Day 3 :
- Track 6: Nanophotonics and Biophotonics
Track 2:Optics and Lasers in Medicine
Track 8: Featured Technologies in Lasers, Optics and Photonics
Chair
Ching-Fuh Lin
National Taiwan University, Taiwan
Co-Chair
Edik U. Rafailov
Aston University, UK
Session Introduction
Jean-Pierre Leburton
University of Illinois
USA
Title: Hot carriers Thz harmonic generation in graphene
Biography:
Dr. Leburton joined the University of Illinois in 1981 from Germany, where he worked as a research scientist with the Siemens A.G. Research Laboratory in Munich. In 1992, he held the Hitachi LTD Chair on Quantum Materials at the University of Tokyo, and was a Visiting Professor in the Federal Polytechnic Institute in Lausanne, Switzerland in 2000. He is involved with research in nanostructures modeling and in quantum device simulation. His present research interest encompasses non-linear transport in quantum wires and carbon nanotubes, and molecular and bio-nanoelectronics. He is author and co-author of more than 300 technical papers in international journals and books.
Abstract:
In this talk, we discuss the onset of sharp resonances exhibited by hot carriers in graphene under the influence of a DC and a-c fields in the presence of spatially and temporarily modulated scattering. These resonances occur when the period of the a-c field corresponds to the time taken by quasi-ballistic carriers to drift over a spatial scattering period, provided the latter is shorter than the distance taken by carriers to emit an optic phonon. Such system can be achieved with inter-digitated gates energized with an a-c bias on graphene layers. Gate separation and fields to achieve ballistic transport would result in resonances in the terahertz range, with the generation of higher harmonics characterized by large Q-factors, which are tunable with gate spacing, and well suited for THz detection.
Luisa Torsi
Dipartimento di Chimica Universita’ di Bari “A. Moro, Italy
Title: Organic bio-electronic sensors for ultra-sensitive chiral differential detection
Time : 09:00-09:20
Biography:
Luisa Torsi is professor at the University of Bari and elected vice-president of the European Material Research Society. She received her PhD in 1993 from the University of Bari and was post-doctoral fellow at Bell Labs (USA). In 2010 she was awarded with the Hedrick Emanuel Merck prize for analytical sciences. Her principal scientific contributions are in the fields of advanced materials and electronic devices mostly employed for sensing applications.. Torsi has more than 200 scientific products, including papers published in Science and in the Nature family journals, gathering over 7000 citations with a HI of 41 (Google scholar).
Abstract:
The energies involved in weak chiral interactions occurring between odorant binding proteins (OBPs) and carvone enantiomers are evaluated, down to a few KJ/mol, by means of a water-gated organic field-effect transistor (WGOFET) whose Au-gate is modified with a porcine-OBP (pOBP) self-assembled monolayer. The output current measured is dependent on the concentration of the analyte and pM concentrations can be detected. The binding curves also are significantly different between the two enantiomers. The modelling of the two curves allows the energies associated with the OBP-carvone complexes formation to be independently extracted, from the very same set of data. From the dissociation constants the standard free-energy the complex formation at the electrode is derived, while the threshold voltage shifts gives information on the electrostatic component. This approach, representing a unique tool to quantitatively investigate low-energy bio-chemical interactions, is rather general as it relies on the relative dielectric constants of the protein-SAMs and of the organic semiconductors being much lower than that of water. The role of the OBPs in the olfaction system is still under debate and the detection of neutral odorant species at the pM level by means of a WGOFET adds relevant pieces of information to the understanding of the odor perception mechanism at the molecular level.
