Biography:

Bernd Witzigmann received his PhD degree (with honors) in Technical Sciences from the ETH Zürich, Switzerland, in 2000. He then joined Bell Laboratories, Murray Hill, NJ, as a Member of Technical Staff. In 2004, he was appointed as Assistant Professor at ETH Zurich in Switzerland. Since 2008, he was Professor at University of Kassel, Germany, and Co-Director of the Centre of Interdisciplinary Nanoscience and Technology. He is author/co-author of more than 180 journal and conference publications, Chairman of a SPIE Photonics West conference, and has been Editor of several journals. He is a Senior Member of the IEEE and SPIE and Co-Director of the Nanocenter CINSaT at Kassel University.

Abstract:

In this presentation, the physical principles of semiconductor nanowire arrays are discussed, with a focus on applications for photovoltaics and solid state lighting. Both of these fields are pivotal for green photonics technologies. As analysis tools, specific physics-based numerical models for nanophotonics and nanoelectronics have been developed, which will be discussed. In particular, the three-dimensional nature of a wire array, including the substrate and the free space on top is included in the study. For the optical extraction efficiency of an LED, absorption of electromagnetic energy in the contacts and the active layers themselves, as well as re-emission (photon-recycling) are investigated. The latter is an effect that couples the electronic and the optical system. In addition, the optical density of states is analyzed and its impact on the extraction efficiency is shown. Finally, the total electro-optical efficiency of a nanowire array LED emitting at 400nm is presented and compared to conventional efficient thin-film LEDs. It is shown that the efficiency droop commonly observed in III-nitride based LEDs can be shifted to high operating currents. For the nanowire array solar cell, a detailed electromagnetic and electronic analysis is presented, from which fundamental rules in terms of materials choice and wire geometry will be derived. It shows that low density regular III-V nanowire arrays can reach absorptivities identical to bulk cells, with the advantage of substrate flexibility, low material consumption, and improved strain engineering for multi-junction cells. As outlook, the integration of III-V nanowire arrays for electronic and optical functional devices will be discussed and some applications are shown.

Figure 1: Optical generation rate in an InGaN/GaN core-shell nanowire solar cell

Recent Publications

[1] B Witzigmann, R Veprek, S Steiger, and J Kupec, J. Comp. El., No. 4, Vol. 4, pp. 389-397, 2009, (invited).

[2] F Yu, D Rümmler, J. Hartmann, L. Caccamo, T. Schimpke, M. Strassburg, A. Gad, A. Bakin, H. Wehmann, B. Witzigmann, H. Wasisto, and A. Waag, Applied Physics Letters, 108, 213503 (2016)

[3] C. Kölper, M. Sabathil, F. Römer, M. Mandl, M. Strassburg, and B. Witzigmann, Phys. Stat. Sol. A, 1-9, 2012.

[4] J. Kupec, R. Stoop, and B. Witzigmann, Optics Express, Vol. 18, No. 26, p. 27589-27605, 2010.

[5] J. Wallentin, N. Anttu, D. Asoli, M. Huffman,I. Åberg, M. Magnusson, G. Siefer, P. Fuss-Kailuweit, F. Dimroth, B. Witzigmann, H. Q. Xu, L. Samuelson, K. Deppert, M. T. Borgström, Science 1 March 2013: Vol. 339 no. 6123 pp. 1057-1060.

Biography:

Jun Hee Choi received his PhD in Materials Science and Engineering from Seoul National University in 2012. He is currently a Research Master and Research Staff Member of the Device and System Research Center at Samsung Advanced Institute of Technology, Samsung Electronics. He has published more than 45 papers in SCI journals, more than 20 conference papers, and more than 50 US patents. His research includes GaN-based optoelectronics on unconventional substrates, and low dimensional electronics based on quantum dots, ZnO nanorods, and graphene.

