Higher sensitivities were observed in smaller structures than possible with most competing devices reported in the literature. This body of work presents slotted photonic crystals as a realistic platform for complete on-chip biosensing; addressing key design, performance and application issues, whilst also opening up exciting new ideas for future study. PMID:23503295

  17. Slotted photonic crystal sensors.

    PubMed

    Scullion, Mark G; Krauss, Thomas F; Di Falco, Andrea

    2013-01-01

    Optical biosensors are increasingly being considered for lab-on-a-chip applications due to their benefits such as small size, biocompatibility, passive behaviour and lack of the need for fluorescent labels. The light guiding mechanisms used by many of them results in poor overlap of the optical field with the target molecules, reducing the maximum sensitivity achievable. This review article presents a new platform for optical biosensors, namely slotted photonic crystals, which provide higher sensitivities due to their ability to confine, spatially and temporally, the optical mode peak within the analyte itself. Loss measurements showed values comparable to standard photonic crystals, confirming their ability to be used in real devices. A novel resonant coupler was designed, simulated, and experimentally tested, and was found to perform better than other solutions within the literature. Combining with cavities, microfluidics and biological functionalization allowed proof-of-principle demonstrations of protein binding to be carried out. Higher sensitivities were observed in smaller structures than possible with most competing devices reported in the literature. This body of work presents slotted photonic crystals as a realistic platform for complete on-chip biosensing; addressing key design, performance and application issues, whilst also opening up exciting new ideas for future study. PMID:23503295

  18. Structural characterization of thin film photonic crystals

    SciTech Connect

    Subramania, G.; Biswas, R.; Constant, K.; Sigalas, M. M.; Ho, K. M.

    2001-06-15

    We quantitatively analyze the structure of thin film inverse-opal photonic crystals composed of ordered arrays of air pores in a background of titania. Ordering of the sphere template and introduction of the titania background were performed simultaneously in the thin film photonic crystals. Nondestructive optical measurements of backfilling with high refractive index liquids, angle-resolved reflectivity, and optical spectroscopy were combined with band-structure calculations. The analysis reveals a thin film photonic crystal structure with a very high filling fraction (92{endash}94%) of air and a substantial compression along the c axis ({similar_to}22{endash}25%).

  19. Photonic control of surface anchoring on solid colloids dispersed in liquid crystals.

    PubMed

    Prathap Chandran, S; Mondiot, F; Mondain-Monval, O; Loudet, J C

    2011-12-20

    The anchoring of liquid-crystal (LC) mesogens to the surfaces of colloids is an important factor in determining intercolloidal interactions and the symmetry of the ensuing colloidal assembly in nematic colloids. The dynamic control of surface anchoring could therefore provide a handle to tune the colloidal organization and resulting properties in these systems. In this article, we report our results on the study of thermotropic nematic LC (E7) dispersions of silica and glass microcolloids bearing photosensitive surface azobenzene groups. By the photoinduced modulation of the colloidal-LC interfacial properties, due to the trans-cis isomerization of azobenzene units, we tune the anchoring on silica colloids from homeotropic (trans-azobenzene) to homogeneous planar (cis-azobenzene) reversibly. In tune with the change in surface anchoring, the interparticle interactions were also dictated by dipolar and quadrupolar symmetries for homeotropic and homogeneous planar anchoring, respectively. In our experiments, we find that, in addition to the isomerization state of the surface-bound azobenzene units, the nature of the colloid plays a crucial role in determining the anchoring state obtained on applying photostimuli. We also study the LC anchoring on colloids as a function of the azobenzene surface density and find that beyond a threshold value the anchoring properties remain invariant.

  20. Natural photonic crystals

    NASA Astrophysics Data System (ADS)

    Vigneron, Jean Pol; Simonis, Priscilla

    2012-10-01

    Photonic structures appeared in nature several hundred millions years ago. In the living world, color is used for communication and this important function strongly impacts the individual chances of survival as well as the chances to reproduce. This has a statistical influence on species populations. Therefore, because they are involved in evolution, natural color-generating structures are - from some point of view - highly optimized. In this short review, a survey is presented of the development of natural photonic crystal-type structures occurring in insects, spiders, birds, fishes and other marine animals, in plants and more, from the standpoint of light-waves propagation. One-, two-, and three-dimensional structures will be reviewed with selected examples.

  1. Optics of globular photonic crystals

    SciTech Connect

    Gorelik, V S

    2007-05-31

    The results of experimental and theoretical studies of the optical properties of globular photonic crystals - new physical objects having a crystal structure with the lattice period exceeding considerably the atomic size, are presented. As globular photonic crystals, artificial opal matrices consisting of close-packed silica globules of diameter {approx}200 nm were used. The reflection spectra of these objects characterising the parameters of photonic bands existing in these crystals in the visible spectral region are presented. The idealised models of the energy band structure of photonic crystals investigated in the review give analytic dispersion dependences for the group velocity and the effective photon mass in a globular photonic crystal. The characteristics of secondary emission excited in globular photonic crystals by monochromatic and broadband radiation are presented. The results of investigations of single-photon-excited delayed scattering of light observed in globular photonic crystals exposed to cw UV radiation and radiation from a repetitively pulsed copper vapour laser are presented. The possibilities of using globular photonic crystals as active media for lasing in different spectral regions are considered. It is proposed to use globular photonic crystals as sensitive sensors in optoelectronic devices for molecular analysis of organic and inorganic materials by the modern methods of laser spectroscopy. The results of experimental studies of spontaneous and stimulated globular scattering of light are discussed. The conditions for observing resonance and two-photon-excited delayed scattering of light are found. The possibility of accumulation and localisation of the laser radiation energy inside a globular photonic crystal is reported. (review)

  2. Photonic crystal fibers in biophotonics

    NASA Astrophysics Data System (ADS)

    Tuchin, Valery V.; Skibina, Julia S.; Malinin, Anton V.

    2011-12-01

    We observed recent experimental results in area of photonic crystal fibers appliance. Possibility of creation of fiberbased broadband light sources for high resolution optical coherence tomography is discussed. Using of femtosecond pulse laser allows for generation of optical radiation with large spectral width in highly nonlinear solid core photonic crystal fibers. Concept of exploitation of hollow core photonic crystal fibers in optical sensing is demonstrated. The use of photonic crystal fibers as "smart cuvette" gives rise to efficiency of modern optical biomedical analysis methods.

  3. Development of optical biosensor based on photonic crystal made of TiO2 using liquid phase deposition

    NASA Astrophysics Data System (ADS)

    Aono, Keigo; Aki, Shoma; Sueyoshi, Kenji; Hisamoto, Hideaki; Endo, Tatsuro

    2016-08-01

    We fabricated a titanium dioxide (TiO2)-based photonic crystal (PhC) using liquid phase deposition (LPD) to develop highly sensitive optical biosensors. The optical characteristics of the PhCs in the visible region were sensitive to the change in the refractive index of the surrounding medium due to an antigen–antibody reaction; thus, applications using the optical biosensor are expected to be highly sensitive. However, a base material with a high refractive index is indispensable for the fabrication of the PhC. Here, TiO2, which has optical transparency in the visible region, was selected as the high refractive index base material. The present LPD method allowed fabrication using low-cost apparatus. Furthermore, the mild conditions of the LPD method led to formation of TiO2-based PhC with fewer crack structures. Finally, the anti-neuron-specific enolase antibody was immobilized onto the TiO2-based PhC surface, and 1–1000 ng/mL of the neuron-specific enolase antigen was successfully detected.

  4. Development of optical biosensor based on photonic crystal made of TiO2 using liquid phase deposition

    NASA Astrophysics Data System (ADS)

    Aono, Keigo; Aki, Shoma; Sueyoshi, Kenji; Hisamoto, Hideaki; Endo, Tatsuro

    2016-08-01

    We fabricated a titanium dioxide (TiO2)-based photonic crystal (PhC) using liquid phase deposition (LPD) to develop highly sensitive optical biosensors. The optical characteristics of the PhCs in the visible region were sensitive to the change in the refractive index of the surrounding medium due to an antigen-antibody reaction; thus, applications using the optical biosensor are expected to be highly sensitive. However, a base material with a high refractive index is indispensable for the fabrication of the PhC. Here, TiO2, which has optical transparency in the visible region, was selected as the high refractive index base material. The present LPD method allowed fabrication using low-cost apparatus. Furthermore, the mild conditions of the LPD method led to formation of TiO2-based PhC with fewer crack structures. Finally, the anti-neuron-specific enolase antibody was immobilized onto the TiO2-based PhC surface, and 1-1000 ng/mL of the neuron-specific enolase antigen was successfully detected.

  5. Photonic Crystal Nanolaser Biosensors

    NASA Astrophysics Data System (ADS)

    Kita, Shota; Otsuka, Shota; Hachuda, Shoji; Endo, Tatsuro; Imai, Yasunori; Nishijima, Yoshiaki; Misawa, Hiroaki; Baba, Toshihiko

    High-performance and low-cost sensors are critical devices for high-throughput analyses of bio-samples in medical diagnoses and life sciences. In this paper, we demonstrate photonic crystal nanolaser sensor, which detects the adsorption of biomolecules from the lasing wavelength shift. It is a promising device, which balances a high sensitivity, high resolution, small size, easy integration, simple setup and low cost. In particular with a nanoslot structure, it achieves a super-sensitivity in protein sensing whose detection limit is three orders of magnitude lower than that of standard surface-plasmon-resonance sensors. Our investigations indicate that the nanoslot acts as a protein condenser powered by the optical gradient force, which arises from the strong localization of laser mode in the nanoslot.

  6. Spherical colloidal photonic crystals.

    PubMed

    Zhao, Yuanjin; Shang, Luoran; Cheng, Yao; Gu, Zhongze

    2014-12-16

    CONSPECTUS: Colloidal photonic crystals (PhCs), periodically arranged monodisperse nanoparticles, have emerged as one of the most promising materials for light manipulation because of their photonic band gaps (PBGs), which affect photons in a manner similar to the effect of semiconductor energy band gaps on electrons. The PBGs arise due to the periodic modulation of the refractive index between the building nanoparticles and the surrounding medium in space with subwavelength period. This leads to light with certain wavelengths or frequencies located in the PBG being prohibited from propagating. Because of this special property, the fabrication and application of colloidal PhCs have attracted increasing interest from researchers. The most simple and economical method for fabrication of colloidal PhCs is the bottom-up approach of nanoparticle self-assembly. Common colloidal PhCs from this approach in nature are gem opals, which are made from the ordered assembly and deposition of spherical silica nanoparticles after years of siliceous sedimentation and compression. Besides naturally occurring opals, a variety of manmade colloidal PhCs with thin film or bulk morphology have also been developed. In principle, because of the effect of Bragg diffraction, these PhC materials show different structural colors when observed from different angles, resulting in brilliant colors and important applications. However, this angle dependence is disadvantageous for the construction of some optical materials and devices in which wide viewing angles are desired. Recently, a series of colloidal PhC materials with spherical macroscopic morphology have been created. Because of their spherical symmetry, the PBGs of spherical colloidal PhCs are independent of rotation under illumination of the surface at a fixed incident angle of the light, broadening the perspective of their applications. Based on droplet templates containing colloidal nanoparticles, these spherical colloidal PhCs can be

  7. Random photonic crystal optical memory

    NASA Astrophysics Data System (ADS)

    Wirth Lima, A., Jr.; Sombra, A. S. B.

    2012-10-01

    Currently, optical cross-connects working on wavelength division multiplexing systems are based on optical fiber delay lines buffering. We designed and analyzed a novel photonic crystal optical memory, which replaces the fiber delay lines of the current optical cross-connect buffer. Optical buffering systems based on random photonic crystal optical memory have similar behavior to the electronic buffering systems based on electronic RAM memory. In this paper, we show that OXCs working with optical buffering based on random photonic crystal optical memories provides better performance than the current optical cross-connects.

  8. Configurable silicon photonic crystal waveguides

    NASA Astrophysics Data System (ADS)

    Prorok, Stefan; Petrov, Alexander; Eich, Manfred; Luo, Jingdong; Jen, Alex K.-Y.

    2013-12-01

    In this Letter, we demonstrate that the mode cut off of a photonic crystal waveguide can be trimmed with high accuracy by electron beam bleaching of a chromophore doped polymer cladding. Using this method, configurable waveguides are realized, which allow for spatially resolved changes of the photonic crystal's effective lattice constant as small as 7.6 pm. We show three different examples how to take advantage of configurable photonic crystal waveguides: Shifting of the complete transmission spectrum, definition of cavities with high quality factor, and tuning of existing cavities.

  9. Multicolor photonic crystal laser array

    SciTech Connect

    Wright, Jeremy B; Brener, Igal; Subramania, Ganapathi S; Wang, George T; Li, Qiming

    2015-04-28

    A multicolor photonic crystal laser array comprises pixels of monolithically grown gain sections each with a different emission center wavelength. As an example, two-dimensional surface-emitting photonic crystal lasers comprising broad gain-bandwidth III-nitride multiple quantum well axial heterostructures were fabricated using a novel top-down nanowire fabrication method. Single-mode lasing was obtained in the blue-violet spectral region with 60 nm of tuning (or 16% of the nominal center wavelength) that was determined purely by the photonic crystal geometry. This approach can be extended to cover the entire visible spectrum.

  10. Configurable silicon photonic crystal waveguides

    SciTech Connect

    Prorok, Stefan; Petrov, Alexander; Eich, Manfred; Luo, Jingdong; Jen, Alex K.-Y.

    2013-12-23

    In this Letter, we demonstrate that the mode cut off of a photonic crystal waveguide can be trimmed with high accuracy by electron beam bleaching of a chromophore doped polymer cladding. Using this method, configurable waveguides are realized, which allow for spatially resolved changes of the photonic crystal's effective lattice constant as small as 7.6 pm. We show three different examples how to take advantage of configurable photonic crystal waveguides: Shifting of the complete transmission spectrum, definition of cavities with high quality factor, and tuning of existing cavities.

  11. Liquid-metal-cooled, curved-crystal monochromator for Advanced Photon Source bending-magnet beamline 1-BM

    SciTech Connect

    Brauer, S.; Rodricks, B.; Assoufid, L.; Beno, M.A.; Knapp, G.S.

    1996-06-01

    The authors describe a horizontally focusing curved-crystal monochromator that invokes a 4-point bending scheme and a liquid-metal cooling bath. The device has been designed for dispersive diffraction and spectroscopy in the 5--20 keV range, with a predicted focal spot size of {le} 100 {micro}m. To minimize thermal distortions and thermal equilibration time, the 355 x 32 x 0.8 mm crystal will be nearly half submerged in a bath of Ga-In-Sn-Zn alloy. The liquid metal thermally couples the crystal to the water-cooled Cu frame, while permitting the required crystal bending. Calculated thermal profiles and anticipated focusing properties are discussed.

  12. Liquid Crystal Optofluidics

    SciTech Connect

    Vasdekis, Andreas E.; Cuennet, J. G.; Psaltis, D.

    2012-10-11

    By employing anisotropic fluids and namely liquid crystals, fluid flow becomes an additional degree of freedom in designing optofluidic devices. In this paper, we demonstrate optofluidic liquid crystal devices based on the direct flow of nematic liquid crystals in microfluidic channels. Contrary to previous reports, in the present embodiment we employ the effective phase delay acquired by light travelling through flowing liquid crystal, without analysing the polarisation state of the transmitted light. With this method, we demonstrate the variation in the diffraction pattern of an array of microfluidic channels acting as a grating. We also discuss our recent activities in integrating mechanical oscillators for on-chip peristaltic pumping.

  13. Spatial filtering with photonic crystals

    SciTech Connect

    Maigyte, Lina; Staliunas, Kestutis

    2015-03-15

    Photonic crystals are well known for their celebrated photonic band-gaps—the forbidden frequency ranges, for which the light waves cannot propagate through the structure. The frequency (or chromatic) band-gaps of photonic crystals can be utilized for frequency filtering. In analogy to the chromatic band-gaps and the frequency filtering, the angular band-gaps and the angular (spatial) filtering are also possible in photonic crystals. In this article, we review the recent advances of the spatial filtering using the photonic crystals in different propagation regimes and for different geometries. We review the most evident configuration of filtering in Bragg regime (with the back-reflection—i.e., in the configuration with band-gaps) as well as in Laue regime (with forward deflection—i.e., in the configuration without band-gaps). We explore the spatial filtering in crystals with different symmetries, including axisymmetric crystals; we discuss the role of chirping, i.e., the dependence of the longitudinal period along the structure. We also review the experimental techniques to fabricate the photonic crystals and numerical techniques to explore the spatial filtering. Finally, we discuss several implementations of such filters for intracavity spatial filtering.

  14. Experimental study of photonic crystal triangular lattices

    NASA Astrophysics Data System (ADS)

    Qin, Ruhu; Qin, Bo; Jin, Chongjun

    1999-06-01

    Triangular lattice photonic crystal behaving in the electromagnetic zones constructed from fused silica cylinders in styrofoam is fabricated. The transmission spectra of the photonic crystal with and without defects are measured. On this basis, the defect modes of photonic crystal were studied, and the potential applications of the photonic crystal are discussed.

  15. Semiconductor nanorod liquid crystals

    SciTech Connect

    Li, Liang-shi; Walda, Joost; Manna, Liberato; Alivisatos, A. Paul

    2002-01-28

    Rodlike molecules form liquid crystalline phases with orientational order and positional disorder. The great majority of materials in which liquid crystalline phases have been observed are comprised of organic molecules or polymers, even though there has been continuing and growing interest in inorganic liquid crystals. Recent advances in the control of the sizes and shapes of inorganic nanocrystals allow for the formation of a broad class of new inorganic liquid crystals. Here we show the formation of liquid crystalline phases of CdSe semiconductor nanorods. These new liquid crystalline phases may have great importance for both application and fundamental study.

  16. Partial confinement photonic crystal waveguides

    SciTech Connect

    Saini, S.; Hong, C.-Y.; Pfaff, N.; Kimerling, L. C.; Michel, J.

    2008-12-29

    One-dimensional photonic crystal waveguides with an incomplete photonic band gap are modeled and proposed for an integration application that exploits their property of partial angular confinement. Planar apodized photonic crystal structures are deposited by plasma enhanced chemical vapor deposition and characterized by reflectivity as a function of angle and polarization, validating a partial confinement design for light at 850 nm wavelength. Partial confinement identifies an approach for tailoring waveguide properties by the exploitation of conformal film deposition over a substrate with angularly dependent topology. An application for an optoelectronic transceiver is demonstrated.

  17. Manufacturing method of photonic crystal

    SciTech Connect

    Park, In Sung; Lee, Tae Ho; Ahn, Jin Ho; Biswas, Rana; Constant, Kristen P.; Ho, Kai-Ming; Lee, Jae-Hwang

    2013-01-29

    A manufacturing method of a photonic crystal is provided. In the method, a high-refractive-index material is conformally deposited on an exposed portion of a periodic template composed of a low-refractive-index material by an atomic layer deposition process so that a difference in refractive indices or dielectric constants between the template and adjacent air becomes greater, which makes it possible to form a three-dimensional photonic crystal having a superior photonic bandgap. Herein, the three-dimensional structure may be prepared by a layer-by-layer method.

  18. Quantum Hall Liquid Crystals

    NASA Astrophysics Data System (ADS)

    Radzihovsky, Leo

    2003-03-01

    Liquid-crystals, defined as states of matter intermediate in their properties between fully disordered isotropic liquids and fully ordered crystals are ubiquitous in nature. Recent transport measurements on two-dimensional electron systems in moderate magnetic fields suggest the existence of a spontaneously orientationally-ordered, compressible liquid state. I will discuss electronic liquid-crystals interpretation of these experiments, focusing on a recently proposed quantum Hall nematic state that is predicted to exhibit a novel, highly anisotropic q^3 density-director mode and other interesting phenomenology.

  19. Mechanically tunable photonic crystal lens

    NASA Astrophysics Data System (ADS)

    Cui, Y.; Tamma, V. A.; Lee, J.-B.; Park, W.

    2010-08-01

    We designed, fabricated and characterized MEMS-enabled mechanically-tunable photonic crystal lens comprised of 2D photonic crystal and symmetrical electro-thermal actuators. The 2D photonic crystal was made of a honeycomb-lattice of 340 nm thick, 260 nm diameter high-index silicon rods embedded in low-index 10 μm thick SU-8 cladding. Silicon input waveguide and deflection block were also fabricated for light in-coupling and monitoring of focused spot size, respectively. When actuated, the electro-thermal actuators induced mechanical strain which changed the lattice constant of the photonic crystal and consequently modified the photonic band structure. This in turn modified the focal-length of the photonic crystal lens. The fabricated device was characterized using a tunable laser (1400~1602 nm) and an infrared camera during actuation. At the wavelength of 1450 nm, the lateral light spot size observed at the deflection block gradually decreased 40%, as applied current increased from 0 to 0.7 A, indicating changes in focal length in response to the mechanical stretching.

  20. Radiating dipoles in photonic crystals

    PubMed

    Busch; Vats; John; Sanders

    2000-09-01

    The radiation dynamics of a dipole antenna embedded in a photonic crystal are modeled by an initially excited harmonic oscillator coupled to a non-Markovian bath of harmonic oscillators representing the colored electromagnetic vacuum within the crystal. Realistic coupling constants based on the natural modes of the photonic crystal, i.e., Bloch waves and their associated dispersion relation, are derived. For simple model systems, well-known results such as decay times and emission spectra are reproduced. This approach enables direct incorporation of realistic band structure computations into studies of radiative emission from atoms and molecules within photonic crystals. We therefore provide a predictive and interpretative tool for experiments in both the microwave and optical regimes.

  1. [Photonic crystals for analytical chemistry].

    PubMed

    Chen, Yi; Li, Jincheng

    2009-09-01

    Photonic crystals, originally created to control the transmission of light, have found their increasing value in the field of analytical chemistry and are probable to become a hot research area soon. This review is hence composed, focusing on their analytical chemistry-oriented applications, including especially their use in chromatography, capillary- and chip-based electrophoresis.

  2. Photonic crystal surface-emitting lasers

    SciTech Connect

    Chua, Song Liang; Lu, Ling; Soljacic, Marin

    2015-06-23

    A photonic-crystal surface-emitting laser (PCSEL) includes a gain medium electromagnetically coupled to a photonic crystal whose energy band structure exhibits a Dirac cone of linear dispersion at the center of the photonic crystal's Brillouin zone. This Dirac cone's vertex is called a Dirac point; because it is at the Brillouin zone center, it is called an accidental Dirac point. Tuning the photonic crystal's band structure (e.g., by changing the photonic crystal's dimensions or refractive index) to exhibit an accidental Dirac point increases the photonic crystal's mode spacing by orders of magnitudes and reduces or eliminates the photonic crystal's distributed in-plane feedback. Thus, the photonic crystal can act as a resonator that supports single-mode output from the PCSEL over a larger area than is possible with conventional PCSELs, which have quadratic band edge dispersion. Because output power generally scales with output area, this increase in output area results in higher possible output powers.

  3. Surface plasmon induced polarization filter of the gold-coated photonic crystal fiber with a liquid core

    NASA Astrophysics Data System (ADS)

    Jiang, Linghong; Zheng, Yi; Hou, Lantian; Zheng, Kai; Peng, Jiying

    2015-06-01

    A new gold-coated photonic crystal fiber (PCF) which can achieve a specific wavelength filter has been proposed. The polarization filter characteristics of the PCF based on the finite element method are investigated. Numerical results show that moving the two gold-coated holes toward the central core in longitudinal direction and filling pure water in the central defected air-hole can effectively enhance polarization extinction ratio around the resonance wavelength. The resonance strength in y-polarized case is far stronger than that in x-polarized case, the peak loss of the PCF with different coating thickness in y polarization can reach 536.25 dB/cm and 412.91 dB/cm at the communication wavelength of 1.55 μm and 1.31 μm, respectively, while the losses are very low in x polarization. This is beneficial for the study and application in many polarization filter devices.

  4. Magnetically actuated liquid crystals.

    PubMed

    Wang, Mingsheng; He, Le; Zorba, Serkan; Yin, Yadong

    2014-07-01

    Ferrimagnetic inorganic nanorods have been used as building blocks to construct liquid crystals with optical properties that can be instantly and reversibly controlled by manipulating the nanorod orientation using considerably weak external magnetic fields (1 mT). Under an alternating magnetic field, they exhibit an optical switching frequency above 100 Hz, which is comparable to the performance of commercial liquid crystals based on electrical switching. By combining magnetic alignment and lithography processes, it is also possible to create patterns of different polarizations in a thin composite film and control over the transmittance of light in particular areas. Developing such magnetically responsive liquid crystals opens the door toward various applications, which may benefit from the instantaneous and contactless nature of magnetic manipulation.

  5. Fast response liquid crystal devices

    NASA Astrophysics Data System (ADS)

    Wu, Yung-Hsun

    Liquid crystal (LC) has been widely used for displays, spatial light modulators, variable optical attenuators (VOAs) and other tunable photonic devices. The response time of these devices is mainly determined by the employed liquid crystal material. The response time of a LC device depends on the visco-elastic coefficient (gamma1/K11), LC cell gap (d), and applied voltage. Hence, low visco-elastic coefficient LC materials and thinner cell gap are favorable for reducing the response time. However, low visco-elastic coefficient LCs are usually associated with a low birefringence because of shorter molecular conjugation. For display applications, such as LCD TVs, low birefringence (Deltan<0.1) LCs are commonly used. However, for optical communications at 1550 nm, low birefringence requires to a thick cell gap which, in turn, increases the response time. How to obtain fast response for the LC devices is a fundamentally important and technically challenging task. In this dissertation, we investigate several methods to improve liquid crystal response time, for examples, using dual-frequency liquid crystals, polymer stabilized liquid crystals, and sheared polymer network liquid crystals. We discover a new class of material, denoted as sheared polymer network liquid crystal (SPNLC) which exhibits a submillisecond response time. Moreover, this response time is insensitive to the LC cell gap. This is the first LC device exhibiting such an interesting property. Chapters 1 and 2 describe the motivation and background of this dissertation. From chapter 3 to chapter 6, dual-frequency liquid crystals and polymer network methods are demonstrated as examples for the variable optical attenuators. Variable optical attenuator (VOA) is a key component in optical communications. Especially, the sheared PNLC VOA shows the best result; its dynamic range reaches 43 dB while the response time is in the submillisecond range at 1550 nm wavelength, which is 50 times faster than the commercial

  6. Optical Magnetometer Incorporating Photonic Crystals

    NASA Technical Reports Server (NTRS)

    Kulikov, Igor; Florescu, Lucia

    2007-01-01

    According to a proposal, photonic crystals would be used to greatly increase the sensitivities of optical magnetometers that are already regarded as ultrasensitive. The proposal applies, more specifically, to a state-of-the-art type of quantum coherent magnetometer that exploits the electromagnetically-induced-transparency (EIT) method for determining a small change in a magnetic field indirectly via measurement of the shift, induced by that change, in the hyperfine levels of resonant atoms exposed to the field.

  7. Hybrid colloidal plasmonic-photonic crystals.

    PubMed

    Romanov, Sergei G; Korovin, Alexander V; Regensburger, Alois; Peschel, Ulf

    2011-06-17

    We review the recently emerged class of hybrid metal-dielectric colloidal photonic crystals. The hybrid approach is understood as the combination of a dielectric photonic crystal with a continuous metal film. It allows to achieve a strong modification of the optical properties of photonic crystals by involving the light scattering at electronic excitations in the metal component into moulding of the light flow in series to the diffraction resonances occurring in the body of the photonic crystal. We consider different realizations of hybrid plasmonic-photonic crystals based on two- and three-dimensional colloidal photonic crystals in association with flat and corrugated metal films. In agreement with model calculations, different resonance phenomena determine the optical response of hybrid crystals leading to a broadly tuneable functionality of these crystals. PMID:21594906

  8. Tuning and Freezing Disorder in Photonic Crystals using Percolation Lithography.

    PubMed

    Burgess, Ian B; Abedzadeh, Navid; Kay, Theresa M; Shneidman, Anna V; Cranshaw, Derek J; Lončar, Marko; Aizenberg, Joanna

    2016-01-01

    Although common in biological systems, synthetic self-assembly routes to complex 3D photonic structures with tailored degrees of disorder remain elusive. Here we show how liquids can be used to finely control disorder in porous 3D photonic crystals, leading to complex and hierarchical geometries. In these optofluidic crystals, dynamically tunable disorder is superimposed onto the periodic optical structure through partial wetting or evaporation. In both cases, macroscopic symmetry breaking is driven by subtle sub-wavelength variations in the pore geometry. These variations direct site-selective infiltration of liquids through capillary interactions. Incorporating cross-linkable resins into our liquids, we developed methods to freeze in place the filling patterns at arbitrary degrees of partial wetting and intermediate stages of drying. These percolation lithography techniques produced permanent photonic structures with adjustable disorder. By coupling strong changes in optical properties to subtle differences in fluid behavior, optofluidic crystals may also prove useful in rapid analysis of liquids. PMID:26790372

  9. Tuning and Freezing Disorder in Photonic Crystals using Percolation Lithography

    NASA Astrophysics Data System (ADS)

    Burgess, Ian B.; Abedzadeh, Navid; Kay, Theresa M.; Shneidman, Anna V.; Cranshaw, Derek J.; Lončar, Marko; Aizenberg, Joanna

    2016-01-01

    Although common in biological systems, synthetic self-assembly routes to complex 3D photonic structures with tailored degrees of disorder remain elusive. Here we show how liquids can be used to finely control disorder in porous 3D photonic crystals, leading to complex and hierarchical geometries. In these optofluidic crystals, dynamically tunable disorder is superimposed onto the periodic optical structure through partial wetting or evaporation. In both cases, macroscopic symmetry breaking is driven by subtle sub-wavelength variations in the pore geometry. These variations direct site-selective infiltration of liquids through capillary interactions. Incorporating cross-linkable resins into our liquids, we developed methods to freeze in place the filling patterns at arbitrary degrees of partial wetting and intermediate stages of drying. These percolation lithography techniques produced permanent photonic structures with adjustable disorder. By coupling strong changes in optical properties to subtle differences in fluid behavior, optofluidic crystals may also prove useful in rapid analysis of liquids.

  10. Tuning and Freezing Disorder in Photonic Crystals using Percolation Lithography

    PubMed Central

    Burgess, Ian B.; Abedzadeh, Navid; Kay, Theresa M.; Shneidman, Anna V.; Cranshaw, Derek J.; Lončar, Marko; Aizenberg, Joanna

    2016-01-01

    Although common in biological systems, synthetic self-assembly routes to complex 3D photonic structures with tailored degrees of disorder remain elusive. Here we show how liquids can be used to finely control disorder in porous 3D photonic crystals, leading to complex and hierarchical geometries. In these optofluidic crystals, dynamically tunable disorder is superimposed onto the periodic optical structure through partial wetting or evaporation. In both cases, macroscopic symmetry breaking is driven by subtle sub-wavelength variations in the pore geometry. These variations direct site-selective infiltration of liquids through capillary interactions. Incorporating cross-linkable resins into our liquids, we developed methods to freeze in place the filling patterns at arbitrary degrees of partial wetting and intermediate stages of drying. These percolation lithography techniques produced permanent photonic structures with adjustable disorder. By coupling strong changes in optical properties to subtle differences in fluid behavior, optofluidic crystals may also prove useful in rapid analysis of liquids. PMID:26790372

  11. Topological photonic crystal with equifrequency Weyl points

    NASA Astrophysics Data System (ADS)

    Wang, Luyang; Jian, Shao-Kai; Yao, Hong

    2016-06-01

    Weyl points in three-dimensional photonic crystals behave as monopoles of Berry flux in momentum space. Here, based on general symmetry analysis, we show that a minimal number of four symmetry-related (consequently equifrequency) Weyl points can be realized in time-reversal invariant photonic crystals. We further propose an experimentally feasible way to modify double-gyroid photonic crystals to realize four equifrequency Weyl points, which is explicitly confirmed by our first-principle photonic band-structure calculations. Remarkably, photonic crystals with equifrequency Weyl points are qualitatively advantageous in applications including angular selectivity, frequency selectivity, invisibility cloaking, and three-dimensional imaging.

  12. Topological photonic crystal with ideal Weyl points

    NASA Astrophysics Data System (ADS)

    Wang, Luyang; Jian, Shao-Kai; Yao, Hong

    Weyl points in three-dimensional photonic crystals behave as monopoles of Berry flux in momentum space. Here, based on symmetry analysis, we show that a minimal number of symmetry-related Weyl points can be realized in time-reversal invariant photonic crystals. We propose to realize these ``ideal'' Weyl points in modified double-gyroid photonic crystals, which is confirmed by our first-principle photonic band-structure calculations. Photonic crystals with ideal Weyl points are qualitatively advantageous in applications such as angular and frequency selectivity, broadband invisibility cloaking, and broadband 3D-imaging.

  13. Resonant photonic States in coupled heterostructure photonic crystal waveguides.

    PubMed

    Cox, Jd; Sabarinathan, J; Singh, Mr

    2010-01-01

    In this paper, we study the photonic resonance states and transmission spectra of coupled waveguides made from heterostructure photonic crystals. We consider photonic crystal waveguides made from three photonic crystals A, B and C, where the waveguide heterostructure is denoted as B/A/C/A/B. Due to the band structure engineering, light is confined within crystal A, which thus act as waveguides. Here, photonic crystal C is taken as a nonlinear photonic crystal, which has a band gap that may be modified by applying a pump laser. We have found that the number of bound states within the waveguides depends on the width and well depth of photonic crystal A. It has also been found that when both waveguides are far away from each other, the energies of bound photons in each of the waveguides are degenerate. However, when they are brought close to each other, the degeneracy of the bound states is removed due to the coupling between them, which causes these states to split into pairs. We have also investigated the effect of the pump field on photonic crystal C. We have shown that by applying a pump field, the system may be switched between a double waveguide to a single waveguide, which effectively turns on or off the coupling between degenerate states. This reveals interesting results that can be applied to develop new types of nanophotonic devices such as nano-switches and nano-transistors.

  14. Gelled Lyotropic Liquid Crystals.

    PubMed

    Xu, Yang; Laupheimer, Michaela; Preisig, Natalie; Sottmann, Thomas; Schmidt, Claudia; Stubenrauch, Cosima

    2015-08-11

    In our previous work we were able to prove that gelled bicontinuous microemulsions are a novel type of orthogonal self-assembled system. The study at hand aims at complementing our previous work by answering the question of whether gelled lyotropic liquid crystals are also orthogonal self-assembled systems. For this purpose we studied the same system, namely, water-n-decane/12-hydroxyoctadecanoic acid (12-HOA)-n-decyl tetraoxyethylene glycol ether (C10E4). The phase boundaries of the nongelled and the gelled lyotropic liquid crystals were determined visually and with (2)H NMR spectroscopy. Oscillating shear measurements revealed that the absolute values of the storage and loss moduli of the gelled liquid crystalline (LC) phases do not differ very much from those of the binary organogel. While both the phase behavior and the rheological properties of the LC phases support the hypothesis that gelled lyotropic liquid crystals are orthogonal self-assembled systems, freeze-fracture electron microscopy (FFEM) seems to indicate an influence of the gel network on the structure of the Lα phase and vice versa.

  15. Photonic crystal horn and array antennas.

    PubMed

    Weily, Andrew R; Esselle, Karu P; Sanders, Barry C

    2003-07-01

    We introduce a defect-based horn antenna in a two-dimensional photonic crystal. Our numerical simulations demonstrate the efficient, highly directional nature of the antenna. It has a large operating bandwidth, low loss, and an operating frequency that is scalable to various regions of the electromagnetic spectrum. We also show that the photonic crystal horn antenna can be successfully used in an array configuration that uses a feed network made from photonic crystal waveguide circuits. The feed network and antennas have been integrated into a single photonic crystal device. This photonic crystal array antenna is shown to have high directivity and compact size while retaining the advantages of the photonic crystal horn antenna.

  16. Monochromatic Wannier Functions in the Theory of 2D Photonic Crystals and Photonic Crystal Fibers

    SciTech Connect

    Mazhirina, Yu. A.; Melnikov, L. A.

    2011-10-03

    The use of the monochromatic Wannier functions which have the temporal dependence as (exp(-i{omega}t)) in the theory of 2D photonic crystals and photonic crystal fibers is proposed. Corresponding equations and formulae are derived and discussed.

  17. Fabrication of colloidal photonic crystal heterostructures free of interface imperfection based on solvent vapor annealing.

    PubMed

    Liu, Xiaomiao; Zhao, Duobiao; Geng, Chong; Zhang, Lijing; Tan, Tianya; Hu, Mingzhe; Yan, Qingfeng

    2014-11-15

    We describe the transformation of a colloidal photonic crystal into a photonic crystal heterostructure. It was achieved by annealing a polystyrene multilayer colloidal photonic crystal partially immersed in water using a solvent vapor. The floating polystyrene colloidal photonic crystal was divided into two parts by the liquid level, which can be manipulated by the addition of ethanol into the water. The top part protruding out of the water experienced a uniform lattice stretching upon exposure to the solvent vapor. The bottom part that stayed immersed in the water remained unaffected due to the protection by the water. The inconsistent behaviors of the two parts resulted in the formation of a colloidal photonic crystal heterostructure. Such a heterostructure was free of interface imperfection since it was a direct descendant of the original colloidal crystal. Meanwhile, optical measurements demonstrated the presence of a wider photonic band gap along the crystallographic [111] direction in these photonic crystal heterostructures compared with the original colloidal photonic crystals.

  18. Photonic crystals, light manipulation, and imaging in complex nematic structures

    NASA Astrophysics Data System (ADS)

    Ravnik, Miha; Å timulak, Mitja; Mur, Urban; Čančula, Miha; Čopar, Simon; Žumer, Slobodan

    2016-03-01

    Three selected approaches for manipulation of light by complex nematic colloidal and non-colloidal structures are presented using different own custom developed theoretical and modelling approaches. Photonic crystals bands of distorted cholesteric liquid crystal helix and of nematic colloidal opals are presented, also revealing distinct photonic modes and density of states. Light propagation along half-integer nematic disclinations is shown with changes in the light polarization of various winding numbers. As third, simulated light transmission polarization micrographs of nematic torons are shown, offering a new insight into the complex structure characterization. Finally, this work is a contribution towards using complex soft matter in optics and photonics for advanced light manipulation.

  19. Magneto-photonic crystals for optical sensing applications

    NASA Astrophysics Data System (ADS)

    Dissanayake, Neluka

    Among the optical structures investigated for optical sensing purpose, a significant amount of research has been conducted on photonic crystal based sensors. A particular advantage of photonic crystal based sensors is that they show superior sensitivity for ultra-small volume sensing. In this study we investigate polarization changes in response to the changes in the cover index of magneto-optic active photonic band gap structures. One-dimensional photonic-band gap structures fabricated on iron garnet materials yield large polarization rotations at the band gap edges. The enhanced polarization effects serve as an excellent tool for chemical sensing showing high degree of sensitivity for photonic crystal cover refractive index changes. The one dimensional waveguide photonic crystals are fabricated on single-layer bismuth-substituted rare earth iron garnet films ((Bi, Y, Lu)3(Fe, Ga)5O12 ) grown by liquid phase epitaxy on gadolinium gallium garnet substrates. Band gaps have been observed where Bragg scattering conditions links forward-going fundamental waveguide modes to backscattered high-order waveguide modes. Large near-band-edge polarization rotations which increase progressively with backscattered-mode order have been experimentally demonstrated for multiple samples with different composition, film thickness and fabrication parameters. Experimental findings are supported by theoretical analysis of Bloch modes polarization states showing that large near stop-band edge rotations are induced by the magneto-photonic crystal. Theoretical and experimental analysis conducted on polarization rotation sensitivity to waveguide photonic crystal cover refractive index changes shows a monotonic enhancement of the rotation with cover index. The sensor is further developed for selective chemical sensing by employing Polypyrrole as the photonic crystal cover layer. Polypyrrole is one of the extensively studied conducting polymers for selective analyte detection. Successful

  20. Liquid Crystals in Tribology

    PubMed Central

    Carrión, Francisco-José; Martínez-Nicolás, Ginés; Iglesias, Patricia; Sanes, José; Bermúdez, María-Dolores

    2009-01-01

    Two decades ago, the literature dealing with the possible applications of low molar mass liquid crystals, also called monomer liquid crystals (MLCs), only included about 50 references. Today, thousands of papers, conference reports, books or book chapters and patents refer to the study and applications of MLCs as lubricants and lubricant additives and efforts are made to develop new commercial applications. The development of more efficient lubricants is of paramount technological and economic relevance as it is estimated that half the energy consumption is dissipated as friction. MLCs have shown their ability to form ordered boundary layers with good load-carrying capacity and to lower the friction coefficients, wear rates and contact temperature of sliding surfaces, thus contributing to increase the components service life and to save energy. This review includes the use of MLCs in lubrication, and dispersions of MLCs in conventional polymers (PDMLCs). Finally, new lubricating system composed of MLC blends with surfactants, ionic liquids or nanophases are considered. PMID:19865534

  1. Lasing dynamics of photonic crystal reflector laser

    NASA Astrophysics Data System (ADS)

    Bakoz, Andrei P.; Liles, A. A.; Viktorov, E. A.; O'Faolain, L.; Habruseva, T.; Huyet, G.; Hegarty, S. P.

    2016-04-01

    We describe the lasing characteristics of a compact tunable laser source formed by the butt-coupling of a reflective indium phosphide optical amplifier to an SU8 waveguide coupled to few-mode photonic crystal reflector. The short cavity length ensured that only a single longitudinal mode of the device could overlap with each photonic crystal reflection peak.

  2. Photonic crystal scintillators and methods of manufacture

    SciTech Connect

    Torres, Ricardo D.; Sexton, Lindsay T.; Fuentes, Roderick E.; Cortes-Concepcion, Jose

    2015-08-11

    Photonic crystal scintillators and their methods of manufacture are provided. Exemplary methods of manufacture include using a highly-ordered porous anodic alumina membrane as a pattern transfer mask for either the etching of underlying material or for the deposition of additional material onto the surface of a scintillator. Exemplary detectors utilizing such photonic crystal scintillators are also provided.

  3. Photonic crystal technology for terahertz system integration

    NASA Astrophysics Data System (ADS)

    Fujita, Masayuki; Nagatsuma, Tadao

    2016-04-01

    Developing terahertz integration technology is essential for practical use of terahertz electromagnetic waves (0.1-10 THz) in various applications including broadband wireless communication, spectroscopic sensing, and nondestructive imaging. In this paper, we present our recent challenges towards terahertz system integration based on photonic crystal technology such as the development of terahertz transceivers. We use photonic-crystal slabs consisting of a twodimensional lattice of air holes formed in a silicon slab to develop low loss compact terahertz components in planar structures. The demonstration of ultralow loss (< 0.1 dB/cm) waveguides and integrated transceiver devices in the 0.3 THz band shows the potential for the application of photonic crystals to terahertz integration technology. Improving the coupling efficiency between the photonic crystal waveguide and resonant tunneling diode is important to take full advantage of the ultralow loss photonic crystal waveguides.

  4. Surface states in photonic crystals

    NASA Astrophysics Data System (ADS)

    Vojtíšek, P.; Richter, I.

    2013-04-01

    Among many unusual and interesting physical properties of photonic crystals (PhC), in recent years, the propagation of surface electromagnetic waves along dielectric PhC boundaries have attracted considerable attention, also in connection to their possible applications. Such surfaces states, produced with the help of specialized defects on PhC boundaries, similarly to surfaces plasmons, are localized surfaces waves and, as such, can be used in various sensing applications. In this contribution, we present our recent studies on numerical modelling of surface states (SS) for all three cases of PhC dimensionality. Simulations of these states were carried out by the use of plane wave expansion (PWE) method via the MIT MPB package.

  5. Wetting of cholesteric liquid crystals.

    PubMed

    Silvestre, Nuno M; Figueirinhas Pereira, Maria Carolina; Bernardino, Nelson R; Telo da Gama, Margarida M

    2016-02-01

    We investigate theoretically the wetting properties of cholesteric liquid crystals at a planar substrate. If the properties of substrate and of the interface are such that the cholesteric layers are not distorted, the wetting properties are similar to those of a nematic liquid crystal. If, on the other hand, the anchoring conditions force the distortion of the liquid crystal layers the wetting properties are altered, the free cholesteric-isotropic interface is non-planar and there is a layer of topological defects close to the substrate. These deformations can either promote or hinder the wetting of the substrate by a cholesteric, depending on the properties of the cholesteric liquid crystal.

  6. Butterfly wing color: A photonic crystal demonstration

    NASA Astrophysics Data System (ADS)

    Proietti Zaccaria, Remo

    2016-01-01

    We have theoretically modeled the optical behavior of a natural occurring photonic crystal, as defined by the geometrical characteristics of the Teinopalpus Imperialis butterfly. In particular, following a genetic algorithm approach, we demonstrate how its wings follow a triclinic crystal geometry with a tetrahedron unit base. By performing both photonic band analysis and transmission/reflection simulations, we are able to explain the characteristic colors emerging by the butterfly wings, thus confirming their crystal form.

  7. Crystallization of undercooled liquid fenofibrate.

    PubMed

    Amstad, Esther; Spaepen, Frans; Weitz, David A

    2015-11-28

    Formulation of hydrophobic drugs as amorphous materials is highly advantageous as this increases their solubility in water and therefore their bioavailability. However, many drugs have a high propensity to crystallize during production and storage, limiting the usefulness of amorphous drugs. We study the crystallization of undercooled liquid fenofibrate, a model hydrophobic drug. Nucleation is the rate-limiting step; once seeded with a fenofibrate crystal, the crystal rapidly grows by consuming the undercooled liquid fenofibrate. Crystal growth is limited by the incorporation of molecules into its surface. As nucleation and growth both entail incorporation of molecules into the surface, this process likely also limits the formation of nuclei and thus the crystallization of undercooled liquid fenofibrate, contributing to the good stability of undercooled liquid fenofibrate against crystallization.

  8. Photonic crystal microcavity lasers and laser arrays

    NASA Astrophysics Data System (ADS)

    Cao, Jiang-Rong

    As a state-of-the-art technology, photonic crystal microcavity lasers have great potentials to resolve many semiconductor laser performance challenges, owing to their compact size, high spontaneous emission factor, and inherent advantages in dimension scalability. This thesis describes efficient numerical analyzing methods for multimode photonic crystal microcavities, including a parallel computing three-dimensional finite-difference time-domain method combined with Pade interpolation, point group projection, and vectorial Green's function method. With the help of these analyzing tools, various experimental photonic crystal microcavity devices fabricated in InGaAsP/InP based materials were studies. Room temperature optical pumped InGaAsP suspended membrane photonic crystal microcavity lasers were demonstrated. Their lithographical fine-tuning, above room temperature operations, mode identifications and polarizations were demonstrated. Room temperature continuous wave (CW) optically pumped photonic crystal microcavity lasers at diameter less than 3.2 mum were demonstrated with crystalline alpha-Al 2O3 (sapphire) as a cladding layer to the InGaAsP membrane. The far-field radiation profiles from these microcavity lasers were measured and compared with our numerical modeling predictions. Two electrical injection scenes for photonic crystal microcavity lasers were introduced, together with some preliminary results including the demonstrations of optically pumped lasing of highly doped cavities and cavities with an electrical conduction post underneath. Electrically excited photonic crystal microcavity light emitting diodes (LEDs) were also experimentally demonstrated.