Ching-Fuh Lin
National Taiwan University, Taiwan
Title: Environmentally affordable fluorescent nanotechnology for efficient lighting
Time : 09:20-09:40
Biography:
Ching-Fuh Lin obtained the BS degree from National Taiwan University in 1983, MS and PhD degrees from Cornell University, Ithaca, NY, in 1989 and 1993, respectively, all in electrical engineering. He is now the Director of Innovative Photonics Advanced Research Center (i-PARC) and a joint distinguished Professor in the Graduate Institute of Photonics and Optoelectronics, Graduate Institute of Electronics Engineering, and Department of Electrical Engineering at National Taiwan University. His major research area is in photonics, including organic-inorganic composites for light-emission devices and solar cells, single-crystal Si thin-film solar cells, Si-based photonics, and physics in broadband semiconductor lasers and optical amplifiers. He is a Fellow of IEEE, a Fellow of SPIE, Member of Asia-Pacific Academy of Materials, and a member of OSA. He has published over 160 journal papers and 460 conference papers and holds more than 60 patents. He is also the sole author of two books. He obtained the Distinguished Research Award and several Class A Research Awards from National Science Council of Taiwan, ROC, and the Outstanding Electrical Engineering Professor Award from the Chinese Institute of Electrical Engineering.
Abstract:
A novel nanotechnology for environmentally benign as well as efficient white light generation is developed. Compared to conventional phosphors that overly rely on rare-earth elements (REEs), this proposed nanotechnology is REE free and is instead based on the integration of II-VI semiconductor nanoparticles and polymeric materials. ZnO and ZnS:Mn nanoparticles are combined with poly (9,9-di-n-hexylfluorenyl-2,7-diyl) to create efficient warm-light-emissive nanocomposites. The resultant nanocomposites encompass three different photon-generating routes, which can lead to blue, green and orange emissions, respectively. White light thus can be directly generated from the nanocomposites as pumping by commercial UV- or blue-LED. Moreover, a wide tunability of color temperatures ranging from below 3000K to 6000K, which embraces both candle light and white light, is achievable by the nanocomposite. A warm-white light emission with above 90% high quantum efficiency has also been demonstrated under the commercial UV-LED excitation. Additionally, we successfully explore an innovative technique to synthesize II-VI-based nanoparticles without quantum-confinement effect. The prepared nanoparticles can exhibit a strong absorption at 453 nm, which well fits the wavelength of commercial blue-LEDs (450-460 nm), and efficiently convert blue light to brightly orange light. The proposed nanoparticle-based technology can serve as a promising solution not only to the health issues involved in current blue-LED-YAG lighting systems, but also to the eco-friendly affordable efficient-lighting technology.
Nolwenn Huby
University of Rennes 1, France
Title: Sub-wavelength optical propagation in passive and active 1D-nanostructures
Time : 09:40-10:00
Biography:
Nolwenn Huby has completed her PhD at the age of 26 years from University of Bordeaux (France) on OLEDs fabrication and optimization. Then she performed Postdoctoral studies on integrated hybrid memories from Materials and Devices for Microelectronics laboratory in Milan (Italy). She is Associate Professor at the Optics and Photonics department of the Institute of Physics of Rennes, France, and is working on organic integrated photonics. She has published 30 papers in reputed journals.
Abstract:
In the field of nanophotonics, the understanding of optical phenomena related to sub-wavelength guiding in 1D-nanostructures is a fundamental interest for devices down-scaling. We present theoretical and experimental investigation of light propagation in original passive and active organic nanotubes. For this, polymer nanotubes has been designed and developed by the template wetting method. To characterize their optical behaviour and in particular the sub-wavelength propagation, numerical and experimental tools have been developed. Modelling phenomena propagating in these nanofibers was performed by the numerical FDTD method. The effects of the geometry of these nanotubes and nanowires have been investigated. In particular, the effect of the diameter (outer and inner diameter for nanotubes) on the propagation behaviour, (energy distribution, losses) as well as the effect of the substrate has been determined. Experimentally, two types of nanofibers were studied. First, direct injection into passive nanofibers of SU8 polymer was performed through a micro lensed optical fiber. A striking result is the assessment of optical losses measured by the cut-back around 1.25 dB/mm for nanotubes of external and internal diameters respectively 240 nm and 120 nm. This appears very competitive compared to other systems currently envisaged for integrated nanophotonics. Second, active polymer nanofibers (polyfluorene PFO) embedded in a wave guiding polymer were elaborated and appeared to be an efficient design for a nano-source.
