Engineering triangular carbon quantum dots with unprecedented narrow bandwidth emission for multicolored LEDs.

PubMed

Yuan, Fanglong; Yuan, Ting; Sui, Laizhi; Wang, Zhibin; Xi, Zifan; Li, Yunchao; Li, Xiaohong; Fan, Louzhen; Tan, Zhan'ao; Chen, Anmin; Jin, Mingxing; Yang, Shihe

2018-06-08

Carbon quantum dots (CQDs) have emerged as promising materials for optoelectronic applications on account of carbon's intrinsic merits of high stability, low cost, and environment-friendliness. However, the CQDs usually give broad emission with full width at half maximum exceeding 80 nm, which fundamentally limit their display applications. Here we demonstrate multicolored narrow bandwidth emission (full width at half maximum of 30 nm) from triangular CQDs with a quantum yield up to 54-72%. Detailed structural and optical characterizations together with theoretical calculations reveal that the molecular purity and crystalline perfection of the triangular CQDs are key to the high color-purity. Moreover, multicolored light-emitting diodes based on these CQDs display good stability, high color-purity, and high-performance with maximum luminance of 1882-4762 cd m -2 and current efficiency of 1.22-5.11 cd A -1 . This work will set the stage for developing next-generation high-performance CQDs-based light-emitting diodes.

Low-noise low-jitter 32-pixels CMOS single-photon avalanche diodes array for single-photon counting from 300 nm to 900 nm

DOE Office of Scientific and Technical Information (OSTI.GOV)

Scarcella, Carmelo; Tosi, Alberto, E-mail: alberto.tosi@polimi.it; Villa, Federica

2013-12-15

We developed a single-photon counting multichannel detection system, based on a monolithic linear array of 32 CMOS SPADs (Complementary Metal-Oxide-Semiconductor Single-Photon Avalanche Diodes). All channels achieve a timing resolution of 100 ps (full-width at half maximum) and a photon detection efficiency of 50% at 400 nm. Dark count rate is very low even at room temperature, being about 125 counts/s for 50 μm active area diameter SPADs. Detection performance and microelectronic compactness of this CMOS SPAD array make it the best candidate for ultra-compact time-resolved spectrometers with single-photon sensitivity from 300 nm to 900 nm.

Neutron detection using a current biased kinetic inductance detector

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shishido, Hiroaki, E-mail: shishido@pe.osakafu-u.ac.jp; Miyajima, Shigeyuki; Ishida, Takekazu

2015-12-07

We demonstrate neutron detection using a solid state superconducting current biased kinetic inductance detector (CB-KID), which consists of a superconducting Nb meander line of 1 μm width and 40 nm thickness. {sup 10}B-enriched neutron absorber layer of 150 nm thickness is placed on top of the CB-KID. Our neutron detectors are able to operate in a wide superconducting region in the bias current–temperature diagram. This is in sharp contrast with our preceding current-biased transition edge detector, which can operate only in a narrow range just below the superconducting critical temperature. The full width at half maximum of the signals remains of the ordermore » of a few tens of ns, which confirms the high speed operation of our detectors.« less

High angular and spectral selectivity of purple emperor (Lepidoptera: Apatura iris and A. ilia) butterfly wings.

PubMed

Pantelić, Dejan; Curčić, Srećko; Savić-Šević, Svetlana; Korać, Aleksandra; Kovačević, Aleksander; Curčić, Božidar; Bokić, Bojana

2011-03-28

The iridescent features of the butterfly species Apatura iris (Linnaeus, 1758) and A. ilia (Denis & Schiffermüller, 1775) were studied. We recognized the structural color of scales only on the dorsal side of both the fore and hind wings of males of both of the aforementioned butterfly species. The scale dimensions and microstructure were analyzed by a scanning electron microscope (SEM) and transmission electron microscope (TEM). The optical properties were measured and it was found that the peak reflectivity is around 380 nm, with a spectral width (full width at half maximum) of approximately 50 nm in both species. The angular selectivity is high and a purple iridescent color is observed within the angular range of only 18 degrees in both species.

Time and spatial evolution of spin-orbit torque-induced magnetization switching in W/CoFeB/MgO structures with various sizes

NASA Astrophysics Data System (ADS)

Zhang, Chaoliang; Fukami, Shunsuke; DuttaGupta, Samik; Sato, Hideo; Ohno, Hideo

2018-04-01

We study spin-orbit torque (SOT) switching in W/CoFeB/MgO structures with various dot sizes (120-3500 nm) using pulsed current of various widths τ (800 ps-100 ms) to examine the time and spatial evolution of magnetization switching. We show that the switching behavior and the resultant threshold switching current density J th strongly depend on device size and pulse width. The switching mode in a 3500 nm dot device changes from probabilistic switching to reproducible partial switching as τ decreases. At τ = 800 ps, J th becomes more than 3 times larger than that in the long-pulse regime. A decrease in dot size to 700 nm does not significantly change the switching characteristics, suggesting that domain-wall propagation among the nucleated multiple domains governs switching. In contrast, devices with further reduced size (120 nm) show normal full switching with increasing probability with current and insignificant dependence of J th on τ, indicating that nucleation governs switching.

Atmospheric pressure scanning transmission electron microscopy.

PubMed

de Jonge, Niels; Bigelow, Wilbur C; Veith, Gabriel M

2010-03-10

Scanning transmission electron microscope (STEM) images of gold nanoparticles at atmospheric pressure have been recorded through a 0.36 mm thick mixture of CO, O2, and He. This was accomplished using a reaction cell consisting of two electron-transparent silicon nitride membranes. Gold nanoparticles of a full width at half-maximum diameter of 1.0 nm were visible above the background noise, and the achieved edge resolution was 0.4 nm in accordance with calculations of the beam broadening.

1.9 W continuous-wave single transverse mode emission from 1060 nm edge-emitting lasers with vertically extended lasing area

DOE Office of Scientific and Technical Information (OSTI.GOV)

Miah, M. J., E-mail: jarez.miah@tu-berlin.de; Posilovic, K.; Kalosha, V. P.

2014-10-13

High-brightness edge-emitting semiconductor lasers having a vertically extended waveguide structure emitting in the 1060 nm range are investigated. Ridge waveguide (RW) lasers with 9 μm stripe width and 2.64 mm cavity length yield highest to date single transverse mode output power for RW lasers in the 1060 nm range. The lasers provide 1.9 W single transverse mode optical power under continuous-wave (cw) operation with narrow beam divergences of 9° in lateral and 14° (full width at half maximum) in vertical direction. The beam quality factor M{sup 2} is less than 1.9 up to 1.9 W optical power. A maximum brightness of 72 MWcm{sup −2}sr{supmore » −1} is obtained. 100 μm wide and 3 mm long unpassivated broad area lasers provide more than 9 W optical power in cw operation.« less

Old and new techniques mixed up into optical photomask measurement method

NASA Astrophysics Data System (ADS)

Fukui, Jumpei; Tachibana, Yusaku; Osanai, Makoto

2017-07-01

It has been still highly required for cost efficient solution with easy operation for full-automated CD measurement for line width about 500nm up to 5μm on photomask, because it is frequently use such photomask in the process of manufacturing MEMS sensor for IoT and some devices made in BCD (Bipola CMOS DMOS). As reply to such demand in photomask manufacturing field, we try to take a low noise digital camera technology and LED light source for i-line, which are recently developed, into new measuring tool in order to achieve 1nm (3σ) repeatability for line width measurement between 300nm to 10μm. In addition, for the purpose of full-automated operation, it is very important to find where an initial target line in dense pattern. To achieve such auto line detection precisely, we have improved accuracy of high precision stage (20nm as 3σ) and an alignment algorithm of MEMS Stepper to combine with this tool. As for user-friendly interface, Windows based software helps a lot for not only the operation but also recipe creation or edition in Excel. Actually, in the MEMS manufacturing process, there are various photomasks which need to be check and measure frequently therefore various recipe files are also have to be created and edited frequently.. In order to meet such a requirement in photomask management, we try to make it true by mixing old and new techniques together into one system, which comes to fully automated and cost efficient tool with 1nm repeatability in CD measurement.

Note: Broadly tunable all-fiber ytterbium laser with 0.05 nm spectral width based on multimode interference filter.

PubMed

Mukhopadhyay, Pranab K; Gupta, Pradeep K; Singh, Amarjeet; Sharma, Sunil K; Bindra, Kushvinder S; Oak, Shrikant M

2014-05-01

A multimode interference filter with narrow transmission bandwidth and large self-imaging wavelength interval is constructed and implemented in an ytterbium doped fiber laser in all-fiber format for broad wavelength tunability as well as narrow spectral width of the output beam. The peak transmission wavelength of the multimode interference filter was tuned with the help of a standard in-fiber polarization controller. With this simple mechanism more than 30 nm (1038 nm-1070 nm) tuning range is demonstrated. The spectral width of the output beam from the laser was measured to be 0.05 nm.

Note: Broadly tunable all-fiber ytterbium laser with 0.05 nm spectral width based on multimode interference filter

NASA Astrophysics Data System (ADS)

Mukhopadhyay, Pranab K.; Gupta, Pradeep K.; Singh, Amarjeet; Sharma, Sunil K.; Bindra, Kushvinder S.; Oak, Shrikant M.

2014-05-01

A multimode interference filter with narrow transmission bandwidth and large self-imaging wavelength interval is constructed and implemented in an ytterbium doped fiber laser in all-fiber format for broad wavelength tunability as well as narrow spectral width of the output beam. The peak transmission wavelength of the multimode interference filter was tuned with the help of a standard in-fiber polarization controller. With this simple mechanism more than 30 nm (1038 nm-1070 nm) tuning range is demonstrated. The spectral width of the output beam from the laser was measured to be 0.05 nm.

Optical track width measurements below 100 nm using artificial neural networks

NASA Astrophysics Data System (ADS)

Smith, R. J.; See, C. W.; Somekh, M. G.; Yacoot, A.; Choi, E.

2005-12-01

This paper discusses the feasibility of using artificial neural networks (ANNs), together with a high precision scanning optical profiler, to measure very fine track widths that are considerably below the conventional diffraction limit of a conventional optical microscope. The ANN is trained using optical profiles obtained from tracks of known widths, the network is then assessed by applying it to test profiles. The optical profiler is an ultra-stable common path scanning interferometer, which provides extremely precise surface measurements. Preliminary results, obtained with a 0.3 NA objective lens and a laser wavelength of 633 nm, show that the system is capable of measuring a 50 nm track width, with a standard deviation less than 4 nm.

Widely tunable chaotic fiber laser for WDM-PON detection

NASA Astrophysics Data System (ADS)

Zhang, Juan; Yang, Ling-zhen; Xu, Nai-jun; Wang, Juan-fen; Zhang, Zhao-xia; Liu, Xiang-lian

2014-05-01

A widely tunable high precision chaotic fiber laser is proposed and experimentally demonstrated. A tunable fiber Bragg grating (TFBG) filter is used as a tuning element to determine the turning range from 1533 nm to 1558 nm with a linewidth of 0.5 nm at any wavelength. The wide tuning range is capable of supporting 32 wavelength-division multiplexing (WDM) channels with 100 GHz channel spacing. All single wavelengths are found to be chaotic with 10 GHz bandwidth. The full width at half maximum (FWHM) of the chaotic correlation curve of the different wavelengths is on a picosecond time scale, thereby offering millimeter spatial resolution in WDM detection.

Investigation of optical properties and local structure of Gd3+ doped nano-crystalline GeSe2

NASA Astrophysics Data System (ADS)

Hantour, Hanan Hassan

2017-04-01

Pure and Gd-doped nano-crystalline GeSe2 were prepared by the melt-quenching technique. Structure analysis using Rietveld program suggests monoclinic structure for both virgin and doped samples with nano-particle size 41 nm for GeSe2 and 48 nm for Gd-doped sample. A wide optical band gap as estimated from absorbance measurements is 4.1 and 4.8 eV for pure and doped samples in accordance with the confinement effects. Raman spectra show two unresolved components at ˜202 cm-1 with broad line width. Also, well identified low intensity (υ < 145 cm-1) and high intensity (υ > 250 cm-1) bands are detected. For Gd-doped sample, the main band is shifted to lower energies and its full width at half maximum (FWHM) is reduced by ˜50% accompanied by an intensity increase of about ˜17 fold times. The photoluminescence analysis of the pure sample shows a main emission band at ˜604 nm. This band is split into two separated bands with higher intensity. The detected emission bands at wavelength >650 nm are assigned to transmission from 6GJ to the different 6PJ terms.

VizieR Online Data Catalog: Halpha measurements in Abell 2465 (Wegner+, 2015)

NASA Astrophysics Data System (ADS)

Wegner, G. A.; Chu, D. S.; Hwang, H. S.

2015-07-01

The wavelength of the Hα line at the redshift of Abell 2465 is near 817nm in a clear spectral region between the many telluric emission lines. A custom narrow-band filter for observing Hα was obtained from the Andover Corp. It has a peak transmission at 817.7nm (m817) and a full width at half-maximum (FWHM) of 8.77nm. The wide filter was a Gunn i (ig) filter with nearly the same central wavelength of 820nm and a FWHM of 185nm, and was manufactured by Custom Scientific. Hα observations of Abell 2465 were obtained 2012 September 19-23 using the 2.4m Hiltner telescope at the MDM Observatory on Kitt Peak. The 'Nellie' CCD was used. (1 data file).

STED microscopy visualizes energy deposition of single ions in a solid-state detector beyond diffraction limit

NASA Astrophysics Data System (ADS)

Niklas, M.; Henrich, M.; Jäkel, O.; Engelhardt, J.; Abdollahi, A.; Greilich, S.

2017-05-01

Fluorescent nuclear track detectors (FNTDs) allow for visualization of single-particle traversal in clinical ion beams. The point spread function of the confocal readout has so far hindered a more detailed characterization of the track spots—the ion’s characteristic signature left in the FNTD. Here we report on the readout of the FNTD by optical nanoscopy, namely stimulated emission depletion microscopy. It was firstly possible to visualize the track spots of carbon ions and protons beyond the diffraction limit of conventional light microscopy with a resolving power of approximately 80 nm (confocal: 320 nm). A clear discrimination of the spatial width, defined by the full width half maximum of track spots from particles (proton and carbon ions), with a linear energy transfer (LET) ranging from approximately 2-1016 keV µm-1 was possible. Results suggest that the width depends on LET but not on particle charge within the uncertainties. A discrimination of particle type by width thus does not seem possible (as well as with confocal microscopy). The increased resolution, however, could allow for refined determination of the cross-sectional area facing substantial energy deposition. This work could pave the way towards development of optical nanoscopy-based analysis of radiation-induced cellular response using cell-fluorescent ion track hybrid detectors.

A frequency doubled pressure-tunable oscillator-amplifier dye laser system

NASA Technical Reports Server (NTRS)

Moriarty, A.; Heaps, W.; Davis, D. D.

1976-01-01

A tunable high-repetition-rate oscillator-amplifier dye-laser system is reported. The dye laser described was longitudinally pumped with the second harmonic of a Nd-YAG laser operating at 10 Hz. Using three Faraday-Perot etalons and pressure tuning, a maximum fundamental output power of the order of 6 MW with a corresponding spectral width of less than 0.003 nm at 564 nm was obtained. The fundamental at 564 nm was frequency doubled to give a maximum power level of 0.6 MW of second-harmonic output power with a spectral width less than 0.0015 nm at 282 nm. Frequency stability could be maintained to within approximately 15% of the line-width.

Enhancement mode GaN-based multiple-submicron channel array gate-recessed fin metal-oxide-semiconductor high-electron mobility transistors

NASA Astrophysics Data System (ADS)

Lee, Ching-Ting; Wang, Chun-Chi

2018-04-01

To study the function of channel width in multiple-submicron channel array, we fabricated the enhancement mode GaN-based gate-recessed fin metal-oxide-semiconductor high-electron mobility transistors (MOS-HEMTs) with a channel width of 450 nm and 195 nm, respectively. In view of the enhanced gate controllability in a narrower fin-channel structure, the transconductance was improved from 115 mS/mm to 151 mS/mm, the unit gain cutoff frequency was improved from 6.2 GHz to 6.8 GHz, and the maximum oscillation frequency was improved from 12.1 GHz to 13.1 GHz of the devices with a channel width of 195 nm, compared with the devices with a channel width of 450 nm.

Note: Broadly tunable all-fiber ytterbium laser with 0.05 nm spectral width based on multimode interference filter

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mukhopadhyay, Pranab K., E-mail: pkm@rrcat.gov.in; Gupta, Pradeep K.; Singh, Amarjeet

2014-05-15

A multimode interference filter with narrow transmission bandwidth and large self-imaging wavelength interval is constructed and implemented in an ytterbium doped fiber laser in all-fiber format for broad wavelength tunability as well as narrow spectral width of the output beam. The peak transmission wavelength of the multimode interference filter was tuned with the help of a standard in-fiber polarization controller. With this simple mechanism more than 30 nm (1038 nm–1070 nm) tuning range is demonstrated. The spectral width of the output beam from the laser was measured to be 0.05 nm.

Narrowband ultraviolet photodetector based on MgZnO and NPB heterojunction.

PubMed

Hu, Zuofu; Li, Zhenjun; Zhu, Lu; Liu, Fengjuan; Lv, Yanwu; Zhang, Xiqing; Wang, Yongsheng

2012-08-01

An ultraviolet photodetector was fabricated based on Mg0.07Zn0.93O heterojunction. N, N'-bis (naphthalen-1-y1)-N, N'-bis(pheny) benzidine was selected as the hole transporting layer. I-V characteristic curves of the device were measured in the dark and under the illumination of 340 nm UV light with density of 1.33 mW/cm2. The device showed a low dark current of about 3×10(-10) A and a high photo-dark current ratio of 1×10(5) at -2 V bias. A narrowband photoresponse was observed from 300 to 400 nm and centered at 340 nm with a full width at half-maximum of only 30 nm. The maximum peak response is at 340 nm, which is 0.192 A/W at the bias of -1 V.

Deep-UV Based Acousto-Optic Tunable Filter for Spectral Sensing Applications

NASA Technical Reports Server (NTRS)

Prasad, Narasimha S.

2006-01-01

In this paper, recent progress made in the development of quartz and KDP crystal based acousto-optic tunable filters (AOTF) are presented. These AOTFs are developed for operation over deep-UV to near-UV wavelengths of 190 nm to 400 nm. Preliminary output performance measurements of quartz AOTF and design specifications of KDP AOTF are presented. At 355 nm, the quartz AOTF device offered approx.15% diffraction efficiency with a passband full-width-half-maximum (FWHM) of less than 0.0625 nm. Further characterization of quartz AOTF devices at deep-UV wavelengths is progressing. The hermetic packaging of KDP AOTF is nearing completion. The solid-state optical sources being used for excitation include nonlinear optics based high-energy tunable UV transmitters that operate around 320 nm and 308 nm wavelengths, and a tunable deep-UV laser operating over 193 nm to 210 nm. These AOTF devices have been developed as turn-key devices for primarily for space-based chemical and biological sensing applications using laser induced Fluorescence and resonance Raman techniques.

Structural and magnetic properties of ultra-thin Fe films on metal-organic chemical vapour deposited GaN(0001)

NASA Astrophysics Data System (ADS)

Kim, Jun-Young; Ionescu, Adrian; Mansell, Rhodri; Farrer, Ian; Oehler, Fabrice; Kinane, Christy J.; Cooper, Joshaniel F. K.; Steinke, Nina-Juliane; Langridge, Sean; Stankiewicz, Romuald; Humphreys, Colin J.; Cowburn, Russell P.; Holmes, Stuart N.; Barnes, Crispin H. W.

2017-01-01

Structural and magnetic properties of 1-10 nm thick Fe films deposited on GaN(0001) were investigated. In-situ reflecting high energy electron diffraction images indicated a α-Fe(110)/GaN(0001) growth of the 3D Volmer-Weber type. The α-Fe(110) X-ray diffraction peak showed a 1° full-width at half-maximum, indicating ≈20 nm grain sizes. A significant reduction in Fe atomic moment from its bulk value was observed for films thinner than 4 nm. Both GaN/Fe interface roughness and Fe film coercivity increased with Fe thickness, indicating a possible deterioration of Fe crystalline quality. Magnetic anisotropy was mainly uniaxial for all films while hexagonal anisotropies appeared for thicknesses higher than 3.7 nm.

Transformational Optics

DTIC Science & Technology

2016-12-19

32λ (angular divergence of 1.8°) which is quasi -monochromatic with a full width at half maximum of 70 nm. These experimental results show good...devices; plasmonic TO structures; and tapered waveguide analog TO devices. Of particular relevance is the development of quasi - conformal (QC...the development of quasi -conformal (QC) optimization techniques that lead to more realizable TO designs, appropriate for the shorter wavelengths of

Graphene FETs Based on High Resolution Nanoribbons for HF Low Power Applications

NASA Astrophysics Data System (ADS)

Mele, David; Mehdhbi, Sarah; Fadil, Dalal; Wei, Wei; Ouerghi, Abdelkarim; Lepilliet, Sylvie; Happy, Henri; Pallecchi, Emiliano

2018-03-01

In this paper we present high frequency field effect transistors based on graphene nanoribbons arrays (GNRFETs). The nanoribbons serve as a channel for the transistors and are fabricated with a process based on e-beam lithography and dry etching of high mobility hydrogen intercalated epitaxial graphene. The widths of the nanoribbons vary from 50 to 20 nm, less than half those measured in previous reports for GNRFETs. Hall measurements reveal that the devices are p-doped, with mobility on the order of 2300 cm2/Vs. From DC characteristics, we find that the maximum ratio IMAX/IMIN is 5 obtained at 50 nm ribbons width. The IV characteristics of the GNRFETs are slightly non-linear at high bias without a full saturation. Therefore, despite the aggressive scaling of the graphene nanoribbon width, a bandgap is still not observed in our measurements. The high frequency performances of our GNRFETs are already significant at low bias. At 300 mV drain source voltage, the highest intrinsic (extrinsic) cut-off frequency ft reaches 82 (18) GHz and the extrinsic maximum oscillation frequency fmax is 20 GHz, which is promising for low power applications.

Nonlinear optical properties of As20S80 system chalcogenide glass using Z-scan and its strip waveguide under bandgap light using the self-phase modulation

NASA Astrophysics Data System (ADS)

Zou, L. E.; He, P. P.; Chen, B. X.; Iso, M.

2017-02-01

Optical nonlinearities in the undoped As20S80, low doped P2As20S78 and Sn1As20S79 chacogenide glasses are investigated by using Z-scan method. These experiments show that at 1064 nm the figure of merit (FOM) for As20S80 is ˜1.02, while for Sn1As20S79 increases to ˜1.42, and for P2As20S78 decreases to ˜0.83. These resulted data indicate the addition of Sn in As20S80 system chalcogenide glass can enhance FOM due to creating narrow energy gaps. In addition, the self-phase modulation (SPM) width experiment for Sn1As20S79 strip waveguide displays that the full width half maximum (FWHM) of spectral width increases approximately 0.8 nm under the induction of bandgap light, meaning that the bandgap light can induce to enhance its optical nonlinearity with the nonlinear refractive index of n2≅5.27×10-14 cm2/W.

Micro-fractional ablative skin resurfacing with two novel erbium laser systems.

PubMed

Dierickx, Christine C; Khatri, Khalil A; Tannous, Zeina S; Childs, James J; Cohen, Richard H; Erofeev, Andrei; Tabatadze, David; Yaroslavsky, Ilya V; Altshuler, Gregory B

2008-02-01

Fractional ablation offers the potential benefits of full-surface ablative skin resurfacing while minimizing adverse effects. The purpose of this study was to evaluate the safety, damage profile, and efficacy of erbium fractional lasers. Histology from animal and human skin as well as clinical evaluations were conducted with erbium YAG (2,940 nm) and erbium YSGG (2,790 nm) fractional lasers varying pulse width, microbeam (microb) energy, number of passes, and stacking of pulses. Single-pulse treatment parameters from 1 to 12 mJ per 50-70 microm diameter microbeam and 0.25-5 milliseconds pulse widths produced microcolumns of ablation with border coagulation of up to 100 microm width and 450 microm depth. Stacking of pulses generated deeper microcolumns. Clinical observations and in vivo histology demonstrate rapid re-epithelization and limited adverse side effects. Facial treatments were performed in the periorbital and perioral areas using 1-8 passes of single and stacked pulses. Treatments were well-tolerated and subjects could resume their normal routine in 4 days. A statistically significant reduction in wrinkle scores at 3 months was observed for both periorbital and perioral wrinkles using blinded grading. For periorbital treatments of four passes or more, over 90% had > or =1 score wrinkle reduction (0-9 scale) and 42% had > or =2. For perioral wrinkles, over 50% had substantial improvements (> or =2). The clinical observations and histology findings demonstrate that micro-fractional ablative treatment with 2,790 and 2,940 nm erbium lasers resulted in safe and effective wrinkle reduction with minimal patient downtime. The depth and width of the ablated microcolumns and varying extent of surrounding coagulation can be controlled and used to design new treatment procedures targeted for specific indications and areas such as moderate to severe rhytides and photodamaged skin.

CLARREO Pathfinder Mission to ISS: Demonstrating Greatly Increased Accuracy for Reflected Solar Space Based Observations: Calibration and Intercalibration

NASA Astrophysics Data System (ADS)

Wielicki, B. A.

2016-12-01

The CLARREO (Climate Absolute Radiance and Refractivity) Pathfinder mission is a new mission started by NASA in 2016. CLARREO Pathfinder will fly a new generation of high accuracy reflected solar spectrometer in orbit on the Inernational Space Station (ISS) to demonstrate the ability to increase accuracy of reflected solar observations from space by a factor of 3 to 20. The spectrometer will use the sun and moon as calibration sources with a baseline objective of 0.3% (1 sigma) reflectance calibration uncertainty for the contiguous spectrum from 350nm to 2300nm, covering over 95% of the Earth's reflected solar spectrum. Spectral sampling is 3nm with resolution of 6nm. The spectrometer is mounted on a 2-axis gimbal enabling a new ability to use the same optical path to view the sun, moon, and Earth. Planned launch is 2020 with at least 1 year on orbit to demonstrate the new capability. The mission will also demonstrate the ability to use the new spectrometer as a reference transfer spectrometer in orbit to achieve intercalibration of reflected solar instruments to within 0.3% (1 sigma) using space, time, spectral, and angle matched observations across the full scan width of remote sensing instruments. Intercalibration to 0.3% will be demonstrated across the full scan width of the NASA CERES broadband radiometer and the NOAA VIIRS imager reflected solar spectral channels. This mission will demonstrate reflected solar intercalibration across the full swath width as opposed to current nadir only intercalibration used by GSICS (Global Space Based InterCalibration System). Intercalibration will include a new capability to determine scan angle dependence of polarization sensitivity of instruments like VIIRS. The high accuracy goals of this mission are driven primarily by the accuracy required to more rapidly and accurately observe climate change signals such as cloud feedback (see Wielicki et al. 2013 Bulletin of the American Meteorological Society). The new high accuracy and intercalibration capability will also be very useful for serving as a reference calibrator for constellations of operational instruments in Geostationary or Low Earth Orbit (e.g. land resource imagers, ocean color, cloud imagers). The higher accuracy will enable operational sensors to more effectively serve as climate change sensors.

Extremely small polarization beam splitter based on a multimode interference coupler with a silicon hybrid plasmonic waveguide.

PubMed

Guan, Xiaowei; Wu, Hao; Shi, Yaocheng; Dai, Daoxin

2014-01-15

A novel polarization beam splitter (PBS) with an extremely small footprint is proposed based on a multimode interference (MMI) coupler with a silicon hybrid plasmonic waveguide. The MMI section, covered with a metal strip partially, is designed to achieve mirror imaging for TE polarization. On the other hand, for TM polarization, there is almost no MMI effect since the higher-order TM modes are hardly excited due to the hybrid plasmonic effect. With this design, the whole PBS including the 1.1 μm long MMI section as well as the output section has a footprint as small as ∼1.8 μm×2.5 μm. Besides, the fabrication process is simple since the waveguide dimension is relatively large (e.g., the input/output waveguides widths w ≥300 nm and the MMI width w(MMI)=800 nm). Numerical simulations show that the designed PBS has a broad band of ∼80 nm for an ER >10 dB as well as a large fabrication tolerance to allow a silicon core width variation of -30 nm<Δw<50 nm and a metal strip width variation of -200 nm<Δw(m)<0.

Orange a-plane InGaN/GaN light-emitting diodes grown on r-plane sapphire substrates.

PubMed

Seo, Yong Gon; Baik, Kwang Hyeon; Song, Hooyoung; Son, Ji-Su; Oh, Kyunghwan; Hwang, Sung-Min

2011-07-04

We report on orange a-plane light-emitting diodes (LEDs) with InGaN single quantum well (SQW) grown on r-plane sapphire substrates by metal organic chemical vapor deposition (MOCVD). The peak wavelength and the full-width at half maximum (FWHM) at a drive current of 20mA were 612.2 nm and 72 nm, respectively. The device demonstrated a blue shift in emission wavelength from 614.6 nm at 10 mA to 607.5 nm at 100 mA, representing a net shift of 7.1 nm over a 90 mA range, which is the longest wavelength compared with reported values in nonpolar LEDs. The polarization ratio values obtained from the orange LED varied between 0.36 and 0.44 from 10 to 100mA and a weak dependence of the polarization ratio on the injection current was observed.

Scanning electron microscope measurement of width and shape of 10nm patterned lines using a JMONSEL-modeled library.

PubMed

Villarrubia, J S; Vladár, A E; Ming, B; Kline, R J; Sunday, D F; Chawla, J S; List, S

2015-07-01

The width and shape of 10nm to 12 nm wide lithographically patterned SiO2 lines were measured in the scanning electron microscope by fitting the measured intensity vs. position to a physics-based model in which the lines' widths and shapes are parameters. The approximately 32 nm pitch sample was patterned at Intel using a state-of-the-art pitch quartering process. Their narrow widths and asymmetrical shapes are representative of near-future generation transistor gates. These pose a challenge: the narrowness because electrons landing near one edge may scatter out of the other, so that the intensity profile at each edge becomes width-dependent, and the asymmetry because the shape requires more parameters to describe and measure. Modeling was performed by JMONSEL (Java Monte Carlo Simulation of Secondary Electrons), which produces a predicted yield vs. position for a given sample shape and composition. The simulator produces a library of predicted profiles for varying sample geometry. Shape parameter values are adjusted until interpolation of the library with those values best matches the measured image. Profiles thereby determined agreed with those determined by transmission electron microscopy and critical dimension small-angle x-ray scattering to better than 1 nm. Published by Elsevier B.V.

Strontium and barium iodide high light yield scintillators

NASA Astrophysics Data System (ADS)

Cherepy, Nerine J.; Hull, Giulia; Drobshoff, Alexander D.; Payne, Stephen A.; van Loef, Edgar; Wilson, Cody M.; Shah, Kanai S.; Roy, Utpal N.; Burger, Arnold; Boatner, Lynn A.; Choong, Woon-Seng; Moses, William W.

2008-02-01

Europium-doped strontium and barium iodide are found to be readily growable by the Bridgman method and to produce high scintillation light yields. SrI2(Eu ) emits into the Eu2+ band, centered at 435nm, with a decay time of 1.2μs and a light yield of ˜90000photons/MeV. It offers energy resolution better than 4% full width at half maximum at 662keV, and exhibits excellent light yield proportionality. BaI2(Eu ) produces >30000photons/MeV into the Eu2+ band at 420nm (<1μs decay). An additional broad impurity-mediated recombination band is present at 550nm (>3μs decay), unless high-purity feedstock is used.

Study of broadband near-infrared emission in Tm3+-Er3+ codoped TeO2-WO3-PbO glasses.

PubMed

Balda, R; Fernández, J; Fernández-Navarro, J M

2009-05-25

In this work, we report the near-infrared emission properties of Tm(3+)-Er(3+) codoped tellurite TeO(2)-WO(3)-PbO glasses under 794 nm excitation. A broad emission from 1350 to 1750 nm corresponding to the Tm(3+) and Er(3+) emissions is observed. The full width at half-maximum of this broadband increases with increasing [Tm]/[Er] concentration ratio up to a value of ~ 160 nm. The energy transfer between Tm(3+) and Er(3+) ions is evidenced by both the temporal behavior of the near-infrared luminescence and the effect of Tm3+ codoping on the visible upconversion of Er(3+) ions.

Nonlinear structured-illumination enhanced temporal focusing multiphoton excitation microscopy with a digital micromirror device.

PubMed

Cheng, Li-Chung; Lien, Chi-Hsiang; Da Sie, Yong; Hu, Yvonne Yuling; Lin, Chun-Yu; Chien, Fan-Ching; Xu, Chris; Dong, Chen Yuan; Chen, Shean-Jen

2014-08-01

In this study, the light diffraction of temporal focusing multiphoton excitation microscopy (TFMPEM) and the excitation patterning of nonlinear structured-illumination microscopy (NSIM) can be simultaneously and accurately implemented via a single high-resolution digital micromirror device. The lateral and axial spatial resolutions of the TFMPEM are remarkably improved through the second-order NSIM and projected structured light, respectively. The experimental results demonstrate that the lateral and axial resolutions are enhanced from 397 nm to 168 nm (2.4-fold) and from 2.33 μm to 1.22 μm (1.9-fold), respectively, in full width at the half maximum. Furthermore, a three-dimensionally rendered image of a cytoskeleton cell featuring ~25 nm microtubules is improved, with other microtubules at a distance near the lateral resolution of 168 nm also able to be distinguished.

Broadband full-color monolithic InGaN light-emitting diodes by self-assembled InGaN quantum dots

PubMed Central

Li, Hongjian; Li, Panpan; Kang, Junjie; Ding, Jiianfeng; Ma, Jun; Zhang, Yiyun; Yi, Xiaoyan; Wang, Guohong

2016-01-01

We have presented broadband full-color monolithic InGaN light-emitting diodes (LEDs) by self-assembled InGaN quantum dots (QDs) using metal organic chemical vapor deposition (MOCVD). The electroluminescence spectra of the InGaN QDs LEDs are extremely broad span from 410 nm to 720 nm with a line-width of 164 nm, covering entire visible wavelength range. A color temperature of 3370 K and a color rendering index of 69.3 have been achieved. Temperature-dependent photoluminescence measurements reveal a strong carriers localization effect of the InGaN QDs layer by obvious blue-shift of emission peak from 50 K to 300 K. The broadband luminescence spectrum is believed to be attributed to the injected carriers captured by the different localized states of InGaN QDs with various sizes, shapes and indium compositions, leading to a full visible color emission. The successful realization of our broadband InGaN QDs LEDs provide a convenient and practical method for the fabrication of GaN-based monolithic full-color LEDs in wafer scale. PMID:27734917

Gamma-ray spectroscopy and pulse shape discrimination with a plastic scintillator

NASA Astrophysics Data System (ADS)

van Loef, E.; Markosyan, G.; Shirwadkar, U.; McClish, M.; Shah, K.

2015-07-01

The scintillation properties of a novel plastic scintillator loaded with an organolead compound are presented. Under X-ray and gamma-ray excitation, emission is observed peaking at 435 nm. The scintillation light output is 9000 ph/MeV. An energy resolution (full width at half maximum over the peak position) of about 16% was observed for the 662 keV full absorption peak. Excellent pulse shape discrimination between neutrons and gamma-rays with a Figure of Merit of 2.6 at 1 MeVee was observed.

A 15 W 1152 nm Raman fiber laser with 6 nm spectral width for Ho3+-doped crystal's pumping source

NASA Astrophysics Data System (ADS)

Chen, Xiuyan; Jiang, Huawei

2016-12-01

A 11.5 W 1152 nm Raman fiber laser with 6 nm spectral width was demonstrated based on the resonator constructed with one fiber loop mirror and one fiber Bragg grating. By mans of experimental measurement and theoretical calculation, the reflectivity of the fiber loop mirror was confirmed as 0.93. The Yb3+-doped 1090 nm fiber length was about 5 m. When the maximum pumping power of 976 nm laser was 54.8 W, 32.2 W 1090 nm laser was obtained and the optical to optical conversion efficiency from 1090 nm to 1152 nm light was 48%. Finally, the 1152 nm Raman fiber laser was used for pumping Ho3+:LLF crystal, and the 1194 nm fluorescence emission peak was detected for the first time.

A Si nanocube array polarizer

NASA Astrophysics Data System (ADS)

Chen, Linghua; Jiang, Yingjie; Xing, Li; Yao, Jun

2017-10-01

We have proposed a full dielectric (silicon) nanocube array polarizer based on a silicon dioxide substrate. Each polarization unit column includes a plurality of equal spaced polarization units. By optimizing the length, the width, the height of the polarization units and the center distance of adjacent polarization unit (x direction and y direction), an extinction ratio (ER) of higher than 25dB was obtained theoretically when the incident light wavelength is 1550nm. while for applications of most polarization optical elements, ER above 10dB is enough. With this condition, the polarizer we designed can work in a wide wavelength range from 1509.31nm to 1611.51nm. Compared with the previous polarizer, we have introduced a polarizer which is a full dielectric device, which solves the problems of low efficiency caused by Ohmic loss and weak coupling. Furthermore, compared with the existing optical polarizers, our polarizer has the advantages of thin thickness, small size, light weight, and low processing difficulty, which is in line with the future development trend of optical elements.

Brillouin light scattering investigation of interfacial Dzyaloshinskii–Moriya interaction in ultrathin Co/Pt nanostripe arrays

NASA Astrophysics Data System (ADS)

Bouloussa, H.; Yu, J.; Roussigné, Y.; Belmeguenai, M.; Stashkevitch, A.; Yang, H.; Chérif, S. M.

2018-06-01

Interface Dzyaloshinskii–Moriya interaction (iDMI) is known to induce spinwaves non-reciprocity in ultrathin films. Indeed, Brillouin light scattering has been used to investigate how the lateral size reduction can affect the iDMI constant in Pt (6 nm)/Co (3 nm) based-nanostripe arrays. For this, 100 and 300 nm-width nanostripes have been fabricated using e-beam lithography and ion etching, and their behaviour has then been compared to the reference continuous film. The experimental data showed that the measured iDMI induced non-reciprocity is slightly different for the 100 nm-width nanostripes with respect to the other samples. This suggests that the width of the nanostripes can influence the strength of the apparent iDMI if this dimension is comparable to the spin waves attenuation length propagating within the nanostripes. Indeed, in contrast to the other samples, the linear frequency difference (non-reciprocity) behaviour versus wavenumber for the 100 nm-width nanostripes has been analysed and discussed through two approaches: either a different iDMI constant or an iDMI constant similar to one of the continuous films with a non-zero intercept for a zero wavenumber.

Studies on nanosecond 532nm and 355nm and ultrafast 515nm and 532nm laser cutting super-hard materials

NASA Astrophysics Data System (ADS)

Zhang, Jie; Tao, Sha; Wang, Brian; Zhao, Jay

2017-02-01

In this paper, micro-processing of three kinds of super-hard materials of poly-crystal diamond (PCD)/tungsten-carbide (WC), CVD-diamond and cubic boron nitride (CNB) has been systematically studied using nanosecond laser (532nm and 355nm), and ultrafast laser (532nm and 515nm). Our purpose is to investigate a full laser micro-cutting solution to achieve a ready-to-use cutting tool insert (CTI). The results show a clean cut with little burns and recasting at edge. The cutting speed of 2-10mm/min depending on thickness was obtained. The laser ablation process was also studied by varying laser parameters (wavelength, pulse width, pulse energy, repetition rate) and tool path to improve cutting speed. Also, studies on material removal efficiency (MRE) of PCD/WC with 355nm-ns and 515nm-fs laser as a function of laser fluence show that 355nm-ns laser is able to achieve higher MRE for PCD and WC. Thus, ultrafast laser is not necessarily used for superhard material cutting. Instead, post-polishing with ultrafast laser can be used to clean cutting surface and improve smoothness.

Efficient broad color luminescence from InGaN/GaN single quantum-well nanocolumn crystals on Si (111) substrate

NASA Astrophysics Data System (ADS)

Zhang, Wei; Zhang, Xuehua; Wang, Yongjin; Hu, Fangren

2017-10-01

Nanocolumn InGaN/GaN single quantum well crystals were deposited on Si (111) substrate with nitrified Ga dots as buffer layer. Transmission electron microscopy image shows the crystals' diameter of 100-130 nm and length of about 900 nm. Nanoscale spatial phase separation of cubic and hexagonal GaN was observed by selective area electron diffraction on the quantum well layer. Raman spectrum of the quantum well crystals proved that the crystals were fully relaxed. Room temperature photoluminescence from 450 to 750 nm and full width at half maximum of about 420 meV indicate broad color luminescence covering blue, green, yellow and red emission, which is helpful for the fabrication of tunable optoelectronic devices and colorful light emitting diodes.

Optical notch filter with tunable bandwidth based on guided-mode resonant polarization-sensitive spectral feature.

PubMed

Qian, Linyong; Zhang, Dawei; Dai, Bo; Wang, Qi; Huang, Yuanshen; Zhuang, Songlin

2015-07-13

A novel bandwidth-tunable notch filter is proposed based on the guided-mode resonance effect. The notch is created due to the superposition spectra response of two guided-mode resonant filters. The compact, bandwidth tuning capability is realized by taking advantage the effect of spectra-to-polarization sensitivity in one-dimensional classical guided-mode resonance filter, and using a liquid crystal polarization rotator for precise and simple polarization control. The operation principle and the design of the device are presented, and we demonstrate it experimentally. The central wavelength is fixed at 766.4 nm with a relatively symmetric profile. The full width at half maximum bandwidth could be tuned from 8.6 nm to 18.2 nm by controlling the applied voltage in electrically-driving polarization rotator.

Fabrication and characterization of microcavity lasers in rhodamine B doped SU8 using high energy proton beam

NASA Astrophysics Data System (ADS)

Venugopal Rao, S.; Bettiol, A. A.; Vishnubhatla, K. C.; Bhaktha, S. N. B.; Narayana Rao, D.; Watt, F.

2007-03-01

The authors present their results on the characterization of individual dye-doped microcavity polymer lasers fabricated using a high energy proton beam. The lasers were fabricated in rhodamine B doped SU8 resist with a single exposure step followed by chemical processing. The resulting trapezoidal shaped cavities had dimensions of ˜250×250μm2. Physical characterization of these structures was performed using a scanning electron microscope while the optical characterization was carried out by recording the emission subsequent to pumping the lasers with 532nm, 6 nanosecond pulses. The authors observed intense, narrow emission near 624nm with the best emission linewidth full width at half maximum of ˜9nm and a threshold ˜150μJ/mm2.

Highly selective and compact tunable MOEMS photonic crystal Fabry-Perot filter.

PubMed

Boutami, S; Ben Bakir, B; Leclercq, J-L; Letartre, X; Rojo-Romeo, P; Garrigues, M; Viktorovitch, P; Sagnes, I; Legratiet, L; Strassner, M

2006-04-17

The authors report a compact and highly selective tunable filter using a Fabry-Perot resonator combining a bottom micromachined 3-pair-InP/air-gap Bragg reflector with a top photonic crystal slab mirror. It is based on the coupling between radiated vertical cavity modes and waveguided modes of the photonic crystal. The full-width at half maximum (FWHM) of the resonance, as measured by microreflectivity experiments, is close to 1.5nm (around 1.55 microm). The presence of the photonic crystal slab mirror results in a very compact resonator, with a limited number of layers. The demonstrator was tuned over a 20nm range for a 4V tuning voltage, the FWHM being kept below 2.5nm. Bending of membranes is a critical issue, and better results (FWHM=0.5nm) should be obtained on the same structure if this technological point is fixed.

Nonlinear structured-illumination enhanced temporal focusing multiphoton excitation microscopy with a digital micromirror device

PubMed Central

Cheng, Li-Chung; Lien, Chi-Hsiang; Da Sie, Yong; Hu, Yvonne Yuling; Lin, Chun-Yu; Chien, Fan-Ching; Xu, Chris; Dong, Chen Yuan; Chen, Shean-Jen

2014-01-01

In this study, the light diffraction of temporal focusing multiphoton excitation microscopy (TFMPEM) and the excitation patterning of nonlinear structured-illumination microscopy (NSIM) can be simultaneously and accurately implemented via a single high-resolution digital micromirror device. The lateral and axial spatial resolutions of the TFMPEM are remarkably improved through the second-order NSIM and projected structured light, respectively. The experimental results demonstrate that the lateral and axial resolutions are enhanced from 397 nm to 168 nm (2.4-fold) and from 2.33 μm to 1.22 μm (1.9-fold), respectively, in full width at the half maximum. Furthermore, a three-dimensionally rendered image of a cytoskeleton cell featuring ~25 nm microtubules is improved, with other microtubules at a distance near the lateral resolution of 168 nm also able to be distinguished. PMID:25136483

Broadband infrared luminescence from Li2O-Al2O3-ZnO-SiO2 glasses doped with Bi2O3.

PubMed

Peng, Mingying; Qiu, Jianrong; Chen, Danping; Meng, Xiangeng; Zhu, Congshan

2005-09-05

The broadband emission in the 1.2~1.6mum region from Li2O-Al2O3-ZnO-SiO2 ( LAZS ) glass codoped with 0.01mol.%Cr2O3 and 1.0mol.%Bi2O3 when pumped by the 808nm laser at room temperature is not initiated from Cr4+ ions, but from bismuth, which is remarkably different from the results reported by Batchelor et al. The broad ~1300nm emission from Bi2O3-containing LAZS glasses possesses a FWHM ( Full Width at Half Maximum ) more than 250nm and a fluorescent lifetime longer than 500mus when excited by the 808nm laser. These glasses might have the potential applications in the broadly tunable lasers and the broadband fiber amplifiers.

Line width measurement below 60 nm using an optical interferometer and artificial neural network

NASA Astrophysics Data System (ADS)

See, Chung W.; Smith, Richard J.; Somekh, Michael G.; Yacoot, Andrew

2007-03-01

We have recently described a technique for optical line-width measurements. The system currently is capable of measuring line-width down to 60 nm with a precision of 2 nm, and potentially should be able to measure down to 10nm. The system consists of an ultra-stable interferometer and artificial neural networks (ANNs). The former is used to generate optical profiles which are input to the ANNs. The outputs of the ANNs are the desired sample parameters. Different types of samples have been tested with equally impressive results. In this paper we will discuss the factors that are essential to extend the application of the technique. Two of the factors are signal conditioning and sample classification. Methods, including principal component analysis, that are capable of performing these tasks will be considered.

Development of stable, narrow spectral line-width, fiber delivered laser source for spin exchange optical pumping

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, Bo; Tong, Xin; Jiang, Chenyang

2015-06-05

In this study, we developed a stable, narrow spectral line-width, fiber delivered laser source for spin exchange optical pumping. An optimized external cavity equipped with an off-the-shelf volume holographic grating narrowed the spectral line-width of a 100 W high-power diode laser and stabilized the laser spectrum. The laser spectrum showed a high side mode suppression ratio of >30 dB and good long-term stability (center wavelength drifting within ±0.002 nm during 220 h of operation). Finally, our laser is delivered by a multimode fiber with power ~70 W, center wavelength of 794.77 nm, and spectral bandwidth of ~0.12 nm.

Sub-5 nm, globally aligned graphene nanoribbons on Ge(001)

DOE PAGES

Kiraly, Brian; Mannix, Andrew J.; Jacobberger, Robert M.; ...

2016-05-23

Graphene nanoribbons (GNRs) hold great promise for future electronics because of their edge and width dependent electronic bandgaps and exceptional transport properties. While significant progress toward such devices has been made, the field has been limited by difficulties achieving narrow widths, global alignment, and atomically pristine GNR edges on technologically relevant substrates. A recent advance has challenged these limits by using Ge(001) substrates to direct the bottom-up growth of GNRs with nearly pristine armchair edges and widths near ~10 nm via atmospheric pressure chemical vapor deposition. In this work, we extend the growth of GNRs on Ge(001) to ultra-high vacuummore » conditions and realize GNRs narrower than 5 nm. Armchair graphene nanoribbons directed along the Ge <110> surface directions are achieved with excellent width control and relatively large bandgaps. As a result, the bandgap magnitude and electronic uniformity make these new materials excellent candidates for future developments in nanoelectronics.« less

Hyperspectral Analysis of Soil Nitrogen, Carbon, Carbonate, and Organic Matter Using Regression Trees

PubMed Central

Gmur, Stephan; Vogt, Daniel; Zabowski, Darlene; Moskal, L. Monika

2012-01-01

The characterization of soil attributes using hyperspectral sensors has revealed patterns in soil spectra that are known to respond to mineral composition, organic matter, soil moisture and particle size distribution. Soil samples from different soil horizons of replicated soil series from sites located within Washington and Oregon were analyzed with the FieldSpec Spectroradiometer to measure their spectral signatures across the electromagnetic range of 400 to 1,000 nm. Similarity rankings of individual soil samples reveal differences between replicate series as well as samples within the same replicate series. Using classification and regression tree statistical methods, regression trees were fitted to each spectral response using concentrations of nitrogen, carbon, carbonate and organic matter as the response variables. Statistics resulting from fitted trees were: nitrogen R2 0.91 (p < 0.01) at 403, 470, 687, and 846 nm spectral band widths, carbonate R2 0.95 (p < 0.01) at 531 and 898 nm band widths, total carbon R2 0.93 (p < 0.01) at 400, 409, 441 and 907 nm band widths, and organic matter R2 0.98 (p < 0.01) at 300, 400, 441, 832 and 907 nm band widths. Use of the 400 to 1,000 nm electromagnetic range utilizing regression trees provided a powerful, rapid and inexpensive method for assessing nitrogen, carbon, carbonate and organic matter for upper soil horizons in a nondestructive method. PMID:23112620

Magnetic Nature of Light Transmission through a 5-nm Gap.

PubMed

Yang, Hyosim; Kim, Dai-Sik; Kim, Richard H Joon-Yeon; Ahn, Jae Sung; Kang, Taehee; Jeong, Jeeyoon; Lee, Dukhyung

2018-02-09

Slot antennas have been exploited as important building blocks of optical magnetism because their radiations are invoked by the magnetic fields along the axes, as vectorial Babinet principle predicts. However, optical magnetism of a few-nanometer-width slit, for which fascinating applications are found due to the colossal field enhancement but Babinet principle fails due to the nonnegligible thickness, has not been investigated. In this paper, we demonstrated that the magnetic field plays a dominant role in light transmission through a 5-nm slit on a 150-nm-thick gold film. The 5-nm slit was fabricated by atomic layer lithography, and the transmission was investigated for various incident angles by experiment and simulation at 785-nm wavelength. We found that, due to the deep subwavelength gap width, the transmission has the same incident angle dependence as the tangential magnetic field on the metal surface and this magnetic nature of a nanogap holds up to ~100-nm width. Our analysis establishes conditions for nanogap optical magnetism and suggests new possibilities in realizing magnetic-field-driven optical nonlinearities.

Effects of ultra-thin Si-fin body widths upon SOI PMOS FinFETs

NASA Astrophysics Data System (ADS)

Liaw, Yue-Gie; Chen, Chii-Wen; Liao, Wen-Shiang; Wang, Mu-Chun; Zou, Xuecheng

2018-05-01

Nano-node tri-gate FinFET devices have been developed after integrating a 14 Å nitrided gate oxide upon the silicon-on-insulator (SOI) wafers established on an advanced CMOS logic platform. These vertical double gate (FinFET) devices with ultra-thin silicon fin (Si-fin) widths ranging from 27 nm to 17 nm and gate length down to 30 nm have been successfully developed with a 193 nm scanner lithography tool. Combining the cobalt fully silicidation and the CESL strain technology beneficial for PMOS FinFETs was incorporated into this work. Detailed analyses of Id-Vg characteristics, threshold voltage (Vt), and drain-induced barrier lowering (DIBL) illustrate that the thinnest 17 nm Si-fin width FinFET exhibits the best gate controllability due to its better suppression of short channel effect (SCE). However, higher source/drain resistance (RSD), channel mobility degradation due to dry etch steps, or “current crowding effect” will slightly limit its transconductance (Gm) and drive current.

Neoplasms treatment by diode laser with and without real time temperature control on operation zone

NASA Astrophysics Data System (ADS)

Belikov, Andrey V.; Gelfond, Mark L.; Shatilova, Ksenia V.; Sosenkova, Svetlana A.; Lazareva, Anastasia A.; Semyashkina, Yulia V.

2016-04-01

Results of nevus, papilloma, dermatofibroma, and basal cell skin cancer in vivo removal by a 980+/-10 nm diode laser with "blackened" tip operating in continuous (CW) mode and automatic power control (APC) mode are presented. The collateral damage width and width of graze wound area around the collateral damage area were demonstrated. The total damage area width was calculated as sum of collateral damage width and graze wound area width. The mean width of total damage area reached 1.538+/-0.254 mm for patient group with nevus removing by 980 nm diode laser operating in CW mode, papilloma - 0.586+/-0.453 mm, dermatofibroma - 1.568+/-0.437 mm, and basal cell skin cancer - 1.603+/-0.613 mm. The mean width of total damage area reached 1.201+/-0.292 mm for patient group with nevus removing by 980 nm diode laser operating in APC mode, papilloma - 0.413+/-0.418 mm, dermatofibroma - 1.240+/-0.546 mm, and basal cell skin cancer - 1.204+/-0.517 mm. It was found that using APC mode decreases the total damage area width at removing of these nosological neoplasms of human skin, and decreases the width of graze wound area at removing of nevus and basal cell skin cancer. At the first time, the dynamic of output laser power and thermal signal during laser removal of nevus in CW and APC mode is presented. It was determined that output laser power during nevus removal for APC mode was 1.6+/-0.05 W and for CW mode - 14.0+/-0.1 W. This difference can explain the decrease of the total damage area width and width of graze wound area for APC mode in comparison with CW mode.

Identification of endogenous flurophores in the layered retina

NASA Astrophysics Data System (ADS)

Xu, Gaixia; Chen, Danni; Sun, Yiwen; Qu, Junle; Lin, Ziyang; Ding, Zhihua; Niu, Hanben

2007-05-01

In this paper, we measured and analyzed the characteristic of endogenous fluorophores in porcine layered retina by using advanced fluorescence spectroscopy and microscopy imaging technology. It was found that there were obvious contrasts corresponding to the different layers of retina, which may be important for fundus disease diagnosis. The retinal pigment epithelium cells exhibited strong autofluorescence with as emission peak of 600+/-10nm when excited with 860-nm light. The emission peak of photoreceptors was at 652+/-5nm, and the emission peak of retinal vessels layer was weak and at 640~700nm, when excited with 488-nm light. Autofluorescence images of three layers of retina were obtained using the same setup. We concluded that the main endogenous fluorophore in PRE was lipofuscin and that in retinal vessels was porphyrin. What's more, the FMHW (full width at half. maximum) of retinal fluorescence spectrum was broad, which suggested that there wasn't only one endogenous fluorophores of tissues excited.

High-power single-stage thulium-doped superfluorescent fiber source

NASA Astrophysics Data System (ADS)

Hu, Z. Y.; Yan, P.; Liu, Q.; Ji, E. C.; Xiao, Q. R.; Gong, M. L.

2015-01-01

In this paper, we report a high-power thulium (Tm)-doped superfluorescent fiber source (SFS) in the 2-μm spectral region. The SFS is based on double angle-cleaved facet operation and uses a simple single-stage geometry. The copropagating amplified spontaneous emission (ASE) yields a maximum output of 20.7 W at a center wavelength of 1,960.7 nm, with a full width at half maximum (FWHM) of ~45 nm. The counterpropagating ASE yields a maximum output of 25.2 W at a center wavelength of 1,948.2 nm, with a FWHM of ~50 nm. The maximum combined output of the SFS is as much as 45.9 W, which corresponds to a slope efficiency of 38.9 %. In addition, a model of the ~2 μm SFS in Tm-doped silica fibers pumped at ~790 nm is developed, and the influence of fiber length and end-facet reflectivity on the ASE output performance and the parasitic lasing threshold are studied numerically.

Advances in 7xx-nm fiber-coupled modules with application to Tm fiber laser pumping and DPAL (Conference Presentation)

NASA Astrophysics Data System (ADS)

Patterson, Steven G.; Guiney, Tina; Stapleton, Dean; Braker, Joseph; Alegria, Kim; Irwin, David A.; Ebert, Christopher

2017-02-01

DILAS has leveraged its industry-leading work in manufacturing low SWaP fiber-coupled modules extending the wavelength range to 793nm for Tm fiber laser pumping. Ideal for medical, industrial and military applications, modules spanning from single emitter-based 9W to TBar-based 200W of 793nm pump power will be discussed. The highlight is a lightweight module capable of <200W of 793nm pump power out of a package weighing < 400 grams. In addition, other modules spanning from single emitter-based 9W to TBar-based 200W of 793nm pump power will be presented. In addition, advances in DPAL modules, emitting at the technologically important wavelengths near 766nm and 780nm, will be detailed. Highlights include a fully microprocessor controlled fiber-coupled module that produces greater than 400W from a 600 micron core fiber and a line width of only 56.3pm. The micro-processor permits the automated center wavelength and line width tuning of the output over a range of output powers while retaining excellent line center and line width stability over time.

The ammonia absorption behavior on Jupiter during 2005-2015

NASA Astrophysics Data System (ADS)

Tejfel, Victor G.; V.G.Tejfel, V.D.Vdovichenko, A.M.Karimov, P.G.Lysenko, , G.A.Kirienko, , V.A.Filippov, G.A.Kharitonova, A.S. Khozhenetz

2017-10-01

V.G.Tejfel, V.D.Vdovichenko, A.M.Karimov, P.G.Lysenko, , G.A.Kirienko, , V.A.Filippov, G.A.Kharitonova, A.S. KhozhenetzFessenkov Astrophysical Institute, Almaty, KazakhstanWe measured the intensity of the 645 and 787 nm NH3 absorption bands in five latitudinal belts of Jupiter (STrZ, SEB, EZ, NEB and NTrZ) during almost full period of its revolution around the Sun: from 2005 to 2015. The variations in the equivalent widths of the bands were investigated. The permanently lowered intensity of the 787 nm NH3 band in NEB is confirmed. There are also some systematic differences in latitudinal and temporal variations between the 645 and 787 nm ammonia bands. The equivalent width of the 787 nm NH3 band was averaged for all years of observations. Its maximum (W = 18.95 ± 0.75 A) corresponds to EZ, its minimum (W = 15.82 ± 0.68 A) corresponds to NEB. The 645 nm NH3 band shows the maximum in SEB (W = 6.78 ± 0.45 A), and the minimum in NTrZ (W = 5.38 ± 0.36 A). The weakened ammonia absorption is also observed in the Great Red Spot. However, this is due to the increased density of the clouds inside the Spot storm, but not to decreased gaseous ammonia abundance, in contrast to NEB. The brightness temperature of GRS in the infrared and millimeter ranges of thermal radiation is lower, in contrast to NEB, where an increased brightness temperature is observed. The enhanced cloud density may explain also a pretty high brightness of GRS observed in strong methane absorption bands such as the 887 nm CH4 band and more long waved ones.

Fine pattern replication on 10 x 10-mm exposure area using ETS-1 laboratory tool in HIT

NASA Astrophysics Data System (ADS)

Hamamoto, K.; Watanabe, Takeo; Hada, Hideo; Komano, Hiroshi; Kishimura, Shinji; Okazaki, Shinji; Kinoshita, Hiroo

2002-07-01

Utilizing ETS-1 laboratory tool in Himeji Institute of Technology (HIT), as for the fine pattern replicated by using the Cr mask in static exposure, it is replicated in the exposure area of 10 mm by 2 mm in size that the line and space pattern width of 60 nm, the isolated line pattern width of 40 nm, and hole pattern width of 150 nm. According to the synchronous scanning of the mass and wafer with EUVL laboratory tool with reduction optical system which consisted of three-aspherical-mirror in the NewSUBARU facilities succeeded in the line of 60 nm and the space pattern formation in the exposure region of 10mm by 10mm. From the result of exposure characteristics for positive- tone resist for KrF and EB, KrF chemically amplified resist has better characteristics than EB chemically amplified resist.

Narrow bandpass steep edge optical filter for the JAST/T80 telescope instrumentation

NASA Astrophysics Data System (ADS)

Reichel, S.; Brauneck, U.; Bourquin, S.; Marín-Franch, A.

2013-09-01

The Observatorio Astrofisico de Javalambre in Spain observes with its JAST/T80 telescope galaxies in the Local Universe in a systematic study. This is accomplished with a multi-band photometric all sky survey called Javalambre Photometric Local Universe Survey (J-PLUS). A wide field camera receives the signals from universe via optical filters. In this presentation the development and design of a narrow bandpass steep edge filter with wide suppression will be shown. The filter has a full width half maximum in the range of 13-15 nm (with <1 nm tolerance) with central wavelengths in the range 350-860nm and an average transmission larger than 90% in the passband. Signals beyond the passband (blocking range) have to be suppressed down to 250nm and up to 1050nm (spectral regime), where a blocking of OD 5 (transmission < 10-5) is required. The edges have to be steep for a small transition width from 5% to 80%. The spectral requirements result in a large number of layers which are deposited with magnetron sputtering. The transmitted wavefront error of the optical filter must be less than lambda/2 over the 100mm aperture and the central wavelength uniformity must be better than +/- 0.4% over the clear aperture. The filter consists of optical filter glass and a coated substrate in order to reach the spectral requirements. The substrate is coated with more than 120 layers. The total filter thickness was specified to be 8.0mm. Results of steep edge narrow bandpass filters will be demonstrated fulfilling all these demanding requirements.

Full-field x-ray nano-imaging at SSRF

NASA Astrophysics Data System (ADS)

Deng, Biao; Ren, Yuqi; Wang, Yudan; Du, Guohao; Xie, Honglan; Xiao, Tiqiao

2013-09-01

Full field X-ray nano-imaging focusing on material science is under developing at SSRF. A dedicated full field X-ray nano-imaging beamline based on bending magnet will be built in the SSRF phase-II project. The beamline aims at the 3D imaging of the nano-scale inner structures. The photon energy range is of 5-14keV. The design goals with the field of view (FOV) of 20μm and a spatial resolution of 20nm are proposed at 8 keV, taking a Fresnel zone plate (FZP) with outermost zone width of 25 nm. Futhermore, an X-ray nano-imaging microscope is under developing at the SSRF BL13W beamline, in which a larger FOV will be emphasized. This microscope is based on a beam shaper and a zone plate using both absorption contrast and Zernike phase contrast, with the optimized energy set to 10keV. The detailed design and the progress of the project will be introduced.

Inactivation of Viruses by Coherent Excitations with a Low Power Visible Femtosecond Laser

DTIC Science & Technology

2007-06-05

visible femtosecond laser having a wavelength of 425 nm and a pulse width of 100 fs, we show that M13 phages were inactivated when the laser power density...was greater than or equal to 50 MW/cm2. The inactivation of M13 phages was determined by plaque counts and had been found to depend on the pulse width...visible femtosecond laser having a wavelength of 425 nm and a pulse width of 100 fs, we show that M13 phages were inactivated when the laser power

Lateral Tip Control Effects in CD-AFM Metrology: The Large Tip Limit.

PubMed

Dixson, Ronald G; Orji, Ndubuisi G; Goldband, Ryan S

2016-01-25

Sidewall sensing in critical dimension atomic force microscopes (CD-AFMs) usually involves continuous lateral dithering of the tip or the use of a control algorithm and fast response piezo actuator to position the tip in a manner that resembles touch-triggering of coordinate measuring machine (CMM) probes. All methods of tip position control, however, induce an effective tip width that may deviate from the actual geometrical tip width. Understanding the influence and dependence of the effective tip width on the dither settings and lateral stiffness of the tip can improve the measurement accuracy and uncertainty estimation for CD-AFM measurements. Since CD-AFM typically uses tips that range from 15 nm to 850 nm in geometrical width, the behavior of effective tip width throughout this range should be understood. The National Institute of Standards and Technology (NIST) has been investigating the dependence of effective tip width on the dither settings and lateral stiffness of the tip, as well as the possibility of material effects due to sample composition. For tip widths of 130 nm and lower, which also have lower lateral stiffness, the response of the effective tip width to lateral dither is greater than for larger tips. However, we have concluded that these effects will not generally result in a residual bias, provided that the tip calibration and sample measurement are performed under the same conditions. To validate that our prior conclusions about the dependence of effective tip width on lateral stiffness are valid for large CD-tips, we recently performed experiments using a very large non-CD tip with an etched plateau of approximately 2 μm width. The effective lateral stiffness of these tips is at least 20 times greater than typical CD-AFM tips, and these results supported our prior conclusions about the expected behavior for larger tips. The bottom-line importance of these latest observations is that we can now reasonably conclude that a dither slope of 3 nm/V is the baseline response due to the induced motion of the cantilever base.

Lateral Tip Control Effects in CD-AFM Metrology: The Large Tip Limit

PubMed Central

Dixson, Ronald G.; Orji, Ndubuisi G.; Goldband, Ryan S.

2016-01-01

Sidewall sensing in critical dimension atomic force microscopes (CD-AFMs) usually involves continuous lateral dithering of the tip or the use of a control algorithm and fast response piezo actuator to position the tip in a manner that resembles touch-triggering of coordinate measuring machine (CMM) probes. All methods of tip position control, however, induce an effective tip width that may deviate from the actual geometrical tip width. Understanding the influence and dependence of the effective tip width on the dither settings and lateral stiffness of the tip can improve the measurement accuracy and uncertainty estimation for CD-AFM measurements. Since CD-AFM typically uses tips that range from 15 nm to 850 nm in geometrical width, the behavior of effective tip width throughout this range should be understood. The National Institute of Standards and Technology (NIST) has been investigating the dependence of effective tip width on the dither settings and lateral stiffness of the tip, as well as the possibility of material effects due to sample composition. For tip widths of 130 nm and lower, which also have lower lateral stiffness, the response of the effective tip width to lateral dither is greater than for larger tips. However, we have concluded that these effects will not generally result in a residual bias, provided that the tip calibration and sample measurement are performed under the same conditions. To validate that our prior conclusions about the dependence of effective tip width on lateral stiffness are valid for large CD-tips, we recently performed experiments using a very large non-CD tip with an etched plateau of approximately 2 μm width. The effective lateral stiffness of these tips is at least 20 times greater than typical CD-AFM tips, and these results supported our prior conclusions about the expected behavior for larger tips. The bottom-line importance of these latest observations is that we can now reasonably conclude that a dither slope of 3 nm/V is the baseline response due to the induced motion of the cantilever base. PMID:27087883

LASER APPLICATIONS AND OTHER TOPICS IN QUANTUM ELECTRONICS: Study of emission of a volume nanosecond discharge plasma in xenon, krypton and argon at high pressures

NASA Astrophysics Data System (ADS)

Baksht, E. Kh; Lomaev, Mikhail I.; Rybka, D. V.; Tarasenko, Viktor F.

2006-06-01

The emission properties of a volume nanosecond discharge plasma produced in xenon, krypton and argon at high pressures in a discharge gap with a cathode having a small radius of curvature are studied. Spectra in the range 120-850 nm and amplitude—time characteristics of xenon emission at different regimes and excitation techniques are recorded and analysed. It is shown that upon excitation of the volume discharge initiated by a beam of avalanche electrons, at least 90% of the energy in the spectral range 120-850 nm is emitted by xenon dimers. For xenon at a pressure of 1.2 atm, ~45 mJ of the spontaneous emission energy was obtained in the full solid angle in a pulse with the full width at half-maximum ~130 ns.

Balloon and surface UV radiation measurements with the NILU-CUBE instrument

NASA Astrophysics Data System (ADS)

Kylling, A.; Danielsen, T.; Webb, A.; Blumthaler, M.; Schreder, J.

2003-04-01

The NILU-CUBE instrument measures the irradiance on the six faces of a cube. On each face the radiation is measured at 312~nm and 340~nm with a bandwidth of approximately 10~nm at full width half maximum. The instrument is designed to be flown as part of balloon payloads. It may also readily be operated on the ground. The instrument and its characteristics are presented and the calibration procedure outlined. Photodissociation rates derived from measurements made during a twilight stratospheric balloon flight from Gap-Tallard, France, are presented. From two hot-air balloon flights over East-Anglia, England, measurements by the instrument were used to derive the surface albedo. Finally, surface measurements are used to describe the incoming irradiance on vertical and horizontal surfaces. All measurements are compared with model simulations.

Solvent-Controlled Synthesis of Highly Luminescent Carbon Dots with a Wide Color Gamut and Narrowed Emission Peak Widths.

PubMed

Ding, Hui; Wei, Ji-Shi; Zhang, Peng; Zhou, Zi-Yuan; Gao, Qing-Yu; Xiong, Huan-Ming

2018-05-01

Carbon dots (CDs) have tremendous potential applications in bioimaging, biomedicine, and optoelectronics. By far, it is still difficult to produce photoluminescence (PL) tunable CDs with high quantum yield (QY) across the entire visible spectrum and narrow the emission peak widths of CDs close to those of typical quantum dots. In this work, a series of CDs with tunable emission from 443 to 745 nm, quantum yield within 13-54%, and narrowed full width at half maximum (FWHM) from 108 to 55 nm, are obtained by only adjusting the reaction solvents in a one-pot solvothermal route. The distinct optical features of these CDs are based on their differences in the particle size, and the content of graphitic nitrogen and oxygen-containing functional groups, which can be modulated by controlling the dehydration and carbonization processes during solvothermal reactions. Blue, green, yellow, red, and even pure white light emitting films (Commission Internationale de L'Eclairage (CIE)= 0.33, 0.33, QY = 39%) are prepared by dispersing one or three kinds of CDs into polyvinyl alcohol with appropriate ratios. The near-infrared emissive CDs are excellent fluorescent probes for both in vitro and in vivo bioimaging because of their high QY in water, long-term stability, and low cytotoxicity. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

CD-measurement technique for hole patterns on stencil mask

NASA Astrophysics Data System (ADS)

Ishikawa, Mikio; Yusa, Satoshi; Takikawa, Tadahiko; Fujita, Hiroshi; Sano, Hisatake; Hoga, Morihisa; Hayashi, Naoya

2004-12-01

EB lithography has a potential to successfully form hole patterns as small as 80 nm with a stencil mask. In a previous paper we proposed a technique using a HOLON dual-mode critical dimension (CD) SEM ESPA-75S in the transmission mode for CD measurement of line-and-space patterns on a stencil mask. In this paper we extend our effort of developing a CD measurement technique to contact hole features and determine it in comparison of measured values between features on mask and those printed on wafer. We have evaluated the width method and the area methods using designed 80-500 nm wide contact hole patterns on a large area membrane mask and their resist images on wafer printed by a LEEPL3000. We find that 1) the width method and the area methods show an excellent mask-wafer correlation for holes over 110 nm, and 2) the area methods show a better mask-wafer correlation than the width method does for holes below 110 nm. We conclude that the area calculated from the transmission SEM image is more suitable in defining the hole dimensions than the width for contact holes on a stencil mask.

