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Sample records for continuously tunable all-in-fiber

  1. Continuously-tunable single-frequency semiconductor lasers

    SciTech Connect

    Coldren, L.A.; Corzine, S.W.

    1987-06-01

    The design of ''ideal'' tunable laser sources that are capable of being continuously turned over the entire gain bandwith with maximum mode suppression are considered. It is shown that certain extended-cavity three-section configurations satisfy the necessary conditions for such electronic tunability, but that phase shifters with advanced capabilities are necessary. It is also shown that it is not possible to achieve this goal in a two-section configuration, although continuous tuning up to about one longitudinal mode spacing should be possible with some compromise in spurious mode suppression.

  2. Colloids with continuously tunable surface charge.

    PubMed

    van Ravensteijn, Bas G P; Kegel, Willem K

    2014-09-01

    In this paper, we present a robust way to tune the surface potential of polystyrene colloids without changing the pH, ionic strength, etc. The colloids are composed of a cross-linked polystyrene core and a cross-linked vinylbenzyl chloride layer. Besides the chlorine groups, the particle surface contains sulfate/sulfonate groups (arising from the polymerization initiators) that provide a negative surface potential. Performing a Menschutkin reaction on the surface chlorine groups with tertiary amines allows us to introduce quaternary, positively charged amines. The overall charge on the particles is then determined by the ratio between the sulfate/sulfonate moieties and the quaternary amines. Using this process, we were able to invert the charge in a continuous manner without losing colloidal stability upon passing the isoelectric point. The straightforward reaction mechanism together with the fact that the reaction could be quenched rapidly resulted in a colloidal system in which the ζ potential can be tuned between -80 and 45 mV. As proof of principle, the positively charged particles were used in heterocoagulation experiments with nanometer- and micrometer-sized negatively charged silica particles to create geometrically well-defined colloidal (nano) clusters. PMID:25127340

  3. Continuously tunable Yb:KYW femtosecond oscillator based on a tunable highly dispersive semiconductor mirror.

    PubMed

    Wnuk, P; Wasylczyk, P; Zinkiewicz, Ł; Dems, M; Hejduk, K; Regiński, K; Wójcik-Jedlińska, A; Jasik, A

    2014-07-28

    The optimized nonuniform growth process was used to achieve spatially dependent reflectivity and dispersions characteristics in a highly dispersive semiconductor mirror. The mirror, together with a semiconductor saturable absorber mirror (SESAM), was used to demonstrate a tunable femtosecond Yb:KYW oscillator. In the passive modelocking regime the laser could be continuously tuned over 3.5 nm spectral band around 1032 nm with high resolution, maintaining the average output power above 140 mW. PMID:25089448

  4. Continuous tunability in three-terminal coupled-cavity lasers

    SciTech Connect

    Corzine, S.W.; Coldren, L.A.; Burrus, C.A.; Koch, T.L.

    1986-05-05

    The continuous tunability of various coupled-cavity semiconductor lasers has been investigated. Monolithic etched groove and cleaved coupled cavity (C/sup 3/) geometries are included. Using a special method of modulating the laser currents, appreciable tuning ranges have been achieved (approx.8 A) without mode hops. Also, electronic tuning of a laser with no amplitude variation is illustrated. A tuning range of 4 A with <5% AM depth is observed. Review of the theory and a comparison of the different laser geometries are included.

  5. Fast and precise continuous focusing with focus tunable lenses

    NASA Astrophysics Data System (ADS)

    Casutt, Selina; Bueeler, Michael; Blum, Mark; Aschwanden, Manuel

    2014-03-01

    Focusing in milliseconds without translational mechanics involved is possible with electrically tunable lenses. Fast shape-changing lenses enable fast imaging systems which can focus at distances from infinity to a few centimeters with a high optical quality. Furthermore, rapid laser processing in three dimensions is realized without mechanical translation of the focusing lens or the sample. With tunable lenses the entire optics can be made compact, robust and abrasion-free. Different configurations are discussed, how to integrate the tunable lens in the optical path. For machine vision applications, the achievable optical quality depends on the chosen combination of the tunable lens with a fixed focal length lens and a camera. It is recommended to use a fixed focus lens with a short distance between the stop position and the front of the lens. Furthermore, important points are presented how to achieve optimal performance in laser processing applications such as orientation and position of the tunable lens and the diameter of the beam incident on the lens. Additionally, different approaches will be discussed for monitoring the focal length of the tunable lens. The focal length of the tunable lens is sensitive to temperature changes, as the lens material is a fluid. However, in contrast to conventional lenses, the focal length of the tunable lens can be corrected electrically. For that purpose, the tunable lens exhibits an integrated temperature sensor for temperature compensation. Also optical feedback solutions will be presented for applications requiring highest precision and tracking of the absolute focal length value.

  6. Optimal fidelity of teleportation with continuous variables using three tunable parameters in a realistic environment

    NASA Astrophysics Data System (ADS)

    Hu, Li-Yun; Liao, Zeyang; Ma, Shengli; Zubairy, M. Suhail

    2016-03-01

    We introduce three tunable parameters to optimize the fidelity of quantum teleportation with continuous variables in a nonideal scheme. By using the characteristic-function formalism, we present the condition that the teleportation fidelity is independent of the amplitude of input coherent states for any entangled resource. Then we investigate the effects of tunable parameters on the fidelity with or without the presence of the environment and imperfect measurements by analytically deriving the expression of fidelity for three different input coherent-state distributions. It is shown that, for the linear distribution, the optimization with three tunable parameters is the best one with respect to single- and two-parameter optimization. Our results reveal the usefulness of tunable parameters for improving the fidelity of teleportation and the ability against decoherence.

  7. High-order harmonics as a continuously tunable coherent femtosecond x-ray source

    NASA Astrophysics Data System (ADS)

    Nam, Chang Hee; Kim, Hyung Taek; Hong, Kyung-Han; Lee, Dong Gun; Kim, Jung-Hoon

    2002-11-01

    With the application of appropriately chirped laser pulses, harmonic chirp can be coherently controlled so that sharp harmonics be produced. Using the strong blueshift property and coherently controlling harmonic generation process, we demonstrated a continuously tunable high-order harmonic generation, without losing spectral sharpness.

  8. Continuously Tunable Wettability by Using Surface Patterned Shape Memory Polymers with Giant Deformability.

    PubMed

    Zhao, Lingyu; Zhao, Jun; Liu, Yayun; Guo, Yufeng; Zhang, Liangpei; Chen, Zhuo; Zhang, Hui; Zhang, Zhong

    2016-06-01

    Designing smart surfaces with tunable wettability has drawn much attention in recent years for academic research and practical applications. Most of the previous methods to achieve such surfaces demand some particular materials that inherently have special features or complicated structures which are usually not easy to obtain. A novel strategy to achieve such smart surfaces is proposed by using the surface patterned shape memory polymers of chemically crosslinked polycyclooctene which shows a giant deformability of up to ≈730% strain. The smart surfaces possess the ability to continuously tune the wettability by controlling the recovery temperature and/or time. Coating the modified titanium dioxide nanoparticles onto such surfaces renders the surface superhydrophobicity and expands the tunable range of contact angles (CAs). Theoretical calculations of the CAs at different strains via modified Cassie model well explain the tunable wettability behaviors of such smart surfaces. PMID:27167599

  9. Balancing continuous-variable quantum key distribution with source-tunable linear optics cloning machine

    NASA Astrophysics Data System (ADS)

    Guo, Ying; Lv, Geli; Zeng, Guihua

    2015-11-01

    We show that the tolerable excess noise can be dynamically balanced in source preparation while inserting a tunable linear optics cloning machine (LOCM) for balancing the secret key rate and the maximal transmission distance of continuous-variable quantum key distribution (CVQKD). The intensities of source noise are sensitive to the tunable LOCM and can be stabilized to the suitable values to eliminate the impact of channel noise and defeat the potential attacks even in the case of the degenerated linear optics amplifier (LOA). The LOCM-additional noise can be elegantly employed by the reference partner of reconciliation to regulate the secret key rate and the transmission distance. Simulation results show that there is a considerable improvement in the secret key rate of the LOCM-based CVQKD while providing a tunable LOCM for source preparation with the specified parameters in suitable ranges.

  10. Continuously tunable single-frequency 1.52-{mu}m diode laser for gas analysis

    SciTech Connect

    Gladyshev, A V; Belovolov, M I; Vasil'ev, Sergei A; Medvedkov, O I; Duraev, V P; Nedelin, E T; Nadezhdinskii, Aleksandr I; Ponurovskii, Ya Ya

    2005-03-31

    A single-frequency continuously tunable diode laser with a hybrid fibre Bragg grating resonator (hybrid laser) is built for recording the absorption line of ammonia. The continuous tuning within 40 GHz (1.33 cm{sup -1}) was achieved for the first time for a hybrid laser emitting 5 mW in the line of width {delta}{nu} {<=} 15 MHz (0.0005 cm{sup -1}) with the side-mode suppression exceeding 20 dB. (lasers)

  11. Laser-induced transient grating setup with continuously tunable period

    SciTech Connect

    Vega-Flick, A.; Eliason, J. K.; Maznev, A. A.; Nelson, K. A.; Khanolkar, A.; Abi Ghanem, M.; Boechler, N.; Alvarado-Gil, J. J.

    2015-12-15

    We present a modification of the laser-induced transient grating setup enabling continuous tuning of the transient grating period. The fine control of the period is accomplished by varying the angle of the diffraction grating used to split excitation and probe beams. The setup has been tested by measuring dispersion of bulk and surface acoustic waves in both transmission and reflection geometries. The presented modification is fully compatible with optical heterodyne detection and can be easily implemented in any transient grating setup.

  12. All-in-fiber optofluidic sensor fabricated by femtosecond laser assisted chemical etching.

    PubMed

    Yuan, Lei; Huang, Jie; Lan, Xinwei; Wang, Hanzheng; Jiang, Lan; Xiao, Hai

    2014-04-15

    An all-in-fiber prototype optofluidic device was fabricated by femtosecond laser irradiation and subsequent selective chemical wet etching. Horizontal and vertical microchannels can be flexibly created into an optical fiber to form a fluidic cavity with inlets/outlets. The fluidic cavity also functions as an optical Fabry-Perot cavity in which the filled liquid can be probed. The assembly-free microdevice exhibited a fringe visibility of 20 dB and was demonstrated for measurement of the refractive index of the filling liquids. The proposed all-in-fiber optofluidic micro device is attractive for chemical and biomedical sensing because it is flexible in design, simple to fabricate, mechanically robust, and miniaturized in size. PMID:24978992

  13. Continuous glucose determination using fiber-based tunable mid-infrared laser spectroscopy

    NASA Astrophysics Data System (ADS)

    Yu, Songlin; Li, Dachao; Chong, Hao; Sun, Changyue; Xu, Kexin

    2014-04-01

    Wavelength-tunable laser spectroscopy in combination with a small-sized fiber-optic attenuated total reflection (ATR) sensor (fiber-based evanescent field analysis, FEFA) is reported for the continuous measurement of the glucose level. We propose a method of controlling and stabilizing the wavelength and power of laser emission and present a newly developed mid-infrared wavelength-tunable laser with a broad emission spectrum band of 9.19-9.77 μm (1024-1088 cm-1). The novel small-sized flow-through fiber-optic ATR sensor with long optical sensing length was used for glucose level determination. The experimental results indicate that the noise-equivalent concentration of this laser measurement system is as low as 3.8 mg/dL, which is among the most precise glucose measurements using mid-infrared spectroscopy. The sensitivity, which is three times that of conventional Fourier transform infrared spectrometer, was acquired because of the higher laser power and higher spectral resolution. The best prediction of the glucose concentration in phosphate buffered saline solution was achieved using the five-variable partial least-squares model, yielding a root-mean-square error of prediction as small as 3.5 mg/dL. The high sensitivity, multiple tunable wavelengths and small fiber-based sensor with long optical sensing length make glucose determination possible in blood or interstitial fluid in vivo.

  14. Tunable recombinant protein expression in E. coli: enabler for continuous processing?

    PubMed

    Marschall, Lukas; Sagmeister, Patrick; Herwig, Christoph

    2016-07-01

    Tuning of transcription is a powerful process technological tool for efficient recombinant protein production in Escherichia coli. Many challenges such as product toxicity, formation of inclusion bodies, cell death, and metabolic burden are associated with non-suitable (too high or too low) levels of recombinant protein expression. Tunable expression systems allow adjusting the recombinant protein expression using process technological means. This enables to exploit the cell's metabolic capacities to a maximum. Within this article, we review genetic and process technological aspects of tunable expression systems in E. coli, providing a roadmap for the industrial exploitation of the reviewed technologies. We attempt to differentiate the term "expression tuning" from its inflationary use by providing a concise definition and highlight interesting fields of application for this versatile new technology. Dependent on the type of inducer (metabolizable or non-metabolizable), different process strategies are required in order to achieve tuning. To fully profit from the benefits of tunable systems, an independent control of growth rate and expression rate is indispensable. Being able to tackle problems such as long-term culture stability and constant product quality expression tuning is a promising enabler for continuous processing in biopharmaceutical production. PMID:27170324

  15. Continuous-Wave, Diode-Pumped, Tunable Tm,Ho:YLF Laser

    NASA Technical Reports Server (NTRS)

    Mcguckin, Brendan T.; Menzies, Robert T.

    1994-01-01

    Unique features include high efficiency and tunability at wavelengths near 2.067 micrometers. Continuous-wave, diode-pumped Tm,Ho:YLF laser tuned by tilting Fabry-Perot etalon and/or adjusting temperature of Tm,Ho:YLF crystal. Proposed for use in remote sensing of winds and in remote sensing of CO2 and H2O, of which many strong absorption lines over-lap laser tuning range. Range extended by tuning to wave-length between CO2 and H2O absorption peaks.

  16. High power continuous operation of a widely tunable quantum cascade laser with an integrated amplifier

    SciTech Connect

    Slivken, S.; Sengupta, S.; Razeghi, M.

    2015-12-21

    Wide electrical tuning and high continuous output power is demonstrated from a single mode quantum cascade laser emitting at a wavelength near 4.8 μm. This is achieved in a space efficient manner by integrating an asymmetric sampled grating distributed feedback tunable laser with an optical amplifier. An initial demonstration of high peak power operation in pulsed mode is demonstrated first, with >5 W output over a 270 nm (113 cm{sup −1}) spectral range. Refinement of the geometry leads to continuous operation with a single mode spectral coverage of 300 nm (120 cm{sup −1}) and a maximum continuous power of 1.25 W. The output beam is shown to be nearly diffraction-limited, even at high amplifier current.

  17. Preparation and analysis of anodic aluminum oxide films with continuously tunable interpore distances

    NASA Astrophysics Data System (ADS)

    Qin, Xiufang; Zhang, Jinqiong; Meng, Xiaojuan; Deng, Chenhua; Zhang, Lifang; Ding, Guqiao; Zeng, Hao; Xu, Xiaohong

    2015-02-01

    Nanoporous anodic aluminum oxides are often used as templates for preparation of nanostructures such as nanodot, nanowire and nanotube arrays. The interpore distance of anodic aluminum oxide is the most important parameter in controlling the periodicity of these nanostructures. Herein we demonstrate a simple and yet powerful method to fabricate ordered anodic aluminum oxides with continuously tunable interpore distances. By using mixed solution of citric and oxalic acids with different molar ratio, the range of anodizing voltages within which self-ordered films can be formed were extended to between 40 and 300 V, resulting in the interpore distances change from 100 to 750 nm. Our work realized very broad range of interpore distances in a continuously tunable fashion and the experiment processes are easily controllable and reproducible. The dependence of the interpore distances on acid ratios in mixed solutions was discussed through analysis of anodizing current and it was found that the effective dissociation constant of the mixed acids is of great importance. The interpore distances achieved are comparable to wavelengths ranging from UV to near IR, and may have potential applications in optical meta-materials for photovoltaics and optical sensing.

  18. Second-order interference of two independent and tunable single-mode continuous-wave lasers

    NASA Astrophysics Data System (ADS)

    Jianbin, Liu; Dong, Wei; Hui, Chen; Yu, Zhou; Huaibin, Zheng; Hong, Gao; Fu-Li, Li; Zhuo, Xu

    2016-03-01

    The second-order temporal interference of two independent single-mode continuous-wave lasers is discussed by employing two-photon interference in Feynman’s path integral theory. It is concluded that whether the second-order temporal interference pattern can or cannot be retrieved via two-photon coincidence counting rate is dependent on the resolution time of the detection system and the frequency difference between these two lasers. Two identical and tunable single-mode continuous-wave diode lasers are employed to verify the predictions. These studies are helpful to understand the physics of two-photon interference with photons of different spectra. Project supported by the National Natural Science Foundation of China (Grant No. 11404255) and the Doctor Foundation of Education Ministry of China (Grant No. 20130201120013).

  19. Frequency-tunable continuous-wave terahertz sources based on GaAs plasmonic photomixers

    NASA Astrophysics Data System (ADS)

    Yang, Shang-Hua; Jarrahi, Mona

    2015-09-01

    We present frequency-tunable, continuous-wave terahertz sources based on GaAs plasmonic photomixers, which offer high terahertz radiation power levels at 50% radiation duty cycle. The use of plasmonic contact electrodes enhances photomixer quantum efficiency while maintaining its ultrafast operation by concentrating a large number of photocarriers in close proximity to the device contact electrodes. Additionally, the relatively high thermal conductivity and high resistivity of GaAs allow operation under high optical pump power levels and long duty cycles without reaching the thermal breakdown limit of the photomixer. We experimentally demonstrate continuous-wave terahertz radiation with a radiation frequency tuning range of more than 2 THz and a record-high radiation power of 17 μW at 1 THz through plasmonic photomixers fabricated on a low temperature grown GaAs substrate at 50% radiation duty cycle.

  20. Frequency-tunable continuous-wave terahertz sources based on GaAs plasmonic photomixers

    SciTech Connect

    Yang, Shang-Hua; Jarrahi, Mona

    2015-09-28

    We present frequency-tunable, continuous-wave terahertz sources based on GaAs plasmonic photomixers, which offer high terahertz radiation power levels at 50% radiation duty cycle. The use of plasmonic contact electrodes enhances photomixer quantum efficiency while maintaining its ultrafast operation by concentrating a large number of photocarriers in close proximity to the device contact electrodes. Additionally, the relatively high thermal conductivity and high resistivity of GaAs allow operation under high optical pump power levels and long duty cycles without reaching the thermal breakdown limit of the photomixer. We experimentally demonstrate continuous-wave terahertz radiation with a radiation frequency tuning range of more than 2 THz and a record-high radiation power of 17 μW at 1 THz through plasmonic photomixers fabricated on a low temperature grown GaAs substrate at 50% radiation duty cycle.

  1. Digitally tunable physicochemical coding of material composition and topography in continuous microfibres

    NASA Astrophysics Data System (ADS)

    Kang, Edward; Jeong, Gi Seok; Choi, Yoon Young; Lee, Kwang Ho; Khademhosseini, Ali; Lee, Sang-Hoon

    2011-11-01

    Heterotypic functional materials with compositional and topographical properties that vary spatiotemporally on the micro- or nanoscale are common in nature. However, fabricating such complex materials in the laboratory remains challenging. Here we describe a method to continuously create microfibres with tunable morphological, structural and chemical features using a microfluidic system consisting of a digital, programmable flow control that mimics the silk-spinning process of spiders. With this method we fabricated hydrogel microfibres coded with varying chemical composition and topography along the fibre, including gas micro-bubbles as well as nanoporous spindle-knots and joints that enabled directional water collection. We also explored the potential use of the coded microfibres for tissue engineering applications by creating multifunctional microfibres with a spatially controlled co-culture of encapsulated cells.

  2. Compact continuously tunable microwave photonic filters based on cascaded silicon microring resonators

    NASA Astrophysics Data System (ADS)

    Liu, Li; He, Mengying; Dong, Jianji

    2016-03-01

    We propose and experimentally demonstrate a photonic approach to achieving tunable bandpass microwave photonic filters (MPFs) based on cascaded microring resonators (CMRRs). The optical spectrum of the silicon CMRRs could offer two bandpass response to separately filter the optical carrier and one of the sidebands generated by the phase modulation. Thus we could achieve a bandpass MPF. Moreover, as the central frequencies and bandwidths of the two bandpass response can be tuned by adjusting the laser wavelength and voltages applied on one MRR, the central operating frequency or 3-dB bandwidth of the MPF can be continuously tuned in wide ranges respectively. A proof-of-concept experiment illustrates a central frequency tuning range from 19 GHz to 40 GHz, and a wide bandwidth tuning range from 5.5 GHz to 17.5 GHz.

  3. A continuously tunable and filterless optical millimeter-wave generation via frequency octupling.

    PubMed

    Lin, Chun-Ting; Shih, Po-Tsung; Jiang, Wen-Jr; Chen, Jason Jyehong; Peng, Peng-Chun; Chi, Sien

    2009-10-26

    This work proposes a cost-effective, continuously tunable and filterless optical millimeter-wave (MMW) signal generation employing frequency octupling. Optical MMW signals with 30-dB undesired sideband suppression ratios can be obtained. Since no optical filtering is required, the proposed system can be readily implemented in wavelength-division-multiplexing (WDM) systems. V-band 60-GHz and W-band 80-GHz optical MMW signals are experimentally demonstrated. Because of the high undesired sideband suppression ratio, 60-GHz waveform with 50% duty cycle is observed. The single-sideband (SSB) phase noise of the generated 60-GHz signal is -73 dBc/Hz at 10 kHz. The proposed system is a viable solution for the future ultra-high frequency MMW applications up to 320 GHz using the external modulator with a limited bandwidth of 40 GHz. PMID:19997195

  4. Continuous Production of Janus and Composite Liquid Marbles with Tunable Coverage.

    PubMed

    Castro, Jasmine O; Neves, Bruna M; Rezk, Amgad R; Eshtiaghi, Nicky; Yeo, Leslie Y

    2016-07-20

    We report a simple method for on-demand continuous processing of composite liquid marbles with the aid of a 3D printed slide platform, which offers the potential for engineering novel functional surfaces for the production of combination drug therapies, particle-based barcode biomarkers and smart membranes, among other applications. Unlike other attempts at producing such liquid marbles, this novel technique not only facilitates controllable and reproducible production of the liquid marbles but also allows the selection of different morphologies such as banded, patchy, and Janus structures by controlling the coalescence conditions, with the possibility for tunable symmetric and asymmetric patterns, the latter by varying the particle species partitioning ratio. PMID:27389811

  5. Continuously-tunable, narrow-linewidth, Q-switched Cr:LiSAF laser for lidar applications

    SciTech Connect

    Early, J.W.; Lester, C.S.; Quick, C.R.; Tiee, J.J.; Shimada, T.; Cockroft, N.J.

    1995-02-01

    A continuously-tunable, narrow-linewidth, flashlamp-pumped, Q-switched Cr:LiSAF laser has been developed (energy: 30 mJ, pulsewidth: 40 ns, linewidth:<2 GHz) and was used successfully for the DIAL(differential absorption lidar) measurements of atmospheric water vapor and LIF lidar for the remote detection of metal oxide fluorescence.

  6. Continuously-tunable, narrow-linewidth, Q-switched Cr:LiSAF laser for lidar applications

    SciTech Connect

    Shimada, Tsutomu; Early, J.W.; Lester, C.S.; Quick, C.R.; Tiee, J.J.; Cockroft, N.J.

    1994-10-01

    A continuously-tunable, narrow-linewidth, flashlamp-pumped, Q-switched Cr:LiSAF laser has been developed (energy: 30 mJ, pulsewidth: 40 ns, linewidth: <2 GHz) and was used successfully for the DIAL (differential absorption lidar) measurements of atmospheric water vapor.

  7. Continuous wavelength tunable laser source with optimum positioning of pivot axis for grating

    DOEpatents

    Pushkarsky, Michael; Amone, David F.

    2010-06-08

    A laser source (10) for generating a continuously wavelength tunable light (12) includes a gain media (16), an optical output coupler (36F), a cavity collimator (38A), a diffraction grating (30), a grating beam (54), and a beam attacher (56). The diffraction grating (30) is spaced apart from the cavity collimator (38A) and the grating (30) cooperates with the optical output coupler (36F) to define an external cavity (32). The grating (30) includes a grating face surface (42A) that is in a grating plane (42B). The beam attacher (56) retains the grating beam (54) and allows the grating beam (54) and the grating (30) to effectively pivot about a pivot axis (33) that is located approximately at an intersection of a pivot plane (50) and the grating plane (42B). As provided herein, the diffraction grating (30) can be pivoted about the unique pivot axis (33) to move the diffraction grating (30) relative to the gain media (16) to continuously tune the lasing frequency of the external cavity (32) and the wavelength of the output light (12) so that the output light (12) is mode hop free.

  8. Multiwatt diode-pumped Yb:YAG thin disk laser continuously tunable between 1018 and 1053 nm.

    PubMed

    Brauch, U; Giesen, A; Karszewski, M; Stewen, C; Voss, A

    1995-04-01

    A new powerful source of broadly (35-nm) tunable laser radiation in the near-infrared (near 1030 nm) wavelength range is presented. Inserting a birefringent filter into a 10-W diode-pumped Yb:YAG thin disk laser resonator gives several watts of narrow-linewidth (0.07-nm) continuously tunable cw output power. By taking advantage of the power scalability of the thin disk concept, even hundreds of watts of tunable power with near-diffraction-limited beam quality and high efficiency are feasible. Generation and amplification of subpicosecond pulses with high average and peak powers are also promising applications of the Yb:YAG thin disk laser. PMID:19859306

  9. Continuously tunable photonic fractional Hilbert transformer using a high-contrast germanium-doped silica-on-silicon microring resonator.

    PubMed

    Shahoei, Hiva; Dumais, Patrick; Yao, Jianping

    2014-05-01

    We propose and experimentally demonstrate a continuously tunable fractional Hilbert transformer (FHT) based on a high-contrast germanium-doped silica-on-silicon (SOS) microring resonator (MRR). The propagation loss of a high-contrast germanium-doped SOS waveguide can be very small (0.02 dB/cm) while the lossless bend radius can be less than 1 mm. These characteristics lead to the fabrication of an MRR with a high Q-factor and a large free-spectral range (FSR), which is needed to implement a Hilbert transformer (HT). The SOS MRR is strongly polarization dependent. By changing the polarization direction of the input signal, the phase shift introduced at the center of the resonance spectrum is changed. The tunable phase shift at the resonance wavelength can be used to implement a tunable FHT. A germanium-doped SOS MRR with a high-index contrast of 3.8% is fabricated. The use of the fabricated MRR for the implementation of a tunable FHT with tunable orders at 1, 0.85, 0.95, 1.05, and 1.13 for a Gaussian pulse with the temporal full width at half-maximum of 80 ps is experimentally demonstrated. PMID:24784101

  10. Self-ordered anodic alumina with continuously tunable pore intervals from 410 to 530 nm.

    PubMed

    Sun, Chuanmin; Luo, Jia; Wu, Longmin; Zhang, Junyan

    2010-05-01

    We report a "mild anodization" (MA) process using aluminum oxalate (Alox) as an additive to suppress breakdown of porous anodic alumina (PAA) in the electrolyte of phosphoric acid at high potentials and comparatively high temperatures. It is shown for the first time that continuously tunable pore intervals (D(int)) from 410 to 530 nm with ordered hexagonal pore arrangement can be controlled by varying the concentrations of phosphoric acid and Alox at anodization voltages (U(a)) from 180 to 230 V, far beyond the U(a) in the single electrolyte of phosphoric acid or oxalic acid. The fabricated PAA films are uniform without any burning spots, and the anodization temperature can be increased to 10-20 degrees C with a much higher growth rate of PAA films than that at a low temperature. Meanwhile, a typical two-step anodization process could also be performed under our conditions. Our results could not only extend the applications of PAA templates but also facilitate understanding of the effects of anions in the process of anodic oxidation. PMID:20408596

  11. Developing a narrow-line laser spectrometer based on a tunable continuous-wave dye laser

    SciTech Connect

    Wang, Chun; Lv, Shasha; Bi, Jin; Liu, Fang; Li, Liufeng; Chen, Lisheng

    2014-08-15

    We present the development of a dye-laser-based spectrometer operating at 550–600 nm. The spectrometer will be used to detect an ultra-narrow clock transition ({sup 1}S{sub 0}-{sup 3}P{sub 0}) in an Ytterbium optical lattice clock and perform high-resolution spectroscopy of iodine molecules trapped in the sub-nanometer channels of zeolite crystal (AlPO{sub 4}-11). Two-stage Pound-Drever-Hall frequency stabilization is implemented on the tunable continuous-wave dye laser to obtain a reliable operation and provide stable laser radiations with two different spectral linewidths. In the first-stage frequency locking, a compact home-built intracavity electro-optic modulator is adopted for suppressing fast frequency noise. With an acquisition time of 0.1 s the 670-kHz linewidth of the free-running dye laser is reduced to 2 kHz when locked to a pre-stabilization optical cavity with a finesse of 1170. When the pre-stabilized laser is locked to a high-finesse optical cavity, a linewidth of 1.4 Hz (2 s) is observed and the frequency stability is 3.7 × 10{sup −15} (3 s). We also measure and analyze the individual noise contributions such as those from residual amplitude modulation and electronic noise. The ongoing upgrades include improving long-term frequency stability at time scales from 10 to 100 s and implementing continuous frequency scan across 10 GHz with radio-frequency precision.

  12. Developing a narrow-line laser spectrometer based on a tunable continuous-wave dye laser

    NASA Astrophysics Data System (ADS)

    Wang, Chun; Lv, Shasha; Liu, Fang; Bi, Jin; Li, Liufeng; Chen, Lisheng

    2014-08-01

    We present the development of a dye-laser-based spectrometer operating at 550-600 nm. The spectrometer will be used to detect an ultra-narrow clock transition (1S0-3P0) in an Ytterbium optical lattice clock and perform high-resolution spectroscopy of iodine molecules trapped in the sub-nanometer channels of zeolite crystal (AlPO4-11). Two-stage Pound-Drever-Hall frequency stabilization is implemented on the tunable continuous-wave dye laser to obtain a reliable operation and provide stable laser radiations with two different spectral linewidths. In the first-stage frequency locking, a compact home-built intracavity electro-optic modulator is adopted for suppressing fast frequency noise. With an acquisition time of 0.1 s the 670-kHz linewidth of the free-running dye laser is reduced to 2 kHz when locked to a pre-stabilization optical cavity with a finesse of 1170. When the pre-stabilized laser is locked to a high-finesse optical cavity, a linewidth of 1.4 Hz (2 s) is observed and the frequency stability is 3.7 × 10-15 (3 s). We also measure and analyze the individual noise contributions such as those from residual amplitude modulation and electronic noise. The ongoing upgrades include improving long-term frequency stability at time scales from 10 to 100 s and implementing continuous frequency scan across 10 GHz with radio-frequency precision.

  13. Single-frequency and tunable operation of a continuous intracavity-frequency-doubled singly resonant optical parametric oscillator.

    PubMed

    My, Thu-Hien; Drag, Cyril; Bretenaker, Fabien

    2008-07-01

    A widely tunable continuous intracavity-frequency-doubled singly resonant optical parametric oscillator based on MgO-doped periodically poled stoichiometric lithium tantalate crystal is described. The idler radiation resonating in the cavity is frequency doubled by an intracavity BBO crystal. Pumped in the green, this system can provide up to 485 mW of single-frequency orange radiation. The system is continuously temperature tunable between 1170 and 1355 nm for the idler, 876 and 975 nm for the signal, and between 585 and 678 nm for the doubled idler. The free-running power and frequency stability of the system have been observed to be better than those for a single-mode dye laser. PMID:18594663

  14. Atmospheric remote sensing of water vapor, HCl and CH4 using a continuously tunable Co:MgF2 laser

    NASA Technical Reports Server (NTRS)

    Menyuk, Norman; Killinger, Dennis K.

    1987-01-01

    A differential-absorption lidar system has been developed which uses a continuously tunable (1.5-2.3 micron) cobalt-doped magnesium fluoride laser as the radiation source. Preliminary atmospheric measurements of water vapor, HCl, and CH4 have been made with this system, including both path-averaged and ranged-resolved DIAL measurements at ranges up to 6 and 3 km, respectively.

  15. Tunable diode lasers as continuous emission monitors for thermal waste treatment processes

    NASA Astrophysics Data System (ADS)

    Allendorf, S. W.; Ottesen, D. K.; Johnsen, H. A.; Wang, J.; Frish, M. D.; Trembley, D. G.; Severance, R.; Boni, A. A.

    In this paper the ongoing program to develop and apply a family of on-line process monitors is described. This technique detects molecular gas-phase species by optical absorption using vibrational transitions in the near-infrared region. Near-infrared, tunable diode lasers are used that emit extremely narrow, single-mode radiation. Current efforts include laboratory work to identify the optimum absorption lines for the molecular species of interest. Sensors based on tunable diode lasers are being developed in parallel with this scoping work. One such instrument, designed to monitor ammonia, has been constructed and field-tested; its specification and performance are discussed.

  16. Tunable diode lasers as continuous emission monitors for thermal waste treatment processes

    SciTech Connect

    Allendorf, S.W.; Ottesen, D.K.; Johnsen, H.A.; Wang, J.; Frish, M.D.; Trembley, D.G.; Severance, R.; Boni, A.A.

    1994-12-01

    In this paper the ongoing program to develop and apply a family of on-line process monitors is described. This technique detects molecular gas-phase species by optical absorption using vibrational transitions in the near-infrared region. Near-infrared, tunable diode lasers are used that emit extremely narrow, single-mode radiation. Current efforts include laboratory work to identify the optimum absorption lines for the molecular species of interest. Sensors based on tunable diode lasers are being developed in parallel with this scoping work. One such instrument, designed to monitor ammonia, has been constructed and field-tested; its specification and performance are discussed.

  17. Continuously-tunable microwave photonic true-time-delay based on a fiber-coupled beam deflector and diffraction grating.

    PubMed

    Schermer, Ross T; Bucholtz, Frank; Villarruel, Carl A

    2011-03-14

    This paper reports the demonstration of a continuously-tunable true-time delay line for microwave photonics and optical communications capable of high-resolution phase control throughout the 1-100 GHz modulation range. A fiber-coupled device is demonstrated with 75 ps of continuous delay tuning range, 3 dB optical insertion loss, and minimal RF amplitude and phase variation over the 4-18 GHz band. Measured delay ripple was less than 0.2 ps. Theoretical analysis is also presented which indicates scalability to delay tuning ranges over 1000 ps and modulation bandwidths over 10 THz. PMID:21445175

  18. Tunable diode laser-pumped Tm,Ho:YLF laser operated in continuous-wave and Q-switched modes

    NASA Technical Reports Server (NTRS)

    Mcguckin, B. T.; Hemmati, H.; Menzies, R. T.

    1992-01-01

    Tunable continuous-wave and pulsed laser output was obtained from a Tm-sensitized Ho:YLiF4 crystal at subambient temperatures when longitudinally pumped with a diode laser array. A conversion efficiency of 42 percent and slope efficiency of approximately 60 percent relative to the absorbed pumped power have been achieved at a crystal temperature of 275 K. The emission spectrum was etalon tunable over a range of 16/cm centered at 2067 nm with fine tuning capability of the transition frequency with crystal temperature at measured rate of -0.03/cm/K. Output energies of 0.22 mJ per pulse and 22 ns pulse duration were recorded at Q-switch frequencies that correspond to an effective upper laser level lifetime of 6 ms, and a pulse energy extraction efficiency of 64 percent.

  19. A continuously tunable multi-tap complex-coefficient microwave photonic filter based on a tilted fiber Bragg grating.

    PubMed

    Shahoei, Hiva; Yao, Jianping

    2013-03-25

    The coupling coefficients of the cladding-mode resonances of a tilted fiber Bragg grating (TFBG) are linearly increasing or decreasing in different wavelength regions. Based on the Kramers-Kronig relations, when the coupling coefficients are linearly increasing, the phase shifts are linearly increasing correspondingly. This feature is employed, for the first time, for the implementation of a multi-tap continuously tunable microwave photonic filter with complex coefficients by using a TFBG. By locating the optical carriers of single-sideband-modulated signals at the cladding-mode resonances of the TFBG which has linearly increasing depths, linearly increasing phase shifts are introduced to the optical carriers. By beating the optical carriers with the single sidebands, the phase shifts are translated to the microwave signals, and thus complex coefficients with the required linearly increasing phase shifts are generated. The tunability of the complex coefficients is realized by optically pumping the TFBG which is written in an erbium/ytterbium (Er/Yb) co-doped fiber. A proof-of-concept experiment is performed; a three- and four-tap filter with a frequency tunable range of 150 and 120 MHz, respectively, are demonstrated. PMID:23546134

  20. Tunable, high-power, continuous-wave dual-polarization Yb-fiber oscillator.

    PubMed

    Zeil, Peter; Pasiskevicius, Valdas; Laurell, Fredrik

    2015-06-29

    We demonstrate a high-power, dual-polarization Yb-fiber oscillator, by separately locking the two linear polarization states defined by slow and fast axis of a polarization-maintaining gain fiber with volume Bragg gratings. Dual-line lasing is achieved with a tunable wavelength separation from 0.03 to 2 THz, while exceeding output powers of 78 W over the entire tuning range, maintaining a high beam-quality with M(2)<1.2. With this laser configuration we achieve a peak-to-peak power variation of <1% for the dual-line signal and <3% for the individual signals. PMID:26191754

  1. Continuous-wave broadly tunable diode laser array-pumped mid-infrared Cr2+:CdSe laser

    NASA Astrophysics Data System (ADS)

    Lazarev, V. A.; Tarabrin, M. K.; Kovtun, A. A.; Karasik, V. E.; Kireev, A. N.; Kozlovsky, V. I.; Korostelin, Yu V.; Podmar'kov, Yu P.; Frolov, M. P.; Gubin, M. A.

    2015-12-01

    We demonstrate the operation of a room-temperature, solid-state, broadly tunable Cr-doped CdSe single-crystal continuous-wave laser. Longitudinal pumping with a continuous-wave diode laser array at 1.94 μm produced a broadband output of 280 mW at 2.6 μm with an incident power slope efficiency of 12%. With an intracavity Brewster-cut CaF2 prism, we tuned the Cr2+:CdSe laser from 2.45 to 3.06 μm with a resolution of 10 nm and an output power up to 55 mW.

  2. Continuous-wave VECSEL Raman laser with tunable lime-yellow-orange output.

    PubMed

    Lin, Jipeng; Pask, Helen M; Spence, David J; Hamilton, Craig J; Malcolm, Graeme P A

    2012-02-27

    We report a compact CW KGW Raman laser with intracavity nonlinear mixing, pumped by the intracavity field of a VECSEL. By temperature tuning an intracavity LBO crystal, we obtained two separate tunable emissions bands, namely 548.5 - 566 nm for sum-frequency-generation (SFG) of the fundamental and Stokes wavelengths, and 577.5 - 596 nm for second-harmonic-generation (SHG) of the Stokes wavelength. The maximum output powers for SFG and SHG were 0.8 W @ 560 nm and 0.52 W @ 592.5 nm, with corresponding diode-to-visible optical conversion efficiencies of 4.2% and 2.9%. These preliminary results show strong potential for expanding the spectral coverage of VECSEL lasers. PMID:22418328

  3. Ocular hazards of tunable continuous-wave near-infrared laser sources

    NASA Astrophysics Data System (ADS)

    Lund, David J.; Edsall, Peter R.; Fuller, Douglas F.; Hoxie, Stephen W.

    1996-04-01

    Retinal damage thresholds (ED50s) were determined in Rhesus monkey eyes for 100 ms exposures to collimated radiation from a tunable Ti:Sapphire laser at several wavelengths from 700 nm to 900 nm. Prior research using 15 ns duration laser pulses showed a strong variability of ED50 with wavelength for retinal exposure in Rhesus monkeys to laser radiation in the near infrared spectrum. Current studies with the Ti:Sapphire laser show similar variability of ED50 with wavelength for 100 ms retinal exposures. Previously measured light transmission and absorption properties of ocular tissues do not provide a complete or obvious explanation for the significant variations of threshold with small changes in wavelength. Similar wavelength dependencies of ED50 for the two exposure durations in the wavelength range of 750 nm to 830 nm suggest that linear absorption is a cause of the variability. However, differences in the ED50 curves at other wavelengths show that nonlinear mechanisms also contribute.

  4. Broadly continuously tunable slot waveguide quantum cascade lasers based on a continuum-to-continuum active region design

    SciTech Connect

    Meng, Bo; Zeng, Yong Quan; Liang, Guozhen; Hu, Xiao Nan; Rodriguez, Etienne; Wang, Qi Jie

    2015-09-14

    We report our progress in the development of broadly tunable single-mode slot waveguide quantum cascade lasers based on a continuum-to-continuum active region design. The electroluminescence spectrum of the continuum-to-continuum active region design has a full width at half maximum of 440 cm{sup −1} at center wavelength ∼10 μm at room temperature (300 K). Devices using the optimized slot waveguide structure and the continuum-to-continuum design can be tuned continuously with a lasing emission over 42 cm{sup −1}, from 9.74 to 10.16 μm, at room temperature by using only current tuning scheme, together with a side mode suppression ratio of above 15 dB within the whole tuning range.

  5. Reconfigurable liquid metal fiber-optic mirror for continuous, widely-tunable true-time-delay.

    PubMed

    Schermer, Ross T; Villarruel, Carl A; Bucholtz, Frank; McLaughlin, Colin V

    2013-02-11

    This paper reports the demonstration of a widely-translatable fiber-optic mirror based on the motion of liquid metal through the hollow core of a photonic bandgap fiber. By moving a liquid metal mirror within the hollow core of an optical fiber, large, continuous changes in optical path length are achieved in a comparatively small package. A fiber-optic device is demonstrated which provided a continuously-variable optical path length of over 3.6 meters, without the use of free-space optics or resonant optical techniques (i.e. slow light). This change in path length corresponds to a continuously-variable true-time delay of over 12 ns, or 120 periods at a modulation frequency of 10 GHz. Wavelength dependence was shown to be negligible across the C and L bands. PMID:23481731

  6. A continuously and widely tunable analog baseband chain with digital-assisted calibration for multi-standard DBS applications

    NASA Astrophysics Data System (ADS)

    Songting, Li; Jiancheng, Li; Xiaochen, Gu; Hongyi, Wang

    2013-06-01

    This paper presents a continuously and widely tunable analog baseband chain with a digital-assisted calibration scheme implemented on a 0.13 μm CMOS technology. The analog baseband is compliant with several digital broadcasting system (DBS) standards, including DVB-S, DVB-S2, and ABS-S. The cut-off frequency of the baseband circuit can be changed continuously from 4.5 to 32 MHz. The gain adjustment range is from 6 to 55.5 dB with 0.5 dB step. The calibration includes automatic frequency tuning (AFT) and automatic DC offset calibration (DCOC) to achieve less than 6% cut-off frequency deviation and 3 mV residual output offset. The out-of-band IIP2 and IIP3 of the overall chain are 45 dBm and 18 dBm respectively, while the input referred noise (IRN) is 17.4 nV/√Hz. All circuit blocks are operated at 2.8 V from LDO and consume current of 20.4 mA in the receiving mode.

  7. Photonic devices for tunable continuous-wave terahertz generation and detection

    NASA Astrophysics Data System (ADS)

    Park, Kyung Hyun; Kim, Namje; Moon, Kiwon; Ko, Hyunsung; Park, Jeong-Woo; Lee, Eui Su; Lee, Il-Min; Han, Sang-Pil

    2014-03-01

    A novel type of semiconductor beating source, a monolithically integrated dual-mode laser, and continuous-wave terahertz (THz) system adopting it will be investigated. The combined system of the beating source with broadbandantenna- integrated low-temperature-grown semiconductor photomixers shows the possibility of the realization of the cost-effective and compact continuous-wave THz systems. Such a system is highly-demanded to examine the THz finger prints of specimens without limitations. Since the optimized performance depends not only on the characteristics of functional devices but also module configurations, various approaches such as traveling-wave photomixers, Schottky barrier diodes, and nano-structure contained photomixers have been investigated to implement high-performance THz platforms as the main building blocks of a THz system. Semiconductor-based compact and cost-effective photonics technologies will envisage the bright future of THz systems.

  8. Continuously tunable reflective-type optical delay lines using microring resonators.

    PubMed

    Xie, Jingya; Zhou, Linjie; Zou, Zhi; Wang, Jinting; Li, Xinwan; Chen, Jianping

    2014-01-13

    We present a reflective-type optical delay line using waveguide side-coupled 13 microring resonators terminated with a sagnac loop reflector. Light passes through the microring resonator sequence twice, doubling the delay-bandwidth product. Group delay is tuned by p-i-p type microheaters integrated directly in the microring waveguides. Experiment demonstrates that the delay line can potentially buffer 18 bits and the delay can be continuously tuned for 100 ps with a power tuning efficiency of 0.34 ps/mW. Eye diagrams of a 20-Gbps PRBS signal after 10 and 110 ps delays are also examined. PMID:24515041

  9. Sum-frequency generation of continuous-wave tunable ultraviolet coherent light in BBO-installed external cavity

    NASA Astrophysics Data System (ADS)

    Mukoyama, Kenta; Tokuyama, Kazuhiro; Kumagai, Hiroshi; Inoue, Norihiro; Fukuda, Naoaki; Takiya, Toshio

    2012-02-01

    Recently, we have tried to develop a continuous wave (CW), tunable, and ultraviolet (UV) coherent light source through sum-frequency generation (SFG) using a BBO nonlinear crystal with a two-stage frequency-conversion system using two different external cavities for the enhancement of CW lights. In the first stage, we obtained the 532-nm light with the second harmonic generation (SHG) of the 1064-nm light. A bow-tie external cavity incorporating four mirrors, whose cavity length was controlled by the frequency stabilization method proposed by Hänsch and Couillaud, was employed there. In the second stage, to generate the 312-nm light, we demonstrated doubly resonant sum frequency generation of the 532-nm light from the first-stage and the 754-nm light from a single-frequency CW Ti:Sapphire laser. Considering a nonlinear coefficient, it should be preferable to use a BiBO crystal for high-efficient SFG, but the 312-nm light might be absorbed by the BiBO crystal. Therefore, we chose a BBO as a nonlinear crystal to avoid the absorption of the 312-nm light.

  10. Tunable continuous wave emission via phase-matched second harmonic generation in a ZnSe microcylindrical resonator

    PubMed Central

    Vukovic, N.; Healy, N.; Sparks, J. R.; Badding, J. V.; Horak, P.; Peacock, A. C.

    2015-01-01

    Whispering gallery mode microresonators made from crystalline materials are of great interest for studies of low threshold nonlinear phenomena. Compared to amorphous materials, crystalline structures often exhibit desirable properties such as high indices of refraction, high nonlinearities, and large windows of transparency, making them ideal for use in frequency comb generation, microlasing and all-optical processing. In particular, crystalline materials can also possess a non-centrosymmetric structure which gives rise to the second order nonlinearity, necessary for three photon processes such as frequency doubling and parametric down-conversion. Here we report a novel route to fabricating crystalline zinc selenide microcylindrical resonators from our semiconductor fibre platform and demonstrate their use for tunable, low power continuous wave second harmonic generation. Visible red light is observed when pumped with a telecommunications band source by a process that is phase-matched between different higher order radial modes, possible due to the good spatial overlap between the pump and signal in the small volume resonator. By exploiting the geometrical flexibility offered by the fibre platform together with the ultra-wide 500–22000 nm transmission window of the ZnSe material, we expect these resonators to find use in applications ranging from spectroscopy to quantum information systems. PMID:26135636

  11. Continuous-wave operation of a broadly tunable thermoelectrically cooled external cavity quantum-cascade laser.

    PubMed

    Maulini, Richard; Yarekha, Dmitri A; Bulliard, Jean-Marc; Giovannini, Marcella; Faist, Jérôme; Gini, Emilio

    2005-10-01

    Continuous-wave operation of an external cavity quantum-cascade laser on a thermoelectric cooler is reported. The active region of the gain element was based on a bound-to-continuum design emitting near 5.15 microm. The external cavity setup was arranged in a Littrow configuration. The front facet of the gain chip was antireflection coated. The laser could be tuned over more than 170 cm(-1) from 4.94 to 5.4 microm and was single mode over more than 140 cm(-1). The output power was in excess of 10 mW over approximately 100 cm(-1) and in excess of 5 mW over approximately 130 cm(-1) at -30 degrees C. PMID:16208907

  12. Continuously tunable fibre attenuator operating in the wavelength range near 1.5 {mu}m

    SciTech Connect

    Baum, Ol'ga I; Mishakov, Gennadii V; Sokolov, Viktor I; Varlamova, Nina V; Zapadinskii, Boris I

    2004-09-30

    A fibre attenuator is fabricated for the telecommunication wavelength range near 1.5 {mu}m in which a single-mode silica fibre with side polishing is used. The fibre surface is covered by a layer of fluorine-containing polymer with a large thermooptic coefficient. The principle of attenuator operation is based on a change in the conditions of total internal reflection for a guided mode in the polished region due to thermally induced variation in the refractive index of the fluoropolymer layer. The attenuator is insensitive to light polarisation, it has a continuously variable attenuation coefficient in the range 0.2-27 dB, and can be easily incorporated into fibreoptic links. (fibre optics)

  13. Tunable, continuous-wave single-resonant optical parametric oscillator with output coupling for resonant wave

    NASA Astrophysics Data System (ADS)

    Xiong-Hua, Zheng; Bao-Fu, Zhang; Zhong-Xing, Jiao; Biao, Wang

    2016-01-01

    We present a continuous-wave singly-resonant optical parametric oscillator with 1.5% output coupling of the resonant signal wave, based on an angle-polished MgO-doped periodically poled lithium niobate (MgO:PPLN), pumped by a commercial Nd:YVO4 laser at 1064 nm. The output-coupled optical parametric oscillator delivers a maximum total output power of 4.19 W with 42.8% extraction efficiency, across a tuning range of 1717 nm in the near- and mid-infrared region. This indicates improvements of 1.87 W in output power, 19.1% in extraction efficiency and 213 nm in tuning range extension in comparison with the optical parametric oscillator with no output coupling, while at the expense of increasing the oscillation threshold by a factor of ˜ 2. Moreover, it is confirmed that the finite output coupling also contributes to the reduction of the thermal effects in crystal. Project supported by the National Natural Science Foundation of China (Grant Nos. 61308056, 11204044, 11232015, and 11072271), the Research Fund for the Doctoral Program of Higher Education of China (Grant Nos. 20120171110005 and 20130171130003), the Fundamental Research Funds for the Central Universities of China (Grant No. 14lgpy07), and the Opening Project of Science and Technology on Reliability Physics and Application Technology of Electronic Component Laboratory, China (Grant No. ZHD201203).

  14. Continuous-wave generation and tunability of eye-safe resonantly diode-pumped Er:YAG laser

    NASA Astrophysics Data System (ADS)

    Němec, Michal; Indra, Lukás.; Šulc, Jan; Jelínková, Helena

    2016-03-01

    Laser sources generating radiation in the spectral range from 1.5 to 1.7 μm are very attractive for many applications such as satellite communication, range finding, spectroscopy, and atmospheric sensing. The goal of our research was an investigation of continuous-wave generation and wavelength tuning possibility of diode pumped eye-safe Er:YAG laser emitting radiation around 1645 nm. We used two 0.5 at. % doped Er:YAG active media with lengths of 10 mm and 25 mm (diameter 5 mm). As a pumping source, a fibre-coupled 1452 nm laser-diode was utilized, which giving possibility of the in-band pumping with a small quantum defect and low thermal stress of the active bulk laser material. The 150 mm long resonator was formed by a pump mirror (HT @ 1450 nm, HR @ 1610 - 1660 nm) and output coupler with 96 % reflectivity at 1610 - 1660 nm. For continuous-wave generation, the maximal output powers were 0.7 W and 1 W for 10 mm and 25 mm long laser crystals, respectively. The corresponding slope efficiencies with respect to absorbed pump power for these Er:YAG lasers were 26.5 % and 37.8 %, respectively. The beam spatial structure was close to the fundamental Gaussian mode. A wavelength tunability was realized by a birefringent plate and four local spectral maxima at 1616, 1633, 1645, and 1657 nm were reached. The output characteristics of the designed and realized resonantly diode-pumped eye-safe Er:YAG laser show that this compact system has a potential for usage mainly in spectroscopic fields.

  15. Application of Continuously Frequency-Tunable 0.4 THz Gyrotron to Dynamic Nuclear Polarization for 600 MHz Solid-State NMR

    NASA Astrophysics Data System (ADS)

    Matsuki, Yoh; Ueda, Keisuke; Idehara, Toshitaka; Ikeda, Ryosuke; Kosuga, Kosuke; Ogawa, Isamu; Nakamura, Shinji; Toda, Mitsuru; Anai, Takahiro; Fujiwara, Toshimichi

    2012-07-01

    In this paper we present results that demonstrate the utility of a continuously frequency-tunable 0.4 THz-gyrotron in a dynamic nuclear polarization (DNP)-enhanced solid-state NMR (SSNMR) spectroscopy at one of the highest magnetic fields, B 0 = 14.1 T (600 MHz for 1H Larmor frequency). Our gyrotron called FU CW VI generates sub-mm wave at a frequency near 0.4 THz with an output power of 4-25 W and a tunability over a range of more than 1 GHz by sweeping the magnetic field at the gyrotron cavity. We observed overall down shifting of the central frequency by up to ~1 GHz at high radiation duty factors and beam current, presumably due to the cavity thermal expansion by a heating, but the tunable range was not significantly changed. The frequency tunability facilitated the optimization of the DNP resonance condition without time-consuming field-sweep of the high-resolution NMR magnet, and enabled us to observe substantial enhancement of the SSNMR signal ( ɛ DNP = 12 at 90 K).

  16. Continuous-Wave Operation of a Frequency-Tunable 460-GHz Second-Harmonic Gyrotron for Enhanced Nuclear Magnetic Resonance.

    PubMed

    Torrezan, Antonio C; Han, Seong-Tae; Mastovsky, Ivan; Shapiro, Michael A; Sirigiri, Jagadishwar R; Temkin, Richard J; Barnes, Alexander B; Griffin, Robert G

    2010-06-01

    The design, operation, and characterization of a continuous-wave (CW) tunable second-harmonic 460-GHz gyrotron are reported. The gyrotron is intended to be used as a submillimeter-wave source for 700-MHz nuclear magnetic resonance experiments with sensitivity enhanced by dynamic nuclear polarization. The gyrotron operates in the whispering-gallery mode TE(11,2) and has generated 16 W of output power with a 13-kV 100-mA electron beam. The start oscillation current measured over a range of magnetic field values is in good agreement with theoretical start currents obtained from linear theory for successive high-order axial modes TE(11,2,q). The minimum start current is 27 mA. Power and frequency tuning measurements as a function of the electron cyclotron frequency have also been carried out. A smooth frequency tuning range of 1 GHz was obtained for the operating second-harmonic mode either by magnetic field tuning or beam voltage tuning. Long-term CW operation was evaluated during an uninterrupted period of 48 h, where the gyrotron output power and frequency were kept stable to within ±0.7% and ±6 ppm, respectively, by a computerized control system. Proper operation of an internal quasi-optical mode converter implemented to transform the operating whispering-gallery mode to a Gaussian-like beam was also verified. Based on the images of the gyrotron output beam taken with a pyroelectric camera, the Gaussian-like mode content of the output beam was computed to be 92% with an ellipticity of 12%. PMID:21243088

  17. Continuous-Wave Operation of a Frequency-Tunable 460-GHz Second-Harmonic Gyrotron for Enhanced Nuclear Magnetic Resonance.

    PubMed

    Torrezan, Antonio C; Han, Seong-Tae; Mastovsky, Ivan; Shapiro, Michael A; Sirigiri, Jagadishwar R; Temkin, Richard J; Griffin, Robert G; Barnes, Alexander B

    2010-06-01

    The design, operation, and characterization of a continuous-wave (CW) tunable second-harmonic 460-GHz gyrotron are reported. The gyrotron is intended to be used as a submillimeter-wave source for 700-MHz nuclear magnetic resonance experiments with sensitivity enhanced by dynamic nuclear polarization. The gyrotron operates in the whispering-gallery mode TE11,2 and has generated 16 W of output power with a 13-kV 100-mA electron beam. The start oscillation current measured over a range of magnetic field values is in good agreement with theoretical start currents obtained from linear theory for successive high-order axial modes TE11,2,q. The minimum start current is 27 mA. Power and frequency tuning measurements as a function of the electron cyclotron frequency have also been carried out. A smooth frequency tuning range of 1 GHz was obtained for the operating second-harmonic mode either by magnetic field tuning or beam voltage tuning. Long-term CW operation was evaluated during an uninterrupted period of 48 h, where the gyrotron output power and frequency were kept stable to within ±0.7% and ±6 ppm, respectively, by a computerized control system. Proper operation of an internal quasi-optical mode converter implemented to transform the operating whispering-gallery mode to a Gaussian-like beam was also verified. Based on the images of the gyrotron output beam taken with a pyroelectric camera, the Gaussian-like mode content of the output beam was computed to be 92% with an ellipticity of 12%. PMID:23761938

  18. Continuous-Wave Operation of a Frequency-Tunable 460-GHz Second-Harmonic Gyrotron for Enhanced Nuclear Magnetic Resonance

    PubMed Central

    Torrezan, Antonio C.; Han, Seong-Tae; Mastovsky, Ivan; Shapiro, Michael A.; Sirigiri, Jagadishwar R.; Temkin, Richard J.; Barnes, Alexander B.; Griffin, Robert G.

    2011-01-01

    The design, operation, and characterization of a continuous-wave (CW) tunable second-harmonic 460-GHz gyrotron are reported. The gyrotron is intended to be used as a submillimeter-wave source for 700-MHz nuclear magnetic resonance experiments with sensitivity enhanced by dynamic nuclear polarization. The gyrotron operates in the whispering-gallery mode TE11,2 and has generated 16 W of output power with a 13-kV 100-mA electron beam. The start oscillation current measured over a range of magnetic field values is in good agreement with theoretical start currents obtained from linear theory for successive high-order axial modes TE11,2,q. The minimum start current is 27 mA. Power and frequency tuning measurements as a function of the electron cyclotron frequency have also been carried out. A smooth frequency tuning range of 1 GHz was obtained for the operating second-harmonic mode either by magnetic field tuning or beam voltage tuning. Long-term CW operation was evaluated during an uninterrupted period of 48 h, where the gyrotron output power and frequency were kept stable to within ±0.7% and ±6 ppm, respectively, by a computerized control system. Proper operation of an internal quasi-optical mode converter implemented to transform the operating whispering-gallery mode to a Gaussian-like beam was also verified. Based on the images of the gyrotron output beam taken with a pyroelectric camera, the Gaussian-like mode content of the output beam was computed to be 92% with an ellipticity of 12%. PMID:21243088

  19. Continuous-Wave Operation of a Frequency-Tunable 460-GHz Second-Harmonic Gyrotron for Enhanced Nuclear Magnetic Resonance

    PubMed Central

    Torrezan, Antonio C.; Han, Seong-Tae; Mastovsky, Ivan; Shapiro, Michael A.; Sirigiri, Jagadishwar R.; Temkin, Richard J.; Griffin, Robert G.; Barnes, Alexander B.

    2012-01-01

    The design, operation, and characterization of a continuous-wave (CW) tunable second-harmonic 460-GHz gyrotron are reported. The gyrotron is intended to be used as a submillimeter-wave source for 700-MHz nuclear magnetic resonance experiments with sensitivity enhanced by dynamic nuclear polarization. The gyrotron operates in the whispering-gallery mode TE11,2 and has generated 16 W of output power with a 13-kV 100-mA electron beam. The start oscillation current measured over a range of magnetic field values is in good agreement with theoretical start currents obtained from linear theory for successive high-order axial modes TE11,2,q. The minimum start current is 27 mA. Power and frequency tuning measurements as a function of the electron cyclotron frequency have also been carried out. A smooth frequency tuning range of 1 GHz was obtained for the operating second-harmonic mode either by magnetic field tuning or beam voltage tuning. Long-term CW operation was evaluated during an uninterrupted period of 48 h, where the gyrotron output power and frequency were kept stable to within ±0.7% and ±6 ppm, respectively, by a computerized control system. Proper operation of an internal quasi-optical mode converter implemented to transform the operating whispering-gallery mode to a Gaussian-like beam was also verified. Based on the images of the gyrotron output beam taken with a pyroelectric camera, the Gaussian-like mode content of the output beam was computed to be 92% with an ellipticity of 12%. PMID:23761938

  20. High power, widely tunable, mode-hop free, continuous wave external cavity quantum cascade laser for multi-species trace gas detection

    SciTech Connect

    Centeno, R.; Marchenko, D.; Mandon, J.; Cristescu, S. M.; Harren, F. J. M.; Wulterkens, G.