  9. Quantum Cascade Photonic Crystal lasers

    NASA Astrophysics Data System (ADS)

    Capasso, Federico

    2004-03-01

    QC lasers have emerged in recent years as the dominant laser technology for the mid-to far infrared spectrum in light of their room temperature operation, their tunability, ultrahigh speed operation and broad range of applications to chemical sensing, spectroscopy etc. (Ref. 1-3). After briefly reviewing the latter, I will describe a new class of mid-infrared QC lasers, Quantum Cascade Photonic Crystal Surface Emitting Lasers (QCPCSELS), that combine electronic and photonic band structure engineering to achieve vertical emission from the surface (Ref. 4). Devices operating on bandedge mode and on defect modes will be discussed. Exciting potential uses of these new devices exist in nonlinear optics, microfluidics as well as novel sensors. Finally a bird's eye view of other exciting areas of QC laser research will be given including broadband QCLs and new nonlinear optical sources based on multiwavelength QCLs. 1. F. Capasso, C. Gmachl, D. L. Sivco, and A. Y. Cho, Physics Today 55, 34 (May 2002) 2. F. Capasso, C. Gmachl, R. Paiella, A. Tredicucci, A. L. Hutchinson, D. L. Sivco, J. N. Baillargeon, A. Y. Cho and H. C. Liu, IEEE Journal of Selected Topics in Quantum Electronics, 6, 931 (2000). 3. F. Capasso, R. Paiella, R. Martini, R. Colombelli, C. Gmachl, T. L. Myers, M. S. Taubman, R. M. Williams, C. G. Bethea, K. Unterrainer, H. Y. Hwang, D. L. Sivco, A. Y. Cho, A. M. Sergent, H. C. Liu, E. A. Whittaker, IEEE J. Quantum Electron. 38, 511 (2002) 4. R. Colombelli, K. Srivasan, M. Troccoli, O. Painter, C. Gmachl, D. M. Tennant, A. M. Sergent, D. L. Sivco, A. Y. Cho and F. Capasso, Science 302, 1374 (2003)

  10. Novel photonic crystal cavities and related structures.

    SciTech Connect

    Luk, Ting Shan

    2007-11-01

    The key accomplishment of this project is to achieve a much more in-depth understanding of the thermal emission physics of metallic photonic crystal through theoretical modeling and experimental measurements. An improved transfer matrix technique was developed to enable incorporation of complex dielectric function. Together with microscopic theory describing emitter radiative and non-radiative relaxation dynamics, a non-equilibrium thermal emission model is developed. Finally, experimental methodology was developed to measure absolute emissivity of photonic crystal at high temperatures with accuracy of +/-2%. Accurate emissivity measurements allow us to validate the procedure to treat the effect of the photonic crystal substrate.

  11. Electromechanically tunable carbon nanofiber photonic crystal.

    PubMed

    Rehammar, Robert; Ghavanini, Farzan Alavian; Magnusson, Roger; Kinaret, Jari M; Enoksson, Peter; Arwin, Hans; Campbell, Eleanor E B

    2013-02-13

    We demonstrate an electrically tunable 2D photonic crystal array constructed from vertically aligned carbon nanofibers. The nanofibers are actuated by applying a voltage between adjacent carbon nanofiber pairs grown directly on metal electrodes, thus dynamically changing the form factor of the photonic crystal lattice. The change in optical properties is characterized using optical diffraction and ellipsometry. The experimental results are shown to be in agreement with theoretical predictions and provide a proof-of-principle for rapidly switchable photonic crystals operating in the visible that can be fabricated using standard nanolithography techniques combined with plasma CVD growth of the nanofibers.

  12. Tunable Meta-Liquid Crystals.

    PubMed

    Liu, Mingkai; Fan, Kebin; Padilla, Willie; Powell, David A; Zhang, Xin; Shadrivov, Ilya V

    2016-02-24

    Meta-liquid crystals, a novel form of tunable 3D metamaterials, are proposed and experimentally demonstrated in the terahertz frequency regime. A morphology change under a bias electric field and a strong modulation of the transmission are observed. In comparison to conventional liquid crystals, there is considerable freedom to prescribe the electromagnetic properties through the judicious design of the meta-atom geometry.

  13. Modeling liquid crystal polymeric devices

    NASA Astrophysics Data System (ADS)

    Gimenez Pinto, Vianney Karina

    The main focus of this work is the theoretical and numerical study of materials that combine liquid crystal and polymer. Liquid crystal elastomers are polymeric materials that exhibit both the ordered properties of the liquid crystals and the elastic properties of rubbers. Changing the order of the liquid crystal molecules within the polymer network can induce shape change. These materials are very valuable for applications such as actuators, sensors, artificial muscles, haptic displays, etc. In this work we apply finite element elastodynamics simulations to study the temperature induced shape deformation in nematic elastomers with complex director microstructure. In another topic, we propose a novel numerical method to model the director dynamics and microstructural evolution of three dimensional nematic and cholesteric liquid crystals. Numerical studies presented in this work are in agreement with experimental observations and provide insight into the design of application devices.

  14. Tunable photonic Bloch oscillations in electrically modulated photonic crystals.

    PubMed

    Wang, Gang; Huang, Ji Ping; Yu, Kin Wah

    2008-10-01

    We exploit theoretically the occurrence and tunability of photonic Bloch oscillations (PBOs) in one-dimensional photonic crystals (PCs) containing nonlinear composites. Because of the enhanced third-order nonlinearity (Kerr-type nonlinearity) of composites, photons undergo oscillations inside tilted photonic bands, which are achieved by the application of graded external-pump electric fields on such PCs, varying along the direction perpendicular to the surface of layers. The tunability of PBOs (including amplitude and period) is readily achieved by changing the field gradient. With an appropriate graded pump ac or dc electric field, terahertz PBOs can appear and cover a terahertz band in an electromagnetic spectrum.

  15. Graphene-based liquid crystal device.

    PubMed

    Blake, Peter; Brimicombe, Paul D; Nair, Rahul R; Booth, Tim J; Jiang, Da; Schedin, Fred; Ponomarenko, Leonid A; Morozov, Sergey V; Gleeson, Helen F; Hill, Ernie W; Geim, Andre K; Novoselov, Kostya S

    2008-06-01

    Graphene is only one atom thick, optically transparent, chemically inert, and an excellent conductor. These properties seem to make this material an excellent candidate for applications in various photonic devices that require conducting but transparent thin films. In this letter, we demonstrate liquid crystal devices with electrodes made of graphene that show excellent performance with a high contrast ratio. We also discuss the advantages of graphene compared to conventionally used metal oxides in terms of low resistivity, high transparency and chemical stability.

  16. Dichroic Liquid Crystal Displays

    NASA Astrophysics Data System (ADS)

    Bahadur, Birendra

    The following sections are included: * INTRODUCTION * DICHROIC DYES * Chemical Structure * Chemical and Photochemical Stability * THEORETICAL MODELLING * DEFECTS CAUSED BY PROLONGED LIGHT IRRADIATION * CHEMICAL STRUCTURE AND PHOTOSTABILITY * OTHER PARAMETERS AFFECTING PHOTOSTABILITY * CELL PREPARATION * DICHROIC PARAMETERS AND THEIR MEASUREMENTS * Order Parameter and Dichroic Ratio Of Dyes * Absorbance, Order Parameter and Dichroic Ratio Measurements * IMPACT OF DYE STRUCTURE AND LIQUID CRYSTAL HOST ON PHYSICAL PROPERTIES OF A DICHROIC MIXTURE * Order Parameter and Dichroic Ratio * EFFECT OF LENGTH OF DICHROIC DYES ON THE ORDER PARAMETER * EFFECT OF THE BREADTH OF DYE ON THE ORDER PARAMETER * EFFECT OF THE HOST ON THE ORDER PARAMETER * TEMPERATURE VARIATION OF THE ORDER PARAMETER OF DYES IN A LIQUID CRYSTAL HOST * IMPACT OF DYE CONCENTRATION ON THE ORDER PARAMETER * Temperature Range * Viscosity * Dielectric Constant and Anisotropy * Refractive Indices and Birefringence * solubility43,153-156 * Absorption Wavelength and Auxochromic Groups * Molecular Engineering of Dichroic Dyes * OPTICAL, ELECTRO-OPTICAL AND LIFE PARAMETERS * Colour And CIE Colour space120,160-166 * CIE 1931 COLOUR SPACE * CIE 1976 CHROMATICITY DIAGRAM * CIE UNIFORM COLOUR SPACES & COLOUR DIFFERENCE FORMULAE120,160-166 * Electro-Optical Parameters120 * LUMINANCE * CONTRAST AND CONTRAST RATIO * SWITCHING SPEED * Life Parameters and Failure Modes * DICHROIC MIXTURE FORMULATION * Monochrome Mixture * Black Mixture * ACHROMATIC BLACK MIXTURE FOR HEILMEIER DISPLAYS * Effect of Illuminant on Display Colour * Colour of the Field-On State * Effect of Dye Linewidth * Optimum Centroid Wavelengths * Effect of Dye Concentration * Mixture Formulation Using More Than Three Dyes * ACHROMATIC MIXTURE FOR WHITE-TAYLOR TYPE DISPLAYS * HEILMEIER DISPLAYS * Theoretical Modelling * Threshold Characteristic * Effects of Dye Concentration on Electro-optical Parameters * Effect of Cholesteric Doping * Effect of Alignment

  17. Nanoparticles in liquid crystals, and liquid crystals in nanoparticles

    NASA Astrophysics Data System (ADS)

    de Pablo, Juan

    2015-03-01

    Liquid crystals are remarkably sensitive to interfacial interactions. Small perturbations at a liquid crystal interface, for example, can be propagated over relatively long length scales, thereby providing the basis for a wide range of applications that rely on amplification of molecular events into macroscopic observables. Our recent research efforts have focused on the reverse phenomenon; that is, we have sought to manipulate the interfacial assembly of nanoparticles or the organization of surface active molecules by controlling the structure of a liquid crystal. This presentation will consist of a review of the basic principles that are responsible for liquid crystal-mediated interactions, followed by demonstrations of those principles in the context of two types of systems. In the first, a liquid crystal is used to direct the assembly of nanoparticles; through a combination of molecular and continuum models, it is found that minute changes in interfacial energy and particle size lead to liquid-crystal induced attractions that can span multiple orders of magnitude. Theoretical predictions are confirmed by experimental observations, which also suggest that LC-mediated assembly provides an effective means for fabrication of plasmonic devices. In the second type of system, the structure of a liquid crystal is controlled by confinement in submicron droplets. The morphology of the liquid crystal in a drop depends on a delicate balance between bulk and interfacial contributions to the free energy; that balance can be easily perturbed by adsorption of analytes or nanoparticles at the interface, thereby providing the basis for development of hierarchical assembly of responsive, anisotropic materials. Theoretical predictions also indicate that the three-dimensional order of a liquid crystal can be projected onto a two-dimensional interface, and give rise to novel nanostructures that are not found in simple isotropic fluids.

  18. Sensitivity enhancement in photonic crystal slab biosensors.

    PubMed

    El Beheiry, Mohamed; Liu, Victor; Fan, Shanhui; Levi, Ofer

    2010-10-25

    Refractive index sensitivity of guided resonances in photonic crystal slabs is analyzed. We show that modal properties of guided resonances strongly affect spectral sensitivity and quality factors, resulting in substantial enhancement of refractive index sensitivity. A three-fold spectral sensitivity enhancement is demonstrated for suspended slab designs, in contrast to designs with a slab resting over a substrate. Spectral sensitivity values are additionally shown to be unaffected by quality factor reductions, which are common to fabricated photonic crystal nano-structures. Finally, we determine that proper selection of photonic crystal slab design parameters permits biosensing of a wide range of analytes, including proteins, antigens, and cells. These photonic crystals are compatible with large-area biosensor designs, permitting direct access to externally incident optical beams in a microfluidic device.

  19. Photonic crystal: energy-related applications

    SciTech Connect

    Ye, Zhuo; Park, Joong-Mok; Constant, Kristen; Kim, Tae-Geun; Ho, Kai-Ming

    2012-06-08

    We review recent work on photonic-crystal fabrication using soft-lithography techniques. We consider applications of the resulting structures in energy-related areas such as lighting and solar-energy harvesting. In general, our aim is to introduce the reader to the concepts of photonic crystals, describe their history, development, and fabrication techniques and discuss a selection of energy-related applications.

  20. Metallic photonic crystals for thermophotovoltaic applications

    NASA Astrophysics Data System (ADS)

    Walsh, Timothy A.

    Since the idea of a photonic bandgap was proposed over two decades ago, photonic crystals have been the subject of significant interest due to their novel optical properties which enable new and varied applications. In this research, the photonic bandgap effect is exploited to tailor the thermal radiation spectrum to a narrow range of wavelengths determined by the lattice symmetry and dimensions of the photonic crystal structure. This sharp emission peak can be matched to the electronic bandgap energy of a p-n junction photovoltaic cell for high efficiency thermophotovoltaic energy conversion. This thesis explores aspects of photonic crystal design, materials considerations, and manufacture for thermophotovoltaic applications. Photonic crystal structures come in many forms, exhibiting various types of 1D, 2D, and 3D lattice symmetry. In this work, the "woodpile" 3D photonic crystal is studied. One advantage of the woodpile lattice is that it can be readily fabricated on a large scale using common integrated circuit manufacturing techniques. Additionally this structure lends itself to efficient and accurate modeling with the use of a plane-wave expansion based transfer matrix method to calculate the scattering properties and band structure of the photonic crystal. This method is used to explore the geometric design parameters of the woodpile structure. Optimal geometric proportions for the structure are found which yield the highest narrowband absorption peak possible. By Kirchoffs law of thermal emission, this strong and sharp absorptance will yield high power and narrowband thermal radiation. The photonic crystal thermal emission spectrum is then evaluated in a TPV system model to evaluate the electrical power density and system efficiency achievable. The results produced by the photonic crystal emitter are compared with the results assuming a blackbody thermal radiation spectrum. The blackbody represents a universal standard against which any selective emitter

  1. Optical trapping apparatus, methods and applications using photonic crystal resonators

    SciTech Connect

    Erickson, David; Chen, Yih-Fan

    2015-06-16

    A plurality of photonic crystal resonator optical trapping apparatuses and a plurality optical trapping methods using the plurality of photonic crystal resonator optical trapping apparatuses include located and formed over a substrate a photonic waveguide that is coupled (i.e., either separately coupled or integrally coupled) with a photonic crystal resonator. In a particular embodiment, the photonic waveguide and the photonic crystal resonator comprise a monocrystalline silicon (or other) photonic material absent any chemical functionalization. In another particular embodiment, the photonic waveguide and the photonic crystal resonator comprise a silicon nitride material which when actuating the photonic crystal resonator optical trapping apparatus with a 1064 nanometer resonant photonic radiation wavelength (or other resonant photonic radiation wavelength in a range from about 700 to about 1200 nanometers) provides no appreciable heating of an aqueous sample fluid that is analyzed by the photonic crystal resonator optical trapping apparatus.

  2. Molecular reorientation of a nematic liquid crystal by thermal expansion

    PubMed Central

    Kim, Young-Ki; Senyuk, Bohdan; Lavrentovich, Oleg D.

    2012-01-01

    A unique feature of nematic liquid crystals is orientational order of molecules that can be controlled by electromagnetic fields, surface modifications and pressure gradients. Here we demonstrate a new effect in which the orientation of nematic liquid crystal molecules is altered by thermal expansion. Thermal expansion (or contraction) causes the nematic liquid crystal to flow; the flow imposes a realigning torque on the nematic liquid crystal molecules and the optic axis. The optical and mechanical responses activated by a simple temperature change can be used in sensing, photonics, microfluidic, optofluidic and lab-on-a-chip applications as they do not require externally imposed gradients of temperature, pressure, surface realignment, nor electromagnetic fields. The effect has important ramifications for the current search of the biaxial nematic phase as the optical features of thermally induced structural changes in the uniaxial nematic liquid crystal mimic the features expected of the biaxial nematic liquid crystal. PMID:23072803

  3. Pressure sensor using liquid crystals

    NASA Technical Reports Server (NTRS)

    Parmar, Devendra S. (Inventor); Holmes, Harlan K. (Inventor)

    1994-01-01

    A pressure sensor includes a liquid crystal positioned between transparent, electrically conductive films (18 and 20), that are biased by a voltage (V) which induces an electric field (E) that causes the liquid crystal to assume a first state of orientation. Application of pressure (P) to a flexible, transparent film (24) causes the conductive film (20) to move closer to or farther from the conductive film (18), thereby causing a change in the electric field (E'(P)) which causes the liquid crystal to assume a second state of orientation. Polarized light (P.sub.1) is directed into the liquid crystal and transmitted or reflected to an analyzer (A or 30). Changes in the state of orientation of the liquid crystal induced by applied pressure (P) result in a different light intensity being detected at the analyzer (A or 30) as a function of the applied pressure (P). In particular embodiments, the liquid crystal is present as droplets (10) in a polymer matrix (12) or in cells (14) in a polymeric or dielectric grid (16) material in the form of a layer (13) between the electrically conductive films (18 and 20). The liquid crystal fills the open wells in the polymer matrix (12) or grid (16) only partially.

  4. Liquid crystal alignment in cylindrical microcapillaries

    NASA Astrophysics Data System (ADS)

    Chychłowski, M.; Yaroshchuk, O.; Kravchuk, R.; Woliński, T.

    2011-09-01

    A variety of alignment configurations of liquid crystals (LCs) inside the glassy cylindrical capillaries is realized by using alignment materials providing different anchoring. The radial configuration with central disclination line is obtained for homeotropic boundary conditions. In turn, the axial, transversal and tilted alignment structures are realized by using materials for planar anchoring. The uniformity and controlling of the latter structures were provided by photoalignment method. This approach can be further used to control LC alignment in the photonic crystal fibers recognized as advanced elements for different optical devices.

  5. Liquid crystal alignment in cylindrical microcapillaries

    NASA Astrophysics Data System (ADS)

    Chychłowski, M.; Yaroshchuk, O.; Kravchuk, R.; Woliński, T.

    2012-03-01

    A variety of alignment configurations of liquid crystals (LCs) inside the glassy cylindrical capillaries is realized by using alignment materials providing different anchoring. The radial configuration with central disclination line is obtained for homeotropic boundary conditions. In turn, the axial, transversal and tilted alignment structures are realized by using materials for planar anchoring. The uniformity and controlling of the latter structures were provided by photoalignment method. This approach can be further used to control LC alignment in the photonic crystal fibers recognized as advanced elements for different optical devices.

  6. Liquid encapsulated crystal growth

    NASA Technical Reports Server (NTRS)

    Morrison, Andrew D. (Inventor)

    1987-01-01

    Low-defect crystals are grown in a closed ampoule under a layer of encapsulant. After crystal growth, the crystal is separated from the melt and moved into the layer of encapsulant and cooled to a first temperature at which crystal growth stops. The crystal is then moved into the inert gas ambient in the ampoule and further cooled. The crystal can be separated from the melt by decanting the melt into and adjacent reservoir or by rotating the ampoule to rotate the crystal into the encapsulant layer.

  7. Liquid encapsulated crystal growth

    NASA Technical Reports Server (NTRS)

    Morrison, Andrew D. (Inventor)

    1989-01-01

    Low-defect crystals are grown in a closed ampoule under a layer of encapsulant. After crystal growth, the crystal is separated from the melt and moved into the layer of encapsulant and cooled to a first temperature at which crystal growth stops. The crystal is then moved into the inert gas ambient in the ampoule and further cooled. The crystal can be separated from the melt by decanting the melt into an adjacent reservoir or by rotating the ampoule to rotate the crystal into the encapsulant layer.

  8. Controlling spontaneous emission in bioreplica photonic crystals

    NASA Astrophysics Data System (ADS)

    Jorgensen, Matthew R.; Butler, Elizabeth S.; Bartl, Michael H.

    2012-04-01

    Sophisticated methods have been created by nature to produce structure-based colors as a way to address the need of a wide variety of organisms. This pallet of available structures presents a unique opportunity for the investigation of new photonic crystal designs. Low-temperature sol-gel biotemplating methods were used to transform a single biotemplate into a variety of inorganic oxide structures. The density of optical states was calculated for a diamond-based natural photonic crystal, as well as several structures templated from it. Calculations were experimentally probed by spontaneous emission studies using time correlated single photon counting measurements.

  9. Biological liquid crystal elastomers.

    PubMed

    Knight, David P; Vollrath, Fritz

    2002-02-28

    Liquid crystal elastomers (LCEs) have recently been described as a new class of matter. Here we review the evidence for the novel conclusion that the fibrillar collagens and the dragline silks of orb web spiders belong to this remarkable class of materials. Unlike conventional rubbers, LCEs are ordered, rather than disordered, at rest. The identification of these biopolymers as LCEs may have a predictive value. It may explain how collagens and spider dragline silks are assembled. It may provide a detailed explanation for their mechanical properties, accounting for the variation between different members of the collagen family and between the draglines in different spider species. It may provide a basis for the design of biomimetic collagen and dragline silk analogues by genetic engineering, peptide- or classical polymer synthesis. Biological LCEs may exhibit a range of exotic properties already identified in other members of this remarkable class of materials. In this paper, the possibility that other transversely banded fibrillar proteins are also LCEs is discussed.

  10. A Three-Dimensional Optical Photonic Crystal

    SciTech Connect

    Fleming, J.G.; Lin, S.

    1998-12-17

    The search for a photonic crystal to confine optical waves in all three dimensions (3D) has proven to be a formidable task. It evolves from an early theoretical suggestion [1,2], a brief skepticism [3-5] and triumph in developing the mm-wave [6-8] and infrared 3D photonic crystals [9]. Yet, the challenge remains, as the ultimate goal for optoelectronic applications is to realize a 3D crystal at X=1.5 pm communication wavelengths. Operating at visible and near infrared wavelengths, X=1-2 pm, a photonic crystal may enhance the spontaneous emission rate [1, 10] and give rise to a semiconductor lasers with a zero lasing threshold[11, 12]. Another important application is optically switching, routing and interconnecting light [13,14] with an ultrafast transmission speed of terabits per second. A photonic crystal may also serve as a platform for integrating an all-optical circuitry with multiple photonic components, such as waveguides and switches, built on one chip [15]. In this Letter, we report on the successful fabrication of a working 3D crystal operating at optical L The minimum feature size of the 3D structure is 180 nanometers. The 3D crystal is free from defects over the entire 6-inch silicon wafer and has an absolute photonic band gap centered at A.-1.6 pm. Our data provides the first conclusive evidence for the existence of a full 3D photonic band gap in optical A. This development will pave the way to tinier, cheaper, more effective waveguides, optical switches and lasers.

  11. Progress in 2D photonic crystal Fano resonance photonics

    NASA Astrophysics Data System (ADS)

    Zhou, Weidong; Zhao, Deyin; Shuai, Yi-Chen; Yang, Hongjun; Chuwongin, Santhad; Chadha, Arvinder; Seo, Jung-Hun; Wang, Ken X.; Liu, Victor; Ma, Zhenqiang; Fan, Shanhui

    2014-01-01

    In contrast to a conventional symmetric Lorentzian resonance, Fano resonance is predominantly used to describe asymmetric-shaped resonances, which arise from the constructive and destructive interference of discrete resonance states with broadband continuum states. This phenomenon and the underlying mechanisms, being common and ubiquitous in many realms of physical sciences, can be found in a wide variety of nanophotonic structures and quantum systems, such as quantum dots, photonic crystals, plasmonics, and metamaterials. The asymmetric and steep dispersion of the Fano resonance profile promises applications for a wide range of photonic devices, such as optical filters, switches, sensors, broadband reflectors, lasers, detectors, slow-light and non-linear devices, etc. With advances in nanotechnology, impressive progress has been made in the emerging field of nanophotonic structures. One of the most attractive nanophotonic structures for integrated photonics is the two-dimensional photonic crystal slab (2D PCS), which can be integrated into a wide range of photonic devices. The objective of this manuscript is to provide an in depth review of the progress made in the general area of Fano resonance photonics, focusing on the photonic devices based on 2D PCS structures. General discussions are provided on the origins and characteristics of Fano resonances in 2D PCSs. A nanomembrane transfer printing fabrication technique is also reviewed, which is critical for the heterogeneous integrated Fano resonance photonics. The majority of the remaining sections review progress made on various photonic devices and structures, such as high quality factor filters, membrane reflectors, membrane lasers, detectors and sensors, as well as structures and phenomena related to Fano resonance slow light effect, nonlinearity, and optical forces in coupled PCSs. It is expected that further advances in the field will lead to more significant advances towards 3D integrated photonics, flat

  12. Thermotropic liquid crystals from biomacromolecules

    PubMed Central

    Liu, Kai; Chen, Dong; Marcozzi, Alessio; Zheng, Lifei; Su, Juanjuan; Pesce, Diego; Zajaczkowski, Wojciech; Kolbe, Anke; Pisula, Wojciech; Müllen, Klaus; Clark, Noel A.; Herrmann, Andreas

    2014-01-01

    Complexation of biomacromolecules (e.g., nucleic acids, proteins, or viruses) with surfactants containing flexible alkyl tails, followed by dehydration, is shown to be a simple generic method for the production of thermotropic liquid crystals. The anhydrous smectic phases that result exhibit biomacromolecular sublayers intercalated between aliphatic hydrocarbon sublayers at or near room temperature. Both this and low transition temperatures to other phases enable the study and application of thermotropic liquid crystal phase behavior without thermal degradation of the biomolecular components. PMID:25512508

  13. Adaptive Liquid Crystal Windows

    SciTech Connect

    Taheri, Bahman; Bodnar, Volodymyr

    2011-12-31

    Energy consumption by private and commercial sectors in the U.S. has steadily grown over the last decade. The uncertainty in future availability of imported oil, on which the energy consumption relies strongly, resulted in a dramatic increase in the cost of energy. About 20% of this consumption are used to heat and cool houses and commercial buildings. To reduce dependence on the foreign oil and cut down emission of greenhouse gases, it is necessary to eliminate losses and reduce total energy consumption by buildings. To achieve this goal it is necessary to redefine the role of the conventional windows. At a minimum, windows should stop being a source for energy loss. Ideally, windows should become a source of energy, providing net gain to reduce energy used to heat and cool homes. It is possible to have a net energy gain from a window if its light transmission can be dynamically altered, ideally electronically without the need of operator assistance, providing optimal control of the solar gain that varies with season and climate in the U.S. In addition, the window must not require power from the building for operation. Resolution of this problem is a societal challenge and of national interest and will have a broad global impact. For this purpose, the year-round, allclimate window solution to provide an electronically variable solar heat gain coefficient (SHGC) with a wide dynamic range is needed. AlphaMicron, Inc. (AMI) developed and manufactured 1ft × 1ft prototype panels for the world’s first auto-adjusting Adaptive Liquid Crystal Windows (ALCWs) that can operate from sunlight without the need for external power source and demonstrate an electronically adjustable SHGC. This novel windows are based on AlphaMicron’s patented e-Tint® technology, a guesthost liquid crystal system implemented on flexible, optically clear plastic films. This technology is suitable both for OEM and aftermarket (retro-fitting) lamination to new and existing windows. Low level of

  14. Photonic crystals with active organic materials

    NASA Astrophysics Data System (ADS)

    Wu, Yeheng

    The concept of photonic crystals, which involves periodically arranged dielectrics that form a new type of material having novel photonic properties, was first proposed about two decades ago. Since then, a number of applications in photonic technology have been explored. Specifically, organic and hybrid photonic crystals are promising because of the unique advantages of the organic materials. A one-dimensional (1D) photonic crystal (multilayer) has high reflectance across a certain wavelength range. We report on studies of 1D multilayer polymer films that were fabricated using spin-coating, free film stacking, and co-extrusion techniques. For example, a stack fabricated by placing a laser dye-doped gain medium between two multilayer reflecting polymer films forms a micro-resonator laser or distributed Bragg laser. The resulting laser system is made entirely of plastic and is only several tens of micrometers in thickness. When the gain, a dye-doped medium, comprises one type of a two-type multilayer film, it results a laser exhibiting distributed feedback. At the edge of the photonic band, the group velocity becomes small and the density of photon states becomes high, which leads to laser emission. Such distributed feedback lasers were fabricated using the co-extrusion technique. The refractive indices and the photonic lattice determine the photonic band gap, which can be tuned by changing these parameters. Materials with Kerr nonlinearity exhibit a change in refractive index depending on the incident intensity of the light. To demonstrate such switching, electrochemical etching techniques on silicon wafers were used to form two-dimensional (2D) photonic crystals. By incorporating the nonlinear organic material into the 2D structure, we have made all-optical switches. The reflection of a beam from the 2D photonic crystal can be controlled by another beam because it induces a refractive index change in the active material by altering the reflection band. A mid

  15. Design of photonic crystal splitters/combiners

    NASA Astrophysics Data System (ADS)

    Kim, Sangin; Park, Ikmo; Lim, Hanjo

    2004-10-01

    Photonic band gap (PBG) structures or photonic crystals have attracted a lot of interest since one of their promising applications is to build compact photonic integrated circuits (PIC). One of key components in PICs is a 1 x 2 optical power splitter or a 2 x 1 combiner. Design of 1 x 2 optical power splitters based on photonic crystal has been investigated by several research groups, but no attention has been paid to the design of 2 x 1 optical combiners. In conventional dielectric waveguide based circuits, optical combiners are obtained just by operating the splitters in the opposite direction and the isolation between two input ports in the combiners is naturally achieved. In photonic crystal based circuits, however, we have found that reciprocal operation of the splitters as combiners will not provide proper isolation between the input ports of the combiners. In this work, microwave-circuit concept has been adopted to obtain isolation between two input ports of the combiner and compact optical power splitters/combiners of good performance have been designed using 2-D photonic crystal. Numerical analysis of the designed splitters/combiners has been performed with the finite-difference time-domain method. The designed splitters/combiners show good isolation between input ports in combiner operation with small return losses.

  16. Photon Molecules in Atomic Gases Trapped Near Photonic Crystal Waveguides

    NASA Astrophysics Data System (ADS)

    Douglas, James S.; Caneva, Tommaso; Chang, Darrick E.

    2016-07-01

    Realizing systems that support robust, controlled interactions between individual photons is an exciting frontier of nonlinear optics. To this end, one approach that has emerged recently is to leverage atomic interactions to create strong and spatially nonlocal interactions between photons. In particular, effective photonic interactions have been successfully created via interactions between atoms excited to Rydberg levels. Here, we investigate an alternative approach, in which atomic interactions arise via their common coupling to photonic crystal waveguides. This technique takes advantage of the ability to separately tailor the strength and range of interactions via the dispersion engineering of the structure itself, which can lead to qualitatively new types of phenomena. For example, much of the work on photon-photon interactions relies on the linear optical effect of electromagnetically induced transparency, in combination with the use of interactions to shift optical pulses into or out of the associated transparency window. Here, we identify a large new class of "correlated transparency windows," in which photonic states of a certain number and shape selectively propagate through the system. Through this technique, we show that molecular bound states of photon pairs can be created.

  17. Ultrafast optical switching using photonic molecules in photonic crystal waveguides.

    PubMed

    Zhao, Yanhui; Qian, Chenjiang; Qiu, Kangsheng; Gao, Yunan; Xu, Xiulai

    2015-04-01

    We study the coupling between photonic molecules and waveguides in photonic crystal slab structures using finite-difference time-domain method and coupled mode theory. In a photonic molecule with two cavities, the coupling of cavity modes results in two super-modes with symmetric and anti-symmetric field distributions. When two super-modes are excited simultaneously, the energy of electric field oscillates between the two cavities. To excite and probe the energy oscillation, we integrate photonic molecule with two photonic crystal waveguides. In coupled structure, we find that the quality factors of two super-modes might be different because of different field distributions of super-modes. After optimizing the radii of air holes between two cavities of photonic molecule, nearly equal quality factors of two super-modes are achieved, and coupling strengths between the waveguide modes and two super-modes are almost the same. In this case, complete energy oscillations between two cavities can be obtained with a pumping source in one waveguide, which can be read out by another waveguide. Finally, we demonstrate that the designed structure can be used for ultrafast optical switching with a time scale of a few picoseconds.

  18. Photonic quasi-crystal terahertz lasers

    NASA Astrophysics Data System (ADS)

    Vitiello, Miriam Serena; Nobile, Michele; Ronzani, Alberto; Tredicucci, Alessandro; Castellano, Fabrizio; Talora, Valerio; Li, Lianhe; Linfield, Edmund H.; Davies, A. Giles

    2014-12-01

    Quasi-crystal structures do not present a full spatial periodicity but are nevertheless constructed starting from deterministic generation rules. When made of different dielectric materials, they often possess fascinating optical properties, which lie between those of periodic photonic crystals and those of a random arrangement of scatterers. Indeed, they can support extended band-like states with pseudogaps in the energy spectrum, but lacking translational invariance, they also intrinsically feature a pattern of ‘defects’, which can give rise to critically localized modes confined in space, similar to Anderson modes in random structures. If used as laser resonators, photonic quasi-crystals open up design possibilities that are simply not possible in a conventional periodic photonic crystal. In this letter, we exploit the concept of a 2D photonic quasi crystal in an electrically injected laser; specifically, we pattern the top surface of a terahertz quantum-cascade laser with a Penrose tiling of pentagonal rotational symmetry, reaching 0.1-0.2% wall-plug efficiencies and 65 mW peak output powers with characteristic surface-emitting conical beam profiles, result of the rich quasi-crystal Fourier spectrum.

  19. Photonic quasi-crystal terahertz lasers

    PubMed Central

    Vitiello, Miriam Serena; Nobile, Michele; Ronzani, Alberto; Tredicucci, Alessandro; Castellano, Fabrizio; Talora, Valerio; Li, Lianhe; Linfield, Edmund H.; Davies, A. Giles

    2014-01-01

    Quasi-crystal structures do not present a full spatial periodicity but are nevertheless constructed starting from deterministic generation rules. When made of different dielectric materials, they often possess fascinating optical properties, which lie between those of periodic photonic crystals and those of a random arrangement of scatterers. Indeed, they can support extended band-like states with pseudogaps in the energy spectrum, but lacking translational invariance, they also intrinsically feature a pattern of ‘defects’, which can give rise to critically localized modes confined in space, similar to Anderson modes in random structures. If used as laser resonators, photonic quasi-crystals open up design possibilities that are simply not possible in a conventional periodic photonic crystal. In this letter, we exploit the concept of a 2D photonic quasi crystal in an electrically injected laser; specifically, we pattern the top surface of a terahertz quantum-cascade laser with a Penrose tiling of pentagonal rotational symmetry, reaching 0.1–0.2% wall-plug efficiencies and 65 mW peak output powers with characteristic surface-emitting conical beam profiles, result of the rich quasi-crystal Fourier spectrum. PMID:25523102

  20. Veselago lens by photonic hyper-crystals

    SciTech Connect

    Huang, Zun Narimanov, Evgenii E.

    2014-07-21

    Based on the recent concept of the photonic hyper-crystal—an artificial optical medium that combines the properties of hyperbolic materials and photonic crystals, we present the imaging system functioning as a Veselago lens. This planar lens shows a nearly constant negative refractive index with substantially reduced image aberrations, and can find potential applications in photolithography and hot-spots detection of silicon-based integrated circuits.

  1. Ultra compact spectrometer apparatus and method using photonic crystals

    NASA Technical Reports Server (NTRS)

    Ting, David Z. (Inventor); Hill, Cory J. (Inventor); Bandara, Sumith V. (Inventor); Gunapala, Sarath D. (Inventor)

    2009-01-01

    The present invention is directed to methods of photonic crystal formation, and to methods and apparatus for using such photonic crystals, particularly in conjunction with detector arrays. Photonic crystal parameters and detector array parameters are compared to optimize the selection and orientation of a photonic crystal shape. A photonic crystal is operatively positioned relative to a plurality of light sensors. The light sensors can be separated by a pitch distance and positioned within one half of the pitch distance of an exit surface of the photonic crystals.

  2. Integrated photonic crystal selective emitter for thermophotovoltaics

    NASA Astrophysics Data System (ADS)

    Zhou, Zhiguang; Yehia, Omar; Bermel, Peter

    2016-01-01

    Converting blackbody thermal radiation to electricity via thermophotovoltaics (TPV) is inherently inefficient. Photon recycling using cold-side filters offers potentially improved performance but requires extremely close spacing between the thermal emitter and the receiver, namely a high view factor. Here, we propose an alternative approach for thermal energy conversion, the use of an integrated photonic crystal selective emitter (IPSE), which combines two-dimensional photonic crystal selective emitters and filters into a single device. Finite difference time domain and current transport simulations show that IPSEs can significantly suppress sub-bandgap photons. This increases heat-to-electricity conversion for photonic crystal based emitters from 35.2 up to 41.8% at 1573 K for a GaSb photovoltaic (PV) diode with matched bandgaps of 0.7 eV. The physical basis of this enhancement is a shift from a perturbative to a nonperturbative regime, which maximized photon recycling. Furthermore, combining IPSEs with nonconductive optical waveguides eliminates a key difficulty associated with TPV: the need for precise alignment between the hot selective emitter and cool PV diode. The physical effects of both the IPSE and waveguide can be quantified in terms of an extension of the concept of an effective view factor.

  3. Integrated photonic crystal selective emitter for thermophotovoltaics

    NASA Astrophysics Data System (ADS)

    Zhou, Zhiguang; Yehia, Omar; Bermel, Peter

    2016-01-01

    Converting blackbody thermal radiation to electricity via thermophotovoltaics (TPV) is inherently inefficient. Photon recycling using cold-side filters offers potentially improved performance but requires extremely close spacing between the thermal emitter and the receiver, namely a high view factor. Here, we propose an alternative approach for thermal energy conversion, the use of an integrated photonic crystal selective emitter (IPSE), which combines two-dimensional photonic crystal selective emitters and filters into a single device. Finite difference time domain and current transport simulations show that IPSEs can significantly suppress sub-bandgap photons. This increases heat-to-electricity conversion for photonic crystal based emitters from 35.2 up to 41.8% at 1573 K for a GaSb photovoltaic (PV) diode with matched bandgaps of 0.7 eV. The physical basis of this enhancement is a shift from a perturbative to a nonperturbative regime, which maximized photon recycling. Furthermore, combining IPSEs with nonconductive optical waveguides eliminates a key difficulty associated with TPV: the need for precise alignment between the hot selective emitter and cool PV diode. The physical effects of both the IPSE and waveguide can be quantified in terms of an extension of the concept of an effective view factor.

  4. Self-assembled tunable photonic hyper-crystals

    NASA Astrophysics Data System (ADS)

    Smolyaninov, Igor; Smolyaninova, Vera; Yost, Bradley; Lahneman, David; Gresock, Thomas; Narimanov, Evgenii

    2015-03-01

    We demonstrate a novel artificial optical material, the photonic hyper-crystal, which combines the most interesting features of hyperbolic metamaterials and photonic crystals. Similar to hyperbolic metamaterials, photonic hyper-crystals exhibit broadband divergence in their photonic density of states due to the lack of usual diffraction limit on the photon wave vector. On the other hand, similar to photonic crystals, hyperbolic dispersion law of extraordinary photons is modulated by forbidden gaps near the boundaries of photonic Brillouin zones. Three dimensional self-assembly of photonic hyper-crystals has been achieved by application of external magnetic field to a cobalt nanoparticle-based ferrofluid. Unique spectral properties of photonic hyper-crystals lead to extreme sensitivity of the material to monolayer coatings of cobalt nanoparticles, which should find numerous applications in biological and chemical sensing. This work was supported in part by NSF Grant DMR-1104676, NSF Center for Photonic and Multiscale Nanomaterials, ARO MURI and Gordon and Berry Moore Foundation.

  5. Hybrid photonic-plasmonic crystal nanocavities.

    PubMed

    Yang, Xiaodong; Ishikawa, Atsushi; Yin, Xiaobo; Zhang, Xiang

    2011-04-26

    We propose a hybrid optical nanocavity consisting of photonic crystals coupled to a metal surface with a nanoscale air gap between. The hybridization of photonic crystal modes and surface plasmons across the gap forms hybrid cavity modes, which are highly confined in the low-loss air gap region. Deep subwavelength mode volume and high quality factor are demonstrated at telecommunication wavelength, resulting in an extremely large Q/V(m) ratio of 60,000 λ(-3). This new type of high-Q/V(m) broad-band hybrid nanocavity opens up opportunities for various applications in enhanced light-matter interactions.

  6. Optical amplification enhancement in photonic crystals

    SciTech Connect

    Sapienza, R.; Leonetti, M.; Froufe-Perez, L. S.; Galisteo-Lopez, J. F.; Lopez, C.; Conti, C.

    2011-02-15

    Improving and controlling the efficiency of a gain medium is one of the most challenging problems of laser research. By measuring the gain length in an opal-based photonic crystal doped with laser dye, we demonstrate that optical amplification is more than twenty-fold enhanced along the {Gamma}-K symmetry directions of the face-centered-cubic photonic crystal. These results are theoretically explained by directional variations of the density of states, providing a quantitative connection between density of the states and light amplification.

  7. Two-dimensional photonic crystal surfactant detection.

    PubMed

    Zhang, Jian-Tao; Smith, Natasha; Asher, Sanford A

    2012-08-01

    We developed a novel two-dimensional (2-D) crystalline colloidal array photonic crystal sensing material for the visual detection of amphiphilic molecules in water. A close-packed polystyrene 2-D array monolayer was embedded in a poly(N-isopropylacrylamide) (PNIPAAm)-based hydrogel film. These 2-D photonic crystals placed on a mirror show intense diffraction that enables them to be used for visual determination of analytes. Binding of surfactant molecules attaches ions to the sensor that swells the PNIPAAm-based hydrogel. The resulting increase in particle spacing red shifts the 2-D diffracted light. Incorporation of more hydrophobic monomers increases the sensitivity to surfactants. PMID:22720790

  8. Anomalous reflections at photonic crystal surfaces.

    PubMed

    Yu, Xiaofang; Fan, Shanhui

    2004-11-01

    We explore the reflection phenomena when a light beam propagating in a photonic crystal is incident upon the interfaces between the crystal and a uniform dielectric. We prove that a generalized wave-vector conservation relation still applies even when the interface is not aligned with special crystal directions. Using this conservation relation, we show that neither the phase velocity nor the group velocity directions of the reflected beam satisfies Snell's law. Rather, the system exhibits remarkable and unusual reflection effects. In particular, total internal reflection is absent except at discrete angular values. The direction of the reflected beam can also be pinned along special crystal directions, independent of the orientation of the interface. And finally, at glancing incidences, strong backward reflections may occur. These effects may be important for creating integrated photonic circuits, and for on-chip image transfer.

  9. Fiber based photonic-crystal acoustic sensor

    NASA Astrophysics Data System (ADS)

    Kilic, Onur

    Photonic-crystal slabs are two-dimensional photonic crystals etched into a dielectric layer such as silicon. Standard micro fabrication techniques can be employed to manufacture these structures, which makes it feasible to produce them in large areas, usually an important criterion for practical applications. An appealing feature of these structures is that they can be employed as free-space optical devices such as broadband reflectors. The small thickness of the slab (usually in the vicinity of half a micron) also makes it deflectable. These combined optical and mechanical properties make it possible to employ photonic-crystal slabs in a range of practical applications, including displacement sensors, which in turn can be used for example to detect acoustic waves. An additional benefit of employing a photonic-crystal slab is that it is possible to tailor its optical and mechanical properties by adjusting the geometrical parameters of the structure such as hole radius or shape, pitch, and the slab thickness. By altering the hole radius and pitch, it is possible to make broadband reflectors or sharp transmission filters out of these structures. Adjusting the thickness also affects its deformability, making it possible to make broadband mirrors compliant to acoustic waves. Altering the hole shape, for example by introducing an asymmetry, extends the functionalities of photonic-crystal slabs even further. Breaking the symmetry by introducing asymmetric holes enables polarization-sensitive devices such as retarders, polarization beam splitters, and photonic crystals with additional non-degenerate resonances useful for increased sensitivity in sensors. All these practical advantages of photonic-crystal slabs makes them suitable as key components in micromachined sensor applications. We report one such example of an application of photonic-crystal slabs in the form of a micromachined acoustic sensor. It consists of a Fabry-Perot interferometer made of a photonic-crystal

  10. Self-assembled tunable photonic hyper-crystals.

    PubMed

    Smolyaninova, Vera N; Yost, Bradley; Lahneman, David; Narimanov, Evgenii E; Smolyaninov, Igor I

    2014-01-01

    We demonstrate a novel artificial optical material, the "photonic hyper-crystal", which combines the most interesting features of hyperbolic metamaterials and photonic crystals. Similar to hyperbolic metamaterials, photonic hyper-crystals exhibit broadband divergence in their photonic density of states due to the lack of usual diffraction limit on the photon wave vector. On the other hand, similar to photonic crystals, hyperbolic dispersion law of extraordinary photons is modulated by forbidden gaps near the boundaries of photonic Brillouin zones. Three dimensional self-assembly of photonic hyper-crystals has been achieved by application of external magnetic field to a cobalt nanoparticle-based ferrofluid. Unique spectral properties of photonic hyper-crystals lead to extreme sensitivity of the material to monolayer coatings of cobalt nanoparticles, which should find numerous applications in biological and chemical sensing. PMID:25027947

  11. Self-assembled tunable photonic hyper-crystals

    NASA Astrophysics Data System (ADS)

    Smolyaninova, Vera N.; Yost, Bradley; Lahneman, David; Gresock, Thomas; Narimanov, Evgenii E.; Smolyaninov, Igor I.

    2014-09-01

    We demonstrate a novel artificial optical material, the "photonic hyper-crystal", which combines the most interesting features of hyperbolic metamaterials and photonic crystals. Similar to hyperbolic metamaterials, photonic hyper-crystals exhibit broadband divergence in their photonic density of states due to the lack of usual diffraction limit on the photon wave vector. On the other hand, similar to photonic crystals, hyperbolic dispersion law of extraordinary photons is modulated by forbidden gaps near the boundaries of photonic Brillouin zones. Three dimensional self-assembly of photonic hyper-crystals has been achieved by application of external magnetic field to a cobalt nanoparticle-based ferrofluid. Unique spectral properties of photonic hyper-crystals lead to extreme sensitivity of the material to monolayer coatings of cobalt nanoparticles, which should find numerous applications in biological and chemical sensing.

  12. Self-assembled tunable photonic hyper-crystals

    NASA Astrophysics Data System (ADS)

    Smolyaninova, Vera N.; Yost, Bradley; Lahneman, David; Narimanov, Evgenii E.; Smolyaninov, Igor I.

    2014-07-01

    We demonstrate a novel artificial optical material, the ``photonic hyper-crystal'', which combines the most interesting features of hyperbolic metamaterials and photonic crystals. Similar to hyperbolic metamaterials, photonic hyper-crystals exhibit broadband divergence in their photonic density of states due to the lack of usual diffraction limit on the photon wave vector. On the other hand, similar to photonic crystals, hyperbolic dispersion law of extraordinary photons is modulated by forbidden gaps near the boundaries of photonic Brillouin zones. Three dimensional self-assembly of photonic hyper-crystals has been achieved by application of external magnetic field to a cobalt nanoparticle-based ferrofluid. Unique spectral properties of photonic hyper-crystals lead to extreme sensitivity of the material to monolayer coatings of cobalt nanoparticles, which should find numerous applications in biological and chemical sensing.