Recent progress of hard x-ray imaging microscopy and microtomography at BL37XU of SPring-8

DOE Office of Scientific and Technical Information (OSTI.GOV)

Suzuki, Yoshio, E-mail: yoshio@spring8.or.jp; Takeuchi, Akihisa; Terada, Yasuko

2016-01-28

A hard x-ray imaging microscopy and microtomography system is now being developed at the beamline 37XU of SPring-8. In the latest improvement, a spatial resolution of about 50 nm is achieved in two-dimensional imaging at 6 keV x-ray energy using a Fresnel zone plate objective with an outermost zone width of 35 nm. In the tomographic measurement, a spatial resolution of about 100 nm is achieved at 8 keV using an x-ray guide tube condenser optic and a Fresnel zone plate objective with an outermost zone width of 50 nm.

Fabrication of controllably variable sub-100  nm gaps in silver nanowires by photothermal-induced stress.

PubMed

Ghosh, Pintu; Lu, Jinsheng; Luo, Hao; Xu, Ziquan; Yan, Xiaoyuan; Wang, Yewu; Lu, Jun; Qiu, Min; Li, Qiang

2018-05-15

A technique to fabricate nanogaps with controllably variable gap width in silver (Ag) nanowires (NWs) by photothermal-induced stress utilizing a focused continuous-wave laser (532 nm) is presented. For the case of an Ag NW on gold thin film, a gap width starting from ∼20  nm is achieved with a critical minimum power (CMP) of about 160 mW, whereas in the case of an Ag NW placed on top of a zinc oxide NW, the attained gap width is as small as a few nm (<10  nm) with a CMP of only ∼100  mW. In both cases, the CMP is much lower as compared to the required CMP (∼280  mW) for an Ag NW placed on a bare silica substrate. The photothermal-induced stress combined with Rayleigh instability, melting, and sublimation of Ag aids in breaking the Ag NW. In particular, the former one plays a key role in attaining an extremely narrow gap. This technique to fabricate sub-100 nm nanogaps in metal NWs can be extensively implemented in fabrication and maintenance of nanomechanical, nanoplasmonic, and nanoelectronic devices.

Narrow line width dual wavelength semiconductor optical amplifier based random fiber laser

NASA Astrophysics Data System (ADS)

Shawki, Heba A.; Kotb, Hussein E.; Khalil, Diaa

2018-02-01

A novel narrow line-width Single longitudinal mode (SLM) dual wavelength random fiber laser of 20 nm separation between wavelengths of 1530 and 1550 nm is presented. The laser is based on Rayleigh backscattering in a standard single mode fiber of 2 Km length as distributed mirrors, and a semiconductor optical amplifier (SOA) as the optical amplification medium. Two optical bandpass filters are used for the two wavelengths selectivity, and two Faraday Rotator mirrors are used to stabilize the two lasing wavelengths against fiber random birefringence. The optical signal to noise ratio (OSNR) was measured to be 38 dB. The line-width of the laser was measured to be 13.3 and 14 KHz at 1530 and 1550 nm respectively, at SOA pump current of 370 mA.

Acoustoelectric photoresponse of graphene nanoribbons

NASA Astrophysics Data System (ADS)

Poole, T.; Nash, G. R.

2018-04-01

The acoustoelectric current in graphene nanoribbons, with widths ranging between 350 nm and 600 nm, has been investigated as a function of illumination. For all nanoribbon widths, the acoustoelectric current was observed to decrease on illumination, in contrast to the increase in acoustoelectric current measured in unpatterned graphene sheet devices. This is thought to be due to the higher initial conductivities of the nanoribbons compared to unpatterned devices.

Growth and optical properties of Co,Nd:LaMgAl11O19

NASA Astrophysics Data System (ADS)

Xu, Peng; Xia, Changtai; Di, Juqing; Xu, Xiaodong; Sai, Qinglin; Wang, Lulu

2012-12-01

Nd,Co:LaMgAl11O19 (abbreviated as Co,Nd:LMA) was grown using the Czochralski method. The structure, polarized absorption spectrum, fluorescence spectrum, and fluorescence decay time were analyzed. The as-grown crystal had very wide absorption bands at 794 nm, which can be pumped by GaAs laser diode without temperature stabilization. Two strong emission bands were present at 1056 nm and 1082 nm with full-width at half-maximum (FWHM) of 6 and 8 nm, respectively. The large FWHM is due to the inhomogeneity of the Nd ion sites. The lifetimes of the 4F3/2 manifold of Co,Nd:LMA at room temperature monitored at 905 nm, 1056 nm, and 1344 nm were 292, 288, and 350 μs, respectively, which was caused by the different contribution of the three different sites with D3h and C2v symmetry. The absorption band of Co is from 1.3 μm to 1.6 μm, and Co,Nd:LMA still has a strong emission around the 1.38 μm, indicating that the Co,Nd:LMA can be applied as a potential self-Q-switched material operating at 1.3 μm.

Spin-coated Films of Squarylium Dye J-Aggregates Exhibiting Ultrafast Optical Responses

NASA Astrophysics Data System (ADS)

Tatsuura, Satoshi; Tian, Minquan; Furuki, Makoto; Sato, Yasuhiro; Pu, Lyong Sun; Wada, Osamu

2000-08-01

The formation of J-aggregates of squarylium dye derivatives in spin-coated films is reported. Squarylium dye derivatives with dipropylamino bases are found to spontaneously aggregate in a spin-coated film. Aggregation is promoted when dye molecules are dispersed in a poly(vinyl alcohol) film, and when a spin-coated film of dye molecules is heated in the presence of acid vapor. In particular, J-aggregates formed by exposure to acetic acid vapor show the narrowest spectral width. J-aggregates formed by the acid treatment method are stable at room temperature and the spectral full-width at half maximum of the J-band is 20 nm. Optical response of the acid-treated film is confirmed to exhibit a short relaxation time of bleached absorption of 300 fs.

Characteristics of a broadband dye laser using Pyrromethene and Rhodamine dyes.

PubMed

Tedder, Sarah A; Wheeler, Jeffrey L; Danehy, Paul M

2011-02-20

A broadband dye laser pumped by a frequency-doubled Nd:YAG laser with a full width at half-maximum from 592 to 610 nm was created for the use in a dual-pump broadband coherent anti-Stokes Raman spectroscopy (CARS) system called width increased dual-pump enhanced CARS (WIDECARS). The desired broadband dye laser was generated with a mixture of Pyrromethene dyes as an oscillator gain medium and a spectral selective optic in the oscillator cavity. A mixture of Rhodamine dyes was used in the amplifier dye cell. To create this laser, a study was performed to characterize the spectral behavior of broadband dye lasers created with Rhodamine dyes 590, 610, and 640 and Pyrromethene dyes 597 and 650, as well as mixtures of these dyes.

Passively synchronized Q-switched and mode-locked dual-band Tm3+:ZBLAN fiber lasers using a common graphene saturable absorber

NASA Astrophysics Data System (ADS)

Jia, Chenglai; Shastri, Bhavin J.; Abdukerim, Nurmemet; Rochette, Martin; Prucnal, Paul R.; Saad, Mohammed; Chen, Lawrence R.

2016-11-01

Dual-band fiber lasers are emerging as a promising technology to penetrate new industrial and medical applications from their dual-band properties, in addition to providing compactness and environmental robustness from the waveguide structure. Here, we demonstrate the use of a common graphene saturable absorber and a single gain medium (Tm3+:ZBLAN fiber) to implement (1) a dual-band fiber ring laser with synchronized Q-switched pulses at wavelengths of 1480 nm and 1840 nm, and (2) a dual-band fiber linear laser with synchronized mode-locked pulses at wavelengths of 1480 nm and 1845 nm. Q-switched operation at 1480 nm and 1840 nm is achieved with a synchronized repetition rate from 20 kHz to 40.5 kHz. For synchronous mode-locked operation, pulses with full-width at half maximum durations of 610 fs and 1.68 ps at wavelengths of 1480 nm and 1845 nm, respectively, are obtained at a repetition rate of 12.3 MHz. These dual-band pulsed sources with an ultra-broadband wavelength separation of ~360 nm will add new capabilities in applications including optical sensing, spectroscopy, and communications.

Passively synchronized Q-switched and mode-locked dual-band Tm3+:ZBLAN fiber lasers using a common graphene saturable absorber.

PubMed

Jia, Chenglai; Shastri, Bhavin J; Abdukerim, Nurmemet; Rochette, Martin; Prucnal, Paul R; Saad, Mohammed; Chen, Lawrence R

2016-11-02

Dual-band fiber lasers are emerging as a promising technology to penetrate new industrial and medical applications from their dual-band properties, in addition to providing compactness and environmental robustness from the waveguide structure. Here, we demonstrate the use of a common graphene saturable absorber and a single gain medium (Tm 3+ :ZBLAN fiber) to implement (1) a dual-band fiber ring laser with synchronized Q-switched pulses at wavelengths of 1480 nm and 1840 nm, and (2) a dual-band fiber linear laser with synchronized mode-locked pulses at wavelengths of 1480 nm and 1845 nm. Q-switched operation at 1480 nm and 1840 nm is achieved with a synchronized repetition rate from 20 kHz to 40.5 kHz. For synchronous mode-locked operation, pulses with full-width at half maximum durations of 610 fs and 1.68 ps at wavelengths of 1480 nm and 1845 nm, respectively, are obtained at a repetition rate of 12.3 MHz. These dual-band pulsed sources with an ultra-broadband wavelength separation of ~360 nm will add new capabilities in applications including optical sensing, spectroscopy, and communications.

Studies on 405nm blue-violet diode laser with external grating cavity

NASA Astrophysics Data System (ADS)

Li, Bin; Gao, Jun; Zhao, Jun; Yu, Anlan; Luo, Shiwen; Xiong, Dongsheng; Wang, Xinbing; Zuo, Duluo

2016-03-01

Spectroscopy applications of free-running laser diodes (LD) are greatly restricted as its broad band spectral emission. And the power of a single blue-violet LD is around several hundred milliwatts by far, it is of great importance to obtain stable and narrow line-width laser diodes with high efficiency. In this paper, a high efficiency external cavity diode laser (ECDL) with high output power and narrow band emission at 405 nm is presented. The ECDL is based on a commercially available LD with nominal output power of 110 mW at an injection current of 100 mA. The spectral width of the free-running LD is about 1 nm (FWHM). A reflective holographic grating which is installed on a home-made compact adjustable stage is utilized for optical feedback in Littrow configuration. In this configuration, narrow line-width operation is realized and the effects of grating groove density as well as the groove direction related to the beam polarization on the performances of the ECDL are experimentally investigated. In the case of grating with groove density of 3600 g/mm, the threshold is reduced from 21 mA to 18.3 mA or 15.6 mA and the tuning range is 3.95 nm or 6.01 nm respectively when the grating is orientated in TE or TM polarization. In addition, an output beam with a line-width of 30 pm and output power of 92.7 mW is achieved in TE polarization. With these narrow line-width and high efficiency, the ECDL is capable to serve as a light source for spectroscopy application such as Raman scattering and laser induced fluorescence.

InGaAs/InAlAs single photon avalanche diode for 1550 nm photons.

PubMed

Meng, Xiao; Xie, Shiyu; Zhou, Xinxin; Calandri, Niccolò; Sanzaro, Mirko; Tosi, Alberto; Tan, Chee Hing; Ng, Jo Shien

2016-03-01

A single photon avalanche diode (SPAD) with an InGaAs absorption region, and an InAlAs avalanche region was designed and demonstrated to detect 1550 nm wavelength photons. The characterization included leakage current, dark count rate and single photon detection efficiency as functions of temperature from 210 to 294 K. The SPAD exhibited good temperature stability, with breakdown voltage dependence of approximately 45 mV K(-1). Operating at 210 K and in a gated mode, the SPAD achieved a photon detection probability of 26% at 1550 nm with a dark count rate of 1 × 10(8) Hz. The time response of the SPAD showed decreasing timing jitter (full width at half maximum) with increasing overbias voltage, with 70 ps being the smallest timing jitter measured.

InGaAs/InAlAs single photon avalanche diode for 1550 nm photons

PubMed Central

Xie, Shiyu; Zhou, Xinxin; Calandri, Niccolò; Sanzaro, Mirko; Tosi, Alberto; Tan, Chee Hing; Ng, Jo Shien

2016-01-01

A single photon avalanche diode (SPAD) with an InGaAs absorption region, and an InAlAs avalanche region was designed and demonstrated to detect 1550 nm wavelength photons. The characterization included leakage current, dark count rate and single photon detection efficiency as functions of temperature from 210 to 294 K. The SPAD exhibited good temperature stability, with breakdown voltage dependence of approximately 45 mV K−1. Operating at 210 K and in a gated mode, the SPAD achieved a photon detection probability of 26% at 1550 nm with a dark count rate of 1 × 108 Hz. The time response of the SPAD showed decreasing timing jitter (full width at half maximum) with increasing overbias voltage, with 70 ps being the smallest timing jitter measured. PMID:27069647

Nanoepitaxy of GaAs on a Si(001) substrate using a round-hole nanopatterned SiO2 mask.

PubMed

Hsu, Chao-Wei; Chen, Yung-Feng; Su, Yan-Kuin

2012-12-14

GaAs is grown by metal-organic vapor-phase epitaxy on a 55 nm round-hole patterned Si substrate with SiO(2) as a mask. The threading dislocations, which are stacked on the lowest energy facet plane, move along the SiO(2) walls, reducing the number of dislocations. The etching pit density of GaAs on the 55 nm round-hole patterned Si substrate is about 3.3 × 10(5) cm(-2). Compared with the full width at half maximum measurement from x-ray diffraction and photoluminescence spectra of GaAs on a planar Si(001) substrate, those of GaAs on the 55 nm round-hole patterned Si substrate are reduced by 39.6 and 31.4%, respectively. The improvement in material quality is verified by transmission electron microscopy, field-emission scanning electron microscopy, Hall measurements, Raman spectroscopy, photoluminescence, and x-ray diffraction studies.

Characterization and on-sky demonstration of an integrated photonic spectrograph for astronomy.

PubMed

Cvetojevic, N; Lawrence, J S; Ellis, S C; Bland-Hawthorn, J; Haynes, R; Horton, A

2009-10-12

We present results from the first on-sky demonstration of a prototype astronomical integrated photonic spectrograph (IPS) using the Anglo-Australian Telescope near-infrared imaging spectrometer (IRIS2) at Siding Spring Observatory to observe atmospheric molecular OH emission lines. We have succeeded in detecting upwards of 27 lines, and demonstrated the practicality of the IPS device for astronomy. Furthermore, we present a laboratory characterization of the device, which is a modified version of a commercial arrayed-waveguide grating multiplexer. We measure the spectral resolution full-width-half-maximum to be 0.75 +/- 0.05 nm (giving R = lambda/deltalambda = 2100 +/- 150 at 1500 nm). We find the free spectral range to be 57.4 +/- 0.6 nm and the peak total efficiency to be approximately 65%. Finally, we briefly discuss the future steps required to realize an astronomical instrument based on this technology concept.

Wavelength-tunable thulium-doped fiber laser by employing a self-made Fabry-Perot filter

NASA Astrophysics Data System (ADS)

Wang, Y. P.; Ju, Y. L.; Wu, C. T.; Liu, W.; Yang, C.

2017-06-01

In this demonstration, we proposed a novel wavelength-tunable thulium-doped fiber laser (TDFL) with a self-made Fabry-Perot (F-P) filter. When the F-P filter was not inserted, the maximum output power of 11.1 W was achieved when the pump power was 70.2 W. The corresponding optical-to-optical conversion efficiency was 15.8% and the slope efficiency was 22.1%. When the F-P filter was inserted, the output wavelength could be tuned from 1952.9 to 1934.9 nm with the change of cavity length of F-P filter which was fixed on a piezoelectric ceramic transducer (PZT) controlled by the voltage applied to it. The full width at half maximum (FWHM) was no more than 0.19 nm. Furthermore, the wavelength fluctuations of the tunable fiber laser were kept within  ±0.2 nm.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lorente-Crespo, M.; Mateo-Segura, C., E-mail: C.Mateo-Segura@hw.ac.uk

Nanoantennas enhance the conversion between highly localized electromagnetic fields and far-field radiation. Here, we investigate the response of a nano-patch partially reflective surface backed with a silver mirror to an optical source embedded at the centre of the structure. Using full wave simulations, we demonstrate a two orders of magnitude increased directivity compared to the isotropic radiator, 50% power confinement to a 13.8° width beam and a ±16 nm bandwidth. Our antenna does not rely on plasmonic phenomena thus reducing non-radiative losses and conserving source coherence.

Laser plasma x-ray line spectra fitted using the Pearson VII function

NASA Astrophysics Data System (ADS)

Michette, A. G.; Pfauntsch, S. J.

2000-05-01

The Pearson VII function, which is more general than the Gaussian, Lorentzian and other profiles, is used to fit the x-ray spectral lines produced in a laser-generated plasma, instead of the more usual, but computationally expensive, Voigt function. The mean full-width half-maximum of the fitted lines is 0.102+/-0.014 nm, entirely consistent with the value expected from geometrical considerations, and the fitted line profiles are generally inconsistent with being either Lorentzian or Gaussian.

Strong modification of photoluminescence in erbium-doped porous silicon microcavities

NASA Astrophysics Data System (ADS)

Zhou, Y.; Snow, P. A.; Russell, P. St. J.

2000-10-01

A microcavity composed of porous silicon multilayer mirrors was electrochemically etched and doped with erbium. Measurements of the reflectivity and photoluminescence spectra are presented. Thermal processing under a nitrogen atmosphere optically activated the erbium ions. Photopumping yielded room temperature emission around 1.54 μm from the erbium-doped samples with the emitted light strongly modified by the microcavity structure. Emission spectra with a peak at 1.536 μm had a full width at half maximum of ˜6 nm.

Picosecond 1064-nm fiber laser with tunable pulse width and low timing jitter

NASA Astrophysics Data System (ADS)

Tian, Wenyan; Zhang, Shukui

2018-02-01

We report an all-fiber, linearly polarized, 1.1-W, 1064-nm fiber laser based on a two-stage Ytterbium-doped fiber amplifier seeded by a gain-switched diode laser with tunable pulse width from 21 to 200 ps at repetition rates of 0.5-1.5 GHz. Timing jitter of our 1064-nm fiber laser was measured to be 0.60 ps over 10 Hz-40 MHz when the gain-switched diode laser was operated at a repetition rate of 0.5, 1, and 1.5 GHz. The fiber laser offers an excellent long term power stability of +/- 0.3% and wavelength stability of +/- 0.01 nm over 8 hours

Ultraviolet electroluminescence from hybrid inorganic/organic ZnO/GaN/poly(3-hexylthiophene) dual heterojunctions.

PubMed

Chen, Yungting; Shih, Hanyu; Wang, Chunhsiung; Hsieh, Chunyi; Chen, Chihwei; Chen, Yangfang; Lin, Taiyuan

2011-05-09

Based on hybrid inorganic/organic n-ZnO nanorods/p-GaN thin film/poly(3-hexylthiophene)(P3HT) dual heterojunctions, the light emitting diode (LED) emits ultraviolet (UV) radiation (370 nm - 400 nm) and the whole visible light (400 nm -700 nm) at the low injection current density. Meanwhile, under the high injection current density, the UV radiation overwhelmingly dominates the room-temperature electroluminescence spectra, exponentially increases with the injection current density and possesses a narrow full width at half maximum less than 16 nm. Comparing electroluminescence with photoluminescence spectra, an enormously enhanced transition probability of the UV luminescence in the electroluminescence spectra was found. The P3HT layer plays an essential role in helping the UV emission from p-GaN material because of its hole-conductive characteristic as well as the band alignment with respect to p-GaN. With our new finding, the result shown here may pave a new route for the development of high brightness LEDs derived from hybrid inorganic/organic heterojuctions.

Development of scanning x-ray fluorescence microscope with spatial resolution of 30 nm using Kirkpatrick-Baez mirror optics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Matsuyama, S.; Mimura, H.; Yumoto, H.

We developed a high-spatial-resolution scanning x-ray fluorescence microscope (SXFM) using Kirkpatrick-Baez mirrors. As a result of two-dimensional focusing tests at BL29XUL of SPring-8, the full width at half maximum of the focused beam was achieved to be 50x30 nm{sup 2} (VxH) under the best focusing conditions. The measured beam profiles were in good agreement with simulated results. Moreover, beam size was controllable within the wide range of 30-1400 nm by changing the virtual source size, although photon flux and size were in a trade-off relationship. To demonstrate SXFM performance, a fine test chart fabricated using focused ion beam system wasmore » observed to determine the best spatial resolution. The element distribution inside a logo mark of SPring-8 in the test chart, which has a minimum linewidth of approximately 50-60 nm, was visualized with a spatial resolution better than 30 nm using the smallest focused x-ray beam.« less

III-N light emitting diodes fabricated using RF nitrogen gas source MBE

NASA Astrophysics Data System (ADS)

Van Hove, J. M.; Carpenter, G.; Nelson, E.; Wowchak, A.; Chow, P. P.

1996-07-01

Homo- and heterojunction III-N light emitting diodes using RF atomic nitrogen plasma molecular beam epitaxy have been grown. GaN films deposited on sapphire using this growth technique exhibited an extremely sharp X-ray diffraction with a full width half maximum of 112 arc sec. p-type doping of the nitride films was done with elemental Mg and resulted in as-grown p-type material with resistivities as low as 2 Ω · cm. Both homo- and heterojunction LEDs showed clear rectification. Emission from the GaN homojunction deposited on n-type SiC was peaked at 410 nm while the AlGaNGaN(Zn)AlGaN double heterojunction LEDs emission was centered about 520 nm.

Three-stage Fabry-Perot liquid crystal tunable filter with extended spectral range.

PubMed

Zheng, Zhenrong; Yang, Guowei; Li, Haifeng; Liu, Xu

2011-01-31

A method to extend spectral range of tunable optical filter is proposed in this paper. Two same tunable Fabry-Perot filters and an additional tunable filter with different free spectral range are cascaded to extend spectral range and reduce sidelobes. Over 400 nm of free spectral range and 4 nm of full width at half maximum of the filter were achieved. Design procedure and simulation are described in detail. An experimental 3-stage tunable Fabry-Perot filter with visible and infrared spectra is demonstrated. The experimental results and the theoretical analysis are presented in detail to verify this method. The results revealed that a compact and extended tunable spectral range of Fabry-Perot filter can be easily attainable by this method.

Enhanced broadband near-infrared luminescence from transparent Yb3+/Ni2+ codoped silicate glass ceramics.

PubMed

Wu, Botao; Zhou, Shifeng; Ruan, Jian; Qiao, Yanbo; Chen, Danping; Zhu, Congshan; Qiu, Jianrong

2008-02-04

The near-infrared emission intensity of Ni(2+) in Yb(3+)/Ni(2+) codoped transparent MgO-Al(2)O(3)-Ga(2)O(3)-SiO(2)-TiO(2) glass ceramics could be enhanced up to 4.4 times via energy transfer from Yb(3+) to Ni(2+) in nanocrystals. The best Yb(2)O(3) concentration was about 1.00 mol%. For the Yb(3+)/Ni(2+) codoped glass ceramic with 1.00 mol% Yb(2)O(3), a broadband near-infrared emission centered at 1265 nm with full width at half maximum of about 300 nm and lifetime of about 220 mus was observed. The energy transfer mechanism was also discussed.

Fabrication of sub-12 nm thick silicon nanowires by processing scanning probe lithography masks

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kyoung Ryu, Yu; Garcia, Ricardo, E-mail: r.garcia@csic.es; Aitor Postigo, Pablo

2014-06-02

Silicon nanowires are key elements to fabricate very sensitive mechanical and electronic devices. We provide a method to fabricate sub-12 nm silicon nanowires in thickness by combining oxidation scanning probe lithography and anisotropic dry etching. Extremely thin oxide masks (0.3–1.1 nm) are transferred into nanowires of 2–12 nm in thickness. The width ratio between the mask and the silicon nanowire is close to one which implies that the nanowire width is controlled by the feature size of the nanolithography. This method enables the fabrication of very small single silicon nanowires with cross-sections below 100 nm{sup 2}. Those values are the smallest obtained withmore » a top-down lithography method.« less

Domain wall structure and interactions in 50 nm wide Cobalt nanowires

NASA Astrophysics Data System (ADS)

Tu, Kun-Hua; Ojha, Shuchi; Ross, Caroline A.

2018-05-01

Arrays of cobalt nanowires with widths of 50 nm, thickness of 5 and 20 nm and periodicity of 70 nm were fabricated by pattern transfer from a self-assembled block copolymer film. Transverse domain walls (DWs) were imaged by magnetic force microscopy, indicating repulsive interactions between DWs of the same sign in the 20 nm thick wires. Micromagnetic simulations were used to identify the interactions in the six distinct cases of a pair of transverse DWs in adjacent wires, considering all the possible combinations of head-to-head and tail-to-tail DWs and the orientation of the core magnetization. The boundary between repulsive and attractive DW interactions is mapped out for wires as a function of thickness, width and interwire spacing.

Sub-0.1 μm optical track width measurement

NASA Astrophysics Data System (ADS)

Smith, Richard J.; See, Chung W.; Somekh, Mike G.; Yacoot, Andrew

2005-08-01

In this paper, we will describe a technique that combines a common path scanning optical interferometer with artificial neural networks (ANN), to perform track width measurements that are significantly beyond the capability of conventional optical systems. Artificial neural networks have been used for many different applications. In the present case, ANNs are trained using profiles of known samples obtained from the scanning interferometer. They are then applied to tracks that have not previously been exposed to the networks. This paper will discuss the impacts of various ANN configurations, and the processing of the input signal on the training of the network. The profiles of the samples, which are used as the inputs to the ANNs, are obtained with a common path scanning optical interferometer. It provides extremely repeatable measurements, with very high signal to noise ratio, both are essential for the working of the ANNs. The characteristics of the system will be described. A number of samples with line widths ranging from 60nm-3μm have been measured to test the system. The system can measure line widths down to 60nm with a standard deviation of 3nm using optical wavelength of 633nm and a system numerical aperture of 0.3. These results will be presented in detail along with a discussion of the potential of this technique.

Multichannel extremely broadband near-IR radiation sources for optical coherence tomography

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wojtkowski, M; Fujimoto, J G; Lapin, P I

The construction and output parameters of two experimental samples of near-IR radiation sources based on the superposition of radiation from several superluminescent diodes are described. The first, three-channel sample emitting 18 mW of cw output power in a spectral band of width 105 nm through a single-mode fibre, is optimised for ophthalmology coherence tomography. The second, four-channel sample emits the 870-nm band of width more than 200 nm, which corresponds to the record coherence length smaller than 4 {mu}m. (laser applications and other topics in quantum electronics)

Experimental strategies for imaging bioparticles with femtosecond hard X-ray pulses

DOE PAGES

Daurer, Benedikt J.; Okamoto, Kenta; Bielecki, Johan; ...

2017-04-07

This study explores the capabilities of the Coherent X-ray Imaging Instrument at the Linac Coherent Light Source to image small biological samples. The weak signal from small samples puts a significant demand on the experiment. AerosolizedOmono River virusparticles of ~40 nm in diameter were injected into the submicrometre X-ray focus at a reduced pressure. Diffraction patterns were recorded on two area detectors. The statistical nature of the measurements from many individual particles provided information about the intensity profile of the X-ray beam, phase variations in the wavefront and the size distribution of the injected particles. The results point to amore » wider than expected size distribution (from ~35 to ~300 nm in diameter). This is likely to be owing to nonvolatile contaminants from larger droplets during aerosolization and droplet evaporation. The results suggest that the concentration of nonvolatile contaminants and the ratio between the volumes of the initial droplet and the sample particles is critical in such studies. The maximum beam intensity in the focus was found to be 1.9 × 10 12photons per µm 2per pulse. The full-width of the focus at half-maximum was estimated to be 500 nm (assuming 20% beamline transmission), and this width is larger than expected. Under these conditions, the diffraction signal from a sample-sized particle remained above the average background to a resolution of 4.25 nm. Finally, the results suggest that reducing the size of the initial droplets during aerosolization is necessary to bring small particles into the scope of detailed structural studies with X-ray lasers.« less

Wavelength dependence of the Brillouin spectral width of boron doped germanosilicate optical fibers.

PubMed

Law, Pi-Cheng; Dragic, Peter D

2010-08-30

Boron co-doped germanosilicate fibers are investigated via the Brillouin light scattering technique using two wavelengths, 1534 nm and 1064 nm. Several fibers are investigated, including four drawn from the same preform but at different draw temperatures. The Stokes' shifts and the Brillouin spectral widths are found to increase with increasing fiber draw temperature. A frequency-squared law has adequately described the wavelength dependence of the Brillouin spectral width of conventional Ge-doped fibers. However, it is found that unlike conventional Ge-doped fibers these fibers do not follow the frequency-squared law. This is explained through a frequency-dependent dynamic viscosity that modifies this law.

Temperature Dependence of Molecular Line Strengths and Fei 1565 nm Zeeman Splitting in a Sunspot

NASA Astrophysics Data System (ADS)

Penn, M. J.; Walton, S.; Chapman, G.; Ceja, J.; Plick, W.

2003-03-01

Spectroscopic observations at 1565 nm were made in the eastern half of the main umbra of NOAA 9885 on 1 April 2002 using the National Solar Observatory McMath-Pierce Telescope at Kitt Peak with a tip-tilt image stabilization system and the California State University Northridge-National Solar Observatory infrared camera. The line depth of the OH blend at 1565.1 nm varies with the observed continuum temperature; the variation fits previous observations except that the continuum temperature is lower by 600 K. The equivalent width of the OH absorption line at 1565.2 nm shows a temperature dependence similar to previously published umbral molecular observations at 640 nm. A simple model of expected OH abundance based upon an ionization analogy to molecular dissociation is produced and agrees well with the temperature variation of the line equivalent width. A CN absorption line at 1564.6 nm shows a very different temperature dependence, likely due to complicated formation and destruction processes. Nonetheless a numerical fit of the temperature variation of the CN equivalent width is presented. Finally a comparison of the Zeeman splitting of the Fei 1564.8 nm line with the sunspot temperature derived from the continuum intensity shows an umbra somewhat cooler for a given magnetic field strength than previous comparisons using this infrared 1564.8 nm line, but consistent with these previous infrared measurements the umbra is hotter for a given magnetic field strength than magnetic and temperature measurements at 630.2 nm would suggest. Differences between the 630.2 nm and 1564.8 nm umbral temperature and magnetic field relations are explained with the different heights of formation of the lines and continua at these wavelengths.

PTFE-based microreactor system for the continuous synthesis of full-visible-spectrum emitting cesium lead halide perovskite nanocrystals.

PubMed

Zhang, Chengxi; Luan, Weiling; Yin, Yuhang; Yang, Fuqian

2017-01-01

Colloidal perovskite nanocrystals comprised of all inorganic cesium lead halide (CsPbX 3 , X = Cl, Br, I or a mixture thereof) have potential as optical gain materials due to their high luminescence efficiency. In this work, cesium lead halide nanocrystals are continuously synthesized via a microreactor system consisting of poly(tetrafluoroethylene) (PTFE) capillaries. The synthesized nanocrystals possess excellent optical properties, including a full width at half maximum of 19-35 nm, high fluorescence quantum yield of 47.8-90.55%, and photoluminescence emission in the range of 450-700 nm. For the same precursor concentrations, the photoluminescence emission peak generally increases with increasing reaction temperature, revealing a controllable temperature effect on the photoluminescence characteristics of the synthesized nanocrystals. For quantum dots synthesized with a Br/I ratio of 1:3, a slight blue shift was observed for reaction temperatures greater than 100 °C. This PTFE-based microreactor system provides the unique capability of continuously synthesizing high-quality perovskite nanocrystals that emit over the full visible spectrum with applications ranging from displays and optoelectronic devices.

PTFE-based microreactor system for the continuous synthesis of full-visible-spectrum emitting cesium lead halide perovskite nanocrystals

PubMed Central

Zhang, Chengxi; Yin, Yuhang

2017-01-01

Colloidal perovskite nanocrystals comprised of all inorganic cesium lead halide (CsPbX3, X = Cl, Br, I or a mixture thereof) have potential as optical gain materials due to their high luminescence efficiency. In this work, cesium lead halide nanocrystals are continuously synthesized via a microreactor system consisting of poly(tetrafluoroethylene) (PTFE) capillaries. The synthesized nanocrystals possess excellent optical properties, including a full width at half maximum of 19–35 nm, high fluorescence quantum yield of 47.8–90.55%, and photoluminescence emission in the range of 450–700 nm. For the same precursor concentrations, the photoluminescence emission peak generally increases with increasing reaction temperature, revealing a controllable temperature effect on the photoluminescence characteristics of the synthesized nanocrystals. For quantum dots synthesized with a Br/I ratio of 1:3, a slight blue shift was observed for reaction temperatures greater than 100 °C. This PTFE-based microreactor system provides the unique capability of continuously synthesizing high-quality perovskite nanocrystals that emit over the full visible spectrum with applications ranging from displays and optoelectronic devices. PMID:29259867

From Broadband to Electrochromic Notch Filters with Printed Monochiral Carbon Nanotubes

PubMed Central

2018-01-01

Dense layers of semiconducting single-walled carbon nanotubes (SWNTs) serve as electrochromic (EC) materials in the near-infrared with high optical density and high conductivity. EC cells with tunable notch filter properties instead of broadband absorption are created via highly selective dispersion of specific semiconducting SWNTs through polymer-wrapping followed by deposition of thick films by aerosol-jet printing. A simple planar geometry with spray-coated mixed SWNTs as the counter electrode renders transparent metal oxides redundant and facilitates complete bleaching within a few seconds through iongel electrolytes with high ionic conductivities. Monochiral (6,5) SWNT films as working electrodes exhibit a narrow absorption band at 997 nm (full width at half-maximum of 55–73 nm) with voltage-dependent optical densities between 0.2 and 4.5 and a modulation depth of up to 43 dB. These (6,5) SWNT notch filters can retain more than 95% of maximum bleaching for several hours under open-circuit conditions. In addition, different levels of transmission can be set by applying constant low voltage (1.5 V) pulses with modulated width or by a given number of fixed short pulses. PMID:29521086

Spectral Feature Analysis for Quantitative Estimation of Cyanobacteria Chlorophyll-A

NASA Astrophysics Data System (ADS)

Lin, Yi; Ye, Zhanglin; Zhang, Yugan; Yu, Jie

2016-06-01

In recent years, lake eutrophication caused a large of Cyanobacteria bloom which not only brought serious ecological disaster but also restricted the sustainable development of regional economy in our country. Chlorophyll-a is a very important environmental factor to monitor water quality, especially for lake eutrophication. Remote sensed technique has been widely utilized in estimating the concentration of chlorophyll-a by different kind of vegetation indices and monitoring its distribution in lakes, rivers or along coastline. For each vegetation index, its quantitative estimation accuracy for different satellite data might change since there might be a discrepancy of spectral resolution and channel center between different satellites. The purpose this paper is to analyze the spectral feature of chlorophyll-a with hyperspectral data (totally 651 bands) and use the result to choose the optimal band combination for different satellites. The analysis method developed here in this study could be useful to recognize and monitor cyanobacteria bloom automatically and accrately. In our experiment, the reflectance (from 350nm to 1000nm) of wild cyanobacteria in different consistency (from 0 to 1362.11ug/L) and the corresponding chlorophyll-a concentration were measured simultaneously. Two kinds of hyperspectral vegetation indices were applied in this study: simple ratio (SR) and narrow band normalized difference vegetation index (NDVI), both of which consists of any two bands in the entire 651 narrow bands. Then multivariate statistical analysis was used to construct the linear, power and exponential models. After analyzing the correlation between chlorophyll-a and single band reflectance, SR, NDVI respetively, the optimal spectral index for quantitative estimation of cyanobacteria chlorophyll-a, as well corresponding central wavelength and band width were extracted. Results show that: Under the condition of water disturbance, SR and NDVI are both suitable for quantitative estimation of chlorophyll-a, and more effective than the traditional single band model; the best regression models for SR, NDVI with chlorophyll-a are linear and power, respectively. Under the condition without water disturbance, the single band model works the best. For the SR index, there are two optimal band combinations, which is comprised of infrared (700nm-900nm) and blue-green range (450nm-550nm), infrared and red range (600nm-650nm) respectively, with band width between 45nm to 125nm. For NDVI, the optimal band combination includes the range from 750nm to 900nm and 700nm to 750nm, with band width less than 30nm. For single band model, band center located between 733nm-935nm, and its width mustn't exceed the interval where band center located in. This study proved , as for SR or NDVI, the centers and widths are crucial factors for quantitative estimating chlorophyll-a. As for remote sensor, proper spectrum channel could not only improve the accuracy of recognizing cyanobacteria bloom, but reduce the redundancy of hyperspectral data. Those results will provide better reference for designing the suitable spectrum channel of customized sensors for cyanobacteria bloom monitoring at a low altitude. In other words, this study is also the basic research for developing the real-time remote sensing monitoring system with high time and high spatial resolution.

Resolution Limits of Nanoimprinted Patterns by Fluorescence Microscopy

NASA Astrophysics Data System (ADS)

Kubo, Shoichi; Tomioka, Tatsuya; Nakagawa, Masaru

2013-06-01

The authors investigated optical resolution limits to identify minimum distances between convex lines of fluorescent dye-doped nanoimprinted resist patterns by fluorescence microscopy. Fluorescent ultraviolet (UV)-curable resin and thermoplastic resin films were transformed into line-and-space patterns by UV nanoimprinting and thermal nanoimprinting, respectively. Fluorescence immersion observation needed an immersion medium immiscible to the resist films, and an ionic liquid of triisobutyl methylphosphonium tosylate was appropriate for soluble thermoplastic polystyrene patterns. Observation with various numerical aperture (NA) values and two detection wavelength ranges showed that the resolution limits were smaller than the values estimated by the Sparrow criterion. The space width to identify line patterns became narrower as the line width increased. The space width of 100 nm was demonstrated to be sufficient to resolve 300-nm-wide lines in the detection wavelength range of 575-625 nm using an objective lens of NA= 1.40.

Method of simultaneous measurement of two direction force and temperature using FBG sensor head.

PubMed

Kisała, Piotr; Cięszczyk, Sławomir

2015-04-01

This paper presents a method for measuring two components of bending force and temperature using one sensor head. Indirect inference based on the spectra of two fiber Bragg gratings (FBGs) placed on a cantilever beam is used. The method was developed during work on the inverse problem of determining a nonuniform stress distribution based on FBG spectra. A gradient in the FBG stress profile results in a characteristic shape of its reflective spectrum. The simultaneous measurements of force and temperature were possible through the use of an appropriate layout of the sensor head. The spectral characteristics of the sensor's gratings do not retain full symmetry, which is due to the geometry of the sensor's head and the related difference in the distribution of the axial stress of the gratings. In the proposed approach, the change in width of the sum of the normalized transmission spectra was used to determine the value of the applied force. In the presented method, an increase in the sensitivity of this change to the force is obtained relative to the other known systems. A change in the spectral width was observed for an increase in bending forces from 0 to 150 N. The sensitivity coefficient of the spectral width to force, defined as the ratio of the change of the spectral half-width to the change in force was 2.6e-3  nm/N for the first grating and 1.2e-3  nm/N for the second grating. However, the sensitivity of the whole sensor system was 5.8e-3  nm/N, which is greater than the sum of the sensitivities of the individual gratings. For the purpose of this work, a station with a thermal chamber has been designed with a bracket on which fiber optic transducers have been mounted for use in further measurements. The sensor head in this experiment is considered to be a universal device with potential applications in other types of optical sensors, and it can be treated as a module for development through its multiplication on a single optical fiber.

Dark-field microscopy studies of single metal nanoparticles: understanding the factors that influence the linewidth of the localized surface plasmon resonance

PubMed Central

Hu, Min; Novo, Carolina; Funston, Alison; Wang, Haining; Staleva, Hristina; Zou, Shengli; Mulvaney, Paul; Xia, Younan; Hartland, Gregory V.

2008-01-01

This article provides a review of our recent Rayleigh scattering measurements on single metal nanoparticles. Two different systems will be discussed in detail: gold nanorods with lengths between 30 and 80 nm, and widths between 8 and 30 nm; and hollow gold–silver nanocubes (termed nanoboxes or nanocages depending on their exact morphology) with edge lengths between 100 and 160 nm, and wall thicknesses of the order of 10 nm. The goal of this work is to understand how the linewidth of the localized surface plasmon resonance depends on the size, shape, and environment of the nanoparticles. Specifically, the relative contributions from bulk dephasing, electron–surface scattering, and radiation damping (energy loss via coupling to the radiation field) have been determined by examining particles with different dimensions. This separation is possible because the magnitude of the radiation damping effect is proportional to the particle volume, whereas, the electron–surface scattering contribution is inversely proportional to the dimensions. For the nanorods, radiation damping is the dominant effect for thick rods (widths greater than 20 nm), while electron–surface scattering is dominant for thin rods (widths less than 10 nm). Rods with widths in between these limits have narrow resonances—approaching the value determined by the bulk contribution. For nanoboxes and nanocages, both radiation damping and electron–surface scattering are significant at all sizes. This is because these materials have thin walls, but large edge lengths and, therefore, relatively large volumes. The effect of the environment on the localized surface plasmon resonance has also been studied for nanoboxes. Increasing the dielectric constant of the surroundings causes a red-shift and an increase in the linewidth of the plasmon band. The increase in linewidth is attributed to enhanced radiation damping. PMID:18846243

Dark-field microscopy studies of single metal nanoparticles: understanding the factors that influence the linewidth of the localized surface plasmon resonance.

PubMed

Hu, Min; Novo, Carolina; Funston, Alison; Wang, Haining; Staleva, Hristina; Zou, Shengli; Mulvaney, Paul; Xia, Younan; Hartland, Gregory V

2008-01-01

This article provides a review of our recent Rayleigh scattering measurements on single metal nanoparticles. Two different systems will be discussed in detail: gold nanorods with lengths between 30 and 80 nm, and widths between 8 and 30 nm; and hollow gold-silver nanocubes (termed nanoboxes or nanocages depending on their exact morphology) with edge lengths between 100 and 160 nm, and wall thicknesses of the order of 10 nm. The goal of this work is to understand how the linewidth of the localized surface plasmon resonance depends on the size, shape, and environment of the nanoparticles. Specifically, the relative contributions from bulk dephasing, electron-surface scattering, and radiation damping (energy loss via coupling to the radiation field) have been determined by examining particles with different dimensions. This separation is possible because the magnitude of the radiation damping effect is proportional to the particle volume, whereas, the electron-surface scattering contribution is inversely proportional to the dimensions. For the nanorods, radiation damping is the dominant effect for thick rods (widths greater than 20 nm), while electron-surface scattering is dominant for thin rods (widths less than 10 nm). Rods with widths in between these limits have narrow resonances-approaching the value determined by the bulk contribution. For nanoboxes and nanocages, both radiation damping and electron-surface scattering are significant at all sizes. This is because these materials have thin walls, but large edge lengths and, therefore, relatively large volumes. The effect of the environment on the localized surface plasmon resonance has also been studied for nanoboxes. Increasing the dielectric constant of the surroundings causes a red-shift and an increase in the linewidth of the plasmon band. The increase in linewidth is attributed to enhanced radiation damping.

Niobium oxide nanocolumns formed via anodic alumina with modulated pore diameters

NASA Astrophysics Data System (ADS)

Pligovka, A.; Zakhlebayeva, A.; Lazavenka, A.

2018-03-01

Niobium oxide nanocolumns with modulated diameters were formed for the first time. An Al/Nb bilayer specimen was prepared by successive sputter-deposition of 300 nm niobium layer and 1200 nm aluminum layer onto silicon wafer. Regular anodic alumina matrix with modulated pore diameters was formed by sequential anodization of initial specimen in tartaric acid at 180 V, and in oxalic acid at 37 V. Further potentiodynamic reanodization of the specimen up to 400 V causes the simultaneous growth of 440 nm continuous niobium oxide layer beneath the alumina film and two types of an array of oxide nanocolumns (thick – with 100 nm width and 630 nm high and thin – with 25 nm width and 170 nm high), which are the filling of the alumina pores. The morphology of the formed anodic niobium oxide nanocolumns with modulated diameters was determined by field emission scanning electron microscopy. The formed nanostructures can be used for perspective devices of nano- and optoelectronics such as photonic crystals.

Adiabatic Nanofocusing in Hybrid Gap Plasmon Waveguides on the Silicon-on-Insulator Platform.

PubMed

Nielsen, Michael P; Lafone, Lucas; Rakovich, Aliaksandra; Sidiropoulos, Themistoklis P H; Rahmani, Mohsen; Maier, Stefan A; Oulton, Rupert F

2016-02-10

We present an experimental demonstration of a new class of hybrid gap plasmon waveguides on the silicon-on-insulator (SOI) platform. Created by the hybridization of the plasmonic mode of a gap in a thin metal sheet and the transverse-electric (TE) photonic mode of an SOI slab, this waveguide is designed for efficient adiabatic nanofocusing simply by varying the gap width. For gap widths greater than 100 nm, the mode is primarily photonic in character and propagation lengths can be many tens of micrometers. For gap widths below 100 nm, the mode becomes plasmonic in character with field confinement predominantly within the gap region and with propagation lengths of a few microns. We estimate the electric field intensity enhancement in hybrid gap plasmon waveguide tapers at 1550 nm by three-photon absorption of selectively deposited CdSe/ZnS quantum dots within the gap. Here, we show electric field intensity enhancements of up to 167 ± 26 for a 24 nm gap, proving the viability of low loss adiabatic nanofocusing on a commercially relevant photonics platform.

Compact cantilever couplers for low-loss fiber coupling to silicon photonic integrated circuits.

PubMed

Wood, Michael; Sun, Peng; Reano, Ronald M

2012-01-02

We demonstrate coupling from tapered optical fibers to 450 nm by 250 nm silicon strip waveguides using compact cantilever couplers. The couplers consist of silicon inverse width tapers embedded within silicon dioxide cantilevers. Finite difference time domain simulations are used to design the length of the silicon inverse width taper to as short as 6.5 μm for a cantilever width of 2 μm. Modeling of various strip waveguide taper profiles shows reduced coupling losses for a quadratic taper profile. Infrared measurements of fabricated devices demonstrate average coupling losses of 0.62 dB per connection for the quasi-TE mode and 0.50 dB per connection for the quasi-TM mode across the optical telecommunications C band. In the wavelength range from 1477 nm to 1580 nm, coupling losses for both polarizations are less than 1 dB per connection. The compact, broadband, and low-loss coupling scheme enables direct access to photonic integrated circuits on an entire chip surface without the need for dicing or cleaving the chip.

Broadband supercontinuum generation with femtosecond pulse width in erbium-doped fiber laser (EDFL)

NASA Astrophysics Data System (ADS)

Rifin, S. N. M.; Zulkifli, M. Z.; Hassan, S. N. M.; Munajat, Y.; Ahmad, H.

2016-11-01

We demonstrate two flat plateaus and the low-noise spectrum of supercontinuum generation (SCG) in a highly nonlinear fiber (HNLF), injected by an amplified picosecond pulse seed of a carbon nanotube-based passively mode locked erbium-doped fiber laser. A broad spectrum of width approximately 1090 nm spanning the range 1130-2220 nm is obtained and the pulse width is compressed to the shorter duration of 70 fs. Variations of the injected peak power up to 33.78 kW into the HNLF are compared and the broad spectrum SCG profiles slightly expand for each of the injected peak powers. This straightforward configuration of SCG offers low output power and ultra-narrow femtosecond pulse width. The results facilitate the development of all fiber time-domain spectroscopy systems based on the photoconductive antenna technique.

A photostable near-infrared fluorescent tracker with pH-independent specificity to lysosomes for long time and multicolor imaging.

PubMed

Zhang, Xinfu; Wang, Chao; Han, Zhuo; Xiao, Yi

2014-12-10

A new boron-dipyrromethene-based lysosome tracker, Lyso-NIR, is facilely synthesized. Besides the intensive near-infrared (NIR) fluorescence and high photostability, Lyso-NIR shows the capability to stably localize in lysosomes, which is independent of the local pH. Lyso-NIR does not have the problematic alkalization effect suffered by the commonly used lysotrackers; thus, it shows ignorable cytotoxicity and slightly affects normal physiological functions of lysosomes. The above advantages of Lyso-NIR make it feasible to track lysosomes' dynamic changes in a relatively long time during the full cellular processes such as apoptosis, heavy metal stimulation, and endocytosis, as is demonstrated in this work. Moreover, Lyso-NIR's narrow NIR emission at 740 nm with a full width at half-maximum smaller than 50 nm makes it easy to avoid the crosstalk with the emissions from other common fluorescent probes, which strengthens Lyso-NIR's competitiveness as a standard lysosome tracker for multicolor bioimaging.

Hard X-ray Full Field Nano-imaging of Bone and Nanowires at SSRL

NASA Astrophysics Data System (ADS)

Andrews, Joy C.; Pianetta, Piero; Meirer, Florian; Chen, Jie; Almeida, Eduardo; van der Meulen, Marjolein C. H.; Alwood, Joshua S.; Lee, Cathy; Zhu, Jia; Cui, Yi

2010-06-01

A hard X-ray full field microscope from Xradia Inc. has been installed at SSRL on a 54-pole wiggler end station at beam line 6-2. It has been optimized to operate from 5-14 keV with resolution as high as 30 nm. High quality images are achieved using a vertical beam stabilizer and condenser scanner with high efficiency zone plates with 30 nm outermost zone width. The microscope has been used in Zernike phase contrast, available at 5.4 keV and 8 keV, as well as absorption contrast to image a variety of biological, environmental and materials samples. Calibration of the X-ray attenuation with crystalline apatite enabled quantification of bone density of plate-like and rod-like regions of mouse bone trabecula. 3D tomography of individual lacuna revealed the surrounding cell canaliculi and processes. 3D tomography of chiral branched PbSe nanowires showed orthogonal branches around a central nanowire.

Hard X-ray Full Field Nano-imaging of Bone and Nanowires at SSRL.

PubMed

Andrews, Joy C; Pianetta, Piero; Meirer, Florian; Chen, Jie; Almeida, Eduardo; van der Meulen, Marjolein C H; Alwood, Joshua S; Lee, Cathy; Zhu, Jia; Cui, Yi

2010-06-23

A hard X-ray full field microscope from Xradia Inc. has been installed at SSRL on a 54-pole wiggler end station at beam line 6-2. It has been optimized to operate from 5-14 keV with resolution as high as 30 nm. High quality images are achieved using a vertical beam stabilizer and condenser scanner with high efficiency zone plates with 30 nm outermost zone width. The microscope has been used in Zernike phase contrast, available at 5.4 keV and 8 keV, as well as absorption contrast to image a variety of biological, environmental and materials samples. Calibration of the X-ray attenuation with crystalline apatite enabled quantification of bone density of plate-like and rod-like regions of mouse bone trabecula. 3D tomography of individual lacuna revealed the surrounding cell canaliculi and processes. 3D tomography of chiral branched PbSe nanowires showed orthogonal branches around a central nanowire.

Characteristics of nanolite crystallization in volcanic pyroclasts

NASA Astrophysics Data System (ADS)

Mujin, M.; Nakamura, M.; Miyake, A.

2017-12-01

Crystal nucleation and initial growth in silicate melt may control the number density and later stage growth of crystals, such as twinning and morphology, and are therefore fundamental but still poorly understood processes in magma crystallization. Petrographic and experimental studies on groundmass microlites shed light on their importance for understanding eruption dynamics, but most studies did not focus on nanometer scale crystals. Recently, we reported "nanolites (30 nm-1 µm in width)" and "ultrananolites (< 30 nm in diameter)", which are nanoscale crystals with extremely high number density, in the interstices of microlites in pyroclasts. In this presentation, we summarize their mineralogical and petrological characteristics in pyroclasts of the 2011 eruption of Shinmoedake (Kirishima volcano group)1. By covering a wide size-range of crystals (down to 1 nm in diameter) based on scanning electron microscopy with tungsten filament (W-SEM), field emission (FE)-SEM, and transmission electron microscopy (TEM), we found a clear size gap (hiatus) in the size distribution and presence of minimum crystal size. In a dense juvenile fragment, crystals were absent or their number densities were too low to measure the sizes of pyroxene with a diameter of < 20 nm and a width of 30-100 nm, plagioclase with a width of < 100 nm, and Fe-Ti oxide with a diameter of 2-10 nm and a width of 20-100 nm. In pumice clasts, crystals smaller than 100 nm were not found. These observations show that nucleation of nanoscale crystals almost paused (froze) in the late stage of crystallization, possibly due to a decrease in undercooling, increase in interfacial free energy, and decrease in diffusivity in a dehydrated melt, whereas crystal growth was mostly continuous. Ultrananolites were found in pyroxene and Fe-Ti oxide; notably, these were spherical, whereas nanolites and microlites were rectangular. The observed ultrananolite-sized particles might partly include "subcritical clusters", which are particles smaller than the critical nucleation size assumed in the transient nucleation models. References 1) Mujin and Nakamura, 2014, Geology, v.42, p.611-614, and Mujin et al, in revision, Am. Min.

Wavelength stabilized multi-kW diode laser systems

NASA Astrophysics Data System (ADS)

Köhler, Bernd; Unger, Andreas; Kindervater, Tobias; Drovs, Simon; Wolf, Paul; Hubrich, Ralf; Beczkowiak, Anna; Auch, Stefan; Müntz, Holger; Biesenbach, Jens

2015-03-01

We report on wavelength stabilized high-power diode laser systems with enhanced spectral brightness by means of Volume Holographic Gratings. High-power diode laser modules typically have a relatively broad spectral width of about 3 to 6 nm. In addition the center wavelength shifts by changing the temperature and the driving current, which is obstructive for pumping applications with small absorption bandwidths. Wavelength stabilization of high-power diode laser systems is an important method to increase the efficiency of diode pumped solid-state lasers. It also enables power scaling by dense wavelength multiplexing. To ensure a wide locking range and efficient wavelength stabilization the parameters of the Volume Holographic Grating and the parameters of the diode laser bar have to be adapted carefully. Important parameters are the reflectivity of the Volume Holographic Grating, the reflectivity of the diode laser bar as well as its angular and spectral emission characteristics. In this paper we present detailed data on wavelength stabilized diode laser systems with and without fiber coupling in the spectral range from 634 nm up to 1533 nm. The maximum output power of 2.7 kW was measured for a fiber coupled system (1000 μm, NA 0.22), which was stabilized at a wavelength of 969 nm with a spectral width of only 0.6 nm (90% value). Another example is a narrow line-width diode laser stack, which was stabilized at a wavelength of 1533 nm with a spectral bandwidth below 1 nm and an output power of 835 W.

SPM local oxidation nanolithography with active control of cantilever dynamics

NASA Astrophysics Data System (ADS)

Nishimura, S.; Takemura, Y.; Shirakashi, J.

2007-04-01

Local oxidation nanolithography using scanning probe microscope (SPM) has enabled us to fabricate nanometer-scale oxide wires on material surfaces. Here, we study tapping mode SPM local oxidation experiments for silicon by controlling the dynamic properties of the cantilever. Dependence of feature size of fabricated oxide wires on the amplitude of the cantilever was precisely investigated. The quality factor (Q) was fixed at a natural value of ~500. By enhancing the amplitude of the cantilever, both width and height of fabricated Si oxide wires were decreased. With the variation of the amplitude of the cantilever from 0.5 V to 3.0 V (DC voltage = 22.5 V, scanning speed = 20 nm/s), the feature size of Si oxide wires was well controlled, ranging from 40 nm to 18 nm in width and 2.3 nm to 0.6 nm in height. Standard deviation of width on Si oxide wires formed by tapping mode SPM is around 2.0 nm, which is smaller than that of contact mode Si oxide wires. Furthermore, the variation of the oscillation amplitude of the cantilever does not affect the size uniformity of the wires. These results imply that the SPM local oxidation nanolithography with active control of cantilever dynamics is a useful technique for producing higher controllability on the nanometer-scale fabrication of Si oxide wires.

Reflective photoluminescence fiber temperature probe based on the CdSe/ZnS quantum dot thin film

NASA Astrophysics Data System (ADS)

Wang, Helin; Yang, Aijun; Chen, Zhongshi; Geng, Yan

2014-08-01

A reflective fiber temperature sensor based on the optical temperature dependent characteristics of a quantum dots (QDs) thin film is developed by depositing the CdSe/ZnS core/shell quantum dots on the SiO2 glass substrates. As the temperature is changed from 30 to 200°C, the peak wavelengths of PL spectra from the sensing head increase linearly with the temperature, while the peak intensity and the full width at half maximum (FWHM) of PL spectra vary exponentially according to the specific physical law. Using the obtained temperature-dependent peak-wavelength shift, the average resolution of the designed fiber temperature sensor can reach 0.12 nm/°C, while it reaches 0.056 nm/°C according to the FWHM of PL spectrum.

Mode-locked Er-doped fiber laser based on liquid phase exfoliated Sb2Te3 topological insulator

NASA Astrophysics Data System (ADS)

Boguslawski, J.; Sotor, J.; Sobon, G.; Tarka, J.; Jagiello, J.; Macherzynski, W.; Lipinska, L.; Abramski, K. M.

2014-10-01

In this paper, femtosecond pulse generation in an Er-doped fiber laser is reported. The laser is passively mode-locked by an antimony telluride (Sb2Te3) topological insulator (TI) saturable absorber (SA) placed on a side-polished fiber. The Sb2Te3/chitosan suspension used to prepare the SA was obtained via liquid phase exfoliation from bulk Sb2Te3.Ultra-short 449 fs soliton pulses were generated due to the interaction between the evanescent field propagated in the fiber cladding and the Sb2Te3 layers. The optical spectrum is centered at 1556 nm with 6 nm of full-width at half maximum bandwidth. The presented method benefits from a much better repeatability compared to mechanical exfoliation.

Formation of 2D bright spatial solitons in lithium niobate with photovoltaic response and incoherent background

NASA Astrophysics Data System (ADS)

Pustozerov, A.; Shandarov, V.

2017-12-01

The influence of incoherent background illumination produced by light-emitting diodes (LED's) of different average wavelengths and laser diode emitting in blue region of visible on diffraction characteristics of narrow coherent light beams of He-Ne laser due to refractive index changes of Fe-doped lithium niobate sample are studied. It has been experimentally demonstrated that nonlinear diffraction of red beams with wavelength 633 nm and diameters on full width of half maximum (FWHM) near to 15 μm may be totally compensated using background light with average wavelengths 450 - 465 nm. To provide the necessary intensity of incoherent background, the combinations of spherical and cylindrical concave lenses with blue LED and laser diode module without focusing its beam have been used.

10th order laterally coupled GaN-based DFB laser diodes with V-shaped surface gratings

NASA Astrophysics Data System (ADS)

Kang, J. H.; Wenzel, H.; Hoffmann, V.; Freier, E.; Sulmoni, L.; Unger, R.-S.; Einfeldt, S.; Wernicke, T.; Kneissl, M.

2018-02-01

Single longitudinal mode operation of laterally coupled distributed feedback (DFB) laser diodes (LDs) based on GaN containing 10th-order surface Bragg gratings with V-shaped grooves is demonstrated using i-line stepper lithography and inductively coupled plasma etching. A threshold current of 82 mA, a slope efficiency of 1.7 W/A, a single peak emission at 404.5 nm with a full width at half maximum of 0.04 nm and a side mode suppression ratio of > 23 dB at an output power of about 46 mW were achieved under pulsed operation. The shift of the lasing wavelength of DFB LDs with temperature was around three times smaller than that of conventional ridge waveguide LDs.

Hard X-ray nanofocusing using adaptive focusing optics based on piezoelectric deformable mirrors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Goto, Takumi; Nakamori, Hiroki; Sano, Yasuhisa

2015-04-15

An adaptive Kirkpatrick–Baez mirror focusing optics based on piezoelectric deformable mirrors was constructed at SPring-8 and its focusing performance characteristics were demonstrated. By adjusting the voltages applied to the deformable mirrors, the shape errors (compared to a target elliptical shape) were finely corrected on the basis of the mirror shape determined using the pencil-beam method, which is a type of at-wavelength figure metrology in the X-ray region. The mirror shapes were controlled with a peak-to-valley height accuracy of 2.5 nm. A focused beam with an intensity profile having a full width at half maximum of 110 × 65 nm (Vmore » × H) was achieved at an X-ray energy of 10 keV.« less

Plasmonic resonance in planer split ring trimer

NASA Astrophysics Data System (ADS)

Xu, Haiqing; Li, Hongjian; Xiao, Gang

2014-12-01

We have numerically investigated the plasmon properties supported by asymmetry planer split ring trimer structures. We investigate the modification of gap distance, thickness and gap width on the transmission properties of the weak coupling model (g is larger than or equal to 120 nm, d=48 nm, t is larger than 30 nm, w1=200 nm, and w2=40 nm), as the coupling becomes weaker, the first peak sharply attenuates, the second peak slightly decreases, the transmission dip in the near-infrared region becomes shallow, and they are very sensitive to the gap distance between two small split ring pairs and the thickness and gap width of the big split ring. We also study the change of gap distance on the strong coupling model (g is smaller than or equal to 40 nm, d=24 nm, t=10 nm, w1=80 nm, and w2=20 nm), there exists a new Fano resonance peak, the strongest peak in visible region becomes symmetry, while the peak in near-infrared region becomes asymmetry. The resonator design strategy opens up a rich pathway for the implementation of optimized optical properties for specific applications.

Theoretical study on effects of photodecomposable quenchers in line-and-space pattern fabrication with 7 nm quarter-pitch using chemically amplified electron beam resist process

NASA Astrophysics Data System (ADS)

Kozawa, Takahiro

2017-04-01

The line width roughness (LWR) is a significant issue in the development of chemically amplified resists. The increase in sensitizer concentration is inevitable for the suppression of LWR in the sub-10 nm fabrication. In this study, we investigated the effects of photodecomposable quenchers from the viewpoint of the excluded volume effect, assuming line-and-space patterns with 7 nm quarter-pitch (7 nm space width and 28 nm pitch). The pattern formation of chemically amplified electron beam resists with photodecomposable quenchers was calculated and compared with those with conventional quenchers. It was found that the sum of the concentrations of acid generators and quenchers (photodecomposable or conventional quenchers) can be reduced without decreasing the chemical gradient (an indicator of LWR) by using the photodecomposable quenchers. The photodecomposable quenchers are considered essential in the high-resolution fabrication.

970-nm ridge waveguide diode laser bars for high power DWBC systems

NASA Astrophysics Data System (ADS)

Wilkens, Martin; Erbert, Götz; Wenzel, Hans; Knigge, Andrea; Crump, Paul; Maaßdorf, Andre; Fricke, Jörg; Ressel, Peter; Strohmaier, Stephan; Schmidt, Berthold; Tränkle, Günther

2018-02-01

de lasers are key components in material processing laser systems. While mostly used as pump sources for solid state or fiber lasers, direct diode laser systems using dense wavelength multiplexing have come on the market in recent years. These systems are realized with broad area lasers typically, resulting in beam quality inferior to disk or fiber lasers. We will present recent results of highly efficient ridge waveguide (RW) lasers, developed for dense-wavelength-beamcombining (DWBC) laser systems expecting beam qualities comparable to solid state laser systems and higher power conversion efficiencies (PCE). The newly developed RW lasers are based on vertical structures with an extreme double asymmetric large optical cavity. Besides a low vertical divergence these structures are suitable for RW-lasers with (10 μm) broad ridges, emitting in a single mode with a good beam quality. The large stripe width enables a lateral divergence below 10° (95 % power content) and a high PCE by a comparably low series resistance. We present results of single emitters and small test arrays under different external feedback conditions. Single emitters can be tuned from 950 nm to 975 nm and reach 1 W optical power with more than 55 % PCE and a beam quality of M2 < 2 over the full wavelength range. The spectral width is below 30 pm FWHM. 5 emitter arrays were stabilized using the same setup. Up to now we reached 3 W optical power, limited by power supply, with 5 narrow spectral lines.

Full-range k-domain linearization in spectral-domain optical coherence tomography.

PubMed

Jeon, Mansik; Kim, Jeehyun; Jung, Unsang; Lee, Changho; Jung, Woonggyu; Boppart, Stephen A

2011-03-10

A full-bandwidth k-domain linearization method for spectral-domain optical coherence tomography (SD-OCT) is demonstrated. The method uses information of the wavenumber-pixel-position provided by a translating-slit-based wavelength filter. For calibration purposes, the filter is placed either after a broadband source or at the end of the sample path, and the filtered spectrum with a narrowed line width (∼0.5 nm) is incident on a line-scan camera in the detection path. The wavelength-swept spectra are co-registered with the pixel positions according to their central wavelengths, which can be automatically measured with an optical spectrum analyzer. For imaging, the method does not require a filter or a software recalibration algorithm; it simply resamples the OCT signal from the detector array without employing rescaling or interpolation methods. The accuracy of k-linearization is maximized by increasing the k-linearization order, which is known to be a crucial parameter for maintaining a narrow point-spread function (PSF) width at increasing depths. The broadening effect is studied by changing the k-linearization order by undersampling to search for the optimal value. The system provides more position information, surpassing the optimum without compromising the imaging speed. The proposed full-range k-domain linearization method can be applied to SD-OCT systems to simplify their hardware/software, increase their speed, and improve the axial image resolution. The experimentally measured width of PSF in air has an FWHM of 8 μm at the edge of the axial measurement range. At an imaging depth of 2.5 mm, the sensitivity of the full-range calibration case drops less than 10 dB compared with the uncompensated case.

Super-narrow, extremely high quality collective plasmon resonances at telecom wavelengths and their application in a hybrid graphene-plasmonic modulator.

PubMed

Thackray, Benjamin D; Thomas, Philip A; Auton, Gregory H; Rodriguez, Francisco J; Marshall, Owen P; Kravets, Vasyl G; Grigorenko, Alexander N

2015-05-13

We present extremely narrow collective plasmon resonances observed in gold nanostripe arrays fabricated on a thin gold film, with the spectral line full width at half-maximum (fwhm) as low as 5 nm and quality factors Q reaching 300, at important fiber-optic telecommunication wavelengths around 1.5 μm. Using these resonances, we demonstrate a hybrid graphene-plasmonic modulator with the modulation depth of 20% in reflection operated by gating of a single layer graphene, the largest measured so far.

Nano-optical single-photon response mapping of waveguide integrated molybdenum silicide (MoSi) superconducting nanowires.

PubMed

Li, Jian; Kirkwood, Robert A; Baker, Luke J; Bosworth, David; Erotokritou, Kleanthis; Banerjee, Archan; Heath, Robert M; Natarajan, Chandra M; Barber, Zoe H; Sorel, Marc; Hadfield, Robert H

2016-06-27

We present low temperature nano-optical characterization of a silicon-on-insulator (SOI) waveguide integrated SNSPD. The SNSPD is fabricated from an amorphous Mo₈₃Si₁₇ thin film chosen to give excellent substrate conformity. At 350 mK, the SNSPD exhibits a uniform photoresponse under perpendicular illumination, corresponding to a maximum system detection efficiency of approximately 5% at 1550 nm wavelength. Under these conditions 10 Hz dark count rate and 51 ps full width at half maximum (FWHM) timing jitter is observed.

MOEMS FPI sensors for NIR-MIR microspectrometer applications

NASA Astrophysics Data System (ADS)

Akujärvi, A.; Guo, B.; Mannila, R.; Rissanen, A.

2016-03-01

This paper presents near- and mid- infrared (NIR-MIR) wavelength range optical MEMS Fabry-Perot interferometers (FPIs) developed for automotive and multi-gas sensing applications. MEMS FPI platform for NIR-range consist of LPCVD (low-pressure chemical vapour) deposited polySi-SiN λ/4-thin film Bragg reflectors, with the air gap formed by sacrificial SiO2 etching in HF vapour. Characterization results for the NIR MFPI devices for λ = 1.5 - 2.0 μm show resolution of 15 nm at the optimization wavelength of 1750 nm. We also present a MIR-range MEMS FPI for λ = 2.5 - 3.5 μm, which utilizes silicon and air in within the Bragg reflector structure to provide a high contrast for improved resolution. Characterization results show a FWHM (Full Width Half Maximum) of 20 nm in comparison to the 50 nm resolution provided by earlier MEMS FPIs realized for hydrocarbon sensing with conventional CVD-thin film materials. The improved resolution and the extended operation region shows potential to enable simultaneous sensing of CO2 and multiple hydrocarbons.

X-ray microfocusing with off-axis ellipsoidal mirror

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yumoto, Hirokatsu, E-mail: yumoto@spring8.or.jp; Koyama, Takahisa; Matsuyama, Satoshi

2016-07-27

High-precision ellipsoidal mirrors for two-dimensionally focusing X-rays to nanometer sizes have not been realized because of technical problems in their fabrication processes. The objective of the present study is to develop fabrication techniques for ellipsoidal focusing mirrors in the hard-X-ray region. We design an off-axis ellipsoidal mirror for use under total reflection conditions up to the X-ray energy of 8 keV. We fabricate an ellipsoidal mirror with a surface roughness of 0.3 nm RMS (root-mean-square) and a surface figure error height of 3.0 nm RMS by utilizing a surface profiler and surface finishing method developed by us. The focusing propertiesmore » of the mirror are evaluated at the BL29XUL beamline in SPring-8. A focusing beam size of 270 nm × 360 nm FWHM (full width at half maximum) at an X-ray energy of 7 keV is observed with the use of the knife-edge scanning method. We expect to apply the developed fabrication techniques to construct ellipsoidal nanofocusing mirrors.« less

Experimental strategies for imaging bioparticles with femtosecond hard X-ray pulses

PubMed Central

Okamoto, Kenta; Bielecki, Johan; Maia, Filipe R. N. C.; Mühlig, Kerstin; Seibert, M. Marvin; Hantke, Max F.; Benner, W. Henry; Svenda, Martin; Ekeberg, Tomas; Loh, N. Duane; Pietrini, Alberto; Zani, Alessandro; Rath, Asawari D.; Westphal, Daniel; Kirian, Richard A.; Awel, Salah; Wiedorn, Max O.; van der Schot, Gijs; Carlsson, Gunilla H.; Hasse, Dirk; Sellberg, Jonas A.; Barty, Anton; Andreasson, Jakob; Boutet, Sébastien; Williams, Garth; Koglin, Jason; Hajdu, Janos; Larsson, Daniel S. D.