    2014-12-29

    We present a high power, widely tunable, continuous wave external cavity quantum cascade laser designed for infrared vibrational spectroscopy of molecules exhibiting broadband and single line absorption features. The laser source exhibits single mode operation with a tunability up to 303 cm{sup −1} (∼24% of the center wavelength) at 8 μm, with a maximum optical output power of 200 mW. In combination with off-axis integrated output spectroscopy, trace-gas detection of broadband absorption gases such as acetone was performed and a noise equivalent absorption sensitivity of 3.7 × 10{sup −8 }cm{sup −1 }Hz{sup −1/2} was obtained.

  1. Microelectromechanical tunable inductor

    DOEpatents

    Stalford, Harold L.; Hietala, Vincent M.; Fleming, James G.; Fleming, legal representative, Carol

    2010-05-04

    A microelectromechanical tunable inductor is formed from a pair of substantially-identically-sized coils arranged side by side and coiled up about a central axis which is parallel to a supporting substrate. An in-plane stress gradient is responsible for coiling up the coils which. The inductance provided by the tunable inductor can be electrostatically changed either continuously or in discrete steps using electrodes on the substrate and on each coil. The tunable inductor can be formed with processes which are compatible with conventional IC fabrication so that, in some cases, the tunable inductor can be formed on a semiconductor substrate alongside or on top of an IC.

  2. Continuously tunable, 6{endash}14 {mu}m silver-gallium selenide optical parametric oscillator pumped at 1.57 {mu}m

    SciTech Connect

    Chandra, S.; Allik, T.H.; Catella, G.; Utano, R.; Hutchinson, J.A.

    1997-08-01

    An angle tuned silver gallium selenide (AgGaSe{sub 2}) optical parametric oscillator (OPO), pumped by the fixed wavelength 1.57 {mu}m output of a noncritically phase-matched KTiOPO{sub 4} OPO, yielded radiation continuously tunable from 6 to 14 {mu}m. Energies of up to 1.2 mJ/pulse with bandwidths of {approximately}5cm{sup {minus}1} (full width at half-maximum) were obtained using a 6.5{times}6.5{times}35.3mm long, type I AgGaSe{sub 2} crystal. {copyright} {ital 1997 American Institute of Physics.}

  3. Continuously tunable 1.16 micros optical delay of 100 Gbit/s DQPSK and 50 Gbit/s DPSK signals using wavelength conversion and chromatic dispersion.

    PubMed

    Nuccio, S R; Yilmaz, O F; Wang, X; Wang, J; Wu, X; Willner, A E

    2010-06-01

    We demonstrate a variable optical delay element that uses tunable wavelength conversion and phase conjugation in highly nonlinear fiber and uses chromatic dispersion in dispersion-compensating fiber. A continuous delay of up to 1.16mus, equaling a >110,000 time-delay bit-rate product for 100 Gbit/s non-return-to-zero differential quadrature phase-shift-keying (NRZ-DQSPK) and >55,000 for 50 Gbit/s NRZ differential phase-shift-keying (NRZ-DPSK) modulation formats, is demonstrated. Bit error rates <10(-9) are demonstrated for each waveform at various delay settings. PMID:20517427

  4. High-power continuous-wave tunable 544- and 272-nm beams based on a diode-oscillator fiber-amplifier for calcium spectroscopy

    NASA Astrophysics Data System (ADS)

    Ko, Kwang-Hoon; Kim, Yonghee; Park, Hyunmin; Cha, Yong-Ho; Kim, Taek-Soo; Lee, Lim; Lim, Gwon; Han, Jaemin; Ko, Kwang-Hee; Jeong, Do-Young

    2015-08-01

    Continuous-wave single-frequency tunable 544- and 272-nm beams have been demonstrated by the second- and fourth-harmonic conversions of a 1088-nm fundamental beam from a diode-oscillator fiber-amplifier. The single-pass second-harmonic generation with a MgO-doped periodically poled stoichiometric LiTaO3 crystal and the external-cavity frequency-doubling technique with a bulk BBO crystal were employed to achieve an approximately 6-W 544-nm beam and a 1.5-W 272-nm beam, respectively. We characterized the second- and fourth-harmonic generations and discussed their applications to calcium spectroscopy.

  5. Tunable circuit for tunable capacitor devices

    SciTech Connect

    Rivkina, Tatiana; Ginley, David S.

    2006-09-19

    A tunable circuit (10) for a capacitively tunable capacitor device (12) is provided. The tunable circuit (10) comprises a tunable circuit element (14) and a non-tunable dielectric element (16) coupled to the tunable circuit element (16). A tunable capacitor device (12) and a method for increasing the figure of merit in a tunable capacitor device (12) are also provided.

  6. High power and spectral purity continuous-wave photonic THz source tunable from 1 to 4.5 THz for nonlinear molecular spectroscopy

    NASA Astrophysics Data System (ADS)

    Kiessling, J.; Breunig, I.; Schunemann, P. G.; Buse, K.; Vodopyanov, K. L.

    2013-10-01

    We report a diffraction-limited photonic terahertz (THz) source with linewidth <10 MHz that can be used for nonlinear THz studies in the continuous wave (CW) regime with uninterrupted tunability in a broad range of THz frequencies. THz output is produced in orientation-patterned (OP) gallium arsenide (GaAs) via intracavity frequency mixing between the two closely spaced resonating signal and idler waves of an optical parametric oscillator (OPO) operating near λ = 2 μm. The doubly resonant type II OPO is based on a periodically poled lithium niobate (PPLN) pumped by a single-frequency Yb:YAG disc laser at 1030 nm. We take advantage of the enhancement of both optical fields inside a high-finesse OPO cavity: with 10 W of 1030 nm pump, 100 W of intracavity power near 2 μm was attained with GaAs inside cavity. This allows dramatic improvement in terms of generated THz power, as compared to the state-of-the art CW methods. We achieved >25 μW of single-frequency tunable CW THz output power scalable to >1 mW with proper choice of pump laser wavelength.

  7. Intersubband Rabi oscillations in asymmetric nanoheterostructures: implications for a tunable continuous-wave source of a far-infrared and THz radiation.

    PubMed

    Kukushkin, V A

    2012-06-01

    A tunable continuous-wave source of a far-infrared and THz radiation based on a semiconductor nanoheterostructure with asymmetric quantum wells is suggested. It utilizes Rabi oscillations at a transition between quantum well subbands excited by external femtosecond pulses of a mid-infrared electromagnetic field. Due to quantum well broken inversion symmetry the subbands possess different average dipole moments, which enables the creation of polarization at the Rabi frequency as the subband populations change. It is shown that if this polarization is excited so that it is periodic in space, then, though being pulsed, it can produce continuous-wave output radiation. Changing the polarization space period and the time intervals between the exciting pulses, one can tune the frequency of this radiation throughout the far-infrared and THz range. In the present work a concrete multiple quantum well heterostructure design and a scheme of its space-periodic polarization are suggested. It is shown that for existing sources of mid-infrared femtosecond pulses the proposed scheme can provide a continuous-wave output power of order the power of far-infrared and THz quantum cascade lasers. Being added to the possibility of its output frequency tuning, this can make the suggested device attractive for fundamental research and various applications. PMID:22905512

  8. Continuous Flow Atmospheric Pressure Laser Desorption/Ionization Using a 6–7-µm-Band Mid-Infrared Tunable Laser for Biomolecular Mass Spectrometry

    PubMed Central

    Hiraguchi, Ryuji; Hazama, Hisanao; Senoo, Kenichirou; Yahata, Yukinori; Masuda, Katsuyoshi; Awazu, Kunio

    2014-01-01

    A continuous flow atmospheric pressure laser desorption/ionization technique using a porous stainless steel probe and a 6–7-µm-band mid-infrared tunable laser was developed. This ion source is capable of direct ionization from a continuous flow with a high temporal stability. The 6–7-µm wavelength region corresponds to the characteristic absorption bands of various molecular vibration modes, including O–H, C=O, CH3 and C–N bonds. Consequently, many organic compounds and solvents, including water, have characteristic absorption peaks in this region. This ion source requires no additional matrix, and utilizes water or acetonitrile as the solvent matrix at several absorption peak wavelengths (6.05 and 7.27 µm, respectively). The distribution of multiply-charged peptide ions is extremely sensitive to the temperature of the heated capillary, which is the inlet of the mass spectrometer. This ionization technique has potential for the interface of liquid chromatography/mass spectrometry (LC/MS). PMID:24937686

  9. Ultrawide continuously tunable 1.55-μm vertical air-cavity wavelength-selective elements for VCSELs using micromachined electrostatic actuation

    NASA Astrophysics Data System (ADS)

    Hillmer, Hartmut H.; Daleiden, Juergen; Prott, Cornelia; Roemer, Friedhard; Irmer, Soeren; Ataro, Edwin; Tarraf, Amer; Gutermuth, D.; Kommallein, I.; Strassner, Martin

    2003-08-01

    Surface-micromachined 1.55μm vertical-resonator-based devices, capable of wide, continuous, monotonic and kink-free tuning are designed, technologically implemented and characterized. Tuning is achieved by mechanically actuating one or several membranes in a vertical resonator including two ultra-highly reflective DBR mirrors. The tuning is controlled by a single parameter (actuation voltage). The two different layers composing the mirrors reveal a very strong refractive index contrast. Filters including InP/air-gap DBR's (3.5 periods) using GaInAs sacrificial layers reveal a continuous tuning of up to 9% of the absolute wavelength. Varying a reverse voltage (U=0 .. -3.2V) between the membranes, a tuning range up to 142nm was obtained by electrostatic actuation. The correlation of the wavelength and the applied voltage is accurately reproducible without any hysteresis. Theoretical model calculations are performed for symmetric and asymmetric device structures, varying layer thickness and compositions. Models of highly sophisticated color tuning can be found in nature, e.g. in tunable spectral light filtering by trogon and butterfly wings. Bionics transfers the principles of success of nature into natural science, engineering disciplines and applications (here filters and VCSELs for optical communication on the basis of WDM). Light interferes constructively and destructively with nano- and microstructures of appropriate shape, dimensions and materials, both in the artificial DBR structures fabricated in our labs as well as in the natural ones.

  10. Continuous flow atmospheric pressure laser desorption/ionization using a 6-7-µm-band mid-infrared tunable laser for biomolecular mass spectrometry.

    PubMed

    Hiraguchi, Ryuji; Hazama, Hisanao; Senoo, Kenichirou; Yahata, Yukinori; Masuda, Katsuyoshi; Awazu, Kunio

    2014-01-01

    A continuous flow atmospheric pressure laser desorption/ionization technique using a porous stainless steel probe and a 6-7-µm-band mid-infrared tunable laser was developed. This ion source is capable of direct ionization from a continuous flow with a high temporal stability. The 6-7-µm wavelength region corresponds to the characteristic absorption bands of various molecular vibration modes, including O-H, C=O, CH3 and C-N bonds. Consequently, many organic compounds and solvents, including water, have characteristic absorption peaks in this region. This ion source requires no additional matrix, and utilizes water or acetonitrile as the solvent matrix at several absorption peak wavelengths (6.05 and 7.27 µm, respectively). The distribution of multiply-charged peptide ions is extremely sensitive to the temperature of the heated capillary, which is the inlet of the mass spectrometer. This ionization technique has potential for the interface of liquid chromatography/mass spectrometry (LC/MS). PMID:24937686

  11. Linewidth narrowing of a tunable mode-locked pumped continuous-wave Ce:LiCAF laser.

    PubMed

    Wellmann, Barbara; Kitzler, Ondrej; Spence, David J; Coutts, David W

    2015-07-01

    We report birefringent tuning using single and multiple magnesium fluoride (MgF(2)) Brewster tuning plates in a mode-locked pumped continuous-wave Ce:LiCAF laser. Depending on the thickness of the MgF(2) plates used, continuous tuning over a range of up to 13 nm from 284.5 to 297.5 nm with a full width at half-maximum linewidth of 14 pm (50 GHz) was achieved. By combining MgF(2) plates with etalons, the linewidth of the laser was narrowed down to 0.75 pm (2.7 GHz). This generated narrowband output is suitable for many applications in spectroscopy, cold-atom manipulation, and sensing. PMID:26125368

  12. Room temperature continuous wave, monolithic tunable THz sources based on highly efficient mid-infrared quantum cascade lasers

    PubMed Central

    Lu, Quanyong; Wu, Donghai; Sengupta, Saumya; Slivken, Steven; Razeghi, Manijeh

    2016-01-01

    A compact, high power, room temperature continuous wave terahertz source emitting in a wide frequency range (ν ~ 1–5 THz) is of great importance to terahertz system development for applications in spectroscopy, communication, sensing, and imaging. Here, we present a strong-coupled strain-balanced quantum cascade laser design for efficient THz generation based on intracavity difference frequency generation. Room temperature continuous wave emission at 3.41 THz with a side-mode suppression ratio of 30 dB and output power up to 14 μW is achieved with a wall-plug efficiency about one order of magnitude higher than previous demonstrations. With this highly efficient design, continuous wave, single mode THz emissions with a wide frequency tuning range of 2.06–4.35 THz and an output power up to 4.2 μW are demonstrated at room temperature from two monolithic three-section sampled grating distributed feedback-distributed Bragg reflector lasers. PMID:27009375

  13. Room temperature continuous wave, monolithic tunable THz sources based on highly efficient mid-infrared quantum cascade lasers.

    PubMed

    Lu, Quanyong; Wu, Donghai; Sengupta, Saumya; Slivken, Steven; Razeghi, Manijeh

    2016-01-01

    A compact, high power, room temperature continuous wave terahertz source emitting in a wide frequency range (ν~1-5 THz) is of great importance to terahertz system development for applications in spectroscopy, communication, sensing, and imaging. Here, we present a strong-coupled strain-balanced quantum cascade laser design for efficient THz generation based on intracavity difference frequency generation. Room temperature continuous wave emission at 3.41 THz with a side-mode suppression ratio of 30 dB and output power up to 14 μW is achieved with a wall-plug efficiency about one order of magnitude higher than previous demonstrations. With this highly efficient design, continuous wave, single mode THz emissions with a wide frequency tuning range of 2.06-4.35 THz and an output power up to 4.2 μW are demonstrated at room temperature from two monolithic three-section sampled grating distributed feedback-distributed Bragg reflector lasers. PMID:27009375

  14. Room temperature continuous wave, monolithic tunable THz sources based on highly efficient mid-infrared quantum cascade lasers

    NASA Astrophysics Data System (ADS)

    Lu, Quanyong; Wu, Donghai; Sengupta, Saumya; Slivken, Steven; Razeghi, Manijeh

    2016-03-01

    A compact, high power, room temperature continuous wave terahertz source emitting in a wide frequency range (ν ~ 1–5 THz) is of great importance to terahertz system development for applications in spectroscopy, communication, sensing, and imaging. Here, we present a strong-coupled strain-balanced quantum cascade laser design for efficient THz generation based on intracavity difference frequency generation. Room temperature continuous wave emission at 3.41 THz with a side-mode suppression ratio of 30 dB and output power up to 14 μW is achieved with a wall-plug efficiency about one order of magnitude higher than previous demonstrations. With this highly efficient design, continuous wave, single mode THz emissions with a wide frequency tuning range of 2.06–4.35 THz and an output power up to 4.2 μW are demonstrated at room temperature from two monolithic three-section sampled grating distributed feedback-distributed Bragg reflector lasers.

  15. Simultaneous measurements of atmospheric HONO and NO2 via absorption spectroscopy using tunable mid-infrared continuous-wave quantum cascade lasers

    NASA Astrophysics Data System (ADS)

    Lee, B. H.; Wood, E. C.; Zahniser, M. S.; McManus, J. B.; Nelson, D. D.; Herndon, S. C.; Santoni, G. W.; Wofsy, S. C.; Munger, J. W.

    2011-02-01

    Nitrous acid (HONO) is important as a significant source of hydroxyl radical (OH) in the troposphere and as a potent indoor air pollutant. It is thought to be generated in both environments via heterogeneous reactions involving nitrogen dioxide (NO2). In order to enable fast-response HONO detection suitable for eddy-covariance flux measurements and to provide a direct method that avoids interferences associated with derivatization, we have developed a 2-channel tunable infrared laser differential absorption spectrometer (TILDAS) capable of simultaneous high-frequency measurements of HONO and NO2. Beams from two mid-infrared continuous-wave mode quantum cascade lasers (cw-QCLs) traverse separate 210 m paths through a multi-pass astigmatic sampling cell at reduced pressure for the direct detection of HONO (1660 cm-1) and NO2 (1604 cm-1). The resulting one-second detection limits (S/N=3) are 300 and 30 ppt (pmol/mol) for HONO and NO2, respectively. Our HONO quantification is based on revised line-strengths and peak positions for cis-HONO in the 6-micron spectral region that were derived from laboratory measurements. An essential component of ambient HONO measurements is the inlet system and we demonstrate that heated surfaces and reduced pressure minimize sampling artifacts.

  16. Controlled growth of super-aligned carbon nanotube arrays for spinning continuous unidirectional sheets with tunable physical properties.

    PubMed

    Liu, Kai; Sun, Yinghui; Chen, Lei; Feng, Chen; Feng, Xiaofeng; Jiang, Kaili; Zhao, Yonggang; Fan, Shoushan

    2008-02-01

    We report controlled syntheses of super-aligned carbon nanotube (CNT) arrays with the desired tube-diameter, number of walls, and length for spinning continuous unidirectional sheets to meet a variety of industrial demands. The tube-diameter distribution of super-aligned arrays is well controlled by varying the thicknesses of catalyst films, and the length of them is tuned by the growth time. Further investigation indicates that the physical properties of the unidirectional sheets, such as electrical transport, optical transmittance, and light emission properties, can be well tuned by the tube-diameter- and length-controlled growth. This work extends the understanding of the super-aligned CNT arrays and will be very helpful in developing further applications. PMID:18269255

  17. 2 nm continuously tunable 488nm micro-integrated diode-laser-based SHG light source for Raman spectroscopy

    NASA Astrophysics Data System (ADS)

    Braune, M.; Maiwald, M.; Sumpf, B.; Tränkle, G.

    2016-04-01

    Raman spectroscopy in the visible spectral range is of great interest due to resonant Raman effects. Nevertheless, fluorescence and ambient light can mask the weak Raman lines. Shifted excitation Raman difference spectroscopy is a demonstrated tool to overcome this drawback. To apply this method, a light source with two alternating wavelengths is necessary. The spectral distance between these two wavelengths has to be adapted to the width of the Raman signal. According to the sample under investigation the width of the Raman signal could be in the range of 3 cm-1 - 12 cm-1. In this work, a micro-integrated light source emitting at 488 nm with a continuous wavelength tuning range up to 2 nm (83 cm-1) is presented. The pump source, a DFB laser emitting at 976 nm, and a periodically poled lithium niobate (PPLN) ridge waveguide crystal is used for the second harmonic generation (SHG). Both components are mounted on a μ-Peltier-element for temperature control. Here, a common wavelength tuning of the pump wavelength and the acceptance bandwidth of the SHG crystal via temperature is achieved. With the results the light source is suitable for portable Raman and SERDS experiments with a flexible spectral distance between both excitation wavelengths for SERDS with respect to the sample under investigation.

  18. Tunable lasers- an overview

    SciTech Connect

    Guenther, B.D.; Buser, R.G.

    1982-08-01

    This overview of tunable lasers describes their applicability to spectroscopy in the ultraviolet and middle infrared ranges; to rapid on-line diagnostics by ultrashort cavity lasers; to exploration, by the free electron laser, for its wide tuning in the far infrared to submillimeter region; to remote detection, in areas such as portable pollution monitors, on-line chemical analyzers, auto exhaust analyzers, and production line controls; to photochemistry; and to other potential areas in diagnostics, communications, and medical and biological sciences. The following lasers are characterized by their tunability: solid state lasers, primarily alexandrite, with a tuning range of ca 1000 Angstroms; color center lasers; semiconductor lasers; dye lasers; gas lasers, where high-pressure CO/sub 2/ discharges are the best known example for a wide tunability range, and research is continuing in systems such as the alkali dimers; and, at wavelengths beyond 10 micrometers, the possibilities beyond Cerenkov and free electron lasers.

  19. All-optical continuously tunable delay with a high linear-chirp-rate fiber Bragg grating based on four-wave mixing in a highly-nonlinear photonic crystal fiber

    NASA Astrophysics Data System (ADS)

    Liu, Jianguo; Cheng, Tee Hiang; Yeo, Yong Kee; Wang, Yixin; Xue, Lifang; Zhu, Ninghua; Xu, ZhaoWen; Wang, Dawei

    2009-11-01

    A scheme for hi-fi all-optical continuously tunable delay is proposed. The signal wavelength is converted to a desired idler wavelength and converted back after being delayed by a high linear-chirp-rate (HLCR) fiber Bragg grating (FBG) based on four-wave mixing (FWM) in a highly-nonlinear photonic crystal fiber (HN-PCF). In our experiment, 400 ps (more than 8 full width of half maximum, FWHM) tunable delay is achieved for a 10 GHz clock pulse with relative pulse width broaden ratio (RPWBR) of 2.08%. The power penalty is only 0.3 dB at 10 -9 BER for a 10 Gb/s 2 31-1 pseudo random bit sequence (PRBS) data.

  20. Tunable beam displacer

    SciTech Connect

    Salazar-Serrano, Luis José; Valencia, Alejandra; Torres, Juan P.

    2015-03-15

    We report the implementation of a tunable beam displacer, composed of a polarizing beam splitter (PBS) and two mirrors, that divides an initially polarized beam into two parallel beams whose separation can be continuously tuned. The two output beams are linearly polarized with either vertical or horizontal polarization and no optical path difference is introduced between them. The wavelength dependence of the device as well as the maximum separation between the beams achievable is limited mainly by the PBS characteristics.

  1. Switchable dual-wavelength SOA-based fiber laser with continuous tunability over the C-band at room-temperature.

    PubMed

    Ummy, M A; Madamopoulos, N; Razani, M; Hossain, A; Dorsinville, R

    2012-10-01

    We propose and demonstrate a simple compact, inexpensive, SOA-based, dual-wavelength tunable fiber laser, that can potentially be used for photoconductive mixing and generation of waves in the microwave and THz regions. A C-band semiconductor optical amplifier (SOA) is placed inside a linear cavity with two Sagnac loop mirrors at its either ends, which act as both reflectors and output ports. The selectivity of dual wavelengths and the tunability of the wavelength difference (Δλ) between them is accomplished by placing a narrow bandwidth (e.g., 0.3 nm) tunable thin film-based filter and a fiber Bragg grating (with bandwidth 0.28 nm) inside the loop mirror that operates as the output port. A total output power of + 6.9 dBm for the two wavelengths is measured and the potential for higher output powers is discussed. Optical power and wavelength stability are measured at 0.33 dB and 0.014 nm, respectively. PMID:23188300

  2. Femtosecond tunable light source

    NASA Astrophysics Data System (ADS)

    Miesak, Edward Jozef

    1999-09-01

    A practical source of continuously tunable coherent visible and infrared light would have an enormous impact on science, medicine and technology. While microwave and radio transmitters offer wide tunability at the ``turn of a knob,'' the best known source of coherent optical radiation, the laser, does not possess the same versatility. Dye lasers provide some degree of tunability, but many dyes are needed to cover even the visible region. Ti:sapphire lasers are tunable only over the red to near infra-red portion of the spectrum (about 65 0 nm to about 1.1μm). This presentation documents the development of a unique pulsed light source tunable across the visible and near infrared portion of the spectrum, a femtosecond optical parametric amplifier (OPA). Much work was expended in developing the system itself. But a great deal of work was also done in developing the support equipment (hardware and software) necessary to build as well as maintain and operate an OPA. Once completed, the system characteristics were measured and documented. Initially it possessed ``personality'' which had to be understood and removed as much as possible. In addition, the pump source for this OPA, a regenerative amplifier, is unique in that it uses Cr3+:LiSGaF as the gain medium. This regen was also characterized and compared to other more standard regenerative amplifiers. System verification was done by performing a standard experiment (Z-scan) on well known samples, several of which are well characterized at specific wavelengths (1.06 μm, 0.523 μm) in the nanosecond and picosecond regimes. The results were compared against previously published results. The OPA was also compared against another very similar system which became commercially available during the time of this research. The results were helpful in analyzing the light source(s) and data acquisition systems for areas that could be improved.

  3. Continuously tunable wavelength output from an Er-doped fiber femtosecond optical frequency comb with single-point frequency-doubling technique

    NASA Astrophysics Data System (ADS)

    Liu, H.; Cao, S. Y.; Meng, F.; Lin, B. K.; Fang, Z. J.

    2015-07-01

    Femtosecond optical frequency combs (FOFCs) with wavelengths covering the visible range have potential applications in the absolute frequency measurement of iodine-stabilized lasers and optical clock lasers. In this paper, an Er-FOFC with a tunable wavelength output from 689 to 813 nm based on the single-point frequency-doubling technique is demonstrated. Meanwhile, a beat frequency signal between the Er-FOFC and a tested laser at 729 nm with a signal-to-noise ratio of 30 dB at a resolution bandwidth of 100 kHz is obtained.

  4. Femtosecond wavelength-tunable OPCPA system based on picosecond fiber laser seed and picosecond DPSS laser pump.

    PubMed

    Danilevičius, R; Zaukevičius, A; Budriūnas, R; Michailovas, A; Rusteika, N

    2016-07-25

    We present a compact and stable femtosecond wavelength-tunable optical parametric chirped pulse amplification (OPCPA) system. A novel OPCPA front-end was constructed using a multi-channel picosecond all-in-fiber source for seeding DPSS pump laser and white light supercontinuum generation. Broadband chirped pulses were parametrically amplified up to 1 mJ energy and compressed to less than 40 fs duration. Pulse wavelength tunability in the range from 680 nm to 930 nm was experimentally demonstrated. PMID:27464199

  5. Tunable infrared laser sources and applications

    NASA Astrophysics Data System (ADS)

    Libatique, Nathaniel Joseph C.

    Fiber lasers are emerging as attractive alternative technologies for wavelength-selectable WDM sources because of a number of reasons which include: (1) their direct compatibility with the fiber-optic transmission medium, (2) the excellent amplifying properties of rare-earth doped fibers and the rapidly continuing progress in novel fiber gain media (i.e. L-Band, S-band, and Raman fiber amplifiers), (3) the potential for order-of-magnitude power scalability via the use of double-clad geometries, (4) the maturity and robustness of the laser diode pumps used, and (5) the ready availability of fiber-based components and fiber-pigtailed devices (i.e. fused couplers, Bragg gratings, polarization controllers, etalons). The tunable laser applications of interest to this work have two distinct performance requirements, the need for either continuous tunability (the ability to tune the lasing emission through a continuous range of wavelengths) or discrete tunability (the ability to switch the lasing emission to an arbitrarily-fixed set of wavelengths). The latter class of "push-button" switchability to pre-set wavelength channels is especially critical for WDM optical communications. In this Thesis, I will discuss experimental achievements and key issues related to the design and demonstration of these two classes of tunable lasers, with a special emphasis on channel-selectable sources for optical communications. In particular I will discuss: (1) Novel FBG-based rapidly wavelength-selectable WDM sources, the scaling of such FBG-string-based tunable sources to intermediate channel counts, and the demonstration of single frequency tunable WDM sources based on line-narrowed tunable FBGs. (2) The first demonstration of a potentially all-fiber wavelength-selectable WDM laser source based on a fiber Sagnac loop filter. (3) Wavelength-selectable WDM laser sources based on the novel use of a current-tunable (semiconductor Fabry-Perot) grid filter. (4) The first demonstration of a

  6. Wavelength-tunable laser based on electro-optic effect

    NASA Astrophysics Data System (ADS)

    Wu, Pengfei; Tang, Suning

    2015-03-01

    Currently available wavelength-tunable lasers have technical difficulty in combining high-speed, continuous and wide wavelength tunability with high output power. We demonstrated a high-speed wavelength-tunable laser based on a fast electro-optic effect. We observed that the wavelength-swept speed exceeds 107 nm/s at center wavelength of 1550 nm with continuous wavelength tunability. Moreover, the maximum output power is over 100 mW and the wavelength tuning range is near 100 nm with a full width at half maximum of less than 0.5 nm.

  7. Tunable liquid crystal photonic devices

    NASA Astrophysics Data System (ADS)

    Fan, Yun-Hsing

    2005-07-01

    Liquid crystal (LC)-based adaptive optics are important for information processing, optical interconnections, photonics, integrated optics, and optical communications due to their tunable optical properties. In this dissertation, we describe novel liquid crystal photonic devices. In Chap. 3, we demonstrate a novel electrically tunable-efficiency Fresnel lens which is devised for the first time using nanoscale PDLC. The tunable Fresnel lens is very desirable to eliminate the need of external spatial light modulator. The nanoscale LC devices are polarization independent and exhibit a fast response time. Because of the small droplet sizes, the operating voltage is higher than 100 Vrms. To lower the driving voltage, in Chap. 2 and Chap. 3, we have investigated tunable Fresnel lens using polymer-network liquid crystal (PNLC) and phase-separated composite film (PSCOF). The operating voltage is below 12 Vrms. The PNLC and PSCOF devices are polarization dependent. To overcome this shortcoming, stacking two cells with orthogonal alignment directions is a possibility. Using PNLC, we also demonstrated LC blazed grating. The diffraction efficiency of these devices is continuously controlled by the electric field. We also develop a system with continuously tunable focal length. A conventional mechanical zooming system is bulky and power hungry. In Chap. 4, we developed an electrically tunable-focus flat LC spherical lens and microlens array. A huge tunable range from 0.6 m to infinity is achieved by the applied voltage. In Chap. 5, we describe a LC microlens array whose focal length can be switched from positive to negative by the applied voltage. The fast response time feature of our LC microlens array will be very helpful in developing 3-D animated images. In Chap. 6, we demonstrate polymer network liquid crystals for switchable polarizers and optical shutters. The use of dual-frequency liquid crystal and special driving scheme leads to a sub-millisecond response time. In

  8. Continuously Frequency Tunable High Power Sub-THz Radiation Source—Gyrotron FU CW VI for 600 MHz DNP-NMR Spectroscopy

    NASA Astrophysics Data System (ADS)

    Idehara, Toshitaka; Kosuga, Kosuke; Agusu, La; Ikeda, Ryosuke; Ogawa, Isamu; Saito, Teruo; Matsuki, Yoh; Ueda, Keisuke; Fujiwara, Toshimichi

    2010-07-01

    A high frequency gyrotron with a 15 T superconducting magnet named Gyrotron FU CW VI has achieved continuous frequency tuning through the relatively wide range of 1.5 GHz near 400 GHz. The operation is at the fundamental cyclotron resonance of the TE06 cavity mode with many higher order axial modes. The output power measured at the end of the circular waveguide system ranges from 10 to 50 watts at the low acceleration voltage of 12 kV for beam electrons. The beam current is also low. It is around 250 mA. This gyrotron is designed as a demountable radiation source for the 600 MHz DNP-NMR spectroscopy. The design and operation results of the gyrotron FU CW VI are presented.

  9. Tunable plasmonic crystal

    DOEpatents

    Dyer, Gregory Conrad; Shaner, Eric A.; Reno, John L.; Aizin, Gregory

    2015-08-11

    A tunable plasmonic crystal comprises several periods in a two-dimensional electron or hole gas plasmonic medium that is both extremely subwavelength (.about..lamda./100) and tunable through the application of voltages to metal electrodes. Tuning of the plasmonic crystal band edges can be realized in materials such as semiconductors and graphene to actively control the plasmonic crystal dispersion in the terahertz and infrared spectral regions. The tunable plasmonic crystal provides a useful degree of freedom for applications in slow light devices, voltage-tunable waveguides, filters, ultra-sensitive direct and heterodyne THz detectors, and THz oscillators.

  10. Synchronized ps fiber lasers with pulse durations (25, 50, 100-2000ps) and repetition rates (100kHz-150Mhz) continuously tunable over three orders of magnitude

    NASA Astrophysics Data System (ADS)

    Dupuis, Alexandre; Burgoyne, Bryan; Pena, Guido; Archambault, André; Lemieux, Dominic; Solomonean, Vasile; Duong, Maxime; Villeneuve, Alain

    2013-03-01

    Ultrafast lasers are enabling precision machining of a wide variety of materials. However, the optimal laser parameters for proper material processing can differ greatly from one material to another. In order to cut high aspect-ratio features at high processing speeds the laser parameters such as pulse energy, repetition rate, and cutting speed need to be optimized. In particular, a shorter pulse duration plays an important role in reducing the thermal damage in the Heat-Affected Zones. In this paper we present a novel ps fiber laser whose electronically tunable parameters aim to facilitate the search for optimal processing parameters. The 20W 1064nm Yb fiber laser is based on a Master Oscillator Power Amplifier (MOPA) architecture with a repetition rate that can be tuned continuously from 120kHz to 120MHz. More importantly, the integration of three different pulse generators enables the pulse duration to be switched from 25ps to 50ps, or to any value within the 55ps to 2000ps range. By reducing the pulse duration from the ns-regime down to 25ps, the laser approaches the transition from the thermal processing regime to the ablation regime of most materials. Moreover, in this paper we demonstrate the synchronization of the pulses from two such MOPA lasers. This enables more elaborate multipulse processing schemes where the pulses of each laser can be set to different parameter values, such as an initial etching pulse followed by a thermal annealing pulse. It should be noted that all the laser parameters are controlled electronically with no moving parts, including the synchronization.

  11. Magnetic field tunability of optical microfiber taper integrated with ferrofluid.

    PubMed

    Miao, Yinping; Wu, Jixuan; Lin, Wei; Zhang, Kailiang; Yuan, Yujie; Song, Binbin; Zhang, Hao; Liu, Bo; Yao, Jianquan

    2013-12-01

    Optical microfiber taper has unique propagation properties, which provides versatile waveguide structure to design the tunable photonic devices. In this paper, the S-tapered microfiber is fabricated by using simple fusion spicing. The spectral characteristics of microfiber taper integrated with ferrofluid under different magnetic-field intensities have been theoretically analyzed and experimentally demonstrated. The spectrum are both found to become highly magnetic-field-dependent. The results indicate the transmission and wavelength of the dips are adjustable by changing magnetic field intensity. The response of this device to the magnetic field intensity exhibits a Langvin function. Moreover, there is a linear relationship between the transmission loss and magnetic field intensity for a magnetic field intensity range of 25 to 200Oe, and the sensitivities as high as 0.13056dB/Oe and 0.056nm/Oe have been achieved, respectively. This suggests a potential application of this device as a tunable all-in-fiber photonic device, such as magneto-optic modulator, filter, and sensing element. PMID:24514542

  12. Tunable nanowire nonlinear optical probe

    SciTech Connect

    Nakayama, Yuri; Pauzauskie, Peter J.; Radenovic, Aleksandra; Onorato, Robert M.; Saykally, Richard J.; Liphardt, Jan; Yang, Peidong

    2008-02-18

    One crucial challenge for subwavelength optics has been thedevelopment of a tunable source of coherent laser radiation for use inthe physical, information, and biological sciences that is stable at roomtemperature and physiological conditions. Current advanced near-fieldimaging techniques using fiber-optic scattering probes1,2 have alreadyachieved spatial resolution down to the 20-nm range. Recently reportedfar-field approaches for optical microscopy, including stimulatedemission depletion (STED)3, structured illumination4, and photoactivatedlocalization microscopy (PALM)5, have also enabled impressive,theoretically-unlimited spatial resolution of fluorescent biomolecularcomplexes. Previous work with laser tweezers6-8 has suggested the promiseof using optical traps to create novel spatial probes and sensors.Inorganic nanowires have diameters substantially below the wavelength ofvisible light and have unique electronic and optical properties9,10 thatmake them prime candidates for subwavelength laser and imagingtechnology. Here we report the development of an electrode-free,continuously-tunable coherent visible light source compatible withphysiological environments, from individual potassium niobate (KNbO3)nanowires. These wires exhibit efficient second harmonic generation(SHG), and act as frequency converters, allowing the local synthesis of awide range of colors via sum and difference frequency generation (SFG,DFG). We use this tunable nanometric light source to implement a novelform of subwavelength microscopy, in which an infrared (IR) laser is usedto optically trap and scan a nanowire over a sample, suggesting a widerange of potential applications in physics, chemistry, materials science,and biology.

  13. Graphene: Tunable superdoping

    NASA Astrophysics Data System (ADS)

    Dai, Liming

    2016-04-01

    Doping graphitic materials is desirable to enhance their performance for energy conversion and storage applications, but achieving high dopant concentrations remains a challenge. Researchers now demonstrate synthesis of such materials with very high doping levels and facile tunability.

  14. Tunable resonant structures for photonic integrated circuits

    NASA Astrophysics Data System (ADS)

    Ptasinski, Joanna Nina

    Photonics is an evolving field allowing for optical devices to be made cost effectively using standard semiconductor fabrication techniques, which in turn enables integration with microelectronic chips. Chip scale photonics will play an increasing role in the future of communications as the demand for bandwidth and reduced power consumption per bit continues to grow. Tunable optical circuit components are one of the essential technologies in the development of photonic analogues for classical electronic devices, where tunable photonic resonant structures allow for altering of their electromagnetic spectrum and find applications in optical switching, filtering, buffering, lasers and biosensors. The scope of this work is focused on tunable resonant structures for photonic integrated circuits. Specifically, this work demonstrates active tuning of silicon photonic resonant structures using the properties of dye doped nematic liquid crystals, temperature stabilization of silicon photonics using the passive properties of liquid crystals, and the effects of low density plasma enhanced chemical vapor deposition (PECVD) claddings on ring resonator device performance.

  15. Tunable semiconductor lasers

    NASA Technical Reports Server (NTRS)

    Taghavi-Larigani, Shervin (Inventor); Vanzyl, Jakob J. (Inventor); Yariv, Amnon (Inventor)

    2006-01-01

    Tunable semiconductor lasers are disclosed requiring minimized coupling regions. Multiple laser embodiments employ ring resonators or ring resonator pairs using only a single coupling region with the gain medium are detailed. Tuning can be performed by changing the phase of the coupling coefficient between the gain medium and a ring resonator of the laser. Another embodiment provides a tunable laser including two Mach-Zehnder interferometers in series and a reflector coupled to a gain medium.

  16. Tunable terahertz fishnet metamaterial

    NASA Astrophysics Data System (ADS)

    Chang, Cheng-Ling; Wang, Wei-Chih; Lin, Hong-Ren; Ju Hsieh, Feng; Pun, Yue-Bun; Chan, Chi-Hou

    2013-04-01

    This paper describes and demonstrates a terahertz (THz) frequency tunable fishnet metamaterial (TFMM) using an electrically controlled polymer dispersed liquid crystal (PDLC) matrix. In contrast to other PDLC-based devices, the TFMM employs a novel method for encapsulating PDLC using a thin (1.5 μm) polyimide "skin layer" to form a uniform surface for metal electrodes while minimizing the Fabry-Perot effect of the skin layer on the TFMM measurements. The tunability was verified by measuring the frequency shift in the reflection coefficient (0.01 THz), with an observed minimum negative refractive index of -15 at 0.55 THz.

  17. Electrically tunable hot-silicon terahertz attenuator

    NASA Astrophysics Data System (ADS)

    Wang, Minjie; Vajtai, Robert; Ajayan, Pulickel M.; Kono, Junichiro

    2014-10-01

    We have developed a continuously tunable, broadband terahertz attenuator with a transmission tuning range greater than 103. Attenuation tuning is achieved electrically, by simply changing the DC voltage applied to a heating wire attached to a bulk silicon wafer, which controls its temperature between room temperature and ˜550 K, with the corresponding free-carrier density adjusted between ˜1011 cm-3 and ˜1017 cm-3. This "hot-silicon"-based terahertz attenuator works most effectively at 450-550 K (corresponding to a DC voltage variation of only ˜7 V) and completely shields terahertz radiation above 550 K in a frequency range of 0.1-2.5 THz. Both intrinsic and doped silicon wafers were tested and demonstrated to work well as a continuously tunable attenuator. All behaviors can be understood quantitatively via the free-carrier Drude model taking into account thermally activated intrinsic carriers.

  18. Tunability enhanced electromagnetic wiggler

    DOEpatents

    Schlueter, R.D.; Deis, G.A.

    1992-03-24

    The invention discloses a wiggler used in synchrotron radiation sources and free electron lasers, where each pole is surrounded by at least two electromagnetic coils. The electromagnetic coils are energized with different amounts of current to provide a wide tunable range of the on-axis magnetic flux density, while preventing magnetic saturation of the poles. 14 figs.

  19. Tunability enhanced electromagnetic wiggler

    DOEpatents

    Schlueter, Ross D.; Deis, Gary A.

    1992-01-01

    The invention discloses a wiggler used in synchrotron radiation sources and free electron lasers, where each pole is surrounded by at least two electromagnetic coils. The electromagnetic coils are energized with different amounts of current to provide a wide tunable range of the on-axis magnetic flux density, while preventing magnetic saturation of the poles.

  20. Dynamically tunable gyroscopes: Theory and design

    NASA Astrophysics Data System (ADS)

    Pel'Por, Dmitrii S.; Matveev, Valerii A.; Arsen'ev, Valerii D.

    The general design, principle of operation, and applications of dynamically tunable gyroscopes are discussed. The discussion covers equations of motion for dynamically tunable gyroscopes, an error model for dynamically tunable gyroscopes and determination of its components, and statics and gas dynamics of dynamically tunable gyroscopes. Attention is also given to thermal processes in dynamically tunable gyroscopes and their effect on the proper precession velocity, design schemes of dynamically tunable gyroscope, and tuning, balancing, and adjustment of dynamically tunable gyroscopes.

  1. Tunable liquid crystal lasers

    NASA Astrophysics Data System (ADS)

    Woltman, Scott J.

    Liquid crystal lasers are dye-doped distributed feedback lasing systems. Fabricated by coupling the periodic structure of a liquid crystal medium with a fluorescent dye, the emission from these systems is tunable by controlling the liquid crystal system---be it through electric or thermal field effects, photochemical reactions, mechanical deformations, etc. The laser action arises from an extended interaction time between the radiation field, the laser emission, and the matter field, the periodic liquid crystal medium, at the edge of the photonic band gap. In this thesis, several tunable liquid crystal laser systems are investigated: cholesteric liquid crystals, holographic-polymer dispersed liquid crystals and liquid crystal polarization gratings. The primary focus has been to fabricate systems that are tunable through electrical means, as applications requiring mechanical or thermal changes are often difficult to control. Cholesteric liquid crystal lasers are helical Bragg reflectors, with a band gap for circularly polarized light of equivalent handedness to their helix. These materials were doped with a laser dye and laser emission was observed. The use of an in-plane electric field tends to unwind the helical pitch of the film and in doing so tunable emission was demonstrated for ˜15 nm. Holographic-polymer dispersed liquid crystals (H-PDLCs) are grating structures consisting of alternating layers of polymer and liquid crystal, with different indices of refraction. The application of an electric field index matches these layers and switches off the grating. Thus, laser emission can be switched on and off through the use of an electric field. Spatially tunable H-PDLC lasers were fabricated by creating chirped gratings, formed by divergent beams. The emission was shown to tune ˜5 nm as the pump beam was translated across a 1 inch film. Liquid crystal polarization gratings use photo-patterned alignment layers, through a polarization holography exposure, to

  2. Tunable eye-safe Er:YAG laser

    NASA Astrophysics Data System (ADS)

    Němec, M.; Šulc, J.; Indra, L.; Fibrich, M.; Jelínková, H.

    2015-01-01

    Er:YAG crystal was investigated as the gain medium in a diode (1452 nm) pumped tunable laser. The tunability was reached in an eye-safe region by an intracavity birefringent filter. The four tuning bands were obtained peaking at wavelengths 1616, 1632, 1645, and 1656 nm. The broadest continuous tunability was 6 nm wide peaking at 1616 nm. The laser was operating in a pulsed regime (10 ms pulse length, 10 Hz repetition rate). The maximum mean output power was 26.5 mW at 1645 nm. The constructed system demonstrated the tunability of a resonantly diode-pumped Er:YAG laser which could be useful in the development of compact diode-pumped lasers for spectroscopic applications.

  3. Spectrally tunable pixel sensors

    NASA Astrophysics Data System (ADS)

    Langfelder, G.; Buffa, C.; Longoni, A. F.; Zaraga, F.

    2013-01-01

    They are here reported the developments and experimental results of fully operating matrices of spectrally tunable pixels based on the Transverse Field Detector (TFD). Unlike several digital imaging sensors based on color filter arrays or layered junctions, the TFD has the peculiar feature of having electrically tunable spectral sensitivities. In this way the sensor color space is not fixed a priori but can be real-time adjusted, e.g. for a better adaptation to the scene content or for multispectral capture. These advantages come at the cost of an increased complexity both for the photosensitive elements and for the readout electronics. The challenges in the realization of a matrix of TFD pixels are analyzed in this work. First experimental results on an 8x8 (x 3 colors) and on a 64x64 (x 3 colors) matrix will be presented and analyzed in terms of colorimetric and noise performance, and compared to simulation predictions.

  4. Tunable surface plasmon devices

    DOEpatents

    Shaner, Eric A.; Wasserman, Daniel

    2011-08-30

    A tunable extraordinary optical transmission (EOT) device wherein the tunability derives from controlled variation of the dielectric constant of a semiconducting material (semiconductor) in evanescent-field contact with a metallic array of sub-wavelength apertures. The surface plasmon resonance wavelength can be changed by changing the dielectric constant of the dielectric material. In embodiments of this invention, the dielectric material is a semiconducting material. The dielectric constant of the semiconducting material in the metal/semiconductor interfacial region is controllably adjusted by adjusting one or more of the semiconductor plasma frequency, the concentration and effective mass of free carriers, and the background high-frequency dielectric constant in the interfacial region. Thermal heating and/or voltage-gated carrier-concentration changes may be used to variably adjust the value of the semiconductor dielectric constant.

  5. Tunable Resonant Scanners

    NASA Astrophysics Data System (ADS)

    Montagu, Jean I.

    1987-01-01

    The most attractive features of resonant scanners are high reliability and eternal life as well as extremely low wobble and jitter. Power consumption is also low, electronic drive is simple, and the device is capable of handling large beams. All of these features are delivered at a low cost in a small package. The resonant scanner's use in numerous high precision applications, however, has been limited because of the difficulty in controlling its phase and resonant frequency. This paper introduces the concept of tunable/controllable resonant scanners, discusses their features, and offers a number of tuning techniques. It describes two angular scanner designs and presents data on tunable range and life tests. It also reviews applications for these new tunable resonant scanners that preserve the desirable features of earlier models while removing the old problems with synchronization or time base flexibility. The three major types of raster scanning applications where the tunable resonant scanner may be of benefit are: 1. In systems with multiple time bases such as multiple scanner networks or with scanners keyed to a common clock (the line frequency or data source) or a machine with multiple resonant scanners. A typical application is image and text transmission, also a printer with a large data base where a buffer is uneconomical. 2. In systems sharing data processing or laser equipment for reasons of cost or capacity, typically multiple work station manufacturing processes or graphic processes. 3. In systems with extremely precise time bases where the frequency stability of conventional scanners cannot be relied upon.

  6. Tunable high pressure lasers

    NASA Technical Reports Server (NTRS)

    Hess, R. V.

    1976-01-01

    Atmospheric transmission of high energy CO2 lasers is considerably improved by high pressure operation which, due to pressure broadening, permits tuning the laser lines off atmospheric absorption lines. Pronounced improvement is shown for horizontal transmission at altitudes above several kilometers and for vertical transmission through the entire atmosphere. Applications of tunable high pressure CO2 lasers to energy transmission and to remote sensing are discussed along with initial efforts in tuning high pressure CO2 lasers.

  7. Tunable optofluidic distributed feedback dye lasers

    NASA Astrophysics Data System (ADS)

    Li, Zhenyu; Zhang, Zhaoyu; Emery, Teresa; Scherer, Axel; Psaltis, Demetri

    2006-08-01

    We demonstrated a continuously tunable optofluidic distributed feedback (DFB) dye laser on a monolithic poly(dimethylsiloxane) (PDMS) elastomer chip. The optical feedback was provided by a phase-shifted higher order Bragg grating embedded in the liquid core of a single mode buried channel waveguide. We achieved nearly 60nm continuously tunable output by mechanically varying the grating period with two dye molecules Rhodamine 6G (Rh6G) and Rhodamine 101 (Rh101). Single-mode operation was obtained with <0.1nm linewidth. Because of the higher order grating, a single laser, when operated with different dye solutions, can provide tunable output covering from near UV to near IR spectral region. The low pump threshold (< 1uJ) makes it possible to use a single high energy pulsed laser to pump hundreds of such lasers on a chip. An integrated array of five DFB dye lasers with different lasing wavelengths was also demonstrated. Such laser arrays make it possible to build highly parallel optical sensors on a chip. The laser chip is fully compatible with PDMS based soft microfluidics.

  8. Tunable X-ray source

    DOEpatents

    Boyce, James R.

    2011-02-08

    A method for the production of X-ray bunches tunable in both time and energy level by generating multiple photon, X-ray, beams through the use of Thomson scattering. The method of the present invention simultaneously produces two X-ray pulses that are tunable in energy and/or time.

  9. Thermally tunable polymer microlenses

    NASA Astrophysics Data System (ADS)

    Huang, Xian; Cheng, Chao-Min; Wang, Li; Wang, Bin; Su, Chih-Chuan; Ho, Mon-Shu; LeDuc, Philip R.; Lin, Qiao

    2008-06-01

    Polymer microlenses capable of using heat to control its focal length are presented. The microlenses are created by exposing droplets of the polymer SU-8 to UV light. By altering the temperature of the microlenses via on-chip heating, their curvature and focal length are actively controlled without mechanical movements. By directly and indirectly measuring temperature-dependent changes of the focal length, we test the ability of the microlenses as a tunable imaging component. The microlenses have potential use in applications such as laser systems, functional biomimetics, and endoscopy.

  10. Tunable chromium lasers

    SciTech Connect

    Chase, L.L.; Payne, S.A.

    1989-01-01

    During the decade that has passed since the discovery of the alexandrite laser, many other tunable vibronic sideband lasers based on Cr/sup 3 +/ have been developed. These lasers span the wavelength range from 700 nm to at least 1235 nm. Experimental and theoretical research has provided an understanding of the important factors that influence the performance of these Cr/sup 3 +/ lasers and other solid state vibronic lasers. The intrinsic performance levels of some of the most promising Cr/sup 3 +/ lasers are evaluated from extrapolated slope efficiency measurements. 7 refs., 4 figs., 2 tabs.

  11. Frequency Tunable Wire Lasers

    NASA Technical Reports Server (NTRS)

    Hu, Qing (Inventor)

    2013-01-01

    The present invention provides frequency tunable solid-state radiation-generating devices, such as lasers and amplifiers, whose active medium has a size in at least one transverse dimension (e.g., its width) that is much smaller than the wavelength of radiation generated and/or amplified within the active medium. In such devices, a fraction of radiation travels as an evanescent propagating mode outside the active medium. It has been discovered that in such devices the radiation frequency can be tuned by the interaction of a tuning mechanism with the propagating evanescent mode.

  12. Tunable multiwalled nanotube resonator

    DOEpatents

    Zettl, Alex K.; Jensen, Kenneth J.; Girit, Caglar; Mickelson, William E.; Grossman, Jeffrey C.

    2011-03-29

    A tunable nanoscale resonator has potential applications in precise mass, force, position, and frequency measurement. One embodiment of this device consists of a specially prepared multiwalled carbon nanotube (MWNT) suspended between a metal electrode and a mobile, piezoelectrically controlled contact. By harnessing a unique telescoping ability of MWNTs, one may controllably slide an inner nanotube core from its outer nanotube casing, effectively changing its length and thereby changing the tuning of its resonance frequency. Resonant energy transfer may be used with a nanoresonator to detect molecules at a specific target oscillation frequency, without the use of a chemical label, to provide label-free chemical species detection.

  13. Tunable multiwalled nanotube resonator

    DOEpatents

    Jensen, Kenneth J; Girit, Caglar O; Mickelson, William E; Zettl, Alexander K; Grossman, Jeffrey C

    2013-11-05

    A tunable nanoscale resonator has potential applications in precise mass, force, position, and frequency measurement. One embodiment of this device consists of a specially prepared multiwalled carbon nanotube (MWNT) suspended between a metal electrode and a mobile, piezoelectrically controlled contact. By harnessing a unique telescoping ability of MWNTs, one may controllably slide an inner nanotube core from its outer nanotube casing, effectively changing its length and thereby changing the tuning of its resonance frequency. Resonant energy transfer may be used with a nanoresonator to detect molecules at a specific target oscillation frequency, without the use of a chemical label, to provide label-free chemical species detection.

  14. Tunable Topological Phononic Crystals

    NASA Astrophysics Data System (ADS)

    Chen, Ze-Guo; Wu, Ying

    2016-05-01

    Topological insulators first observed in electronic systems have inspired many analogues in photonic and phononic crystals in which remarkable one-way propagation edge states are supported by topologically nontrivial band gaps. Such band gaps can be achieved by breaking the time-reversal symmetry to lift the degeneracy associated with Dirac cones at the corners of the Brillouin zone. Here, we report on our construction of a phononic crystal exhibiting a Dirac-like cone in the Brillouin zone center. We demonstrate that simultaneously breaking the time-reversal symmetry and altering the geometric size of the unit cell result in a topological transition that we verify by the Chern number calculation and edge-mode analysis. We develop a complete model based on the tight binding to uncover the physical mechanisms of the topological transition. Both the model and numerical simulations show that the topology of the band gap is tunable by varying both the velocity field and the geometric size; such tunability may dramatically enrich the design and use of acoustic topological insulators.

  15. Tunable filters for JWST Fine Guidance Sensor

    NASA Astrophysics Data System (ADS)

    Rowlands, Neil; Evans, Clinton; Greenberg, Elliot; Gregory, Phil; Scott, Alan; Thibault, Simon; Poirier, Michel; Doyon, Rene; Hutchings, John B.; Alexander, Russ

    2004-10-01

    The Canadian contribution to the James Webb Space Telescope (JWST) mission will be the Fine Guidance Sensor (FGS), incorporating a science-observing mode using tunable filters. We describe here the requirements, the opto-mechanical design concept and bread-board test results for the JWST FGS tunable filters. The FGS requires two continuously tunable filters over the wavelength ranges 1.2 - 2.4 microns and 2.4 - 4.8 microns each having a spectral resolution in the range of R~70 to 200. The selected implementation uses dielectric coated Fabry-Perot etalon plates with a small air gaps. The design finesse is ~30 and the filters are used in 3rd order. The operating temperature is ~35K. Current coating designs provide implementations that require only five blocking filters in each wavelength range to suppress unwanted orders. The filters will be scanned via the use of low voltage piezo-electric transducers. We present results from cryogenic tests of coating samples, PZT actuators and a structural model. The PZT actuators were found have a displacement of ~3.3 microns at 30K with an applied voltage of 125V, more than sufficient for the required scan of the Fabry-Perot plate spacing. The prototype etalon coating was found to be very stable cryogenically, having a measured change of transmission of only ~1% at 77K. The same coating on a 12.7 mm thick substrate, similar to that planned for the filter, was found to have a 18 nm peak-to-valley surface figure change when cooled to 30K. These results demonstrate that the development of tunable filters for the JWST FGS is on track to meet the technology readiness requirements of the program.

  16. Voltage tunable polymer laser device

    NASA Astrophysics Data System (ADS)

    Döring, Sebastian; Kollosche, Matthias; Rabe, Torsten; Kofod, Guggi; Stumpe, Joachim

    2012-03-01

    Since organic laser materials offer broad optical gain spectra they are predestined for the realization of widely tunable laser sources. Here we report on a compact organic laser device that allows for voltage controlled continuously wavelength tuning in the visible range of the spectrum by external deformation. The device consists of an elastomeric distributed feedback (DFB) laser and an electro-active elastomer actuator also known as artificial muscle. Second order DFB lasing is realized by a grating line structured elastomer substrate covered with a thin layer of dye doped polymer. To enable wavelength tuning the elastomer laser is placed at the center of the electro-active elastomer actuator. Chosen design of the actuator gives rise to homogeneous compression at this position. The voltage induced deformation of the artificial muscle is transferred to the elastomer laser and results in a decrease of grating period. This leads to an emission wavelength shift of the elastomer laser. The increase of actuation voltage to 3.25 kV decreased the emission wavelength from 604 nm to 557 nm, a change of 47 nm or 7.8%.

  17. Fibonacci optical lattices for tunable quantum quasicrystals

    NASA Astrophysics Data System (ADS)

    Singh, K.; Saha, K.; Parameswaran, S. A.; Weld, D. M.

    2015-12-01

    We describe a quasiperiodic optical lattice, created by a physical realization of the abstract cut-and-project construction underlying all quasicrystals. The resulting potential is a generalization of the Fibonacci tiling. Calculation of the energies and wave functions of ultracold atoms loaded into such a lattice demonstrate a multifractal energy spectrum, a singular continuous momentum-space structure, and the existence of controllable edge states. These results open the door to cold atom quantum simulation experiments in tunable or dynamic quasicrystalline potentials, including topological pumping of edge states and phasonic spectroscopy.

  18. A TUNABLE DIODE LASER STACK MONITOR FOR SULFURIC ACID VAPOR

    EPA Science Inventory

    A field prototype instrument for continuous in-situ monitoring of sulfuric acid vapor in industrial smoke stacks has been developed. The method of detection is dual wavelength differential absorption in the infrared. Two tunable diode lasers are locked to two specific frequencies...

  19. Mid-infrared tunable metamaterials

    DOEpatents

    Brener, Igal; Miao, Xiaoyu; Shaner, Eric A; Passmore, Brandon Scott; Jun, Young Chul

    2015-04-28

    A mid-infrared tunable metamaterial comprises an array of resonators on a semiconductor substrate having a large dependence of dielectric function on carrier concentration and a semiconductor plasma resonance that lies below the operating range, such as indium antimonide. Voltage biasing of the substrate generates a resonance shift in the metamaterial response that is tunable over a broad operating range. The mid-infrared tunable metamaterials have the potential to become the building blocks of chip based active optical devices in mid-infrared ranges, which can be used for many applications, such as thermal imaging, remote sensing, and environmental monitoring.

  20. Tunable-Bandwidth Filter System

    NASA Technical Reports Server (NTRS)

    Bailey, John W.

    2004-01-01

    A tunable-bandwidth filter system (TBFS), now undergoing development, is intended to be part of a remote sensing multispectral imaging system that will operate in the visible and near infrared spectral region (wavelengths from 400 to 900 nm). Attributes of the TBFS include rapid tunability of the pass band over a wide wavelength range and high transmission efficiency. The TBFS is based on a unique integration of two pairs of broadband Raman reflection holographic filters with two rotating spherical lenses. In experiments, a prototype of the TBFS, was shown to be capable of spectral sampling of images in the visible range over a 200 nm spectral range with a spectral resolution of 30 nm. The figure depicts the optical layout of a prototype of the TBFS as part of a laboratory multispectral imaging system for the spectral sampling of color test images in two orthogonal polarizations. Each pair of broadband Raman reflection holographic filters is mounted at an equatorial plane between two halves of a spherical lens. The two filters in each pair are characterized by steep spectral slopes (equivalently, narrow spectral edges), no ripple or side lobes in their pass bands, and a few nanometers of non-overlapping wavelength range between their pass bands. Each spherical lens and thus the filter pair within it is rotated in order to rapidly tune its pass band. The rotations of are effected by electronically controlled, programmable, high-precision rotation stages. The rotations are coordinated by electronic circuits operating under overall supervision of a personal computer in order to obtain the desired variation of the overall pass bands with time. Embedding the filters inside the spherical lenses increases the range of the hologram incidence angles, making it possible to continuously tune the pass and stop bands of the filters over a wider wavelength range. In addition, each spherical lens also serves as part of the imaging optics: The telephoto lens focuses incoming light

  1. Tunable-Bandwidth Filter System

    NASA Technical Reports Server (NTRS)

    Aye, Tin; Yu, Kevin; Dimov, Fedor; Savant, Gajendra

    2006-01-01

    A tunable-bandwidth filter system (TBFS), now undergoing development, is intended to be part of a remote-sensing multispectral imaging system that will operate in the visible and near infrared spectral region (wavelengths from 400 to 900 nm). Attributes of the TBFS include rapid tunability of the pass band over a wide wavelength range and high transmission efficiency. The TBFS is based on a unique integration of two pairs of broadband Raman reflection holographic filters with two rotating spherical lenses. In experiments, a prototype of the TBFS was shown to be capable of spectral sampling of images in the visible range over a 200-nm spectral range with a spectral resolution of .30 nm. The figure depicts the optical layout of a prototype of the TBFS as part of a laboratory multispectral imaging system for the spectral sampling of color test images in two orthogonal polarizations. Each pair of broadband Raman reflection holographic filters is mounted at an equatorial plane between two halves of a spherical lens. The two filters in each pair are characterized by steep spectral slopes (equivalently, narrow spectral edges), no ripple or side lobes in their pass bands, and a few nanometers of non-overlapping wavelength range between their pass bands. Each spherical lens and thus the filter pair within it is rotated in order to rapidly tune its pass band. The rotations of the lenses are effected by electronically controlled, programmable, high-precision rotation stages. The rotations are coordinated by electronic circuits operating under overall supervision of a personal computer in order to obtain the desired variation of the overall pass bands with time. Embedding the filters inside the spherical lenses increases the range of the hologram incidence angles, making it possible to continuously tune the pass and stop bands of the filters over a wider wavelength range. In addition, each spherical lens also serves as part of the imaging optics: The telephoto lens focuses

  2. A tunable microcavity

    NASA Astrophysics Data System (ADS)

    Barbour, Russell J.; Dalgarno, Paul A.; Curran, Arran; Nowak, Kris M.; Baker, Howard J.; Hall, Denis R.; Stoltz, Nick G.; Petroff, Pierre M.; Warburton, Richard J.