  13. Assembly of optical-scale dumbbells into dense photonic crystals.

    PubMed

    Forster, Jason D; Park, Jin-Gyu; Mittal, Manish; Noh, Heeso; Schreck, Carl F; O'Hern, Corey S; Cao, Hui; Furst, Eric M; Dufresne, Eric R

    2011-08-23

    We describe the self-assembly of nonspherical particles into crystals with novel structure and optical properties combining a partial photonic band gap with birefringence that can be modulated by an external field or quenched by solvent evaporation. Specifically, we study symmetric optical-scale polymer dumbbells with an aspect ratio of 1.58. Hard particles with this geometry have been predicted to crystallize in equilibrium at high concentrations. However, unlike spherical particles, which readily crystallize in the bulk, previous experiments have shown that these dumbbells crystallize only under strong confinement. Here, we demonstrate the use of an external electric field to align and assemble the dumbbells to make a birefringent suspension with structural color. When the electric field is turned off, the dumbbells rapidly lose their orientational order and the color and birefringence quickly go away. In this way, dumbbells combine the structural color of photonic crystals with the field addressability of liquid crystals. In addition, we find that if the solvent is removed in the presence of an electric field, the particles self-assemble into a novel, dense crystalline packing hundreds of particles thick. Analysis of the crystal structure indicates that the dumbbells have a packing fraction of 0.7862, higher than the densest known packings of spheres and ellipsoids. We perform numerical experiments to more generally demonstrate the importance of controlling the orientation of anisotropic particles during a concentration quench to achieve long-range order.

  14. Fabrication and Analysis of Photonic Crystals

    ERIC Educational Resources Information Center

    Campbell, Dean J.; Korte, Kylee E.; Xia, Younan

    2007-01-01

    These laboratory experiments are designed to explore aspects of nanoscale chemistry by constructing and spectroscopically analyzing thin films of photonic crystals. Films comprised of colloidal spheres and polydimethylsiloxane exhibit diffraction-based stop bands that shift reversibly upon exposure to some common solvents. Topics covered in these…

  15. Visible stealth materials based on photonic crystals

    NASA Astrophysics Data System (ADS)

    Yao, Guozheng; Liu, Ying

    2014-08-01

    Optical thin film can be used for invisible cloak. As a kind of low-dimension photonic crystal, it is a candidate for metamaterial with designed Σ and μ. As a coating, it is convenient to be stacked to mimic continuous changing of electromagnetic media. Anti-reflection film is suitable for matching coating between layers of media.

  16. A liquid crystal adaptive lens

    NASA Technical Reports Server (NTRS)

    Kowel, S. T.; Cleverly, D.

    1981-01-01

    Creation of an electronically controlled liquid crystal lens for use as a focusing mechanism in a multi-element lens system or as an adaptive optical element is analyzed. Varying the index of refraction is shown to be equivalent to the shaping of a solid refracting material. Basic characteristics of liquid crystals, essential for the creation of a lens, are reviewed. The required variation of index of refraction is provided by choosing appropriate electrode voltages. The configuration required for any incoming polarization is given and its theoretical performance in terms of modulation transfer function derived.

  17. Liquid crystal Fresnel lens display

    NASA Astrophysics Data System (ADS)

    Wang, Xiao-Qian; Abhishek Kumar, Srivastava; Alwin Tam, Ming-Wai; Zheng, Zhi-Gang; Shen, Dong; Vladimir, Chigrinov G.; Kwok, Hoi-Sing

    2016-09-01

    A novel see-through display with a liquid crystal lens array was proposed. A liquid crystal Fresnel lens display (LCFLD) with a holographic screen was demonstrated. The proposed display system has high efficiency, simple fabrication, and low manufacturing cost due to the absence of a polarizer and color filter. Project supported by Partner State Key Laboratory on Advanced Displays and Optoelectronics Technologies HKUST, China, the National Natural Science Foundation of China (Grant Nos. 61435008 and 61575063), and the Fundamental Research Funds for the Central Universities, China (Grant No. WM1514036).

  18. Liquid crystal Fresnel lens display

    NASA Astrophysics Data System (ADS)

    Wang, Xiao-Qian; Abhishek Kumar, Srivastava; Alwin Tam, Ming-Wai; Zheng, Zhi-Gang; Shen, Dong; Vladimir, Chigrinov G.; Kwok, Hoi-Sing

    2016-09-01

    A novel see-through display with a liquid crystal lens array was proposed. A liquid crystal Fresnel lens display (LCFLD) with a holographic screen was demonstrated. The proposed display system has high efficiency, simple fabrication, and low manufacturing cost due to the absence of a polarizer and color filter. Project supported by Partner State Key Laboratory on Advanced Displays and Optoelectronics Technologies HKUST, China, the National Natural Science Foundation of China (Grant Nos. 61435008 and 61575063), and the Fundamental Research Funds for the Central Universities, China (Grant No. WM1514036).

  19. Ionic Liquid Crystals: Versatile Materials.

    PubMed

    Goossens, Karel; Lava, Kathleen; Bielawski, Christopher W; Binnemans, Koen

    2016-04-27

    This Review covers the recent developments (2005-2015) in the design, synthesis, characterization, and application of thermotropic ionic liquid crystals. It was designed to give a comprehensive overview of the "state-of-the-art" in the field. The discussion is focused on low molar mass and dendrimeric thermotropic ionic mesogens, as well as selected metal-containing compounds (metallomesogens), but some references to polymeric and/or lyotropic ionic liquid crystals and particularly to ionic liquids will also be provided. Although zwitterionic and mesoionic mesogens are also treated to some extent, emphasis will be directed toward liquid-crystalline materials consisting of organic cations and organic/inorganic anions that are not covalently bound but interact via electrostatic and other noncovalent interactions.

  20. Quasicompactons in inverted nonlinear photonic crystals

    SciTech Connect

    Li Yongyao; Malomed, Boris A.; Wu Jianxiong; Pang Wei; Wang Sicong; Zhou Jianying

    2011-10-15

    We study large-amplitude one-dimensional solitary waves in photonic crystals featuring competition between linear and nonlinear lattices, with minima of the linear potential coinciding with maxima of the nonlinear pseudopotential, and vice versa (inverted nonlinear photonic crystals, INPCs), in the case of the saturable self-focusing nonlinearity. Such crystals were recently fabricated using a mixture of SU-8 and Rhodamine-B optical materials. By means of numerical methods and analytical approximations, we find that large-amplitude solitons are broad sharply localized stable pulses (quasicompactons, QCs). With the increase of the total power, P, the QC's centroid performs multiple switchings between minima and maxima of the linear potential. Unlike cubic INPCs, the large-amplitude solitons are mobile in the medium with the saturable nonlinearity. The threshold value of the kick necessary to set the soliton in motion is found as a function of P. Collisions between moving QCs are considered too.

  1. Optical tuning of three-dimensional photonic crystals fabricated by femtosecond direct writing

    NASA Astrophysics Data System (ADS)

    McPhail, Dennis; Straub, Martin; Gu, Min

    2005-08-01

    In this letter, we report on an optically tunable three-dimensional photonic crystal that exhibits main gaps in the 3-4μm range. The photonic crystal is manufactured via a femtosecond direct writing technique. Optical tuning is achieved by a luminary polling technique with a low-power polarized laser beam. The refractive index variation resulting from liquid-crystal rotation causes a shift in the photonic band gap of up to 65 nm with an extinction of transmission of up to 70% in the stacking direction. Unlike other liquid-crystal tuning techniques where a pregenerated structure is infiltrated, this optical tuning method is a one-step process that allows arbitrary structures to be written into a solid liquid-crystal-polymer composite and leads to a high dielectric contrast.

  2. Self-assembled tunable photonic hyper-crystals

    PubMed Central

    Smolyaninova, Vera N.; Yost, Bradley; Lahneman, David; Narimanov, Evgenii E.; Smolyaninov, Igor I.

    2014-01-01

    We demonstrate a novel artificial optical material, the “photonic hyper-crystal”, which combines the most interesting features of hyperbolic metamaterials and photonic crystals. Similar to hyperbolic metamaterials, photonic hyper-crystals exhibit broadband divergence in their photonic density of states due to the lack of usual diffraction limit on the photon wave vector. On the other hand, similar to photonic crystals, hyperbolic dispersion law of extraordinary photons is modulated by forbidden gaps near the boundaries of photonic Brillouin zones. Three dimensional self-assembly of photonic hyper-crystals has been achieved by application of external magnetic field to a cobalt nanoparticle-based ferrofluid. Unique spectral properties of photonic hyper-crystals lead to extreme sensitivity of the material to monolayer coatings of cobalt nanoparticles, which should find numerous applications in biological and chemical sensing. PMID:25027947

  3. Copper sulfate: Liquid or crystals?

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Two separate experiments were conducted to evaluate copper toxicity to channel catfish and free-swimming Ichthyophthirius multifiliis or Ich (the stage of Ich that can be treated); the compounds we used were CuSO4 crystals and a non-chelated liquid CuSO4 product. In 96 hr tests conducted in aquaria...

  4. Liquid-Crystal Optical Correlator

    NASA Technical Reports Server (NTRS)

    Liu, Hua-Kuang

    1989-01-01

    Optical correlator uses commercially-available liquid-crystal television (LCTV) screen as spatial light modulator. Correlations with this device done at video frame rates, making such operations as bar-code recognition possible at reasonable cost. With further development, such correlator useful in automation, robotic vision, and optical image processing.

  5. Experiments with Cholesteric Liquid Crystals

    ERIC Educational Resources Information Center

    Fergason, James L.

    1970-01-01

    Describes laboratory experiments designed to demonstrate (1) the properties of cholesteric liquid crystals, (2) thermal mapping, (3) thermal diffusivity, (4) adiabatic expansion of rubber, and (5) measurement of radiated energy by a point source. Contains all of the information on materials and apparatus needed to perform the experiments.…

  6. Flexible single-crystal silicon nanomembrane photonic crystal cavity.

    PubMed

    Xu, Xiaochuan; Subbaraman, Harish; Chakravarty, Swapnajit; Hosseini, Amir; Covey, John; Yu, Yalin; Kwong, David; Zhang, Yang; Lai, Wei-Cheng; Zou, Yi; Lu, Nanshu; Chen, Ray T

    2014-12-23

    Flexible inorganic electronic devices promise numerous applications, especially in fields that could not be covered satisfactorily by conventional rigid devices. Benefits on a similar scale are also foreseeable for silicon photonic components. However, the difficulty in transferring intricate silicon photonic devices has deterred widespread development. In this paper, we demonstrate a flexible single-crystal silicon nanomembrane photonic crystal microcavity through a bonding and substrate removal approach. The transferred cavity shows a quality factor of 2.2×10(4) and could be bent to a curvature of 5 mm radius without deteriorating the performance compared to its counterparts on rigid substrates. A thorough characterization of the device reveals that the resonant wavelength is a linear function of the bending-induced strain. The device also shows a curvature-independent sensitivity to the ambient index variation.

  7. The bifoil photodyne: a photonic crystal oscillator

    NASA Astrophysics Data System (ADS)

    Lugo, J. E.; Doti, R.; Sanchez, N.; de La Mora, M. B.; Del Rio, J. A.; Faubert, J.

    2014-01-01

    Optical tweezers is an example how to use light to generate a physical force. They have been used to levitate viruses, bacteria, cells, and sub cellular organisms. Nonetheless it would be beneficial to use such force to develop a new kind of applications. However the radiation pressure usually is small to think in moving larger objects. Currently, there is some research investigating novel photonic working principles to generate a higher force. Here, we studied theoretically and experimentally the induction of electromagnetic forces in one-dimensional photonic crystals when light impinges on the off-axis direction. The photonic structure consists of a micro-cavity like structure formed of two one-dimensional photonic crystals made of free-standing porous silicon, separated by a variable air gap and the working wavelength is 633 nm. We show experimental evidence of this force when the photonic structure is capable of making auto-oscillations and forced-oscillations. We measured peak displacements and velocities ranging from 2 up to 35 microns and 0.4 up to 2.1 mm/s with a power of 13 mW. Recent evidence showed that giant resonant light forces could induce average velocity values of 0.45 mm/s in microspheres embedded in water with 43 mW light power.

  8. The bifoil photodyne: a photonic crystal oscillator.

    PubMed

    Lugo, J E; Doti, R; Sanchez, N; de la Mora, M B; del Rio, J A; Faubert, J

    2014-01-15

    Optical tweezers is an example how to use light to generate a physical force. They have been used to levitate viruses, bacteria, cells, and sub cellular organisms. Nonetheless it would be beneficial to use such force to develop a new kind of applications. However the radiation pressure usually is small to think in moving larger objects. Currently, there is some research investigating novel photonic working principles to generate a higher force. Here, we studied theoretically and experimentally the induction of electromagnetic forces in one-dimensional photonic crystals when light impinges on the off-axis direction. The photonic structure consists of a micro-cavity like structure formed of two one-dimensional photonic crystals made of free-standing porous silicon, separated by a variable air gap and the working wavelength is 633 nm. We show experimental evidence of this force when the photonic structure is capable of making auto-oscillations and forced-oscillations. We measured peak displacements and velocities ranging from 2 up to 35 microns and 0.4 up to 2.1 mm/s with a power of 13 mW. Recent evidence showed that giant resonant light forces could induce average velocity values of 0.45 mm/s in microspheres embedded in water with 43 mW light power.

  9. The bifoil photodyne: a photonic crystal oscillator

    PubMed Central

    Lugo, J. E.; Doti, R.; Sanchez, N.; de la Mora, M. B.; del Rio, J. A.; Faubert, J.

    2014-01-01

    Optical tweezers is an example how to use light to generate a physical force. They have been used to levitate viruses, bacteria, cells, and sub cellular organisms. Nonetheless it would be beneficial to use such force to develop a new kind of applications. However the radiation pressure usually is small to think in moving larger objects. Currently, there is some research investigating novel photonic working principles to generate a higher force. Here, we studied theoretically and experimentally the induction of electromagnetic forces in one-dimensional photonic crystals when light impinges on the off-axis direction. The photonic structure consists of a micro-cavity like structure formed of two one-dimensional photonic crystals made of free-standing porous silicon, separated by a variable air gap and the working wavelength is 633 nm. We show experimental evidence of this force when the photonic structure is capable of making auto-oscillations and forced-oscillations. We measured peak displacements and velocities ranging from 2 up to 35 microns and 0.4 up to 2.1 mm/s with a power of 13 mW. Recent evidence showed that giant resonant light forces could induce average velocity values of 0.45 mm/s in microspheres embedded in water with 43 mW light power. PMID:24423985

  10. Defect modes of chiral photonic crystals with an isotropic defect

    NASA Astrophysics Data System (ADS)

    Gevorgyan, A. H.; Oganesyan, K. B.

    2011-06-01

    Specific features of the defect modes of cholesteric liquid crystals (CLCs) with an isotropic defect, as well as their photonic density of states, Q factor, and emission, have been investigated. The effect of the thicknesses of the defect layer and the system as a whole, the position of the defect layer, and the dielectric boundaries on the features of the defect modes have been analyzed. It is shown that when the CLC layer is thin the density of states and emission intensity are maximum for the defect mode, whereas when the CLC layer is thick, these peaks are observed at the edges of the photonic band gap. Similarly, when the gain is low, the density of states and emission intensity are maximum for the defect mode, whereas at high gains these peaks are also observed at the edges of the photonic band gap. The possibilities of low-threshold lasing and obtaining high- Q microcavities have been investigated.

  11. Photonic crystal slab quantum cascade detector

    NASA Astrophysics Data System (ADS)

    Reininger, Peter; Schwarz, Benedikt; Harrer, Andreas; Zederbauer, Tobias; Detz, Hermann; Maxwell Andrews, Aaron; Gansch, Roman; Schrenk, Werner; Strasser, Gottfried

    2013-12-01

    In this Letter, we demonstrate the design, fabrication, and characterization of a photonic crystal slab quantum cascade detector (PCS-QCD). By employing a specifically designed resonant cavity, the performance of the photodetector is improved in three distinct ways. The PCS makes the QCD sensitive to surface normal incident light. It resonantly enhances the photon lifetime inside the active zone, thus increasing the photocurrent significantly. And, the construction form of the device inherently decreases the noise. Finally, we compare the characteristics of the PCS-QCD to a PCS - quantum well infrared photodetector and outline the advantages for certain fields of applications.

  12. Photonic crystal slab quantum cascade detector

    SciTech Connect

    Reininger, Peter Schwarz, Benedikt; Harrer, Andreas; Zederbauer, Tobias; Detz, Hermann; Maxwell Andrews, Aaron; Gansch, Roman; Schrenk, Werner; Strasser, Gottfried

    2013-12-09

    In this Letter, we demonstrate the design, fabrication, and characterization of a photonic crystal slab quantum cascade detector (PCS-QCD). By employing a specifically designed resonant cavity, the performance of the photodetector is improved in three distinct ways. The PCS makes the QCD sensitive to surface normal incident light. It resonantly enhances the photon lifetime inside the active zone, thus increasing the photocurrent significantly. And, the construction form of the device inherently decreases the noise. Finally, we compare the characteristics of the PCS-QCD to a PCS - quantum well infrared photodetector and outline the advantages for certain fields of applications.

  13. Photonic crystal electro-optical switching cell

    NASA Astrophysics Data System (ADS)

    Lima, A. Wirth; Sombra, A. S. B.

    2012-06-01

    We investigated the physical mechanism of a photonic crystal (PhC) switching cell based on an optical directional coupler (ODC). This ODC is driven by a low power external electrical command signal, inserted in the central coupling region, which causes the changes in the refractive index. The switching process is based on the change of the bar state to the cross state owing to the external command signal. In our simulations we used the following methods: Plane Wave Expansion by MPB (MIT Photonic-Bands), Finite-Difference Time-Domain by MEEP (MIT Electromagnetic Equation Propagation), Finite Element by COMSOL Multiphysics and our own Binary Propagation Method.

  14. Breakdown of Bose-Einstein Distribution in Photonic Crystals

    PubMed Central

    Lo, Ping-Yuan; Xiong, Heng-Na; Zhang, Wei-Min

    2015-01-01

    In the last two decades, considerable advances have been made in the investigation of nano-photonics in photonic crystals. Previous theoretical investigations of photon dynamics were carried out at zero temperature. Here, we investigate micro/nano cavity photonics in photonic crystals at finite temperature. Due to photonic-band-gap-induced localized long-lived photon dynamics, we discover that cavity photons in photonic crystals do not obey Bose-Einstein statistical distribution. Within the photonic band gap and in the vicinity of the band edge, cavity photons combine the long-lived non-Markovain dynamics with thermal fluctuations together to form photon states that memorize the initial cavity state information. As a result, Bose-Einstein distribution is completely broken down in these regimes, even if the thermal energy is larger or much larger than the cavity detuning energy. In this investigation, a crossover phenomenon from equilibrium to nonequilibrium steady states is also revealed. PMID:25822135

  15. Breakdown of Bose-Einstein distribution in photonic crystals.

    PubMed

    Lo, Ping-Yuan; Xiong, Heng-Na; Zhang, Wei-Min

    2015-01-01

    In the last two decades, considerable advances have been made in the investigation of nano-photonics in photonic crystals. Previous theoretical investigations of photon dynamics were carried out at zero temperature. Here, we investigate micro/nano cavity photonics in photonic crystals at finite temperature. Due to photonic-band-gap-induced localized long-lived photon dynamics, we discover that cavity photons in photonic crystals do not obey Bose-Einstein statistical distribution. Within the photonic band gap and in the vicinity of the band edge, cavity photons combine the long-lived non-Markovain dynamics with thermal fluctuations together to form photon states that memorize the initial cavity state information. As a result, Bose-Einstein distribution is completely broken down in these regimes, even if the thermal energy is larger or much larger than the cavity detuning energy. In this investigation, a crossover phenomenon from equilibrium to nonequilibrium steady states is also revealed.

  16. Orthoconic liquid crystals--a case study.

    PubMed

    Lagerwall, Sven T

    2014-06-01

    Since the early investigations on liquid crystals it was realized how the confining surfaces often determine the textures and even properties of the material. This influence is particularly complex and important for chiral materials. When we come to chiral smectics the surfaces may have dramatic effects. These are illustrated on the ferroelectric liquid crystals; they then again increase in importance for the antiferroelectric liquid crystals where the most recent example is given by the orthoconic liquid crystals.

  17. Liquid crystal polyester thermosets

    DOEpatents

    Benicewicz, Brian C.; Hoyt, Andrea E.

    1992-01-01

    The present invention provides (1) curable liquid crystalline polyester monomers represented by the formula: R.sup.1 --A.sup.1 --B.sup.1 --A.sup.2 --B.sup.2 --A.sup.3 --R.sup.2 where R.sup.1 and R.sup.2 are radicals selected from the group consisting of maleimide, substituted maleimide, nadimide, substituted naimide, ethynyl, and (C(R.sup.3).sub.2).sub.2 where R.sup.3 is hydrogen with the proviso that the two carbon atoms of (C(R.sup.3).sub.2).sub.2 are bound on the aromatic ring of A.sup.1 or A.sup.3 to adjacent carbon atoms, A.sup.1 and A.sup.3 are 1,4-phenylene and the same where said group contains one or more substituents selected from the group consisting of halo, e.g., fluoro, chloro, bromo, or iodo, nitro lower alkyl, e.g., methyl, ethyl, or propyl, alkoxy, e.g., methoxy, ethoxy, or propoxy, and fluoroalkyl, e.g., trifluoromethyl, pentafluoroethyl and the like, A.sup.2 is selected from the group consisting of 1,4-phenylene, 4,4'-biphenyl, 2,6-naphthylene and the same where said groups contain one or more substituents selected from the group consisting of halo, e.g., fluoro, chloro, bromo, or iodo, nitro, lower alkyl, e.g., methyl, ethyl, and propyl, lower alkoxy, e.g., methoxy, ethoxy, or propoxy, and fluoroalkyl or fluoroalkoxy, e.g., trifluoromethyl, pentafluoroethyl and the like, and B.sup.1 and B.sup.2 are selected from the group consisting of --C(O)--O-- and --O--C(O)--, (2) thermoset liquid crystalline polyester compositions comprised of heat-cured segments derived from monomers represented by the formula: R.sup.1 --A.sup.1 --B.sup.1 --A.sup.2 --B.sup.2 --A.sup.3 --R.sup.2 as described above, (3) curable blends of at least two of the polyester monomers and (4) processes of preparing the curable liquid crystalline polyester monomers.

  18. UV sensors based on liquid crystals mixtures

    NASA Astrophysics Data System (ADS)

    Chanishvili, Andro; Petriashvili, Gia; Chilaya, Guram; Barberi, Riccardo; De Santo, Maria P.; Matranga, Mario A.; Ciuchi, F.

    2006-04-01

    The Erythemal Response Spectrum is a scientific expression that describes the sensitivity of the skin to the ultraviolet radiation. The skin sensitivity strongly depends on the UV wavelength: a long exposition to UV radiation causes erythema once a threshold dose has been exceeded. In the past years several devices have been developed in order to monitor the UV exposure, most of them are based on inorganic materials that are able to mimic the human skin behaviour under UV radiation. We present a new device based on liquid crystals technology. The sensor is based on a liquid crystalline mixture that absorbs photons at UV wavelength and emits them at a longer one. This system presents several innovative features: the absorption range of the mixture can be varied to be sensitive to different wavelengths, the luminescence intensity can be tuned, the system can be implemented on flexible devices.

  19. Liquid Crystals: The Phase of the Future.

    ERIC Educational Resources Information Center

    Ondris-Crawford, Renate; And Others

    1992-01-01

    Liquid crystal displays are currently utilized to convey information via graphic displays. Presents experiments and explanations that employ the concept of liquid crystals to learn concepts related to the various states of matter, electric and magnetic forces, refraction of light, and optics. Discusses applications of liquid crystal technology.…

  20. Amplifying magneto-optical photonic crystal

    NASA Astrophysics Data System (ADS)

    Grishin, A. M.

    2010-08-01

    We modeled transmission and Faraday rotation characteristics of Er-doped all-garnet [Bi3Fe5O12/Gd3Ga5O12]m photonic crystals in view of their application in C-band magneto-optical amplifiers. It is found that 48 layered 11.4 μm thick crystal at λ =1532 nm provides 45° Faraday rotation and transmission as high as 85% being pumped with 100 mW/980 nm solid state laser diode.

  1. Transmission character of general function photonic crystals

    NASA Astrophysics Data System (ADS)

    Wu, Xiang-Yao; Zhang, Bo-Jun; Yang, Jing-Hai; Zhang, Si-Qi; Liu, Xiao-Jing; Wang, Jing; Ba, Nuo; Hua, Zhong; Yin, Xin-Guo

    2012-08-01

    In the paper, we present a new general function photonic crystals (GFPCs), whose refractive index of medium is a arbitrary function of space position. Unlike conventional photonic crystals (PCs), whose structure grows from two mediums A and B, with different constant refractive indexes na and nb. Based on the Fermat principle, we give the motion equations of light in one-dimensional GFPCs, and calculate its transfer matrix, which is different from the conventional PCs. We choose the linearity refractive index function for two mediums A and B, and find the transmissivity of one-dimensional GFPCs can be much larger or smaller than 1 for different slope linearity refractive index functions, which are different from the transmissivity of conventional PCs (its transmissivity is in the range of 0 and 1). Otherwise, we study the effect of different incident angles, the number of periods and optical thickness on the transmissivity, and obtain some new results different from the conventional PCs.

  2. Photonic Crystal Geometry for Organic Solar Cells

    NASA Astrophysics Data System (ADS)

    Samulski, Edward; Lopez, Rene; Ko, Doo-Hyun; Tumbleston, John

    2010-03-01

    Efficient absorption of light calls for thicker PV active layers whereas carrier transport always benefits from thinner ones, and this dichotomy is at the heart of an efficiency/cost conundrum that has kept solar energy expensive relative to fossil fuels. We report a 2-D, photonic crystal morphology that enhances the efficiency of organic photovoltaic cells relative to conventional planar cells.[1] The morphology is developed by patterning an organic photoactive bulk heterojunction blend using PRINT a process that lends itself to large area fabrication of nanostructures.[2] The photonic crystal cell morphology increases photocurrents generally, and particularly through the excitation of resonant modes near the band edge of the organic PV material. [1] Ko, D.-H.; Tumbleston, J. R.; Zhang, L.; Williams, S.; DeSimone, J. M.; Rene, L.; Samulski, E. T. Nano Lett. 2009, 9, 2742--2746. [2] Hampton et al. Adv. Mater. 2008, 20, 2667.

  3. Erbium doped tellurite photonic crystal optical fiber

    NASA Astrophysics Data System (ADS)

    Osorio, Sergio P.; Fernandez, Enver; Rodriguez, Eugenio; Cesar, Carlos L.; Barbosa, Luiz C.

    2005-04-01

    In this work we present the fabrication of tellurite glass photonic crystal fiber doped with a very large erbium concentration. Tellurite glasses are important hosts for rare earth ions due to its very high solubility, which allows up to 10,000 ppm Er3+ concentrations. The photonic crystal optical fibers and tellurite glasses can be, therefore, combined in an efficient way to produce doped fibers for large bandwidth optical amplifiers. The preform was made of a 10 mm external diameter tellurite tube filled with an array of non-periodic tellurite capillaries and an erbium-doped telluride rod that constitute the fiber core. The preform was drawn in a Heathway Drawing Tower, producing fibers with diameters between 120 - 140 μm. We show optical microscope photography of the fiber"s transverse section. The ASE spectra obtained with a spectra analyzer show a red shift as the length of the optical fiber increases.

  4. A tunable microwave plasma photonic crystal filter

    SciTech Connect

    Wang, B.; Cappelli, M. A.

    2015-10-26

    The integration of gaseous plasma elements into a microwave photonic crystal band gap cavity structure allows for active tuning of the device. An alumina rod array microwave photonic crystal waveguide resonator is simulated and characterized through finite difference time domain methods. A gaseous plasma element is integrated into the cavity structure and the effect of plasma density on the transmission properties of the structure is investigated. We show, through both simulations and experiments, that the permittivity of the plasma can be adjusted to shift the peak resonance to allow for both switching and tunability of transmission. The experimentally measured peak shifts in transmission are compared to those simulated and the electron density of the gaseous plasma element is calculated and compared to values determined from the measured discharge current density.

  5. Nonreciprocal photonic crystal add-drop filter

    NASA Astrophysics Data System (ADS)

    Tao, Keyu; Xiao, Jun-Jun; Yin, Xiaobo

    2014-11-01

    We present a versatile add-drop integrated photonic filter (ADF) consisting of nonreciprocal waveguides in which the propagation of light is restricted in one predetermined direction. With the bus and add/drop waveguides symmetrically coupled through a cavity, the four-port device allows each individual port to add and/or drop a signal of the same frequency. The scheme is general and we demonstrate the nonreciprocal ADF with magneto-optical photonic crystals. The filter is immune to waveguide defects, allowing straightforward implementation of multi-channel ADFs by cascading the four-port designs. The results should find applications in wavelength-division multiplexing and related integrated photonic techniques.

  6. Nonreciprocal photonic crystal add-drop filter

    SciTech Connect

    Tao, Keyu; Xiao, Jun-Jun; Yin, Xiaobo

    2014-11-24

    We present a versatile add-drop integrated photonic filter (ADF) consisting of nonreciprocal waveguides in which the propagation of light is restricted in one predetermined direction. With the bus and add/drop waveguides symmetrically coupled through a cavity, the four-port device allows each individual port to add and/or drop a signal of the same frequency. The scheme is general and we demonstrate the nonreciprocal ADF with magneto-optical photonic crystals. The filter is immune to waveguide defects, allowing straightforward implementation of multi-channel ADFs by cascading the four-port designs. The results should find applications in wavelength-division multiplexing and related integrated photonic techniques.

  7. Photonic Crystal Microcavities for Quantum Information Science

    NASA Astrophysics Data System (ADS)

    Hagemeier, Jenna Nicole

    Quantum information science and technology is a broad and fascinating field, encompassing diverse research areas such as materials science, atomic physics, superconductors, solid-state physics, and photonics. A goal of this field is to demonstrate the basic functions of information initialization, manipulation, and read-out in systems that take advantage of quantum physics to greatly enhance computing performance capabilities. In a hybrid quantum information network, different systems are used to perform different functions, to best exploit the advantageous properties of each system. For example, matter quantum bits (qubits) can be used for local data storage and manipulation while photonic qubits can be used for long-distance communication between storage points of the network. Our research focuses on the following two solid-state realizations of a matter qubit for the purpose of building such a hybrid quantum network: the electronic spin of a self-assembled indium arsenide quantum dot and the electronic spin of a nitrogen-vacancy defect center in diamond. Light--matter interactions are necessary to transfer the information from the matter qubit to the photonic qubit, and this interaction can be enhanced by embedding the spin system in an optical cavity. We focus on photonic crystal microcavities for this purpose, and we study interactions between the optical cavity modes and incorporated spin systems. To improve the performance of this spin--photon interface, it is important to maximize the coupling strength between the spin and photonic systems and to increase the read-out efficiency of information stored in the cavity. In this thesis, we present our work to deterministically couple a nitrogen-vacancy center in diamond to a photonic crystal microcavity in gallium phosphide. This is achieved by nanopositioning a pre-selected diamond nanocrystal in the intensity maximum of the optical cavity mode. We also present an optimized design of a photonic crystal

  8. Multifrequency gap solitons in nonlinear photonic crystals.

    PubMed

    Xie, Ping; Zhang, Zhao-Qing

    2003-11-21

    We predict the existence of multifrequency gap solitons (MFGSs) in both one- and two-dimensional nonlinear photonic crystals. A MFGS is a single intrinsic mode possessing multiple frequencies inside the gap. Its existence is a result of synergic nonlinear coupling among solitons or soliton trains at different frequencies. Its formation can either lower the threshold fields of the respective frequency components or stabilize their excitations. These MFGSs form a new class of stable gap solitons.

  9. Photocurrent response from photonic crystal defect modes.

    PubMed

    Schartner, Stephan; Nobile, Michele; Schrenk, Werner; Andrews, Aaron M; Klang, Pavel; Strasser, Gottfried

    2008-03-31

    The authors use a quantum well intersubband photodetector fabricated into a two dimensional photonic crystal to investigate the optical defect modes of a single missing hole defect. The modes appear as a local enhancement in spectral photocurrent due to an increased in-coupling of surface incident light when a defect mode is present. The frequencies of these localized modes are tracked as they are varied by the defect geometry and compared to simulations. PMID:18542578

  10. Luminescent Magneto-Optical Photonic Crystals

    NASA Astrophysics Data System (ADS)

    Grishin, A. M.; Khartsev, S. I.

    2012-03-01

    We compare luminescent properties of several Er-doped garnet films as building blocks in all-garnet heteroepitaxial magneto-optical photonic crystals: La3Ga5O12, Gd3Ga5O12, Y3Fe5O12, Bi3Fe5O12, and Bi2.97Er0.03Fe4Al0.5Ga0.5O12. Er substituents on the dodecahedral lattice sites do not decrease giant Faraday rotation in Bi3Fe5O12 garnet; meanwhile providing intense room temperature C-band photoluminescence (PL). Fe3+ ion works as a sensitizer for Er resulting in fivefold PL enhancement in iron garnets compared to gallium ones. PL lifetime in gallium garnets is in millisecond range reaching 6 ms in Gd2.9Er0.1Ga5O12. The first luminescent one-dimensional heteroepitaxial all-garnet magneto-optical (MO) photonic crystal was composed from diamagnetic Sm3Ga5O12 and MO-active Bi2.97Er0.03Al0.5Ga0.5O12 garnet layers by rf-magnetron sputtering on Gd3Ga5O12(111) substrate. Substitution of ferric ions by aluminum and gallium improved transparency and induced perpendicular anisotropy in pure Bi3Fe5O12. Photonic crystals owned a record high magneto-optical quality and a latching type (magnetic remnant) Faraday rotation (FR). At the resonance wavelength 775 nm, specific FR θF = - 14.1 deg/μm and MO-quality factor Q = 99.3 deg represent the highest MO performance achieved so far. Long-lived near-IR luminescence in Er substituted gallium and iron garnet layers used both as Bragg mirrors and microcavities promises magneto-optical photonic crystals to become an active lasing medium.

  11. Electromagnetic waves: Negative refraction by photonic crystals

    NASA Astrophysics Data System (ADS)

    Ozbay, Ekmel

    2004-03-01

    Recently left-handed materials (LHM) attracted great attention since these materials exhibit negative effective index, which is due to simultaneously negative permeability and permittivity. Pendry proposed that negative effective index in left-handed materials can be used for constructing a perfect lens, which is not limited by diffraction(J. B. Pendry, Negative refraction makes a perfect lens, Phys. Rev. Lett. vol. 85, 3966 (2000)). Negative refraction is also achievable in a dielectric photonic crystal (PC) that has a periodically modulated positive permittivity and a permeability of unity. Luo et al. has studied negative refraction and subwavelength imaging in photonic crystals(C. Luo, S. G. Johnson, J. D. Joannopoulos, J. B. Pendry, Subwavelength Imaging in Photonic Crystals Phys. Rev. B 68, 045115 (2003)). In this presentation, we report our experimental and theoretical investigation of negative refraction and subwavelength focusing of electromagnetic waves in a 2D PC. Our structure consists of a square array of dielectric rods in air. Transmission measurements are performed for experimentally verifying the predicted negative refraction behavior in our structure. Negative index of refraction determined from the experiment is -1.94 which is very close to the theoretical value of -2.06. Negative refraction is observed for the incidence angles of > 20°(Ertugrul Cubukcu, Koray Aydin, Ekmel Ozbay, S. Foteinopolou, and Costas Soukoulis, Negative Refraction by Photonic Crystals, Nature, vol. 423, 604 (2003)). Since we know the optimum frequency for a broad angle negative refraction, we can use our crystal to test the superlensing effect that was predicted for negative refractive materials. Scanning transmission measurement technique is used to measure the spatial power distribution of the focused electromagnetic waves that radiate from a point source. Full width at half maximum of the focused beam is measured to be 0.21λ, which is in good agreement with the finite

  12. Nanoimprinted polymer photonic crystal dye lasers

    NASA Astrophysics Data System (ADS)

    Christiansen, Mads B.; Smith, Cameron L. C.; Buss, Thomas; Xiao, Sanshui; Mortensen, Niels A.; Kristensen, Anders

    2010-05-01

    Optically pumped polymer photonic crystal band-edge dye lasers are presented. The photonic crystal is a rectangular lattice providing laser feedback as well as an optical resonance for the pump light. The lasers are defined in a thin film of photodefinable Ormocore hybrid polymer, doped with the laser dye Pyrromethene 597. A compact frequency doubled Nd:YAG laser (352 nm, 5 ns pulses) is used to pump the lasers from above the chip. The laser devices are 450 nm thick slab waveguides with a rectangular lattice of 100 nm deep air holes imprinted into the surface. The 2-dimensional rectangular lattice is described by two orthogonal unit vectors of length a and b, defining the ΓP and ΓX directions. The frequency of the laser can be tuned via the lattice constant a (187 nm - 215 nm) while pump light is resonantly coupled into the laser from an angle (θ) depending on the lattice constant b (355 nm). The lasers are fabricated in parallel on a 10 cm diameter wafer by combined nanoimprint and photolithography (CNP). CNP relies on a UV transparent quartz nanoimprint stamp with an integrated metal shadow mask. In the CNP process the photonic crystal is formed by mechanical deformation (imprinting) while the larger features are defined by UV exposure through the combined mask/mold.

  13. Function Spaces for Liquid Crystals

    NASA Astrophysics Data System (ADS)

    Bedford, Stephen

    2016-02-01

    We consider the relationship between three continuum liquid crystal theories: Oseen-Frank, Ericksen and Landau-de Gennes. It is known that the function space is an important part of the mathematical model and by considering various function space choices for the order parameters s, n, and Q, we establish connections between the variational formulations of these theories. We use these results to justify a version of the Oseen-Frank theory using special functions of bounded variation. This proposed model can describe both orientable and non-orientable defects. Finally we study a number of frustrated nematic and cholesteric liquid crystal systems and show that the model predicts the existence of point and surface discontinuities in the director.

  14. Chip scale humidity sensing based on a microfluidic infiltrated photonic crystal

    NASA Astrophysics Data System (ADS)

    Casas-Bedoya, A.; Shahnia, S.; Di Battista, D.; Mägi, E.; Eggleton, B. J.

    2013-10-01

    This work presents an optical on-a-chip humidity sensor based on the hydroscopic behavior of an infiltrated liquid into the sub-micron holes of a silicon photonic crystal. Direct measurements of the liquid refractive index in combination with numerical simulations show that the sensitivity of the device is due to changes of both the liquid's refractive index and volume. We report humidity sensing with a response time of 0.1 ms and study the stability and reversibility of the sensor. This demonstration highlights the sensitivity offered by optofluidics in photonic crystal circuits and the potential for realizing ultra-compact integrated humidity sensing components.

  15. Design and fabrication of photonic crystal quantum cascade lasers for optofluidics.

    PubMed

    Loncar, Marko; Lee, Benjamin G; Diehl, Laurent; Belkin, Mikhail A; Capasso, Federico; Giovannini, Marcella; Faist, Jérôme; Gini, Emilio

    2007-04-16

    We present novel designs and demonstrate a fabrication platform for electrically driven lasers based on high quality-factor photonic crystal cavities realized in mid-infrared quantum cascade laser material. The structures are based on deep-etched ridges with their sides perforated with photonic crystal lattice, using focused ion beam milling. In this way, a photonic gap is opened for the emitted TM polarized light. Detailed modeling and optimization of the optical properties of the lasers are presented, and their application in optofluidics is investigated. Porous photonic crystal quantum cascade lasers have potential for on-chip, intracavity chemical and biological sensing in fluids using mid infrared spectroscopy. These lasers can also be frequency tuned over a large spectral range by introducing transparent liquid in the photonic crystal holes.

  16. Optical switching of near infrared light transmission in metamaterial-liquid crystal cell structure.

    PubMed

    Kang, Boyoung; Woo, J H; Choi, E; Lee, Hyun-Hee; Kim, E S; Kim, J; Hwang, Tae-Jong; Park, Young-Soon; Kim, D H; Wu, J W

    2010-08-01

    A metamaterial-liquid crystal cell structure is fabricated with the metamaterial as one of the liquid crystal alignment layers. Nano-sized double-split ring resonator in the metamaterial accommodates two distinct resonances in the near infrared regime. By adopting an azo-nematic liquid crystal in a twisted nematic liquid crystal cell structure, a photo-isomerization process is utilized to achieve an optical switching of light transmissions between two resonances. A single device of the metamaterial-liquid crystal cell structure has a potential application in the photonic switching in optical fiber telecommunications.

  17. Optical switching of near infrared light transmission in metamaterial-liquid crystal cell structure.

    PubMed

    Kang, Boyoung; Woo, J H; Choi, E; Lee, Hyun-Hee; Kim, E S; Kim, J; Hwang, Tae-Jong; Park, Young-Soon; Kim, D H; Wu, J W

    2010-08-01

    A metamaterial-liquid crystal cell structure is fabricated with the metamaterial as one of the liquid crystal alignment layers. Nano-sized double-split ring resonator in the metamaterial accommodates two distinct resonances in the near infrared regime. By adopting an azo-nematic liquid crystal in a twisted nematic liquid crystal cell structure, a photo-isomerization process is utilized to achieve an optical switching of light transmissions between two resonances. A single device of the metamaterial-liquid crystal cell structure has a potential application in the photonic switching in optical fiber telecommunications. PMID:20721037

  18. Swimming bacteria in liquid crystal

    NASA Astrophysics Data System (ADS)

    Sokolov, Andrey; Zhou, Shuang; Aranson, Igor; Lavrentovich, Oleg

    2014-03-01

    Dynamics of swimming bacteria can be very complex due to the interaction between the bacteria and the fluid, especially when the suspending fluid is non-Newtonian. Placement of swimming bacteria in lyotropic liquid crystal produces a new class of active materials by combining features of two seemingly incompatible constituents: self-propelled live bacteria and ordered liquid crystals. Here we present fundamentally new phenomena caused by the coupling between direction of bacterial swimming, bacteria-triggered flows and director orientations. Locomotion of bacteria may locally reduce the degree of order in liquid crystal or even trigger nematic-isotropic phase transition. Microscopic flows generated by bacterial flagella disturb director orientation. Emerged birefringence patterns allow direct optical observation and quantitative characterization of flagella dynamics. At high concentration of bacteria we observed the emergence of self-organized periodic texture caused by bacteria swimming. Our work sheds new light on self-organization in hybrid bio-mechanical systems and can lead to valuable biomedical applications. Was supported by the US DOE, Office of Basic Energy Sciences, Division of Materials Science and Engineering, under the Contract No. DE AC02-06CH11357.

  19. Bent core liquid crystal elastomers

    SciTech Connect

    Verduzco, R.; DiMasi, E.; Luchette, P.; Ho Hong, S.; Harden, J.; Palffy-Muhoray, P.; Kilbey II, S.M.; Sprunt, S.; Gleeson, G.T. Jakli, A.

    2010-07-28

    Liquid crystal (LC) elastomers with bent-core side-groups incorporate the properties of bent-core liquid crystals in a flexible and self-supporting polymer network. Bent-core liquid crystal elastomers (BCEs) with uniform alignment were prepared by attaching a reactive bent-core LC to poly(hydrogenmethylsiloxane) and crosslinking with a divinyl crosslinker. Phase behavior studies indicate a nematic phase over a wide temperature range that approaches room temperature, and thermoelastic measurements show that these BCEs can reversibly change their length by more than a factor of two upon heating and cooling. Small-angle X-ray scattering studies reveal multiple, broad low-angle peaks consistent with short-range smectic C order of the bent-core side groups. A comparison of these patterns with predictions of a Landau model for short-range smectic C order shows that the length scale for smectic ordering in BCEs is similar to that seen in pure bent-core LCs. The combination of rubber elasticity and smectic ordering of the bent-core side groups suggests that BCEs may be promising materials for sensing, actuating, and other advanced applications.

  20. Amorphous photonic crystals with only short-range order.

    PubMed

    Shi, Lei; Zhang, Yafeng; Dong, Biqin; Zhan, Tianrong; Liu, Xiaohan; Zi, Jian

    2013-10-01

    Distinct from conventional photonic crystals with both short- and long-range order, amorphous photonic crystals that possess only short-range order show interesting optical responses owing to their unique structural features. Amorphous photonic crystals exhibit unique light scattering and transport, which lead to a variety of interesting phenomena such as isotropic photonic bandgaps or pseudogaps, noniridescent structural colors, and light localization. Recent experimental and theoretical advances in the study of amorphous photonic crystals are summarized, focusing on their unique optical properties, artificial fabrication, bionspiration, and potential applications.

  1. Tracking transient temperatures with liquid crystals

    NASA Technical Reports Server (NTRS)

    Grodzka, P. G.; Facemire, B. R.

    1975-01-01

    The theoretical basis of the use of the liquid crystal technique to obtain transient thermal data is discussed. Results of calibrations of liquid crystal temperature sensors are given. The effects of crystal aging, lighting effects, observer bias, etc., on accuracy are discussed. The sensitivity of liquid crystal tapes as sensors of dynamic temperature changes is quite high. The accuracy of the technique is determined primarily by the type of calibration apparatus used.

  2. High-Visibility Photonic Crystal Fiber Interferometer as Multifunctional Sensor

    PubMed Central

    Cárdenas-Sevilla, G.A.; Fávero, Fernando C.; Villatoro, Joel

    2013-01-01

    A photonic crystal fiber (PCF) interferometer that exhibits record fringe contrast (∼40 dB) is demonstrated along with its sensing applications. The device operates in reflection mode and consists of a centimeter-long segment of properly selected PCF fusion spliced to single mode optical fibers. Two identical collapsed zones in the PCF combined with its modal properties allow high-visibility interference patterns. The interferometer is suitable for refractometric and liquid level sensing. The measuring refractive index range goes from 1.33 to 1.43 and the maximum resolution is ∼1.6 × 10−5. PMID:23396192

  3. Photonic crystal biosensor based on optical surface waves.

    PubMed

    Konopsky, Valery N; Karakouz, Tanya; Alieva, Elena V; Vicario, Chiara; Sekatskii, Sergey K; Dietler, Giovanni

    2013-01-01

    A label-free biosensor device based on registration of photonic crystal surface waves is described. Angular interrogation of the optical surface wave resonance is used to detect changes in the thickness of an adsorbed layer, while an additional simultaneous detection of the critical angle of total internal reflection provides independent data of the liquid refractive index. The abilities of the device are demonstrated by measuring of biotin molecule binding to a streptavidin monolayer, and by measuring association and dissociation kinetics of immunoglobulin G proteins. Additionally, deposition of PSS / PAH polyelectrolytes is recorded in situ resulting calculation of PSS and PAH monolayer thicknesses separately. PMID:23429517

  4. Feasibility of tunable MEMS photonic crystal devices.

    PubMed

    Rajic, S; Corbeil, J L; Datskos, P G

    2003-01-01

    Periodic photonic crystal structures channel electromagnetic waves much as semiconductors/quantum wells channel electrons. Photonic bandgap crystals (PBC) are fabricated by arranging sub-wavelength alternating materials with high and low dielectric constants to produce a desired effective bandgap. Photons with energy within this bandgap cannot propagate through the structure. This property has made these structures useful for microwave applications such as frequency-selective surfaces, narrowband filters, and antenna substrates when the dimensions are on the order of millimeters. They are also potentially very useful, albeit much more difficult to fabricate, in the visible/near-infrared region for various applications when the smallest dimensions are at the edge of current micro-lithography fabrication tools. We micro-fabricated suspended free standing micro-structure bridge waveguides to serve as substrates for PBC features. These micro-bridges were fabricated onto commercial silicon-on-insulator wafers. Nanoscale periodic features were fabricated onto these micro-structure bridges to form a tunable system. When this combined structure is perturbed, such as mechanical deflection of the suspended composite structure at resonance, there can be a realtime shift in the material effective bandgap due to slight geometric alterations due to the induced mechanical stress. Extremely high resonance frequencies/device speeds are possible with these very small dimension MEMS.