2017-01-01

This study explores the capabilities of the Coherent X-ray Imaging Instrument at the Linac Coherent Light Source to image small biological samples. The weak signal from small samples puts a significant demand on the experiment. Aerosolized Omono River virus particles of ∼40 nm in diameter were injected into the submicrometre X-ray focus at a reduced pressure. Diffraction patterns were recorded on two area detectors. The statistical nature of the measurements from many individual particles provided information about the intensity profile of the X-ray beam, phase variations in the wavefront and the size distribution of the injected particles. The results point to a wider than expected size distribution (from ∼35 to ∼300 nm in diameter). This is likely to be owing to nonvolatile contaminants from larger droplets during aerosolization and droplet evaporation. The results suggest that the concentration of nonvolatile contaminants and the ratio between the volumes of the initial droplet and the sample particles is critical in such studies. The maximum beam intensity in the focus was found to be 1.9 × 1012 photons per µm2 per pulse. The full-width of the focus at half-maximum was estimated to be 500 nm (assuming 20% beamline transmission), and this width is larger than expected. Under these conditions, the diffraction signal from a sample-sized particle remained above the average background to a resolution of 4.25 nm. The results suggest that reducing the size of the initial droplets during aerosolization is necessary to bring small particles into the scope of detailed structural studies with X-ray lasers. PMID:28512572

978-nm square-wave in an all-fiber single-mode ytterbium-doped fiber laser

NASA Astrophysics Data System (ADS)

Li, Shujie; Xu, Lixin; Gu, Chun

2018-01-01

A 978 nm single mode passively mode-locked all-fiber laser delivering square-wave pulses was demonstrated using a figure-8 cavity and a 75 cm commercial double-clad ytterbium-doped fiber. We found the three-level system near 978 nm was able to operate efficiently under clad pumping, simultaneously oscillation around 1030 nm well inhibited. The optimized nonlinear amplifying loop mirror made the mode locking stable and performed the square-pulses shaping. To the best of our knowledge, it is the first time to report the square-wave pulse fiber laser operating at 980 nm. The spectral width of the 978 mode-locked square pulses was about 4 nm, far greater than that of the mode-locked square pulses around 1060 nm reported before, which would be helpful to deeply understand the various square-wave pulses' natures and forming mechanisms. Compared with modulated single-mode or multimode 980 nm LDs, this kind of 980 nm square-wave sources having higher brightness, more steeper rising and falling edge and shorter pulse width, might have potential applications in pumping nanosecond ytterbium or erbium fiber lasers and amplifiers.

Double exposure technique for 45nm node and beyond

NASA Astrophysics Data System (ADS)

Hsu, Stephen; Park, Jungchul; Van Den Broeke, Douglas; Chen, J. Fung

2005-11-01

The technical challenges in using F2 lithography for the 45nm node, along with the insurmountable difficulties in EUV lithography, has driven the semiconductor chipmaker into the low k1 lithography era under the pressure of ever decreasing feature sizes. Extending lithography towards lower k1 puts heavy demand on the resolution enhancement technique (RET), exposure tool, and the need for litho friendly design. Hyper numerical aperture (NA) exposure tools, immersion, and double exposure techniques (DET's) are the promising methods to extend lithography manufacturing to the 45nm node at k1 factors below 0.3. Scattering bars (SB's) have become an integral part of the lithography process as chipmakers move to production at ever lower k1 factors. To achieve better critical dimension (CD) control, polarization is applied to enhance the image contrast in the preferential imaging orientation, which increases the risk of SB printability. The optimum SB width is approximately (0.20 ~ 0.25)*(λ/NA). When the SB width becomes less than the exposure wavelength on the 4X mask, Kirchhoff's scalar theory under predicts the SB intensity. The optical weighting factor of the SB increases (Figure 1b) and the SB's become more susceptible to printing. Meanwhile, under hyper NA conditions, the effectiveness of "subresolution" SB's is significantly diminished. A full-sized scattering bars (FSB) scheme becomes necessary. Double exposure methods, such as using ternary 6% attenuated PSM (attPSM) for DDL, are good imaging solutions that can reach and likely go beyond the 45nm node. Today DDL, using binary chrome masks, is capable of printing 65 nm device patterns. In this work, we investigate the use of DET with 6% attPSM masks to target 45nm node device. The SB scalability and printability issues can be taken cared of by using "mutual trimming", i.e., with the combined energy from the two exposures. In this study, we share our findings of using DET to pattern a 45nm node device design with polarization and immersion. We also explore other double patterning methods which in addition to having two exposures, incorporates double coat/developing/etch processing to break the 0.25 k1 barrier.

1.55-μm mode-locked quantum-dot lasers with 300 MHz frequency tuning range

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sadeev, T., E-mail: tagir@mailbox.tu-berlin.de; Arsenijević, D.; Bimberg, D.

2015-01-19

Passive mode-locking of two-section quantum-dot mode-locked lasers grown by metalorganic vapor phase epitaxy on InP is reported. 1250-μm long lasers exhibit a wide tuning range of 300 MHz around the fundamental mode-locking frequency of 33.48 GHz. The frequency tuning is achieved by varying the reverse bias of the saturable absorber from 0 to −2.2 V and the gain section current from 90 to 280 mA. 3 dB optical spectra width of 6–7 nm leads to ex-facet optical pulses with full-width half-maximum down to 3.7 ps. Single-section quantum-dot mode-locked lasers show 0.8 ps broad optical pulses after external fiber-based compression. Injection current tuning from 70 tomore » 300 mA leads to 30 MHz frequency tuning.« less

A universal route for the simultaneous extraction and functionalization of cellulose nanocrystals from industrial and agricultural celluloses

NASA Astrophysics Data System (ADS)

Chen, Guo-Yin; Yu, Hou-Yong; Zhang, Cai-Hong; Zhou, Ying; Yao, Ju-Ming

2016-02-01

A simple route was designed to extract the cellulose nanocrystals (CNCs) with formate groups from industrial and agricultural celluloses like microcrystalline cellulose (MCC), viscose fiber, ginger fiber, and bamboo fiber. The effect of reaction time on the microstructure and properties of the CNCs was investigated in detail, while microstructure and properties of different CNCs were compared. The rod-like CNCs (MCC) with hundreds of nanometers in length and about 10 nm in width, nanofibrillated CNCs (ginger fiber bamboo fiber) with average width of 30 nm and the length of 1 μm, and spherical CNCs (viscose fiber) with the width of 56 nm were obtained by one-step HCOOH/HCl hydrolysis. The CNCs with improved thermal stability showed the maximum degradation temperature ( T max) of 368.9-388.2 °C due to the introduction of formate groups (reducibility) and the increased crystallinity. Such CNCs may be used as an effective template for the synthesis of nanohybrids or reinforcing material for high-performance nanocomposites.

Efficient extreme ultraviolet plasma source generated by a CO2 laser and a liquid xenon microjet target

NASA Astrophysics Data System (ADS)

Ueno, Yoshifumi; Ariga, Tatsuya; Soumagne, George; Higashiguchi, Takeshi; Kubodera, Shoichi; Pogorelsky, Igor; Pavlishin, Igor; Stolyarov, Daniil; Babzien, Marcus; Kusche, Karl; Yakimenko, Vitaly

2007-05-01

We demonstrated efficacy of a CO2-laser-produced xenon plasma in the extreme ultraviolet (EUV) spectral region at 13.5nm at variable laser pulse widths between 200ps and 25ns. The plasma target was a 30μm liquid xenon microjet. To ensure the optimum coupling of CO2 laser energy with the plasma, they applied a prepulse yttrium aluminum garnet laser. The authors measured the conversion efficiency (CE) of the 13.5nm EUV emission for different pulse widths of the CO2 laser. A maximum CE of 0.6% was obtained for a CO2 laser pulse width of 25ns at an intensity of 5×1010W/cm2.

Theoretical study of fabrication of line-and-space patterns with 7 nm quarter-pitch using electron beam lithography with chemically amplified resist process: III. Post exposure baking on quartz substrates

NASA Astrophysics Data System (ADS)

Kozawa, Takahiro

2015-09-01

Electron beam (EB) lithography is a key technology for the fabrication of photomasks for ArF immersion and extreme ultraviolet (EUV) lithography and molds for nanoimprint lithography. In this study, the temporal change in the chemical gradient of line-and-space patterns with a 7 nm quarter-pitch (7 nm space width and 21 nm line width) was calculated until it became constant, independently of postexposure baking (PEB) time, to clarify the feasibility of single nano patterning on quartz substrates using EB lithography with chemically amplified resist processes. When the quencher diffusion constant is the same as the acid diffusion constant, the maximum chemical gradient of the line-and-space pattern with a 7 nm quarter-pitch did not differ much from that with a 14 nm half-pitch under the condition described above. Also, from the viewpoint of process control, a low quencher diffusion constant is considered to be preferable for the fabrication of line-and-space patterns with a 7 nm quarter-pitch on quartz substrates.

Tapping mode SPM local oxidation nanolithography with sub-10 nm resolution

NASA Astrophysics Data System (ADS)

Nishimura, S.; Ogino, T.; Takemura, Y.; Shirakashi, J.

2008-03-01

Tapping mode SPM local oxidation nanolithography with sub-10 nm resolution is investigated by optimizing the applied bias voltage (V), scanning speed (S) and the oscillation amplitude of the cantilever (A). We fabricated Si oxide wires with an average width of 9.8 nm (V = 17.5 V, S = 250 nm/s, A = 292 nm). In SPM local oxidation with tapping mode operation, it is possible to decrease the size of the water meniscus by enhancing the oscillation amplitude of cantilever. Hence, it seems that the water meniscus with sub-10 nm dimensions could be formed by precisely optimizing the oxidation conditions. Moreover, we quantitatively explain the size (width and height) of Si oxide wires with a model based on the oxidation ratio, which is defined as the oxidation time divided by the period of the cantilever oscillation. The model allows us to understand the mechanism of local oxidation in tapping mode operation with amplitude modulation. The results imply that the sub-10 nm resolution could be achieved using tapping mode SPM local oxidation technique with the optimization of the cantilever dynamics.

Optical diagnostic suite (schlieren, interferometry, and grid image refractometry) on OMEGA EP using a 10-ps, 263-nm probe beam.

PubMed

Froula, D H; Boni, R; Bedzyk, M; Craxton, R S; Ehrne, F; Ivancic, S; Jungquist, R; Shoup, M J; Theobald, W; Weiner, D; Kugland, N L; Rushford, M C

2012-10-01

A 10-ps, 263-nm (4ω) laser is being built to probe plasmas produced on the OMEGA EP [J. H. Kelly, L. J. Waxer, V. Bagnoud, I. A. Begishev, J. Bromage, B. E. Kruschwitz, T. E. Kessler, S. J. Loucks, D. N. Maywar, R. L. McCrory et al., J. Phys. IV France 133, 75-80 (2006)]. A suite of optical diagnostics (schlieren, interferometry, and grid image refractometry) has been designed to diagnose and characterize a wide variety of plasmas. Light scattered by the probe beam is collected by an f/4 catadioptric telescope and a transport system is designed to image with a near-diffraction-limited resolution (~1 - μm full width at half maximum) over a 5-mm field of view to a diagnostic table. The transport system provides a contrast greater than 1 : 10(4) with respect to all wavelengths outside of the 263 ± 2 nm measurement range.

Optical diagnostic suite (schlieren, interferometry, and grid image refractometry) on OMEGA EP using a 10-ps, 263-nm probe beama)

NASA Astrophysics Data System (ADS)

Froula, D. H.; Boni, R.; Bedzyk, M.; Craxton, R. S.; Ehrne, F.; Ivancic, S.; Jungquist, R.; Shoup, M. J.; Theobald, W.; Weiner, D.; Kugland, N. L.; Rushford, M. C.

2012-10-01

A 10-ps, 263-nm (4ω) laser is being built to probe plasmas produced on the OMEGA EP [J. H. Kelly, L. J. Waxer, V. Bagnoud, I. A. Begishev, J. Bromage, B. E. Kruschwitz, T. E. Kessler, S. J. Loucks, D. N. Maywar, R. L. McCrory et al., J. Phys. IV France 133, 75-80 (2006)], 10.1051/jp4:2006133015. A suite of optical diagnostics (schlieren, interferometry, and grid image refractometry) has been designed to diagnose and characterize a wide variety of plasmas. Light scattered by the probe beam is collected by an f/4 catadioptric telescope and a transport system is designed to image with a near-diffraction-limited resolution (˜1 - μm full width at half maximum) over a 5-mm field of view to a diagnostic table. The transport system provides a contrast greater than 1 : 104 with respect to all wavelengths outside of the 263 ± 2 nm measurement range.

980 nm diode laser with automatic power control mode for dermatological applications

NASA Astrophysics Data System (ADS)

Belikov, Andrey V.; Gelfond, Mark L.; Shatilova, Ksenia V.; Sosenkova, Svetlana A.; Lazareva, Anastasia A.

2015-07-01

Results of nevus, papilloma, dermatofibroma, and basal cell skin cancer removal by a 980+/-10 nm diode laser with "blackened" tip operating in continuous (CW) mode and automatic power control (APC) mode are compared. It was demonstrated that using APC mode decreases the width of collateral damage at removing of these nosological neoplasms of human skin. The mean width of collateral damage reached 0.846+/-0.139 mm for patient group with nevus removing by 980 nm diode laser operating in CW mode, papilloma - 0.443+/-0.312 mm, dermatofibroma - 0.923+/-0.271 mm, and basal cell skin cancer - 0.787+/-0.325 mm. The mean width of collateral damage reached 0.592+/-0.197 mm for patient group with nevus removing by 980 nm diode laser operating in APC mode, papilloma - 0.191+/-0.162 mm, dermatofibroma - 0.476+/-0.366 mm, and basal cell skin cancer - 0.517+/-0.374 mm. It was found that the percentage of laser wounds with collateral damage less than 300 μm of quantity of removed nosological neoplasms in APC mode is 50%, that significantly higher than the percentage of laser wounds obtained using CW mode (13.4%).

Williamson-Hall analysis and optical properties of small sized ZnO nanocrystals

NASA Astrophysics Data System (ADS)

Kalita, Amarjyoti; Kalita, Manos P. C.

2017-08-01

We apply Williamson-Hall (WH) method of X-ray diffraction (XRD) line profile analysis for lattice strain estimation of small sized ZnO nanocrystals (crystallite size≈4 nm). The ZnO nanocrystals are synthesized by room temperature chemical co-precipitation followed by heating at 40 °C. Zinc acetate, sodium hydroxide and 2-mercaptoethanol (ME) are used for the synthesis of the nanocrystals. {100}, {002}, {101} and {200}, {112}, {201} line profiles in the XRD pattern are significantly merged, therefore determination of the full width at half maximum values and peak positions of the line profiles required for WH analysis has been carried out by executing Rietveld refinement of the XRD pattern. Lattice strain of the 4 nm sized ZnO nanocrystals is found to be 5.8×10-3 which is significantly higher as compared to the literature reported values for larger ones (crystallite size≈17-47 nm). Role of ME as capping agent is confirmed by Fourier transform infrared spectroscopy. The band gap of the nanocrystals is determined from the UV-Visible absorption spectrum and is found to be 3.68 eV. The photoluminescence spectrum exhibits emissions in the visible (408 nm-violet, 467 nm-blue and 538 nm-green) regions showing presence of zinc interstitial and oxygen vacancy in the ZnO nanocrystals.

Passive, active, and hybrid mode-locking in a self-optimized ultrafast diode laser

NASA Astrophysics Data System (ADS)

Alloush, M. Ali; Pilny, Rouven H.; Brenner, Carsten; Klehr, Andreas; Knigge, Andrea; Tränkle, Günther; Hofmann, Martin R.

2018-02-01

Semiconductor lasers are promising sources for generating ultrashort pulses. They are directly electrically pumped, allow for a compact design, and therefore they are cost-effective alternatives to established solid-state systems. Additionally, their emission wavelength depends on the bandgap which can be tuned by changing the semiconductor materials. Theoretically, the obtained pulse width can be few tens of femtoseconds. However, the generated pulses are typically in the range of several hundred femtoseconds only. Recently, it was shown that by implementing a spatial light modulator (SLM) for phase and amplitude control inside the resonator the optical bandwidth can be optimized. Consequently, by using an external pulse compressor shorter pulses can be obtained. We present a Fourier-Transform-External-Cavity setup which utilizes an ultrafast edge-emitting diode laser. The used InGaAsP diode is 1 mm long and emits at a center wavelength of 850 nm. We investigate the best conditions for passive, active and hybrid mode-locking operation using the method of self-adaptive pulse shaping. For passive mode-locking, the bandwidth is increased from 2.34 nm to 7.2 nm and ultrashort pulses with a pulse width of 216 fs are achieved after external pulse compression. For active and hybrid mode-locking, we also increased the bandwidth. It is increased from 0.26 nm to 5.06 nm for active mode-locking and from 3.21 nm to 8.7 nm for hybrid mode-locking. As the pulse width is strongly correlated with the bandwidth of the laser, we expect further reduction in the pulse duration by increasing the bandwidth.

Internal quantum efficiency and carrier dynamics in semipolar (2021) InGaN/GaN light-emitting diodes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Okur, Serdal; Nami, Mohsen; Rishinaramangalam, Ashwin K.

Here, the internal quantum efficiencies (IQE) and carrier lifetimes of semipolar (more » $$20\\bar{2}$$$\\bar{1}$$) InGaN/GaN LEDs with different active regions are measured using temperature-dependent, carrier-density-dependent, and time-resolved photoluminescence. Three active regions are investigated: one 12-nm-thick single quantum well (SQW), two 6-nm-thick QWs, and three 4-nm-thick QWs. The IQE is highest for the 12-nm-thick SQW and decreases as the well width decreases. The radiative lifetimes are similar for all structures, while the nonradiative lifetimes decrease as the well width decreases. The superior IQE and longer nonradiative lifetime of the SQW structure suggests using thick SQW active regions for high brightness semipolar ($$20\\bar{2}$$$\\bar{1}$$) LEDs.« less

Internal quantum efficiency and carrier dynamics in semipolar (2021) InGaN/GaN light-emitting diodes

DOE PAGES

Okur, Serdal; Nami, Mohsen; Rishinaramangalam, Ashwin K.; ...

2017-01-26

Here, the internal quantum efficiencies (IQE) and carrier lifetimes of semipolar (more » $$20\\bar{2}$$$\\bar{1}$$) InGaN/GaN LEDs with different active regions are measured using temperature-dependent, carrier-density-dependent, and time-resolved photoluminescence. Three active regions are investigated: one 12-nm-thick single quantum well (SQW), two 6-nm-thick QWs, and three 4-nm-thick QWs. The IQE is highest for the 12-nm-thick SQW and decreases as the well width decreases. The radiative lifetimes are similar for all structures, while the nonradiative lifetimes decrease as the well width decreases. The superior IQE and longer nonradiative lifetime of the SQW structure suggests using thick SQW active regions for high brightness semipolar ($$20\\bar{2}$$$\\bar{1}$$) LEDs.« less

Magnetization dynamics of Ni80Fe20 nanowires with continuous width modulation

NASA Astrophysics Data System (ADS)

Xiong, L. L.; Kostylev, M.; Adeyeye, A. O.

2017-06-01

A systematic investigation of the magnetization reversal and the dynamic behaviors of uncoupled Ni80Fe20 nanowires (NWs) with artificial continuous width modulation is presented. In contrast with the single resonance mode observed in the homogeneous NWs from the broadband ferromagnetic resonance spectroscopy, the NWs with continuous width modulation display three to five distinct resonance modes with increasing wire thickness in the range from 5 to 70 nm due to the nonuniform demagnetizing field. The highest frequency mode and the frequency difference between the two distinct highest modes are shown to be markedly sensitive to the NW thickness. Interestingly, we found that these modes can be described in terms of the quantization of the standing spin waves due to confined varied width. In addition, the easy axis coercive field for the width modulated NWs is much higher than homogeneous NWs of the same thickness when less than 70 nm. Our experimental results are in good qualitative agreement with the micromagnetic simulations. The results may find potential applications in the design and optimization of tunable magnonic filters.

Narrow-band generation in random distributed feedback fiber laser.

PubMed

Sugavanam, Srikanth; Tarasov, Nikita; Shu, Xuewen; Churkin, Dmitry V

2013-07-15

Narrow-band emission of spectral width down to ~0.05 nm line-width is achieved in the random distributed feedback fiber laser employing narrow-band fiber Bragg grating or fiber Fabry-Perot interferometer filters. The observed line-width is ~10 times less than line-width of other demonstrated up to date random distributed feedback fiber lasers. The random DFB laser with Fabry-Perot interferometer filter provides simultaneously multi-wavelength and narrow-band (within each line) generation with possibility of further wavelength tuning.

1164.4  nm and 1174.7  nm dual-wavelength Nd : GdVO4/Cr4+ : YAG/YVO4 passively Q-switched Raman microchip laser.

PubMed

Wang, Xiaojie; Wang, Xiaolei; Zheng, Zhifen; Qiao, Xihao; Dong, Jun

2018-04-20

A synchronous pulsed, dual-wavelength Raman laser at 1164.4 nm and 1174.7 nm has been demonstrated in a Nd:GdVO 4 /Cr 4+ :YAG/YVO 4 passively Q-switched Raman microchip laser (PQSRML). The 1164.4 nm and 1174.7 nm dual-wavelength first-order Stokes laser oscillation is attributed to the conversion of the 1063.2 nm and 1063.43 nm two-longitudinal-mode fundamental lasers with Raman frequency shifts of 816  cm -1 and 890  cm -1 , respectively. Stable dual-wavelength Raman laser pulses with nearly equal spectral intensities have been achieved independent of the pump power. A pulse repetition rate as high as 139.4 kHz has been achieved with T 0 =85%, and the pulse width has been shortened to 825 ps with T 0 =70%. A dual-wavelength Raman laser with sub-nanosecond pulse width and peak power of over 1 kW has been achieved in the Nd:GdVO 4 /Cr 4+ :YAG/YVO 4 PQSRML.

A reflective hydrogen sensor based on fiber ring laser with PCF modal interferometer

NASA Astrophysics Data System (ADS)

Zhang, Ya-Nan; Zhang, Aozhuo; Han, Bo; E, Siyu

2018-06-01

A new hydrogen sensor based on a fiber ring laser with a photonic crystal fiber (PCF) modal interferometer is proposed. The reflective PCF modal interferometer, which is fabricated by forming two collapse regions on the two ends of PCF with a fusion discharge technique, is utilized as the sensing head and filter. Particularly, the Pd/WO3 hydrogen-sensitive thin film is coated on the PCF for hydrogen sensing. The combination of the fiber ring laser and PCF modal interferometer gives the sensor a high signal-to-noise ratio and an improved detection limit. Experimental results show that the sensing system can achieve a hydrogen sensitivity of 1.28 nm/%, a high signal-to-noise ratio (∼30 dB), a narrow full width at half maximum (∼0.05 nm), and low detection limit of 0.0133%.

Non-polar a-plane ZnO films grown on r-Al2O3 substrates using GaN buffer layers

NASA Astrophysics Data System (ADS)

Xu, C. X.; Chen, W.; Pan, X. H.; Chen, S. S.; Ye, Z. Z.; Huang, J. Y.

2016-09-01

In this work, GaN buffer layer has been used to grow non-polar a-plane ZnO films by laser-assisted and plasma-assisted molecular beam epitaxy. The thickness of GaN buffer layer ranges from ∼3 to 12 nm. The GaN buffer thickness effect on the properties of a-plane ZnO thin films is carefully investigated. The results show that the surface morphology, crystal quality and optical properties of a-plane ZnO films are strongly correlated with the thickness of GaN buffer layer. It was found that with 6 nm GaN buffer layer, a-plane ZnO films display the best crystal quality with X-ray diffraction rocking curve full-width at half-maximum of only 161 arcsec for the (101) reflection.

High-velocity projectile impact induced 9R phase in ultrafine-grained aluminium.

PubMed

Xue, Sichuang; Fan, Zhe; Lawal, Olawale B; Thevamaran, Ramathasan; Li, Qiang; Liu, Yue; Yu, K Y; Wang, Jian; Thomas, Edwin L; Wang, Haiyan; Zhang, Xinghang

2017-11-21

Aluminium typically deforms via full dislocations due to its high stacking fault energy. Twinning in aluminium, although difficult, may occur at low temperature and high strain rate. However, the 9R phase rarely occurs in aluminium simply because of its giant stacking fault energy. Here, by using a laser-induced projectile impact testing technique, we discover a deformation-induced 9R phase with tens of nm in width in ultrafine-grained aluminium with an average grain size of 140 nm, as confirmed by extensive post-impact microscopy analyses. The stability of the 9R phase is related to the existence of sessile Frank loops. Molecular dynamics simulations reveal the formation mechanisms of the 9R phase in aluminium. This study sheds lights on a deformation mechanism in metals with high stacking fault energies.

Geometrically tunable Fabry-Perot filters based on reflection phase shift of high contrast gratings

NASA Astrophysics Data System (ADS)

Fang, Liang; Shi, Zhendong; Cheng, Xin; Peng, Xiang; Zhang, Hui

2016-03-01

We propose tunable Fabry-Perot filters constituted by double high contrast gratings (HCGs) arrays with different periods acting as reflectors separated by a fixed short cavity, based on high reflectivity and the variety reflection phase shift of HCG array which realize dynamic regulation of the filtering condition. Single optimized HCG obtains the reflectivity of higher than 99% in a grating period ranging from 0.68μm to 0.8μm across a bandwidth of 30nm near the 1.55μm wavelength. The filters can achieve the full width at half maximum (FWHM) of spectral line of less than 0.15nm, and the linear relationship of peak wavelengths and grating periods is established. The simulation results indicate a potential new approach to design a tunable narrowband transmission filter.

Molecular beam epitaxy of single-crystalline aluminum film for low threshold ultraviolet plasmonic nanolasers

NASA Astrophysics Data System (ADS)

Liu, Shuanglong; Sheng, Bowen; Wang, Xinqiang; Dong, Dashan; Wang, Ping; Chen, Zhaoying; Wang, Tao; Rong, Xin; Li, Duo; Yang, Liuyun; Liu, Shangfeng; Li, Mo; Zhang, Jian; Ge, Weikun; Shi, Kebin; Tong, Yuzhen; Shen, Bo

2018-06-01

High-quality single-crystalline aluminum films have been grown on Si(111) substrates by molecular beam epitaxy. The x-ray diffraction rocking curve of the (111) plane of the Al film shows a full width at half maximum of 564 arc sec for the sample grown at 100 °C, where the surface is atomically flat with a root-mean-square roughness of 0.40 nm in a scanned area of 3 × 3 μm2. By using such a high-quality Al film, we have demonstrated a room temperature ultraviolet surface-plasmon-polariton nanolaser at a wavelength of 360 nm with a threshold as low as ˜0.2 MW/cm2, which provides a powerful evidence for potential application of the single-crystalline Al film in plasmonic devices.

All-fiber bandpass filter based on asymmetrical modes exciting and coupling

NASA Astrophysics Data System (ADS)

Zhang, Qiang; Zhu, Tao; Shi, Leilei; Liu, Min

2013-01-01

A low cost all-fiber bandpass filter is demonstrated by fabricating an asymmetric long-period fiber grating (LPFG) in an off-set splicing fiber structure of two single mode fibers in this paper. The main principle of the filter is that the asymmetric LPFG written by single-side CO2 laser irradiation is used to couple the asymmetric cladding modes excited by the offset-coupling of the splicing point between the single mode fiber and the grating, and the left core mode of the splicing point cannot be coupled to the right fiber core, hence the interference effect is avoided. So the bandpass characteristics in the transmission spectrum are achieved. The designed filter exhibits a pass band at a central wavelength of 1565.0 nm with a full-width at half-maximum bandwidth of 12.3 nm.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Brummer, Gordie, E-mail: gbrummer@bu.edu; Photonics Center, Boston University, Boston, Massachusetts 02215; Nothern, Denis

Distributed Bragg reflectors (DBRs) with peak reflectivity at approximately 280 nm, based on compositionally graded Al{sub x}Ga{sub 1−x}N alloys, were grown on 6H-SiC substrates by plasma-assisted molecular beam epitaxy. DBRs with square, sinusoidal, triangular, and sawtooth composition profiles were designed with the transfer matrix method. The crystal structure of these DBRs was studied with high-resolution x-ray diffraction of the (1{sup ¯}015) reciprocal lattice point. The periodicity of the DBR profiles was confirmed with cross-sectional Z-contrast scanning transmission electron microscopy. The peak reflectance of these DBRs with 15.5 periods varies from 77% to 56% with corresponding full width at half maximum ofmore » 17–14 nm. Coupled mode analysis was used to explain the dependence of the reflectivity characteristics on the profile of the graded composition.« less

Exploiting solitons in all-optical networks

NASA Astrophysics Data System (ADS)

Atieh, Ahmad K.

Two key components, the pulse generator and optical signal demultiplexer, needed for the implementation of all-optical soliton-based local area and wide area networks are investigated. The technology of generating a bright soliton pulse train from a sinusoidal pulse train produced as the beat signal of two distributed feedback laser diodes passed through a so-called comblike fiber structure is developed. A design methodology for this structure is discussed, and using this approach a soliton pulse source is constructed generating 1553 nm pulses at a repetition rate of 50 GHz, with pulses of full width at half maximum of 2.0 ps. The fiber structure used to generate the bright soliton pulse train employs the lowest average power for the beat signal ever reported in the literature, and the shortest length of fiber. The same structure (with a different design) is also used to produce a 47.6 GHz dark soliton pulse train with a full width at half maximum of 3.8 ps. This is the first reported use of this structure to generate dark solitons. It is shown that the comblike dispersion profile fiber structures may also be exploited for soliton pulse compression producing widths as short as 200 fs. Two approaches to implementation of optical signal demultiplexing are discussed. These are the nonlinear optical loop mirror (NOLM) and the separation of multilevel time division multiplexed signal pulses in the frequency domain by exploiting the relationship between the pulse's energy (i.e. pulse amplitude and width) and the Raman self-frequency shift. A modification of the NOLM scheme is investigated where feedback that adjusts the power of the control signal (by controlling the gain of an erbium-doped fiber amplifier introduced into the control signal input path) is employed to make the structure insensitive to the state of polarization of the signal and control pulses. In order to better understand the physical phenomena exploited in optical fiber soliton transmission and the above schemes, two experiments are conducted to measure the fiber nonlinear ratio (n2/Aeff) and the Raman time constant (TR) in single-mode fibers at 1550 nm. The fiber nonlinear ratio was measured for standard telecommunication fiber, dispersion shifted fiber, and dispersion compensating fiber. A value of 3.0 fs for the Raman time constant was measured and is recommended for soliton pulse propagation modeling in single-mode optical fibers.

Seesaw-like polarized transmission behavior of silver nanowire arrays aligned by off-center spin-coating

NASA Astrophysics Data System (ADS)

Kang, Lu; Chen, Hui; Yang, Zhong-Jian; Yuan, Yongbo; Huang, Han; Yang, Bingchu; Gao, Yongli; Zhou, Conghua

2018-05-01

Straight silver nanowires were synthesized by accelerated oxidization and then aligned into ordered arrays by off-center spin-coating. Seesaw-like behavior was observed in the polarized transmission spectra of the arrays. With the increment of polarization angle (θP, defined as the angle between axis of nanowires and direction of electric field of light), transmission changed repeatedly with a period of 180°, but it moved to opposite directions between the two regions separated by supporting points locating at 494 nm. The behavior is ascribed to the competition between the extinction behaviors of the two modes of surface plasma polaritons on silver nanowires. One is the longitudinal mode which is excited by long wavelengths and tuned by function of cos2( θ p ) and the other is the transverse mode that is excited by short wavelengths and tuned by function of sin2( θ p ). Simulation was performed based on the finite-difference time domain method. The effect of the nanowire diameter and length (aspect ratio) on the position of the supporting point was studied. As nanowire width increased from 20 nm to 350 nm, the supporting point moved from 400 to 500 nm. While it changed slightly when the nanowire length increased from 3 μm to infinitely long (width fixed at 260 nm). In current study, the position of the supporting point is mainly determined by the nanowire width.

Breaking Through the Multi-Mesa-Channel Width Limited of Normally Off GaN HEMTs Through Modulation of the Via-Hole-Length.

PubMed

Chien, Cheng-Yen; Wu, Wen-Hsin; You, Yao-Hong; Lin, Jun-Huei; Lee, Chia-Yu; Hsu, Wen-Ching; Kuan, Chieh-Hsiung; Lin, Ray-Ming

2017-12-01

We present new normally off GaN high-electron-mobility transistors (HEMTs) that overcome the typical limitations in multi-mesa-channel (MMC) width through modulation of the via-hole-length to regulate the charge neutrality screen effect. We have prepared enhancement-mode (E-mode) GaN HEMTs having widths of up to 300 nm, based on an enhanced surface pinning effect. E-mode GaN HEMTs having MMC structures and widths as well as via-hole-lengths of 100 nm/2 μm and 300 nm/6 μm, respectively, exhibited positive threshold voltages (V th ) of 0.79 and 0.46 V, respectively. The on-resistances of the MMC and via-hole-length structures were lower than those of typical tri-gate nanoribbon GaN HEMTs. In addition, the devices not only achieved the E-mode but also improved the power performance of the GaN HEMTs and effectively mitigated the device thermal effect. We controlled the via-hole-length sidewall surface pinning effect to obtain the E-mode GaN HEMTs. Our findings suggest that via-hole-length normally off GaN HEMTs have great potential for use in next-generation power electronics.

Boundary-based cellwise OPC for standard-cell layouts

NASA Astrophysics Data System (ADS)

Pawlowski, David M.; Deng, Liang; Wong, Martin D. F.

2007-03-01

Model based optical proximity correction (OPC) has become necessary at 90nm technology node. Cellwise OPC is an attractive technique to reduce the mask data size as well as the prohibitive runtime of full-chip OPC. As feature dimensions have gotten smaller, the radius of influence for edge features has extended further into neighboring cells such that it is no longer sufficient to perform cellwise OPC independent of neighboring cells, especially for the critical layers. The methodology described in this work accounts for features in neighboring cells and allows a cellwise approach to be applied to cells with a printed gate length of 45nm with the projection that it can also be applied to future technology nodes. OPC-ready cells are generated at library creation (independent of placement) using a boundary-based technique. Each cell has a tractable number of OPC-ready versions due to an intelligent characterization of standard cell layout features. Results are very promising: the average edge placement error (EPE) for all metal1 features in 100 layouts is 0.731nm which is less than 1% of metal1 width; the maximum EPE for poly features reduced to 1/3, compared to cellwise OPC without considering boundaries, creating similar levels of lithographic accuracy while obviating any of the drawbacks inherent in layout specific full-chip model-based OPC.

Pushing indium phosphide quantum dot emission deeper into the near infrared

NASA Astrophysics Data System (ADS)

Saeboe, A. M.; Kays, J.; Mahler, A. H.; Dennis, A. M.

2018-02-01

Cadmium-free near infrared (NIR) emitting quantum dots (QDs) have significant potential for multiplexed tissue-depth imaging applications in the first optical tissue window (i.e., 650 - 900 nm). Indium phosphide (InP) chemistry provides one of the more promising cadmium-free options for biomedical imaging, but the full tunability of this material has not yet been achieved. Specifically, InP QD emission has been tuned from 480 - 730 nm in previous literature reports, but examples of samples emitting from 730 nm to the InP bulk bandgap limit of 925 nm are lacking. We hypothesize that by generating inverted structures comprising ZnSe/InP/ZnS in a core/shell/shell heterostructure, optical emission from the InP shell can be tuned by changing the InP shell thickness, including pushing deeper into the NIR than current InP QDs. Colloidal synthesis methods including hot injection precipitation of the ZnSe core and a modified successive ion layer adsorption and reaction (SILAR) method for stepwise shell deposition were used to promote growth of core/shell/shell materials with varying thicknesses of the InP shell. By controlling the number of injections of indium and phosphorous precursor material, the emission peak was tuned from 515 nm to 845 nm (2.41 - 1.47 eV) with consistent full width half maximum (FWHM) values of the emission peak 0.32 eV. To confer water solubility, the nanoparticles were encapsulated in PEGylated phospholipid micelles, and multiplexing of NIR-emitting InP QDs was demonstrated using an IVIS imaging system. These materials show potential for multiplexed imaging of targeted QD contrast agents in the first optical tissue window.

Tuning all-Optical Analog to Electromagnetically Induced Transparency in nanobeam cavities using nanoelectromechanical system.

PubMed

Shi, Peng; Zhou, Guangya; Deng, Jie; Tian, Feng; Chau, Fook Siong

2015-09-29

We report the observations of all-optical electromagnetically induced transparency in nanostructures using waveguide side-coupled with photonic crystal nanobeam cavities, which has measured linewidths much narrower than individual resonances. The quality factor of transparency resonance can be 30 times larger than those of measured individual resonances. When the gap between cavity and waveguide is reduced to 10 nm, the bandwidth of destructive interference region can reach 10 nm while the width of transparency resonance is 0.3 nm. Subsequently, a comb-drive actuator is introduced to tune the line shape of the transparency resonance. The width of the peak is reduced to 15 pm and the resulting quality factor exceeds 10(5).

Hard X-ray multilayer zone plate with 25-nm outermost zone width

NASA Astrophysics Data System (ADS)

Takano, H.; Sumida, K.; Hirotomo, H.; Koyama, T.; Ichimaru, S.; Ohchi, T.; Takenaka, H.; Kagoshima, Y.

2017-06-01

We have improved the performance of a previously reported multilayer zone plate by reducing its outermost zone width, using the same multilayer materials (MoSi2 and Si) and fabrication technique. The focusing performance was evaluated at the BL24XU of SPring-8 using 20-keV X-rays. The line spread function (LSF) in the focal plane was measured using a dark-field knife-edge scan method, and the point spread function was obtained from the LSF through a tomographic reconstruction principle. The spatial resolution was estimated to be 30 nm, which is in relatively good agreement with the calculated diffraction-limited value of 25 nm, while the measured diffraction efficiency of the +1st order was 24%.

Electronic transport properties of suspended few-nm black phosphorus nanoribbons

NASA Astrophysics Data System (ADS)

Masih Das, Paul; Danda, Gopinath; Cupo, Andrew; Jothi Thiruraman, Priyanka; Meunier, Vincent; Drndic, Marija

Theoretical studies of few-nm wide black phosphorus nanoribbons have revealed highly tunable, width-dependent properties such as modulation of bandgap magnitude and carrier mobility. Due to the atmospheric instability of black phosphorus in the few-layer regime and a lack of suitable lithographic patterning techniques, these structures have yet to be reported. Here, we demonstrate the fabrication of few-nm wide and thick black phosphorus nanoribbons via in situ electron beam nanosculpting. We also present in situ orientation- and width-dependent two-terminal electronic transport measurements of these structures. These measurements yield valuable insight into the semiconducting properties of black phosphorus and its associated lower-dimensional nanostructures. NIH Grant R21HG007856, NSF Grant EFRI 2-DARE (EFRI-1542707).

Shock-tube studies of atomic silicon emission in the spectral range 180 to 300 nm. [environment simulation for Jupiter probes

NASA Technical Reports Server (NTRS)

Prakash, S. G.; Park, C.

1978-01-01

Emission spectroscopy of shock-heated atomic silicon was performed in the spectral range 180 to 300 nm, in an environment simulating the ablation layer expected around a Jovian entry probe with a silica heat shield. From the spectra obtained at temperatures from 6000 to 10,000 K and electron number densities from 1 quadrillion to 100 quadrillion per cu cm, the Lorentzian line-widths were determined. The results showed that silicon lines are broadened significantly by both electrons (Stark broadening) and hydrogen atoms (Van der Waals broadening), and the combined line-widths are much larger than previously assumed. From the data, the Stark and the Van der Waals line-widths were determined for 34 silicon lines. Radiative transport through a typical shock layer was computed using the new line-width data. The computations showed that silicon emission in the hot region is large, but it is mostly absorbed in the colder region adjacent to the wall.

Control of Angular Intervals for Angle-Multiplexed Holographic Memory

NASA Astrophysics Data System (ADS)

Kinoshita, Nobuhiro; Muroi, Tetsuhiko; Ishii, Norihiko; Kamijo, Koji; Shimidzu, Naoki

2009-03-01

In angle-multiplexed holographic memory, the full width at half maximum of the Bragg selectivity curves is dependent on the angle formed between the medium and incident laser beams. This indicates the possibility of high density and high multiplexing number by varying the angular intervals between adjacent holograms. We propose an angular interval scheduling for closely stacking holograms into medium even when the angle range is limited. We obtained bit error rates of the order of 10-4 under the following conditions: medium thickness of 1 mm, laser beam wavelength of 532 nm, and angular multiplexing number of 300.

Spectrum-agile hundred-watt-level high-power random fiber laser enabled by watt-level tunable optical filter

NASA Astrophysics Data System (ADS)

Ye, Jun; Xu, Jiangming; Song, Jiaxin; Wu, Hanshuo; Zhang, Hanwei; Wu, Jian; Zhou, Pu

2018-06-01

Through high-fidelity numerical modeling and careful system-parameter design, we demonstrate the spectral manipulation of a hundred-watt-level high-power random fiber laser (RFL) by employing a watt-level tunable optical filter. Consequently, a >100-W RFL with the spectrum-agile property is achieved. The central wavelength can be continuously tuned with a range of ∼20 nm, and the tuning range of the full width at half maximum linewidth, which is closely related to the central wavelength, covers ∼1.1 to ∼2.7 times of the minimum linewidth.

Reflectance Spectra of Peacock Feathers and the Turning Angles of Melanin Rods in Barbules.

PubMed

Okazaki, Toshio

2018-02-01

I analyzed the association between the reflectance spectra and melanin rod arrangement in barbules of the eyespot of peacock feathers. The reflectance spectra from the yellow-green feather of the eyespot indicated double peaks of 430 and 540 nm. The maximum reflectance spectrum of the blue feather was 480 nm, and that of the dark blue feather was 420 nm. The reflectance spectra from brown feathers indicated double peaks of 490 and 610 nm. Transmission electron microscopic analysis confirmed that melanin rods were arranged fanwise in the outer layer toward the barbule tips. In addition, using polarized light microscope, I attempted to determine whether the turning angles of melanin rods in the barbules reflected different colors. The turning angle of the polarizing axis of the barbules was supported by that of the melanin rods, observed using transmission electron microscopic images. To compare the turning angle of melanin rods in the respective barbules, I calculated the opening width of the fanwise melanin rods by dividing the width of the barbules by the turning angle of the polarizing axis of barbules and obtained a positive correlation between the reflectance spectra and opening width of the fanwise melanin rods. Moreover, the widely spreading reflection from the barbules may occur because of the fanwise melanin rod arrangement.

A general route for the rapid synthesis of one-dimensional nanostructured single-crystal Te, Se and Se Te alloys directly from Te or/and Se powders

NASA Astrophysics Data System (ADS)

Zhou, Bo; Zhu, Jun-Jie

2006-03-01

A general and template-free 'disproportionation and reversal' route was developed to synthesize one-dimensional (1D) nanostructures of Te, Se and Se-Te alloys directly from Te or/and Se powders. The products were characterized by x-ray diffraction (XRD), transmission electron microscopy (TEM), selected area electron diffraction (SAED), and scanning electron microscopy (SEM). Te nanorods and nanowires with a width varying from about 40 nm to about 300 nm, Se nanowires with a width of 60-100 nm and a length of 4-6 µm, and SexTe100-x alloy nanorods with x in a wide range, and with a width of 30-70 nm and an aspect ratio of three to five, were prepared. The mechanism of formation of the nanorods and nanowires and the effects of the experimental conditions, such as solution concentration, cooling rate, solvent nature and heating process, on the morphology and size of the products have been discussed. We believe that this general route and some other proper reversible processes between solid state and solution state can be extended to the transformations from various bulk materials into nanosized materials with various morphologies.

Novel ultra-short and ultra-broadband polarization beam splitter based on a bent directional coupler.

PubMed

Dai, Daoxin; Bowers, John E

2011-09-12

A novel ultra-short polarization beam splitter (PBS) based on a bent directional coupler is proposed by utilizing the evanescent coupling between two bent optical waveguides with different core widths. For the bent directional coupler, there is a significant phase-mismatch for TE polarization while the phase-matching condition is satisfied for TM polarization. Therefore, the TM polarized light can be coupled from the narrow input waveguide to the adjacent wide waveguide while the TE polarization goes through the coupling region without significant coupling. An ultra-short (<10 μm-long) PBS is designed based on silicon-on-insulator nanowires and the length of the bent coupling region is as small as 4.5 μm while the gap width is chosen as 200 nm (large enough to simplify the fabrication). Numerical simulations show that the present PBS has a good fabrication tolerance for the variation of the waveguide width (more than ± 60 nm) and a very broad band (~200 nm) for an extinction ratio of >10 dB.

Structural and optical properties of CuS thin films deposited by Thermal co-evaporation

NASA Astrophysics Data System (ADS)

Sahoo, A. K.; Mohanta, P.; Bhattacharyya, A. S.

2015-02-01

Copper sulfide (CuS) thin films with thickness 100, 150 and 200 nm have been deposited on glass substrates by thermal co-evaporation of Copper and Sulphur. The effect of CuS film thickness on the structural and optical properties have investigated and discussed. Structural and optical investigations of the films were carried out by X-ray diffraction, atomic force microscopy, high-resolution transmission electron microscopy and UV spectroscopy. XRD and selected area electron diffraction conforms that polycrystalline in nature with hexagonal crystal structure. AFM studies revealed a smooth surface morphology with root mean-square roughness values increases from 24 nm to 42 nm as the film thickness increase from 100 nm to 200 nm. AFM image showed that grain size increases with thickness of film increases and good agreement with the calculated from full width half maximum of the X-ray diffraction peak using Scherrer's formula and Williamson-Hall plot. The absorbance of the thin films were absorbed decreases with wavelength through UV-visible regions but showed a increasing in the near-infrared regions. The reflectance spectra also showed lower reflectance peak (25% to 32%) in visible region and high reflectance peak (49 % to 54 %) in near-infrared region. These high absorbance films made them for photo-thermal conversion of solar energy.

Assessment of growth and spectral properties of Cr3+-doped La0.83Y0.29Sc2.88(BO3)4 crystal

NASA Astrophysics Data System (ADS)

Huang, Yisheng; Sun, Shijia; Lin, Zhoubin; Zhang, Lizhen; Wang, Guofu

2017-10-01

This paper reports the spectral characteristic of Cr3+-doped La0.83Y0.29 Sc2.88 (BO3)4 crystal. Cr3+-doped La0.83Y0.29Sc2.88 (BO3)4 crystal was grown from a flux of Li6B4O9 by the top seeded Solution growth method. Cr3+:La0.83Y0.29 Sc2.88 (BO3)4 crystal exhibits broad absorption and emission bands of Cr3+ ions. The absorption cross-section σa is 3.38 × 10-20 cm2 at 467 nm and 4.40 × 10-20 cm2 at 656 nm for E//c, respectively. The emission band with a peak at 906 nm has a full width at half maximum (FWHM) of 188 nm for E//c. The emission cross-section σe at 906 nm is 2.35 × 10-20 cm2 for E//c axis and 2.03 × 10-20 cm2 for E⊥c axis. The fluorescence lifetime of 4T2 → 4A2 transition is 37.7 μs. The investigated result indicates that it may be considered as a potential CW tunable laser crystal material.

Quasi-periodic photonic crystal Fabry–Perot optical filter based on Si/SiO2 for visible-laser spectral selectivity

NASA Astrophysics Data System (ADS)

Qi, Dong; Wang, Xian; Cheng, Yongzhi; Chen, Fu; Liu, Lei; Gong, Rongzhou

2018-06-01

We report on a 1D quasi-periodic photonic crystal Fabry–Perot optical filter Cs(Si/SiO2)3(SiO2/Si)3 for spectral selectivity of visible light and 1.55 µm laser. A material transparency interval of 1.03–2.06 µm makes Si a unique choice of high refractive index material. Owing to the CIE 1931 standard and equal inclination interference, the designed structure can be successfully fabricated with a certain color (brown, khaki, or blue) corresponding to the different Cs physical thickness d and response R(λ). In addition, the peak transmittance T max of the proposed structure can reach as high as 92.56% (Cs  =  20 nm), 90.83% (Cs  =  40 nm), and 88.85% (Cs  =  60 nm) with a relatively narrow full width at half maximum of 4.4, 4.6, and 4.8 nm at 1.55 µm. The as-prepared structure indicates that it is feasible for a photonic crystal Fabry–Perot optical filter to achieve visible-laser (1.55 µm) spectral selectivity.

Progress and process improvements for multiple electron-beam direct write

NASA Astrophysics Data System (ADS)

Servin, Isabelle; Pourteau, Marie-Line; Pradelles, Jonathan; Essomba, Philippe; Lattard, Ludovic; Brandt, Pieter; Wieland, Marco

2017-06-01

Massively parallel electron beam direct write (MP-EBDW) lithography is a cost-effective patterning solution, complementary to optical lithography, for a variety of applications ranging from 200 to 14 nm. This paper will present last process/integration results to achieve targets for both 28 and 45 nm nodes. For 28 nm node, we mainly focus on line-width roughness (LWR) mitigation by playing with stack, new resist platform and bias design strategy. The lines roughness was reduced by using thicker spin-on-carbon (SOC) hardmask (-14%) or non-chemically amplified (non-CAR) resist with bias writing strategy implementation (-20%). Etch transfer into trilayer has been demonstrated by preserving pattern fidelity and profiles for both CAR and non-CAR resists. For 45 nm node, we demonstrate the electron-beam process integration within optical CMOS flows. Resists based on KrF platform show a full compatibility with multiple stacks to fit with conventional optical flow used for critical layers. Electron-beam resist performances have been optimized to fit the specifications in terms of resolution, energy latitude, LWR and stack compatibility. The patterning process overview showing the latest achievements is mature enough to enable starting the multi-beam technology pre-production mode.

Spectrum radial velocity analyser (SERVAL). High-precision radial velocities and two alternative spectral indicators

NASA Astrophysics Data System (ADS)

Zechmeister, M.; Reiners, A.; Amado, P. J.; Azzaro, M.; Bauer, F. F.; Béjar, V. J. S.; Caballero, J. A.; Guenther, E. W.; Hagen, H.-J.; Jeffers, S. V.; Kaminski, A.; Kürster, M.; Launhardt, R.; Montes, D.; Morales, J. C.; Quirrenbach, A.; Reffert, S.; Ribas, I.; Seifert, W.; Tal-Or, L.; Wolthoff, V.

2018-01-01

Context. The CARMENES survey is a high-precision radial velocity (RV) programme that aims to detect Earth-like planets orbiting low-mass stars. Aims: We develop least-squares fitting algorithms to derive the RVs and additional spectral diagnostics implemented in the SpEctrum Radial Velocity AnaLyser (SERVAL), a publicly available python code. Methods: We measured the RVs using high signal-to-noise templates created by coadding all available spectra of each star. We define the chromatic index as the RV gradient as a function of wavelength with the RVs measured in the echelle orders. Additionally, we computed the differential line width by correlating the fit residuals with the second derivative of the template to track variations in the stellar line width. Results: Using HARPS data, our SERVAL code achieves a RV precision at the level of 1 m/s. Applying the chromatic index to CARMENES data of the active star YZ CMi, we identify apparent RV variations induced by stellar activity. The differential line width is found to be an alternative indicator to the commonly used full width half maximum. Conclusions: We find that at the red optical wavelengths (700-900 nm) obtained by the visual channel of CARMENES, the chromatic index is an excellent tool to investigate stellar active regions and to identify and perhaps even correct for activity-induced RV variations.

A laser-Compton scattering prototype experiment at 100 MeV linac of Shanghai Institute of Applied Physics.

PubMed

Luo, W; Xu, W; Pan, Q Y; Cai, X Z; Chen, J G; Chen, Y Z; Fan, G T; Fan, G W; Guo, W; Li, Y J; Liu, W H; Lin, G Q; Ma, Y G; Shen, W Q; Shi, X C; Xu, B J; Xu, J Q; Xu, Y; Zhang, H O; Yan, Z; Yang, L F; Zhao, M H

2010-01-01

As a prototype of the Shanghai Laser Electron Gamma Source in the Shanghai Synchrotron Radiation Facility, an x-ray source based on laser-Compton scattering (LCS) has been installed at the terminal of the 100 MeV linac of the Shanghai Institute of Applied Physics. LCS x-rays are generated by interactions between Q-switched Nd:yttrium aluminum garnet laser pulses [with wavelength of 1064 nm and pulse width of 21 ns (full width at half maximum)] and electron bunches [with energy of 108 MeV and pulse width of 0.95 ns (rms)] at an angle of 42 degrees between laser and electron beam. In order to measure the energy spectrum of LCS x-rays, a Si(Li) detector along the electron beam line axis is positioned at 9.8 m away from a LCS chamber. After background subtraction, the LCS x-ray spectrum with the peak energy of 29.1+/-4.4|(stat)+/-2.1|(syst) keV and the peak width (rms) of 7.8+/-2.8|(stat)+/-0.4|(syst) keV is observed. Normally the 100 MeV linac operates with the electron macropulse charge of 1.0 nC/pulse, and the electron and laser collision repetition rate of 20 Hz. Therefore, the total LCS x-ray flux of (5.2+/-2.0) x 10(2) Hz can be achieved.

Effect of Ru thickness on spin pumping in Ru/Py bilayer

DOE Office of Scientific and Technical Information (OSTI.GOV)

Behera, Nilamani; Singh, M. Sanjoy; Chaudhary, Sujeet

2015-05-07

We report the effect of Ru thickness (t{sub Ru}) on ferromagnetic resonance (FMR) line-width of Ru(t{sub Ru})/Py(23 nm) bilayer samples grown on Si(100)/SiO{sub 2} substrates at room temperature by magnetron sputtering. The FMR line-width is found to vary linearly with frequency for all thicknesses of Ru, indicating intrinsic origin of damping. For Ru thicknesses below 15 nm, Gilbert-damping parameter, α is almost constant. We ascribe this behavior to spin back flow that is operative for Ru thicknesses lower than the spin diffusion length in Ru, λ{sub sd}. For thicknesses >15 nm (>λ{sub sd}), the damping constant increases with Ru thickness, indicating spin pumpingmore » from Py into Ru.« less

Enhanced absorption of TM waves in conductive nanoparticles structure

NASA Astrophysics Data System (ADS)

Mousa, H. M.; Shabat, M. M.; Ouda, A. K.; Schaadt, D. M.

2018-05-01

This paper tackles anti-reflection coating structure for silicon solar cell where conductive nanoparticle (CNP) film is sandwiched between a semi-infinite glass cover and a semi-infinite silicon substrate. The transmission and reflection coefficients are derived by the transfer matrix method and simulated for values of unit cell sizes, gab widths in visible and near-infrared radiation. We also illustrated the dependence of the absorption, transmission and reflection coefficients on several angles of incidence of the transverse magnetic polarized (TM) waves. We found out that reflection decreases by the increase of incident angle to 50∘. If nanoparticles are suitably located and sized at gab width of 3.5 nm, unit cell of 250 nm and CNP layer thickness of 150 nm, the absorptivity of the structure achieves 100%.

Cadmium-free quantum dot light emitting devices: energy-transfer realizing pure blue emission.

PubMed

Ji, Wenyu; Jing, Pengtao; Fan, Yi; Zhao, Jialong; Wang, Yunjun; Kong, Xianggui

2013-01-01

In this study, deep blue, pure electroluminescence (EL) at 441.5 nm from a ZnSe/ZnS quantum dot light-emitting device (QD-LED) is obtained by using poly (4-butylphenyl-diphenyl-amine) (poly-TPD) as the hole-transport layer (HTL) to open up the channel for energy transfer from poly-TPD to QDs. The emission originating from HTL is observed in the QD-LED with N,N'-bis (tolyl)-N,N'-diphenyl-1,1'-biphenyl-4,4'-diamine functionalized with two styryl groups (2-TPD) as the HTL due to inefficient energy-transfer from 2-TPD to QDs. The poly-TPD based device exhibits color-saturated blue emission with a narrow spectral bandwidth of full width at half maximum (~17.2 nm). These results explore the operating mechanism of the QD EL and signify a remarkable progress in deep blue QD-LEDs based on environmental-friendly QD materials.

Self-starting, self-regulating Fourier domain mode locked fiber laser for OCT imaging

PubMed Central

Murari, Kartikeya; Mavadia, Jessica; Xi, Jiefeng; Li, Xingde

2011-01-01

We present a Fourier domain mode locking (FDML) fiber laser with a feedback loop allowing automatic startup without a priori knowledge of the fundamental drive frequency. The feedback can also regulate the drive frequency making the source robust against environmental variations. A control system samples the energy of the light traversing the FDML cavity and uses a voltage controlled oscillator (VCO) to drive the tunable fiber Fabry-Perot filter in order to maximize that energy. We demonstrate a prototype self-starting, self-regulating FDML operating at 40 kHz with a full width tuning range of 140 nm around 1305 nm and a power output of ~40 mW. The laser starts up with no operator intervention in less than 5 seconds and exhibits improved spectral stability over a conventional FDML source. In OCT applications the source achieved over 120 dB detection sensitivity and an ~8.9-µm axial resolution. PMID:21750775

Transverse diode-pumped neodymium-doped yttrium vanadate laser of simple design

NASA Astrophysics Data System (ADS)

Agüero, Mónica B.; Hnilo, Alejandro A.; Kovalsky, Marcelo G.

2010-03-01

The design and performance of an all-solid-state Nd:YVO4 laser, transversely pumped by a single 20-W (at 808 nm) diode with no coupling optics, are presented. The prototype, which is devised to be the source of a micro-LIDAR station, is very simple, easy to align, compact, and stable. The key element is a roof prism as the end mirror of the laser cavity, which is used to symmetrize the effects of the thermal distortion and the inhomogeneity of the population inversion distribution. Typical numbers are 4.2-W cw with a slightly astigmatic (3:2) homogeneous spot and a divergence of 0.5 mrad. The protoype is also tested in the active Q-switching mode, providing pulses 50-ns full width at half maximum (FWHM) at 14 KHz, 3.5 W average. Frequency doubling external to the cavity in a nonoptimized configuration provides 700 mW at 532 nm.

Engineering photonic nanojet by a graded-index micro-cuboid

NASA Astrophysics Data System (ADS)

Liu, Cheng-Yang; Yen, Tzu-Ping; Minin, Oleg V.; Minin, Igor V.

2018-04-01

In the present paper the basic characteristics (length, peak intensity, and full-width half-maximum) of nanojets formed in the vicinity of dielectric core-shell cuboids with different types of index grading are investigated by finite-difference time domain method. The latitudinal and longitudinal sizes of a nanojet and its peak intensity depending on the optical contrast variation of cuboids core-shells are numerically investigated. It has been shown that it is possible to control and elongate the nanojet abnormally. It also was shown that graded cuboid with dimensions of 4 × 4 × 4 wavelength may has FWHM of a jet less than uniform cuboid with dimensions of 1 × 1 × 1 wavelength. At wavelength of 600 nm graded index cuboid with dimensions of 4 × 4 × 4 wavelength and index grading = 2 allow to form photonic jet with FWHM about 232 nm or 0.39 wavelength.

Solution-Grown ZnO Films toward Transparent and Smart Dual-Color Light-Emitting Diode.

PubMed

Huang, Xiaohu; Zhang, Li; Wang, Shijie; Chi, Dongzhi; Chua, Soo Jin

2016-06-22

An individual light-emitting diode (LED) capable of emitting different colors of light under different bias conditions not only allows for compact device integration but also extends the functionality of the LED beyond traditional illumination and display. Herein, we report a color-switchable LED based on solution-grown n-type ZnO on p-GaN/n-GaN heterojunction. The LED emits red light with a peak centered at ∼692 nm and a full width at half-maximum of ∼90 nm under forward bias, while it emits green light under reverse bias. These two lighting colors can be switched repeatedly by reversing the bias polarity. The bias-polarity-switched dual-color LED enables independent control over the lighting color and brightness of each emission with two-terminal operation. The results offer a promising strategy toward transparent, miniaturized, and smart LEDs, which hold great potential in optoelectronics and optical communication.

Short-wavelength InAlGaAs/AlGaAs quantum dot superluminescent diodes

NASA Astrophysics Data System (ADS)

Liang, De-Chun; An, Qi; Jin, Peng; Li, Xin-Kun; Wei, Heng; Wu, Ju; Wang, Zhan-Guo

2011-10-01

This paper reports the fabrication of J-shaped bent-waveguide superluminescent diodes utilizing an InAlGaAs/AlGaAs quantum dot active region. The emission spectrum of the device is centred at 884 nm with a full width at half maximum of 37 nm and an output power of 18 mW. By incorporating an Al composition into the quantum dot active region, short-wavelength superluminescent diode devices can be obtained. An intersection was found for the light power-injection current curves measured from the straight-waveguide facet and the bent-waveguide facet, respectively. The result is attributed to the conjunct effects of the gain and the additional loss of the bent waveguide. A numerical simulation is performed to verify the qualitative explanation. It is shown that bent waveguide loss is an important factor that affects the output power of J-shaped superluminescent diode devices.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Froula, D. H.; Boni, R.; Bedzyk, M.

A 10-ps, 263-nm (4{omega}) laser is being built to probe plasmas produced on the OMEGA EP [J. H. Kelly, L. J. Waxer, V. Bagnoud, I. A. Begishev, J. Bromage, B. E. Kruschwitz, T. E. Kessler, S. J. Loucks, D. N. Maywar, R. L. McCrory et al., J. Phys. IV France 133, 75-80 (2006)]. A suite of optical diagnostics (schlieren, interferometry, and grid image refractometry) has been designed to diagnose and characterize a wide variety of plasmas. Light scattered by the probe beam is collected by an f/4 catadioptric telescope and a transport system is designed to image with a near-diffraction-limitedmore » resolution ({approx}1 -{mu}m full width at half maximum) over a 5-mm field of view to a diagnostic table. The transport system provides a contrast greater than 1 : 10{sup 4} with respect to all wavelengths outside of the 263 {+-} 2 nm measurement range.« less

Sub-one-third wavelength focusing of surface plasmon polaritons excited by linearly polarized light.

PubMed

Wang, Jiayuan; Zhang, Jiasen

2018-05-28

We report the generation of a subwavelength focal spot for surface plasmon polaritons (SPPs) by increasing the proportion of high-spatial-frequency components in the plasmonic focusing field. We have derived an analytical expression for the angular-dependent contribution of an arbitrary-shaped SPP line source to the focal field and have found that the proportion for high-spatial-frequency components can be significantly increased by launching SPPs from a horizontal line source. Accordingly, we propose a rectangular-groove plasmonic lens (PL) consisting of horizontally-arrayed central grooves and slantingly-arrayed flanking grooves on gold film. We demonstrate both numerically and experimentally that, under linearly polarized illumination, such a PL generates a focal spot of full width half maximum 274 nm at an operating wavelength of 830 nm. The method we describe provides guidance to the further structure design and optimization for plasmonic focusing devices.

Optical transitions of Er3+/Yb3+ codoped TeO2-WO3-Bi2O3 glass.

PubMed

Shen, Xiang; Nie, Qiuhua; Xu, Tiefeng; Gao, Yuan

2005-10-01

Optical absorption and emission properties of the Er3+/Yb3+ codoped TeO2-WO3-Bi2O3 (TWB) glass has been investigated. The transition probabilities, excited state lifetimes, and the branching ratios have been predicted for Er3+ based on the Judd-Ofelt theory. The broad 1.5 microm fluorescence was observed under 970 nm excitation, and its full width at half maximum (FWHM) is 77 nm. The emission cross-section is calculated using the McCumber theory, and the peak emission cross-section is 1.03 x 10(-21) cm2 at 1.531 microm. This value is much larger than those of the silicate and phosphate glasses. Efficient green and weak red upconversion luminescence from Er3+ centers in the glass sample was observed at room temperature, and the upconversion excitation processes have been analyzed.

Pure ultraviolet emission from ZnO quantum dots-based/GaN heterojunction diodes by MgO interlayer

NASA Astrophysics Data System (ADS)

Chen, Cheng; Liang, Renli; Chen, Jingwen; Zhang, Jun; Wang, Shuai; Zhao, Chong; Zhang, Wei; Dai, Jiangnan; Chen, Changqing

2017-07-01

We demonstrate the fabrication and characterization of ZnO/GaN-based heterojunction light-emitting diodes (LEDs) by using air-stable and solution-processable ZnO quantum dots (QDs) with a thin MgO interlayer acting as an electron blocking layer (EBL). The ZnO QDs/MgO/ p-GaN heterojunction can only display electroluminescence (EL) characteristic in reverse bias regime. Under sufficient reverse bias, a fairly pure ultraviolet EL emission located at 370 nm deriving from near band edge of ZnO with a full width at half maximum (FWHM) of 8.3 nm had been obtained, while the deep-level emission had been almost totally suppressed. The EL origination and corresponding carrier transport mechanisms were investigated qualitatively in terms of photoluminescence (PL) results and energy band diagram.[Figure not available: see fulltext.

High-Quality Crystal Growth and Characteristics of AlGaN-Based Solar-Blind Distributed Bragg Reflectors with a Tri-layer Period Structure

PubMed Central

Chang, Jianjun; Chen, Dunjun; Yang, Lianhong; Liu, Yanli; Dong, Kexiu; Lu, Hai; Zhang, Rong; Zheng, Youdou

2016-01-01

To realize AlGaN-based solar-blind ultraviolet distributed Bragg reflectors (DBRs), a novel tri-layer AlGaN/AlInN/AlInGaN periodical structure that differs from the traditional periodically alternating layers of high- and low-refractive-index materials was proposed and grown on an Al0.5Ga0.5N template via metal-organic chemical vapour deposition. Because of the intentional design of the AlInGaN strain transition layer, a state-of-the-art DBR structure with atomic-level-flatness interfaces was achieved using an AlGaN template. The fabricated DBR exhibits a peak reflectivity of 86% at the centre wavelength of 274 nm and a stopband with a full-width at half-maximum of 16 nm. PMID:27381651

Superconducting properties of NbN film, bridge and meanders

NASA Astrophysics Data System (ADS)

Joshi, Lalit M.; Verma, Apoorva; Gupta, Anurag; Rout, P. K.; Husale, Sudhir; Budhani, R. C.

2018-05-01

The transport properties of superconducting NbN nanostructures in the form of thin film, bridge of width (w) = 50 μm and three meanders of w = 500, 250 and 100 nm have been investigated by resistance (R) measurements in temperature (T) range = 2 -300 K and magnetic field (B) range = 0 - 7 Tesla. The nanostructuring was carried out using Focused Ion Beam (FIB) milling. Reduction of sample width results in significant changes in the normal and superconducting state properties. For instance, the observed metallic behavior in the thin film sample is lost and the normal state resistance increases drastically from 2.4 Ω to 418 kΩ for the 100 nm meander. In the superconducting state, the value of critical temperature Tc (upper critical field Bc2 at T = 0 K) reduces gradually with width reduction, it changes from 13.15 K (42.8 Tesla) in the case of thin film sample to 5.7 K (12.7 Tesla) for the 100 nm meander sample. The superconducting transitions are found to get broader for the bridge sample and the meanders additionally show low-temperature resistive tails. In case of all the samples with reduced width, the transition onsets are found to be rounded at surprisingly high values of T ˜ 25 K >> Tc. These results are discussed in terms of the possible effects of FIB processing and weak localization in our samples.

A graphite based STT-RAM cell with reduction in switching current

NASA Astrophysics Data System (ADS)

Varghani, Ali; Peiravi, Ali

2015-10-01

Spin Transfer Torque Random Access Memory (STT-RAM) is a serious candidate for "universal memory" because of its non-volatility, fast access time, high density, good scalability, high endurance and relatively low power dissipation. However, problems with low write speed and large write current are important existing challenges in STT-RAM design and there is a tradeoff between them and data retention time. In this study, a novel STT-RAM cell structure which uses perfect graphite based Magnetic Tunnel Junction (MTJ) is proposed. First, the cross-section of the structure is selected to be an ellipse of 45 nm and 180 nm dimensions and a six-layer graphite is used as tunnel barrier. By passing a lateral current with a short pulse width (before applying STT current and independent of it) through four middle graphene layers of the tunnel barrier, a 27% reduction in the amplitude of the switching current (for fast switching time of 2 ns) or a 58% reduction in its pulse width is achieved without any reduction in data retention time. Finally, the effect of downscaling of technology on the proposed structure is evaluated. A reduction of 31.6% and 9% in switching current is achieved for 90 and 22 nm cell width respectively by passing sufficient current (100 μA with 0.1 ns pulse width) through the tunnel barrier. Simulations are done using Object Oriented Micro Magnetic Framework (OOMMF).

Effects of 532 nm pulsed-KTP laser parameters on vessel ablation in the avian chorioallantoic membrane: implications for vocal fold mucosa.

PubMed

Broadhurst, Matthew S; Akst, Lee M; Burns, James A; Kobler, James B; Heaton, James T; Anderson, R Rox; Zeitels, Steven M

2007-02-01

Selective vascular ablation (photoangiolysis) using pulsed lasers that target hemoglobin is an effective treatment strategy for many vocal fold lesions. However, vessel rupture with extravasation of blood reduces selectivity for vessels, which is frequently observed with the 0.45-ms, 585-nm pulsed dye laser. Previous studies have shown that vessel rupture is the result of vaporization of blood, an event that varies with laser pulse width and pulse fluence (energy per unit area). Clinical observations using a 532-nm wavelength pulsed potassium-titanyl-phosphate (KTP) laser revealed less laser-induced hemorrhage than the pulsed dye laser. This study investigated settings for the pulsed KTP laser to achieve selective vessel destruction without rupture using the avian chorioallantoic membrane under conditions similar to flexible laryngoscopic delivery of the laser in clinical practice. The chick chorioallantoic membrane offers convenient access to many small blood vessels similar in size to those targeted in human vocal fold. Using a 532-nm pulsed KTP laser, pulse width, pulse energy, and working distance from the optical delivery fiber were varied to assess influence on the ability to achieve vessel coagulation without vessel wall rupture. Third-order vessels (n = 135) were irradiated: Energy (471-550 mJ), pulse width (10, 15, 30 ms), and fiber-to-tissue distance (1 mm, 3 mm) were varied systematically. Selective vessel destruction without vessel wall rupture was more often achieved by increasing pulse width, increasing the fiber-to-tissue distance, and decreasing energy. Vessel destruction without rupture was consistently achieved using 15- or 30-ms pulses with a fiber-to-tissue distance of 3 mm (pulse fluence of 13-16 J/cm). This study substantiates our clinical observation that a 532-nm pulsed KTP laser was effective for ablating microcirculation while minimizing vessel wall rupture and hemorrhage.

Strongly Coupled Tin-Halide Perovskites to Modulate Light Emission: Tunable 550-640 nm Light Emission (FWHM 36-80 nm) with a Quantum Yield of up to 6.4.