Damian C Onwudiwe
North-West University (Mafikeng Campus), South Africa
Title: Growth of semiconductor nanoparticles in polymer matrices by nanosecond laser
Time : 10:00-10:20
Biography:
Damian C Onwudiwe completed his PhD in 2011 from University of Fort-Hare and Post-doctoral research studies in North-West University, South Africa. He is presently a Senior Lecturer at the Mafikeng campus of the North-West University, where he conducts research on the controlled synthesis and manipulation of materials' physical and chemical properties using different approaches. He has published more than 35 papers in international journals, and also serves as Editorial Member of different journals of repute.
Abstract:
Semiconductors nanoparticles have been extensively studied due to their potential applications and novel properties. Although different methods have been reported for the synthesis of these semiconductor materials, more environmental-friendly approaches continue to attract attention. Here, we focus on the II–VI types of semiconductor nanoparticles as they represent ideal systems for dimension-dependent properties. In this report, nanosecond laser was used to effect the decomposition of metal complexes, and also the nucleation process of nanoparticles in polymer solutions. CdS, ZnS, and ZnO nanoparticles were successfully prepared. The effect of change in concentration of the polymer solutions on the properties of the nanoparticles was studied. The morphology, structure, and optical properties of the nanoparticles were investigated. An increase in concentration of the polymer solution influenced the morphology of the nanoparticles, and also resulted in a decrease in the band gap energy of the nanoparticles. These are ascribed to the increase in adsorption centres and reduction in the coalescent process of the nanoparticles in the polymeric matrix.
Heinrich Hoerber
University of Bristol
UK
Title: Trends in nano-optics and their biomedical applications
Biography:
J.K.H. Hoerber has completed his PhD 1986 from Technical University of Munich and did postdoctoral studies at Ludwig Maximilians University Munich with Theodor Haensch. He worked at IBM Research Rueschlikon, Max Planck Institute for Medical Research and the European Molecular Biology Laboratory. His first professorial appointment was at Wayne State University Medical School in 2001. Since 2005 he is Professor of Nanobiophysics at the University of Bristol and serving as an editorial board member of JMR.
Abstract:
The development of the field of nano-optics during recent years, and the knowledge acquired meanwhile about the interaction of light with nano-structures opens up new ways for remote sensing even inside live cells. The Photonic Force Microscope (PFM) able to manipulate and track nano-particles with nano-meter precision can provide the instrumental framework. Depending on size and shape, metal nano-structures have plasmon resonances at distinct frequencies. With a tunable laser adjusted to their resonance the light scattering cross-section increases significantly allowing to track small particles down to a size of about 5 nm. Furthermore, metal particles can be used as “nano-lenses” concentrating the electromagnetic field of light at their surface. In this way, only fluorophores in close vicinity will be excited. For fluorescence measurements inside a cell this provides the same advantage of very low background fluorescence, as total internal reflection fluorescence (TIRF) excitation provides close to a surface allowing single molecule fluorescence measurements with nano-meter resolution everywhere inside cells. An even more exciting possibility lays in the identification of single molecules without labeling by measuring a Raman “fingerprint”. Certain geometric features of metal nano-particles can enhance the Raman signal of a molecule by a million times when in contact and so nano-meter sized particles become chemical sensors with single molecule sensitivity. In this way metal nano-particles within a PFM provide a new analytical tool with single molecule sensitivity and nano-meter position resolution with huge potential for cell-biological studies on regulation and transport processes within living cells.
Edik U Rafailov
Aston University, UK
Title: Novel compact laser sources for biomedical photonics: Diagnostics and treatment
Time : 10:20-10:40
Biography:
Edik U Rafailov received his PhD degree from the Ioffe Institute. In 2005 he established new group and in 2014 he and his Optoelectronics and Biomedical Photonics Group moved to Aston University. He has authored and co-authored over 350 articles in refereed journals and conference proceedings. He coordinated a €14.7M FP7 FAST-DOT project – development of new ultrafast lasers for Biophotonics applications. Currently, he coordinated the €11.8M NEWLED project aims to develop a new generation of white LEDs. He also leads a few others projects funded by FP7 EU and EPSRC. His current research interests include high-power CW, ultrashort-pulse lasers; generation of UV/visible/IR/MIR and THz radiation, nano-structures; nonlinear and integrated optics; Biophotonics.