  5. Raman cooling in silicon photonic crystals

    NASA Astrophysics Data System (ADS)

    Chen, Yin-Chung; Bahl, Gaurav

    2016-03-01

    Laser cooling of solids can be achieved through various photon up-conversion processes including anti-Stokes photoluminescence and anti-Stokes light scattering. While it has been shown that cooling using photoluminescence-based methods can achieve efficiency comparable to that of thermoelectric cooling, the reliance on specific transitions of the rare-earth dopants limits material choice. Light scattering, on the other hand, occurs in all materials, and has the potential to enable cooling in most materials. We show that by engineering the photonic density of states of a material, one can suppress the Stokes process, and enhance the anti-Stokes radiation. We employ the well-known diamond-structured photonic crystal patterned in crystalline silicon to demonstrate theoretically that when operating within a high transparency regime, the net energy removal rate from phonon annihilation can overcome the optical absorption. The engineered photonic density of states can thus enable simultaneous cooling of all Raman-active phonon modes and the net cooling of the solid.

  6. Photonic Crystal Emitters for Thermophotovoltaic Energy Conversion

    NASA Astrophysics Data System (ADS)

    Stelmakh, Veronika; Chan, Walker R.; Ghebrebrhan, Michael; Soljacic, Marin; Joannopoulos, John D.; Celanovic, Ivan

    2015-12-01

    This paper reports the design, fabrication, and characterization of 2D photonic crystal (PhC) thermal emitters for a millimeter-scale hydrocarbon TPV microgenerator as a possible replacement for batteries in portable microelectronics, robotics, etc. In our TPV system, combustion heats a PhC emitter to incandescence and the resulting radiation is converted by a low-bandgap TPV cell. The PhC tailors the photonic density of states to produce spectrally confined thermal emission that matches the bandgap of the TPV cell, enabling high heat-to-electricity conversion efficiency. The work builds on a previously developed fabrication process to produce a square array of cylindrical cavities in a metal substrate. We will present ongoing incremental improvements in the optical and thermo-mechanical properties, the fabrication process, and the system integration, as recently combined with fabrication using novel materials, such as sputtered coatings, to enable a monolithic system.

  7. Chalcogenide glass hollow core photonic crystal fibers

    NASA Astrophysics Data System (ADS)

    Désévédavy, Frédéric; Renversez, Gilles; Troles, Johann; Houizot, Patrick; Brilland, Laurent; Vasilief, Ion; Coulombier, Quentin; Traynor, Nicholas; Smektala, Frédéric; Adam, Jean-Luc

    2010-09-01

    We report the first hollow core photonic crystal fibers (HC PCF) in chalcogenide glass. To design the required HC PCF profiles for such high index glass, we use both band diagram analysis to define the required photonic bandgap and numerical simulations of finite size HC PCFs to compute the guiding losses. The material losses have also been taken into account to compute the overall losses of the HC PCF profiles. These fibers were fabricated by the stack and draw technique from TeAsSe (TAS) glass. The fibers we drew in this work are composed of six rings of holes and regular microstructures. Two profiles are presented, one is known as a kagome lattice and the other one corresponds to a triangular lattice. Geometrical parameters are compared to the expected parameters obtained by computation. Applications of such fibers include power delivery or fiber sensors among others.

  8. Slab photonic crystals with dimer colloid bases

    SciTech Connect

    Riley, Erin K.; Liddell Watson, Chekesha M.

    2014-06-14

    The photonic band gap properties for centered rectangular monolayers of asymmetric dimers are reported. Colloids in suspension have been organized into the phase under confinement. The theoretical model is inspired by the range of asymmetric dimers synthesized via seeded emulsion polymerization and explores, in particular, the band structures as a function of degree of lobe symmetry and degree of lobe fusion. These parameters are varied incrementally from spheres to lobe-tangent dimers over morphologies yielding physically realizable particles. The work addresses the relative scarcity of theoretical studies on photonic crystal slabs with vertical variation that is consistent with colloidal self-assembly. Odd, even and polarization independent gaps in the guided modes are determined for direct slab structures. A wide range of lobe symmetry and degree of lobe fusion combinations having Brillouin zones with moderate to high isotropy support gaps between odd mode band indices 3-4 and even mode band indices 1-2 and 2-3.

  9. Photonic crystal devices formed by a charged-particle beam

    DOEpatents

    Lin, Shawn-Yu; Koops, Hans W. P.

    2000-01-01

    A photonic crystal device and method. The photonic crystal device comprises a substrate with at least one photonic crystal formed thereon by a charged-particle beam deposition method. Each photonic crystal comprises a plurality of spaced elements having a composition different from the substrate, and may further include one or more impurity elements substituted for spaced elements. Embodiments of the present invention may be provided as electromagnetic wave filters, polarizers, resonators, sources, mirrors, beam directors and antennas for use at wavelengths in the range from about 0.2 to 200 microns or longer. Additionally, photonic crystal devices may be provided with one or more electromagnetic waveguides adjacent to a photonic crystal for forming integrated electromagnetic circuits for use at optical, infrared, or millimeter-wave frequencies.

  10. Broadband photon-photon interactions mediated by cold atoms in a photonic crystal fiber

    PubMed Central

    Litinskaya, Marina; Tignone, Edoardo; Pupillo, Guido

    2016-01-01

    We demonstrate theoretically that photon-photon attraction can be engineered in the continuum of scattering states for pairs of photons propagating in a hollow-core photonic crystal fiber filled with cold atoms. The atoms are regularly spaced in an optical lattice configuration and the photons are resonantly tuned to an internal atomic transition. We show that the hard-core repulsion resulting from saturation of the atomic transitions induces bunching in the photonic component of the collective atom-photon modes (polaritons). Bunching is obtained in a frequency range as large as tens of GHz, and can be controlled by the inter-atomic separation. We provide a fully analytical explanation for this phenomenon by proving that correlations result from a mismatch of the quantization volumes for atomic excitations and photons in the continuum. Even stronger correlations can be observed for in-gap two-polariton bound states. Our theoretical results use parameters relevant for current experiments and suggest a simple and feasible way to induce interactions between photons. PMID:27170160

  11. Super-collimation by axisymmetric photonic crystals

    SciTech Connect

    Purlys, V.; Gailevičius, D.; Peckus, M.; Gadonas, R.; Maigyte, L.; Staliunas, K.

    2014-06-02

    We propose and experimentally show the mechanism of beam super-collimation by axisymmetric photonic crystals, specifically by periodic (in propagation direction) structure of layers of concentric rings. The physical mechanism behind the effect is an inverse scattering cascade of diffracted wave components back into on- and near-axis angular field components, resulting in substantial enhancement of intensity of these components. We explore the super-collimation by numerical calculations and prove it experimentally. We demonstrate experimentally the axial field enhancement up to 7 times in terms of field intensity.

  12. Photonic crystal self-collimation sensor.

    PubMed

    Wang, Yufei; Wang, Hailing; Xue, Qikun; Zheng, Wanhua

    2012-05-21

    A novel refractive index sensor based on the two dimensional photonic crystal folded Michelson interferometer employing the self-collimation effect is proposed and its performances are theoretically investigated. Two sensing areas are included in the sensor. Simulation results indicate the branch area is suitable for the small index variety range and fine detection, whereas the reflector area prone to the large index change range and coarse detection. Because of no defect waveguides and no crosstalk of signal, the sensor is desirable to perform monolithic integrated, low-cost, label-free real-time parallel sensing. In addition, a flexible design of self-collimation sensors array is demonstrated. PMID:22714197

  13. Reversed Doppler effect in photonic crystals.

    PubMed

    Reed, Evan J; Soljacić, Marin; Joannopoulos, John D

    2003-09-26

    Nonrelativistic reversed Doppler shifts have never been observed in nature and have only been speculated to occur in pathological systems with simultaneously negative effective permittivity and permeability. This Letter presents a different, new physical phenomenon that leads to a nonrelativistic reversed Doppler shift in light. It arises when light is reflected from a moving shock wave propagating through a photonic crystal. In addition to reflection of a single frequency, multiple discrete reflected frequencies or a 10 GHz periodic modulation can also be observed when a single carrier frequency of wavelength 1 microm is incident.

  14. Anomalous bending effect in photonic crystal fibers

    PubMed Central

    Tu, Haohua; Jiang, Zhi; Marks, Daniel. L.; Boppart, Stephen A.

    2010-01-01

    An unexpected transmission loss up to 50% occurs to intense femtosecond pulses propagating along an endlessly single-mode photonic crystal fiber over a length of 1 m. A specific leaky-fiber mode gains amplification along the fiber at the expense of the fundamental fiber mode through stimulated four-wave mixing and Raman scattering, leading to this transmission loss. Bending near the fiber entrance dissipates the propagating seed of this leaky mode, preventing the leaky mode amplification and therefore enhancing the transmission of these pulses. PMID:18542666

  15. Reciprocity theorem and perturbation theory for photonic crystal waveguides.

    PubMed

    Michaelis, D; Peschel, U; Wächter, C; Bräuer, A

    2003-12-01

    Starting from Maxwell's equations we derive a reciprocity theorem for photonic crystal waveguides. A set of strongly coupled discrete equations results, which can be applied to the simulation of perturbed photonic crystal waveguides. As an example we analytically study the influence of the dispersion of a two level system on the band structure of a photonic crystal waveguide. In particular, the formation of polariton gaps is discussed.

  16. Young's double-slit experiment in photonic crystals

    SciTech Connect

    Zhang, Lei; Koschny, Thomas; Soukoulis, Costas M.

    2012-10-01

    We present an experimental and numerical study of the transmission of a photonic crystal perforated by two sub-wavelength slits, separated by two wavelengths.The experimental near-field image of the double-slit design of the photonic crystal shows an interference pattern, which is analogous to Young’s experiment. This interference arises as a consequence of the excitation of surface states of the photonic crystals and agrees very well with the simulations.

  17. Photoluminescence analysis of self induced planer alignment in azo dye dispersed nematic liquid crystal complex

    SciTech Connect

    Kumar, Rishi Sood, Srishti Raina, K. K.

    2014-04-24

    We have developed azo dye doped nematic liquid crystal complex for advanced photonic liquid crystal display technology aspects. Disperse orange azo dye self introduced planer alignment in the nematic liquid crystal without any surface anchoring treatment. Planer alignment was characterized by optical polarizing microscopy. The electro-optical switching response of dye disperse planer aligned nematic cell was investigated as a function of applied voltage with the help of photoluminescence spectrophotometer for the tuning of photoluminescence contrast.

  18. Perspectives in active liquid crystals.

    PubMed

    Majumdar, Apala; Cristina, Marchetti M; Virga, Epifanio G

    2014-11-28

    Active soft matter is a young, growing field, with potential applications to a wide variety of systems. This Theme Issue explores this emerging new field by highlighting active liquid crystals. The collected contributions bridge theory to experiment, mathematical theories of passive and active nematics, spontaneous flows to defect dynamics, microscopic to continuum levels of description, spontaneous activity to biological activation. While the perspectives offered here only span a small part of this rapidly evolving field, we trust that they might provide the interested reader with a taste for this new class of non-equilibrium systems and their rich behaviour.

  19. Computer simulations of liquid crystals

    NASA Astrophysics Data System (ADS)

    Smondyrev, Alexander M.

    Liquid crystal physics is an exciting interdisciplinary field of research with important practical applications. Their complexity and the presence of strong translational and orientational fluctuations require a computational approach, especially in the studies of nonequlibrium phenomena. In this dissertation we present the results of computer simulation studies of liquid crystals using the molecular dynamics technique. We employed the Gay-Berne phenomenological model of liquid crystals to describe the interaction between the molecules. Both equilibrium and non-equilibrium phenomena were studied. In the first case we studied the flow properties of the liquid crystal system in equilibrium as well as the dynamics of the director. We measured the viscosities of the Gay-Berne model in the nematic and isotropic phases. The temperature-dependence of the rotational and shear viscosities, including the nonmonotonic behavior of one shear viscosity, are in good agreement with experimental data. The bulk viscosities are significantly larger than the shear viscosities, again in agreement with experiment. The director motion was found to be ballistic at short times and diffusive at longer times. The second class of problems we focused on is the properties of the system which was rapidly quenched to very low temperatures from the nematic phase. We find a glass transition to a metastable phase with nematic order and frozen translational and orientational degrees of freedom. For fast quench rates the local structure is nematic-like, while for slower quench rates smectic order is present as well. Finally, we considered a system in the isotropic phase which is then cooled to temperatures below the isotropic-nematic transition temperature. We expect topological defects to play a central role in the subsequent equilibration of the system. To identify and study these defects we require a simulation of a system with several thousand particles. We present the results of large

  20. Perspectives in active liquid crystals

    PubMed Central

    Majumdar, Apala; Cristina, Marchetti M.; Virga, Epifanio G.

    2014-01-01

    Active soft matter is a young, growing field, with potential applications to a wide variety of systems. This Theme Issue explores this emerging new field by highlighting active liquid crystals. The collected contributions bridge theory to experiment, mathematical theories of passive and active nematics, spontaneous flows to defect dynamics, microscopic to continuum levels of description, spontaneous activity to biological activation. While the perspectives offered here only span a small part of this rapidly evolving field, we trust that they might provide the interested reader with a taste for this new class of non-equilibrium systems and their rich behaviour. PMID:25332386

  1. Biomimetic Photonic Crystals based on Diatom Algae Frustules

    NASA Astrophysics Data System (ADS)

    Mishler, Jonathan; Alverson, Andrew; Herzog, Joseph

    2015-03-01

    Diatom algae are unicellular, photosynthetic microorganisms with a unique external shell known as a frustule. Frustules, which are composed of amorphous silica, exhibit a unique periodic nano-patterning, distinguishing diatoms from other types of phytoplankton. Diatoms have been studied for their distinctive optical properties due to their resemblance of photonic crystals. In this regard, diatoms are not only considered for their applications as photonic crystals, but also for their use as biomimetic templates for artificially fabricated photonic crystals. Through the examination and measurement of the physical characteristics of many scanning electron microscope (SEM) images of diatom frustules, a biomimetic photonic crystal derived from diatom frustules can be recreated and modeled with the finite element method. In this approach, the average geometries of the diatom frustules are used to recreate a 2-dimensional photonic crystal, after which the electric field distribution and optical transmission through the photonic crystal are both measured. The optical transmission is then compared to the transmission spectra of a regular hexagonal photonic crystal, revealing the effects of diatom geometry on their optical properties. Finally, the dimensions of the photonic crystal are parametrically swept, allowing for further control over the transmission of light through the photonic crystal.

  2. Dual-frequency addressed hybrid-aligned nematic liquid crystal

    NASA Astrophysics Data System (ADS)

    Lu, Yan-Qing; Liang, Xiao; Wu, Yung-Hsun; Du, Fang; Wu, Shin-Tson

    2004-10-01

    Dual-frequency addressed hybrid-aligned nematic (HAN) liquid crystal cell is demonstrated as a variable optical attenuator at 1.55μm wavelength. By controlling the low- and high-frequency electric field, the dual-frequency liquid crystal (DFLC) molecules can be reoriented parallel or perpendicular to the substrates so that the maximum obtainable phase modulation is doubled. In comparison to a homogeneous cell, the DFLC HAN cell shows a lower operating voltage and faster response time. Furthermore, the DFLC HAN cell exhibits three stable states that have some applications such as ternary photonic devices.

  3. Electrically modulated transparent liquid crystal -optical grating projection.

    PubMed

    Buss, Thomas; Smith, Cameron L C; Kristensen, Anders

    2013-01-28

    A transparent, fully integrated electrically modulated projection technique is presented based on light guiding through a thin liquid crystal layer covering sub-wavelength gratings. The reported device operates at 10 V with response times of 4.5 ms. Analysis of the liquid crystal alignment shows that director-reorientation occurs over timescales on the order of 90 µs close to the grating surface. The technology is suitable for next generation heads-up-displays and reconfigurable multilayer photonic integrated circuits. PMID:23389166

  4. Wigner Crystallization of Single Photons in Cold Rydberg Ensembles

    NASA Astrophysics Data System (ADS)

    Otterbach, Johannes; Moos, Matthias; Muth, Dominik; Fleischhauer, Michael

    2013-09-01

    The coupling of weak light fields to Rydberg states of atoms under conditions of electromagnetically induced transparency leads to the formation of Rydberg polaritons which are quasiparticles with tunable effective mass and nonlocal interactions. Confined to one spatial dimension their low energy physics is that of a moving-frame Luttinger liquid which, due to the nonlocal character of the repulsive interaction, can form a Wigner crystal of individual photons. We calculate the Luttinger K parameter using density-matrix renormalization group simulations and find that under typical slow-light conditions kinetic energy contributions are too strong for crystal formation. However, adiabatically increasing the polariton mass by turning a light pulse into stationary spin excitations allows us to generate true crystalline order over a finite length. The dynamics of this process and asymptotic correlations are analyzed in terms of a time-dependent Luttinger theory.

  5. Wigner crystallization of single photons in cold Rydberg ensembles.

    PubMed

    Otterbach, Johannes; Moos, Matthias; Muth, Dominik; Fleischhauer, Michael

    2013-09-13

    The coupling of weak light fields to Rydberg states of atoms under conditions of electromagnetically induced transparency leads to the formation of Rydberg polaritons which are quasiparticles with tunable effective mass and nonlocal interactions. Confined to one spatial dimension their low energy physics is that of a moving-frame Luttinger liquid which, due to the nonlocal character of the repulsive interaction, can form a Wigner crystal of individual photons. We calculate the Luttinger K parameter using density-matrix renormalization group simulations and find that under typical slow-light conditions kinetic energy contributions are too strong for crystal formation. However, adiabatically increasing the polariton mass by turning a light pulse into stationary spin excitations allows us to generate true crystalline order over a finite length. The dynamics of this process and asymptotic correlations are analyzed in terms of a time-dependent Luttinger theory. PMID:24074081

  6. Porous photonic crystal external cavity laser biosensor

    NASA Astrophysics Data System (ADS)

    Huang, Qinglan; Peh, Jessie; Hergenrother, Paul J.; Cunningham, Brian T.

    2016-08-01

    We report the design, fabrication, and testing of a photonic crystal (PC) biosensor structure that incorporates a porous high refractive index TiO2 dielectric film that enables immobilization of capture proteins within an enhanced surface-area volume that spatially overlaps with the regions of resonant electromagnetic fields where biomolecular binding can produce the greatest shifts in photonic crystal resonant wavelength. Despite the nanoscale porosity of the sensor structure, the PC slab exhibits narrowband and high efficiency resonant reflection, enabling the structure to serve as a wavelength-tunable element of an external cavity laser. In the context of sensing small molecule interactions with much larger immobilized proteins, we demonstrate that the porous structure provides 3.7× larger biosensor signals than an equivalent nonporous structure, while the external cavity laser (ECL) detection method provides capability for sensing picometer-scale shifts in the PC resonant wavelength caused by small molecule binding. The porous ECL achieves a record high figure of merit for label-free optical biosensors.

  7. Fabrication and evaluation of photonic metamaterial crystal

    NASA Astrophysics Data System (ADS)

    Tanabete, S.; Nakagawa, Y.; Okamoto, T.; Haraguchi, M.; Isu, T.; Shinomiya, G.

    2013-09-01

    Many researching efforts have been reported to seek various fundamental LC resonance structures, recently. But still the Split Ring Resonator (SRR) is the most famous and major fundamental LC-resonance structure used in the metamaterial. We employed SRR structure as the fundamental LC-resonance mechanism to fabricate photonic crystal with periodic arrangement of two different metamaterial areas composed from SRR arrays on the dielectric substrate. We developed Photonic Metamaterial Crystal (PMC) to realize the more advanced and versatile functions of the metamaterial by 1 dimensional or 2 dimensional periodic arranging of two metamaterial sections which have different dispersion properties due to the different size of SRR structures each other. In this paper, we report the fabrication process, estimation of PMC properties and some possible future application prospects, for instance the PMC waveguide structures and nonlinear properties of PMC observed as selective LC-resonant properties in Raman mapping analysis of PMC. These are quite interesting characters of PMC and the attractive applications as the PMC devices.

  8. Photonic Crystal Laser-Driven Accelerator Structures

    SciTech Connect

    Cowan, Benjamin M.

    2007-08-22

    Laser-driven acceleration holds great promise for significantly improving accelerating gradient. However, scaling the conventional process of structure-based acceleration in vacuum down to optical wavelengths requires a substantially different kind of structure. We require an optical waveguide that (1) is constructed out of dielectric materials, (2) has transverse size on the order of a wavelength, and (3) supports a mode with speed-of-light phase velocity in vacuum. Photonic crystals---structures whose electromagnetic properties are spatially periodic---can meet these requirements. We discuss simulated photonic crystal accelerator structures and describe their properties. We begin with a class of two-dimensional structures which serves to illustrate the design considerations and trade-offs involved. We then present a three-dimensional structure, and describe its performance in terms of accelerating gradient and efficiency. We discuss particle beam dynamics in this structure, demonstrating a method for keeping a beam confined to the waveguide. We also discuss material and fabrication considerations. Since accelerating gradient is limited by optical damage to the structure, the damage threshold of the dielectric is a critical parameter. We experimentally measure the damage threshold of silicon for picosecond pulses in the infrared, and determine that our structure is capable of sustaining an accelerating gradient of 300 MV/m at 1550 nm. Finally, we discuss possibilities for manufacturing these structures using common microfabrication techniques.

  9. Negative Refraction experiments in Photonic Crystal prisms

    NASA Astrophysics Data System (ADS)

    Vodo, Plarenta; Parimi, Patanjali. V.; Lu, Wentao. T.; di Gennaro, Emiliano; Sridhar, Srinivas

    2004-03-01

    We have experimentally demonstrated negative refraction in metallic photonic crystal (PC) prisms [1]. The refracted fields in the parallel plate waveguide (PPW) are measured by an automated dipole antenna, which scans the desired area, while the free space (FS) measurements, performed in a anechoic chamber, are measured by a rectangular X-band horn that swings in an arc in far field area. Both TE and TM excitation modes are used in FS experiments. Numerical calculations of the band structure and equi-frequency surface simulations are used to determine frequency regions of negative refraction of the triangular lattice PC. Angle of refraction determined by theoretical simulations and experimental results, are in exceptional good agreement, yielding the negative refraction index. FS and PPW refraction experimental results agree remarkably with simulations. 1. "Negative Refraction and Left-handed electromagnetism in Microwave Photonic Crystals", P.V Parimi, W.T Lu, P.Vodo J. Sokoloff and S.Sridhar, cond-mat/0306109 (2003)

  10. Gallium nitride based logpile photonic crystals.

    PubMed

    Subramania, Ganapathi; Li, Qiming; Lee, Yun-Ju; Figiel, Jeffrey J; Wang, George T; Fischer, Arthur J

    2011-11-01

    We demonstrate a nine-layer logpile three-dimensional photonic crystal (3DPC) composed of single crystalline gallium nitride (GaN) nanorods, ∼100 nm in size with lattice constants of 260, 280, and 300 nm with photonic band gap in the visible region. This unique GaN structure is created through a combined approach of a layer-by-layer template fabrication technique and selective metal organic chemical vapor deposition (MOCVD). These GaN 3DPC exhibit a stacking direction band gap characterized by strong optical reflectance between 380 and 500 nm. By introducing a "line-defect" cavity in the fifth (middle) layer of the 3DPC, a localized transmission mode with a quality factor of 25-30 is also observed within the photonic band gap. The realization of a group III nitride 3DPC with uniform features and a band gap at wavelengths in the visible region is an important step toward realizing complete control of the electromagnetic environment for group III nitride based optoelectronic devices.

  11. Nanoscopic Manipulation and Imaging of Liquid Crystals

    SciTech Connect

    Rosenblatt, Charles S.

    2014-02-04

    This is the final project report. The project’s goals centered on nanoscopic imaging and control of liquid crystals and surfaces. We developed and refined techniques to control liquid crystal orientation at surfaces with resolution as small as 25 nm, we developed an optical imaging technique that we call Optical Nanotomography that allows us to obtain images inside liquid crystal films with resolution of 60 x 60 x 1 nm, and we opened new thrust areas related to chirality and to liquid crystal/colloid composites.

  12. Extended-Range Ultrarefractive 1D Photonic Crystal Prisms

    NASA Technical Reports Server (NTRS)

    Ting, David Z.

    2007-01-01

    A proposal has been made to exploit the special wavelength-dispersive characteristics of devices of the type described in One-Dimensional Photonic Crystal Superprisms (NPO-30232) NASA Tech Briefs, Vol. 29, No. 4 (April 2005), page 10a. A photonic crystal is an optical component that has a periodic structure comprising two dielectric materials with high dielectric contrast (e.g., a semiconductor and air), with geometrical feature sizes comparable to or smaller than light wavelengths of interest. Experimental superprisms have been realized as photonic crystals having three-dimensional (3D) structures comprising regions of amorphous Si alternating with regions of SiO2, fabricated in a complex process that included sputtering. A photonic crystal of the type to be exploited according to the present proposal is said to be one-dimensional (1D) because its contrasting dielectric materials would be stacked in parallel planar layers; in other words, there would be spatial periodicity in one dimension only. The processes of designing and fabricating 1D photonic crystal superprisms would be simpler and, hence, would cost less than do those for 3D photonic crystal superprisms. As in 3D structures, 1D photonic crystals may be used in applications such as wavelength-division multiplexing. In the extended-range configuration, it is also suitable for spectrometry applications. As an engineered structure or artificially engineered material, a photonic crystal can exhibit optical properties not commonly found in natural substances. Prior research had revealed several classes of photonic crystal structures for which the propagation of electromagnetic radiation is forbidden in certain frequency ranges, denoted photonic bandgaps. It had also been found that in narrow frequency bands just outside the photonic bandgaps, the angular wavelength dispersion of electromagnetic waves propagating in photonic crystal superprisms is much stronger than is the angular wavelength dispersion obtained

  13. Holographic polymer-dispersed liquid crystals: Physics and applications

    NASA Astrophysics Data System (ADS)

    Qi, Jun

    Holographic polymer-dispersed liquid crystals are composite materials that are rich in physical phenomena and useful for electrically or thermally switchable hologram and grating applications. They are formed through a self-diffusion process using an interference pattern to initiate and drive the kinetics of formation, which is generated through two or more coherent laser beams. The information from the interference pattern is permanently recorded through a phase separation process or optical alignment of polymer in liquid crystal/polymer composites. The recorded holograms are erasable or tunable by applying sufficient external field or temperature variation. The formation kinetics of holographic polymer-dispersed liquid crystals can be modeled by a set of reaction-diffusion equations. By analyzing the optical performance of resulting gratings, we found that the phase separation process is dominated by a photo-polymerization induced diffusion in the fast polymerization regime rather than the thermal diffusion in the slow polymerization regime. The effective diffusion constant of oligomers can be enhanced by two orders of magnitude. This diffusion model is verified by in-situ spectroscopy measurements of reflective holographic polymer-dispersed liquid crystals. Through experiments and modeling, the shrinkage of the polymer matrix is determined. In addition, we have expanded our diffusion formalism to model two-dimensional and three-dimensional cases and temporally multiplexed systems. The Freedericksz transition, based on the elastic theory of liquid crystals, is used to model various morphologies of confined liquid crystals. A polymer scaffolding model and a cylindrical cavity model are proposed, which enable us to make an order of magnitude estimation of the surface anchoring strength of liquid crystal/polymer interfaces in different systems. From the applied physics standpoint, we have also made a number of valuable contributions to optical and photonic

  14. Polymer Crystallization at Curved Liquid/Liquid Interface

    NASA Astrophysics Data System (ADS)

    Wang, Wenda

    Liquid/liquid interface, either flat or curved, is a unique template for studying self-assembly of a variety of nanomaterials such as nanoparticles and nanorods. The resultant monolayer films can be ordered or disordered depending on the regularity of the nanomaterials. Integration of nanoparticles into two-dimensional structure leads to intriguing collective properties of the nanoparticles. Crystallization can also be guided by liquid/liquid interface. Due to the particular shape of the interface, crystallization can happen in a different manner comparing to the normal solution crystallization. In this dissertation, liquid/liquid interface is employed to guide the crystallization of polymers, mainly focusing on using curved liquid/liquid interface. Due to the unique shape of the interface and feasibility to control the curvature, polymer crystallization can take place in different manner and lead to the formation of curved or vesicular crystals. Curved liquid/liquid interface is typically created through o/w emulsions. With the presence of surfactant, the emulsions are controlled to be stable at least for the polymer crystallization periods. The difference to normal solution crystallization is: the nuclei will diffuse to the curved interface due to the Pickering effect and guide the crystallization along the curved liquid/liquid interface. If the supercooling can be controlled to be very small, crystal growth in the bulk droplets can be avoided. The advantages of this strategy are: 1) the formation process of vesicular type crystals can be monitored by controlling the polymer supply; 2) curved crystals, bowl-like structures and enclosed capsules can be easily obtained comparing to the self-assembly method for vesicle formation; 3) the obtained vesicles will be made of polymer crystals, which will possess the extraordinary mechanical properties. Based on the nucleation type, this dissertation is divided into two parts. The first part is focused on the self

  15. A 1-D dusty plasma photonic crystal

    SciTech Connect

    Mitu, M. L.; Ticoş, C. M.; Toader, D.; Banu, N.; Scurtu, A.

    2013-09-21

    It is demonstrated numerically that a 1-D plasma crystal made of micron size cylindrical dust particles can, in principle, work as a photonic crystal for terahertz waves. The dust rods are parallel to each other and arranged in a linear string forming a periodic structure of dielectric-plasma regions. The dispersion equation is found by solving the waves equation with the boundary conditions at the dust-plasma interface and taking into account the dielectric permittivity of the dust material and plasma. The wavelength of the electromagnetic waves is in the range of a few hundred microns, close to the interparticle separation distance. The band gaps of the 1-D plasma crystal are numerically found for different types of dust materials, separation distances between the dust rods and rod diameters. The distance between levitated dust rods forming a string in rf plasma is shown experimentally to vary over a relatively wide range, from 650 μm to about 1350 μm, depending on the rf power fed into the discharge.

  16. Simulation of coherent backscattering of light in nematic liquid crystals

    SciTech Connect

    Aksenova, E. V. Kokorin, D. I. Romanov, V. P.

    2012-08-15

    Multiple scattering of light by the fluctuations of the director in a nematic liquid crystal (NLC) aligned by a magnetic field is considered. A peak of coherent backscattering is calculated by numerical simulation. Since the indicatrix of single scattering for a liquid crystal (LC) is known exactly, the calculations are carried out without any simplifying assumptions on the parameters of the liquid crystal. Multiple scattering is simulated as a random walk of photons in the medium. A peak of coherent backscattering in such a medium is very narrow; therefore, the so-called semianalytical method is applied. The parameters of the backscattering peak obtained by numerical simulation are compared with the available experimental data and with the results of analytical approximations. It turns out that the experimental data are in good agreement with the results of simulation. The results of numerical simulation adequately describe the anisotropy and the width of the backscattering peak.

  17. [Recent advancement of photonic-crystal-based analytical chemistry].

    PubMed

    Chen, Yun; Guo, Zhenpeng; Wang, Jinyi; Chen, Yi

    2014-04-01

    Photonic crystals are a type of novel materials with ordered structure, nanopores/channels and optical band gap. They have hence important applications in physics, chemistry, biological science and engineering fields. This review summarizes the recent advancement of photonic crystals in analytical chemistry applications, with focus on sensing and separating fields happening in the nearest 5 years.

  18. Interface electromagnetic waves between Kronig-Penney photonic crystals

    NASA Astrophysics Data System (ADS)

    Mehrany, Khashayar; Momeni, Babak; Khorasani, Sina; Rashidian, Bizhan

    2003-02-01

    The electromagnetic interface states formed in a heterostructure composed of two semi-infinite Kronig-Penny photonic crystals have been studied. Modified transfer matrices have been used for study of Kronig-Penny photonic crystals (heterostructures with conducting interfaces) to show strong similarity between solid-state physics and electromagnetics. Our calculations are limited to TE polarization.

  19. Heteroplasmon hybridization in stacked complementary plasmo-photonic crystals.

    PubMed

    Iwanaga, Masanobu; Choi, Bongseok

    2015-03-11

    We constructed plasmo-photonic crystals in which efficient light-trapping, plasmonic resonances couple with photonic guided resonances of large density of states and high-quality factor. We have numerically and experimentally shown that heteroplasmon hybrid modes emerge in stacked complementary (SC) plasmo-photonic crystals. The resonant electromagnetic-field distributions evidence that the two hybrid modes originate from two different heteroplasmons, exhibiting a large energy splitting of 300 meV. We further revealed a series of plasmo-photonic modes in the SC crystals.

  20. Waveguide circuits in three-dimensional photonic crystals

    SciTech Connect

    Biswas, Rana; Christensen, C.; Muehlmeier, J.; Tuttle, G.; Ho, K.-M.

    2008-04-07

    Waveguide circuits in three-dimensional photonic crystals with complete photonic band gaps are simulated with finite difference time domain (FDTD) simulations, and compared with measurements on microwave scale photonic crystals. The transmission through waveguide bends critically depends on the photonic crystal architecture in the bend region. We have found experimentally and theoretically, a new waveguide bend configuration consisting of overlapping rods in the bend region, that performs better than the simple waveguide bend of terminated rods, especially in the higher frequency portion of the band. Efficient beam splitters with this junction geometry are also simulated.

  1. Strongly-Refractive One-Dimensional Photonic Crystal Prisms

    NASA Technical Reports Server (NTRS)

    Ting, David Z. (Inventor)

    2004-01-01

    One-dimensional (1D) photonic crystal prisms can separate a beam of polychromatic electromagnetic waves into constituent wavelength components and can utilize unconventional refraction properties for wavelength dispersion over significant portions of an entire photonic band rather than just near the band edges outside the photonic band gaps. Using a ID photonic crystal simplifies the design and fabrication process and allows the use of larger feature sizes. The prism geometry broadens the useful wavelength range, enables better optical transmission, and exhibits angular dependence on wavelength with reduced non-linearity. The properties of the 1 D photonic crystal prism can be tuned by varying design parameters such as incidence angle, exit surface angle, and layer widths. The ID photonic crystal prism can be fabricated in a planar process, and can be used as optical integrated circuit elements.

  2. Two-photon-induced singlet fission in rubrene single crystal.

    PubMed

    Ma, Lin; Galstyan, Gegham; Zhang, Keke; Kloc, Christian; Sun, Handong; Soci, Cesare; Michel-Beyerle, Maria E; Gurzadyan, Gagik G

    2013-05-14

    The two-photon-induced singlet fission was observed in rubrene single crystal and studied by use of femtosecond pump-probe spectroscopy. The location of two-photon excited states was obtained from the nondegenerate two-photon absorption (TPA) spectrum. Time evolution of the two-photon-induced transient absorption spectra reveals the direct singlet fission from the two-photon excited states. The TPA absorption coefficient of rubrene single crystal is 52 cm∕GW at 740 nm, as obtained from Z-scan measurements. Quantum chemical calculations based on time-dependent density functional theory support our experimental data. PMID:23676057

  3. All-polymer photonic crystal slab sensor.

    PubMed

    Hermannsson, Pétur G; Sørensen, Kristian T; Vannahme, Christoph; Smith, Cameron L C; Klein, Jan J; Russew, Maria-Melanie; Grützner, Gabi; Kristensen, Anders

    2015-06-29

    An all-polymer photonic crystal slab sensor is presented, and shown to exhibit narrow resonant reflection with a FWHM of less than 1 nm and a sensitivity of 31 nm/RIU when sensing media with refractive indices around that of water. This results in a detection limit of 4.5 × 10(-6) RIU when measured in conjunction with a spectrometer of 12 pm/pixel resolution. The device is a two-layer structure, composed of a low refractive index polymer with a periodically modulated surface height, covered with a smooth upper-surface high refractive index inorganic-organic hybrid polymer modified with ZrO2based nanoparticles. Furthermore, it is fabricated using inexpensive vacuum-less techniques involving only UV nanoreplication and polymer spin-casting, and is thus well suited for single-use biological and refractive index sensing applications. PMID:26191664

  4. Terahertz wave filter based on photonic crystal

    NASA Astrophysics Data System (ADS)

    Liu, Yu-hang; Li, Jiu-sheng

    2011-11-01

    In the past decade, spectroscopy and imaging in the terahertz region (0.1-10 THz) of the electromagnetic spectrum has been applied in both basic research and potential industrial applications, such as medical diagnosis, security screening, radio astronomy, atmospheric studies, short-range indoor communication, chemical, biological sensing, medical and biological imaging, and detection of explosives. In this paper, we design a narrow bandpass terahertz wave filter using three kinds of two-dimensional photonic crystals. By using finite-difference time-domain (FDTD) method, we examined the transmittance spectra for the proposed terahertz wave filter. The simulated results show that the proposed filter exhibit excellent transmission performance such as high transmission at the central frequency, adjustable bandpass, and good rejection of the sideband frequencies.

  5. Terahertz wave filter based on photonic crystal

    NASA Astrophysics Data System (ADS)

    Liu, Yu-hang; Li, Jiu-sheng

    2012-03-01

    In the past decade, spectroscopy and imaging in the terahertz region (0.1-10 THz) of the electromagnetic spectrum has been applied in both basic research and potential industrial applications, such as medical diagnosis, security screening, radio astronomy, atmospheric studies, short-range indoor communication, chemical, biological sensing, medical and biological imaging, and detection of explosives. In this paper, we design a narrow bandpass terahertz wave filter using three kinds of two-dimensional photonic crystals. By using finite-difference time-domain (FDTD) method, we examined the transmittance spectra for the proposed terahertz wave filter. The simulated results show that the proposed filter exhibit excellent transmission performance such as high transmission at the central frequency, adjustable bandpass, and good rejection of the sideband frequencies.

  6. Enhanced photoacoustic detection using photonic crystal substrate

    NASA Astrophysics Data System (ADS)

    Zhao, Yunfei; Liu, Kaiyang; McClelland, John; Lu, Meng

    2014-04-01

    This paper demonstrates the enhanced photoacoustic sensing of surface-bound light absorbing molecules and metal nanoparticles using a one-dimensional photonic crystal (PC) substrate. The PC structure functions as an optical resonator at the wavelength where the analyte absorption is strong. The optical resonance of the PC sensor provides an intensified evanescent field with respect to the excitation light source and results in enhanced optical absorption by surface-immobilized samples. For the analysis of a light absorbing dye deposited on the PC surface, the intensity of photoacoustic signal was enhanced by more than 10-fold in comparison to an un-patterned acrylic substrate. The technique was also applied to detect gold nanorods and exhibited more than 40 times stronger photoacoustic signals. The demonstrated approach represents a potential path towards single molecule absorption spectroscopy with greater performance and inexpensive instrumentation.

  7. Simplified hollow-core photonic crystal fiber.

    PubMed

    Gérôme, Frédéric; Jamier, Raphaël; Auguste, Jean-Louis; Humbert, Georges; Blondy, Jean-Marc

    2010-04-15

    An original design of hollow-core photonic crystal fiber composed of a thin silica ring suspended in air by six silica struts is proposed. This structure can be viewed as a simplified Kagomé-lattice fiber reduced to one layer of air holes. By working on the core surround parameters, an efficient antiresonant air guiding was successfully demonstrated. Two large low-loss windows (visible/IR) were measured with a minimum attenuation less than 0.2 dB radicalm at yellow wavelengths, comparable with state-of-the-art designs. The curvature behavior was also studied, showing low bending loss sensitivity for the fundamental transmission band. These relevant features might open a new route to propose original hollow-core fiber designs while making their production simpler and faster than previously.

  8. Enhanced photoacoustic detection using photonic crystal substrate

    SciTech Connect

    Zhao, Yunfei; Liu, Kaiyang; McClelland, John; Lu, Meng

    2014-04-21

    This paper demonstrates the enhanced photoacoustic sensing of surface-bound light absorbing molecules and metal nanoparticles using a one-dimensional photonic crystal (PC) substrate. The PC structure functions as an optical resonator at the wavelength where the analyte absorption is strong. The optical resonance of the PC sensor provides an intensified evanescent field with respect to the excitation light source and results in enhanced optical absorption by surface-immobilized samples. For the analysis of a light absorbing dye deposited on the PC surface, the intensity of photoacoustic signal was enhanced by more than 10-fold in comparison to an un-patterned acrylic substrate. The technique was also applied to detect gold nanorods and exhibited more than 40 times stronger photoacoustic signals. The demonstrated approach represents a potential path towards single molecule absorption spectroscopy with greater performance and inexpensive instrumentation.

  9. 2D photonic-crystal optomechanical nanoresonator.

    PubMed

    Makles, K; Antoni, T; Kuhn, A G; Deléglise, S; Briant, T; Cohadon, P-F; Braive, R; Beaudoin, G; Pinard, L; Michel, C; Dolique, V; Flaminio, R; Cagnoli, G; Robert-Philip, I; Heidmann, A

    2015-01-15

    We present the optical optimization of an optomechanical device based on a suspended InP membrane patterned with a 2D near-wavelength grating (NWG) based on a 2D photonic-crystal geometry. We first identify by numerical simulation a set of geometrical parameters providing a reflectivity higher than 99.8% over a 50-nm span. We then study the limitations induced by the finite value of the optical waist and lateral size of the NWG pattern using different numerical approaches. The NWG grating, pierced in a suspended InP 265-nm thick membrane, is used to form a compact microcavity involving the suspended nanomembrane as an end mirror. The resulting cavity has a waist size smaller than 10 μm and a finesse in the 200 range. It is used to probe the Brownian motion of the mechanical modes of the nanomembrane. PMID:25679837

  10. Photonic crystal cavities with metallic Schottky contacts

    SciTech Connect

    Quiring, W.; Al-Hmoud, M.; Reuter, D.; Zrenner, A.; Rai, A.; Wieck, A. D.

    2015-07-27

    We report about the fabrication and analysis of high Q photonic crystal cavities with metallic Schottky-contacts. The structures are based on GaAs n-i membranes with an InGaAs quantum well in the i-region and nanostructured low ohmic metal top-gates. They are designed for photocurrent readout within the cavity and fast electric manipulations. The cavity structures are characterized by photoluminescence and photocurrent spectroscopy under resonant excitation. We find strong cavity resonances in the photocurrent spectra and surprisingly high Q-factors up to 6500. Temperature dependent photocurrent measurements in the region between 4.5 K and 310 K show an exponential enhancement of the photocurrent signal and an external quantum efficiency up to 0.26.

  11. Electric-field-tuned color in photonic crystal elastomers

    NASA Astrophysics Data System (ADS)

    Zhao, Qibin; Haines, Andrew; Snoswell, David; Keplinger, Christoph; Kaltseis, Rainer; Bauer, Siegfried; Graz, Ingrid; Denk, Richard; Spahn, Peter; Hellmann, Goetz; Baumberg, Jeremy J.

    2012-03-01

    Electrically tuned photonic crystals are produced by applying fields across shear-assembled elastomeric polymer opal thin films. At increasing voltages, the polymer opal films stretch biaxially under Maxwell stress, deforming the nanostructure and producing marked color changes. This quadratic electro-optic tuning of the photonic bandgap is repeatable over many cycles, switches within 100 ms, and bridges the gap between electro-active materials and photonic crystals.

  12. Liquid crystal-templated conducting organic polymers

    DOEpatents

    Stupp, Samuel I.; Hulvat, James F.

    2004-01-20

    A method of preparing a conductive polymeric film, includes providing a liquid crystal phase comprising a plurality of hydrophobic cores, the phase on a substrate, introducing a hydrophobic component to the phase, the component a conductive polymer precursor, and applying an electric potential across the liquid crystal phase, the potential sufficient to polymerize the said precursor.

  13. Liquid-Crystal Point-Diffraction Interferometer

    NASA Technical Reports Server (NTRS)

    Mercer, Carolyn R.

    1996-01-01

    Liquid-crystal point-diffraction interferometer (LCPDI) invented to combine flexible control of liquid-crystal phase-shifts with robustness of point-diffraction interferometers. Produces interferograms indicative of shapes of wavefronts of laser beams having passed through or reflected from objects of interest. Interferograms combined in computers to produce phase maps describing wavefronts.

  14. Demonstrations with a Liquid Crystal Shutter

    ERIC Educational Resources Information Center

    Kraftmakher, Yaakov

    2012-01-01

    The experiments presented show the response of a liquid crystal shutter to applied electric voltages and the delay of the operations. Both properties are important for liquid crystal displays of computers and television sets. Two characteristics of the shutter are determined: (i) the optical transmittance versus applied voltage of various…

  15. Liquid Crystals in Education--The Basics

    ERIC Educational Resources Information Center

    Cepic, Mojca

    2012-01-01

    The introduction of teaching about liquid crystals is discussed from several points of view: the rationale why to teach them, the basics about liquid crystals or what the teacher should teach about them, the fundamental pre-knowledge of students required, the set of experiments accompanying the teaching and the brief report on the already…

  16. Development of a 2D Photonic Crystal Biosensing Platform

    NASA Astrophysics Data System (ADS)

    Baker, James; Sriram, Rashmi; Miller, Benjamin

    2014-03-01

    The importance of early disease diagnosis both for initiating successful clinical treatment and preventing disease transmission continues to propel the development of rapid, ultrasensitive, label-free biosensors. Sensors that implement two-dimensional photonic bandgap crystal structures, in particular, have demonstrated the potential to achieve single-pathogen detection. To reach such high sensitivity, the architecture of the photonic crystal must be designed in a way that pathogen infiltration events are evident in the optical transmission spectrum of the crystal. Computational modeling results are useful both when designing an appropriate photonic crystal geometry and when interpreting experimental observations. Results of ongoing work are presented.

  17. Chemical and biological sensing using liquid crystals

    PubMed Central

    Carlton, Rebecca J.; Hunter, Jacob T.; Miller, Daniel S.; Abbasi, Reza; Mushenheim, Peter C.; Tan, Lie Na; Abbott, Nicholas L.

    2014-01-01

    The liquid crystalline state of matter arises from orientation-dependent, non-covalent interaction between molecules within condensed phases. Because the balance of intermolecular forces that underlies formation of liquid crystals is delicate, this state of matter can, in general, be easily perturbed by external stimuli (such as an electric field in a display). In this review, we present an overview of recent efforts that have focused on exploiting the responsiveness of liquid crystals as the basis of chemical and biological sensors. In this application of liquid crystals, the challenge is to design liquid crystalline systems that undergo changes in organization when perturbed by targeted chemical and biological species of interest. The approaches described below revolve around the design of interfaces that selectively bind targeted species, thus leading to surface-driven changes in the organization of the liquid crystals. Because liquid crystals possess anisotropic optical and dielectric properties, a range of different methods can be used to read out the changes in organization of liquid crystals that are caused by targeted chemical and biological species. This review focuses on principles for liquid crystal-based sensors that provide an optical output. PMID:24795857

  18. Absorption and emission in defective cholesteric liquid crystal cells

    NASA Astrophysics Data System (ADS)

    Gevorgyan, A. H.; Harutyunyan, M. Z.; Matinyan, G. K.; Oganesyan, K. B.; Rostovtsev, Yu V.; Kurizki, G.; Scully, M. O.

    2016-04-01

    We investigated peculiarities of absorption, emission and photonic density of states of a cholesteric liquid crystal with an isotropic defect layer inside. The influence of the defect layer position on absorption and emission in the system was studied. It was shown that for non-diffracting circularly polarized incident light absorption/emission is maximum if the defect is in the centre of the system; and for diffracting circularly polarized incident light absorption/emission is maximum if the defect is shifted from the centre of the system to its left border from where light is incident. We also investigated influence of the defect layer thickness and those parameters which characterize loss and gain on absorption and emission. The influence of anisotropic absorption in the cholesteric liquid crystal layer on photonic density states was investigated, too.

