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Nonpolar InGaN/GaN multi-quantum-well core-shell nanowire lasers

CLEO: Science and Innovations, CLEO-SI 2015

Li, Changyi; Wright, Jeremy B.; Liu, Sheng; Lu, Ping; Figiel, Jeffrey J.; Leung, Benjamin; Luk, Ting S.; Brener, Igal; Feezell, Daniel; Brueck, S.R.J.; Wang, George T.

Lasing is demonstrated from nonpolar III-nitride core-shell multi-quantum-well nanowires. The nanowire lasers were fabricated by coupling a top-down and bottom-up methodology and achieved lasing at wavelengths below the GaN bandedge. © OSA 2015.

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TYPE Conference Poster YEAR 2015
OSTIScopus

Enhanced third harmonic generation from the epsilon-near-zero modes of ultrathin films

Applied Physics Letters

Luk, Ting S.; De Ceglia, Domenico; Liu, Sheng; Keeler, Gordon A.; Prasankumar, Rohit P.; Vincenti, Maria A.; Scalora, Michael; Sinclair, Michael B.; Campione, Salvatore

We experimentally demonstrate efficient third harmonic generation from an indium tin oxide nanofilm (λ/42 thick) on a glass substrate for a pump wavelength of 1.4 μm. A conversion efficiency of 3.3 × 10-6 is achieved by exploiting the field enhancement properties of the epsilon-near-zero mode with an enhancement factor of 200. This nanoscale frequency conversion method is applicable to other plasmonic materials and reststrahlen materials in proximity of the longitudinal optical phonon frequencies.

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TYPE Journal Article YEAR 2015
DOIOSTIScopus

Tunneling-enabled spectrally selective thermal emitter based on flat metallic films

Applied Physics Letters

Luk, Ting S.; Wang, Zhu; Tan, Yixuan; Ji, Dengxin; Zhou, Ming; Gan, Qiaoqiang; Yu, Zongfu

Infrared thermal emission from metals has important energy applications in thermophotovoltaics, radiative cooling, and lighting. Unfortunately, the emissivity of flat metal films is close to zero because the screening effect prevents metals' fluctuating currents from emitting to the far field. As a result, metal films are often used as reflecting mirrors instead of thermal emitters. Recently, nanostructured metals, such as metamaterials, have emerged as an interesting way to enhance and to spectrally control thermal emission based on plasmonic resonant effects. However, they require sophisticated lithography. Here, we proposed and experimentally demonstrated a completely different mechanism to achieve spectrally selective metallic emitters based on a tunneling effect. This effect allows a simple flat metal film to achieve a near-unity emissivity with controlled spectral selectivity for efficient heat-to-light energy conversion.

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TYPE Journal Article YEAR 2015
DOIOSTIScopus

Realizing high-quality, ultralarge momentum states and ultrafast topological transitions using semiconductor hyperbolic metamaterials

Journal of the Optical Society of America B: Optical Physics

Campione, Salvatore; Liu, Sheng; Luk, Ting S.; Sinclair, Michael B.

We employ both the effective medium approximation (EMA) and Bloch theory to compare the dispersion properties of semiconductor hyperbolic metamaterials (SHMs) at mid-infrared frequencies and metallic hyperbolic metamaterials (MHMs) at visible frequencies. This analysis reveals the conditions under which the EMA can be safely applied for both MHMs and SHMs. We find that the combination of precise nanoscale layering and the longer infrared operating wavelengths puts the SHMs well within the effective medium limit and, in contrast to MHMs, allows for the attainment of very high photon momentum states. In addition, SHMs allow for new phenomena such as ultrafast creation of the hyperbolic manifold through optical pumping. In particular, we examine the possibility of achieving ultrafast topological transitions through optical pumping which can photo-dope appropriately designed quantum wells on the femtosecond time scale.

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TYPE Journal Article YEAR 2015
DOIOSTIScopus

Optical properties of transiently-excited semiconductor hyperbolic metamaterials

Optical Materials Express

Campione, Salvatore; Luk, Ting S.; Liu, Sheng; Sinclair, Michael B.

Ultrafast optical excitation of photocarriers has the potential to transform undoped semiconductor superlattices into semiconductor hyperbolic metamaterials (SHMs). In this paper, we investigate the optical properties associated with such ultrafast topological transitions. We first show reflectance, transmittance, and absorption under TE and TM plane wave incidence. In the unpumped state, the superlattice exhibits a frequency region with high reflectance (>80%) and a region with low reflectance (<1%) for both TE and TM polarizations over a wide range of incidence angles. In contrast, in the photopumped state, the reflectance for both frequencies and polarizations is very low (<1%) for a similar range of angles. Interestingly, this system can function as an all-optical reflection switch on ultrafast timescales. Furthermore, for TM incidence and close to the epsilon-near-zero point of the longitudinal permittivity, directional perfect absorption on ultrafast timescales may also be achieved. Finally, we discuss the onset of negative refraction in the photopumped state.