Abstract:

There have been significant recent developments in the growth of single crystal gallium nitride (GaN) on unconventional templates for large-area blue or green light-emitting diodes (LEDs) which, together with layer transfer onto foreign substrates, can enable flexible and stretchable lighting applications. Here, the heteroepitaxial growth of GaN on amorphous and single-crystal substrates employing various interlayers and nucleation layers is discussed, as well as the use of weak interfaces for layer-transfer onto foreign substrates. Layer-transfer techniques with various interlayers are also discussed. These heteroepitaxial GaN growth and layer-transfer technologies are expected to lead to new lighting and display devices with high efficiency and full-color tunability, which are suitable for large-area, stretchable display and lighting applications. We shall also discuss blue light enhancement in CdS/ZnS quantum dots using surface plasmon resonance to achieve near-unity quantum yield. Finally, nanostructured GaN-based LEDs for white light generation will be reviewed.

Figure 1: Atomic arrangement of various hetero-epitaxial interfaces for different multilayer structures: a) GaN/ZnO (NL)/graphite (IL/SB): (left) GaN/ZnO and (right) ZnO/graphene. b) GaN/AlN (NL)/BN (IL)/sapphire (SB): (left) GaN/AlN, (center) AlN/BN, and (right) BN/sapphire. c) GaN/Ti (IL)/glass (SB): GaN/Ti. d) GaN/AlN (IL)/Si (SB): AlN/Si. e) Interfaces connected by (left) dangling bonds (3D on 3D), (center) van der Waals gap (2D on 2D), and (right) quasi van der Waals gap (2D on dangling-bond passivated 3D).

Recent Publications

1. J H Choi (2016) Heteroepitaxial growth of GaN on unconventional templates and layer-transfer techniques for large-area, flexible/stretchable light-emitting diodes. Adv. Optical Mater. 4: 505-521.

2. J H Choi (2014) Fully flexible GaN light‐emitting diodes through nanovoid‐mediated transfer. Adv. Optical Mater. 2: 267-274.
    
3. J H Choi (2012) GaN light-emitting diodes on glass substrates with enhanced electroluminescence. Journal of Materials Chemistry 22: 22942-22948.
    
4. J H Choi (2011) Nearly single-crystalline GaN light-emitting diodes on amorphous glass substrates. Nature Photonics 5: 763-769.

Biography:

Shien-Kuei Liaw received Double Doctorate from National Chiao-Tung University in Photonics Engineering and from National Taiwan University in Mechanical Engineering, respectively. He joined the Chunghua Telecommunication, Taiwan, in 1993. Since then, he has been working on Optical Communication and Fiber Based Technologies. He joined the Department of Electronic Engineering, National Taiwan University of Science and Technology (NTUST) in 2000. He has ever been Director of the Optoelectronics Research Center and the Technology Transfer Center, NTUST. He was a Visiting Researcher at Bellcore (now Telcordia), USA for six months in 1996 and a Visiting Professor at University of Oxford, UK for three months in 2011. He owned six US patents, and authored or coauthored for 250 journal articles and international conference presentations. He earned many domestic honors and international honors. He has been actively contributing for numerous conferences as a conference chair, technical program chair, organizing committee chair, steering committee and/or keynote speaker. He serves as an Associate Editor for Fiber and Integrated Optics. Currently, he is a Distinguished Professor of National Taiwan University of Science and Technology (NTUST), Vice President of the Optical Society (OSA) Taiwan Chapter and Secretary-General of Taiwan Photonic Society. His research interests are in Optical Sensing, Optical Communication and Reliability Testing

Abstract:

In this talk, several types of single-longitudinal mode (SLM) linear cavity tunable fiber lasers will be reviewed and discussed. Integrating a partial reflectance fiber Bragg grating (FBG) as the front cavity end, the rear cavity end elements may be a loopback optical circulator (OC), a broadband fiber mirror, a Faraday rotator mirror or a 2x2 fiber coupler. For SLM selection, using multiple subring cavities based on the Vernier effect, a piece of gain fiber saturable absorber as modes filter or their hybrid type. For wide-tuning range fiber laser, the wavelength tuning mechanism may be tunable FBGs, a 3-point bending device or a four-lamina composite device to facilitate wavelength tuning of FBGs, a large tuning range cover C+L band with good resolution of 0.1 nm was achieved. Laser characteristics such as output power, optical signal-to-noise ratio, laser linewidth, threshold pump power and pumping slope efficiency are measured. An example characteristic of 1 MHz, 59 dB, 13% and 0.1 dB for linewidth, side-mode suppression ratio, quantum efficiency and power variation of whole tuning range, respectively, are obtained. The pumping power efficiency may be 10% improved by recycling the residual pump power to the gain medium and has the advantages of simple structure, large pump slope efficiency and short cavity. The proposed fiber lasers may find various potential applications

Biography:

Emily Wilson specializes in Instrument Development for measurement of atmospheric trace gases. She joined NASA in 2005 after working there as an NRC Postdoc. She leads two instrument developments: a laser heterodyne radiometer for column measurements of CO₂, CH₄, and H₂O, and a miniaturized gas correlation radiometer for measurements of CH₄, CH₂O, H₂O, and CO₂ in the Martian atmosphere.