  19. Patterned cholesteric liquid crystal polymer film.

    PubMed

    Hsu, Wei-Liang; Ma, Ji; Myhre, Graham; Balakrishnan, Kaushik; Pau, Stanley

    2013-02-01

    Herein, the ability to create arbitrarily patterned circular polarized optical devices is demonstrated by using cholesteric liquid crystal polymer. Photoalignment with polarized ultraviolet light is utilized to create aligned cholesteric liquid crystal films. Two different methods, thermal annealing and solvent rinse, are utilized for patterning cholesteric liquid crystal films over large areas. The patterned cholesteric liquid crystal films are measured using a Mueller matrix imaging polarimeter, and the polarization properties, including depolarization index, circular diattenuation (CD), and circular retardance are derived. Patterned nonlinearly polarized optical devices can be fabricated with feature sizes as small as 20 μm with a CD of 0.812±0.015. Circular polarizing filters based on polymer cholesteric liquid crystal films have applications in three-dimensional displays, medical imaging, polarimetry, and interferometry. PMID:23456060

  20. Nonequilibrium molecular dynamics of liquid crystals

    NASA Astrophysics Data System (ADS)

    Sarman, S. S.; Cummings, P. T.; Evans, D. J.

    1994-11-01

    During the last 15 years, noneyuilibrium molecular dynamics (NEMD) has been successfully applied to study transport phenomena in fluids that are isotropic at equilibrium. A natural extension is therefore to study liquid crystals, which are anisotropic al equilibrium. The lower symmetry of these systems means that the linear transport coefficients are considerably more complicated than in an isotropic system. Part of the reason for this is that there are crosscouplings between tensors of different rank and parity. Such couplings arc symmetry-forbidden in isotropic phases. In this paper. we review some of fundamental theoretical results we have derived concerning the rheology of liquid crystals. report NEMD simulations of thermal conductivity and shear viscosity of liquid crystals, and present NEMD simulations of shear cessation phenomena. All of the NEMD results are presented for a model liquid crystal fluid which is a modification of the Gay-Borne fluid. The results obtained are in qualitative agreement with experimental measurements on liquid crystal systems.

  1. Liquid crystal device and method thereof

    DOEpatents

    Shiyanovskii, Sergij V; Gu, Mingxia; Lavrentovich, Oleg D

    2012-10-23

    The invention provides a liquid crystal device and method thereof. Subsequent to applying a first electrical voltage on a liquid crystal to induce a reorientation of the liquid crystal, a second electrical voltage with proper polarity is applied on the liquid crystal to assist the relaxation of the reorientation that was induced by the first electrical voltage. The "switch-off" phase of the liquid crystal can therefore be accelerated or temporally shortened, and the device can exhibit better performance such as fast response to on/off signals. The invention can be widely used LCD, LC shutter, LC lens, spatial light modulator, telecommunication device, tunable filter, beam steering device, and electrically driven LC device, among others.

  2. Transient Plasma Photonic Crystals for High-Power Lasers.

    PubMed

    Lehmann, G; Spatschek, K H

    2016-06-01

    A new type of transient photonic crystals for high-power lasers is presented. The crystal is produced by counterpropagating laser beams in plasma. Trapped electrons and electrically forced ions generate a strong density grating. The lifetime of the transient photonic crystal is determined by the ballistic motion of ions. The robustness of the photonic crystal allows one to manipulate high-intensity laser pulses. The scheme of the crystal is analyzed here by 1D Vlasov simulations. Reflection or transmission of high-power laser pulses are predicted by particle-in-cell simulations. It is shown that a transient plasma photonic crystal may act as a tunable mirror for intense laser pulses. Generalizations to 2D and 3D configurations are possible. PMID:27314721

  3. Transient Plasma Photonic Crystals for High-Power Lasers

    NASA Astrophysics Data System (ADS)

    Lehmann, G.; Spatschek, K. H.

    2016-06-01

    A new type of transient photonic crystals for high-power lasers is presented. The crystal is produced by counterpropagating laser beams in plasma. Trapped electrons and electrically forced ions generate a strong density grating. The lifetime of the transient photonic crystal is determined by the ballistic motion of ions. The robustness of the photonic crystal allows one to manipulate high-intensity laser pulses. The scheme of the crystal is analyzed here by 1D Vlasov simulations. Reflection or transmission of high-power laser pulses are predicted by particle-in-cell simulations. It is shown that a transient plasma photonic crystal may act as a tunable mirror for intense laser pulses. Generalizations to 2D and 3D configurations are possible.

  4. Optical limiter based on two-dimensional nonlinear photonic crystals

    NASA Astrophysics Data System (ADS)

    Belabbas, Amirouche; Lazoul, Mohamed

    2016-04-01

    The aim behind this work is to investigate the capabilities of nonlinear photonic crystals to achieve ultra-fast optical limiters based on third order nonlinear effects. The purpose is to combine the actions of nonlinear effects with the properties of photonic crystals in order to activate the photonic band according to the magnitude of the nonlinear effects, themselves a function of incident laser power. We are interested in designing an optical limiter based nonlinear photonic crystal operating around 1064 nm and its second harmonic at 532 nm. Indeed, a very powerful solid-state laser that can blind or destroy optical sensors and is widely available and easy to handle. In this work, we perform design and optimization by numerical simulations to determine the better structure for the nonlinear photonic crystal to achieve compact and efficient integrated optical limiter. The approach consists to analyze the band structures in Kerr-nonlinear two-dimensional photonic crystals as a function of the optical intensity. We confirm that these bands are dynamically red-shifted with regard to the bands observed in linear photonic crystals or in the case of weak nonlinear effects. The implemented approach will help to understand such phenomena as intensitydriven optical limiting with Kerr-nonlinear photonic crystals.

  5. Nanotube networks in liquid crystals

    NASA Astrophysics Data System (ADS)

    Urbanski, Martin; Lagerwall, Jan Peter F.; Scalia, Giusy

    2016-03-01

    Liquid crystals (LCs) are very attractive hosts for the organization of anisotropic nanoparticles such as carbon nanotubes (CNTs) because of the macroscopic organization resulting in properties of nanoparticles manifest at a macroscopic scale. Different types of LCs have demonstrated the ability to organize nanotubes, showing the generality of the approach, i.e., that the liquid crystallinity per se is the driving factor for the organization. Compared to standard nanotube composites (e.g. with disordered polymer hosts) the introduction of carbon nanotubes into an LC allows not only the transfer of the outstanding CNT properties to the macroscopic phase, providing strength and conductivity, but these properties also become anisotropic, following the transfer of the orientational order from the LC to the CNTs. The LC molecular structure plays an important even if ancillary role since it enters in the surface interactions, fulfilling a mediating action between the particle and the bulk of the LC. Isolated nanotubes can be obtained by optimized dispersions at lower concentrations and this process requires the use or development of tailored strategies like using solvents or even another LC for pre-dispersing CNTs. Aggregates or networks can be observed in poor dispersions and at higher nanoparticle concentrations. In those, due to surface interactions, the LC behaviour can be strongly affected with changes in phase sequences or transition temperatures and the effect is expected to be more pronounced as the concentration of nanotubes increases. We present preliminary investigations and observations on nanotube - LC systems based on a smectic LC host.

  6. Experimental GVD engineering in slow light slot photonic crystal waveguides

    PubMed Central

    Serna, Samuel; Colman, Pierre; Zhang, Weiwei; Le Roux, Xavier; Caer, Charles; Vivien, Laurent; Cassan, Eric

    2016-01-01

    The use in silicon photonics of the new optical materials developed in soft matter science (e.g. polymers, liquids) is delicate because their low refractive index weakens the confinement of light and prevents an efficient control of the dispersion properties through the geometry. We experimentally demonstrate that such materials can be incorporated in 700 μm long slot photonic crystal waveguides, and hence can benefit from both slow-light field enhancement effect and slot-induced ultra-small effective areas. Additionally, we show that their dispersion can be engineered from anomalous to normal regions, along with the presence of multiple zero group velocity dispersion (ZGVD) points exhibiting Normalized Delay Bandwidth Product as high as 0.156. The reported results provide experimental evidence for an accurate control of the dispersion properties of fillable periodical slotted structures in silicon photonics, which is of direct interest for on-chip all-optical data treatment using nonlinear optical effects in hybrid-on-silicon technologies. PMID:27243377

  7. Experimental GVD engineering in slow light slot photonic crystal waveguides

    NASA Astrophysics Data System (ADS)

    Serna, Samuel; Colman, Pierre; Zhang, Weiwei; Le Roux, Xavier; Caer, Charles; Vivien, Laurent; Cassan, Eric

    2016-05-01

    The use in silicon photonics of the new optical materials developed in soft matter science (e.g. polymers, liquids) is delicate because their low refractive index weakens the confinement of light and prevents an efficient control of the dispersion properties through the geometry. We experimentally demonstrate that such materials can be incorporated in 700 μm long slot photonic crystal waveguides, and hence can benefit from both slow-light field enhancement effect and slot-induced ultra-small effective areas. Additionally, we show that their dispersion can be engineered from anomalous to normal regions, along with the presence of multiple zero group velocity dispersion (ZGVD) points exhibiting Normalized Delay Bandwidth Product as high as 0.156. The reported results provide experimental evidence for an accurate control of the dispersion properties of fillable periodical slotted structures in silicon photonics, which is of direct interest for on-chip all-optical data treatment using nonlinear optical effects in hybrid-on-silicon technologies.

  8. Bistable liquid crystal device fabricated via microscale liquid crystal alignment

    NASA Astrophysics Data System (ADS)

    Honma, Michinori; Toyoshima, Wataru; Nose, Toshiaki

    2016-10-01

    Bistable liquid crystal (LC) molecular orientation properties in micropatterned LC cells were investigated experimentally and theoretically. When an LC cell was heated to the phase-transition temperature and then cooled, an LC orientation with ±π/2-twist domains (±π/2-twist mode) was obtained. Furthermore, a different LC orientation with ±π-twist domains (±π-twist mode) was observed when a 10-V potential was applied across a sample LC cell. Both orientation states were stably retained over a long period. Herein, cross-sectional LC orientation models in the ±π/2- and ±π-twist modes are proposed to explain the generation and behavior of two different disclination lines. The total energies within one period in the ±π/2- and ±π-twist modes (F±π/2 and F±π, respectively) were estimated theoretically. These energies were found to depend on the LC layer thickness and to cross over at a certain thickness; this indicates that F±π is equal to F±π/2 at this equilibrium thickness. The best temporal stability is likely attained at this equilibrium thickness. We demonstrated a bistable color-switching device by combining a full-wave plate and crossed polarizers. When these optical components were configured properly, stable bistable switching between two colors was achieved.

  9. Coupling light in photonic crystal waveguides: A review

    NASA Astrophysics Data System (ADS)

    Dutta, Hemant Sankar; Goyal, Amit Kumar; Srivastava, Varun; Pal, Suchandan

    2016-07-01

    Submicron scale structures with high index contrast are key to compact structures for realizing photonic integrated structures. Ultra-compact optical devices in silicon-on-insulator (SOI) substrates serve compatibility with semiconductor fabrication technology leading to reduction of cost and mass production. Photonic crystal structures possess immense potential for realizing various compact optical devices. However, coupling light to photonic crystal waveguide structures is crucial in order to achieve strong transmission and wider bandwidth of signal. Widening of bandwidth will increase potential for various applications and high transmission will make easy signal detection at the output. In this paper, the techniques reported so far for coupling light in photonic crystal waveguides have been reviewed and analyzed so that a comprehensive guide for an efficient coupling to photonic crystal waveguides can be made possible.

  10. Photonic-crystal slab for terahertz-wave technology platform

    NASA Astrophysics Data System (ADS)

    Fujita, Masayuki

    2016-03-01

    Photonic crystals manipulate photons in a manner analogous to solid-state crystals, and are composed of a dielectric material with a periodic refractive index distribution. In particular, two-dimensional photonic-crystal slabs with high index contrasts (semiconductor/air) are promising for practical applications, owing to the strong optical confinement in simple, thin planar structures. This paper presents the recent progress on a silicon photonic-crystal slab as a technology platform in the terahertz-wave region, which is located between the radio and light wave regions (0.1-10 THz). Extremely low-loss (<0.1 dB/cm) terahertz waveguides based on the photonic-bandgap effect as well as dynamic control and modulation of a terahertz-wave transmission in a photonic-crystal slab by the effective interaction between photoexcited carriers and the terahertz-wave trapping due to the photonic band-edge effect are demonstrated. Terahertz photonic-crystal slabs hold the potential for developing ultralow-loss, compact terahertz components and integrated devices used in applications including wireless communication, spectroscopic sensing, and imaging.

  11. Photonic crystal channel drop filters based on fractal structures

    NASA Astrophysics Data System (ADS)

    Dideban, Ali; Habibiyan, Hamidreza; Ghafoorifard, Hassan

    2014-09-01

    In this paper we introduce new configurations of channel drop filters based on two-dimensional photonic crystals. Structures consist of two photonic crystal waveguides and a fractal-shaped resonator between them. The effect of structural parameters on resonance frequency and drop efficiency is investigated. Calculations of band structure and propagation of electromagnetic field through devices are done by plane wave expansion (PWE) and finite difference time domain (FDTD) methods, respectively. In our designs more than 95% drop efficiency with quality factor of ~1150 is achievable at wavelength near 1540 nm, which in comparison with other photonic crystal resonator structures is a very satisfactory and acceptable result.

  12. Three dimensional reflectance properties of superconductor-dielectric photonic crystal

    NASA Astrophysics Data System (ADS)

    Pandey, G. N.; Pandey, J. P.; Pandey, U. K.; Sancheti, Bhagyashree; Ojha, S. P.

    2016-05-01

    In this present communication, we have studied the optical properties of Photonics Crystals with super conducting constituent using the TMM method for a stratified medium. We also studied the three dimensional reflectance property of superconductor-dielectric photonic crystal at different temperature and thickness. From above study we show that the superconductor-dielectric photonic crystal may be used as broad band reflector and omnidirectional reflector at low temperature below to the critical temperature. Such property may be applied to make of the reflector which can be used in low temperature region.

  13. Two distinct crystallization processes in supercooled liquid.

    PubMed

    Tane, Masakazu; Kimizuka, Hajime; Ichitsubo, Tetsu

    2016-05-21

    Using molecular dynamics simulations we show that two distinct crystallization processes, depending on the temperature at which crystallization occurs, appear in a supercooled liquid. As a model for glass-forming materials, an Al2O3 model system, in which both the glass transition and crystallization from the supercooled liquid can be well reproduced, is employed. Simulations in the framework of an isothermal-isobaric ensemble indicate that the calculated time-temperature-transformation curve for the crystallization to γ(defect spinel)-Al2O3 exhibited a typical nose shape, as experimentally observed in various glass materials. During annealing above the nose temperature, the structure of the supercooled liquid does not change before the crystallization, because of the high atomic mobility (material transport). Thus, the crystallization is governed by the abrupt crystal nucleation, which results in the formation of a stable crystal structure. In contrast, during annealing below the nose temperature, the structure of the supercooled liquid gradually changes before the crystallization, and the formed crystal structure is less stable than that formed above the nose temperature, because of the restricted material transport. PMID:27208956

  14. Two distinct crystallization processes in supercooled liquid

    NASA Astrophysics Data System (ADS)

    Tane, Masakazu; Kimizuka, Hajime; Ichitsubo, Tetsu

    2016-05-01

    Using molecular dynamics simulations we show that two distinct crystallization processes, depending on the temperature at which crystallization occurs, appear in a supercooled liquid. As a model for glass-forming materials, an Al2O3 model system, in which both the glass transition and crystallization from the supercooled liquid can be well reproduced, is employed. Simulations in the framework of an isothermal-isobaric ensemble indicate that the calculated time-temperature-transformation curve for the crystallization to γ(defect spinel)-Al2O3 exhibited a typical nose shape, as experimentally observed in various glass materials. During annealing above the nose temperature, the structure of the supercooled liquid does not change before the crystallization, because of the high atomic mobility (material transport). Thus, the crystallization is governed by the abrupt crystal nucleation, which results in the formation of a stable crystal structure. In contrast, during annealing below the nose temperature, the structure of the supercooled liquid gradually changes before the crystallization, and the formed crystal structure is less stable than that formed above the nose temperature, because of the restricted material transport.

  15. Advancements of vertically aligned liquid crystal displays.

    PubMed

    Kumar, Pankaj; Jaggi, Chinky; Sharma, Vandna; Raina, Kuldeep Kumar

    2016-02-01

    This review describes the recent advancements in the field of the vertical aligned (VA) liquid crystal displays. The process and formation of different vertical alignment modes such as conventional VA, patterned VA, multi-domain VA, and polymer stabilised VA etc are widely discussed. Vertical alignment of liquid crystal due to nano particle dispersion in LC host, bifunctional PR-SAM formed by silane coupling reaction to oxide surfaces, azo dye etc., are also highlighted and discussed. Overall, the article highlights the advances in the research of vertical aligned liquid crystal in terms of their scientific and technological aspects.

  16. Liquid Crystal Research Shows Deformation By Drying

    NASA Technical Reports Server (NTRS)

    2003-01-01

    These images, from David Weitz's liquid crystal research, show ordered uniform sized droplets (upper left) before they are dried from their solution. After the droplets are dried (upper right), they are viewed with crossed polarizers that show the deformation caused by drying, a process that orients the bipolar structure of the liquid crystal within the droplets. When an electric field is applied to the dried droplets (lower left), and then increased (lower right), the liquid crystal within the droplets switches its alignment, thereby reducing the amount of light that can be scattered by the droplets when a beam is shone through them.

  17. Tactoids of chiral liquid crystals

    NASA Astrophysics Data System (ADS)

    Palacio-Betancur, Viviana; Villada-Gil, Stiven; Zhou, Ye; Armas-Pérez, Julio C.; de Pablo, Juan José; Hernández-Ortiz, Juan Pablo

    The phase diagram of chiral liquid crystals confined in ellipsoids is obtained, by following a theoretically informed Monte Carlo relaxation of the tensor alignment field Q. The free energy of the system is described by a functional in the framework of the Landau-de Gennes formalism. This study also includes the effect of anchoring strength, curvature, and chirality of the system. In the low chirality region of the phase diagram we found the twist bipolar (BS) phase and some cholesteric phases such as the radial spherical structure (RSS), twist cylinder (TC) and double twist cylinder (DTC) whose axis of rotation is not necessarily aligned with the major axis of the geometry. For high chirality scenarios, the disclination lines are twisted or bent near the surface preventing the formation of symmetric networks of defects, although an hexagonal pattern is formed on the surface which might serve as open sites for collocation of colloids. By analyzing the free energies of isochoric systems, prolate geometries tend to be more favorable for high chirality and low anchoring conditions. Universidad Nacional de Colombia Ph.D. grant and COLCIENCIAS under the Contract No. 110-165-843-748. CONACYT for Postdoctoral Fellowships Nos. 186166 and 203840.

  18. Liquid crystals for laser applications

    NASA Astrophysics Data System (ADS)

    Jacobs, S. D.; Marshall, K. L.; Schmid, A.

    1992-10-01

    This article highlights some of the advances made in the use of liquid crystals for laser applications from 1982 through 1992. New materials and new effects were discovered, many new devices were developed, and novel applications for well-understood phenomena were conceived. This was quite an eventful time period. Several new books were published on the broad subject of LC's, and the international scientific community organized a society devoted to encouraging further scientific and educational advancement in the field. Attention was focused on LC's in October of 1991 when the Nobel Prize in Physics was awarded to Pierre-Gilles de Gennes for his pioneering work toward understanding order phenomena in LC's and polymers. This article is divided into four sections. The first section discusses new materials, specifically ferroelectric LC's and LC polymers. The former have opened up the realm of submicrosecond response for LC devices, and the latter have significantly reduced the sensitivity of LC optics to temperature. Some new insights into the optical properties of materials are also mentioned. The second section reviews new developments in passive applications for cholesterics and nematics. Included here are the fabrication of cholesteric laser mirrors and apodizers, the use of LC polymers for notch filters and as optical storage media, and some novel nematic retarder concepts such as the distributed polarization rotator.

  19. Stretchable liquid-crystal blue-phase gels.

    PubMed

    Castles, F; Morris, S M; Hung, J M C; Qasim, M M; Wright, A D; Nosheen, S; Choi, S S; Outram, B I; Elston, S J; Burgess, C; Hill, L; Wilkinson, T D; Coles, H J

    2014-08-01

    Liquid-crystalline polymers are materials of considerable scientific interest and technological value. An important subset of these materials exhibit rubber-like elasticity, combining the optical properties of liquid crystals with the mechanical properties of rubber. Moreover, they exhibit behaviour not seen in either type of material independently, and many of their properties depend crucially on the particular mesophase employed. Such stretchable liquid-crystalline polymers have previously been demonstrated in the nematic, chiral-nematic, and smectic mesophases. Here, we report the fabrication of a stretchable gel of blue phase I, which forms a self-assembled, three-dimensional photonic crystal that remains electro-optically switchable under a moderate applied voltage, and whose optical properties can be manipulated by an applied strain. We also find that, unlike its undistorted counterpart, a mechanically deformed blue phase exhibits a Pockels electro-optic effect, which sets out new theoretical challenges and possibilities for low-voltage electro-optic devices.

  20. Hierarchical Organization in Liquid Crystal-in-Liquid Crystal Emulsions

    PubMed Central

    Mushenheim, Peter C.

    2014-01-01

    We report the formation and characterization of hierarchical ordering in systems comprised of micrometer-sized droplets of thermotropic nematic liquid crystals (LCs) dispersed in continuous nematic phases of a lyotropic chromonic LC (disodium cromoglycate (DSCG)). Significantly, we find the orientations of the two LC phases to be coupled, with nematic droplets of 4′-pentyl-4-cyanobiphenyl (5CB) exhibiting a bipolar configuration with an axis of symmetry aligned orthogonal to the far-field director of the DSCG phase. We determine that this coupling of orientations does not result from either anisometric LC droplet shape or interfacial ionic phenomena but rather is consistent with the influence of van der Waals interactions that arise from the anisotropic polarizabilities of nematic 5CB (Δn = + 0.18) and DSCG (Δn = − 0.02) phases. We also find that it is possible to rotate and uniformly align the nematic droplets by using a weak magnetic field (B ∼ 0.3 T). An analysis of the dynamics of relaxation of the orientations of the 5CB droplets following removal of the magnetic field reveals the DSCG and 5CB droplets to be coupled by energies of ∼104kT, consistent with a simple theoretical estimate of the influence of anisotropic van der Waals interactions. We also observed the nematic 5CB droplets to form dimers and larger assemblies mediated by the elasticity of the nematic DSCG. Overall, these results reveal that LC-in-LC emulsions define a new class of hierarchically ordered soft matter in which both thermotropic and lyotropic LCs are coupled in their ordering. PMID:25278032

  1. Synthesis and characterization of novel glassy liquid crystals

    NASA Astrophysics Data System (ADS)

    Chen, Huang-Ming Philip

    As an emerging class of photonic and electronic materials, glassy liquid crystals are capable of preserving in the solid state molecular order characteristic of liquid crystals. Because of superior chemical purity and favorable rheological properties, glassy liquid crystals can be readily processed into large-area monodomain films. This thesis aimed at deterministic synthesis of glassy chiral nematics, photochromic glassy nematics, and glassy discotics. The most significant contributions are recapitulated as follows: (1) Through deterministic synthesis of multifunctional materials via enzymatic and chemical approaches, enantiomeric glassy chiral nematics were prepared efficiently and shown to possess a glass transition temperature over 60°C and a cholesteric fluid temperature range wider than 100°C. Device concepts were also demonstrated for high-performance circular polarizers, notch filters and reflectors in the ultraviolet, across the visible, and to the infrared region. (2) The first photochromic glassy nematic liquid crystal was successfully designed, synthesized and characterized to possess a glass transition temperature over 100°C and a clearing point over 200°C. A large-area solid film was prepared through melt processing to demonstrate high-speed switching of anisotropic refractive indices and optical birefringence as a novel approach to rewritable optical memory and photonic switching in solid films. (3) Glassy discotic liquid crystals were synthesized and characterized by x-ray diffraction, polarizing optical microscopy, differential scanning calorimetry, and dynamic mechanical analysis to reveal sub-freezing glass transition temperatures. However, the absence of recrystallization at room temperature over a period of over four years was a manifestation of morphological stability of the discotics.

  2. Hollow core photonic crystal fiber as a robust Raman biosensor

    NASA Astrophysics Data System (ADS)

    Khetani, Altaf; Momenpour T. Monfared, Ali; Tiwari, Vidhu S.; Anis, Hanan; Riordon, Jason; Godin, Michel

    2013-03-01

    The present work demonstrates the integration of hollow core photonic crystal fibers (HC-PCF), microfluidics, and statistical analysis for monitoring biomolecules using Raman spectroscopy. HC-PCF as a signal enhancer has been proven by many researchers. However, there have been challenges in using HC-PCF for practical applications due to limitations such as coupling, stability, evaporation, clogging, consistent filling, and reusing the same fiber. This limited the potential of HC-PCF to detect low concentrations of liquid samples, which is why HC-PCF still hasn't transcended the lab barriers. The current device is based on an H-design lay-out which uses the pressure difference between the two ends of the fiber for filling and flushing the liquid samples. This mitigated several issues related to device performance by allowing us to fill the fiber with liquid samples consistently, rapidly and reproducibly. The resulting Raman signals were significantly more stable as various concentrations of ethanol in water were sequentially introduced into the fiber. The scheme also allowed us to overcome the barrier of predicting low concentrations by applying Partial Least Square (PLS) technique which was done for the first time using HC-PCF. Thus, the present scheme paves path for the inclusion of HC-PCF in the main stream point-of-care technology.

  3. Nanomanipulation using silicon photonic crystal resonators.

    PubMed

    Mandal, Sudeep; Serey, Xavier; Erickson, David

    2010-01-01

    Optical tweezers have enabled a number of microscale processes such as single cell handling, flow-cytometry, directed assembly, and optical chromatography. To extend this functionality to the nanoscale, a number of near-field approaches have been developed that yield much higher optical forces by confining light to subwavelength volumes. At present, these techniques are limited in both the complexity and precision with which handling can be performed. Here, we present a new class of nanoscale optical trap exploiting optical resonance in one-dimensional silicon photonic crystals. The trapping of 48 nm and 62 nm dielectric nanoparticles is demonstrated along with the ability to transport, trap, and manipulate larger nanoparticles by simultaneously exploiting the propagating nature of the light in a coupling waveguide and its stationary nature within the resonator. Field amplification within the resonator is shown to produce a trap several orders of magnitude stronger than conventional tweezers and an order of magnitude stiffer than other near-field techniques. Our approach lays the groundwork for a new class of optical trapping platforms that could eventually enable complex all-optical single molecule manipulation and directed assembly of nanoscale material.

  4. Color changing photonic crystals detect blast exposure.

    PubMed

    Cullen, D Kacy; Xu, Yongan; Reneer, Dexter V; Browne, Kevin D; Geddes, James W; Yang, Shu; Smith, Douglas H

    2011-01-01

    Blast-induced traumatic brain injury (bTBI) is the "signature wound" of the current wars in Iraq and Afghanistan. However, with no objective information of relative blast exposure, warfighters with bTBI may not receive appropriate medical care and are at risk of being returned to the battlefield. Accordingly, we have created a colorimetric blast injury dosimeter (BID) that exploits material failure of photonic crystals to detect blast exposure. Appearing like a colored sticker, the BID is fabricated in photosensitive polymers via multi-beam interference lithography. Although very stable in the presence of heat, cold or physical impact, sculpted micro- and nano-structures of the BID are physically altered in a precise manner by blast exposure, resulting in color changes that correspond with blast intensity. This approach offers a lightweight, power-free sensor that can be readily interpreted by the naked eye. Importantly, with future refinement this technology may be deployed to identify soldiers exposed to blast at levels suggested to be supra-threshold for non-impact blast-induced mild TBI.

  5. Optics in Microstructured and Photonic Crystal Fibers

    NASA Astrophysics Data System (ADS)

    Knight, J. C.

    2008-10-01

    The development of optical fibers with two-dimensional patterns of air holes running down their length has reinvigorated research in the field of fiber optics. It has greatly—and fundamentally—broadened the range of specialty optical fibers, by demonstrating that optical fibers can be more "special" than previously thought. Fibers with air cores have made it possible to deliver energetic femtosecond-scale optical pulses, transform limited, as solitons, using single-mode fiber. Other fibers with anomalous dispersion at visible wavelengths have spawned a new generation of single-mode optical supercontinuum sources, spanning visible and near-infrared wavelengths and based on compact pump sources. A third example is in the field of fiber lasers, where the use of photonic crystal fiber concepts has led to a new hybrid laser technology, in which the very high numerical aperture available sing air holes have enabled fibers so short they are more naturally held straight than bent. This paper describes some of the basic physics and technology behind these developments, illustrated with some of the impressive demonstrations of the past 18 months.

  6. Color changing photonic crystals detect blast exposure

    PubMed Central

    Cullen, D. Kacy; Xu, Yongan; Reneer, Dexter V.; Browne, Kevin D.; Geddes, James W.; Yang, Shu; Smith, Douglas H.

    2010-01-01

    Blast-induced traumatic brain injury (bTBI) is the “signature wound” of the current wars in Iraq and Afghanistan. However, with no objective information of relative blast exposure, warfighters with bTBI may not receive appropriate medical care and are at risk of being returned to the battlefield. Accordingly, we have created a colorimetric blast injury dosimeter (BID) that exploits material failure of photonic crystals to detect blast exposure. Appearing like a colored sticker, the BID is fabricated in photosensitive polymers via multi-beam interference lithography. Although very stable in the presence of heat, cold or physical impact, sculpted micro- and nano-structures of the BID are physically altered in a precise manner by blast exposure, resulting in color changes that correspond with blast intensity. This approach offers a lightweight, power-free sensor that can be readily interpreted by the naked eye. Importantly, with future refinement this technology may be deployed to identify soldiers exposed to blast at levels suggested to be supra-threshold for non-impact blast-induced mild TBI. PMID:21040795

  7. Topological Z2 Gapless Photonic Crystals

    NASA Astrophysics Data System (ADS)

    Xie, Biye; Wang, Zidan

    Topological properties of electronic materials with gapless band structure such as Topological Semimetals(TSMs) and Topological Metals(TMs) have drew lots of attention to both theoretical and experimental physicists recently. Although theoretical prediction of TSMs and TMs have been done well, experimental study of them is quite difficult to perform due to the fact that it is very difficult to control and design certain electronic materials. However, since the topological properties stem from the geometric feature, we can study them in Photonic Crystals(PhCs) which are much easy to be controlled and designed. Here we study 2-dimension PhCs consisting of gyrotropic materials with hexagonal structure. In the Brillouin corner, the dispersion relation has gapless points which are similar to Dirac Cones in electronic materials. We firstly derive the effective Hamiltonian of this system and show that if certain perturbation is added to this effective Hamiltonian, this system belongs to AII class according to Altland and Zirbauer topological classification and is described by a Z2 topological charge. Finally we also propose a way to detect this Z2 topological charge using momentum space Aharonov-Bohm interferometer which is firstly proposed by L.Duca and T.Li,etc.

  8. Photonic crystal fiber interferometric vector bending sensor.

    PubMed

    Villatoro, Joel; Minkovich, Vladimir P; Zubia, Joseba

    2015-07-01

    A compact and highly sensitive interferometric bending sensor (inclinometer) capable of distinguishing the bending or inclination orientation is demonstrated. The device operates in reflection mode and consists of a short segment of photonic crystal fiber (PCF) inserted in conventional single-mode optical fiber (SMF). A microscopic collapsed zone in the PCF-SMF junction allows the excitation and recombination of core modes, hence, to build a mode interferometer. Bending on the device induces asymmetric refractive index changes in the PCF core as well as losses. As a result, the effective indices and intensities of the interfering modes are altered, which makes the interference pattern shift and shrink. The asymmetric index changes in the PCF make our device capable of distinguishing the bending orientation. The sensitivity of our sensor is up to 1225 pm/degree and it can be used to monitor small bending angles (±2°). We believe that the attributes of our sensor make it appealing in a number of applications. PMID:26125380

  9. Two-pattern compound photonic crystals with a large complete photonic band gap

    SciTech Connect

    Jia Lin; Thomas, Edwin L.

    2011-09-15

    We present a set of two-dimensional aperiodic structures with a large complete photonic band gap (PBG), which are named two-pattern photonic crystals. By superposing two substructures without regard to registration, we designed six new aperiodic PBG structures having a complete PBG larger than 15% for {epsilon}{sub 2}/{epsilon}{sub 1} = 11.4. The rod-honeycomb two-pattern photonic crystal provides the largest complete PBG to date. An aperiodic structure becomes the champion structure with the largest PBG. Surprisingly, the TM and TE gaps of a two-pattern photonic crystal are much less interdependent than the PBGs of conventional photonic crystals proposed before, affording interesting capabilities for us to tune the TM and TE PBGs separately. By altering the respective substructures, optical devices for different polarizations (TE, TM, or both) can readily be designed.

  10. Negative refraction, subwavelength focusing and beam formation by photonic crystals

    NASA Astrophysics Data System (ADS)

    Ozbay, Ekmel; Aydin, Koray; Bulu, Irfan; Guven, Kaan

    2007-05-01

    We present a review of our experimental and numerical studies on the negative refraction related phenomena in two-dimensional dielectric photonic crystals (PCs). By employing photonic bands with appropriate dispersion, the propagation of the electromagnetic wave through a PC can be controlled to a large extent, and diverse and completely novel electromagnetic phenomena can be generated. We perform the spectral analysis of the negative refraction arising from a convex TM polarized photonic band of a hexagonal PC. As a consequence of negative refraction, we demonstrate a photonic crystal flat lens, which has the ability to focus electromagnetic waves and provide subwavelength resolution laterally. Finally, a photonic crystal with an embedded source is shown to provide a highly directional beam, which can be utilized in certain antenna applications.

  11. Photonic crystals for improving light absorption in organic solar cells

    SciTech Connect

    Duché, D. Le Rouzo, J.; Masclaux, C.; Gourgon, C.

    2015-02-07

    We theoretically and experimentally study the structuration of organic solar cells in the shape of photonic crystal slabs. By taking advantage of the optical properties of photonic crystals slabs, we show the possibility to couple Bloch modes with very low group velocities in the active layer of the cells. These Bloch modes, also called slow Bloch modes (SBMs), allow increasing the lifetime of photons within the active layer. Finally, we present experimental demonstration performed by using nanoimprint to directly pattern the standard poly-3-hexylthiophène:[6,6]-phenyl-C61-butiryc acid methyl ester organic semiconductor blend in thin film form in the shape of a photonic crystal able to couple SBMs. In agreement with the model, optical characterizations will demonstrate significant photonic absorption gains.

  12. Polymer single crystal membrane from liquid/liquid interface

    NASA Astrophysics Data System (ADS)

    Wang, Wenda; Li, Christopher; Soft Matter Research Group-Drexel University Team

    2013-03-01

    Vesicles, mimicking the structure of cell membrane at the molecular scale, are small membrane-enclosed sacks that can store or transport substances. The weak mechanical properties and the nature of environment-sensitivity of the current available vesicles: liposomes, polymersomes, colloidsomes limit their applications as an excellent candidate for targeting delivery of drugs/genes in biomedical engineering and treatment. Recently, we developed an emulsion-based method to grow curved polymer single crystals. Varying the polymer concentration and/or the emulsification conditions (such as surfactant concentration, water-oil volume ratio), curved crystals with different sizes and different openness could be obtained. This growing process was attributed to polymer crystal growth along the liquid/liquid interface. In addition, the liquid/liquid interfacial crystal growth is promising for synthesis of enclosed hollow sphere.

  13. Pendellösung effect in photonic crystals

    NASA Astrophysics Data System (ADS)

    Savo, S.; di Gennaro, E.; Miletto, C.; Andreone, A.; Dardano, P.; Moretti, L.; Mocella, V.

    2008-06-01

    At the exit surface of a photonic crystal, the intensity of the diffracted wave can be periodically modulated, showing a maximum in the "positive" (forward diffracted) or in the "negative" (diffracted) direction, depending on the slab thickness. This thickness dependence is a direct result of the so-called Pendellosung phenomenon, consisting of the periodic exchange inside the crystal of the energy between direct and diffracted beams. We report the experimental observation of this effect in the microwave region at about 14 GHz by irradiating 2D photonic crystal slabs of different thickness and detecting the intensity distribution of the electromagnetic field at the exit surface and inside the crystal itself.

  14. Rapid leak detection with liquid crystals

    NASA Technical Reports Server (NTRS)

    Heisman, R. M.; Iceland, W. F.; Ruppe, E. P.

    1978-01-01

    Small leaks in vacuum lines are detected by applying liquid-crystal coating, warming suspected area, and observing color change due to differential cooling by leak jet. Technique is used on inside or outside walls of vacuum-jacketed lines.

  15. Liquid crystal television spatial light modulators

    NASA Technical Reports Server (NTRS)

    Liu, Hua-Kuang; Chao, Tien-Hsin

    1989-01-01

    The spatial light modulation characteristics and capabilities of the liquid crystal television (LCTV) spatial light modulators (SLMs) are discussed. A comparison of Radio Shack, Epson, and Citizen LCTV SLMs is made.

  16. Liquid crystal on subwavelength metal gratings

    NASA Astrophysics Data System (ADS)

    Palto, S. P.; Barnik, M. I.; Artemov, V. V.; Shtykov, N. M.; Geivandov, A. R.; Yudin, S. G.; Gorkunov, M. V.

    2015-06-01

    Optical and electrooptical properties of a system consisting of subwavelength metal gratings and nematic liquid crystal layer are studied. Aluminium gratings that also act as interdigitated electrodes are produced by focused ion beam lithography. It is found that a liquid crystal layer strongly influences both the resonance and light polarization properties characteristic of the gratings. Enhanced transmittance is observed not only for the TM-polarized light in the near infrared spectral range but also for the TE-polarized light in the visible range. Although the electrodes are separated by nanosized slits, and the electric field is strongly localized near the surface, a pronounced electrooptical effect is registered. The effect is explained in terms of local reorientation of liquid crystal molecules at the grating surface and propagation of the orientational deformation from the surface into the bulk of the liquid crystal layer.

  17. Slow light in liquid crystal media

    NASA Astrophysics Data System (ADS)

    Bortolozzo, Umberto; Wei, Dong; Huignard, Jean-Pierre; Residori, Stefania

    2014-10-01

    Liquid crystal media are characterized by large and tunable dispersive properties and hence allow achievement of large group delays. At the same time, liquid crystals provide large areas and are easily reconfigurable and highly sensitive devices; they are, therefore, well adapted for interferometric applications. Two different ways of achieving slow light in liquid crystals are presented. The first method consists of exploiting photoisomerization-induced transparency in dye-doped chiral liquid crystals, and the second method makes use of two-wave mixing optical resonance in pure nematics. In both mechanisms, two beams are sent to the medium, where they create a grating, either of absorption or of refractive index. Both physical mechanisms are elucidated in the context of slow light, then, as examples of sensing applications, Doppler shift measurements and adaptive holography are presented.

  18. Thermal Conductivity and Liquid Crystal Thermometers.

    ERIC Educational Resources Information Center

    Edge, R. D., Ed.

    1993-01-01

    Describes using stock liquid crystal postcards as inexpensive classroom thermometers. Also suggests using these postcards as a good visual temperature indicator for classroom demonstrations such as temperature gradients. One such activity is provided. (MVL)

  19. Liquid crystal on subwavelength metal gratings

    SciTech Connect

    Palto, S. P.; Barnik, M. I.; Artemov, V. V.; Shtykov, N. M.; Geivandov, A. R.; Yudin, S. G.; Gorkunov, M. V.

    2015-06-14

    Optical and electrooptical properties of a system consisting of subwavelength metal gratings and nematic liquid crystal layer are studied. Aluminium gratings that also act as interdigitated electrodes are produced by focused ion beam lithography. It is found that a liquid crystal layer strongly influences both the resonance and light polarization properties characteristic of the gratings. Enhanced transmittance is observed not only for the TM-polarized light in the near infrared spectral range but also for the TE-polarized light in the visible range. Although the electrodes are separated by nanosized slits, and the electric field is strongly localized near the surface, a pronounced electrooptical effect is registered. The effect is explained in terms of local reorientation of liquid crystal molecules at the grating surface and propagation of the orientational deformation from the surface into the bulk of the liquid crystal layer.

  20. Experimental and theoretical investigations of three-dimensional photonic crystals with unique architectures

    NASA Astrophysics Data System (ADS)

    Galusha, Jeremy Wayne

    Three dimensional photonic crystals based on self-assembled opal frameworks and naturally occurring diamond-based architectures were studied. The optical behavior of the photonic crystals was investigated using reflectance spectroscopy. Structural characteristics were determined using a combination of scanning electron and optical microscopy. Titania photonic crystal structures were fabricated using a variety of infiltration/replication strategies. A simple sol-gel chemistry-based opal infiltration method for the fabrication of high quality planar titania photonic crystals was developed. Polystyrene synthetic opals were infiltrated with a hydrophobic and air/moisture-stable liquid titania precursor. The high stability and hydrophobicity of the titania precursor enabled a new "lift-off/turn-over" backfilling technique that after calcination gives planar titania inverse opals with a flat and completely open surface. Two different infiltration strategies and their influence on the structural and photonic properties were investigated. The obtained inverse opals display excellent photonic properties as evidenced by the presence of first-, second-, and third-order Bragg reflection peaks in accordance with theoretical photonic band structure calculations. The photonic crystal structure inside iridescent scales of the weevil Lamprocyphus augustus was investigated. By combining a high-resolution structure analysis technique based on sequential focused ion beam milling and scanning electron microscopy imaging with theoretical modeling and photonic band-structure calculations, the structure was determined to be a natural three-dimensional photonic structure with a diamond-based crystal lattice operating at visible wavelengths. A bio-templating route was developed to fabricate high-dielectric diamond-based photonic crystals with lattice periodicities at visible wavelengths. A sol-gel double-imprint strategy via a mesostructured organo-silica intermediary is developed to

  1. Higher-order photon correlations in pulsed photonic crystal nanolasers

    SciTech Connect

    Elvira, D.; Hachair, X.; Braive, R.; Beaudoin, G.; Robert-Philip, I.; Sagnes, I.; Abram, I.; Beveratos, A.; Verma, V. B.; Baek, B.; Nam, S. W.; Stevens, M. J.; Dauler, E. A.

    2011-12-15

    We report on the higher-order photon correlations of a high-{beta} nanolaser under pulsed excitation at room temperature. Using a multiplexed four-element superconducting single-photon detector we measured g{sup (n)}(0-vector) with n=2,3,4. All orders of correlation display partially chaotic statistics, even at four times the threshold excitation power. We show that this departure from coherence and Poisson statistics is due to the quantum fluctuations associated with the small number of photons at the lasing threshold.

  2. Photonic-crystal time-domain simulations using Wannier functions.

    PubMed

    Blum, Christian; Wolff, Christian; Busch, Kurt

    2011-01-15

    We present a Wannier-function-based time-domain method for photonic-crystal integrated optical circuits. In contrast to other approaches, this method allows one to trade CPU time against memory consumption and therefore is particularly well suited for the treatment of large-scale systems. As an illustration, we apply the method to the design of a photonic-crystal-based sensor, which utilizes a dual Mach-Zehnder-Fano interferometer. PMID:21263535

  3. Use of a photonic crystal for optical amplifier gain control

    DOEpatents

    Lin, Shawn-Yu; Fleming, James G.; El-Kady, Ihab

    2006-07-18

    An optical amplifier having a uniform gain profile uses a photonic crystal to tune the density-of-states of a gain medium so as to modify the light emission rate between atomic states. The density-of-states of the gain medium is tuned by selecting the size, shape, dielectric constant, and spacing of a plurality of microcavity defects in the photonic crystal. The optical amplifier is particularly useful for the regeneration of DWDM signals in long optical fibers.

  4. Semiclassical model of stimulated Raman scattering in photonic crystals.

    PubMed

    Florescu, Lucia; Zhang, Xiang

    2005-07-01

    We study the stimulated Raman scattering (SRS) of light from an atomic system embedded in a photonic crystal and coherently pumped by a laser field. In our study, the electromagnetic field is treated classically and the atomic system is described quantum mechanically. Considering a decomposition of the pump and Stokes fields into the Bloch modes of the photonic crystals and using a multiscale analysis, we derive the Maxwell-Bloch equations for SRS in photonic crystals. These equations contain effective parameters that characterize the SRS gain, the nonlinear atomic response to the electromagnetic field, and the group velocity and that can be calculated in terms of the Bloch modes of the unperturbed photonic crystal. We show that if the pump laser frequency is tuned near a photonic band edge and the atomic system is carefully chosen such that the Stokes mode matches another photonic band edge, low-threshold, enhanced Raman amplification is possible. Possible physical realizations of SRS in photonic crystals are also discussed.

  5. Molecular Models of Liquid Crystal Elastomers

    NASA Astrophysics Data System (ADS)

    Rajshekhar

    Liquid crystal elastomers combine the elastic properties of conventional rubbers with the optical properties of liquid crystals. This dual nature gives rise to unusual physical properties, including the stress induced transition from a polydomain state, consisting of multiple nematic regions with independent orientations, to a monodomain state consisting of a single nematic region with a uniform director. We propose several molecular-scale coarse-grained models of liquid crystal elastomers with varying degrees of resolution. The models employ the Gay-Berne soft potential, and exhibit the chain connectivity of a diamond network. Simulation results show that these models are able to capture the polydomain state exhibited by liquid crystal elastomers in the absence of any external stress. When subjected to uniaxial stress, our models exhibit a polydomain to monodomain transition. We explain that the polydomain state occurs through the aggregation of liquid crystal molecules assisted by crosslinking sites, and conclude that the transition mechanism to the monodomain state is based on the reorientation of nematic domains along the direction of applied stress. Our modeling efforts are primarily focused on three models. The first two models consider the effects of rigid and flexible crosslinkers in liquid crystal elastomers with a diamond topology for chain connectivity. The third model deviates from the diamond network topology and adopts a random network topology.

  6. Biosensing using smectic and cholesteric liquid crystals

    NASA Astrophysics Data System (ADS)

    Popov, Piotr; Mann, Elizabeth; Jakli, Antal

    2015-03-01

    Liquid-crystal-based biosensors utilize liquid crystal alignment's high sensitivity to the presence of lipids and proteins self-assembled at the liquid crystal/aqueous solution interface. The optical response of the bulk liquid crystal to the interface offers inexpensive, easy optical detection of such biologically relevant molecules. Present technique uses nematic liquid crystal phase state that typically has a planar-to-homeotropic response only. Here we show that smectic and cholesteric phase states of liquid crystals can be used as new sensing modes that can provide additional information or improve the characteristics of a potential biosensor device. Smectic-A phase extends the detection range both toward the lower and higher concentration. Cholesteric phase (nematic with a chiral dopant) may be sensitive to the chirality of biological surface-active molecules such as phospholipids. Additionally, the ``finger-print'' texture of a cholesteric phase may show the differences between biomolecule homologues, thus providing a promising way of distinguishing between subtle differences of hydrocarbon chain or head-group size and structure.

  7. Semiconductor liquid crystal composition and methods for making the same

    DOEpatents

    Alivisatos, A. Paul; Li, Liang-shi

    2005-04-26

    Semiconductor liquid crystal compositions and methods for making such compositions are disclosed. One embodiment of the invention is directed to a liquid crystal composition including a solvent and semiconductor particles in the solvent. The solvent and the semiconductor particles are in an effective amount in the liquid crystal composition to form a liquid crystal phase.