Abstract:
In the last decades, progress in compact semiconductor based laser technologies has brought to science and industry an enormous number of new applications. Such laser systems which were mostly utilized in the communication and other industries are now becoming adopted in biomedicine and related fields. Here we would like to outline some of the most promising applications where compact laser diode based light sources in UV/visible, near and mid infrared wavelength ranges are being used in biophotonics, particularly focussing on CVDs, diabetes, and cancer diagnostics and photo treatment.
Ehsan Vaghefi
University of Auckland, New Zealand
Title: Physiological optics, a laser ray-tracing system to measure the 3d refractive indices of in-vitro lenses
Time : 11:00-11:20
Biography:
Ehsan Vaghefi is a bioengineer who has developed the biomedical imaging methods (MRI, micro-CT and laser ray-tracing) to image the physiological optics of the ocular lens. He obtained his PhD in 2010 from the Auckland Bioengineering Institute (ABI) at the University of Auckland. In that project he used MRI techniques to visualize circulating ion and fluid fluxes in the lens and to develop a 3D finite element model that encapsulates lens structure and function. He has continued this work as a Post Doctoral Research Fellow within the Molecular Vision Lab, while contributing to the teaching of physiological optics to undergraduate Optometry students. Jason Turuwhenua is currently a Research Fellow at the Auckland Bioengineering Institute, University of Auckland, New Zealand, with a joint appointment in the Department of Optometry and Vision Science, where he teaches physiological optics. His research interests include optics, computer vision and image processing, with a particular emphasis on understanding how engineering approaches can be applied for clinical use. Previous work has included research on numerical methods for reconstructing corneal topography, and modeling the optics of the eye using ray-tracing.
Abstract:
Age-related changes to the optical properties of the ocular lens are the leading causes of presbyopia and cataract. We know little about how the optical properties of the lens are established and maintained at the molecular and cellular levels during the natural aging process. The ocular lens has an inherent Gradient of Refractive Index (GRIN) which we have recently shown is altered by perturbing lens physiology. In order to study the changes of GRIN with aging, we have constructed a laser ray-tracing system to allow us to measure the optical properties of organ cultured lenses, while manipulating the underlying physiology of the lens. Our present system design includes two Single Reflex Lens (SLR) cameras and a highly precise illumination stage, which has enabled us to introduce the laser beams onto the lens at any desired angle and off-center offsets. Our current setup has laser beam angle measurement accuracy of ±0.2Ëš and image acquisition in-plane resolution of 30μm and pixel back-projection error of less than 0.3 of a pixel size. Also, our current calibrated setup is capable of measuring lens surface profile to an accuracy of <40µm, using SLR cameras which we have validated using in-vitro topography measurements from a number of bovine lenses. We have also implemented a BIONKO customized incubation chamber to control and manipulate the physiology and accommodative state of the imaged lens. By precisely controlling the laser beam delivery and tracing its path through the lens, mapping the lens’s surface profile while controlling its physiological and mechanical states, we are studying the effects of aging on the lens’ optical properties.
Xuewen Shu
Huazhong University of Science and Technology, China
Title: Advanced fiber grating devices fabricated for all-optical signal processing
Biography:
Xuewen Shu has completed his PhD at the age of 27 years from Huazhong University of Science and Technology (HUST), China. He worked as a senior scientist at Aston University & Indigo Photonics Ltd, UK during 2001-2013. He is currently a full professor at HUST. He has published more than 150 papers in reputed journals and conferences. His research interests include fiber gratings, optical fiber communications, fiber lasers and optical sensors.