PubMed

Chen, Min-Yi; Lin, Jin-Tai; Hsu, Chia-Shuo; Chang, Chung-Kai; Chiu, Ching-Wen; Chen, Hao Ming; Chou, Pi-Tai

2018-05-01

Colloidal perovskite quantum dots represent one of the most promising materials for applications in solar cells and photoluminescences. These devices require a low density of crystal defects and a high yield of photogenerated carriers, which are difficult to realize in tin-halide perovskite because of the intrinsic instability of tin during nucleation. Here, an enhancement in the luminescent property of tin-halide perovskite nanoplates (TPNPs) that are composed of strongly coupled layered structures with the chemical formula of PEA 2 SnX 4 (PEA = C 6 H 5 (CH 2 ) 2 NH 3 , X = Br, I) is reported. TPNPs (X = I) show an emission at a wavelength of 640 nm, with high quantum yield of 6.40 ± 0.14% and full width at half maximum (FWHM) as small as 36 nm. The presence of aliphatic carboxylic acid is found to play a key role in reducing the tin perovskite defect density, which significantly improves the emission intensity and stability of TPNPs. Upon mixing iodo- and bromo- precursors, the emission wavelength is successfully tuned from 640 nm (PEA 2 SnI 4 ) to 550 nm (PEA 2 SnBr 4 ), with a corresponding emission quantum yield and FWHM of 0.16-6.40% and 36-80 nm, respectively. The results demonstrate a major advance for the emission yield and tunability of tin-halide perovskites. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Crystal growth and scintillation properties of strontium iodide scintillators

DOE Office of Scientific and Technical Information (OSTI.GOV)

van Loef, Edgar; Wilson, Cody; Cherepy, Nerine

2009-06-01

Single crystals of SrI{sub 2}:Eu and SrI{sub 2}:Ce/Na were grown from anhydrous iodides by the vertical Bridgman technique in evacuated silica ampoules. Growth rates were of the order of 5-30 mm/day. Radioluminescence spectra of SrI{sub 2}:Eu and SrI{sub 2}:Ce/Na exhibit a broad band due to Eu{sup 2+} and Ce{sup 3+} emission, respectively. The maximum in the luminescence spectrum of SrI{sub 2}:Eu is found at 435 nm. The spectrum of SrI{sub 2}:Ce/Na exhibits a doublet peaking at 404 and 435 nm attributed to Ce{sup 3+} emission, while additional impurity - or defected - related emission is present at approximately 525 nm.more » The strontium iodide scintillators show very high light yields of up to 120,000 photons/MeV, have energy resolutions down to 3% at 662 keV (Full Width Half Maximum) and exhibit excellent light yield proportionality with a standard deviation of less than 5% between 6 and 460 keV.« less

Enhanced ultraviolet electroluminescence and spectral narrowing from ZnO quantum dots/GaN heterojunction diodes by using high-k HfO{sub 2} electron blocking layer

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mo, Xiaoming; Long, Hao; Wang, Haoning

2014-08-11

We demonstrated the capability of realizing enhanced ZnO-related UV emissions by using the low-cost and solution-processable ZnO quantum dots (QDs) with the help of a high-k HfO{sub 2} electron blocking layer (EBL) for the ZnO QDs/p-GaN light-emitting diodes (LEDs). Full-width at half maximum of the LED devices was greatly decreased from ∼110 to ∼54 nm, and recombinations related to nonradiative centers were significantly suppressed with inserting HfO{sub 2} EBL. The electroluminescence of the ZnO QDs/HfO{sub 2}/p-GaN LEDs demonstrated an interesting spectral narrowing effect with increasing HfO{sub 2} thickness. The Gaussian fitting revealed that the great enhancement of the Zn{sub i}-related emissionmore » at ∼414 nm whereas the deep suppression of the interfacial recombination at ∼477 nm should be the main reason for the spectral narrowing effect.« less

Control of resonant wavelength from organic light-emitting materials by use of a Fabry-Perot microcavity structure.

PubMed

Jung, Boo Young; Kim, Nam Young; Lee, Changhee; Hwangbo, Chang Kwon; Seoul, Chang

2002-06-01

We report the fabrication of Fabry-Perot microcavity structures with the organic light-emitting material tris-(8-hydroxyquinoline) aluminum (Alq3) and derive their optical properties by measuring their photoluminescence (PL) and absorption. Silver and a TiO2-SiO2 multilayer were used as metal and dielectric reflectors, respectively, in a Fabry-Perot microcavity structure. Three types of microcavity were prepared: type A consisted of [air[Ag[Alq3]Ag]glass]; type B, of [air[dielectric[Alq3]dielectric]glass]; and type C, of [air[Ag[Alq2]dielectric]glass]. A bare Alq3 film of [air[Alq3]glass] had its PL peak near 514 nm, and its full width at half-maximum (FWHM) was 80 nm. The broad FWHM of a bare Alq3 film was reduced to 15-27.5, 7-10.5, and 16-16.6 nm for microcavity types A, B, and C, respectively. Also, we could control the PL peak of the microcavity structure by changing the spacer thickness, the amount of phase change on reflection, and the angle of incidence.

Ultraviolet Raman Wide-Field Hyperspectral Imaging Spectrometer for Standoff Trace Explosive Detection.

PubMed

Hufziger, Kyle T; Bykov, Sergei V; Asher, Sanford A

2017-02-01

We constructed the first deep ultraviolet (UV) Raman standoff wide-field imaging spectrometer. Our novel deep UV imaging spectrometer utilizes a photonic crystal to select Raman spectral regions for detection. The photonic crystal is composed of highly charged, monodisperse 35.5 ± 2.9 nm silica nanoparticles that self-assemble in solution to produce a face centered cubic crystalline colloidal array that Bragg diffracts a narrow ∼1.0 nm full width at half-maximum (FWHM) UV spectral region. We utilize this photonic crystal to select and image two different spectral regions containing resonance Raman bands of pentaerythritol tetranitrate (PETN) and NH 4 NO 3 (AN). These two deep UV Raman spectral regions diffracted were selected by angle tuning the photonic crystal. We utilized this imaging spectrometer to measure 229 nm excited UV Raman images containing ∼10-1000 µg/cm 2 samples of solid PETN and AN on aluminum surfaces at 2.3 m standoff distances. We estimate detection limits of ∼1 µg/cm 2 for PETN and AN films under these experimental conditions.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gao, Bing; Shen, Chao; Zhang, Mengya

Green synthesis of CdSe quantum dots for application in the quantum-dots-sensitized solar cells (QDSCs) is investigated in this work. The CdSe QDs were prepared with glycerol as the solvent, with sharp emission peak, full width at half maximum around 30 nm, and absorption peak from 475 nm to 510 nm. The reaction is environmental friendly and energy saving. What's more, the green synthesized CdSe QDs are coherence to the maximum remittance region of the solar spectrum and suitable as sensitizers to assemble onto TiO{sub 2} electrodes for cell devices application. What's more, the dynamic procedure of the carriers' excitation, transportation, and recombination inmore » the QDSCs are discussed. Because the recombination of the electrons from the conduction band of TiO{sub 2}'s to the electrolyte affects the efficiency of the solar cells greatly, 3-Mercaptopropionic acid capped water-dispersible QDs were used to cover the surface of TiO{sub 2}. The resulting green synthesized CdSe QDSCs with Cu{sub 2}S as the electrode show a photovoltaic performance with a conversion efficiency of 3.39%.« less

Fabrication and luminescent properties of Al2O3:Cr3 + microspheres via a microwave solvothermal route followed by heat treatment

NASA Astrophysics Data System (ADS)

Zhu, Zhenfeng; Liu, Dianguang; Liu, Hui; Du, Juan; Yu, Hongguang; Deng, Jie

2012-06-01

AlOOH:Cr3 + powders were synthesized via a microwave solvothermal route at 433 K for 30 min and were used as the precursor and template for the preparation of γ-Al2O3:Cr3 + by thermal transformation at 773 K for 2 h in air. The obtained γ-Al2O3 based powders were microspheres with an average diameter about 1.9 μm. Photoluminescence (PL) spectra showed that the Al2O3:Cr3 + particles presented a symmetric broad R band at 696 nm without appreciable splitting when excited at 462 nm. It is shown that the 0.04 mol% of doping concentration of Cr3 + ions in γ-Al2O3:Cr3 + is optimum. According to Dexter's theory, the critical distance between Cr3 + ions for energy transfer was determined to be 47.54 Å. Based on the corresponding PL spectrum, full width at half maximum (FWHM) of Al2O3:Cr3 + (0.04 mol%) was calculated to be 3.35 nm.

120nm resolution in thick samples with structured illumination and adaptive optics

NASA Astrophysics Data System (ADS)

Thomas, Benjamin; Sloan, Megan; Wolstenholme, Adrian J.; Kner, Peter

2014-03-01

μLinear Structured Illumination Microscopy (SIM) provides a two-fold increase over the diffraction limited resolution. SIM produces excellent images with 120nm resolution in tissue culture cells in two and three dimensions. For SIM to work correctly, the point spread function (PSF) and optical transfer function (OTF) must be known, and, ideally, should be unaberrated. When imaging through thick samples, aberrations will be introduced into the optical system which will reduce the peak intensity and increase the width of the PSF. This will lead to reduced resolution and artifacts in SIM images. Adaptive optics can be used to correct the optical wavefront restoring the PSF to its unaberrated state, and AO has been used in several types of fluorescence microscopy. We demonstrate that AO can be used with SIM to achieve 120nm resolution through 25m of tissue by imaging through the full thickness of an adult C. elegans roundworm. The aberrations can be corrected over a 25μm × 45μm field of view with one wavefront correction setting, demonstrating that AO can be used effectively with widefield superresolution techniques.

Direct writing of 150 nm gratings and squares on ZnO crystal in water by using 800 nm femtosecond laser.

PubMed

Liu, Jukun; Jia, Tianqing; Zhou, Kan; Feng, Donghai; Zhang, Shian; Zhang, Hongxin; Jia, Xin; Sun, Zhenrong; Qiu, Jianrong

2014-12-29

We present a controllable fabrication of nanogratings and nanosquares on the surface of ZnO crystal in water based on femtosecond laser-induced periodic surface structures (LIPSS). The formation of nanogrooves depends on both laser fluence and writing speed. A single groove with width less than 40 nm and double grooves with distance of 150 nm have been produced by manipulating 800 nm femtosecond laser fluence. Nanogratings with period of 150 nm, 300 nm and 1000 nm, and nanosquares with dimensions of 150 × 150 nm² were fabricated by using this direct femtosecond laser writing technique.

Comment on Sub-15 nm Hard X-Ray Focusing with a New Total-Reflection Zone Plate

DOE Office of Scientific and Technical Information (OSTI.GOV)

Specht, Eliot D

2011-01-01

Takano et al. report the focusing of 10-keV X-rays to a size of 14.4 nm using a total-reflection zone plate (TRZP). This focal size is at the diffraction limit for the optic's aperture. This would be a noteworthy result, since the TRZP was fabricated using conventional lithography techniques. Alternative nanofocusing optics require more demanding fabrication methods. However, as I will discuss in this Comment, the intensity distribution presented by Takano et al. (Fig. 4 of ref. 1) is more consistent with the random speckle pattern produced by the scattering of a coherent incident beam by a distorted optic than withmore » a diffraction-limited focus. When interpreted in this manner, the true focal spot size is {approx}70 nm: 5 times the diffraction limit. When a coherent photon beam illuminates an optic containing randomly distributed regions which introduce different phase shifts, the scattered diffraction pattern consists of a speckle pattern. Each speckle will be diffraction-limited: the peak width of a single speckle depends entirely on the source coherence and gives no information about the optic. The envelope of the speckle distribution corresponds to the focal spot which would be observed using incoherent illumination. The width of this envelope is due to the finite size of the coherently-diffracting domains produced by slope and position errors in the optic. The focal intensity distribution in Fig. 4 of ref. 1 indeed contains a diffraction-limited peak, but this peak contains only a fraction of the power in the focused, and forms part of a distribution of sharp peaks with an envelope {approx}70 nm in width, just as expected for a speckle pattern. At the 4mm focal distance, the 70 nm width corresponds to a slope error of 18 {micro}rad. To reach the 14 nm diffraction limit, the slope error must be reduced to 3 {micro}rad. Takano et al. have identified a likely source of this error: warping due to stress as a result of zone deposition. It will be interesting to see whether the use of a more rigid substrate gives improved results.« less

Efficient generation of 509 nm light by sum-frequency mixing between two tapered diode lasers

NASA Astrophysics Data System (ADS)

Tawfieq, Mahmoud; Jensen, Ole Bjarlin; Hansen, Anders Kragh; Sumpf, Bernd; Paschke, Katrin; Andersen, Peter E.

2015-03-01

We demonstrate a concept for visible laser sources based on sum-frequency generation of beam combined tapered diode lasers. In this specific case, a 1.7 W sum-frequency generated green laser at 509 nm is obtained, by frequency adding of 6.17 W from a 978 nm tapered diode laser with 8.06 W from a 1063 nm tapered diode laser, inside a periodically poled MgO doped lithium niobate crystal. This corresponds to an optical to optical conversion efficiency of 12.1%. As an example of potential applications, the generated nearly diffraction-limited green light is used for pumping a Ti:sapphire laser, thus demonstrating good beam quality and power stability. The maximum output powers achieved when pumping the Ti:sapphire laser are 226 mW (CW) and 185 mW (mode-locked) at 1.7 W green pump power. The optical spectrum emitted by the mode-locked Ti:sapphire laser shows a spectral width of about 54 nm (FWHM), indicating less than 20 fs pulse width.

Phonon Conduction in Silicon Nanobeam Labyrinths

DOE PAGES

Park, Woosung; Romano, Giuseppe; Ahn, Ethan C.; ...

2017-07-24

Here we study single-crystalline silicon nanobeams having 470 nm width and 80 nm thickness cross section, where we produce tortuous thermal paths (i.e. labyrinths) by introducing slits to control the impact of the unobstructed “line-of-sight” (LOS) between the heat source and heat sink. The labyrinths range from straight nanobeams with a complete LOS along the entire length to nanobeams in which the LOS ranges from partially to entirely blocked by introducing slits, s = 95, 195, 245, 295 and 395 nm. The measured thermal conductivity of the samples decreases monotonically from ~47 W m -1K -1 for straight beam tomore » ~31 W m -1 K -1 for slit width of 395 nm. A model prediction through a combination of the Boltzmann transport equation and ab initio calculations shows an excellent agreement with the experimental data to within ~8%. The model prediction for the most tortuous path (s = 395 nm) is reduced by ~14% compared to a straight beam of equivalent cross section. This study suggests that LOS is an important metric for characterizing and interpreting phonon propagation in nanostructures.« less

Improving performance of armchair graphene nanoribbon field effect transistors via boron nitride doping

NASA Astrophysics Data System (ADS)

Goharrizi, A. Yazdanpanah; Sanaeepur, M.; Sharifi, M. J.

2015-09-01

Device performance of 10 nm length armchair graphene nanoribbon field effect transistors with 1.5 nm and 4 nm width (13 and 33 atoms in width respectively) are compared in terms of Ion /Ioff , trans-conductance, and sub-threshold swing. While narrow devices suffer from edge roughness wider devices are subject to more substrate surface roughness and reduced bandgap. Boron Nitride doping is employed to compensate reduced bandgap in wider devices. Simultaneous effects of edge and substrate surface roughness are considered. Results show that in the presence of both the edge and substrate surface roughness the 4 nm wide device with boron nitride doping shows improved performance with respect to the 1.5 nm one (both of which incorporate the same bandgap AGNR as channel material). Electronic simulations are performed via NEGF method along with tight-binding Hamiltonian. Edge and surface roughness are created by means of one and two dimensional auto correlation functions respectively. Electronic characteristics are averaged over a large number of devices due to statistic nature of both the edge and surface roughness.

Top-down fabrication of sub-nanometre semiconducting nanoribbons derived from molybdenum disulfide sheets.

PubMed

Liu, Xiaofei; Xu, Tao; Wu, Xing; Zhang, Zhuhua; Yu, Jin; Qiu, Hao; Hong, Jin-Hua; Jin, Chuan-Hong; Li, Ji-Xue; Wang, Xin-Ran; Sun, Li-Tao; Guo, Wanlin

2013-01-01

Developments in semiconductor technology are propelling the dimensions of devices down to 10 nm, but facing great challenges in manufacture at the sub-10 nm scale. Nanotechnology can fabricate nanoribbons from two-dimensional atomic crystals, such as graphene, with widths below the 10 nm threshold, but their geometries and properties have been hard to control at this scale. Here we find that robust ultrafine molybdenum-sulfide ribbons with a uniform width of 0.35 nm can be widely formed between holes created in a MoS2 sheet under electron irradiation. In situ high-resolution transmission electron microscope characterization, combined with first-principles calculations, identifies the sub-1 nm ribbon as a Mo5S4 crystal derived from MoS2, through a spontaneous phase transition. Further first-principles investigations show that the Mo5S4 ribbon has a band gap of 0.77 eV, a Young's modulus of 300GPa and can demonstrate 9% tensile strain before fracture. The results show a novel top-down route for controllable fabrication of functional building blocks for sub-nanometre electronics.

Synthesis of quantum dots via microreaction: structure optimization for microreactor system

NASA Astrophysics Data System (ADS)

Yang, Hongwei; Luan, Weiling; Cheng, Rui; Chu, Haijian; Tu, Shan-tung

2011-08-01

Microreactor systems existed as a powerful tool for the continuous synthesis of quantum dots. However, the lack of structure optimization for the discrete units led to empirical determination of the length scale, and the properties of the formed products varied in different cases. In this article, the optimizations for the micromixer volume and capillary diameter were presented based on the synthesis of CdSe nanocrystals (NCs). Spectra investigation revealed that the application of a small convective mixer of 36 μL led to 1/3 increase of CdSe concentration in the crude solution. The enhanced mixing of the precursors in this case was also demonstrated favorable to achieve CdSe NCs with narrow PL width. Fast heating and uniform reaction condition achieved in a narrow channel favored the preparation of high quality CdSe NCs under short residence time. However, the application of wide channel did not necessarily result in CdSe NCs with poor quality. Here, we demonstrated that high-quality CdSe NCs with narrow full width at half maximum (FWHM) as 32 nm and high quantum yield (QY) 34.7% could be prepared using an 844 μm inner diameter capillary. Based on the obtained results, the scaled-up synthesis of CdSe NCs was demonstrated, and a high quantity of 0.8 g dry CdSe NCs powder (3.5 nm, σ 8.2%) was obtained within 1 h.

Photoluminescence of patterned CdSe quantum dot for anti-counterfeiting label on paper

NASA Astrophysics Data System (ADS)

Isnaeni, Yulianto, Nursidik; Suliyanti, Maria Margaretha

2016-03-01

We successfully developed a method utilizing colloidal CdSe nanocrystalline quantum dot for anti-counterfeiting label on a piece of glossy paper. We deposited numbers and lines patterns of toluene soluble CdSe quantum dot using rubber stamper on a glossy paper. The width of line pattern was about 1-2 mm with 1-2 mm separation between lines. It required less than one minute for deposited CdSe quantum dot on glossy paper to dry and become invisible by naked eyes. However, patterned quantum dot become visible using long-pass filter glasses upon excitation of UV lamp or blue laser. We characterized photoluminescence of line patterns of quantum dot, and we found that emission boundaries of line patterns were clearly observed. The error of line size and shape were mainly due to defect of the original stamper. The emission peak wavelength of CdSe quantum dot was 629 nm. The emission spectrum of deposited quantum dot has full width at half maximum (FWHM) of 30-40 nm. The spectra similarity between deposited quantum dot and the original quantum dot in solution proved that our stamping method can be simply applied on glossy paper without changing basic optical property of the quantum dot. Further development of this technique is potential for anti-counterfeiting label on very important documents or objects.

1.5  kW ytterbium-doped single-transverse-mode, linearly polarized monolithic fiber master oscillator power amplifier.

PubMed

Huang, Long; Ma, Pengfei; Tao, Rumao; Shi, Chen; Wang, Xiaolin; Zhou, Pu

2015-04-01

A linearly polarized monolithic fiber laser based on a master oscillator power amplifier structure with a master oscillator and a one-stage power amplifier is reported. We design a homemade oscillator based on the theory that, in the coiled gain fiber, the higher modes and the polarized mode of the fundamental mode along the fast axis are suppressed effectively because of their obviously higher bend loss than that of the polarized mode of the fundamental mode along the slow axis. The oscillator operates at 1080 nm, launching a 30 W seed laser with a high polarization extinction ratio of 19 dB into the power amplifier via a mode field adapter. The power amplifier utilizes Yb-doped polarization-maintaining fiber of 20/400  μm, which produces nearly diffraction-limited output power of about 1.5 kW with an optical-optical efficiency of 81.5% and a polarization extinction ratio of 13.8 dB. Both the M(x)² factor and the M(y)² factor of the collimated beam are measured to be about 1.2. The spectral width of the output power is broadened approximately linearly, and the full width at half maximum of the spectrum at the maximum output power is about 5.8 nm. It is known as the highest linearly polarized output power to the best of our knowledge.

Photoluminescence of patterned CdSe quantum dot for anti-counterfeiting label on paper

DOE Office of Scientific and Technical Information (OSTI.GOV)

Isnaeni,, E-mail: isnaeni@lipi.go.id; Yulianto, Nursidik; Suliyanti, Maria Margaretha

We successfully developed a method utilizing colloidal CdSe nanocrystalline quantum dot for anti-counterfeiting label on a piece of glossy paper. We deposited numbers and lines patterns of toluene soluble CdSe quantum dot using rubber stamper on a glossy paper. The width of line pattern was about 1-2 mm with 1-2 mm separation between lines. It required less than one minute for deposited CdSe quantum dot on glossy paper to dry and become invisible by naked eyes. However, patterned quantum dot become visible using long-pass filter glasses upon excitation of UV lamp or blue laser. We characterized photoluminescence of line patterns of quantummore » dot, and we found that emission boundaries of line patterns were clearly observed. The error of line size and shape were mainly due to defect of the original stamper. The emission peak wavelength of CdSe quantum dot was 629 nm. The emission spectrum of deposited quantum dot has full width at half maximum (FWHM) of 30-40 nm. The spectra similarity between deposited quantum dot and the original quantum dot in solution proved that our stamping method can be simply applied on glossy paper without changing basic optical property of the quantum dot. Further development of this technique is potential for anti-counterfeiting label on very important documents or objects.« less

Nanostructured polymer brushes.

PubMed

Schmelmer, Ursula; Paul, Anne; Küller, Alexander; Steenackers, Marin; Ulman, Abraham; Grunze, Michael; Gölzhäuser, Armin; Jordan, Rainer

2007-03-01

Nanopatterned polymer brushes with sub-50-nm resolution were prepared by a combination of electron-beam chemical lithography (EBCL) of self-assembled monolayers (SAMs) and surface-initiated photopolymerization (SIPP). As a further development of our previous work, selective EBCL was performed with a highly focused electron beam and not via a mask, to region-selectively convert a SAM of 4'-nitro-1,1'-biphenyl-4-thiol to defined areas of crosslinked 4'-amino-1,1'-biphenyl-4-thiol. These "written" structures were then used to prepare surface-bonded, asymmetric, azo initiator sites of 4'-azomethylmalonodinitrile-1,1'-biphenyl-4-thiol. In the presence of bulk styrene, SIPP amplified the primary structures of line widths from 500 to 10 nm to polystyrene structures of line widths 530 nm down to approximately 45 nm at a brush height of 10 or 7 nm, respectively, as measured by scanning electron microscopy and atomic force microscopy (AFM). The relative position of individual structures was within a tolerance of a few nanometers, as verified by AFM. At line-to-line spacings down to 50-70 nm, individual polymer brush structures are still observable. Below this threshold, neighboring structures merge due to chain overlap.

Wafer-scale Fabrication of Non-Polar Mesoporous GaN Distributed Bragg Reflectors via Electrochemical Porosification.

PubMed

Zhu, Tongtong; Liu, Yingjun; Ding, Tao; Fu, Wai Yuen; Jarman, John; Ren, Christopher Xiang; Kumar, R Vasant; Oliver, Rachel A

2017-03-27

Distributed Bragg reflectors (DBRs) are essential components for the development of optoelectronic devices. For many device applications, it is highly desirable to achieve not only high reflectivity and low absorption, but also good conductivity to allow effective electrical injection of charges. Here, we demonstrate the wafer-scale fabrication of highly reflective and conductive non-polar gallium nitride (GaN) DBRs, consisting of perfectly lattice-matched non-polar (11-20) GaN and mesoporous GaN layers that are obtained by a facile one-step electrochemical etching method without any extra processing steps. The GaN/mesoporous GaN DBRs exhibit high peak reflectivities (>96%) across the entire visible spectrum and wide spectral stop-band widths (full-width at half-maximum >80 nm), while preserving the material quality and showing good electrical conductivity. Such mesoporous GaN DBRs thus provide a promising and scalable platform for high performance GaN-based optoelectronic, photonic, and quantum photonic devices.

Experimental Determination of Ultra-Sharp Stray Field Distribution from a Magnetic Vortex Core Structure

DOE Office of Scientific and Technical Information (OSTI.GOV)

Huang, L.; Zhu, Y.; Zhong, H.

2009-08-01

The fine magnetic stray field from a vortex structure of micron-sized permalloy (Ni{sub 80}Fe{sub 20}) elements has been studied by high-resolution magnetic force microscopy. By systematically studying the width of the stray field gradient distribution at different tip-to-sample distances, we show that the half-width at half-maximum (HWHM) of the signal from vortex core can be as narrow as {approx}21 nm at a closest tip-to-sample distance of 23 nm, even including the convolution effect of the finite size of the magnetic tip. A weak circular reverse component is found around the center of the magnetic vortex in the measured magnetic forcemore » microscope (MFM) signals, which can be attributed to the reverse magnetization around the vortex core. Successive micromagnetic and MFM imaging simulations show good agreements with our experimental results on the width of the stray field distribution.« less

Purification of Nanoscale Electron-Beam-Induced Platinum Deposits via a Pulsed Laser-Induced Oxidation Reaction

DOE PAGES

Stanford, Michael G.; Lewis, Brett B.; Noh, Joo Hyon; ...

2014-11-05

Platinum–carbon deposits made via electron-beam-induced deposition were purified in this study via a pulsed laser-induced oxidation reaction and erosion of the amorphous carbon to form pure platinum. Purification proceeds from the top down and is likely catalytically facilitated via the evolving platinum layer. Thermal simulations suggest a temperature threshold of ~485 K, and the purification rate is a function of the PtC 5 thickness (80–360 nm) and laser pulse width (1–100 μs) in the ranges studied. The thickness dependence is attributed to the ~235 nm penetration depth of the PtC 5 composite at the laser wavelength, and the pulse-width dependencemore » is attributed to the increased temperatures achieved at longer pulse widths. Finally, remarkably fast purification is realized at cumulative laser exposure times of less than 1 s.« less

Purification of Nanoscale Electron-Beam-Induced Platinum Deposits via a Pulsed Laser-Induced Oxidation Reaction

DOE Office of Scientific and Technical Information (OSTI.GOV)

Stanford, Michael G.; Lewis, Brett B.; Noh, Joo Hyon

Platinum–carbon deposits made via electron-beam-induced deposition were purified in this study via a pulsed laser-induced oxidation reaction and erosion of the amorphous carbon to form pure platinum. Purification proceeds from the top down and is likely catalytically facilitated via the evolving platinum layer. Thermal simulations suggest a temperature threshold of ~485 K, and the purification rate is a function of the PtC 5 thickness (80–360 nm) and laser pulse width (1–100 μs) in the ranges studied. The thickness dependence is attributed to the ~235 nm penetration depth of the PtC 5 composite at the laser wavelength, and the pulse-width dependencemore » is attributed to the increased temperatures achieved at longer pulse widths. Finally, remarkably fast purification is realized at cumulative laser exposure times of less than 1 s.« less

Three-mode all-optical (de)multiplexing on a SOI chip

NASA Astrophysics Data System (ADS)

Le, Yan-Si; Wang, Zhi; Li, Zhi-Yong; Li, Ying; Li, Qiang; Cui, Can; Wu, Chong-Qing

2018-01-01

An on-chip three-mode division multiplexing circuit using a simple ADC-based TE0 & TE1 & TE2 (de)multiplexer is demonstrated to improve the link capacity of on-chip optical interconnects. The proposed (de)multiplexer does not contain any tapered waveguide which is different from the previous mode (de)multiplexer based on ADCs. Here, we choose multimode waveguide width first and then confirm corresponding width of the other two waveguides. Thus the bus waveguide without any tapers can not only reduce complexity of (de)multiplexer but also reduce difficulty of the fabrication. Our simulation results show that the hybrid multiplexer has relatively low loss and low crosstalk about -40 dB, -26.99 dB and -28.72 dB for each mode around 1550 nm with a width-variation w =± 25 nm. These properties make the proposed mode-(de)multiplexer suitable for application in high-capacity data transmission.

Graphene nanoribbons epitaxy on boron nitride

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lu, Xiaobo; Wang, Shuopei; Wu, Shuang

2016-03-14

In this letter, we report a pilot study on epitaxy of monolayer graphene nanoribbons (GNRs) on hexagonal boron nitride (h-BN). We found that GNRs grow preferentially from the atomic steps of h-BN, forming in-plane heterostructures. GNRs with well-defined widths ranging from ∼15 nm to ∼150 nm can be obtained reliably. As-grown GNRs on h-BN have high quality with a carrier mobility of ∼20 000 cm{sup 2} V{sup −1} s{sup −1} for ∼100-nm-wide GNRs at a temperature of 1.7 K. Besides, a moiré pattern induced quasi-one-dimensional superlattice with a periodicity of ∼15 nm for GNR/h-BN was also observed, indicating zero crystallographic twisting angle between GNRs and h-BNmore » substrate. The superlattice induced band structure modification is confirmed by our transport results. These epitaxial GNRs/h-BN with clean surfaces/interfaces and tailored widths provide an ideal platform for high-performance GNR devices.« less

Physically transient photonics: random versus distributed feedback lasing based on nanoimprinted DNA.

PubMed

Camposeo, Andrea; Del Carro, Pompilio; Persano, Luana; Cyprych, Konrad; Szukalski, Adam; Sznitko, Lech; Mysliwiec, Jaroslaw; Pisignano, Dario

2014-10-28

Room-temperature nanoimprinted, DNA-based distributed feedback (DFB) laser operation at 605 nm is reported. The laser is made of a pure DNA host matrix doped with gain dyes. At high excitation densities, the emission of the untextured dye-doped DNA films is characterized by a broad emission peak with an overall line width of 12 nm and superimposed narrow peaks, characteristic of random lasing. Moreover, direct patterning of the DNA films is demonstrated with a resolution down to 100 nm, enabling the realization of both surface-emitting and edge-emitting DFB lasers with a typical line width of <0.3 nm. The resulting emission is polarized, with a ratio between the TE- and TM-polarized intensities exceeding 30. In addition, the nanopatterned devices dissolve in water within less than 2 min. These results demonstrate the possibility of realizing various physically transient nanophotonics and laser architectures, including random lasing and nanoimprinted devices, based on natural biopolymers.

Wavelength tunable InGaN/GaN nano-ring LEDs via nano-sphere lithography

PubMed Central

Wang, Sheng-Wen; Hong, Kuo-Bin; Tsai, Yu-Lin; Teng, Chu-Hsiang; Tzou, An-Jye; Chu, You-Chen; Lee, Po-Tsung; Ku, Pei-Cheng; Lin, Chien-Chung; Kuo, Hao-Chung

2017-01-01

In this research, nano-ring light-emitting diodes (NRLEDs) with different wall width (120 nm, 80 nm and 40 nm) were fabricated by specialized nano-sphere lithography technology. Through the thinned wall, the effective bandgaps of nano-ring LEDs can be precisely tuned by reducing the strain inside the active region. Photoluminescence (PL) and time-resolved PL measurements indicated the lattice-mismatch induced strain inside the active region was relaxed when the wall width is reduced. Through the simulation, we can understand the strain distribution of active region inside NRLEDs. The simulation results not only revealed the exact distribution of strain but also predicted the trend of wavelength-shifted behavior of NRLEDs. Finally, the NRLEDs devices with four-color emission on the same wafer were demonstrated. PMID:28256529

Metal/Dielectric Multilayers for High Resolution Imaging

DTIC Science & Technology

2012-08-07

of a silicon waveguide coated by thin metal film. The proposed PWG structure consists of narrow silicon waveguide clad by gold film without top...where the waveguide thickness is 220nm and the lower oxide cladding is 2μm. The device consists of main waveguide (of waveguide width WSOI=450nm...evaporation, where 3nm thick titanium was used as adhesion layer before 40nm gold deposition took place. Finally, the samples were spun coated with

Absolute second order nonlinear susceptibility of Pt nanowire arrays on MgO faceted substrates with various cross-sectional shapes

NASA Astrophysics Data System (ADS)

Ogata, Yoichi; Mizutani, Goro

2013-08-01

We have measured optical second harmonic generation (SHG) intensity from three types of Pt nanowires with 7 nm widths of elliptical and boomerang cross-sectional shapes and with 2 nm width elliptical cross-sectional shapes on the MgO faceted templates. From the SHG intensities, we calculated the absolute value of the nonlinear susceptibility χ(2) integrated in the direction of the wire-layer thickness. The tentatively obtained bulk χ(2)B of the wire layer was very large, approaching the value of the well-known nonlinear optical material BaTiO3.

Femtosecond soliton source with fast and broad spectral tunability.

PubMed

Masip, Martin E; Rieznik, A A; König, Pablo G; Grosz, Diego F; Bragas, Andrea V; Martinez, Oscar E

2009-03-15

We present a complete set of measurements and numerical simulations of a femtosecond soliton source with fast and broad spectral tunability and nearly constant pulse width and average power. Solitons generated in a photonic crystal fiber, at the low-power coupling regime, can be tuned in a broad range of wavelengths, from 850 to 1200 nm using the input power as the control parameter. These solitons keep almost constant time duration (approximately 40 fs) and spectral widths (approximately 20 nm) over the entire measured spectra regardless of input power. Our numerical simulations agree well with measurements and predict a wide working wavelength range and robustness to input parameters.

Dislocation-driven growth of two-dimensional lateral quantum-well superlattices

PubMed Central

Chen, Jianyi; Li, Dongdong

2018-01-01

The advent of two-dimensional (2D) materials has led to extensive studies of heterostructures for novel applications. 2D lateral multiheterojunctions and superlattices have been recently demonstrated, but the available growth methods can only produce features with widths in the micrometer or, at best, 100-nm scale and usually result in rough and defective interfaces with extensive chemical intermixing. Widths smaller than 5 nm, which are needed for quantum confinement effects and quantum-well applications, have not been achieved. We demonstrate the growth of sub–2-nm quantum-well arrays in semiconductor monolayers, driven by the climb of misfit dislocations in a lattice-mismatched sulfide/selenide heterointerface. Density functional theory calculations provide an atom-by-atom description of the growth mechanism. The calculated energy bands reveal type II alignment suitable for quantum wells, suggesting that the structure could, in principle, be turned into a “conduit” of conductive nanoribbons for interconnects in future 2D integrated circuits via n-type modulation doping. This misfit dislocation–driven growth can be applied to different combinations of 2D monolayers with lattice mismatch, paving the way to a wide range of 2D quantum-well superlattices with controllable band alignment and nanoscale width. PMID:29740600

Free energy barriers to evaporation of water in hydrophobic confinement.

PubMed

Sharma, Sumit; Debenedetti, Pablo G

2012-11-08

We use umbrella sampling Monte Carlo and forward and reverse forward flux sampling (FFS) simulation techniques to compute the free energy barriers to evaporation of water confined between two hydrophobic surfaces separated by nanoscopic gaps, as a function of the gap width, at 1 bar and 298 K. The evaporation mechanism for small (1 × 1 nm(2)) surfaces is found to be fundamentally different from that for large (3 × 3 nm(2)) surfaces. In the latter case, the evaporation proceeds via the formation of a gap-spanning tubular cavity. The 1 × 1 nm(2) surfaces, in contrast, are too small to accommodate a stable vapor cavity. Accordingly, the associated free energy barriers correspond to the formation of a critical-sized cavity for sufficiently large confining surfaces, and to complete emptying of the gap region for small confining surfaces. The free energy barriers to evaporation were found to be of O(20kT) for 14 Å gaps, and to increase by approximately ~5kT with every 1 Å increase in the gap width. The entropy contribution to the free energy of evaporation was found to be independent of the gap width.

Laser direct writing (LDW) of magnetic structures

NASA Astrophysics Data System (ADS)

Alasadi, Alaa; Claeyssens, F.; Allwood, D. A.

2018-05-01

Laser direct writing (LDW) has been used to pattern 90nm thick permalloy (Ni81Fe19) into 1-D and 2-D microstructures with strong shape anisotropy. Sub-nanosecond laser pulses were focused with a 0.75 NA lens to a 1.85μm diameter spot, to achieve a fluence of approximately 350 mJ.cm-2 and ablate the permalloy film. Computer-controlled sample scanning then allowed structures to be defined. Scan speeds were controlled to give 30% overlap between successive laser pulses and reduce the extent of width modulation in the final structures. Continuous magnetic wires that adjoined the rest of the film were fabricated with widths from 650 nm - 6.75μm and magneto-optical measurements showed coercivity reducing across this width range from 47 Oe to 11 Oe. Attempts to fabricate wires narrower than 650nm resulted in discontinuities in the wires and a marked decrease in coercivity. This approach is extremely rapid and was carried out in air, at room temperature and with no chemical processing. The 6-kHz laser pulse repetition rate allowed wire arrays across an area of 4 mm x 0.18 mm to be patterned in 85 s.

Nano-Forging of Bulk Metallic Glasses

DTIC Science & Technology

2006-09-13

zirconia powder . Arrows indicate the width of ridges on the BMG surface. Fig. 3.3 Imprinted BMG using die made with 250 nm zirconia powder . 9...Fig. 3.4 Imprinted BMG using die made with 50 nm zirconia powder . On each of the imprinted BMG surfaces, linear features

Sensitivity Enhancement of Transition Metal Dichalcogenides/Silicon Nanostructure-based Surface Plasmon Resonance Biosensor

PubMed Central

Ouyang, Qingling; Zeng, Shuwen; Jiang, Li; Hong, Liying; Xu, Gaixia; Dinh, Xuan-Quyen; Qian, Jun; He, Sailing; Qu, Junle; Coquet, Philippe; Yong, Ken-Tye

2016-01-01

In this work, we designed a sensitivity-enhanced surface plasmon resonance biosensor structure based on silicon nanosheet and two-dimensional transition metal dichalcogenides. This configuration contains six components: SF10 triangular prism, gold thin film, silicon nanosheet, two-dimensional MoS2/MoSe2/WS2/WSe2 (defined as MX2) layers, biomolecular analyte layer and sensing medium. The minimum reflectivity, sensitivity as well as the Full Width at Half Maximum of SPR curve are systematically examined by using Fresnel equations and the transfer matrix method in the visible and near infrared wavelength range (600 nm to 1024 nm). The variation of the minimum reflectivity and the change in resonance angle as the function of the number of MX2 layers are presented respectively. The results show that silicon nanosheet and MX2 layers can be served as effective light absorption medium. Under resonance conditions, the electrons in these additional dielectric layers can be transferred to the surface of gold thin film. All silicon-MX2 enhanced sensing models show much better performance than that of the conventional sensing scheme where pure Au thin film is used, the highest sensitivity can be achieved by employing 600 nm excitation light wavelength with 35 nm gold thin film and 7 nm thickness silicon nanosheet coated with monolayer WS2. PMID:27305974

All-fibre ytterbium laser tunable within 45 nm

DOE Office of Scientific and Technical Information (OSTI.GOV)

Abdullina, S R; Babin, S A; Vlasov, A A

2007-12-31

A tunable ytterbium-doped fibre laser is fabricated. The laser is tuned by using a tunable fibre Bragg grating (FBG) as a selecting intracavity element. The laser is tunable within 45 nm (from 1063 to 1108 nm) and emits {approx}6 W in the line of width {approx}0.15 nm, the output power and linewidth being virtually invariable within the tuning range. The method is proposed for synchronous tuning the highly reflecting and output FBGs, and a tunable ytterbium all-fibre laser is built. (lasers)

Continuously tunable optical notch filter and band-pass filter systems that cover the visible to near-infrared spectral ranges.

PubMed

Jeong, Mi-Yun; Mang, Jin Yeob

2018-03-10

Spatially continuous tunable optical notch and band-pass filter systems that cover the visible (VIS) and near-infrared (NIR) spectral ranges from ∼460  nm to ∼1,000  nm are realized by combining left- and right-handed circular cholesteric liquid crystal (CLC) wedge cells with continuous pitch gradient. The notch filter system is polarization independent in all of the spectral ranges. The band-pass filter system, when the left- and right-handed CLCs are arranged in a row, is polarization independent, while when they are arranged at right angles, they are polarization dependent; furthermore, the full-width at half-maximum of the band-pass filter can be changed reversibly from the original bandwidth of 36 nm to 16 nm. Depending on the CLC materials, this strategy could be applied to the UV, VIS, and IR spectral ranges. Due to the high performance in the broad spectral range, cost-effective facile fabrication process, simple mechanical control, and small size, it is expected that our optical tunable filter strategies could become one of the key parts of laser-based Raman spectroscopy, fluorescence, life science devices, optical communication systems, astronomical telescopes, and so forth.

Multi-Shaped Ag Nanoparticles in the Plasmonic Layer of Dye-Sensitized Solar Cells for Increased Power Conversion Efficiency.

PubMed

Song, Da Hyun; Kim, Ho-Sub; Suh, Jung Sang; Jun, Bong-Hyun; Rho, Won-Yeop

2017-06-04

The use of dye-sensitized solar cells (DSSCs) is widespread owing to their high power conversion efficiency (PCE) and low cost of manufacturing. We prepared multi-shaped Ag nanoparticles (NPs) and introduced them into DSSCs to further enhance their PCE. The maximum absorption wavelength of the multi-shaped Ag NPs is 420 nm, including the shoulder with a full width at half maximum (FWHM) of 121 nm. This is a broad absorption wavelength compared to spherical Ag NPs, which have a maximum absorption wavelength of 400 nm without the shoulder of 61 nm FWHM. Therefore, when multi-shaped Ag NPs with a broader plasmon-enhanced absorption were coated on a mesoporous TiO₂ layer on a layer-by-layer structure in DSSCs, the PCE increased from 8.44% to 10.22%, equivalent to an improvement of 21.09% compared to DSSCs without a plasmonic layer. To confirm the plasmon-enhanced effect on the composite film structure in DSSCs, the PCE of DSSCs based on the composite film structure with multi-shaped Ag NPs increased from 8.58% to 10.34%, equivalent to an improvement of 20.51% compared to DSSCs without a plasmonic layer. This concept can be applied to perovskite solar cells, hybrid solar cells, and other solar cells devices.

Ridge Minimization of Ablated Morphologies on ITO Thin Films Using Squared Quasi-Flat Top Beam

PubMed Central

Jeon, Jin-Woo; Choi, Wonsuk; Shin, Young-Gwan; Ji, Suk-Young

2018-01-01

In this study, we explore the improvements in pattern quality that was obtained with a femtosecond laser with quasi-flat top beam profiles at the ablated edge of indium tin oxide (ITO) thin films for the patterning of optoelectronic devices. To ablate the ITO thin films, a femtosecond laser is used that has a wavelength and pulse duration of 1030 nm and 190 fs, respectively. The squared quasi-flat top beam is obtained from a circular Gaussian beam using slits with varying x-y axes. Then, the patterned ITO thin films are measured using both scanning electron and atomic force microscopes. In the case of the Gaussian beam, the ridge height and width are approximately 39 nm and 1.1 μm, respectively, whereas, when the quasi-flat top beam is used, the ridge height and width are approximately 7 nm and 0.25 μm, respectively. PMID:29601515

High-voltage nano-oxidation in deionized water and atmospheric environments by atomic force microscopy.

PubMed

Huang, Jen-Ching; Chen, Chung-Ming

2012-01-01

This study used atomic force microscopy (AFM), metallic probes with a nanoscale tip, and high-voltage generators to investigate the feasibility of high-voltage nano-oxidation processing in deionized water (DI water) and atmospheric environments. Researchers used a combination of wire-cutting and electrochemical etching to transform a 20-μm-thick stainless steel sheet into a conductive metallic AFM probe with a tip radius of 60 nm, capable of withstanding high voltages. The combination of AFM, high-voltage generators, and nanoscale metallic probes enabled nano-oxidation processing at 200 V in DI water environments, producing oxides up to 66.6 nm in height and 467.03 nm in width. Oxides produced through high-voltage nano-oxidation in atmospheric environments were 117.29 nm in height and 551.28 nm in width, considerably exceeding the dimensions of those produced in DI water. An increase in the applied bias voltage led to an apparent logarithmic increase in the height of the oxide dots in the range of 200-400 V. The performance of the proposed high-voltage nano-oxidation technique was relatively high with seamless integration between the AFM machine and the metallic probe fabricated in this study. © Wiley Periodicals, Inc.

Top–down fabrication of sub-nanometre semiconducting nanoribbons derived from molybdenum disulfide sheets

PubMed Central

Liu, Xiaofei; Xu, Tao; Wu, Xing; Zhang, Zhuhua; Yu, Jin; Qiu, Hao; Hong, Jin-Hua; Jin, Chuan-Hong; Li, Ji-Xue; Wang, Xin-Ran; Sun, Li-Tao; Guo, Wanlin

2013-01-01

Developments in semiconductor technology are propelling the dimensions of devices down to 10 nm, but facing great challenges in manufacture at the sub-10 nm scale. Nanotechnology can fabricate nanoribbons from two-dimensional atomic crystals, such as graphene, with widths below the 10 nm threshold, but their geometries and properties have been hard to control at this scale. Here we find that robust ultrafine molybdenum-sulfide ribbons with a uniform width of 0.35 nm can be widely formed between holes created in a MoS2 sheet under electron irradiation. In situ high-resolution transmission electron microscope characterization, combined with first-principles calculations, identifies the sub-1 nm ribbon as a Mo5S4 crystal derived from MoS2, through a spontaneous phase transition. Further first-principles investigations show that the Mo5S4 ribbon has a band gap of 0.77 eV, a Young’s modulus of 300GPa and can demonstrate 9% tensile strain before fracture. The results show a novel top–down route for controllable fabrication of functional building blocks for sub-nanometre electronics. PMID:23653188

PCF based high power narrow line width pulsed fiber laser

NASA Astrophysics Data System (ADS)

Chen, H.; Yan, P.; Xiao, Q.; Wang, Y.; Gong, M.

2012-09-01

Based on semiconductor diode seeded multi-stage cascaded fiber amplifiers, we have obtained 88-W average power of a 1063-nm laser with high repetition rate of up to 1.5 MHz and a constant 2-ns pulse duration. No stimulated Brillouin scattering pulse or optical damage occurred although the maximum pulse peak power has exceeded 112 kW. The output laser exhibits excellent beam quality (M2x = 1.24 and M2y = 1.18), associated with a spectral line width as narrow as 0.065 nm (FWHM). Additionally, we demonstrate high polarization extinction ratio of 18.4 dB and good pulse stabilities superior to 1.6 % (RMS).

Nanoscale patterning of Si surface using SPM scratching

NASA Astrophysics Data System (ADS)

Ogino, T.; Nishimura, S.; Shirakashi, J.

2008-03-01

Nanolithography of Si surface using scanning probe microscopy (SPM) scratching with a diamond-coated tip was systematically investigated at a low force regime below 9 μN. The groove patterns with controlled width and depth could be achieved by adjusting the applied force, scan direction and the number of scan cycles. There was no effect of scan speed on the groove size. The minimum groove width of 10 nm was obtained on Si surfaces. Furthermore, more complex nanostructures such as line and space patterns of 30 nm pith and dot arrays of 2.6×1010 cm-2 density were realized. SPM scratching with a diamond-coated tip allows nanoscale patterning of Si surfaces to be performed simply.

Four different diode lasers comparison on soft tissues surgery: a preliminary ex vivo study.

PubMed

Fornaini, Carlo; Merigo, Elisabetta; Sozzi, Michele; Rocca, Jean-Paul; Poli, Federica; Selleri, Stefano; Cucinotta, Annamaria

2016-06-29

Objectives: The introduction of diode lasers in dentistry had several advantages, principally consisting on the reduced size, reduced cost and possibility to beam delivering by optical fibbers. Up today only the wavelengths around 810 and 980 nm were the most utilized in oral surgery but recently more different lasers had been proposed. The aim of this study was to compare the efficacy of four diode laser wavelengths (810, 980, 1470 and 1950 nm) for the ablation of soft tissues. Material and methods: Specimens were surgically collected from the dorsal surface of four bovine tongues and irradiated by four different diode wavelengths. Thermal increase was measured by two thermocouples, the first at a depth of 0.5 mm, and the second at a depth of 2 mm. Initial and final surface temperatures were recorded by IR thermometer. Epithelial changes, connective tissue modifications, presence of vascular modification and incision morphology were histologically evaluated by two blind pathologists. Results: The time necessary to perform the excision varied between 271 seconds (808 nm, 2W) and 112 seconds (1950 nm, 4W). Temperature increase superficial level varied from 16.3° (980 nm, 4W) and 9.2° (1950 nm, 2 W). The most significant deep temperature increase was recorded by 980 nm, 4 W (17.3°) and the lowest by 1950 nm, 2 W (9.7°). The width of epithelial tissue injuries varied between 74 pm from 1950 nm diode laser at 2 W to 540 pm for 1470 nm diode laser at 4 W. Conclusion: The quality of incision was better and the width of overall tissue injuries was minor in the specimens obtained with higher wavelength (1950 nm) at lower power (2W).

Four different diode lasers comparison on soft tissues surgery: a preliminary ex vivo study

PubMed Central

Merigo, Elisabetta; Sozzi, Michele; Rocca, Jean-Paul; Poli, Federica; Selleri, Stefano; Cucinotta, Annamaria

2016-01-01

Objectives: The introduction of diode lasers in dentistry had several advantages, principally consisting on the reduced size, reduced cost and possibility to beam delivering by optical fibbers. Up today only the wavelengths around 810 and 980 nm were the most utilized in oral surgery but recently more different lasers had been proposed. The aim of this study was to compare the efficacy of four diode laser wavelengths (810, 980, 1470 and 1950 nm) for the ablation of soft tissues. Material and methods: Specimens were surgically collected from the dorsal surface of four bovine tongues and irradiated by four different diode wavelengths. Thermal increase was measured by two thermocouples, the first at a depth of 0.5 mm, and the second at a depth of 2 mm. Initial and final surface temperatures were recorded by IR thermometer. Epithelial changes, connective tissue modifications, presence of vascular modification and incision morphology were histologically evaluated by two blind pathologists. Results: The time necessary to perform the excision varied between 271 seconds (808 nm, 2W) and 112 seconds (1950 nm, 4W). Temperature increase superficial level varied from 16.3° (980 nm, 4W) and 9.2° (1950 nm, 2 W). The most significant deep temperature increase was recorded by 980 nm, 4 W (17.3°) and the lowest by 1950 nm, 2 W (9.7°). The width of epithelial tissue injuries varied between 74 pm from 1950 nm diode laser at 2 W to 540 pm for 1470 nm diode laser at 4 W. Conclusion: The quality of incision was better and the width of overall tissue injuries was minor in the specimens obtained with higher wavelength (1950 nm) at lower power (2W). PMID:27721562

Efficient biosensing through 1D silver nanostructured devices using plasmonic effect.

PubMed

Afsheen, Sumera; Munir, Musarat; Isa Khan, Muhammad; Iqbal, Tahir; Abrar, M; Tahir, Muhammad Bilal; Rehman, Jalil Ur; Nadeem, Khalid; Ijaz, Mohsin; Nabi, Ghulam

2018-06-22

The current work explores the excitation of surface plasmon polarities on one dimensional (1D) silver nano grating device simulated on glass substrate, which can sense a very small change in refractive index of an analyte adjacent to it. The most recent modeling technique finite element analysis (FEA) is applied in this work by using COMSOL RF module. The models of 1D grating device of different slit widths with fixed periodicity and film thickness are simulated. The data is collected and then used to study higher refractive index unit per nanometer (RIU/nm) as well as effect of slits width on RIU. Numbers of investigations are done by the simulated data, like a dip in the transmission spectra of p-polarized light. This dip is due to SPP resonance with the variation of slit width. Furthermore, the most fascinating part of the research is COMSOL modeling that provides an opportunity to look into factors affecting higher RIU/nm while visualizing the cross-sectional view of the grating device and strong electric field enhancement at the surface of the metallic device. When the slit width is almost equal to half of the periodicity of the grating device, SPP resonance increases and it is maximum for the slit width equal to 2/3rd of the periodicity because the coupling efficiency is maximum. © 2018 IOP Publishing Ltd.

Dislocation-driven growth of two-dimensional lateral quantum-well superlattices

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhou, Wu; Zhang, Yu -Yang; Chen, Jianyi

Here, the advent of two-dimensional (2D) materials has led to extensive studies of heterostructures for novel applications. 2D lateral multiheterojunctions and superlattices have been recently demonstrated, but the available growth methods can only produce features with widths in the micrometer or, at best, 100-nm scale and usually result in rough and defective interfaces with extensive chemical intermixing. Widths smaller than 5 nm, which are needed for quantum confinement effects and quantum-well applications, have not been achieved. We demonstrate the growth of sub–2-nm quantum-well arrays in semiconductor monolayers, driven by the climb of misfit dislocations in a lattice-mismatched sulfide/selenide heterointerface. Densitymore » functional theory calculations provide an atom-by-atom description of the growth mechanism. The calculated energy bands reveal type II alignment suitable for quantum wells, suggesting that the structure could, in principle, be turned into a “conduit” of conductive nanoribbons for interconnects in future 2D integrated circuits via n-type modulation doping. This misfit dislocation–driven growth can be applied to different combinations of 2D monolayers with lattice mismatch, paving the way to a wide range of 2D quantum-well superlattices with controllable band alignment and nanoscale width.« less

Dislocation-driven growth of two-dimensional lateral quantum-well superlattices

DOE PAGES

Zhou, Wu; Zhang, Yu -Yang; Chen, Jianyi; ...

2018-03-23

Here, the advent of two-dimensional (2D) materials has led to extensive studies of heterostructures for novel applications. 2D lateral multiheterojunctions and superlattices have been recently demonstrated, but the available growth methods can only produce features with widths in the micrometer or, at best, 100-nm scale and usually result in rough and defective interfaces with extensive chemical intermixing. Widths smaller than 5 nm, which are needed for quantum confinement effects and quantum-well applications, have not been achieved. We demonstrate the growth of sub–2-nm quantum-well arrays in semiconductor monolayers, driven by the climb of misfit dislocations in a lattice-mismatched sulfide/selenide heterointerface. Densitymore » functional theory calculations provide an atom-by-atom description of the growth mechanism. The calculated energy bands reveal type II alignment suitable for quantum wells, suggesting that the structure could, in principle, be turned into a “conduit” of conductive nanoribbons for interconnects in future 2D integrated circuits via n-type modulation doping. This misfit dislocation–driven growth can be applied to different combinations of 2D monolayers with lattice mismatch, paving the way to a wide range of 2D quantum-well superlattices with controllable band alignment and nanoscale width.« less

Collimation testing using slit Fresnel diffraction

NASA Astrophysics Data System (ADS)

Luo, Xiaohe; Hui, Mei; Wang, Shanshan; Hou, Yinlong; Zhou, Siyu; Zhu, Qiudong

2018-03-01

A simple collimation testing method based on slit Fresnel diffraction is proposed. The method needs only a CMOS and a slit with no requirement in dimensional accuracy. The light beam to be tested diffracts across the slit and forms a Fresnel diffraction pattern received by CMOS. After analysis, the defocusing amount and the distance between the primary peak point and secondary peak point of diffraction pattern fulfill an expression relationship and then the defocusing amount can be deduced from the expression. The method is applied to both the coherent beam and partially coherent beam, and these two beams are emitted from a laser and light-emitting diode (LED) with a spectrum width of about 50 nm in this paper. Simulations show that the wide spectrum of LED has the effect of smooth filtering to provide higher accuracy. Experiments show that the LED with a spectrum width of about 50 nm has a lower limitation error than the laser and can achieve up to 58.1601 μm with focal length 200 mm and slit width 15 mm.

Optical waveguide and room temperature high-quality nanolasers from tin-catalyzed CdSSe nanostructures

NASA Astrophysics Data System (ADS)

Guo, Pengfei; Shen, Xia; Zhang, Baolong; Sun, Haibin; Zou, Zhijun; Yang, Wenchao; Gong, Ke; Luo, Yongsong

2018-05-01

A simple two-step CVD method is developed to realize the growth of high-quality tin-catalyzed CdSSe alloy nanowires. Microstructural characterizations demonstrate that these wires are high-quality crystalline nanostructures. Local photoluminescence investigation of these nanostructures shows a typical band edge emission at 656 nm with a full-width at half-maximum of 22.3 nm. Optical waveguide measurement along an individual nanowire indicates that the output signal of the guided light has a rapid linear decrease accompanied with maximum red-shift about 109 meV after the transmission of 102 μm. This obvious red-shift is caused by the intensive band-tail absorption during the optical transmission process. Moreover, optically pumped nanolasers are successfully realized at room temperature based on these unique wires, further demonstrating the achievement of stimulated emission from spontaneous emission, promoted by the pump power intensity. This work may find a simple route to the manufacture of superior nanowires for applications in waveguide and integrated photonic devices.

Red persistent luminescence in rare earth-free AlN:Mn 2+ phosphor

DOE PAGES

Xu, Jian; Cherepy, Nerine J.; Ueda, Jumpei; ...

2017-07-03

Here, we investigated the persistent luminescence (PersL) properties of a rare earth-free Mn 2+ doped AlN (AlN:Mn) red phosphor together with a commercial SrAl 2O 4:Eu 2+, Dy 3+ green persistent phosphor as a reference. Similar to its photoluminescence (PL) spectrum, the PersL spectrum of the AlN:Mn phosphor exhibited a red emission band centered at 600 nm due to the Mn 2+: 4T 1( 4G) → 6A 1( 6S) transition with a relatively narrow full width at half maximum (FWHM) of 43 nm. The luminance of AlN:Mn powders was 0.65 mcd/m 2 at 60 min after ceasing ultraviolet (UV) illumination,more » and its duration upon 0.32 mcd/m 2 could reach over 110 min. An extremely broad thermoluminescence (TL) glow curve was observed ranging from 100 K to 600 K and peaked at around 310 K, indicating a wide trap distribution in this material.« less

Fabry-Perot color filter with antireflective nano-grating surface

NASA Astrophysics Data System (ADS)

Zhang, Jiayuan; Zhang, Jie; Dong, Xiaoxuan

2013-12-01

In order to improve the color saturation of reflective Fabry-Perot(FP) color filter, we proposed a reflective color filter incorporating FP resonator with a dielectric grating. The FP resonator consists of high reflection metal film, dielectric film and semi-transparent metal film. The dielectric grating, above the semi-transparent metal film, can reduce the reflection from the semi-transparent film in which case high saturation will be achieved. By using Finite Difference Time Domain(FDTD) method, the reflection spectra characteristic is analyzed as a function of duty cycle, period, refractive index and thickness of the dielectric grating. Based on the simulation results, a high performance color filter is proposed by optimizing the structural parameters. The full width at half-maximum (FWHM) reflection spectrum of the filters are reduced from 100 nm to 70 nm and the peak reflection efficiency of the filters are about 90%. The overlap of the tricolor output spectra decreases effectively, which will increase the color saturation of the color filter.

Optical waveguide and room temperature high-quality nanolasers from tin-catalyzed CdSSe nanostructures.

PubMed

Guo, Pengfei; Shen, Xia; Zhang, Baolong; Sun, Haibin; Zou, Zhijun; Yang, Wenchao; Gong, Ke; Luo, Yongsong

2018-05-04

A simple two-step CVD method is developed to realize the growth of high-quality tin-catalyzed CdSSe alloy nanowires. Microstructural characterizations demonstrate that these wires are high-quality crystalline nanostructures. Local photoluminescence investigation of these nanostructures shows a typical band edge emission at 656 nm with a full-width at half-maximum of 22.3 nm. Optical waveguide measurement along an individual nanowire indicates that the output signal of the guided light has a rapid linear decrease accompanied with maximum red-shift about 109 meV after the transmission of 102 μm. This obvious red-shift is caused by the intensive band-tail absorption during the optical transmission process. Moreover, optically pumped nanolasers are successfully realized at room temperature based on these unique wires, further demonstrating the achievement of stimulated emission from spontaneous emission, promoted by the pump power intensity. This work may find a simple route to the manufacture of superior nanowires for applications in waveguide and integrated photonic devices.

Blue and green electroluminescence from CdSe nanocrystal quantum-dot-quantum-wells

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lu, Y. F.; Cao, X. A., E-mail: xacao@mail.wvu.edu

2014-11-17

CdS/CdSe/ZnS quantum dot quantum well (QDQW) nanocrystals were synthesized using the successive ion layer adsorption and reaction technique, and their optical properties were tuned by bandgap and strain engineering. 3-monolayer (ML) CdSe QWs emitted blue photoluminescence at 467 nm with a spectral full-width-at-half-maximum of ∼30 nm. With a 3 ML ZnS cladding layer, which also acts as a passivating and strain-compensating layer, the QDQWs acquired a ∼35% quantum yield of the QW emission. Blue and green electroluminescence (EL) was obtained from QDQW light-emitting devices with 3–4.5 ML CdSe QWs. It was found that as the peak blueshifted, the overall EL was increasinglymore » dominated by defect state emission due to poor hole injection into the QDQWs. The weak EL was also attributed to strong field-induced charge separation resulting from the unique QDQW geometry, weakening the oscillator strength of optical transitions.« less

Polarization filtering in the visible wavelength range using surface plasmon resonance and a sunflower-type photonic quasi-crystal fiber

NASA Astrophysics Data System (ADS)

Yan, Bei; Wang, Anran; Liu, Exian; Tan, Wei; Xie, Jianlan; Ge, Rui; Liu, Jianjun

2018-04-01

A novel polarization filter based on a sunflower-type photonic quasi-crystal fiber (PQF) is proposed in this paper. We also discuss different methods to tune the filter wavelength. The proposed filter can efficiently produce polarized light with visible wavelengths by using the resonance between the second-order surface plasmon polariton mode and the core mode of the PQF. The filtered wavelength can be tuned between 0.55 µm and 0.68 µm by adjusting the thickness of the gold film. When the thickness of the gold film is 25.3 nm, the resonance loss in the y-polarized direction reaches 11707 dB m‑1 for a wavelength of 0.6326 µm, and the full width at half maximum is only 5 nm. Due to the flexible design and absence of both polarization coupling and polarization dispersion, this polarization filter can be used in devices that require narrow-band filtering.

Red persistent luminescence in rare earth-free AlN:Mn 2+ phosphor

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xu, Jian; Cherepy, Nerine J.; Ueda, Jumpei

Here, we investigated the persistent luminescence (PersL) properties of a rare earth-free Mn 2+ doped AlN (AlN:Mn) red phosphor together with a commercial SrAl 2O 4:Eu 2+, Dy 3+ green persistent phosphor as a reference. Similar to its photoluminescence (PL) spectrum, the PersL spectrum of the AlN:Mn phosphor exhibited a red emission band centered at 600 nm due to the Mn 2+: 4T 1( 4G) → 6A 1( 6S) transition with a relatively narrow full width at half maximum (FWHM) of 43 nm. The luminance of AlN:Mn powders was 0.65 mcd/m 2 at 60 min after ceasing ultraviolet (UV) illumination,more » and its duration upon 0.32 mcd/m 2 could reach over 110 min. An extremely broad thermoluminescence (TL) glow curve was observed ranging from 100 K to 600 K and peaked at around 310 K, indicating a wide trap distribution in this material.« less

A filterless, visible-blind, narrow-band, and near-infrared photodetector with a gain

NASA Astrophysics Data System (ADS)

Shen, Liang; Zhang, Yang; Bai, Yang; Zheng, Xiaopeng; Wang, Qi; Huang, Jinsong

2016-06-01

In many applications of near-infrared (NIR) light detection, a band-pass filter is needed to exclude the noise caused by visible light. Here, we demonstrate a filterless, visible-blind, narrow-band NIR photodetector with a full-width at half-maximum of <50 nm for the response spectrum. These devices have a thick (>4 μm) nanocomposite absorbing layers made of polymer-fullerene:lead sulfide (PbS) quantum dots (QDs). The PbS QDs yield a photoconductive gain due to their hole-trapping effect, which effectively enhances both the responsivity and the visible rejection ratio of the external quantum efficiency by >10 fold compared to those without PbS QDs. Encouragingly, the inclusion of the PbS QDs does not increase the device noise. We directly measured a noise equivalent power (NEP) of 6.1 pW cm-2 at 890 nm, and a large linear dynamic range (LDR) over 11 orders of magnitude. The highly sensitive visible-blind NIR narrow-band photodetectors may find applications in biomedical engineering.

Emission analysis of RE3+ (RE = Sm, Dy):B2O3-TeO2-Li2O-AlF3 glasses.

PubMed

Raju, C Nageswara; Sailaja, S; Kumari, S Pavan; Dhoble, S J; Kumar, V Ramesh; Ramanaiah, M V; Reddy, B Sudhakar

2013-01-01

This article reports on the optical properties of 0.5% mol of Sm(3+), Dy(3+) ion-doped B2O3-TeO2-Li2O-AlF3 (LiAlFBT) glasses. The glass samples were characterized by optical absorption and emission spectra. Judd-Ofelt theory was applied to analyze the optical absorption spectra and calculate the intensity parameters and radiative properties of the emission transitions. The emission spectra of Sm(3+) and Dy(3+):LiAlFBT glasses showed a bright reddish-orange emission at 598 nm ((4)G5/2 → (6)H7/2) and an intense yellow emission at 574 nm ((4)F9/2 → (6)H13/2), respectively. Full width at half maximum (FWHM), stimulated emission cross section, gain bandwidth and optical gain values were also calculated to extend the applications of the Sm(3+) and Dy(3+):LiAlFBT glasses. Copyright © 2012 John Wiley & Sons, Ltd.

Red fluorescent protein responsible for pigmentation in trematode-infected Porites compressa tissues.

PubMed

Palmer, Caroline V; Roth, Melissa S; Gates, Ruth D

2009-02-01

Reports of coral disease have increased dramatically over the last decade; however, the biological mechanisms that corals utilize to limit infection and resist disease remain poorly understood. Compromised coral tissues often display non-normal pigmentation that potentially represents an inflammation-like response, although these pigments remain uncharacterized. Using spectral emission analysis and cryo-histological and electrophoretic techniques, we investigated the pink pigmentation associated with trematodiasis, infection with Podocotyloides stenometre larval trematode, in Porites compressa. Spectral emission analysis reveals that macroscopic areas of pink pigmentation fluoresce under blue light excitation (450 nm) and produce a broad emission peak at 590 nm (+/-6) with a 60-nm full width at half maximum. Electrophoretic protein separation of pigmented tissue extract confirms the red fluorescence to be a protein rather than a low-molecular-weight compound. Histological sections demonstrate green fluorescence in healthy coral tissue and red fluorescence in the trematodiasis-compromised tissue. The red fluorescent protein (FP) is limited to the epidermis, is not associated with cells or granules, and appears unstructured. These data collectively suggest that the red FP is produced and localized in tissue infected by larval trematodes and plays a role in the immune response in corals.

Identifying fecal matter contamination in produce fields using multispectral reflectance imaging under ambient solar illumination

NASA Astrophysics Data System (ADS)

Everard, Colm D.; Kim, Moon S.; Lee, Hoonsoo; O'Donnell, Colm P.

2016-05-01

An imaging device to detect fecal contamination in fresh produce fields could allow the producer avoid harvesting fecal contaminated produce. E.coli O157:H7 outbreaks have been associated with fecal contaminated leafy greens. In this study, in-field spectral profiles of bovine fecal matter, soil, and spinach leaves are compared. A common aperture imager designed with two identical monochromatic cameras, a beam splitter, and optical filters was used to simultaneously capture two-spectral images of leaves contaminated with both fecal matter and soil. The optical filters where 10 nm full width half maximum bandpass filters, one at 690 nm and the second at 710 nm. These were mounted in front of the object lenses. New images were created using the ratio of these two spectral images on a pixel by pixel basis. Image analysis results showed that the fecal matter contamination could be distinguished from soil and leaf on the ratio images. The use of this technology has potential to allow detection of fecal contamination in produce fields which can be a source of foodbourne illnesses. It has the added benefit of mitigating cross-contamination during harvesting and processing.

Two-dimensional CdS nanosheet-based TFT and LED nanodevices.

PubMed

Ye, Yu; Yu, Bin; Gao, Zhiwei; Meng, Hu; Zhang, Hui; Dai, Lun; Qin, Guogang

2012-05-17

Semiconductor nanosheets have several unique applications in electronic and optoelectronic nanodevices. We have successfully synthesized single-crystalline n-type CdS nanosheets via a chemical vapor deposition (CVD) method in a Cd-enriched ambient. The as-synthesized nanosheets are typically 40-100 nm thick, 10-300 µm wide, and up to several millimeters long. Using the nanosheets, we fabricated for the first time (to our knowledge), nano thin-film transistors (nano-TFTs) based on individual CdS nanosheets. A typical unit of such nanosheet TFTs has a high on-off ratio (∼1.7 ×10(9)) and peak transconductance (∼14.1µS), which to our knowledge are the best values reported so far for semiconductor nano-TFTs. In addition, we fabricated n-CdS nanosheet/p(+)-Si heterojunction light emitting diodes (LEDs) with a top electrode structure. This structure, where the n-type electrode is directly above the junction, has the advantage of a large active region and injection current favorable for high-efficiency electroluminescence (EL) and lasing. Room-temperature spectra of the LEDs consist of only an intense CdS band-edge emission peak (∼507.7 nm) with a full width at half-maximum of about 14 nm.

Reflectively Coupled Waveguide Photodetector for High Speed Optical Interconnection

PubMed Central

Hsu*, Shih-Hsiang

2010-01-01

To fully utilize GaAs high drift mobility, techniques to monolithically integrate In0.53Ga0.47As p-i-n photodetectors with GaAs based optical waveguides using total internal reflection coupling are reviewed. Metal coplanar waveguides, deposited on top of the polyimide layer for the photodetector’s planarization and passivation, were then uniquely connected as a bridge between the photonics and electronics to illustrate the high-speed monitoring function. The photodetectors were efficiently implemented and imposed on the echelle grating circle for wavelength division multiplexing monitoring. In optical filtering performance, the monolithically integrated photodetector channel spacing was 2 nm over the 1,520–1,550 nm wavelength range and the pass band was 1 nm at the −1 dB level. For high-speed applications the full-width half-maximum of the temporal response and 3-dB bandwidth for the reflectively coupled waveguide photodetectors were demonstrated to be 30 ps and 11 GHz, respectively. The bit error rate performance of this integrated photodetector at 10 Gbit/s with 27-1 long pseudo-random bit sequence non-return to zero input data also showed error-free operation. PMID:22163502

Synthesis of blue emitting InP/ZnS quantum dots through control of competition between etching and growth.

PubMed

Lim, Kipil; Jang, Ho Seong; Woo, Kyoungja

2012-12-07

Blue (<480 nm) emitting Cd-free quantum dots (QDs) are in great demand for various applications. However, their synthesis has been challenging. Here we present blue emitting InP/ZnS core/shell QDs with a band edge emission of 475 nm and a full width at half maximum of 39 nm (215 meV) from their quantum confined states. The drastic temperature drop immediately after mixing of the precursors and holding them at a temperature below 150 °C was the critical factor for the synthesis of blue emitting QDs, because the blue QDs are formed by the etching of ultra-small InP cores by residual acetic acid below 150 °C. Etching was dominant at temperatures below 150 °C, whereas growth was dominant at temperatures above 150 °C. ZnS shells were formed successfully at 150 °C, yielding blue emitting InP/ZnS QDs. The colour of the InP/ZnS QDs depicted on the CIE 1931 chromaticity diagram is located close to the edge, indicating a pure blue colour compared to other InP-based QDs.