    2011-09-01

    We present a generic microcavity platform for cavity experiments on optically active nanostructures, such as quantum dots, nanocrystals, color centers, and carbon nanotubes. The cavity is of the Fabry-Pérot type with a planar back mirror and a miniature concave top mirror with radius of curvature ˜ 100 μm. Optical access is achieved by free beam coupling, allowing good mode-matching to the cavity mode. The cavity has a high Q-factor, reasonably small mode volume, open access, spatial and spectral tunability, and operates at cryogenic temperatures. Spectral and spatial tuning of the Purcell effect (weak coupling regime) on a single InGaAs quantum dot is demonstrated.

  3. Optically tunable optical filter

    NASA Astrophysics Data System (ADS)

    James, Robert T. B.; Wah, Christopher; Iizuka, Keigo; Shimotahira, Hiroshi

    1995-12-01

    We experimentally demonstrate an optically tunable optical filter that uses photorefractive barium titanate. With our filter we implement a spectrum analyzer at 632.8 nm with a resolution of 1.2 nm. We simulate a wavelength-division multiplexing system by separating two semiconductor laser diodes, at 1560 nm and 1578 nm, with the same filter. The filter has a bandwidth of 6.9 nm. We also use the same filter to take 2.5-nm-wide slices out of a 20-nm-wide superluminescent diode centered at 840 nm. As a result, we experimentally demonstrate a phenomenal tuning range from 632.8 to 1578 nm with a single filtering device.

  4. 80 nm tunable DBR-free semiconductor disk laser

    NASA Astrophysics Data System (ADS)

    Yang, Z.; Albrecht, A. R.; Cederberg, J. G.; Sheik-Bahae, M.

    2016-07-01

    We report a widely tunable optically pumped distributed Bragg reflector (DBR)-free semiconductor disk laser with 6 W continuous wave output power near 1055 nm when using a 2% output coupler. Using only high reflecting mirrors, the lasing wavelength is centered at 1034 nm and can be tuned up to a record 80 nm by using a birefringent filter. We attribute such wide tunability to the unique broad effective gain bandwidth of DBR-free semiconductor disk lasers achieved by eliminating the active mirror geometry.

  5. L-band wavelength-tunable dissipative soliton fiber laser.

    PubMed

    Yan, Dan; Li, Xingliang; Zhang, Shumin; Han, Mengmeng; Han, Huiyun; Yang, Zhenjun

    2016-01-25

    A tunable L-band dissipative soliton (DS) fiber laser with nonlinear polarization rotation (NPR) playing the roles of both a saturable absorber (SA) and a tunable filter has been demonstrated experimentally and numerically. By appropriate adjustment of the states of the polarization controllers (PCs) and the pump power, DSs with continuously tunable wavelengths have been observed over the wavelength range from 1583.0 to 1602.4 nm with a 3-dB spectral bandwidth of around 20 nm and from 1581.9 nm to 1602.6 nm with a 3-dB spectral bandwidth of around 4 nm. In addition, we have observed that by increasing the pump power, the 3-dB spectral bandwidth of the DS could be increased without pulse breaking. Numerical results for the characteristics of the DSs are in accord with the experimental data. PMID:26832459

  6. Frequency-tunable superconducting resonators via nonlinear kinetic inductance

    SciTech Connect

    Vissers, M. R.; Hubmayr, J.; Sandberg, M.; Gao, J.; Chaudhuri, S.; Bockstiegel, C.

    2015-08-10

    We have designed, fabricated, and tested a frequency-tunable high-Q superconducting resonator made from a niobium titanium nitride film. The frequency tunability is achieved by injecting a DC through a current-directing circuit into the nonlinear inductor whose kinetic inductance is current-dependent. We have demonstrated continuous tuning of the resonance frequency in a 180 MHz frequency range around 4.5 GHz while maintaining the high internal quality factor Q{sub i} > 180 000. This device may serve as a tunable filter and find applications in superconducting quantum computing and measurement. It also provides a useful tool to study the nonlinear response of a superconductor. In addition, it may be developed into techniques for measurement of the complex impedance of a superconductor at its transition temperature and for readout of transition-edge sensors.

  7. Ferroelectric-dielectric tunable composites

    NASA Astrophysics Data System (ADS)

    Sherman, Vladimir O.; Tagantsev, Alexander K.; Setter, Nava; Iddles, David; Price, Tim

    2006-04-01

    The dielectric response of ferroelectric-dielectric composites is theoretically addressed. Dielectric permittivity, tunability (relative change of the permittivity driven by dc electric field), and loss tangent are evaluated for various composite models. The analytical results for small dielectric concentration and relative tunability are obtained in terms of the traditional electrostatic consideration. The results for large tunability are obtained numerically. A method is proposed for the evaluation of the tunability and loss at large concentrations of the dielectric. The basic idea of the method is to reformulate the effective medium approach in terms of electrical energies stored and dissipated in the composite. The important practical conclusion of the paper is that, for random ferroelectric-dielectric composite, the addition of small amounts of a linear dielectric into the tunable ferroelectric results in an increase of the tunability of the mixture. The loss tangent of such composites is shown to be virtually unaffected by the addition of moderate amounts of the low-loss dielectric. The experimental data for (Ba,Sr)TiO3 based composites are analyzed in terms of the theory developed and shown to be in a reasonable agreement with the theoretical results.

  8. Mechanically Tunable Slippery Behavior on Soft Poly(dimethylsiloxane)-Based Anisotropic Wrinkles Infused with Lubricating Fluid.

    PubMed

    Roy, Pritam Kumar; Pant, Reeta; Nagarajan, Arun Kumar; Khare, Krishnacharya

    2016-06-14

    We demonstrate a novel technique to fabricate mechanically tunable slippery surfaces using one-dimensional (anisotropic) elastic wrinkles. Such wrinkles show tunable topography (amplitude) on the application of mechanical strain. Following Nepenthes pitcher plants, lubricating fluid infused solid surfaces show excellent slippery behavior for test liquid drops. Therefore, combining the above two, that is, infusing suitable lubricating fluid on elastic wrinkles, would enable us to fabricate mechanically tunable slippery surfaces. Completely stretched (flat) wrinkles have uniform coating of lubricating fluid, whereas completely relaxed (full amplitude) wrinkles have most of the lubricating oil in the wrinkle grooves. Therefore, water drops on completely stretched surface show excellent slippery behavior, whereas on completely relaxed surface they show reduced slippery behavior. Therefore, continuous variation of wrinkle stretching provides reversibly tunable slippery behavior on such a system. Because the wrinkles are one-dimensional, they show anisotropic tunability of slippery behavior depending upon whether test liquid drops slip parallel or perpendicular to the wrinkles. PMID:27221199

  9. Electrically Tunable Hot-Silicon Terahertz Attenuator

    NASA Astrophysics Data System (ADS)

    Wang, Minjie; Vajtai, Robert; Ajayan, Pulickel; Kono, Junichiro

    2015-03-01

    We have developed a continuously tunable, broadband terahertz attenuator with a transmission tuning range greater than 103. Attenuation tuning is achieved electrically, by simply changing the DC voltage applied to a heating wire attached to a bulk silicon wafer, which controls its temperature between room temperature and 550 K, with the corresponding free-carrier density adjusted between 1011 cm-3 and 1017 cm-3. This `hot-silicon'-based terahertz attenuator works most effectively at 450-550 K (corresponding to a DC voltage variation of only 7 V) and completely shields terahertz radiation above 550 K in a frequency range of 0.1-2.5 THz. Both intrinsic and doped silicon wafers were tested and demonstrated to work well as a continuously tunable attenuator, but they exhibited slightly different behaviors before a dramatic transmission drop at 450-550 K: intrinsic silicon wafers showed a monotonic transmission decrease with temperature while doped wafers showed a slight increase in transmission before the drop. All behaviors can be understood quantitatively via the free-carrier Drude model taking into account thermally activated intrinsic carriers. This work was supported by the National Science Foundation through Grant No. OISE-0968405.

  10. Electrically tunable hot-silicon terahertz attenuator

    SciTech Connect

    Wang, Minjie; Vajtai, Robert; Ajayan, Pulickel M.; Kono, Junichiro

    2014-10-06

    We have developed a continuously tunable, broadband terahertz attenuator with a transmission tuning range greater than 10{sup 3}. Attenuation tuning is achieved electrically, by simply changing the DC voltage applied to a heating wire attached to a bulk silicon wafer, which controls its temperature between room temperature and ∼550 K, with the corresponding free-carrier density adjusted between ∼10{sup 11 }cm{sup −3} and ∼10{sup 17 }cm{sup −3}. This “hot-silicon”-based terahertz attenuator works most effectively at 450–550 K (corresponding to a DC voltage variation of only ∼7 V) and completely shields terahertz radiation above 550 K in a frequency range of 0.1–2.5 THz. Both intrinsic and doped silicon wafers were tested and demonstrated to work well as a continuously tunable attenuator. All behaviors can be understood quantitatively via the free-carrier Drude model taking into account thermally activated intrinsic carriers.

  11. Tunable superconducting microstrip resonators

    NASA Astrophysics Data System (ADS)

    Adamyan, A. A.; Kubatkin, S. E.; Danilov, A. V.

    2016-04-01

    We report on a simple yet versatile design for a tunable superconducting microstrip resonator. Niobium nitride is employed as the superconducting material and aluminum oxide, produced by atomic layer deposition, as the dielectric layer. We show that the high quality of the dielectric material allows to reach the internal quality factors in the order of Qi˜104 in the single photon regime. Qi rapidly increases with the number of photons in the resonator N and exceeds 105 for N ˜10 -50 . A straightforward modification of the basic microstrip design allows to pass a current bias through the strip and to control its kinetic inductance. We achieve a frequency tuning δf =62 MHz around f0=2.4 GHz for a fundamental mode and δf =164 MHz for a third harmonic. This translates into a tuning parameter Qiδf /f0=150 . The presented design can be incorporated into essentially any superconducting circuitry operating at temperatures below 2.5 K.

  12. Tunable perovskite microdisk lasers

    NASA Astrophysics Data System (ADS)

    Sun, Wenzhao; Wang, Kaiyang; Gu, Zhiyuan; Xiao, Shumin; Song, Qinghai

    2016-04-01

    Perovskite microdisk lasers have been intensively studied recently. But their lasing properties are usually fixed once the devices are synthesized. Here, for the first time, we demonstrated the switchable and tunable perovskite microdisk lasers by surrounding them with 5CB liquid crystals. With the increase of the environmental temperature from 24 °C to 34 °C, the lasing wavelength slightly changed from 552.91 nm to 552.11 nm at the beginning and suddenly shifted to around 552.54 nm at T = 32 °C, where the phase transition of liquid crystals occurs. Our numerical calculation shows that the wavelength shift is caused by the changes of the refractive index of liquid crystals. More than tuning of the wavelength, a more dramatic wavelength transition from ~554 nm to 550 nm has also been observed. This sudden transition is mainly induced by the reduction of scattering rather than the change in the refractive index when the liquid crystals are changed from the nematic phase to the isotropic phase. We believe that our research can shed light on the applications of perovskite optoelectronics.

  13. Tunable perovskite microdisk lasers.

    PubMed

    Sun, Wenzhao; Wang, Kaiyang; Gu, Zhiyuan; Xiao, Shumin; Song, Qinghai

    2016-04-28

    Perovskite microdisk lasers have been intensively studied recently. But their lasing properties are usually fixed once the devices are synthesized. Here, for the first time, we demonstrated the switchable and tunable perovskite microdisk lasers by surrounding them with 5CB liquid crystals. With the increase of the environmental temperature from 24 °C to 34 °C, the lasing wavelength slightly changed from 552.91 nm to 552.11 nm at the beginning and suddenly shifted to around 552.54 nm at T = 32 °C, where the phase transition of liquid crystals occurs. Our numerical calculation shows that the wavelength shift is caused by the changes of the refractive index of liquid crystals. More than tuning of the wavelength, a more dramatic wavelength transition from ∼554 nm to 550 nm has also been observed. This sudden transition is mainly induced by the reduction of scattering rather than the change in the refractive index when the liquid crystals are changed from the nematic phase to the isotropic phase. We believe that our research can shed light on the applications of perovskite optoelectronics. PMID:27064838

  14. High power continuous-wave GaSb-based superluminescent diodes as gain chips for widely tunable laser spectroscopy in the 1.95-2.45 μm wavelength range

    NASA Astrophysics Data System (ADS)

    Vizbaras, K.; Dvinelis, E.; ŠimonytÄ--, I.; TrinkÅ«nas, A.; Greibus, M.; Songaila, R.; Žukauskas, T.; Kaušylas, M.; Vizbaras, A.

    2015-07-01

    We present high-power single-spatial mode electrically pumped GaSb-based superluminescent diodes (SLDs) operating in the 1.95 to 2.45 μm wavelength range in continuous-wave (CW). MBE grown GaSb-based heterostructures were fabricated into single-angled facet ridge-waveguide devices that demonstrate more than 40 mW CW output power at 2.05 μm, to >5 mW at 2.40 μm at room-temperature. We integrated these SLDs into an external cavity (Littrow configuration) as gain chips and achieved single-mode CW lasing with maximum output powers exceeding 18 mW. An extremely wide tuning range of 120 nm per chip with side-mode-suppression-ratios >25 dB was demonstrated while maintaining optical output power level above 3 mW across the entire tuning range.

  15. Tunable silicon CROW delay lines

    NASA Astrophysics Data System (ADS)

    Morichetti, Francesco; Canciamilla, Antonio; Torregiani, Matteo; Ferrari, Carlo; Melloni, Andrea; Martinelli, Mario

    2010-05-01

    Tunable coupled resonator optical waveguides (CROWs) are powerful and versatile devices that can be used to dynamically control the delay of optical data streams on chip. In this contribution we show that CROW delay lines fabricated on a silicon on insulator (SOI) platform are suitable for applications in the emerging scenario of optical systems at 100 Gbit/s. Issues concerning technology, design, limits and applications of SOI CROWs are discussed. The performances of silicon CROW delay lines activated by thermal tuning are compared to those of glass CROW in terms of power consumption, thermal crosstalk and reconfiguration speed. The continuous delay of 10-ps long optical pulses by 8 bit length is demonstrated by using a silicon CROW with a bandwidth of 87 GHz and made of 12 RRs. At 100 Gbit/s this structure provides comparable figures of merit (fractional delay of 0.75 bit/RR and fractional loss of 0.7 dB per bit-delay) of state-of-the art glass CROW operating at 10 Gbit/s, yet the area of the latter being three order of magnitude larger. The compatibility of silicon CROW with the emerging 100 Gbit/s systems is demonstrated by showing error-free phase-preserving propagation of a 100 Gbit/s return-to-zero (RZ) polarization-division-multiplexing (PolDM) differential quaternary phase shit keying (DQPSK) signal dynamically delayed by the CROW. It is also demonstrated that a silicon CROW can be used in a PolDM system to introduce a polarization selective delay in order to optimize the time interleaving of the two orthogonally polarized data streams.

  16. Hybrid interlayer excitons with tunable dispersion relation

    NASA Astrophysics Data System (ADS)

    Skinner, Brian

    When two semiconducting materials are layered on top of each other, interlayer excitons can be formed by the Coulomb attraction of an electron in one layer to a hole in the opposite layer. The resulting exciton is a composite boson with a dispersion relation that is a hybrid between the dispersion relations of the electron and the hole separately. In this talk I show how such hybridization is particularly interesting when one layer has a ``Mexican hat''-shaped dispersion relation and the other has a conventional parabolic dispersion. In this case the interlayer exciton can have a range of qualitatively different dispersion relations, which can be continuously altered by an external field. This tunability in principle allows one to continuously tune a collection of interlayer excitons between different quantum many-body phases, including Bose-Einstein condensate, Wigner crystal, and fermion-like ``moat band'' phases.

  17. Tunable Soft X-Ray Oscillators

    SciTech Connect

    Wurtele, Jonathan; Gandhi, Punut; Gu, X-W; Fawley, William M; Reinsch, Matthia; Penn, Gregory; Kim, K-J; Lindberg, Ryan; Zholents, Alexander

    2010-09-17

    A concept for a tunable soft x-ray free electron laser (FEL) photon source is presented and studied numerically. The concept is based on echo-enabled harmonic generation (EEHG), wherein two modulator-chicane sections impose high harmonic structure with much greater efficacy as compared to conventional high harmonic FELs that use only one modulator-chicane section. The idea proposed here is to replace the external laser power sources in the EEHG modulators with FEL oscillators, and to combine the bunching of the beam with the production of radiation. Tunability is accomplished by adjusting the magnetic chicanes while the two oscillators remain at a fixed frequency. This scheme eliminates the need to develop coherent sources with the requisite power, pulse length, and stability requirements by exploiting the MHz bunch repetition rates of FEL continuous wave (CW) sources driven by superconducting (SC) linacs. We present time-dependent GINGER simulation results for an EEHG scheme with an oscillator modulator at 43 nm employing 50percent reflective dielectric mirrors and a second modulator employing an external, 215-nm drive laser. Peak output of order 300 MW is obtained at 2.7 nm, corresponding to the 80th harmonic of 215 nm. An alternative single-cavity echo-oscillator scheme based on a 13.4 nm oscillator is investigated with time-independent simulations that a 180-MW peak power at final wavelength of 1.12 nm. Three alternate configurations that use separate bunches to produce the radiation for EEHG microbunching are also presented. Our results show that oscillator-based soft x-ray FELs driven by CWSC linacs are extremely attractive because of their potential to produce tunable radiation at high average power together with excellent longitudinal coherence and narrow spectral bandwidth.

  18. A tunable optoelectronic oscillator based on a tunable microwave attenuator

    NASA Astrophysics Data System (ADS)

    Wei, Zhihu; Wang, Rong; Pu, Tao; Sun, Guodan; Fang, Tao; Zheng, Jilin

    2013-10-01

    A novel realization of a wideband tunable optoelectronic oscillator (OEO) based on dual-port electrode Mach-Zehnder modulator (DMZM), a tunable microwave attenuator (TMA), and a chirped fiber Bragg grating (CFBG) is proposed and demonstrated. By simply adjusting the power ratio between the two arms of DMZM, the chirp of the DMZM will be tuned, and the center frequency of the microwave photonic filter will be tuned. When the OEO loop in the proposed system is closed, the output frequency of OEO is determined by the microwave photonic filter, and a high spectral purity microwave signal with a tunable frequency from 5.8 to 11 GHz is generated. The single sideband (SSB) phase noise of the generated signal could reach -107.4 dBc/Hz at an offset frequency of 10 kHz.

  19. Generating Tunable Far-Infrared Laser Sidebands

    NASA Technical Reports Server (NTRS)

    Pickett, H. M.; Farhoomand, J.

    1986-01-01

    New tunable source extends infrared spectroscopy into far infrared wavelengths. Frequency-Tunable far-infrared radiation produced by mixing of fixed-frequency far-infrared laser beam with output of frequency-tunable klystron. By sweeping klystron frequency in synchronism with video display of detector output, one obtains direct presentation of absorption-cell spectrum. Immediate applications are local oscillator for heterodyne systems and tunable source for spectroscopy.

  20. Tunable features of magnetoelectric transformers.

    PubMed

    Dong, Shuxiang; Zhai, Junyi; Priya, Shashank; Li, Jie-Fang; Viehland, Dwight

    2009-06-01

    We have found that magnetostrictive FeBSiC alloy ribbons laminated with piezoelectric Pb(Zr,Ti)O(3) fiber can act as a tunable transformer when driven under resonant conditions. These composites were also found to exhibit the strongest resonant magnetoelectric voltage coefficient of 750 V/cm-Oe. The tunable features were achieved by applying small dc magnetic biases of -5 tunable transformer features can be attributed to large changes in the piezomagnetic coefficient and permeability of the magnetostrictive phase under H(dc). PMID:19574118

  1. Parametric infrared tunable laser system

    NASA Technical Reports Server (NTRS)

    Garbuny, M.; Henningsen, T.; Sutter, J. R.

    1980-01-01

    A parametric tunable infrared laser system was built to serve as transmitter for the remote detection and density measurement of pollutant, poisonous, or trace gases in the atmosphere. The system operates with a YAG:Nd laser oscillator amplifier chain which pumps a parametric tunable frequency converter. The completed system produced pulse energies of up to 30 mJ. The output is tunable from 1.5 to 3.6 micrometers at linewidths of 0.2-0.5 /cm (FWHM), although the limits of the tuning range and the narrower line crystals presently in the parametric converter by samples of the higher quality already demonstrated is expected to improve the system performance further.

  2. Tunable plasmonic emission of radiation in graphene

    NASA Astrophysics Data System (ADS)

    Atwater, Harry

    2015-03-01

    Materials at finite temperatures emit electromagnetic radiation due to the thermally induced motion of particles and quasiparticles. The radiated power is dictated by the electromagnetic energy density and emissivity, which are ordinarily fixed properties of the material and temperature. Recent experiments have shown, however, that the emissivity of a material may be modified through surface patterning to allow for thermal radiation that is coherent, unidirectional and spectrally narrow. We show that electronically tunable, dynamic control of emissivity can be achieved in blackbody radiators whose surface is coated with a thin layer of variable emissivity. Specifically, we experimentally demonstrate tunable electronic control of blackbody emission from graphene plasmonic resonators on a silicon nitride substrate at temperatures up to 250° C. We show that the graphene resonators produce antenna-coupled blackbody radiation, manifest as narrow spectral emission peaks in the mid-IR. By continuously varying the nanoresonator carrier density, the frequency and intensity of these spectral features can be modulated via an electrostatic gate. We describe these phenomena as plasmonically enhanced radiative emission originating from loss channels associated with both plasmon decay in the graphene sheet and from vibrational modes in the SiNx. This work opens the door for future devices that may control blackbody radiation at timescales beyond the limits of conventional thermo-optic modulation.

  3. Pneumatically tunable optofluidic dye laser

    NASA Astrophysics Data System (ADS)

    Song, Wuzhou; Psaltis, Demetri

    2010-02-01

    We presented a tunable optofluidic dye laser with integrated elastomeric air-gap etalon controlled by air pressure. The chip was fabricated with polydimethylsiloxane (PDMS) via replica molding. It comprises a liquid waveguide and microscale air-gap mirrors providing the feedback. The lasing wavelength is chosen by the interference between two parallel PDMS-air interfaces inside the internal tunable air-gap etalon, of which pneumatic tuning can be realized by inflating the air-gap etalon with compressed air. This dye laser exhibits a pumping threshold of 1.6 μJ/pulse, a lasing linewidth of 3 nm, and a tuning range of 14 nm.

  4. Coherent tunable far infrared radiation

    NASA Technical Reports Server (NTRS)

    Jennings, D. A.

    1989-01-01

    Tunable, CW, FIR radiation has been generated by nonlinear mixing of radiation from two CO2 lasers in a metal-insulator-metal (MIM) diode. The FIR difference-frequency power was radiated from the MIM diode antenna to a calibrated InSb bolometer. FIR power of 200 nW was generated by 250 mW from each of the CO2 lasers. Using the combination of lines from a waveguide CO2 laser, with its larger tuning range, with lines from CO2, N2O, and CO2-isotope lasers promises complete coverage of the entire FIR band with stepwise-tunable CW radiation.

  5. Wavelength-Tunable Microlasers Based on the Encapsulation of Organic Dye in Metal-Organic Frameworks.

    PubMed

    Wei, Yanhui; Dong, Haiyun; Wei, Cong; Zhang, Wei; Yan, Yongli; Zhao, Yong Sheng

    2016-09-01

    A wavelength-tunable microlaser is realized based on the controlled intramolecular charge transfer (ICT) process in dye-encapsulated metal-organic framework (MOF) material. The confinement effect of the MOFs is beneficial for low-threshold lasing. By effectively controlling the polarity of the MOF pores, the population distribution between the locally excited and ICT states is continuously modulated, thus achieving broadband tunable MOF-based microlasers. PMID:27314453

  6. Tunable phase diagram and vortex pinning in a superconductor-ferromagnet bilayer

    NASA Astrophysics Data System (ADS)

    Zhu, L. Y.; Cieplak, Marta Z.; Chien, C. L.

    2010-08-01

    We have observed the evolution of phase diagram and vortex pinning using a single ferromagnet/superconductor bilayer of [Co/Pt]8/Nb through a special demagnetization procedure. It induces a continuous and reversible change in the domain width with equal positive/negative domains enabling the observation of the predicted tunable phase diagram. The tunable domain pattern also systematically affects vortex pinning. We have determined the dependence of the activation energy of vortex pinning on domain width, temperature, and magnetic field.

  7. Tunable single-mode slot waveguide quantum cascade lasers

    SciTech Connect

    Meng, Bo; Tao, Jin; Quan Zeng, Yong; Wu, Sheng; Jie Wang, Qi

    2014-05-19

    We report experimental demonstration of tunable, monolithic, single-mode quantum cascade lasers (QCLs) at ∼10 μm with a two-section etched slot structure. A single-mode tuning range of 77 cm{sup −1} (785 nm), corresponding to ∼7.8% of the relative tuning range, was realized with a ∼20 dB side mode suppression ratio within the whole tuning range. Compared with integrated distributed feedback QCLs, our devices have the advantages of easy fabrication and a broader tuning range. Further theoretical analyses and numerical simulations show that it is possible to achieve a broad continuous tuning range by optimizing the slot structures. The proposed slot-waveguide design could provide an alternative but simple approach to the existing tuning schemes for realizing broadly continuous tunable single-mode QCLs.

  8. Reliability test procedures for tunable lasers

    NASA Astrophysics Data System (ADS)

    Ciminelli, Caterina; Armenise, Mario Nicola; Passaro, Vittorio M. N.

    2003-04-01

    Widely tunable lasers are promising sources for future high-capacity dense wavelength divison multiplexing and photonic switching systems. These devices can be used for sparing in the cold standby mode, restoring in hot standby restoring, rerouting wavelength rerouting or conversion, or fast switching in all-optical networks. Tunable lasers need to demonstrate some featuers such as wide tunability range, optical output power of 10 dBm or more, cost and structure similar to those of commercial DFB lasers. High performance devices would require low laser chirp, high modulation speed, small size and very high reliability. For system applications, requirements on the tunable laser reliability are very stringent. Reliability studies and appropriate related testing procedures are necessary to define stability of tunable lasers and their expected lifetime. In this paper we propose some reliabilty test 'strategies' useful for qualification of tunable lasers with reference to some critical issues of the main technologies used to achieve the tunability feature.

  9. Optical Determination of Gate--Tunable Bandgap in Bilayer Graphene

    SciTech Connect

    Zhang, Yuanbo; Tang, Tsung-Ta; Girit, Caglar; Hao, Zhao; Martin, Michael C.; Zettl, Alex; Crommie, Michael F.; Shen, Y. Ron; Wang, Feng

    2009-08-11

    The electronic bandgap is an intrinsic property of semiconductors and insulators that largely determines their transport and optical properties. As such, it has a central role in modern device physics and technology and governs the operation of semiconductor devices such as p-n junctions, transistors, photodiodes and lasers. A tunable bandgap would be highly desirable because it would allow great flexibility in design and optimization of such devices, in particular if it could be tuned by applying a variable external electric field. However, in conventional materials, the bandgap is fixed by their crystalline structure, preventing such bandgap control. Here we demonstrate the realization of a widely tunable electronic bandgap in electrically gated bilayer graphene. Using a dual-gate bilayer graphene field-effect transistor (FET) and infrared microspectroscopy, we demonstrate a gate-controlled, continuously tunable bandgap of up to 250 meV. Our technique avoids uncontrolled chemical doping and provides direct evidence of a widely tunable bandgap -- spanning a spectral range from zero to mid-infrared -- that has eluded previous attempts. Combined with the remarkable electrical transport properties of such systems, this electrostatic bandgap control suggests novel nanoelectronic and nanophotonic device applications based on graphene.

  10. Tunable Diffractive Optical Elements Based on Shape-Memory Polymers Fabricated via Hot Embossing.

    PubMed

    Schauer, Senta; Meier, Tobias; Reinhard, Maximilian; Röhrig, Michael; Schneider, Marc; Heilig, Markus; Kolew, Alexander; Worgull, Matthias; Hölscher, Hendrik

    2016-04-13

    We introduce actively tunable diffractive optical elements fabricated from shape-memory polymers (SMPs). By utilizing the shape-memory effect of the polymer, at least one crucial attribute of the diffractive optical element (DOE) is tunable and adjustable subsequent to the completed fabrication process. A thermoplastic, transparent, thermoresponsive polyurethane SMP was structured with diverse diffractive microstructures via hot embossing. The tunability was enabled by programming a second, temporary shape into the diffractive optical element by mechanical deformation, either by stretching or a second embossing cycle at low temperatures. Upon exposure to the stimulus heat, the structures change continuously and controllable in a predefined way. We establish the novel concept of shape-memory diffractive optical elements by illustrating their capabilities, with regard to tunability, by displaying the morphing diffractive pattern of a height tunable and a period tunable structure, respectively. A sample where an arbitrary structure is transformed to a second, disparate one is illustrated as well. To prove the applicability of our tunable shape-memory diffractive optical elements, we verified their long-term stability and demonstrated the precise adjustability with a detailed analysis of the recovery dynamics, in terms of temperature dependence and spatially resolved, time-dependent recovery. PMID:26998646

  11. Porous Carbon Nanoparticle Networks with Tunable Absorbability

    PubMed Central

    Dai, Wei; Kim, Seong Jin; Seong, Won-Kyeong; Kim, Sang Hoon; Lee, Kwang-Ryeol; Kim, Ho-Young; Moon, Myoung-Woon

    2013-01-01

    Porous carbon materials with high specific surface areas and superhydrophobicity have attracted much research interest due to their potential application in the areas of water filtration, water/oil separation, and oil-spill cleanup. Most reported superhydrophobic porous carbon materials are fabricated by complex processes involving the use of catalysts and high temperatures but with low throughput. Here, we present a facile single-step method for fabricating porous carbon nanoparticle (CNP) networks with selective absorbability for water and oils via the glow discharge of hydrocarbon plasma without a catalyst at room temperature. Porous CNP networks were grown by the continuous deposition of CNPs at a relatively high deposition pressure. By varying the fluorine content, the porous CNP networks exhibited tunable repellence against liquids with various degrees of surface tension. These porous CNP networks could be applied for the separation of not only water/oil mixtures but also mixtures of liquids with different surface tension levels. PMID:23982181

  12. Single beam optical vortex tweezers with tunable orbital angular momentum

    SciTech Connect

    Gecevičius, Mindaugas; Drevinskas, Rokas Beresna, Martynas; Kazansky, Peter G.

    2014-06-09

    We propose a single beam method for generating optical vortices with tunable optical angular momentum without altering the intensity distribution. With the initial polarization state varying from linear to circular, we gradually control the torque transferred to the trapped non-absorbing and non-birefringent silica beads. The continuous transition from the maximum rotation speed to zero without changing the trapping potential gives a way to study the complex tribological interactions.

  13. Ultrabright continuously tunable terahertz-wave generation at room temperature

    PubMed Central

    Hayashi, Shin'ichiro; Nawata, Kouji; Taira, Takunori; Shikata, Jun-ichi; Kawase, Kodo; Minamide, Hiroaki

    2014-01-01

    The hottest frequency region in terms of research currently lies in the ‘frequency gap' region between microwaves and infrared: terahertz waves. Although new methods for generating terahertz radiation have been developed, most sources cannot generate high-brightness terahertz beams. Here we demonstrate the generation of ultrabright terahertz waves (brightness ~0.2 GW/sr·cm2, brightness temperature of ~1018 K, peak power of >50 kW) using parametric wavelength conversion in a nonlinear crystal; this is brighter than many specialized sources such as far-infrared free-electron lasers (~1016 K, ~2 kW). We revealed novel parametric wavelength conversion using stimulated Raman scattering in LiNbO3 without stimulated Brillouin scattering using recently-developed microchip laser. Furthermore, nonlinear up-conversion techniques allow the intense terahertz waves to be visualized and their frequency determined. These results are very promising for extending applied research into the terahertz region, and we expect that this source will open up new research fields such as nonlinear optics in the terahertz region. PMID:24898269

  14. Ultrabright continuously tunable terahertz-wave generation at room temperature.

    PubMed

    Hayashi, Shin'ichiro; Nawata, Kouji; Taira, Takunori; Shikata, Jun-ichi; Kawase, Kodo; Minamide, Hiroaki

    2014-01-01

    The hottest frequency region in terms of research currently lies in the 'frequency gap' region between microwaves and infrared: terahertz waves. Although new methods for generating terahertz radiation have been developed, most sources cannot generate high-brightness terahertz beams. Here we demonstrate the generation of ultrabright terahertz waves (brightness ~0.2 GW/sr·cm(2), brightness temperature of ~10(18) K, peak power of >50 kW) using parametric wavelength conversion in a nonlinear crystal; this is brighter than many specialized sources such as far-infrared free-electron lasers (~10(16) K, ~2 kW). We revealed novel parametric wavelength conversion using stimulated Raman scattering in LiNbO3 without stimulated Brillouin scattering using recently-developed microchip laser. Furthermore, nonlinear up-conversion techniques allow the intense terahertz waves to be visualized and their frequency determined. These results are very promising for extending applied research into the terahertz region, and we expect that this source will open up new research fields such as nonlinear optics in the terahertz region. PMID:24898269

  15. Analysis of adaptive laser scanning optical system with focus-tunable components

    NASA Astrophysics Data System (ADS)

    Pokorný, P.; Mikš, A.; Novák, J.; Novák, P.

    2015-05-01

    This work presents a primary analysis of an adaptive laser scanner based on two-mirror beam-steering device and focustunable components (lenses with tunable focal length). It is proposed an optical scheme of an adaptive laser scanner, which can focus the laser beam in a continuous way to a required spatial position using the lens with tunable focal length. This work focuses on a detailed analysis of the active optical or opto-mechanical components (e.g. focus-tunable lenses) mounted in the optical systems of laser scanners. The algebraic formulas are derived for ray tracing through different configurations of the scanning optical system and one can calculate angles of scanner mirrors and required focal length of the tunable-focus component provided that the position of the focused beam in 3D space is given with a required tolerance. Computer simulations of the proposed system are performed using MATLAB.

  16. Tunable superconductivity in decorated graphene

    NASA Astrophysics Data System (ADS)

    Han, Zheng; Allain, Adrien; Marty, Laetitia; Bendiab, Nedjma; Toulemonde, Pierre; Strobel, Pierre; Coraux, Johann; Bouchiat, Vincent

    2013-03-01

    Graphene offers an exposed bidimensional gas of high mobility charge carriers with gate tunable density. Its chemical inertness offers an outstanding platform to explore exotic 2D superconductivity. Superconductivity can be induced in graphene by means of proximity effect (by depositing a set of superconducting metal clusters such as lead or tin nanoparticles). The influence of decoration material, density or particles and disorder of graphene will be discussed. In the case of disordered graphene, Tin decoration leads to a gate-tunable superconducting-to-insulator quantum phase transition. Superconductivity in graphene is also expected to occur under strong charge doping (induced either by gating or under chemical decoration, in analogy with graphite intercalated compounds). I will also show preliminary results showing the influence of Calcium intercalation of few layer graphene and progress toward the demonstration of intrinsic superconductivity in such systems. Work supported by EU GRANT FP7-NMP GRENADA.

  17. Tunable graded rod laser assembly

    NASA Technical Reports Server (NTRS)

    AuYeung, John C. (Inventor)

    1985-01-01

    A tunable laser assembly including a pair of radially graded indexed optical segments aligned to focus the laser to form an external resonant cavity with an optical axis, the respective optical segments are retativity moveable along the optical axis and provide a variable et aion gap sufficient to permit variable tuning of the laser wavelength without altering the effective length of the resonant cavity. The gap also include a saturable absorbing material providing a passive mode-locking of the laser.

  18. Molecularly Tunable Fluorescent Quantum Defects.

    PubMed

    Kwon, Hyejin; Furmanchuk, Al'ona; Kim, Mijin; Meany, Brendan; Guo, Yong; Schatz, George C; Wang, YuHuang

    2016-06-01

    We describe the chemical creation of molecularly tunable fluorescent quantum defects in semiconducting carbon nanotubes through covalently bonded surface functional groups that are themselves nonemitting. By variation of the surface functional groups, the same carbon nanotube crystal is chemically converted to create more than 30 distinct fluorescent nanostructures with unique near-infrared photoluminescence that is molecularly specific, systematically tunable, and significantly brighter than that of the parent semiconductor. This novel exciton-tailoring chemistry readily occurs in aqueous solution and creates functional defects on the sp(2) carbon lattice with highly predictable C-C bonding from virtually any iodine-containing hydrocarbon precursor. Our new ability to control nanostructure excitons through a single surface functional group opens up exciting possibilities for postsynthesis chemical engineering of carbon nanomaterials and suggests that the rational design and creation of a large variety of molecularly tunable quantum emitters-for applications ranging from in vivo bioimaging and chemical sensing to room-temperature single-photon sources-can now be anticipated. PMID:27159413

  19. Highly tunable elastomeric silk biomaterials

    PubMed Central

    Partlow, Benjamin P.; Hanna, Craig W.; Rnjak-Kovacina, Jelena; Moreau, Jodie E.; Applegate, Matthew B.; Burke, Kelly A.; Marelli, Benedetto; Mitropoulos, Alexander N.; Omenetto, Fiorenzo G.

    2014-01-01

    Elastomeric, fully degradable and biocompatible biomaterials are rare, with current options presenting significant limitations in terms of ease of functionalization and tunable mechanical and degradation properties. We report a new method for covalently crosslinking tyrosine residues in silk proteins, via horseradish peroxidase and hydrogen peroxide, to generate highly elastic hydrogels with tunable properties. The tunable mechanical properties, gelation kinetics and swelling properties of these new protein polymers, in addition to their ability to withstand shear strains on the order of 100%, compressive strains greater than 70% and display stiffness between 200 – 10,000 Pa, covering a significant portion of the properties of native soft tissues. Molecular weight and solvent composition allowed control of material mechanical properties over several orders of magnitude while maintaining high resilience and resistance to fatigue. Encapsulation of human bone marrow derived mesenchymal stem cells (hMSC) showed long term survival and exhibited cell-matrix interactions reflective of both silk concentration and gelation conditions. Further biocompatibility of these materials were demonstrated with in vivo evaluation. These new protein-based elastomeric and degradable hydrogels represent an exciting new biomaterials option, with a unique combination of properties, for tissue engineering and regenerative medicine. PMID:25395921

  20. Tunable filters using wideband elastic resonators.

    PubMed

    Kadota, Michio; Ogami, Takashi; Kimura, Tetsuya; Daimon, Katsuya

    2013-10-01

    Currently, an ultra-wideband resonator is greatly needed to realize a tunable filter with a wide tunable range, because mobile phones with multiple bands and cognitive radio systems require such tunable filters to simplify their circuits. Although tunable filters have been studied using SAW resonators, their tunable range was insufficient for the filters even when wideband SAW resonators with a bandwidth of 17% were used. Therefore, the fabrication of wider-bandwidth resonators has been attempted with the goal of realizing tunable filters with wide tunable ranges. In this study, an SH0- mode plate wave resonator in a 27.5°YX-LiNbO3 plate with an ultra-wide bandwidth of 29.1%, a high impedance ratio of 98 dB, and a high Q (Q(r) = 700 and Q(a) = 720) was realized. Two types of tunable filters were constructed using such SH0-mode resonators and capacitors. As a result, tunable ranges (bands) of 13% to 19% were obtained. The possibility of applying the SH0-mode resonator in the high-frequency gigahertz range is discussed. PMID:24081261

  1. 1550-nm wavelength-tunable HCG VCSELs

    NASA Astrophysics Data System (ADS)

    Chase, Christopher; Rao, Yi; Huang, Michael; Chang-Hasnain, Connie

    2014-02-01

    We demonstrate wavelength-tunable VCSELs using high contrast gratings (HCGs) as the top output mirror on VCSELs, operating at 1550 nm. Tunable HCG VCSELs with a ~25 nm mechanical tuning range as well as VCSELs with 2 mW output power were realized. Error-free operation of an optical link using directly-modulated tunable HCG VCSELs transmitting at 1.25 Gbps over 18 channels spaced by 100 GHz and transmitted over 20 km of single mode fiber is demonstrated, showing the suitability of the HCG tunable VCSEL as a low cost source for WDM communications systems.

  2. Liquid Tunable Microlenses based on MEMS techniques

    PubMed Central

    Zeng, Xuefeng; Jiang, Hongrui

    2013-01-01

    The recent rapid development in microlens technology has provided many opportunities for miniaturized optical systems, and has found a wide range of applications. Of these microlenses, tunable-focus microlenses are of special interest as their focal lengths can be tuned using micro-scale actuators integrated with the lens structure. Realization of such tunable microlens generally relies on the microelectromechanical system (MEMS) technologies. Here, we review the recent progress in tunable liquid microlenses. The underlying physics relevant to these microlenses are first discussed, followed by description of three main categories of tunable microlenses involving MEMS techniques, mechanically driven, electrically driven, and those integrated within microfluidic systems. PMID:24163480

  3. Liquid tunable microlenses based on MEMS techniques

    NASA Astrophysics Data System (ADS)

    Zeng, Xuefeng; Jiang, Hongrui

    2013-08-01

    The recent rapid development in microlens technology has provided many opportunities for miniaturized optical systems, and has found a wide range of applications. Of these microlenses, tunable-focus microlenses are of special interest as their focal lengths can be tuned using micro-scale actuators integrated with the lens structure. Realization of such tunable microlens generally relies on the microelectromechanical system (MEMS) technologies. Here, we review the recent progress in tunable liquid microlenses. The underlying physics relevant to these microlenses are first discussed, followed by description of three main categories of tunable microlenses involving MEMS techniques, mechanically driven, electrically driven and those integrated within microfluidic systems.

  4. Remote sensing with a tunable alexandrite laser transmitter

    NASA Technical Reports Server (NTRS)

    Korb, C. L.; Schwemmer, G. K.; Dombrowski, M.; Kagann, R. H.

    1985-01-01

    A high-resolution, tunable alexandrite laser system is described. Two alexandrite lasers are continuously tunable from 725-790 nm and have a bandwidth of 0.02/cm. The stability of the two lasers is evaluated. The line shape of the laser emission and spectral purity of the system were measured. The data reveal that the output consists of three axial modes with an overall width of 0.026/cm, and the spectral impurity of the alexandrite laser output is less than 0.01 percent. The ground-based lidar system is utilized for measuring atmospheric pressure profiles; the integrated absorption in the wings of lines in the O2 A band is studied to produce the profiles. An example of lidar-collected atmospheric pressure data is presented and compared with radiosonde data; only a 0.3 percent deviation between the data is observed.

  5. Graphene-based tunable terahertz plasmon-induced transparency metamaterial.

    PubMed

    Zhao, Xiaolei; Yuan, Cai; Zhu, Lin; Yao, Jianquan

    2016-08-18

    A novel terahertz plasmon induced transparency (PIT) metamaterial structure consisting of single-layered graphene microstructures was proposed and numerically studied in this study. A pronounced transparency peak was obtained in the transmission spectrum, which resulted from the destructive interference between the graphene dipole and monopole antennas. Further investigations have shown that the spectral location and lineshape of the transparency peak can be dynamically controlled by tuning the Fermi level in graphene. Since the monopole antennas in our designed structure exist in a continuous form, a more convenient method for tunablity is available by applying a gate voltage compared to those structures with discrete graphene patterns. This work may open up new avenues for designing tunable terahertz functional devices and slow light devices. PMID:27500393

  6. Broadly tunable terahertz source

    NASA Astrophysics Data System (ADS)

    Powers, Peter E.; Kramb, Kevan; Haus, Joseph W.

    2010-02-01

    We present the results of a terahertz (THz) source based on difference frequency generation (DFG) that tunes seamlessly from 1.4 to 13.3 THz. The outputs from two seeded periodically poled lithium niobate (PPLN) optical parametric generators (OPGs) are mixed in a DAST crystal to generate the THz frequencies. The OPG's have ~1 nsec pulse duration and an output energy of approximately 200 μJ. The corresponding high peak intensities in the DAST crystal leads to appreciable conversion efficiency such that a room temperature pyro-electric detector is used to measure the THz signal. In one of the OPGs a continuously varying periodicity PPLN crystal is used to tune the output wavelength by translating the crystal. The crystal position and seed laser are computer-controlled and synchronized such that any wavelength within the seed laser's tuning range is randomly accessible, and hence any THz difference frequency between the two seed lasers is also randomly accessible. Phase matching in DAST requires the DFG inputs to have the same polarization. We demonstrate a scheme where the output of one of the OPGs is sent through the second OPG such that the two beams are collinear with the same polarization without using a beam splitter.

  7. Wideband tunable optoelectronic oscillator based on a phase modulator and a tunable optical filter.

    PubMed

    Xie, Xiaopeng; Zhang, Cheng; Sun, Tao; Guo, Peng; Zhu, Xiaoqi; Zhu, Lixin; Hu, Weiwei; Chen, Zhangyuan

    2013-03-01

    A widely tunable optoelectronic oscillator (OEO) based on a broadband phase modulator and a tunable optical bandpass filter is proposed and experimentally demonstrated. A tunable range from 4.74 to 38.38 GHz is realized by directly tuning the bandwidth of the optical bandpass filter. To the best of our knowledge, this is the widest fundamental frequency tunable range ever achieved by an OEO. The phase noise performance of the generated signal is also investigated. The single-sideband phase noise is below -120 dBc/Hz at an offset of 10 KHz within the whole tunable range. PMID:23455255

  8. Wavelength-tunable actively mode-locked erbium-doped fiber ring laser using a distributed feedback semiconductor laser as mode locker and tunable filter

    NASA Astrophysics Data System (ADS)

    Li, Shenping; Chan, K. T.

    1999-07-01

    A wavelength-tunable actively mode-locked erbium fiber ring laser was demonstrated using a distributed feedback semiconductor laser as an intensity mode locker and a tunable optical filter. Very stable optical pulse trains at gigabit repetition rates were generated using harmonica mode locking. The supermode noise was suppressed to 60 dB below the signal level and the root-mean-square timing jitter (0.45 kHz-1 MHz) was found to be about 1% of the pulse duration. A continuous wavelength tuning range of 1.8 nm was achieved by changing the semiconductor laser temperature from 11.4 to 30 °C.

  9. All-fiber widely wavelength-tunable thulium-doped fiber ring laser incorporating a Fabry-Perot filter

    NASA Astrophysics Data System (ADS)

    Wei, Y.; Hu, K.; Sun, B.; Wang, T.

    2012-04-01

    We demonstrate 1940 to 2010 nm continuous CW wavelength-tuning in a thulium-doped fiber laser (TDFL), using only fiber-format components. A fiber Fabry-Perot (FP) tunable filter is employed to achieve the wavelength tunability of 70 nm. By imposing a 200 Hz triangle wave signal on the filter, rapid wavelength-sweeping is demonstrated from 1952 to 1992 nm every 5 ms, corresponding to 8 nm/ms. This all-fiber wavelength-tunable and swept laser may find applications such as gas monitoring in the wavelength region of 2 μm.

  10. Graphene Q-switched, tunable fiber laser

    NASA Astrophysics Data System (ADS)

    Popa, D.; Sun, Z.; Hasan, T.; Torrisi, F.; Wang, F.; Ferrari, A. C.

    2011-02-01

    We demonstrate a wideband-tunable Q-switched fiber laser exploiting a graphene saturable absorber. We get ˜2 μs pulses, tunable between 1522 and 1555 nm with up to ˜40 nJ energy. This is a simple and low-cost light source for metrology, environmental sensing, and biomedical diagnostics.

  11. Multiple-wavelength tunable laser

    NASA Technical Reports Server (NTRS)

    Barnes, Norman P. (Inventor); Walsh, Brian M. (Inventor); Reichle, Donald J. (Inventor)

    2010-01-01

    A tunable laser includes dispersion optics for separating generated laser pulses into first and second wavelength pulses directed along first and second optical paths. First and second reflective mirrors are disposed in the first and second optical paths, respectively. The laser's output mirror is partially reflective and partially transmissive with respect to the first wavelength and the second wavelength in accordance with provided criteria. A first resonator length is defined between the output mirror and the first mirror, while a second resonator length is defined between the output mirror and the second mirror. The second resonator length is a function of the first resonator length.

  12. Tunable quantum well infrared detector

    NASA Technical Reports Server (NTRS)

    Maserjian, Joseph (Inventor)

    1990-01-01

    A novel infrared detector (20, 20', 20), is provided, which is characterized by photon-assisted resonant tunneling between adjacent quantum wells (22a, 22b) separated by barrier layers (28) in an intrinsic semiconductor layer (24) formed on an n.sup.+ substrate (26), wherein the resonance is electrically tunable over a wide band of wavelengths in the near to long infrared region. An n.sup.+ contacting layer (34) is formed over the intrinsic layer and the substrate is n.sup.+ doped to provide contact to the quantum wells. The detector permits fabrication of arrays (30) (one-dimensional and two-dimensional) for use in imaging and spectroscopy applications.

  13. A tunable carbon nanotube polarizer.

    PubMed

    Kang, Byeong Gyun; Lim, Young Jin; Jeong, Kwang-Un; Lee, Kyu; Lee, Young Hee; Lee, Seung Hee

    2010-10-01

    The electro-optic response of a carbon nanotube (CNT) cluster has been investigated. The cluster absorbs incident light before stretching. In the presence of an electric field, the cluster starts stretching along the field direction and contracts back to its original stage when the applied voltage is removed. The stretched cluster absorbs and transmits incident light with its electric vector propagating parallel and perpendicular to the long axis of the stretched cluster, respectively. Utilizing this selective light absorption property of a CNT cluster, a tunable polarizer or non-emissive light modulator can be realized. PMID:20829567

  14. Wavelength tunable alexandrite regenerative amplifier

    SciTech Connect

    Harter, D.J.; Bado, P.

    1988-11-01

    We describe a wavelength tunable alexandrite regenerative amplifier which is used to amplify nanosecond slices from a single-frequency cw dye laser or 50-ps pulses emitted by a diode laser to energies in the 10-mJ range. The amplified 5-ns slices generated by the cw-pumped line narrowed dye laser are Fourier transform limited. The 50-ps pulses emitted by a gain-switched diode laser are amplified by more than 10 orders of magnitude in a single stage.

  15. Tunable synthesis of copper nanotubes

    NASA Astrophysics Data System (ADS)

    Kaniukov, E.; Kozlovsky, A.; Shlimas, D.; Yakimchuk, D.; Zdorovets, M.; Kadyrzhanov, K.

    2016-02-01

    Simple method of tunable synthesis of copper nanotubes based on template synthesis was developed. A comprehensive study of the structural, morphological and electrical characteristics of the obtained nanostructures was carried out. Characterization of structural features was made by methods of scanning electron microscopy, energy dispersive spectroscopy and X-ray diffractometry analysis. Evaluation of wall thickness is made by methods of gas permeability. Electrical conductivity of nanotubes was define in the study of their current-voltage characteristics. The possibility to control of copper nanotubes physical properties by variation of the deposition parameters was shown.

  16. Tunable Optical Filters for Space Exploration

    NASA Technical Reports Server (NTRS)

    Crandall, Charles; Clark, Natalie; Davis, Patricia P.

    2007-01-01

    Spectrally tunable liquid crystal filters provide numerous advantages and several challenges in space applications. We discuss the tradeoffs in design elements for tunable liquid crystal birefringent filters with special consideration required for space exploration applications. In this paper we present a summary of our development of tunable filters for NASA space exploration. In particular we discuss the application of tunable liquid crystals in guidance navigation and control in space exploration programs. We present a summary of design considerations for improving speed, field of view, transmission of liquid crystal tunable filters for space exploration. In conclusion, the current state of the art of several NASA LaRC assembled filters is presented and their performance compared to the predicted spectra using our PolarTools modeling software.

  17. Ultrahigh magnetically responsive microplatelets with tunable fluorescence emission.

    PubMed

    Libanori, Rafael; Reusch, Frieder B; Erb, Randall M; Studart, André R

    2013-11-26

    Tuning the optical properties of suspensions by controlling the orientation and spatial distribution of suspended particles with magnetic fields is an interesting approach to creating magnetically controlled displays, microrheology sensors, and materials with tunable light emission. However, the relatively high concentration of magnetic material required to manipulate these particles very often reduces the optical transmittance of the system. In this study, we describe a simple method of generating particles with magnetically tunable optical properties via sol-gel deposition and functionalization of a continuous layer of silica on ultrahigh magnetically responsive (UHMR) alumina microplatelets. UHMR microplatelets with tunable magnetic response in the range of 15-36 G are obtained by the electrostatic adsorption of 2 to 13% of superparamagnetic iron oxide nanoparticles (SPIONs) on the alumina surface. The magnetized platelets are coated with a 20-50 nm layer of SiO2 through the controlled hydrolysis and condensation reactions of tetraethylorthosilicate (TEOS) in an NH3/ethanol mixture. Finally, the silica surface is covalently modified with an organic fluorescent dye by conventional silane chemistry. Because of the anisotropic shape of the particles, control of their orientation and distribution using magnetic fields and field gradients enables easy tuning of the optical properties of the suspension. This strategy allows us to gain both spatial and temporal control over the fluorescence emission from the particle surface, making the multifunctional platelets interesting building blocks for the manipulation of light in colloid-based smart optical devices and sensors. PMID:24175712

  18. Plasma Tunable LC Resonator for High-Power Electromagnetic Applications

    NASA Astrophysics Data System (ADS)

    Semnani, Abbas; Macheret, Sergey; Peroulis, Dimitrios

    2015-09-01

    High-power tunable filters are in high demand in transmitters found in radars and many communication systems such as satellite and broadcasting stations. Limited power handling renders most semiconductor technologies inherently suboptimal options for these systems. Therefore, mechanically-tunable cavity-based filters are often employed in such cases, resulting in bulky, slow, and heavy systems. In this work, we study the application of plasma as an alternative frequency tuning mechanism for high-power applications even in environmentally and/or mechanically harsh conditions. For a given gas type and pressure, the real and imaginary parts of the dielectric permittivity of a plasma can be varied by changing the electron density, which, depending on the discharge regime, can be implemented by changing the discharge current, voltage, or the magnitude of an auxiliary electric field. In this work, a simple LC resonator tuned to several hundred MHz was fabricated and tested. The tunable capacitor of the resonator was implemented by a commercially available gas discharge tube (GDT), a mm-scale plasma device with gas pressure of 100s of mTorr. Measurement results reveal a continuous tuning range of more than 50% when the applied discharge current is increased from zero to 90 mA.

  19. The systematic tunability of nanoparticle dimensions through the controlled loading of surface-deposited diblock copolymer micelles.

    PubMed

    Krishnamoorthy, S; Pugin, R; Hinderling, C; Brugger, J; Heinzelmann, H

    2008-04-30

    The continuous tunability of iron oxide nanoparticle dimensions is demonstrated using the pH controlled loading of ferric nitrate from aqueous solution into polystyrene-block-polyacrylic acid reverse micelles deposited on a silicon substrate. Quasi-hexagonally ordered two-dimensional arrays of iron oxide nanoparticles with a systematic tunability of particle heights in the sub-10 nm regime and a constant periodicity are obtained and characterized with atomic force microscopy and x-ray photoelectron spectroscopy. PMID:21825665

  20. Broadly tunable picosecond ir source

    DOEpatents

    Campillo, A.J.; Hyer, R.C.; Shapiro, S.L.

    1980-04-23

    A picosecond traveling-wave parametric device capable of controlled spectral bandwidth and wavelength in the infrared is reported. Intense 1.064 ..mu..m picosecond pulses (1) pass through a 4.5 cm long LiNbO/sub 3/ optical parametric oscillator crystal (2) set at its degeneracy angle. A broad band emerges, and a simple grating (3) and mirror (4) arrangement is used to inject a selected narrow-band into a 2 cm long LiNbO/sub 3/ optical parametric amplifier crystal (5) along a second pump line. Typical input energies at 1.064 ..mu..m along both pump lines are 6 to 8 mJ for the oscillator and 10 mJ for the amplifier. This yields 1 mJ of tunable output in the range 1.98 to 2.38 ..mu..m which when down-converted in a 1 cm long CdSe crystal mixer (6) gives 2 ..mu..J of tunable radiation over the 14.8 to 18.5 ..mu..m region. The bandwidth and wavelength of both the 2 and 16 ..mu..m radiation output are controlled solely by the diffraction grating.

  1. MEMS for Tunable Plasmonic Coupling

    NASA Astrophysics Data System (ADS)

    Stark, Tom; Imboden, Matthias; Kaya, Sabri; Mertiri, Alket; Erramilli, Shyamsunder; Bishop, David

    2015-03-01

    The localized surface plasmon resonance (LSPR) of sub-wavelength holes in metals depends upon the geometry, composition, refractive index, and near field coupling to neighboring particles. Sub-wavelength holes in metals can exhibit extraordinary optical transmission (EOT) at the resonance frequency and, for certain geometries, polarization-dependent transmission. We present a microelectromechanical system, tunable Fabry-Perot etalon. One interface is a suspended gold metamaterial and the other is a gold reflector. The reflectance, measured with a Fourier transform infrared spectrometer, exhibits the convolution of the EOT through the holes and Fabry-Perot resonances. Using MEMS, we modulate the etalon length from 1 to 20 μm, thereby tuning the free spectral range from about 5000 to 250 cm-1 and shifting the reflection minima and maxima across the infrared. When the separation between the metamaterial and gold reflector approaches the decay length of the LSP electric fields, interactions with image currents generated in the gold reflector become significant. By tuning the separation in this regime, we will tune the near field coupling between the LSPR and image currents and tune the LSPR of the system, effectively creating a sensing substrate with a tunable LSPR frequency.

  2. Broadly tunable picosecond IR source

    DOEpatents

    Campillo, Anthony J.; Hyer, Ronald C.; Shapiro, Stanley J.

    1982-01-01

    A picosecond traveling-wave parametric device capable of controlled spectral bandwidth and wavelength in the infrared is reported. Intense 1.064 .mu.m picosecond pulses (1) pass through a 4.5 cm long LiNbO.sub.3 optical parametric oscillator crystal (2) set at its degeneracy angle. A broad band emerges, and a simple grating (3) and mirror (4) arrangement is used to inject a selected narrow-band into a 2 cm long LiNbO.sub.3 optical parametric amplifier crystal (5) along a second pump line. Typical input energies at 1.064 .mu.m along both pump lines are 6-8 mJ for the oscillator and 10 mJ for the amplifier. This yields 1 mJ of tunable output in the range 1.98 to 2.38 .mu.m which when down-converted in a 1 cm long CdSe crystal mixer (6) gives 2 .mu.J of tunable radiation over the 14.8 to 18.5 .mu.m region. The bandwidth and wavelength of both the 2 and 16 .mu.m radiation output are controlled solely by the diffraction grating.

  3. Color temperature tunable white light LED system

    NASA Astrophysics Data System (ADS)

    Speier, Ingo; Salsbury, Marc

    2006-08-01

    Efficient white light LED systems with continuously tunable color temperature (CT) over a range of 3000 K to 6500 K are reviewed. Typically, white light sources have a fixed CT and color rendering index (CRI). White light with user-specified color temperatures is currently generated by solid-state systems with red green blue ("R/G/B"), red green blue amber ("R/G/B/A"), and warm white cool white ("WW/CW") LED combinations, but their performance is suboptimal for architectural lighting applications. We propose and discuss an LED module with a combination of warm white, green and blue ("WW/G/B") LEDs. In this scenario, the white LEDs have fixed intensity, while the blue and green LED intensities are adjusted to shift the LED module chromaticity along the blackbody locus. We also propose and discuss an LED module with a combination of red, green, blue, and cool white ("R/G/B/CW") LEDs. The white LEDs still have a fixed intensity, while the intensities of the red, green, and blue LEDs are again adjusted to shift the LED module chromaticity along the blackbody locus. The white LEDs ensure that an improved CRI is maintained in comparison to a simple "R/G/B" solution.

