Emerging Technologies 2018 Session Listing
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Session E4: Optical Materials and Devices
Start Time: 09:00, Friday, May 11
Room: Sutcliffe B
Chaired by Guangrui (Maggie) Xia, University of British Columbia (firstname.lastname@example.org)
- 9:00 Magnus Borgström, Lund University
Nanowires for tandem junction solar cells
Semiconducting nanowires are promising materials for high-performance electronics and optics for which optical and electrical properties can be tuned individually. The nanowires are suggested for future high efficiency solar cells due to excellent light absorbing properties. Using nanowires covering only about 12 % of the surface, record efficiencies of VLS grown nanowires has been reported for InP nanowires of 13.8 % and for GaAs nanowires of 15.3%. Recently 17.8 % efficiency was reported for top down fabricated nanowires. In order to further optimize the performance of nanowire photovoltaics, and integrate them on Si in a tandem junction configuration, nanowires with dimensions corresponding to optimal light harvesting capability are necessary. We developed nano imprint lithography for large area patterning of catalytic metal particles with a diameter of 200 nm in a hexagonal pitch of 500 nm. We found that a pre anneal and nucleation step was necessary to keep the particles in place during high temperature annealing to remove surface oxides. We intend to transfer these grown nanowires to a Si platform either by direct growth on Si PV, or by nanowire peel off in polymer, followed by transfer and electrical contacting, or by aerotaxy and alignment for transfer to Si. This work was performed within NanoLund and supported by the Swedish Research Council, the Swedish Foundation for Strategic Research (SSF), the Knut and Alice Wallenberg Foundation and the Swedish Energy Agency. This project has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 641023 (Nano-Tandem) and the European Union’s FP7 programme under grant agreement No 608153 (PhD4Energy). This publication reflects only the author’s views and the funding agency is not responsible for any use that may be made of the information it contains.
- 9:20 Yukio Kawano, Tokyo Institute of Technology
Multi-view terahertz imaging with nano-carbon flexible scanners
- 9:40 François Léonard, Sandia National Laboratories
Inkjet printed terahertz detector
Terahertz waves have shown promise for a number of applications but challenges in developing sources and detectors in this frequency range have prevented broader adoption of the technology. On the detector side, recent work has focused on developing imaging arrays and in improving their performance, which often requires cooling of devices made by photolithography on rigid substrates. Here we present a different approach that focuses on room-temperature detection using inkjet-printed carbon nanotube (CNT) devices. The inkjet printing approach allows for facile, on-the-fly design and printing of devices, including in array format. The structural flexibility of the devices opens new avenues for imaging in non-planar geometries. In this presentation, I will discuss the challenges in developing and printing CNT inks for this particular application, and their properties in the THz. Results of THz detection of CNT pixel arrays will be presented, as well as the factors that impact performance.
- 10:00 Peter Bermel, Purdue University
Toward an integrated system for compact solar thermophotovoltaic generation
Solar thermophotovoltaics (STPV) can convert solar heat into electricity via solar heating, followed by thermal radiation illuminating a photovoltaic diode. STPV can operate with high power densities, no moving parts, and can potentially exceed the standard photovoltaic efficiency limit of ~31%, because of spectral squeezing. However, state-of-the-art STPV demonstrations are still well below theoretical limits, because of losses from collecting solar thermal power, as well as generating and efficiently converting thermal radiation. In response, we present the following experimental demonstrations of key components needed for improved performance: (1) a thin-film Si-based selective solar thermal absorber and emitter, stable up to ~700 degrees C; and (2) a passive radiative cooler to reduce the operating temperature and thus increase the operating voltage of low-bandgap photovoltaic diodes. Finally, we will examine how these components can be integrated into a full STPV demonstration that includes selective solar absorbers, thermal emitters and all-passive, radiatively-enhanced cooling. This work may help pave the way to demonstrating reliable, quiet, light-weight, and sustainable STPV power generation.
- 10:20 COFFEE BREAK
(Mt. Curie Foyer, Sutcliffe Foyer)
- 10:40 Nathaniel Kinsey, Virginia Commonwealth University
Applications for emerging materials in nonlinear optics and integrated photonics
The recent flurry of research in fields such as nanophotonics, metamaterials, and parity time symmetry have spurred a large effort to develop tailorable, durable, and cost-effective optical materials. Through this research, several material classes with unique collections of properties have been identified, capable of impacting broader alcoves of optics research. In this presentation, we will discuss the recent advances of two particularly powerful material classes, the transparent conducting oxides, and the transition metal nitrides. These material classes are shown to provide exceptional linear and nonlinear optical responses, demonstrating a nonlinear refractive index change which exceeds the linear contribution and hot-electron relaxation more than two orders of magnitude slower than comparable materials. Together, these properties are poised to enhance applications in fields such as all-optical signal processing, energy harvesting, and on-chip integrated systems.
- 11:00 Cun-Zheng Ning, Arizona State University
Nanolasers based on integrated silicon cavity and 2D monolayer gain material
- 11:20 Han Yun, University of British Columbia
with N. Jaeger
Broadband optical power splitters for integrated photonic circuits using Si metamaterial on an SOI platform
Adiabatic 3-dB couplers are 2x2 optical power splitters that are used in photonic integrated circuits for splitting/combining light. In them, light injected into one port of the coupler is split evenly between the two output ports. Due to the high- index-contrast, silicon-on-insulator (SOI) adiabatic 3-dB couplers usually suffer from large footprints. Si metamaterial based structures, e.g., sub-wavelength-grating-based (SWG-based) structures, provide the flexibility to engineer both the refractive index and the dispersion properties of SOI devices and can be used in adiabatic 3-dB couplers to achieve compact sizes.
Here, we summarize our recent work done towards achieving compact broadband 2x2 adiabatic 3-dB couplers using Si metamaterial based waveguides. First, we present work towards a 3-dB coupler having two parallel 20 μm long conventional SWG waveguides for adiabatic mode evolution of transverse electric modes to achieve 3-dB power splitting over an operating bandwidth of 130 nm with a splitting imbalance of <0.3 dB. Then, we present work towards an adiabatic 3-dB coupler using two parallel 15 μm long SWG-assisted strip waveguides having a theoretically predicted operating bandwidth of 500 nm.
- 11:40 Boris Mizaikoff, Universität Ulm
Mid-infrared photonics: towards IR-lab-on-chip systems
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