Abstract:
A fiber grating is an optical fiber for which the refractive index in the core has a periodic or quasi-periodic perturbation profile. Fiber gratings can be created with various laser sources such as UV lasers (photosensitivity is required) and femtosecond lasers (no photosensitivity is required). Fiber grating technology has attracted considerable research interests in past two decades since it has wide applications in optical communications and sensing. Due to their natural compatibility, fiber gratings can serve as a perfect platform for all-optical signal processing in optical fiber communication systems. They can directly process optical signals in optical fiber without the need for coupling/re-coupling alignments required by bulk-optics or chip based devices, thus provide a low-loss, stable, cost-effective and ultra-fast solution for optical signal processing. Moreover, they can offer very strong design flexibility to achieve almost arbitrary spectral characteristics. Here we will report our recent progress on all-optical signal processing based on fiber grating technology. We will present fiber gratings designed and fabricated for optical differentiation, optical pulse shaping, optical format conversion and so on. The gratings were designed with layer-peeling method and fabricated with UV direct-writing technique. The performances of their use as optical signal processors were also evaluated experimentally.
Valerio Pruneri
ICFO-The Institute of Photonic Sciences and ICREA, Spain
Title: Optics on nano-structured surfaces
Time : 11:20-11:40
Biography:
Valerio Pruneri is an ICREA Industrial Professor, Corning Inc. Chair and group leader at the Institute of Photonic Sciences (ICFO). Previously he worked for Avanex, Corning, Pirelli, and the Optoelectronics Research Centre (University of Southampton). He has more than 30 patent families, 60 invited talks and 300 refereed papers. He serves on the European QEOD board, the advisory board of ACREO Fiber Optic Centre, VLC Photonics and Medlumics SL. He received the Philip Morris Prize for Scientific and Technological Research, the Pirelli Research Fellowship, the IBM Faculty Award, the Corning Inc. Professorship and the Duran Farell Prize for Technological Research.
Abstract:
Ultrathin materials and nano-structuring are becoming essential for the functionalization of optical surfaces. In the talk we will show how ultrathin metals can be exploited to create competitive transparent electrodes while graphene and phase change materials to modulate the optical response. Ultrathin metals can also be used to create nanostructured surfaces through mass scalable dewetting and etching techniques. We will also provide examples of applications enabled by these materials and techniques, including efficient high speed electro-optic modulators, indium-free light emitting diodes, solar cells and easy-to-clean display screens.
Drouhin Henri-Jean
University Paris Saclay, France
Title: Transport at spin-orbit and exchange-split interfaces : giant universal asymmetry
Time : 11:40-12:00
Biography:
Henri-Jean M. Drouhin graduated from the École Polytechnique, France in 1979 and obtained his Ph.D. degree with habilitation (Doctorat d’État) in 1984 from Paris-Sud University, Orsay, France. He has made major contributions to the field of semiconductor spin physics and spintronics. He is Associate Professor, Vice President of the Physics Department, and researcher (Physics and Chemistry of Nano-objects group leader) at Irradiated Solids Lab., (CNRS & CEA/DSM/IRAMIS, École Polytechnique). He was the Dean of Studies for the École Polytechnique from 2000 to 2008 and Deputy Vice- President for Research from 2008 to 2014. He is the author of more than 80 scientific publications as well as being decorated with the Chevalier Legion of Honour (French Pres., 2002) and being made an Officer of the National Order of Merit (French Pres., 2009). He was elected as a Fellow of SPIE in 2007.
Abstract:
We report on theoretical investigations and k.p calculations of carrier tunneling in model systems and heterostructures composed of exchange-split III-V semiconductors, involving spin-orbit interaction. The media are possibly separated by thin tunnel barriers. In a 2x2 exchange-split band model, we prove that, when spin-orbit interaction is included in the conduction band of two exchange-split semiconductors, the electrons can be differently transmitted with respect to an axis orthogonal to both the axis normal to the interface and the magnetization direction. The transmission asymmetry between +k// and -k// incidence is shown to reach100% at some points of the Brillouin zone corresponding to a totally quenched transmission for given incidence angles. We establish the universal character of the transmission asymmetry, independent on the spin-orbit strength and material parameters. Particular asymmetry features are reproduced by more complete 14x14 bands calculations involving interband coupling. On the other hand, calculations performed in the valence-band of model heterostructures and including tunnel barriers in both 6x6 (without inversion asymmetry) and 14x14 k.p band models more astonishingly highlight the same trends in the transmission asymmetry which is shown to be related to the difference of orbital chirality and to the related branching of the corresponding evanescent states responsible for tunneling current. In both cases (electrons and holes), the asymmetry appears to be robust and persists even when only a single electrode is magnetic. This paves the way to new functionnalties with spinorbitronics devices.