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TYPE Conference Poster YEAR 2015
DOIOSTIScopus

Gallium nitride nanotube lasers

Applied Physics Letters

Li, Changyi; Liu, Sheng; Hurtado, Antonio; Wright, Jeremy B.; Xu, Huiwen; Luk, Ting S.; Figiel, Jeffrey J.; Brener, Igal; Brueck, Steven R.J.; Wang, George T.

Lasing is demonstrated from gallium nitride nanotubes fabricated using a two-step top-down technique. By optically pumping, we observed characteristics of lasing: a clear threshold, a narrow spectral, and guided emission from the nanotubes. In addition, annular lasing emission from the GaN nanotube is also observed, indicating that cross-sectional shape control can be employed to manipulate the properties of nanolasers. The nanotube lasers could be of interest for optical nanofluidic applications or application benefitting from a hollow beam shape.

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TYPE Journal Article YEAR 2014
DOIOSTI

Doping-tunable thermal emission from plasmon polaritons in semiconductor epsilon-near-zero thin films

Applied Physics Letters

Brener, Igal; Klem, John F.; Luk, Ting S.; Jun, Young C.; Ellis, R.

We utilize the unique dispersion properties of leaky plasmon polaritons in epsilon-near-zero (ENZ) thin films to demonstrate thermal radiation control. Owing to its highly flat dispersion above the light line, a thermally excited leaky wave at the ENZ frequency out-couples into free space without any scattering structures, resulting in a narrowband, wide-angle, p-polarized thermal emission spectrum. We demonstrate this idea by measuring angle- and polarization-resolved thermal emission spectra from a single layer of unpatterned, doped semiconductors with deep-subwavelength film thickness (d / λ 0 ∼ 6 × 10 - 3, where d is the film thickness and λ 0 is the free space wavelength). We show that this semiconductor ENZ film effectively works as a leaky wave thermal radiation antenna, which generates far-field radiation from a thermally excited mode. The use of semiconductors makes the radiation frequency highly tunable by controlling doping densities and also facilitates device integration with other components. Therefore, this leaky plasmon polariton emission from semiconductor ENZ films provides an avenue for on-chip control of thermal radiation.

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TYPE Journal Article YEAR 2014
DOIOSTIScopus

Gallium nitride nanowire distributed feedback lasers

Conference on Lasers and Electro-Optics Europe - Technical Digest

Wright, Jeremy B.; Campione, Salvatore; Liu, Sheng; Martinez, Julio A.; Xu, Huiwen; Luk, Ting S.; Li, Qiming; Wang, George T.; Swartzentruber, Brian; Brener, Igal

We have demonstrated single-mode lasing in a single gallium nitride nanowire using distributed feedback by external coupling to a dielectric grating. By adjusting the nanowire grating alignment we achieved a mode suppression ratio of 17dB.

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TYPE Conference YEAR 2014
ScopusOSTI

Single-mode GaN nanowire lasers

Optics Express

Li, Qiming L.; Wright, Jeremy B.; Chow, Weng W.; Luk, Ting S.; Brener, Igal; Lester, Luke F.; Wang, George T.

We demonstrate stable, single-frequency output from single, asfabricated GaN nanowire lasers operating far above lasing threshold. Each laser is a linear, double-facet GaN nanowire functioning as gain medium and optical resonator, fabricated by a top-down technique that exploits a tunable dry etch plus anisotropic wet etch for precise control of the nanowire dimensions and high material gain. A single-mode linewidth of ∼0.12 nm and >18dB side-mode suppression ratio are measured. Numerical simulations indicate that single-mode lasing arises from strong mode competition and narrow gain bandwidth. © 2012 Optical Society of America.

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TYPE Journal Article YEAR 2012
ScopusOSTIDOI

Top-down fabrication of GaN-based nanorod LEDs and lasers

Proceedings of SPIE - The International Society for Optical Engineering

Wang, George T.; Li, Qiming L.; Wierer, Jonathan J.; Figiel, Jeffrey J.; Wright, Jeremy B.; Luk, Ting S.; Brener, Igal

Although planar heterostructures dominate current optoelectronic architectures, 1D nanowires and nanorods have distinct and advantageous properties that may enable higher efficiency, longer wavelength, and cheaper devices. We have developed a top-down approach for fabricating ordered arrays of high quality GaN-based nanorods with controllable height, pitch and diameter. This approach avoids many of the limitations of bottom-up synthesis methods. In addition to GaN nanorods, the fabrication and characterization of both axial and radial-type GaN/InGaN nanorod LEDs have been achieved. The precise control over nanorod geometry achiveable by this technique also enables single-mode single nanowire lasing with linewidths of less than 0.1 nm and low lasing thresholds of ∼250kW/cm 2. © 2012 Copyright Society of Photo-Optical Instrumentation Engineers (SPIE).