  4. MEMS tunable filter for telecom applications

    NASA Astrophysics Data System (ADS)

    Overstolz, Thomas; Niederer, Guido; Noell, Wilfried; Gale, Michael T.; Herzig, Hans Peter; Obi, Samuel; Thiele, Hans; de Rooij, Nicolaas F.

    2004-08-01

    We report on an angle-tunable oblique incidence resonant grating filter that can be used to drop individual channels from the C-band for incident TE-polarized light. For tuning purpose, the filter is glued onto a tiltable platform of a MEMS device. Continues scanning of the platform allows to monitor channel presence and power. The reflected wavelength is tuned by changing the angle of incidence of the resonant grating filter, which is composed of two thin films with a grating pattern on top of it. The first layer on a glass substrate acts as a waveguide, and the second layer separates the waveguide from the grating. The grating has been patterned by holographic recording and dry etching. The filter works over a wavelength range of 1520-1580 nm and its response has a Lorentian shape with 0.5 nm FWHM peak width. The MEMS part is based on SOI technology and is processed in only two DRIE steps. The platform measures 2 x 2 mm2 with a through-hole of 1.6 x 1.8 mm2 for light transmission. Two arrays of combs attached to the platform as well as a set of four static combs are used to electrostatically incline the platform by +/- 4° with a driving voltage of about 60 V.

  5. A flat lens with tunable phase gradient by using random access reconfigurable metamaterial.

    PubMed

    Zhu, Weiming; Song, Qinghua; Yan, Libin; Zhang, Wu; Wu, Pin-Chieh; Chin, Lip Ket; Cai, Hong; Tsai, Din Ping; Shen, Zhong Xiang; Deng, Tian Wei; Ting, Sing Kwong; Gu, Yuandong; Lo, Guo Qiang; Kwong, Dim Lee; Yang, Zhen Chuan; Huang, Ru; Liu, Ai-Qun; Zheludev, Nikolay

    2015-08-26

    The first demonstration of an optofluidic metamaterial is reported where resonant properties of every individual metamolecule can be continuously tuned at will using a microfluidic system. This is called a random-access reconfigurable metamaterial, which is used to provide the first demonstration of a tunable flat lens with wavefront-reshaping capabilities. PMID:26184076

  6. Narrowband multispectral liquid crystal tunable filter.

    PubMed

    Abuleil, Marwan; Abdulhalim, Ibrahim

    2016-05-01

    Multispectral tunable filters with high performance are desirable components in various biomedical and industrial applications. In this Letter, we present a new narrowband multispectral tunable filter with high throughput over a wide dynamic range. It is composed from a wideband large dynamic range liquid crystal tunable filter combined with a multiple narrowbands spectral filter made of two stacks of photonic crystals and cavity layer in between. The filter tunes between nine spectral bands covering the range 450-1000 nm with bandwidth <10  nm and throughput >80%. PMID:27128048

  7. Graphene cardboard: From ripples to tunable metamaterial

    NASA Astrophysics Data System (ADS)

    Koskinen, Pekka

    2014-03-01

    Recently, graphene was introduced with tunable ripple texturing, a nanofabric enabled by graphene's remarkable elastic properties. However, one can further envision sandwiching the ripples, thus constructing composite nanomaterial, graphene cardboard. Here, the basic mechanical properties of such structures are investigated computationally. It turns out that graphene cardboard is highly tunable material, for its elastic figures of merit vary orders of magnitude, with Poisson ratio tunable from 10 to -0.5 as one example. These trends set a foundation to guide the design and usage of metamaterials made of rippled van der Waals solids.

  8. Tunable protein degradation in bacteria.

    PubMed

    Cameron, D Ewen; Collins, James J

    2014-12-01

    Tunable control of protein degradation in bacteria would provide a powerful research tool. Here we use components of the Mesoplasma florum transfer-messenger RNA system to create a synthetic degradation system that provides both independent control of steady-state protein level and inducible degradation of targeted proteins in Escherichia coli. We demonstrate application of this system in synthetic circuit development and control of core bacterial processes and antibacterial targets, and we transfer the system to Lactococcus lactis to establish its broad functionality in bacteria. We create a 238-member library of tagged essential proteins in E. coli that can serve as both a research tool to study essential gene function and an applied system for antibiotic discovery. Our synthetic protein degradation system is modular, does not require disruption of host systems and can be transferred to diverse bacteria with minimal modification. PMID:25402616

  9. Electrically tunable infrared metamaterial devices

    DOEpatents

    Brener, Igal; Jun, Young Chul

    2015-07-21

    A wavelength-tunable, depletion-type infrared metamaterial optical device is provided. The device includes a thin, highly doped epilayer whose electrical permittivity can become negative at some infrared wavelengths. This highly-doped buried layer optically couples with a metamaterial layer. Changes in the transmission spectrum of the device can be induced via the electrical control of this optical coupling. An embodiment includes a contact layer of semiconductor material that is sufficiently doped for operation as a contact layer and that is effectively transparent to an operating range of infrared wavelengths, a thin, highly doped buried layer of epitaxially grown semiconductor material that overlies the contact layer, and a metallized layer overlying the buried layer and patterned as a resonant metamaterial.

  10. Artificial graphene with tunable interactions.

    PubMed

    Uehlinger, Thomas; Jotzu, Gregor; Messer, Michael; Greif, Daniel; Hofstetter, Walter; Bissbort, Ulf; Esslinger, Tilman

    2013-11-01

    We create an artificial graphene system with tunable interactions and study the crossover from metallic to Mott insulating regimes, both in isolated and coupled two-dimensional honeycomb layers. The artificial graphene consists of a two-component spin mixture of an ultracold atomic Fermi gas loaded into a hexagonal optical lattice. For strong repulsive interactions, we observe a suppression of double occupancy and measure a gapped excitation spectrum. We present a quantitative comparison between our measurements and theory, making use of a novel numerical method to obtain Wannier functions for complex lattice structures. Extending our studies to time-resolved measurements, we investigate the equilibration of the double occupancy as a function of lattice loading time. PMID:24237536

  11. Tunable surface plasmon wave plates.

    PubMed

    Djalalian-Assl, Amir; Cadusch, Jasper J; Balaur, Eugeniu; Aramesh, Morteza

    2016-07-01

    The highest resonant transmission through an array of holes perforated in metallic screens occurs when the dielectric constant of the substrate, the superstrate, and the hole are the same. Changes in the refractive index of the homogenous environment also produce the largest shift in resonances per refractive index unit. In this Letter, we first propose and apply a technique in realization of a freestanding bi-periodic array of holes perforated in a silver film. We then show both numerically and experimentally that shifts in (1,0) and (0,1) modes in response to changes in the refractive index of the surrounding dielectric provide a mechanism for realization of a miniaturized tunable quarter-wave plate that operates in an extraordinary optical transmission mode with a high throughput and a near unity state of circularly polarized light. PMID:27367123

  12. Tunable Vapor-Condensed Nanolenses

    PubMed Central

    2015-01-01

    Nanostructured optical components, such as nanolenses, direct light at subwavelength scales to enable, among others, high-resolution lithography, miniaturization of photonic circuits, and nanoscopic imaging of biostructures. A major challenge in fabricating nanolenses is the appropriate positioning of the lens with respect to the sample while simultaneously ensuring it adopts the optimal size and shape for the intended use. One application of particular interest is the enhancement of contrast and signal-to-noise ratio in the imaging of nanoscale objects, especially over wide fields-of-view (FOVs), which typically come with limited resolution and sensitivity for imaging nano-objects. Here we present a self-assembly method for fabricating time- and temperature-tunable nanolenses based on the condensation of a polymeric liquid around a nanoparticle, which we apply to the high-throughput on-chip detection of spheroids smaller than 40 nm, rod-shaped particles with diameter smaller than 20 nm, and biofunctionalized nanoparticles, all across an ultralarge FOV of >20 mm2. Previous nanoparticle imaging efforts across similar FOVs have detected spheroids no smaller than 100 nm, and therefore our results demonstrate the detection of particles >15-fold smaller in volume, which in free space have >240 times weaker Rayleigh scattering compared to the particle sizes detected in earlier wide-field imaging work. This entire platform, with its tunable nanolens condensation and wide-field imaging functions, is also miniaturized into a cost-effective and portable device, which might be especially important for field use, mobile sensing, and diagnostics applications, including, for example, the measurement of viral load in bodily fluids. PMID:24979060

  13. Widely tunable terahertz source based on intra-cavity frequency mixing in quantum cascade laser arrays

    SciTech Connect

    Jiang, Aiting; Jung, Seungyong; Jiang, Yifan; Kim, Jae Hyun; Belkin, Mikhail A.; Vijayraghavan, Karun

    2015-06-29

    We demonstrate a compact monolithic terahertz source continuously tunable from 1.9 THz to 3.9 THz with the maximum peak power output of 106 μW at 3.46 THz at room temperature. The source consists of an array of 10 electrically tunable quantum cascade lasers with intra-cavity terahertz difference-frequency generation. To increase fabrication yield and achieve high THz peak power output in our devices, a dual-section current pumping scheme is implemented using two electrically isolated grating sections to independently control gain for the two mid-IR pumps.

  14. Arbitrarily tunable orbital angular momentum of photons

    PubMed Central

    Pan, Yue; Gao, Xu-Zhen; Ren, Zhi-Cheng; Wang, Xi-Lin; Tu, Chenghou; Li, Yongnan; Wang, Hui-Tian

    2016-01-01

    Orbital angular momentum (OAM) of photons, as a new fundamental degree of freedom, has excited a great diversity of interest, because of a variety of emerging applications. Arbitrarily tunable OAM has gained much attention, but its creation remains still a tremendous challenge. We demonstrate the realization of well-controlled arbitrarily tunable OAM in both theory and experiment. We present the concept of general OAM, which extends the OAM carried by the scalar vortex field to the OAM carried by the azimuthally varying polarized vector field. The arbitrarily tunable OAM we presented has the same characteristics as the well-defined integer OAM: intrinsic OAM, uniform local OAM and intensity ring, and propagation stability. The arbitrarily tunable OAM has unique natures: it is allowed to be flexibly tailored and the radius of the focusing ring can have various choices for a desired OAM, which are of great significance to the benefit of surprising applications of the arbitrary OAM. PMID:27378234

  15. Electrically tunable materials for microwave applications

    SciTech Connect

    Ahmed, Aftab Goldthorpe, Irene A.; Khandani, Amir K.

    2015-03-15

    Microwave devices based on tunable materials are of vigorous current interest. Typical applications include phase shifters, antenna beam steering, filters, voltage controlled oscillators, matching networks, and tunable power splitters. The objective of this review is to assist in the material selection process for various applications in the microwave regime considering response time, required level of tunability, operating temperature, and loss tangent. The performance of a variety of material types are compared, including ferroelectric ceramics, polymers, and liquid crystals. Particular attention is given to ferroelectric materials as they are the most promising candidates when response time, dielectric loss, and tunability are important. However, polymers and liquid crystals are emerging as potential candidates for a number of new applications, offering mechanical flexibility, lower weight, and lower tuning voltages.

  16. Recent development of infrared tunable filter

    NASA Astrophysics Data System (ADS)

    Liu, Dafu; Xu, Qinfei; Mo, Defeng

    2015-04-01

    Researchers are engaging on tunable infrared (IR) filters, miniature Fabry-Perot optical devices, to operate IR detector like a spectrometer. This kind of devices was used in astronomical detection field in the 1950s. To meet the miniature, lightweight requirements of the optical detection system, researchers began to make small, lightweight, and cheap tunable IR filters. Nowadays researchers have applied a variety of different structures and the IR filter, and are attempting to integrate them with IR detectors directly. Tunable filter thin film mechanical and thermal properties, and working conditions will affect the tunable filter optical performance. In this article we give two main influencing factors, interface roughness and curvature effect. we also present and discuss the current development of FPF in different groups around the world.

  17. Electrically tunable materials for microwave applications

    NASA Astrophysics Data System (ADS)

    Ahmed, Aftab; Goldthorpe, Irene A.; Khandani, Amir K.

    2015-03-01

    Microwave devices based on tunable materials are of vigorous current interest. Typical applications include phase shifters, antenna beam steering, filters, voltage controlled oscillators, matching networks, and tunable power splitters. The objective of this review is to assist in the material selection process for various applications in the microwave regime considering response time, required level of tunability, operating temperature, and loss tangent. The performance of a variety of material types are compared, including ferroelectric ceramics, polymers, and liquid crystals. Particular attention is given to ferroelectric materials as they are the most promising candidates when response time, dielectric loss, and tunability are important. However, polymers and liquid crystals are emerging as potential candidates for a number of new applications, offering mechanical flexibility, lower weight, and lower tuning voltages.

  18. Thermally tunable ferroelectric thin film photonic crystals.

    SciTech Connect

    Lin, P. T.; Wessels, B. W.; Imre, A.; Ocola, L. E.; Northwestern Univ.

    2008-01-01

    Thermally tunable PhCs are fabricated from ferroelectric thin films. Photonic band structure and temperature dependent diffraction are calculated by FDTD. 50% intensity modulation is demonstrated experimentally. This device has potential in active ultra-compact optical circuits.

  19. Tunable beam steering enabled by graphene metamaterials.

    PubMed

    Orazbayev, B; Beruete, M; Khromova, I

    2016-04-18

    We demonstrate tunable mid-infrared (MIR) beam steering devices based on multilayer graphene-dielectric metamaterials. The effective refractive index of such metamaterials can be manipulated by changing the chemical potential of each graphene layer. This can arbitrarily tailor the spatial distribution of the phase of the transmitted beam, providing mechanisms for active beam steering. Three different beam steerer (BS) designs are discussed: a graded-index (GRIN) graphene-based metamaterial block, an array of metallic waveguides filled with graphene-dielectric metamaterial and an array of planar waveguides created in a graphene-dielectric metamaterial block with a specific spatial profile of graphene sheets doping. The performances of the BSs are numerically analyzed, showing the tunability of the proposed designs for a wide range of output angles (up to approximately 70°). The proposed graphene-based tunable beam steering can be used in tunable transmitter/receiver modules for infrared imaging and sensing. PMID:27137318

  20. Arbitrarily tunable orbital angular momentum of photons.

    PubMed

    Pan, Yue; Gao, Xu-Zhen; Ren, Zhi-Cheng; Wang, Xi-Lin; Tu, Chenghou; Li, Yongnan; Wang, Hui-Tian

    2016-01-01

    Orbital angular momentum (OAM) of photons, as a new fundamental degree of freedom, has excited a great diversity of interest, because of a variety of emerging applications. Arbitrarily tunable OAM has gained much attention, but its creation remains still a tremendous challenge. We demonstrate the realization of well-controlled arbitrarily tunable OAM in both theory and experiment. We present the concept of general OAM, which extends the OAM carried by the scalar vortex field to the OAM carried by the azimuthally varying polarized vector field. The arbitrarily tunable OAM we presented has the same characteristics as the well-defined integer OAM: intrinsic OAM, uniform local OAM and intensity ring, and propagation stability. The arbitrarily tunable OAM has unique natures: it is allowed to be flexibly tailored and the radius of the focusing ring can have various choices for a desired OAM, which are of great significance to the benefit of surprising applications of the arbitrary OAM. PMID:27378234

  1. A spectrally tunable all-graphene-based flexible field-effect light-emitting device

    NASA Astrophysics Data System (ADS)

    Wang, Xiaomu; Tian, He; Mohammad, Mohammad Ali; Li, Cheng; Wu, Can; Yang, Yi; Ren, Tian-Ling

    2015-07-01

    The continuous tuning of the emission spectrum of a single light-emitting diode (LED) by an external electrical bias is of great technological significance as a crucial property in high-quality displays, yet this capability has not been demonstrated in existing LEDs. Graphene, a tunable optical platform, is a promising medium to achieve this goal. Here we demonstrate a bright spectrally tunable electroluminescence from blue (~450 nm) to red (~750 nm) at the graphene oxide/reduced-graphene oxide interface. We explain the electroluminescence results from the recombination of Poole-Frenkel emission ionized electrons at the localized energy levels arising from semi-reduced graphene oxide, and holes from the top of the π band. Tuning of the emission wavelength is achieved by gate modulation of the participating localized energy levels. Our demonstration of current-driven tunable LEDs not only represents a method for emission wavelength tuning but also may find applications in high-quality displays.

  2. Anisotropic Nanoantenna-Based Magnetoplasmonic Crystals for Highly Enhanced and Tunable Magneto-Optical Activity.

    PubMed

    Maccaferri, Nicolò; Bergamini, Luca; Pancaldi, Matteo; Schmidt, Mikolaj K; Kataja, Mikko; Dijken, Sebastiaan van; Zabala, Nerea; Aizpurua, Javier; Vavassori, Paolo

    2016-04-13

    We present a novel concept of a magnetically tunable plasmonic crystal based on the excitation of Fano lattice surface modes in periodic arrays of magnetic and optically anisotropic nanoantennas. We show how coherent diffractive far-field coupling between elliptical nickel nanoantennas is governed by the two in-plane, orthogonal and spectrally detuned plasmonic responses of the individual building block, one directly induced by the incident radiation and the other induced by the application of an external magnetic field. The consequent excitation of magnetic field-induced Fano lattice surface modes leads to highly tunable and amplified magneto-optical effects as compared to a continuous film or metasurfaces made of disordered noninteracting magnetoplasmonic anisotropic nanoantennas. The concepts presented here can be exploited to design novel magnetoplasmonic sensors based on coupled localized plasmonic resonances, and nanoscale metamaterials for precise control and magnetically driven tunability of light polarization states. PMID:26967047

  3. Tunable photonic cavities for in-situ spectroscopic trace gas detection

    DOEpatents

    Bond, Tiziana; Cole, Garrett; Goddard, Lynford

    2012-11-13

    Compact tunable optical cavities are provided for in-situ NIR spectroscopy. MEMS-tunable VCSEL platforms represents a solid foundation for a new class of compact, sensitive and fiber compatible sensors for fieldable, real-time, multiplexed gas detection systems. Detection limits for gases with NIR cross-sections such as O.sub.2, CH.sub.4, CO.sub.x and NO.sub.x have been predicted to approximately span from 10.sup.ths to 10s of parts per million. Exemplary oxygen detection design and a process for 760 nm continuously tunable VCSELS is provided. This technology enables in-situ self-calibrating platforms with adaptive monitoring by exploiting Photonic FPGAs.

  4. Micro-electro-mechanically tunable metamaterial with enhanced electro-optic performance

    SciTech Connect

    Pitchappa, Prakash; Pei Ho, Chong; Lin, Yu-Sheng; Lee, Chengkuo; Kropelnicki, Piotr; Singh, Navab; Huang, Chia-Yi

    2014-04-14

    We experimentally demonstrate a micro-electro-mechanically tunable metamaterial with enhanced electro-optical performance by increasing the number of movable cantilevers in the symmetrical split ring resonator metamaterial unit cell. Simulations were carried out to understand the interaction of the incident terahertz radiation with out-of-plane deforming metamaterial resonator. In order to improve the overall device performance, the number of released cantilever in a unit cell was increased from one to two, and it was seen that the tunable range was doubled and the switching contrast improved by a factor of around five at 0.7 THz. This simple design approach can be adopted for a wide range of high performance electro-optical devices such as continuously tunable filters, modulators, and electro-optic switches to enable future photonic circuit applications.

  5. Quantum rainbow scattering at tunable velocities

    NASA Astrophysics Data System (ADS)

    Strebel, M.; Müller, T.-O.; Ruff, B.; Stienkemeier, F.; Mudrich, M.

    2012-12-01

    Elastic scattering cross sections are measured for lithium atoms colliding with rare-gas atoms and SF6 molecules at tunable relative velocities down to ˜50 m/s. Our scattering apparatus combines a velocity-tunable molecular beam with a magneto-optic trap which provides an ultracold cloud of lithium atoms as a scattering target. Comparison with theory reveals the quantum nature of the collision dynamics in the studied regime, including rainbows as well as orbiting resonances.

  6. The Berkeley tunable far infrared laser spectrometers

    NASA Technical Reports Server (NTRS)

    Blake, G. A.; Laughlin, K. B.; Cohen, R. C.; Busarow, K. L.; Gwo, D.-H.

    1991-01-01

    A detailed description is presented for a tunable far infrared laser spectrometer based on frequency mixing of an optically pumped molecular gas laser with tunable microwave radiation in a Schottky point contact diode. The system has been operated on over 30 laser lines in the range 10-100/cm and exhibits a maximum absorption sensitivity near one part in a million. Each laser line can be tuned by + or - 110 GHz with first-order sidebands.

  7. Hysteresis and Frequency Tunability of Gyrotrons

    NASA Astrophysics Data System (ADS)

    Dumbrajs, O.; Khutoryan, E. M.; Idehara, T.

    2016-06-01

    We present the first devoted theoretical and experimental study of the hysteresis phenomenon in relation to frequency tunability of gyrotrons. In addition, we generalize the theory describing electron tuning of frequency in gyrotrons developed earlier to arbitrary harmonics. It is found that theoretical magnetic and voltage hysteresis loops are about two times larger than experimental loops. In gyrotrons whose cavities have high quality factors, hysteresis allows one only little to broaden the frequency tunability range.

  8. Underwater tunable organ-pipe sound source.

    PubMed

    Morozov, Andrey K; Webb, Douglas C

    2007-08-01

    A highly efficient frequency-controlled sound source based on a tunable high-Q underwater acoustic resonator is described. The required spectrum width was achieved by transmitting a linear frequency-modulated signal and simultaneously tuning the resonance frequency, keeping the sound source in resonance at the instantaneous frequency of the signal transmitted. Such sound sources have applications in ocean-acoustic tomography and deep-penetration seismic tomography. Mathematical analysis and numerical simulation show the Helmholtz resonator's ability for instant resonant frequency switching and quick adjustment of its resonant frequency to the instantaneous frequency signal. The concept of a quick frequency adjustment filter is considered. The discussion includes the simplest lumped resonant source as well as the complicated distributed system of a tunable organ pipe. A numerical model of the tunable organ pipe is shown to have a form similar to a transmission line segment. This provides a general form for the principal results, which can be applied to tunable resonators of a different physical nature. The numerical simulation shows that the "state-switched" concept also works in the high-Q tunable organ pipe, and the speed of frequency sweeping in a high-Q tunable organ pipe is analyzed. The simulation results were applied to a projector design for ocean-acoustic tomography. PMID:17672628

  9. Power-scalable tunable UV, visible, and NIR generation from an ultrafast fiber OPA based on four wave mixing in PCF

    NASA Astrophysics Data System (ADS)

    Yarrow, Michael J.; Wadsworth, William J.; Lavoute, Laure; Clowes, John R.; Grudinin, Anatoly B.

    2012-02-01

    An ultrafast fiber MOPA was developed which delivered high average power and rapid and continuous tunability over the range 1035 - 1070 nm. Through FWM in a single PCF, this source generated greater than 30% conversion efficiency to a narrow linewidth signal with tunability from 720 to 880 nm and a corresponding idler tunable from 1370 to 1880 nm. Generation of tunable signal SHG, signal-pump SFG, pump SHG and pump-idler SFG were demonstrated in a single angle tuned BBO crystal. The combined system enabled tunability over large portions of the UV, visible and NIR spectral range from 370 - 1900 nm with a very simple setup. There is scope for power scaling of the source and extending the wavelength coverage.

  10. Color tunable LED spot lighting

    NASA Astrophysics Data System (ADS)

    Hoelen, C.; Ansems, J.; Deurenberg, P.; van Duijneveldt, W.; Peeters, M.; Steenbruggen, G.; Treurniet, T.; Valster, A.; ter Weeme, J. W.

    2006-08-01

    A new trend in illumination is to use dynamic light to set or dynamically vary the ambience of a room or office. For this we need color tunable spots that can reliably vary over at least a wide range of color temperatures, and preferably also more saturated colors. LEDs are in principle ideally suited for this application thanks to their nature of emitting light in a relatively narrow band. For color tunable spot lighting based on the concept of mixing RGB LED colors, the key results have been presented before. Limitations of these 3-intrinsic-color mixing systems with high color rendering properties are found in a limited operating temperature range due to wavelength shifts, a limited color temperature range, and a low maximum operating temperature due to a strong flux decrease with increasing temperature. To overcome these limitations, a 3-color R pcGB system with phosphor-converted red (R pc) and a 4-color RAGB system have been investigated. With both systems, a CRI of at least 80 can be maintained over the relevant color temperature range of approximately 2700 K to 6500 K. In this paper we compare these concepts on overall system aspects and report on the performance of prototype spot lamps. The main features of the RAGB and R pcGB spot lamp concepts can be summarized as: 1) The RAGB spot overcomes CRI and gamut shortcomings of RGB light sources and gives much freedom in wavelength selection, but suffers from temperature sensitivity and complex controls; 2) The R pcGB spot overcomes shortcomings concerning CRI and thermal dependence of RGB sources and enables relatively simple controls, but needs an improved overall red efficacy. With both color concepts, prototype spot lamps have been built. The amber to red emitting nitridosilicate-based phosphors can be wavelength-tuned for optimal performance, which is found at a peak emission around 610 nm for high color quality systems. This results in a simple and very robust system with good color consistency. For the

  11. Tunable Micro- and Nanomechanical Resonators

    PubMed Central

    Zhang, Wen-Ming; Hu, Kai-Ming; Peng, Zhi-Ke; Meng, Guang

    2015-01-01

    Advances in micro- and nanofabrication technologies have enabled the development of novel micro- and nanomechanical resonators which have attracted significant attention due to their fascinating physical properties and growing potential applications. In this review, we have presented a brief overview of the resonance behavior and frequency tuning principles by varying either the mass or the stiffness of resonators. The progress in micro- and nanomechanical resonators using the tuning electrode, tuning fork, and suspended channel structures and made of graphene have been reviewed. We have also highlighted some major influencing factors such as large-amplitude effect, surface effect and fluid effect on the performances of resonators. More specifically, we have addressed the effects of axial stress/strain, residual surface stress and adsorption-induced surface stress on the sensing and detection applications and discussed the current challenges. We have significantly focused on the active and passive frequency tuning methods and techniques for micro- and nanomechanical resonator applications. On one hand, we have comprehensively evaluated the advantages and disadvantages of each strategy, including active methods such as electrothermal, electrostatic, piezoelectrical, dielectric, magnetomotive, photothermal, mode-coupling as well as tension-based tuning mechanisms, and passive techniques such as post-fabrication and post-packaging tuning processes. On the other hand, the tuning capability and challenges to integrate reliable and customizable frequency tuning methods have been addressed. We have additionally concluded with a discussion of important future directions for further tunable micro- and nanomechanical resonators. PMID:26501294

  12. Widely tunable hybrid semiconductor lasers

    NASA Astrophysics Data System (ADS)

    Koh, Ping-Chiek; Plumb, Richard G. S.

    1999-04-01

    A new hybrid design tunable semiconductor laser, with a wide tuning range, a narrow linewidth, simple tuning/control algorithms, low variations in output power across its tuning range and simple fabrication, is introduced. This hybrid laser consists of a large spot reflective amplifier (LS-RA) coupled to a Lithium Niobate Acousto-Optic Filter (AOF), giving wavelength selective feedback. The LS-RA waveguide is angled by 10 degrees to the coupling facet, but is normal to the other facet, giving reflectivities of 5 X 10-5 and 3 X 10-1 respectively. This amplifier structure allows maximum coupling to the AOF without stringent alignment tolerance. THe AOF consists of a 2-stage acoustic TE/TM converter with a high TE reflectivity coating at the end. A propagating surface acoustic wave is employed to phase-match the TE and TM modes of a specific wavelength, achieving a narrow-band feedback into the LS-RA. Output power and wavelength of the hybrid laser are controlled by the LS-RA current and RF drive frequency of the AOF respectively. Simulations using a Time-Domain Model and initial experiments have shown that the hybrid laser have a wide tuning range, narrow linewidth, SMSR >= 30 dB and low power variations across its tuning range.

  13. Multiplexed gas spectroscopy using tunable VCSELs

    SciTech Connect

    Bond, T; Bond, S; McCarrick, J; Zumstein, J; Chang, A; Moran, B; Benett, W J

    2012-04-10

    Detection and identification of gas species using tunable laser diode laser absorption spectroscopy has been performed using vertical cavity surface emitting lasers (VCSEL). Two detection methods are compared: direct absorbance and wavelength modulation spectroscopy (WMS). In the first, the output of a DC-based laser is directly monitored to detect for any quench at the targeted specie wavelength. In the latter, the emission wavelength of the laser is modulated by applying a sinusoidal component on the drive current of frequency {omega}, and measuring the harmonics component (2{omega}) of the photo-detected current. This method shows a better sensitivity measured as signal to noise ratio, and is less susceptible to interference effects such as scattering or fouling. Gas detection was initially performed at room temperature and atmospheric conditions using VCSELs of emission wavelength 763 nm for oxygen and 1392 nm for water, scanning over a range of approximately 10 nm, sufficient to cover 5-10 gas specific absorption lines that enable identification and quantization of gas composition. The amplitude and frequency modulation parameters were optimized for each detected gas species, by performing two dimensional sweeps for both tuning current and either amplitude or frequency, respectively. We found that the highest detected signal is observed for a wavelength modulation amplitude equal to the width of the gas absorbance lines, in good agreement with theoretical calculations, and for modulation frequencies below the time response of the lasers (<50KHz). In conclusion, we will discuss limit of detection studies and further implementation and packaging of VCSELs in diode arrays for continuous and simultaneous monitoring of multiple species in gaseous mixtures.

  14. Infrared frequency-tunable coherent thermal sources

    NASA Astrophysics Data System (ADS)

    Wang, Hao; Yang, Yue; Wang, Liping

    2015-04-01

    In this work, we numerically demonstrate an infrared (IR) frequency-tunable selective thermal emitter made of graphene-covered silicon carbide (SiC) gratings. Rigorous coupled-wave analysis shows temporally-coherent emission peaks associated with magnetic polariton (MP), whose resonance frequency can be dynamically tuned within the phonon absorption band of SiC by varying graphene chemical potential. An analytical inductor-capacitor circuit model is introduced to quantitatively predict the resonance frequency and further elucidate the mechanism for the tunable emission peak. The effects of grating geometric parameters, such as grating height, groove width and grating period, on the selective emission peak are explored. The direction-independent behavior of MP and associated coherent emission are also demonstrated. Moreover, by depositing four layers of graphene sheets onto the SiC gratings, a large tunability of 8.5% in peak frequency can be obtained to yield the coherent emission covering a broad frequency range from 820 to 890 cm-1. The novel tunable metamaterial could pave the way to a new class of tunable thermal sources in the IR region.

  15. CMOS-controlled rapidly tunable photodetectors

    NASA Astrophysics Data System (ADS)

    Chen, Ray

    With rapidly increasing data bandwidth demands, wavelength-division-multiplexing (WDM) optical access networks seem unavoidable in the near future. To operate WDM optical networks in an efficient scheme, wavelength reconfigurability and scalability of the network are crucial. Unfortunately, most of the existing wavelength tunable technologies are neither rapidly tunable nor spectrally programmable. This dissertation presents a tunable photodetector that is designed for dynamic-wavelength allocation WDM network environments. The wavelength tuning mechanism is completely different from existing technologies. The spectrum of this detector is programmable through low-voltage digital patterns. Since the wavelength selection is achieved by electronic means, the device wavelength reconfiguration time is as fast as the electronic switching time. In this dissertation work, we have demonstrated a tunable detector that is hybridly integrated with its customized CMOS driver and receiver with nanosecond wavelength reconfiguration time. In addition to its nanosecond wavelength reconfiguration time, the spectrum of this detector is digitally programmable, which means that it can adapt to system changes without re-fabrication. We have theoretically developed and experimentally demonstrated two device operating algorithms based on the same orthogonal device-optics basis. Both the rapid wavelength tuning time and the scalability make this novel device very viable for new reconfigurable WDM networks. By taking advantage of CMOS circuit design, this detector concept can be further extended for simultaneous multiple wavelength detection. We have developed one possible chip architecture and have designed a CMOS tunable optical demux for simultaneous controllable two-wavelength detection.

  16. Quantum dot device tunable from single to triple dot system

    SciTech Connect

    Rogge, M. C.; Haug, R. J.; Pierz, K.

    2013-12-04

    We present a lateral quantum dot device which has a tunable number of quantum dots. Depending on easily tunable gate voltages, one, two or three quantum dots are found. They are investigated in transport and charge detection.

  17. Continuous Problem of Function Continuity

    ERIC Educational Resources Information Center

    Jayakody, Gaya; Zazkis, Rina

    2015-01-01

    We examine different definitions presented in textbooks and other mathematical sources for "continuity of a function at a point" and "continuous function" in the context of introductory level Calculus. We then identify problematic issues related to definitions of continuity and discontinuity: inconsistency and absence of…

  18. Narrow linewidth broadband tunable semiconductor laser at 840 nm with dual acousto-optic tunable configuration for OCT applications

    NASA Astrophysics Data System (ADS)

    Chamorovskiy, Alexander; Shramenko, Mikhail V.; Lobintsov, Andrei A.; Yakubovich, Sergei D.

    2016-03-01

    We demonstrate a tunable narrow linewidth semiconductor laser for the 840 nm spectral range. The laser has a linear cavity comprised of polarization maintaining (PM) fiber. A broadband semiconductor optical amplifier (SOA) in in-line fiber-coupled configuration acts as a gain element. It is based on InGaAs quantum-well (QW) active layer. SOA allows for tuning bandwidth exceeding 25 nm around 840 nm. Small-signal fiber-to-fiber gain of SOA is around 30 dB. A pair of acousto-optic tunable filters (AOTF) with a quasi-collinear interaction of optical and acoustic waves are utilized as spectrally selective elements. AOTF technology benefits in continuous tuning, broadband operation, excellent reproducibility and stability of the signal, as well as a high accuracy of wavelength selectivity due to the absence of mechanically moving components. A single AOTF configuration has typical linewidth in 0.05-0.15 nm range due to a frequency shift obtained during each roundtrip. A sequential AOTF arrangement enables instantaneous linewidth generation of <0.01 nm by compensating for this shift. Linewidth as narrow as 0.0036 nm is observed at 846 nm wavelength using a scanning Fabry-Perot interferometer with 50 MHz spectral resolution. Output power is in the range of 1 mW. While the majority of commercial tunable sources operate in 1060-1550 nm spectral ranges, the 840 nm spectral range is beneficial for optical coherence tomography (OCT). The developed narrow linewidth laser can be relevant for OCT with extended imaging depth, as well as spectroscopy, non-destructive testing and other applications.

  19. Tunable-cavity QED with phase qubits

    NASA Astrophysics Data System (ADS)

    Whittaker, Jed D.; da Silva, Fabio; Allman, Michael Shane; Lecocq, Florent; Cicak, Katarina; Sirois, Adam; Teufel, John; Aumentado, Jose; Simmonds, Raymond W.

    2014-03-01

    We describe a tunable-cavity QED architecture with an rf SQUID phase qubit inductively coupled to a single-mode, resonant cavity with a tunable frequency that allows for both tunneling and dispersive measurements. Dispersive measurement is well characterized by a three-level model, strongly dependent on qubit anharmonicity, qubit-cavity coupling and detuning. The tunable cavity frequency provides dynamic control over the coupling strength and qubit-cavity detuning helping to minimize Purcell losses and cavity-induced dephasing during qubit operation. The maximum decay time T1 = 1 . 5 μs is limited by dielectric losses from a design geometry similar to planar transmon qubits. This work supported by NIST and NSA grant EAO140639.

  20. Perovskite Superlattices as Tunable Microwave Devices

    NASA Technical Reports Server (NTRS)

    Christen, H. M.; Harshavardhan, K. S.

    2003-01-01

    Experiments have shown that superlattices that comprise alternating epitaxial layers of dissimilar paraelectric perovskites can exhibit large changes in permittivity with the application of electric fields. The superlattices are potentially useful as electrically tunable dielectric components of such microwave devices as filters and phase shifters. The present superlattice approach differs fundamentally from the prior use of homogeneous, isotropic mixtures of base materials and dopants. A superlattice can comprise layers of two or more perovskites in any suitable sequence (e.g., ABAB..., ABCDABCD..., ABACABACA...). Even though a single layer of one of the perovskites by itself is not tunable, the compositions and sequence of the layers can be chosen so that (1) the superlattice exhibits low microwave loss and (2) the interfacial interaction between at least two of the perovskites in the superlattice renders either the entire superlattice or else at least one of the perovskites tunable.

  1. Adaptive Tunable Laser Spectrometer for Space Applications

    NASA Technical Reports Server (NTRS)

    Flesch, Gregory; Keymeulen, Didier

    2010-01-01

    An architecture and process for the rapid prototyping and subsequent development of an adaptive tunable laser absorption spectrometer (TLS) are described. Our digital hardware/firmware/software platform is both reconfigurable at design time as well as autonomously adaptive in real-time for both post-integration and post-launch situations. The design expands the range of viable target environments and enhances tunable laser spectrometer performance in extreme and even unpredictable environments. Through rapid prototyping with a commercial RTOS/FPGA platform, we have implemented a fully operational tunable laser spectrometer (using a highly sensitive second harmonic technique). With this prototype, we have demonstrated autonomous real-time adaptivity in the lab with simulated extreme environments.

  2. Widely tunable opto-electronic oscillator

    NASA Astrophysics Data System (ADS)

    Maxin, J.; Pillet, G.; Morvan, L.; Dolfi, D.

    2012-03-01

    We present here a widely tunable opto-electronic oscillator (OEO) based on an Er,Yb:glass Dual Frequency Laser (DFL) at 1.53 μm. The beatnote is stabilized with an optical fiber delay line. Compared to classical optoelectronic oscillators, this architecture does not need RF filter and offers a wide tunability. We measured a reduction of 67 dB of the phase noise power spectral density (PSD) at 10 Hz of the carrier optical fiber leading to a level of -27 dBc/Hz with only 100 m optical fiber. Moreover, the scheme offers a microwave signal tunability from 2.5 to 5.5 GHz limited by the RF components.

  3. A vibration energy harvesting device with bidirectional resonance frequency tunability

    NASA Astrophysics Data System (ADS)

    Challa, Vinod R.; Prasad, M. G.; Shi, Yong; Fisher, Frank T.

    2008-02-01

    Vibration energy harvesting is an attractive technique for potential powering of wireless sensors and low power devices. While the technique can be employed to harvest energy from vibrations and vibrating structures, a general requirement independent of the energy transfer mechanism is that the vibration energy harvesting device operate in resonance at the excitation frequency. Most energy harvesting devices developed to date are single resonance frequency based, and while recent efforts have been made to broaden the frequency range of energy harvesting devices, what is lacking is a robust tunable energy harvesting technique. In this paper, the design and testing of a resonance frequency tunable energy harvesting device using a magnetic force technique is presented. This technique enabled resonance tuning to ± 20% of the untuned resonant frequency. In particular, this magnetic-based approach enables either an increase or decrease in the tuned resonant frequency. A piezoelectric cantilever beam with a natural frequency of 26 Hz is used as the energy harvesting cantilever, which is successfully tuned over a frequency range of 22-32 Hz to enable a continuous power output 240-280 µW over the entire frequency range tested. A theoretical model using variable damping is presented, whose results agree closely with the experimental results. The magnetic force applied for resonance frequency tuning and its effect on damping and load resistance have been experimentally determined.

  4. MEMS tunable terahertz metamaterials using out-of-plane mechanisms

    NASA Astrophysics Data System (ADS)

    Lin, Yu-Sheng; Pitchappa, Prakash; Ho, Chong Pei; Lee, Chengkuo

    2015-03-01

    The tunable terahertz metamaterial (TTM) has attracted intense research interest, since the electromagnetic response of the metamaterial can be actively controlled through external stimulus, which is of great significance in real time applications. The active control of metamaterial characteristics is crucial in order to provide a flexible and versatile platform for mimicking fundamental physical effects. To realize the electromagnetic tunability, various approaches have been demonstrated to increase the flexibility in applications, such as changing the effective electromagnetic properties. Alternatively, MEMS-based techniques are well developed. The structural reconfiguration is a straightforward way to control the electromagnetic properties. The metamaterial properties can be directly modified by reconfiguring the unit cell which is the fundamental building block of metamaterials. Currently, our research works are focusing on MEMS-based TTM adopting stress-induced curved actuators (SICA) to adjust the resonant frequency of devices. Herein, the proposed TTM designs are double split-ring resonator (DSRR), electric split-ring resonator (eSRR), Omega-ring metamaterial (ORM), symmetric and asymmetric T-shape metamaterial (STM and ATM), respectively. We demonstrated these TTM can be active, continuous, and recoverable control the resonant frequency by using electrostatic or electrothermal actuation mechanism. Therefore, the TTM devices can be effectively used for sensors, optical switches, and filters applications.

  5. A tunable crystal diffraction telescope for the International Space Station

    SciTech Connect

    Ballmoos, P. von; Kohnle, A.; Olive, J.F.; Vedrenne, G.; Smither, R.K.; Fernandez, P.B.; Graber, T.

    1997-02-01

    Even though technically innovative, a tunable crystal diffraction telescope for use in nuclear astrophysics has become feasible today. The focusing gamma-ray telescope the authors intended to propose for the space station consists of a tunable crystal diffraction lens, focusing gamma-rays onto a small array of Germanium detectors perched on an extendible boom. While the weight of such an instrument is less than 500 kg, it features an angular resolution of 15 inches, an energy resolution of 2 keV and a 3 {sigma} sensitivity of a few times 10{sup {minus}7} photons{center_dot}s{sup {minus}1}{center_dot}cm{sup {minus}2} (10{sup 6} sec observation) for any individual narrow line at energies between 200--1,300 keV. This experience would greatly profit from the continuous presence of man on the station. Besides of the infrastructure for maintenance and servicing of the various innovative techniques used for the first time in space, the available extra-vehicular robotics will facilitate deployment of the required boom structure.

  6. Research on imaging spectrometer using LC-based tunable filter

    NASA Astrophysics Data System (ADS)

    Shen, Zhixue; Li, Jianfeng; Huang, Lixian; Luo, Fei; Luo, Yongquan; Zhang, Dayong; Long, Yan

    2012-09-01

    A liquid crystal tunable filter (LCTF) with large aperture is developed using PDLC liquid crystal. A small scale imaging spectrometer is established based on this tunable filter. This spectrometer can continuously tuning, or random-access selection of any wavelength in the visible and near infrared (VNIR) band synchronized with the imaging processes. Notable characteristics of this spectrometer include the high flexibility control of its operating channels, the image cubes with high spatial resolution and spectral resolution and the strong ability of acclimation to environmental temperature. The image spatial resolution of each tuning channel is almost near the one of the same camera without the LCTF. The spectral resolution is about 20 nm at 550 nm. This spectrometer works normally under 0-50°C with a maximum power consumption of 10 Watts (with exclusion of the storage module). Due to the optimization of the electrode structure and the driving mode of the Liquid Crystal cell, the switch time between adjacent selected channels can be reduced to 20 ms or even shorter. Spectral imaging experiments in laboratory are accomplished to verify the performance of this spectrometer, which indicate that this compact imaging spectrometer works reliably, and functionally. Possible applications of this imaging spectrometer include medical science, protection of historical relics, criminal investigation, disaster monitoring and mineral detection by remote sensing.

  7. Fully Tunable Silicon Nanowire Arrays Fabricated by Soft Nanoparticle Templating.

    PubMed

    Rey, By Marcel; Elnathan, Roey; Ditcovski, Ran; Geisel, Karen; Zanini, Michele; Fernandez-Rodriguez, Miguel-Angel; Naik, Vikrant V; Frutiger, Andreas; Richtering, Walter; Ellenbogen, Tal; Voelcker, Nicolas H; Isa, Lucio

    2016-01-13

    We demonstrate a fabrication breakthrough to produce large-area arrays of vertically aligned silicon nanowires (VA-SiNWs) with full tunability of the geometry of the single nanowires and of the whole array, paving the way toward advanced programmable designs of nanowire platforms. At the core of our fabrication route, termed "Soft Nanoparticle Templating", is the conversion of gradually compressed self-assembled monolayers of soft nanoparticles (microgels) at a water-oil interface into customized lithographical masks to create VA-SiNW arrays by means of metal-assisted chemical etching (MACE). This combination of bottom-up and top-down techniques affords excellent control of nanowire etching site locations, enabling independent control of nanowire spacing, diameter and height in a single fabrication route. We demonstrate the fabrication of centimeter-scale two-dimensional gradient photonic crystals exhibiting continuously varying structural colors across the entire visible spectrum on a single silicon substrate, and the formation of tunable optical cavities supported by the VA-SiNWs, as unambiguously demonstrated through numerical simulations. Finally, Soft Nanoparticle Templating is combined with optical lithography to create hierarchical and programmable VA-SiNW patterns. PMID:26672801

  8. Guided transmission for 10 micron tunable lasers

    NASA Technical Reports Server (NTRS)

    Yu, C.; Sabzali, A.; Yekrangian, A.

    1986-01-01

    Performance characteristics are reported for two types of IR tunable laser guided transmission, one of which incorporates a CO2 laser, metallic piping or fiber-optics, and a detector system, while the other employs a tunable diode laser, fiber-optics, and a detector system. While existing technology furnishes low loss, rugged, near-single mode piping, fiber-optics exhibits appreciably higher loss, and its multimode fibers are fragile and chemically unstable. Studies have accordingly concentrated on such relevant fiber parameters as loss, toxicity, hygroscopicity, refractive index, flexibility, and thermal behavior at low temperature.

  9. Tunable Terahertz Hybrid Metal-Graphene Plasmons.

    PubMed

    Jadidi, Mohammad M; Sushkov, Andrei B; Myers-Ward, Rachael L; Boyd, Anthony K; Daniels, Kevin M; Gaskill, D Kurt; Fuhrer, Michael S; Drew, H Dennis; Murphy, Thomas E

    2015-10-14

    We report here a new type of plasmon resonance that occurs when graphene is connected to a metal. These new plasmon modes offer the potential to incorporate a tunable plasmonic channel into a device with electrical contacts, a critical step toward practical graphene terahertz optoelectronics. Through theory and experiments, we demonstrate, for example, anomalously high resonant absorption or transmission when subwavelength graphene-filled apertures are introduced into an otherwise conductive layer. These tunable plasmon resonances are essential yet missing ingredients needed for terahertz filters, oscillators, detectors, and modulators. PMID:26397718

  10. Widely tunable room temperature semiconductor terahertz source

    SciTech Connect

    Lu, Q. Y.; Slivken, S.; Bandyopadhyay, N.; Bai, Y.; Razeghi, M.

    2014-11-17

    We present a widely tunable, monolithic terahertz source based on intracavity difference frequency generation within a mid-infrared quantum cascade laser at room temperature. A three-section ridge waveguide laser design with two sampled grating sections and a distributed-Bragg section is used to achieve the terahertz (THz) frequency tuning. Room temperature single mode THz emission with a wide tunable frequency range of 2.6–4.2 THz (∼47% of the central frequency) and THz power up to 0.1 mW is demonstrated, making such device an ideal candidate for THz spectroscopy and sensing.

  11. A tunable electromechanical Helmholtz resonator

    NASA Astrophysics Data System (ADS)

    Liu, Fei

    Acoustic liners are used in turbofan engine nacelles for the suppression of engine noise. For a given engine, there are different optimum impedance distributions associated with take-off, cut-back, and approach flight conditions. The impedance of conventional acoustic liners is fixed for a given geometry, and conventional active liner approaches are impractical. This project addresses the need for a tunable impedance through the development of an electromechanical Helmholtz resonator (EMHR). The device consists of a Helmholtz resonator with the standard rigid backplate replaced by a compliant piezoelectric composite. Analytical models (i.e., a lumped element model (LEM) and a transfer matrix (TM) representation of the EMHR) are developed to predict the acoustic behavior of the EMHR. The EMHR is experimentally investigated using the standard two-microphone method (TMM). The measurement results validate both the LEM and the TM of the EMHR. Good agreement between predicted and measured impedance is obtained. Short- and open-circuit loads define the limits of the tuning range using resistive and capacitive loads. There is approximately a 9% tuning limit under these conditions for the non-optimized resonator configuration studied. Inductive shunt loads result in a 3 degree-of-freedom (DOF) system and an enhanced tuning range of over 47% that is not restricted by the short- and open-circuit limits. Damping coefficient measurements for a piezoelectric backplate in a vacuum chamber are performed and indicate that the damping is dominated by structural damping losses. A Pareto optimization design based on models of the EMHR is performed with non-inductive loads. The EMHR with non-inductive loads has 2DOF and two resonant frequencies. The tuning ranges of the two resonant frequencies of the EMHR with non-inductive loads cannot be optimized simultaneously, so a trade-off (Pareto solution) must be reached. The Pareto solution shows how design trade-offs can be used to satisfy

  12. Tunable broadband light coupler based on two parallel all-fiber acousto-optic tunable filters.

    PubMed

    Zhang, Wending; Huang, Ligang; Gao, Feng; Bo, Fang; Zhang, Guoquan; Xu, Jingjun

    2013-07-15

    Based on the evanescent-field coupling between the cladding modes of two adjacent and parallel all-fiber acousto-optic tunable filters, tunable broadband light coupling with relatively uniform insertion loss of trapping spectrum was achieved. In the experiments, a wide spectral tuning range from 1490 nm to 1610 nm, covering the whole C- and L-band and parts of S-bands, was demonstrated with a wavelength tunability slope of -0.72 nm/kHz. The insertion loss of the trapping spectrum was uniform (around -5.0 dB, which can be improved with a longer evanescent-field coupling length) within the whole tuning spectral range. Such a light coupling structure would be useful in tunable broadband light coupler and broadband optical fiber add/drop multiplexer for applications in coarse wavelength division multiplexing systems. PMID:23938513

  13. Electrically Tunable Terahertz Quantum-Cascade Lasers

    NASA Technical Reports Server (NTRS)

    Gunapala, Sarath; Soidel, Alexander; Mansour, Kamjou

    2006-01-01

    Improved quantum-cascade lasers (QCLs) are being developed as electrically tunable sources of radiation in the far infrared spectral region, especially in the frequency range of 2 to 5 THz. The structures of QCLs and the processes used to fabricate them have much in common with those of multiple- quantum-well infrared photodetectors.

  14. Tunable metamaterial dual-band terahertz absorber

    NASA Astrophysics Data System (ADS)

    Luo, C. Y.; Li, Z. Z.; Guo, Z. H.; Yue, J.; Luo, Q.; Yao, G.; Ji, J.; Rao, Y. K.; Li, R. K.; Li, D.; Wang, H. X.; Yao, J. Q.; Ling, F. R.

    2015-11-01

    We report a design of a temperature controlled tunable dual band terahertz absorber. The compact single unit cell consists of two nested closed square ring resonators and a layer metallic separated by a substrate strontium titanate (STO) dielectric layer. It is found that the absorber has two distinctive absorption peaks at frequencies 0.096 THz and 0.137 THz, whose peaks are attained 97% and 75%. Cooling the absorber from 400 K to 250 K causes about 25% and 27% shift compared to the resonance frequency of room temperature, when we cooling the temperature to 150 K, we could attained both the two tunabilities exceeding 53%. The frequency tunability is owing to the variation of the dielectric constant of the low-temperature co-fired ceramic (LTCC) substrate. The mechanism of the dual band absorber is attributed to the overlapping of dual resonance frequencies, and could be demonstrated by the distributions of the electric field. The method opens up avenues for designing tunable terahertz devices in detection, imaging, and stealth technology.

  15. Monolithically, widely tunable quantum cascade lasers based on a heterogeneous active region design

    NASA Astrophysics Data System (ADS)

    Zhou, Wenjia; Bandyopadhyay, Neelanjan; Wu, Donghai; McClintock, Ryan; Razeghi, Manijeh

    2016-06-01

    Quantum cascade lasers (QCLs) have become important laser sources for accessing the mid-infrared (mid-IR) spectral range, achieving watt-level continuous wave operation in a compact package at room temperature. However, up to now, wavelength tuning, which is desirable for most applications, has relied on external cavity feedback or exhibited a limited monolithic tuning range. Here we demonstrate a widely tunable QCL source over the 6.2 to 9.1 μm wavelength range with a single emitting aperture by integrating an eight-laser sampled grating distributed feedback laser array with an on-chip beam combiner. The laser gain medium is based on a five-core heterogeneous QCL wafer. A compact tunable laser system was built to drive the individual lasers within the array and produce any desired wavelength within the available spectral range. A rapid, broadband spectral measurement (520 cm‑1) of methane using the tunable laser source shows excellent agreement to a measurement made using a standard low-speed infrared spectrometer. This monolithic, widely tunable laser technology is compact, with no moving parts, and will open new opportunities for MIR spectroscopy and chemical sensing.

  16. Resonantly enhanced method for generation of tunable, coherent vacuum-ultraviolet radiation

    DOEpatents

    Glownia, J.H.; Sander, R.K.

    1982-06-29

    Carbon Monoxide vapor is used to generate coherent, tunable vacuum ultraviolet radiation by third-harmonic generation using a single tunable dye laser. The presence of a nearby electronic level resonantly enhances the nonlinear susceptibility of this molecule allowing efficient generation of the vuv light at modest pump laser intensities, thereby reducing the importance of a six-photon multiple-photon ionization process which is also resonantly enhanced by the same electronic level but no higher order. By choosing the pump radiation wavelength to be of shorter wavelength than individual vibronic levels used to extend tunability stepwise from 154.4 to 124.6 nm, and the intensity to be low enough, multiple-photon ionization can be eliminated. Excitation spectra of the third-harmonic emission output exhibit shifts to shorter wavelength and broadening with increasing CO pressure due to phase matching effects. Increasing the carbon monoxide pressure, therefore, allows the substantial filling in of gaps arising from the stepwise tuning thereby providing almost continuous tunability over the quoted range of wavelength emitted.

  17. Monolithically, widely tunable quantum cascade lasers based on a heterogeneous active region design

    PubMed Central

    Zhou, Wenjia; Bandyopadhyay, Neelanjan; Wu, Donghai; McClintock, Ryan; Razeghi, Manijeh

    2016-01-01

    Quantum cascade lasers (QCLs) have become important laser sources for accessing the mid-infrared (mid-IR) spectral range, achieving watt-level continuous wave operation in a compact package at room temperature. However, up to now, wavelength tuning, which is desirable for most applications, has relied on external cavity feedback or exhibited a limited monolithic tuning range. Here we demonstrate a widely tunable QCL source over the 6.2 to 9.1 μm wavelength range with a single emitting aperture by integrating an eight-laser sampled grating distributed feedback laser array with an on-chip beam combiner. The laser gain medium is based on a five-core heterogeneous QCL wafer. A compact tunable laser system was built to drive the individual lasers within the array and produce any desired wavelength within the available spectral range. A rapid, broadband spectral measurement (520 cm−1) of methane using the tunable laser source shows excellent agreement to a measurement made using a standard low-speed infrared spectrometer. This monolithic, widely tunable laser technology is compact, with no moving parts, and will open new opportunities for MIR spectroscopy and chemical sensing. PMID:27270634

  18. Resonantly enhanced method for generation of tunable, coherent vacuum ultraviolet radiation

    DOEpatents

    Glownia, James H.; Sander, Robert K.

    1985-01-01

    Carbon Monoxide vapor is used to generate coherent, tunable vacuum ultraviolet radiation by third-harmonic generation using a single tunable dye laser. The presence of a nearby electronic level resonantly enhances the nonlinear susceptibility of this molecule allowing efficient generation of the vuv light at modest pump laser intensities, thereby reducing the importance of a six-photon multiple-photon ionization process which is also resonantly enhanced by the same electronic level but to higher order. By choosing the pump radiation wavelength to be of shorter wavelength than individual vibronic levels used to extend tunability stepwise from 154.4 to 124.6 nm, and the intensity to be low enough, multiple-photon ionization can be eliminated. Excitation spectra of the third-harmonic emission output exhibit shifts to shorter wavelength and broadening with increasing CO pressure due to phase matching effects. Increasing the carbon monoxide pressure, therefore, allows the substantial filling in of gaps arising from the stepwise tuning thereby providing almost continuous tunability over the quoted range of wavelength emitted.

  19. Monolithically, widely tunable quantum cascade lasers based on a heterogeneous active region design.

    PubMed

    Zhou, Wenjia; Bandyopadhyay, Neelanjan; Wu, Donghai; McClintock, Ryan; Razeghi, Manijeh

    2016-01-01

    Quantum cascade lasers (QCLs) have become important laser sources for accessing the mid-infrared (mid-IR) spectral range, achieving watt-level continuous wave operation in a compact package at room temperature. However, up to now, wavelength tuning, which is desirable for most applications, has relied on external cavity feedback or exhibited a limited monolithic tuning range. Here we demonstrate a widely tunable QCL source over the 6.2 to 9.1 μm wavelength range with a single emitting aperture by integrating an eight-laser sampled grating distributed feedback laser array with an on-chip beam combiner. The laser gain medium is based on a five-core heterogeneous QCL wafer. A compact tunable laser system was built to drive the individual lasers within the array and produce any desired wavelength within the available spectral range. A rapid, broadband spectral measurement (520 cm(-1)) of methane using the tunable laser source shows excellent agreement to a measurement made using a standard low-speed infrared spectrometer. This monolithic, widely tunable laser technology is compact, with no moving parts, and will open new opportunities for MIR spectroscopy and chemical sensing. PMID:27270634

  20. The 1.083 micron tunable CW semiconductor laser

    NASA Technical Reports Server (NTRS)

    Wang, C. S.; Chen, Jan-Shin; Lu, Ken-Gen; Ouyang, Keng

    1991-01-01

    A tunable CW laser is desired to produce light equivalent to the helium spectral line at 1.08 microns. This laser will serve as an optical pumping source for He-3 and He-4 atoms used in space magnetometers. This light source can be fabricated either as a semiconductor laser diode or a pumped solid state laser. Continuous output power of greater than 10 mW is desired. Semiconductor lasers can be thermally tuned, but must be capable of locking onto the helium resonance lines. Solid state lasers must have efficient pumping sources suitable for space configuration. Additional requirements are as follows: space magnetometer applications will include low mass (less than 0.5 kg), low power consumption (less than 0.75 W), and high stability/reliability for long missions (5-10 years).

  1. Tunable band gap of boron nitride interfaces under uniaxial pressure

    NASA Astrophysics Data System (ADS)

    Moraes, Elizane E.; Manhabosco, Taíse M.; de Oliveira, Alan B.; Batista, Ronaldo J. C.

    2012-11-01

    In this work we show, by means of a density functional theory formalism, that the interaction between hydrogen terminated boron nitride surfaces gives rise to a metallic interface with free carriers of opposite sign at each surface. A band gap can be induced by decreasing the surface separation. The size of the band gap changes continuously from zero up to 4.4 eV with decreasing separation, which is understood in terms of the interaction between surface states. Due to the high thermal conductivity of cubic boron nitride and the coupling between band gap and applied pressure, such tunable band gap interfaces may be used in highly stable electronic and electromechanical devices. In addition, the spatial separation of charge carriers at the interface may lead to photovoltaic applications.