Pascale Roy
Synchrotron SOLEIL, France
Title: Ultra high resolution spectroscopy and ultra-fast THz measurements using coherent synchrotron radiation
Time : 12:00-12:20
Biography:
Pascale Roy performed her PhD research in LURE, Orsay France and received her PhD in Physics from Université Laval, Canada. She was a Postdoctoral fellow at Los Alamosin 1986-89 and was hired as CNRS Researcher at LURE, Orsay France in 1989. She became CNRS Senior Scientist in 1992 and moved her research activity to Synchrotron Soleil in 2004. Her research is focused on the implementation of synchrotron radiation based Infrared and THz beamline, new spectroscopic methods and the development of associated spectroscopic studies. She is currently in charge of the AILES (Advanced Infrared Line Exploited for Spectroscopy) at SOLEIL. The AILES group currently investigates the physical properties of confined material, the optical properties of condensed matter, the edge radiation and coherent sources, the rovibrational spectroscopy of molecules of interest for atmospheric and astrophysics. She is responsible for the Condensed Matter Physical Chemistry group at Synchrotron SOLEIL.
Abstract:
Recently, an unprecedented high power source of THz radiation was made scientifically available: coherent synchrotron radiation (CSR). This radiation produced from relativistic electron bunches of picoseconds duration opens up new territory in the THz range with intensities up to 4 orders of magnitude higher than previous sources. In this mode of operation (200 electron bunches of 100µA each), the total emitted power is 2 mW and its stability is sufficient to perform bunch per bunch spectroscopic measurements based on Electro Optics sampling technique. These promising results clearly lead to the development of new applications including terahertz spectroscopy at the nsec rate without the need for a pump probe technique, as well as ultra-high resolution spectroscopy based on heterodyne mixing technique. We will show how these new techniques have been demonstrated on the AILES beamline of synchrotron SOLEIL.
Biography:
Ephraim Greenfield has an M.Sc. from The University of Chicago and a PhD from Hebrew University in Physics. He is one of the founders of Ophir Optronics, was the R&D manager and is presently the CTO of the company. He has developed many devices in the area of laser measurement and has 5 patents in the area.
Abstract:
The trend in lasers used for material processing has been to higher and higher powers that today have reached as much as 100kW and above. Measuring the power and beam quality of such high powers is an increasing challenge. Ophir has developed a power meter capable of measuring up to 120kW of power and a beam profiler capable of measuring the beam profile at the focal spot at similar powers. The power meter is a relatively compact device carefully designed to spread the beam in a manner so as not to exceed the damage threshold of the materials used. The beam profiler uses Rayleigh scattering to measure the beam profile with no physical contact at all with the beam. We will describe in detail how these devices operate.
Tomofumi Hamamura
University of Bordeaux, France
Title: Dye-sensitized solar cells using ethynyl-linked porphyrin trimers for nir photoelectric conversion
Time : 12:20-12:40
Biography:
Tomofumi HAMAMURA was born in 1984 in Tokyo, Japan. He was a research fellow of the Japan Society for the Promotion of Science (JSPS) from 2011-2013. He received a PhD degree from The University of Tokyo in 2014. In April 2014, he became a post-doctoral fellow at The University of Tokyo. In September 2014, he joined the research group of University of Bordeaux as a visiting researcher of LIA-Next PV project between French institutes and The University of Tokyo. My current interests include the development of large π-conjugated organic molecules for organic electronics.