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TYPE Conference YEAR 2012
OSTIScopus

A Summary of the Theory and Design Team Efforts for the Sandia Metamaterials Science and Technology Grand Challenge LDRD

Basilio, Lorena I.; Brener, Igal; Burckel, David B.; Shaner, Eric A.; Wendt, Joel R.; Luk, Ting S.; Ellis, A.R.; Bender, Daniel A.; Clem, Paul; Rasberry, Roger D.; Langston, William L.; Ihlefeld, Jon F.; Dirk, Shawn M.; Warne, Larry K.; Peters, David; El-Kady, Ihab F.; Reinke, Charles M.; Loui, Hung; Williams, Jeffery T.; Sinclair, Michael B.; Mccormick, Frederick B.

Abstract not provided.

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TYPE Presentation YEAR 2012
OSTI

Hyperspectral imaging of microalgae using two-photon excitation

Jones, Howland D.T.; Sinclair, Michael B.; Luk, Ting S.; Collins, Aaron M.; Garcia, Omar F.; Melgaard, David K.; Timlin, Jerilyn A.; Reichardt, Thomas A.

A considerable amount research is being conducted on microalgae, since microalgae are becoming a promising source of renewable energy. Most of this research is centered on lipid production in microalgae because microalgae produce triacylglycerol which is ideal for biodiesel fuels. Although we are interested in research to increase lipid production in algae, we are also interested in research to sustain healthy algal cultures in large scale biomass production farms or facilities. The early detection of fluctuations in algal health, productivity, and invasive predators must be developed to ensure that algae are an efficient and cost-effective source of biofuel. Therefore we are developing technologies to monitor the health of algae using spectroscopic measurements in the field. To do this, we have proposed to spectroscopically monitor large algal cultivations using LIDAR (Light Detection And Ranging) remote sensing technology. Before we can deploy this type of technology, we must first characterize the spectral bio-signatures that are related to algal health. Recently, we have adapted our confocal hyperspectral imaging microscope at Sandia to have two-photon excitation capabilities using a chameleon tunable laser. We are using this microscope to understand the spectroscopic signatures necessary to characterize microalgae at the cellular level prior to using these signatures to classify the health of bulk samples, with the eventual goal of using of LIDAR to monitor large scale ponds and raceways. By imaging algal cultures using a tunable laser to excite at several different wavelengths we will be able to select the optimal excitation/emission wavelengths needed to characterize algal cultures. To analyze the hyperspectral images generated from this two-photon microscope, we are using Multivariate Curve Resolution (MCR) algorithms to extract the spectral signatures and their associated relative intensities from the data. For this presentation, I will show our two-photon hyperspectral imaging results on a variety of microalgae species and show how these results can be used to characterize algal ponds and raceways.

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TYPE Conference YEAR 2010
OSTI

Final LDRD report : enhanced spontaneous emission rate in visible III-nitride LEDs using 3D photonic crystal cavities

Fischer, Arthur J.; Subramania, Ganapathi S.; Lee, Yun-Ju; Koleske, Daniel; Li, Qiming L.; Wang, George T.; Luk, Ting S.; Fullmer, Kristine W.

The fundamental spontaneous emission rate for a photon source can be modified by placing the emitter inside a periodic dielectric structure allowing the emission to be dramatically enhanced or suppressed depending on the intended application. We have investigated the relatively unexplored realm of interaction between semiconductor emitters and three dimensional photonic crystals in the visible spectrum. Although this interaction has been investigated at longer wavelengths, very little work has been done in the visible spectrum. During the course of this LDRD, we have fabricated TiO{sub 2} logpile photonic crystal structures with the shortest wavelength band gap ever demonstrated. A variety of different emitters with emission between 365 nm and 700 nm were incorporated into photonic crystal structures. Time-integrated and time-resolved photoluminescence measurements were performed to measure changes to the spontaneous emission rate. Both enhanced and suppressed emission were demonstrated and attributed to changes to the photonic density of states.

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TYPE SAND Report YEAR 2009
DOIOSTI

Novel photonic crystal cavities and related structures

Luk, Ting S.

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.

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TYPE SAND Report YEAR 2007
DOIOSTI

Large-area metallic photonic lattices for military applications

Luk, Ting S.

In this project we developed photonic crystal modeling capability and fabrication technology that is scaleable to large area. An intelligent optimization code was developed to find the optimal structure for the desired spectral response. In terms of fabrication, an exhaustive survey of fabrication techniques that would meet the large area requirement was reduced to Deep X-ray Lithography (DXRL) and nano-imprint. Using DXRL, we fabricated a gold logpile photonic crystal in the <100> plane. For the nano-imprint technique, we fabricated a cubic array of gold squares. These two examples also represent two classes of metallic photonic crystal topologies, the connected network and cermet arrangement.

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TYPE SAND Report YEAR 2007
DOIOSTI
Results 101–200 of 213
Results 101–200 of 213