  2. Tunable Band Gap of Boron Nitride Interfaces under Uniaxial Pressure

    NASA Astrophysics Data System (ADS)

    Moraes, Elizane; Manhabosco, Taise; de Oliveira, Alan; Batista, Ronaldo

    2013-03-01

    In this work we show, by means of a density functional theory formalism, that the interaction between hydrogen terminated boron nitride surfaces gives rise to a metallic interface with free carries of opposite sign at each surface. A band gap can be induced by decreasing the surface separation. The size of the band gap changes continuously from zero up to 4.4 eV with decreasing separation, which is understood in terms of the interaction between surface states.Due to the high thermal conductivity of cubic boron nitride and the coupling between band gap and applied pressure, such tunable band gap interfaces may be used in high stable electronic and electromechanical devices. In addition, the spacial separation of charge carries at the interface may lead to photovoltaic applications. The authors thank tha brazilian agencies Fapemig, CNPq and Capes

  3. Electrically Tunable Bandgaps in Bilayer MoS₂.

    PubMed

    Chu, Tao; Ilatikhameneh, Hesameddin; Klimeck, Gerhard; Rahman, Rajib; Chen, Zhihong

    2015-12-01

    Artificial semiconductors with manufactured band structures have opened up many new applications in the field of optoelectronics. The emerging two-dimensional (2D) semiconductor materials, transition metal dichalcogenides (TMDs), cover a large range of bandgaps and have shown potential in high performance device applications. Interestingly, the ultrathin body and anisotropic material properties of the layered TMDs allow a wide range modification of their band structures by electric field, which is obviously desirable for many nanoelectronic and nanophotonic applications. Here, we demonstrate a continuous bandgap tuning in bilayer MoS2 using a dual-gated field-effect transistor (FET) and photoluminescence (PL) spectroscopy. Density functional theory (DFT) is employed to calculate the field dependent band structures, attributing the widely tunable bandgap to an interlayer direct bandgap transition. This unique electric field controlled spontaneous bandgap modulation approaching the limit of semiconductor-to-metal transition can open up a new field of not yet existing applications. PMID:26560813

  4. Highly Efficient Perovskite Solar Cells with Tunable Structural Color

    PubMed Central

    2015-01-01

    The performance of perovskite solar cells has been progressing over the past few years and efficiency is likely to continue to increase. However, a negative aspect for the integration of perovskite solar cells in the built environment is that the color gamut available in these materials is very limited and does not cover the green-to-blue region of the visible spectrum, which has been a big selling point for organic photovoltaics. Here, we integrate a porous photonic crystal (PC) scaffold within the photoactive layer of an opaque perovskite solar cell following a bottom-up approach employing inexpensive and scalable liquid processing techniques. The photovoltaic devices presented herein show high efficiency with tunable color across the visible spectrum. This now imbues the perovskite solar cells with highly desirable properties for cladding in the built environment and encourages design of sustainable colorful buildings and iridescent electric vehicles as future power generation sources. PMID:25650872

  5. Optofluidic lens with tunable focal length and asphericity.

    PubMed

    Mishra, Kartikeya; Murade, Chandrashekhar; Carreel, Bruno; Roghair, Ivo; Oh, Jung Min; Manukyan, Gor; van den Ende, Dirk; Mugele, Frieder

    2014-01-01

    Adaptive micro-lenses enable the design of very compact optical systems with tunable imaging properties. Conventional adaptive micro-lenses suffer from substantial spherical aberration that compromises the optical performance of the system. Here, we introduce a novel concept of liquid micro-lenses with superior imaging performance that allows for simultaneous and independent tuning of both focal length and asphericity. This is achieved by varying both hydrostatic pressures and electric fields to control the shape of the refracting interface between an electrically conductive lens fluid and a non-conductive ambient fluid. Continuous variation from spherical interfaces at zero electric field to hyperbolic ones with variable ellipticity for finite fields gives access to lenses with positive, zero, and negative spherical aberration (while the focal length can be tuned via the hydrostatic pressure). PMID:25224851

  6. Tunable Circularly Polarized Terahertz Radiation from Magnetized Gas Plasma.

    PubMed

    Wang, W-M; Gibbon, P; Sheng, Z-M; Li, Y-T

    2015-06-26

    It is shown, by simulation and theory, that circularly or elliptically polarized terahertz radiation can be generated when a static magnetic (B) field is imposed on a gas target along the propagation direction of a two-color laser driver. The radiation frequency is determined by √[ω(p)(2)+ω(c)(2)/4]+ω(c)/2, where ω(p) is the plasma frequency and ω(c) is the electron cyclotron frequency. With the increase of the B field, the radiation changes from a single-cycle broadband waveform to a continuous narrow-band emission. In high-B-field cases, the radiation strength is proportional to ω(p)(2)/ω(c). The B field provides a tunability in the radiation frequency, spectrum width, and field strength. PMID:26197126

  7. Optofluidic lens with tunable focal length and asphericity

    PubMed Central

    Mishra, Kartikeya; Murade, Chandrashekhar; Carreel, Bruno; Roghair, Ivo; Oh, Jung Min; Manukyan, Gor; van den Ende, Dirk; Mugele, Frieder

    2014-01-01

    Adaptive micro-lenses enable the design of very compact optical systems with tunable imaging properties. Conventional adaptive micro-lenses suffer from substantial spherical aberration that compromises the optical performance of the system. Here, we introduce a novel concept of liquid micro-lenses with superior imaging performance that allows for simultaneous and independent tuning of both focal length and asphericity. This is achieved by varying both hydrostatic pressures and electric fields to control the shape of the refracting interface between an electrically conductive lens fluid and a non-conductive ambient fluid. Continuous variation from spherical interfaces at zero electric field to hyperbolic ones with variable ellipticity for finite fields gives access to lenses with positive, zero, and negative spherical aberration (while the focal length can be tuned via the hydrostatic pressure). PMID:25224851

  8. Highly efficient perovskite solar cells with tunable structural color.

    PubMed

    Zhang, Wei; Anaya, Miguel; Lozano, Gabriel; Calvo, Mauricio E; Johnston, Michael B; Míguez, Hernán; Snaith, Henry J

    2015-03-11

    The performance of perovskite solar cells has been progressing over the past few years and efficiency is likely to continue to increase. However, a negative aspect for the integration of perovskite solar cells in the built environment is that the color gamut available in these materials is very limited and does not cover the green-to-blue region of the visible spectrum, which has been a big selling point for organic photovoltaics. Here, we integrate a porous photonic crystal (PC) scaffold within the photoactive layer of an opaque perovskite solar cell following a bottom-up approach employing inexpensive and scalable liquid processing techniques. The photovoltaic devices presented herein show high efficiency with tunable color across the visible spectrum. This now imbues the perovskite solar cells with highly desirable properties for cladding in the built environment and encourages design of sustainable colorful buildings and iridescent electric vehicles as future power generation sources. PMID:25650872

  9. Optofluidic lens with tunable focal length and asphericity

    NASA Astrophysics Data System (ADS)

    Mishra, Kartikeya; Murade, Chandrashekhar; Carreel, Bruno; Roghair, Ivo; Oh, Jung Min; Manukyan, Gor; van den Ende, Dirk; Mugele, Frieder

    2014-09-01

    Adaptive micro-lenses enable the design of very compact optical systems with tunable imaging properties. Conventional adaptive micro-lenses suffer from substantial spherical aberration that compromises the optical performance of the system. Here, we introduce a novel concept of liquid micro-lenses with superior imaging performance that allows for simultaneous and independent tuning of both focal length and asphericity. This is achieved by varying both hydrostatic pressures and electric fields to control the shape of the refracting interface between an electrically conductive lens fluid and a non-conductive ambient fluid. Continuous variation from spherical interfaces at zero electric field to hyperbolic ones with variable ellipticity for finite fields gives access to lenses with positive, zero, and negative spherical aberration (while the focal length can be tuned via the hydrostatic pressure).

  10. Tunable frequency stabilized diode-laser-pumped Tm,Ho:YLiF4 laser at room temperature

    NASA Technical Reports Server (NTRS)

    Mcguckin, Brendan T.; Menzies, Robert T.; Esproles, Carlos

    1993-01-01

    A diode-laser-pumped single-frequency thulium holmium yttrium lithium fluoride laser that exhibits a closed-loop stability of a few megahertz and a continuous single-mode tuning range of 800 MHz is described. The laser output power is 25 mW, and is tunable over about 8/cm at 25 C.

  11. Tunable Microwave Filter Design Using Thin-Film Ferroelectric Varactors

    NASA Astrophysics Data System (ADS)

    Haridasan, Vrinda

    Military, space, and consumer-based communication markets alike are moving towards multi-functional, multi-mode, and portable transceiver units. Ferroelectric-based tunable filter designs in RF front-ends are a relatively new area of research that provides a potential solution to support wideband and compact transceiver units. This work presents design methodologies developed to optimize a tunable filter design for system-level integration, and to improve the performance of a ferroelectric-based tunable bandpass filter. An investigative approach to find the origins of high insertion loss exhibited by these filters is also undertaken. A system-aware design guideline and figure of merit for ferroelectric-based tunable band- pass filters is developed. The guideline does not constrain the filter bandwidth as long as it falls within the range of the analog bandwidth of a system's analog to digital converter. A figure of merit (FOM) that optimizes filter design for a specific application is presented. It considers the worst-case filter performance parameters and a tuning sensitivity term that captures the relation between frequency tunability and the underlying material tunability. A non-tunable parasitic fringe capacitance associated with ferroelectric-based planar capacitors is confirmed by simulated and measured results. The fringe capacitance is an appreciable proportion of the tunable capacitance at frequencies of X-band and higher. As ferroelectric-based tunable capac- itors form tunable resonators in the filter design, a proportionally higher fringe capacitance reduces the capacitance tunability which in turn reduces the frequency tunability of the filter. Methods to reduce the fringe capacitance can thus increase frequency tunability or indirectly reduce the filter insertion-loss by trading off the increased tunability achieved to lower loss. A new two-pole tunable filter topology with high frequency tunability (> 30%), steep filter skirts, wide stopband

  12. Multifrequency continuous wave terahertz spectroscopy for absolute thickness determination

    SciTech Connect

    Scheller, Maik; Baaske, Kai; Koch, Martin

    2010-04-12

    We present a tunable multifrequency continuous wave terahertz spectrometer based on two laser diodes, photoconductive antennas, and a coherent detection scheme. The system is employed to determine the absolute thickness of samples utilizing a proposed synthetic difference frequency method to circumvent the 2pi uncertainty known from conventional photomixing systems while preserving a high spatial resolution.

  13. Tunable microwave bandpass filter integrated power divider based on the high anisotropy electro-optic nematic liquid crystal.

    PubMed

    Liu, Yupeng; Liu, Yang; Li, Haiyan; Jiang, Di; Cao, Weiping; Chen, Hui; Xia, Lei; Xu, Ruimin

    2016-07-01

    A novel, compact microwave tunable bandpass filter integrated power divider, based on the high anisotropy electro-optic nematic liquid crystal, is proposed in this letter. Liquid crystal, as the electro-optic material, is placed between top inverted microstrip line and the metal plate. The proposed structure can realize continuous tunable bandpass response and miniaturization. The proposed design concept is validated by the good performance of simulation results and experimental results. The electro-optic material has shown great potential for microwave application. PMID:27475583

  14. Tunable microwave bandpass filter integrated power divider based on the high anisotropy electro-optic nematic liquid crystal

    NASA Astrophysics Data System (ADS)

    Liu, Yupeng; Liu, Yang; Li, Haiyan; Jiang, Di; Cao, Weiping; Chen, Hui; Xia, Lei; Xu, Ruimin

    2016-07-01

    A novel, compact microwave tunable bandpass filter integrated power divider, based on the high anisotropy electro-optic nematic liquid crystal, is proposed in this letter. Liquid crystal, as the electro-optic material, is placed between top inverted microstrip line and the metal plate. The proposed structure can realize continuous tunable bandpass response and miniaturization. The proposed design concept is validated by the good performance of simulation results and experimental results. The electro-optic material has shown great potential for microwave application.

  15. A liquid crystalline polymer microlens array with tunable focal intensity by the polarization control of a liquid crystal layer

    NASA Astrophysics Data System (ADS)

    Choi, Yoonseuk; Kim, Hak-Rin; Lee, Kwang-Ho; Lee, Yong-Min; Kim, Jae-Hoon

    2007-11-01

    We propose a focal intensity tunable microlens array by using a birefringent liquid crystalline polymer for lensing action. Due to the difference of effective refractive indices, it acts as a positive or negative microlens with respect to the polarization state. As we control the incident polarization by adding a liquid crystal layer, the focal intensity can be tuned by an applied voltage. Twisted nematic and bistable ferroelectric liquid crystal modes were applied to demonstrate the possibility of various driving features such as a continuously tunable focal intensity or fast switching with memory effect.

  16. Mid-infrared tunable laser based on the Cr:ZnSe active crystal

    NASA Astrophysics Data System (ADS)

    Koranda, Petr; Jelínková, Helena; Nemec, Michal; Šulc, Jan; Doroshenko, Maxim E.; Basiev, Tasoltan T.; Komar, Vitaly K.; Gerasimenko, Andriy S.; Puzikov, Vyacheslav M.; Badikov, V. V.; Badikov, D. V.

    2008-02-01

    Broadly tunable mid-infrared laser sources operated at room-temperature are desired in many technological and medical applications. The aim of the project was to design and construct broadly tunable powerful Cr:ZnSe laser. The investigated Cr:ZnSe various shaped bulk crystals were grown by the Bridgman method or by the floating zone method. The absorption spectrum was measured to be from 1500 to 2000 nm and the emission spectrum was from 2100 to 2800 nm. Three different lasers were utilized for coherent longitudinal pumping of Cr:ZnSe laser, namely flashlamp-pumped Er:YAP laser (generated wavelength 1660 nm), diode-pumped Tm:YLF laser (generated wavelength 1912 nm) and diode-pumped Tm:YAP laser (generated wavelength 1980 nm). The constructed Cr:ZnSe laser operated in pulsed as well as in continuous-wave regime. In the first case the Cr:ZnSe crystal grown by the floating zone method was studied. The maximal output power in continuous-wave regime was 310 mW with the slope-efficiency 73% for the Tm:YAP laser pumping. In the second case the Cr:ZnSe prism grown by the Bridgman method which served simultaneously as laser active medium and intracavity dispersive element was investigated. For the Er:YAP laser pumping the maximal output energy was 20 mJ with the slope-efficiency 36%. The output radiation was tunable in the range from 2050 nm up to 2750 nm. For the Tm:YAP laser pumping the maximal output power in continuous-wave regime was 175 mW with the slope-efficiency 24%. The output radiation was tunable in the interval from 2220 nm up to 2680 nm. The generated radiation beam spatial structure was close to TEM00.

  17. Mechanically stretchable and tunable metamaterial absorber

    NASA Astrophysics Data System (ADS)

    Zhang, Fuli; Feng, Shuqi; Qiu, Kepeng; Liu, Zijun; Fan, Yuancheng; Zhang, Weihong; Zhao, Qian; Zhou, Ji

    2015-03-01

    In this letter, we present experimental demonstration of a mechanically stretchable and tunable metamaterial absorber composed of dielectric resonator stacked on a thin conductive rubber layer. A near unity absorption is observed due to strong local field confinement around magnetic Mie resonance of dielectric resonator. Furthermore, the interspacing between unit cells is modulated dynamically under uniaxial stress. Owing to the decreases of longitudinal coupling between neighboring unit cells, the resonant absorption peak is reversibly tuned by 410 MHz, as the stain varies up to 180% along H field direction. On the contrary, the resonant absorption state is nearly independent on strain variation when external stress is applied along E field direction, due to the weak transverse interplaying. The mechanically tunable metamaterial absorber featured by flexibility paves a way forwards for actual application.

  18. Tunable magneto-granular phononic crystals

    NASA Astrophysics Data System (ADS)

    Allein, F.; Tournat, V.; Gusev, V. E.; Theocharis, G.

    2016-04-01

    This paper reports on the study of the dynamics of 1D magneto-granular phononic crystals composed of a chain of spherical steel beads inside a properly designed magnetic field. This field is induced by an array of permanent magnets, located in a holder at a given distance from the chain. The theoretical and experimental results of the band gap structure are displayed, including all six degrees of freedom for the beads, i.e., three translations and three rotations. Experimental evidence of transverse-rotational modes of propagation is presented; moreover, by changing the strength of the magnetic field, the dynamic response of the granular chain is tuned. The combination of non-contact tunability with the potentially strong nonlinear behavior of granular systems ensures the suitability of magneto-granular phononic crystals as nonlinear, tunable mechanical metamaterials for use in controlling elastic wave propagation.

  19. Tunable dwell time in gated silicene nanostructures

    NASA Astrophysics Data System (ADS)

    Zhu, B. S.; Wang, Y.; Lou, Y. Y.

    2016-01-01

    Residing on the gate-tunable electronic properties of silicene, we have systematically examined the dwell time for quantum tunneling through the single and multiple-gated silicene nanostructures. It is shown that unlike the graphene, superluminal tunneling is observable even at the normal incidence due to the sizeable spin-orbit gap of silicene. Together with its field-tunable bandgap, we show that this superluminal tunneling can be further flexibly switched on and off via electric mean. By simulating the dwell time through the symmetric and asymmetric double barrier structures, it is also shown here that the dwell time displays the distinct dependence on the former and latter barrier profiles. Those observations provide some favorable strategies to experimentally examine and fundamentally understand the time-dependent aspect of tunneling in solid state nanosystems.

  20. Undulator tunability and ring-energy

    SciTech Connect

    Viccaro, P.J.; Shenoy, G.K.

    1996-09-01

    An Undulator has two properties which make it an extremely attractive source of electromagnetic radiation. The first is that the radiation is concentrated in a number of narrow energy bands known as harmonics of the device. The second characteristic is that under favorable operating conditions, the energy of these harmonics can be shifted or {open_quotes}tuned{close_quotes} over an energy interval which can be as large as two or three times the value of the lowest energy harmonic. Both the photon energy of an undulator as well as its tunability are determined by the period, {lambda}, of the device, the magnetic gap, G (which is larger than the minimum aperture required for injection and operation of the storage ring), and the storage ring energy, E{sub R}. Given the photon energy, E{sub p}, the above parameters ultimately define the limits of operation or tunability of the undulator.

  1. Integrated optical, acoustically tunable wavelength filter

    NASA Astrophysics Data System (ADS)

    Frangen, J.; Herrmann, H.; Ricken, R.; Seibert, H.; Sohler, W.

    1989-11-01

    A TM/TE convertor is combined with a TE-pass polarizer on a common LiNbO3 chip to obtain an integrated optical, acoustically tunable wavelength filter. Its tuning range is 1.45-1.57 micron wavelength with a filter half-width of 2.8 nm. Due to the combined acoustical/optical strip guide structure used in the mode convertor, a very low acoustic drive power of only 9 mW is required.

  2. Tunable infrared source employing Raman mixing

    DOEpatents

    Byer, Robert L.; Herbst, Richard L.

    1980-01-01

    A tunable source of infrared radiation is obtained by irradiating an assemblage of Raman active gaseous atoms or molecules with a high intensity pumping beam of coherent radiation at a pump frequency .omega..sub.p to stimulate the generation of Stokes wave energy at a Stokes frequency .omega..sub.s and to stimulate the Raman resonant mode at the Raman mode frequency .omega..sub.R within the irradiated assemblage where the pump frequency .omega..sub.p minus the Stokes frequency .omega..sub.s is equal to the Raman mode frequency .omega..sub.R. The stimulated assemblage is irradiated with a tunable source of coherent radiation at a frequency .omega..sub.i to generate the output infrared radiation of the frequency .omega..sub.0 which is related to the Raman mode frequency .omega..sub.R and the input wave .omega..sub.i by the relation .omega..sub.0 =.omega..sub.i .+-..omega..sub.R. In one embodiment the interaction between the pump wave energy .omega..sub.p and the tunable input wave energy .omega..sub.i is collinear and the ratio of the phase velocity mismatch factor .DELTA.k to the electric field exponential gain coefficient T is within the range of 0.1 to 5. In another embodiment the pump wave energy .omega..sub.p and the tunable input wave energy .omega..sub.i have velocity vectors k.sub.p and k.sub.i which cross at an angle to each other to compensate for phase velocity mismatches in the medium. In another embodiment, the Stokes wave energy .omega..sub.s is generated by pump energy .omega..sub.p in a first Raman cell and .omega..sub.s, .omega..sub.i and .omega..sub.p are combined in a second Raman mixing cell to produce the output at .omega..sub.i.

  3. Rugged, Tunable Extended-Cavity Diode Laser

    NASA Technical Reports Server (NTRS)

    Moore, Donald; Brinza, David; Seidel, David; Klipstein, William; Choi, Dong Ho; Le, Lam; Zhang, Guangzhi; Iniguez, Roberto; Tang, Wade

    2007-01-01

    A rugged, tunable extended-cavity diode laser (ECDL) has been developed to satisfy stringent requirements for frequency stability, notably including low sensitivity to vibration. This laser is designed specifically for use in an atomic-clock experiment to be performed aboard the International Space Station (ISS). Lasers of similar design would be suitable for use in terrestrial laboratories engaged in atomic-clock and atomic-physics research.

  4. Resonant Cavities for Frequency Tunable Gyrotrons

    NASA Astrophysics Data System (ADS)

    Sabchevski, S.; Idehara, T.

    2008-01-01

    In this paper we present, discuss and compare several concepts based on both well-known and novel ideas for tunable gyrotron cavities. Although theoretical and design considerations are presented and discussed together the main focus is on the underlying principles and feasibility of different approaches rather than on their specific implementations. Illustrative examples are provided for configurations and frequency range appropriate for gyrotrons used as radiation sources for NMR spectroscopy with signal enhancement through DNP.

  5. Tunable impedance matching network fundamental limits and practical considerations

    NASA Astrophysics Data System (ADS)

    Allen, Wesley N.

    As wireless devices continue to increase in utility while decreasing in dimension, design of the RF front-end becomes more complex. It is common for a single handheld device to operate on a plethora of frequency bands, utilize multiple antennae, and be subjected to a variety of environments. One complexity in particular which arises from these factors is that of impedance mismatch. Recently, tunable impedance matching networks have begun to be implemented to address this problem. This dissertation presents the first in-depth study on the frequency tuning range of tunable impedance matching networks. Both the fundamental limitations of ideal networks as well as practical considerations for design and implementation are addressed. Specifically, distributed matching networks with a single tuning element are investigated for use with parallel resistor-capacitor and series resistor-inductor loads. Analytical formulas are developed to directly calculate the frequency tuning range TR of ideal topologies. The theoretical limit of TR for these topologies is presented and discussed. Additional formulas are developed which address limitations in transmission line characteristic impedance and varactor range. Equations to predict loss due to varactor quality factor are demonstrated and the ability of parasitics to both increase and decrease TR are shown. Measured results exemplify i) the potential to develop matching networks with a small impact from parasitics, ii) the need for accurate knowledge of parasitics when designing near transition points in optimal parameters, iii) the importance of using a transmission line with the right characteristic impedance, and iv) the ability to achieve extremely low loss at the design frequency with a lossy varactor under the right conditions (measured loss of -0.07 dB). In the area of application, tunable matching networks are designed and measured for mobile handset antennas, demonstrating up to a 3 dB improvement in power delivered to a

  6. Quantitative nanometer-scale mapping of dielectric tunability

    DOE PAGESBeta

    Tselev, Alexander; Klein, Andreas; Gassmann, Juergen; Jesse, Stephen; Li, Qian; Kalinin, Sergei V.; Wisinger, Nina Balke

    2015-08-21

    Two scanning probe microscopy techniques—near-field scanning microwave microscopy (SMM) and piezoresponse force microscopy (PFM)—are used to characterize and image tunability in a thin (Ba,Sr)TiO3 film with nanometer scale spatial resolution. While sMIM allows direct probing of tunability by measurement of the change in the dielectric constant, in PFM, tunability can be extracted via electrostrictive response. The near-field microwave imaging and PFM provide similar information about dielectric tunability with PFM capable to deliver quantitative information on tunability with a higher spatial resolution close to 15 nm. This is the first time that information about the dielectric tunability is available on suchmore » length scales.« less

  7. LTCC Phase Shifters Based on Tunable Ferroelectric Composite Thick Films

    NASA Astrophysics Data System (ADS)

    Nikfalazar, M.; Kohler, C.; Heunisch, A.; Wiens, A.; Zheng, Y.; Schulz, B.; Mikolajek, M.; Sohrabi, M.; Rabe, T.; Binder, J. R.; Jakoby, R.

    2015-11-01

    This paper presents, the investigation of tunable components based on LTCC technology, implementing ferroelectric tunable thick-film dielectric. The tunable loaded line phase shifters are fabricated with metal-insulator-metal (MIM) varactors to demonstrate the capabilities of this method for packaging of the tunable components. The MIM varactors consist of one tunable dielectric paste layer that is printed between two silver layers. The tunable ferroelectric paste is optimized for LTCC sintering temperature around 850°C. The phase shifters are fabricated in two different process. They were achieved a figure of merit of 24°/dB (phase shift 192°) at 3 GHz and 18°/dB (phase shift 98°) at 4.4 GHz by using seven unit cells that each unit cell consisting of two MIM varactors.

  8. Quantitative nanometer-scale mapping of dielectric tunability

    SciTech Connect

    Tselev, Alexander; Klein, Andreas; Gassmann, Juergen; Jesse, Stephen; Li, Qian; Kalinin, Sergei V.; Wisinger, Nina Balke

    2015-08-21

    Two scanning probe microscopy techniques—near-field scanning microwave microscopy (SMM) and piezoresponse force microscopy (PFM)—are used to characterize and image tunability in a thin (Ba,Sr)TiO3 film with nanometer scale spatial resolution. While sMIM allows direct probing of tunability by measurement of the change in the dielectric constant, in PFM, tunability can be extracted via electrostrictive response. The near-field microwave imaging and PFM provide similar information about dielectric tunability with PFM capable to deliver quantitative information on tunability with a higher spatial resolution close to 15 nm. This is the first time that information about the dielectric tunability is available on such length scales.

  9. Phononic Crystal Tunable via Ferroelectric Phase Transition

    NASA Astrophysics Data System (ADS)

    Xu, Chaowei; Cai, Feiyan; Xie, Shuhong; Li, Fei; Sun, Rong; Fu, Xianzhu; Xiong, Rengen; Zhang, Yi; Zheng, Hairong; Li, Jiangyu

    2015-09-01

    Phononic crystals (PCs) consisting of periodic materials with different acoustic properties have potential applications in functional devices. To realize more smart functions, it is desirable to actively control the properties of PCs on demand, ideally within the same fabricated system. Here, we report a tunable PC made of Ba0.7Sr0.3Ti O3 (BST) ceramics, wherein a 20-K temperature change near room temperature results in a 20% frequency shift in the transmission spectra induced by a ferroelectric phase transition. The tunability phenomenon is attributed to the structure-induced resonant excitation of A0 and A1 Lamb modes that exist intrinsically in the uniform BST plate, while these Lamb modes are sensitive to the elastic properties of the plate and can be modulated by temperature in a BST plate around the Curie temperature. The study finds opportunities for creating tunable PCs and enables smart temperature-tuned devices such as the Lamb wave filter or sensor.

  10. Tunable pulsed narrow bandwidth light source

    DOEpatents

    Powers, Peter E.; Kulp, Thomas J.

    2002-01-01

    A tunable pulsed narrow bandwidth light source and a method of operating a light source are provided. The light source includes a pump laser, first and second non-linear optical crystals, a tunable filter, and light pulse directing optics. The method includes the steps of operating the pump laser to generate a pulsed pump beam characterized by a nanosecond pulse duration and arranging the light pulse directing optics so as to (i) split the pulsed pump beam into primary and secondary pump beams; (ii) direct the primary pump beam through an input face of the first non-linear optical crystal such that a primary output beam exits from an output face of the first non-linear optical crystal; (iii) direct the primary output beam through the tunable filter to generate a sculpted seed beam; and direct the sculpted seed beam and the secondary pump beam through an input face of the second non-linear optical crystal such that a secondary output beam characterized by at least one spectral bandwidth on the order of about 0.1 cm.sup.-1 and below exits from an output face of the second non-linear optical crystal.

  11. Tetravalent chromium (Cr(4+)) as laser-active ion for tunable solid-state lasers

    NASA Technical Reports Server (NTRS)

    Seas, A.; Petricevic, V.; Alfano, Robert R.

    1992-01-01

    Generation of femtosecond pulses from a continuous-wave mode-locked chromium-doped forsterite (Cr(4+):Mg2SiO4) laser has been accomplished. The forsterite laser was actively mode-locked using an acousto-optic modulator operating at 78 MHz with two Brewster high-dispersion glass prisms for intra-cavity chirp compensation. Transform-limited sub-100-fs pulses were routinely generated in the TEM(sub 00) mode with 85 mW of continuous power (with 1 percent output coupler), tunable over 1230-1280 nm. The shortest pulses of 60-fs pulsewidth were measured.

  12. Tunable Bragg filters with a phase transition material defect layer.

    PubMed

    Wang, Xi; Gong, Zilun; Dong, Kaichen; Lou, Shuai; Slack, Jonathan; Anders, Andre; Yao, Jie

    2016-09-01

    We propose an all-solid-state tunable Bragg filter with a phase transition material as the defect layer. Bragg filters based on a vanadium dioxide defect layer sandwiched between silicon dioxide/titanium dioxide Bragg gratings are experimentally demonstrated. Temperature dependent reflection spectroscopy shows the dynamic tunability and hysteresis properties of the Bragg filter. Temperature dependent Raman spectroscopy reveals the connection between the tunability and the phase transition of the vanadium dioxide defect layer. This work paves a new avenue in tunable Bragg filter designs and promises more applications by combining phase transition materials and optical cavities. PMID:27607643

  13. All-fibre ytterbium laser tunable within 45 nm

    SciTech Connect

    Abdullina, S R; Babin, S A; Vlasov, A A; Kablukov, S I; Shelemba, I S; Kurkov, A S

    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)

  14. Wavelength-tunable colloidal quantum dot laser on ultra-thin flexible glass

    SciTech Connect

    Foucher, C.; Guilhabert, B.; Laurand, N.; Dawson, M. D.

    2014-04-07

    A mechanically flexible and wavelength-tunable laser with an ultra-thin glass membrane as substrate is demonstrated. The optically pumped hybrid device has a distributed feedback cavity that combines a colloidal quantum dot gain film with a grating-patterned polymeric underlayer, all on a 30-μm thick glass sheet. The total thickness of the structure is only 75 μm. The hybrid laser has an average threshold fluence of 450 ± 80 μJ/cm{sup 2} (for 5-ns excitation pulses) at an emitting wavelength of 607 nm. Mechanically bending the thin-glass substrate enables continuous tuning of the laser emission wavelength over an 18-nm range, from 600 nm to 618 nm. The correlation between the wavelength tunability and the mechanical properties of the thin laser structure is verified theoretically and experimentally.

  15. Cascaded four-wave mixing for broadband tunable laser sideband generation.

    PubMed

    Liu, Weimin; Zhu, Liangdong; Wang, Liang; Fang, Chong

    2013-06-01

    We demonstrate the versatile broadband wavelength tunability of frequency upconverted multicolor cascaded four-wave-mixing (CFWM) signals spanning the continuous wavelength range from UV to near IR in a thin type-I BBO crystal using 35 fs, 800 nm fundamental and chirped IR supercontinuum white light pulses. Two sets of spatially dispersed CFWM laser sidebands are concomitantly generated from two incident pulses as well as their second-harmonic-generation and sum-frequency-generation pulses in a crossing geometry. The tunable cascaded signals with ultrabroad bandwidth can be readily achieved via spatially rotating the BBO crystal to different phase-matching conditions and temporally varying the time delay between the two incident near-IR pulses. PMID:23722739

  16. Tunable dielectric properties and excellent microwave absorbing properties of elliptical Fe3O4 nanorings

    NASA Astrophysics Data System (ADS)

    Tong, Guoxiu; Liu, Yun; Cui, Tingting; Li, Yana; Zhao, Yanting; Guan, Jianguo

    2016-02-01

    Elliptical Fe3O4 nanorings (NRs) with continuously tunable axes that range from 40 nm to 145 nm in length were prepared through a precursor-directed synthetic route to determine the electromagnetic responses generated at 2-18 GHz. The tunability of the dielectric properties of Fe3O4 NRs depends on the long axis rather than on the specific surface area, internal stress, and grain size. Elliptical Fe3O4 NRs exhibit the excellent microwave absorbing properties due to the unique ring-like configuration, which significantly enhances permittivity, multiple scattering, oscillation resonance absorption, microantenna radiation, and interference. These findings indicate that ring-like nanostructures are promising for devising effective microwave absorbers.

  17. Electrically-tunable optical zoom system by using liquid crystal lenses

    NASA Astrophysics Data System (ADS)

    Lin, Yi-Hsin; Chen, Ming-Syuan; Lin, Hung-Chun

    2012-03-01

    An electrically-tunable optical zoom system using liquid crystal (LC) lenses is demonstrated. The mechanism of the optical zoom system is to use two lenses and a camera system to achieve focusing and zooming function. In this paper, we analyzed the imaging conditions and the magnification of the optical zoom system. The relation between the focusing properties of LC lenses and zoom ratio of the optical zoom system is also discussed. The electrically-tunable optical zoom system using two LC lenses has high zoom ratio (~7.9:1 to ~5.5:1), short system length (<10 cm) and the object can be zoomed in or zoomed out continuously at the objective distance of infinity to 10 cm. The potential applications are cell phones, cameras, telescopes and pico projectors.

  18. Optotune focus tunable lenses and laser speckle reduction based on electroactive polymers

    NASA Astrophysics Data System (ADS)

    Blum, M.; Büeler, M.; Grätzel, C.; Giger, J.; Aschwanden, M.

    2012-03-01

    Based on selected liquid and elastic polymers, Optotune has developed adaptive optical components, such as focus tunable lenses and laser speckle reducers. The lenses range from 2 to 55mm in aperture, are mechanically or electrically actuated and offer a continuous range of focal powers of several 10 diopters. This additional degree of freedom enables the design of compact optical systems, typically with less mechanics. We show how tunable lenses can be used to improve optical designs for imaging and illumination systems in terms of size, quality and speed. The speckle reducers are based on electroactive polymers and offer an extremely compact and low cost solution for removing speckles, which is a key benefit for laser projectors and illumination systems.

  19. Giant and tunable valley degeneracy splitting in MoTe2

    NASA Astrophysics Data System (ADS)

    Li, Xiao; Qi, Jingshan; Niu, Qian; Feng, Ji

    Valleys in monolayer transition-metal dichalcogenides seamlessly connect two basic carriers of quantum information, namely, the electron spin and photon helicity. Lifting the valley degeneracy is an attractive route to achieve further optoelectronic manipulations. However, the magnetic field only creates a very small valley splitting. We propose a strategy to create giant valley splitting by the proximity-induced Zeeman effect. Our first principles calculations of monolayer MoTe2 on a EuO substrate show that valley splitting over 300 meV can be generated. Interband transition energies become valley dependent, leading to selective spin-photon coupling by optical frequency tuning. The valley splitting is also continuously tunable by rotating the substrate magnetization. The giant and tunable valley splitting adds a different dimension to the exploration of unique optoelectronic devices based on magneto-optical coupling and magnetoelectric coupling.

  20. Single linearly polarized, widely and freely tunable two wavelengths Yb3+-doped fiber laser

    NASA Astrophysics Data System (ADS)

    Liu, Dongfeng; Wang, Chinhua

    2010-01-01

    We report a novel single linearly polarized, widely, freely and continuously tunable two wavelengths Yb3+-doped fiber laser. The laser generates stable arbitrary two wavelengths output between 1003.1 and 1080.7 nm peak wavelengths simultaneously with a 346.0 mW CW power by using polarization beam splitting (PBS) for separation of two wavelengths. Each lasing line shows a single polarization with a polarization extinction ratio of >20 dB under different pump levels. The central and the interval of the two wavelengths can be tuned smoothly and independently in the entire gain region of >70 nm of PM Yb3+-doped single mode fiber. Strongly enhanced polarization-hole burning (PHB) phenomena in polarization maintain (PM) Yb3+-doped fiber was observed in the tunable two wavelengths Yb3+-doped fiber laser.

  1. Electronically tunable coherent Raman spectroscopy using acousto-optics tunable filter.

    PubMed

    Petrov, Georgi I; Meng, Zhaokai; Yakovlev, Vladislav V

    2015-09-21

    Fast and sensitive Raman spectroscopy measurements are imperative for a large number of applications in biomedical imaging, remote sensing and material characterization. In this report, by introducing an electronically-tunable acousto-optical filter as a wavelength selector, we demonstrated a novel instrumentation to the broadband coherent Raman spectroscopy. System's tunability allows assessing Raman transitions ranging from <400 cm(-1) to 4500 cm(-1). We validated the use of the new instrumentation by collecting coherent anti-Stokes spectra and stimulated Raman spectra of various samples. PMID:26406668

  2. Cross-Interface Emulsification for Generating Size-Tunable Droplets.

    PubMed

    Xu, Peng; Zheng, Xu; Tao, Yi; Du, Wenbin

    2016-03-15

    We report cross-interface emulsification (XiE), a simple method for the generation of monodisperse droplets of controllable volumes from picoliter to nanoliter. A device is set up in which a fused-silica capillary is vibrating across the surface of the continuous phase (mineral oil) in a reservoir, and the flow of the dispersed phase (aqueous solution) in the capillary is segmented into monodisperse droplets at the air/oil interface. We find that the volume of droplets is mainly dominated by the flow rate and vibrating frequency and not significantly influenced by other factors, such as the viscosity of the continuous phase and dispersed phase, the inner diameter of the capillary (20-100 μm), or the shape of the tip (tapered or flat). These features reflect high robustness, flexibility, and precision of XiE for on-demand volume control of droplets. The droplets automatically assemble into planar monolayer droplet arrays (PMDA) in flat-bottomed microwells of 96-well plates, offering excellent convenience for imaging of droplets. As a representative application, we carry out digital loop-mediated isothermal amplification using PMDAs with multivolume droplets for the absolute quantification of nucleic acids. Our results demonstrate that XiE is simple and controllable for the production of monodisperse size-tunable droplets, and it offers opportunities for common laboratories, even without microfabrication facilities, to perform digital quantification, single cell analysis, and other biochemical assays with high throughput. PMID:26849419

  3. Microwave tunable laser source: A stable, precision tunable heterodyne local oscillator

    NASA Technical Reports Server (NTRS)

    Sachse, G. W.

    1980-01-01

    The development and capabilities of a tunable laser source utilizing a wideband electro-optic modulator and a CO2 laser are described. The precision tunability and high stability of the device are demonstrated with examples of laboratory spectroscopy. Heterodyne measurements are also presented to demonstrate the performance of the laser source as a heterodyne local oscillator. With the use of five CO2 isotope lasers and the 8 to 18 GHz sideband offset tunability of the modulator, calculations indicate that 50 percent spectral coverage in the 9 to 12 micron region is achievable. The wavelength accuracy and stability of this laser source is limited by the CO2 laser and is more than adequate for the measurement of narrow Doppler-broadened line profiles. The room-temperature operating capability and the programmability of the microwave tunable laser source are attractive features for its in-the-field implementation. Although heterodyne measurements indicated some S/N degradation when using the device as a local oscillator, there does not appear to be any fundamental limitation to the heterodyne efficiency of this laser source. Through the use of a lower noise-figure traveling wave tube amplifier and optical matching of the output beam with the photomixer, a substantial increase in the heterodyne S/N is expected.

  4. Wavelength-tunable filter utilizing non-cyclic arrayed waveguide grating to create colorless, directionless, contentionless ROADMs

    NASA Astrophysics Data System (ADS)

    Niwa, Masaki; Takashina, Shoichi; Mori, Yojiro; Hasegawa, Hiroshi; Sato, Ken-ichi; Watanabe, Toshio

    2015-01-01

    With the continuous increase in Internet traffic, reconfigurable optical add-drop multiplexers (ROADMs) have been widely adopted in the core and metro core networks. Current ROADMs, however, allow only static operation. To realize future dynamic optical-network services, and to minimize any human intervention in network operation, the optical signal add/drop part should have colorless/directionless/contentionless (C/D/C) capabilities. This is possible with matrix switches or a combination of splitter-switches and optical tunable filters. The scale of the matrix switch increases with the square of the number of supported channels, and hence, the matrix-switch-based architecture is not suitable for creating future large-scale ROADMs. In contrast, the numbers of splitter ports, switches, and tunable filters increase linearly with the number of supported channels, and hence the tunable-filter-based architecture will support all future traffic. So far, we have succeeded in fabricating a compact tunable filter that consists of multi-stage cyclic arrayed-waveguide gratings (AWGs) and switches by using planar-lightwave-circuit (PLC) technologies. However, this multistage configuration suffers from large insertion loss and filter narrowing. Moreover, power-consuming temperature control is necessary since it is difficult to make cyclic AWGs athermal. We propose here novel tunable-filter architecture that sandwiches a single-stage non-cyclic athermal AWG having flatter-topped passbands between small-scale switches. With this configuration, the optical tunable filter attains low insertion loss, large passband bandwidths, low power consumption, compactness, and high cost-effectiveness. A prototype is monolithically fabricated with PLC technologies and its excellent performance is experimentally confirmed utilizing 80-channel 30-GBaud dual-polarization quadrature phase-shift-keying (QPSK) signals.

  5. High-speed broadband tunable lasers

    NASA Astrophysics Data System (ADS)

    Adams, Laura E.; Nykolak, Gerald; Bethea, Clyde G.; Tanbun-Ek, Tawee; People, Roosevelt; Sergent, A. M.; Sciortino, Paul F., Jr.; Fullowan, Thomas R.

    1997-12-01

    New enabling technologies are needed for optical communication systems to accommodate rapidly growing traffic demands. Wavelength conversion and high-speed optical packet switching/routing will be key technology components for realizing more flexible and efficient optical networks. Lasers capable of wide-band, high-speed wavelength tuning will be essential to support these advanced functions. Also, many applications will require high launch powers in order to access an increasing number of users, nodes, or base stations. Hence, laser transmitters capable of suppressing stimulated Brillouin scattering (SBS) would be highly desirable. We have developed an ultrafast, broadband tunable laser, based on an electroabsorption modulator laser (EML), which exhibits wavelength switching speeds as fast as 56 ps. Here, we report system performance results on wavelength conversion high-speed optical packet switching, and SBS suppression using this device. We have tested multiple wavelength conversion sequences and demonstrated penalty-free transmission through two cascaded wavelength conversion stages including 200 km of standard non-DS fiber. When used to perform packet switching at 2.5 Gb/s, the tunable laser allows switching between optical packets on 4 wavelength channels in less than 1 bit period, thereby requiring no significant guardband. The modulated data packets have been transmitted through 200 km of non-DSF and yield open eye diagrams. The tunable laser has also been used to perform SBS suppression. We have measured SBS thresholds of approximately 25 dBm on 4 separate WDM channels. The required modulation signal is very small, 95 mVpp, and the residual AM is only approximately 1%.

  6. Narrow-Band WGM Optical Filters With Tunable FSRs

    NASA Technical Reports Server (NTRS)

    Mohageg, Makan; Matsko, Andrey; Savchenkov, Anatoliy; Maleki, Lute; Iltchenko, Vladimir; Strekalov, Dmitry

    2007-01-01

    Optical resonators of the whispering-gallery-mode (WGM) type featuring DC-tunable free spectral ranges (FSRs) have been demonstrated. By making the FSR tunable, one makes it possible to adjust, during operation, the frequency of a microwave signal generated by an optoelectronic oscillator in which an WGM optical resonator is utilized as a narrow-band filter.

  7. Reversibly tunable coupled and decoupled super absorbing structures

    NASA Astrophysics Data System (ADS)

    Zhang, Nan; Dong, Ziye; Ji, Dengxin; Song, Haomin; Zeng, Xie; Liu, Zhejun; Jiang, Suhua; Xu, Yun; Bernussi, Ayrton; Li, Wei; Gan, Qiaoqiang

    2016-02-01

    We differentiate the spacer-dependent peak shift in coupled and decoupled super absorbing structures based on magnetic resonance and interference mechanism, respectively, which is experimentally validated by low-cost and large-area structures fabricated using lithography-free processes. The reversible real-time spectral tunability is then demonstrated by incorporating a thermally tunable polymeric spacer layer.

  8. Imaging Spectrometer Using a Liquid Crystal Tunable Filter

    NASA Technical Reports Server (NTRS)

    Chrien, Tomas G.; Chovit, Christopher; Miller, Peter J.

    1993-01-01

    A demonstration imaging spectrometer using a liquid crystal tunable filter (LCTF) was built and tested on a hot air balloon platform. The LCTF is a tunable polarization interference or Lyot filter. The LCTF enables a small, light weight, low power, band sequential imaging spectrometer design.

  9. Industrial integration of high coherence tunable VECSEL in the NIR and MIR

    NASA Astrophysics Data System (ADS)

    Denet, Stéphane; Chomet, Baptiste; Lecocq, Vincent; Ferrières, Laurence; Myara, Mikhaël.; Cerutti, Laurent; Sagnes, Isabelle; Garnache, Arnaud

    2016-03-01

    Laser technology is finding applications in areas such as high resolution spectroscopy, radar-lidar, velocimetry, or atomic clock where highly coherent tunable high power light sources are required. The Vertical External Cavity Surface Emitting Laser (VECSEL) technology [1] has been identified for years as a good candidate to reach high power, high coherence and broad tunability while covering a wide emission wavelength range exploiting III-V semiconductor technologies. Offering such performances in the Near- and Middle-IR range, GaAs- and Sb-based VECSEL technologies seem to be a well suited path to meet the required specifications of demanding applications. Built up in this field, our expertise allows the realization of compact and low power consumption marketable products, with performances that do not exist on the market today in the 0.8- 1.1 μm and 2-2.5 μm spectral range. Here we demonstrate highly coherent broadly tunable single frequency micro-chip, intracavity element free, patented VECSEL technology, integrated into a compact module with driving electronics. VECSEL devices emitting in the Near and Middle-IR developed in the frame of this work [2] exhibit exciting features compared to diode-pumped solid-state lasers and DFB diode lasers; they combine high power (>100mW) high coherence with a low divergence diffraction limited TEM00 beam, class A dynamics with Relative Intensity Noise as low as -140dB/Hz and at shot noise level above 200MHz RF frequency (up to 160GHz), free running narrow linewidth at sub MHz level (fundamental limit at Hz level) with high spectral purity (SMSR >55dB), linear polarization (50dB suppression ratio), and broadband continuous tunability greater than 400GHz (< 30V piezo voltage, 6kHz cut off frequency) with total tunability up to 3THz. Those performances can all be reached thanks to the high finesse cavity of VECSEL technology, associated to ideal homogeneous QW gain behaviour [3]. In addition, the compact design without any

  10. Integrated Optical, Acoustically Tunable Wavelength Filter

    NASA Astrophysics Data System (ADS)

    Frangen, J.; Herrmann, Harald; Ricken, Raimund; Seibert, Holger; Sohler, Wolfgang; Strake, E.

    1989-12-01

    An integrated optical, acoustically tunable wavelength filter, consisting of a combination of TM-TE converter and integrated polarizer in LiNbO3, is demonstrated. The filter bandwidth is 2.8 nm; the center wavelength can be tuned from λ = 1.45 pm to λ = 1.57 pm by adjusting the driving acoustic frequency. Due to the combined acoustical/optical strip guide structure, used in the mode converter, a very low acoustic drive power of only 9 mW is required.

  11. Plasmonic nanogels with robustly tunable optical properties

    NASA Astrophysics Data System (ADS)

    Cong, Tao; Wani, Satvik N.; Zhou, Georo; Baszczuk, Elia; Sureshkumar, Radhakrishna

    2011-10-01

    Low viscosity fluids with tunable optical properties can be processed to manufacture thin film and interfaces for molecular detection, light trapping in photovoltaics and reconfigurable optofluidic devices. In this work, self-assembly in wormlike micelle solutions is used to uniformly distribute various metallic nanoparticles to produce stable suspensions with localized, multiple wavelength or broad-band optical properties. Their spectral response can be robustly modified by varying the species, concentration, size and/or shape of the nanoparticles. Structure, rheology and optical properties of these plasmonic nanogels as well as their potential applications to efficient photovoltaics design are discussed.

  12. 600-GHz Electronically Tunable Vector Measurement System

    NASA Technical Reports Server (NTRS)

    Dengler, Robert; Maiwald, Frank; Siegel, Peter

    2007-01-01

    A compact, high-dynamic-range, electronically tunable vector measurement system that operates in the frequency range from approximately 560 to approximately 635 GHz has been developed as a prototype of vector measurement systems that would be suitable for use in nearly-real-time active submillimeter-wave imaging. As used here, 'vector measurement system" signifies an instrumentation system that applies a radio-frequency (RF) excitation to an object of interest and measures the resulting amplitude and phase response, relative to either the applied excitatory signal or another reference signal related in a known way to applied excitatory signal.

  13. Experimental demonstration of a tunable microwave undulator.

    PubMed

    Tantawi, Sami; Shumail, Muhammad; Neilson, Jeffery; Bowden, Gordon; Chang, Chao; Hemsing, Erik; Dunning, Michael

    2014-04-25

    Static magnetic undulators used by x-ray light sources are fundamentally too limited to achieve shorter undulator periods and dynamic control. To overcome these limitations, we report experimental demonstration of a novel short-period microwave undulator, essentially a Thomson scattering device, that has yielded tunable spontaneous emission and seeded coherent radiation. Its equivalent undulator period (λu) is 13.9 mm while it has achieved an equivalent magnetic field of 0.65 T. For future-generation light sources, this device promises a shorter undulator period, a large aperture, and fast dynamic control. PMID:24815654

  14. A tunable plasmon resonance in gold nanobelts.

    PubMed

    Anderson, Lindsey J E; Payne, Courtney M; Zhen, Yu-Rong; Nordlander, Peter; Hafner, Jason H

    2011-11-01

    Plasmonic nanowires with sub-100-nm rectangular cross sections were found to exhibit a strong transverse plasmon peak at visible wavelengths. By correlating atomic force microscopy measurements of individual nanobelts with their dark-field scattering spectra, it is seen that the transverse peak tunes with cross-sectional aspect ratio. Simulations revealed that the scattering plasmonic modes are transverse antisymmetric excitations across the nanobelt width. Unlike larger diameter silver nanowires, these nanobelts exhibit sharp, tunable plasmon resonances similar to those of nanoparticles. PMID:21973047

  15. Tunable dielectric liquid lens on flexible substrate

    NASA Astrophysics Data System (ADS)

    Lu, Yen-Sheng; Tu, Hongen; Xu, Yong; Jiang, Hongrui

    2013-12-01

    We demonstrate the fabrication of a tunable-focus dielectric liquid lens (DLL) on a flexible substrate made of polydimethylsiloxane, which was wrapped onto a goggle surface to show its functionality. As a positive meniscus converging lens, the DLL has the focal length variable from 14.2 to 6.3 mm in 1.3 s when the driving voltage increases to 125 Vrms. The resolving power of the DLL is 17.95 line pairs per mm. The DLL on a flexible, curvilinear surface is promising for expanded field of view covered as well as in reconfigurable optical systems.

  16. Tunable superconducting qudit mediated by microwave photons

    SciTech Connect

    Cho, Sung Un; Bae, Myung-Ho; Kim, Nam; Kang, Kicheon

    2015-08-15

    We have investigated the time-domain characteristics of the Autler-Townes doublet in a superconducting circuit. The transition probabilities between the ground state and the Autler-Townes doublet states are shown to be controlled in a phase-coherent manner using a well-known microwave pulse pattern technique. The experimental results are well explained by a numerical simulation based on the Markovian master equation. Our result indicates that the Autler-Townes doublet states might be useful as a tunable qudit for implementation of quantum information processing, in particular as a multivalued quantum logic element.

  17. Processable Cyclic Peptide Nanotubes with Tunable Interiors

    SciTech Connect

    Hourani, Rami; Zhang, Chen; van der Weegen, Rob; Ruiz, Luis; Li, Changyi; Keten, Sinan; Helms, Brett A.; Xu, Ting

    2011-09-06

    A facile route to generate cyclic peptide nanotubes with tunable interiors is presented. By incorporating 3-amino-2-methylbenzoic acid in the d,l-alternating primary sequence of a cyclic peptide, a functional group can be presented in the interior of the nanotubes without compromising the formation of high aspect ratio nanotubes. The new design of such a cyclic peptide also enables one to modulate the nanotube growth process to be compatible with the polymer processing window without compromising the formation of high aspect ratio nanotubes, thus opening a viable approach toward molecularly defined porous membranes.

  18. Tunable skewed edges in puckered structures

    NASA Astrophysics Data System (ADS)

    Grujić, Marko M.; Ezawa, Motohiko; Tadić, Milan Ž.; Peeters, François M.

    2016-06-01

    We propose a type of edges arising due to the anisotropy inherent in the puckered structure of a honeycomb system such as in phosphorene. Skewed-zigzag and skewed-armchair nanoribbons are semiconducting and metallic, respectively, in contrast to their normal edge counterparts. Their band structures are tunable, and a metal-insulator transition is induced by an electric field. We predict a field-effect transistor based on the edge states in skewed-armchair nanoribbons, where the edge state is gapped by applying arbitrary small electric field Ez. A topological argument is presented, revealing the condition for the emergence of such edge states.

  19. Cascaded Mach–Zehnder interferometer tunable filters

    NASA Astrophysics Data System (ADS)

    Ovvyan, A. P.; Gruhler, N.; Ferrari, S.; Pernice, W. H. P.

    2016-06-01

    By cascading compact and low-loss Mach–Zehnder interferometers (MZIs) embedded within nanophotonic circuits we realize thermo-optically tunable optical filters for the visible wavelength range. Through phase tuning in either arm of the MZI, the filter response with maximum extinction can be shifted beyond one free-spectral range with low electrical power consumption. The working wavelength of our device is aligned with the emission wavelength of the silicon vacancy color center in diamond around 740 nm where we realize a filter depth beyond 36.5 dB. Our approach allows for efficient isolation of the emitted signal intensity in future hybrid nanodiamond-nanophotonic circuits.

  20. Concave nanomagnets with widely tunable anisotropy

    DOEpatents

    Lambson, Brian; Gu, Zheng; Carlton, David; Bokor, Jeffrey

    2014-07-01

    A nanomagnet having widely tunable anisotropy is disclosed. The disclosed nanomagnet is a magnetic particle with a convex shape having a first magnetically easy axis. The convex shape is modified to include at least one concavity to urge a second magnetically easy axis to form substantially offset from the first magnetically easy axis. In at least one embodiment, the convex shape is also modified to include at least one concavity to urge a second magnetically easy axis to form with a magnetic strength substantially different from the first magnetically easy axis.

  1. Tunable, superconducting, surface-emitting teraherz source

    SciTech Connect

    Welp, Ulrich; Koshelev, Alexei E.; Gray, Kenneth E.; Kwok, Wai-Kwong; Vlasko-Vlasov, Vitalii

    2009-10-27

    A compact, solid-state THz source based on the driven Josephson vortex lattice in a highly anisotropic superconductor such as Bi.sub.2Sr.sub.2CaCu.sub.2O.sub.8 that allows cw emission at tunable frequency. A second order metallic Bragg grating is used to achieve impedance matching and to induce surface emission of THz-radiation from a Bi.sub.2Sr.sub.2CaCu.sub.2O.sub.8 sample. Steering of the emitted THz beam is accomplished by tuning the Josephson vortex spacing around the grating period using a superimposed magnetic control field.

  2. Three Cavity Tunable MEMS Fabry Perot Interferometer

    PubMed Central

    Parashar, Avinash; Shah, Ankur; Packirisamy, Muthukumaran; Sivakumar, Narayanswamy

    2007-01-01

    In this paper a four-mirror tunable micro electro-mechanical systems (MEMS) Fabry Perot Interferometer (FPI) concept is proposed with the mathematical model. The spectral range of the proposed FPI lies in the infrared spectrum ranging from 2400 to 4018 (nm). FPI can be finely tuned by deflecting the two middle mirrors (or by changing the three cavity lengths). Two different cases were separately considered for the tuning. In case one, tuning was achieved by deflecting mirror 2 only and in case two, both mirrors 2 and 3 were deflected for the tuning of the FPI.

  3. Wavelength-spacing-tunable multichannel filter incorporating a sampled chirped fiber Bragg grating based on a symmetrical chirp-tuning technique without center wavelength shift

    NASA Astrophysics Data System (ADS)

    Han, Young-Geun; Dong, Xinyong; Lee, Ju Han; Lee, Sang Bae

    2006-12-01

    We propose and experimentally demonstrate a simple and flexible scheme for a wavelength-spacing-tunable multichannel filter exploiting a sampled chirped fiber Bragg grating based on a symmetrical modification of the chirp ratio. Symmetrical bending along a sampled chirped fiber Bragg grating attached to a flexible cantilever beam induces a variation of the chirp ratio and a reflection chirp bandwidth of the grating without a center wavelength shift. Accordingly, the wavelength spacing of a sampled chirped fiber Bragg grating is continuously controlled by the reflection chirp bandwidth variation of the grating corresponding to the bending direction, which allows for realization of an effective wavelength-spacing-tunable multichannel filter. Based on the proposed technique, we achieve the continuous tunability of the wavelength spacing in a range from 1.51 to 6.11 nm, depending on the bending direction of the cantilever beam.

  4. Magnetically tunable Mie resonance-based dielectric metamaterials

    PubMed Central

    Bi, Ke; Guo, Yunsheng; Liu, Xiaoming; Zhao, Qian; Xiao, Jinghua; Lei, Ming; Zhou, Ji

    2014-01-01

    Electromagnetic materials with tunable permeability and permittivity are highly desirable for wireless communication and radar technology. However, the tunability of electromagnetic parameters is an immense challenge for conventional materials and metamaterials. Here, we demonstrate a magnetically tunable Mie resonance-based dielectric metamaterials. The magnetically tunable property is derived from the coupling of the Mie resonance of dielectric cube and ferromagnetic precession of ferrite cuboid. Both the simulated and experimental results indicate that the effective permeability and permittivity of the metamaterial can be tuned by modifying the applied magnetic field. This mechanism offers a promising means of constructing microwave devices with large tunable ranges and considerable potential for tailoring via a metamaterial route. PMID:25384397

  5. Magnetically tunable Mie resonance-based dielectric metamaterials.

    PubMed

    Bi, Ke; Guo, Yunsheng; Liu, Xiaoming; Zhao, Qian; Xiao, Jinghua; Lei, Ming; Zhou, Ji

    2014-01-01

    Electromagnetic materials with tunable permeability and permittivity are highly desirable for wireless communication and radar technology. However, the tunability of electromagnetic parameters is an immense challenge for conventional materials and metamaterials. Here, we demonstrate a magnetically tunable Mie resonance-based dielectric metamaterials. The magnetically tunable property is derived from the coupling of the Mie resonance of dielectric cube and ferromagnetic precession of ferrite cuboid. Both the simulated and experimental results indicate that the effective permeability and permittivity of the metamaterial can be tuned by modifying the applied magnetic field. This mechanism offers a promising means of constructing microwave devices with large tunable ranges and considerable potential for tailoring via a metamaterial route. PMID:25384397

  6. Tunable photonic filters: a digital signal processing design approach.

    PubMed

    Binh, Le Nguyen

    2009-05-20

    Digital signal processing techniques are used for synthesizing tunable optical filters with variable bandwidth and centered reference frequency including the tunability of the low-pass, high-pass, bandpass, and bandstop optical filters. Potential applications of such filters are discussed, and the design techniques and properties of recursive digital filters are outlined. The basic filter structures, namely, the first-order all-pole optical filter (FOAPOF) and the first-order all-zero optical filter (FOAZOF), are described, and finally the design process of tunable optical filters and the designs of the second-order Butterworth low-pass, high-pass, bandpass, and bandstop tunable optical filters are presented. Indeed, we identify that the all-zero and all-pole networks are equivalent with well known principles of optics of interference and resonance, respectively. It is thus very straightforward to implement tunable optical filters, which is a unique feature. PMID:19458728

  7. Graphene based tunable metamaterial absorber and polarization modulation in terahertz frequency.

    PubMed

    Zhang, Yin; Feng, Yijun; Zhu, Bo; Zhao, Junming; Jiang, Tian

    2014-09-22

    Graphene can be utilized in designing tunable terahertz devices due to its tunability of sheet conductivity. In this paper, we combine the metamaterial having unit cell of cross-shaped metallic resonator with the double layer graphene wires to realize polarization independent absorber with spectral tuning at terahertz frequency. The absorption performance with a peak frequency tuning range of 15% and almost perfect peak absorption has been demonstrated by controlling the Fermi energy of the graphene that can be conveniently achieved by adjusting the bias voltage on the graphene double layers. The mechanism of the proposed absorber has been explored by a transmission line model and the tuning is explained by the changing of the effective inductance of the graphene wires under gate voltage biasing. Further more, we also propose a polarization modulation scheme of terahertz wave by applying similar polarization dependent absorbers. Through the proposed polarization modulator, it is able to electrically control the reflected wave with a linear polarization of continuously tunable azimuth angle of the major axis from 0° to 90° at the working frequency. These design approaches enable us to electrically control the absorption spectrum and the polarization state of terahertz waves more flexibly. PMID:25321743

  8. Review Of Progress In Remote Sensing By Tunable Diode Laser Heterodyne Spectroscopy

    NASA Astrophysics Data System (ADS)

    Glenar, David A.

    1983-11-01

    Heterodyne spectroscopy at infrared wavelengths is a unique approach to the study of atmospheric species and astrophysical objects. It's coherent detection properties ma4 it 7 the only optical technique to combine ultra-high frequency resolving power (v/A = 106- 107) with diffraction-limited spatial resolution. The use of lead-salt tunable diode lasers (TDL's) as local oscillators in a heterodyne instrument offers the additional advantage of continuous tunability, permitting operation over the entire nominal tuning range of the device. Previous investigators have obtained high signal-to-noise TDL heterodyne spectra of terrestrial atmospheric features in solar absorption and molecular features in sunspots. Until recently, however, the noisy character and low output power of TDL's have precluded their use for heterodyne detection of objects much fainter than the sun. Attempts to observe planets and astrophysical infrared sources have produced only a handful of weak continuum detections. The major categories of TDL excess noise are now fairly well understood, and new device fabrication techniques have produced dramatic improvements in noise reduction, power output, single mode tunability and operation at long wavelengths (X > 10 microns). These next generation devices should result in ground-based instrument performance which rivals the CO2 laser heterodyne technique throughout the 8 to 13 micron atmospheric window.