Abstract:

Laser heterodyne radiometry is a technique based on radio receiver technology that has been in use since the 1970s for measuring trace gases in the atmosphere such as ozone, water vapor, methane, ammonia, and chlorine monoxide. Earlier iterations of this technique featured large, high-powered lasers that limited widespread use and the potential for commericalization. With the relatively recent availability of distributive feedback (DFB) lasers, it has become possible to make this technique low-cost, low-power, and portable. The miniaturized laser heterodyne radiometer (mini-LHR) is a passive variation of this technology developed at NASA Goddard Space Flight Center that measures methane (CH₄) and carbon dioxide (CO₂) in the atmospheric column by mixing sunlight and DFB laser light in the infrared. The entire instrument fits on a backpack and operates on a fold-out 35 watt solar panel. Over the course of its development, the mini-LHR has been field tested in a range of locations and conditions including urban locations in Washington, DC and Los Angeles, a high-altitude site at Mauna Loa observatory in Hawaii, a rural location in upper Wisconsin, and a dairy farm in California. Recently, the mini-LHR was used to monitor CH₄ and CO₂ over varying thawing permafrost terrains. In the image, the mini-LHR (right) is shown in a collapse scar bog next to an eddy flux tower (left) at a field site near Fairbanks, Alaska. The mini-LHR operates in tandem with AERONET - a global network of more than 500 sensors that measure aerosol optical depth. The benefit of this partnership is that the mini-LHR could be readily deployed into this global network and provide validation for satellite missions as well as a long-term stand alone data product.

1.Wilson E L et al. (2017) A 4 U laser heterodyne radiometer for methane (CH₄) and carbon dioxide (CO₂) measurements from an occultation-viewing CubeSat, Measurement Science and Technology 28: 035902.

2.Melroy H R et al. (2015) Autonomous field measurements of CO₂ in the atmospheric column with the miniaturized laser heterodyne radiometer (Mini‑LHR). Applied Physics B 120: 609-615.

3.Wilson E L et al. (2014) Miniaturized laser heterodyne radiometer for measurements of CO₂ in the atmospheric column. Applied Physics B: Lasers & Optics 114, 385-393, doi:10.1007/s00340-013-5531-1.

4.Clarke G B, Wilson E L, Miller J H, Melroy H R (2014) Uncertainty analysis for the miniaturized laser heterodyne radiometer (mini-LHR). Measurement Science and Technology 25: 055204-055209.

5.Sinclair J A, Irwin P G J, Calcutt S B Calcutt, Wilson E L (2015) On the detectability of trace chemical species in the martian atmosphere using gas correlation filter radiometry.

Biography:

Dror Malka received his BSc and MSc degrees in Electrical Engineering from Holon Institute of Technology (HIT), Israel in 2008 and 2010, respectively. He has also completed a BSc degree in Applied Mathematics at HIT in 2008 and received his PhD degree in Electrical Engineering from Bar-Ilan University (BIU) in 2015, Israel. Currently, he is a Lecturer in the Faculty of Engineering at HIT. His major fields of research are Nanophotonics, Super-resolution, Silicon Photonics and Fiber Optics. He has published around 21 refereed journal papers, 20 conference proceeding papers, and 2 book chapters.