  8. 21 CFR 880.6970 - Liquid crystal vein locator.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 8 2012-04-01 2012-04-01 false Liquid crystal vein locator. 880.6970 Section 880... Devices § 880.6970 Liquid crystal vein locator. (a) Identification. A liquid crystal vein locator is a... skin by displaying the color changes of heat sensitive liquid crystals (cholesteric esters)....

  9. 21 CFR 880.6970 - Liquid crystal vein locator.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Liquid crystal vein locator. 880.6970 Section 880... Devices § 880.6970 Liquid crystal vein locator. (a) Identification. A liquid crystal vein locator is a... skin by displaying the color changes of heat sensitive liquid crystals (cholesteric esters)....

  10. 21 CFR 880.6970 - Liquid crystal vein locator.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 8 2013-04-01 2013-04-01 false Liquid crystal vein locator. 880.6970 Section 880... Devices § 880.6970 Liquid crystal vein locator. (a) Identification. A liquid crystal vein locator is a... skin by displaying the color changes of heat sensitive liquid crystals (cholesteric esters)....

  11. Polarisation singularities in photonic crystals for an on-chip spin-photon interface

    NASA Astrophysics Data System (ADS)

    Beggs, Daryl M.; Young, Andrew B.; Thijssen, Arthur C. T.; Oulton, Ruth

    2015-03-01

    Integrated quantum photonic chips are a leading contender for future quantum technologies, which aim to use the entanglement and superposition properties of quantum physics to speed up the manipulation of data. Quantum information may be stored and transmitted in photons, which make excellent flying qubits. Photons suffer little from decoherence, and single qubit gates performed by changing photon phase, are straightforward. Less straightforward is the ability to create two qubit gates, where one photon is used to switch another's state; inherently difficult due to the extremely small interaction cross-section between photons. The required deterministic two-qubit interactions will likely need a hybrid scheme with the ``flying'' photonic qubit interacting with a ``static'' matter qubit. Here we present the design of a photonic crystal waveguide structure that can couple electron-spin to photon path, thus providing an interface between a static and a flying qubit. We will show that the complex polarization properties inherent in the photonic crystal eigenmodes supports polarization singularities - positions in the electric field vector where one of the parameters describing the local polarization ellipse is singular - and that these singularities are ideal for a range of quantum information applications. In particular, we will show that by placing a quantum dot at one of these singularities, the electron-spin becomes correlated with the photon emission direction, creating an in-plane spin-photon interface that can transfer quantum information from static to flying qubits.

  12. Temperature dependence of liquid crystals electrical response by impedance analysis

    NASA Astrophysics Data System (ADS)

    Torres, J. C.; Gaona, N.; Pérez, I.; Urruchi, V.; Pena, J. M. S.

    2007-05-01

    Liquid crystals are a growing technology bringing solutions for a number of applications in high performance displays featuring video-rate, color and high resolution images, and in prototypes of photonic devices. Electrooptic response of antiferroelectric liquid crystals (AFLC) might be superior to nematic liquid crystals that are been customarily employed nowadays. AFLC show reduced time response being promising candidates for portable multimedia devices, optical routing applications, among others. In this work, temperature and frequency dependence of impedance measurements, in passive devices of commercial antiferroelectric liquid crystals, has been studied. Measurements of the temperature dependence of optical transmission have been obtained. 1Hz triangular waveforms with different amplitude have been applied to the devices to carry out such characterization. Simultaneous measurements of optical transmission and electrical impedance have been performed. Specific addressing schemes have been tested in order to obtain the optimum electrooptical performance. Display blanking takes place when a saturation pulse is applied. Results achieved show that increasing temperature shifts the dynamic range of the analogue grayscale towards lower voltages. Impedance analysis of these devices upon switching has been performed as well. Temperature and frequency dependence of the impedance measurements have been characterized. Negative phase responses show there is a combined capacitive and resistive behavior. As the frequency increases the capacitive effect grows. Magnitude shows a linear decrease on a log-log frequency scale. As temperature increases, phase profile becomes slight more complex. New capacitive effects are suggested in a model of the electric response of AFLC cells at low frequencies.

  13. Chalcogenide glass-based three-dimensional photonic crystals

    NASA Astrophysics Data System (ADS)

    Feigel, A.; Kotler, Z.; Sfez, B.; Arsh, A.; Klebanov, M.; Lyubin, V.

    2000-11-01

    AsSeTe chalcogenide glasses are materials that are photosensitive and have a large refractive index. These properties make these glasses particularly suitable for the fabrication of photonic crystals. We present a way to build three-dimensional photonic structures from chalcogenide glasses using vapor deposition and direct holographic writing. We show that this technique is intrinsically self-aligned, providing a simple way to build layer-by-layer photonic crystals and a four-layer structure demonstrating the principle of the technique.

  14. Spontaneous emission from photonic crystals: full vectorial calculations

    PubMed

    Li; Lin; Zhang

    2000-05-01

    Quantum electrodynamics of atom spontaneous emission from a three-dimensional photonic crystal is studied in a full vectorial framework. The electromagnetic fields are quantized via solving the eigenproblem of photonic crystals with use of a plane-wave expansion method. It is found that the photon density of states and local density of states (LDOS) with a full band gap vary slowly near the edge of band gap, in significant contrast to the singular character predicted by the previous isotropic model. Therefore, the spontaneous emission can be solved by conventional Weisskopf-Wigner approximate theory, which yields a pure exponentially decaying behavior with a rate proportional to the LDOS.

  15. Fluorescence and lasing in liquid crystalline photonic bandgap materials

    NASA Astrophysics Data System (ADS)

    Cao, Wenyi

    Cholesteric liquid crystals (CLCs) and cholesteric blue phases (BPs) are one-dimensional and three-dimensional photonic bandgap (PGB) materials. In this work, fluorescence and lasing are experimentally studied in dye-doped CLC films and BPs, together with the calculations of density of states rho in CLC films. The normal modes of light propagation in a CLC film in the direction along the helical axis have been obtained analytically, using transfer matrix method. Two normal modes are elliptically polarized and their rho differ greatly. The value and wavelength of the largest rho depend on the CLC film thickness. The fluorescence spectra of dye DCM in CLC films are greatly altered: suppressed in the stop band and enhanced at band edges with intensity oscillations. The altered fluorescence spectra are in good agreement with the calculated spectra from rho. The fluorescence lifetimes, however, have no measurable difference. At high dye concentration, the fluorescence intensity is quenched by the formation of dye excimers. Mirrorless lasing in CLC films has been studied systematically. The lasing wavelengths and thresholds are in good agreement with the calculated values from rho. The threshold is optimized over CLC film thickness and dye concentration. Lasing at defect modes has been observed in CLC composite structures. Photon-counting statistics confirms the transition from the incoherent fluorescence to coherent laser emission with increasing pump energy. The totally coherent emitting area is estimated from the diffraction pattern of the CLC laser emission. The structures of BPs are characterized through textures and reflection measurements. In BP I, the stimulated emission is due to the multiple reflection of the fluorescence by small BP I crystals. In large BP II single crystals, the fluorescence is altered and lasing occurs at edges of the reflection peak or at defect modes. Lasing in three dimensions has been observed for the first time in PGB materials, and

  16. Alignment of crystal orientations of the multi-domain photonic crystals in Parides sesostris wing scales.

    PubMed

    Yoshioka, S; Fujita, H; Kinoshita, S; Matsuhana, B

    2014-03-01

    It is known that the wing scales of the emerald-patched cattleheart butterfly, Parides sesostris, contain gyroid-type photonic crystals, which produce a green structural colour. However, the photonic crystal is not a single crystal that spreads over the entire scale, but it is separated into many small domains with different crystal orientations. As a photonic crystal generally has band gaps at different frequencies depending on the direction of light propagation, it seems mysterious that the scale is observed to be uniformly green under an optical microscope despite the multi-domain structure. In this study, we have carefully investigated the structure of the wing scale and discovered that the crystal orientations of different domains are not perfectly random, but there is a preferred crystal orientation that is aligned along the surface normal of the scale. This finding suggests that there is an additional factor during the developmental process of the microstructure that regulates the crystal orientation. PMID:24352678

  17. Electro-osmosis in nematic liquid crystals.

    PubMed

    Tovkach, O M; Calderer, M Carme; Golovaty, Dmitry; Lavrentovich, Oleg; Walkington, Noel J

    2016-07-01

    We derive a mathematical model of a nematic electrolyte based on a variational formulation of nematodynamics. We verify the model by comparing its predictions to the results of the experiments on the substrate-controlled liquid-crystal-enabled electrokinetics. In the experiments, a nematic liquid crystal confined to a thin planar cell with surface-patterned anchoring conditions exhibits electro-osmotic flows along the "guiding rails" imposed by the spatially varying director. Extending our previous work, we consider a general setup which incorporates dielectric anisotropy of the liquid-crystalline matrix and the full set of nematic viscosities.

  18. Electro-osmosis in nematic liquid crystals

    NASA Astrophysics Data System (ADS)

    Tovkach, O. M.; Calderer, M. Carme; Golovaty, Dmitry; Lavrentovich, Oleg; Walkington, Noel J.

    2016-07-01

    We derive a mathematical model of a nematic electrolyte based on a variational formulation of nematodynamics. We verify the model by comparing its predictions to the results of the experiments on the substrate-controlled liquid-crystal-enabled electrokinetics. In the experiments, a nematic liquid crystal confined to a thin planar cell with surface-patterned anchoring conditions exhibits electro-osmotic flows along the "guiding rails" imposed by the spatially varying director. Extending our previous work, we consider a general setup which incorporates dielectric anisotropy of the liquid-crystalline matrix and the full set of nematic viscosities.

  19. Electro-osmosis in nematic liquid crystals.

    PubMed

    Tovkach, O M; Calderer, M Carme; Golovaty, Dmitry; Lavrentovich, Oleg; Walkington, Noel J

    2016-07-01

    We derive a mathematical model of a nematic electrolyte based on a variational formulation of nematodynamics. We verify the model by comparing its predictions to the results of the experiments on the substrate-controlled liquid-crystal-enabled electrokinetics. In the experiments, a nematic liquid crystal confined to a thin planar cell with surface-patterned anchoring conditions exhibits electro-osmotic flows along the "guiding rails" imposed by the spatially varying director. Extending our previous work, we consider a general setup which incorporates dielectric anisotropy of the liquid-crystalline matrix and the full set of nematic viscosities. PMID:27575193

  20. Liquid nitrogen dewar for protein crystal growth

    NASA Technical Reports Server (NTRS)

    2001-01-01

    Gaseous Nitrogen Dewar apparatus developed by Dr. Alex McPherson of the University of California, Irvine for use aboard Mir and the International Space Station allows large quantities of protein samples to be crystallized in orbit. The specimens are contained either in plastic tubing (heat-sealed at each end). Biological samples are prepared with a precipitating agent in either a batch or liquid-liquid diffusion configuration. The samples are then flash-frozen in liquid nitrogen before crystallization can start. On orbit, the Dewar is placed in a quiet area of the station and the nitrogen slowly boils off (it is taken up by the environmental control system), allowing the proteins to thaw to begin crystallization. The Dewar is returned to Earth after one to four months on orbit, depending on Shuttle flight opportunities. The tubes then are analyzed for crystal presence and quality

  1. Tetrahedral Order in Liquid Crystals

    NASA Astrophysics Data System (ADS)

    Pleiner, Harald; Brand, Helmut R.

    2016-10-01

    We review the impact of tetrahedral order on the macroscopic dynamics of bent-core liquid crystals. We discuss tetrahedral order comparing with other types of orientational order, like nematic, polar nematic, polar smectic, and active polar order. In particular, we present hydrodynamic equations for phases, where only tetrahedral order exists or tetrahedral order is combined with nematic order. Among the latter, we discriminate between three cases, where the nematic director (a) orients along a fourfold, (b) along a threefold symmetry axis of the tetrahedral structure, or (c) is homogeneously uncorrelated with the tetrahedron. For the optically isotropic T d phase, which only has tetrahedral order, we focus on the coupling of flow with, e.g., temperature gradients and on the specific orientation behavior in external electric fields. For the transition to the nematic phase, electric fields lead to a temperature shift that is linear in the field strength. Electric fields induce nematic order, again linear in the field strength. If strong enough, electric fields can change the tetrahedral structure and symmetry leading to a polar phase. We briefly deal with the T phase that arises when tetrahedral order occurs in a system of chiral molecules. To case (a), defined above, belong (i) the non-polar, achiral, optically uniaxial D2d phase with ambidextrous helicity (due to a linear gradient free energy contribution) and with orientational frustration in external fields, (ii) the non-polar tetragonal S4 phase, (iii) the non-polar, orthorhombic D2 phase that is structurally chiral featuring ambidextrous chirality, (iv) the polar orthorhombic C2v phase, and (v) the polar, structurally chiral, monoclinic C2 phase. Case (b) results in a trigonal C3v phase that behaves like a biaxial polar nematic phase. An example for case (c) is a splay bend phase, where the ground state is inhomogeneous due to a linear gradient free energy contribution. Finally, we discuss some experiments

  2. Inverse opal photonic crystal of chalcogenide glass by solution processing.

    PubMed

    Kohoutek, Tomas; Orava, Jiri; Sawada, Tsutomu; Fudouzi, Hiroshi

    2011-01-15

    Chalcogenide opal and inverse opal photonic crystals were successfully fabricated by low-cost and low-temperature solution-based process, which is well developed in polymer films processing. Highly ordered silica colloidal crystal films were successfully infilled with nano-colloidal solution of the high refractive index As(30)S(70) chalcogenide glass by using spin-coating method. The silica/As-S opal film was etched in HF acid to dissolve the silica opal template and fabricate the inverse opal As-S photonic crystal. Both, the infilled silica/As-S opal film (Δn ~ 0.84 near λ=770 nm) and the inverse opal As-S photonic structure (Δn ~ 1.26 near λ=660 nm) had significantly enhanced reflectivity values and wider photonic bandgaps in comparison with the silica opal film template (Δn ~ 0.434 near λ=600 nm). The key aspects of opal film preparation by spin-coating of nano-colloidal chalcogenide glass solution are discussed. The solution fabricated "inorganic polymer" opal and the inverse opal structures exceed photonic properties of silica or any organic polymer opal film. The fabricated photonic structures are proposed for designing novel flexible colloidal crystal laser devices, photonic waveguides and chemical sensors.

  3. High birefringence and low viscosity liquid crystals

    NASA Astrophysics Data System (ADS)

    Wen, Chien-Hui

    In this dissertation, liquid crystal (LC) materials and devices are investigated in order to meet the challenges for photonics and displays applications. We have studied three kinds of liquid crystal materials: positive dielectric anisotropic LCs, negative dielectric anisotropic LCs, and dual-frequency LCs. For the positive dielectric anisotropic LCs, we have developed some high birefringence isothiocyanato tolane LC compounds with birefringence ˜0.4, and super high birefringence isothiocyanato biphenyl-bistolane LC compounds with birefringence as high as ˜0.7. Moreover, we have studied the photostability of several high birefringence LC compounds, mixtures, and LC alignment layers in order to determine the failure mechanism concerning the lifetime of LC devices. Although cyano and isothiocyanato LC compounds have similar absorption peaks, the isothiocyanato compounds are more stable than their cyano counterparts under the same illumination conditions. This ultraviolet-durable performance of isothiocyanato compounds originates from its molecular structure and the delocalized electron distribution. We have investigated the alignment performance of negative dielectric anisotropic LCs in homeotropic (vertical aligned, VA) LC cell. Some (2, 3) laterally difluorinated biphenyls, terphenyls and tolanes are selected for this study. Due to the strong repulsive force between LCs and alignment layer, (2,3) laterally difluorinated terphenyls and tolanes do not align well in a VA cell resulting in a poor contrast ratio for the LC panel. We have developed a novel method to suppress the light leakage at dark state. By doping positive Deltaepsilon or non-polar LC compounds or mixtures into the host negative LC mixtures, the repulsive force is reduced and the cell exhibits an excellent dark state. In addition, these dopants increase the birefringence and reduce the viscosity of the host LCs which leads to a faster response time. In this dissertation, we investigate the

  4. Key Developments in Ionic Liquid Crystals.

    PubMed

    Alvarez Fernandez, Alexandra; Kouwer, Paul H J

    2016-05-16

    Ionic liquid crystals are materials that combine the classes of liquid crystals and ionic liquids. The first one is based on the multi-billion-dollar flat panel display industry, whilst the latter quickly developed in the past decades into a family of highly-tunable non-volatile solvents. The combination yields materials with a unique set of properties, but also with many challenges ahead. In this review, we provide an overview of the key concepts in ionic liquid crystals, particularly from a molecular perspective. What are the important molecular parameters that determine the phase behavior? How should they be introduced into the molecules? Finally, which other tools does one have to realize specific properties in the material?

  5. Key Developments in Ionic Liquid Crystals

    PubMed Central

    Alvarez Fernandez, Alexandra; Kouwer, Paul H. J.

    2016-01-01

    Ionic liquid crystals are materials that combine the classes of liquid crystals and ionic liquids. The first one is based on the multi-billion-dollar flat panel display industry, whilst the latter quickly developed in the past decades into a family of highly-tunable non-volatile solvents. The combination yields materials with a unique set of properties, but also with many challenges ahead. In this review, we provide an overview of the key concepts in ionic liquid crystals, particularly from a molecular perspective. What are the important molecular parameters that determine the phase behavior? How should they be introduced into the molecules? Finally, which other tools does one have to realize specific properties in the material? PMID:27196890

  6. Blue shift of laser mode in photonic crystal microcavity

    NASA Astrophysics Data System (ADS)

    Zhao, Pengchao; Feng, Z. G.; Qi, Fan; Qi, Aiyi; Wang, Yufei; Zheng, W. H.

    2014-11-01

    We report the first demonstration of blue shift of optical pumping photonic crystal (PhC) laser. A femtosecond laser was used to pump the InGaAsP based two dimensional photonic crystal laser at room temperature. Linear dependence of the resonance wavelength with respect to the pump power is observed: dλ/dP=-1.5×10-2 nm/μW . Blue shift of overall 1.1nm was obtained with the increase power of pump laser. These results are in agreement with theoretical expectation while the carrier-induced index change is introduced into the PhC semiconductor laser. It shows a possibility that by proper wafer design and careful optimization, we may obtain wavelength stable photonic crystal laser, which is important in photonic integration.

  7. Electrical control of silicon photonic crystal cavity by graphene.

    PubMed

    Majumdar, Arka; Kim, Jonghwan; Vuckovic, Jelena; Wang, Feng

    2013-02-13

    The efficient conversion of an electrical signal to an optical signal in nanophotonics enables solid state integration of electronics and photonics. The combination of graphene with photonic crystals is promising for electro-optic modulation. In this paper, we demonstrate that by electrostatic gating a single layer of graphene on top of a photonic crystal cavity, the cavity resonance can be changed significantly. A ~2 nm change in the cavity resonance line width and almost 400% (6 dB) change in resonance reflectivity is observed. In addition, our analysis shows that a graphene-photonic crystal device can potentially be useful for a high speed and low power absorptive and refractive modulator, while maintaining a small physical footprint.

  8. Design, fabrication and transmitted properties of terahertz paper photonic crystals.

    PubMed

    Zhang, Wentao; Lin, Xian; Jin, Zuanming; Ma, Guohong; Zhong, Minjian

    2013-11-18

    The terahertz paper photonic crystals, including one-dimensional stacks, two-dimensional square and hexagonal lattices as well as three-dimensional body-centered cubic lattice, are designed and fabricated. Femtosecond laser direct writing is employed to process paper layers. The transmission properties of these photonic crystals in THz range are characterized using time-domain THz spectroscopy. The experimental results are in good agreement with the numerical simulations and well explained by the photonic band-structure calculated by the plane wave expansion method. Our results demonstrate that paper photonic crystals have a good performance on molding the flow of THz radiation. From another point of view, the fabrication method proposed in this work can be widely extended to manufacture different micro-structures on various materials.

  9. Hybrid genetic optimization for design of photonic crystal emitters

    NASA Astrophysics Data System (ADS)

    Rammohan, R. R.; Farfan, B. G.; Su, M. F.; El-Kady, I.; Reda Taha, M. M.

    2010-09-01

    A unique hybrid-optimization technique is proposed, based on genetic algorithms (GA) and gradient descent (GD) methods, for the smart design of photonic crystal (PhC) emitters. The photonic simulation is described and the granularity of photonic crystal dimensions is considered. An innovative sliding-window method for performing local heuristic search is demonstrated. Finally, the application of the proposed method on two case studies for the design of a multi-pixel photonic crystal emitter and the design of thermal emitter in thermal photovoltaic is demonstrated. Discussion in the report includes the ability of the optimal PhC structures designed using the proposed method, to produce unprecedented high emission efficiencies of 54.5% in a significantly long wavelength region and 84.9% at significantly short wavelength region.

  10. Polymer Crystallization at Curved Liquid-Liquid Interface

    NASA Astrophysics Data System (ADS)

    Li, Christopher; Wang, Wenda; Qi, Hao; Huang, Ziyin

    2013-03-01

    Curved space is incommensurate with typical ordered structures with three-dimensional (3D) translational symmetry. However, upon assembly, soft matter, including colloids, amphiphiles, and block copolymers (BCPs), often forms structures depicting curved surface/interface. Examples include liposomes, colloidosomes, spherical micelles, worm-like micelles, and vesicles (also known as polymersomes). For crystalline BCPs, crystallization oftentimes overwrites curved geometries since the latter is incommensurate with crystalline order. On the other hand, twisted and curved crystals are often observed in crystalline polymers. Various mechanisms have been proposed for these non-flat crystalline morphologies. In this presentation, we will demonstrate that curved liquid/liquid (L/L) interface can guide polymer single crystal growth. The crystal morphology is strongly dependent on the nucleation mechanism. A myriad of controlled curved single crystals can be readily obtained.

  11. Manipulating light propagation and emission using photonic crystals

    SciTech Connect

    Nair, Rajesh V.; Jagatap, B. N.

    2014-03-31

    We discuss the synthesis and characterization of self-assembled photonic crystals using polymer colloids having sub-micron diameters. The angle resolved optical reflectivity measurements indicate the hybridization between stop gaps in the multiple Bragg diffraction regimes. Each diffraction resonances in the multiple Bragg diffraction regimes are assigned to respective crystal planes. We also discuss laser-induced studies of spontaneous emission in self-assembled photonic crystals having Rhodamine-B dye doped colloids. Our experimental results reveal more than 51% inhibition in emission intensity within the stop gap as compared to a proper reference sample.

  12. Electrically tuned photoluminescence in large pitch cholesteric liquid crystal

    SciTech Connect

    Middha, Manju Kumar, Rishi Raina, K. K.

    2014-04-24

    Cholesteric liquid crystals are known as 1-D photonic band gap materials due to their periodic helical supramolecular structure and larger birefringence. Depending upon the helical twisted pitch length, they give the characteristic contrast due to selective Bragg reflections when viewed through the polarizing optical microscope and hence affect the electro-optic properties. So the optimization of chiral dopant concentration in nematic liquid crystal leads to control the transmission of polarized light through the microscope. Hence transmission based polarizing optical microscope is used for the characterization of helical pitch length in the optical texture. The unwinding of helical pitch was observed with the application of electric field which affects the intensity of photoluminescence.

  13. Investigations into complex liquid crystal mixtures

    NASA Astrophysics Data System (ADS)

    Kirchhoff, Jennifer

    Liquid crystal phases exhibit physical characteristics that lie between those of liquid and crystal phases. The many liquid crystal sub-phases are defined based on the degree of positional and orientational ordering the molecules have and the materials that make up these liquid crystal phases. This thesis presents a study of the molecular packing and physical properties of complex liquid crystal phases using dopants to better examine the stability and packing mechanisms of these phases. It also looks at the dispersion of quantum dots in liquid crystal materials, examining the electro-optical properties of the mixtures. The main goal of this thesis is to examine the effects of dopants on the properties of liquid crystal phases using optical microscopy, differential scanning calorimetry, electro-optical measurements, and X-ray scattering. For those mixtures with quantum dots fluorescence microscopy and photoluminescence measurements were also conducted. Rod-like liquid crystals are commonly used in display applications when the material is in a nematic liquid crystal phase, which is the least ordered phase exhibiting no positional ordering. The more complicated chiral smectic liquid crystal phases, which have a one dimensional layer structure, show potential for faster and tri-stable switching. A chiral rod-like liquid crystal material is doped with both chiral and achiral rod-like liquid crystals to examine the stability of one of the chiral smectic sub-phase, the SmC* FI1 phase. This phase consists of tilted molecules rotating about the cone defined by the tilt angle with a periodicity of three layers and an overall helical structure. The SmC*FI1 phase is stabilized by the competition between antiferroelectric and ferroelectric interactions, and small amounts of the achiral dopant broadens the range of this phase by almost 5°C. Higher dopant concentrations of the achiral material result in the destabilization of not just the SmC*FI1 phase but all tilted sub

  14. Photonic crystal engineering in glancing angle deposition thin films

    NASA Astrophysics Data System (ADS)

    Jensen, Hans Martin Overgaard

    2005-11-01

    From living rooms to operating rooms, our world is becoming dependent on information technology. For half a century a transformation in computing and communications has been borne by semiconductor microelectronics, but to serve us tomorrow, new materials transcending the performance and cost of current technology must be developed. An emerging optical material is the photonic bandgap crystal, which so fundamentally manipulates the emission and propagation of light that photons may be harnessed to eclipse what electronics accomplish today. However, the crystals consist of intricate, sub micrometre structures that are complex to fabricate, and even harder to engineer for technological applications. Indeed, fabrication challenges have inhibited photonic crystal progress. This thesis responds by enabling photonic crystal engineering through a chiral thin film fabrication technique known as glancing angle deposition. By oblique vapour deposition onto rotating substrates, the approach creates tetragonal lattices of square spirals with widths of a few hundred nanometres, predicted to yield strong photonic bandgaps at useful optical wavelengths. Within the scope of the thesis research, high resolution, high density direct write lithography is developed to deliver large area crystal substrates with extensive design freedom. The evolution of square spiral photonic crystal thin films on such substrates is analyzed, and new deposition methods are devised to allow engineering of the photonic bandgap by reducing the dimensions and enhancing the fine structure of the square spirals. Optical characterization is performed to evaluate the presence of a complete, three dimensional photonic bandgap, confirm an engineered bandgap at 1.65 mum, and quantify the improvement in crystal quality to a bandgap width of 10.9%. With a potential for use as photonic waveguides, the engineering of embedded, functional air and dielectric defects is also established. Furthermore, the thesis develops

  15. Enhanced two photon fluorescence microfluidic sensor based on dual cladding photonic-crystal fiber

    NASA Astrophysics Data System (ADS)

    Amitonova, Lyubov; Fedotov, Ilya; Fedotov, Andrey; Zheltikov, Aleksei

    2012-11-01

    The architecture of photonic-crystal fibers (PCFs) suggests a variety of strategies for optical sensing. A combination of TPA approaches with capabilities of fiber-optic probes offers numerous advantages, suggesting a convenient format for beam delivery, facilitating manipulation of excitation radiation, and allowing this excitation to be applied locally and selectively. In this work, we show that a PCF with a special design can realize different protocols of optical sensing, simultaneously serving, whenever necessary, for the collection and on-line monitoring of liquid-phase samples. Specially designed PCF is shown to substantially increase the guided-wave luminescent response from molecules excited through two-photon absorption (TPA) by femtosecond near-infrared laser pulses. Biophotonic implications of this waveguide TPL-response enhancement include fiber-format solutions for online monitoring of drug delivery and drug activation, interrogation of neural activity, biosensing, endoscopy, and locally controlled singlet oxygen generation in photodynamic therapy. This work was supported by the Russian Foundation for Basic Research, project 11-04-12185-ofi-m.

  16. Photon Cascade from a Single Crystal Phase Nanowire Quantum Dot.

    PubMed

    Bouwes Bavinck, Maaike; Jöns, Klaus D; Zieliński, Michal; Patriarche, Gilles; Harmand, Jean-Christophe; Akopian, Nika; Zwiller, Val

    2016-02-10

    We report the first comprehensive experimental and theoretical study of the optical properties of single crystal phase quantum dots in InP nanowires. Crystal phase quantum dots are defined by a transition in the crystallographic lattice between zinc blende and wurtzite segments and therefore offer unprecedented potential to be controlled with atomic layer accuracy without random alloying. We show for the first time that crystal phase quantum dots are a source of pure single-photons and cascaded photon-pairs from type II transitions with excellent optical properties in terms of intensity and line width. We notice that the emission spectra consist often of two peaks close in energy, which we explain with a comprehensive theory showing that the symmetry of the system plays a crucial role for the hole levels forming hybridized orbitals. Our results state that crystal phase quantum dots have promising quantum optical properties for single photon application and quantum optics. PMID:26806321

  17. Tunable optical anisotropy in three-dimensional photonic crystals

    SciTech Connect

    Che Ming; Li Zhiyuan; Liu Rongjuan

    2007-08-15

    Artificial optical birefringence can be realized in three-dimensional photonic crystals with a uniaxial structural symmetry: e.g., woodpile photonic crystals with a tetragonal lattice structure in the long-wavelength limit. The ordinary and extraordinary indices of refraction are determined from calculation of the reflection coefficient for a plane wave incident on the surface of a semi-infinite photonic crystal at different angles. We find that the anisotropy can be widely tuned by simply changing the width and thickness of the dielectric rod. A large relative negative anisotropy over 33% is found. A transition from positive anisotropy to negative anisotropy can be readily achieved. At certain parameters, a structurally anisotropic nanostructure can behave like an optically isotropic medium. Our study opens a window to use artificial nanostructures to create an arbitrary optical anisotropy that is not possible in natural crystals.

  18. Controlling single-photon transport with three-level quantum dots in photonic crystals

    NASA Astrophysics Data System (ADS)

    Yan, Cong-Hua; Jia, Wen-Zhi; Wei, Lian-Fu

    2014-03-01

    We investigate how to control single-photon transport along the photonic crystal waveguide with the recent experimentally demonstrated artificial atoms [i.e., Λ-type quantum dots (QDs)] [S. G. Carter et al., Nat. Photon. 7, 329 (2013), 10.1038/nphoton.2013.41] in an all-optical way. Adopting full quantum theory in real space, we analytically calculate the transport coefficients of single photons scattered by a Λ-type QD embedded in single- and two-mode photonic crystal cavities (PCCs), respectively. Our numerical results clearly show that the photonic transmission properties can be exactly manipulated by adjusting the coupling strengths of waveguide-cavity and QD-cavity interactions. Specifically, for the PCC with two degenerate orthogonal polarization modes coupled to a Λ-type QD with two degenerate ground states, we find that the photonic transmission spectra show three Rabi-splitting dips and the present system could serve as single-photon polarization beam splitters. The feasibility of our proposal with the current photonic crystal technique is also discussed.

  19. Lowring Lasing Threshold in Chiral Nematic Liquid Crystal Structure with Different Anisotropies

    NASA Astrophysics Data System (ADS)

    Chee, Mu Guen; Song, Myoung Hoon; Kim, Doseok; Takezoe, Hideo; Chung, In Jae

    2007-05-01

    Cholesteric liquid crystal (CLC) cells were fabricated using three kinds of nematic liquid crystal (NLC) materials with different optical birefringent anisotropies Δ n. A larger Δ n of NLCs results in a larger photonic band gap (PBG) width and higher density of states (DOS) at the PBG edge for each CLC cell. We were able to lower the threshold energy by a factor of more than two using CLC cells with a broader PBG width.

  20. Novel ferroelectric liquid crystals consisting glassy liquid crystal as chiral dopants

    NASA Astrophysics Data System (ADS)

    Chen, Huang-Ming Philip; Tsai, Yun-Yen; Lin, Chi-Wen; Shieh, Han-Ping David

    2006-08-01

    A series of ferroelectric liquid crystals consisting new glassy liquid crystals (GLCs) as chiral dopants were prepared and evaluated for their potentials in fast switching ability less than 1 ms. The properties of pure ferroelectric glassy liquid crystals (FGLCs) and mixtures were reported in this paper. In particular, the novel FGLC possessing wide chiral smectic C mesophase over 100 °C is able to suppress smectic A phase of host. The mixture containing 2.0 % GLC-1 performs greater alignment ability and higher contrast ratio than R2301 (Clariant, Japan) in a 2 μm pre-made cell (EHC, Japan). These results indicate that novel FLC mixtures consisting glassy liquid crystals present a promising liquid crystal materials for fast switching field sequential color displays.

  1. Polymer's anchoring behavior in liquid crystal cells

    NASA Astrophysics Data System (ADS)

    Cui, Yue

    The current dissertation mainly discusses about the polymers anchoring behavior in liquid crystal cells in two aspects: surface interaction and bulk interaction. The goal of the research is to understand the fundamental physics of anchoring strength and apply the knowledge to liquid crystal display devices. Researchers proposed two main contributors to the surface anchoring strength: the micro grooves generated by external force and the polymer chain's alignment. Both of them has experimental proofs. In the current study, explorations were made to understand the mechanisms of surface anchoring strength and easy axis of surface liquid crystal provided by rubbed polymer alignment layer. The work includes not only the variation of the alignment layer itself such as thickness(Chapter 3) and polymer side chain (Chapter 5), but also the variation of external conditions such as temperature (Chapter 4) and rubbing condition (Chapter 6). To determine the polar and azimuthal anchoring strengths, Rapini-Papoular's expression was applied. However, it was discovered that higher order terms may be required in order to fit the experimental result or theoretically predict unique anchoring behaviors (Chapter 2, Chapter 6). SEM and AFM technologies were introduced to gather the actual structures of polymer alignment layer and extrapolate the alignment of liquid crystal in a micro scale. The result shows that the anchoring strength can be adjusted by the layer thickness, side chain structure, while the easy axis direction can be adjusted by a second rubbing direction. In addition, different anchoring conditions combined with liquid crystal's elastic energy can generate quite different forms of liquid crystals (Chapter 7). In the study of bulk alignment, the main contrition from the current dissertation is applying the understanding of anchoring behavior to optimizing actual switchable devices. Conventional PDLC performance can be tuned with the knowledge of the polymer and the liquid

  2. Research on interferometric photonic crystal fiber hydrophone

    NASA Astrophysics Data System (ADS)

    Luo, Hong; Zhang, Zhen-hui; Wang, Fu-yin; Xiong, Shui-dong

    2013-08-01

    Current research on photonic crystal fiber (PCF) for acoustic sensing was focused on the PCF's pressure sensitivity enhancement. However, whether the enhancement of the PCF's pressure sensitivity can be actually realized is still controversial. Practical hydrophone, utilizing PCFs, to manifest its superior sensitivity to normal single mode fibers (SMFs) for acoustic sensing, should be made. Account to this point of view, actual hydrophone was fabricated. Index guiding PCF was used, the fiber core is solid silicon dioxide (SiO2), and the cladding is SiO2 filled with lots of periodical transverse circular air hollows. The PCF, mounted on an air-backed mandrel for structural sensitivity enhancement, was used as a sensing arm of the fiber Michelson interferometer. The other arm, so called reference arm, was made of SMF. Faraday rotator mirrors (FRM) were spliced in the end of each interferometric arm account for polarization induced phase fading, which is a common scheme in fiber interferometric sensing systems. A similar hydrophone, with all the same structure except that the PCF was exchanged into SMF, was also fabrication to make the contrast. The narrowlinewidth and frequency-tunable optical fiber laser was used to achieve high accuracy optical interferometric measurement. Meanwhile, the phase generated carrier (PGC) modulation-demodulation scheme was adopted to interrogate the measurand signal. Experiment was done by using acoustic standing-wave test apparatus. Linearity characteristics of the two hydrophones were measured at frequency 100Hz, 500Hz, and 1000Hz, experimental results showed that the maximum error of the linearity was 10%, a little larger than the theoretical results. Pressure sensitivities of the PCF hydrophone and the SMF hydrophone were measured using a reference standard PZT hydrophone in the frequency range from 20 Hz to 1600 Hz, the measurement data showed that the sensitivity of the PCF hydrophone was about -162.8 dB re. rad/μPa, with a

  3. Rugged and drapable cholesteric liquid crystal displays

    NASA Astrophysics Data System (ADS)

    Shiyanovskaya, Irina; Khan, Asad; Green, Seth; Magyar, Greg; Pishnyak, Oleg; Doane, J. W.

    2005-05-01

    We developed a novel technology for the fabrication of reflective cholesteric liquid crystal displays coatable on a single substrate using a layer-by-layer approach. Encapsulated cholesteric liquid crystals serving as an electro-optical layer and transparent conducting polymer films serving as electrodes are coated and printed on a variety of unconventional substrates, including ultra-thin plastic, paper, and textile materials to create conformable displays. The displays are capable of offering excellent electro-optical properties of the bulk cholesteric liquid crystals, including full-color, IR capability, bistability, low power, high brightness and contrast, combined with the ruggedness and pressure insensitivity of the liquid crystal droplets embedded in a polymer matrix. Durability of encapsulated cholesteric liquid crystals and single substrate approach allows for display flexing, folding, rolling and draping during image addressing without any image distortion. Our single substrate approach with natural cell-gap control significantly simplifies the fabrication process of the LCDs especially for large area displays. This paper will discuss the development, status, and merits of this novel display technology.

  4. Charge transfer reactions in nematic liquid crystals

    SciTech Connect

    Wiederrecht, G.P.; Wasielewski, M.R. |; Galili, T.; Levanon, H.

    1998-07-01

    Ultrafast transient absorption studies of intramolecular photoinduced charge separation and thermal charge recombination were carried out on a molecule consisting of a 4-(N-pyrrolidino)naphthalene-1,8-imide donor (PNI) covalently attached to a pyromellitimide acceptor (PI) dissolved in the liquid crystal 4{prime}-(n-pentyl)-4-cyanobiphenyl (5CB). The temperature dependencies of the charge separation and recombination rates were obtained at temperatures above the nematic-isotropic phase transition of 5CB, where ordered microdomains exist and scattering of visible light by these domains is absent. The authors show that excited state charge separation is dominated by molecular reorientation of 5CB perpendicular to the director within the liquid crystal microdomains. They also show that charge recombination is adiabatic and is controlled by the comparatively slow collective reorientation of the liquid crystal microdomains relative to the orientation of PNI{sup +}-PI{sup {minus}}. They also report the results of time resolved electron paramagnetic resonance (TREPR) studies of photoinduced charge separation in a series of supramolecular compounds dissolved in oriented liquid crystal solvents. These studies permit the determination of the radical pair energy levels as the solvent reorganization energy increases from the low temperature crystalline phase, through the soft glass phase, to the nematic phase of the liquid crystal.

  5. Liquid crystal thermography in boiling heat transfer

    SciTech Connect

    Klausner, J.F.; Mei, R.; Chen, W.C.

    1995-12-31

    The utilization of liquid crystal thermography to study heterogeneous boiling phenomena has gained popularity in recent years. In order not to disturb the nucleation process, which occurs in the microstructure of the heating surface, the crystals are applied to the backside of a thin heater. This work critically examines the ability of liquid crystal thermography to quantitatively capture the thermal field on the boiling surface. The thermal field identified experimentally through liquid crystal thermography is compared against that computed in the vicinity of a growing vapor bubble using a simulation which considers the simultaneous heat transfer between three phases: the solid heater, the liquid microlayer, and the growing vapor bubble. The temperature history beneath a growing vapor bubble elucidates the high frequency response required to capture the transient thermal fields commonly encountered in boiling experiments. Examination of the governing equations and numerical results reveal that due to the heater thermal inertia, the temperature variation on the bottom of the heater is significantly different than that on the boiling surface. In addition, the crystals themselves have a finite spatial resolution and frequency response which filter out much of the microscale phenomenon associated with boiling heat transfer. Analysis of existing pool and flow boiling liquid crystal thermographs indicate that the typical spacial resolution is on the order of 0.25 mm and the response time is on the order of 5 ms which are insufficient to resolve the fine spacial and temporal details of the heating surface thermal field. Thus the data obtained from liquid crystal thermography applied to boiling heat transfer must be cautiously interpreted.

  6. Optical nonlinearities near single photon level with a quantum dot coupled to a photonic crystal cavity

    NASA Astrophysics Data System (ADS)

    Sridharan, Deepak

    Over the last decade, exponential increase of information bandwidth over the internet and other communication media has increased the total power consumed by the devices associated with information exchange. With ever increasing number of users, and packing of a higher number of devices onto a chip, there is a great need for reduction in not only the power consumption of the devices but also the costs associated with information transfer. Currently, the benchmark in the energy consumption per logic operation is at femtojoule level and is set by the CMOS industry. However, optical devices based on single photon emitters coupled to a microcavity have the potential to reduce the optical power dissipation down to attojoule levels wherein only few 10s of photons are consumed for a logic operation. This work presents our theoretical and experimental efforts towards realization of all optical device based on the enhanced nonlinearities of a single photon emitter in a photonic crystal cavity. We show that a single quantum dot coupled to a photonic crystal cavity can be used to route an incoming optical beam with optical power dissipation of 14 attojoules, corresponding to only 65 photons. This value is well below the operational level for current CMOS devices indicating the potential for chip based optical transistors for reduction in energy consumption. The single photon emitters that we use to create the nonlinearity are the quantum dots, which are semiconductor nanostructures that exhibit a discrete energy spectrum. The interaction of the quantum dot, with light confined inside a photonic crystal cavity, results in strong atom-photon interactions which can be used for ultra-low power all optical switching. The strong interactions between a quantum dot and photonic crystal cavity can be further utilized to realize quantum computation schemes on a chip. I also describe techniques for integrating this transistor into an optical circuit, and discuss methods for post

  7. Magnetic assembly of nonmagnetic particles into photonic crystal structures.

    PubMed

    He, Le; Hu, Yongxing; Kim, Hyoki; Ge, Jianping; Kwon, Sunghoon; Yin, Yadong

    2010-11-10

    We report the rapid formation of photonic crystal structures by assembly of uniform nonmagnetic colloidal particles in ferrofluids using external magnetic fields. Magnetic manipulation of nonmagnetic particles with size down to a few hundred nanometers, suitable building blocks for producing photonic crystals with band gaps located in the visible regime, has been difficult due to their weak magnetic dipole moment. Increasing the dipole moment of magnetic holes has been limited by the instability of ferrofluids toward aggregation at high concentration or under strong magnetic field. By taking advantage of the superior stability of highly surface-charged magnetite nanocrystal-based ferrofluids, in this paper we have been able to successfully assemble 185 nm nonmagnetic polymer beads into photonic crystal structures, from 1D chains to 3D assemblies as determined by the interplay of magnetic dipole force and packing force. In a strong magnetic field with large field gradient, 3D photonic crystals with high reflectance (83%) in the visible range can be rapidly produced within several minutes, making this general strategy promising for fast creation of large-area photonic crystals using nonmagnetic particles as building blocks.

  8. 3D holographic polymer photonic crystal for superprism application

    NASA Astrophysics Data System (ADS)

    Chen, Jiaqi; Jiang, Wei; Chen, Xiaonan; Wang, Li; Zhang, Sasa; Chen, Ray T.

    2007-02-01

    Photonic crystal based superprism offers a new way to design new optical components for beam steering and DWDM application. 3D photonic crystals are especially attractive as they could offer more control of the light beam based on the needs. A polygonal prism based holographic fabrication method has been demonstrated for a three-dimensional face-centered-cubic (FCC)-type submicron polymer photonic crystal using SU8 as the photo-sensitive material. Therefore antivibration equipment and complicated optical alignment system are not needed and the requirement for the coherence of the laser source is relaxed compared with the traditional holographic setup. By changing the top-cut prism structure, the polarization of the laser beam, the exposure and development conditions we can achieve different kinds of triclinic or orthorhombic photonic crystals on demand. Special fabrication treatments have been introduced to ensure the survivability of the fabricated large area (cm2) nano-structures. Scanning electron microscopy and diffraction results proved the good uniformity of the fabricated structures. With the proper design of the refraction prism we have achieved a partial bandgap for S+C band (1460-1565nm) in the [111] direction. The transmission and reflection spectra obtained by Fourier transform infrared spectroscopy (FTIR) are in good agreement with simulated band structure. The superprism effects around 1550nm wavelength for the fabricated 3D polymer photonic crystal have been theoretically calculated and such effects can be used for beam steering purpose.

  9. Tunable negative-index photonic crystals using colloidal magnetic fluids

    NASA Astrophysics Data System (ADS)

    Geng, Tao; Wang, Xin; Wang, Yan; Dong, Xiang-Mei

    2015-12-01

    The model of using colloidal magnetic fluid to build tunable negative-index photonic crystal is established. The effective permittivity ɛe and permeability μe of the two-dimensional photonic crystal are investigated in detail. For transverse magnetic polarization, both ɛe and μe exhibit a Lorentz-type anomalous dispersion, leading to a region where ɛe and μe are simultaneously negative. Then, considering a practical case, in which the thickness of photonic crystal is finite, the band structures for odd modes are calculated by the plane wave expansion method and the finite-difference time-domain method. The results suggest that reducing the external magnetic field strength or slab thickness will weaken the periodic modulation strength of the photonic crystal. Simulation results prove that the negative-index can be tuned by varying the external magnetic field strength or the slab thickness. The work presented in this paper gives a guideline for realizing the flat photonic crystal lens with tunable properties at optical frequencies, which may have potential applications in tunable near-field imaging systems. Project supported by the National Basic Research Program of China (Grant No. 2015CB352001), the Shanghai Rising-Star Program, China (Grant No. 12QA1402300), the China Scholarship Council (CSC) Program, and the Basic Research Program of Shanghai, China (Grant No. 14ZR1428500).

  10. Thermally tunable ferroelectric thin film photonic crystals.

    SciTech Connect

    Lin, P. T.; Wessels, B. W.; Imre, A.; Ocola, L. E.; Northwestern Univ.

    2008-01-01

    Thermally tunable PhCs are fabricated from ferroelectric thin films. Photonic band structure and temperature dependent diffraction are calculated by FDTD. 50% intensity modulation is demonstrated experimentally. This device has potential in active ultra-compact optical circuits.

  11. A phase-field-crystal model for liquid crystals.

    PubMed

    Löwen, Hartmut

    2010-09-15

    On the basis of static and dynamical density functional theory, a phase-field-crystal model is derived which involves both the translational density and the orientational degree of ordering as well as a local director field. The model exhibits stable isotropic, nematic, smectic A, columnar, plastic-crystalline and orientationally ordered crystalline phases. As far as the dynamics is concerned, the translational density is a conserved order parameter while the orientational ordering is non-conserved. The derived phase-field-crystal model can serve for use in efficient numerical investigations of various nonequilibrium situations in liquid crystals.

  12. Polymer-dispersed liquid crystal elastomers

    NASA Astrophysics Data System (ADS)

    Rešetič, Andraž; Milavec, Jerneja; Zupančič, Blaž; Domenici, Valentina; Zalar, Boštjan

    2016-10-01

    The need for mechanical manipulation during the curing of conventional liquid crystal elastomers diminishes their applicability in the field of shape-programmable soft materials and future applications in additive manufacturing. Here we report on polymer-dispersed liquid crystal elastomers, novel composite materials that eliminate this difficulty. Their thermal shape memory anisotropy is imprinted by curing in external magnetic field, providing for conventional moulding of macroscopically sized soft, thermomechanically active elastic objects of general shapes. The binary soft-soft composition of isotropic elastomer matrix, filled with freeze-fracture-fabricated, oriented liquid crystal elastomer microparticles as colloidal inclusions, allows for fine-tuning of thermal morphing behaviour. This is accomplished by adjusting the concentration, spatial distribution and orientation of microparticles or using blends of microparticles with different thermomechanical characteristics. We demonstrate that any Gaussian thermomechanical deformation mode (bend, cup, saddle, left and right twist) of a planar sample, as well as beat-like actuation, is attainable with bilayer microparticle configurations.