  9. A compact frequency tunable radio frequency phase shifter with patterned Py enabled transmission line

    SciTech Connect

    Rahman, B.M. Farid; Divan, Ralu; Rosenmann, Daniel; Wang, Tengxing; Peng, Yujia; Wang, Guoan

    2015-01-01

    A well designed frequency tunable phase shifter using patterned Py with different thickness has been demonstrated. Phase shifter is implemented with a slow wave coplanar wave guide (CPW)transmission line, where the signal line has alternate short narrow and wide sections. Py is patterned on the top of narrow section for high inductance density, and inter-digital capacitor is implemented in wide section for high capacitance density. Compared with phase shifter using regular CPW, the dimension of the developed phase shifter has been reduced from 14.86 mm to4.70 mm at 2 GHz. Phase shifter based on 100 nm and 200 nm thick patterned Py with the same dimensions (14lm10lm) are implemented and investigated comprehensively. FMR frequency of 3.2 GHz and 3.6 GHz without any external magnetic field has been achieved for100 nm and 200 nm thick Py film, respectively. Thicker Py has increased inductance density from 1067.2 nH/m to 1193.2 nH/m while the center frequency of the phase shifter has been shifted to 1.80 GHz. Frequency tunability of the phase shifter has been also demonstrated withDC current. The phase shifter can provide 90phase shift continuously from 2 GHz to 1.80 GHz with DC current from 0 mA to 150 mA. The design concept has great potential in design arbitrary tunable RF components such as filters and couplers.

  10. Membrane invaginations facilitate reversible water flux driving tunable iridescence in a dynamic biophotonic system

    PubMed Central

    DeMartini, Daniel G.; Krogstad, Daniel V.; Morse, Daniel E.

    2013-01-01

    Squids have used their tunable iridescence for camouflage and communication for millions of years; materials scientists have more recently looked to them for inspiration to develop new “biologically inspired” adaptive optics. Iridocyte cells produce iridescence through constructive interference of light with intracellular Bragg reflectors. The cell’s dynamic control over the apparent lattice constant and dielectric contrast of these multilayer stacks yields the corresponding optical control of brightness and color across the visible spectrum. Here, we resolve remaining uncertainties in iridocyte cell structure and determine how this unusual morphology enables the cell’s tunable reflectance. We show that the plasma membrane periodically invaginates deep into the iridocyte to form a potential Bragg reflector consisting of an array of narrow, parallel channels that segregate the resulting high refractive index, cytoplasmic protein-containing lamellae from the low-index channels that are continuous with the extracellular space. In response to control by a neurotransmitter, the iridocytes reversibly imbibe or expel water commensurate with changes in reflection intensity and wavelength. These results allow us to propose a comprehensive mechanism of adaptive iridescence in these cells from stimulation to color production. Applications of these findings may contribute to the development of unique classes of tunable photonic materials. PMID:23359694

  11. An electrically tunable liquid crystal lens coupler for the fiber communication systems

    NASA Astrophysics Data System (ADS)

    Chen, Chyong-Hua; Chen, Michael; Lin, Yi-Hsin

    2015-03-01

    In this study, we demonstrated an electrically tunable lens coupler for both variable optical attenuation (VOA) and polarization selection. This coupler consists of a liquid crystal (LC) lens sandwiched between two GRIN lens. A GRIN lens is used to couple the light into the single mode fiber, and a LC lens is used to electrically manipulate the beam size of light. It is known that the lens power of a LC lens is tunable with high polarization sensitivity. Then, as the applied voltage on the LC lens is zero, the incident light is focused due to GRIN lens and coupled into the fiber. On the other hand, the beam size of the transformed e-ray becomes larger because the lens power of a LC lens for the e-ray decreases with the increase of the applied voltage. This results in the decrease of the coupling efficiency, and the optical power coupled into the fiber is smaller. This lens coupler for the e-ray functions as a VOA due to a continuous optical attenuation. On the contrary, the lens power of this LC lens for the o-ray does not vary because of optical anisotropy of the LC layer, and then the coupling efficiency for the o-ray remains high. For an arbitrary polarized incidence, this tunable lens coupler acts as a broadband polarizer for the fiber systems. The polarization dependent loss is larger than 30 dB and the switching time is around 1 second.

  12. A spectrally tunable all-graphene-based flexible field-effect light-emitting device

    PubMed Central

    Wang, Xiaomu; Tian, He; Mohammad, Mohammad Ali; Li, Cheng; Wu, Can; Yang, Yi; Ren, Tian-Ling

    2015-01-01

    The continuous tuning of the emission spectrum of a single light-emitting diode (LED) by an external electrical bias is of great technological significance as a crucial property in high-quality displays, yet this capability has not been demonstrated in existing LEDs. Graphene, a tunable optical platform, is a promising medium to achieve this goal. Here we demonstrate a bright spectrally tunable electroluminescence from blue (∼450 nm) to red (∼750 nm) at the graphene oxide/reduced-graphene oxide interface. We explain the electroluminescence results from the recombination of Poole–Frenkel emission ionized electrons at the localized energy levels arising from semi-reduced graphene oxide, and holes from the top of the π band. Tuning of the emission wavelength is achieved by gate modulation of the participating localized energy levels. Our demonstration of current-driven tunable LEDs not only represents a method for emission wavelength tuning but also may find applications in high-quality displays. PMID:26178323

  13. High-sensitivity high-selectivity detection of CWAs and TICs using tunable laser photoacoustic spectroscopy

    NASA Astrophysics Data System (ADS)

    Pushkarsky, Michael; Webber, Michael; Patel, C. Kumar N.

    2005-03-01

    We provide a general technique for evaluating the performance of an optical sensor for the detection of chemical warfare agents (CWAs) in realistic environments and present data from a simulation model based on a field deployed discretely tunable 13CO2 laser photoacoustic spectrometer (L-PAS). Results of our calculations show the sensor performance in terms of usable sensor sensitivity as a function of probability of false positives (PFP). The false positives arise from the presence of many other gases in the ambient air that could be interferents. Using the L-PAS as it exists today, we can achieve a detection threshold of about 4 ppb for the CWAs while maintaining a PFP of less than 1:106. Our simulation permits us to vary a number of parameters in the model to provide guidance for performance improvement. We find that by using a larger density of laser lines (such as those obtained through the use of tunable semiconductor lasers), improving the detector noise and maintaining the accuracy of laser frequency determination, optical detection schemes can make possible CWA sensors having sub-ppb detection capability with <1:108 PFP. We also describe the results of a preliminary experiment that verifies the results of the simulation model. Finally, we discuss the use of continuously tunable quantum cascade lasers in L-PAS for CWA and TIC detection.

  14. Elastic metamaterial beam with remotely tunable stiffness

    NASA Astrophysics Data System (ADS)

    Qian, Wei; Yu, Zhengyue; Wang, Xiaole; Lai, Yun; Yellen, Benjamin B.

    2016-02-01

    We demonstrate a dynamically tunable elastic metamaterial, which employs remote magnetic force to adjust its vibration absorption properties. The 1D metamaterial is constructed from a flat aluminum beam milled with a linear array of cylindrical holes. The beam is backed by a thin elastic membrane, on which thin disk-shaped permanent magnets are mounted. When excited by a shaker, the beam motion is tracked by a Laser Doppler Vibrometer, which conducts point by point scanning of the vibrating element. Elastic waves are unable to propagate through the beam when the driving frequency excites the first elastic bending mode in the unit cell. At these frequencies, the effective mass density of the unit cell becomes negative, which induces an exponentially decaying evanescent wave. Due to the non-linear elastic properties of the membrane, the effective stiffness of the unit cell can be tuned with an external magnetic force from nearby solenoids. Measurements of the linear and cubic static stiffness terms of the membrane are in excellent agreement with experimental measurements of the bandgap shift as a function of the applied force. In this implementation, bandgap shifts by as much as 40% can be achieved with ˜30 mN of applied magnetic force. This structure has potential for extension in 2D and 3D, providing a general approach for building dynamically tunable elastic metamaterials for applications in lensing and guiding elastic waves.

  15. Tunable magnetism in nanomaterials and systems

    NASA Astrophysics Data System (ADS)

    Guo, Wanlin; Zhang, Zhuhua

    2011-03-01

    Tunable magnetism in nanomaterials and systems are especially attractive and hold great promise for applications in nanoelectronics and spintronics. Here we show some of our recent findings along this direction. First, we present a novel magnetoelectric effect in graphene nanoribbons settled on silicon substrates whereby the ribbon edge magnetization can be tuned linearly by applied bias voltage (Phys.Rev.Lett, 103, 187204, 2009), and this effect is robust to material and geometry variations (Phys.Rev.B 81, 155428, 2010). We also realize an electrical control of magnetism in ZnO ribbons (ACS Nano 4, 2124, 2010 , and even a tunable magnetic ordering in sandwich nanowires by changing charge states (J.Am.Chem.Soc. 132, 10215, 2010). Contrast to the zero-gap graphene, both hexagon-BN sheets and nanotubes are generally insulating. We provide two efficient recipes to narrow the wide gap of BN: applying external electric fields for nanoribbons and increasing tube curvature for nanotubes. Of more interesting is that ferromagnetic ordering is obtained in BN nanotubes by fluorination and it can be remarkably modulated by applying radial pressure (J.Am.Chem.Soc. 131, 6874, 2009). Our revealed control of magnetism in a wide range of nanomaterials may open up new vistas towards spintronics.

  16. Optically tunable chiral nematic mesoporous cellulose films.

    PubMed

    Schlesinger, Maik; Hamad, Wadood Y; MacLachlan, Mark J

    2015-06-21

    Demand for sustainable functional materials has never been larger. The introduction of functionality into pure cellulose might be one step forward in this field as it is one of the most abundant natural biopolymers. In this paper, we demonstrate a straightforward and scalable way to produce iridescent, mesoporous cellulose membranes with tunable colors and porosity. Concomitant assembly of cellulose nanocrystals (CNCs) and condensation of silica precursors results in CNC-silica composites with chiral nematic structures and tunable optical properties. Removal of the stabilizing silica matrix by alkaline or acid treatment gives access to novel chiral nematic mesoporous cellulose (CNMC) films. Importantly, the optical properties and the mesoporosity can be controlled by either varying the silica-to-CNC ratio, or by varying the substrate used during the evaporation-induced self-assembly process. In order to introduce additional functionality, CNMC has been used to stabilize gold nanoparticles with three different concentrations by wet impregnation. These materials are stable in water and can potentially function in sensors, tissue engineering or functional membranes. PMID:25972020

  17. Silver nanoparticles with tunable work functions

    SciTech Connect

    Wang, Pangpang; Tanaka, Daisuke; Ryuzaki, Sou; Araki, Shohei; Okamoto, Koichi; Tamada, Kaoru

    2015-10-12

    To improve the efficiencies of electronic devices, materials with variable work functions are required to decrease the energy level differences at the interfaces between working layers. Here, we report a method to obtain silver nanoparticles with tunable work functions, which have the same silver core of 5 nm in diameter and are capped by myristates and 1-octanethoilates self-assembled monolayers, respectively. The silver nanoparticles capped by organic molecules can form a uniform two-dimensional sheet at air-water interface, and the sheet can be transferred on various hydrophobic substrates. The surface potential of the two-dimensional nanoparticle sheet was measured in terms of Kelvin probe force microscopy, and the work function of the sheet was then calculated from the surface potential value by comparing with a reference material. The exchange of the capping molecules results in a work function change of approximately 150–250 meV without affecting their hydrophobicity. We systematically discussed the origin of the work function difference and found it should come mainly from the anchor groups of the ligand molecules. The organic molecule capped nanoparticles with tunable work functions have a potential for the applications in organic electronic devices.

  18. MMTF: THE MARYLAND-MAGELLAN TUNABLE FILTER

    SciTech Connect

    Veilleux, S.; Weiner, B. J.; Rupke, D. S. N. E-mail: bjw@as.arizona.edu

    2010-01-15

    This paper describes the Maryland-Magellan Tunable Filter (MMTF) on the Magellan-Baade 6.5 m telescope. MMTF is based on a 150 mm clear aperture Fabry-Perot (FP) etalon that operates in low orders and provides transmission bandpass and central wavelength adjustable from {approx}5 A to {approx}15 A and from {approx}5000 A to over {approx}9200 A, respectively. It is installed in the Inamori Magellan Areal Camera and Spectrograph and delivers an image quality of {approx}0.''5 over a field of view of 27' in diameter (monochromatic over {approx}10'). This versatile and easy-to-operate instrument has been used over the past three years for a wide variety of projects. This paper first reviews the basic principles of FP tunable filters, and then provides a detailed description of the hardware and software associated with MMTF and the techniques developed to observe with this instrument and reduce the data. The main lessons learned in the course of the commissioning and implementation of MMTF are highlighted next, before concluding with a brief outlook on the future of MMTF and of similar facilities which are soon coming on line.

  19. Tunable Magnetic Resonance via Interlayer Exchange Interaction

    NASA Astrophysics Data System (ADS)

    Chen, Yunpeng; Fan, Xin; Xie, Yunsong; Wilson, Jeffrey; Simons, Rainee; Chui, Sui-Tat; Xiao, John

    Magnetic resonance is a critical property of magnetic materials for the applications in microwave devices and novel spintronics devices. The resonance frequency is commonly controlled with an external magnetic field generated by an energy-inefficient and bulky electromagnet. The search for tuning the resonance frequency without electromagnets has attracted tremendous attention. The voltage control of resonance frequency has been demonstrated in multiferroic heterostructures through magnetoelastic effect. However, the frequency tunable range is limited. We propose a paradigm to tune the magnetic resonance frequency by recognizing the huge interlayer exchange field and the existence of the high-frequency modes in coupled oscillators. We demonstrate the optical mode in exchange coupled magnetic layers which occurred at much higher frequencies than coherent ferromagnetic resonance. We further demonstrated a large resonance frequency tunable range from 11GHz to 21 GHz in a spin valve device by in-situ manipulating of the exchange interaction. The technique developed here is far more efficient than the conventional methods of using electromagnets and multiferroics. This new scheme will have an immediate impact on applications based on magnetic resonance.

  20. Fine droplet generation using tunable electrohydrodynamic pulsation

    NASA Astrophysics Data System (ADS)

    Yuan, Xin; Ba, Zhengyu; Xiong, Zhenhua

    2015-07-01

    High-efficiency generation of fine droplets is significant for many microfluidic chips and sensor applications. To produce fine droplets, nozzles with small diameters are needed, which results in a high cost for nozzles and low efficiency of droplet generation. In this paper, a tunable electrohydrodynamic pulsation method which can generate fine droplets with high frequency and controllable size is presented using low conductivity liquids. The effects of flow rates and voltage parameters with respect to deposition frequency and droplet size are investigated. The influence of these parameters on Taylor cone formation time are also discussed and simple scaling laws are proposed to reveal and guide the droplet generation process. Experimental results show that single cycle deposition frequency decreases with increasing voltage frequency, but is only slightly influenced by the flow rates. The droplet size also decreases with voltage frequency, while large flow rates can make this decline gradual allowing better control. Moreover, the Taylor cone formation time may greatly affect the stability of the deposition frequency when the voltage frequency is larger than 30 Hz. Due to the short cycle time of high voltage frequencies, the hydrodynamic behavior in the emission process may be considerably affected by the increase of volume, which is also related to the flow rates. Tunable micropatterns consisting of fine droplets can be achieved by using this method in combination with motion stages.

  1. MMTF: The Maryland-Magellan Tunable Filter

    NASA Astrophysics Data System (ADS)

    Veilleux, S.; Weiner, B. J.; Rupke, D. S. N.; McDonald, M.; Birk, C.; Bland-Hawthorn, J.; Dressler, A.; Hare, T.; Osip, D.; Pietraszewski, C.; Vogel, S. N.

    2010-01-01

    This paper describes the Maryland-Magellan Tunable Filter (MMTF) on the Magellan-Baade 6.5 m telescope. MMTF is based on a 150 mm clear aperture Fabry-Perot (FP) etalon that operates in low orders and provides transmission bandpass and central wavelength adjustable from ~5 Å to ~15 Å and from ~5000 Å to over ~9200 Å, respectively. It is installed in the Inamori Magellan Areal Camera and Spectrograph and delivers an image quality of ~0farcs5 over a field of view of 27' in diameter (monochromatic over ~10'). This versatile and easy-to-operate instrument has been used over the past three years for a wide variety of projects. This paper first reviews the basic principles of FP tunable filters, and then provides a detailed description of the hardware and software associated with MMTF and the techniques developed to observe with this instrument and reduce the data. The main lessons learned in the course of the commissioning and implementation of MMTF are highlighted next, before concluding with a brief outlook on the future of MMTF and of similar facilities which are soon coming on line.

  2. Tunable Antireflection Layers for Planar Bolometer Arrays

    NASA Technical Reports Server (NTRS)

    Brown, Ari-David; Chuss, David; Woolack, Edward; Chervenak, James; Henry, Ross; Wray, James

    2007-01-01

    It remains a challenge to obtain high-efficiency coupling of far-infrared through millimeter radiation to large-format detector arrays. The conventional approach of increasing detector coupling is to use reflective backshorts. However, this approach often results in excessive systematic errors resulting from reflections off the backshort edge. An alternate approach to both increasing quantum efficiency and reducing systematics associated with stray light is to place an antireflective coating near the front surface of the array. When incorporated with a resistive layer and placed behind the detector focal plane, the AR coating can serve to prevent optical ghosting by capturing radiation transmitted through the detector. By etching a hexagonal pattern in silicon, in which the sizes of the hexes are smaller than the wavelength of incident radiation, it is possible to fabricate a material that has a controllable dielectric constant, thereby allowing for simple tunable optical device fabrication. To this end, we have fabricated and tested tunable silicon "honeycomb" AR layers and AR/resistive layer devices. These devices were fabricated entirely out of silicon in order to eliminate problems associated with differential contraction upon detector cooling.

  3. Highly Tunable Colloidal Perovskite Nanoplatelets through Variable Cation, Metal, and Halide Composition.

    PubMed

    Weidman, Mark C; Seitz, Michael; Stranks, Samuel D; Tisdale, William A

    2016-08-23

    Colloidal perovskite nanoplatelets are a promising class of semiconductor nanomaterials-exhibiting bright luminescence, tunable and spectrally narrow absorption and emission features, strongly confined excitonic states, and facile colloidal synthesis. Here, we demonstrate the high degree of spectral tunability achievable through variation of the cation, metal, and halide composition as well as nanoplatelet thickness. We synthesize nanoplatelets of the form L2[ABX3]n-1BX4, where L is an organic ligand (octylammonium, butylammonium), A is a monovalent metal or organic molecular cation (cesium, methylammonium, formamidinium), B is a divalent metal cation (lead, tin), X is a halide anion (chloride, bromide, iodide), and n-1 is the number of unit cells in thickness. We show that variation of n, B, and X leads to large changes in the absorption and emission energy, while variation of the A cation leads to only subtle changes but can significantly impact the nanoplatelet stability and photoluminescence quantum yield (with values over 20%). Furthermore, mixed halide nanoplatelets exhibit continuous spectral tunability over a 1.5 eV spectral range, from 2.2 to 3.7 eV. The nanoplatelets have relatively large lateral dimensions (100 nm to 1 μm), which promote self-assembly into stacked superlattice structures-the periodicity of which can be adjusted based on the nanoplatelet surface ligand length. These results demonstrate the versatility of colloidal perovskite nanoplatelets as a material platform, with tunability extending from the deep-UV, across the visible, into the near-IR. In particular, the tin-containing nanoplatelets represent a significant addition to the small but increasingly important family of lead- and cadmium-free colloidal semiconductors. PMID:27471862

  4. Tunable thermoelectric transport in nanomeshes via elastic strain engineering

    SciTech Connect

    Piccione, Brian; Gianola, Daniel S.

    2015-03-16

    Recent experimental explorations of silicon nanomeshes have shown that the unique metastructures exhibit reduced thermal conductivity while preserving bulk electrical conductivity via feature sizes between relevant phonon and electron mean free paths, aiding in the continued promise that nanometer-scale engineering may further enhance thermoelectric behavior. Here, we introduce a strategy for tuning thermoelectric transport phenomena in semiconductor nanomeshes via heterogeneous elastic strain engineering, using silicon as a model material for demonstration of the concept. By combining analytical models for electron mobility in uniformly stressed silicon with finite element analysis of strained silicon nanomeshes in a lumped physical model, we show that the nonuniform and multiaxial strain fields defined by the nanomesh geometry give rise to spatially varying band shifts and warping, which in aggregate accelerate electron transport along directions of applied stress. This allows for global electrical conductivity and Seebeck enhancements beyond those of homogenous samples under equivalent far-field stresses, ultimately increasing thermoelectric power factor nearly 50% over unstrained samples. The proposed concept and structures—generic to a wide class of materials with large dynamic ranges of elastic strain in nanoscale volumes—may enable a new pathway for active and tunable control of transport properties relevant to waste heat scavenging and thermal management.

  5. Tunable thermoelectric transport in nanomeshes via elastic strain engineering

    NASA Astrophysics Data System (ADS)

    Piccione, Brian; Gianola, Daniel S.

    2015-03-01

    Recent experimental explorations of silicon nanomeshes have shown that the unique metastructures exhibit reduced thermal conductivity while preserving bulk electrical conductivity via feature sizes between relevant phonon and electron mean free paths, aiding in the continued promise that nanometer-scale engineering may further enhance thermoelectric behavior. Here, we introduce a strategy for tuning thermoelectric transport phenomena in semiconductor nanomeshes via heterogeneous elastic strain engineering, using silicon as a model material for demonstration of the concept. By combining analytical models for electron mobility in uniformly stressed silicon with finite element analysis of strained silicon nanomeshes in a lumped physical model, we show that the nonuniform and multiaxial strain fields defined by the nanomesh geometry give rise to spatially varying band shifts and warping, which in aggregate accelerate electron transport along directions of applied stress. This allows for global electrical conductivity and Seebeck enhancements beyond those of homogenous samples under equivalent far-field stresses, ultimately increasing thermoelectric power factor nearly 50% over unstrained samples. The proposed concept and structures—generic to a wide class of materials with large dynamic ranges of elastic strain in nanoscale volumes—may enable a new pathway for active and tunable control of transport properties relevant to waste heat scavenging and thermal management.

  6. [Infrared tunable difference frequency laser source]. Final technical report, September 15, 1990--September 14, 1992

    SciTech Connect

    Curl, R.F.

    1992-01-01

    Purpose of grant was to purchase equipment necessary to construct an infrared laser source based on difference frequency generation in AgGaS[sub 2]. This continuous wave, single frequency, tunable infrared source has been assembled and is being used for infrared kinetic spectroscopy of small free radicals important in combustion. Infrared spectra are given for the Q-branch of a combination band (11[sup 1]1) of N[sub 2]O, and for the transient in CO produced by flash photolysis of acetone in various vibrational states.

  7. [Infrared tunable difference frequency laser source]. Final technical report, September 15, 1990--September 14, 1992

    SciTech Connect

    Curl, R.F.

    1992-12-31

    Purpose of grant was to purchase equipment necessary to construct an infrared laser source based on difference frequency generation in AgGaS{sub 2}. This continuous wave, single frequency, tunable infrared source has been assembled and is being used for infrared kinetic spectroscopy of small free radicals important in combustion. Infrared spectra are given for the Q-branch of a combination band (11{sup 1}1) of N{sub 2}O, and for the transient in CO produced by flash photolysis of acetone in various vibrational states.

  8. Tunable Real Space Transfer Oscillator by Delayed Feedback Control of Chaos

    NASA Astrophysics Data System (ADS)

    Cooper, D. P.; Schöll, E.

    1995-03-01

    It is demonstrated numerically that by using Pyragas' method of chaos self-control a stable semiconductor oscillator can be designed based on driven real-space transfer oscillations in a modulation-doped heterostructure. By application of a small time-continuous delayed feedback voltage control signal, different unstable periodic orbits embedded in the chaotic attractor can be stabilized. Thus different modes of self-generated periodic voltage oscillations can be selected by choosing an appropriate delay time. This provides tunability to different discrete frequencies.

  9. Broadly tunable, low timing jitter, high repetition rate optoelectronic comb generator

    PubMed Central

    Metcalf, A. J.; Quinlan, F.; Fortier, T. M.; Diddams, S. A.; Weiner, A. M.

    2016-01-01

    We investigate the low timing jitter properties of a tunable single-pass optoelectronic frequency comb generator. The scheme is flexible in that both the repetition rate and center frequency can be continuously tuned. When operated with 10 GHz comb spacing, the integrated residual pulse-to-pulse timing jitter is 11.35 fs (1 Hz to 10 MHz) with no feedback stabilization. The corresponding phase noise at 1 Hz offset from the photodetected 10 GHz carrier is −100 dBc/Hz. PMID:26865734

  10. Tunable-Sized Polymeric Micelles and Their Assembly for the Preparation of Large Mesoporous Platinum Nanoparticles.

    PubMed

    Jiang, Bo; Li, Cuiling; Tang, Jing; Takei, Toshiaki; Kim, Jung Ho; Ide, Yusuke; Henzie, Joel; Tominaka, Satoshi; Yamauchi, Yusuke

    2016-08-16

    Platinum nanoparticles with continuously tunable mesoporous structures were prepared by a simple, one-step polymeric approach. By virtue of their large pore size, these structures have a high surface area that is accessible to reagents. In the synthetic method, variation of the solvent composition plays an essential role in the systematic control of pore size and particle shape. The mesoporous Pt catalyst exhibited superior electrocatalytic activity for the methanol oxidation reaction compared to commercially available Pt catalysts. This polymeric-micelle approach provides an additional design concept for the creation of next generation of metallic catalysts. PMID:27439561

  11. Type II InAs/GaAsSb quantum dots: Highly tunable exciton geometry and topology

    SciTech Connect

    Llorens, J. M.; Wewior, L.; Cardozo de Oliveira, E. R.; Alén, B.; Ulloa, J. M.; Utrilla, A. D.; Guzmán, A.; Hierro, A.

    2015-11-02

    External control over the electron and hole wavefunctions geometry and topology is investigated in a p-i-n diode embedding a dot-in-a-well InAs/GaAsSb quantum structure with type II band alignment. We find highly tunable exciton dipole moments and largely decoupled exciton recombination and ionization dynamics. We also predicted a bias regime where the hole wavefunction topology changes continuously from quantum dot-like to quantum ring-like as a function of the external bias. All these properties have great potential in advanced electro-optical applications and in the investigation of fundamental spin-orbit phenomena.

  12. Broadly tunable KNbO3 OPOs pumped by Ti:sapphire lasers

    NASA Astrophysics Data System (ADS)

    Vezin, Brigitte; Rambaldi, Patrick; Douard, M.; Rytz, Daniel; Wolf, Jean-Pierre

    1997-05-01

    We present the first broadly tunable KNbO3 OPO in tracking-free configuration (TFC), pumped by a flashlamp- pumped Ti:Sapphire laser. Tuning the pump laser from 733 to 841 nm yielded to an OPO tuning range from 908 nm to 1402 nm for the signal, and 2103 to 3803 nm for the idler. This range was limited by the mirror coatings, and continuous tuning should be achievable up to and beyond 400 nm. Threshold was as low as 15 MW/cm2 and efficiencies up to 10% have been observed without AR-coatings on the crystal.

  13. Electrically tunable liquid-crystal wave plate using quadripolar electrode configuration and transparent conductive polymer layers.

    PubMed

    Fraval, Nicolas; Joffre, Pascal; Formont, Stéphane; Chazelas, Jean

    2009-10-01

    We present the realization of an electrically tunable wave plate, which uses a nematic liquid-crystal (LC) phase retarder that allows fast and continuous control of the polarization state. This device is built using a quadripolar electrode design and transparent conductive polymer layers in order to obtain a uniform electric field distribution in the interelectrode area. With this realization, we obtain a high degree of control of the orientation of the electric field and, consequently, of the LC director. Indeed, this modulator outperforms classical bipolar LC cells in both optical path variation (>4 microm) and LC rotation speed (0.4 degrees/micros). PMID:19798369

  14. Chiral THz metamaterial with tunable optical activity

    SciTech Connect

    Zhou, Jiangfeng; Taylor, Antoinette; O' Hara, John; Chowdhury, Roy; Zhao, Rongkuo; Soukoullis, Costas M

    2010-01-01

    Optical activity in chiral metamaterials is demonstrated in simulation and shows actively tunable giant polarization rotation at THz frequencies. Electric current distributions show that pure chirality is achieved by our bi-Iayer chiral metamaterial design. The chirality can be optically controlled by illumination with near-infrared light. Optical activity, occurring in chiral materials such as DNA, sugar and many other bio-molecules, is a phenomenon of great importance to many areas of science including molecular biology, analytical chemistry, optoelectronics and display applications. This phenomenon is well understood at an effective medium level as a magnetic/electric moment excited by the electric/magnetic field of the incident electromagnetic (EM) wave. Usually, natural chiral materials exhibit very weak optical activity e.g. a gyrotropic quartz crystal. The optical activity of chiral metamaterials, however, can be five orders of magnitude stronger. Chiral metamaterials are made of sub-wavelength resonators lacking symmetry planes. The asymmetry allows magnetic moments to be excited by the electric field of the incident EM wave and vice versa. Recently, chiral metamaterials have been demonstrated and lead to prospects in giant optical activity, circular dichroism, negative refraction and reversing the Casmir force. These fascinating optical properties require strong chirality, which may be designed through the microscopic structure of chiral metamaterials. However, these metamaterials have a fixed response function, defined by the geometric structuring, which limits their ability to manipulate EM waves. Active metamaterials realize dynamic control of response functions and have produced many influential applications such as ultra-fast switching devices, frequency and phase modulation and memory devices. Introducing active designs to chiral metamaterials will give additional freedom in controlling the optical activity, and therefore enable dynamic manipulation

  15. Asymmetric and connected graphene dimers for a tunable plasmonic response

    NASA Astrophysics Data System (ADS)

    Rosolen, G.; Maes, B.

    2015-11-01

    We investigate the infrared response of graphene dimers with various doping and polarization configurations. The interaction between the plasmonic resonances of graphene nanodisks leads to a rich, tunable behavior. The hybridization of the nanodisk modes enables the excitation of resonances that would be invisible or dark in a single disk. The simulation results show various anticrossings that depend on dark-bright or bright-bright mode coupling, which we can describe via a simple Hamiltonian model. In addition, we determine the response of a dimer bridged by a tunable graphene junction. This structure leads to charge transfer plasmons, with an even higher absorption efficiency and tunability than nonbridged dimers.

  16. Microwave photonic comb filter with ultra-fast tunability.

    PubMed

    Jiang, H Y; Yan, L S; Pan, Y; Pan, W; Luo, B; Zou, X H; Eggleton, B J

    2015-11-01

    A microwave comb filter with ultra-fast tunability is proposed based on the fundamental delay-line microwave photonic filter. The central frequency of the passband or stopband in such a filter can be rapidly adjusted, along with the independent tunability of the free spectral range (FSR). Experimental results show that the central frequency of the transfer function is electronically tuned with a frequency difference of half of the FSR at a speed of <100  ps. Such high-speed tunability is vital for high-speed microwave switching, frequency hopping, cognitive radio, and next-generation radar systems. PMID:26512477

  17. Tunable plasmon-induced transparency with graphene-sheet structure

    NASA Astrophysics Data System (ADS)

    Wang, Yueke; Shen, Xinru; Chen, Quansheng

    2016-07-01

    We investigate theoretically and numerically the tunable plasmon-induced transparency (PIT) phenomenon in graphene-sheet system in infrared range. We show that when surface plasmon polaritons (SPPs) propagate along a monolayer graphene sheet with two detuned side-coupled resonators, the PIT-like transmission spectra of SPPs appear. Thanks to the tunable permittivity of graphene by bias voltages, the resonant wavelength of side-coupled resonators can be changed. So the transmission spectra can be tuned dynamically and the tunable PIT phenomenon is achieved. Numerical simulation by finite element method is conducted to verify our design.

  18. A Compact Ring Design with Tunable Momentum Compaction

    SciTech Connect

    Sun, Y.; /SLAC

    2012-05-17

    A storage ring with tunable momentum compaction has the advantage in achieving different RMS bunch length with similar RF capacity, which is potentially useful for many applications, such as linear collider damping ring and predamping ring where injected beam has a large energy spread and a large transverse emittance. A tunable bunch length also makes the commissioning and fine tuning easier in manipulating the single bunch instabilities. In this paper, a compact ring design based on a supercell is presented, which achieves a tunable momentum compaction while maintaining a large dynamic aperture.

  19. Optically pumped type-II mid-infrared tunable distributed feedback lasers

    NASA Astrophysics Data System (ADS)

    He, Xiang

    Optically-pumped type-II mid-infrared index-coupled tunable distributed feed-back (DFB) semiconductor lasers have been developed to provide continuous-wave (CW) single longitudinal mode (SLM) operation with features including narrow spectral linewidth, high output power, good beam quality and wide continuous wavelength tunability for applications such as remote sensing or spectroscopy in the 3 to 5 microm midwave-infrared range of atmospheric transmission window. In the demonstration of this type of laser, a hyperbolically chirped grating was patterned using interferometric lithography (IL) with spherical wavefronts which was then transferred into the top clad of the slab waveguide epi-structure of the laser device. Wavelength tuning is achieved by translationally projecting pump stripe at different positions of this chirped grating on the laser device, thus different grating periods along the pump stripe at different pump positions select different lasing wavelengths. Primary results were acquired on one device of 4 mm in lateral dimension with continuously tuning range of about 80 nm centered at 3100 nm, single facet output power of 830 mW and typical spectral linewidth of 1.2 nm at 2.5xthreshold pumping. Fabry-Perot (F-P) interferometer was used as artificial target gas to demonstrate potential application of gas spectroscopy with this type of laser.

  20. A tunable microwave plasma photonic crystal filter

    SciTech Connect

    Wang, B.; Cappelli, M. A.

    2015-10-26

    The integration of gaseous plasma elements into a microwave photonic crystal band gap cavity structure allows for active tuning of the device. An alumina rod array microwave photonic crystal waveguide resonator is simulated and characterized through finite difference time domain methods. A gaseous plasma element is integrated into the cavity structure and the effect of plasma density on the transmission properties of the structure is investigated. We show, through both simulations and experiments, that the permittivity of the plasma can be adjusted to shift the peak resonance to allow for both switching and tunability of transmission. The experimentally measured peak shifts in transmission are compared to those simulated and the electron density of the gaseous plasma element is calculated and compared to values determined from the measured discharge current density.

  1. Plasmonic spectral tunability of conductive ternary nitrides

    NASA Astrophysics Data System (ADS)

    Kassavetis, S.; Bellas, D. V.; Abadias, G.; Lidorikis, E.; Patsalas, P.

    2016-06-01

    Conductive binary transition metal nitrides, such as TiN and ZrN, have emerged as a category of promising alternative plasmonic materials. In this work, we show that ternary transition metal nitrides such as TixTa1-xN, TixZr1-xN, TixAl1-xN, and ZrxTa1-xN share the important plasmonic features with their binary counterparts, while having the additional asset of the exceptional spectral tunability in the entire visible (400-700 nm) and UVA (315-400 nm) spectral ranges depending on their net valence electrons. In particular, we demonstrate that such ternary nitrides can exhibit maximum field enhancement factors comparable with gold in the aforementioned broadband range. We also critically evaluate the structural features that affect the quality factor of the plasmon resonance and we provide rules of thumb for the selection and growth of materials for nitride plasmonics.

  2. Tunable unidirectional scattering of ellipsoidal single nanoparticle

    NASA Astrophysics Data System (ADS)

    Reena, Kalra, Yogita; Kumar, Ajeet; Sinha, R. K.

    2016-06-01

    We report unidirectional scattering by tri-axial single ellipsoidal dielectric nanoparticle, which is applicable in the design and development of tunable, low-loss and ultra-compact nanoantennas. Based on the orientation and rotation of the ellipsoidal nanoparticle, three types of modes, one longitudinal mode and two transverse modes, have been excited. Electric and magnetic dipoles have been optically induced in the nanoparticle. Generalized Kerker's conditions have been applied at the interference of optically induced electric and magnetic dipoles. Azimuthally symmetric forward scattering with complete suppression of backward scattering using first Generalized Kerker's condition has been achieved at three different wavelengths for the allowed longitudinal mode and transverse modes in the optical region using single ellipsoidal nanoparticle. Due to 3-fold symmetry, forward scattering can be tuned at different wavelengths, using single ellipsoidal nanoparticle just by changing the direction of the incident electric field.

  3. Tunable Magnetic Resonance in Microwave Spintronics Devices

    NASA Technical Reports Server (NTRS)

    Chen, Yunpeng; Fan, Xin; Xie, Yungsong; Zhou, Yang; Wang, Tao; Wilson, Jeffrey D.; Simons, Rainee N.; Chui, Sui-Tat; Xiao, John Q.

    2015-01-01

    Magnetic resonance is one of the key properties of magnetic materials for the application of microwave spintronics devices. The conventional method for tuning magnetic resonance is to use an electromagnet, which provides very limited tuning range. Hence, the quest for enhancing the magnetic resonance tuning range without using an electromagnet has attracted tremendous attention. In this paper, we exploit the huge exchange coupling field between magnetic interlayers, which is on the order of 4000 Oe and also the high frequency modes of coupled oscillators to enhance the tuning range. Furthermore, we demonstrate a new scheme to control the magnetic resonance frequency. Moreover, we report a shift in the magnetic resonance frequency as high as 20 GHz in CoFe-based tunable microwave spintronics devices, which is 10X higher than conventional methods.

  4. Tunable Magnetic Resonance in Microwave Spintronics Devices

    NASA Technical Reports Server (NTRS)

    Chen, Yunpeng; Fan, Xin; Xie, Yunsong; Zhou, Yang; Wang, Tao; Wilson, Jeffrey D.; Simons, Rainee N.; Chui, Sui-Tat; Xiao, John Q.

    2015-01-01

    Magnetic resonance is one of the key properties of magnetic materials for the application of microwave spintronics devices. The conventional method for tuning magnetic resonance is to use an electromagnet, which provides very limited tuning range. Hence, the quest for enhancing the magnetic resonance tuning range without using an electromagnet has attracted tremendous attention. In this paper, we exploit the huge exchange coupling field between magnetic interlayers, which is on the order of 4000 Oe and also the high frequency modes of coupled oscillators to enhance the tuning range. Furthermore, we demonstrate a new scheme to control the magnetic resonance frequency. Moreover, we report a shift in the magnetic resonance frequency as high as 20 GHz in CoFe based tunable microwave spintronics devices, which is 10X higher than conventional methods.

  5. Spectral tunability of realistic plasmonic nanoantennas

    SciTech Connect

    Portela, Alejandro; Matsui, Hiroaki; Tabata, Hitoshi; Yano, Takaaki; Hayashi, Tomohiro; Hara, Masahiko; Santschi, Christian; Martin, Olivier J. F.

    2014-09-01

    Single nanoantenna spectroscopy was carried out on realistic dipole nanoantennas with various arm lengths and gap sizes fabricated by electron-beam lithography. A significant difference in resonance wavelength between realistic and ideal nanoantennas was found by comparing their spectral response. Consequently, the spectral tunability (96 nm) of the structures was significantly lower than that of simulated ideal nanoantennas. These observations, attributed to the nanofabrication process, are related to imperfections in the geometry, added metal adhesion layer, and shape modifications, which are analyzed in this work. Our results provide important information for the design of dipole nanoantennas clarifying the role of the structural modifications on the resonance spectra, as supported by calculations.

  6. Switchable and Tunable Aerodynamic Drag on Cylinders

    NASA Astrophysics Data System (ADS)

    Guttag, Mark; Lopez Jimenez, Francisco; Reis, Pedro

    2015-11-01

    We report results on the performance of Smart Morphable Surfaces (Smporhs) that can be mounted onto cylindrical structures to actively reduce their aerodynamic drag. Our system comprises of an elastomeric thin shell with a series of carefully designed subsurface cavities that, once depressurized, lead to a dramatic deformation of the surface topography, on demand. Our design is inspired by the morphology of the giant cactus (Carnegiea gigantea) which possesses an array of axial grooves, which are thought to help reduce aerodynamic drag, thereby enhancing the structural robustness of the plant under wind loading. We perform systematic wind tunnel tests on cylinders covered with our Smorphs and characterize their aerodynamic performance. The switchable and tunable nature of our system offers substantial advantages for aerodynamic performance when compared to static topographies, due to their operation over a wider range of flow conditions.

  7. Switchable and Tunable Aerodynamic Drag on Cylinders

    NASA Astrophysics Data System (ADS)

    Guttag, Mark; Lopéz Jiménez, Francisco; Upadhyaya, Priyank; Kumar, Shanmugam; Reis, Pedro

    We report results on the performance of Smart Morphable Surfaces (Smporhs) that can be mounted onto cylindrical structures to actively reduce their aerodynamic drag. Our system comprises of an elastomeric thin shell with a series of carefully designed subsurface cavities that, once depressurized, lead to a dramatic deformation of the surface topography, on demand. Our design is inspired by the morphology of the giant cactus (Carnegiea gigantea) which possesses an array of axial grooves, thought to help reduce aerodynamic drag, thereby enhancing the structural robustness of the plant under wind loading. We perform systematic wind tunnel tests on cylinders covered with our Smorphs and characterize their aerodynamic performance. The switchable and tunable nature of our system offers substantial advantages for aerodynamic performance when compared to static topographies, due to their operation over a wider range of flow conditions.

  8. Protein separation using an electrically tunable membrane

    NASA Astrophysics Data System (ADS)

    Jou, Ining; Melnikov, Dmitriy; Gracheva, Maria

    Separation of small proteins by charge with a solid-state porous membrane requires control over the protein's movement. Semiconductor membrane has this ability due to the electrically tunable electric potential profile inside the nanopore. In this work we investigate the possibility to separate the solution of two similar sized proteins by charge. As an example, we consider two small globular proteins abundant in humans: insulin (negatively charged) and ubiquitin (neutral). We find that the localized electric field inside the pore either attracts or repels the charged protein to or from the pore wall which affects the delay time before a successful translocation of the protein through the nanopore. However, the motion of the uncharged ubiquitin is unaffected. The difference in the delay time (and hence the separation) can be further increased by the application of the electrolyte bias which induces an electroosmotic flow in the pore. NSF DMR and CBET Grant No. 1352218.

  9. Electro-optical tunable birefringent filter

    SciTech Connect

    Levinton, Fred M.

    2012-01-31

    An electrically tunable Lyot type filter is a Lyot that include one or more filter elements. Each filter element may have a planar, solid crystal comprised of a material that exhibits birefringence and is electro-optically active. Transparent electrodes may be coated on each face of the crystal. An input linear light polarizer may be located on one side of the crystal and oriented at 45 degrees to the optical axis of the birefringent crystal. An output linear light polarizer may be located on the other side of the crystal and oriented at -45 degrees with respect to the optical axis of the birefringent crystal. When an electric voltage is applied between the electrodes, the retardation of the crystal changes and so does the spectral transmission of the optical filter.

  10. Tunable lifetime multiplexing using luminescent nanocrystals

    NASA Astrophysics Data System (ADS)

    Lu, Yiqing; Zhao, Jiangbo; Zhang, Run; Liu, Yujia; Liu, Deming; Goldys, Ewa M.; Yang, Xusan; Xi, Peng; Sunna, Anwar; Lu, Jie; Shi, Yu; Leif, Robert C.; Huo, Yujing; Shen, Jian; Piper, James A.; Robinson, J. Paul; Jin, Dayong

    2014-01-01

    Optical multiplexing plays an important role in applications such as optical data storage, document security, molecular probes and bead assays for personalized medicine. Conventional fluorescent colour coding is limited by spectral overlap and background interference, restricting the number of distinguishable identities. Here, we show that tunable luminescent lifetimes τ in the microsecond region can be exploited to code individual upconversion nanocrystals. In a single colour band, one can generate more than ten nanocrystal populations with distinct lifetimes ranging from 25.6 µs to 662.4 µs and decode their well-separated lifetime identities, which are independent of both colour and intensity. Such `τ-dots' potentially suit multichannel bioimaging, high-throughput cytometry quantification, high-density data storage, as well as security codes to combat counterfeiting. This demonstration extends the optical multiplexing capability by adding the temporal dimension of luminescent signals, opening new opportunities in the life sciences, medicine and data security.

  11. Broad band tunable dye laser development

    NASA Astrophysics Data System (ADS)

    Lee, Jong Min; Kim, Jung Bog; Kim, Sung Ho; Go, Do Kyung; Lim, Chang Hwan; Rho, Si Pyo; Song, Kyu Seok; Lee, Byung Cheol; Rhi, Jong Hoon; Han, Jae Min

    1992-12-01

    The technical goal and objectives are the development of a tunable laser which can be tuned from UV to near IR and commercialization for uses in various fields. Two kinds of resonators are developed. The user can select one resonator and change into the other without changing other parts. GIM type has a linewidth of 5 GHz which is able to be used usually, and a SLM type which has a very narrow linewidth of less than 1 GHz. Each system can have one or two amplifiers depending on output power or cost. High stability and safety, cost-down, and modules into about 30 components have been tried. We hope that this laser can help developments in researches of university, industry, and institute.

  12. Highly stable piezoelectrically tunable optical cavities

    NASA Astrophysics Data System (ADS)

    Möhle, Katharina; Kovalchuk, Evgeny V.; Döringshoff, Klaus; Nagel, Moritz; Peters, Achim

    2013-05-01

    We have implemented highly stable and tunable frequency references using optical high finesse cavities which incorporate a piezo actuator. As piezo material we used ceramic PZT, crystalline quartz, or PZN-PT single crystals. Lasers locked to these cavities show a relative frequency stability better than 1× 10^{-14}, which is most likely not limited by the piezo actuators. The piezo cavities can be electrically tuned over more than one free spectral range (>1.5 GHz) with only a minor decrease in frequency stability. Furthermore, we present a novel cavity design, where the piezo actuator is prestressed between the cavity spacer components. This design features a hermetically sealable intra cavity volume suitable for, e.g., cavity enhanced spectroscopy.

  13. Stakeholder acceptance analysis: Tunable hybrid plasma

    SciTech Connect

    Peterson, T.

    1995-12-01

    This report resents evaluations, recommendations, and requirements concerning Tunable Hybrid Plasma (THP) derived from a three-year program of stake holder involvement. THP destroys volatile organic compounds by directing a moderate energy electron beam into a flow of air containing organic contaminants. This report is for technology developers and for those responsible for making decisions about the use of technology to remediate contamination by volatile organic compounds. Stakeholders` perspectives help those responsible for technology deployment make good decisions concerning the acceptability and applicability of THP to the remediation problems the face. In addition, this report presents data requirements for the technology`s field demonstration defined by stakeholders associated with the Hanford site in Washington State, as well as detailed comments on THP from stakeholders from four other sites throughout the western United States.

  14. Modulus-tunable magnetorheological elastomer microcantilevers

    NASA Astrophysics Data System (ADS)

    Lee, Dongkyu; Lee, Moonchan; Jung, Namchul; Yun, Minhyuk; Lee, Jungchul; Thundat, Thomas; Jeon, Sangmin

    2014-05-01

    Modulus-tunable microcantilevers are fabricated from magnetorheological elastomers (MREs) consisting of polydimethylsiloxane and carbonyl iron particles by using a simple sandwich molding method. Depending on the presence or absence of an external magnetic field during curing, isotropic or anisotropic MRE cantilevers are obtained. Randomly distributed particles are present in the polymer matrix of the isotropic microcantilevers, whereas the particles in the anisotropic microcantilevers are aligned in the direction of the magnetic field. The fractional changes in the resonance frequencies of the MRE cantilevers are measured as functions of the magnetic field intensity and the quantity of particles in the matrix. The anisotropic microcantilevers undergo greater changes in frequency than the isotropic microcantilevers when exposed to external magnetic fields, which indicates that larger changes in modulus are induced in the anisotropic microcantilevers. In addition, the dissipation and damping ratios of the MRE microcantilevers are determined by fitting the exponential decays of their deflection amplitudes with time.

  15. Electronic thermometry in tunable tunnel junction

    DOEpatents

    Maksymovych, Petro

    2016-03-15

    A tunable tunnel junction thermometry circuit includes a variable width tunnel junction between a test object and a probe. The junction width is varied and a change in thermovoltage across the junction with respect to the change in distance across the junction is determined. Also, a change in biased current with respect to a change in distance across the junction is determined. A temperature gradient across the junction is determined based on a mathematical relationship between the temperature gradient, the change in thermovoltage with respect to distance and the change in biased current with respect to distance. Thermovoltage may be measured by nullifying a thermoelectric tunneling current with an applied voltage supply level. A piezoelectric actuator may modulate the probe, and thus the junction width, to vary thermovoltage and biased current across the junction. Lock-in amplifiers measure the derivatives of the thermovoltage and biased current modulated by varying junction width.

  16. A tunable microwave plasma photonic crystal filter

    NASA Astrophysics Data System (ADS)

    Wang, B.; Cappelli, M. A.

    2015-10-01

    The integration of gaseous plasma elements into a microwave photonic crystal band gap cavity structure allows for active tuning of the device. An alumina rod array microwave photonic crystal waveguide resonator is simulated and characterized through finite difference time domain methods. A gaseous plasma element is integrated into the cavity structure and the effect of plasma density on the transmission properties of the structure is investigated. We show, through both simulations and experiments, that the permittivity of the plasma can be adjusted to shift the peak resonance to allow for both switching and tunability of transmission. The experimentally measured peak shifts in transmission are compared to those simulated and the electron density of the gaseous plasma element is calculated and compared to values determined from the measured discharge current density.

  17. 10 kW Tunable Ultrafast Laser

    SciTech Connect

    Michael Kelley

    2003-06-01

    Since the first demonstration in 1977 that laser-like light can be made by direct interaction of an electron beam with a tailored magnet array (wiggler), more than 30 free electron lasers have come into operation world-wide. Unique among them, the JLab FEL has already reliably delivered more than 2 kW of tunable picosecond light to users. An upgrade to more than 10 kW average power is underway for start-up in Spring '03 and first results are presented. Design and performance for a successor 100 kW plus FEL is described. The JLab FEL is available to users; see www.jab.org/FEL.

  18. Tunable surface properties from bioinspired polymers

    NASA Astrophysics Data System (ADS)

    van Zoelen, Wendy; Rosales, Adrianne; Murnen, Hannah; Zuckermann, Ronald; Segalman, Rachel

    2011-03-01

    Anti-fouling properties can be derived from patterned or ``ambiguous'' surfaces displaying multiple surface properties. Biological polymers with precisely controlled chain shapes and self-assembled structures are attractive materials for these applications, in which tunability is of great importance. We have investigated the surface properties of polypeptoids, a class of non-natural biomimetic polymers based on an N-substituted glycine backbone, that combine many of the advantageous properties of bulk polymers with those of synthetically produced proteins. Polypeptoids are of particular interest as they can be made in a sequence controlled fashion with functionalities already known to impart fouling-resistance (ethers, zwitterions, hydrophobicity, and nanoscale patterning). We demonstrate their surface stability and processibility from the standpoint of coating performance and also discuss controlled self-assembly of these materials. Used strategies include mediation of crystallization by incorporating chain defects and specific interactions.

  19. Tunable plasmonic lattices of silver nanocrystals

    SciTech Connect

    Tao, Andrea; Sinsermsuksakul, Prasert; Yang, Peidong

    2008-02-18

    Silver nanocrystals are ideal building blocks for plasmonicmaterials that exhibit a wide range of unique and potentially usefuloptical phenomena. Individual nanocrystals display distinct opticalscattering spectra and can be assembled into hierarchical structures thatcouple strongly to external electromagnetic fields. This coupling, whichis mediated by surface plasmons, depends on their shape and arrangement.Here we demonstrate the bottom-up assembly of polyhedral silvernanocrystals into macroscopic two-dimensional superlattices using theLangmuir-Blodgett technique. Our ability to control interparticlespacing, density, and packing symmetry allows for tunability of theoptical response over the entire visible range. This assembly strategyoffers a new, practical approach to making novel plasmonic materials forapplication in spectroscopic sensors, sub-wavelength optics, andintegrated devices that utilize field enhancement effects.

  20. Tunable lenses using transparent dielectric elastomer actuators.

    PubMed

    Shian, Samuel; Diebold, Roger M; Clarke, David R

    2013-04-01

    Focus tunable, adaptive lenses provide several advantages over traditional lens assemblies in terms of compactness, cost, efficiency, and flexibility. To further improve the simplicity and compact nature of adaptive lenses, we present an elastomer-liquid lens system which makes use of an inline, transparent electroactive polymer actuator. The lens requires only a minimal number of components: a frame, a passive membrane, a dielectric elastomer actuator membrane, and a clear liquid. The focal length variation was recorded to be greater than 100% with this system, responding in less than one second. Through the analysis of membrane deformation within geometrical constraints, it is shown that by selecting appropriate lens dimensions, even larger focusing dynamic ranges can be achieved. PMID:23571956

  1. Experimental demonstration of water based tunable metasurface

    NASA Astrophysics Data System (ADS)

    Odit, Mikhail; Kapitanova, Polina; Andryieuski, Andrei; Belov, Pavel; Lavrinenko, Andrei V.

    2016-07-01

    A simple dynamically tunable metasurface (two-dimensional metamaterial) operating at microwave frequencies is developed and experimentally investigated. Conceptually, the simplicity of the approach is granted by reconfigurable properties of unit cells partially filled with distilled water. The transmission spectra of the metasurface for linear and circular polarizations of the incident wave were experimentally measured under the metasurface rotation around a horizontal axis. The changes in the transmission coefficient magnitude up to 8 dB at 1.25 GHz are reported while rotating the metasurface by the 90° angle. The proposed approach manifests the cheap and accessible route for the electromagnetic wave control in the microwave region with the help of metasurfaces.

  2. Tunable VO2/Au hyperbolic metamaterial

    NASA Astrophysics Data System (ADS)

    Prayakarao, S.; Mendoza, B.; Devine, A.; Kyaw, C.; van Dover, R. B.; Liberman, V.; Noginov, M. A.

    2016-08-01

    Vanadium dioxide (VO2) is known to have a semiconductor-to-metal phase transition at ˜68 °C. Therefore, it can be used as a tunable component of an active metamaterial. The lamellar metamaterial studied in this work is composed of subwavelength VO2 and Au layers and is designed to undergo a temperature controlled transition from the optical hyperbolic phase to the metallic phase. VO2 films and VO2/Au lamellar metamaterial stacks have been fabricated and studied in electrical conductivity and optical (transmission and reflection) experiments. The observed temperature-dependent changes in the reflection and transmission spectra of the metamaterials and VO2 thin films are in a good qualitative agreement with theoretical predictions. The demonstrated optical hyperbolic-to-metallic phase transition is a unique physical phenomenon with the potential to enable advanced control of light-matter interactions.

  3. Nanostructured electrocatalysts with tunable activity and selectivity

    NASA Astrophysics Data System (ADS)

    Mistry, Hemma; Varela, Ana Sofia; Kühl, Stefanie; Strasser, Peter; Cuenya, Beatriz Roldan

    2016-04-01

    The field of electrocatalysis has undergone tremendous advancement in the past few decades, in part owing to improvements in catalyst design at the nanoscale. These developments have been crucial for the realization of and improvement in alternative energy technologies based on electrochemical reactions such as fuel cells. Through the development of novel synthesis methods, characterization techniques and theoretical methods, rationally designed nanoscale electrocatalysts with tunable activity and selectivity have been achieved. This Review explores how nanostructures can be used to control electrochemical reactivity, focusing on three model reactions: O2 electroreduction, CO2 electroreduction and ethanol electrooxidation. The mechanisms behind nanoscale control of reactivity are discussed, such as the presence of low-coordinated sites or facets, strain, ligand effects and bifunctional effects in multimetallic materials. In particular, studies of how particle size, shape and composition in nanostructures can be used to tune reactivity are highlighted.

  4. Interfaces with Tunable Mechanical and Radiosensitizing Properties.

    PubMed

    Berg, Nora G; Pearce, Brady L; Snyder, Patrick J; Rohrbaugh, Nathaniel; Nolan, Michael W; Adhikari, Prajesh; Khan, Saad A; Ivanisevic, Albena

    2016-08-31

    We report the fabrication of a composite containing nanostructured GaOOH and Matrigel with tunable radiosensitizing and stiffness properties. Composite characterization was done with microscopy and rheology. The utility of the interface was tested in vitro using fibroblasts. Cell viability and reactive oxygen species assays quantified the effects of radiation dosages and GaOOH concentrations. Fibroblasts' viability decreased with increasing concentration of GaOOH and composite stiffness. During ionizing radiation experiments the presence of the scintillating GaOOH triggered a different cellular response. Reactive oxygen species data demonstrated that one can reduce the amount of radiation needed to modulate the behavior of cells on interfaces with different stiffness containing a radiosensitizing material. PMID:26882455

  5. Tunable Broadband Printed Carbon Transparent Conductor

    NASA Astrophysics Data System (ADS)

    Xu, Yue; Wan, Jiayu

    Transparent conductors have been widely applied in solar cells, transparent smart skins, and sensing/imaging antennas, etc. Carbon-based transparent conductor has attracted great attention for its low cost and broad range transparency. Ion intercalation has been known to highly dope graphitic materials, thereby tuning materials' optoelectronic properties. For the first time, we successfully tune the optical transmittance of a reduced graphene oxide (RGO)/CNT network from mid-IR range to visible range by means of Li-ion intercalation/deintercalation. We also observed a simultaneous increase of the electrical conductivity with the Li-ion intercalation. This printed carbon hybrid thin film was prepared through all solution processes and was easily scalable. This study demonstrates the possibility of using ion intercalation for low cost, tunable broadband transparent conductors.

  6. Tunable hyperbolic metamaterials utilizing phase change heterostructures

    SciTech Connect

    Krishnamoorthy, Harish N. S.; Menon, Vinod M.; Zhou, You; Ramanathan, Shriram; Narimanov, Evgenii

    2014-03-24

    We present a metal-free tunable anisotropic metamaterial where the iso-frequency surface is tuned from elliptical to hyperbolic dispersion by exploiting the metal-insulator phase transition in the correlated material vanadium dioxide (VO{sub 2}). Using VO{sub 2}-TiO{sub 2} heterostructures, we demonstrate the transition in the effective dielectric constant parallel to the layers to undergo a sign change from positive to negative as the VO{sub 2} undergoes the phase transition. The possibility to tune the iso-frequency surface in real time using external perturbations such as temperature, voltage, or optical pulses creates new avenues for controlling light-matter interaction.

  7. Electronically tunable aperiodic distributed feedback terahertz lasers

    NASA Astrophysics Data System (ADS)

    Marshall, O. P.; Chakraborty, S.; Khairuzzaman, Md.; Folland, T.; Gholinia, A.; Beere, H. E.; Ritchie, D. A.

    2013-05-01

    Focussed ion beam milling can be used to introduce aperiodic distributed feedback (ADFB) gratings into fully packaged, operational terahertz (THZ) quantum cascade lasers to achieve electronically controlled, discretely tunable laser emission. These aperiodic gratings—designed using computer-generated hologram techniques—consist of multiple slits in the surface plasmon waveguide, distributed along the length of the laser cavity. Tuning behaviour and output power in ADFB lasers operating around 2.9 THz are investigated with a variety of slit dimensions and grating scales. Mode selectivity and grating losses are found to be strongly dependent on milling depth into the upper waveguide layers, dramatically increasing as the metallic layers are penetrated, then rising more slowly with deeper milling into the laser active region. Grating scale and placement along the laser cavity length are also shown to influence mode selection.

  8. Tunable plasticity in amorphous silicon carbide films.

    PubMed

    Matsuda, Yusuke; Kim, Namjun; King, Sean W; Bielefeld, Jeff; Stebbins, Jonathan F; Dauskardt, Reinhold H

    2013-08-28

    Plasticity plays a crucial role in the mechanical behavior of engineering materials. For instance, energy dissipation during plastic deformation is vital to the sufficient fracture resistance of engineering materials. Thus, the lack of plasticity in brittle hybrid organic-inorganic glasses (hybrid glasses) often results in a low fracture resistance and has been a significant challenge for their integration and applications. Here, we demonstrate that hydrogenated amorphous silicon carbide films, a class of hybrid glasses, can exhibit a plasticity that is even tunable by controlling their molecular structure and thereby leads to an increased and adjustable fracture resistance in the films. We decouple the plasticity contribution from the fracture resistance of the films by estimating the "work-of-fracture" using a mean-field approach, which provides some insight into a potential connection between the onset of plasticity in the films and the well-known rigidity percolation threshold. PMID:23876200

  9. Tunable focus graphene-based terahertz lens

    NASA Astrophysics Data System (ADS)

    Li, Jiu-Sheng

    2016-01-01

    To extend the usage of the terahertz wave, we present a simple method for variable focus length terahertz wave lens based on graphene. The focus length of the graphene-based terahertz lens can be tunable by changing the applied electric field without change the configuration. To demonstrate the feasibility of the approach, numerical simulation performed with the aid of the finite element method is used to evaluate the terahertz performance of the proposed device. With an appropriate design, the focal length of the proposed device can be tuned from 7.3 μm to 15.2 μm. The total size of the present graphene lens is only 3.5 μm×13 μm. It is believed to be applicable for future communication, imaging and sensing in terahertz range.