Synthesis of blue emitting InP/ZnS quantum dots through control of competition between etching and growth

NASA Astrophysics Data System (ADS)

Lim, Kipil; Jang, Ho Seong; Woo, Kyoungja

2012-12-01

Blue (<480 nm) emitting Cd-free quantum dots (QDs) are in great demand for various applications. However, their synthesis has been challenging. Here we present blue emitting InP/ZnS core/shell QDs with a band edge emission of 475 nm and a full width at half maximum of 39 nm (215 meV) from their quantum confined states. The drastic temperature drop immediately after mixing of the precursors and holding them at a temperature below 150 °C was the critical factor for the synthesis of blue emitting QDs, because the blue QDs are formed by the etching of ultra-small InP cores by residual acetic acid below 150 °C. Etching was dominant at temperatures below 150 °C, whereas growth was dominant at temperatures above 150 °C. ZnS shells were formed successfully at 150 °C, yielding blue emitting InP/ZnS QDs. The colour of the InP/ZnS QDs depicted on the CIE 1931 chromaticity diagram is located close to the edge, indicating a pure blue colour compared to other InP-based QDs.

Surface Plasmon Scattering in Exposed Core Optical Fiber for Enhanced Resolution Refractive Index Sensing.

PubMed

Klantsataya, Elizaveta; François, Alexandre; Ebendorff-Heidepriem, Heike; Hoffmann, Peter; Monro, Tanya M

2015-09-29

Refractometric sensors based on optical excitation of surface plasmons on the side of an optical fiber is an established sensing architecture that has enabled laboratory demonstrations of cost effective portable devices for biological and chemical applications. Here we report a Surface Plasmon Resonance (SPR) configuration realized in an Exposed Core Microstructured Optical Fiber (ECF) capable of optimizing both sensitivity and resolution. To the best of our knowledge, this is the first demonstration of fabrication of a rough metal coating suitable for spectral interrogation of scattered plasmonic wave using chemical electroless plating technique on a 10 μm diameter exposed core of the ECF. Performance of the sensor in terms of its refractive index sensitivity and full width at half maximum (FWHM) of SPR response is compared to that achieved with an unstructured bare core fiber with 140 μm core diameter. The experimental improvement in FWHM, and therefore the detection limit, is found to be a factor of two (75 nm for ECF in comparison to 150 nm for the large core fiber). Refractive index sensitivity of 1800 nm/RIU was achieved for both fibers in the sensing range of aqueous environment (1.33-1.37) suitable for biosensing applications.

Ion concentrations and velocity profiles in nanochannel electroosmotic flows

NASA Astrophysics Data System (ADS)

Qiao, R.; Aluru, N. R.

2003-03-01

Ion distributions and velocity profiles for electroosmotic flow in nanochannels of different widths are studied in this paper using molecular dynamics and continuum theory. For the various channel widths studied in this paper, the ion distribution near the channel wall is strongly influenced by the finite size of the ions and the discreteness of the solvent molecules. The classical Poisson-Boltzmann equation fails to predict the ion distribution near the channel wall as it does not account for the molecular aspects of the ion-wall and ion-solvent interactions. A modified Poisson-Boltzmann equation based on electrochemical potential correction is introduced to account for ion-wall and ion-solvent interactions. The electrochemical potential correction term is extracted from the ion distribution in a smaller channel using molecular dynamics. Using the electrochemical potential correction term extracted from molecular dynamics (MD) simulation of electroosmotic flow in a 2.22 nm channel, the modified Poisson-Boltzmann equation predicts the ion distribution in larger channel widths (e.g., 3.49 and 10.00 nm) with good accuracy. Detailed studies on the velocity profile in electro-osmotic flow indicate that the continuum flow theory can be used to predict bulk fluid flow in channels as small as 2.22 nm provided that the viscosity variation near the channel wall is taken into account. We propose a technique to embed the velocity near the channel wall obtained from MD simulation of electroosmotic flow in a narrow channel (e.g., 2.22 nm wide channel) into simulation of electroosmotic flow in larger channels. Simulation results indicate that such an approach can predict the velocity profile in larger channels (e.g., 3.49 and 10.00 nm) very well. Finally, simulation of electroosmotic flow in a 0.95 nm channel indicates that viscosity cannot be described by a local, linear constitutive relationship that the continuum flow theory is built upon and thus the continuum flow theory is not applicable for electroosmotic flow in such small channels.

Electroluminescence properties of LEDs based on electron-irradiated p-Si

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sobolev, N. A., E-mail: nick@sobolev.ioffe.rssi.ru; Shtel’makh, K. F.; Kalyadin, A. E.

2016-02-15

The electroluminescence (EL) in n{sup +}–p–p{sup +} light-emitting-diode (LED) structures based on Si irradiated with electrons and annealed at high temperature is studied. The LEDs are fabricated by the chemical- vapor deposition of polycrystalline silicon layers doped with high concentrations of boron and phosphorus. Transformation of the EL spectra with current in the LEDs is well described by six Gaussian curves. The peak positions of these curves are current-independent and equal to 1233, 1308, 1363, 1425, 1479, and 1520 nm. The dependences of the integrated EL intensity and of the full-width at half-maximum (FWHM) of the lines on current aremore » examined.« less

Power splitting of 1 × 16 in multicore photonic crystal fibers

NASA Astrophysics Data System (ADS)

Malka, Dror; Peled, Aaron

2017-09-01

A novel concept of 1 × 16 power splitter based on a variable multicore photonic crystal fiber (PCF) structure is described. Numerical simulations showed how the optical signal can be split in a PCF structure having dimensions of 60 μm × 60 μm × 3.582 mm. The coupled mode analysis and beam propagation method (BPM) was used for analyzing the multicore PCF based 1 × 16 splitter. The input optical signal at a wavelength of 1.55 μm inserted into the central core was divided into sixteen output cores, each with a 6.25% of the total power. The full width half maximum (FWHM) bandwidth found for each core was 100 nm.

Characteristics of a Broadband Dye Laser Using Pyrromethene and Rhodamine Dyes

NASA Technical Reports Server (NTRS)

Tedder, Sarah A.; Danehy, Paul M.; Wheeler, Jeffrey L.

2011-01-01

A broadband dye laser pumped by a frequency-doubled Nd:YAG laser with a full-width half-maximum (FWHM) from 592 to 610 nm was created for the use in a dual-pump broadband CARS system called WIDECARS. The desired broadband dye laser was generated with a mixture of Pyrromethene dyes as an oscillator gain medium and a spectral selective optic in the oscillator cavity. A mixture of Rhodamine dyes were used in the amplifier dye cell. To create this laser a study was performed to characterize the spectral behavior of broadband dye lasers created with Rhodamine dyes 590, 610, and 640, Pyrromethene dyes 597 and 650 as well as mixture of these dyes.

Structural and optical studies of Er3+-doped alkali/alkaline oxide containing zinc boro-aluminosilicate glasses for 1.5 μm optical amplifier applications

NASA Astrophysics Data System (ADS)

Kaky, Kawa M.; Lakshminarayana, G.; Baki, S. O.; Lira, A.; Caldiño, U.; Meza-Rocha, A. N.; Falcony, C.; Kityk, I. V.; Taufiq-Yap, Y. H.; Halimah, M. K.; Mahdi, M. A.

2017-07-01

In the present work, we report on the optical spectral properties of Er3+-doped zinc boro-aluminosilicate glasses with an addition of 10 mol % alkali/alkaline modifier regarding the fabrication of new optical materials for optical amplifiers. A total of 10 glasses were prepared using melt-quenching technique with the compositions (40-x)B2O3 - 10SiO2 - 10Al2O3 - 30ZnO - 10Li2O - xEr2O3 and (40-x)B2O3 - 10SiO2 - 10Al2O3 - 30ZnO - 10MgO - xEr2O3 (x = 0.1, 0.25, 0.5, 1.0, and 2.0 mol %). We confirm the amorphous-like structure for all the prepared glasses using X-ray diffraction (XRD). To study the functional groups of the glass composition after the melt-quenching process, Raman spectroscopy was used, and various structural units such as triangular and tetrahedral-borates (BO3 and BO4) have been identified. All the samples were characterized using optical absorption for UV, visible and NIR regions. Judd-Ofelt (JO) intensity parameters (Ωλ, λ = 2, 4 and 6) were calculated from the optical absorption spectra of two glasses LiEr 2.0 and MgEr 2.0 (doped with 2 mol % of Er3+). JO parameters for LiEr 2.0 and MgEr 2.0 glasses follow the trend as Ω6>Ω2>Ω4. Using Judd-Ofelt intensity parameters, we obtained radiative probability A (S-1), branching ratios (β), radiative decay lifetimes τrad (μs) of emissions from excited Er+3 ions in LiEr 2.0 and MgEr 2.0 to all lower levels. Quantum efficiency (η) of 4I13/2 and 4S3/2 levels for LiEr 2.0 and MgEr 2.0 with and without 4D7/2 level was calculated using the radiative decay lifetimes τrad. (μs) and measured lifetimes τexp. (μs). We measured the visible photoluminescence under 377 nm excitation for both LiEr and MgEr glass series within the region 390-580 nm. Three bands were observed in the visible region at 407 nm, 530 nm, and 554 nm, as a result of 2H9/2 → 4I15/2, 2H11/2 → 4I15/2 and 4S3/2 → 4I15/2 transitions, respectively. Decay lifetimes for emissions at 407 nm, 530 nm, and 554 nm were measured and they show single exponential behavior for all the LiEr and MgEr glass series. From the photoluminescence and radiative decay lifetimes (τrad), we calculated the full-width at half-maximum (FWHM), emission cross-section (σPE) and bandwidth gain (FWHM × σPE) parameters. Near-infrared photoluminescence under 980 nm excitation was measured for all the LiEr and MgEr glass series in the region 1420-1620 nm. NIR emissions show a broadband centered at ∼1530 nm due to the transition of Er3+: 4I13/2 → 4I15/2. Decay lifetimes for NIR emission at ∼1530 nm were measured and they show a quite exponential nature for all the LiEr and MgEr glass series. From the NIR emission spectra and decay lifetimes, we calculated the full-width at half-maximum (FWHM), the emission cross-section (σPE) and the bandwidth gain (FWHM × σPE) for the NIR emission and it shows FWHM of 50-70 nm for prepared glasses, emission cross-section of (∼3.5) × 10-20 cm2, while bandwidth gain was (∼25) × 10-26 cm3.

Gold reflective metallic gratings with high absorption efficiency

NASA Astrophysics Data System (ADS)

Zhang, Zhaojian; Liang, Linmei; Yang, Junbo

2017-10-01

Electromagnetic (EM) wave absorbers are devices in which the incident radiation at the operating wavelengths can be efficiently absorbed and then transformed into ohmic heat or other forms of energy. Especially, EM absorbers based on metallic structures have distinct advantages in comparison with the traditional counterparts. Thus, they have different potential applications at different frequency ranges such as absorbing devices in solar energy harvesting systems. The reflective metallic grating is a kind of metallic EM absorbers and has the fascinating property of efficiently absorbing the incident light due to the excitation of surface plasmon polaritons (SPPs), consequently drawing more and more attention. In this paper, the absorption effect of a reflective metallic grating made of gold is studied by changing grating parameters such as the period, polarization direction of the incident light and so on. We use finite difference time-domain (FDTD) method to design the grating, and simulate the process and detect the absorption spectrum. In our design, the grating has rectangular shaped grooves and has the absorption efficiency 99% for the vertically incident transverse magnetic (TM) light at the wavelength of 818nm with the period of 800 nm, the width of 365 nm and the height of 34 nm. And then we find that the absorption spectrum is blue-shifted about 87 nm with decreasing period from 800 nm to700 nm and red-shifted about 14 nm with increasing the width of the block from 305 nm to 405 nm. The absorption becomes gradually weaker from 98% to almost zero with the polarization angle from 0° to 90°. Finally, we make a theoretical explanation to these phenomena in details. It is believed that the results may provide useful guidance for the design of EM wave absorbers with high absorption efficiency.

Exploration of BEOL line-space patterning options at 12 nm half-pitch and below

NASA Astrophysics Data System (ADS)

Decoster, S.; Lazzarino, F.; Petersen Barbosa Lima, L.; Li, W.; Versluijs, J.; Halder, S.; Mallik, A.; Murdoch, G.

2018-03-01

While the semiconductor industry is almost ready for high-volume manufacturing of the 7 nm technology node, research centers are defining and troubleshooting the patterning options for the 5 nm technology node (N5) and below. The target dimension for imec's N5 BEOL applications is 20-24 nm Metal Pitch (MP), which requires Self-Aligned multiple (Double/Quadruple/Octuple) Patterning approaches (SAxP) in combination with EUV or immersion lithography at 193 nm. There are numerous technical challenges to enable gratings at the hard mask level such as good uniformity across wafer, low line edge/width roughness (LER/LWR), large process window, and all of this at low cost. An even greater challenge is to transfer these gratings into the dielectric material at such critical dimensions, where increased line edge roughness, line wiggling and even pattern collapse can be expected for materials with small mechanical stability such as highly porous low-k dielectrics. In this work we first compare three different patterning options for 12 nm half-pitch gratings at the hard mask level: EUV-based SADP and 193i-based SAQP and SAOP. This comparison will be based on process window, line edge/width roughness and cost. Next, the transfer of 12 nm line/space gratings in the dielectric material is discussed and presented. The LER of the dielectric lines is investigated as a function of the dielectric material, the trench depth, and the stress in the sacrificial hard mask. Finally, we elaborate on the different options to enable scaling down from 24 nm MP to 16 nm MP, and demonstrate 8 nm line/space gratings with 193i-based SAOP.

Folded inflatable protective device and method for making same

DOEpatents

Behr, V.L.; Nelsen, J.M.; Gwinn, K.W.

1998-10-20

An apparatus and method are disclosed for making an inflatable protective device made of lightweight material that can withstand the initial stress from inflation and enhance radial inflation. The device includes a cushion and an inflator port. The invention further includes several stacks of folded cushion material including a combination of full-width stacks and half-width stacks: a first full-width stack defined by one or more fan folds in a first lateral half of the cushion wherein the folds are substantially centered above a first center line and are substantially over the inflator port; a second full-width stack defined by one or more fan folds in a second lateral half of the cushion wherein the folds are substantially centered above the first center line and substantially over the inflator port in the first full-width stack; a first half-width stack defined by a plurality of fan folds in the bottom of the cushion where neither edge of each fold extends substantially over the second center line; and a second half-width stack defined by a plurality of fan folds in the top of the cushion wherein neither edge of each fold extends substantially over the second center line. 22 figs.

Folded inflatable protective device and method for making same

DOEpatents

Behr, Vance L.; Nelsen, James M.; Gwinn, Kenneth W.

1998-01-01

An apparatus and method for making an inflatable protective device made of lightweight material that can withstand the initial stress from inflation and enhance radial inflation. The device includes a cushion and an inflator port. The invention further includes several stacks of folded cushion material including a combination of full-width stacks and half-width stacks: a first full-width stack defined by one or more fan folds in a first lateral half of the cushion wherein the folds are substantially centered above a first center line and are substantially over the inflator port; a second full-width stack defined by one or more fan folds in a second lateral half of the cushion wherein the folds are substantially centered above the first center line and substantially over the inflator port in the first full-width stack; a first half-width stack defined by a plurality of fan folds in the bottom of the cushion where neither edge of each fold extends substantially over the second center line; and a second half-width stack defined by a plurality of fan folds in the top of the cushion wherein neither edge of each fold extends substantially over the second center line.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Peng; State Key Laboratory of Superhard Materials, College of Physics, Jilin University, Changchun 130012; Bai, Xue, E-mail: baix@jlu.edu.cn, E-mail: yuzhang@jlu.edu.cn

High quantum yield, narrow full width at half-maximum and tunable emission color of perovskite quantum dots (QDs) make this kind of material good prospects for light-emitting diodes (LEDs). However, the relatively poor stability under high temperature and air condition limits the device performance. To overcome this issue, the liquid-type packaging structure in combination with blue LED chip was employed to fabricate the fluorescent perovskite quantum dot-based LEDs. A variety of monochromatic LEDs with green, yellow, reddish-orange, and red emission were fabricated by utilizing the inorganic cesium lead halide perovskite quantum dots as the color-conversion layer, which exhibited the narrow fullmore » width at half-maximum (<35 nm), the relatively high luminous efficiency (reaching 75.5 lm/W), and the relatively high external quantum efficiency (14.6%), making it the best-performing perovskite LEDs so far. Compared to the solid state LED device, the liquid-type LED devices exhibited excellent color stability against the various working currents. Furthermore, we demonstrated the potential prospects of all-inorganic perovskite QDs for the liquid-type warm white LEDs.« less

Passively Q-switched Nd3+ solid-state lasers with antimonene as saturable absorber.

PubMed

Wang, Mengixa; Zhang, Fang; Wang, Zhengping; Wu, Zhixin; Xu, Xinguang

2018-02-19

Based on the saturable absorption feature of a two-dimensional (2D) nano-material, antimonene, the passively Q-switched operation for solid-state laser was realized for the first time. For the 946 and 1064 nm laser emissions of the Nd:YAG crystal, the Q-switched pulse widths were 209 and 129 ns, and the peak powers were 1.48, 1.77 W, respectively. For the 1342 nm laser emission of the Nd:YVO 4 crystal, the Q-switched pulse width was 48 ns, giving a peak power of 28.17 W. Our research shows that antimonene can be used as a stable, broadband optical modulating device for a solid-state laser, which will be particularly effective for long wavelength operation.

Development and applications of tunable, narrow band lasers and stimulated Raman scattering devices for atmospheric lidar

NASA Technical Reports Server (NTRS)

Wilkerson, Thomas D.

1993-01-01

The main thrust of the program was the study of stimulated Raman processes for application to atmospheric lidar measurements. This has involved the development of tunable lasers, the detailed study of stimulated Raman scattering, and the use of the Raman-shifted light for new measurements of molecular line strengths and line widths. The principal spectral region explored in this work was the visible and near-IR wavelengths between 500 nm and 1.5 microns. Recent alexandrite ring laser experiments are reported. The experiments involved diode injection-locking, Raman shifting, and frequency-doubling. The experiments succeeded in producing tunable light at 577 and 937 nm with line widths in the range 80-160 MHz.

Pulse Width Dependence Of Pigment Cell Damage At 694 nm In Guinea Pig Skin

NASA Astrophysics Data System (ADS)

Dover, Jeffrey S.; Polla, Luigi L.; Margolis, Randall J.; Whitaker, Diana; Watanabe, Schinichi; Murphy, George F.; Parrish, John A.; Anderson, R. R.

1987-03-01

351 nm, 20-nsec XeF excimer laser irradiation has previously been shown to selectively target and damage melanosomes in human skin. In the following studies selective targeting with melanosomal photodisruption has been demonstrated in pigmented guinea pig skin with a Q-switched 40-nsec ruby laser, and a 750-nsec pulsed dye laser but not with a 400-usec pulsed dye laser. The pulse width dependence of melanosomal disruption, occurring only at pulsewidths shorter than the thermal relaxation time of the melanosome (0.5 - 1.0 usec), is in accordance with the theory of selective photothermolysis. Possible mechanisms of melanosomal photodisruption include development of sudden thermal gradients leading to cavitation or shock wave production.

VizieR Online Data Catalog: Catalog of Eq.Widths of Interstellar 217nm Band (Friedemann 1992)

NASA Astrophysics Data System (ADS)

Friedemann, C.

2005-03-01

(from CDS Inf. Bull. 40, 31) The main task of the catalogue consists in a comprehensive collection of equivalent widths of the 217nm band derived from both spectrophotometric and filterphotometric measurements obtained with TD-1, OAO-2 and ANS satellites. These data concern reddened O, B stars with color excesses E(B-V) >= 0.02 mag. The extinction curve is approximated by the empirical formula introduced by Guertler et al. (1982AN....303..105G) e({lambda}) = A(i/{lambda} - 1/{lambda}o)n + B + C {kappa}({lambda}) The relative errors amount to about {delta}A/A = +/- 0.10, {delta}B/B = +/- 0.02 and {delta}C/C = +/- 0.03. (1 data file).

Short wavelength (visible) GaAs quantum well lasers grown by molecular beam epitaxy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Woodbridge, K.; Blood, P.; Fletcher, E.D.

1984-07-01

GaAs-AlGaAs multiple quantum well (MQW) injection lasers with well widths from 55 to 13 A have been grown by molecular beam epitaxy and operated at room temperature, showing emission at wavelengths down to 704 nm, the shortest reported for a MQW injection laser with GaAs wells. In a device with 25-A wells some evidence of coupling was apparent when barrier widths were reduced to 40 A. For devices with 80-A barriers there is a difference of about 20 nm between the calculated n = 1 (e--hh) transition wavelength and the lasing wavelength, whereas the calculation agrees with photovoltage absorption measurementsmore » on the same structures.« less

Effect of heat treatment on absorption and fluorescence properties of PbS-doped silica optical fibre

NASA Astrophysics Data System (ADS)

Qin, Fu; Dong, Yanhua; Wen, Jianxiang; Pang, Fufei; Luo, Yanhua; Peng, Gang-Ding; Chen, Zhenyi; Wang, Tingyun

2017-02-01

The effect of heat treatment on the optical properties of a PbS-doped silica optical fibre was investigated. The experimental results showed that the absorption peak of the fibre red shifted from 1032 to 1133 nm when the heat treatment temperatures were carried out at 900, 950, 1000, and 1100 °C for 1 h, respectively. At the same time, when the heat treatment at 900 °C was carried out for 2, 5, 10, 20, and 40 h, the absorption spectra of the fibre showed a red shift from 1074 to 1143 nm. In addition, the intensity of the absorption peak increased from 0.258 to 1.384 dB/m and the full width at half maximum (FWHM) became narrower (from 130 to 50 nm) as the heat treatment proceeded. Moreover, the photoluminescence (PL) intensity in the wavelength range of 1100-1500 nm decreased with an increase in the heat treatment temperature. The theoretical analysis, using an effective mass method, showed that the effective band gap energy and average size of the lead sulphide (PbS) quantum dots (QDs) in the silica fibre core varied from 1.199 to 1.083 eV and from 4.28 to 4.81 nm, respectively. The results indicate that the size of the PbS QDs present in the silica fibre core could be controlled by a proper heat treatment, which is of great interest in optical fibre amplifiers and other fibre optic devices.

Rattlesnake Mountain Observatory (46.4° N, 119.6° W) Multispectral Optical Depth Measurements: 1979-1994 (NDP-053)

DOE Data Explorer

Larson, Nels R. [Pacific Northwest Laboratory (PNNL), Richland, WA (USA); Michalsky, Joseph J. [Atmospheric Sciences Research Center, Albany, NY (USA); LeBaron, Brock A. [Utah Bureau of Air Quality, Salt Lake City, Utah (USA)

2012-01-01

Surface measurements of solar irradiance of the atmosphere were made by a multipurpose computer-controlled scanning photometer at the Rattlesnake Mountain Observatory in eastern Washington. The observatory is located at 46.4° N, 119.6° W at an elevation of 1088 m above mean sea level. The photometer measures the attenuation of direct solar radiation for different wavelengths using 12 filters. Five of these filters (i.e., at 428 nm, 486 nm, 535 nm, 785 nm, and 1010 nm, with respective half-power widths of 2, 2, 3, 18, and 28 nm) are suitable for monitoring variations in the total optical depth of the atmosphere.

Dissecting the actin cortex density and membrane-cortex distance in living cells by super-resolution microscopy

NASA Astrophysics Data System (ADS)

Clausen, M. P.; Colin-York, H.; Schneider, F.; Eggeling, C.; Fritzsche, M.

2017-02-01

Nanoscale spacing between the plasma membrane and the underlying cortical actin cytoskeleton profoundly modulates cellular morphology, mechanics, and function. Measuring this distance has been a key challenge in cell biology. Current methods for dissecting the nanoscale spacing either limit themselves to complex survey design using fixed samples or rely on diffraction-limited fluorescence imaging whose spatial resolution is insufficient to quantify distances on the nanoscale. Using dual-color super-resolution STED (stimulated-emission-depletion) microscopy, we here overcome this challenge and accurately measure the density distribution of the cortical actin cytoskeleton and the distance between the actin cortex and the membrane in live Jurkat T-cells. We found an asymmetric cortical actin density distribution with a mean width of 230 (+105/-125) nm. The spatial distances measured between the maximum density peaks of the cortex and the membrane were bi-modally distributed with mean values of 50  ±  15 nm and 120  ±  40 nm, respectively. Taken together with the finite width of the cortex, our results suggest that in some regions the cortical actin is closer than 10 nm to the membrane and a maximum of 20 nm in others.

InGaN Light-Emitting Diodes with an Embedded Nanoporous GaN Distributed Bragg Reflectors.

PubMed

Shiu, Guo-Yi; Chen, Kuei-Ting; Fan, Feng-Hsu; Huang, Kun-Pin; Hsu, Wei-Ju; Dai, Jing-Jie; Lai, Chun-Feng; Lin, Chia-Feng

2016-07-01

InGaN light emitting diodes (LED) structure with an embedded 1/4λ-stack nanoporous-GaN/undoped-GaN distributed Bragg reflectors (DBR) structure have been demonstrated. Si-heavily doped GaN epitaxial layers (n(+)-GaN) in the 12-period n(+)-GaN/u-GaN stack structure are transformed into low refractive index nanoporous GaN structure through the doping-selective electrochemical wet etching process. The central wavelength of the nanoporous DBR structure was located at 442.3 nm with a 57 nm linewidth and a 97.1% peak reflectivity. The effective cavity length (6.0λ), the effective penetration depth (278 nm) in the nanoporous DBR structure, and InGaN active layer matching to Fabry-Pérot mode order 12 were observed in the far-field photoluminescence radiative spectra. High electroluminescence emission intensity and line-width narrowing effect were measured in the DBR-LED compared with the non-treated LED structure. Non-linear emission intensity and line-width reducing effect, from 11.8 nm to 0.73 nm, were observed by increasing the laser excited power. Resonant cavity effect was observed in the InGaN LED with bottom nanoporous-DBR and top GaN/air interface.

InGaN Light-Emitting Diodes with an Embedded Nanoporous GaN Distributed Bragg Reflectors

PubMed Central

Shiu, Guo-Yi; Chen, Kuei-Ting; Fan, Feng-Hsu; Huang, Kun-Pin; Hsu, Wei-Ju; Dai, Jing-Jie; Lai, Chun-Feng; Lin, Chia-Feng

2016-01-01

InGaN light emitting diodes (LED) structure with an embedded 1/4λ-stack nanoporous-GaN/undoped-GaN distributed Bragg reflectors (DBR) structure have been demonstrated. Si-heavily doped GaN epitaxial layers (n+-GaN) in the 12-period n+-GaN/u-GaN stack structure are transformed into low refractive index nanoporous GaN structure through the doping-selective electrochemical wet etching process. The central wavelength of the nanoporous DBR structure was located at 442.3 nm with a 57 nm linewidth and a 97.1% peak reflectivity. The effective cavity length (6.0λ), the effective penetration depth (278 nm) in the nanoporous DBR structure, and InGaN active layer matching to Fabry-Pérot mode order 12 were observed in the far-field photoluminescence radiative spectra. High electroluminescence emission intensity and line-width narrowing effect were measured in the DBR-LED compared with the non-treated LED structure. Non-linear emission intensity and line-width reducing effect, from 11.8 nm to 0.73 nm, were observed by increasing the laser excited power. Resonant cavity effect was observed in the InGaN LED with bottom nanoporous-DBR and top GaN/air interface. PMID:27363290

Wide-band fanned-out supercontinuum source covering O-, E-, S-, C-, L- and U-bands

NASA Astrophysics Data System (ADS)

Ahmad, H.; Latif, A. A.; Awang, N. A.; Zulkifli, M. Z.; Thambiratnam, K.; Ghani, Z. A.; Harun, S. W.

2012-10-01

A wide-band supercontinuum source generated by mode-locked pulses injected into a Highly Non-Linear Fiber (HNLF) is proposed and demonstrated. A 49 cm long Bismuth-Erbium Doped Fiber (Bi-EDF) pumped by two 1480 nm laser diodes acts as the active gain medium for a ring fiber laser, from which mode-locked pulses are obtained using the Non-Polarization Rotation (NPR) technique. The mode-locked pulses are then injected into a 100 m long HLNF with a dispersion of 0.15 ps/nm km at 1550 nm to generate a supercontinuum spectrum spanning from 1340 nm to more than 1680 nm with a pulse width of 0.08 ps and an average power of -17 dBm. The supercontinuum spectrum is sliced using a 24 channel Arrayed Waveguide Grating (AWG) with a channel spacing of 100 GHz to obtain a fanned-out laser output covering the O-, E-, S-, C-, L- and U-bands. The lasing wavelengths obtained have an average pulse width of 9 ps with only minor fluctuations and a mode-locked repetition rate of 40 MHz, and is sufficiently stable to be used in a variety of sensing and communication applications, most notably as cost-effective sources for Fiber-to-the-Home (FTTH) networks.

Isolation and characterization of two lytic cold-active bacteriophages infecting Pseudomonas fluorescens from the Napahai plateau wetland.

PubMed

Xiang, Yingying; Wang, Shuang; Li, Jiankai; Wei, Yunlin; Zhang, Qi; Lin, Lianbing; Ji, Xiuling

2018-03-01

As the "kidneys of the Earth", wetlands play important roles as biodiversity reservoirs, in water purification, and in flood control. In this study, 2 lytic cold-active bacteriophages, named VW-6S and VW-6B, infecting Pseudomonas fluorescens W-6 cells from the Napahai plateau wetland in China were isolated and characterized. Electron microscopy showed that both VW-6S and VW-6B had an icosahedral head (66.7 and 61.1 nm, respectively) and a long tail (8.3 nm width × 233.3 nm length and 11.1 nm width × 166.7 nm length, respectively). The bacteriophages VW-6S and VW-6B were classified as Siphoviridae and had an approximate genome size of 30-40 kb. The latent and burst periods of VW-6S were 60 and 30 min, whereas those of VW-6B were 30 and 30 min, respectively. The optimal pH values for the bacteriophages VW-6S and VW-6B were 8.0 and 10.0, respectively, and their activity decreased rapidly at temperatures higher than 60 °C. These cold-active bacteriophages provide good materials for further study of cold-adaptation mechanisms and interaction with the host P. fluorescens.

Normal-incidence reflectance of optimized W/B4C x-ray multilayers in the range 1.4 nm < λ < 2.4 nm

NASA Astrophysics Data System (ADS)

Windt, David L.; Gullikson, Eric M.; Walton, Christopher C.

2002-12-01

We have fabricated W/B4C multilayers having periods in the range d = 0.8-1.2 nm and measured their soft-x-ray performance near normal incidence in the wavelength range 1.4 < λ < 2.4 nm. By adjusting the fractional layer thickness of W we have produced structures having interface widths σ ~ 0.29 nm (i.e., as determined from normal-incidence reflectometry), thus having optimal soft-x-ray performance. We describe our results and discuss their implications, particularly with regard to the development of short-wavelength normal-incidence x-ray optics.

Resolution of 90 nm (lambda/5) in an optical transmission microscope with an annular condenser.

PubMed

Vainrub, Arnold; Pustovyy, Oleg; Vodyanoy, Vitaly

2006-10-01

Resolution of 90 nm was achieved with a research microscope simply by replacing the standard bright-field condenser with a homebuilt illumination system with a cardioid annular condenser. Diffraction gratings with 100 nm width lines as well as less than 100 nm size features of different-shaped objects were clearly visible on a calibrated microscope test slide. The resolution increase results from a known narrower diffraction pattern in coherent illumination for the annular aperture compared with the circular aperture. This explanation is supported by an excellent accord of calculated and measured diffraction patterns for a 50 nm radius disk.

A blue optical filter for narrow-band imaging in endoscopic capsules

NASA Astrophysics Data System (ADS)

Silva, M. F.; Ghaderi, M.; Goncalves, L. M.; de Graaf, G.; Wolffenbuttel, R. F.; Correia, J. H.

2014-05-01

This paper presents the design, simulation, fabrication, and characterization of a thin-film Fabry-Perot resonator composed of titanium dioxide (TiO2) and silicon dioxide (SiO2) thin-films. The optical filter is developed to be integrated with a light emitting diode (LED) for enabling narrow-band imaging (NBI) in endoscopy. The NBI is a high resolution imaging technique that uses spectrally centered blue light (415 nm) and green light (540 nm) to illuminate the target tissue. The light at 415 nm enhances the imaging of superficial veins due to their hemoglobin absorption, while the light at 540 nm penetrates deeper into the mucosa, thus enhances the sub-epithelial vessels imaging. Typically the endoscopes and endoscopic capsules use white light for acquiring images of the gastrointestinal (GI) tract. However, implementing the NBI technique in endoscopic capsules enhances their capabilities for the clinical applications. A commercially available blue LED with a maximum peak intensity at 404 nm and Full Width Half Maximum (FWHM) of 20 nm is integrated with a narrow band blue filter as the NBI light source. The thin film simulations show a maximum spectral transmittance of 36 %, that is centered at 415 nm with FWHM of 13 nm for combined the blue LED and a Fabry Perot resonator system. A custom made deposition scheme was developed for the fabrication of the blue optical filter by RF sputtering. RF powered reactive sputtering at 200 W with the gas flows of argon and oxygen that are controlled for a 5:1 ratio gives the optimum optical conditions for TiO2 thin films. For SiO2 thin films, a non-reactive RF sputtering at 150 W with argon gas flow at 15 sccm results in the best optical performance. The TiO2 and SiO2 thin films were fully characterized by an ellipsometer in the wavelength range between 250 nm to 1600 nm. Finally, the optical performance of the blue optical filter is measured and presented.

Experimental investigation on a diode-pumped cesium-vapor laser stably operated at continuous-wave and pulse regime.

PubMed

Chen, Fei; Xu, Dongdong; Gao, Fei; Zheng, Changbin; Zhang, Kuo; He, Yang; Wang, Chunrui; Guo, Jin

2015-05-04

Employing a fiber-coupled diode-laser with a center wavelength of 852.25 nm and a line width of 0.17 nm, experimental investigation on diode-end-pumped cesium (Cs) vapor laser stably operated at continuous-wave (CW) and pulse regime is carried out. A 5 mm long cesium vapor cell filled with 60 kPa helium and 20 kPa ethane is used as laser medium. Using an output coupler with reflectivity of 48.79%, 1.26 W 894.57 nm CW laser is obtained at an incident pump power of 4.76 W, corresponding an optical-optical efficiency of 26.8% and a slope-efficiency of 28.8%, respectively. The threshold temperature is 67.5 °C. Stable pulsed cesium laser with a maximum average output power of 2.6 W is obtained at a repetition rate of 76 Hz, and the pulse repetition rate can be extend to 1 kHz with a pulse width of 18 μs.

Viscosity and Wetting Property of Water Confined in Extended Nanospace Simultaneously Measured from Highly-Pressurized Meniscus Motion.

PubMed

Li, Lixiao; Kazoe, Yutaka; Mawatari, Kazuma; Sugii, Yasuhiko; Kitamori, Takehiko

2012-09-06

Understanding fluid and interfacial properties in extended nanospace (10-1000 nm) is important for recent advances of nanofluidics. We studied properties of water confined in fused-silica nanochannels of 50-1500 nm sizes with two types of cross-section: (1) square channel of nanoscale width and depth, and (2) plate channel of microscale width and nanoscale depth. Viscosity and wetting property were simultaneously measured from capillary filling controlled by megapascal external pressure. The viscosity increased in extended nanospace, while the wetting property was almost constant. Especially, water in the square nanochannels had much higher viscosity than the plate channel, which can be explained considering loosely coupled water molecules by hydrogen bond on the surface within 24 nm. This study suggests specificity of fluids two-dimensionally confined in extended nanoscale, in which the liquid is highly viscous by the specific water phase, while the wetting dynamics is governed by the well-known adsorbed water layer of several-molecules thickness.

Periodically structured Si pillars for high-performing heterojunction photodetectors

NASA Astrophysics Data System (ADS)

Melvin David Kumar, M.; Yun, Ju-Hyung; Kim, Joondong

2015-03-01

A periodical array of silicon (Si) micro pillar structures was fabricated on Si substrates using PR etching process. Indium tin oxide (ITO) layer of 80 nm thickness was deposited over patterned Si substrates so as to make ITO/n-Si heterojunction devices. The influences of width and period of pillars on the optical and electrical properties of prepared devices were investigated. The surface morphology of the Si substrates revealed the uniform array of pillar structures. The 5/10 (width/period) Si pillar pattern reduced the optical reflectance to 6.5% from 17% which is of 5/7 pillar pattern. The current rectifying ratio was found higher for the device in which the pillars are situated in optimum periods. At both visible (600 nm) and near infrared (900 nm) range of wavelengths, the 5/7 and 5/10 pillar patterned device exhibited the better photoresponses which are suitable for making advanced photodetectors. This highly transmittance and photoresponsive pillar patterned Si substrates with an ITO layer would be a promising device for various photoelectric applications.

One-pot hydrothermal synthesis of an assembly of magnetite nanoneedles on a scaffold of cyclic-diphenylalanine nanorods

NASA Astrophysics Data System (ADS)

Togashi, Takanari; Umetsu, Mitsuo; Naka, Takashi; Ohara, Satoshi; Hatakeyama, Yoshiharu; Adschiri, Tadafumi

2011-09-01

The assembly of metal oxide nanoparticles (NPs) on a biomolecular template by a one-pot hydrothermal synthesis method is achieved for the first time. Magnetite (Fe3O4) nanoneedles (length: 100 nm; width: 10 nm) were assembled on cyclic-diphenylalanine (cFF) nanorods (length: 2-10 μm; width: 200 nm). The Fe3O4 nanoneedles and cFF nanorods were simultaneously synthesized from FeSO4 and l-phenylalanine by hydrothermal synthesis (220 °C and 22 MPa), respectively. The samples were analyzed by powder X-ray diffraction (XRD), Fourier transform infrared spectroscopy (IR), transmission electron microscopy (TEM), and superconducting quantum interference device (SQUID) magnetometry. Experimental results indicate that Fe3O4 nanoneedles were assembled on cFF nanorods during the hydrothermal reaction. The composite contained 3.3 wt% Fe3O4 nanoneedles without any loss of the original magnetic properties of Fe3O4.

Green, yellow and bright red (In,Ga,Al)P-GaP diode lasers grown on high-index GaAs substrates

NASA Astrophysics Data System (ADS)

Ledentsov, N. N.; Shchukin, V. A.; Shernyakov, Yu. M.; Kulagina, M. M.; Payusov, A. S.; Gordeev, N. Yu.; Maximov, M. V.; Cherkashin, N. A.

2017-02-01

Low threshold current density (<400 A/cm2) injection lasing in (AlxGa1-x)0.5In0.5P-GaAs-based diodes down to the green spectral range (<570 nm) is obtained. The epitaxial structures are grown on high-index (611)A and (211)A GaAs substrates by metal-organic vapor phase epitaxy and contain tensile-strained GaP-enriched insertions aimed at preventing escape of the injected nonequilibrium electrons from the active region. Extended waveguide concept results in a vertical beam divergence with a full width at half maximum of 15o for (611)A substrates. The lasing at 569 nm is realized at 85 K. In the orange-red laser diode structure low threshold current density (200 A/cm2) in the orange spectral range (598 nm) is realized at 85 K. The latter devices demonstrate room temperature lasing at 628 nm at 2 kA/cm2 and a total power above 3W. The red laser diodes grown on (211)A substrates demonstrate vertically multimode lasing far field pattern indicating a lower optical confinement factor for the fundamental mode as compared to the devices grown on (611)A. However the temperature stability of the threshold current and the wavelength stability are significantly higher for (211)A-grown structures in agreement with the conduction band modeling data.

High-quality AlN film grown on a nanosized concave-convex surface sapphire substrate by metalorganic vapor phase epitaxy

NASA Astrophysics Data System (ADS)

Yoshikawa, Akira; Nagatomi, Takaharu; Morishita, Tomohiro; Iwaya, Motoaki; Takeuchi, Tetsuya; Kamiyama, Satoshi; Akasaki, Isamu

2017-10-01

We developed a method for fabricating high-crystal-quality AlN films by combining a randomly distributed nanosized concavo-convex sapphire substrate (NCC-SS) and a three-step growth method optimized for NCC-SS, i.e., a 3-nm-thick nucleation layer (870 °C), a 150-nm-thick high-temperature layer (1250 °C), and a 3.2-μm-thick medium-temperature layer (1110 °C). The NCC-SS is easily fabricated using a conventional metalorganic vapor phase epitaxy reactor equipped with a showerhead plate. The resultant AlN film has a crack-free and single-step surface with a root-mean-square roughness of 0.5 nm. The full-widths at half-maxima of the X-ray rocking curve were 50/250 arcsec for the (0002)/(10-12) planes, revealing that the NCC surface is critical for achieving such a high-quality film. Hexagonal-pyramid-shaped voids at the AlN/NCC-SS interface and confinement of dislocations within the 150-nm-thick high-temperature layer were confirmed. The NCC surface feature and resultant faceted voids play an important role in the growth of high-crystal-quality AlN films, likely via localized and/or disordered growth of AlN at the initial stage, contributing to the alignment of high-crystal-quality nuclei and dislocations.

Fabrication of 0.25-um electrode width SAW filters using x-ray lithography with a laser plasma source

NASA Astrophysics Data System (ADS)

Bobkowski, Romuald; Li, Yunlei; Fedosejevs, Robert; Broughton, James N.

1996-05-01

A process for the fabrication of surface acoustic wave (SAW) devices with line widths of 250 nm and less, based on x-ray lithography using a laser-plasma source has been developed. The x-ray lithography process is based on keV x-ray emission from Cu plasma produced by 15 Hz, 50 ps, 248 nm KrF excimer laser pulses. The full structure of a 2 GHz surface acoustic wave filter with interdigital transducers in a split-electrode geometry has been manufactured. The devices require patterning a 150 nm thick aluminum layer on a LiNbO3 substrate with electrodes 250 nm wide. The manufacturing process has two main steps: x-ray mask fabrication employing e-beam lithography and x-ray lithography to obtain the final device. The x-ray masks are fabricated on 1 micrometers thick membranes of Si2N4. The line patterns on the masks are written into PMMA resist using a scanning electron microscope which has been interfaced to a personal computer equipped to control the x and y scan voltages. The opaque regions of the x-ray mask are then formed by electroplating fine grain gold into the open spaces in the etched PMMA. The mask and sample are mounted in an exposure cassette with a fixed spacer of 10 micrometers separating them. The sample consists of a LiNbO3 substrate coated with Shipley XP90104C x-ray resist which has been previously characterized. The x-ray patterning is carried out in an exposure chamber with flowing helium background gas in order to minimize debris deposition on the filters. After etching the x-ray resist, the final patterns are produced using metallization and a standard lift-off technique. The SAW filters are then bonded and packaged onto impedance matching striplines. The resultant devices are tested using Scalar Network Analyzers. The final devices produced had a center frequency of 1.93 GHz with a bandwidth of 98 MHz, close to the expected performance of our simple design.

THE FORMATION OF IRIS DIAGNOSTICS. VIII. IRIS OBSERVATIONS IN THE C ii 133.5 nm MULTIPLET

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rathore, Bhavna; Pereira, Tiago M. D.; Carlsson, Mats

The C ii 133.5 nm multiplet has been observed by NASA’s Interface Region Imaging Spectrograph (IRIS) in unprecedented spatial resolution. The aims of this work are to characterize these new observations of the C ii lines, place them in context with previous work, and to identify any additional value the C ii lines bring when compared with other spectral lines. We make use of wide, long exposure IRIS rasters covering the quiet Sun and an active region. Line properties such as velocity shift and width are extracted from individual spectra and analyzed. The lines have a variety of shapes (mostlymore » single-peak or double-peak), are strongest in active regions and weaker in the quiet Sun. The ratio between the 133.4 and 133.5 nm components is always less than 1.8, indicating that their radiation is optically thick in all locations. Maps of the C ii line widths are a powerful new diagnostic of chromospheric structures, and their line shifts are a robust velocity diagnostic. Compared with earlier quiet Sun observations, we find similar absolute intensities and mean line widths, but smaller redshifts; this difference can perhaps be attributed to differences in spectral resolution and spatial coverage. The C ii intensity maps are somewhat similar to those of transition region lines, but also share some features with chromospheric maps such as those from the Mg ii k line, indicating that they are formed between the upper chromosphere and transition region. C ii intensity, width, and velocity maps can therefore be used to gather additional information about the upper chromosphere.« less

From 1D to 3D: Tunable Sub-10 nm Gaps in Large Area Devices.

PubMed

Zhou, Ziwei; Zhao, Zhiyuan; Yu, Ye; Ai, Bin; Möhwald, Helmuth; Chiechi, Ryan C; Yang, Joel K W; Zhang, Gang

2016-04-20

Tunable sub-10 nm 1D nanogaps are fabricated based on nanoskiving. The electric field in different sized nanogaps is investigated theoretically and experimentally, yielding nonmonotonic dependence and an optimized gap-width (5 nm). 2D nanogap arrays are fabricated to pack denser gaps combining surface patterning techniques. Innovatively, 3D multistory nanogaps are built via a stacking procedure, processing higher integration, and much improved electric field. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Nonequilibrium ferroelectric-ferroelastic 10 nm nanodomains: wrinkles, period-doubling, and power-law relaxation

NASA Astrophysics Data System (ADS)

Scott, James F.; Evans, Donald M.; Katiyar, Ram S.; McQuaid, Raymond G. P.; Gregg, J. Marty

2017-08-01

Since the 1935 work of Landau-Lifshitz and of Kittel in 1946 all ferromagnetic, ferroelectric, and ferroelastic domains have been thought to be straight-sided with domain widths proportional to the square root of the sample thickness. We show in the present work that this is not true. We also discover period doubling domains predicted by Metaxas et al (2008 Phys. Rev. Lett. 99 217208) and modeled by Wang and Zhao (2015 Sci. Rep. 5 8887). We examine non-equilibrium ferroic domain structures in perovskite oxides with respect to folding, wrinkling, and relaxation and suggest that structures are kinetically limited and in the viscous flow regime predicted by Metaxas et al in 2008 but never observed experimentally. Comparisons are made with liquid crystals and hydrodynamic instabilities, including chevrons, and fractional power-law relaxation. As Shin et al (2016 Soft Matter 12 3502) recently emphasized: ‘An understanding of how these folds initiate, propagate, and interact with each other is still lacking’. Inside each ferroelastic domain are ferroelectric 90° nano-domains with 10 nm widths and periodicity in agreement with the 10 nm theoretical minima predicted by Feigl et al (2014 Nat. Commun. 5 4677). Evidence is presented for domain-width period doubling, which is common in polymer films but unknown in ferroic domains. A discussion of the folding-to-period doubling phase transition model of Wang and Zhao is included.

Synchrotron radiation-based quasi-elastic scattering using time-domain interferometry with multi-line gamma rays.

PubMed

Saito, Makina; Masuda, Ryo; Yoda, Yoshitaka; Seto, Makoto

2017-10-02

We developed a multi-line time-domain interferometry (TDI) system using 14.4 keV Mössbauer gamma rays with natural energy widths of 4.66 neV from 57 Fe nuclei excited using synchrotron radiation. Electron density fluctuations can be detected at unique lengths ranging from 0.1 nm to a few nm on time scales from several nanoseconds to the sub-microsecond order by quasi-elastic gamma-ray scattering (QGS) experiments using multi-line TDI. In this report, we generalize the established expression for a time spectrum measured using an identical single-line gamma-ray emitter pair to the case of a nonidentical pair of multi-line gamma-ray emitters by considering the finite energy width of the incident synchrotron radiation. The expression obtained illustrates the unique characteristics of multi-line TDI systems, where the finite incident energy width and use of a nonidentical emitter pair produces further information on faster sub-picosecond-scale dynamics in addition to the nanosecond dynamics; this was demonstrated experimentally. A normalized intermediate scattering function was extracted from the spectrum and its relaxation form was determined for a relaxation time of the order of 1 μs, even for relatively large momentum transfer of ~31 nm -1 . The multi-line TDI method produces a microscopic relaxation picture more rapidly and accurately than conventional single-line TDI.

High-Throughput Mechanobiology Screening Platform Using Micro- and Nanotopography.

PubMed

Hu, Junqiang; Gondarenko, Alexander A; Dang, Alex P; Bashour, Keenan T; O'Connor, Roddy S; Lee, Sunwoo; Liapis, Anastasia; Ghassemi, Saba; Milone, Michael C; Sheetz, Michael P; Dustin, Michael L; Kam, Lance C; Hone, James C

2016-04-13

We herein demonstrate the first 96-well plate platform to screen effects of micro- and nanotopographies on cell growth and proliferation. Existing high-throughput platforms test a limited number of factors and are not fully compatible with multiple types of testing and assays. This platform is compatible with high-throughput liquid handling, high-resolution imaging, and all multiwell plate-based instrumentation. We use the platform to screen for topographies and drug-topography combinations that have short- and long-term effects on T cell activation and proliferation. We coated nanofabricated "trench-grid" surfaces with anti-CD3 and anti-CD28 antibodies to activate T cells and assayed for interleukin 2 (IL-2) cytokine production. IL-2 secretion was enhanced at 200 nm trench width and >2.3 μm grating pitch; however, the secretion was suppressed at 100 nm width and <0.5 μm pitch. The enhancement on 200 nm grid trench was further amplified with the addition of blebbistatin to reduce contractility. The 200 nm grid pattern was found to triple the number of T cells in long-term expansion, a result with direct clinical applicability in adoptive immunotherapy.

Buckling Behavior of Substrate Supported Graphene Sheets

PubMed Central

Yang, Kuijian; Chen, Yuli; Pan, Fei; Wang, Shengtao; Ma, Yong; Liu, Qijun

2016-01-01

The buckling of graphene sheets on substrates can significantly degrade their performance in materials and devices. Therefore, a systematic investigation on the buckling behavior of monolayer graphene sheet/substrate systems is carried out in this paper by both molecular mechanics simulations and theoretical analysis. From 70 simulation cases of simple-supported graphene sheets with different sizes under uniaxial compression, two different buckling modes are investigated and revealed to be dominated by the graphene size. Especially, for graphene sheets with length larger than 3 nm and width larger than 1.1 nm, the buckling mode depends only on the length/width ratio. Besides, it is revealed that the existence of graphene substrate can increase the critical buckling stress and strain to 4.39 N/m and 1.58%, respectively, which are about 10 times those for free-standing graphene sheets. Moreover, for graphene sheets with common size (longer than 20 nm), both theoretical and simulation results show that the critical buckling stress and strain are dominated only by the adhesive interactions with substrate and independent of the graphene size. Results in this work provide valuable insight and guidelines for the design and application of graphene-derived materials and nano-electromechanical systems. PMID:28787831

Laboratory measurements of VUV N2 photoabsorption cross sections and line widths: applications to planetary atmospheric transmission models

NASA Astrophysics Data System (ADS)

Smith, P. L.; Stark, G.; Yoshino, K.

2003-05-01

The analyses of VUV occultation measurements of the N2-rich atmospheres of Titan and Triton are hampered by the lack of fundamental spectroscopic data for N2. There is a need for reliable photoabsorption cross sections and line widths for the 100 electronic bands of N2 in the 80 to 100 nm wavelength region. We present analyses of new measurements of individual line strengths and widths in N2 bands in the region 94 to 100 nm. Within individual bands, we find significant departures from the predicted line strength distributions based on isolated band models. Line width analyses within each band indicate that predissociation-broadening is often highly dependent on the rotational quantum number. We illustrate the importance of N2 line widths in the analysis of occultation measurements via N2 transmission models over selected wavelength regions. We have continued to compile on-line molecular spectroscopic atlas based on our N2 laboratory data: http://cfa-www.harvard.edu/amdata/ampdata/N2ARCHIVE/n2home.html. The archive includes published and unpublished 14N2, 14N15N, and 15N2 line lists and spectroscopic identifications, excited state energy levels, band and line f-values, a summary of published band f-value and line width measurements, and a cross-referenced summary of the relevant N2 literature. The listings are searchable by wavelength interval or band identification and are suitable for down-loading in a convenient format. We gratefully acknowledge funding support from NASA grant NAG5-9059 and the Smithsonian Institution Atherton-Seidell Grant Program.

Crystal phase-controlled synthesis of rod-shaped AgInTe2 nanocrystals for in vivo imaging in the near-infrared wavelength region

NASA Astrophysics Data System (ADS)

Kameyama, Tatsuya; Ishigami, Yujiro; Yukawa, Hiroshi; Shimada, Taisuke; Baba, Yoshinobu; Ishikawa, Tetsuya; Kuwabata, Susumu; Torimoto, Tsukasa

2016-03-01

Rod-shaped AgInTe2 nanocrystals (NCs) exhibiting intense near-band edge photoluminescence in the near-infrared (NIR) wavelength region, were successfully prepared by the thermal reaction of metal acetates and Te precursors in 1-dodecanethiol. Increasing the reaction temperature resulted in the formation of larger AgInTe2 NCs with crystal structures varying from hexagonal to tetragonal at reaction temperatures of 280 °C or higher. The energy gap was increased from 1.13 to 1.20 eV with a decrease in rod width from 8.3 to 5.6 nm, accompanied by a blue shift in the photoluminescence (PL) peak wavelength from 1097 to 1033 nm. The optimal PL quantum yield was approximately 18% for AgInTe2 NCs with rod widths of 5.6 nm. The applicability of AgInTe2 NCs as a NIR-emitting material for in vivo biological imaging was examined by injecting AgInTe2 NC-incorporated liposomes into the back of a C57BL/6 mouse, followed by in vivo photoluminescence imaging in the NIR region.Rod-shaped AgInTe2 nanocrystals (NCs) exhibiting intense near-band edge photoluminescence in the near-infrared (NIR) wavelength region, were successfully prepared by the thermal reaction of metal acetates and Te precursors in 1-dodecanethiol. Increasing the reaction temperature resulted in the formation of larger AgInTe2 NCs with crystal structures varying from hexagonal to tetragonal at reaction temperatures of 280 °C or higher. The energy gap was increased from 1.13 to 1.20 eV with a decrease in rod width from 8.3 to 5.6 nm, accompanied by a blue shift in the photoluminescence (PL) peak wavelength from 1097 to 1033 nm. The optimal PL quantum yield was approximately 18% for AgInTe2 NCs with rod widths of 5.6 nm. The applicability of AgInTe2 NCs as a NIR-emitting material for in vivo biological imaging was examined by injecting AgInTe2 NC-incorporated liposomes into the back of a C57BL/6 mouse, followed by in vivo photoluminescence imaging in the NIR region. Electronic supplementary information (ESI) available: A detailed synthesis procedure of DSPC-AgInTe2 and analytical data of AgInTe2 NCs. See DOI: 10.1039/c5nr07532g

Thermally stable surface-emitting tilted wave laser

NASA Astrophysics Data System (ADS)

Shchukin, V. A.; Ledentsov, N. N.; Kalosha, V. P.; Ledentsov, N.; Agustin, M.; Kropp, J. R.; Maximov, M. V.; Zubov, F. I.; Shernyakov, Yu. M.; Payusov, A. S.; Gordeev, N. Yu; Kulagina, M. M.; Zhukov, A. E.

2018-02-01

Novel lasing modes in a vertical-cavity surface-emitting laser (VCSEL)-type structure based on an antiwaveguding cavity are studied. Such a VCSEL cavity has an effective refractive index in the cavity region lower than the average index of the distributed Bragg reflectors (DBRs). Such device in a stripe geometry does not support in-plane waveguiding mode, and all modes with a high Q-factor are exclusively VCSEL-like modes with similar near field profile in the vertical direction. A GaAlAs-based VCSEL structure studied contains a resonant cavity with multiple GaInAs quantum wells as an active region. The VCSEL structure is processed as an edge-emitting laser with cleaved facets and top contact representing a non-alloyed metal grid. Rectangular-shaped 400x400 µm pieces are cleaved with perpendicular facets. The contact grid region has a total width of 70 μm. 7 μm-wide metal stripes serve as non-alloyed metal contact and form periodic rectangular openings having a size of 10x40 μm. Surface emission through the windows on top of the chip is measured at temperatures from 90 to 380 K. Three different types of modes are observed. The longest wavelength mode (mode A) is a VCSEL-like mode at 854 nm emitting normal to the surface with a full width at half maximum (FWHM) of the far field 10°. Accordingly the lasing wavelength demonstrates a thermal shift of the wavelength of 0.06 nm/K. Mode B is at shorter wavelengths of 840 nm at room temperature, emitting light at two symmetric lobes at tilt angles 40° with respect to the normal to the surface in the directions parallel to the stripe. The emission wavelength of this mode shifts at a rate 0.22 nm/K according to the GaAs bandgap shift. The angle of mode B with respect to the normal reduces as the wavelength approaches the vertical cavity etalon wavelength and this mode finally merges with the VCSEL mode. Mode B hops between different lateral modes of the VCSEL forming a dense spectrum due to significant longitudinal cavity length, and the thermal shift of its wavelength is governed by the shift of the gain spectrum. The most interesting observation is Mode C, which shifts at a rate 0.06 nm/K and has a spectral width of 1 nm. Mode C matches the wavelength of the critical angle for total internal reflection for light impinging from semiconductor chip on semiconductor/air interface and propagates essentially as an in-plane mode. According to modeling data we conclude that the lasing mode represents a coupled state between the TM-polarized surface-trapped optical mode and the VCSEL cavity mode. The resulting mode has an extended near field zone and low propagation losses. The intensity of the mode drastically enhances once is appears at resonance with Mode B. A clear threshold is revealed in the L-I curves of all modes and there is a strong competition of the lasing mechanisms once the gain maximum is scanned over the related wavelength range by temperature change.

Process Parameters on the Crystallization and Morphology of Hydroxyapatite Powders Prepared by a Hydrolysis Method

NASA Astrophysics Data System (ADS)

Wang, Moo-Chin; Hon, Min-Hsiung; Chen, Hui-Ting; Yen, Feng-Lin; Hung, I.-Ming; Ko, Horng-Huey; Shih, Wei-Jen

2013-07-01

The effects of process parameters on the crystallization and morphology of hydroxyapatite (Ca10(PO4)6(OH)2, HA) powders synthesized from dicalcium phosphate dihydrate (CaHPO4·2H2O, DCPD) using a hydrolysis method have been investigated. X-ray diffraction (XRD), Fourier-transform infrared (FT-IR) spectra, scanning electron microscopy (SEM), transmission electron microscopy (TEM), and selected area electron diffraction (SAED) were used to characterize the synthesized powders. When DCPD underwent hydrolysis in 2.5 NaOH solution (Na(aq)) at 303 K to 348 K (30 °C to 75 °C) for 1 hour, the XRD results revealed that HA was obtained for all the as-dried samples. The SEM morphology of the HA powders for DCPD hydrolysis produced at 348 K (75 °C) shows regular alignment and a short rod shape with a size of 200 nm in length and 50 nm in width. With DCPD hydrolysis in 2.5 M NaOH(aq) holding at 348 K (75 °C) for 1 to 24 hours, XRD results demonstrated that all samples were HA and no other phases could be detected. Moreover, the XRD results also show that all the as-dried powders still maintained the HA structure when DCPD underwent hydrolysis in 0.1 to 5 M NaOH(aq) at 348 K (75 °C) for 1 hour. Otherwise, the full transformation from HA to octa-calcium phosphate (OCP, Ca8H2(PO4)6·5H2O) occurred when hydrolysis happened in 10 M NaOH(aq). FT-IR spectra analysis revealed that some carbonated HA (Ca10(PO4)6(CO3), CHA) had formed. The SEM morphology results show that the 60 to 65 nm width of the uniformly long rods with regular alignment formed in the HA powder aggregates when DCPD underwent hydrolysis in 2.5 M NaOH(aq) at 348 K (75 °C) for 1 hour.

Ring-shaped active mode-locked tunable laser using quantum-dot semiconductor optical amplifier

NASA Astrophysics Data System (ADS)

Zhang, Mingxiao; Wang, Yongjun; Liu, Xinyu

2018-03-01

In this paper, a lot of simulations has been done for ring-shaped active mode-locked lasers with quantum-dot semiconductor optical amplifier (QD-SOA). Based on the simulation model of QD-SOA, we discussed about the influence towards mode-locked waveform frequency and pulse caused by QD-SOA maximum mode peak gain, active layer loss coefficient, bias current, incident light pulse, fiber nonlinear coefficient. In the meantime, we also take the tunable performance of the laser into consideration. Results showed QD-SOA a better performance than original semiconductor optical amplifier (SOA) in recovery time, line width, and nonlinear coefficients, which makes it possible to output a locked-mode impulse that has a higher impulse power, narrower impulse width as well as the phase is more easily controlled. After a lot of simulations, this laser can realize a 20GHz better locked-mode output pulse after 200 loops, where the power is above 17.5mW, impulse width is less than 2.7ps, moreover, the tunable wavelength range is between 1540nm-1580nm.

Facile fabrication of a silicon nanowire sensor by two size reduction steps for detection of alpha-fetoprotein biomarker of liver cancer

NASA Astrophysics Data System (ADS)

Binh Pham, Van; ThanhTung Pham, Xuan; Nhat Khoa Phan, Thanh; Thanh Tuyen Le, Thi; Chien Dang, Mau

2015-12-01

We present a facile technique that only uses conventional micro-techniques and two size-reduction steps to fabricate wafer-scale silicon nanowire (SiNW) with widths of 200 nm. Initially, conventional lithography was used to pattern SiNW with 2 μm width. Then the nanowire width was decreased to 200 nm by two size-reduction steps with isotropic wet etching. The fabricated SiNW was further investigated when used with nanowire field-effect sensors. The electrical characteristics of the fabricated SiNW devices were characterized and pH sensitivity was investigated. Then a simple and effective surface modification process was carried out to modify SiNW for subsequent binding of a desired receptor. The complete SiNW-based biosensor was then used to detect alpha-fetoprotein (AFP), one of the medically approved biomarkers for liver cancer diagnosis. Electrical measurements showed that the developed SiNW biosensor could detect AFP with concentrations of about 100 ng mL-1. This concentration is lower than the necessary AFP concentration for liver cancer diagnosis.

Experimental demonstration of wavelength conversion between ps-pulses based on cascaded sum- and difference frequency generation (SFG+DFG) in LiNbO3 waveguides

NASA Astrophysics Data System (ADS)

Wang, Jian; Sun, Junqiang; Lou, Chuanhong; Sun, Qizhen

2005-09-01

All-optical wavelength conversion between ps-pulses based on cascaded sum- and difference frequency generation (SFG+DFG) is proposed and experimentally demonstrated in periodically poled LiNbO3 (PPLN) waveguides. The signal pulse with 40-GHz repetition rate and 1.57- ps pulse width is adopted. The converted idler wavelength can be tuned from 1527.4 to 1540.5nm as the signal wavelength is varied from 1561.9 to 1548.4nm. No obvious changes of the pulse shape and width, also no chirp are observed in the converted idler pulse. The results imply that single-to-multiple channel wavelength conversions can be achieved by appropriately tuning the two pump wavelengths.

Experimental demonstration of wavelength conversion between ps-pulses based on cascaded sum- and difference frequency generation (SFG+DFG) in LiNbO3 waveguides.

PubMed

Wang, Jian; Sun, Junqiang; Lou, Chuanhong; Sun, Qizhen

2005-09-19

All-optical wavelength conversion between ps-pulses based on cascaded sum- and difference frequency generation (SFG+DFG) is proposed and experimentally demonstrated in periodically poled LiNbO3 (PPLN) waveguides. The signal pulse with 40-GHz repetition rate and 1.57- ps pulse width is adopted. The converted idler wavelength can be tuned from 1527.4 to 1540.5nm as the signal wavelength is varied from 1561.9 to 1548.4nm. No obvious changes of the pulse shape and width, also no chirp are observed in the converted idler pulse. The results imply that single-to-multiple channel wavelength conversions can be achieved by appropriately tuning the two pump wavelengths.

Generation of 70 fs broadband pulses in a hybrid nonlinear amplification system with mode-locked Yb:YAG ceramic oscillator

NASA Astrophysics Data System (ADS)

Liu, Yang; Wang, Chao; Luo, Daping; Yang, Chao; Li, Jiang; Ge, Lin; Pan, Yubai; Li, Wenxue

2017-12-01

We demonstrate the passively mode-locked laser performances of bulk Yb:YAG ceramic prepared by non-aqueous tape casting, which generates initial pulses in temporal width of 3 ps and spectrum width of 3 nm without intra-cavity dispersion management. The ceramic laser is further used as seeding oscillator in a fiber nonlinear amplification system, where ultrashort pulses in maximum output power of ˜100 W and pulse duration of 70 fs are achieved. Moreover, the laser spectrum is broadened to be ˜41 nm due to self-phase modulation effects in the gain fiber, overcoming the narrow spectrum limitations of ceramic materials. Our approach opens a new avenue for power-scaling and spectrum-expanding of femtosecond ceramic lasers.

Tunable double-clad ytterbium-doped fiber laser based on a double-pass Mach-Zehnder interferometer

NASA Astrophysics Data System (ADS)

Meng, Yichang; Zhang, Shumin; Wang, Xinzhan; Du, Juan; Li, Hongfei; Hao, Yanping; Li, Xingliang

2012-03-01

We have demonstrated an adjustable double-clad Yb 3+-doped fiber laser using a double-pass Mach-Zehnder interferometer. The laser is adjustable over a range of 40 nm from 1064 nm to 1104 nm. By adjusting the state of the polarization controller, which is placed in the double-pass Mach-Zehnder interferometer, we obtained central lasing wavelengths that can be accurately tuned with controllable spacing between different tunable wavelengths. The laser has a side mode suppression ratio of 42 dB, the 3 dB spectral width is less than 0.2 nm, and the slope efficiencies at 1068 nm, 1082 nm and 1098 nm are 23%, 32% and 26%, respectively. In addition, we have experimentally observed tunable multi-wavelengths lasing output.

Characteristic measurement for femtosecond laser pulses using a GaAs PIN photodiode as a two-photon photovoltaic receiver

NASA Astrophysics Data System (ADS)

Chen, Junbao; Xia, Wei; Wang, Ming

2017-06-01

Photodiodes that exhibit a two-photon absorption effect within the spectral communication band region can be useful for building an ultra-compact autocorrelator for the characteristic inspection of optical pulses. In this work, we develop an autocorrelator for measuring the temporal profile of pulses at 1550 nm from an erbium-doped fiber laser based on the two-photon photovoltaic (TPP) effect in a GaAs PIN photodiode. The temporal envelope of the autocorrelation function contains two symmetrical temporal side lobes due to the third order dispersion of the laser pulses. Moreover, the joint time-frequency distribution of the dispersive pulses and the dissimilar two-photon response spectrum of GaAs and Si result in different delays for the appearance of the temporal side lobes. Compared with Si, GaAs displays a greater sensitivity for pulse shape reconstruction at 1550 nm, benefiting from the higher signal-to-noise ratio of the side lobes and the more centralized waveform of the autocorrelation trace. We also measure the pulse width using the GaAs PIN photodiode, and the resolution of the measured full width at half maximum of the TPP autocorrelation trace is 0.89 fs, which is consistent with a conventional second-harmonic generation crystal autocorrelator. The GaAs PIN photodiode is shown to be highly suitable for real-time second-order autocorrelation measurements of femtosecond optical pulses. It is used both for the generation and detection of the autocorrelation signal, allowing the construction of a compact and inexpensive intensity autocorrelator.

A compact high current pulsed electron gun with subnanosecond electron pulse widths

NASA Technical Reports Server (NTRS)

Khakoo, M. A.; Srivastava, S. K.

1984-01-01

A magnetically-collimated, double-pulsed electron gun capable of generating electron pulses with a peak instantaneous current of approximately 70 microamps and a temporal width of 0.35 ns (FWHM) has been developed. Calibration is accomplished by measuring the lifetime of the well known 2(1P)-to-1(1S) transition in helium (58.4nm) at a near-threshold electron-impact energy by use of the delayed-coincidence technique.

Highly crystalline MoS{sub 2} thin films grown by pulsed laser deposition

DOE Office of Scientific and Technical Information (OSTI.GOV)

Serrao, Claudy R.; You, Long; Gadgil, Sushant

2015-02-02

Highly crystalline thin films of MoS{sub 2} were prepared over large area by pulsed laser deposition down to a single monolayer on Al{sub 2}O{sub 3} (0001), GaN (0001), and SiC-6H (0001) substrates. X-ray diffraction and selected area electron diffraction studies show that the films are quasi-epitaxial with good out-of-plane texture. In addition, the thin films were observed to be highly crystalline with rocking curve full width half maxima of 0.01°, smooth with a RMS roughness of 0.27 nm, and uniform in thickness based on Raman spectroscopy. From transport measurements, the as-grown films were found to be p-type.

First results of the front-end ASIC for the strip detector of the PANDA MVD

NASA Astrophysics Data System (ADS)

Quagli, T.; Brinkmann, K.-T.; Calvo, D.; Di Pietro, V.; Lai, A.; Riccardi, A.; Ritman, J.; Rivetti, A.; Rolo, M. D.; Stockmanns, T.; Wheadon, R.; Zambanini, A.

2017-03-01

PANDA is a key experiment of the future FAIR facility and the Micro Vertex Detector (MVD) is the innermost part of its tracking system. PASTA (PAnda STrip ASIC) is the readout chip for the strip part of the MVD. The chip is designed to provide high resolution timestamp and charge information with the Time over Threshold (ToT) technique. Its architecture is based on Time to Digital Converters with analog interpolators, with a time bin width of 50 ps. The chip implements Single Event Upset (SEU) protection techniques for its digital parts. A first full-size prototype with 64 channels was produced in a commercial 110 nm CMOS technology and the first characterizations of the prototype were performed.

Improved output power of GaN-based light-emitting diodes grown on a nanopatterned sapphire substrate

NASA Astrophysics Data System (ADS)

Chan, Chia-Hua; Hou, Chia-Hung; Tseng, Shao-Ze; Chen, Tsing-Jen; Chien, Hung-Ta; Hsiao, Fu-Li; Lee, Chien-Chieh; Tsai, Yen-Ling; Chen, Chii-Chang

2009-07-01

This letter describes the improved output power of GaN-based light-emitting diodes (LEDs) formed on a nanopatterned sapphire substrate (NPSS) prepared through etching with a self-assembled monolayer of 750-nm-diameter SiO2 nanospheres used as the mask. The output power of NPSS LEDs was 76% greater than that of LEDs on a flat sapphire substrate. Three-dimensional finite-difference time-domain calculation predicted a 40% enhancement in light extraction efficiency of NPSS LEDs. In addition, the reduction of full widths at half maximum in the ω-scan rocking curves for the (0 0 2) and (1 0 2) planes of GaN on NPSS suggested improved crystal quality.

HD{sup +} in a short strong laser pulse: Practical consideration of the observability of carrier-envelope phase effects

DOE Office of Scientific and Technical Information (OSTI.GOV)

Roudnev, V.; Esry, B. D.

2007-08-15

We summarize the results of numerical calculations of HD{sup +} in a 7.1 fs (intensity full width at half maximum) 790 nm laser pulse. The molecule is assumed to be aligned with the linearly polarized laser field and includes two electronic and one nuclear degrees of freedom. We report total dissociation and ionization probabilities from the lowest 10 vibrational states for a range of intensities from 10{sup 13} to 7x10{sup 14} W/cm{sup 2}. The conditions for the observability of carrier-envelope phase (CEP) effects for a mixed initial state and for intensity averaging over the laser focal volume are discussed inmore » detail.« less

Frequency non-degenerate phase-sensitive optical parametric amplification based on four-wave-mixing in width-modulated silicon waveguides.