  13. Diastereomeric liquid crystal domains at the mesoscale.

    PubMed

    Chen, Dong; Tuchband, Michael R; Horanyi, Balazs; Korblova, Eva; Walba, David M; Glaser, Matthew A; Maclennan, Joseph E; Clark, Noel A

    2015-08-07

    In many technologies used to achieve separation of enantiomers, chiral selectors are designed to display differential affinity for the two enantiomers of a chiral compound. Such complexes are diastereomeric, differing in structure and free energy for the two enantiomers and enabling chiral discrimination. Here we present evidence for strong diastereomeric interaction effects at the mesoscale, manifested in chiral liquid crystal guest materials confined in a chiral, nanoporous network of semi-crystalline helical nanofilaments. The nanoporous host is itself an assembly of achiral, bent-core liquid crystal molecules that phase-separate into a conglomerate of 100 micron-scale, helical nanofilament domains that differ in structure only in the handedness of their homogeneous chirality. With the inclusion of a homochiral guest liquid crystal, these enantiomeric domains become diastereomeric, exhibiting unexpected and markedly different mesoscale structures and orientation transitions producing optical effects in which chirality has a dominant role.

  14. Diastereomeric liquid crystal domains at the mesoscale

    NASA Astrophysics Data System (ADS)

    Chen, Dong; Tuchband, Michael R.; Horanyi, Balazs; Korblova, Eva; Walba, David M.; Glaser, Matthew A.; Maclennan, Joseph E.; Clark, Noel A.

    2015-08-01

    In many technologies used to achieve separation of enantiomers, chiral selectors are designed to display differential affinity for the two enantiomers of a chiral compound. Such complexes are diastereomeric, differing in structure and free energy for the two enantiomers and enabling chiral discrimination. Here we present evidence for strong diastereomeric interaction effects at the mesoscale, manifested in chiral liquid crystal guest materials confined in a chiral, nanoporous network of semi-crystalline helical nanofilaments. The nanoporous host is itself an assembly of achiral, bent-core liquid crystal molecules that phase-separate into a conglomerate of 100 micron-scale, helical nanofilament domains that differ in structure only in the handedness of their homogeneous chirality. With the inclusion of a homochiral guest liquid crystal, these enantiomeric domains become diastereomeric, exhibiting unexpected and markedly different mesoscale structures and orientation transitions producing optical effects in which chirality has a dominant role.

  15. Photonic crystals composed of virtual pillars with magnetic walls: Photonic band gaps and double Dirac cones

    NASA Astrophysics Data System (ADS)

    Kim, Seong-Han; Kim, Soeun; Kee, Chul-Sik

    2016-08-01

    Photonic crystals composed of virtual pillars with magnetic walls are proposed. A virtual pillar with a magnetic wall can be created inside a parallel perfect electric conductor plate waveguide by introducing a circular perfect magnetic conductor patch in the upper perfect electric conductor plate of the waveguide. The virtual pillar mimics a perfect magnetic conductor pillar with a radius less than that of the circular patch because electromagnetic waves can slightly penetrate the wall. Furthermore, the photonic band structures of a triangular photonic crystal composed of virtual pillars for the transverse electromagnetic modes of the waveguide are investigated. They are very similar to those of a triangular photonic crystal composed of infinitely long perfect electric conductor cylinders for transverse magnetic modes. The similarity between the two different photonic crystals is well understood by the boundary conditions of perfect electric and magnetic conductor surfaces. A double Dirac cone at the center of the Brillouin zone is observed and thus the virtual pillar triangular photonic crystal can act a zero-refractive-index material at the Dirac point frequency.

  16. Optically tunable and rewritable diffraction grating with photoaligned liquid crystals.

    PubMed

    Sun, J; Srivastava, A K; Wang, L; Chigrinov, V G; Kwok, H S

    2013-07-01

    An optically tunable and rewritable liquid crystal (LC) diffraction grating cell has been revealed that consists of an optically active and an optically passive alignment layer. The grating profile is created by confining the LC director distribution in alternate planar and twisted alignment domains by means of photoalignment of the LCs. The proposed grating is optically tunable for diffractive and nondiffractive states with a small response time that depends on the exposure energy and LC parameters. In addition, the grating can be erased and rewritten for different diffracting characteristics. These optically tunable diffractive elements could find application in various photonic devices. PMID:23811922

  17. Orientation of nematic liquid crystal in open glass microstructures

    NASA Astrophysics Data System (ADS)

    Azarinia, H.; Beeckman, J.; Neyts, K.; Schacht, E.; Gironès, J.; James, R.; Fernandez, F. A.

    2009-09-01

    Liquid crystal materials can have bulk reorientation due to surface interaction and are therefore of interest for biosensing applications. We present a setup, with holes etched in a substrate, filled with liquid crystal and covered by a sample fluid. The influence of the depth of the microcavities and the type of liquid on the liquid crystal orientation is investigated by experiments and simulations.

  18. Smart dust: self-assembling, self-orienting photonic crystals of porous Si.

    PubMed

    Link, Jamie R; Sailor, Michael J

    2003-09-16

    Micrometer-sized one-dimensional photonic crystals of porous Si that spontaneously assemble, orient, and sense their local environment are prepared. The photonic crystals are generated by electrochemically etching two discrete porous multilayered dielectric mirrors into Si, one on top of the other. The first mirror is chemically modified by hydrosilylation with dodecene before the etching of the second mirror, which is prepared with an optical reflectivity spectrum that is distinct from the first. The entire film is removed from the substrate, and the second mirror is then selectively modified by mild thermal oxidation. The films are subsequently fractured into small particles by sonication. The chemically asymmetric particles spontaneously align at an organic liquid-water interface, with the hydrophobic side oriented toward the organic phase and the hydrophilic side toward the water. Sensing is accomplished when liquid at the interface infuses into the porous mirrors, inducing predictable shifts in the optical spectra of both mirrors. PMID:12947036

  19. Surfaces and chirality in liquid crystals

    NASA Astrophysics Data System (ADS)

    Kang, Daeseung

    1999-10-01

    The effects of surfaces and chirality in liquid crystals were studied in this thesis. Four different experiments were presented to investigate the different aspects of their role in liquid crystal physics. A liquid crystal cell treated for homeotropic alignment with different surfactants at the two surfaces was subjected to an electric field E in the plane of the cell. The longitudinal polarization at the surface couples with the external field, and in consequence exerts a torque on molecules. The differential optical retardation deltaalpha due to a slight deformation was found to be linear in field over a frequency range 10 < o < 105 Hz, where d(deltaalpha)/dE is proportional to o -1. As a different aspect of the surface, the phenomenon of a chiral liquid crystal in highly restricted geometry was also investigated, where the random surface dominates the bulk. The optical rotatory power of the chiral liquid crystal in the porous medium was drastically altered from that of the bulk liquid crystal. The observed behavior may be attributed to a combination of surface interactions and finite size effects, which are discussed in terms of an infrared cutoff in the orientational pair correlation function. Chirality manifests itself not only as an optical activity in nematics, but more strikingly in forms of ferroelectric and antiferroelectric phases in smectics. The anticlinic interlayer coupling coefficient U between smectic layers was evaluated for a pitch-compensated antiferroelectric liquid crystal by optical observation of the optic mode response to an in-plane electric field. The result is in good agreement with Us estimated from the threshold field for the onset of solitary waves, and provides a strong support for the switching model based on the free energy. Finally, a new trimer liquid crystal based on a terminal-lateral-lateral-terminal connection was investigated. Magnetically induced Freedericksz measurements were performed to extract the elastic constants of

  20. Topology and bistability in liquid crystal devices

    SciTech Connect

    Majumdar, A.; Newton, C. J. P.; Robbins, J. M.; Zyskin, M.

    2007-05-15

    We study nematic liquid crystal configurations in a prototype bistable device--the post aligned bistable nematic (PABN) cell. Working within the Oseen-Frank continuum model, we describe the liquid crystal configuration by a unit-vector field n, in a model version of the PABN cell. First, we identify four distinct topologies in this geometry. We explicitly construct trial configurations with these topologies which are used as initial conditions for a numerical solver, based on the finite-element method. The morphologies and energetics of the corresponding numerical solutions qualitatively agree with experimental observations and suggest a topological mechanism for bistability in the PABN cell geometry.

  1. Dynamic Theory of Polydomain Liquid Crystal Elastomers.

    PubMed

    Duzgun, Ayhan; Selinger, Jonathan V

    2015-10-30

    When liquid crystal elastomers are prepared without any alignment, disordered polydomain structures emerge as the materials are cooled into the nematic phase. These polydomain structures are often attributed to quenched disorder in the cross-linked polymer network. As an alternative explanation, we develop a theory for the dynamics of the isotropic-nematic transition in liquid crystal elastomers, and show that the dynamics can induce a polydomain structure with a characteristic length scale, through a mechanism analogous to the Cahn-Hilliard equation for phase separation. PMID:26565497

  2. Dynamic Theory of Polydomain Liquid Crystal Elastomers

    NASA Astrophysics Data System (ADS)

    Duzgun, Ayhan; Selinger, Jonathan V.

    2015-10-01

    When liquid crystal elastomers are prepared without any alignment, disordered polydomain structures emerge as the materials are cooled into the nematic phase. These polydomain structures are often attributed to quenched disorder in the cross-linked polymer network. As an alternative explanation, we develop a theory for the dynamics of the isotropic-nematic transition in liquid crystal elastomers, and show that the dynamics can induce a polydomain structure with a characteristic length scale, through a mechanism analogous to the Cahn-Hilliard equation for phase separation.

  3. Photonic-crystal-based all-optical NOT logic gate.

    PubMed

    Singh, Brahm Raj; Rawal, Swati

    2015-12-01

    In the present paper, we have utilized the concept of photonic crystals for the implementation of an optical NOT gate inverter. The designed structure has a hexagonal arrangement of silicon rods in air substrate. The logic function is based on the phenomenon of the existence of the photonic bandgap and resulting guided modes in defect photonic crystal waveguides. We have plotted the transmission, extinction ratio, and tolerance analysis graphs for the structure, and it has been observed that the maximum output is obtained for a telecom wavelength of 1.554 μm. Dispersion curves are obtained using the plane wave expansion method, and the transmission is simulated using the finite element method. The proposed structure is applicable for photonic integrated circuits due to its simple structure and clear operating principle.

  4. Parametric Simulations of Slanted 1D Photonic Crystal Sensors.

    PubMed

    Breuer-Weil, Aaron; Almasoud, Naif Nasser; Abbasi, Badaruddin; Yetisen, Ali K; Yun, Seok-Hyun; Butt, Haider

    2016-12-01

    Photonic crystals and band gap materials act as manipulators of light and have a plethora of applications. They are made up of stacks of alternating dielectric constants. This article shows the simulations of an inclined, one dimensional and tuneble photonic crystal, using numerical finite element methods. The photonic crystal was made up of silver nanoparticles embedded in a hydrogel matrix and it has the ability to change and recover its periodicity. A series of factors concerning the geometry of the lattice were tested in order to analyze the efficiency, performance and optimize the properties of the optical sensor. These factors range from the size of the nanoparticles and their density within the stacks, to observing the effect of diffraction angle in readouts. PMID:27000025

  5. Ultrahigh-Q modes in anisotropic 2D photonic crystal

    NASA Astrophysics Data System (ADS)

    Bouleghlimat, Oussama; Hocini, Abdesselam

    2014-10-01

    In this work, we design a two-dimensional photonic crystal cavity made with a substrate of an anisotropic material. We consider triangular lattice photonic crystal made from air holes in tellurium. The cavity itself is then created by three missing holes in the centre. Using the three-dimensional finite-difference time-domain simulation and optimization of the geometrical parameters and the symmetric displacement of the edge air holes on the quality factor, the cavity’s structural parameters yield an ultrahigh-Q mode cavity with quality factor Q = 2.95 × 1011 for a filling factor r/a = 0.45 and lateral displacement of 10 nm. This shows great enhancement compared with previous studies in which silicon material has been used. The designed structure can be helpful in a number of applications associated with photonic crystal cavities, including quantum information processing, filters, and nanoscale sensors.

  6. Optical modulator based on coupled photonic crystal cavities

    NASA Astrophysics Data System (ADS)

    Serafimovich, Pavel G.; Kazanskiy, Nikolay L.

    2016-07-01

    We propose and numerically investigate an optical signal modulator based on two-photonic crystal nanobeam cavities coupled through a waveguide. The suggested modulator shifts the resonant frequency over a scalable range. We design a compact optical modulator based on photonic crystal nanobeams cavities that exhibits high stability to manufacturing. Photonic crystal waveguide tuning in the low-intensity region of the resonant mode is demonstrated. The advantages of the suggested approach over the single-resonator optical modulator approaches include the possibilities to shift the modulator frequency over a scalable range that depends on switching energy level and to effectively electrically tune the device in the low-intensity region of the resonant mode.

  7. Mode conversion in a magnetic photonic crystal waveguide

    NASA Astrophysics Data System (ADS)

    Otmani, H.; Bouchemat, M.; Hocini, A.; Boumaza, T.

    2014-06-01

    In this work, we have reported a theoretical study of a magnetic photonic crystal waveguide (also called a magneto photonic crystal waveguide). This structure is formed by a triangular lattice of air holes in a bismuth iron garnet (BIG) film, grown on gallium gadolinium garnet substrates. Nonreciprocal TE-TM mode conversion is caused by the Faraday rotation if the magnetization is aligned along the z-axis, parallel to mode of propagation. The properties of this phenomenon are simulated using the beam propagation method. The conversion output has been simulated, and the Faraday rotation and modal birefringence have been calculated by varying the gyrotropy and the thickness of the BIG film. This magnetic photonic crystal waveguide has the advantage of enhancing Faraday rotation in optical isolators.

  8. Excitation enhancement and extraction enhancement with photonic crystals

    SciTech Connect

    Shapira, Ofer; Soljacic, Marin; Zhen, Bo; Chua, Song-Liang; Lee, Jeongwon; Joannopoulos, John

    2015-03-03

    Disclosed herein is a system for stimulating emission from at least one an emitter, such as a quantum dot or organic molecule, on the surface of a photonic crystal comprising a patterned dielectric substrate. Embodiments of this system include a laser or other source that illuminates the emitter and the photonic crystal, which is characterized by an energy band structure exhibiting a Fano resonance, from a first angle so as to stimulate the emission from the emitter at a second angle. The coupling between the photonic crystal and the emitter may result in spectral and angular enhancement of the emission through excitation and extraction enhancement. These enhancement mechanisms also reduce the emitter's lasing threshold. For instance, these enhancement mechanisms enable lasing of a 100 nm thick layer of diluted organic molecules solution with reduced threshold intensity. This reduction in lasing threshold enables more efficient organic light emitting devices and more sensitive molecular sensing.

  9. Self-assembled photonic crystals for a chemical sensing

    NASA Astrophysics Data System (ADS)

    Bourdillon, C.; Gam Derouich, S.; Daney de Marcillac, W.; Coolen, L.; Maître, A.; Mangeney, C.; Schwob, C.

    2016-03-01

    As they allow the control of light propagation, photonic crystals find many fields of application. Among them, self-assembled 3D-photonic crystals are ordered at the nanometric scale over centrimetric areas. Furthermore, self-assembly allows the design of complexes structures leading, for example, to the controlled disruption of the crystal periodicity (called defect) and the appearance of permitted optical frequency bands within the photonic bandgap. Light frequencies included in the corresponding passband are then localized in the defect allowing manipulation of nano-emitters fluorescence. We present the fabrication and the optical characterization of a heterostructure composed of a sputtered silica layer sandwiched between two silica opals. We show by photoluminescence measurements than this structure strongly modifies the transmitted fluorescence of nanocrystals.

  10. Optical solitons in liquid crystals

    SciTech Connect

    Yung, Y.S.; Lam, L.; Los Alamos National Lab., NM )

    1989-01-01

    In this paper, we will discuss theoretically the possible existence of optical solitons in the isotropic liquid and in the nematic phase. For the same compound, when heated, the nematic phase will go through a first order transition at temperature T{sub c} to the isotropic liquid phase. As temperature increases from below T{sub c}, the orientation order parameter, Q, decreases, drops to zero abruptly at T{sub c} and remains zero for T > T{sub c}. 10 refs., 1 fig.

  11. Two-dimensional photonic crystals from semiconductor material with polymer filled holes

    NASA Astrophysics Data System (ADS)

    van der Heijden, Rob; Kjellander, Charlotte; Carlström, Carl-Fredrik; Snijders, Juri; van der Heijden, Rob W.; Bastiaansen, Kees; Broer, Dick; Karouta, Fouad; Nötzel, Richard; van der Drift, Emile; Salemink, Huub W. M.

    2006-04-01

    Polymer filling of the air holes of indiumphosphide based two-dimensional photonic crystals is reported. The filling is performed by infiltration with a liquid monomer and solidification of the infill in situ by thermal polymerization. Complete hole filling is obtained with infiltration under ambient pressure. This conclusion is based both on cross-sectional scanning electron microscope inspection of the filled samples as well as on optical transmission measurements.

  12. Ion crystal transducer for strong coupling between single ions and single photons.

    PubMed

    Lamata, L; Leibrandt, D R; Chuang, I L; Cirac, J I; Lukin, M D; Vuletić, V; Yelin, S F

    2011-07-15

    A new approach for the realization of a quantum interface between single photons and single ions in an ion crystal is proposed and analyzed. In our approach the coupling between a single photon and a single ion is enhanced via the collective degrees of freedom of the ion crystal. Applications including single-photon generation, a memory for a quantum repeater, and a deterministic photon-photon, photon-phonon, or photon-ion entangler are discussed.

  13. Confinement effects on Brillouin scattering in semiconductor nanowire photonic crystal

    NASA Astrophysics Data System (ADS)

    Mante, Pierre-Adrien; Anttu, Nicklas; Zhang, Wei; Wallentin, Jesper; Chen, I.-Ju; Lehmann, Sebastian; Heurlin, Magnus; Borgström, Magnus T.; Pistol, Mats-Erik; Yartsev, Arkady

    2016-07-01

    Scattering of photons by phonons, or Brillouin scattering, enables manipulation and control of light and has led to revolutionary applications, from slow light to saser and cooling of micromechanical resonators. Recently, enhanced light and sound interaction has been demonstrated in waveguides. However, the design of the waveguide geometry tunes and alters the phonon and photon dispersion simultaneously. Here we investigate, through femtosecond pump-probe spectroscopy and theoretical modeling, the light and sound interaction in a bottom-up fabricated vertical nanowire photonic crystal. In such a system, the phonon dispersion can be tuned by varying the geometry of the constituent nanowires. In contrast, the placement of the nanowires in the photonic crystal can be used for tuning optical array modes, without altering the phonon dispersion. We demonstrate the forward and backward scattering, by acoustic phonons in the nanowires, of (1) such optical array modes and (2) guided modes of the constituent nanowires. Furthermore, our results reveal an enhanced interaction of array modes with phonons that we attribute to the specific scattering mechanism. Our results enable the design of a photonic crystal with separately tailored photon and phonon dispersion for Brillouin scattering. We anticipate these advances to be a starting point for enhanced control of light at the nanoscale.

  14. Direct fiber-coupled single photon source based on a photonic crystal waveguide

    SciTech Connect

    Ahn, Byeong-Hyeon Lee, Chang-Min; Lim, Hee-Jin; Schlereth, Thomas W.; Kamp, Martin; Höfling, Sven; Lee, Yong-Hee

    2015-08-24

    A single photon source plays a key role in quantum applications such as quantum computers and quantum communications. Epitaxially grown quantum dots are one of the promising platforms to implement a good single photon source. However, it is challenging to realize an efficient single photon source based on semiconductor materials due to their high refractive index. Here we demonstrate a direct fiber coupled single photon source with high collection efficiency by employing a photonic crystal (PhC) waveguide and a tapered micro-fiber. To confirm the single photon nature, the second-order correlation function g{sup (2)}(τ) is measured with a Hanbury Brown-Twiss setup. The measured g{sup (2)}(0) value is 0.15, and we can estimate 24% direct collection efficiency from a quantum dot to the fiber.

  15. Photonic-crystal diplexers for terahertz-wave applications.

    PubMed

    Yata, Masahiro; Fujita, Masayuki; Nagatsuma, Tadao

    2016-04-01

    A compact diplexer is designed using a silicon photonic-crystal directional coupler of length comparable to the incident wavelength. The diplexer theoretically and experimentally exhibits a cross state bandwidth as broad as 2% of the operation frequency, with over 40-dB isolation between the cross and bar ports. We also demonstrate 1.5-Gbit/s frequency-division communication in the 0.32- and 0.33-THz bands using a single-wavelength-sized diplexer, and discuss the transmission bandwidth. Our study demonstrates the potential for application of photonic crystals as terahertz-wave integration platforms.

  16. Absorption and emission properties of photonic crystals and metamaterials

    SciTech Connect

    Peng, Lili

    2007-01-01

    We study the emission and absorption properties of photonic crystals and metamaterials using Comsol Multiphysics and Ansoft HFSS as simulation tools. We calculate the emission properties of metallic designs using drude model and the results illustrate that an appropriate termination of the surface of the metallic structure can significantly increase the absorption and therefore the thermal emissivity. We investigate the spontaneous emission rate modifications that occur for emitters inside two-dimensional photonic crystals and find the isotropic and directional emissions with respect to different frequencies as we have expected.

  17. Inhibited coupling hollow-core photonic crystal fiber

    NASA Astrophysics Data System (ADS)

    Benabid, F.; Gérôme, F.; Vincetti, L.; Debord, B.; Alharbi, M.; Bradley, T.

    2014-02-01

    We review the recent progress on the enhanced inhibited coupling in kagome hollow-core photonic crystal fiber by introducing negative curvature in the fiber-core shape. We show that increasing the hypocycloid contour curvature leads to a dramatic decrease in transmission loss and optical overlap with the silica surround and to a single modedness. Fabricated hypocycloid-core hollow-core photonic crystal fibers with a transmission loss in the range of 20-40 dB/km and for a spectral range of 700 nm-2000 nm have now become typical.

  18. Polarized quantum dot emission in electrohydrodynamic jet printed photonic crystals

    SciTech Connect

    See, Gloria G.; Xu, Lu; Nuzzo, Ralph G.; Sutanto, Erick; Alleyne, Andrew G.; Cunningham, Brian T.

    2015-08-03

    Tailored optical output, such as color purity and efficient optical intensity, are critical considerations for displays, particularly in mobile applications. To this end, we demonstrate a replica molded photonic crystal structure with embedded quantum dots. Electrohydrodynamic jet printing is used to control the position of the quantum dots within the device structure. This results in significantly less waste of the quantum dot material than application through drop-casting or spin coating. In addition, the targeted placement of the quantum dots minimizes any emission outside of the resonant enhancement field, which enables an 8× output enhancement and highly polarized emission from the photonic crystal structure.

  19. Molecular dynamics of biaxial nematic liquid crystals

    NASA Astrophysics Data System (ADS)

    Sarman, Sten

    1996-01-01

    We devise a constraint algorithm that makes the angular velocity of the director of a liquid crystal a constant of motion. When the angular velocity is set equal to zero, a director based coordinate system becomes an inertial frame. This is a great advantage because most thermodynamic properties and time correlation functions of a liquid crystal are best expressed relative to a director based coordinate system. One also prevents the director reorientation from interfering with the tails of the time correlation functions. When the angular velocity is forced to be zero the constraints do not do any work on the system. This makes it possible to prove that ensemble averages of phase functions and time correlation functions are unaffected by the director constraint torques. The constraint algorithm also facilitates generalization of nonequilibrium molecular dynamics algorithms to liquid crystal phases. In order to test the algorithm numerically we have simulated a biaxial nematic phase of a variant of the Gay-Berne fluid [J. G. Gay and B. J. Berne, J. Chem. Phys. 74, 3316 (1981)]. The director constraint algorithm works very well. We have calculated the velocity autocorrelation functions and the self diffusion coefficients. In a biaxial nematic liquid crystal there are three independent components of the self-diffusion tensor. They have been found to be finite and different thus proving that we really simulate a liquid rather than a solid and that the symmetry is biaxial. Simulation of biaxial liquid crystals requires fairly large systems. We have therefore developed an algorithm that we run on a parallel computer instead of an ordinary work station.

  20. Two-dimensional photonic crystal chemical and biomolecular sensors.

    PubMed

    Cai, Zhongyu; Smith, Natasha L; Zhang, Jian-Tao; Asher, Sanford A

    2015-01-01

    We review recent progress in the development of two-dimensional (2-D) photonic crystal (PC) materials for chemical and biological sensing applications. Self-assembly methods were developed in our laboratory to fabricate 2-D particle array monolayers on mercury and water surfaces. These hexagonal arrays strongly forward Bragg diffract light to report on their array spacings. By embedding these 2-D arrays onto responsive hydrogel surfaces, 2-D PC sensing materials can be fabricated. The 2-D PC sensors utilize responsive polymer hydrogels that are chemically functionalized to show volume phase transitions in selective response to particular chemical species. Novel hydrogels were also developed in our laboratory by cross-linking proteins while preserving their native structures to maintain their selective binding affinities. The volume phase transitions swell or shrink the hydrogels, which alter their 2-D array spacings, and shift their diffraction wavelengths. These shifts can be visually detected or spectrally measured. These 2-D PC sensing materials have been used for the detection of many analytes, such as pH, surfactants, metal ions, proteins, anionic drugs, and ammonia. We are exploring the use of organogels that use low vapor pressure ionic liquids as their mobile phases for sensing atmospheric analytes. PMID:25867803

  1. Enhanced tunable Bragg diffraction in large-pore inverse opals using dual-frequency liquid crystal

    NASA Astrophysics Data System (ADS)

    Graugnard, E.; Dunham, S. N.; King, J. S.; Lorang, D.; Jain, S.; Summers, C. J.

    2007-09-01

    Large-pore TiO2 inverse opals were fabricated by atomic layer deposition in sintered polystyrene colloidal crystal templates and infiltrated with dual-frequency liquid crystal. The optical properties of the hybrid organic/inorganic structure were characterized by reflectance measurements of the Bragg peak, the position of which was tuned using a frequency dependent applied electric field. A 6nm blueshift was observed for frequencies less than 13kHz and a 13nm redshift for frequencies above 13kHz. These results demonstrate enhanced optical tunability in three-dimensional photonic crystals and are important for the development of active photonic devices.

  2. Investigations into complex liquid crystal mixtures

    NASA Astrophysics Data System (ADS)

    Kirchhoff, Jennifer

    Liquid crystal phases exhibit physical characteristics that lie between those of liquid and crystal phases. The many liquid crystal sub-phases are defined based on the degree of positional and orientational ordering the molecules have and the materials that make up these liquid crystal phases. This thesis presents a study of the molecular packing and physical properties of complex liquid crystal phases using dopants to better examine the stability and packing mechanisms of these phases. It also looks at the dispersion of quantum dots in liquid crystal materials, examining the electro-optical properties of the mixtures. The main goal of this thesis is to examine the effects of dopants on the properties of liquid crystal phases using optical microscopy, differential scanning calorimetry, electro-optical measurements, and X-ray scattering. For those mixtures with quantum dots fluorescence microscopy and photoluminescence measurements were also conducted. Rod-like liquid crystals are commonly used in display applications when the material is in a nematic liquid crystal phase, which is the least ordered phase exhibiting no positional ordering. The more complicated chiral smectic liquid crystal phases, which have a one dimensional layer structure, show potential for faster and tri-stable switching. A chiral rod-like liquid crystal material is doped with both chiral and achiral rod-like liquid crystals to examine the stability of one of the chiral smectic sub-phase, the SmC* FI1 phase. This phase consists of tilted molecules rotating about the cone defined by the tilt angle with a periodicity of three layers and an overall helical structure. The SmC*FI1 phase is stabilized by the competition between antiferroelectric and ferroelectric interactions, and small amounts of the achiral dopant broadens the range of this phase by almost 5°C. Higher dopant concentrations of the achiral material result in the destabilization of not just the SmC*FI1 phase but all tilted sub

  3. Liquid-Crystal Thermal-Control Panels

    NASA Technical Reports Server (NTRS)

    Dehaye, R. F.; Edge, T. M.; Feltner, W. R.

    1987-01-01

    Radiative temperature regulators have no moving parts. Conceptual temperature-regulating system proposed for spacecraft useful in automatic or remotely controlled regulation of solar heating in buildings, provided cost reduced sufficiently. System consists of liquid-crystal panels made to absorb or reflect sunlight.

  4. Infrared diagnosis using liquid crystal detectors

    NASA Technical Reports Server (NTRS)

    Hugenschmidt, M.; Vollrath, K.

    1986-01-01

    The possible uses of pulsed carbon dioxide lasers for analysis of plasmas and flows need appropriate infrared image converters. Emphasis was placed on liquid crystal detectors and their operational modes. Performance characterstics and selection criteria, such as high sensitivity, short reaction time, and high spatial resolution are discussed.

  5. Photosensitive Polymers for Liquid Crystal Alignment

    NASA Astrophysics Data System (ADS)

    Mahilny, U. V.; Stankevich, A. I.; Trofimova, A. V.; Muravsky, A. A.; Murauski, A. A.

    The peculiarities of alignment of liquid crystal (LC) materials by the layers of photocrosslinkable polymers with side benzaldehyde groups are considered. The investigation of mechanism of photostimulated alignment by rubbed benzaldehyde layer is performed. The methods of creation of multidomain aligning layers on the basis of photostimulated rubbing alignment are described.

  6. Helmet-Mounted Liquid-Crystal Display

    NASA Technical Reports Server (NTRS)

    Smith, Steve; Plough, Alan; Clarke, Robert; Mclean, William; Fournier, Joseph; Marmolejo, Jose A.

    1991-01-01

    Helmet-mounted binocular display provides text and images for almost any wearer; does not require fitting for most users. Accommodates users from smallest interpupillary distance to largest. Two liquid-crystal display units mounted in helmet. Images generated seen from any position head can assume inside helmet. Eyes directed to position for best viewing.

  7. Inexpensive Electrooptic Experiments on Liquid Crystal Displays.

    ERIC Educational Resources Information Center

    Ciferno, Thomas M.; And Others

    1995-01-01

    Describes the construction and use of an electrooptic apparatus that can be incorporated into the classroom to test liquid crystal displays (LCDs) and introduce students to experiments of an applied physics nature with very practical implications. Presents experiments that give students hands-on experience with technologies of current interest to…

  8. Sub-wavelength phononic crystal liquid sensor

    NASA Astrophysics Data System (ADS)

    Ke, Manzhu; Zubtsov, Mikhail; Lucklum, Ralf

    2011-07-01

    We introduce an acoustic liquid sensor based on phononic crystals consisting of steel plate with an array of holes filled with liquid. We both theoretically and experimentally demonstrate sensor properties considering the mechanism of the extraordinary acoustic transmission as underlying phenomenon. The frequency of this resonant transmission peak is shown to rely on the speed of sound of the liquid, and the resonant frequency can be used as a measure of speed of sound and related properties, like concentration of a component in the liquid mixture. The finite-difference time domain method has been applied for sensor design. Ultrasonic transmission experiments are performed. Good consistency of the resonant frequency shift has been found between theoretical results and experiments. The proposed scheme offers a platform for an acoustic liquid sensor.

  9. Polarization-modulated smectic liquid crystal phases.

    PubMed

    Coleman, D A; Fernsler, J; Chattham, N; Nakata, M; Takanishi, Y; Körblova, E; Link, D R; Shao, R-F; Jang, W G; Maclennan, J E; Mondainn-Monval, O; Boyer, C; Weissflog, W; Pelzl, G; Chien, L-C; Zasadzinski, J; Watanabe, J; Walba, D M; Takezoe, H; Clark, N A

    2003-08-29

    Any polar-ordered material with a spatially uniform polarization field is internally frustrated: The symmetry-required local preference for polarization is to be nonuniform, i.e., to be locally bouquet-like or "splayed." However, it is impossible to achieve splay of a preferred sign everywhere in space unless appropriate defects are introduced into the field. Typically, in materials like ferroelectric crystals or liquid crystals, such defects are not thermally stable, so that the local preference is globally frustrated and the polarization field remains uniform. Here, we report a class of fluid polar smectic liquid crystals in which local splay prevails in the form of periodic supermolecular-scale polarization modulation stripes coupled to layer undulation waves. The polar domains are locally chiral, and organized into patterns of alternating handedness and polarity. The fluid-layer undulations enable an extraordinary menagerie of filament and planar structures that identify such phases.

  10. Improving image quality and stability of two-dimensional photonic crystal slab by changing surface structure of the photonic crystal

    NASA Astrophysics Data System (ADS)

    Zhu, Zhao-Jie; Liu, Peng-Fang; Tong, Yuan-Wei

    2016-03-01

    The propagation of electromagnetic (EM) waves in two-dimensional hexagon-lattice photonic crystals (PCs) is investigated through dispersion characteristics analysis and numerical simulation of field pattern. The full width at half maximum (FWHM) of the image reach 0.37λ which is much smaller than 0.5λ by changing surface structure of the photonic crystal, and the variance of FWHM of image focused by the changed slab seems to be less than the variance of FWHM of image focused by the original slab with the changing of source position.

  11. Colloidal cholesteric liquid crystal in spherical confinement.

    PubMed

    Li, Yunfeng; Jun-Yan Suen, Jeffrey; Prince, Elisabeth; Larin, Egor M; Klinkova, Anna; Thérien-Aubin, Héloïse; Zhu, Shoujun; Yang, Bai; Helmy, Amr S; Lavrentovich, Oleg D; Kumacheva, Eugenia

    2016-01-01

    The organization of nanoparticles in constrained geometries is an area of fundamental and practical importance. Spherical confinement of nanocolloids leads to new modes of packing, self-assembly, phase separation and relaxation of colloidal liquids; however, it remains an unexplored area of research for colloidal liquid crystals. Here we report the organization of cholesteric liquid crystal formed by nanorods in spherical droplets. For cholesteric suspensions of cellulose nanocrystals, with progressive confinement, we observe phase separation into a micrometer-size isotropic droplet core and a cholesteric shell formed by concentric nanocrystal layers. Further confinement results in a transition to a bipolar planar cholesteric morphology. The distribution of polymer, metal, carbon or metal oxide nanoparticles in the droplets is governed by the nanoparticle size and yields cholesteric droplets exhibiting fluorescence, plasmonic properties and magnetic actuation. This work advances our understanding of how the interplay of order, confinement and topological defects affects the morphology of soft matter. PMID:27561545

  12. Colloidal cholesteric liquid crystal in spherical confinement

    PubMed Central

    Li, Yunfeng; Jun-Yan Suen, Jeffrey; Prince, Elisabeth; Larin, Egor M.; Klinkova, Anna; Thérien-Aubin, Héloïse; Zhu, Shoujun; Yang, Bai; Helmy, Amr S.; Lavrentovich, Oleg D.; Kumacheva, Eugenia

    2016-01-01

    The organization of nanoparticles in constrained geometries is an area of fundamental and practical importance. Spherical confinement of nanocolloids leads to new modes of packing, self-assembly, phase separation and relaxation of colloidal liquids; however, it remains an unexplored area of research for colloidal liquid crystals. Here we report the organization of cholesteric liquid crystal formed by nanorods in spherical droplets. For cholesteric suspensions of cellulose nanocrystals, with progressive confinement, we observe phase separation into a micrometer-size isotropic droplet core and a cholesteric shell formed by concentric nanocrystal layers. Further confinement results in a transition to a bipolar planar cholesteric morphology. The distribution of polymer, metal, carbon or metal oxide nanoparticles in the droplets is governed by the nanoparticle size and yields cholesteric droplets exhibiting fluorescence, plasmonic properties and magnetic actuation. This work advances our understanding of how the interplay of order, confinement and topological defects affects the morphology of soft matter. PMID:27561545

  13. Colloidal cholesteric liquid crystal in spherical confinement

    NASA Astrophysics Data System (ADS)

    Li, Yunfeng; Jun-Yan Suen, Jeffrey; Prince, Elisabeth; Larin, Egor M.; Klinkova, Anna; Thérien-Aubin, Héloïse; Zhu, Shoujun; Yang, Bai; Helmy, Amr S.; Lavrentovich, Oleg D.; Kumacheva, Eugenia

    2016-08-01

    The organization of nanoparticles in constrained geometries is an area of fundamental and practical importance. Spherical confinement of nanocolloids leads to new modes of packing, self-assembly, phase separation and relaxation of colloidal liquids; however, it remains an unexplored area of research for colloidal liquid crystals. Here we report the organization of cholesteric liquid crystal formed by nanorods in spherical droplets. For cholesteric suspensions of cellulose nanocrystals, with progressive confinement, we observe phase separation into a micrometer-size isotropic droplet core and a cholesteric shell formed by concentric nanocrystal layers. Further confinement results in a transition to a bipolar planar cholesteric morphology. The distribution of polymer, metal, carbon or metal oxide nanoparticles in the droplets is governed by the nanoparticle size and yields cholesteric droplets exhibiting fluorescence, plasmonic properties and magnetic actuation. This work advances our understanding of how the interplay of order, confinement and topological defects affects the morphology of soft matter.

  14. Electric heating effects in nematic liquid crystals

    NASA Astrophysics Data System (ADS)

    Yin, Y.; Shiyanovskii, S. V.; Lavrentovich, O. D.

    2006-07-01

    Electric heating effects in the nematic liquid crystal change the liquid crystal physical properties and dynamics. We propose a model to quantitatively describe the heating effects caused by dielectric dispersion and ionic conductivity in the nematic liquid crystals upon the application of an ac electric field. The temperature increase of the liquid crystal cell is related to the properties of the liquid crystal such as the imaginary part of the dielectric permittivity, thermal properties of the bounding plates, and the surrounding medium as well as frequency and amplitude of the electric field. To study the temperature dynamics experimentally, we use a small thermocouple inserted directly into the nematic bulk; we assure that the thermocouple does not alter the thermal behavior of the system by comparing the results to those obtained by a noncontact birefringent probing technique recently proposed by Wen and Wu [Appl. Phys. Lett. 86, 231104 (2005)]. We determine how the temperature dynamics and the stationary value of the temperature increase depend on the parameters of the materials and the applied field. We used different surrounding media, from extremely good heat conductors such as aluminum cooling device to extremely poor conductor, Styrofoam; these two provide two limiting cases as compared to typical conditions of nematic cell exploitation in a laboratory or in commercial devices. The experiments confirm the theoretical predictions, namely, that the temperature rise is controlled not only by the heat transfer coefficient of the surrounding medium (as in the previous model) but also by the thickness and the thermal conductivity coefficient of the bounding plates enclosing the nematic layer. The temperature increase strongly depends on the director orientation and can change nonmonotonously with the frequency of the applied field.

  15. Metal-ion-ligand interactions in thermotropic liquid crystals

    NASA Astrophysics Data System (ADS)

    Diehl, P.; Wasser, H. R.; Gowda, G. A. Nagana; Suryaprakash, N.; Khetrapal, C. L.

    1989-07-01

    The interactions of lithium perchlorate with ligands such as dimethyl sulphoxide, acetonitrile, pyridine and the Schiff base liquid crystals are investigated. The experiments open a new field for the study of metal-ion-ligand interactions in thermotropic liquid crystals.

  16. Dual concentric crystal low energy photon detector

    DOEpatents

    Guilmette, R.A.

    A photon detector for biological samples includes a block of NaI(T1) having a hole containing a thin walled cylinder of CsI(T1). At least three photo multiplier tubes are evenly spaced around the parameter of the block. Biological samples are placed within the hole, and emissions which are sensed by at least two of the photo multipliers from only the NaI(T1) detector are counted.

  17. Liquid Crystals: Graphene Oxide Liquid Crystals: Discovery, Evolution and Applications (Adv. Mater. 16/2016).

    PubMed

    Narayan, Rekha; Kim, Ji Eun; Kim, Ju Young; Lee, Kyung Eun; Kim, Sang Ouk

    2016-04-01

    Graphene-oxide liquid crystals (GOLCs) have recently been discovered as a novel 2D material with remarkable properties. On page 3045, S. O. Kim and co-workers review the discovery of different GOLC mesophases and recent progress on fundamental studies and applications. The image displays the nematic schlieren texture (in the background) formed by flowing domains of graphene-oxide liquid crystals and their potential applications in energy storage, optoelectronics and wet-spun fibers.

  18. Silicon photonic crystal thermal emitter at near-infrared wavelengths

    PubMed Central

    O’Regan, Bryan J.; Wang, Yue; Krauss, Thomas F.

    2015-01-01

    Controlling thermal emission with resonant photonic nanostructures has recently attracted much attention. Most of the work has concentrated on the mid-infrared wavelength range and/or was based on metallic nanostructures. Here, we demonstrate the experimental operation of a resonant thermal emitter operating in the near-infrared (≈1.5 μm) wavelength range. The emitter is based on a doped silicon photonic crystal consisting of a two dimensional square array of holes and using silicon-on-insulator technology with a device-layer thickness of 220 nm. The device is resistively heated by passing current through the photonic crystal membrane. At a temperature of ≈1100 K, we observe relatively sharp emission peaks with a Q factor around 18. A support structure system is implemented in order to achieve a large area suspended photonic crystal thermal emitter and electrical injection. The device demonstrates that weak absorption together with photonic resonances can be used as a wavelength-selection mechanism for thermal emitters, both for the enhancement and the suppression of emission. PMID:26293111

  19. Silicon photonic crystal thermal emitter at near-infrared wavelengths.

    PubMed

    O'Regan, Bryan J; Wang, Yue; Krauss, Thomas F

    2015-08-21

    Controlling thermal emission with resonant photonic nanostructures has recently attracted much attention. Most of the work has concentrated on the mid-infrared wavelength range and/or was based on metallic nanostructures. Here, we demonstrate the experimental operation of a resonant thermal emitter operating in the near-infrared (≈1.5 μm) wavelength range. The emitter is based on a doped silicon photonic crystal consisting of a two dimensional square array of holes and using silicon-on-insulator technology with a device-layer thickness of 220 nm. The device is resistively heated by passing current through the photonic crystal membrane. At a temperature of ≈1100 K, we observe relatively sharp emission peaks with a Q factor around 18. A support structure system is implemented in order to achieve a large area suspended photonic crystal thermal emitter and electrical injection. The device demonstrates that weak absorption together with photonic resonances can be used as a wavelength-selection mechanism for thermal emitters, both for the enhancement and the suppression of emission.

  20. Shear-Sensitive Monomer/Polymer Liquid Crystal System

    NASA Technical Reports Server (NTRS)

    Singh, Jag J.; Eftekhari, Abe; Parmar, D. S.

    1993-01-01

    Report describes preliminary investigation of new monomer/polymer liquid crystal system, thin film of shear-sensitive cholesteric monomer liquid crystal (TI 511) on Xydar (STR800) (or equivalent) liquid crystal polymer substrate. Monomer/polymer liquid crystal films applied to surfaces provide quantitative indications of shear stresses caused by winds blowing along surfaces. Effects of shear stresses reversible in new coating system. System provides quantitative data on flows in wind tunnels.

  1. Multicolor fluorescence enhancement from a photonics crystal surface

    NASA Astrophysics Data System (ADS)

    Pokhriyal, A.; Lu, M.; Huang, C. S.; Schulz, S.; Cunningham, B. T.

    2010-09-01

    A photonic crystal substrate exhibiting resonant enhancement of multiple fluorophores has been demonstrated. The device, fabricated uniformly from plastic materials over a ˜3×5 in.2 surface area by nanoreplica molding, utilizes two distinct resonant modes to enhance electric field stimulation of a dye excited by a λ =632.8 nm laser (cyanine-5) and a dye excited by a λ =532 nm laser (cyanine-3). Resonant coupling of the laser excitation to the photonic crystal surface is obtained for each wavelength at a distinct incident angle. Compared to detection of a dye-labeled protein on an ordinary glass surface, the photonic crystal surface exhibited a 32× increase in fluorescent signal intensity for cyanine-5 conjugated streptavidin labeling, while a 25× increase was obtained for cyanine-3 conjugated streptavidin labeling. The photonic crystal is capable of amplifying the output of any fluorescent dye with an excitation wavelength in the 532 nm<λ<633 nm range by selection of an appropriate incident angle. The device is designed for biological assays that utilize multiple fluorescent dyes within a single imaged area, such as gene expression microarrays.

  2. Multicolor fluorescence enhancement from a photonics crystal surface

    PubMed Central

    Pokhriyal, A.; Lu, M.; Huang, C. S.; Schulz, S.; Cunningham, B. T.

    2010-01-01

    A photonic crystal substrate exhibiting resonant enhancement of multiple fluorophores has been demonstrated. The device, fabricated uniformly from plastic materials over a ∼3×5 in.2 surface area by nanoreplica molding, utilizes two distinct resonant modes to enhance electric field stimulation of a dye excited by a λ=632.8 nm laser (cyanine-5) and a dye excited by a λ=532 nm laser (cyanine-3). Resonant coupling of the laser excitation to the photonic crystal surface is obtained for each wavelength at a distinct incident angle. Compared to detection of a dye-labeled protein on an ordinary glass surface, the photonic crystal surface exhibited a 32× increase in fluorescent signal intensity for cyanine-5 conjugated streptavidin labeling, while a 25× increase was obtained for cyanine-3 conjugated streptavidin labeling. The photonic crystal is capable of amplifying the output of any fluorescent dye with an excitation wavelength in the 532 nm<λ<633 nm range by selection of an appropriate incident angle. The device is designed for biological assays that utilize multiple fluorescent dyes within a single imaged area, such as gene expression microarrays. PMID:20957067

  3. Ultraflat supercontinuum generation in soft-glass photonic crystal fibers

    NASA Astrophysics Data System (ADS)

    Miret, J. J.; Silvestre, E.; Andrés, P.

    2009-05-01

    We recognize some photonic-crystal-fiber structures, made up of soft glass, that generate ultrawide (over an octave), very smooth and highly coherent supercontinuum spectrum when illuminated with femtosecond pulsed light around 1.55 μm. The design of soft-glass microstructured fiber geometry with nearly ultraflattened, positive and low dispersion is crucial to accomplish the above goals.

  4. [INVITED] New perspectives in photonic crystal fibre sensors

    NASA Astrophysics Data System (ADS)

    Villatoro, Joel; Zubia, Joseba

    2016-04-01

    In this paper we analyse the recent advances on sensors based on photonic crystal fibres(PCFs) and discuss their advantages and disadvantages. Some innovative approaches to overcome the main limitations of PCF sensors are also analysed. In addition, we discuss some opportunities and challenges in PCF sensing for the coming years.

  5. Soft-glass hollow-core photonic crystal fibers

    NASA Astrophysics Data System (ADS)

    Melnikov, Leonid; Khromova, Irina; Scherbakov, Andrey; Nikishin, Nikolay

    2005-09-01

    The results of numerical modeling and experimental investigations of manufactured diamond-shaped and large area hollow core photonic crystal fibers with periodical cladding (kagome-lattice and closely packed tubes) are presented. The use of soft glasses allows to fabricate high-quality structures with moderate losses. Numerical methods, designing strategies and fabrication issues of these promising fiber structures are discussed.