  10. Stretchable graphene thermistor with tunable thermal index.

    PubMed

    Yan, Chaoyi; Wang, Jiangxin; Lee, Pooi See

    2015-02-24

    Stretchable graphene thermistors with intrinsic high stretchability were fabricated through a lithographic filtration method. Three-dimensional crumpled graphene was used as the thermal detection channels, and silver nanowires were used as electrodes. Both the detection channel and electrodes were fully embedded in an elastomer matrix to achieve excellent stretchability. Detailed temperature sensing properties were characterized at different strains up to 50%. It is evident that the devices can maintain their functionalities even at high stretched states. The devices demonstrated strain-dependent thermal indices, and the sensitivity of the thermistors can be effectively tuned using strain. The unique tunable thermal index is advantageous over conventional rigid ceramic thermistors for diverse and adaptive applications in wearable electronics. PMID:25671368

  11. Tunable anti-Stokes Raman laser

    SciTech Connect

    White, J.C.

    1984-12-04

    An anti-Stokes Raman laser is disclosed which is tunable over a range of 10-70 cm-/sup 1/. An alkali halide is used as the lasing medium and a metastable halide population inversion is created with respect to the ground state of the halide by selective photodissociation of the alkali halide. A pump laser is then employed to move the population from the metastable state to a region near an intermediate state of the halide. The population subsequently falls back to the initial ground state, thereby creating the anti-Stokes Raman emission. Since the intensity of the photodissociation is directly proportional to the amount of population inversion achieved, and hence, to the region the population may be pumped to, the tuning of the output anti-Stokes Raman lasing is a function of the intensity of the initial photodissoiation.

  12. Characterizing tunable dynamics in an active gel

    NASA Astrophysics Data System (ADS)

    Henkin, Gil; Decamp, Stephen; Chen, Daniel; Dogic, Zvonimir

    2014-03-01

    We experimentally investigate dynamics of an active gel of bundled microtubules that is driven to far-from-equilibrium steady states by clusters of kinesin molecular motors. Upon the addition of ATP, the coordinated action of thousands of molecular motors drives this gel to an active, percolating state that persists for hours and is only limited by the stability of constituent proteins and the availability of the chemical fuel ATP. We extensively characterize how enhanced transport in emergent macroscopic flows depends on relevant molecular parameters, including ATP, motor, and depletant concentrations, microtubule concentration and length, as well as structure of the motor clusters. Our results show that the properties and dynamics of this active isotropic gel are highly tunable, suggesting that this is an ideal system for studying the behavior of active materials.

  13. Development of a Tunable Electromechanical Acoustic Liner for Engine Nacelles

    NASA Technical Reports Server (NTRS)

    Liu, Fei; Sheplak, Mark; Cattafesta, Louis N., III

    2007-01-01

    provides the information for a designer that shows how design trade-offs can be used to satisfy specific design requirements. The optimization design of the EMHR with inductive loads aims at optimal tuning of these three resonant fiequencies. The results indicate that it is possible to keep the acoustic reactance of the resonator close to a constant over a given frequency range. An effort to mimic the second layer of the NASA 2DOF liner using a piezoelectric composite diaphragm has been made. The optimal acoustic reactance of the second layer of the NASA 2DOF liner is achieved using a thin PVDF composite diaphragm, but matching the acoustic resistance requires further investigation. Acoustic energy harvesting is achieved by connecting the EMHR to an energy reclamation circuit that converts the ac voltage signal across the piezoceramic to a conditioned dc signal. Energy harvesting experiment yields 16 m W continuous power for an incident SPL of 153 dB. Such a level is sufficient to power a variety of low power electronic devices. Finally, technology transfer has been achieved by converting the original NASA ZKTL FORTRAN code to a MATLAB code while incorporating the models of the EMHR. Initial studies indicate that the EMHR is a promising technology that may enable lowpower, light weight, tunable engine nacelle liners. This technology, however, is very immature, and additional developments are required. Recommendations for future work include testing of sample EMHR liner designs in NASA Langley s normal incidence dual-waveguide and the grazing-incidence flow facility to evaluating both the impedance characteristics as well as the energy reclamation abilities. Additional design work is required for more complex tuning circuits with greater performance. Poor electromechanical coupling limited the electromechanical tuning capabilities of the proof of concept EMHR. Different materials than those studies and perhaps novel composite material systems may dramatically improvehe

  14. High-energy, broadly tunable, narrow-bandwidth mid-infrared optical parametric system pumped by quasi-phase-matched devices.

    PubMed

    Saikawa, Jiro; Miyazaki, Mitsuhiko; Fujii, Masaaki; Ishizuki, Hideki; Taira, Takunori

    2008-08-01

    We have developed a tunable, narrow-bandwidth (<2 cm(-1)) mid-infrared (MIR) optical parametric system with a large-aperture periodically poled Mg-doped LiNbO(3) (LA-PPMgLN)-based high-energy pump source. The system has a continuously tunable tuning range from 4.6 to 11.2 mum and produces a maximum output energy of 2.0 mJ at 5.1 mum. Practical use of the MIR source is demonstrated by MIR-UV double-resonance spectroscopy of jet-cooled acetanilide. PMID:18670508

  15. Design of a varactor-tunable metamaterial absorber

    NASA Astrophysics Data System (ADS)

    Lin, Bao-Qin; Da, Xin-Yu; Zhao, Shang-Hong; Meng, Wen; Li, Fan; Fang, Ying-Wu; Wang, Jia-Fu

    2014-06-01

    In this paper, we design a varactor-tunable metamaterial absorber (MA). The tunable MA is based on a mushroom-type high impedance surface (HIS), in which varactors are loaded between adjacent metal patches to adjust the capacitance and tune the resonance frequency, the primary ground plane is etched as the bias network to bias all of the varactors in parallel, and another ultra-thin grounded film is attached to the bottom. Its absorption characteristics are realized for electrically dielectric loss. The simulated values of a sample indicate that a tunable frequency range from 2.85 GHz to 2.22 GHz is achieved by adjusting the varactor capacitance from 0.1 pF to 2.0 pF, and better than 0.97 absorbance is realized; in addition, the tunable frequency range is expanded from 4.12 GHz to 1.70 GHz after optimization.

  16. Mechanical and vibrational responses of gate-tunable graphene resonator

    NASA Astrophysics Data System (ADS)

    Lei, Yuqing; Sun, Jiangping; Gong, Xionghui

    2015-03-01

    The vibrational mechanical properties of gate-tunable graphene resonator were investigated in detail using finite element analysis (FEA) and simulation. Treating the graphene resonator as a two-dimensional (2D) thin plate, the relationship between resonance frequency and driving force was explored. The effects of built-in tension, adsorbates and graphene size on the performance of resonator including resonance frequency and tunability were also studied. It was shown that resonance frequency could be tuned by the electrostatically induced average tension due to driving force, and exponentially increased with increasing driving force. When the single-layer graphene resonator without any adsorbates had no or very small built-in tension, the tunability of resonator was greater. However, for a high-frequency-range resonator, the resonator with high built-in tension should be used. The simulation results suggested potential applications of graphene resonators tuned by a driving force, such as widely tunable or ultrahigh frequency nanoelectromechanical systems (NEMS) devices.

  17. Tunable lasers for water vapor measurements and other lidar applications

    NASA Technical Reports Server (NTRS)

    Gammon, R. W.; Mcilrath, T. J.; Wilkerson, T. D.

    1977-01-01

    A tunable dye laser suitable for differential absorption (DIAL) measurements of water vapor in the troposphere was constructed. A multi-pass absorption cell for calibration was also constructed for use in atmospheric DIAL measurements of water vapor.

  18. Linewidth-tunable laser diode array for rubidium laser pumping

    SciTech Connect

    Li Zhiyong; Tan Rongqing; Xu Cheng; Li Lin

    2013-02-28

    To optimise the pump source for a high-power diodepumped rubidium vapour laser, we have designed a laser diode array (LDA) with a narrowed and tunable linewidth and an external cavity formed by two volume Bragg gratings (VBGs). Through controlling the temperature differences between the two VBGs, the LDA linewidth, which was 1.8 nm before mounting the two VBGs, was tunable from 100 pm to 0.2 nm, while the output power changed by no more than 4 %. By changing simultaneously the temperature in both VBGs, the centre wavelength in air of the linewidth-tunable LDA was tunable from 779.40 nm to 780.05 nm. (control of laser radiation parameters)

  19. Freely tunable broadband polarization rotator for terahertz waves.

    PubMed

    Fan, Ren-Hao; Zhou, Yu; Ren, Xiao-Ping; Peng, Ru-Wen; Jiang, Shang-Chi; Xu, Di-Hu; Xiong, Xiang; Huang, Xian-Rong; Wang, Mu

    2015-02-18

    A freely tunable polarization rotator for broadband terahertz waves is demonstrated using a three-rotating-layer metallic grating structure, which can conveniently rotate the polarization of a linearly polarized terahertz wave to any desired direction with nearly perfect conversion efficiency. This low-cost, high-efficiency, and freely tunable device has potential applications as material analysis, wireless communication, and THz imaging. PMID:25545177

  20. Multiple-bipolar-tap tunable spectrum sliced microwave photonic filter.

    PubMed

    Chen, Tong; Yi, Xiaoke; Huang, Thomas; Minasian, Robert A

    2010-12-01

    A spectrum sliced microwave photonic signal processor structure, which is all-fiber based and features simplicity, together with the ability to realize tunability, reconfigurability, bipolar taps, and multiple-tap rf filtering, is presented. It is based on thermally controlled optical slicing filters induced into two linearly chirped fiber Bragg gratings. Experimental results demonstrate the realization of versatile microwave photonic filters with frequency tunable, reconfiguration, and bipolar-tap generation capabilities. PMID:21124570

  1. Investigations on an all-tunable fiber ring resonator

    NASA Astrophysics Data System (ADS)

    Saleh, K.; Fernandez, A.; Llopis, O.

    2016-01-01

    The architecture of an all-tunable optical fiber ring resonator is described in detail in this paper. This architecture has been firstly modeled using an original CAD approach. The simulation results demonstrate a total control of both the absolute frequency and the free spectral range of the final optical resonance comb generated by the optical resonator. The different experimental setups used to characterize the tunable resonator are described and the obtained results proving the concept are also provided.

  2. Tunable UV source for UV fluorescence remote sensing

    SciTech Connect

    Mead, R.D.; Lowenthal, D.D.; Raymond, T.D.; Alford, W.J.; Smith, A.V.; Johnson, M.S.

    1994-08-01

    Efficient generation of ultraviolet radiation tunable over the 240--410 nm range has been achieved in a system suitable for ultraviolet (uv) fluorescence remote sensing. Light from an Optical Parametric Oscillator/Amplifier turning in the 0.7--2.1 {mu}m range is mixed with the second or third harmonic from a Nd:YAG laser, to obtain up to 30 mJ of broadly tunable output in the ultraviolet.

  3. Optimal design of tunable phononic bandgap plates under equibiaxial stretch

    NASA Astrophysics Data System (ADS)

    Hedayatrasa, Saeid; Abhary, Kazem; Uddin, M. S.; Guest, James K.

    2016-05-01

    Design and application of phononic crystal (PhCr) acoustic metamaterials has been a topic with tremendous growth of interest in the last decade due to their promising capabilities to manipulate acoustic and elastodynamic waves. Phononic controllability of waves through a particular PhCr is limited only to the spectrums located within its fixed bandgap frequency. Hence the ability to tune a PhCr is desired to add functionality over its variable bandgap frequency or for switchability. Deformation induced bandgap tunability of elastomeric PhCr solids and plates with prescribed topology have been studied by other researchers. Principally the internal stress state and distorted geometry of a deformed phononic crystal plate (PhP) changes its effective stiffness and leads to deformation induced tunability of resultant modal band structure. Thus the microstructural topology of a PhP can be altered so that specific tunability features are met through prescribed deformation. In the present study novel tunable PhPs of this kind with optimized bandgap efficiency-tunability of guided waves are computationally explored and evaluated. Low loss transmission of guided waves throughout thin walled structures makes them ideal for fabrication of low loss ultrasound devices and structural health monitoring purposes. Various tunability targets are defined to enhance or degrade complete bandgaps of plate waves through macroscopic tensile deformation. Elastomeric hyperelastic material is considered which enables recoverable micromechanical deformation under tuning finite stretch. Phononic tunability through stable deformation of phononic lattice is specifically required and so any topology showing buckling instability under assumed deformation is disregarded. Nondominated sorting genetic algorithm (GA) NSGA-II is adopted for evolutionary multiobjective topology optimization of hypothesized tunable PhP with square symmetric unit-cell and relevant topologies are analyzed through finite

  4. Magnetic field tunable capacitive dielectric:ionic-liquid sandwich composites

    NASA Astrophysics Data System (ADS)

    Wu, Ye; Bhalla, Amar; Guo, Ruyan

    2016-03-01

    We examined the tunability of the capacitance for GaFeO3-ionic liquid-GaFeO3 composite material by external magnetic and electric field. Up to 1.6 folds of capacitance tunability could be achieved at 957 kHz with voltage 4 V and magnetic field 0.02 T applied. We show that the capacitance enhancement is due to the polarization coupling between dielectric layer and ionic liquid layer.

  5. Tunable multi-wavelength polymer laser based on a triangular-lattice photonic crystal structure

    NASA Astrophysics Data System (ADS)

    Huang, Wenbin; Pu, Donglin; Qiao, Wen; Wan, Wenqiang; Liu, Yanhua; Ye, Yan; Wu, Shaolong; Chen, Linsen

    2016-08-01

    A continuously tunable multi-wavelength polymer laser based on a triangular-lattice photonic crystal cavity is demonstrated. The triangular-lattice resonator was initially fabricated through multiple interference exposure and was then replicated into a low refractive index polymer via UV-nanoimprinting. The blend of a blue-emitting conjugated polymer and a red-emitting one was used as the gain medium. Three periods in the scalene triangular-lattice structure yield stable tri-wavelength laser emission (625.5 nm, 617.4 nm and 614.3 nm) in six different directions. A uniformly aligned liquid crystal (LC) layer was incorporated into the cavity as the top cladding layer. Upon heating, the orientation of LC molecules and thus the effective refractive index of the lasing mode changes which continuously shifts the lasing wavelength. A maximum tuning range of 12.2 nm was observed for the lasing mode at 625.5 nm. This tunable tri-wavelength polymer laser is simple constructed and cost-effective. It may find application in the fields of biosensors and photonic integrated circuits.

  6. Combinatorial Block Copolymer Ordering on Tunable Rough

    SciTech Connect

    Kulkarni M. M.; Yager K.; Sharma, A.; Karim, A.

    2012-05-01

    Morphology control of block copolymer (BCP) thin films through substrate interaction via controlled roughness parameters is of significant interest for numerous high-tech applications ranging from solar cells to high-density storage media. While effects of substrate surface energy (SE) and roughness (R) on BCP morphology have been individually investigated, their synergistic effects have not been explored in any systematic manner. Interestingly, orientation response of BCP to changes in SE can be similar to what can be accomplished with variations in R. Here we present a novel approach for orienting lamellar BCP films of poly(styrene)-block-poly(methyl methacrylate) (PS-PMMA) on spin-coated xerogel (a dried gel of silica nanoparticle network) substrate with simultaneously tunable surface energy, {gamma}{sub s} {approx} 29-53 mJ/m{sup 2}, by UVO exposure and roughness, R{sub rms} {approx} 0.5-30 nm, by sol-gel processing steps of regulating the catalyst concentration and sol aging time. As in previous BCP orientation studies on 20 nm diameter monodisperse silica nanoparticle coated surface, we find a similar but broadened oscillatory BCP orientation behavior with film thickness due to the random rather than periodic rough surfaces. We also find that higher random roughness amplitude is not the necessary criteria for obtaining a vertical orientation of BCP lamellae. Rather, a high surface fractal dimension (D{sub f} > 2.4) of the rough substrate in conjunction with an optimal substrate surface energy {gamma}{sub s} 29 mJ/m{sup 2} results in 100% vertically oriented lamellar microdomains. The AFM measured film surface microstructure correlates well with the internal 3D BCP film structure probed by grazing incidence small-angle X-ray scattering (GISAXS) and rotational small-angle neutron scattering (SANS). In contrast to tunable self-assembled monolayer (SAM)-coated substrates, the xerogel films are very durable and retain their chemical properties over period of

  7. Superconductors and Complex Transition Metal Oxides for Tunable THz Plasmonic Metamaterials

    SciTech Connect

    Singh, Ranjan; Xiong, Jie; Azad, Md A.; Yang, Hao; Trugman, Stuart A.; Jia, Quanxi; Taylor, Antoinette; Chen, Houtong

    2012-07-13

    The outline of this presentation are: (1) Motivation - Non-tunability of metal metamaterials; (2) Superconductors for temperature tunable metamaterials; (3) Ultrafast optical switching in superconductor metamaterials; (4) Controlling the conductivity with infrared pump beam; (5) Complex metal oxides as active substrates - Strontium Titanate; and (6) Conclusion. Conclusions are: (1) High Tc superconductors good for tunable and ultrafast metamaterials; (2) Large frequency and amplitude tunability in ultrathin superconductor films; (3) Such tunable properties cannot be accessed using metals; (4) Complex metal oxides can be used as active substrates - large tunability; (5) Complex oxides fail to address the issue of radiation losses in THz metamaterials.

  8. Highly efficient, widely tunable, 10-Hz parametric amplifier pumped by frequency-doubled femtosecond Ti:sapphire laser pulses.

    PubMed

    Zhang, J Y; Xu, Z; Kong, Y; Yu, C; Wu, Y

    1998-05-20

    We report a 10-Hz, highly efficient, widely tunable (from the visible to the IR), broadband femtosecond optical parametric generator and optical parametric amplifier (OPA) in BBO, LBO, and CBO crystals pumped by the frequency-doubled output of a regeneratively amplified Ti:sapphire laser at 400 nm. The output of the system is continuously tunable from 440 nm to 2.5 microm with a maximum overall efficiency of approximately 25% at 670 nm and an optical conversion efficiency of more than 36% in the OPA stage. The effects of the seed beam energy, the type of the crystal and the crystal length, and the pumping energy of the output of the OPA, such as the optical efficiency, the bandwidth, the pulse duration, and the group velocity mismatch between the signal and the idler and between the seeder and the pump, are investigated. The results provide useful information for optimization of the design of the system. PMID:18273287

  9. Continuously tunable orbital angular momentum generation using a polarization-maintaining fiber.

    PubMed

    Niederriter, Robert D; Siemens, Mark E; Gopinath, Juliet T

    2016-07-15

    We demonstrate the generation of orbital angular momentum (OAM) in a two-mode polarization-maintaining (PM) optical fiber. We combine two linearly polarized modes of PM fiber to generate linearly polarized optical vortex beams with OAM. The average OAM can be finely varied by changing the phase between modes. We have quantitatively measured the resulting OAM to vary between ±1ℏ per photon while varying the relative phase between the LP11e- and LP11o-like fiber modes. The modal purity is 97%. PMID:27420498

  10. Continuously Tunable 250 GHz Gyrotron with a Double Disk Window for DNP-NMR Spectroscopy

    PubMed Central

    Jawla, Sudheer; Ni, Qing Zhe; Barnes, Alexander; Guss, William; Daviso, Eugenio; Herzfeld, Judith; Griffin, Robert; Temkin, Richard

    2012-01-01

    In this paper, we describe the design and experimental results from the rebuild of a 250 GHz gyrotron used for Dynamic Nuclear Polarization enhanced Nuclear Magnetic Resonance spectroscopy on a 380 MHz spectrometer. Tuning bandwidth of approximately 2 GHz is easily achieved at a fixed magnetic field of 9.24 T and a beam current of 95 mA producing an average output power of >10 W over the entire tuning band. This tube incorporates a double disk output sapphire window in order to maximize the transmission at 250.58 GHz. DNP Signal enhancement of >125 is achieved on a 13C-Urea sample using this gyrotron. PMID:23539422

  11. Trapping and Characterization of a Single Hydrogen Molecule in a Continuously Tunable Nanocavity.

    PubMed

    Wang, Hui; Li, Shaowei; He, Haiyan; Yu, Arthur; Toledo, Freddy; Han, Zhumin; Ho, W; Wu, Ruqian

    2015-09-01

    Using inelastic electron tunneling spectroscopy with the scanning tunneling microscope (STM-IETS) and density functional theory calculations (DFT), we investigated properties of a single H2 molecule trapped in nanocavities with controlled shape and separation between the STM tip and the Au (110) surface. The STM tip not only serves for the purpose of characterization, but also is directly involved in modification of chemical environment of molecule. The bond length of H2 expands in the atop cavity, with a tendency of dissociation when the gap closes, whereas it remains unchanged in the trough cavity. The availability of two substantially different cavities in the same setup allows understanding of H2 adsorption on noble metal surfaces and sets a path for manipulating a single chemical bond by design. PMID:26291093

  12. Development of a powerful continuously tunable mid-infrared cw PPLN OPO for trace gas detection

    NASA Astrophysics Data System (ADS)

    van Herpen, Maarten; te Lintel Hekkert, Sacco; Bisson, Scott E.; Harren, Frans J. M.

    2002-08-01

    A new Optical Parametric Oscillator for the mid infrared wavelength region of 3-3.8 micrometer is developed with an idler output power of more than 1 Watt. The OPO is pumped with a 10 Watt, cw, Nd:YAG Laser and consists of a bowtie ring cavity (FSR 320 MHz) resonating at the signal wavelength. The wavelength is controlled with a fan-out PPLN crystal and a low finesse intracavity Fabry-Perot. The idler output could be tuned over more than 24 Ghz modehop-free, by tuning the pump laser and keep the OPO cavity fixed. Mode hop tuning over 100 Ghz could be obtained changing the length of the intracavity Fabry-Perot. This high power OPO is combined with photoacoustic spectroscopy in order to develop a sensitive trace gas detector for LifeScience applications.

  13. Continuously Tunable, Polarization Controlled, Colour Palette Produced from Nanoscale Plasmonic Pixels.

    PubMed

    Balaur, Eugeniu; Sadatnajafi, Catherine; Kou, Shan Shan; Lin, Jiao; Abbey, Brian

    2016-01-01

    Colour filters based on nano-apertures in thin metallic films have been widely studied due to their extraordinary optical transmission and small size. These properties make them prime candidates for use in high-resolution colour displays and high accuracy bio-sensors. The inclusion of polarization sensitive plasmonic features in such devices allow additional control over the electromagnetic field distribution, critical for investigations of polarization induced phenomena. Here we demonstrate that cross-shaped nano-apertures can be used for polarization controlled color tuning in the visible range and apply fundamental theoretical models to interpret key features of the transmitted spectrum. Full color transmission was achieved by fine-tuning the periodicity of the apertures, whilst keeping the geometry of individual apertures constant. We demonstrate this effect for both transverse electric and magnetic fields. Furthermore we have been able to demonstrate the same polarization sensitivity even for nano-size, sub-wavelength sets of arrays, which is paramount for ultra-high resolution compact colour displays. PMID:27312072

  14. Continuously Tunable, Polarization Controlled, Colour Palette Produced from Nanoscale Plasmonic Pixels

    NASA Astrophysics Data System (ADS)

    Balaur, Eugeniu; Sadatnajafi, Catherine; Kou, Shan Shan; Lin, Jiao; Abbey, Brian

    2016-06-01

    Colour filters based on nano-apertures in thin metallic films have been widely studied due to their extraordinary optical transmission and small size. These properties make them prime candidates for use in high-resolution colour displays and high accuracy bio-sensors. The inclusion of polarization sensitive plasmonic features in such devices allow additional control over the electromagnetic field distribution, critical for investigations of polarization induced phenomena. Here we demonstrate that cross-shaped nano-apertures can be used for polarization controlled color tuning in the visible range and apply fundamental theoretical models to interpret key features of the transmitted spectrum. Full color transmission was achieved by fine-tuning the periodicity of the apertures, whilst keeping the geometry of individual apertures constant. We demonstrate this effect for both transverse electric and magnetic fields. Furthermore we have been able to demonstrate the same polarization sensitivity even for nano-size, sub-wavelength sets of arrays, which is paramount for ultra-high resolution compact colour displays.

  15. Continuously Tunable 250 GHz Gyrotron with a Double Disk Window for DNP-NMR Spectroscopy.

    PubMed

    Jawla, Sudheer; Ni, Qing Zhe; Barnes, Alexander; Guss, William; Daviso, Eugenio; Herzfeld, Judith; Griffin, Robert; Temkin, Richard

    2013-01-01

    In this paper, we describe the design and experimental results from the rebuild of a 250 GHz gyrotron used for Dynamic Nuclear Polarization enhanced Nuclear Magnetic Resonance spectroscopy on a 380 MHz spectrometer. Tuning bandwidth of approximately 2 GHz is easily achieved at a fixed magnetic field of 9.24 T and a beam current of 95 mA producing an average output power of >10 W over the entire tuning band. This tube incorporates a double disk output sapphire window in order to maximize the transmission at 250.58 GHz. DNP Signal enhancement of >125 is achieved on a (13)C-Urea sample using this gyrotron. PMID:23539422

  16. Continuously Tunable, Polarization Controlled, Colour Palette Produced from Nanoscale Plasmonic Pixels

    PubMed Central

    Balaur, Eugeniu; Sadatnajafi, Catherine; Kou, Shan Shan; Lin, Jiao; Abbey, Brian

    2016-01-01

    Colour filters based on nano-apertures in thin metallic films have been widely studied due to their extraordinary optical transmission and small size. These properties make them prime candidates for use in high-resolution colour displays and high accuracy bio-sensors. The inclusion of polarization sensitive plasmonic features in such devices allow additional control over the electromagnetic field distribution, critical for investigations of polarization induced phenomena. Here we demonstrate that cross-shaped nano-apertures can be used for polarization controlled color tuning in the visible range and apply fundamental theoretical models to interpret key features of the transmitted spectrum. Full color transmission was achieved by fine-tuning the periodicity of the apertures, whilst keeping the geometry of individual apertures constant. We demonstrate this effect for both transverse electric and magnetic fields. Furthermore we have been able to demonstrate the same polarization sensitivity even for nano-size, sub-wavelength sets of arrays, which is paramount for ultra-high resolution compact colour displays. PMID:27312072

  17. Continuously Tunable 250 GHz Gyrotron with a Double Disk Window for DNP-NMR Spectroscopy

    NASA Astrophysics Data System (ADS)

    Jawla, Sudheer; Ni, Qing Zhe; Barnes, Alexander; Guss, William; Daviso, Eugenio; Herzfeld, Judith; Griffin, Robert; Temkin, Richard

    2013-01-01

    In this paper, we describe the design and experimental results from the rebuild of a 250 GHz gyrotron used for Dynamic Nuclear Polarization enhanced Nuclear Magnetic Resonance spectroscopy on a 380 MHz spectrometer. Tuning bandwidth of approximately 2 GHz is easily achieved at a fixed magnetic field of 9.24 T and a beam current of 95 mA producing an average output power of >10 W over the entire tuning band. This tube incorporates a double disk output sapphire window in order to maximize the transmission at 250.58 GHz. DNP Signal enhancement of >125 is achieved on a 13C-Urea sample using this gyrotron.

  18. Tunable damper for an acoustic wave guide

    SciTech Connect

    Rogers, S.C.

    1984-06-05

    A damper for tunably damping acoustic waves in an ultrasonic waveguide is provided which may be used in a hostile environment such as a nuclear reactor. The area of the waveguide, which may be a selected size metal rod in which acoustic waves are to be damped, is wrapped, or surrounded, by a mass of stainless steel wool. The wool wrapped portion is then sandwiched between tuning plates, which may also be stainless steel, by means of clamping screws which may be adjusted to change the clamping force of the sandwiched assembly along the waveguide section. The plates are preformed along their length in a sinusoidally bent pattern with a period approximately equal to the acoustic wavelength which is to be damped. The bent pattern of the opposing plates are in phase along their length relative to their sinusoidal patterns so that as the clamping screws are tightened a bending stress is applied to the waveguide at 180/sup 0/ intervals along the damping section to oppose the acoustic wave motions in the waveguide and provide good coupling of the wool to the guide. The damper is tuned by selectively tightening the clamping screws while monitoring the amplitude of the acoustic waves launched in the waveguide. It may be selectively tuned to damp particular acoustic wave modes (torsional or extensional, for example) and/or frequencies while allowing others to pass unattenuated.

  19. Quasi-monolithic tunable optical resonator

    NASA Technical Reports Server (NTRS)

    Arbore, Mark (Inventor); Tapos, Francisc (Inventor)

    2003-01-01

    An optical resonator has a piezoelectric element attached to a quasi-monolithic structure. The quasi-monolithic structure defines an optical path. Mirrors attached to the structure deflect light along the optical path. The piezoelectric element controllably strains the quasi-monolithic structure to change a length of the optical path by about 1 micron. A first feedback loop coupled to the piezoelectric element provides fine control over the cavity length. The resonator may include a thermally actuated spacer attached to the cavity and a mirror attached to the spacer. The thermally actuated spacer adjusts the cavity length by up to about 20 microns. A second feedback loop coupled to the sensor and heater provides a coarse control over the cavity length. An alternative embodiment provides a quasi-monolithic optical parametric oscillator (OPO). This embodiment includes a non-linear optical element within the resonator cavity along the optical path. Such an OPO configuration is broadly tunable and capable of mode-hop free operation for periods of 24 hours or more.

  20. Coherently Tunable Triangular Trefoil Phaseonium Metamaterial

    PubMed Central

    Nguyen, D. M.; Soci, Cesare; Ooi, C. H. Raymond

    2016-01-01

    Phaseonium is a three-level Λ quantum system, in which a coherent microwave and an optical control (pump) beams can be used to actively modulate the dielectric response. Here we propose a new metamaterial structure comprising of a periodic array of triangular phaseonium metamolecules arranged as a trefoil. We present a computational study of the spatial distribution of magnetic and electric fields of the probe light and the corresponding transmission and reflection, for various parameters of the optical and microwave beams. For specific values of the probing frequencies and control fields, the phaseonium can display either metallic or dielectric optical response. We find that, in the metallic regime, the phaseonium metamaterial structure supports extremely large transmission, with optical amplification at large enough intensity of the microwave thanks to strong surface plasmon coupling; while, in the dielectric regime without microwave excitation, the transmission bandwidth can be tuned by varying the control beam intensity. Implementation of such phaseonium metamaterial structure in solid-state systems, such as patterned crystals doped with rare-earth elements or dielectric matrices embedded with quantum dots, could enable a new class of actively tunable quantum metamaterials. PMID:26879520

  1. Tunable magnetocaloric effect in transition metal alloys.

    PubMed

    Belyea, Dustin D; Lucas, M S; Michel, E; Horwath, J; Miller, Casey W

    2015-01-01

    The unpredictability of geopolitical tensions and resulting supply chain and pricing instabilities make it imperative to explore rare earth free magnetic materials. As such, we have investigated fully transition metal based "high entropy alloys" in the context of the magnetocaloric effect. We find the NiFeCoCrPdx family exhibits a second order magnetic phase transition whose critical temperature is tunable from 100 K to well above room temperature. The system notably displays changes in the functionality of the magnetic entropy change depending on x, which leads to nearly 40% enhancement of the refrigerant capacity. A detailed statistical analysis of the universal scaling behavior provides direct evidence that heat treatment and Pd additions reduce the distribution of exchange energies in the system, leading to a more magnetically homogeneous alloy. The general implications of this work are that the parent NiFeCoCr compound can be tuned dramatically with FCC metal additives. Together with their relatively lower cost, their superior mechanical properties that aid manufacturability and their relative chemical inertness that aids product longevity, NiFeCoCr-based materials could ultimately lead to commercially viable magnetic refrigerants. PMID:26507636

  2. Zoom optical system using tunable polymer lens

    NASA Astrophysics Data System (ADS)

    Liang, Dan; Wang, Xuan Yin

    2016-07-01

    This paper demonstrated a zoom optical system with variable magnification based on the tunable polymer lens. The designed system mainly consists of two polymer lenses, voice coil motors, a doublet lens and CMOS chip. The zoom magnification can be adjusted by altering the focal length of the two elastic polymer lenses synergistically through controlling the output displacement of the voice coil motor. A static doublet lens in combination with the polymer lenses stabilize the image plane at the CMOS chip. The optical structure of the zoom system is presented, as well as a detailed description including the lens materials and fabrication process. Images with each zoom magnification are captured, and the Spot diagram and MTF are simulated using Zemax software. A change in magnification from 0.13×to 8.44×is demonstrated within the tiny 0.4 mm variation of the displacement load, and produce a 16.1×full range of magnification experimentally. Simulation analyses show that all the radii of the spot diagram under different magnifications are less than 11.3 um, and the modulation transfer function reaches 107 line pairs per mm. The designed optical system shows the potential for developing stable, integrated, and low-cost zoom systems with large magnification range.

  3. Tunable damper for an acoustic wave guide

    DOEpatents

    Rogers, Samuel C.

    1984-01-01

    A damper for tunably damping acoustic waves in an ultrasonic waveguide is provided which may be used in a hostile environment such as a nuclear reactor. The area of the waveguide, which may be a selected size metal rod in which acoustic waves are to be damped, is wrapped, or surrounded, by a mass of stainless steel wool. The wool wrapped portion is then sandwiched between tuning plates, which may also be stainless steel, by means of clamping screws which may be adjusted to change the clamping force of the sandwiched assembly along the waveguide section. The plates are preformed along their length in a sinusoidally bent pattern with a period approximately equal to the acoustic wavelength which is to be damped. The bent pattern of the opposing plates are in phase along their length relative to their sinusoidal patterns so that as the clamping screws are tightened a bending stress is applied to the waveguide at 180.degree. intervals along the damping section to oppose the acoustic wave motions in the waveguide and provide good coupling of the wool to the guide. The damper is tuned by selectively tightening the clamping screws while monitoring the amplitude of the acoustic waves launched in the waveguide. It may be selectively tuned to damp particular acoustic wave modes (torsional or extensional, for example) and/or frequencies while allowing others to pass unattenuated.

  4. Sterically stabilized colloids with tunable repulsions.

    PubMed

    van Gruijthuijsen, Kitty; Obiols-Rabasa, Marc; Heinen, Marco; Nägele, Gerhard; Stradner, Anna

    2013-09-10

    When studying tunable electrostatic repulsions in aqueous suspensions of charged colloids, irreversible colloid aggregation or gelation may occur at high salt concentrations. For many commonly used synthetic colloids, such as polystyrene and silica particles, the reason for coagulation is the presence of unbalanced, strongly attractive, and short-ranged van der Waals (VDW) forces. Here, we present an aqueous polystyrene model colloid that is sterically stabilized against VDW attractions. We show that the synthesis procedure, based on a neutral initiator couple and a nonionic surfactant, introduces surface charges that can be further increased by the addition of charged comonomer methacrylic acid. Thus, the interactions between the polystyrene spheres can be conveniently tuned from hard-sphere-like to charge-stabilized with long-ranged electrostatic repulsions described by a Yukawa-type pair potential. The particle size, grafting density, core-shell structure, and surface charge are characterized by light and neutron scattering. Using X-ray and neutron scattering in combination with an accurate analytic integral equation scheme for the colloidal static structure factor, we deduce effective particle charges for colloid volume fractions ≥0.1 and salt concentrations in the range of 1.5 to 50 mM. PMID:23937718

  5. Tunable magnetocaloric effect in transition metal alloys

    PubMed Central

    Belyea, Dustin D.; Lucas, M. S.; Michel, E.; Horwath, J.; Miller, Casey W.

    2015-01-01

    The unpredictability of geopolitical tensions and resulting supply chain and pricing instabilities make it imperative to explore rare earth free magnetic materials. As such, we have investigated fully transition metal based “high entropy alloys” in the context of the magnetocaloric effect. We find the NiFeCoCrPdx family exhibits a second order magnetic phase transition whose critical temperature is tunable from 100 K to well above room temperature. The system notably displays changes in the functionality of the magnetic entropy change depending on x, which leads to nearly 40% enhancement of the refrigerant capacity. A detailed statistical analysis of the universal scaling behavior provides direct evidence that heat treatment and Pd additions reduce the distribution of exchange energies in the system, leading to a more magnetically homogeneous alloy. The general implications of this work are that the parent NiFeCoCr compound can be tuned dramatically with FCC metal additives. Together with their relatively lower cost, their superior mechanical properties that aid manufacturability and their relative chemical inertness that aids product longevity, NiFeCoCr-based materials could ultimately lead to commercially viable magnetic refrigerants. PMID:26507636

  6. Microelectromechanically tunable multiband metamaterial with preserved isotropy

    NASA Astrophysics Data System (ADS)

    Pitchappa, Prakash; Ho, Chong Pei; Qian, You; Dhakar, Lokesh; Singh, Navab; Lee, Chengkuo

    2015-06-01

    We experimentally demonstrate a micromachined reconfigurable metamaterial with polarization independent characteristics for multiple resonances in terahertz spectral region. The metamaterial unit cell consists of eight out-of-plane deformable microcantilevers placed at each corner of an octagon ring. The octagon shaped unit cell geometry provides the desired rotational symmetry, while the out-of-plane movable cantilevers preserves the symmetry at different configurations of the metamaterial. The metamaterial is shown to provide polarization independent response for both electrical inductive-capacitive (eLC) resonance and dipolar resonance at all states of actuation. The proposed metamaterial has a switching range of 0.16 THz and 0.37 THz and a transmission intensity change of more than 0.2 and 0.7 for the eLC and dipolar resonances, respectively for both TE and TM modes. Further optimization of the metal layer thickness, provides an improvement of up to 80% modulation at 0.57 THz. The simultaneously tunable dual band isotropic metamaterial will enable the realization of high performance electro-optic devices that would facilitate numerous terahertz applications such as compressive terahertz imaging, miniaturized terahertz spectroscopy and next generation high speed wireless communication possible in the near future.

  7. Airborne tunable diode laser measurements of formaldehyde

    NASA Astrophysics Data System (ADS)

    Fried, Alan; Wert, Bryan P.; Henry, Bruce; Drummond, James R.

    1999-09-01

    Accurate measurements of formaldehyde (CH 2O) in the atmosphere are essential to further our understanding of various atmospheric cycles involving hydrogen and carbon-containing species. Comparisons among independent measurements of this gas and between measurements and model calculations have raised numerous questions regarding the veracity of both endeavors. The present paper describes a long-term effort by our group to develop and employ tunable diode laser absorption spectroscopy (TDLAS) for highly accurate measurements of this gas on both ground-based and aircraft platforms. A highly sensitive and selective TDLAS system, which has successfully flown on three different aircraft campaigns, will be described. Many new hardware and software features, which have been implemented, now make it possible to detect ambient CH 2O concentrations as low as 55 parts-per-trillion employing a 20-s integration time. This paper will also discuss the many aspects associated with high accuracy and its verification, including a brief discussion of our aircraft sampling system and inlet surface effects.

  8. Microelectromechanically tunable multiband metamaterial with preserved isotropy.

    PubMed

    Pitchappa, Prakash; Ho, Chong Pei; Qian, You; Dhakar, Lokesh; Singh, Navab; Lee, Chengkuo

    2015-01-01

    We experimentally demonstrate a micromachined reconfigurable metamaterial with polarization independent characteristics for multiple resonances in terahertz spectral region. The metamaterial unit cell consists of eight out-of-plane deformable microcantilevers placed at each corner of an octagon ring. The octagon shaped unit cell geometry provides the desired rotational symmetry, while the out-of-plane movable cantilevers preserves the symmetry at different configurations of the metamaterial. The metamaterial is shown to provide polarization independent response for both electrical inductive-capacitive (eLC) resonance and dipolar resonance at all states of actuation. The proposed metamaterial has a switching range of 0.16 THz and 0.37 THz and a transmission intensity change of more than 0.2 and 0.7 for the eLC and dipolar resonances, respectively for both TE and TM modes. Further optimization of the metal layer thickness, provides an improvement of up to 80% modulation at 0.57 THz. The simultaneously tunable dual band isotropic metamaterial will enable the realization of high performance electro-optic devices that would facilitate numerous terahertz applications such as compressive terahertz imaging, miniaturized terahertz spectroscopy and next generation high speed wireless communication possible in the near future. PMID:26115416

  9. Controlling superconductivity by tunable quantum critical points.

    PubMed

    Seo, S; Park, E; Bauer, E D; Ronning, F; Kim, J N; Shim, J-H; Thompson, J D; Park, Tuson

    2015-01-01

    The heavy fermion compound CeRhIn5 is a rare example where a quantum critical point, hidden by a dome of superconductivity, has been explicitly revealed and found to have a local nature. The lack of additional examples of local types of quantum critical points associated with superconductivity, however, has made it difficult to unravel the role of quantum fluctuations in forming Cooper pairs. Here, we show the precise control of superconductivity by tunable quantum critical points in CeRhIn5. Slight tin-substitution for indium in CeRhIn5 shifts its antiferromagnetic quantum critical point from 2.3 GPa to 1.3 GPa and induces a residual impurity scattering 300 times larger than that of pure CeRhIn5, which should be sufficient to preclude superconductivity. Nevertheless, superconductivity occurs at the quantum critical point of the tin-doped metal. These results underline that fluctuations from the antiferromagnetic quantum criticality promote unconventional superconductivity in CeRhIn5. PMID:25737108

  10. Tunable plasmonic nanobubbles for cell theranostics

    NASA Astrophysics Data System (ADS)

    Lukianova-Hleb, E. Y.; Hanna, E. Y.; Hafner, J. H.; Lapotko, D. O.

    2010-02-01

    Combining diagnostic and therapeutic processes into one (theranostics) and improving their selectivity to the cellular level may offer significant benefits in various research and disease systems and currently is not supported with efficient methods and agents. We have developed a novel method based on the gold nanoparticle-generated transient photothermal vapor nanobubbles, that we refer to as plasmonic nanobubbles (PNB). After delivery and clusterization of the gold nanoparticles (NP) to the target cells the intracellular PNBs were optically generated and controlled through the laser fluence. The PNB action was tuned in individual living cells from non-invasive high-sensitive imaging at lower fluence to disruption of the cellular membrane at higher fluence. We have achieved non-invasive 50-fold amplification of the optical scattering amplitude with the PNBs (relative to that of NPs), selective mechanical and fast damage to specific cells with bigger PNBs, and optical guidance of the damage through the damage-specific signals of the bubbles. Thus the PNBs acted as tunable theranostic agents at the cellular level and in one process that have supported diagnosis, therapy and guidance of the therapy.

  11. Tunable ultrasensitivity: functional decoupling and biological insights.

    PubMed

    Wang, Guanyu; Zhang, Mengshi

    2016-01-01

    Sensitivity has become a basic concept in biology, but much less is known about its tuning, probably because allosteric cooperativity, the best known mechanism of sensitivity, is determined by rigid conformations of interacting molecules and is thus difficult to tune. Reversible covalent modification (RCM), owing to its systems-level ingenuity, can generate concentration based, tunable sensitivity. Using a mathematical model of regulated RCM, we find sensitivity tuning can be decomposed into two orthogonal modes, which provide great insights into vital biological processes such as tissue development and cell cycle progression. We find that decoupling of the two modes of sensitivity tuning is critical to fidelity of cell fate decision; the decoupling is thus important in development. The decomposition also allows us to solve the 'wasteful degradation conundrum' in budding yeast cell cycle checkpoint, which further leads to discovery of a subtle but essential difference between positive feedback and double negative feedback. The latter guarantees revocability of stress-induced cell cycle arrest; while the former does not. By studying concentration conditions in the system, we extend applicability of ultrasensitivity and explain the ubiquity of reversible covalent modification. PMID:26847155

  12. Tunable ultrasensitivity: functional decoupling and biological insights

    PubMed Central

    Wang, Guanyu; Zhang, Mengshi

    2016-01-01

    Sensitivity has become a basic concept in biology, but much less is known about its tuning, probably because allosteric cooperativity, the best known mechanism of sensitivity, is determined by rigid conformations of interacting molecules and is thus difficult to tune. Reversible covalent modification (RCM), owing to its systems-level ingenuity, can generate concentration based, tunable sensitivity. Using a mathematical model of regulated RCM, we find sensitivity tuning can be decomposed into two orthogonal modes, which provide great insights into vital biological processes such as tissue development and cell cycle progression. We find that decoupling of the two modes of sensitivity tuning is critical to fidelity of cell fate decision; the decoupling is thus important in development. The decomposition also allows us to solve the ‘wasteful degradation conundrum’ in budding yeast cell cycle checkpoint, which further leads to discovery of a subtle but essential difference between positive feedback and double negative feedback. The latter guarantees revocability of stress-induced cell cycle arrest; while the former does not. By studying concentration conditions in the system, we extend applicability of ultrasensitivity and explain the ubiquity of reversible covalent modification. PMID:26847155

  13. All-fiber widely tunable thulium laser

    NASA Astrophysics Data System (ADS)

    Stevens, G.; Legg, T.

    2016-03-01

    We present results from an all-fibre thulium laser system that can be tuned to any wavelength between 1710 - 2110 nm, without using any moving mechanical parts. An Acousto-Optic Tunable Filter (AOTF) is used as the tuning element, which allows for the wavelength to be tuned in ~ 20 μs. Core-pumped and cladding pumped thulium fibres are used to enable lasing action across the wavelength range. We use in-house fabricated fused fibre couplers and combiners that have a flattened coupling response with wavelength to allow for the system to be built in an all fibre design. These couplers have a coupling response that only varies by +/- 10% over the 400 nm operating range. The laser can output powers between 1-5 mW over 1710 - 2110 nm and has a linewidth of <0.2 nm. An Acousto-optic modulator is used as a switch on the output of the laser to switch the signal between core-pumped and cladding-pumped amplifier stages. This allows for the output signals to be amplified to ~1W levels.

  14. Control of slippage with tunable bubble mattresses

    PubMed Central

    Karatay, Elif; Haase, A. Sander; Visser, Claas Willem; Sun, Chao; Lohse, Detlef; Tsai, Peichun Amy; Lammertink, Rob G. H.

    2013-01-01

    Tailoring the hydrodynamic boundary condition is essential for both applied and fundamental aspects of drag reduction. Hydrodynamic friction on superhydrophobic substrates providing gas–liquid interfaces can potentially be optimized by controlling the interface geometry. Therefore, establishing stable and optimal interfaces is crucial but rather challenging. Here we present unique superhydrophobic microfluidic devices that allow the presence of stable and controllable microbubbles at the boundary of microchannels. We experimentally and numerically examine the effect of microbubble geometry on the slippage at high resolution. The effective slip length is obtained for a wide range of protrusion angles, θ, of the microbubbles into the flow, using a microparticle image velocimetry technique. Our numerical results reveal a maximum effective slip length, corresponding to a 23% drag reduction at an optimal θ ≈ 10°. In agreement with the simulation results, our measurements correspond to up to 21% drag reduction when θ is in the range of −2° to 12°. The experimental and numerical results reveal a decrease in slip length with increasing protrusion angles when θ ≳ 10°. Such microfluidic devices with tunable slippage are essential for the amplified interfacial transport of fluids and particles. PMID:23650352

  15. Tunable Tensile Ductility in Metallic Glasses

    PubMed Central

    Magagnosc, D. J.; Ehrbar, R.; Kumar, G.; He, M. R.; Schroers, J.; Gianola, D. S.

    2013-01-01

    Widespread adoption of metallic glasses (MGs) in applications motivated by high strength and elasticity combined with plastic-like processing has been stymied by their lack of tensile ductility. One emerging strategy to couple the attractive properties of MGs with resistance to failure by shear localization is to employ sub-micron sample or feature length scales, although conflicting results shroud an atomistic understanding of the responsible mechanisms in uncertainty. Here, we report in situ deformation experiments of directly moulded Pt57.5Cu14.7Ni5.3P22.5 MG nanowires, which show tunable tensile ductility. Initially brittle as-moulded nanowires can be coerced to a distinct glassy state upon irradiation with Ga+ ions, leading to tensile ductility and quasi-homogeneous plastic flow. This behaviour is reversible and the glass returns to a brittle state upon subsequent annealing. Our results suggest a novel mechanism for homogenous plastic flow in nano-scaled MGs and strategies for circumventing the poor damage tolerance that has long plagued MGs.

  16. Tunable Surface Properties from Bioinspired Polymers

    NASA Astrophysics Data System (ADS)

    van Zoelen, Wendy; Rosales, Adrianne M.; Zuckermann, Ronald N.; Segalman, Rachel A.

    2012-02-01

    Tunability of surface properties is of importance for a variety of coating applications, including antifouling coatings. We have investigated the surface properties of polypeptoids, a class of non-natural biomimetic polymers based on an N-substituted glycine backbone, that combine many of the advantageous properties of bulk polymers with those of synthetically produced proteins, including controllable chain shape, sequence, and self-assembled structure. We demonstrate the influence of the amount and sequence of hydrophobic monomers in a predominantly hydrophilic peptoid chain on surface properties. Especially the surface reconstruction behavior of block copolymers of these amphiphilic polypeptoids with polystyrene upon contact with water will be addressed. It has been found that surface reconstruction of peptoid chains that contain a sequence of only three fluorinated monomers and up to forty-two hydrophilic monomers occurs within seconds, whereas reorganization of surfaces containing five fluorinated monomers was an order of magnitude slower. Surfaces with higher fluorine content also showed lower settlement of spores of the green algae Ulva.

  17. Coherently Tunable Triangular Trefoil Phaseonium Metamaterial

    NASA Astrophysics Data System (ADS)

    Nguyen, D. M.; Soci, Cesare; Ooi, C. H. Raymond

    2016-02-01

    Phaseonium is a three-level Λ quantum system, in which a coherent microwave and an optical control (pump) beams can be used to actively modulate the dielectric response. Here we propose a new metamaterial structure comprising of a periodic array of triangular phaseonium metamolecules arranged as a trefoil. We present a computational study of the spatial distribution of magnetic and electric fields of the probe light and the corresponding transmission and reflection, for various parameters of the optical and microwave beams. For specific values of the probing frequencies and control fields, the phaseonium can display either metallic or dielectric optical response. We find that, in the metallic regime, the phaseonium metamaterial structure supports extremely large transmission, with optical amplification at large enough intensity of the microwave thanks to strong surface plasmon coupling; while, in the dielectric regime without microwave excitation, the transmission bandwidth can be tuned by varying the control beam intensity. Implementation of such phaseonium metamaterial structure in solid-state systems, such as patterned crystals doped with rare-earth elements or dielectric matrices embedded with quantum dots, could enable a new class of actively tunable quantum metamaterials.

  18. Tunable, nonlinear Hong-Ou-Mandel interferometer

    NASA Astrophysics Data System (ADS)

    Oehri, D.; Pletyukhov, M.; Gritsev, V.; Blatter, G.; Schmidt, S.

    2015-03-01

    We investigate the two-photon scattering properties of a Jaynes-Cummings (JC) nonlinearity consisting of a two-level system (qubit) interacting with a single-mode cavity, which is coupled to two waveguides, each containing a single incident photon wave packet initially. In this scattering setup, we study the interplay between the Hong-Ou-Mandel (HOM) effect arising due to quantum interference and effective photon-photon interactions induced by the presence of the qubit. We calculate the two-photon scattering matrix of this system analytically and identify signatures of interference and interaction in the second-order auto- and cross-correlation functions of the scattered photons. In the dispersive regime, when qubit and cavity are far detuned from each other, we find that the JC nonlinearity can be used as an almost linear, in situ tunable beam splitter giving rise to ideal Hong-Ou-Mandel interference, generating a highly path-entangled two-photon NOON state of the scattered photons. The latter manifests itself in strongly suppressed waveguide cross-correlations and Poissonian photon number statistics in each waveguide. If the two-level system and the cavity are on resonance, the JC nonlinearity strongly modifies the ideal HOM conditions leading to a smaller degree of path entanglement and sub-Poissonian photon number statistics. In the latter regime, we find that photon blockade is associated with bunched autocorrelations in both waveguides, while a two-polariton resonance can lead to bunched as well as antibunched correlations.

  19. Microelectromechanically tunable multiband metamaterial with preserved isotropy

    PubMed Central

    Pitchappa, Prakash; Ho, Chong Pei; Qian, You; Dhakar, Lokesh; Singh, Navab; Lee, Chengkuo

    2015-01-01

    We experimentally demonstrate a micromachined reconfigurable metamaterial with polarization independent characteristics for multiple resonances in terahertz spectral region. The metamaterial unit cell consists of eight out-of-plane deformable microcantilevers placed at each corner of an octagon ring. The octagon shaped unit cell geometry provides the desired rotational symmetry, while the out-of-plane movable cantilevers preserves the symmetry at different configurations of the metamaterial. The metamaterial is shown to provide polarization independent response for both electrical inductive-capacitive (eLC) resonance and dipolar resonance at all states of actuation. The proposed metamaterial has a switching range of 0.16 THz and 0.37 THz and a transmission intensity change of more than 0.2 and 0.7 for the eLC and dipolar resonances, respectively for both TE and TM modes. Further optimization of the metal layer thickness, provides an improvement of up to 80% modulation at 0.57 THz. The simultaneously tunable dual band isotropic metamaterial will enable the realization of high performance electro-optic devices that would facilitate numerous terahertz applications such as compressive terahertz imaging, miniaturized terahertz spectroscopy and next generation high speed wireless communication possible in the near future. PMID:26115416

  20. Coherently Tunable Triangular Trefoil Phaseonium Metamaterial.

    PubMed

    Nguyen, D M; Soci, Cesare; Ooi, C H Raymond

    2016-01-01

    Phaseonium is a three-level Λ quantum system, in which a coherent microwave and an optical control (pump) beams can be used to actively modulate the dielectric response. Here we propose a new metamaterial structure comprising of a periodic array of triangular phaseonium metamolecules arranged as a trefoil. We present a computational study of the spatial distribution of magnetic and electric fields of the probe light and the corresponding transmission and reflection, for various parameters of the optical and microwave beams. For specific values of the probing frequencies and control fields, the phaseonium can display either metallic or dielectric optical response. We find that, in the metallic regime, the phaseonium metamaterial structure supports extremely large transmission, with optical amplification at large enough intensity of the microwave thanks to strong surface plasmon coupling; while, in the dielectric regime without microwave excitation, the transmission bandwidth can be tuned by varying the control beam intensity. Implementation of such phaseonium metamaterial structure in solid-state systems, such as patterned crystals doped with rare-earth elements or dielectric matrices embedded with quantum dots, could enable a new class of actively tunable quantum metamaterials. PMID:26879520

  1. Tunable magnetocaloric effect in transition metal alloys

    NASA Astrophysics Data System (ADS)

    Belyea, Dustin D.; Lucas, M. S.; Michel, E.; Horwath, J.; Miller, Casey W.

    2015-10-01

    The unpredictability of geopolitical tensions and resulting supply chain and pricing instabilities make it imperative to explore rare earth free magnetic materials. As such, we have investigated fully transition metal based “high entropy alloys” in the context of the magnetocaloric effect. We find the NiFeCoCrPdx family exhibits a second order magnetic phase transition whose critical temperature is tunable from 100 K to well above room temperature. The system notably displays changes in the functionality of the magnetic entropy change depending on x, which leads to nearly 40% enhancement of the refrigerant capacity. A detailed statistical analysis of the universal scaling behavior provides direct evidence that heat treatment and Pd additions reduce the distribution of exchange energies in the system, leading to a more magnetically homogeneous alloy. The general implications of this work are that the parent NiFeCoCr compound can be tuned dramatically with FCC metal additives. Together with their relatively lower cost, their superior mechanical properties that aid manufacturability and their relative chemical inertness that aids product longevity, NiFeCoCr-based materials could ultimately lead to commercially viable magnetic refrigerants.

  2. Composites with mechanically tunable plasmon frequency

    NASA Astrophysics Data System (ADS)

    Schuil, Crystal J.; Amirkhizi, Alireza V.; Bayatpur, Farhad; Nemat-Nasser, Sia

    2011-11-01

    This paper summarizes our efforts to create a composite material with a mechanically tunable plasmon frequency at the microwave band. The permittivity of the composite changes sign at the plasmon frequency. Such composites, therefore, can be used as electromagnetic filters. Theoretically, an array of non-magnetic, metallic wire coils has been shown to have a plasmon behavior that is dependent on the wire thickness, coil inner diameter, pitch and coil spacing. Here, a material is made out of an array of coils placed within a non-metallic frame, and the material plasmon frequency is tuned through altering the pitch. The coils are arranged with alternating handedness to create an effective, non-chiral medium. A transmit/receive setup is used to characterize the electromagnetic behavior of the composite. The setup consists of a vector network analyzer and two horn antennas, which are used to measure the scattering parameters of the material. These parameters are then used to calculate the permittivity. The results show an increase in the plasmon frequency with increase in the pitch. Increasing the pitch 30%, from 3 to 3.9 mm, results in a corresponding increase from 6.3 to 7.5 GHz in the frequency.

  3. Tunable one-dimensional photonic crystal slabs

    NASA Astrophysics Data System (ADS)

    Beccherelli, R.; Bellini, B.; Zografopoulos, D.; Kriezis, E.

    2007-05-01

    A 1D photonic crystal slab based on preferential etching of commercially available silicon-on-insulator wafers is presented. Compared to dry etching, anisotropic wet etching is more tolerant to errors as it is self-stopping on crystallographic {111} planes and it produces a more precise geometry with symmetries and homothetic properties, with surface roughness close to 1 nm. The resulting grooves are infiltrated by low viscosity liquid crystal having large positive optical anisotropy. The use of slanted grooves provides advantages: first of all the complete filling of slanted grooves is simplified when compared to vertical walls structures. Furthermore alignment is significantly facilitated. Indeed the liquid crystal molecules tend to align with their long axis along the submicron grooves. Therefore by forcing reorientation out of a rest position, the liquid crystal presents a choice of refractive indices to the propagating optical field. The liquid crystal behavior is simulated by a finite element method, and coupled to a finite difference time domain method. We investigate different photonic crystal configurations. Large tunability of bandgap edge for TE polarization is demonstrated when switching the liquid crystal with an applied voltage. We have also studied the use of the same device geometry as a very compact microfluidic refractometric sensor.

  4. Tunable plasmonic nanobubbles for cell theranostics

    PubMed Central

    Lukianova-Hleb, EY; Hanna, EY; Hafner, JH; Lapotko, DO

    2010-01-01

    Combining diagnostic and therapeutic processes into one (theranostics) and improving their selectivity to the cellular level may offer significant benefits in various research and disease systems and currently is not supported with efficient methods and agents. We have developed a novel method based on the gold nanoparticle-generated transient photothermal vapor nanobubbles, that we refer to as plasmonic nanobubbles (PNB). After delivery and clusterization of the gold nanoparticles (NP) to the target cells the intracellular PNBs were optically generated and controlled through the laser fluence. The PNB action was tuned in individual living cells from non-invasive high-sensitive imaging at lower fluence to disruption of the cellular membrane at higher fluence. We have achieved non-invasive 50-fold amplification of the optical scattering amplitude with the PNBs (relative to that of NPs), selective mechanical and fast damage to specific cells with bigger PNBs, and optical guidance of the damage through the damage-specific signals of the bubbles. Thus the PNBs acted as tunable theranostic agents at the cellular level and in one process that have supported diagnosis, therapy and guidance of the therapy. PMID:20097970

  5. Parametric resonance in tunable superconducting cavities

    NASA Astrophysics Data System (ADS)

    Wustmann, Waltraut; Shumeiko, Vitaly

    2013-05-01

    We develop a theory of parametric resonance in tunable superconducting cavities. The nonlinearity introduced by the superconducting quantum interference device (SQUID) attached to the cavity and damping due to connection of the cavity to a transmission line are taken into consideration. We study in detail the nonlinear classical dynamics of the cavity field below and above the parametric threshold for the degenerate parametric resonance, featuring regimes of multistability and parametric radiation. We investigate the phase-sensitive amplification of external signals on resonance, as well as amplification of detuned signals, and relate the amplifier performance to that of linear parametric amplifiers. We also discuss applications of the device for dispersive qubit readout. Beyond the classical response of the cavity, we investigate small quantum fluctuations around the amplified classical signals. We evaluate the noise power spectrum both for the internal field in the cavity and the output field. Other quantum-statistical properties of the noise are addressed such as squeezing spectra, second-order coherence, and two-mode entanglement.