PubMed

Wang, Zhaolu; Liu, Hongjun; Sun, Qibing; Huang, Nan; Li, Xuefeng

2014-12-15

A width-modulated silicon waveguide is proposed to realize non-degenerate phase sensitive optical parametric amplification. It is found that the relative phase at the input of the phase sensitive amplifier (PSA) θIn-PSA can be tuned by tailoring the width and length of the second segment of the width-modulated silicon waveguide, which will influence the gain in the parametric amplification process. The maximum gain of PSA is larger by 9 dB compared with the phase insensitive amplifier (PIA) gain, and the gain bandwidth of PSA is larger by 35 nm compared with the gain bandwidth of PIA. Our on-chip PSA can find important potential applications in highly integrated optical circuits for optical chip-to-chip communication and computers.

Substrate Oxide Layer Thickness Optimization for a Dual-Width Plasmonic Grating for Surface-Enhanced Raman Spectroscopy (SERS) Biosensor Applications

PubMed Central

Bauman, Stephen J.; Brawley, Zachary T.; Darweesh, Ahmad A.; Herzog, Joseph B.

2017-01-01

This work investigates a new design for a plasmonic SERS biosensor via computational electromagnetic models. It utilizes a dual-width plasmonic grating design, which has two different metallic widths per grating period. These types of plasmonic gratings have shown larger optical enhancement than standard single-width gratings. The new structures have additional increased enhancement when the spacing between the metal decreases to sub-10 nm dimensions. This work integrates an oxide layer to improve the enhancement even further by carefully studying the effects of the substrate oxide thickness on the enhancement and reports ideal substrate parameters. The combined effects of varying the substrate and the grating geometry are studied to fully optimize the device’s enhancement for SERS biosensing and other plasmonic applications. The work reports the ideal widths and substrate thickness for both a standard and a dual-width plasmonic grating SERS biosensor. The ideal geometry, comprising a dual-width grating structure atop an optimal SiO2 layer thickness, improves the enhancement by 800%, as compared to non-optimized structures with a single-width grating and a non-optimal oxide thickness. PMID:28665308

Efficient HOMO-LUMO separation by multiple resonance effect toward ultrapure blue thermally activated delayed fluorescence

NASA Astrophysics Data System (ADS)

Hatakeyama, Takuji; Ikuta, Toshiaki; Shiren, Kazushi; Nakajima, Kiichi; Nomura, Shintaro; Ni, Jingping

2016-09-01

Organic light-emitting diodes (OLEDs) play an important role in the new generation of flat-panel displays. Conventional OLEDs employing fluorescent materials together with triplet-triplet annihilation suffer from a relatively low internal quantum efficiency (IQE) of 62.5%. On the other hand, the IQE of OLEDs employing phosphorescent or thermally activated delayed fluorescence (TADF) materials can reach 100%. However, these materials exhibit very broad peaks with a full-width at half-maximum (FWHM) of 70-100 nm and cannot satisfy the color-purity requirements for displays. Therefore, the latest commercial OLED displays employ blue fluorescent materials with a relatively low IQE, and efficient blue emitters with a small FWHM are highly needed. In our manuscript, we present organic molecules that exhibit ultrapure blue fluorescence based on TADF. These molecules consist of three benzene rings connected by one boron and two nitrogen atoms, which establish a rigid polycyclic framework and significant localization of the highest occupied and lowest unoccupied molecular orbitals by a multiple resonance effect. An OLED device based on the new emitter exhibits ultrapure blue emission at 467 nm with an FWHM of 28 nm, Commission Internationale de l'Eclairage (CIE) coordinates of (0.12, 0.13), and an IQE of 100%, which represent record-setting performance for blue OLED devices.

Ultra-narrow band perfect absorbers based on Fano resonance in MIM metamaterials

NASA Astrophysics Data System (ADS)

Zhang, Ming; Fang, Jiawen; Zhang, Fei; Chen, Junyan; Yu, Honglin

2017-12-01

Metallic nanostructures have attracted numerous attentions in the past decades due to their attractive plasmonic properties. Resonant plasmonic perfect absorbers have promising applications in a wide range of technologies including photothermal therapy, thermophotovoltaics, heat-assisted magnetic recording and biosensing. However, it remains to be a great challenge to achieve ultra-narrow band in near-infrared band with plasmonic materials due to the large optical losses in metals. In this letter, we introduced Fano resonance in MIM metamaterials composed of an asymmetry double elliptic cylinders (ADEC), which can achieve ultra-narrow band perfect absorbers. In theoretical calculations, we observed an ultranarrow band resonant absorption peak with the full width at half maximum (FWHM) of 8 nm and absorption amplitude exceeding 99% at 930 nm. Moreover, we demonstrate that the absorption increases with the increase of asymmetry and the absorption resonant wavelength can be tuned by changing the size and arrangement of the unit cell. The asymmetry metallic nanostructure also exhibit a higher refractive sensitivity as large as 503 nm/RIU with high figure of merit of 63, which is promising for high sensitive sensors. Results of this work are desirable for various potential applications in micro-technological structures such as biological sensors, narrowband emission, photodetectors and solar thermophotovoltaic (STPV) cells.

Spectral features of the Stokes part of supercontinuum generated by femtosecond light pulses in selected oxide crystals: A comparative study

NASA Astrophysics Data System (ADS)

Macalik, B.; Kowalski, R. M.; Ryba-Romanowski, W.

2018-04-01

The peculiarities of the Stokes part of supercontinuum (SC) generated by femtosecond light pulses at wavelength 800 nm in single crystals of Gd2SiO5(GSO), Ca4GdO(BO3)3(GCOB), Gd3Ga5O12(GGG), LiTaO3 (LTO) and LuVO4 (LVO) were investigated. Spectral bandwidth and intensity of SC were measured as a function of energy of incident 100 fs pulses employing a grating spectrograph coupled with an InGaAs detector and spatial characteristics of the beam inside crystal samples were monitored perpendicularly to the direction of propagation and recorded using an optical microscope coupled with a camera. It was found that spectral widths of the Stokes part of SC increase markedly with increasing energy of incident pulses for all crystals under study. For fixed focusing conditions the spectral widths of generated SC in GSO, GCOB and GGG wide band-gap crystals are relatively large with cut-off wavelengths close to 1500 nm. Bandwidths of SC generated in LVO and LTO crystals, characterized by band-gaps Eg inferior to three times incident photon energy, are markedly smaller with cut-off wavelengths of 1300 nm and 1150 nm, respectively. Increase of incident pulse energy affects SC spectra giving rise to plateau-like regions stretching to ca 1000 nm.

Wide tuning range wavelength-swept laser with a single SOA at 1020 nm for ultrahigh resolution Fourier-domain optical coherence tomography.

PubMed

Lee, Sang-Won; Song, Hyun-Woo; Jung, Moon-Youn; Kim, Seung-Hwan

2011-10-24

In this study, we demonstrated a wide tuning range wavelength-swept laser with a single semiconductor optical amplifier (SOA) at 1020 nm for ultrahigh resolution, Fourier-domain optical coherence tomography (UHR, FD-OCT). The wavelength-swept laser was constructed with an external line-cavity based on a Littman configuration. An optical wavelength selection filter consisted of a grating, a telescope, and a polygon scanner. Before constructing the optical wavelength selection filter, we observed that the optical power, the spectrum bandwidth, and the center wavelength of the SOA were affected by the temperature of the thermoelectric (TE) cooler in the SOA mount as well as the applied current. Therefore, to obtain a wide wavelength tuning range, we adjusted the temperature of the TE cooler in the SOA mount. When the temperature in the TE cooler was 9 °C, our swept source had a tuning range of 142 nm and a full-width at half-maximum (FWHM) of 121.5 nm at 18 kHz. The measured instantaneous spectral bandwidth (δλ) is 0.085 nm, which was measured by an optical spectrum analyzer with a resolution bandwidth of 0.06 nm. This value corresponds to an imaging depth of 3.1 mm in air. Additionally, the averaged optical power of our swept source was 8.2 mW. In UHR, FD/SS-OCT using our swept laser, the measured axial resolution was 4.0 μm in air corresponding to 2.9 μm in tissue (n = 1.35). The sensitivity was measured to be 93.1 dB at a depth of 100 μm. Finally, we obtained retinal images (macular and optic disk) and a corneal image. © 2011 Optical Society of America

Control of crystallographic texture and surface morphology of Pt/Tio2 templates for enhanced PZT thin film texture.

PubMed

Fox, Austin J; Drawl, Bill; Fox, Glen R; Gibbons, Brady J; Trolier-McKinstry, Susan

2015-01-01

Optimized processing conditions for Pt/TiO2/SiO2/Si templating electrodes were investigated. These electrodes are used to obtain [111] textured thin film lead zirconate titanate (Pb[ZrxTi1-x ]O3 0 ≤ x ≤ 1) (PZT). Titanium deposited by dc magnetron sputtering yields [0001] texture on a thermally oxidized Si wafer. It was found that by optimizing deposition time, pressure, power, and the chamber pre-conditioning, the Ti texture could be maximized while maintaining low surface roughness. When oxidized, titanium yields [100]-oriented rutile. This seed layer has as low as a 4.6% lattice mismatch with [111] Pt; thus, it is possible to achieve strongly oriented [111] Pt. The quality of the orientation and surface roughness of the TiO2 and the Ti directly affect the achievable Pt texture and surface morphology. A transition between optimal crystallographic texture and the smoothest templating surface occurs at approximately 30 nm of original Ti thickness (45 nm TiO2). This corresponds to 0.5 nm (2 nm for TiO2) rms roughness as determined by atomic force microscopy and a full-width at half-maximum (FWHM) of the rocking curve 0002 (200) peak of 5.5/spl degrees/ (3.1/spl degrees/ for TiO2). A Pb[Zr0.52Ti 0.48]O3 layer was deposited and shown to template from the textured Pt electrode, with a maximum [111] Lotgering factor of 87% and a minimum 111 FWHM of 2.4/spl degrees/ at approximately 30 nm of original Ti.

Dependence of paranodal junctional gap width on transverse bands.

PubMed

Rosenbluth, Jack; Petzold, Chris; Peles, Elior

2012-08-15

Mouse mutants with paranodal junctional (PNJ) defects display variable degrees of neurological impairment. In this study we compare control paranodes with those from three mouse mutants that differ with respect to a conspicuous PNJ component, the transverse bands (TBs). We hypothesize that TBs link the apposed junctional membranes together at a fixed distance and thereby determine the width of the junctional gap, which may in turn determine the extent to which nodal action currents can be short-circuited underneath the myelin sheath. Electron micrographs of aldehyde-fixed control PNJs, in which TBs are abundant, show a consistent junctional gap of ∼3.5 nm. In Caspr-null PNJs, which lack TBs entirely, the gap is wider (∼6-7 nm) and more variable. In CST-null PNJs, which have only occasional TBs, the mean PNJ gap width is comparable to that in Caspr-null mice. In the shaking mutant, in contrast, which has approximately 60% of the normal complement of TBs, mean PNJ gap width is not significantly different from that in controls. Correspondingly, shaking mice are much less impaired neurologically than either Caspr-null or CST-null mice. We conclude that in the absence or gross diminution of TBs, mean PNJ gap width increases significantly and suggest that this difference could underlie some of the neurological impairment seen in those mutants. Surprisingly, even in the absence of TBs, paranodes are to some extent maintained in their usual form, implying that in addition to TBs, other factors govern the formation and maintenance of overall paranodal structure. Copyright © 2012 Wiley Periodicals, Inc.

Role of defects in laser-induced modifications of silica coatings and fused silica using picosecond pulses at 1053 nm: II Scaling laws and the density of precursors

DOE PAGES

Laurence, T. A.; Negres, R. A.; Ly, S.; ...

2017-06-22

Here, we investigate the role of defects in laser-induced damage of fused silica and of silica coatings produced by e-beam and PIAD processes which are used in damage resistant, multi-layer dielectric, reflective optics. We perform experiments using 1053 nm, 1–60 ps laser pulses with varying beam size, number of shots, and pulse widths in order to understand the characteristics of defects leading to laser-induced damage. This pulse width range spans a transition in mechanisms from intrinsic material ablation for short pulses to defect-dominated damage for longer pulses. We show that for pulse widths as short as 10 ps, laser-induced damagemore » properties of fused silica and silica films are dominated by isolated absorbers. The density of these precursors and their fluence dependence of damage initiation suggest a single photon process for initial energy absorption in these precursors. Higher density precursors that initiate close to the ablation threshold at shorter pulse widths are also observed in fused silica, whose fluence and pulse width scaling suggest a multiphoton initiation process. We also show that these initiated damage sites grow with subsequent laser pulses. We show that scaling laws obtained in more conventional ways depend on the beam size and on the definition of damage for ps pulses. For this reason, coupling scaling laws with the density of precursors are critical to understanding the damage limitations of optics in the ps regime.« less

Emission and material gain spectra of polar compressive strained AlGaN quantum wells grown on virtual AlGaN substrates: Tuning emission wavelength and mixing TE and TM mode of light polarization

NASA Astrophysics Data System (ADS)

Gladysiewicz, Marta; Rudzinski, Mariusz; Hommel, Detlef; Kudrawiec, Robert

2018-07-01

It is shown that compressively strained polar AlxGa1‑xN/AlyGa1‑yN quantum wells (QWs) of various contents grown on virtual AlYGa1‑YN substrates (Y = 20, 40, 60, 80, and 100%) are able to cover the whole UV-A, -B, and -C spectral range but their contents and widths have to be carefully optimized if they are to be used as the active region of light emitting diodes and laser diodes. The emission wavelength from AlGaN multi QWs can be tuned by both the QW width and barrier thickness, but the range of QW width for which an efficient luminescence is expected is very small (2–4 nm) due to a very weak electron-hole overlap for wider QWs. The most effective method for wavelength tuning in this QW system is content engineering, i.e., lowering Al concentration in the QW region. The decrease of Al concentration in the QW shifts the emission peak to red, broadens this peak, weakens its intensity, and changes its polarization from transverse magnetic (TM) to TM mixed with transverse electric (TE). For laser diodes the optimal QW design is more rigorous concerning the QW width since this width should be below 3 nm. Moreover it is shown that the TE and TM mode of materials gain overlap and are strongly blueshifted in comparison to emission spectrum.

Role of defects in laser-induced modifications of silica coatings and fused silica using picosecond pulses at 1053 nm: II Scaling laws and the density of precursors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Laurence, T. A.; Negres, R. A.; Ly, S.

Here, we investigate the role of defects in laser-induced damage of fused silica and of silica coatings produced by e-beam and PIAD processes which are used in damage resistant, multi-layer dielectric, reflective optics. We perform experiments using 1053 nm, 1–60 ps laser pulses with varying beam size, number of shots, and pulse widths in order to understand the characteristics of defects leading to laser-induced damage. This pulse width range spans a transition in mechanisms from intrinsic material ablation for short pulses to defect-dominated damage for longer pulses. We show that for pulse widths as short as 10 ps, laser-induced damagemore » properties of fused silica and silica films are dominated by isolated absorbers. The density of these precursors and their fluence dependence of damage initiation suggest a single photon process for initial energy absorption in these precursors. Higher density precursors that initiate close to the ablation threshold at shorter pulse widths are also observed in fused silica, whose fluence and pulse width scaling suggest a multiphoton initiation process. We also show that these initiated damage sites grow with subsequent laser pulses. We show that scaling laws obtained in more conventional ways depend on the beam size and on the definition of damage for ps pulses. For this reason, coupling scaling laws with the density of precursors are critical to understanding the damage limitations of optics in the ps regime.« less

Anatomical features of pepper plants (Capsicum annuum L.) grown under red light-emitting diodes supplemented with blue or far-red light

NASA Technical Reports Server (NTRS)

Schuerger, A. C.; Brown, C. S.; Stryjewski, E. C.

1997-01-01

Pepper plants (Capsicum annuum L. cv., Hungarian Wax) were grown under metal halide (MH) lamps or light-emitting diode (LED) arrays with different spectra to determine the effects of light quality on plant anatomy of leaves and stems. One LED (660) array supplied 90% red light at 660 nm (25nm band-width at half-peak height) and 1% far-red light between 700-800nm. A second LED (660/735) array supplied 83% red light at 660nm and 17% far-red light at 735nm (25nm band-width at half-peak height). A third LED (660/blue) array supplied 98% red light at 660nm, 1% blue light between 350-550nm, and 1% far-red light between 700-800nm. Control plants were grown under broad spectrum metal halide lamps. Plants were gron at a mean photon flux (300-800nm) of 330 micromol m-2 s-1 under a 12 h day-night photoperiod. Significant anatomical changes in stem and leaf morphologies were observed in plants grown under the LED arrays compared to plants grown under the broad-spectrum MH lamp. Cross-sectional areas of pepper stems, thickness of secondary xylem, numbers of intraxylary phloem bundles in the periphery of stem pith tissues, leaf thickness, numbers of choloplasts per palisade mesophyll cell, and thickness of palisade and spongy mesophyll tissues were greatest in peppers grown under MH lamps, intermediate in plants grown under the 660/blue LED array, and lowest in peppers grown under the 660 or 660/735 LED arrays. Most anatomical features of pepper stems and leaves were similar among plants grown under 660 or 660/735 LED arrays. The effects of spectral quality on anatomical changes in stem and leaf tissues of peppers generally correlate to the amount of blue light present in the primary light source.

Anatomical features of pepper plants (Capsicum annuum L.) grown under red light-emitting diodes supplemented with blue or far-red light.

PubMed

Schuerger, A C; Brown, C S; Stryjewski, E C

1997-03-01

Pepper plants (Capsicum annuum L. cv., Hungarian Wax) were grown under metal halide (MH) lamps or light-emitting diode (LED) arrays with different spectra to determine the effects of light quality on plant anatomy of leaves and stems. One LED (660) array supplied 90% red light at 660 nm (25nm band-width at half-peak height) and 1% far-red light between 700-800nm. A second LED (660/735) array supplied 83% red light at 660nm and 17% far-red light at 735nm (25nm band-width at half-peak height). A third LED (660/blue) array supplied 98% red light at 660nm, 1% blue light between 350-550nm, and 1% far-red light between 700-800nm. Control plants were grown under broad spectrum metal halide lamps. Plants were gron at a mean photon flux (300-800nm) of 330 micromol m-2 s-1 under a 12 h day-night photoperiod. Significant anatomical changes in stem and leaf morphologies were observed in plants grown under the LED arrays compared to plants grown under the broad-spectrum MH lamp. Cross-sectional areas of pepper stems, thickness of secondary xylem, numbers of intraxylary phloem bundles in the periphery of stem pith tissues, leaf thickness, numbers of choloplasts per palisade mesophyll cell, and thickness of palisade and spongy mesophyll tissues were greatest in peppers grown under MH lamps, intermediate in plants grown under the 660/blue LED array, and lowest in peppers grown under the 660 or 660/735 LED arrays. Most anatomical features of pepper stems and leaves were similar among plants grown under 660 or 660/735 LED arrays. The effects of spectral quality on anatomical changes in stem and leaf tissues of peppers generally correlate to the amount of blue light present in the primary light source.

VUV spectroscopic study of the ? state of H2

NASA Astrophysics Data System (ADS)

Dickenson, G. D.; Ubachs, W.

2014-04-01

Spectral lines, probing rotational quantum states J‧ = 0, 1, 2 of the inner well vibrations (υ‧ ≤ 8) in the ? state of molecular hydrogen, were recorded in high resolution using a vacuum ultraviolet Fourier transform absorption spectrometer in the wavelength range 73-86 nm. Accurate line positions and predissociation widths are determined from a fit to the absorption spectra. Improved values for the line positions are obtained, while the predissociation widths agree well with previous investigations.

Performance of a 967 nm CW diode end-pumped Er:GSGG laser at 2.79 μm

NASA Astrophysics Data System (ADS)

Wu, Z. H.; Sun, D. L.; Wang, S. Z.; Luo, J. Q.; Li, X. L.; Huang, L.; Hu, A. L.; Tang, Y. Q.; Guo, Q.

2013-05-01

We demonstrated a 967 nm diode end-pumped Er:GSGG laser operated at 2.794 μm with spectral width 3.6 nm in the continuous wave (CW) mode. A maximum output power of 440 mW is obtained at an incident pumping power of 3.4 W, which corresponds to an optical-to-optical efficiency of 13% and slope efficiency of 13.2%. The results suggest that a short cavity and efficient cooling setup for the crystal help to improve laser performance.

Robust, low-noise, polarization-maintaining mode-locked Er-fiber laser with a planar lightwave circuit (PLC) device as a multi-functional element.

PubMed

Kim, Chur; Kwon, Dohyeon; Kim, Dohyun; Choi, Sun Young; Cha, Sang Jun; Choi, Ki Sun; Yeom, Dong-Il; Rotermund, Fabian; Kim, Jungwon

2017-04-15

We demonstrate a new planar lightwave circuit (PLC)-based device, integrated with a 980/1550 wavelength division multiplexer, an evanescent-field-interaction-based saturable absorber, and an output tap coupler, which can be employed as a multi-functional element in mode-locked fiber lasers. Using this multi-functional PLC device, we demonstrate a simple, robust, low-noise, and polarization-maintaining mode-locked Er-fiber laser. The measured full-width at half-maximum bandwidth is 6 nm centered at 1555 nm, corresponding to 217 fs transform-limited pulse duration. The measured RIN and timing jitter are 0.22% [10 Hz-10 MHz] and 6.6 fs [10 kHz-1 MHz], respectively. Our results show that the non-gain section of mode-locked fiber lasers can be easily implemented as a single PLC chip that can be manufactured by a wafer-scale fabrication process. The use of PLC processes in mode-locked lasers has the potential for higher manufacturability of low-cost and robust fiber and waveguide lasers.

Dual-wavelength and efficient continuous-wave operation of a Yb:CaGd0.1Y0.9AlO4 laser

NASA Astrophysics Data System (ADS)

Di, J. Q.; Sai, Q. L.; Sun, X. H.; Xu, X. D.; Kong, L. C.; Xie, G. Q.; Liu, Y. L.; Teng, F.; Zhu, L.

2018-05-01

The spectra and laser properties of single crystalline Yb:CaGd0.1Y0.9AlO4 were investigated for the first time. The peak absorption cross-sections of 4.01 cm2 and 1.39  ×  10‑20 cm2 with full width at half maximum of 17 and 32 nm, and the maximum emission cross-sections of 2.11 and 1.53  ×  10‑20 cm2 were obtained for π and σ polarizations, respectively. The fluorescence decay time was 638 µs. The maximum continuous-wave laser achieved was 1.60 W with a slope efficiency of 23.4% for an a-cut Yb:CaGd0.1Y0.9AlO4 crystal. Dual-wavelength lasers at 1041.7 and 1044.9 nm were also demonstrated. The results show that Yb:CaGd0.1Y0.9AlO4 crystal is a promising ultra-short and dual-wavelength laser medium.

MOVPE growth of N-polar AlN on 4H-SiC: Effect of substrate miscut on layer quality

NASA Astrophysics Data System (ADS)

Lemettinen, J.; Okumura, H.; Kim, I.; Kauppinen, C.; Palacios, T.; Suihkonen, S.

2018-04-01

We present the effect of miscut angle of SiC substrates on N-polar AlN growth. The N-polar AlN layers were grown on C-face 4H-SiC substrates with a miscut towards 〈 1 bar 1 0 0 〉 by metal-organic vapor phase epitaxy (MOVPE). The optimal V/III ratios for high-quality AlN growth on 1 ° and 4 ° miscut substrates were found to be 20,000 and 1000, respectively. MOVPE grown N-polar AlN layer without hexagonal hillocks or step bunching was achieved using a 4H-SiC substrate with an intentional miscut of 1 ° towards 〈 1 bar 1 0 0 〉 . The 200-nm-thick AlN layer exhibited X-ray rocking curve full width half maximums of 203 arcsec and 389 arcsec for (0 0 2) and (1 0 2) reflections, respectively. The root mean square roughness was 0.4 nm for a 2 μm × 2 μm atomic force microscope scan.

A terahertz-vibration to terahertz-radiation converter based on gold nanoobjects: a feasibility study.

PubMed

Moldosanov, Kamil; Postnikov, Andrei

2016-01-01

The need for practical and adaptable terahertz sources is apparent in the areas of application such as early cancer diagnostics, nondestructive inspection of pharmaceutical tablets, visualization of concealed objects. We outline the operation principle and suggest the design of a simple appliance for generating terahertz radiation by a system of nanoobjects - gold nanobars (GNBs) or nanorings (GNRs) - irradiated by microwaves. Our estimations confirm a feasibility of the idea that GNBs and GNRs irradiated by microwaves could become terahertz emitters with photon energies within the full width at half maximum of the longitudinal acoustic phononic DOS of gold (ca. 16-19 meV, i.e., 3.9-4.6 THz). A scheme of the terahertz radiation source is suggested based on the domestic microwave oven irradiating a substrate with multiple deposited GNBs or GNRs. The size of a nanoobject for optimal conversion is estimated to be approx. 3 nm (thickness) by approx. 100 nm (length of GNB, or along the GNR). This detailed prediction is open to experimental verification. An impact is expected onto further studies of interplay between atomic vibrations and electromagnetic waves in nanoobjects.

Growth of high-quality AlN epitaxial film by optimizing the Si substrate surface

NASA Astrophysics Data System (ADS)

Huang, Liegen; Li, Yuan; Wang, Wenliang; Li, Xiaochan; zheng, Yulin; Wang, Haiyan; Zhang, Zichen; Li, Guoqiang

2018-03-01

High-quality AlN epitaxial films have been grown on Si substrates by optimizing the hydrofluoric acid (HF) solution for cleaning of Si substrates. Effect of the Si substrate surface on the surface morphology and structural property of AlN epitaxial films is investigated in detail. It is revealed that as the concentration of HF solution increases from 0 to 2.0%, the surface morphology and the crystalline quality are initially improved and then get worse, and show an optimized value at 1.5%. The as-grown ∼200 nm-thick AlN epitaxial films on Si substrates grown with HF solution of 1.5% reveal the root-mean-square (RMS) surface roughness of 0.49 nm and the full-width at half-maximum for AlN(0002) X-ray rocking curve of 0.35°, indicating the smooth surface morphology and the high crystalline quality. The corresponding mechanism is proposed to interpret the effect of Si substrate surface on surface morphology and structural property of AlN epitaxial films, and provides an effective approach for the perspective fabrication of AlN-based devices.

Sharp green electroluminescence from 1H-pyrazolo[3,4-b]quinoline-based light-emitting diodes

NASA Astrophysics Data System (ADS)

Tao, Y. T.; Balasubramaniam, E.; Danel, A.; Jarosz, B.; Tomasik, P.

2000-09-01

A multilayer organic light-emitting diode was fabricated using a fluorescent compound {6-N,N-diethylamino-1-methyl-3-phenyl-1H-pyrazolo[3,4-b]quinoline} (PAQ-NEt2) doped into the hole-transporting layer of NPB {4,4'-bis[N-(1-naphthyl-1-)-N-phenyl-amino]-biphenyl}, with the TPBI {2,2',2″-(1,3,5-phenylene)tris[1-phenyl-1H-benzimidazole]} as an electrontransporting material. At 16% PAQ-NEt2 doping concentration, the device gave a sharp, bright, and efficient green electroluminescence (EL) peaked at around 530 nm. The full width at half maximum of the EL is 60 nm, which is 60% of the green emission from typical NPB/AlQ [where AlQ=tris(8-hydroxyquinoline) aluminum] device. For the same concentration, a maximum luminance of 37 000 cd/m2 was obtained at 10.0 V and the maximum power, luminescence, and external quantum efficiencies were obtained 4.2 lm/W, 6.0 cd/A, and 1.6%, respectively, at 5.0 V.

Room temperature synthesis and optical studies on Ag and Au mixed nanocomposite polyvinylpyrrolidone polymer films.

PubMed

Udayabhaskar, R; Mangalaraja, R V; Manikandan, D; Arjunan, V; Karthikeyan, B

2012-12-01

Optical properties of silver, gold and bimetallic (Au:Ag) nanocomposite polymer films which are prepared by chemical method have been reported. The experimental data was correlated with the theoretical calculations using Mie theory. We adopt small change in the theoretical calculations of bimetallic/mixed particle nanocomposite and the theory agrees well with the experimental data. Polyvinylpyrrolidone (PVP) was used as reducing and capping agent. Fourier transform infrared spectroscopy (FTIR) study reveals the presence of different functional groups, the possible mechanism that leads to the formation of nanoparticles by using PVP alone as reducing agent. Optical absorption spectra of Ag and Au nanocomposite polymers show a surface plasmon resonance (SPR) band around 430 and 532 nm, respectively. Thermal annealing effect on the prepared samples at 60 °C for different time durations result in shift of SPR band maximum and varies the full width at half maximum (FWHM). Absorption spectra of Au:Ag bimetallic films show bands at 412 and 547 nm confirms the presence of Ag and Au nanoparticles in the composite. Copyright © 2012 Elsevier B.V. All rights reserved.

Total ozone column retrieval from UV-MFRSR irradiance measurements: evaluation at Mauna Loa station

NASA Astrophysics Data System (ADS)

Zempila, Melina Maria; Fragkos, Konstantinos; Davis, John; Sun, Zhibin; Chen, Maosi; Gao, Wei

2017-09-01

The USDA UV-B Monitoring and Research Program (UVMRP) comprises of 36 climatological sites along with 4 long-duration research sites, in 27 states, one Canadian province, and the south island of New Zealand. Each station is equipped with an Ultraviolet multi-filter rotating shadowband radiometer (UV-MFRSR) which can provide response-weighted irradiances at 7 wavelengths (300, 305.5, 311.4, 317.6, 325.4, and 368 nm) with a nominal full width at half maximun of 2 nm. These UV irradiance data from the long term monitoring station at Mauna Loa, Hawaii, are used as input to a retrieval algorithm in order to derive high time frequency total ozone columns. The sensitivity of the algorithm to the different wavelength inputs is tested and the uncertainty of the retrievals is assessed based on error propagation methods. For the validation of the method, collocated hourly ozone data from the Dobson Network of the Global Monitoring Division (GMD) of the Earth System Radiation Laboratory (ESRL) under the jurisdiction of the US National Oceanic & Atmospheric Administration (NOAA) for the period 2010-2015 were used.

Dopant Distribution in Atomic Layer Deposited ZnO:Al Films Visualized by Transmission Electron Microscopy and Atom Probe Tomography.

PubMed

Wu, Yizhi; Giddings, A Devin; Verheijen, Marcel A; Macco, Bart; Prosa, Ty J; Larson, David J; Roozeboom, Fred; Kessels, Wilhelmus M M

2018-02-27

The maximum conductivity achievable in Al-doped ZnO thin films prepared by atomic layer deposition (ALD) is limited by the low doping efficiency of Al. To better understand the limiting factors for the doping efficiency, the three-dimensional distribution of Al atoms in the ZnO host material matrix has been examined on the atomic scale using a combination of high-resolution transmission electron microscopy (TEM) and atom probe tomography (APT). Although the Al distribution in ZnO films prepared by so-called "ALD supercycles" is often presented as atomically flat δ-doped layers, in reality a broadening of the Al-dopant layers is observed with a full-width-half-maximum of ∼2 nm. In addition, an enrichment of the Al at grain boundaries is observed. The low doping efficiency for local Al densities > ∼1 nm -3 can be ascribed to the Al solubility limit in ZnO and to the suppression of the ionization of Al dopants from adjacent Al donors.

Advances in nanoimprint lithography and applications in plasmonic-enhanced electron source

NASA Astrophysics Data System (ADS)

Liang, Yixing

The research work in this thesis comprises of two parts. The first part focuses on nanofabrication techniques for better control of nanostructures, such as line edge roughness control and critical structure dimensions, for improvement in large area lift-off of ultra-thin (sub-40 nm) and ultra-small (sub-20 nm) nanostructures, and for improvement in mold-substrate separation. The second part of this thesis studies one important application of nanoimprint lithography (NIL) in the field of plasmonic-enhanced electron source. In the first part, a post-fabrication method, termed Self-limited Self Perfection by Liquefaction (SP-SPEL), is studied. SP-SPEL has experimentally demonstrated to reduce the trench width with precise control down to 20 nm from original 90 nm width, - 450% reduction. In addition, SP-SPEL increases the trench width uniformity and reduces the low-frequency line edge roughness. Second, a tri-layer method is studied to offer large area, efficient lift-off of ultra-thin (sub-40 nm) and ultra-fine (sub-20 nm) nanostructures. Using this method, a nanoimprint mold is fabricated. Third, tribo-electronics in NIL has been studied. It has been shown that tribo-charge can not only skew the AFM measurement by over 400%, but also largely increase the mold-substrate separation force. To solve this problem, a new mold structure is firstly proposed by Professor Stephen Y Chou and has demonstrated to reduce the separation force by over 8 fold. In the second part, a plasmonic-enhanced nanostructured electron source is studied, for both semiconducting and metallic photoemissive materials. For the semiconducting photocathode, a vertical cavity structure, comprising a top sub-wavelength mesh, ultra-thin (~ 40 nm) semiconducting materials in the middle and metallic back-plane, has demonstrated a 30 fold enhancement in photoelectron emission over a planar thin film. In addition, for the metallic photocathode, a 3D nanocavity, termed "Disk coupled Dots-on-Pillar Antenna-array (D2PA)", has achieved 8 orders of magnitude more efficiently in emitting photoelectrons for Au and 3 orders of magnitude for CsAu compared with planar thin films respectively. The significant enhancement in photoelectron emission efficiency and brightness is ascribed to nanoplasmonic enhancement (large pumping light absorption and local electric field enhancement) provided by the plasmonic cavity structures.

VIS-NIR multispectral synchronous imaging pyrometer for high-temperature measurements.

PubMed

Fu, Tairan; Liu, Jiangfan; Tian, Jibin

2017-06-01

A visible-infrared multispectral synchronous imaging pyrometer was developed for simultaneous, multispectral, two-dimensional high temperature measurements. The multispectral image pyrometer uses prism separation construction in the spectrum range of 650-950 nm and multi-sensor fusion of three CCD sensors for high-temperature measurements. The pyrometer had 650-750 nm, 750-850 nm, and 850-950 nm channels all with the same optical path. The wavelength choice for each channel is flexible with three center wavelengths (700 nm, 810 nm, and 920 nm) with a full width at half maximum of the spectrum of 3 nm used here. The three image sensors were precisely aligned to avoid spectrum artifacts by micro-mechanical adjustments of the sensors relative to each other to position them within a quarter pixel of each other. The pyrometer was calibrated with the standard blackbody source, and the temperature measurement uncertainty was within 0.21 °C-0.99 °C in the temperatures of 600 °C-1800 °C for the blackbody measurements. The pyrometer was then used to measure the leading edge temperatures of a ceramics model exposed to high-enthalpy plasma aerodynamic heating environment to verify the system applicability. The measured temperature ranges are 701-991 °C, 701-1134 °C, and 701-834 °C at the heating transient, steady state, and cooling transient times. A significant temperature gradient (170 °C/mm) was observed away from the leading edge facing the plasma jet during the steady state heating time. The temperature non-uniformity on the surface occurs during the entire aerodynamic heating process. However, the temperature distribution becomes more uniform after the heater is shut down and the experimental model is naturally cooled. This result shows that the multispectral simultaneous image measurement mode provides a wider temperature range for one imaging measurement of high spatial temperature gradients in transient applications.

Electro-optically Q-switched dual-wavelength Nd:YLF laser emitting at 1047 nm and 1053 nm

NASA Astrophysics Data System (ADS)

Men, Shaojie; Liu, Zhaojun; Cong, Zhenhua; Li, Yongfu; Zhang, Xingyu

2015-05-01

A flash-lamp pumped electro-optically Q-switched dual-wavelength Nd:YLF laser is demonstrated. Two Nd:YLF crystals placed in two cavities are employed to generate orthogonally polarized 1047 nm and 1053 nm radiations, respectively. The two cavities are jointed together by a polarizer and share the same electro-optical Q-switch. Two narrow-band pass filters are used to block unexpected oscillations at the hold-off state of the electro-optical Q-switch. In this case, electro-optical Q-switching is able to operate successfully. With pulse synchronization realized, the maximum output energy of 66.2 mJ and 83.9 mJ are obtained for 1047 nm and 1053 nm lasers, respectively. Correspondingly, the minimum pulse width is both 17 ns for 1047 nm and 1053 nm lasers. Sum frequency generation is realized. This demonstrates the potential of this laser in difference-frequency generations to obtain terahertz wave.

Coherence and linewidth studies of a 4-nm high power FEL

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fawley, W.M.; Sessler, A.M.; Scharlemann, E.T.

Recently the SSRL/SLAC and its collaborators elsewhere have considered the merits of a 2 to 4-nm high power FEL utilizing the SLAC linac electron beam. The FEL would be a single pass amplifier excited by spontaneous emission rather than an oscillator, in order to eliminate the need for a soft X-ray resonant cavity. We have used GINGER, a multifrequency 2D FEL simulation code, to study the expected linewidth and coherence properties of the FEL, in both the exponential and saturated gain regimes. We present results concerning the effective shot noise input power and mode shape, the expected subpercent output linemore » widths, photon flux, and the field temporal and spatial correlation functions. We also discuss the effects of tapering the wiggler upon the output power and line width.« less

Transmission-enabled fiber Fabry-Perot cavity based on a deeply etched slotted micromirror.

PubMed

Othman, Muhammad A; Sabry, Yasser M; Sadek, Mohamed; Nassar, Ismail M; Khalil, Diaa A

2018-06-01

In this work, we report the analysis, fabrication, and characterization of an optical cavity built using a Bragg-coated fiber (BCF) mirror and a metal-coated microelectromechanical systems (MEMS) slotted micromirror, where the latter allows transmission output from the cavity. Theoretical modeling, using Fourier optics analysis for the cavity response based on tracing the propagation of light back and forth between the mirrors, is presented. Detailed simulation analysis is carried out for the spectral response of the cavity under different design conditions. MEMS chips of the slotted micromirror are fabricated using deep reactive ion etching of a silicon-on-insulator substrate with different device-etching depths of 150 μm and 80 μm with aluminum and gold metal coating, respectively. The cavity is characterized as an optical filter using a BCF with reflectivity that is larger than 95% in a 300 nm range across the E-band and the L-band. Versatile filter characteristics were obtained for different values of the MEMS micromirror slit width and cavity length. A free spectral range (FSR) of about 33 nm and a quality factor of about 196 were obtained for a 5.5 μm width aluminum slit, while an FSR of about 148 nm and a quality factor of about 148 were obtained for a 1.5 μm width gold slit. The presented structure opens the door for wide spectral response transmission-type MEMS filters.

Passively Q-switched of EDFL employing multi-walled carbon nanotubes with diameter less than 8 nm as saturable absorber

NASA Astrophysics Data System (ADS)

Nur Fatin Zuikafly, Siti; Ahmad, Fauzan; Haniff Ibrahim, Mohd; Wadi Harun, Sulaiman

2017-11-01

The paper demonstrates passively Q-switched erbium-doped fiber laser implementing multiwalled carbon nanotubes (MWCNTs) based saturable absorber. The paper is the first to report the use of the MWCNTs with diameter less than 8 nm as typically, the diameter used is 10 to 20 nm. The MWCNTs is incorporated with water soluble host polymer, polyvinyl alcohol (PVA) to produce a MWCNTs polymer composite thin film which is then sandwiched between two fiber connectors. The fabricated SA is employed in the laser experimental setup in ring cavity. The Q-switching regime started at threshold pump power of 103 mW and increasable to 215 mW. The stable pulse train from 41.6 kHz to 76.92 kHz with maximum average output power and pulse energy of 0.17 mW and 3.39 nJ are produced. The shortest pulse width of 1.9 μs is obtained in the proposed experimental work, making it the lowest pulse width ever reported using MWCNTs-based saturable absorber.

VizieR Online Data Catalog: M17 massive pms stars X-shooter spectra (Ramirez-Tannus+, 2017)

NASA Astrophysics Data System (ADS)

Ramirez-Tannus, M. C.; Kaper, L.; de Koter, A.; Tramper, F.; Bik, A.; Ellerbroek, L. E.; Ochsendorf, B. B.; Ramirez-Agudelo, O. H.; Sana, H.

2017-05-01

Normalized X-shooter spectra of the PMS and OB stars in M17 studied. The X-shooter spectra were obtained under good weather conditions with seeing ranging from 0.5" and 1" and clear sky. With the exception of the 2012 B289 spectrum and the 2009 B275 science verification spectrum, the spectrograph slit widths used were 1" (UVB, 300-590nm), 0.9" (VIS, 550-1020nm), and 0.4" (NIR, 1000-2480nm), resulting in a spectral resolving power of 5100, 8800, and 11300, respectively. The slit widths for the 2010 B275 observations were 1.6", 0.9", and 0.9" resulting in a resolving power of 3300, 8800, and 5600, respectively. For the 2012 B289 observations we used the 0.8", 0.7", and 0.4" slits corresponding to a resolving power of 6200, 11000, and 11300 for the UVB, VIS, and NIR arms, respectively. The spectra were taken in nodding mode and reduced using the X-shooter pipeline version 2.7.1 running under the ESO Reflex environment version 2.8.4. (2 data files).

Feasibility study of an image slicer for future space application

NASA Astrophysics Data System (ADS)

Calcines, A.; Ichimoto, K.

2014-08-01

This communication presents the feasibility study of an image slicer for future space missions, especially for the integral field unit (IFU) of the SUVIT (Solar UV-Visible-IR telescope) spectro-polarimeter on board the Japanese-led solar space mission Solar-C as a backup option. The MuSICa (Multi-Slit Image slicer based on collimator-Camera) image slicer concept, originally developed for the European Solar Telescope, has been adapted to the SUVIT requirements. The IFU will reorganizes a 2-D field of view of 10 x 10 arcsec2 into three slits of 0.18 arcsec width by 185.12 arcsec length using flat slicer mirrors of 100 μm width. The layout of MuSICa for Solar-C is telecentric and offers an optical quality limited by diffraction. The entrance for the SUVIT spectro-polarimeter is composed by the three IFU slits and one ordinal long slit to study, using high resolution spectro-polarimetry, the solar atmosphere (Photosphere and Chromosphere) within a spectral range between 520 nm (optionally 280 nm) and 1,100 nm.

Laser processing of sapphire with picosecond and sub-picosecond pulses

NASA Astrophysics Data System (ADS)

Ashkenasi, D.; Rosenfeld, A.; Varel, H.; Wähmer, M.; Campbell, E. E. B.

1997-11-01

Laser processing of sapphire using a Ti:sapphire laser at 790 and 395 nm and pulse widths varying between 0.2 and 5 ps is reported. A clear improvement in quality is demonstrated for multi-shot processing with sub-ps laser pulses. For fluences between 3 and 12 J/cm 2 two ablation phases were observed, in agreement with previous work from Tam et al. using 30 ps, 266 nm laser pulses [A.C. Tam, J.L. Brand, D.C. Cheng, W. Zapka, Appl. Phys. Lett. 55 (20) (1994) 2045]. During the `gentle ablation' phase periodic wavelike structures, i.e. ripples, were observed on the Al 2O 3 surface, perpendicular to the laser polarisation and with a spacing almost equalling the laser wavelength, indicating metallic-like behaviour. The ripple modulation depth was in the order of a few tens of nm. For fluences between 1 and 2.5 J/cm 2, below the single-shot surface damage threshold and at a pulse width above 200 fs, microstructures could be produced at the rear side of a 1 mm thick sapphire substrate without affecting the front surface.

Structural defect accumulation in tungsten and tungsten-5wt.% tantalum under incremental proton damage

NASA Astrophysics Data System (ADS)

Ipatova, I.; Harrison, R. W.; Wady, P. T.; Shubeita, S. M.; Terentyev, D.; Donnelly, S. E.; Jimenez-Melero, E.

2018-04-01

We have performed proton irradiation of W and W-5wt.%Ta materials at 350 °C with a step-wise damage level increase up to 0.7 dpa and using two beam energies, namely 40 keV and 3 MeV, in order to probe the accumulation of radiation-induced lattice damage in these materials. Interstitial-type a/2 <111> dislocation loops are formed under irradiation, and their size increases in W-5Ta up to a loop width of 21 ± 4 nm at 0.3 dpa, where loop saturation takes place. In contrast, the loop length in W increases progressively up to 183 ± 50 nm at 0.7 dpa, whereas the loop width remains relatively constant at 29 ± 7 nm at >0.3 dpa, giving rise to dislocation strings. The dislocation loops and tangles are observed in both materials examined after a 3 MeV proton irradiation at 350 °C. Ta doping delays the evolution of radiation-induced dislocation structures in W, and can consequently impact the hydrogen isotope retention under plasma exposure.

Electrical properties of sub-100 nm SiGe nanowires

NASA Astrophysics Data System (ADS)

Hamawandi, B.; Noroozi, M.; Jayakumar, G.; Ergül, A.; Zahmatkesh, K.; Toprak, M. S.; Radamson, H. H.

2016-10-01

In this study, the electrical properties of SiGe nanowires in terms of process and fabrication integrity, measurement reliability, width scaling, and doping levels were investigated. Nanowires were fabricated on SiGe-on oxide (SGOI) wafers with thickness of 52 nm and Ge content of 47%. The first group of SiGe wires was initially formed by using conventional I-line lithography and then their size was longitudinally reduced by cutting with a focused ion beam (FIB) to any desired nanometer range down to 60 nm. The other nanowire group was manufactured directly to a chosen nanometer level by using sidewall transfer lithography (STL). It has been shown that the FIB fabrication process allows manipulation of the line width and doping level of nanowires using Ga atoms. The resistance of wires thinned by FIB was 10 times lower than STL wires which shows the possible dependency of electrical behavior on fabrication method. Project support by the Swedish Foundation for Strategic Research “SSF” (No. EM-011-0002) and the Scientific and Technological Research Council of Turkey (No. TÜBİTAK).

High efficiency single transverse mode photonic band crystal lasers with low vertical divergence

NASA Astrophysics Data System (ADS)

Zhao, Shaoyu; Qu, Hongwei; Liu, Yun; Li, Lunhua; Chen, Yang; Zhou, Xuyan; Lin, Yuzhe; Liu, Anjin; Qi, Aiyi; Zheng, Wanhua

2016-10-01

High efficiency 980 nm longitudinal photonic band crystal (PBC) edge emitting laser diodes are designed and fabricated. The calculated results show that eight periods of Al0.1Ga0.9As and Al0.25Ga0.75As layer pairs can reduce the vertical far field divergence to 10.6° full width at half maximum (FWHM). The broad area (BA) lasers show a very high internal quantum efficiency ηi of 98% and low internal loss αi of 1.92 cm-1. Ridge waveguide (RW) lasers with 3 mm cavity length and 5um strip width provide 430 mW stable single transverse mode output at 500 mA injection current with power conversion efficiency (PCE) of 47% under continuous wave (CW) mode. A maximum PCE of 50% is obtained at the 300 mA injection current. A very low vertical far field divergence of 9.4° is obtained at 100 mA injection. At 500 mA injection, the vertical far field divergence increases to 11°, the beam quality factors M2 values are 1.707 in vertical direction and 1.769 in lateral direction.

On the discrimination between nucleation and propagation in nanomagnetic logic devices

NASA Astrophysics Data System (ADS)

Ziemys, Grazvydas; Csaba, Gyorgy; Becherer, Markus

2018-05-01

In this paper we present the extensive nucleation and propagation characterization of fabricated nanomagnets by applying ns-range magnetic field pulses. For that, an artificial nucleation center (ANC) is created by focused ion beam irradiation (FIB) of a 50 x 50 nm area at the side of a Co/Pt island as typically used in Nanomagnetic Logic with perpendicular anisotropy (pNML). Laser-Kerr Microscope is applied for statistical evaluation of the switching probability of the whole magnet, while the wide-field-Kerr microscopy is employed to discriminate between the nucleation process (which takes place at the irradiated ANC area) and the domain wall propagation process along the magnet. We show that the nanomagnet can be treated as a single Stoner-Wolfhart particle above 100 ns field-pulse width, as the whole magnetization is switched during the field-pulse. By contrary, for field-pulse width below 100 ns, the domain wall (DW) motion is the limiting process hindering full magnetization reversal on that time-scale. However, the nucleation still follows the Arrhenius law. The results allow precise understanding of the reversal process and highlight the need for faster DW speed in pNML materials.

Large-area super-resolution optical imaging by using core-shell microfibers

NASA Astrophysics Data System (ADS)

Liu, Cheng-Yang; Lo, Wei-Chieh

2017-09-01

We first numerically and experimentally report large-area super-resolution optical imaging achieved by using core-shell microfibers. The particular spatial electromagnetic waves for different core-shell microfibers are studied by using finite-difference time-domain and ray tracing calculations. The focusing properties of photonic nanojets are evaluated in terms of intensity profile and full width at half-maximum along propagation and transversal directions. In experiment, the general optical fiber is chemically etched down to 6 μm diameter and coated with different metallic thin films by using glancing angle deposition. The direct imaging of photonic nanojets for different core-shell microfibers is performed with a scanning optical microscope system. We show that the intensity distribution of a photonic nanojet is highly related to the metallic shell due to the surface plasmon polaritons. Furthermore, large-area super-resolution optical imaging is performed by using different core-shell microfibers placed over the nano-scale grating with 150 nm line width. The core-shell microfiber-assisted imaging is achieved with super-resolution and hundreds of times the field-of-view in contrast to microspheres. The possible applications of these core-shell optical microfibers include real-time large-area micro-fluidics and nano-structure inspections.

(In,Ga,Al)P-GaP laser diodes grown on high-index GaAs surfaces emitting in the green, yellow and bright red spectral range

NASA Astrophysics Data System (ADS)

Ledentsov, N. N.; Shchukin, V. A.; Shernyakov, Yu M.; Kulagina, M. M.; Payusov, A. S.; Gordeev, N. Yu; Maximov, M. V.; Cherkashin, N. A.

2017-02-01

We report on low threshold current density (<400 A cm-2) injection lasing in (Al x Ga1-x )0.5In0.5P-GaAs-based diodes down to the green spectral range (<570 nm). The epitaxial structures are grown on high-index (611)A and (211)A GaAs substrates by metal-organic vapor phase epitaxy and contain tensile-strained GaP-enriched insertions aimed at reflection of the injected nonequilibrium electrons preventing their escape from the active region. Extended waveguide concept results in a vertical beam divergence with a full width at half maximum of 15° for (611)A substrates. The lasing at the wavelength of 569 nm is realized at 85 K. In an orange-red laser diode structure low threshold current density (190 A cm-2) in the orange spectral range (598 nm) is realized at 85 K. The latter devices demonstrated room temperature lasing at 628 nm at ˜2 kA cm-2 and a total power above 3 W. The red laser diodes grown on (211)A substrates demonstrated a far field characteristic for vertically multimode lasing indicating a lower optical confinement factor for the fundamental mode as compared to the devices grown on (611)A. However, as expected from previous research, the temperature stability of the threshold current and the wavelength stability were significantly higher for (211)A-grown structures.

Beneficial effects of water in the colloidal synthesis of InP/ZnS core-shell quantum dots for optoelectronic applications.

PubMed

Ramasamy, Parthiban; Kim, Bumjin; Lee, Min-Sang; Lee, Jong-Soo

2016-10-21

We demonstrate that the presence of a small amount of water as an impurity during the hot-injection synthesis can significantly decrease the emission lines full width at half-maximum (FWHM) and improve the quantum yield (QY) of InP/ZnS quantum dots (QDs). By utilizing the water present in the indium precursor and solvent, we obtained InP/ZnS QDs emitting around 530 nm with a FWHM as narrow as 46 nm and a QY up to 45%. Without water, the synthesized QDs have emission around 625 nm with a FWHM of 66 nm and a QY of about 33%. Absorption spectra, XRD and XPS analyses revealed that when water is present, an amorphous phosphate layer is formed over the InP QDs and inhibits the QD growth. This amorphous layer favors the formation of a very thick ZnS shell by decreasing the lattice mismatch between the InP core and the ZnS shell. We further show the possibility to tune the emission wavelengths of InP/ZnS QDs by simply adjusting the amount of water present in the system while keeping all the other reaction parameters (i.e., precursor concentration, reaction temperature and time) constant. As an example of their application in light-emitting diodes (LEDs), the green and red InP/ZnS QDs are combined with a blue LED chip to produce white light.

Molecular Switch for Sub-Diffraction Laser Lithography by Photoenol Intermediate-State Cis-Trans Isomerization.

PubMed

Mueller, Patrick; Zieger, Markus M; Richter, Benjamin; Quick, Alexander S; Fischer, Joachim; Mueller, Jonathan B; Zhou, Lu; Nienhaus, Gerd Ulrich; Bastmeyer, Martin; Barner-Kowollik, Christopher; Wegener, Martin

2017-06-27

Recent developments in stimulated-emission depletion (STED) microscopy have led to a step change in the achievable resolution and allowed breaking the diffraction limit by large factors. The core principle is based on a reversible molecular switch, allowing for light-triggered activation and deactivation in combination with a laser focus that incorporates a point or line of zero intensity. In the past years, the concept has been transferred from microscopy to maskless laser lithography, namely direct laser writing (DLW), in order to overcome the diffraction limit for optical lithography. Herein, we propose and experimentally introduce a system that realizes such a molecular switch for lithography. Specifically, the population of intermediate-state photoenol isomers of α-methyl benzaldehydes generated by two-photon absorption at 700 nm fundamental wavelength can be reversibly depleted by simultaneous irradiation at 440 nm, suppressing the subsequent Diels-Alder cycloaddition reaction which constitutes the chemical core of the writing process. We demonstrate the potential of the proposed mechanism for STED-inspired DLW by covalently functionalizing the surface of glass substrates via the photoenol-driven STED-inspired process exploiting reversible photoenol activation with a polymerization initiator. Subsequently, macromolecules are grown from the functionalized areas and the spatially coded glass slides are characterized by atomic-force microscopy. Our approach allows lines with a full-width-at-half-maximum of down to 60 nm and line gratings with a lateral resolution of 100 nm to be written, both surpassing the diffraction limit.

Construction of 3D Metallic Nanostructures on an Arbitrarily Shaped Substrate.

PubMed

Chen, Fei; Li, Jingning; Yu, Fangfang; Zhao, Di; Wang, Fan; Chen, Yanbin; Peng, Ru-Wen; Wang, Mu

2016-09-01

Constructing conductive/magnetic nanowire arrays with 3D features by electrodeposition remains challenging. An unprecedented fabrication approach that allows to construct metallic (cobalt) nanowires on an arbitrarily shaped surface is reported. The spatial separation of nanowires varies from 70 to 3000 nm and the line width changes from 50 to 250 nm depending on growth conditions. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Fast Response and High Sensitivity of ZnO Nanowires-Cobalt Phthalocyanine Heterojunction Based H2S Sensor.

PubMed

Kumar, Ashwini; Samanta, Soumen; Singh, Ajay; Roy, Mainak; Singh, Surendra; Basu, Saibal; Chehimi, Mohmad M; Roy, Kallol; Ramgir, Niranjan; Navaneethan, M; Hayakawa, Y; Debnath, Anil K; Aswal, Dinesh K; Gupta, Shiv K

2015-08-19

The room temperature chemiresistive response of n-type ZnO nanowire (ZnO NWs) films modified with different thicknesses of p-type cobalt phthalocyanine (CoPc) has been studied. With increasing thickness of CoPc (>15 nm), heterojunction films exhibit a transition from n- to p-type conduction due to uniform coating of CoPc on ZnO. The heterojunction films prepared with a 25 nm thick CoPc layer exhibit the highest response (268% at 10 ppm of H2S) and the fastest response (26 s) among all samples. The X-ray photoelectron spectroscopy and work function measurements reveal that electron transfer takes place from ZnO to CoPc, resulting in formation of a p-n junction with a barrier height of 0.4 eV and a depletion layer width of ∼8.9 nm. The detailed XPS analysis suggests that these heterojunction films with 25 nm thick CoPc exhibit the least content of chemisorbed oxygen, enabling the direct interaction of H2S with the CoPc molecule, and therefore exhibit the fastest response. The improved response is attributed to the high susceptibility of the p-n junctions to the H2S gas, which manipulates the depletion layer width and controls the charge transport.

Picosecond pulsed micro-module emitting near 560 nm using a frequency doubled gain-switched DBR ridge waveguide semiconductor laser

NASA Astrophysics Data System (ADS)

Kaltenbach, André; Hofmann, Julian; Seidel, Dirk; Lauritsen, Kristian; Bugge, Frank; Fricke, Jörg; Paschke, Katrin; Erdmann, Rainer; Tränkle, Günther

2017-02-01

A miniaturized picosecond pulsed semiconductor laser source in the spectral range around 560nm is realized by integrating a frequency doubled distributed Bragg reflector ridge waveguide laser (DBR-RWL) into a micromodule. Such compact laser sources are suitable for mobile application, e.g. in microscopes. The picosecond optical pulses are generated by gain-switching which allows for arbitrary pulse repetition frequencies. For frequency conversion a periodically poled magnesium doped lithium niobate ridge waveguide crystal (PPLN) is used to provide high conversion efficiency with single-pass second harmonic generation (SHG). The coupling of the pulsed radiation into the PPLN crystal is realized by a GRIN-lens. Such types of lenses collect the divergent laser radiation and focus it into the crystal waveguide providing high coupling efficiency at a minimum of space compared to the usage of fast axis collimator(FAC)/slow axis collimator (SAC) lens combinations. The frequency doubled output pulses show a pulse width of about 60 ps FWHM and a spectral width around 0.06nm FWHM at a central wavelength of 557nm at 15Å. The pulse peak power could be determined to be more than 300mW at a repetition frequency of 40 MHz.

Large area nano-patterning /writing on gold substrate using dip - pen nanolithography (DPN)

NASA Astrophysics Data System (ADS)

Saini, Sudhir Kumar; Vishwakarma, Amit; Agarwal, Pankaj B.; Pesala, Bala; Agarwal, Ajay

2014-10-01

Dip Pen Nanolithography (DPN) is utilized to pattern large area (50μmX50μm) gold substrate for application in fabricating Nano-gratings. For Nano-writing 16-MHA ink coated AFM tip was prepared using double dipping procedure. Gold substrate is fabricated on thermally grown SiO2 substrate by depositing ˜5 nm titanium layer followed by ˜30nm gold using DC pulse sputtering. The gratings were designed using period of 800nm and 25% duty cycle. Acquired AFM images indicate that as the AFM tip proceeds for nano-writing, line width decreases from 190nm to 100nm. This occurs probably due to depreciation of 16-MHA molecules in AFM tip as writing proceeds.

Optical performance of W/B4C multilayer mirror in the soft x-ray region

NASA Astrophysics Data System (ADS)

Pradhan, P. C.; Majhi, A.; Nayak, M.

2018-03-01

W/B4C x-ray multilayers (MLs) with 300 layer pairs and a period in the range of d = 2-1.6 nm are fabricated and investigated for the x-ray optical element in the soft x-ray regime. The structural analyses of the MLs are carried out by using hard x-ray reflectivity (HXR) measurements at 8.047 keV. Well-defined successive higher order Bragg peaks (up to 3rd order) in HXR data collected up to glancing incidence angles of ˜9° reveal a good quality of the periodic structure. The ML mirrors have an average interface width of ˜0.35 nm and have a compressive residual stress of ˜0.183 GPa and 0. 827 GPa for d = 1.62 nm and d = 1.98 nm, respectively. MLs maintain structural stability over a long time, with a slight increase in interface widths of the W layers by 0.1 nm due to self-diffusion. Soft x-ray reflectivity (SXR) performances are evaluated in the energy range of 650 to 1500 eV. At energy ˜ 1489 eV, measured reflectivities (energy resolution, ΔE) are ˜ 10% (19 eV) and 4.5% (13 eV) at glancing incident angles of 12.07° and 15° for MLs having periods of 1.98 nm and 1.62 nm, respectively. The optical performance from 1600 eV to 4500 eV is theoretically analysed by considering the measured structural parameters. The structure-stress-optical performance is correlated on the basis of the mechanism of film growth. The implications of W/B4C MLs are discussed, particularly with respect to the development of ML optics with high spectral selectivity and reflectance for soft x-ray instruments.

Effect of edge modification on the zigzag BC2N nanoribbons

NASA Astrophysics Data System (ADS)

Xiao, Xiang; Li, Hong; Tie, Jun; Lu, Jing

2016-08-01

We use first principles calculations to investigate the effects of edge modification with nonmetal species on zigzag-edged BC2N nanoribbons (ZBC2NNRs). These ZBC2NNRs show either semiconducting or metallic behaviors depending on the edge modifications and ribbon widths. We find that the O-modification induces a ferromagnetic ground state with a metallic behavior for all the ribbon widths investigated. And when the ribbon width is more than 3.32 nm (NZ ⩾ 16), an antiferromagnetic ground state with a half-metallic behavior is realized in the H-passivated ZBC2NNRs. These versatile electronic properties render the ZBC2NNRs a promising candidate material in nanoelectronics and nanospintronics.

Experimental demonstration of novel cascaded SFG+DFG wavelength conversion of picosecond pulses in LiNbO 3 waveguides

NASA Astrophysics Data System (ADS)

Wang, Jian; Sun, Junqiang; Luo, Chuanhong

2006-06-01

A novel cascaded χ (2) wavelength conversion of picosecond pulses based on sum frequency generation and difference frequency generation (SFG+DFG) is proposed and experimentally demonstrated in LiNbO 3 waveguides. The signal pulse with 40-GHz repetition rate and 1.57-ps pulse width is adopted. First of all, high conversion efficiency about -18.93dB can be achieved with low power level required for both two pump lights, which is greatly enhanced approximately 8dB compared with the conventional cascaded second-order nonlinear interactions (SHG+DFG) with a single and much higher power pump. Secondly, the wavelength of the converted idler wave can be tuned from 1527.4 to 1540.5nm when the signal wavelength is changed from 1561.9 to 1548.4nm, and about 13.1nm converted idler bandwidth is achieved with the conversion efficiency higher than -31dB. Thirdly, two pump wavelengths can be separated as large as 17.3nm. Meanwhile, when one pump wavelength is fixed at 1549.1nm, the other can be tuned within a wide wavelength range about 7.6nm with the conversion efficiency higher than -34dB, which is much larger than that in the SHG+DFG situation. Finally, the temporal waveform of the converted idler pulse is observed with rather clear appearance achieved, and no obvious changes of the pulse shape and width are found compared with its corresponding original injected signal, showing that our proposed scheme exhibits a very good conversion performance.

Temperature-tunable lasing in negative dielectric chiral nematic liquid crystal

NASA Astrophysics Data System (ADS)

Wu, Ri-Na; Wu, Jie; Wu, Xiao-Jiao; Dai, Qin

2015-05-01

In this work, negative dielectric nematic liquid crystal SLC12V620-400, chiral dopant S811, and laser dye DCM are used to prepare dye-doped chiral nematic liquid crystal laser sample. In order to investigate temperature-tunable lasing in negative dielectric chiral nematic liquid crystal, we measure the transmission and lasing spectrum of this sample. The photonic band gap (PBG) is observed to red shift with its width reducing from 71.2 nm to 40.2 nm, and its short-wavelength band edge moves 55.3 nm while the long-wavelength band edge only moves 24.9 nm. The wavelength of output laser is found to red shift from 614.4 nm at 20 °C to 662.8 nm at 67 °C, which is very different from the previous experimental phenomena. The refractive indices, parallel and perpendicular to the director in chiral nematic liquid crystal have different dependencies on temperature. The experiment shows that the pitch of this chiral nematic liquid crystal increases with the increase of temperature. The decrease in the PBG width, different shifts of band edges, and the red shift of laser wavelength are the results of refractive indices change and pitch thermal elongation. Project supported by the National Natural Science Foundation of China (Grant No. 61378042), the Outstanding Young Scholars Growth Plans of Colleges and Universities in Liaoning Province, China (Grant No. LJQ2013022), the Science and Technology Research of Liaoning Province, China (Grant No. L2010465), the Open Funds of Liaoning Province Key Laboratory of Laser and Optical Information of Shenyang Ligong University, China.

Narrowband light detection via internal quantum efficiency manipulation of organic photodiodes

NASA Astrophysics Data System (ADS)

Armin, Ardalan; Jansen-van Vuuren, Ross D.; Kopidakis, Nikos; Burn, Paul L.; Meredith, Paul

2015-02-01

Spectrally selective light detection is vital for full-colour and near-infrared (NIR) imaging and machine vision. This is not possible with traditional broadband-absorbing inorganic semiconductors without input filtering, and is yet to be achieved for narrowband absorbing organic semiconductors. We demonstrate the first sub-100 nm full-width-at-half-maximum visible-blind red and NIR photodetectors with state-of-the-art performance across critical response metrics. These devices are based on organic photodiodes with optically thick junctions. Paradoxically, we use broadband-absorbing organic semiconductors and utilize the electro-optical properties of the junction to create the narrowest NIR-band photoresponses yet demonstrated. In this context, these photodiodes outperform the encumbent technology (input filtered inorganic semiconductor diodes) and emerging technologies such as narrow absorber organic semiconductors or quantum nanocrystals. The design concept allows for response tuning and is generic for other spectral windows. Furthermore, it is material-agnostic and applicable to other disordered and polycrystalline semiconductors.

Narrowband Light Detection via Internal Quantum Efficiency Manipulation of Organic Photodiodes

DOE PAGES

Armin, A.; Jansen-van Vuuren, R. D.; Kopidakis, N.; ...

2015-02-01

Spectrally selective light detection is vital for full-colour and near-infrared (NIR) imaging and machine vision. This is not possible with traditional broadband-absorbing inorganic semiconductors without input filtering, and is yet to be achieved for narrowband absorbing organic semiconductors. We demonstrate the first sub-100 nm full-width-at-half-maximum visible-blind red and NIR photodetectors with state-of-the-art performance across critical response metrics. These devices are based on organic photodiodes with optically thick junctions. Paradoxically, we use broadband-absorbing organic semiconductors and utilize the electro-optical properties of the junction to create the narrowest NIR-band photoresponses yet demonstrated. In this context, these photodiodes outperform the encumbent technology (inputmore » filtered inorganic semiconductor diodes) and emerging technologies such as narrow absorber organic semiconductors or quantum nanocrystals. The design concept allows for response tuning and is generic for other spectral windows. Furthermore, it is materialagnostic and applicable to other disordered and polycrystalline semiconductors.« less

Criteria for implementing full-width/depth shoulders to accommodate hard shoulder running.

DOT National Transportation Integrated Search

2011-08-22

"WisDOT is considering constructing full-width/depth shoulders along certain freeway segments to carry traffic : during future freeway resurfacing or construction projects. The goal of this measure is to minimize lane closures and : congestion. WisDO...

Estimation of photonic band gap in the hollow core cylindrical multilayer structure

NASA Astrophysics Data System (ADS)

Chourasia, Ritesh Kumar; Singh, Vivek

2018-04-01

The propagation characteristic of two hollow core cylindrical multilayer structures having high and low refractive index contrast of cladding regions have been studied and compared at two design wavelengths i.e. 1550 nm and 632.8 nm. With the help of transfer matrix method a relation between the incoming light wave and outgoing light wave has been developed using the boundary matching technique. In high refractive index contrast, small numbers of layers are sufficient to provide perfect band gap in both design wavelengths. The spectral position and width of band gap is highly depending on the optical path of incident light in all considered cases. For sensing application, the sensitivity of waveguide can be obtained either by monitoring the width of photonic band gap or by monitoring the spectral shift of photonic band gap. Change in the width of photonic band gap with the core refractive index is larger in high refractive index contrast of cladding materials. However, in the case of monitoring the spectral shift of band gap, the obtained sensitivity is large for low refractive index contrast of cladding materials and further it increases with increase of design wavelength.

4Pi microscopy of the nuclear pore complex.

PubMed

Kahms, Martin; Hüve, Jana; Peters, Reiner

2015-01-01

4Pi microscopy is a far-field fluorescence microscopy technique, in which the wave fronts of two opposing illuminating beams are adjusted to constructively interfere in a common focus. This yields a diffraction pattern in the direction of the optical axis, which essentially consists of a main focal spot accompanied by two smaller side lobes. At optimal conditions, the main peak of this so-called point spread function has a full width at half maximum: fixed phrase of 100 nm in the direction of the optical axis, and thus is 6-7-fold smaller than that of a confocal microscope. In this chapter, we describe the basic features of 4Pi microscopy and its application to cell biology using the example of the nuclear pore complex, a large protein assembly spanning the nuclear envelope.

Luminescent high temperature sensor based on the CdSe/ZnS quantum dot thin film

NASA Astrophysics Data System (ADS)

Wang, He-lin; Yang, Ai-jun; Sui, Cheng-hua

2013-11-01

A high temperature sensor based on the multi-parameter temperature dependent characteristic of photoluminescence (PL) of quantum dot (QD) thin film is demonstrated by depositing the CdSe/ZnS core/shell QDs on the SiO2 glass substrates. The variations of the intensity, the peak wavelength and the full width at half maximum (FWHM) of PL spectra with temperature are studied experimentally and theoretically. The results indicate that the peak wavelength of the PL spectra changes linearly with temperature, while the PL intensity and FWHM vary exponentially for the temperature range from 30 °C to 180 °C. Using the obtained temperature dependent optical parameters, the resolution of the designed sensor can reach 0.1 nm/°C.

Single-crystal perovskite CH3NH3PbBr3 prepared by cast capping method for light-emitting diodes

NASA Astrophysics Data System (ADS)

Nguyen, Van-Cao; Katsuki, Hiroyuki; Sasaki, Fumio; Yanagi, Hisao

2018-04-01

In this study, electroluminescence from single crystals of CH3NH3PbBr3 perovskite is explored. The cast capping method was applied to fabricate simple devices with an ITO/CH3NH3PbBr3/ITO structure. The devices showed a low operation voltage of 2 V and a pure green luminescence with full width at half maximum of ∼20 nm. However, the emission occurring at the crystal edges demonstrated blinking with a subsecond time interval, which is similar to the previously reported photoluminescence behavior of nanocrystal perovskites. This electroluminescence blinking may provide new insight into the recombination processes depending on the carrier traps and defects of emission layers in perovskite light-emitting devices.

Temporal measurement on and using pulses from spectrally narrowed emission in styrylpyridinium cyanine dye

NASA Astrophysics Data System (ADS)

Dharmadhikari, Aditya K.; Bhowmik, Achintya K.; Ahyi, Ayayi C.; Thakur, Mrinal

2001-11-01

Highly efficient spectrally narrowed emission (SNE) was observed in the solution of strylpyridinium cyanine dye (SPCD) pumped by fundamental and second harmonic of a picosecond Nd:YAG laser in two separate arrangements. A highly directional emission was observed in both the pumping arrangements without incorporating any mirrors. The pulse duration of the SNE was measured by background free SHG intensity autocorrelation technique. The measured duration of the pulses was 40 ps. These pulses, having a spectral linewidth of 10 nm (full width at half maximum), were used as a probe to measure the transient changes in the transmission in SPCD solution using a pump-probe setup. The transient optical transmission indicated a gain at the overlap and no gain was observed beyond a delay of 40 ps.