Abstract:

A slot-waveguide is a unique structure that enables light to be strongly confined and guided inside a narrow nanometer-scale region of low index material that is surrounded by two layers with high index material. Using this unique structure leads to a variety of advantages such as small beat length of the guided light and strong confinement in the slot region that results in extremely low losses. Choosing a slot material with lower-index value leads to a stronger confinement inside the slot region. However, a multimode interference (MMI) demultiplexer component with closer spacing between ports is very sensitive to the variation of the optical signals in the C-band (1530-1565 nm), which can influence the MMI coupler size and the performance. To overcome this problem, we choose Gallium nitride (GaN) as the slot material. GaN has a low-index value compared to Si material and is also high-index value compared to alumina or silica. Thus, the MMI demultiplexer component based silicon (Si)-GaN slot waveguide is not very sensitive to the variation of the effective refractive index that lead, the ability to separate closer wavelengths in the C-band inside the MMI coupler with good performances. We propose a novel 8-channel wavelength MMI demultiplexer in slot waveguide structures that operate at 1530 nm, 1535 nm, 1540 nm, 1545 nm, 1550 nm, 1555 nm, 1560 nm and 1565 nm. Gallium nitride (GaN) surrounded by silicon (Si) was found to be a suitable material for the slot-waveguide structures. The proposed device was designed by seven 1x2 MMI couplers, fourteen S-band and one input taper. Simulation results show that the proposed device can transmit 8-channel that works in the whole C-band (1530-1565 nm) with low crosstalk ((-19.97)-(-13.77) dB) and bandwidth (1.8-3.6 nm). Thus, the device can be very useful in optical networking systems that work on dense wavelength division multiplexing technology.

Figure 1: Normalized power as function of the operated wavelengths.

Recent Publications

1. G Je, D Malka, H Kim, S Hong, B Shin (2017) A study on micro wave of 355 nm UV-pulsed laser. Applied Surface Science.417:244-249.
2. D Malka, A Peled (2017) Power splitting of 1x16 in multicore photonic crystal fibers. Applied Surface Science. 417:34-39.
3. A Vegerhof, E Barnoy, M Motiei, D Malka, Y Dannan, Z Zalevsky, R Popovtzer (2016) Targeted magnetic nanoparticles for mechanical lysis of tumor cells by low-amplitude alternating magnetic field. Materials. 9(11):1-12.
4. B B Ben-Zaken, T Zanzury, D Malka (2016) An 8-channel wavelength MMI demultiplexer in slot waveguide Structures. Materials. 9(11):881.
5. A Vegerhof, M Motei, A Rudinzky, D Malka, R Popovtzer, Z Zalevsky (2016)  Thermal therapy with magnetic nanoparticles for cell destruction. Biomedical Optics Express. 7(11):4581-4594.

Biography:

Mingshan Zhao received his PhD degree in Electronic Engineering from Ghent University, Belgium, in 2003. He is a Professor in the School of Physics and Optoelectronic Engineering, Dalian University of Technology, Dalian, China. He leads the Photonics Research Center at DUT, which focuses on new concepts for microwave photonic components and systems, polymer-based photonic components, and circuits for optical communication and optical sensing.

Abstract:

Microwave photonics (MWP) provides a unique way to synthesize, deliver and process radio frequency (RF) signal. Thanks to its numerous advantages like low transmission loss, immunity to electromagnetic interference and high bandwidth handling capacity, it is being rapidly applied into radar, satellite communication and metrology. Herein, we would like to introduce some new progresses of our research, which basically includes signal transmission, processing and detection. We proposed some methods to improve the spurious-free dynamic range of microwave photonic link (MPL), such as destructive combination of nonlinear distortions in a balanced photodiode, optical carrier band processing achieved by Stimulated Brillouin Scattering (SBS) processing and Sagnac interferometer-assisted dynamic range improvement strategy. These methods can greatly enhance the fidelity of microwave signal transmitted via an optical link, enabling realization of higher capacity with lower distortion signal transmission. We also developed some photonic techniques to eliminate in-band self-interference exists in Full-Duplex wireless communication system. We have developed a technique of optical RF self-interference cancellation by using the inherent out of phase property between the left and right sidebands of phase-modulated signal, matching their phase and amplitude to achieve self-interference cancellation. Another technique is based on a compact Dual-Parallel Mach-Zehnder Modulator (DPMZM), by detuning the electrical delay line and three bias voltage of DPMZM, the self-interference in received signal can be greatly suppressed. This work offers the possibility to achieve reliable full-duplex communications. Another work we have done is detection of low-power RF signal. It is based on a tunable optoelectronic oscillator (OEO), which can provide gain to the weak RF signals that match the oscillation frequency by tuning the wavelength of the laser. Throughout this work, it is just part of our work on MWP, further research still need to be done in the future.