  6. Solar power conversion efficiency in modulated silicon nanowire photonic crystals

    NASA Astrophysics Data System (ADS)

    Deinega, Alexei; John, Sajeev

    2012-10-01

    It is suggested that using only 1 μm of silicon, sculpted in the form of a modulated nanowire photonic crystal, solar power conversion efficiency in the range of 15%-20% can be achieved. Choosing a specific modulation profile provides antireflection, light trapping, and back-reflection over broad angles in targeted spectral regions for high efficiency power conversion without solar tracking. Solving both Maxwell's equations in the 3D photonic crystal and the semiconductor drift-diffusion equations in each nanowire, we identify optimal junction and contact geometries and study the influence of the nanowire surface curvature on solar cell efficiency. We demonstrate that suitably modulated nanowires enable 20% efficiency improvement over their straight counterparts made of an equivalent amount of silicon. We also discuss the efficiency of a tandem amorphous and crystalline silicon nanowire photonic crystal solar cell. Opportunities for "hot carrier" collection and up-conversion of infrared light, enhanced by photonic crystal geometry, facilitate further improvements in power efficiency.

  7. Light trapping in thin film solar cells using textured photonic crystal

    DOEpatents

    Yi, Yasha; Kimerling, Lionel C.; Duan, Xiaoman; Zeng, Lirong

    2009-01-27

    A solar cell includes a photoactive region that receives light. A photonic crystal is coupled to the photoactive region, wherein the photonic crystal comprises a distributed Bragg reflector (DBR) for trapping the light.

  8. Photonic crystal surface-emitting lasers enabled by an accidental Dirac point

    SciTech Connect

    Chua, Song Liang; Lu, Ling; Soljacic, Marin

    2014-12-02

    A photonic-crystal surface-emitting laser (PCSEL) includes a gain medium electromagnetically coupled to a photonic crystal whose energy band structure exhibits a Dirac cone of linear dispersion at the center of the photonic crystal's Brillouin zone. This Dirac cone's vertex is called a Dirac point; because it is at the Brillouin zone center, it is called an accidental Dirac point. Tuning the photonic crystal's band structure (e.g., by changing the photonic crystal's dimensions or refractive index) to exhibit an accidental Dirac point increases the photonic crystal's mode spacing by orders of magnitudes and reduces or eliminates the photonic crystal's distributed in-plane feedback. Thus, the photonic crystal can act as a resonator that supports single-mode output from the PCSEL over a larger area than is possible with conventional PCSELs, which have quadratic band edge dispersion. Because output power generally scales with output area, this increase in output area results in higher possible output powers.

  9. Enhanced trion emission from colloidal quantum dots with photonic crystals by two-photon excitation

    NASA Astrophysics Data System (ADS)

    Xu, Xingsheng

    2013-11-01

    For colloidal quantum dots, the ongoing biggest problem is their fluorescence blinking. Until now, there is no generally accepted model for this fluorescence blinking. Here, two-photon excited fluorescence from CdSe/ZnS nanocrystals on silicon nitride photonic crystals is studied using a femtosecond laser. From analysis of the spectra and decay processes, most of the relative trion efficiency is larger than 10%, and the largest relative trion efficiency reaches 46.7%. The photonic crystals enhance the trion emission of CdSe/ZnS nanocrystals, where the enhancement is due to the coupling of the trion emission to the leaky mode of the photonic crystal slab. Moreover, the photonic crystals enhance the Auger-assisted trapping efficiency of electrons/holes to surface states, and then enhance the efficiency of the generations of charge separation and DC electric field, which modifies the trion spectrum. Therefore, a model is present for explaining the mechanism of fluorescence blinking including the effect of the environment.

  10. Modified thermal radiation in three-dimensional photonic crystals

    NASA Astrophysics Data System (ADS)

    Li, Zhi-Yuan

    2002-12-01

    Thermal radiation from an empty blackbody cavity follows the conventional Wien’s displacement law. At a temperature T=2500 K, the maximum monochromatic radiation intensity lies at a wavelength of 1.16 μm, and radiation into the visible band occupies only 3% of the total radiation energy. In this paper, we show that when the cavity is filled with a three-dimensional photonic crystal, a strong thermal radiation band can appear in the visible regime, significantly improving the luminescence efficiency. This is attributed to the redistribution of photon density of states (DOS) in different frequency ranges in the photonic crystal leading to orders-of-magnitude enhancement of DOS in the visible wavelength over that in the infrared wavelengths.

  11. Thermal properties photonic crystal fiber transducers with ferromagnetic nanoparticles

    NASA Astrophysics Data System (ADS)

    Przybysz, N.; Marć, P.; Kisielewska, A.; Jaroszewicz, L. R.

    2015-12-01

    The main aim of the research is to design new types of fiber optic transducers based on filled photonic crystal fibers for sensor applications. In our research we propose to use as a filling material nanoparticles' ferrofluids (Fe3O4 NPs). Optical properties of such transducers are studied by measurements of spectral characteristics' changes when transducers are exposed to temperature and magnetic field changes. From synthesized ferrofluid several mixtures with different NPs' concentrations were prepared. Partially filled commercially available photonic crystal fiber LMA 10 (NKT Photonics) was used to design PCF transducers. Their thermo-optic properties were tested in a temperature chamber. Taking into account magnetic properties of synthetized NPs the patch cords based on a partially filled PM 1550 PCF were measured.

  12. Nano-photonic organic solar cell architecture for advanced light management utilizing dual photonic crystals

    NASA Astrophysics Data System (ADS)

    Peer, Akshit; Biswas, Rana

    2015-09-01

    Organic solar cells have rapidly increasing efficiencies, but typically absorb less than half of the incident solar spectrum. To increase broadband light absorption, we rigorously design experimentally realizable solar cell architectures based on dual photonic crystals. Our optimized architecture consists of a polymer microlens at the air-glass interface, coupled with a photonic-plasmonic crystal at the metal cathode. The microlens focuses light on the periodic nanostructure that generates strong light diffraction. Waveguiding modes and surface plasmon modes together enhance long wavelength absorption in P3HT-PCBM. The architecture has a period of 500 nm, with absorption and photocurrent enhancement of 49% and 58%, respectively.

  13. Effect of UV curing conditions on polymerized tunable chiral nematic liquid crystals

    NASA Astrophysics Data System (ADS)

    Mohammadimasoudi, Mohammad; Beeckman, Jeroen; Neyts, Kristiaan

    2014-10-01

    Chiral nematic liquid crystals have attracted substantial interest. They spontaneously self-organize to form a helical structure with no complex fabrication procedure required and exhibit a reflection band for a certain wavelength interval. Since the photonic band gap can be tuned by applying external factors (heat, voltage, light, elasticity) chiral nematic liquid crystals are potentially interesting for large area optical filters and shutters, reflective displays and tunable lasers. In this work, a device which consists of a mixture of photo-polymerizable liquid crystal, non-reactive nematic liquid crystal and a chiral dopant is fabricated. By selecting the appropriate chiral dopant concentration, it is possible to make devices for different operation wavelengths. The influence of UV illumination on a partially polymerized chiral liquid crystal is investigated. A blue-wavelength shift of the photonic band gap is obtained as a function of power, duration time of UV illumination and the thickness of the cells. Interestingly the width and depth of the photonic band gap is unaffected by the change in UV curing conditions, which indicates that there is no degradation by the UV light.

  14. Nanocrystalline diamond photonics platform with high quality factor photonic crystal cavities

    NASA Astrophysics Data System (ADS)

    Checoury, X.; Néel, D.; Boucaud, P.; Gesset, C.; Girard, H.; Saada, S.; Bergonzo, P.

    2012-10-01

    We demonstrate a diamond photonics platform with integrated suspended waveguide-cavity structures and two dimensional photonic crystal (PhC) cavities. PhC cavities with quality factors exceeding 2800 have been fabricated using a top-down approach from thin nanocrystalline diamond films. The developed technological process allows one to access these cavities in a fully planar geometry, including light injection and collection from the outside using lensed-fibers. This diamond platform opens the road to large scale fabrication of photonics devices including optical sensor chips.

  15. 21 CFR 880.2200 - Liquid crystal forehead temperature strip.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Liquid crystal forehead temperature strip. 880... Personal Use Monitoring Devices § 880.2200 Liquid crystal forehead temperature strip. (a) Identification. A liquid crystal forehead temperature strip is a device applied to the forehead that is used to...

  16. 21 CFR 880.6970 - Liquid crystal vein locator.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 8 2014-04-01 2014-04-01 false Liquid crystal vein locator. 880.6970 Section 880... Devices § 880.6970 Liquid crystal vein locator. (a) Identification. A liquid crystal vein locator is a device used to indicate the location of a vein by revealing variations in the surface temperature of...

  17. 21 CFR 880.2200 - Liquid crystal forehead temperature strip.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 8 2013-04-01 2013-04-01 false Liquid crystal forehead temperature strip. 880... Personal Use Monitoring Devices § 880.2200 Liquid crystal forehead temperature strip. (a) Identification. A liquid crystal forehead temperature strip is a device applied to the forehead that is used to...

  18. 21 CFR 880.2200 - Liquid crystal forehead temperature strip.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 8 2011-04-01 2011-04-01 false Liquid crystal forehead temperature strip. 880... Personal Use Monitoring Devices § 880.2200 Liquid crystal forehead temperature strip. (a) Identification. A liquid crystal forehead temperature strip is a device applied to the forehead that is used to...

  19. 21 CFR 880.2200 - Liquid crystal forehead temperature strip.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 8 2014-04-01 2014-04-01 false Liquid crystal forehead temperature strip. 880... Personal Use Monitoring Devices § 880.2200 Liquid crystal forehead temperature strip. (a) Identification. A liquid crystal forehead temperature strip is a device applied to the forehead that is used to...

  20. 21 CFR 880.6970 - Liquid crystal vein locator.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 8 2011-04-01 2011-04-01 false Liquid crystal vein locator. 880.6970 Section 880... Devices § 880.6970 Liquid crystal vein locator. (a) Identification. A liquid crystal vein locator is a device used to indicate the location of a vein by revealing variations in the surface temperature of...

  1. 21 CFR 880.2200 - Liquid crystal forehead temperature strip.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 8 2012-04-01 2012-04-01 false Liquid crystal forehead temperature strip. 880... Personal Use Monitoring Devices § 880.2200 Liquid crystal forehead temperature strip. (a) Identification. A liquid crystal forehead temperature strip is a device applied to the forehead that is used to...

  2. Chem I Supplement: Liquid Crystals--The Chameleon Chemicals.

    ERIC Educational Resources Information Center

    Brown, Glenn H.

    1983-01-01

    Presents information relevant to everyday life so as to stimulate student interest in the properties of the two basic types of liquid crystals: thermotropic and lyotropic. Describes the applications of liquid crystals to electronics, biomedicine, and polymer science and appraises the future of liquid crystal research. (JM)

  3. Three-dimensional colloidal crystals in liquid crystalline blue phases

    PubMed Central

    Ravnik, Miha; Alexander, Gareth P.; Yeomans, Julia M.; Žumer, Slobodan

    2011-01-01

    Applications for photonic crystals and metamaterials put stringent requirements on the characteristics of advanced optical materials, demanding tunability, high Q factors, applicability in visible range, and large-scale self-assembly. Exploiting the interplay between structural and optical properties, colloidal lattices embedded in liquid crystals (LCs) are promising candidates for such materials. Recently, stable two-dimensional colloidal configurations were demonstrated in nematic LCs. However, the question as to whether stable 3D colloidal structures can exist in an LC had remained unanswered. We show, by means of computer modeling, that colloidal particles can self-assemble into stable, 3D, periodic structures in blue phase LCs. The assembly is based on blue phases providing a 3D template of trapping sites for colloidal particles. The particle configuration is determined by the orientational order of the LC molecules: Specifically, face-centered cubic colloidal crystals form in type-I blue phases, whereas body-centered crystals form in type-II blue phases. For typical particle diameters (approximately 100 nm) the effective binding energy can reach up to a few 100 kBT, implying robustness against mechanical stress and temperature fluctuations. Moreover, the colloidal particles substantially increase the thermal stability range of the blue phases, for a factor of two and more. The LC-supported colloidal structure is one or two orders of magnitude stronger bound than, e.g., water-based colloidal crystals. PMID:21368186

  4. Liquid crystal assemblies in biologically inspired systems

    PubMed Central

    Safinya, Cyrus R.; Deek, Joanna; Beck, Roy; Jones, Jayna B.; Leal, Cecilia; Ewert, Kai K.; Li, Youli

    2013-01-01

    In this paper, which is part of a collection in honor of Noel Clark's remarkable career on liquid crystal and soft matter research, we present examples of biologically inspired systems, which form liquid crystal (LC) phases with their LC nature impacting biological function in cells or being important in biomedical applications. One area focuses on understanding network and bundle formation of cytoskeletal polyampholytes (filamentous-actin, microtubules, and neurofilaments). Here, we describe studies on neurofilaments (NFs), the intermediate filaments of neurons, which form open network nematic liquid crystal hydrogels in axons. Synchrotron small-angle-x-ray scattering studies of NF-protein dilution experiments and NF hydrogels subjected to osmotic stress show that neurofilament networks are stabilized by competing long-range repulsion and attractions mediated by the neurofilament's polyampholytic sidearms. The attractions are present both at very large interfilament spacings, in the weak sidearm-interpenetrating regime, and at smaller interfilament spacings, in the strong sidearm-interpenetrating regime. A second series of experiments will describe the structure and properties of cationic liposomes (CLs) complexed with nucleic acids (NAs). CL-NA complexes form liquid crystalline phases, which interact in a structure-dependent manner with cellular membranes enabling the design of complexes for efficient delivery of nucleic acid (DNA, RNA) in therapeutic applications. PMID:24558293

  5. Invited Review Article: Development of crystal lenses for energetic photons

    SciTech Connect

    Smither, Robert K.

    2014-08-15

    This paper follows the development of crystal diffraction lenses designed to focus energetic photons. It begins with the search for a solution to the astrophysics problem of how to detect weak astrophysics sources of gamma rays and x-rays. This led to the basic designs for a lens and to the understanding of basic limitations of lens design. The discussion of the development of crystal diffraction lenses is divided into two parts: lenses using crystals with mosaic structure, and lenses that use crystals with curved crystal planes. This second group divides into two sub-groups: (1) Curved crystals that are used to increase the acceptance angle of the diffraction of a monochromatic beam and to increase the energy bandwidth of the diffraction. (2) Curved crystals used to focus gamma ray beams. The paper describes how these two types of crystals affect the design of the corresponding crystal lenses in different fields: astrophysics, medical imaging, detection of weak, distant, gamma-ray sources, etc. The designs of crystal lenses for these applications are given in enough detail to allow the reader to design a lens for his own application.

  6. Plasmonic photonic crystals realized through DNA-programmable assembly

    PubMed Central

    Park, Daniel J.; Zhang, Chuan; Ku, Jessie C.; Zhou, Yu; Schatz, George C.; Mirkin, Chad A.

    2015-01-01

    Three-dimensional dielectric photonic crystals have well-established enhanced light–matter interactions via high Q factors. Their plasmonic counterparts based on arrays of nanoparticles, however, have not been experimentally well explored owing to a lack of available synthetic routes for preparing them. However, such structures should facilitate these interactions based on the small mode volumes associated with plasmonic polarization. Herein we report strong light-plasmon interactions within 3D plasmonic photonic crystals that have lattice constants and nanoparticle diameters that can be independently controlled in the deep subwavelength size regime by using a DNA-programmable assembly technique. The strong coupling within such crystals is probed with backscattering spectra, and the mode splitting (0.10 and 0.24 eV) is defined based on dispersion diagrams. Numerical simulations predict that the crystal photonic modes (Fabry–Perot modes) can be enhanced by coating the crystals with a silver layer, achieving moderate Q factors (∼102) over the visible and near-infrared spectrum. PMID:25548175

  7. Model calculations for enhanced fluorescence in photonic crystal phosphor.

    PubMed

    Min, Kyungtaek; Choi, Yun-Kyoung; Jeon, Heonsu

    2012-01-30

    We propose a novel photonic structure, based on the photonic crystal (PC) effect, which simulations show results in an improved fluorescence efficiency from embedded phosphor. To be specific, the phosphor pumping efficiency can be significantly improved by tuning the pump photon energy to a photonic band-edge (PBE) of the PC phosphor. We have confirmed this theoretically by calculating optical properties of one-dimensional PC phosphor structures using the transfer-matrix method and plane-wave expansion method. For a particular model structure based on a quantum dot phosphor, the fluorescence enhancement factor was estimated to be as high as 6.9 for a monochromatic pump source and 2.2 for a broad bandwidth (20 nm) pump source.

  8. Two-photon absorption spectroscopy of rubrene single crystals

    NASA Astrophysics Data System (ADS)

    Irkhin, Pavel; Biaggio, Ivan

    2014-05-01

    We determine the wavelength dependence of the two-photon absorption cross section in rubrene single crystals both by direct measurement of nonlinear transmission and from the two-photon excitation spectrum of the photoluminescence. The peak two-photon absorption coefficient for b-polarized light was found to be (4.6±1)×10-11 m/W at a wavelength of 850±10 nm. It is 2.3 times larger for c-polarized light. The lowest energy two-photon excitation peak corresponds to an excited state energy of 2.92±0.04 eV and it is followed by a vibronic progression of higher energy peaks separated by ˜0.14 eV.

  9. Recent Progresses and Future Prospects of Two- and Three-Dimensional Photonic Crystals

    NASA Astrophysics Data System (ADS)

    Noda, Susumu

    2006-12-01

    Photonic crystals, in which the refractive index changes periodically, provide an exciting new tool for the manipulation of photons and have received keen interest from a variety of fields. This paper reviews the recent progress and future prospects of photonic crystals and their applications to photonic-nanostructure devices.

  10. Zeolite-like liquid crystals

    PubMed Central

    Poppe, Silvio; Lehmann, Anne; Scholte, Alexander; Prehm, Marko; Zeng, Xiangbing; Ungar, Goran; Tschierske, Carsten

    2015-01-01

    Zeolites represent inorganic solid-state materials with porous structures of fascinating complexity. Recently, significant progress was made by reticular synthesis of related organic solid-state materials, such as metal-organic or covalent organic frameworks. Herein we go a step further and report the first example of a fluid honeycomb mimicking a zeolitic framework. In this unique self-assembled liquid crystalline structure, transverse-lying π-conjugated rod-like molecules form pentagonal channels, encircling larger octagonal channels, a structural motif also found in some zeolites. Additional bundles of coaxial molecules penetrate the centres of the larger channels, unreachable by chains attached to the honeycomb framework. This creates a unique fluid hybrid structure combining positive and negative anisotropies, providing the potential for tuning the directionality of anisotropic optical, electrical and magnetic properties. This work also demonstrates a new approach to complex soft-matter self-assembly, by using frustration between space filling and the entropic penalty of chain extension. PMID:26486751

  11. Imaging and tuning of coupled photonic crystal cavities (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Gurioli, Massimo

    2016-04-01

    Photonic microcavities (PMC) coupled through their evanescent field are used for a large variety of classical and quantum devices. In such systems, a molecular-like spatial delocalization of the coupled modes is achieved by an evanescent tunnelling. The tunnelling rate depends on the height and depth of the photonic barrier between two adjacent resonators and therefore it is sensitive to the fabrication-induced disorder present in the center of the molecule. In this contribution, we address the problem of developing a post fabrication control of the tunnelling rate in photonic crystal coupled PMCs. The value of the photonic coupling (proportional to the tunnelling rate) is directly measured by the molecular mode splitting at the anticrossing point. By exploiting a combination of tuning techniques such as local infiltration of water, micro-evaporation, and laser induced non thermal micro-oxidation, we are able to either increase or decrease the detuning and the photonic coupling, independently. Near field imaging is also used for mapping the modes and establish delocalization. By water micro-infiltration, we were able to increase the photon coupling by 28%. On the contrary, by laser induced non thermal oxidation, we got a reduction of g by 30%. The combination of the two methods would therefore give a complete control of g with excellent accuracy. This could make possible the realization of array of photonic cavities with on demand tunnelling rate between each pair of coupled resonators. We believe that this peculiar engineering of photonic crystal molecules would open the road to possible progress in the exploitation of coherent interference between coupled optical resonators both for quantum information processing and optical communication.

  12. Three-Dimensional Complex-Shaped Photopolymerized Microparticles at Liquid Crystal Interfaces

    SciTech Connect

    Martinez, A.; Lee, T.; Asavei, T.; Rubinsztein-Dunlop, H.; Smalyukh, I. I.

    2012-02-28

    Microparticles of arbitrary shapes immersed in the bulk of nematic fluids are known to produce dipolar or quadrupolar elastic distortions that can mediate long-range colloidal interactions. We use two-photon photopolymerization to obtain complex-shaped surface-bound microparticles that are then embedded into a nematic liquid crystal host with a uniform far-field director. By means of three-dimensional imaging with multi-photon excitation fluorescence polarizing microscopy, we demonstrate low-symmetry, long-range elastic distortions induced by the particles in the liquid crystal director field. These director distortions may provide a means for controlling elastic interactions in liquid crystals between custom-designed photopolymerized microparticles attached to confining solid substrates and nematic fluid-borne colloids, thus enabling elasticity-mediated templated self-assembly.

  13. Novel photonic crystals: incorporation of nano-CdS into the natural photonic crystals within peacock feathers.

    PubMed

    Han, Jie; Su, Huilan; Song, Fang; Gu, Jiajun; Di, Zhang; Jiang, Limin

    2009-03-01

    In this investigation, the natural 2D photonic crystals (PhCs) within peacock feathers are applied to incorporate CdS nanocrystallites. Peacock feathers are activated by ethylenediaminetetraacetic/dimethylformamide suspension to increase the reactive sites on the keratin component, on which CdS nanoparticles (nano-CdS) are in situ formed in succession and serve as the "seeds" to direct further incorporation during the following solvothermal procedure. Thus, homogeneous nano-CdS are loaded both on the feathers' surface layer and inside the 2D PhCs. The obtained nano-CdS/peacock feathers hybrids are novel photonic crystals whose photonic stop bands are markedly different from that of the natural PhCs within original peacock feathers, as observed by the reflection spectra.

  14. Tetrahedral Order in Banana Liquid Crystals

    NASA Astrophysics Data System (ADS)

    Radzihovsky, Leo

    2005-03-01

    Bent-core liquid crystal molecules can exhibit phases that require a third-rank symmetric-traceless tensor order parameter, as well as a vector order parameter and the usual second-rank nematic order parameter. The combination gives rise to a rich variety of spatially homogeneous phases ranging from the well-known nematic to novel tetrahedratic and chiral liquids. I discuss experimental signatures of these phases and phase transitions between them.[0.3cm] L. Radzihovsky and T.C. Lubensky, Europhys. Lett.54, 206 (2001); Phys. Rev.E 66, 031704 (2002).

  15. Complex Nanoscale-Ordered Liquid Crystal Polymer Film for High Transmittance Holographic Polarizer.

    PubMed

    Du, Tao; Fan, Fan; Tam, Alwin Ming Wai; Sun, Jiatong; Chigrinov, Vladimir G; Sing Kwok, Hoi

    2015-11-25

    A special design of a complex-ordered liquid crystal polymer film is developed into a holographic polarizer. The holographic polarizer shows over 90% transmittance, which provides a simple solution to make LEDs polarized. Furthermore, the holographic polarizer exhibits intensity and polarization maintenance properties, which could be further developed for photonics applications.

  16. High-efficiency and fast-response tunable phase grating using a blue phase liquid crystal.

    PubMed

    Yan, Jin; Li, Yan; Wu, Shin-Tson

    2011-04-15

    We demonstrate a tunable phase grating using a polymer-stabilized blue phase liquid crystal. Because of the electric-field-induced rectangularlike phase profile, a high diffraction efficiency of 40% is achieved. Moreover, this device shows submillisecond response time. The proposed tunable phase grating holds great potential for photonics and display applications. PMID:21499371

  17. Evidence of Broken Reciprocity in Chiral Liquid Crystals

    NASA Astrophysics Data System (ADS)

    Moreira, Michele; Venkataraman, Nithya; Taheri, Bahman; Palffy-Muhoray, Peter

    2008-03-01

    Reciprocity in light scattering is predicated on bounded scattering media with symmetric and linear permittivity, conductivity and permeability. Due to their anisotropy and chirality, cholesteric liquid crystal form periodic dielectric structures. If the periodicity is comparable to the wavelength of light, these phases are self-assembled photonic band gap structures. There appear in the permittivity odd powers of the wave vector resulting from nonlocality and broken inversion symmetry. Evidence of non-reciprocity has been found in optically active crystals by Bennett [1] and in stacks of cholesteric and nematic liquid crystal cells by Takezoe [2]. We present experimental data showing broken reciprocity in transmittance and reflectance in cholesteric cells with different pitches having overlapping but distinct reflection bands. We explain our results in terms of simple analytic descriptions of material properties and propagating modes. [1] P.J. Bennett, S. Dhanjal, Yu. P. Svirko and N. I. Zheludev, Opt. Lett. 21, 1955 (1996) [2] J. Hwang; M.H. Song; B. Park; S. Nishimura; T. Toyooka; J.W. Wu; Y. Takanishi; K. Ishikawa; H. Takezoe, Nat. Mat. 4, 383 (2005).

  18. Nanoparticle interfacial assembly in liquid crystal droplets

    NASA Astrophysics Data System (ADS)

    Rahimi, Mohammad; Roberts, Tyler; Armas-Perez, Julio; Wang, Xiaoguang; Bukusoglu, Emre; Abbott, Nicholas L.; de Pablo, Juan J.

    2015-03-01

    Controlled assembly of nanoparticles at liquid crystal interfaces could lead to easily manufacturable building blocks for assembly of materials with tunable mechanical, optical, and electronic properties. Past work has examined nanoparticle assembly at planar liquid crystal interfaces. In this work we show that nanoparticle assembly on curved interfaces is drastically different, and arises for conditions under which assembly is too weak to occur on planar interfaces. We also demonstrate that LC-mediated nanoparticle interactions are strong, are remarkably sensitive to surface anchoring, and lead to hexagonal arrangements that do not arise in bulk systems. All these elements form the basis for a highly tunable, predictable, and versatile platform for hierarchical materials assembly. National Science Foundation through the UW MRSEC.

  19. Reflective liquid crystal hybrid beam-steerer.

    PubMed

    Willekens, Oliver; Jia, Xiaoning; Vervaeke, Michael; Shang, Xiaobing; Baghdasaryan, Tigran; Thienpont, Hugo; De Smet, Herbert; Neyts, Kristiaan; Beeckman, Jeroen

    2016-09-19

    We report on efficient optical beam-steering using a hot-embossed reflective blazed grating in combination with liquid crystal. A numerical simulation of the electrical switching characteristics of the liquid crystal is performed and the results are used in an FDTD optical simulator to analyze the beam deflection. The corresponding experiment on the realized device is performed and is found to be in good agreement. Beam deflection angles of 4.4° upon perpendicular incidence are found with low applied voltages of 3.4 V. By tilting the device with respect to the incoming optical beam it can be electronically switched such that the beam undergoes either total internal reflection or reflection with a tunable angle. PMID:27661892

  20. Relaxation of Liquid Crystal Alignment Layers

    NASA Astrophysics Data System (ADS)

    Rich, David C.; Sichel, Enid K.; Cebe, Peggy

    1997-03-01

    A new method for investigating thermophysical transitions in liquid crystal alignment layers is discussed. The technique involves curing a set of alignment films at an array of temperatures after the films have been brushed with a cloth, but before liquid crystal cells are constructed from the films. When a thermal transition in the polymer is initiated by a post-brush cure, the aligning ability of the brushed films is destroyed. The technique is demonstrated using polyamide- imide, PMDA-APB polyimide, poly(phenylene ether sulfide) and PVA poly(vinyl alcohol) alignment films. The technique is advantageous for examining brush-aligned surfaces which, due to surface roughness, can not be examined using conventional ellipsometry .

  1. Axial polarizers based on dichroic liquid crystals

    NASA Astrophysics Data System (ADS)

    Nersisyan, Sarik; Tabiryan, Nelson; Steeves, Diane M.; Kimball, Brian R.

    2010-08-01

    Polarizers capable of producing linearly polarized beams with axial (radial and azimuthal) symmetry have been fabricated with the aid of a dichroic liquid crystal. Photoalignment was achieved using a printing technique to reduce the UV exposure time required for production of axially aligning substrates from 1 h, typical for direct writing techniques, to 10 min. The polarizing features of axial polarizers and their pairs are characterized and their differences outlined. We demonstrate that the transmission switching contrast of an axial polarizer/analyzer pair, comprised of an electrically controlled liquid crystal cell, is comparable to conventional systems with linear polarizers. The opportunities for using axial polarizers for polarization imaging, sensor protection, and nonlinear optics are discussed. Particularly, we show that the technology could reduce the fluence of a laser beam on an optical sensor without affecting imaging.

  2. Phototunable reflection notches of cholesteric liquid crystals

    SciTech Connect

    Hrozhyk, Uladzimir A.; Serak, Svetlana V.; Tabiryan, Nelson V.; Bunning, Timothy J.

    2008-09-15

    The reflection notch of cholesteric liquid crystals (CLCs) formed from highly photosenstive azobenzene nematic liquid crystals doped with light-insensitive, large helical twisting power chiral dopants is shown to be widely phototunable by green laser beams. The nonlinear transmission properties of these materials were studied. We have shown that the relative shift in Bragg wavelength is independent of the chiral dopant concentration and develop a predictive theory of such behavior. The theory describes the dynamics of phototuning as well. Reflection shifts greater than 150 nm were driven with low power, cw of 532 nm in these photosensitive CLCs, previously attainable only through UV pre-exposure. A nonlinear feedback mechanism was demonstrated for CLCs of left, right, and both handedness upon laser-induced blueshifting of the reflection notch from a red wavelength using a green cw laser.

  3. Engineered atom-light interactions in 1D photonic crystals

    NASA Astrophysics Data System (ADS)

    Martin, Michael J.; Hung, Chen-Lung; Yu, Su-Peng; Goban, Akihisa; Muniz, Juan A.; Hood, Jonathan D.; Norte, Richard; McClung, Andrew C.; Meenehan, Sean M.; Cohen, Justin D.; Lee, Jae Hoon; Peng, Lucas; Painter, Oskar; Kimble, H. Jeff

    2014-05-01

    Nano- and microscale optical systems offer efficient and scalable quantum interfaces through enhanced atom-field coupling in both resonators and continuous waveguides. Beyond these conventional topologies, new opportunities emerge from the integration of ultracold atomic systems with nanoscale photonic crystals. One-dimensional photonic crystal waveguides can be engineered for both stable trapping configurations and strong atom-photon interactions, enabling novel cavity QED and quantum many-body systems, as well as distributed quantum networks. We present the experimental realization of such a nanophotonic quantum interface based on a nanoscale photonic crystal waveguide, demonstrating a fractional waveguide coupling of Γ1 D /Γ' of 0 . 32 +/- 0 . 08 , where Γ1 D (Γ') is the atomic emission rate into the guided (all other) mode(s). We also discuss progress towards intra-waveguide trapping of ultracold Cs. This work was supported by the IQIM, an NSF Physics Frontiers Center with support from the Moore Foundation, the DARPA ORCHID program, the AFOSR QuMPASS MURI, the DoD NSSEFF program, NSF, and the Kavli Nanoscience Institute (KNI) at Caltech.

  4. Photonic-magnonic crystals: Multifunctional periodic structures for magnonic and photonic applications

    SciTech Connect

    Kłos, J. W. Krawczyk, M.; Dadoenkova, Yu. S.; Dadoenkova, N. N.; Lyubchanskii, I. L.

    2014-05-07

    We investigate the properties of a photonic-magnonic crystal, a complex multifunctional one-dimensional structure with magnonic and photonic band gaps in the GHz and PHz frequency ranges for spin waves and light, respectively. The system consists of periodically distributed dielectric magnetic slabs of yttrium iron garnet and nonmagnetic spacers with an internal structure of alternating TiO{sub 2} and SiO{sub 2} layers which form finite-size dielectric photonic crystals. We show that the spin-wave coupling between the magnetic layers, and thus the formation of the magnonic band structure, necessitates a nonzero in-plane component of the spin-wave wave vector. A more complex structure perceived by light is evidenced by the photonic miniband structure and the transmission spectra in which we have observed transmission peaks related to the repetition of the magnetic slabs in the frequency ranges corresponding to the photonic band gaps of the TiO{sub 2}/SiO{sub 2} stack. Moreover, we show that these modes split to very high sharp (a few THz wide) subpeaks in the transmittance spectra. The proposed novel multifunctional artificial crystals can have interesting applications and be used for creating common resonant cavities for spin waves and light to enhance the mutual influence between them.

  5. Nano-optic label-free biosensors based on photonic crystal platform with negative refraction

    NASA Astrophysics Data System (ADS)

    Aroua, W.; Haxha, S.; AbdelMalek, F.

    2012-04-01

    In this paper, a novel biosensor based on hetero photonic crystal (PC) structures is proposed. The biosensor consists of photonic crystals with negative refraction (PCNR) embedded between two ordinary PC structures. The PCNR is employed in order to produce an image that is as similar as the light source, which is located in the first ordinary PC. Significant enhancement of the image is achieved when a nanocavity is introduced into the PCNR. It is found that the transmission peak shifts when the nanocavity is filled with blood plasma, liquid and dry air. It is shown that by careful selection of the radius of the nanocavity, the sensitivity of the proposed biosensor can be enhanced. The presented PCNR biosensor is investigated by employing the finite-difference time-domain method (FDTD).

  6. Photonic NOT and NOR gates based on a single compact photonic crystal ring resonator.

    PubMed

    Bai, Jibo; Wang, Junqin; Jiang, Junzhen; Chen, Xiyao; Li, Hui; Qiu, Yishen; Qiang, Zexuan

    2009-12-20

    New all-optical NOT and NOR logic gates based on a single ultracompact photonic crystal ring resonator (PCRR) have been proposed. The PCRR was formed by removing the line defect along the GammaM direction instead of the conventional GammaX direction in a square-pattern cylindrical silicon-rod photonic crystal structure. The behavior of the proposed logic gates is qualitatively analyzed with the theory of beam interference and then numerically investigated by use of the two-dimensional finite-difference time-domain method. No nonlinear material is required with less than a 2.2 microm effective ring radius. The wavelengths of the input signal and the probe signal are the same. This new device can potentially be used in on-chip photonic logic-integrated circuits. PMID:20029593

  7. Broadband single-photon-level memory in a hollow-core photonic crystal fibre

    NASA Astrophysics Data System (ADS)

    Sprague, M. R.; Michelberger, P. S.; Champion, T. F. M.; England, D. G.; Nunn, J.; Jin, X.-M.; Kolthammer, W. S.; Abdolvand, A.; Russell, P. St. J.; Walmsley, I. A.

    2014-04-01

    Storing information encoded in light is critical for realizing optical buffers for all-optical signal processing and quantum memories for quantum information processing. These proposals require efficient interaction between atoms and a well-defined optical mode. Photonic crystal fibres can enhance light-matter interactions and have engendered a broad range of nonlinear effects; however, the storage of light has proven elusive. Here, we report the first demonstration of an optical memory in a hollow-core photonic crystal fibre. We store gigahertz-bandwidth light in the hyperfine coherence of caesium atoms at room temperature using a far-detuned Raman interaction. We demonstrate a signal-to-noise ratio of 2.6:1 at the single-photon level and a memory efficiency of 27 +/- 1%. Our results demonstrate the potential of a room-temperature fibre-integrated optical memory for implementing local nodes of quantum information networks.

  8. Polarization Engineering in Photonic Crystal Waveguides for Spin-Photon Entanglers.

    PubMed

    Young, A B; Thijssen, A C T; Beggs, D M; Androvitsaneas, P; Kuipers, L; Rarity, J G; Hughes, S; Oulton, R

    2015-10-01

    By performing a full analysis of the projected local density of states (LDOS) in a photonic crystal waveguide, we show that phase plays a crucial role in the symmetry of the light-matter interaction. By considering a quantum dot (QD) spin coupled to a photonic crystal waveguide (PCW) mode, we demonstrate that the light-matter interaction can be asymmetric, leading to unidirectional emission and a deterministic entangled photon source. Further we show that understanding the phase associated with both the LDOS and the QD spin is essential for a range of devices that can be realized with a QD in a PCW. We also show how suppression of quantum interference prevents dipole induced reflection in the waveguide, and highlight a fundamental breakdown of the semiclassical dipole approximation for describing light-matter interactions in these spin dependent systems. PMID:26550722

  9. Liquid crystal phase shifters for space applications

    NASA Astrophysics Data System (ADS)

    Woehrle, Christopher D.

    Space communication satellites have historically relied heavily on high gain gimbal dish antennas for performing communications. Reflector dish antennas lack flexibility in anti-jamming capabilities, and they tend to have a high risk associated to them given the need for mechanical mechanisms to beam steer. In recent years, a great amount of investment has been made into phased array antenna technologies. Phased arrays offer increased signal flexibility at reduced financial cost and in system risk. The problem with traditional phased arrays is the significant program cost and overall complexity added to the satellite by integrating antenna elements that require many dedicated components to properly perform adaptive beam steering. Several unique methods have been proposed to address the issues that plague traditional phase shifters slated for space applications. Proposed approaches range from complex mechanical switches (MEMS) and ferroelectric devices to more robust molecular changes. Nematic liquid crystals offer adaptive beam steering capabilities that traditional phased arrays have; however, with the added benefit of reduced system cost, complexity, and increased resilience to space environmental factors. The objective of the work presented is to investigate the feasibility of using nematic liquid crystals as a means of phase shifting individual phased array elements slated for space applications. Significant attention is paid to the survivability and performance of liquid crystal and associated materials in the space environment. Performance regarding thermal extremes and interactions with charged particles are the primary factors addressed.

  10. Orientational transitions in antiferromagnetic liquid crystals

    NASA Astrophysics Data System (ADS)

    Zakhlevnykh, A. N.; Petrov, D. A.

    2016-09-01

    The orientational phases in an antiferromagnetic liquid crystal (ferronematic) based on the nematic liquid crystal with the negative anisotropy of diamagnetic susceptibility are studied in the framework of the continuum theory. The ferronematic was assumed to be compensated; i.e., in zero field, impurity ferroparticles with the magnetic moments directed parallel and antiparallel to the director are equiprobably distributed in it. It is established that under the action of a magnetic field the ferronematic undergoes orientational transitions compensated (antiferromagnetic) phase-non-uniform phase-saturation (ferrimagnetic) phase. The analytical expressions for threshold fields of the transitions as functions of material parameters are obtained. It is shown that with increasing magnetic impurity segregation parameter, the threshold fields of the transitions significantly decrease. The bifurcation diagram of the ferronematic orientational phases is built in terms of the energy of anchoring of magnetic particles with the liquid-crystal matrix and magnetic field. It is established that the Freedericksz transition is the second-order phase transition, while the transition to the saturation state can be second- or first-order. In the latter case, the suspension exhibits orientational bistability. The orientational and magnetooptical properties of the ferronematic in different applied magnetic fields are studied.

  11. Optical modeling of liquid crystal biosensors

    NASA Astrophysics Data System (ADS)

    Hwang, Dae Kun; Rey, Alejandro D.

    2006-11-01

    Optical simulations of a liquid crystal biosensor device are performed using an integrated optical/textural model based on the equations of nematodynamics and two optical methods: the Berreman optical matrix method [J. Opt. Soc. Am. 62, 502 (1972)] and the discretization of the Maxwell equations based on the finite difference time domain (FDTD) method. Testing the two optical methods with liquid crystal films of different degrees of orientational heterogeneities demonstrates that only the FDTD method is suitable to model this device. Basic substrate-induced texturing process due to protein adsorption gives rise to an orientation correlation function that is nearly linear with the transmitted light intensity, providing a basis to calibrate the device. The sensitivity of transmitted light to film thickness, protein surface coverage, and wavelength is established. A crossover incident light wavelength close to λco≈500nm is found, such that when λ >λco thinner films are more sensitive to the amount of protein surface coverage, while for λ <λco the reverse holds. In addition it is found that for all wavelengths the sensitivity increases with the amount of protein coverage. The integrated device model based on FDTD optical simulations in conjunction with the Landau-de Gennes nematodynamics model provides a rational basis for further progress in liquid crystal biosensor devices.

  12. Microscale locomotion in a nematic liquid crystal

    NASA Astrophysics Data System (ADS)

    Krieger, Madison S.; Spagnolie, Saverio E.; Powers, Thomas

    Microorganisms often encounter anisotropy, for example in mucus and biofilms. We study how anisotropy and elasticity of the ambient fluid affects the speed of a swimming microorganism with a prescribed stroke. Motivated by recent experiments on swimming bacteria in anisotropic environments, we extend a classical model for swimming microorganisms, the Taylor swimming sheet, actuated either by transverse or longitudinal traveling waves in a three-dimensional nematic liquid crystal without twist. We calculate the swimming speed and entrained volumetric flux as a function of the swimmer's stroke properties as well as the elastic and rheological properties of the liquid crystal. The behavior is quantitatively and qualitatively well-approximated by a hexatic liquid crystal except in the cases of small Ericksen number and in a nematic fluid with tumbling parameter near the transition to a flow-aligning nematic, where anisotropic effects dominate. We also propose a novel method of swimming or pumping in a nematic fluid by passing a traveling wave of director oscillation along a rigid wall.

  13. Polymer-dispersed liquid crystal elastomers

    PubMed Central

    Rešetič, Andraž; Milavec, Jerneja; Zupančič, Blaž; Domenici, Valentina; Zalar, Boštjan

    2016-01-01

    The need for mechanical manipulation during the curing of conventional liquid crystal elastomers diminishes their applicability in the field of shape-programmable soft materials and future applications in additive manufacturing. Here we report on polymer-dispersed liquid crystal elastomers, novel composite materials that eliminate this difficulty. Their thermal shape memory anisotropy is imprinted by curing in external magnetic field, providing for conventional moulding of macroscopically sized soft, thermomechanically active elastic objects of general shapes. The binary soft-soft composition of isotropic elastomer matrix, filled with freeze-fracture-fabricated, oriented liquid crystal elastomer microparticles as colloidal inclusions, allows for fine-tuning of thermal morphing behaviour. This is accomplished by adjusting the concentration, spatial distribution and orientation of microparticles or using blends of microparticles with different thermomechanical characteristics. We demonstrate that any Gaussian thermomechanical deformation mode (bend, cup, saddle, left and right twist) of a planar sample, as well as beat-like actuation, is attainable with bilayer microparticle configurations. PMID:27713478

  14. High Quality Factor Metallodielectric Hybrid Plasmonic-Photonic Crystals

    SciTech Connect

    Yu, Xindi; Shi, Lei; Han, Dezhuan; Zi, Jian; Braun, Paul V.

    2010-05-11

    A 2D polystyrene colloidal crystal self-assembled on a flat gold surface supports multiple photonic and plasmonic propagating resonance modes. For both classes of modes, the quality factors can exceed 100, higher than the quality factor of surface plasmons (SP) at a polymer–gold interface. The spatial energy distribution of those resonance modes are carefully studied by measuring the optical response of the hybrid plasmonic–photonic crystal after coating with dielectric materials under different coating profiles. Computer simulations with results closely matching those of experiments provide a clear picture of the field distribution of each resonance mode. For the SP modes, there is strong confinement of electromagnetic energy near the metal surface, while for optical modes, the field is confined inside the spherical particles, far away from the metal. Coating of dielectric material on the crystal results in a large shift in optical features. A surface sensor based on the hybrid plasmonic–photonic crystal is proposed, and it is shown to have atomic layer sensitivity. An example of ethanol vapor sensing based on physisorption of ethanol onto the sensor surface is demonstrated.

  15. Nonreciprocal optical properties in resonant hybrid photonic crystals

    NASA Astrophysics Data System (ADS)

    D'Andrea, A.; Tomassini, N.

    2016-07-01

    The present work is devoted to the theoretical study of the nonreciprocal optical properties in hybrid (isotropic and anisotropic) periodic multilayers for photon energy values chosen close to the electronic energy gaps of semiconductors (excitons). The optical properties of these resonant nonmagnetic photonic crystals, where linear and quadratic spatial dispersion effects are both present, will be studied in the framework of exciton-polariton self-consistent solutions of the Maxwell and Schrödinger equations in the effective-mass approximation. The main interesting optical properties, namely, giant transmission, absorption suppression, and optical unidirectional propagation, will be computed by implementing a two-layer "minimum model."

  16. Photoscattering effect in supercontinuum-generating photonic crystal fiber

    PubMed Central

    Tu, H.; Marks, D. L.; Jiang, Z.; Boppart, S. A.

    2010-01-01

    A photosensitivity different from that responsible for fiber grating inscription is found in a supercontinuum-generating photonic crystal fiber transmitting intense 818 nm femtosecond pulses. This photosensitivity progressively generates a waveguide at the entrance of the fiber to scatter light of specific wavelengths and is termed as the photoscattering effect. This effect is linked to the ~800 nm photosensitivity in the microlithography of bulk silica glass. While the effect somewhat limits fiber-optic supercontinuum applications, it can be beneficial to produce new photonic devices. PMID:21350681

  17. One-dimensional parabolic-beam photonic crystal laser.

    PubMed

    Ahn, Byeong-Hyeon; Kang, Ju-Hyung; Kim, Myung-Ki; Song, Jung-Hwan; Min, Bumki; Kim, Ki-Soo; Lee, Yong-Hee

    2010-03-15

    We report one-dimensional (1-D) parabolic-beam photonic crystal (PhC) lasers in which the width of the PhC slab waveguide is parabolically tapered. A few high-Q resonant modes are confirmed in the vicinity of the tapered region where Gaussian-shaped photonic well is formed. These resonant modes originate from the dielectric PhC guided mode and overlap with the gain medium efficiently. It is also shown that the far-field radiation profile is closely associated with the symmetry of the structural perturbation.

  18. Luneburg and flat lens based on graded photonic crystal

    NASA Astrophysics Data System (ADS)

    Liu, Wei; Sun, Xiaohong; Gao, Minglei; Wang, Shuai

    2016-04-01

    Square-lattice graded photonic crystals employed for designing Luneburg and Flat Lens is presented. Comparable simulation of the Luneburg lens with TE and TM polarizations predicts that TM lens possesses of enlarged transmission bandwidth and strengthened focusing ability, in comparison with TE lens. As a typical simplified counterpart, the evolution of focusing intensity and numerical aperture of the flat lens is achieved. What is more, those Luneburg and Flat Lens can withstand imperfect gradients in structure design. This will provide a guidance to produce a high quality focusing lens with small size, short focal length and large numerical aperture applied in the integrated photonic devices.

  19. Generation of higher odd harmonics in a defective photonic crystal

    SciTech Connect

    Ramanujam, N. R.; Wilson, K. S. Joseph

    2015-06-24

    A photonic crystal (AB){sup 2}(DB)(AB){sup 2} with high refractive index medium as silicon and low refractive medium as air is considered. Using the transfer matrix method, the transmission properties as a function of wavelength with photonic band gaps has been obtained. We are able to demonstrate the generation of third, fifth, seventh and ninth harmonics in the present work. We show that if the air medium is removed in the defect, the defect modes are generated but not harmonics. It can be designed to have a frequency conversion, and have a potential for becoming the basis for the next generation of optical devices.

  20. High-Q silicon carbide photonic-crystal cavities

    SciTech Connect

    Lee, Jonathan Y.; Lu, Xiyuan; Lin, Qiang

    2015-01-26

    We demonstrate one-dimensional photonic-crystal nanobeam cavities in amorphous silicon carbide. The fundamental mode exhibits intrinsic optical quality factor as high as 7.69 × 10{sup 4} with mode volume ∼0.60(λ/n){sup 3} at wavelength 1.5 μm. A corresponding Purcell factor value of ∼10{sup 4} is the highest reported to date in silicon carbide optical cavities. The device exhibits great potential for integrated nonlinear photonics and cavity nano-optomechanics.