Optimized optical devices for edge-coupling-enabled silicon photonics platform

NASA Astrophysics Data System (ADS)

Png, Ching Eng; Ang, Thomas Y. L.; Ong, Jun Rong; Lim, Soon Thor; Sahin, Ezgi; Chen, G. F. R.; Tan, D. T. H.; Guo, Tina X.; Wang, Hong

2018-02-01

We present a library of high-performance passive and active silicon photonic devices at the C-band that is specifically designed and optimized for edge-coupling-enabled silicon photonics platform. These devices meet the broadband (100 nm), low-loss (< 2dB per device), high speed (>= 25 Gb/s), and polarization diversity requirements (TE and TM polarization extinction ratio <= 25 dB) for optical communication applications. Ultra-low loss edge couplers, broadband directional couplers, high-extinction ratio polarization beam splitters (PBSs), and high-speed modulators are some of the devices within our library. In particular, we have designed and fabricated inverse taper fiber-to-waveguide edge couplers of tip widths ranging from 120 nm to 200 nm, and we obtained a low coupling loss of 1.80+/-0.28 dB for 160 nm tip width. To achieve polarization diversity operation for inverse tapers, we have experimentally realized different designs of polarization beam splitters (PBS). Our optimized PBS has a measured extinction ratio of <= 25 dB for both the quasiTE modes, and quasi-TM modes. Additionally, a broadband (100 nm) directional coupler with a 50/50 power splitting ratio was experimentally realized on a small footprint of 20×3 μm2 . Last but not least, high-speed silicon modulators with a range of carrier doping concentrations and offset of the PN junction can be used to optimise the modulation efficiency, and insertion losses for operation at 25 GHz.

MONTE CARLO SIMULATION OF METASTABLE OXYGEN PHOTOCHEMISTRY IN COMETARY ATMOSPHERES

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bisikalo, D. V.; Shematovich, V. I.; Gérard, J.-C.

2015-01-01

Cometary atmospheres are produced by the outgassing of material, mainly H{sub 2}O, CO, and CO{sub 2} from the nucleus of the comet under the energy input from the Sun. Subsequent photochemical processes lead to the production of other species generally absent from the nucleus, such as OH. Although all comets are different, they all have a highly rarefied atmosphere, which is an ideal environment for nonthermal photochemical processes to take place and influence the detailed state of the atmosphere. We develop a Monte Carlo model of the coma photochemistry. We compute the energy distribution functions (EDF) of the metastable O({supmore » 1}D) and O({sup 1}S) species and obtain the red (630 nm) and green (557.7 nm) spectral line shapes of the full coma, consistent with the computed EDFs and the expansion velocity. We show that both species have a severely non-Maxwellian EDF, that results in broad spectral lines and the suprathermal broadening dominates due to the expansion motion. We apply our model to the atmosphere of comet C/1996 B2 (Hyakutake) and 103P/Hartley 2. The computed width of the green line, expressed in terms of speed, is lower than that of the red line. This result is comparable to previous theoretical analyses, but in disagreement with observations. We explain that the spectral line shape does not only depend on the exothermicity of the photochemical production mechanisms, but also on thermalization, due to elastic collisions, reducing the width of the emission line coming from the O({sup 1}D) level, which has a longer lifetime.« less

Fast and wide tuning wavelength-swept source based on dispersion-tuned fiber optical parametric oscillator.

PubMed

Zhou, Yue; Cheung, Kim K Y; Li, Qin; Yang, Sigang; Chui, P C; Wong, Kenneth K Y

2010-07-15

We demonstrate a dispersion-tuned fiber optical parametric oscillator (FOPO)-based swept source with a sweep rate of 40 kHz and a wavelength tuning range of 109 nm around 1550 nm. The cumulative speed exceeds 4,000,000 nm/s. The FOPO is pumped by a sinusoidally modulated pump, which is driven by a clock sweeping linearly from 1 to 1.0006 GHz. A spool of dispersion-compensating fiber is added inside the cavity to perform dispersion tuning. The instantaneous linewidth is 0.8 nm without the use of any wavelength selective element inside the cavity. 1 GHz pulses with pulse width of 150 ps are generated.

Diode-pumped passively Q-switched Nd:YAG ceramic laser with a gold nanotriangles saturable absorber at 1 µm

NASA Astrophysics Data System (ADS)

Bai, Jinxi; Li, Ping; Chen, Xiaohan; Guo, Lei; Wang, Lili; Liu, Binghai

2017-08-01

Passively Q-switched Nd:YAG ceramic lasers at 1064 and 1123 nm are demonstrated based on a gold nanotriangles saturable absorber (GNTs-SA) for the first time. The maximum average output power reaches 226 mW at 1064 nm and 172 mW at 1123 nm with corresponding shortest pulse widths and maximum pulse repetition rates of (179 ns, 320 kHz) and (231 ns, 457 kHz), respectively. Our results prove that the GNTs-SA is a promising saturable absorber around the 1-µm region.

Direct growth of aligned graphitic nanoribbons from a DNA template by chemical vapour deposition.

PubMed

Sokolov, Anatoliy N; Yap, Fung Ling; Liu, Nan; Kim, Kwanpyo; Ci, Lijie; Johnson, Olasupo B; Wang, Huiliang; Vosgueritchian, Michael; Koh, Ai Leen; Chen, Jihua; Park, Jinseong; Bao, Zhenan

2013-01-01

Graphene, laterally confined within narrow ribbons, exhibits a bandgap and is envisioned as a next-generation material for high-performance electronics. To take advantage of this phenomenon, there is a critical need to develop methodologies that result in graphene ribbons <10 nm in width. Here we report the use of metal salts infused within stretched DNA as catalysts to grow nanoscopic graphitic nanoribbons. The nanoribbons are termed graphitic as they have been determined to consist of regions of sp(2) and sp(3) character. The nanoscopic graphitic nanoribbons are micrometres in length, <10 nm in width, and take on the shape of the DNA template. The DNA strand is converted to a graphitic nanoribbon by utilizing chemical vapour deposition conditions. Depending on the growth conditions, metallic or semiconducting graphitic nanoribbons are formed. Improvements in the growth method have potential to lead to bottom-up synthesis of pristine single-layer graphene nanoribbons.

Aharonov-Bohm oscillations, quantum decoherence and amplitude modulation in mesoscopic InGaAs/InAlAs rings.

PubMed

Ren, S L; Heremans, J J; Gaspe, C K; Vijeyaragunathan, S; Mishima, T D; Santos, M B

2013-10-30

Low-temperature Aharonov-Bohm oscillations in the magnetoresistance of mesoscopic interferometric rings patterned on an InGaAs/InAlAs heterostructure are investigated for their dependence on excitation current and temperature. The rings have an average radius of 650 nm, and a lithographic arm width of 300 nm, yielding pronounced interference oscillations over a wide range of magnetic fields. Apart from a current and temperature dependence, the oscillation amplitude also shows a quasi-periodic modulation with applied magnetic field. The phase coherence length is extracted by analysis of the fundamental and higher Fourier components of the oscillations, and by direct analysis of the amplitude and its dependence on parameters. It is concluded that the Thouless energy forms the measure of excitation energies for quantum decoherence. The amplitude modulation finds an explanation in the effect of the magnetic flux threading the finite width of the interferometer arms.

High sensitivity plasmonic sensor using hybrid structure of graphene stripe combined with gold gap-ring

NASA Astrophysics Data System (ADS)

Du, Zhiyuan; Hu, Bin; Cyril, Planchon; Liu, Juan; Wang, Yongtian

2017-10-01

Local surface plasmonic resonance (LSPR) produced by metallic nano-structures is often sensitive to the refractive index of the surrounding media and can be applied for sensing. However, it often suffers from large line width caused by large plasmonic radiative damping, especially in the infrared (IR) frequencies, which reduces the sensitivity. Here we propose a hybrid structure consists of a graphene stripe and a gold gap-ring at short-IR frequencies (1-3 µm). Due to the low loss and high plasmonic confinement of graphene, LSPR line width of 6 nm is obtained. In addition, due to the strong coupling of the gold gap-ring with graphene stripe, the intensity of graphene LSPR is enhanced by 100 times. Simulation results show that the sensitivity of the sensor is ~1000 nm/RIU (refractive index unit) and the figure of merit (FoM) can reach up to 383.

Fabrication of superconducting nanowires from ultrathin MgB2 films via focused ion beam milling

NASA Astrophysics Data System (ADS)

Zhang, Chen; Wang, Da; Liu, Zheng-Hao; Zhang, Yan; Ma, Ping; Feng, Qing-Rong; Wang, Yue; Gan, Zi-Zhao

2015-02-01

High quality superconducting nanowires were fabricated from ultrathin MgB2 films by a focused ion beam milling technique. The precursor MgB2 films in 10 nm thick were grown on MgO substrates by using a hybrid physical-chemical vapor deposition method. The nanowires, in widths of about 300-600 nm and lengths of 1 or 10 μm, showed high superconducting critical temperatures (Tc's) above 34 K and narrow superconducting transition widths (ΔTc's) of 1-3 K. The superconducting critical current density Jc of the nanowires was above 5 × 107 A/cm2 at 20 K. The high Tc, narrow ΔTc, and high Jc of the nanowires offered the possibility of making MgB2-based nano-devices such as hot-electron bolometers and superconducting nanowire single-photon detectors with high operating temperatures at 15-20 K.

Measurement of Spectral Broadening in PTS-Polydiacetylene

NASA Astrophysics Data System (ADS)

Bhowmik, Achintya; Thakur, Mrinal

1998-03-01

PTS-polydiacetylene has significant potential for future applications in ultrafast all-optical switches and logic gates.(R. Quintero-Torres and M. Thakur, Appl. Phys. Lett., 66, 1310 (1995).) In this work, we have made detailed measurements of the instantaneous spectral line broadening in a 500 μm thick PTS single-crystal as a function of intensity and wavelength. A mode-locked Ti-Sapphire laser with 2 ps pulse-width at 82 MHz repetition rate, and a Nd:YAG laser with 60 ps pulse-width at 10 Hz repetition rate were used for measurements at 720-840 nm and 1064 nm wavelength respectively. The spectral bandwidth of the beam was recorded before and after passing through the PTS single-crystal by a high-resolution spectrometer. The nonlinear refractive index (n_2) of PTS as a function of wavelength has been determined from the spectral broadening data.

Passively mode-locked soliton femtosecond pulses employing graphene saturable absorber

NASA Astrophysics Data System (ADS)

Lau, K. Y.; Muhammad, F. D.; Latif, A. A.; Abu Bakar, M. H.; Yusoff, Z.; Mahdi, M. A.

2017-09-01

We demonstrate a passively mode-locked fiber laser incorporating graphene thin film (GTF) as saturable absorber (SA). The SA is fabricated by sandwiching the GTF between two single mode fiber ferrules through a fiber adaptor. The transmission loss at 1560 nm and non-linear saturation absorption modulation depth for GTF-SA are 0.8 dB and 2.90%, respectively. An erbium-doped fiber laser cavity is constructed to verify the functionality of GTF-SA and is designed to have net anomalous dispersion. It generates large spectral width of 4.99 nm with pulse repetition rate of 9.655 MHz and pulse width of 670 fs. Net anomalous dispersion and time bandwidth product higher than the sech2 transform-limited pulse validate the experimental result. In short, we demonstrate high performance GTF-SA that is able to generate ultrafast pulse duration in femtosecond range effortlessly with simple and green SA fabrication procedures.

Roughness and uniformity improvements on self-aligned quadruple patterning technique for 10nm node and beyond by wafer stress engineering

NASA Astrophysics Data System (ADS)

Liu, Eric; Ko, Akiteru; O'Meara, David; Mohanty, Nihar; Franke, Elliott; Pillai, Karthik; Biolsi, Peter

2017-05-01

Dimension shrinkage has been a major driving force in the development of integrated circuit processing over a number of decades. The Self-Aligned Quadruple Patterning (SAQP) technique is widely adapted for sub-10nm node in order to achieve the desired feature dimensions. This technique provides theoretical feasibility of multiple pitch-halving from 193nm immersion lithography by using various pattern transferring steps. The major concept of this approach is to a create spacer defined self-aligned pattern by using single lithography print. By repeating the process steps, double, quadruple, or octuple are possible to be achieved theoretically. In these small architectures, line roughness control becomes extremely important since it may contribute to a significant portion of process and device performance variations. In addition, the complexity of SAQP in terms of processing flow makes the roughness improvement indirective and ineffective. It is necessary to discover a new approach in order to improve the roughness in the current SAQP technique. In this presentation, we demonstrate a novel method to improve line roughness performances on 30nm pitch SAQP flow. We discover that the line roughness performance is strongly related to stress management. By selecting different stress level of film to be deposited onto the substrate, we can manipulate the roughness performance in line and space patterns. In addition, the impact of curvature change by applied film stress to SAQP line roughness performance is also studied. No significant correlation is found between wafer curvature and line roughness performance. We will discuss in details the step-by-step physical performances for each processing step in terms of critical dimension (CD)/ critical dimension uniformity (CDU)/line width roughness (LWR)/line edge roughness (LER). Finally, we summarize the process needed to reach the full wafer performance targets of LWR/LER in 1.07nm/1.13nm on 30nm pitch line and space pattern.

Cavity mode-width spectroscopy with widely tunable ultra narrow laser.

PubMed

Cygan, Agata; Lisak, Daniel; Morzyński, Piotr; Bober, Marcin; Zawada, Michał; Pazderski, Eugeniusz; Ciuryło, Roman

2013-12-02

We explore a cavity-enhanced spectroscopic technique based on determination of the absorbtion coefficient from direct measurement of spectral width of the mode of the optical cavity filled with absorbing medium. This technique called here the cavity mode-width spectroscopy (CMWS) is complementary to the cavity ring-down spectroscopy (CRDS). While both these techniques use information on interaction time of the light with the cavity to determine absorption coefficient, the CMWS does not require to measure very fast signals at high absorption conditions. Instead the CMWS method require a very narrow line width laser with precise frequency control. As an example a spectral line shape of P7 Q6 O₂ line from the B-band was measured with use of an ultra narrow laser system based on two phase-locked external cavity diode lasers (ECDL) having tunability of ± 20 GHz at wavelength range of 687 to 693 nm.

Nano-scaled graphene platelets with a high length-to-width aspect ratio

DOEpatents

Zhamu, Aruna; Guo, Jiusheng; Jang, Bor Z.

2010-09-07

This invention provides a nano-scaled graphene platelet (NGP) having a thickness no greater than 100 nm and a length-to-width ratio no less than 3 (preferably greater than 10). The NGP with a high length-to-width ratio can be prepared by using a method comprising (a) intercalating a carbon fiber or graphite fiber with an intercalate to form an intercalated fiber; (b) exfoliating the intercalated fiber to obtain an exfoliated fiber comprising graphene sheets or flakes; and (c) separating the graphene sheets or flakes to obtain nano-scaled graphene platelets. The invention also provides a nanocomposite material comprising an NGP with a high length-to-width ratio. Such a nanocomposite can become electrically conductive with a small weight fraction of NGPs. Conductive composites are particularly useful for shielding of sensitive electronic equipment against electromagnetic interference (EMI) or radio frequency interference (RFI), and for electrostatic charge dissipation.

Anomalous broadening and shift of emission lines in a femtosecond laser plasma filament in air

NASA Astrophysics Data System (ADS)

Ilyin, A. A.; Golik, S. S.; Shmirko, K. A.; Mayor, A. Yu.; Proschenko, D. Yu.

2017-12-01

The temporal evolution of the width and shift of N I 746.8 and O I 777.4 nm lines is investigated in a filament plasma produced by a tightly focused femtosecond laser pulse (0.9 mJ, 48 fs). The nitrogen line shift and width are determined by the joint action of electron impact shift and the far-off resonance AC Stark effect. The intensive (I = 1.2·1010 W/cm2) electric field of ASE (amplified spontaneous emission) and post-pulses result in a possible LS coupling break for the O I 3p 5P level and the generation of Rabi sidebands. The blueshifted main femtosecond pulse and Rabi sideband cause the stimulated emission of the N2 1+ system. The maximal widths of emission lines are approximately 6.7 times larger than the calculated Stark widths.

Effect of temperature and ridge-width on the lasing characteristics of InAs/InP quantum-dash lasers: A thermal analysis view

NASA Astrophysics Data System (ADS)

Alkhazraji, E.; Khan, M. T. A.; Ragheb, A. M.; Fathallah, H.; Qureshi, K. K.; Alshebeili, S.; Khan, M. Z. M.

2018-01-01

We investigate the thermal characteristics of multi-stack chirped barrier thickness InAs/InGaAlAs/InP quantum-dash-in-a-well lasers of different ridge widths 2, 3, 4 and 15 μm. The effect of varying this geometrical parameter on the extracted thermal resistance and characteristic temperature, and their stability with temperature are examined. The results show an inverse relation of ridge-width with junction temperature with 2 μm device exhibiting the largest junction temperature buildup owing to an associated high thermal resistance of ∼45 °C/W. Under the light of this thermal analysis, lasing behavior of different ridge-width quantum-dash (Qdash) lasers with injection currents and operating temperatures, is investigated. Thermionic carrier escape and phonon-assisted tunneling are found to be the dominant carrier transport mechanisms resulting in wide thermal spread of carriers across the available transition states of the chirped active region. An emission coverage of ∼75 nm and 3 dB bandwidth of ∼55 nm is exhibited by the 2 μm device, thus possibly exploiting the inhomogeneous optical transitions to the fullest. Furthermore, successful external modulation of a single Qdash Fabry-Perot laser mode via injection locking is demonstrated with eye diagrams at bit rates of 2-12 Gbit/s incorporating various modulation schemes. These devices are being considered as potential light sources for future high-speed wavelength-division multiplexed optical communication systems.

A dedicated H-beta meridian scanning photometer for proton aurora measurement

NASA Astrophysics Data System (ADS)

Unick, Craig W.; Donovan, Eric; Connors, Martin; Jackel, Brian

2017-01-01

An instrument designed to measure the location and brightness of auroral emissions from energetic proton precipitation is described. This photometer scans from the north to south horizon with a stepper motor and mirror. The scans are configured in software for a 30 s cadence with equally spaced samples along a meridian at constant altitude. Broadband light is separated into two channels with a novel optical splitter. This splitter uses a filter that has high transmission for the signal channel and high reflection on both the long- and short-wavelength sides to reflect the combined background passbands, directing each channel to its respective detector. The half-cone angle and angle of incidence of this splitter filter allow for an overall compact optical design that also provides superior sensitivity in both signal and background channels. The signal channel is 3 nm wide full width at half maximum (FWHM) at 486.1 nm, and the background channel comprises two 3 nm wide FWHM passbands at 480 nm and 495 nm created by a single filter. Both of these channels are measured with photomultiplier tubes in photon-counting mode. Calibrations indicate a response of around 1000 c/s per rayleigh. Data are currently acquired in 5 ms bins with a Nyquist frequency of 100 Hz. The first system (Forty-Eight Sixty-One (FESO)-1) has been operating at Athabasca University since February 2014, and the second system (FESO-2) was deployed at Lucky Lake, Saskatchewan, in October 2015. The improved sensitivity over legacy instruments and the simultaneous measurement of signal and background enable operation during intervals with dynamic electron aurora and scattered moonlight.

Nanocell with a pressure-controlled Rb atomic vapor column thickness: Critical influence of the thickness on optical processes

NASA Astrophysics Data System (ADS)

Sargsyan, A.; Amiryan, A.; Cartaleva, S.; Sarkisyan, D.

2017-07-01

A new device is designed: it consists of a nanocell (NC) filled with Rb atom vapors and placed in a vacuum chamber. When the pressure in the chamber changes in the range 0-1 atm, the NC thickness is smoothly varied in the range L = 140-1700 nm, which is caused by the pressure-induced deformation of thin garnet windows in the chamber. The pressure dependence has excellent reproducibility even after many hundreds of cycles of letting in of air and its complete pumping out from the chamber. The accuracy of setting required thickness L is much better than in the wedge-gap NCs to be moved mechanically that were used earlier. The processes of Faraday rotation (FR) of a polarization plane, resonance absorption, and fluorescence are studied using the D 1-line narrow-band continuous laser radiation when the thickness changes from L = λ/2 (398 nm) to L = 2λ (1590 nm) at a step λ/2. The FR signal is shown to be maximal at L = λ/2 and 3λ/2 and to have the minimum spectral width (≈60 MHz). At L = λ and 2λ, the FR signal is minimal and has the maximum spectral width (≈200 MHz). The resonance absorption demonstrates the same oscillating behavior; however, the effect in the case of FR is much more pronounced. The oscillating effect is absent for resonance fluorescence: its spectral width and amplitude increase monotonically with L. The detected effects are explained and possible applications are noted.

X-ray microscopy with high-resolution zone plates: recent developments

NASA Astrophysics Data System (ADS)

Schneider, Gerd; Wilhein, Thomas; Niemann, Bastian; Guttman, P.; Schliebe, T.; Lehr, J.; Aschoff, H.; Thieme, Juergen; Rudolph, Dietbert M.; Schmahl, Guenther A.

1995-09-01

In order to expand the applications of x-ray microscopy, developments in the fields of zone plate technology, specimen preparation and imaging techniques have been made. A new cross- linked polymer chain electron beam resist allows us to record zone plate pattern down to 19 nm outermost zone width. High resolution zone plates in germanium with outermost zone widths down to 19 nm have been developed. In addition, phase zone plates in nickel down to 30 nm zone width have been made by electroplating. In order to enhance the image contrast for weak absorbing objects, the phase contrast method for x-ray microscopy was developed and implemented on the Gottingen x-ray microscope at BESSY. The effects of x ray absorption on the structure of biological specimen limits the maximum applicable radiation dose and therefore the achievable signal to noise ratio for an artifact-free x-ray image. To improve the stability especially of biological specimen, a cryogenic object chamber has been developed and tested. It turns out that at the operating temperature T less than or equal to 130 K unfixed biological specimen can be exposed to a radiation dose of 109 - 1010 Gy without any observable structural changes. A multiple-angle viewing stage allows us to take stereoscopic images with the x-ray microscope, giving a 3D-impression of the object. As an example for the applications of x-ray microscopy in biology, erythrocytes infected by malaria parasite have been examined. Studies of the aggregation of hematite by sodium sulfate gives an example for the application of x-ray microscopy in the field of colloid research.

Characterization of an electrochemical mercury sensor using alternating current, cyclic, square wave and differential pulse voltammetry.

PubMed

Guerreiro, Gabriela V; Zaitouna, Anita J; Lai, Rebecca Y

2014-01-31

Here we report the characterization of an electrochemical mercury (Hg(2+)) sensor constructed with a methylene blue (MB)-modified and thymine-containing linear DNA probe. Similar to the linear probe electrochemical DNA sensor, the resultant sensor behaved as a "signal-off" sensor in alternating current voltammetry and cyclic voltammetry. However, depending on the applied frequency or pulse width, the sensor can behave as either a "signal-off" or "signal-on" sensor in square wave voltammetry (SWV) and differential pulse voltammetry (DPV). In SWV, the sensor showed "signal-on" behavior at low frequencies and "signal-off" behavior at high frequencies. In DPV, the sensor showed "signal-off" behavior at short pulse widths and "signal-on" behavior at long pulse widths. Independent of the sensor interrogation technique, the limit of detection was found to be 10nM, with a linear dynamic range between 10nM and 500nM. In addition, the sensor responded to Hg(2+) rather rapidly; majority of the signal change occurred in <20min. Overall, the sensor retains all the characteristics of this class of sensors; it is reagentless, reusable, sensitive, specific and selective. This study also highlights the feasibility of using a MB-modified probe for real-time sensing of Hg(2+), which has not been previously reported. More importantly, the observed "switching" behavior in SWV and DPV is potentially generalizable and should be applicable to most sensors in this class of dynamics-based electrochemical biosensors. Copyright © 2013 Elsevier B.V. All rights reserved.

Silicon-on-insulator with hybrid orientations for heterogeneous integration of GaN on Si (100) substrate

NASA Astrophysics Data System (ADS)

Zhang, Runchun; Zhao, Beiji; Huang, Kai; You, Tiangui; Jia, Qi; Lin, Jiajie; Zhang, Shibin; Yan, Youquan; Yi, Ailun; Zhou, Min; Ou, Xin

2018-05-01

Heterogeneous integration of materials pave a new way for the development of the microsystem with miniaturization and complex functionalities. Two types of hybrid silicon on insulator (SOI) structures, i.e., Si (100)-on-Si (111) and Si (111)-on-Si (100), were prepared by the smart-cut technique, which is consist of ion-slicing and wafer bonding. The precise calculation of the lattice strain of the transferred films without the epitaxial matching relationship to the substrate was demonstrated based on X-ray diffraction (XRD) measurements. The XRD and Raman measurement results suggest that the transferred films possess single crystalline quality. With a chemical mechanical polishing (CMP) process, the surface roughness of the transferred thin films can be reduced from 5.57 nm to 0.30 nm. The 4-inch GaN thin film epitaxially grown on the as-prepared hybrid SOI of Si (111)-on-Si (100) by metalorganic chemical vapor deposition (MOCVD) is of improved quality with a full width at half maximum (FWHM) of 672.54 arcsec extracted from the XRD rocking curve and small surface roughness of 0.40 nm. The wafer-scale GaN on Si (111)-on-Si (100) can serve as a potential platform for the one chip integration of GaN-based high electron mobility transistors (HEMT) or photonics with the Si (100)-based complementary metal oxide semiconductor (CMOS).

Investigation of graphene-on-metal substrates for SPR-based sensor using finite-difference time domain.

PubMed

Said, Fairus Atida; Menon, Pulliyaseri Susthitha; Rajendran, Venkatachalam; Shaari, Sahbudin; Majlis, Burhanuddin Y

2017-12-01

In this study, the authors investigated the effects of a single layer graphene as a coating layer on top of metal thin films such as silver, gold, aluminum and copper using finite-difference time domain method. To enhance the resolution of surface plasmon resonance (SPR) sensor, it is necessary to increase the SPR reflectivity and decrease the full-width-half maximum (FWHM) of the SPR curve so that there is minimum uncertainty in the determination of the resonance dip. Numerical data was verified with analytical and experimental data where all the data were in good agreement with resonance angle differing in <10% due to noise present in components such as humidity and temperature. In further analysis, reflectivity and FWHM were compared among four types of metal with various thin film thicknesses where graphene was applied on top of the metal layers, and data was compared against pure conventional metal thin films. A 60 nm-thick Au thin film results in higher performance with reflectivity of 92.4% and FWHM of 0.88° whereas single layer graphene-on-60 nm-thick Au gave reflectivity of 91.7% and FWHM of 1.32°. However, a graphene-on-40 nm-thick Ag also gave good performance with narrower FWHM of 0.88° and reflection spectra of 89.2%.

Synthesis and crystal structure of a new aluminum-silicon-nitride phosphor containing boron, Ba5B2Al4Si32N52:Eu

NASA Astrophysics Data System (ADS)

Yoshimura, Fumitaka; Yamane, Hisanori; Nagasako, Makoto

2017-07-01

Single crystals of Ba5B2Al4Si32N52:Eu were grown on the wall of a boron nitride crucible by heating a starting mixture of binary nitrides at 2050 °C and a N2 pressure of 0.85 MPa. The fundamental reflections of X-ray diffraction (XRD) for the crystals were indexed with triclinic cell parameters, a=9.7879(11) Å, b=9.7920(11) Å, c=12.7226(15) Å, α=96.074(4)°, β=112.330(3)°, and γ=94.080(4)°. Streak lines were observed between the fundamental reflections in the direction of the c* axis in the oscillation XRD images and selected area electron diffraction (SAED) patterns, indicating stacking faults in the structure. The atomic images of stacking faults with a slip system of (0 0 1)[-1 1 0]/3, and displacement of a Ba atom layer with (0 0 1)[-1 -1 0]/6 were observed with a scanning transmission electron microscope (STEM). The models of the basic (normal-stacking) structure with space group P1 and local structures of the stacking faults are herein presented. The single crystals emitted blue light with a peak wavelength of 472 nm and a full width at half maximum of 78 nm under 365 nm excitation.

Construction of an instant structured illumination microscope

PubMed Central

Curd, Alistair; Cleasby, Alexa; Makowska, Katarzyna; York, Andrew; Shroff, Hari; Peckham, Michelle

2015-01-01

A challenge in biological imaging is to capture high-resolution images at fast frame rates in live cells. The “instant structured illumination microscope” (iSIM) is a system designed for this purpose. Similarly to standard structured illumination microscopy (SIM), an iSIM provides a twofold improvement over widefield microscopy, in x, y and z, but also allows much faster image acquisition, with real-time display of super-resolution images. The assembly of an iSIM is reasonably complex, involving the combination and alignment of many optical components, including three micro-optics arrays (two lenslet arrays and an array of pinholes, all with a pitch of 222 μm) and a double-sided scanning mirror. In addition, a number of electronic components must be correctly controlled. Construction of the system is therefore not trivial, but is highly desirable, particularly for live-cell imaging. We report, and provide instructions for, the construction of an iSIM, including minor modifications to a previous design in both hardware and software. The final instrument allows us to rapidly acquire fluorescence images at rates faster than 100 fps, with approximately twofold improvement in resolution in both x–y and z; sub-diffractive biological features have an apparent size (full width at half maximum) of 145 nm (lateral) and 320 nm (axial), using a 1.49 NA objective and 488 nm excitation. PMID:26210400

A new approach to epitaxially grow high-quality GaN films on Si substrates: the combination of MBE and PLD.

PubMed

Wang, Wenliang; Wang, Haiyan; Yang, Weijia; Zhu, Yunnong; Li, Guoqiang

2016-04-22

High-quality GaN epitaxial films have been grown on Si substrates with Al buffer layer by the combination of molecular beam epitaxy (MBE) and pulsed laser deposition (PLD) technologies. MBE is used to grow Al buffer layer at first, and then PLD is deployed to grow GaN epitaxial films on the Al buffer layer. The surface morphology, crystalline quality, and interfacial property of as-grown GaN epitaxial films on Si substrates are studied systematically. The as-grown ~300 nm-thick GaN epitaxial films grown at 850 °C with ~30 nm-thick Al buffer layer on Si substrates show high crystalline quality with the full-width at half-maximum (FWHM) for GaN(0002) and GaN(102) X-ray rocking curves of 0.45° and 0.61°, respectively; very flat GaN surface with the root-mean-square surface roughness of 2.5 nm; as well as the sharp and abrupt GaN/AlGaN/Al/Si hetero-interfaces. Furthermore, the corresponding growth mechanism of GaN epitaxial films grown on Si substrates with Al buffer layer by the combination of MBE and PLD is hence studied in depth. This work provides a novel and simple approach for the epitaxial growth of high-quality GaN epitaxial films on Si substrates.

Microstructures and growth mechanisms of GaN films epitaxially grown on AlN/Si hetero-structures by pulsed laser deposition at different temperatures.

PubMed

Wang, Wenliang; Yang, Weijia; Lin, Yunhao; Zhou, Shizhong; Li, Guoqiang

2015-11-13

2 inch-diameter GaN films with homogeneous thickness distribution have been grown on AlN/Si(111) hetero-structures by pulsed laser deposition (PLD) with laser rastering technique. The surface morphology, crystalline quality, and interfacial property of as-grown GaN films are characterized in detail. By optimizing the laser rastering program, the ~300 nm-thick GaN films grown at 750 °C show a root-mean-square (RMS) thickness inhomogeneity of 3.0%, very smooth surface with a RMS surface roughness of 3.0 nm, full-width at half-maximums (FWHMs) for GaN(0002) and GaN(102) X-ray rocking curves of 0.7° and 0.8°, respectively, and sharp and abrupt AlN/GaN hetero-interfaces. With the increase in the growth temperature from 550 to 850 °C, the surface morphology, crystalline quality, and interfacial property of as-grown ~300 nm-thick GaN films are gradually improved at first and then decreased. Based on the characterizations, the corresponding growth mechanisms of GaN films grown on AlN/Si hetero-structures by PLD with various growth temperatures are hence proposed. This work would be beneficial to understanding the further insight of the GaN films grown on Si(111) substrates by PLD for the application of GaN-based devices.

Optical spectroscopy of Ce3+ ions in BaY2F8 single crystals

NASA Astrophysics Data System (ADS)

Francini, R.; Pinelli, S.; Baraldi, A.; Capelletti, R.; Sani, E.; Toncelli, A.; Tonelli, M.

In the present work we report on the spectroscopic properties of the Ce3+ ion in BaY2F8 single crystals. The absorption and excitation spectra of the emission centered at 340 nm have been measured in the temperature range 15-300 K. The 340 nm emission consists of two broad partially overlapping bands, peaking at 324 and 347 nm (at 15 K), respectively. The full width at half maximum is about 0.5 eV at room temperature. The absorption spectrum of the lowest in energy component of the f --> d transition of Ce3+ reveals at low temperature a marked vibronic structure. High resolution (0.02 cm(-1)) Fourier transform infrared spectroscopy in the wave number range 500-5000 cm(-1) and in the temperature range 9-300 K has been exploited to monitor the f level splitting. The absorption transitions from the three Stark components of the F-2(5/2) manifold to the four of the F-2(7/2) one, have been monitored in the wave number range 2000-3400 cm(-1) . The wave number separation at 9 K between the lowest level of the ground F-2(5/2) manifold and lowest one of the F-2 (7/2) manifold is found to be 2197.47 cm(-1) in good agreement with the splitting detected between the two components of the d --> f emission.

The external scanning proton microprobe of Firenze: A comprehensive description

NASA Astrophysics Data System (ADS)

Giuntini, L.; Massi, M.; Calusi, S.

2007-06-01

An external proton scanning microbeam setup is installed on the -30° line of the new 3 MV tandem accelerator in Firenze; the most relevant features of the line, such as detection setup for IBA measurements, target viewing system, beam diagnostic and transport are described here. With our facility we can work with a beam spot on sample better than 10 μm full-width half-maximum (FWHM) and an intensity of some nanoamperes. Standard beam exit windows are silicon nitride (Si 3N 4) TEM membranes, 100 nm thick and 0.5×0.5 mm 2 wide; we also successfully performed measurements using membranes 1×1 mm 2 wide, 100 nm thick, and 2×2 mm 2 wide, 200 and 500 nm thick. Exploiting the yield of Si X-rays produced by the beam in the exit window as an indirect measurement of the charge, a beam charge monitor system was implemented. The analytical capabilities of the microbeam have been extended by integrating a two-detector PIXE setup with BS and PIGE detectors; the external scanning proton microprobe in Firenze is thus a powerful instrument to fully characterize samples by ion beam analysis, through the simultaneous collection of PIXE, PIGE and BS elemental maps. Its characteristics can make it often competitive with traditional in vacuum microbeam for measurements of thick targets.

Solar-blind deep-UV band-pass filter (250 - 350 nm) consisting of a metal nano-grid fabricated by nanoimprint lithography.

PubMed

Li, Wen-Di; Chou, Stephen Y

2010-01-18

We designed, fabricated and demonstrated a solar-blind deep-UV pass filter, that has a measured optical performance of a 27% transmission peak at 290 nm, a pass-band width of 100 nm (from 250 to 350 nm), and a 20dB rejection ratio between deep-UV wavelength and visible wavelength. The filter consists of an aluminum nano-grid, which was made by coating 20 nm Al on a SiO(2) square grid with 190 nm pitch, 30 nm linewidth and 250 nm depth. The performances agree with a rigorous coupled wave analysis. The wavelength for the peak transmission and the pass-bandwidth can be tuned through adjusting the metal nano-grid dimensions. The filter was fabricated by nanoimprint lithography, hence is large area and low cost. Combining with Si photodetectors, the filter offers simple yet effective and low cost solar-blind deep-UV detection at either a single device or large-area complex integrated imaging array level.

Relationship between sensitizer concentration and resist performance of chemically amplified extreme ultraviolet resists in sub-10 nm half-pitch resolution region

NASA Astrophysics Data System (ADS)

Kozawa, Takahiro; Santillan, Julius Joseph; Itani, Toshiro

2017-01-01

The development of lithography processes with sub-10 nm resolution is challenging. Stochastic phenomena such as line width roughness (LWR) are significant problems. In this study, the feasibility of sub-10 nm fabrication using chemically amplified extreme ultraviolet resists with photodecomposable quenchers was investigated from the viewpoint of the suppression of LWR. The relationship between sensitizer concentration (the sum of acid generator and photodecomposable quencher concentrations) and resist performance was clarified, using the simulation based on the sensitization and reaction mechanisms of chemically amplified resists. For the total sensitizer concentration of 0.5 nm-3 and the effective reaction radius for the deprotection of 0.1 nm, the reachable half-pitch while maintaining 10% critical dimension (CD) LWR was 11 nm. The reachable half-pitch was 7 nm for 20% CD LWR. The increase in the effective reaction radius is required to realize the sub-10 nm fabrication with 10% CD LWR.

Propagation losses in undoped and n-doped polycrystalline silicon wire waveguides.

PubMed

Zhu, Shiyang; Fang, Q; Yu, M B; Lo, G Q; Kwong, D L

2009-11-09

Polycrystalline silicon (polySi) wire waveguides with width ranging from 200 to 500 nm are fabricated by solid-phase crystallization (SPC) of deposited amorphous silicon (a-Si) on SiO(2) at a maximum temperature of 1000 degrees C. The propagation loss at 1550 nm decreases from 13.0 to 9.8 dB/cm with the waveguide width shrinking from 500 to 300 nm while the 200-nm-wide waveguides exhibit quite large loss (>70 dB/cm) mainly due to the relatively rough sidewall of waveguides induced by the polySi dry etch. By modifying the process sequence, i.e., first patterning the a-Si layer into waveguides by dry etch and then SPC, the sidewall roughness is significantly improved but the polySi crystallinity is degraded, leading to 13.9 dB/cm loss in the 200-nm-wide waveguides while larger losses in the wider waveguides. Phosphorus implantation causes an additional loss in the polySi waveguides. The doping-induced optical loss increases relatively slowly with the phosphorus concentration increasing up to 1 x 10(18) cm(-3), whereas the 5 x 10(18) cm(-3) doped waveguides exhibit large loss due to the dominant free carrier absorption. For all undoped polySi waveguides, further 1-2 dB/cm loss reduction is obtained by a standard forming gas (10%H(2) + 90%N(2)) annealing owing to the hydrogen passivation of Si dangling bonds present in polySi waveguides, achieving the lowest loss of 7.9 dB/cm in the 300-nm-wide polySi waveguides. However, for the phosphorus doped polySi waveguides, the propagation loss is slightly increased by the forming gas annealing.

Project for millimeter and submillimeter-wave devices, and the experimental equipments

NASA Astrophysics Data System (ADS)

Hirose, Nobumitu; Kiyokawa, Masahiro; Matsui, Toshiaki

1995-09-01

A research and development program on millimeter and submillimeter wave devices is described. The facilities provided for this program are also described. In 1994, construction of the clean room was completed. Since then several machines and tools have been installed. We describe some results which have been obtained using these machines and tools. For example, a resist pattern with a 40 nm width on a 400 nm thick polymethylmethacrylate (PMMA) film was obtained.

Characterization of an optimized light source and comparison to pulsed dye laser for superficial and deep vessel clearance.

PubMed

Weiss, Robert A; Ross, E Victor; Tanghetti, Emil A; Vasily, David B; Childs, James J; Smirnov, Mikhail Z; Altshuler, Gregory B

2011-02-01

An arc lamp-based device providing optimized spectrum and pulse shape was characterized and compared with two pulsed dye laser (PDL) systems using a vascular phantom. Safety and effectiveness for facial telangiectasia are presented in clinical case studies. An optimized pulsed light source's (OPL) spectral and power output were characterized and compared with two 595 nm PDL devices. Purpuric threshold fluences were determined for the OPL and PDLs on Fitzpatrick type II normal skin. A vascular phantom comprising blood-filled quartz capillaries beneath porcine skin was treated by the devices at their respective purpuric threshold fluences for 3 ms pulse widths, while vessel temperatures were monitored with an infrared (IR) camera. Patients with Fitzpatrick skin types II-III received a split-face treatment with the OPL and a 595 nm PDL. The OPL provided a dual-band output spectrum from 500 to 670 nm and 850-1,200 nm, pulse widths from 3 to 100 ms, and fluences to 80 J/cm(2). The smooth output power measured during all pulse widths provides unambiguous vessel size selectivity. Percent energy in the near infra-red increased with decreasing output power from 45% to 60% and contributed 15-26% to heating of deep vessels, respectively. At purpuric threshold fluences the ratio of OPL to PDL vessel temperature rise was 1.7-2.8. OPL treatments of facial telangiectasia were well-tolerated by patients demonstrating significant improvements comparable to PDL with no downtime. Intense pulsed light (IPL) and PDL output pulse and spectral profiles are important for selective treatment of vessels in vascular lesions. The OPL's margin between purpuric threshold fluence and treatment fluence for deeper, larger vessels was greater than the corresponding margin with PDLs. The results warrant further comparison studies with IPLs and other PDLs. Copyright © 2011 Wiley-Liss, Inc.

Assessing the manufacturing tolerances and uniformity of CMOS compatible metamaterial fabrication

DOE Office of Scientific and Technical Information (OSTI.GOV)

Musick, Katherine M.; Wendt, Joel R.; Resnick, Paul J.

Here, the manufacturing tolerances of a stencil-lithography variant, membrane projection lithography, were investigated. In the first part of this work, electron beam lithography was used to create stencils with a range of linewidths. These patterns were transferred into the stencil membrane and used to pattern metallic lines on vertical silicon faces. Only the largest lines, with a nominal width of 84 nm, were resolved, resulting in 45 ± 10 nm (average ± standard deviation) as deposited with 135-nm spacing. Although written in the e-beam write software file as 84-nm in width, the lines exhibited linewidth bias. This can largely bemore » attributed to nonvertical sidewalls inherent to dry etching techniques that cause proportionally larger impact with decreasing feature size. The line edge roughness can be significantly attributed to the grain structure of the aluminum nitride stencil membrane. In the second part of this work, the spatial uniformity of optically defined (as opposed to e-beam written) metamaterial structures over large areas was assessed. A Fourier transform infrared spectrometer microscope was used to collect the reflection spectra of samples with optically defined vertical split ring from 25 spatially resolved 300 × 300 μm regions in a 1-cm 2 area. The technique is shown to provide a qualitative measure of the uniformity of the inclusions.« less

Assessing the manufacturing tolerances and uniformity of CMOS compatible metamaterial fabrication

DOE PAGES

Musick, Katherine M.; Wendt, Joel R.; Resnick, Paul J.; ...

2018-01-18

Here, the manufacturing tolerances of a stencil-lithography variant, membrane projection lithography, were investigated. In the first part of this work, electron beam lithography was used to create stencils with a range of linewidths. These patterns were transferred into the stencil membrane and used to pattern metallic lines on vertical silicon faces. Only the largest lines, with a nominal width of 84 nm, were resolved, resulting in 45 ± 10 nm (average ± standard deviation) as deposited with 135-nm spacing. Although written in the e-beam write software file as 84-nm in width, the lines exhibited linewidth bias. This can largely bemore » attributed to nonvertical sidewalls inherent to dry etching techniques that cause proportionally larger impact with decreasing feature size. The line edge roughness can be significantly attributed to the grain structure of the aluminum nitride stencil membrane. In the second part of this work, the spatial uniformity of optically defined (as opposed to e-beam written) metamaterial structures over large areas was assessed. A Fourier transform infrared spectrometer microscope was used to collect the reflection spectra of samples with optically defined vertical split ring from 25 spatially resolved 300 × 300 μm regions in a 1-cm 2 area. The technique is shown to provide a qualitative measure of the uniformity of the inclusions.« less

Effect of ribbon width on electrical transport properties of graphene nanoribbons

NASA Astrophysics Data System (ADS)

Bang, Kyuhyun; Chee, Sang-Soo; Kim, Kangmi; Son, Myungwoo; Jang, Hanbyeol; Lee, Byoung Hun; Baik, Kwang Hyeon; Myoung, Jae-Min; Ham, Moon-Ho

2018-03-01

There has been growing interest in developing nanoelectronic devices based on graphene because of its superior electrical properties. In particular, patterning graphene into a nanoribbon can open a bandgap that can be tuned by changing the ribbon width, imparting semiconducting properties. In this study, we report the effect of ribbon width on electrical transport properties of graphene nanoribbons (GNRs). Monolayer graphene sheets and Si nanowires (NWs) were prepared by chemical vapor deposition and a combination of nanosphere lithography and metal-assisted electroless etching from a Si wafer, respectively. Back-gated GNR field-effect transistors were fabricated on a heavily p-doped Si substrate coated with a 300 nm-thick SiO2 layer, by O2 reactive ion etching of graphene sheets using etch masks based on Si NWs aligned on the graphene between the two electrodes by a dielectrophoresis method. This resulted in GNRs with various widths in a highly controllable manner, where the on/off current ratio was inversely proportional to ribbon width. The field-effect mobility decreased with decreasing GNR widths due to carrier scattering at the GNR edges. These results demonstrate the formation of a bandgap in GNRs due to enhanced carrier confinement in the transverse direction and edge effects when the GNR width is reduced.

Statistical evaluation of metal fill widths for emulated metal fill in parasitic extraction methodology

NASA Astrophysics Data System (ADS)

J-Me, Teh; Noh, Norlaili Mohd.; Aziz, Zalina Abdul

2015-05-01

In the chip industry today, the key goal of a chip development organization is to develop and market chips within a short time frame to gain foothold on market share. This paper proposes a design flow around the area of parasitic extraction to improve the design cycle time. The proposed design flow utilizes the usage of metal fill emulation as opposed to the current flow which performs metal fill insertion directly. By replacing metal fill structures with an emulation methodology in earlier iterations of the design flow, this is targeted to help reduce runtime in fill insertion stage. Statistical design of experiments methodology utilizing the randomized complete block design was used to select an appropriate emulated metal fill width to improve emulation accuracy. The experiment was conducted on test cases of different sizes, ranging from 1000 gates to 21000 gates. The metal width was varied from 1 x minimum metal width to 6 x minimum metal width. Two-way analysis of variance and Fisher's least significant difference test were used to analyze the interconnect net capacitance values of the different test cases. This paper presents the results of the statistical analysis for the 45 nm process technology. The recommended emulated metal fill width was found to be 4 x the minimum metal width.

Ultrastructural instability of paired helical filaments from corticobasal degeneration as examined by scanning transmission electron microscopy.

PubMed Central

Ksiezak-Reding, H.; Tracz, E.; Yang, L. S.; Dickson, D. W.; Simon, M.; Wall, J. S.

1996-01-01

Paired helical filaments (PHFs) accumulate in the brains of subjects affected with Alzheimer's disease (AD) and certain other neurodegenerative disorders, including corticobasal degeneration (CBD). Electron microscope studies have shown that PHFs from CBD differ from those of AD by being wider and having a longer periodicity of the helical twist. Moreover, PHFs from CBD have been shown to be primarily composed of two rather than three highly phosphorylated polypeptides of tau (PHF-tau), with these polypeptides expressing no exons 3 and 10. To further explore the relationship between the heterogeneity of PHF-tau and the appearance of abnormal filaments, the ultrastructure and physical parameters such as mass per unit length and dimensions were compared in filaments from CBD and AD using high resolution scanning transmission electron microscopy (STEM). Filament-enriched fractions were isolated as Sarcosyl-insoluble pellets and for STEM studies, samples were freeze-dried without prior fixation or staining. Ultrastructurally, PHFs from CBD were shown to be a heterogeneous population as double- and single-stranded filaments could be identified based on their width and physical mass per unit length expressed in kilodaltons (kd) per nanometer (nm). Less abundant, double-stranded filaments had a maximal width of 29 nm and a mass per unit length of 133 kd/nm, whereas three times more abundant single-stranded filaments were 15 nm wide and bad a mass per unit length of 62 kd/nm. Double-stranded filaments also displayed a distinct axial region of less dense mass, which appeared to divide the PHFs into two protofilament-like strands. Furthermore, these filaments were frequently observed to physically separate along the long axis into two single strands or to break longitudinally. In contrast, PHFs from AD were ultrastructurally stable and uniform both in their width (22 nm) and physical mass per unit length (104 kd/nm). The ultrastructural features indicate that filaments of CBD and AD differ both in stability and packing of tau and that CBD filaments, composed of two distinct protofilaments, are more labile under STEM conditions. As fixed and stained filaments from CBD have been shown to be stable and uniform in size by conventional transmission electron microscopy, STEM studies may be particularly suitable for detecting instability of unstained and unfixed filaments. The results also suggest that molecular heterogeneity and/or post-translational modifications of tau may strongly influence the morphology and stability of abnormal filaments. Images Figure 1 Figure 2 Figure 3 PMID:8702002

Aerosol Optical Depth Value-Added Product for the SAS-He Instrument

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ermold, B; Flynn, CJ; Barnard, J

2013-11-27

The Shortwave Array Spectroradiometer – Hemispheric (SAS-He) is a ground-based, shadowband instrument that measures the direct and diffuse solar irradiance. In this regard, the instrument is similar to the Multi-Filter Rotating Shadowband Radiometer (MFRSR) – an instrument that has been in the ARM suite of instruments for more than 15 years. However, the two instruments differ significantly in wavelength resolution and range. In particular, the MFRSR only observes the spectrum in six discrete wavelength channels of about 10 nm width from 415 to 940 nm. The SAS-He, in contrast, incorporates two fiber-coupled grating spectrometers: a Si CCD spectrometer with overmore » 2000 pixels covering the range from 325-1040 nm with ~ 2.5 nm resolution ,and an InGaAs array spectrometer with 256 pixels covering the wavelength range from 960-1700 nm with ~ 6 nm resolution.« less

Continuous modulations of femtosecond laser-induced periodic surface structures and scanned line-widths on silicon by polarization changes.

PubMed

Han, Weina; Jiang, Lan; Li, Xiaowei; Liu, Pengjun; Xu, Le; Lu, YongFeng

2013-07-01

Large-area, uniform laser-induced periodic surface structures (LIPSS) are of wide potential industry applications. The continuity and processing precision of LIPSS are mainly determined by the scanning intervals of adjacent scanning lines. Therefore, continuous modulations of LIPSS and scanned line-widths within one laser scanning pass are of great significance. This study proposes that by varying the laser (800 nm, 50 fs, 1 kHz) polarization direction, LIPSS and the scanned line-widths on a silicon (111) surface can be continuously modulated with high precision. It shows that the scanned line-width reaches the maximum when the polarization direction is perpendicular to the scanning direction. As an application example, the experiments show large-area, uniform LIPSS can be fabricated by controlling the scanning intervals based on the one-pass scanned line-widths. The simulation shows that the initially formed LIPSS structures induce directional surface plasmon polaritons (SPP) scattering along the laser polarization direction, which strengthens the subsequently anisotropic LIPSS fabrication. The simulation results are in good agreement with the experiments, which both support the conclusions of continuous modulations of the LIPSS and scanned line-widths.

Qualification of a Quantitative Laryngeal Imaging System Using Videostroboscopy and Videokymography

PubMed Central

Popolo, Peter S.; Titze, Ingo R.

2008-01-01

Objectives: We sought to determine whether full-cycle glottal width measurements could be obtained with a quantitative laryngeal imaging system using videostroboscopy, and whether glottal width and vocal fold length measurements were repeatable and reliable. Methods: Synthetic vocal folds were phonated on a laboratory bench, and dynamic images were obtained in repeated trials by use of videostroboscopy and videokymography (VKG) with an imaging system equipped with a 2-point laser projection device for measuring absolute dimensions. Video images were also obtained with an industrial videoscope system with a built-in laser measurement capability. Maximum glottal width and vocal fold length were compared among these 3 methods. Results: The average variation in maximum glottal width measurements between stroboscopic data and VKG data was 3.10%. The average variations in width measurements between the clinical system and the industrial system were 1.93% (stroboscopy) and 3.49% (VKG). The variations in vocal fold length were similarly small. The standard deviations across trials were 0.29 mm for width and 0.48 mm for length (stroboscopy), 0.18 mm for width (VKG), and 0.25 mm for width and 0.84 mm for length (industrial). Conclusions: For stable, periodic vibration, the full extent of the glottal width can be reliably measured with the quantitative videostroboscopy system. PMID:18646436

Increased water retention in polymer electrolyte membranes at elevated temperatures assisted by capillary condensation.

PubMed

Park, Moon Jeong; Downing, Kenneth H; Jackson, Andrew; Gomez, Enrique D; Minor, Andrew M; Cookson, David; Weber, Adam Z; Balsara, Nitash P

2007-11-01

We establish a new systematic methodology for controlling the water retention of polymer electrolyte membranes. Block copolymer membranes comprising hydrophilic phases with widths ranging from 2 to 5 nm become wetter as the temperature of the surrounding air is increased at constant relative humidity. The widths of the moist hydrophilic phases were measured by cryogenic electron microscopy experiments performed on humid membranes. Simple calculations suggest that capillary condensation is important at these length scales. The correlation between moisture content and proton conductivity of the membranes is demonstrated.

High temperature irradiation induced creep in Ag nanopillars measured via in situ transmission electron microscopy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jawaharram, Gowtham Sriram; Price, Patrick M.; Barr, Christopher M.

Irradiation induced creep (IIC) rates are measured in compression on Ag nanopillar (square) beams in the sink-limited regime. The IIC rate increases linearly with stress at lower stresses, i.e. below ≈2/3 the high temperature yield stress and parabolically with pillar width, L, for L less than ≈300 nm. Here, the data are obtained by combining in situ transmission electron imaging with simultaneous ion irradiation, laser heating, and nanopillar compression. Results in the larger width regime are consistent with prior literature.

High temperature irradiation induced creep in Ag nanopillars measured via in situ transmission electron microscopy

DOE PAGES

Jawaharram, Gowtham Sriram; Price, Patrick M.; Barr, Christopher M.; ...

2018-01-30

Irradiation induced creep (IIC) rates are measured in compression on Ag nanopillar (square) beams in the sink-limited regime. The IIC rate increases linearly with stress at lower stresses, i.e. below ≈2/3 the high temperature yield stress and parabolically with pillar width, L, for L less than ≈300 nm. Here, the data are obtained by combining in situ transmission electron imaging with simultaneous ion irradiation, laser heating, and nanopillar compression. Results in the larger width regime are consistent with prior literature.

[Development of Micro-Spectrometer with a Function of Timely Temperature Compensation].

PubMed

Bao, Jian-guang; Liu, Zheng-kun; Chen, Huo-yao; Lin, Ji-ping; Fu, Shao-jun

2015-05-01

Temperature drift will be brought to Micro-Spectrometer used for demodulating the Varied Line-Space(VLS) grating position sensor on aircraft due to high-low temperature shock. We successfully made a Micro-Spectrometer, for the VLS grating position sensor on aircraft, which still have stable output under temperature shock enviro nment. In order to present a real time temperature compensation scheme, the effects temperature change has on Micro-Spectrometer are analyzed and the traditional cross Czerny-Turner (C-T)optical structure is optimized. Both optical structures are analyzed by optics design software ZEMAX and proved that comparedwithtraditional cross C-T optical structure, the newone can accomplish not only smaller spectrum drift but also spectrum drift with better linearity. Based on the new optical structure. The scheme of using reference wavelength to accomplish real time temperature compensation was proposed and a Micro-fiber Spectrometer was successfully manufactured, whith is with Volume of 80 mm X 70 mmX 70 mm, integration time of 8 ~1 000 ms and FullWidthHalfMaximum(FWHM) of 2 nm. Experiments show that the new spectrometer meets the design requirement. Under high temperature in the range of nearly 60 °C, the standard error of wavelength of this new spectrometer is smaller than 0. 1 nm, and the maximum error of wavelength is 0. 14 nm, which is much smaller than required 0. 3 nm. Innovations of this paper are the schemeof real time temperature compensation, the new cross C-T optical structure and a Micro-fiber Spectrometer based on it.

Fiber-Optic Gratings for Lidar Measurements of Water Vapor

NASA Technical Reports Server (NTRS)

Vann, Leila B.; DeYoung, Russell J.

2006-01-01

Narrow-band filters in the form of phase-shifted Fabry-Perot Bragg gratings incorporated into optical fibers are being developed for differential-absorption lidar (DIAL) instruments used to measure concentrations of atmospheric water vapor. The basic idea is to measure the relative amounts of pulsed laser light scattered from the atmosphere at two nearly equal wavelengths, one of which coincides with an absorption spectral peak of water molecules and the other corresponding to no water vapor absorption. As part of the DIAL measurement process, the scattered light is made to pass through a filter on the way to a photodetector. Omitting other details of DIAL for the sake of brevity, what is required of the filter is to provide a stop band that: Surrounds the water-vapor spectral absorption peaks at a wavelength of 946 nm, Has a spectral width of at least a couple of nanometers, Contains a pass band preferably no wider than necessary to accommodate the 946.0003-nm-wavelength water vapor absorption peak [which has 8.47 pm full width at half maximum (FWHM)], and Contains another pass band at the slightly shorter wavelength of 945.9 nm, where there is scattering of light from aerosol particles but no absorption by water molecules. Whereas filters used heretofore in DIAL have had bandwidths of =300 pm, recent progress in the art of fiber-optic Bragg-grating filters has made it feasible to reduce bandwidths to less than or equal to 20 pm and thereby to reduce background noise. Another benefit of substituting fiber-optic Bragg-grating filters for those now in use would be significant reductions in the weights of DIAL instruments. Yet another advantage of fiber-optic Bragg-grating filters is that their transmission spectra can be shifted to longer wavelengths by heating or stretching: hence, it is envisioned that future DIAL instruments would contain devices for fine adjustment of transmission wavelengths through stretching or heating of fiber-optic Bragg-grating filters nominally designed and fabricated to have transmission wavelengths that, in the absence of stretching, would be slightly too short.

Capacitor charging FET switcher with controller to adjust pulse width

DOEpatents

Mihalka, Alex M.

1986-01-01

A switching power supply includes an FET full bridge, a controller to drive the FETs, a programmable controller to dynamically control final output current by adjusting pulse width, and a variety of protective systems, including an overcurrent latch for current control. Power MOSFETS are switched at a variable frequency from 20-50 kHz to charge a capacitor load from 0 to 6 kV. A ferrite transformer steps up the DC input. The transformer primary is a full bridge configuration with the FET switches and the secondary is fed into a high voltage full wave rectifier whose output is connected directly to the energy storage capacitor. The peak current is held constant by varying the pulse width using predetermined timing resistors and counting pulses. The pulse width is increased as the capacitor charges to maintain peak current. A digital ripple counter counts pulses, and after the desired number is reached, an up-counter is clocked. The up-counter output is decoded to choose among different resistors used to discharge a timing capacitor, thereby determining the pulse width. A current latch shuts down the supply on overcurrent due to either excessive pulse width causing transformer saturation or a major bridge fault, i.e., FET or transformer failure, or failure of the drive circuitry.

Solution phase synthesis of Na{sub 0.28}V{sub 2}O{sub 5} nanobelts into nanorings and the electrochemical performance in Li battery

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nagaraju, Ganganagappa, E-mail: nagarajugn@rediffmail.com; Department of Chemistry, Central College Campus, Bangalore University, Bangalore; Chandrappa, Gujjarahalli Thimmanna

2012-11-15

Graphical abstract: Hydrothermal method has been adopted first time to prepare Na{sub 0.28}V{sub 2}O{sub 5} nanorings/nanobelts without using any organic surfactant/solvents at 130–160 °C for 1–2 days. TEM analyses reveal that the products consist of nanorings of width about 500 nm and thickness of about 100 nm with inner diameter of 5–7 m. Nanobelts of width 70–100 nm and several tens of micrometers in length are observed. The electrochemical results show that Na{sub 0.28}V{sub 2}O{sub 5} exhibits an initial discharge capacity of 320 mAh g{sup −1} and its capacity still retained 175 mAh g{sup −1} even after 69 cycles. Highlights:more » ► We are the first to report Na{sub 0.28}V{sub 2}O{sub 5} nanorings/nanobelts by solution method. ► Synthesis via hydrothermal method at 130–160 °C/1–2d in acidic medium. ► We have carried out without using any surfactant/templates/organic solvents. ► Shows discharge capacity of 320 mAh g{sup −1} and reach 175 mAh g{sup −1} after 69 cycles. ► A probable reaction mechanism for Na{sub 0.28}V{sub 2}O{sub 5} nanorings formation is also proposed. -- Abstract: In this paper, we are the first to report a simple one step hydrothermal method to synthesize Na{sub 0.28}V{sub 2}O{sub 5} nanorings/nanobelts without using any organic surfactant/solvents at 130–160 °C for 1–2 days. The obtained products have been characterized by X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDS), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, morphology by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) and electrochemical discharge–charge test for lithium battery. XRD pattern exhibit a monoclinic Na{sub 0.28}V{sub 2}O{sub 5} structure. FTIR spectrum shows band at 958 cm{sup −1} is assigned to V=O stretching vibration, which is sensitive to intercalation and suggests that Na{sup +} ions are inserted between the vanadium oxide layers. TEM analyses reveal that the products consist of nanorings of width about 500 nm and thickness of about 100 nm with inner diameter of 5–7 μm. Nanobelts of width 70–100 nm and several tens of micrometers in length are observed. The electrochemical results show that nanorings/nanobelts exhibit an initial discharge capacity of 320 mAh g{sup −1} and its capacity still retained 175 mAh g{sup −1} even after 69 cycles. We have discussed the possible growth mechanism for the formation of nanorings/nanobelts.« less

Electrospray ionization from a gap with adjustable width.

PubMed

Ek, Patrik; Sjödahl, Johan; Roeraade, Johan

2006-01-01

In this paper, we present a new concept for electrospray ionization mass spectrometry, where the sample is applied in a gap which is formed between the edges of two triangular-shaped tips. The size of the spray orifice can be changed by varying the gap width. The tips were fabricated from polyethylene terephthalate film with a thickness of 36 microm. To improve the wetting of the gap and sample confinement, the edges of the tips forming the gap were hydrophilized by means of silicon dioxide deposition. Electrospray was performed with gap widths between 1 and 36 microm and flow rates down to 75 nL/min. The gap width could be adjusted in situ during the mass spectrometry experiments and nozzle clogging could be managed by simply widening the gap. Using angiotensin I as analyte, the signal-to-noise ratio increased as the gap width was decreased, and a shift towards higher charge states was observed. The detection limit for angiotensin I was in the low nM range. Copyright (c) 2006 John Wiley & Sons, Ltd.

Large electron concentration modulation using capacitance enhancement in SrTiO{sub 3}/SmTiO{sub 3} Fin-field effect transistors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Verma, Amit, E-mail: averma@cornell.edu; Nomoto, Kazuki; School of Electrical and Computer Engineering, Cornell University, Ithaca, New York 14853

2016-05-02

Solid-state modulation of 2-dimensional electron gases (2DEGs) with extreme (∼3.3 × 10{sup 14 }cm{sup −2}) densities corresponding to 1/2 electron per interface unit cell at complex oxide heterointerfaces (such as SrTiO{sub 3}/GdTiO{sub 3} or SrTiO{sub 3}/SmTiO{sub 3}) is challenging because it requires enormous gate capacitances. One way to achieve large gate capacitances is by geometrical capacitance enhancement in fin structures. In this work, we fabricate both Au-gated planar field effect transistors (FETs) and Fin-FETs with varying fin-widths on 60 nm SrTiO{sub 3}/5 nm SmTiO{sub 3} thin films grown by hybrid molecular beam epitaxy. We find that the FinFETs exhibit higher gate capacitance comparedmore » to planar FETs. By scaling down the SrTiO{sub 3}/SmTiO{sub 3} fin widths, we demonstrate further gate capacitance enhancement, almost twice compared to the planar FETs. In the FinFETs with narrowest fin-widths, we demonstrate a record 2DEG electron concentration modulation of ∼2.4 × 10{sup 14 }cm{sup −2}.« less

Emission behaviors of unsymmetrical 1,3-diaryl-β-diketones: A model perfectly disclosing the effect of molecular conformation on luminescence of organic solids

NASA Astrophysics Data System (ADS)

Cheng, Xiao; Li, Feng; Han, Shenghua; Zhang, Yufei; Jiao, Chuanjun; Wei, Jinbei; Ye, Kaiqi; Wang, Yue; Zhang, Hongyu

2015-03-01

A series of unsymmetrical 1,3-diaryl-β-diketones 1-6 displaying molecular conformation-dependent fluorescence quantum yields have been synthesized. Crystals with planar molecular conformation such as 1, 2, 3 and 4 are highly fluorescent (φf: 39-53%), and the one holding slightly twisted conformation (5) is moderately luminescent (φf = 17%), while crystal 6 possessing heavily bent structure is completely nonluminous (φf ~ 0). The distinct fluorescence efficiencies are ascribed to their different molecular conformations, since all the crystals hold the same crystal system, space group and crystal packing structures. Additionally, the fluorescent crystals 1-5 display low threshold amplified spontaneous emission (ASE) with small full widths at half-maximum (FWHM: 3-7 nm), indicating their potential as candidates for organic crystal lasing devices.

Characterization of diode-laser stacks for high-energy-class solid state lasers

NASA Astrophysics Data System (ADS)

Pilar, Jan; Sikocinski, Pawel; Pranowicz, Alina; Divoky, Martin; Crump, P.; Staske, R.; Lucianetti, Antonio; Mocek, Tomas

2014-03-01

In this work, we present a comparative study of high power diode stacks produced by world's leading manufacturers such as DILAS, Jenoptik, and Quantel. The diode-laser stacks are characterized by central wavelength around 939 nm, duty cycle of 1 %, and maximum repetition rate of 10 Hz. The characterization includes peak power, electrical-to-optical efficiency, central wavelength and full width at half maximum (FWHM) as a function of diode current and cooling temperature. A cross-check of measurements performed at HiLASE-IoP and Ferdinand-Braun-Institut (FBH) shows very good agreement between the results. Our study reveals also the presence of discontinuities in the spectra of two diode stacks. We consider the results presented here a valuable tool to optimize pump sources for ultra-high average power lasers, including laser fusion facilities.

Properties of epitaxial BaTiO{sub 3} deposited on GaAs

DOE Office of Scientific and Technical Information (OSTI.GOV)

Contreras-Guerrero, R.; Droopad, R.; Veazey, J. P.

2013-01-07

Single crystal BaTiO{sub 3} (BTO) has been grown epitaxially on GaAs using molecular beam epitaxy with a 2 unit cell SrTiO{sub 3} nucleation layer. The oxide film is lattice-matched to GaAs through an in-plane rotation of 45 Degree-Sign relative to the (100) surface leading to c-axis orientation of the BaTiO{sub 3}. X-ray diffraction confirmed the crystallinity and orientation of the oxide film with a full width half maximum of 0.58 Degree-Sign for a 7.5 nm thick layer. Piezoresponse force microscopy was used to characterize the ferroelectric domains in the BaTiO{sub 3} layer, and a coercive voltage of 1-2 V andmore » piezoresponse amplitude {approx}5 pm/V was measured.« less

Passively mode-locked high power Nd:GdVO4 laser with direct in-band pumping at 912 nm

NASA Astrophysics Data System (ADS)

Nadimi, Mohammad; Waritanant, Tanant; Major, Arkady

2018-01-01

We report on the first semiconductor saturable absorber mirror mode-locked Nd:GdVO4 laser directly diode-pumped at 912 nm. The laser generated 10.14 W of averaged output power at 1063 nm with the pulse width of 16 ps at the repetition rate of 85.2 MHz. The optical-to-optical efficiency and slope efficiency in the mode-locked regime were calculated to be 49.6% and 67.4% with respect to the absorbed pump power, respectively. Due to the low quantum defect pumping the output power was limited only by the available pump power.

Focused ion beam direct micromachining of DOEs

NASA Astrophysics Data System (ADS)

Khan Malek, Chantal; Hartley, Frank T.; Neogi, Jayant

2000-09-01

We discuss here the capability of direct manufacture of various high- resolution diffractive optics, in particular regarding micromachining of DOEs in 3D. Preliminary demonstrations were made in 2-D using an automated FIB system operated at 30 KeV with a Gallium liquid metal ion source and equipped with a gas injection system (GIS). Gratings with a 20 nm line width and zone plates with 32 nm outer ring were milled in a reactive atmosphere (iodine) directly through 3.5 (mu) m and 800 nm of gold respectively. Plans for combining FIB and X-ray lithography to make diffractive optical elements (DOEs) for JPL are also mentioned.

Luminescence of quantum-well exciton polaritons from microstructured AlxGa1-xAs-GaAs multiple quantum wells

NASA Astrophysics Data System (ADS)

Kohl, M.; Heitmann, D.; Grambow, P.; Ploog, K.

1988-06-01

Periodic multiple-quantum-well wires have been prepared by etching five-layer quantum-well structures through a holographically prepared mask. The periodicity was 380 nm, the lateral confinement 180 nm, and the quantum-well width 13, nm. The luminescence from these microstructured systems in the frequency regime of the one-electron-one-heavy-hole transition was strongly polarized with the electric field perpendicular to the periodic structure. This effect was caused by the resonantly enhanced emission of quantum-well-exciton (QWE) polaritons. Excitation of QWE polaritons was also observed in reflection measurements on the microstructured samples.

Three-dimensional analysis by electron diffraction methods of nanocrystalline materials.

PubMed

Gammer, Christoph; Mangler, Clemens; Karnthaler, Hans-Peter; Rentenberger, Christian

2011-12-01

To analyze nanocrystalline structures quantitatively in 3D, a novel method is presented based on electron diffraction. It allows determination of the average size and morphology of the coherently scattering domains (CSD) in a straightforward way without the need to prepare multiple sections. The method is applicable to all kinds of bulk nanocrystalline materials. As an example, the average size of the CSD in nanocrystalline FeAl made by severe plastic deformation is determined in 3D. Assuming ellipsoidal CSD, it is deduced that the CSD have a width of 19 ± 2 nm, a length of 18 ± 1 nm, and a height of 10 ± 1 nm.

71-Mbit/s ultraviolet-B LED communication link based on 8-QAM-OFDM modulation.

PubMed

Sun, Xiaobin; Zhang, Zhenyu; Chaaban, Anas; Ng, Tien Khee; Shen, Chao; Chen, Rui; Yan, Jianchang; Sun, Haiding; Li, Xiaohang; Wang, Junxi; Li, Jinmin; Alouini, Mohamed-Slim; Ooi, Boon S

2017-09-18

A demonstration of ultraviolet-B (UVB) communication link is implemented utilizing quadrature amplitude modulation (QAM) orthogonal frequency-division multiplexing (OFDM). The demonstration is based on a 294-nm UVB-light-emitting-diode (UVB-LED) with a full-width at half-maximum (FWHM) of 9 nm and light output power of 190 μW, at 7 V, with a special silica gel lens on top of it. A -3-dB bandwidth of 29 MHz was measured and a high-speed near-solar-blind communication link with a data rate of 71 Mbit/s was achieved using 8-QAM-OFDM at perfect alignment. 23.6 Mbit/s using 2-QAM-OFDM when the angle subtended by the pointing directions of the UVB-LED and photodetector (PD) is 12 degrees, thus establishing a diffuse-line-of-sight (LOS) link. The measured bit-error rate (BER) of 2.8 ×10 -4 and 2.4 ×10 -4 , respectively, are well below the forward error correction (FEC) criterion of 3.8 ×10 -3 . The demonstrated high data-rate OFDM-based UVB communication link paves the way for realizing high-speed non-line-of-sight free-space optical communications.