Recent Publications:

1. Kang Z, Gu Y, Zhu W, et al. (2016) Linearization of microwave photonic link based on nonlinearity of distributed feedback laser [J]. Optical Engineering. 55(2): 026115-026115.

2. Zhu W, Hu J, Gu Y, et al. (2016) Dynamic range improvement of a microwave photonic link based on brillouin processing [J]. IEEE Photonics Technology Letters. 28(23): 2681-2684.

3. Zhu W, Zhao M, Fan F, et al. (2017) Sagnac interferometer-assisted microwave photonic link with improved dynamic range [J]. IEEE Photonics Journal. 9(2): 1-9.

4. Fan F, Hu J, Zhu W, et al. (2017) Dual-loop optoelectronic oscillator based on a compact balanced detection scheme [J]. Optical Engineering 56(2): 026107-026107.

5. Gu Y, Zhao J, Hu J, et al. (2016) All optical up-converted signal generation with high dispersion tolerance using frequency quadrupling technique for radio over fiber system [J]. Optics & Laser Technology 79: 153-157.

Biography:

Shu-Chun Chu received her PhD degree from the Institute of Electro-Optical Engineering, National Chiao Tung Univisity. She currently serves as a Professor in Department of Physics, National Cheng Kung University. She has her expertise in designing laser cavity and finding approaches for generating various structure beams in solid-state lasers. She also has expertise in designing non-imaging optical systems, such as solar concentrators, LED illuminators, backlight modules, etc.

Abstract:

Helmholtz–Gauss beams (HGBs), nearly non-diffraction beams that can propagate a long distance without significant divergence, have attracted considerable attention for their potential applications in science and technology. Mathieu-Gauss beams (MGBs) are one kind of Helmholtz–Gauss beams, which are the ideal non-diffraction Mathieu beams apodized by Gaussian transmittance. Unlike the ideal non-diffracting Mathieu beams, MGBs can be realized experimentally for the reason that MGBs carry a reasonable finite power. The nearly non-diffraction properties of MGM show their potential to lots of practical applications, such as: optical interconnections, laser machining, collimation and measurement, optical manipulation, etc. Alvarez-Elizondo et al. first generated MGBs in an axicon-based stable resonator in a real CO₂ laser by slightly breaking the symmetry of the cavity in 2008. Later, Tokunaga et al., adopted special micro-grain Nd:YAG laser crystals, they also achieved spontaneous MGMs oscillation in end-pumped solid-state lasers. A general approach for the selectively excitation of any specified MGM in a laser system is necessary for the development of future MGBs’ applications. This study investigated in finding a way to selectively excite any specified MGM in an end-pumped solid-state laser system with an intra-cavity spatial light modulator. We drafted codes to simulate the lasing operation of the laser system to explore the selectively exciting a specified MGM in end-pumped solid-state lasers using numerical simulation. This study proposed a systematic approach to the selective excitations of all Mathieu-Gauss modes (MGMs) in end-pumped solid-state lasers with a SLM-based stable laser resonator.

Figure 1: It shows propagation of amplitude profile along plane (x, z) or plane (y, z) of an even MGB from the simulated laser resonator with mode order m=2 and ellipticity parameter q=5.

Recent Publications

1.K F Tsai and S C Chu (2016) Characteristic matrix operation for finding global solution of one-time ray-tracing optimization method. Opt. Express 24(19): 21340-21352.

2. S C Chu, H L Yang, Y H Liao, H Y Wu, and C Wang (2014) One-time ray-tracing optimization method and its application to the design of an illuminator for a tube photo-bioreactor. Opt. Express 22(5): 5357-5374.

3.C F Kuo and S C Chu (2013) Numerical study of the properties of optical vortex array laser tweezers. Opt. Express 21(22): 26418-26431.

4.H Y Wu and S C Chu (2013) Ray-leakage-free sawtooth-shaped planar lightguide solar concentrators. Opt. Express 21(17): 20073-20089.

5.K Otsuka and S C Chu (2013) Microchip solid-state cylindrical vector lasers with orthogonally polarized dual laser-diode end pumping. Opt. Lett. 38: 1434-1436.