Abstract:
Dye-sensitized solar cells (DSSCs) have widely attracted much attention as promising candidates for low-cost next-generation solar cells. For the improvement of the power conversion efficiency of DSSCs, it is important to utilize near-infrared (NIR) light and to induce efficient charge-separation at the interface between dyes and TiO2. The charge-separation process is known to be affected by the adsorption geometry of dyes on the TiO2 surface. In this study, we focused on ethynyl-linked porphyrin trimers as NIR-light harvesting dyes, and investigated the effect of the adsorption geometry of the trimers on the photovoltaic properties of the DSSCs. Some trimers which are different in the number and position of anchoring groups were synthesized for controlling their adsorption geometry. Photo-anodes were prepared by immersing TiO2 electrodes into DMF solution of these compounds containing deoxycholic acid as co-adsorbent. The difference in the number of anchoring groups drastically changed the adsorbed amount of the trimers on the TiO2 surface. On the other hand, the difference in the position of anchoring groups was found to affect not only the adsorbed amount of the trimers, but also charge-separation efficiency. Among these compounds, the trimer with anchoring groups in the long-axial direction showed the highest IPCE value in NIR region (47% at 840 nm). In this talk, we will discuss the difference in the photovoltaic properties of the DSSCs using these compounds in detail.
Vivek Raj Shrestha
Kwangwoon University, South Korea
Title: Polarization-tuned dynamic color filters exploiting a dielectric-loaded one dimensional aluminum grating
Time : 12:40-12:50
Biography:
Vivek Raj Shrestha completed BE in Electronic and Communication Engineering from Nepal in 2010 and he has been pursuing his integrated masters and PhD program in Electronic engineering at Kwangwoon University, Seoul, Korea since 2011. He has worked on integrated optical devices and free space optical modules. His current research interests include the nano-structured devices, serving as the visible optical filters and their application to communication devices, sensors and display devices. He has published more than 12 papers in reputed journals including Nanoletters, Scientific Reports, and Optics Express etc.
Abstract:
Nanostructured spectral filters enabling dynamic color tuning are regarded to be saliently attractive for implementing ultra-compact color displays, holographic imaging, information encoding, and anti-counterfeiting. Realization of polarization-induced dynamic color tuning via one dimensional periodic nanostructures remains as a challenge due to their inherently low transmission for transverse-electric polarization. We report on highly efficient dynamic subtractive color filters incorporating a dielectric-loaded one dimensional Aluminum grating, providing a continuum of customized color in accordance with the polarization of incident light. The dynamic spectral filtering in the visible regime is attributed to selective suppression in transmission spectra originating from plasmonic resonance for a metal-dielectric interface and guided-mode resonance for a metal-clad dielectric waveguide occurring at their characteristic wavelengths for transverse-magnetic and -electric polarizations, respectively. Taking into account that the transmitted color output is initially determined contingent upon periods of a metallic grating, we manufactured several devices with different periods so as to accomplish a broad palette of color with transmission beyond 80%, inclusive of cyan, magenta and yellow, by tailoring the polarization. Moreover, the proposed filters conspicuously feature a dual-mode operation of both transmissive and reflective configurations. Thanks to the functional material of Al, which is advantageous in terms of low cost, high durability, and mass producibility, the proposed device is predicted to offer strong potential for immediate commercial applications.
K M Tanvir Ahmmed
McGill University, Canada
Title: Fabrication of homogenous microstructures by femtoseconds laser micromachining
Time : 12:50-13:00
Biography:
K M Tanvir Ahmmed is a PhD student at McGill University; he is working under Prof. Kietzig’s supervision in Biomimetic Surface Engineering laboratory. He has been working on micro/nano structure fabrication on different materials with femtosecond laser, and he published peer-reviewed journal articles on this topic.
Abstract:
Femtosecond laser micromachining is increasingly investigated as a new technique for micro/nano structure fabrication because of its applicability to virtually all kinds of materials in an easy one-step process that is scalable. Various parameters (such as fluency, number of pulses, laser beam polarization, wavelength, incident angle, scan velocity, number of scans, and processing environment) have a strong influence on the result of the micromachining process. We propose the fluency and pulses-per-spot (F-PPS) and accumulated fluency profile (AFP) models to group, characterize and optimize the microstructures observed on metallic surfaces from single scan machining. Furthermore, these models are also useful to predict the machining result on polymeric surfaces. However, multiple scans of surfaces cannot be described by these models. We present how another formation mechanism seems to be responsible for the formation of randomly distributed elliptical cones observed at very low fluency irradiation and multiple scans.