Low threshold L-band mode-locked ultrafast fiber laser assisted by microfiber-based carbon nanotube saturable absorber

NASA Astrophysics Data System (ADS)

Lau, K. Y.; Ng, E. K.; Abu Bakar, M. H.; Abas, A. F.; Alresheedi, M. T.; Yusoff, Z.; Mahdi, M. A.

2018-04-01

We demonstrate a passively mode-locked erbium-doped fiber laser in L-band wavelength region with low mode-locking threshold employing a 1425 nm pump wavelength. The mode-locking regime is generated by microfiber-based saturable absorber using carbon nanotube-polymer composite in a ring cavity. This carbon nanotube saturable absorber shows saturation intensity of 9 MW/cm2. In this work, mode-locking laser threshold is observed at 36.4 mW pump power. At the maximum pump power of 107.6 mW, we obtain pulse duration at full-width half-maximum point of 490 fs and time bandwidth product of 0.33, which corresponds to 3-dB spectral bandwidth of 5.8 nm. The pulse repetition rate remains constant throughout the experiment at 5.8 MHz due to fixed cavity length of 35.5 m. Average output power and pulse energy of 10.8 mW and 1.92 nJ are attained respectively through a 30% laser output extracted from the mode-locked cavity. This work highlights the feasibility of attaining a low threshold mode-locked laser source to be employed as seed laser in L-band wavelength region.

Green Synthesis of InP/ZnS Core/Shell Quantum Dots for Application in Heavy-Metal-Free Light-Emitting Diodes

NASA Astrophysics Data System (ADS)

Kuo, Tsung-Rong; Hung, Shih-Ting; Lin, Yen-Ting; Chou, Tzu-Lin; Kuo, Ming-Cheng; Kuo, Ya-Pei; Chen, Chia-Chun

2017-09-01

Quantum dot light-emitting diodes (QD-LEDs) have been considered as potential display technologies with the characterizations of high color purity, flexibility, transparency, and cost efficiency. For the practical applications, the development of heavy-metal-free QD-LEDs from environment-friendly materials is the most important issue to reduce the impacts on human health and environmental pollution. In this work, heavy-metal-free InP/ZnS core/shell QDs with different fluorescence were prepared by green synthesis method with low cost, safe, and environment-friendly precursors. The InP/ZnS core/shell QDs with maximum fluorescence peak at 530 nm, superior fluorescence quantum yield of 60.1%, and full width at half maximum of 55 nm were applied as an emission layer to fabricate multilayered QD-LEDs. The multilayered InP/ZnS core/shell QD-LEDs showed the turn-on voltage at 5 V, the highest luminance (160 cd/m2) at 12 V, and the external quantum efficiency of 0.223% at 6.7 V. Overall, the multilayered InP/ZnS core/shell QD-LEDs reveal potential to be the heavy-metal-free QD-LEDs for future display applications.

Synthesis of Phenanthro[1,10,9,8-cdefg]carbazole-Based Conjugated Polymers for Green-Selective Organic Photodiodes.

PubMed

Sung, Min Jae; Yoon, Seongwon; Kwon, Soon-Ki; Kim, Yun-Hi; Chung, Dae Sung

2016-11-16

A push-pull-type donor copolymer, named PP-TPD, was synthesized with the Suzuki coupling reaction using 6H-phenanthro[1,10,9,8-cdefg]carbazole (PCZ) as the donor unit and 1,3-bis(5-bromothiophen-2-yl)-5-octyl-4H-thieno[3,4-c]pyrrole-4,6(5H)-dione (TPD) as the acceptor unit. The synthesized PP-TPD was systematically investigated in terms of crystallinity and thermal, electrical, electrochemical, and optical properties. PP-TPD revealed green-selective absorption with a narrow full width at half-maximum of 138 nm. Green-selective organic photodiodes (OPDs) were constructed using PP-TPD as the green-absorbing donor and ZnO as the nonabsorbing acceptor material. The fabricated OPDs exhibited an extremely low dark current of 0.68 nA/cm 2 at -5 V and a high detectivity above 10 12 Jones at 550 nm. Moreover, they showed a sufficiently high 3-dB frequency and a linear dynamic range, similar to those of ideal-operating OPDs. The origin and physics background of the observed low dark current and high detectivity are discussed in detail.

Polarity inversion of AlN film grown on nitrided a-plane sapphire substrate with pulsed DC reactive sputtering

NASA Astrophysics Data System (ADS)

Noorprajuda, Marsetio; Ohtsuka, Makoto; Fukuyama, Hiroyuki

2018-04-01

The effect of oxygen partial pressure (PO2) on polarity and crystalline quality of AlN films grown on nitrided a-plane sapphire substrates by pulsed direct current (DC) reactive sputtering was investigated as a fundamental study. The polarity inversion of AlN from nitrogen (-c)-polarity to aluminum (+c)-polarity occurred during growth at a high PO2 of 9.4×103 Pa owing to Al-O octahedral formation at the interface of nitrided layer and AlN sputtered film which reset the polarity of AlN. The top part of the 1300 nm-thick AlN film sputtered at the high PO2 was polycrystallized. The crystalline quality was improved owing to the high kinetic energy of Al sputtered atom in the sputtering phenomena. Thinner AlN films were also fabricated at the high PO2 to eliminate the polycrystallization. For the 200 nm-thick AlN film sputtered at the high PO2, the full width at half-maximum values of the AlN (0002) and (10-12) X-ray diffraction rocking curves were 47 and 637 arcsec, respectively.

Locked ortho- and para-core chromophores of green fluorescent protein; dramatic emission enhancement via structural constraint.

PubMed

Hsu, Yen-Hao; Chen, Yi-An; Tseng, Huan-Wei; Zhang, Zhiyun; Shen, Jiun-Yi; Chuang, Wei-Ti; Lin, Tzu-Chieh; Lee, Chun-Shu; Hung, Wen-Yi; Hong, Bor-Cherng; Liu, Shih-Hung; Chou, Pi-Tai

2014-08-20

We report the design strategy and synthesis of a structurally locked GFP core chromophore p-LHBDI, its ortho-derivative, o-LHBDI, and H2BDI possessing both para- and ortho-hydroxyl groups such that the inherent rotational motion of the titled compounds has been partially restricted. o-LHBDI possesses a doubly locked configuration, i.e., the seven-membered ring hydrogen bond and five-membered ring C(4-5-10-13-14) cyclization, from which the excited-state intramolecular proton transfer takes place, rendering a record high tautomer emission yield (0.18 in toluene) and the generation of amplified spontaneous emission. Compared with their unlocked counterparts, a substantial increase in the emission yield is also observed for p-LHBDI and H2BDI in anionic forms in water, and accordingly the structure versus luminescence relationship is fully discussed based on their chemistry and spectroscopy aspect. In solid, o-LHBDI exhibits an H-aggregate-like molecular packing, offers narrow-bandwidth emission, and has been successfully applied to fabricate a yellow organic light emitting diodes (λmax = 568 nm, ηext = 1.9%) with an emission full width at half-maximum as narrow as 70 nm.

Block Copolymer Micelles for Photonic Fluids and Crystals.

PubMed

Poutanen, Mikko; Guidetti, Giulia; Gröschel, Tina I; Borisov, Oleg V; Vignolini, Silvia; Ikkala, Olli; Gröschel, Andre H

2018-04-24

Block copolymer micelles (BCMs) are self-assembled nanoparticles in solution with a collapsed core and a brush-like stabilizing corona typically in the size range of tens of nanometers. Despite being widely studied in various fields of science and technology, their ability to form structural colors at visible wavelength has not received attention, mainly due to the stringent length requirements of photonic lattices. Here, we describe the precision assembly of BCMs with superstretched corona, yet with narrow size distribution to qualify as building blocks for tunable and reversible micellar photonic fluids (MPFs) and micellar photonic crystals (MPCs). The BCMs form free-flowing MPFs with an average interparticle distance of 150-300 nm as defined by electrosteric repulsion arising from the highly charged and stretched corona. Under quiescent conditions, millimeter-sized MPCs with classical FCC lattice grow within the photonic fluid-medium upon refinement of the positional order of the BCMs. We discuss the generic properties of MPCs with special emphasis on surprisingly narrow reflected wavelengths with full width at half-maximum (fwhm) as small as 1 nm. We expect this concept to open a generic and facile way for self-assembled tunable micellar photonic structures.

Irradiation of silver and agar/silver nanoparticles with argon, oxygen glow discharge plasma, and mercury lamp.

PubMed

Ahmad, Mahmoud M; Abdel-Wahab, Essam A; El-Maaref, A A; Rawway, Mohammed; Shaaban, Essam R

2014-01-01

The irradiation effect of argon, oxygen glow discharge plasma, and mercury lamp on silver and agar/silver nanoparticle samples is studied. The irradiation time dependence of the synthesized silver and agar/silver nanoparticle absorption spectra and their antibacterial effect are studied and compared. In the agar/silver nanoparticle sample, as the irradiation time of argon glow discharge plasma or mercury lamp increases, the peak intensity and the full width at half maximum, FWHM, of the surface plasmon resonance absorption band is increased, however a decrease of the peak intensity with oxygen glow plasma has been observed. In the silver nanoparticle sample, as the irradiation time of argon, oxygen glow discharge plasma or mercury lamp increases, the peak intensity of the surface plasmon resonance absorption band is increased, however, there is no significant change in the FWHM of the surface plasmon resonance absorption band. The SEM results for both samples showed nanoparticle formation with mean size about 50 nm and 40 nm respectively. Throughout the irradiation time with the argon, oxygen glow discharge plasma or mercury lamp, the antibacterial activity of several kinds of Gram-positive and Gram-negative bacteria has been examined.

Zn(II)-PEG 300 globules as soft template for the synthesis of hexagonal ZnO micronuts by the hydrothermal reaction method.

PubMed

Shi, Xixi; Pan, Lingling; Chen, Shuoping; Xiao, Yong; Liu, Qiaoyun; Yuan, Liangjie; Sun, Jutang; Cai, Lintao

2009-05-19

Hexagonal ZnO micronuts (HZMNs) have been successfully synthesized with the assistance of poly(ethylene glycol) (PEG) 300 via a hydrothermal method. The structure and morphology of the HZMNs were characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and selected area electron diffraction (SAED). An individual ZnO micronut is revealed as twinned crystals. Time-dependent investigation shows that the growth of HZMNs involves a dissolution-recrystallization process followed by Ostwald ripening, in which is the first formed solid ZnO particles dissolve and transform to HZMNs with hollow structure. PEG 300 has been found to play a crucial role in the growth of this unique hollow structure. TEM observations show that the PEG chains aggregate to globules in water, which then have interaction with the dissolved zinc species to form the globules in a coiled state under hydrothermal conditions. These Zn(II)-PEG 300 globules act as soft template for the growth of HZMNs, and the possible growth mechanism is proposed. The room-temperature photoluminescence (PL) spectrum shows red emission around 612 nm with a full width at half-maximum (fwhm) only about 13 nm.

Careful measurement of first hyperpolarizability spectrum by hyper-Rayleigh scattering (HRS)

NASA Astrophysics Data System (ADS)

Zhu, Jing; Lu, Changgui; Cui, Yiping

2008-01-01

The first hyperpolarizability (β) spectrum of an azobenzene derivative around its two-photon resonance region is detected carefully by hyper-Rayleigh scattering. The present work uses a fluorescence spectrometer (Edinburgh instruments, F900) as the detector instead of interference filter and photoelectric multiplier tube (PMT). For each wavelength, HRS emission spectrum accompanied with two-photon fluorescence (TPF) is carefully detected by changing the detection wavelength around half of the incident wavelength. Full width to half maximum (FWHM) of the spectrum is about 0.4nm, which is similar to that of the laser. When the incident wavelength moves into the two-photon resonance region, TPF signal increases quickly and should be eliminated. In order to receive accurate β spectrum, the data detected by the oscillograph should be made some emendations, such as TPF, incident energy, absorption and pulse width. Compared with the β spectrum detected in previous works, the spectrum received in this work presents a clearer profile. The β spectrum exhibits a similar profile as its UV-visible spectrum just with blue-shift of wavelength. It could be explained that the electronic vibration structure in two-photon progress is different from that in one-photon progress, while the broadening mechanism may be similar, considering the resonant two-state model (RTSM).

Sensors and devices containing ultra-small nanowire arrays

DOEpatents

Xiao, Zhili

2014-09-23

A network of nanowires may be used for a sensor. The nanowires are metallic, each nanowire has a thickness of at most 20 nm, and each nanowire has a width of at most 20 nm. The sensor may include nanowires comprising Pd, and the sensor may sense a change in hydrogen concentration from 0 to 100%. A device may include the hydrogen sensor, such as a vehicle, a fuel cell, a hydrogen storage tank, a facility for manufacturing steel, or a facility for refining petroleum products.

Sensors and devices containing ultra-small nanowire arrays

DOEpatents

Xiao, Zhili

2017-04-11

A network of nanowires may be used for a sensor. The nanowires are metallic, each nanowire has a thickness of at most 20 nm, and each nanowire has a width of at most 20 nm. The sensor may include nanowires comprising Pd, and the sensor may sense a change in hydrogen concentration from 0 to 100%. A device may include the hydrogen sensor, such as a vehicle, a fuel cell, a hydrogen storage tank, a facility for manufacturing steel, or a facility for refining petroleum products.

Effects of the ZnO layer on the structure and white light emission properties of a ZnS:Mn/GaN nanocomposite system.

PubMed

Wang, Cai-Feng; Hu, Bo

2017-10-01

ZnO films were inserted between the ZnS:Mn films and GaN substrates by pulsed laser deposition (PLD). The structure, morphology, and optical properties of the ZnS:Mn/ZnO/GaN nanocomposite systems have been investigated. X-ray diffraction results show that there are three diffraction peaks located at 28.4°, 34.4°, and 34.1°, which correspond to the β-ZnS(111), ZnO(002), and GaN(002) planes, respectively. Due to the insertion of ZnO films, the diffraction peak intensity of ZnS:Mn in ZnS:Mn/ZnO/GaN is stronger than that of ZnS:Mn in ZnS:Mn/GaN, and the full width at half-maximum is smaller. Though the transmittance of ZnS:Mn/ZnO films is slightly lower than that of ZnS:Mn films, the transmittance is still higher than 80%. Compared with ZnS:Mn/GaN, an ultraviolet (UV) emission at 387 nm (originated from the near-band emission of ZnO) and a green light emission at about 520 nm appeared in the photoluminescence (PL) spectra of ZnS:Mn/ZnO/GaN, in addition to the blue emission at 435 nm and the orange-red emission at 580 nm. The emission at 520 nm may be related to the deep-level emission from ZnO and the interface of ZnS:Mn/ZnO. The PL spectrum of ZnS:Mn/ZnO/GaN covers the visible region from the blue light to the red light (400-700 nm), and its color coordinate and color temperature are (0.3103,0.3063) and 6869 K, respectively, presenting strong white light emission.

Technology for detecting spectral radiance by a snapshot multi-imaging spectroradiometer

NASA Astrophysics Data System (ADS)

Zuber, Ralf; Stührmann, Ansgar; Gugg-Helminger, Anton; Seckmeyer, Gunther

2017-12-01

Technologies to determine spectral sky radiance distributions have evolved in recent years and have enabled new applications in remote sensing, for sky radiance measurements, in biological/diagnostic applications and luminance measurements. Most classical spectral imaging radiance technologies are based on mechanical and/or spectral scans. However, these methods require scanning time in which the spectral radiance distribution might change. To overcome this limitation, different so-called snapshot spectral imaging technologies have been developed that enable spectral and spatial non-scanning measurements. We present a new setup based on a facet mirror that is already used in imaging slicing spectrometers. By duplicating the input image instead of slicing it and using a specially designed entrance slit, we are able to select nearly 200 (14 × 14) channels within the field of view (FOV) for detecting spectral radiance in different directions. In addition, a megapixel image of the FOV is captured by an additional RGB camera. This image can be mapped onto the snapshot spectral image. In this paper, the mechanical setup, technical design considerations and first measurement results of a prototype are presented. For a proof of concept, the device is radiometrically calibrated and a 10 mm × 10 mm test pattern measured within a spectral range of 380 nm-800 nm with an optical bandwidth of 10 nm (full width at half maximum or FWHM). To show its potential in the UV spectral region, zenith sky radiance measurements in the UV of a clear sky were performed. Hence, the prototype was equipped with an entrance optic with a FOV of 0.5° and modified to obtain a radiometrically calibrated spectral range of 280 nm-470 nm with a FWHM of 3 nm. The measurement results have been compared to modeled data processed by UVSPEC, which showed deviations of less than 30%. This is far from being ideal, but an acceptable result with respect to available state-of-the-art intercomparisons.

Vacuum ultraviolet molecular nitrogen photoabsorption cross sections for planetary atmospheric transmission models

NASA Astrophysics Data System (ADS)

Stark, G.; Smith, P. L.; Yoshino, K.; Rufus, J.; Huber, K. P.

2001-11-01

The analyses of VUV occultation measurements of the N2-rich atmospheres of Titan and Triton are hampered by the lack of fundamental spectroscopic data for N2. In particular, there is a need for reliable photoabsorption f-values and line widths for the ~ 100 electronic bands of N2 in the 80 to 100 nm wavelength region. As part of our continuing program of laboratory measurements and analyses of the N2 VUV absorption spectrum, we present the results of new measurements of individual line strengths and widths in selected bands. These results indicate that within a number of individual bands there are significant departures from the predicted line strength distributions based on isolated band models. New line width measurements in the 95 to 100 nm region are also presented and compared to other values found in the literature. We have continued to compile on-line molecular spectroscopic atlas based on our N2 laboratory data: http://cfa-www.harvard.edu/amdata/ampdata/N2ARCHIVE/n2home.html. The archive includes published and unpublished 14N2, 14N15N, and 15N2 line lists and spectroscopic identifications, excited state energy levels, band and line f-values, a summary of published band f-value and line width measurements, and a cross-referenced summary of the relevant N2 literature. The listings are searchable by wavelength interval or band identification and are suitable for down-loading in a convenient format. We gratefully acknowledge funding support from NASA grant NAG5-9059 and the Smithsonian Institution Atherton-Seidel grant program.

Bias Dependence of Radiation-Induced Narrow-Width Channel Effects in 65nm NMOSFETs

NASA Astrophysics Data System (ADS)

Zheng, Qi-Wen; Cui, Jiang-Wei; Wei, Ying; Yu, Xue-Feng; Lu, Wu; Ren, Diyuan; Guo, Qi

2018-04-01

Not Available Supported by the National Natural Science Foundation of China under Grant Nos 11605282, 11505282 and U1532261, and the West Light Foundation of the Chinese Academy of Sciences under Grant No 2015-XBQN-B-15.

Silicon Mach-Zehnder interferometer racetrack microring for sensing

NASA Astrophysics Data System (ADS)

Xiong, Yule; Ye, Winnie N.

2014-03-01

SOI-based microring resonators (MRRs) have attracted extensive attentions as ultra-compact sensors. Recently, a new structure design combining a ring and a Mach-Zehnder interferometer (MZI) was proposed as sensors for biomedical applications, and as modulators for communications applications. In this design, the MZI uses two identical couplers, where one arm is formed by connecting the access waveguide of the couplers, while the other arm is part of the microring. Such a device may have only one major resonance with a high extinction ratio in a very broad wavelength span (quasi-free spectral range, quasi-FSR), which offers a very large measurement range for sensing applications. 2×2 multimode interference (MMI) couplers are used to couple the microring and the bus waveguides as MMI couplers have broader wavelength responses. We present the first experimental demonstration of the MMI-coupled MZI racetrack microrings for sensing applications. Two types of MMI-coupled MZI racetrack microrings are discussed: one with wire waveguides, and the other using slotted waveguides. For the MZI racetrack microring using wire waveguides, we achieve a quasi-FSR of 34.3 nm near the wavelength of 1520 nm. The corresponding major resonance of the MZI racetrack microring demonstrates a high extinction ratio of ~22.4 dB with a full-width-half-maximum (FWHM) of 1.94 nm, and a quality factor Q of ~800. On the other hand, the quasi-FSR of the MZI racetrack microring with slot waveguides is 23.2 nm near the wavelength of 1540 nm; and the extinction ratio of the major resonance is ~24.5 dB with λFWHM=0.82 nm and Q=~1,900. To demonstrate the uses for sensing applications, we measure the resonance shifts corresponding to the concentration change of the ambient aqueous solutions of sucrose. DI water is used as the reference for calibration to avoid any other variations, e.g. temperature change. Experiments show that the sensitivities of the MZI racetrack microring sensors with wire and slot waveguides are 101.7 nm/RIU and 166.7 nm/RIU, respectively.

Broadband transverse magnetic pass polarizer with low insertion loss based on silicon nitride waveguide

NASA Astrophysics Data System (ADS)

Sharma, Tarun Kumar; Ranganath, Praveen; Nambiar, Siddharth; Selvaraja, Shankar Kumar

2018-03-01

A horizontally asymmetric transverse magnetic (TM) pass polarizer is presented. The device passes only TM mode and rejects transverse electric (TE) mode. The proposed device has an asymmetricity in the horizontal direction comprising a direction coupler region with a silicon waveguide, silicon nitride waveguide, and an air gap, all residing on silica. Between three equal width Si waveguides, we have one region filled with air and the other with SiN with unequal optimized widths. The device with its optimal dimensions yields an extremely low insertion loss (IL) of 0.16 dB for TM→TM, while TE is rejected by an IL of >48 dB. The proposed polarizer is operated between C&L bands with a high extinction ratio and broadband width of about 110 nm.

Dynamics of short-pulse generation via spectral filtering from intensely excited gain-switched 1.55-μm distributed-feedback laser diodes.

PubMed

Chen, Shaoqiang; Yoshita, Masahiro; Sato, Aya; Ito, Takashi; Akiyama, Hidefumi; Yokoyama, Hiroyuki

2013-05-06

Picosecond-pulse-generation dynamics and pulse-width limiting factors via spectral filtering from intensely pulse-excited gain-switched 1.55-μm distributed-feedback laser diodes were studied. The spectral and temporal characteristics of the spectrally filtered pulses indicated that the short-wavelength component stems from the initial part of the gain-switched main pulse and has a nearly linear down-chirp of 5.2 ps/nm, whereas long-wavelength components include chirped pulse-lasing components and steady-state-lasing components. Rate-equation calculations with a model of linear change in refractive index with carrier density explained the major features of the experimental results. The analysis of the expected pulse widths with optimum spectral widths was also consistent with the experimental data.

Width-Tuned Magnetic Order Oscillation on Zigzag Edges of Honeycomb Nanoribbons.

PubMed

Chen, Wen-Chao; Zhou, Yuan; Yu, Shun-Li; Yin, Wei-Guo; Gong, Chang-De

2017-07-12

Quantum confinement and interference often generate exotic properties in nanostructures. One recent highlight is the experimental indication of a magnetic phase transition in zigzag-edged graphene nanoribbons at the critical ribbon width of about 7 nm [ Magda , G. Z. et al. Nature 2014 , 514 , 608 ]. Here we show theoretically that with further increase in the ribbon width, the magnetic correlation of the two edges can exhibit an intriguing oscillatory behavior between antiferromagnetic and ferromagnetic, driven by acquiring the positive coherence between the two edges to lower the free energy. The oscillation effect is readily tunable in applied magnetic fields. These novel properties suggest new experimental manifestation of the edge magnetic orders in graphene nanoribbons and enhance the hopes of graphene-like spintronic nanodevices functioning at room temperature.

Two-body decays of gluino at full one-loop level in the quark-flavour violating MSSM.

PubMed

Eberl, Helmut; Ginina, Elena; Hidaka, Keisho

2017-01-01

We study the two-body decays of the gluino at full one-loop level in the Minimal Supersymmetric Standard Model with quark-flavour violation (QFV) in the squark sector. The renormalisation is done in the [Formula: see text] scheme. The gluon and photon radiations are included by adding the corresponding three-body decay widths. We discuss the dependence of the gluino decay widths on the QFV parameters. The main dependence stems from the [Formula: see text]-[Formula: see text] mixing in the decays to up-type squarks, and from the [Formula: see text]-[Formula: see text] mixing in the decays to down-type squarks due to the strong constraints from B-physics on the other quark-flavour-mixing parameters. The full one-loop corrections to the gluino decay widths are mostly negative and of the order of about -10%. The QFV part stays small in the total width but can vary up to -8% for the decay width into the lightest [Formula: see text] squark. For the corresponding branching ratio the effect is somehow washed out by at least a factor of two. The electroweak corrections can be as large as 35% of the SUSY QCD corrections.

EUV lithography for 30nm half pitch and beyond: exploring resolution, sensitivity, and LWR tradeoffs

NASA Astrophysics Data System (ADS)

Putna, E. Steve; Younkin, Todd R.; Chandhok, Manish; Frasure, Kent

2009-03-01

The International Technology Roadmap for Semiconductors (ITRS) denotes Extreme Ultraviolet (EUV) lithography as a leading technology option for realizing the 32nm half-pitch node and beyond. Readiness of EUV materials is currently one high risk area according to assessments made at the 2008 EUVL Symposium. The main development issue regarding EUV resist has been how to simultaneously achieve high sensitivity, high resolution, and low line width roughness (LWR). This paper describes the strategy and current status of EUV resist development at Intel Corporation. Data is presented utilizing Intel's Micro-Exposure Tool (MET) examining the feasibility of establishing a resist process that simultaneously exhibits <=30nm half-pitch (HP) L/S resolution at <=10mJ/cm2 with <=4nm LWR.

EUV lithography for 22nm half pitch and beyond: exploring resolution, LWR, and sensitivity tradeoffs

NASA Astrophysics Data System (ADS)

Putna, E. Steve; Younkin, Todd R.; Caudillo, Roman; Chandhok, Manish

2010-04-01

The International Technology Roadmap for Semiconductors (ITRS) denotes Extreme Ultraviolet (EUV) lithography as a leading technology option for realizing the 22nm half pitch node and beyond. Readiness of EUV materials is currently one high risk area according to recent assessments made at the 2009 EUVL Symposium. The main development issue regarding EUV resist has been how to simultaneously achieve high sensitivity, high resolution, and low line width roughness (LWR). This paper describes the strategy and current status of EUV resist development at Intel Corporation. Data collected utilizing Intel's Micro-Exposure Tool (MET) is presented in order to examine the feasibility of establishing a resist process that simultaneously exhibits <=22nm half-pitch (HP) L/S resolution at <= 12.5mJ/cm2 with <= 4nm LWR.

The characteristics of Kerr-lens mode-locked self-Raman Nd:YVO4 1176 nm laser

NASA Astrophysics Data System (ADS)

Li, Zuohan; Peng, Jiying; Yao, Jianquan; Han, Ming

2017-03-01

In this paper we report on a compact and feasible dual-concave cavity CW Kerr-lens mode-locked self-Raman Nd:YVO4 laser. A self-starting diode-pumped picosecond Nd:YVO4 1176 nm laser is demonstrated without any additional components, where the stimulated Stokes Raman scattering and Kerr-lens-induced mode locking are operated in the same crystal. With an incident pump power of 12 W, the average output power at 1176 nm is up to 643 mW. Meanwhile, the repetition rate and the pulse width of the fundamental laser are measured to be 1.53 GHz and 8.6 ps, respectively. In addition, the yellow laser output at 588 nm is realized by frequency doubling with a LiB3O5 crystal.

Spatial distribution of defect luminescence in GaN nanowires.

PubMed

Li, Qiming; Wang, George T

2010-05-12

The spatial distribution of defect-related and band-edge luminescence from GaN nanowires grown by metal-organic chemical vapor deposition was studied by spatially resolved cathodoluminescence imaging and spectroscopy. A surface layer exhibiting strong yellow luminescence (YL) near 566 nm in the nanowires was revealed, compared to weak YL in the bulk. In contrast, other defect-related luminescence near 428 nm (blue luminescence) and 734 nm (red luminescence), in addition to band-edge luminescence (BEL) at 366 nm, were observed in the bulk of the nanowires but were largely absent at the surface. As the nanowire width approaches a critical dimension, the surface YL layer completely quenches the BEL. The surface YL is attributed to the diffusion and piling up of mobile point defects, likely isolated gallium vacancies, at the surface during growth.

Passively Q-switched Nd:YAG/Cr(4+):YAG bonded crystal microchip laser operating at 1112  nm and its application for second-harmonic generation.

PubMed

Fu, S G; Ouyang, X Y; Liu, X J

2015-10-10

A passively Q-switched Nd:YAG/Cr⁴⁺:YAG microchip laser operating at 1112 nm is demonstrated. Under a pump power of 5.5 W, a maximum average output power of 623 mW was obtained with T=6% output coupler, corresponding to an optical-to-optical conversion efficiency of 11.3% and a slope efficiency of 19.5%. The minimum pulse width was 2.8 ns, the pulse energy and peak power were 39.3 μJ and 14 kW, respectively. Additionally, based on the 1112 nm laser, a 230 mW 556 nm green-yellow laser was achieved within an LBO crystal.

Sensitivity enhancement of the high-resolution xMT multi-trigger resist for EUV lithography

NASA Astrophysics Data System (ADS)

Popescu, Carmen; Frommhold, Andreas; McClelland, Alexandra; Roth, John; Ekinci, Yasin; Robinson, Alex P. G.

2017-03-01

Irresistible Materials is developing a new molecular resist system that demonstrates high-resolution capability based on the multi-trigger concept. A series of studies such as resist purification, developer choice,and enhanced resist crosslinking were conducted in order to optimize the performance of this material. The optimized conditions allowed patterning 14 nm half-pitch (hp) lines with a line width roughness (LWR) of 2.7 nm at the XIL beamline of the Swiss Light source. Furthermore it was possible to pattern 14 nm hp features with dose of 14 mJ/cm2 with an LWR of 4.9 nm. We have also begun to investigate the addition of high-Z additives to EUV photoresist as a means to increase sensitivity and modify secondary electron blur.

Investigation of the Performance of an Ultralow-Dark-Count Superconducting Nanowire Single-Photon Detector

NASA Astrophysics Data System (ADS)

Subashchandran, Shanthi; Okamoto, Ryo; Zhang, Labao; Tanaka, Akira; Okano, Masayuki; Kang, Lin; Chen, Jian; Wu, Peiheng; Takeuchi, Shigeki

2013-10-01

The realization of an ultralow-dark-count rate (DCR) along with the conservation of high detection efficiency (DE) is critical for many applications using single photon detectors in quantum information technologies, material sciences, and biological sensing. For this purpose, a fiber-coupled superconducting nanowire single-photon detector (SNSPD) with a meander-type niobium nitride nanowire (width: 50 nm) is studied. Precise measurements of the bias current dependence of DE are carried out for a wide spectral range (from 500 to 1650 nm in steps of 50 nm) using a white light source and a laser line Bragg tunable band-pass filter. An ultralow DCR (0.0015 cps) and high DE (32%) are simultaneously achieved by the SNSPD at a wavelength of 500 nm.

Morphological instability of GaAs (7 1 1)A: A transition between (1 0 0) and (5 1 1) terraces

NASA Astrophysics Data System (ADS)

Yazdanpanah, V. R.; Wang, Zh. M.; Salamo, G. J.

2005-06-01

We report on the use of reflection high-energy electron diffraction (RHEED) and scanning tunneling microscopy (STM) study that indicates that the GaAs (7 1 1)A is right at the transition between vicinal GaAs (1 0 0) and vicinal GaAs (5 1 1)A surfaces and that a variation of the As overpressure switches the surface morphology between the two vicinal surfaces. The steps on the vicinal (1 0 0) surface have a width of 1.5 nm creating a staircase surface with excellent possibilities for growth of quantum wells. As-rich conditions can be described by vicinal (5 1 1)A surfaces with a width of 3.5 nm. This surface could find applications as a template for quantum wire growth. The observation suggests that the transition between these two morphologies is understandable based on the increase in surface energy of a vicinal (1 0 0) surface as the step separation approaches the dimer reconstructed separation.

Ge-cap quantum-well bulk FinFET for 5 nm node CMOS integration

NASA Astrophysics Data System (ADS)

Dwi Kurniawan, Erry; Peng, Kang-Hui; Yang, Shang-Yi; Yang, Yi-Yun; Thirunavukkarasu, Vasanthan; Lin, Yu-Hsien; Wu, Yung-Chun

2018-04-01

We propose the use of Ge-cap quantum-well (QW) bulk FinFET for 5 nm CMOS integration, which is a Si channel wrapped with Ge around three sides of the fin channel. The simulation results show that the Ge-cap FinFET structure demonstrates better performance than pure Si, pure Ge, and Si-cap FinFET structures. By optimizing Si fin width and Ge-cap thickness, the on-state current of nFET and pFET can also be symmetric without changing the total fin width (F Wp = F Wn). The electrons in Ge-cap nFinFET concentrate in the Si channel because of QWs formed in the lowest conduction band of the Ge and Si heterostructure, while the holes in Ge-cap pFinFET prefer to stay in Ge surfaces owing to QWs formed in the Ge valence band. The physics studies of this device have made the design rules relevant for the application of the CMOS inverter and static random access memory (SRAM) application technology.

Direct oriented growth of armchair graphene nanoribbons on germanium

PubMed Central

Jacobberger, Robert M.; Kiraly, Brian; Fortin-Deschenes, Matthieu; Levesque, Pierre L.; McElhinny, Kyle M.; Brady, Gerald J.; Rojas Delgado, Richard; Singha Roy, Susmit; Mannix, Andrew; Lagally, Max G.; Evans, Paul G.; Desjardins, Patrick; Martel, Richard; Hersam, Mark C.; Guisinger, Nathan P.; Arnold, Michael S.

2015-01-01

Graphene can be transformed from a semimetal into a semiconductor if it is confined into nanoribbons narrower than 10 nm with controlled crystallographic orientation and well-defined armchair edges. However, the scalable synthesis of nanoribbons with this precision directly on insulating or semiconducting substrates has not been possible. Here we demonstrate the synthesis of graphene nanoribbons on Ge(001) via chemical vapour deposition. The nanoribbons are self-aligning 3° from the Ge〈110〉 directions, are self-defining with predominantly smooth armchair edges, and have tunable width to <10 nm and aspect ratio to >70. In order to realize highly anisotropic ribbons, it is critical to operate in a regime in which the growth rate in the width direction is especially slow, <5 nm h−1. This directional and anisotropic growth enables nanoribbon fabrication directly on conventional semiconductor wafer platforms and, therefore, promises to allow the integration of nanoribbons into future hybrid integrated circuits. PMID:26258594

Intense deep-blue electroluminescence from ITO/Y₂O₃/Ag structure.

PubMed

Yin, Xue; Wang, Shenwei; Li, Ling; Mu, Guangyao; Tang, Ying; Duan, Wubiao; Yi, Lixin

2015-07-13

ITO/Y₂O₃/Ag devices were fabricated using Y₂O₃ films as insulator. Four intense and sharp lines with half-peak width of 4 nm were observed for the 293.78 nm InI, 316.10 nm InI, 444.82 nm InII and 403.07 nm InIII transitions. Luminescence mechanism was illustrated by cross-section of the devices based on the analysis of surface morphology. Under the action of strong electric field, the loss of K-shell electrons led to the occurrence of characteristic radiation of indium ions. In addition, the device with turn-on voltage of 10V demonstrates typical I-V diode characteristics. Moreover, Y₂O₃/In₂O₃ multiple films as the insulation layer instead of single Y₂O₃ films was found to improve the device performance with excellent CIE (x, y) coordinates (0.16, 0.03).

Soft x-ray microscope with zone plates at UVSOR

NASA Astrophysics Data System (ADS)

Watanabe, Norio; Shimanuki, Yoshio; Taniguchi, Mieko; Kihara, Hiroshi

1993-01-01

A soft x-ray microscope with zone plates was set up at UVSOR (Okazaki, Japan). A 0.41 micrometers line and space pattern was clearly distinguished using an objective zone plate with the outermost zone width of 0.41 micrometers . Modulation transfer functions were measured at wavelengths of 3.1 nm and 5.4 nm, and compared with theoretical calculations. Considering the resolution of a microchannel plate used as a detector, the agreement is fairly good. With this microscope, some biological specimens such as diatoms, spicule of trepang, crab and rabbit muscles, human blood cells, human chromosomes, and magnetotactic bacterium were observed at 3.1 nm and 5.4 nm. With an environmental chamber (wet cell) using polypropylene foils as windows, wet specimens were observed at a wavelength of 4.6 nm. Images of spicule of trepang, human blood cell, and cultured protoplast of plant cell stained by methyl mercury were observed with good contrast.

Effects of 946-nm thermal shift and broadening on Nd3+:YAG laser performance

NASA Astrophysics Data System (ADS)

Seyed Ebrahim, Pourmand; Ghasem, Rezaei

2015-12-01

Spectroscopic properties of flashlamp pumped Nd3+:YAG laser are studied as a function of temperature in a range from -30 °C to 60 °C. The spectral width and shift of quasi three-level 946.0-nm inter-Stark emission within the respective intermanifold transitions of 4F3/2 → 4I9/2 are investigated. The 946.0-nm line shifts toward the shorter wavelength and broadens. In addition, the threshold power and slope efficiency of the 946.0-nm laser line are quantified with temperature. The lower the temperature, the lower the threshold power is and the higher the slope efficiency of the 946.0-nm laser line is, thus the higher the laser output is. This phenomenon is attributed to the ion-phonon interaction and the thermal population in the ground state. Project supported by Estahban Branch, Islamic Azad University.

Thickness-dependent metal-to-insulator transition in epitaxial VO2 films

NASA Astrophysics Data System (ADS)

Zhi, Bowen; Gao, Guanyin; Tan, Xuelian; Chen, Pingfan; Wang, Lingfei; Jin, Shaowei; Wu, Wenbin

2014-12-01

The metal-to-insulator transition (MIT) of VO2 films with a thickness of 3-100 nm on TiO2(001) substrates has been investigated. When varying the film thickness from 10 to 100 nm, the MIT temperature was first kept at 290 K in the range of 10-14 nm, and then increased with thickness increasing due to the strain relaxation. The origin of the suppressed transition in VO2 films thinner than 6 nm was also investigated. When prolonging the in situ annealing time, the sharpness, amplitude and width of the transition for 4 nm thick films were all increased, suggesting improved crystallinity rather than Ti diffusion from the substrates. In addition, the MIT was suppressed when the VO2 films were covered by a TiO2 layer, indicating that the interface effect via the confinement of the dimerization of the V atoms should be the main reason.

Fabrication of Fiber-Optic Tilted Bragg Grating Filter in 40 nm Range with A Single Phase Mask

NASA Technical Reports Server (NTRS)

Grant, Joseph; Wang, Y.; Sharma, A.; Burdine, Robert V. (Technical Monitor)

2002-01-01

Fiber-optic Bragg grating filters are fabricated with a range of Bragg wavelength between 1296 and 1336 nm, using a single phase mask. 30 mW of continuous-wave light at 244 nm is used from a frequency-doubled argon-ion laser having an intracavity etalon. Gratings are fabricated by tilting the photosensitive fiber with respect to the phase mask up to an angle of 15 degrees. The variation of Bragg wavelength with the fiber-tilt is explained with a simple formula. High spatial coherence of 244 nm light makes it possible to displace the fiber as much as 6 mm in front of the phase mask and tilt the fiber by as much as 15 degrees. This results in nearly constant band-width and near 100% reflectively for all gratings throughout the 40 nm range.

Fabrication of high aspect ratio nanogrid transparent electrodes via capillary assembly of Ag nanoparticles

NASA Astrophysics Data System (ADS)

Kang, Juhoon; Park, Chang-Goo; Lee, Su-Han; Cho, Changsoon; Choi, Dae-Geun; Lee, Jung-Yong

2016-05-01

In this report, we describe the fabrication of periodic Ag nanogrid electrodes by capillary assembly of silver nanoparticles (AgNPs) along patterned nanogrid templates. By assembling the AgNPs into these high-aspect-ratio nanogrid patterns, we can obtain high-aspect-ratio nanogratings, which can overcome the inherent trade-off between the optical transmittance and the sheet resistance of transparent electrodes. The junction resistance between the AgNPs is effectively reduced by photochemical welding and post-annealing. The fabricated high-aspect-ratio nanogrid structure with a line width of 150 nm and a height of 450 nm has a sheet resistance of 15.2 Ω sq-1 and an optical transmittance of 85.4%.In this report, we describe the fabrication of periodic Ag nanogrid electrodes by capillary assembly of silver nanoparticles (AgNPs) along patterned nanogrid templates. By assembling the AgNPs into these high-aspect-ratio nanogrid patterns, we can obtain high-aspect-ratio nanogratings, which can overcome the inherent trade-off between the optical transmittance and the sheet resistance of transparent electrodes. The junction resistance between the AgNPs is effectively reduced by photochemical welding and post-annealing. The fabricated high-aspect-ratio nanogrid structure with a line width of 150 nm and a height of 450 nm has a sheet resistance of 15.2 Ω sq-1 and an optical transmittance of 85.4%. Electronic supplementary information (ESI) available. See DOI: 10.1039/c6nr01896c

Nanotopographic Substrates of Poly (Methyl Methacrylate) Do Not Strongly Influence the Osteogenic Phenotype of Mesenchymal Stem Cells In Vitro

PubMed Central

Janson, Isaac A.; Kong, Yen P.; Putnam, Andrew J.

2014-01-01

The chemical, mechanical, and topographical features of the extracellular matrix (ECM) have all been documented to influence cell adhesion, gene expression, migration, proliferation, and differentiation. Topography plays a key role in the architecture and functionality of various tissues in vivo, thus raising the possibility that topographic cues can be instructive when incorporated into biomaterials for regenerative applications. In the literature, there are discrepancies regarding the potential roles of nanotopography to enhance the osteogenic phenotype of mesenchymal stem cells (MSC). In this study, we used thin film substrates of poly(methyl methacrylate) (PMMA) with nanoscale gratings to investigate the influence of nanotopography on the osteogenic phenotype of MSCs, focusing in particular on their ability to produce mineral similar to native bone. Topography influenced focal adhesion size and MSC alignment, and enhanced MSC proliferation after 14 days of culture. However, the osteogenic phenotype was minimally influenced by surface topography. Specifically, alkaline phosphatase (ALP) expression was not increased on nanotopographic films, nor was calcium deposition improved after 21 days in culture. Ca: P ratios were similar to native mouse bone on films with gratings of 415 nm width and 200 nm depth (G415) and 303 nm width and 190 nm depth (G303). Notably, all surfaces had Ca∶P ratios significantly lower than G415 films. Collectively, these data suggest that, PMMA films with nanogratings are poor drivers of an osteogenic phenotype. PMID:24594848

Cellulose nanofibers isolated by TEMPO-oxidation and aqueous counter collision methods.

PubMed

Van Hai, Le; Zhai, Lindong; Kim, Hyun Chan; Kim, Jung Woong; Choi, Eun Sik; Kim, Jaehwan

2018-07-01

In this research, cellulose nanofiber (CNF) was isolated by the combination of chemical 2,2,6,6-tetramethylpiperidine-1-oxylradical (TEMPO)-oxidation and physical aqueous counter collision (ACC) methods The combination of TEMPO-oxidation and ACC is an efficient method to isolate CNFs by reducing chemical usage in TEMPO-oxidation and saving energy in ACC along with controlling the size of CNFs. Two cellulose sources, hardwood bleached kraft pulp (HW) and softwood bleached kraft pulp (SW), were used for the CNF isolation with different TEMPO oxidation time and a defined number of ACC pass. The CNF properties were investigated and compared in term of morphology, crystallinity index, transparency and birefringence. The width of the isolated CNFs from HW is in the range of 15.1 nm-17.5 nm, and that of the SW CNFs is between 18.4 nm and 22 nm depending on the TEMPO oxidation time. This difference is due to the fact that SW is less oxidized than HW under the same chemical dosage, which results in larger width of SW-CNFs than HW-CNFs. The HW-CNF treated with TEMPO for over 2 h and isolated using ACC with 5 pass offers almost 90% transparency. Birefringence of CNFs exhibits that HW-CNFs show better birefringence phenomenon than SW-CNFs. The combination of TEMPO-oxidation and ACC methods is useful for isolating CNFs with its size control. Copyright © 2018 Elsevier Ltd. All rights reserved.

Electrochemical synthesis of multi-armed CuO nanoparticles and their remarkable bactericidal potential against waterborne bacteria

NASA Astrophysics Data System (ADS)

Pandey, Pratibha; Merwyn, S.; Agarwal, G. S.; Tripathi, B. K.; Pant, S. C.

2012-01-01

Copper (II) oxide multi-armed nanoparticles composed of 500-1000 nm long radiating nanospicules with 100-200 nm width near the base and 50-100 nm width at the tapered ends and 25 nm thickness were synthesized by electrochemical deposition in the presence of an oxidant followed by calcination at 150 °C. The nanoparticles were characterized using SEM/EDX for morphology and composition, Raman spectroscopy for compound identification, and broth culture method for antibacterial efficacy. The CuO nanoparticles have shown remarkable bactericidal efficacy against Gram-positive and -negative waterborne disease causing bacteria like Escherichia coli, Salmonella typhi, s taphylococcus aureus and Bacillus subtilis. E. coli has been chosen as representative species for waterborne disease causing bacteria. In antibacterial tests 500 μg/mL nano CuO killed 3 × 108 CFU/mL E. coli bacteria within 4 h of exposure. Moreover, 8.3 × 106 CFU/mL E. coli were killed by 100 and 10 μg/mL nano CuO within 15 min and 4 h of exposure, respectively. Antibacterial activity of nano CuO has been found many-fold compared with commercial bulk CuO. The fate of nanoparticles after antibacterial test has also been studied. The synthesized CuO nanoparticles are expected to have potential antibacterial applications in water purification and in paints and coatings used on frequently touched surfaces and fabrics in hospital settings.

Effect of Channel Thickness, Annealing Temperature and Channel Length on Nanoscale Ga2O3-In2O3-ZnO Thin Film Transistor Performance.

PubMed

Kumaresan, Yogeenth; Pak, Yusin; Lim, Namsoo; Lee, Ryeri; Song, Hui; Kim, Tae Heon; Choi, Boran; Jung, Gun Young

2016-06-01

We demonstrated the effect of active layer (channel) thickness and annealing temperature on the electrical performances of Ga2O3-In2O3-ZnO (GIZO) thin film transistor (TFT) having nanoscale channel width (W/L: 500 nm/100 μm). We found that the electron carrier concentration of the channel was decreased significantly with increasing the annealing temperature (100 degrees C to 300 degrees C). Accordingly, the threshold voltage (V(T)) was shifted towards positive voltage (-12.2 V to 10.8 V). In case of channel thickness, the V(T) was shifted towards negative voltage with increasing the channel thickness. The device with channel thickness of 90 nm annealed at 200 degrees C revealed the best device performances in terms of mobility (10.86 cm2/Vs) and V(T) (0.8 V). The effect of channel length was also studied, in which the channel width, thickness and annealing temperature were kept constant such as 500 nm, 90 nm and 200 degrees C, respectively. The channel length influenced the on-current level significantly with small variation of V(T), resulting in lower value of on/off current ratio with increasing the channel length. The device with channel length of 0.5 μm showed enhanced on/off current ratio of 10(6) with minimum V(T) of 0.26 V.

Pore diameter effects on phase behavior of a gas condensate in graphitic one-and two-dimensional nanopores.

PubMed

Welch, William R W; Piri, Mohammad

2016-01-01

Molecular dynamics (MD) simulations were performed on a hydrocarbon mixture representing a typical gas condensate composed mostly of methane and other small molecules with small fractions of heavier hydrocarbons, representative of mixtures found in tight shale reservoirs. The fluid was examined both in bulk and confined to graphitic nano-scale slits and pores. Numerous widths and diameters of slits and pores respectively were examined under variable pressures at 300 K in order to find conditions in which the fluid at the center of the apertures would not be affected by capillary condensation due to the oil-wet walls. For the bulk fluid, retrograde phase behavior was verified by liquid volumes obtained from Voronoi tessellations. In cases of both one and two-dimensional confinement, for the smallest apertures, heavy molecules aggregated inside the pore space and compression of the gas outside the solid structure lead to decreases in density of the confined fluid. Normal density/pressure relationships were observed for slits having gaps of above 3 nm and pores having diameters above 6 nm. At 70 bar, the minimum gap width at which the fluid could pass through the center of slits without condensation effects was predicted to be 6 nm and the corresponding diameter in pores was predicted to be 8 nm. The models suggest that in nanoscale networks involving pores smaller than these limiting dimensions, capillary condensation should significantly impede transmission of natural gases with similar composition.

Controller for a High-Power, Brushless dc Motor

NASA Technical Reports Server (NTRS)

Fleming, David J.; Makdad, Terence A.

1987-01-01

Driving and braking torques controllable. Control circuit operates 7-kW, 45-lb-ft (61-N-m), three-phase, brushless dc motor in both motor and generator modes. In motor modes, energy from power source is pulse-width modulated to motor through modified "H-bridge" circuit, in generator mode, energy from motor is pulse-width modulated into bank of load resistors to provide variable braking torques. Circuit provides high-resolution torque control in both directions over wide range of speeds and torques. Tested successfully at bus voltages up to 200 Vdc and currents up to 45 A.

Figures of merit for laser beam quality

NASA Technical Reports Server (NTRS)

Milster, T. D.; Walker, E. P.

1993-01-01

It was shown how full-width at half maximum (FWHM), full-width at 1/e(sup 2) (FW1/e(sup 2)), Strehl ratio, and encircled energy figures of merit vary with different types of aberration and measurement methods. The array sampling method and the slit-scan method are examined in detail. Our irradiance in the exit pupil of the optical system is a simple gaussian. It was found that in general the slit-scan method and the array method do not yield the same result. The width measurements for the central lobe of the diffraction pattern are very insensitive to aberration.

Synthesis of Colloidal Nanocrystal Heterostructures for High-Efficiency Light Emission

NASA Astrophysics Data System (ADS)

Lu, Yifei

Group II-VI semiconductor nanocrystals, particularly those based on ZnCdS(Se), can be synthesized using well established chemical colloidal processes, and have been a subject of extensive research over the past decade. Their optical properties can be easily tuned through size and composition variations, making them very attractive for many optoelectronic applications including light-emitting diodes (LEDs) and solar cells. Incorporation of diverse internal heterostructures provides an additional means for tuning the optical and electronic properties of conventional ZnCdS(Se) nanocrystals. Extensive bandgap and strain engineering may be applied to the resultant nanocrystal heterostructures to achieve desirable properties and enhanced performance. Despite the high scientific and practical interests of this unique class of nanomaterials, limited efforts have been made to explore their synthesis and potential device applications. This thesis focuses on the synthesis, engineering, characterization, and device demonstration of two types of CdSe-based nanocrystal heterostructures: core/multishell quantum dots (QDs) and QD quantum wells (QDQWs). Their optical properties have been tuned by bandgap and strain engineering to achieve efficient photoluminescence (PL) and electroluminescence (EL).Firstly, yellow light-emitting CdSe QDs with a strain-compensated ZnS/ZnCdS bilayer shell were synthesized using the successive ion layer adsorption and reaction technique and the effects of the shell on the luminescent properties were investigated. The core/shell/shell QDs enjoyed the benefits of excellent exciton confinement by the ZnS intermediate shell and strain compensation by the ZnCdS outer shell, and exhibited 40% stronger PL and a smaller peak redshift upon shell growth compared to conventional CdSe/ZnCdS/ZnS core/shell/shell QDs with an intermediate lattice adaptor. CdSe/ZnS/ZnCdS QD-LEDs had a luminance of 558 cd/m2 at 20 mA/cm 2, 28% higher than that of CdSe/ZnCdS/ZnS QD-LEDs. Secondly, CdS/CdSe/ZnS QDQWs were synthesized and their luminescence was tuned in an effort to realize efficient blue light emission from CdSe nanocrystals. CdSe QWs with a well width of 1.05 nm emitted at 467 nm with a spectral full-width-at-half-maximum of ~30 nm. With a 3-monolayer ZnS cladding layer which also acts as a passivating and strain-compensating layer, the QDQWs acquired a ~35% PL quantum yield (QY). Blue and green EL was obtained from QDQW-LEDs with 3-4.5 monolayers (MLs) QWs. It was found that as the well width and peak wavelength decreased, the overall EL was increasingly dominated by defect state emission, suggesting the device performance is mainly limited by poor charge injection into the QDQWs.

Design and analysis of O-S-C triple band wavelength division demultiplexer using cascaded MMI couplers

NASA Astrophysics Data System (ADS)

Chack, Devendra; Kumar, V.; Raghuwanshi, Sanjeev Kumar; Singh, Dev Prakash

2017-01-01

Compact triple O-S-C band wavelength demultiplexer, which consists of series cascaded multimode interference (MMI) couplers has been carried out in this paper. The MMI coupler has been used to drop the wavelengths of 1510 nm and 1550 nm at bar port while the wavelength 1300 nm into the cross port. Then another MMI coupler has been designed to separate the wavelength 1510 nminto one port and wavelength 1550 nm into another port. The triple wavelength demultiplexer function has been performed by choosing a suitable refractive index of the guiding region and geometrical parameters such as the width and length of MMI coupler. Numerical simulation with finite difference beam propagation method (BPM) has been utilized to design and optimize the operation of the proposed triple wavelength demultiplexer. The simulation results show that insertion losses of wavelength O, S and C, bands are 1.884 dB, 1.452 dB and 2.568 dB, respectively, with isolations for each output waveguide ranging from 10 dB to 28.72 dB. The 3-dB bandwidth of insertion loss for 1300 nm, 1510 nm and 1550 nm are 80 nm, 20 nm and 10 nm, respectively.

An improved method for characterizing photoresist lithographic and defectivity performance for sub-20nm node lithography

NASA Astrophysics Data System (ADS)

Amblard, Gilles; Purdy, Sara; Cooper, Ryan; Hockaday, Marjory

2016-03-01

The overall quality and processing capability of lithographic materials are critical for ensuring high device yield and performance at sub-20nm technology nodes in a high volume manufacturing environment. Insufficient process margin and high line width roughness (LWR) cause poor manufacturing control, while high defectivity causes product failures. In this paper, we focus on the most critical layer of a sub-20nm technology node LSI device, and present an improved method for characterizing both lithographic and post-patterning defectivity performance of state-of-the-art immersion photoresists. Multiple formulations from different suppliers were used and compared. Photoresists were tested under various process conditions, and multiple lithographic metrics were investigated (depth of focus, exposure dose latitude, line width roughness, etc.). Results were analyzed and combined using an innovative approach based on advanced software, providing clearer results than previously available. This increased detail enables more accurate performance comparisons among the different photoresists. Post-patterning defectivity was also quantified, with defects reviewed and classified using state-of-the-art inspection tools. Correlations were established between the lithographic and post-patterning defectivity performances for each material, and overall ranking was established among the photoresists, enabling the selection of the best performer for implementation in a high volume manufacturing environment.

Growth process, characterization, and modeling of electronic properties of coupled InAsSbP nanostructures

NASA Astrophysics Data System (ADS)

Marquardt, Oliver; Hickel, Tilmann; Neugebauer, Jörg; Gambaryan, Karen M.; Aroutiounian, Vladimir M.

2011-08-01

Quaternary III-V InAsSbP quantum dots (QDs) have been grown in the form of cooperative InAsSb/InAsP structures using a modified version of the liquid phase epitaxy. High resolution scanning electron microscopy, atomic force microscopy, and Fourier-transform infrared spectrometry were used to investigate these so-called nano-camomiles, mainly consisting of a central InAsSb QD surrounded by six InAsP-QDs, that shall be referred to as leaves in the following. The observed QDs average density ranges from 0.8 to 2 × 109 cm-2, with heights and widths dimensions from 2 to 20 nm and 5 to 45 nm, respectively. The average density of the leaves is equal to (6-10) × 109 cm-2 with dimensions of approx. 5 to 40 nm in width and depth. To achieve a first basic understanding of the electronic properties, we have modeled these novel nanostructures using second-order continuum elasticity theory and an eight-band k .p model to calculate the electronic structure. Our calculations found a clear localization of hole states in the central InAsSb dot. The localization of electron states, however, was found to be weak and might thus be easily influenced by external electric fields or strain.

Effect of scanning speed on continuous wave laser scribing of metal thin films: theory and experiment

NASA Astrophysics Data System (ADS)

Shahbazi, AmirHossein; Koohian, Ata; Madanipour, Khosro

2017-01-01

In this paper continuous wave laser scribing of the metal thin films have been investigated theoretically and experimentally. A formulation is presented based on parameters like beam power, spot size, scanning speed and fluence thresholds. The role of speed on the transient temperature and tracks width is studied numerically. By using two frameworks of pulsed laser ablation of thin films and laser printing on paper, the relation between ablation width and scanning speed has been derived. Furthermore, various speeds of the focused 450 nm continuous laser diode with an elliptical beam spot applied to a 290 nm copper thin film coated on glass, experimentally. The beam power was 150 mW after spatial filtering. By fitting the theoretical formulation to the experimental data, the threshold fluence and energy were obtained to be 13.2 J mm-2 and 414~μ J respectively. An anticipated theoretical parameter named equilibrium~border was verified experimentally. It shows that in the scribing of the 290 nm copper thin film, at a distance where the intensity reaches about 1/e of its maximum value, the absorbed fluence on the surface is equal to zero. Therefore the application of continuous laser in metal thin film ablation has different mechanism from pulsed laser drilling and beam scanning in printers.

Optimized 2D array of thin silicon pillars for efficient antireflective coatings in the visible spectrum

PubMed Central

Proust, Julien; Fehrembach, Anne-Laure; Bedu, Frédéric; Ozerov, Igor; Bonod, Nicolas

2016-01-01

Light reflection occuring at the surface of silicon wafers is drastically diminished by etching square pillars of height 110 nm and width 140 nm separated by a 100 nm gap distance in a square lattice. The design of the nanostructure is optimized to widen the spectral tolerance of the antireflective coatings over the visible spectrum for both fundamental polarizations. Angle and polarized resolved optical measurements report a light reflection remaining under 5% when averaged in the visible spectrum for both polarizations in a wide angular range. Light reflection remains almost insensitive to the light polarization even in oblique incidence. PMID:27109643

High energy 523 nm ND:YLF pulsed slab laser with novel pump beam waveguide design

NASA Astrophysics Data System (ADS)

Yang, Qi; Zhu, Xiaolei; Ma, Jian; Lu, Tingting; Ma, Xiuhua; Chen, Weibiao

2015-11-01

A laser diode pumped Nd:YLF master oscillator power amplifier (MOPA) green laser system with high pulse energy and high stable output is demonstrated. At a repetition rate of 50 Hz, 840 mJ pulse energy, 9.1 ns pulse width of 1047 nm infrared laser emitting is obtained from the MOPA system. The corresponding peak power is 93 MW. Extra-cavity frequency doubling with a LiB3O5 crystal, pulse energy of 520 mJ at 523 nm wavelength is achieved. The frequency conversion efficiency reaches up to 62%. The output pulse energy instability of the laser system is less than 0.6% for one hour.

Sub-30 nm patterning of molecular resists based on crosslinking through tip based oxidation

NASA Astrophysics Data System (ADS)

Lorenzoni, Matteo; Wagner, Daniel; Neuber, Christian; Schmidt, Hans-Werner; Perez-Murano, Francesc

2018-06-01

Oxidation Scanning Probe Lithography (o-SPL) is an established method employed for device patterning at the nanometer scale. It represents a feasible and inexpensive alternative to standard lithographic techniques such as electron beam lithography (EBL) and nanoimprint lithography (NIL). In this work we applied non-contact o-SPL to an engineered class of molecular resists in order to obtain crosslinking by electrochemical driven oxidation. By patterning and developing various resist formulas we were able to obtain a reliable negative tone resist behavior based on local oxidation. Under optimal conditions, directly written patterns can routinely reach sub-30 nm lateral resolution, while the final developed features result wider, approaching 50 nm width.

Radiation enhancement in doped AlGaN-structures upon optical pumping

NASA Astrophysics Data System (ADS)

Bokhan, P. A.; Zhuravlev, K. S.; Zakrevsky, D. E.; Malin, T. V.; Osinnykh, I. V.; Fateev, N. V.

2017-01-01

Spectral characteristics of spontaneous and stimulated luminescence have been studied for molecular beam epitaxy synthesized Al x Ga1- x N/AlN solid solutions with x = 0.5 and 0.74 upon optical pumping by pulse laser radiation with λ = 266 nm. Broadband radiation spectra with a width of 260 THz for Al0.5Ga0.5N and 360 THz for Al0.74Ga0.26N have been obtained. The measured enhancement factors are g ≈ 70 cm-1 for Al0.5Ga0.5N at λ ≈ 528 nm and g ≈ 20 cm-1 for Al0.74Ga0.26N at λ ≈ 468 nm.

Optimization of H2 thermal annealing process for the fabrication of ultra-low loss sub-micron silicon-on-insulator rib waveguides

NASA Astrophysics Data System (ADS)

Bellegarde, Cyril; Pargon, Erwine; Sciancalepore, Corrado; Petit-Etienne, Camille; Lemonnier, Olivier; Ribaud, Karen; Hartmann, Jean-Michel; Lyan, Philippe

2018-02-01

The superior confinement of light provided by the high refractive index contrast in Si/SiO2 waveguides allows the use of sub-micron photonic waveguides. However, when downscaling waveguides to sub-micron dimensions, propagation losses become dominated by sidewall roughness scattering. In a previous study, we have shown that hydrogen annealing after waveguide patterning yielded smooth silicon sidewalls. Our optimized silicon patterning process flow allowed us to reduce the sidewall roughness down to 0.25 nm (1σ) while maintaining rectangular Strip waveguides. As a result, record low optical losses of less than 1 dB/cm were measured at telecom wavelengths for waveguides with dimensions larger than 350 nm. With Rib waveguides, losses are expected to be even lower. However, in this case the Si reflow during the H2 anneal leads to the formation of a foot at the bottom of the structure and to a rounding of its top. A compromise is thus to be found between low losses and conservation of the rectangular shape of the Rib waveguide. This work proposes to investigate the impact of temperature and duration of the H2 anneal on the Rib profile, sidewalls roughness and optical performances. The impact of a Si/SiO2 interface is also studied. The introduction of H2 thermal annealing allows to obtain very low losses of 0.5 dB/cm at 1310 nm wavelength for waveguide dimensions of 300-400 nm, but it comes along an increase of the pattern bottom width of 41%, with a final bottom width of 502 nm.

Active region dimensionality and quantum efficiencies of InGaN LEDs from temperature dependent photoluminescence transients

NASA Astrophysics Data System (ADS)

Can, Nuri; Okur, Serdal; Monavarian, Morteza; Zhang, Fan; Avrutin, Vitaliy; Morkoç, Hadis; Teke, Ali; Özgür, Ümit

2015-03-01

Temperature dependent recombination dynamics in c-plane InGaN light emitting diodes (LEDs) with different well thicknesses, 1.5, 2, and 3 nm, were investigated to determine the active region dimensionality and its effect on the internal quantum efficiencies. It was confirmed for all LEDs that the photoluminescence (PL) transients are governed by radiative recombination at low temperatures while nonradiative recombination dominates at room temperature. At photoexcited carrier densities of 3 - 4.5 x 1016 cm-3 , the room-temperature Shockley-Read-Hall (A) and the bimolecular (B) recombination coefficients (A, B) were deduced to be (9.2x107 s-1, 8.8x10-10 cm3s-1), (8.5x107 s-1, 6.6x10-10 cm3s-1), and (6.5x107 s-1, 1.4x10-10 cm3s-1) for the six period 1.5, 2, and 3 nm well-width LEDs, respectively. From the temperature dependence of the radiative lifetimes, τrad α Tn/2, the dimensionality n of the active region was found to decrease consistently with decreasing well width. The 3 nm wide wells exhibited ~T1.5 dependence, suggesting a three-dimensional nature, whereas the 1.5 nm wells were confirmed to be two-dimensional (~T1) and the 2 nm wells close to being two-dimensional. We demonstrate that a combination of temperature dependent PL and time-resolved PL techniques can be used to evaluate the dimensionality as well as the quantum efficiencies of the LED active regions for a better understanding of the relationship between active-region design and the efficiency limiting processes in InGaN LEDs.

Packaging of wavelength stabilized 976nm 100W 105µm 0.15 NA fiber coupled diode lasers

NASA Astrophysics Data System (ADS)

Jiang, Xiaochen; Liu, Rui; Gao, Yanyan; Zhang, Tujia; He, Xiaoguang; Zhu, Jing; Zhang, Qiang; Yang, Thomas; Zhang, Cuipeng

2016-03-01

Fiber coupled diode lasers are widely used in many fields now especially as pumps in fiber laser systems. In many fiber laser applications, high brightness pumps are essential to achieve high brightness fiber lasers. Furthermore, 976nm wavelength absorption band is narrow with Yb3+ doped fiber lasers which is more challenging for controlling wavelength stabilized in diode laser modules. This study designed and implemented commercial available high brightness and narrow wavelength width lasers to be able to use in previous mentioned applications. Base on multiple single emitters using spatial and polarization beam combining as well as fiber coupling techniques, we report a wavelength stabilized, 105μm NA 0.15 fiber coupled diode laser package with 100W of optical output power at 976 nm, which are 14 emitters inside each multiple single emitter module. The emitting aperture of the combined lasers output are designed and optimized for coupling light into a 105μm core NA 0.15 fiber. Volume Bragg grating technology has been used to improve spectral characteristics of high-power diode lasers. Mechanical modular design and thermal simulation are carried out to optimize the package. The spectral width is roughly 0.5 nm (FWHM) and the wavelength shift per °C < 0.02nm. The output spectrum is narrowed and wavelength is stabilized using Volume Bragg gratings (VBGs). The high brightness package has an electrical to optical efficiency better than 45% and power enclosure more than 90% within NA 0.12. Qualification tests have been included on this kind of package. Mechanical shock, vibration and accelerated aging tests show that the package is reliability and the MTTF is calculated to be more than 100k hours at 25°C.

Time integrated optical emission studies of the laser produced germanium plasma

NASA Astrophysics Data System (ADS)

Iqbal, Javed; Ahmed, R.; Baig, M. A.

2017-04-01

We present new time integrated data on the optical emission spectra of laser produced germanium plasma using a Q-switched Nd:YAG laser (1064 nm), power density up to about 5  ×  109 W cm-2 in conjunction with a set of five spectrometers covering a spectral range from 200 nm to 720 nm. Well resolved structure due to the 4p5s  →  4p2 transition array of neutral germanium and a few multiplets of singly ionized germanium have been observed. Plasma temperature has been determined in the range (9000-11 000) K using four different techniques; two line ratio method, Boltzmann plot, Saha-Boltzmann plot and Marotta’s technique whereas electron density has been deduced from the Stark broadened line profiles in the range (0.5-5.0)  ×  1017 cm-3, depending on the laser pulse energy to produce the germanium plasma. Full width at half maximum (FWHM) of a number of neutral and singly ionized germanium lines have been extracted by the Lorentzian fit to the experimentally observed line profiles. In addition, we have compared the experimentally measured relative line strengths for the 4p5s 3P0,1,2  →  4p2 3P0,1,2 multiplet with that calculated in the LS-coupling scheme revealing that the intermediate coupling scheme is more appropriate for the level designations in germanium.

Fabrication of novel two-dimensional nanopatterned conductive PEDOT:PSS films for organic optoelectronic applications.

PubMed

Petti, Lucia; Rippa, Massimo; Capasso, Rossella; Nenna, Giuseppe; De Girolamo Del Mauro, Anna; Pandolfi, Giuseppe; Maglione, Maria Grazia; Minarini, Carla

2013-06-12

This paper presents a novel strategy to fabricate two-dimensional poly(3,4 ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) photonic crystals (PCs) combining electron beam lithography (EBL) and plasma etching (PE) processes. The surface morphology of PEDOT:PSS PCs after mild oxygen plasma treatment was investigated by scanning electron microscopy. The effects on light extraction are studied experimentally. Vertical extraction of light was found to be strongly dependent on the geometric parameters of the PCs. By changing the lattice type from triangular to square and the geometrical parameters of the photonic structures, the resonance peak could be tuned from a narrow blue emission at 445 nm up to a green emission at 525 nm with a full width at half-maximum of 20 nm, which is in good agreement with Bragg's diffraction theory and free photon band structure. Both finite-difference time-domain and plane wave expansion methods are used to calculate the resonant frequencies and the photonic band structures in the two-dimensional photonic crystals showing a very good agreement with the experiment results. A 2D nanopatterned transparent anode was also fabricated onto a flexible polyethylene terephthalate (PET) substrate and it was integrated into an organic light-emitting diode (OLED). The obtained results fully confirm the feasibility of the developed process of micro/nano patterning PEDOT:PSS. Engineered polymer electrodes prepared by this unique method are useful in a wide variety of high-performance flexible organic optoelectronics.

Microstructures and growth mechanisms of GaN films epitaxially grown on AlN/Si hetero-structures by pulsed laser deposition at different temperatures

PubMed Central

Wang, Wenliang; Yang, Weijia; Lin, Yunhao; Zhou, Shizhong; Li, Guoqiang

2015-01-01

2 inch-diameter GaN films with homogeneous thickness distribution have been grown on AlN/Si(111) hetero-structures by pulsed laser deposition (PLD) with laser rastering technique. The surface morphology, crystalline quality, and interfacial property of as-grown GaN films are characterized in detail. By optimizing the laser rastering program, the ~300 nm-thick GaN films grown at 750 °C show a root-mean-square (RMS) thickness inhomogeneity of 3.0%, very smooth surface with a RMS surface roughness of 3.0 nm, full-width at half-maximums (FWHMs) for GaN(0002) and GaN(102) X-ray rocking curves of 0.7° and 0.8°, respectively, and sharp and abrupt AlN/GaN hetero-interfaces. With the increase in the growth temperature from 550 to 850 °C, the surface morphology, crystalline quality, and interfacial property of as-grown ~300 nm-thick GaN films are gradually improved at first and then decreased. Based on the characterizations, the corresponding growth mechanisms of GaN films grown on AlN/Si hetero-structures by PLD with various growth temperatures are hence proposed. This work would be beneficial to understanding the further insight of the GaN films grown on Si(111) substrates by PLD for the application of GaN-based devices. PMID:26563573

Experimental investigation of a pulsed Rb-Ar excimer-pumped alkali laser

NASA Astrophysics Data System (ADS)

Cheng, Hongling; Wang, Zhimin; Zhang, Fengfeng; Wang, Mingqiang; Tian, Zhaoshuo; Peng, Qinjun; Cui, Dafu; Xu, Zuyan

2017-03-01

We present experimental results of an exciplex-pumped alkali laser (XPAL) at 780 nm based on the 52P3/2 → 52S1/2 transition of the Rb atom in mixtures of Rb vapor and Ar. A laboratory-built Ti:sapphire laser with a pulse repetition rate of 3 kHz and a pulse width of 100 ns is used as the pump source. The maximum laser pulse energy of 0.26 µJ at 780 nm is obtained under an absorbed pump pulse energy of 42 µJ at 755 nm in mixtures of Rb vapor and Ar at a temperature of 423 K, corresponding to an optical conversion efficiency of 0.62%. Further experiments show that the output laser at 780 nm can always be detected for pump wavelengths ranging from 754 to 759 nm, indicating that Rb-Ar mixtures can be effectively pumped by commercial laser diodes (LDs) with a bandwidth of 5 nm.