  6. Evolutionary Accessibility in Tunably Rugged Fitness Landscapes

    NASA Astrophysics Data System (ADS)

    Franke, Jasper; Krug, Joachim

    2012-09-01

    The adaptive evolution of a population under the influence of mutation and selection is strongly influenced by the structure of the underlying fitness landscape, which encodes the interactions between mutations at different genetic loci. Theoretical studies of such landscapes have been carried out for several decades, but only recently experimental fitness measurements encompassing all possible combinations of small sets of mutations have become available. The empirical studies have spawned new questions about the accessibility of optimal genotypes under natural selection. Depending on population dynamic parameters such as mutation rate and population size, evolutionary accessibility can be quantified through the statistics of accessible mutational pathways (along which fitness increases monotonically), or through the study of the basin of attraction of the optimal genotype under greedy (steepest ascent) dynamics. Here we investigate these two measures of accessibility in the framework of Kauffman's LK-model, a paradigmatic family of random fitness landscapes with tunable ruggedness. The key parameter governing the strength of genetic interactions is the number K of interaction partners of each of the L sites in the genotype sequence. In general, accessibility increases with increasing genotype dimensionality L and decreases with increasing number of interactions K. Remarkably, however, we find that some measures of accessibility behave non-monotonically as a function of K, indicating a special role of the most sparsely connected, non-trivial cases K=1 and 2. The relation between models for fitness landscapes and spin glasses is also addressed.

  7. Tunable damper for an acoustic wave guide

    DOEpatents

    Rogers, S.C.

    1982-10-21

    A damper for tunably damping acoustic waves in an ultrasonic waveguide is provided which may be used in a hostile environment such as a nuclear reactor. The area of the waveguide, which may be a selected size metal rod in which acoustic waves are to be damped, is wrapped, or surrounded, by a mass of stainless steel wool. The wool wrapped portion is then sandwiched between tuning plates, which may also be stainless steel, by means of clamping screws which may be adjusted to change the clamping force of the sandwiched assembly along the waveguide section. The plates are preformed along their length in a sinusoidally bent pattern with a period approximately equal to the acoustic wavelength which is to be damped. The bent pattern of the opposing plates are in phase along their length relative to their sinusoidal patterns so that as the clamping screws are tightened a bending stress is applied to the waveguide at 180/sup 0/ intervals along the damping section to oppose the acoustic wave motions in the waveguide and provide good coupling of the wool to the guide. The damper is tuned by selectively tightening the clamping screws while monitoring the amplitude of the acoustic waves launched in the waveguide. It may be selectively tuned to damp particular acoustic wave modes (torsional or extensional, for example) and/or frequencies while allowing others to pass unattenuated.

  8. The generation of Continuous-Variable Entanglement Frequency Comb

    PubMed Central

    Yu, Youbin; Cheng, Xiaomin; Wang, Huaijun; Shi, Zhongtao; Zhao, Junwei; Ji, Fengmin; Yin, Zhi; Wang, Yajuan

    2015-01-01

    Continuous-variable (CV) entanglement frequency comb can be produced by enhanced Raman scattering in an above-threshold optical oscillator cavity in which a hexagonally-poled LiTaO3 crystal resides as a Raman gain medium. The Stokes and anti-Stokes Raman signals are enhanced by a coupled quasi-phase-matching optical parametric process and the entanglement natures among these Raman signals and pump are demonstrated by applying a sufficient inseparability criterion for CV entanglement. Such entanglement frequency comb source with different frequencies and continuously tunable frequency interval may be very significant for the applications in quantum communication and networks. PMID:25600617

  9. The generation of continuous-variable entanglement frequency comb.

    PubMed

    Yu, Youbin; Cheng, Xiaomin; Wang, Huaijun; Shi, Zhongtao; Zhao, Junwei; Ji, Fengmin; Yin, Zhi; Wang, Yajuan

    2015-01-01

    Continuous-variable (CV) entanglement frequency comb can be produced by enhanced Raman scattering in an above-threshold optical oscillator cavity in which a hexagonally-poled LiTaO3 crystal resides as a Raman gain medium. The Stokes and anti-Stokes Raman signals are enhanced by a coupled quasi-phase-matching optical parametric process and the entanglement natures among these Raman signals and pump are demonstrated by applying a sufficient inseparability criterion for CV entanglement. Such entanglement frequency comb source with different frequencies and continuously tunable frequency interval may be very significant for the applications in quantum communication and networks. PMID:25600617

  10. The generation of Continuous-Variable Entanglement Frequency Comb

    NASA Astrophysics Data System (ADS)

    Yu, Youbin; Cheng, Xiaomin; Wang, Huaijun; Shi, Zhongtao; Zhao, Junwei; Ji, Fengmin; Yin, Zhi; Wang, Yajuan

    2015-01-01

    Continuous-variable (CV) entanglement frequency comb can be produced by enhanced Raman scattering in an above-threshold optical oscillator cavity in which a hexagonally-poled LiTaO3 crystal resides as a Raman gain medium. The Stokes and anti-Stokes Raman signals are enhanced by a coupled quasi-phase-matching optical parametric process and the entanglement natures among these Raman signals and pump are demonstrated by applying a sufficient inseparability criterion for CV entanglement. Such entanglement frequency comb source with different frequencies and continuously tunable frequency interval may be very significant for the applications in quantum communication and networks.

  11. Widely tunable Sampled Grating Distributed Bragg Reflector Quantum Cascade laser for gas spectroscopy applications

    NASA Astrophysics Data System (ADS)

    Diba, Abdou Salam

    Since the advent of semiconductor lasers, the development of tunable laser sources has been subject of many efforts in industry and academia arenas. This interest towards broadly tunable lasers is mainly due to the great promise they have in many applications ranging from telecommunication, to environmental science and homeland security, just to name a few. After the first demonstration of quantum cascade laser (QCL) in the early nineties, QCL has experienced a rapid development, so much so that QCLs are now the most reliable and efficient laser source in the Mid-IR range covering between 3 microm to 30 microm region of the electromagnetic spectrum. QCLs have almost all the desirable characteristics of a laser for spectroscopy applications such as narrow spectral linewidth ideal for high selectivity measurement, high power enabling high sensitivity sensing and more importantly they emit in the finger-print region of most of the trace gases and large molecules. The need for widely tunable QCLs is now more pressing than ever before. A single mode quantum cascade laser (QCL) such as a distributed feedback (DFB) QCL, is an ideal light source for gas sensing in the MIR wavelength range. Despite their performance and reliability, DFB QCLs are limited by their relatively narrow wavelength tuning range determined by the thermal rollover of the laser. An external cavity (EC) QCL, on the other hand, is a widely tunable laser source, and so far is the choice mid-infrared single frequency light sources for detecting multiple species/large molecules. However, EC QCLs can be complex, bulky and expensive. In the quest for finding alternative broadly wavelength tunable sources in the mid-infrared, many monolithic tunable QCLs are recently proposed and fabricated, including SG-DBR, DFB-Arrays, Slot-hole etc. and they are all of potentially of interest as a candidate for multi-gas sensing and monitoring applications, due to their large tuning range (>50 cm-1), and potentially low

  12. Millisecond Coherence Time in a Tunable Molecular Electronic Spin Qubit

    PubMed Central

    2015-01-01

    Quantum information processing (QIP) could revolutionize areas ranging from chemical modeling to cryptography. One key figure of merit for the smallest unit for QIP, the qubit, is the coherence time (T2), which establishes the lifetime for the qubit. Transition metal complexes offer tremendous potential as tunable qubits, yet their development is hampered by the absence of synthetic design principles to achieve a long T2. We harnessed molecular design to create a series of qubits, (Ph4P)2[V(C8S8)3] (1), (Ph4P)2[V(β-C3S5)3] (2), (Ph4P)2[V(α-C3S5)3] (3), and (Ph4P)2[V(C3S4O)3] (4), with T2s of 1–4 μs at 80 K in protiated and deuterated environments. Crucially, through chemical tuning of nuclear spin content in the vanadium(IV) environment we realized a T2 of ∼1 ms for the species (d20-Ph4P)2[V(C8S8)3] (1′) in CS2, a value that surpasses the coordination complex record by an order of magnitude. This value even eclipses some prominent solid-state qubits. Electrochemical and continuous wave electron paramagnetic resonance (EPR) data reveal variation in the electronic influence of the ligands on the metal ion across 1–4. However, pulsed measurements indicate that the most important influence on decoherence is nuclear spins in the protiated and deuterated solvents utilized herein. Our results illuminate a path forward in synthetic design principles, which should unite CS2 solubility with nuclear spin free ligand fields to develop a new generation of molecular qubits. PMID:27163013

  13. Dynamically reconfigurable complex emulsions via tunable interfacial tensions

    PubMed Central

    Zarzar, Lauren D.; Sresht, Vishnu; Sletten, Ellen M.; Kalow, Julia A.; Blankschtein, Daniel; Swager, Timothy M.

    2015-01-01

    Emulsification is a powerful, well-known technique for mixing and dispersing immiscible components within a continuous liquid phase. Consequently, emulsions are central components of medicine, food and performance materials. Complex emulsions, including multiple emulsions and Janus droplets which contain hemispheres of differing material, are of increasing importance1 in pharmaceuticals and medical diagnostics2, in the fabrication of microparticles and capsules3–5 for food6, in chemical separations7, in cosmetics8, and in dynamic optics9. Because complex emulsion properties and functions are related to the droplet geometry and composition, the development of rapid, simple fabrication approaches allowing precise control over the droplets’ physical and chemical characteristics is critical. Significant advances in the fabrication of complex emulsions have been made using a number of procedures, ranging from large-scale, less precise techniques that give compositional heterogeneity using high-shear mixers and membranes10, to small-volume but more precise microfluidic methods11,12. However, such approaches have yet to create droplet morphologies that can be controllably altered after emulsification. Reconfigurable complex liquids potentially have greatly increased utility as dynamically tunable materials. Here we describe an approach to the one-step fabrication of three- and four-phase complex emulsions with highly controllable and reconfigurable morphologies. The fabrication makes use of the temperature-sensitive miscibility of hydrocarbon, silicone and fluorocarbon liquids, and is applied to both the microfluidic and the scalable batch production of complex droplets. We demonstrate that droplet geometries can be alternated between encapsulated and Janus configurations by varying the interfacial tensions using hydrocarbon and fluorinated surfactants including stimuli-responsive and cleavable surfactants. This yields a generalizable strategy for the fabrication of

  14. Dynamically reconfigurable complex emulsions via tunable interfacial tensions

    NASA Astrophysics Data System (ADS)

    Zarzar, Lauren D.; Sresht, Vishnu; Sletten, Ellen M.; Kalow, Julia A.; Blankschtein, Daniel; Swager, Timothy M.

    2015-02-01

    Emulsification is a powerful, well-known technique for mixing and dispersing immiscible components within a continuous liquid phase. Consequently, emulsions are central components of medicine, food and performance materials. Complex emulsions, including Janus droplets (that is, droplets with faces of differing chemistries) and multiple emulsions, are of increasing importance in pharmaceuticals and medical diagnostics, in the fabrication of microparticles and capsules for food, in chemical separations, in cosmetics, and in dynamic optics. Because complex emulsion properties and functions are related to the droplet geometry and composition, the development of rapid, simple fabrication approaches allowing precise control over the droplets' physical and chemical characteristics is critical. Significant advances in the fabrication of complex emulsions have been made using a number of procedures, ranging from large-scale, less precise techniques that give compositional heterogeneity using high-shear mixers and membranes, to small-volume but more precise microfluidic methods. However, such approaches have yet to create droplet morphologies that can be controllably altered after emulsification. Reconfigurable complex liquids potentially have great utility as dynamically tunable materials. Here we describe an approach to the one-step fabrication of three- and four-phase complex emulsions with highly controllable and reconfigurable morphologies. The fabrication makes use of the temperature-sensitive miscibility of hydrocarbon, silicone and fluorocarbon liquids, and is applied to both the microfluidic and the scalable batch production of complex droplets. We demonstrate that droplet geometries can be alternated between encapsulated and Janus configurations by varying the interfacial tensions using hydrocarbon and fluorinated surfactants including stimuli-responsive and cleavable surfactants. This yields a generalizable strategy for the fabrication of multiphase emulsions with

  15. Millisecond Coherence Time in a Tunable Molecular Electronic Spin Qubit.

    PubMed

    Zadrozny, Joseph M; Niklas, Jens; Poluektov, Oleg G; Freedman, Danna E

    2015-12-23

    Quantum information processing (QIP) could revolutionize areas ranging from chemical modeling to cryptography. One key figure of merit for the smallest unit for QIP, the qubit, is the coherence time (T 2), which establishes the lifetime for the qubit. Transition metal complexes offer tremendous potential as tunable qubits, yet their development is hampered by the absence of synthetic design principles to achieve a long T 2. We harnessed molecular design to create a series of qubits, (Ph4P)2[V(C8S8)3] (1), (Ph4P)2[V(β-C3S5)3] (2), (Ph4P)2[V(α-C3S5)3] (3), and (Ph4P)2[V(C3S4O)3] (4), with T 2s of 1-4 μs at 80 K in protiated and deuterated environments. Crucially, through chemical tuning of nuclear spin content in the vanadium(IV) environment we realized a T 2 of ∼1 ms for the species (d 20-Ph4P)2[V(C8S8)3] (1') in CS2, a value that surpasses the coordination complex record by an order of magnitude. This value even eclipses some prominent solid-state qubits. Electrochemical and continuous wave electron paramagnetic resonance (EPR) data reveal variation in the electronic influence of the ligands on the metal ion across 1-4. However, pulsed measurements indicate that the most important influence on decoherence is nuclear spins in the protiated and deuterated solvents utilized herein. Our results illuminate a path forward in synthetic design principles, which should unite CS2 solubility with nuclear spin free ligand fields to develop a new generation of molecular qubits. PMID:27163013

  16. High power continuous-wave Alexandrite laser with green pump

    NASA Astrophysics Data System (ADS)

    Ghanbari, Shirin; Major, Arkady

    2016-07-01

    We report on a continuous-wave (CW) Alexandrite (Cr:BeAl2O4) laser, pumped by a high power green source at 532 nm with a diffraction limited beam. An output power of 2.6 W at 755 nm, a slope efficiency of 26%, and wavelength tunability of 85 nm have been achieved using 11 W of green pump. To the best of our knowledge, this is the highest CW output power of a high brightness laser pumped Alexandrite laser reported to date. The results obtained in this experiment can lead to the development of a high power tunable CW and ultrafast sources of the near-infrared or ultraviolet radiation through frequency conversion.

  17. Tunable Metasurface and Flat Optical Zoom Lens on a Stretchable Substrate.

    PubMed

    Ee, Ho-Seok; Agarwal, Ritesh

    2016-04-13

    A mechanically reconfigurable metasurface that can continuously tune the wavefront is demonstrated in the visible frequency range by changing the lattice constant of a complex Au nanorod array fabricated on a stretchable polydimethylsiloxane substrate. It is shown that the anomalous refraction angle of visible light at 632.8 nm interacting with the tunable metasurface can be adjusted from 11.4° to 14.9° by stretching the substrate by ∼30%. An ultrathin flat 1.7× zoom lens whose focal length can continuously be changed from 150 to 250 μm is realized, which also demonstrates the potential of utilizing metasurfaces for reconfigurable flat optics. PMID:26986191

  18. Tunable broadband terahertz wave plate based on one-dimensional superconductor-dielectric photonic crystals

    NASA Astrophysics Data System (ADS)

    Liu, Yang; Liu, Ming; Hu, Xin-Guang; Yu, Li; Xie, Yan-Ding; Yi, Lin

    2016-04-01

    The reflection phase difference between transverse electric (TE) and transverse magnetic (TM) waves in a one-dimensional superconductor-dielectric photonic crystal is studied by the transfer matrix method. The simulation results indicate that wide frequency regions exist within the terahertz range, in which the reflection phase differences can remain constant for a fixed incident angle and can vary continuously from 0 to π (or 0 to -π ) by increasing the incident angle. The shift and the number of such wide frequency regions can be manipulated through changing the thickness of the dielectric layers. The influences of temperature and the normal conducting electrons on the properties of the reflection phase difference are also numerically investigated. Based on these properties, a continuously tunable broadband terahertz wave plate can be designed.

  19. Nanoscale Tunable Strong Carrier Density Modulation of 2D Materials for Metamaterials and Other Tunable Optoelectronics

    NASA Astrophysics Data System (ADS)

    Peng, Cheng; Efetov, Dmitri; Shiue, Ren-Jye; Nanot, Sebastien; Hempel, Marek; Kong, Jing; Koppens, Frank; Englund, Dirk

    Strong spatial tunability of the charge carrier density at nanoscale is essential to many 2D-material-based electronic and optoelectronic applications. As an example, plasmonic metamaterials with nanoscale dimensions would make graphene plasmonics at visible and near-infrared wavelengths possible. However, existing gating techniques based on conventional dielectric gating geometries limit the spatial resolution and achievable carrier concentration, strongly restricting the available wavelength, geometry, and quality of the devices. Here, we present a novel spatially selective electrolyte gating approach that allows for in-plane spatial Fermi energy modulation of 2D materials of more than 1 eV (carrier density of n = 1014 cm-2) across a length of 2 nm. We present electrostatic simulations as well as electronic transport, photocurrent, cyclic voltammetry and optical spectroscopy measurements to characterize the performance of the gating technique applied to graphene devices. The high spatial resolution, high doping capacity, full tunability and self-aligned device geometry of the presented technique opens a new venue for nanoscale metamaterial engineering of 2D materials for complete optical absorption, nonlinear optics and sensing, among other applications.

  20. Ultrahigh frequency tunability of aperture-coupled microstrip antenna via electric-field tunable BST

    NASA Astrophysics Data System (ADS)

    Du, Hong-Lei; Xue, Qian; Gao, Xiao-Yang; Yao, Feng-Rui; Lu, Shi-Yang; Wang, Ye-Long; Liu, Chun-Heng; Zhang, Yong-Cheng; Lü, Yue-Guang; Li, Shan-Dong

    2015-12-01

    A composite ceramic with nominal composition of 45.0 wt%(Ba0.5Sr0.5)TiO3-55.0 wt%MgO (acronym is BST-MgO) is sintered for fabricating a frequency reconfigurable aperture-coupled microstrip antenna. The calcined BST-MgO composite ceramic exhibits good microwave dielectric properties at X-band with appropriate dielectric constant ɛr around 85, lower dielectric loss tan δ about 0.01, and higher permittivity tunability 14.8% at 8.33 kV/cm. An ultrahigh E-field tunability of working frequency up to 11.0% (i.e., from 9.1 GHz to 10.1 GHz with a large frequency shift of 1000 MHz) at a DC bias field from 0 to 8.33 kV/cm and a considerably large center gain over 7.5 dB are obtained in the designed frequency reconfigurable microstrip antenna. These results demonstrate that BST materials are promising for the frequency reconfigurable antenna. Project supported by the National Natural Science Foundation of China (Grant No. 11074040) and the Key Project of Shandong Provincial Department of Science and Technology, China (Grant No. ZR2012FZ006).

  1. Single-frequency tunable 447.3 nm laser by frequency doubling of tapered amplified diode laser at cesium D1 line.

    PubMed

    Zhang, Yan; Liu, Jinhong; Wu, Jinze; Ma, Rong; Wang, Dan; Zhang, Junxiang

    2016-08-22

    A continuous single-frequency tunable blue laser at 447.3 nm is developed by external-cavity frequency doubling of a tapered amplifier-boosted continuous-wave diode laser at cesium (Cs) D1 line. A maximum blue power of 178 mW with 50.8% conversion efficiency is obtained. It can be continuously tuned over a range around 1.6 GHz as the diode laser frequency is scanned across the F=4→F'=3 transition of 133Cs D1 line. The generated tunable and stable blue laser source has potential applications in constructing quantum light-atom interfaces in quantum networks. PMID:27557253

  2. Tunable Fano quantum-interference dynamics using a topological phase transition in (Bi1-xI nx ) 2S e3

    NASA Astrophysics Data System (ADS)

    Sim, Sangwan; Koirala, Nikesh; Brahlek, Matthew; Sung, Ji Ho; Park, Jun; Cha, Soonyoung; Jo, Moon-Ho; Oh, Seongshik; Choi, Hyunyong

    2015-06-01

    Asymmetric Fano resonance arises from quantum interference between discrete and continuum states. The characteristic asymmetry has attracted strong interests in understanding light-induced optoelectronic responses and corresponding applications. In conventional solids, however, the tunability of Fano resonance is generally limited by a material's intrinsic property. Topological insulators are unique states of matter embodying both conducting Dirac surface and underlying bulk. If it is possible to manipulate the two coexisting states, then it should form an ideal laboratory for realizing a tunable topological Fano system. Here, with the recently discovered topological phase transition in (Bi1-xI nx ) 2S e3 , we report tunable Fano interference phenomena. By engineering the spatial overlap between surface Dirac electrons (continuous terahertz transitions) and bulk phonon (discrete mode at ˜2 terahertz), we continuously tune, abruptly switch, and dynamically modulate the Fano resonance. Eliminating the topological surface via decreasing spin-orbit coupling―that is, across topological and nontopological phases, we find that the asymmetric Fano spectra return to the symmetric profile. Laser-excited ultrafast terahertz spectroscopy reveals that the controlled spatial overlap is responsible for the picosecond tunability of the Fano resonance, suggesting potentials toward optically controllable topological Fano systems.

  3. Development of a Tunable LED-Based Colorimetric Source

    PubMed Central

    Brown, Steven W.; Santana, Carlos; Eppeldauer, George P.

    2002-01-01

    A novel, spectrally tunable light-source utilizing light emitting diodes (LEDs) for radiometric, photometric, and colorimetric applications is described. The tunable source can simulate standard sources and can be used as a transfer source to propagate photometric and colorimetric scales from calibrated reference instruments to test artifacts with minimal increase in uncertainty. In this prototype source, 40 LEDs with 10 different spectral distributions were mounted onto an integrating sphere. A voltage-to-current control circuit was designed and implemented, enabling independent control of the current sent to each set of four LEDs. The LEDs have been characterized for stability and dependence on drive current. The prototype source demonstrates the feasibility of development of a spectrally tunable LED source using LEDs with up to 40 different spectral distributions. Simulations demonstrate that such a source would be able to approximate standard light-source distributions over the visible spectral range—from 380 nm to 780 nm—with deviations on the order of 2 %. The tunable LED source can also simulate spectral distributions of special sources such as discharge lamps and display monitors. With this tunable source, a test instrument can be rapidly calibrated against a variety of different source distributions tailored to the anticipated uses of the artifact. Target uncertainties for the calibration of test artifacts are less than 2 % in luminance and 0.002 in chromaticity for any source distribution.

  4. Bioinspired solid-liquid mixed tunable lens with multilayered structure

    NASA Astrophysics Data System (ADS)

    Liang, Dan; Wang, Xuan-Yin; Du, Jia-Wei

    2015-06-01

    A solid-liquid mixed tunable lens with multilayered structure is proposed. The designed lens utilizes a solid-state elastic polymer, optical liquid, and glass as the optical medium, and adjusts the focus by changing the surface curvature of the elastic polymer. The integrated structure of the tunable lens is presented, as well as detailed descriptions of the lens materials, fabrication, and assembling process. Images captured through the tunable lens under different displacement loads are presented, and the relationship among the displacement load, curvature radius, and effective focal length is analyzed. Additionally, the optical property of the tunable lens is simulated using the ZEMAX software. A change in focal length from 14.8 mm to 30 mm is demonstrated within the tiny 0.12 mm variation of the displacement load. Numerical analyses show that the lens distortion is less than 2%, and the modulation transfer function reaches 67 line pairs per mm. The solid-liquid mixed tunable lens shows the potential for developing a compact, low-aberration, and stable optical system.

  5. Trends in gas sensors with tunable thin films

    NASA Astrophysics Data System (ADS)

    Domash, Lawrence; Cohen, Mitchell; Wagner, Matthias

    2004-10-01

    A new family of miniature nano-tunable narrowband infrared filters has been developed based on the thermo-optic properties of thin film semiconductors. Originally developed for fiber optic telecommunications networks at 1.5 μm, the technology has now been extended to the 3-5 μm range, leading to very compact tunable filters with passbands on the order of 0.5% of center wavelength and tuning ranges up to 4% of center wavelength. Two applications are described. First, a prototype carbon monoxide sensor testbed based on a 4550-4650 nm tunable filter is shown to be capable of detecting less than 20 ppm of CO. Second, we show how nano-tunable thin film filters can be integrated with miniature blackbody sources to create a new family of ultra low cost integrated tunable IR emitters, which we have named Firefly. Packaged in TO cans, Firefly devices enable precision detection of gases including carbon dioxide, carbon monoxide, sulphur dioxide, hydrogen cyanide, water vapor, nitric oxide or methane.

  6. Tunable Optical Filters Having Electro-optic Whispering-gallery-mode Resonators

    NASA Technical Reports Server (NTRS)

    Savchenkov, Anatoliy (Inventor); Ilchenko, Vladimir (Inventor); Matsko, Andrey B. (Inventor); Maleki, Lutfollah (Inventor)

    2006-01-01

    Tunable optical filters using whispering-gallery-mode (WGM) optical resonators are described. The WGM optical resonator in a filter exhibits an electro-optical effect and hence is tunable by applying a control electrical signal.

  7. A continuous sampling air-ICP for metals emission monitoring

    SciTech Connect

    Baldwin, D.P.; Zamzow, D.S.; Eckels, D.E.; Miller, G.P.

    1999-09-19

    An air-inductively coupled plasma (air-ICP) system has been developed for continuous sampling and monitoring of metals as a continuous emission monitor (CEM). The plasma is contained in a metal enclosure to allow reduced-pressure operation. The enclosure and plasma are operated at a pressure slightly less than atmospheric using a Roots blower, so that sample gas is continuously drawn into the plasma. A Teflon sampling chamber, equipped with a sampling pump, is connected to the stack that is to be monitored to isokinetically sample gas from the exhaust line and introduce the sample into the air-ICP. Optical emission from metals in the sampled gas stream is detected and monitored using an acousto-optic tunable filter (AOTF)--echelle spectrometer system. A description of the continuous sampling air-ICP system is given, along with some preliminary laboratory data for continuous monitoring of metals.

  8. Continuous sampling air-ICP for metals emission monitoring

    NASA Astrophysics Data System (ADS)

    Baldwin, David P.; Zamzow, Daniel S.; Eckels, David E.; Miller, George P.

    1999-12-01

    An air-inductively coupled plasma (air-ICP) system has been developed for continuous sampling and monitoring of metals as a continuous emission monitor (CEM). The plasma is contained in a metal enclosure to allow reduced-pressure operation. The enclosure and plasma are operated at a pressure slightly less than atmospheric using a Roots blower, so that sample gas is continuously drawn into the plasma. A Teflon sampling chamber, equipped with a sampling pump, is connected to the stack that is to be monitored to isokinetically sample gas from the exhaust line and introduce the sample into the air-ICP. Optical emission from metals in the sampled gas stream is detected and monitored using an acousto-optic tunable filter (AOTF)-echelle spectrometer system. A description of the continuous sampling air-ICP system is given, along with some preliminary laboratory data for continuous monitoring of metals.

  9. Tunable Interfacial Thermal Conductance by Molecular Dynamics

    NASA Astrophysics Data System (ADS)

    Shen, Meng

    We study the mechanism of tunable heat transfer through interfaces between solids using a combination of non-equilibrium molecular dynamics simulation (NEMD), vibrational mode analysis and wave packet simulation. We investigate how heat transfer through interfaces is affected by factors including pressure, interfacial modulus, contact area and interfacial layer thickness, with an overreaching goal of developing fundamental knowledge that will allow one to tailor thermal properties of interfacial materials. The role of pressure and interfacial stiffness is unraveled by our studies on an epitaxial interface between two Lennard-Jones (LJ) crystals. The interfacial stiffness is varied by two different methods: (i) indirectly by applying pressure which due to anharmonic nature of bonding, increases interfacial stiffness, and (ii) directly by changing the interfacial bonding strength by varying the depth of the potential well of the LJ potential. When the interfacial bonding strength is low, quantitatively similar behavior to pressure tuning is observed when the interfacial thermal conductance is increased by directly varying the potential-well depth parameter of the LJ potential. By contrast, when the interfacial bonding strength is high, thermal conductance is almost pressure independent, and even slightly decreases with increasing pressure. This decrease can be explained by the change in overlap between the vibrational densities of states of the two crystalline materials. The role of contact area is studied by modeling structures comprised of Van der Waals junctions between single-walled nanotubes (SWCNT). Interfacial thermal conductance between SWCNTs is obtained from NEMD simulation as a function of crossing angle. In this case the junction conductance per unit area is essentially a constant. By contrast, interfacial thermal conductance between multiwalled carbon nanotubes (MWCNTs) is shown to increase with diameter of the nanotubes by recent experimental studies [1

  10. Magnetic-Field-Tunable Superconducting Rectifier

    NASA Technical Reports Server (NTRS)

    Sadleir, John E.

    2009-01-01

    Superconducting electronic components have been developed that provide current rectification that is tunable by design and with an externally applied magnetic field to the circuit component. The superconducting material used in the device is relatively free of pinning sites with its critical current determined by a geometric energy barrier to vortex entry. The ability of the vortices to move freely inside the device means this innovation does not suffer from magnetic hysteresis effects changing the state of the superconductor. The invention requires a superconductor geometry with opposite edges along the direction of current flow. In order for the critical current asymmetry effect to occur, the device must have different vortex nucleation conditions at opposite edges. Alternative embodiments producing the necessary conditions include edges being held at different temperatures, at different local magnetic fields, with different current-injection geometries, and structural differences between opposite edges causing changes in the size of the geometric energy barrier. An edge fabricated with indentations of the order of the coherence length will significantly lower the geometric energy barrier to vortex entry, meaning vortex passage across the device at lower currents causing resistive dissipation. The existing prototype is a two-terminal device consisting of a thin-film su - perconducting strip operating at a temperature below its superconducting transition temperature (Tc). Opposite ends of the strip are connected to electrical leads made of a higher Tc superconductor. The thin-film lithographic process provides an easy means to alter edge-structures, current-injection geo - metries, and magnetic-field conditions at the edges. The edge-field conditions can be altered by using local field(s) generated from dedicated higher Tc leads or even using the device s own higher Tc superconducting leads.

  11. Tunable Optical Assembly with Vibration Dampening

    NASA Technical Reports Server (NTRS)

    Shams, Qamar A.; Allison, Sidney G.; Fox, Robert L.

    2008-01-01

    Since their market introduction in 1995, fiber Bragg gratings (FBGs) have emerged as excellent means of measuring such parameters as strain and temperature. Distributed-grating sensing is particularly beneficial for such structural-health monitoring applications such as those of 'smart' structures or integrated vehicle health management in aerospace vehicles. Because of the variability of their output wavelengths, tunable lasers have become widely used as means of measuring FBGs. Several versions of a lightweight assembly for strain-tuning an FBG and dampening its vibrations have been constructed. The main components of such an assembly are one or more piezoelectric actuators, an optical fiber containing one or more Bragg grating(s), a Bragg-grating strain-measurement system, and a voltage source for actuation. The piezoelectric actuators are, more specifically, piezoceramic fiber composite actuators and, can be, still more specifically, of a type known in the art as macro-fiber composite (MFC) actuators. In fabrication of one version of the assembly, the optical fiber containing the Bragg grating(s) is sandwiched between the piezoelectric actuators along with an epoxy that is used to bond the optical fiber to both actuators, then the assembly is placed in a vacuum bag and kept there until the epoxy is cured. Bonding an FBG directly into an MFC actuator greatly reduces the complexity, relative to assemblies, that include piezoceramic fiber composite actuators, hinges, ferrules, and clamp blocks with setscrews. Unlike curved actuators, MFC actuators are used in a flat configuration and are less bulky. In addition, the MFC offers some vibration dampening and support for the optical fiber whereas, in a curved piezoelectric actuator assembly, the optical fiber is exposed, and there is nothing to keep the exposed portion from vibrating.

  12. GIANT DIELECTRIC TUNABLE BEHAVIOR OF Pr-DOPED SrTiO3 AT LOW TEMPERATURE

    NASA Astrophysics Data System (ADS)

    Wei, T.; Song, Q. G.; Zhou, Q. J.; Li, Z. P.; Chen, Y. F.; Qi, X. L.; Guo, S. Q.; Liu, J.-M.

    2012-03-01

    Contrast with conventional dielectric tunable materials such as barium strontium titanate (BST), here, we report one new dielectric tunable behavior for Sr1-xPrxTiO3 system at low temperature. Giant dielectric tunability is confirmed in this system. More importantly, the efficient dielectric tunability can be realized just using small bias field. In addition, critical threshold electric field is also confirmed. This phenomenon may be related with the competition interaction of polar state with quantum fluctuations.

  13. An electronically tunable duct silencer using dielectric elastomer actuators.

    PubMed

    Lu, Zhenbo; Godaba, Hareesh; Cui, Yongdong; Foo, Choon Chiang; Debiasi, Marco; Zhu, Jian

    2015-09-01

    A duct silencer with tunable acoustic characteristics is presented in this paper. Dielectric elastomer, a smart material with lightweight, high elastic energy density and large deformation under high direct current/alternating current voltages, was used to fabricate this duct silencer. The acoustic performances and tunable mechanisms of this duct silencer were experimentally investigated. It was found that all the resonance peaks of this duct silencer could be adjusted using external control signals without any additional mechanical part. The physics of the tunable mechanism is further discussed based on the electro-mechanical interactions using finite element analysis. The present promising results also provide insight into the appropriateness of the duct silencer for possible use as next generation acoustic treatment device to replace the traditional acoustic treatment. PMID:26428819

  14. Tunable solid-state fluorescent materials for supramolecular encryption

    NASA Astrophysics Data System (ADS)

    Hou, Xisen; Ke, Chenfeng; Bruns, Carson J.; McGonigal, Paul R.; Pettman, Roger B.; Stoddart, J. Fraser

    2015-04-01

    Tunable solid-state fluorescent materials are ideal for applications in security printing technologies. A document possesses a high level of security if its encrypted information can be authenticated without being decoded, while also being resistant to counterfeiting. Herein, we describe a heterorotaxane with tunable solid-state fluorescent emissions enabled through reversible manipulation of its aggregation by supramolecular encapsulation. The dynamic nature of this fluorescent material is based on a complex set of equilibria, whose fluorescence output depends non-linearly on the chemical inputs and the composition of the paper. By applying this system in fluorescent security inks, the information encoded in polychromic images can be protected in such a way that it is close to impossible to reverse engineer, as well as being easy to verify. This system constitutes a unique application of responsive complex equilibria in the form of a cryptographic algorithm that protects valuable information printed using tunable solid-state fluorescent materials.

  15. Tunable solid-state fluorescent materials for supramolecular encryption

    PubMed Central

    Hou, Xisen; Ke, Chenfeng; Bruns, Carson J.; McGonigal, Paul R.; Pettman, Roger B.; Stoddart, J. Fraser

    2015-01-01

    Tunable solid-state fluorescent materials are ideal for applications in security printing technologies. A document possesses a high level of security if its encrypted information can be authenticated without being decoded, while also being resistant to counterfeiting. Herein, we describe a heterorotaxane with tunable solid-state fluorescent emissions enabled through reversible manipulation of its aggregation by supramolecular encapsulation. The dynamic nature of this fluorescent material is based on a complex set of equilibria, whose fluorescence output depends non-linearly on the chemical inputs and the composition of the paper. By applying this system in fluorescent security inks, the information encoded in polychromic images can be protected in such a way that it is close to impossible to reverse engineer, as well as being easy to verify. This system constitutes a unique application of responsive complex equilibria in the form of a cryptographic algorithm that protects valuable information printed using tunable solid-state fluorescent materials. PMID:25901677

  16. Magnetically tunable broadband transmission through a single small aperture

    PubMed Central

    Bi, Ke; Liu, Wenjun; Guo, Yunsheng; Dong, Guoyan; Lei, Ming

    2015-01-01

    Extraordinary transmission through a small aperture is of great interest. However, it faces a limitation that most of approaches can not realize the tunable transmission property, which is not benefit for the miniaturization of the microwave system. Here, we demonstrate a magnetically tunable broadband transmission through a small aperture. By placing two ferrite rods symmetrically on both sides of a single small aperture, the strongly localized electromagnetic fields are effectively coupled to the two ferrite rods. Both the simulated and experimental results indicate that such structure not only realizes a nearly total transmission through a small aperture, but also obtains a magnetically tunable property. This work offers new opportunities for the miniaturization of the microwave system. PMID:26198543

  17. Narrow bandpass tunable terahertz filter based on photonic crystal cavity.

    PubMed

    He, Jinglong; Liu, Pingan; He, Yalan; Hong, Zhi

    2012-02-20

    We have fabricated a very narrow bandpass tunable terahertz (THz) filter based on a one-dimensional photonic crystal cavity. Since the filter consists of silicon wafers and air spacers, it has a very high quality factor of about 1500. The full width at half maximum (FWHM) of the passband is only about 200 MHz, and the peak transmission is higher than -4 dB. Besides, the central frequency can be tuned rapidly over the entire bandgap with the length of cavity adjusted by a motorized linear stage. Further analytical calculations indicate that a high-Q tunable filter with both high peak transmission and wide tunable range is possible if thinner silicon layers are used. PMID:22358169

  18. Tunable defect mode realized by graphene-based photonic crystal

    NASA Astrophysics Data System (ADS)

    Fu, Jiahui; Chen, Wan; Lv, Bo

    2016-04-01

    In this literature, we propose an active terahertz 1D photonic crystal, which consists of silicon layers and air layers. A graphene sheet is embedded at the interface between dielectric and air. Tunable photonic band gap is realized by changing the Fermi level of graphene. Transmission Matrix Method is utilized to explain the influence of the graphene layer. We also demonstrate that a dielectric slab attached with a thin sheet made of single-negative metamaterial acts like a pure dielectric slab with a thinner thickness. A tunable blue shift of the band gap can be realized by simply applying different chemical potentials on the graphene sheet. This feature can be utilized for the design of tunable high-gain antenna array and force generator in terahertz band.

  19. Magnetically tunable broadband transmission through a single small aperture.

    PubMed

    Bi, Ke; Liu, Wenjun; Guo, Yunsheng; Dong, Guoyan; Lei, Ming

    2015-01-01

    Extraordinary transmission through a small aperture is of great interest. However, it faces a limitation that most of approaches can not realize the tunable transmission property, which is not benefit for the miniaturization of the microwave system. Here, we demonstrate a magnetically tunable broadband transmission through a small aperture. By placing two ferrite rods symmetrically on both sides of a single small aperture, the strongly localized electromagnetic fields are effectively coupled to the two ferrite rods. Both the simulated and experimental results indicate that such structure not only realizes a nearly total transmission through a small aperture, but also obtains a magnetically tunable property. This work offers new opportunities for the miniaturization of the microwave system. PMID:26198543

  20. Magnetically tunable broadband transmission through a single small aperture

    NASA Astrophysics Data System (ADS)

    Bi, Ke; Liu, Wenjun; Guo, Yunsheng; Dong, Guoyan; Lei, Ming

    2015-07-01

    Extraordinary transmission through a small aperture is of great interest. However, it faces a limitation that most of approaches can not realize the tunable transmission property, which is not benefit for the miniaturization of the microwave system. Here, we demonstrate a magnetically tunable broadband transmission through a small aperture. By placing two ferrite rods symmetrically on both sides of a single small aperture, the strongly localized electromagnetic fields are effectively coupled to the two ferrite rods. Both the simulated and experimental results indicate that such structure not only realizes a nearly total transmission through a small aperture, but also obtains a magnetically tunable property. This work offers new opportunities for the miniaturization of the microwave system.

  1. Photo-excited broadband tunable terahertz metamaterial absorber

    NASA Astrophysics Data System (ADS)

    Zhang, Jianna; Wang, Guocui; Zhang, Bo; He, Ting; He, Yanan; Shen, Jingling

    2016-04-01

    We demonstrate a photo-excited broadband tunable metamaterial absorber for use in the terahertz region. The metamaterial absorber consists of a hybrid metal-semiconductor square split ring and a metallic ground plane that are separated by a dielectric resonator spacer. The conductivity of the silicon used to fill the gap in the metallic resonator is tuned actively as a function of the incident pump power, which results in frequency modulation of the resonance absorption peak. Broadband tunable metamaterial absorbers are produced by suitable placement of the photoconductive silicon in different critical regions of the metallic resonator. In addition, the proposed method is applicable to a concentric rings-based metallic resonator. The proposed photo-excited broadband tunable metamaterial absorber has numerous potential applications, including uses as terahertz modulators and switches.

  2. Optimization algorithm based characterization scheme for tunable semiconductor lasers.

    PubMed

    Chen, Quanan; Liu, Gonghai; Lu, Qiaoyin; Guo, Weihua

    2016-09-01

    In this paper, an optimization algorithm based characterization scheme for tunable semiconductor lasers is proposed and demonstrated. In the process of optimization, the ratio between the power of the desired frequency and the power except of the desired frequency is used as the figure of merit, which approximately represents the side-mode suppression ratio. In practice, we use tunable optical band-pass and band-stop filters to obtain the power of the desired frequency and the power except of the desired frequency separately. With the assistance of optimization algorithms, such as the particle swarm optimization (PSO) algorithm, we can get stable operation conditions for tunable lasers at designated frequencies directly and efficiently. PMID:27607701

  3. Tunable Single-Frequency Near IR Lasers for DIAL Applications

    NASA Technical Reports Server (NTRS)

    Henderson, Sammy W.; Marquardt, John H.; Carrig, Timothy J.; Gatt, Phil; Smith, Duane D.; Hale, Charley P.

    2000-01-01

    Tunable single-frequency sources in the 2-4 micron wavelength region are useful for remote DIAL measurements of chemicals and pollutants. We are developing tunable single-frequency transmitters and receivers for both direct and coherent detection lidar measurement applications. We have demonstrated a direct-diode-pumped PPLN-based OPO that operates single frequency, produces greater than 10 mW cw and is tunable over the 2.5 - 3.9 micron wavelength region. This laser has been used to injection seed a pulsed PPLN OPO, pumped by a 1.064 micron Nd:YAG laser, producing 50-100 microJoule single-frequency pulses at 100 Hz PRF near 3.6 micron wavelength. In addition, we have demonstrated a cw Cr:ZnSe laser that is tunable over the 2.1 - 2.8 micron wavelength region. This laser is pumped by a cw diode-pumped Tm:YALO laser and has produced over 1.8 W cw. Tm- and Tm, Ho-doped single-frequency solid-state lasers that produce over 50 mW cw and are tunable over approximately 10 nm in the 2 -2.1 micron band with fast PZT tuning have also been demonstrated. A fast PZT-tunable Tm, Ho:YLF laser was used for a direct-detection column content DIAL measurement of atmospheric CO2. Modeling shows that that all these cw and pulsed sources are useful for column-content coherent DIAL measurements at several km range using topographic targets.

  4. Tunable thin-film optical filters for hyperspectral microscopy

    NASA Astrophysics Data System (ADS)

    Favreau, Peter F.; Rich, Thomas C.; Prabhat, Prashant; Leavesley, Silas J.

    2013-02-01

    Hyperspectral imaging was originally developed for use in remote sensing applications. More recently, it has been applied to biological imaging systems, such as fluorescence microscopes. The ability to distinguish molecules based on spectral differences has been especially advantageous for identifying fluorophores in highly autofluorescent tissues. A key component of hyperspectral imaging systems is wavelength filtering. Each filtering technology used for hyperspectral imaging has corresponding advantages and disadvantages. Recently, a new optical filtering technology has been developed that uses multi-layered thin-film optical filters that can be rotated, with respect to incident light, to control the center wavelength of the pass-band. Compared to the majority of tunable filter technologies, these filters have superior optical performance including greater than 90% transmission, steep spectral edges and high out-of-band blocking. Hence, tunable thin-film optical filters present optical characteristics that may make them well-suited for many biological spectral imaging applications. An array of tunable thin-film filters was implemented on an inverted fluorescence microscope (TE 2000, Nikon Instruments) to cover the full visible wavelength range. Images of a previously published model, GFP-expressing endothelial cells in the lung, were acquired using a charge-coupled device camera (Rolera EM-C2, Q-Imaging). This model sample presents fluorescently-labeled cells in a highly autofluorescent environment. Linear unmixing of hyperspectral images indicates that thin-film tunable filters provide equivalent spectral discrimination to our previous acousto-optic tunable filter-based approach, with increased signal-to-noise characteristics. Hence, tunable multi-layered thin film optical filters may provide greatly improved spectral filtering characteristics and therefore enable wider acceptance of hyperspectral widefield microscopy.

  5. Tunable High-Intensity Electron Bunch Train Production Based on Nonlinear Longitudinal Space Charge Oscillation.

    PubMed

    Zhang, Zhen; Yan, Lixin; Du, Yingchao; Zhou, Zheng; Su, Xiaolu; Zheng, Lianmin; Wang, Dong; Tian, Qili; Wang, Wei; Shi, Jiaru; Chen, Huaibi; Huang, Wenhui; Gai, Wei; Tang, Chuanxiang

    2016-05-01

    High-intensity trains of electron bunches with tunable picosecond spacing are produced and measured experimentally with the goal of generating terahertz (THz) radiation. By imposing an initial density modulation on a relativistic electron beam and controlling the charge density over the beam propagation, density spikes of several-hundred-ampere peak current in the temporal profile, which are several times higher than the initial amplitudes, have been observed for the first time. We also demonstrate that the periodic spacing of the bunch train can be varied continuously either by tuning launching phase of a radio-frequency gun or by tuning the compression of a downstream magnetic chicane. Narrow-band coherent THz radiation from the bunch train was also measured with μJ-level energies and tunable central frequency of the spectrum in the range of ∼0.5 to 1.6 THz. Our results pave the way towards generating mJ-level narrow-band coherent THz radiation and driving high-gradient wakefield-based acceleration. PMID:27203327

  6. Highly versatile confocal microscopy system based on a tunable femtosecond Er:fiber source.

    PubMed

    Träutlein, D; Adler, F; Moutzouris, K; Jeromin, A; Leitenstorfer, A; Ferrando-May, E

    2008-03-01

    The performance of a confocal microscopy setup based on a single femtosecond fiber system is explored over a broad range of pump wavelengths for both linear and nonlinear imaging techniques. First, the benefits of a laser source in linear fluorescence excitation that is continuously tunable over most of the visible spectrum are demonstrated. The influences of subpicosecond pulse durations on the bleaching behavior of typical fluorophores are discussed. We then utilize the tunable near-infrared output of the femtosecond system in connection with a specially designed prism compressor for dispersion control. Pulses as short as 33 fs are measured in the confocal region. As a consequence, 2 mW of average power are sufficient for two-photon microscopy in an organotypic sample from the mouse brain. This result shows great prospect for deep-tissue imaging in the optimum transparency window around 1100 nm. In a third experiment, we prove that our compact setup is powerful enough to exploit even higher-order nonlinearities such as three-photon absorption that we use to induce spatially localized photodamage in DNA. PMID:19343635

  7. Tunable High-Intensity Electron Bunch Train Production Based on Nonlinear Longitudinal Space Charge Oscillation

    NASA Astrophysics Data System (ADS)

    Zhang, Zhen; Yan, Lixin; Du, Yingchao; Zhou, Zheng; Su, Xiaolu; Zheng, Lianmin; Wang, Dong; Tian, Qili; Wang, Wei; Shi, Jiaru; Chen, Huaibi; Huang, Wenhui; Gai, Wei; Tang, Chuanxiang

    2016-05-01

    High-intensity trains of electron bunches with tunable picosecond spacing are produced and measured experimentally with the goal of generating terahertz (THz) radiation. By imposing an initial density modulation on a relativistic electron beam and controlling the charge density over the beam propagation, density spikes of several-hundred-ampere peak current in the temporal profile, which are several times higher than the initial amplitudes, have been observed for the first time. We also demonstrate that the periodic spacing of the bunch train can be varied continuously either by tuning launching phase of a radio-frequency gun or by tuning the compression of a downstream magnetic chicane. Narrow-band coherent THz radiation from the bunch train was also measured with μ J -level energies and tunable central frequency of the spectrum in the range of ˜0.5 to 1.6 THz. Our results pave the way towards generating mJ-level narrow-band coherent THz radiation and driving high-gradient wakefield-based acceleration.

  8. Far-field emission characteristics and linewidth measurements of surface micro-machined MEMS tunable VCSELs

    NASA Astrophysics Data System (ADS)

    Paul, Sujoy; Gierl, Christian; Gründl, Tobias; Zogal, Karolina; Meissner, Peter; Amann, Markus-Christian; Küppers, Franko

    2013-03-01

    In this paper, we demonstrate for the first time the far-field experimental results and the linewidth characteris- tics for widely tunable surface-micromachined micro-electro-mechanical system (MEMS) vertical-cavity surface- emitting lasers (VCSELs) operating at 1550 nm. The fundamental Gaussian mode emission is confirmed by optimizing the radius of curvature of top distributed Bragg reflector (DBR) membrane and by choosing an ap- propriate diameter of circular buried tunnel junctions (BTJs) so that only the fundamental Gaussian mode can sustain. For these VCSELs, a mode-hop free continuous tuning over 100 nm has already been demonstrated, which is achieved by electro-thermal tuning of the MEMS mirror. The fiber-coupled optical power of 2mW over the entire tuning range has been reported. The singlemode laser emission has more than 40 dB of side-mode suppression ratio (SMSR). The smallest linewidth achieved with these of MEMS tunable VCSELs is 98MHz which is one order of magnitude higher than that of fixed-wavelength VCSELs.

  9. Frequency tunable electromagnetic metamaterial using ferroelectric loaded split rings

    NASA Astrophysics Data System (ADS)

    Hand, Thomas H.; Cummer, Steven A.

    2008-03-01

    Measurements of a frequency tunable magnetic metamaterial using metallic split rings loaded with barium strontium titanate thin film capacitors are presented. The resonant frequency of this medium is voltage tunable across a 140MHz band centered at 1.75GHz. S-parameter measurements in a microstrip waveguide reveal that the effective relative permeability of the slab has a roughly Lorentzian shape that reaches minimum values between -2 and -3 for biases from 0to5V. The permeability of the slab can tune between positive and negative values, making it useful in applications requiring a state switchable magnetic permeability.

  10. Microwave photonic bandstop filter with wide tunability and adjustable bandwidth.

    PubMed

    Li, Wei; Yang, Chengwu; Wang, Ling; Yuan, Zhilin; Liu, Jianguo; Li, Ming; Zhu, Ninghua

    2015-12-28

    A microwave photonic bandstop filter is proposed and experimentally demonstrated in this work. The filter exhibits promising performance combination of reconfigurability, frequency tunability, and bandwidth adjustment. The phase modulation on two orthogonal polarization states produces a bandpass and a lowpass MPF, respectively. The key concept of destructive interference between the bandpass and lowpass MPF enables the reconfiguration of MPF from bandpass to bandstop. By adjusting the wavelength of two orthogonally polarized optical carriers and the bandwidth of an optical bandpass filter, the bandstop filter is tunable in terms of center frequency and bandwidth. PMID:26832021

  11. Capacitive micromachined ultrasonic transducer arrays as tunable acoustic metamaterials

    SciTech Connect

    Lani, Shane W. E-mail: karim.sabra@me.gatech.edu Sabra, Karim G.; Wasequr Rashid, M.; Hasler, Jennifer; Levent Degertekin, F.

    2014-02-03

    Capacitive Micromachined Ultrasonic Transducers (CMUTs) operating in immersion support dispersive evanescent waves due to the subwavelength periodic structure of electrostatically actuated membranes in the array. Evanescent wave characteristics also depend on the membrane resonance which is modified by the externally applied bias voltage, offering a mechanism to tune the CMUT array as an acoustic metamaterial. The dispersion and tunability characteristics are examined using a computationally efficient, mutual radiation impedance based approach to model a finite-size array and realistic parameters of variation. The simulations are verified, and tunability is demonstrated by experiments on a linear CMUT array operating in 2-12 MHz range.

  12. Electrically tunable polymer stabilized liquid-crystal lens

    NASA Astrophysics Data System (ADS)

    Presnyakov, Vladimir V.; Galstian, Tigran V.

    2005-05-01

    A tunable focal lens using flat electro-optical liquid-crystal cell with uniform pixel-free electrodes is developed. The lenslike gradient refractive index profile is created in the cell via the spatially distributed polymer network obtained by photopolymerization using a spatially nonuniform laser beam. The conditions of the polymer network generation are optimized to improve the optical quality of the lens and its focusing properties. Low optical loss (scattering) is achieved for a focal length smoothly tunable from infinity to 0.8m. Obtained results can be applied to develop lenses that have no moving parts and allow the electro-optical zooming.

  13. Widely tunable femtosecond solitonic radiation in photonic crystal fiber cladding

    SciTech Connect

    Peng Jiahui; Sokolov, Alexei V.; Benabid, F.; Light, P. S.; Couny, F.; Biancalana, F.; Roberts, P. J.

    2010-03-15

    We report on a means to generate tunable ultrashort optical pulses. We demonstrate that dispersive waves generated by solitons within the small-core features of a photonic crystal fiber cladding can be used to obtain femtosecond pulses tunable over an octave-wide spectral range. The generation process is highly efficient and occurs at the relatively low laser powers available from a simple Ti:sapphire laser oscillator. The described phenomenon is general and will play an important role in other systems where solitons are known to exist.

  14. Multilaser Herriott Cell for Planetary Tunable Laser Spectrometers

    NASA Technical Reports Server (NTRS)

    Tarsitano, Christopher G.; Webster, Christopher R.

    2007-01-01

    Geometric optics and matrix methods are used to mathematically model multilaser Herriott cells for tunable laser absorption spectrometers for planetary missions. The Herriott cells presented accommodate several laser sources that follow independent optical paths but probe a single gas cell. Strategically placed output holes located in the far mirrors of the Herriott cells reduce the size of the spectrometers. A four-channel Herriott cell configuration is presented for the specific application as the sample cell of the tunable laser spectrometer instrument selected for the sample analysis at Mars analytical suite on the 2009 Mars Science Laboratory mission.

  15. Computer Processing Of Tunable-Diode-Laser Spectra

    NASA Technical Reports Server (NTRS)

    May, Randy D.

    1991-01-01

    Tunable-diode-laser spectrometer measuring transmission spectrum of gas operates under control of computer, which also processes measurement data. Measurements in three channels processed into spectra. Computer controls current supplied to tunable diode laser, stepping it through small increments of wavelength while processing spectral measurements at each step. Program includes library of routines for general manipulation and plotting of spectra, least-squares fitting of direct-transmission and harmonic-absorption spectra, and deconvolution for determination of laser linewidth and for removal of instrumental broadening of spectral lines.

  16. Tunable cavity resonator including a plurality of MEMS beams

    SciTech Connect

    Peroulis, Dimitrios; Fruehling, Adam; Small, Joshua Azariah; Liu, Xiaoguang; Irshad, Wasim; Arif, Muhammad Shoaib

    2015-10-20

    A tunable cavity resonator includes a substrate, a cap structure, and a tuning assembly. The cap structure extends from the substrate, and at least one of the substrate and the cap structure defines a resonator cavity. The tuning assembly is positioned at least partially within the resonator cavity. The tuning assembly includes a plurality of fixed-fixed MEMS beams configured for controllable movement relative to the substrate between an activated position and a deactivated position in order to tune a resonant frequency of the tunable cavity resonator.

  17. New tunable lasers for potential use in LIDAR systems

    SciTech Connect

    Payne, S.A.; Page, R.H.; Marshall, C.D.; Schaffers, K.I.; Bayramian, A.J.; Krupke, W.F.

    1996-06-01

    We discuss the optical and laser properties of two new tunable laser crystals, Ce:LiSrAlF{sub 6} and Cr:ZnSe. These crystals are unique in that they provide a practical alternative to optical parametric oscillators as a means of generating tunable radiation in the near ultraviolet and mid-infrared regions (their tuning ranges are at least 285-315 nm and 2.2-2.8 microns, respectively). While these crystals are relatively untested in field deployment, they are promising and likely to be useful in the near future.

  18. Tunable ring laser using a tapered single mode fiber tip.

    PubMed

    Wang, Xiaozhen; Li, Yi; Bao, Xiaoyi

    2009-12-10

    A tunable ring laser using a tapered single mode fiber tip as a bandpass filter has been proposed and demonstrated for the first time to our knowledge. This is a simple and cost-effective tunable source. It is found that the tuning range and bandwidth of the laser are related to the relaxation time of the optical amplifier, the current of the amplifier, and the steepness of the tip shape. The calculations and experimental results show that the laser has a tuning range of 9 nm in the L-band and the spectral linewidth can be varied from 0.06 nm to 0.17 nm. PMID:20011024

  19. A novel tunable cascaded IIR microwave photonic filter

    NASA Astrophysics Data System (ADS)

    Zhou, Lina; Zhang, Xinliang; Xu, Enming; Yu, Yuan; Li, Xiang; Huang, Dexiu

    2010-07-01

    A new tunable cascaded infinite impulse response (IIR) microwave photonic filter is presented, based on a novel configuration in which a semiconductor optical amplifier (SOA) is inserted between two active recirculating delay line (RDL) loops. Due to wavelength conversion with cross-gain modulation (XGM) in SOA, interferences between light beams traveling different paths are canceled, ensuring a stable transmission. By employing this configuration, a cascaded IIR microwave photonic filter is firstly achieved. The free spectral range (FSR) and the Q factor are both increased significantly by adopting "vernier effect" technique in the IIR filter. The structure is also tunable by adjusting the length of one RDL loop.

  20. Single to quadruple quantum dots with tunable tunnel couplings

    SciTech Connect

    Takakura, T.; Noiri, A.; Obata, T.; Yoneda, J.; Yoshida, K.; Otsuka, T.; Tarucha, S.

    2014-03-17

    We prepare a gate-defined quadruple quantum dot to study the gate-tunability of single to quadruple quantum dots with finite inter-dot tunnel couplings. The measured charging energies of various double dots suggest that the dot size is governed by the gate geometry. For the triple and quadruple dots, we study the gate-tunable inter-dot tunnel couplings. For the triple dot, we find that the effective tunnel coupling between side dots significantly depends on the alignment of the center dot potential. These results imply that the present quadruple dot has a gate performance relevant for implementing spin-based four-qubits with controllable exchange couplings.

  1. Tunable graphene antennas for selective enhancement of THz-emission.

    PubMed

    Filter, R; Farhat, M; Steglich, M; Alaee, R; Rockstuhl, C; Lederer, F

    2013-02-11

    In this paper, we will introduce THz graphene antennas that strongly enhance the emission rate of quantum systems at specific frequencies. The tunability of these antennas can be used to selectively enhance individual spectral features. We will show as an example that any weak transition in the spectrum of coronene can become the dominant contribution. This selective and tunable enhancement establishes a new class of graphene-based THz devices, which will find applications in sensors, novel light sources, spectroscopy, and quantum communication devices. PMID:23481830

  2. Plasmonic tunable metamaterial absorber as ultraviolet protection film

    NASA Astrophysics Data System (ADS)

    Hedayati, M. K.; Zillohu, A. U.; Strunskus, T.; Faupel, F.; Elbahri, M.

    2014-01-01

    Plasmonic metamaterials designed for optical frequency have to be shrunk down to few 10th of nanometer which turns their manufacturing cumbersome. Here, we shift the performance of metamaterial down to ultraviolet (UV) by using ultrathin nanocomposite as a tunable plasmonic metamaterial fabricated with tandem co-deposition. It provides the possibility to realize a plasmonic metamaterial absorber for UV frequency with marginal angle sensitivity. Its resonance frequency and intensity can be adjusted by changing thickness and filling factor of the composite. Presented approach for tunable metamaterials for high frequency could pave the way for their application for thermo-photovoltaic, stealth technology, and UV-protective coating.

  3. Strain engineered barium strontium titanate for tunable thin film resonators

    SciTech Connect

    Khassaf, H.; Khakpash, N.; Sun, F.; Sbrockey, N. M.; Tompa, G. S.; Kalkur, T. S.; Alpay, S. P.

    2014-05-19

    Piezoelectric properties of epitaxial (001) barium strontium titanate (BST) films are computed as functions of composition, misfit strain, and temperature using a non-linear thermodynamic model. Results show that through adjusting in-plane strains, a highly adaptive rhombohedral ferroelectric phase can be stabilized at room temperature with outstanding piezoelectric response exceeding those of lead based piezoceramics. Furthermore, by adjusting the composition and the in-plane misfit, an electrically tunable piezoelectric response can be obtained in the paraelectric state. These findings indicate that strain engineered BST films can be utilized in the development of electrically tunable and switchable surface and bulk acoustic wave resonators.

  4. Electrically tunable polymer stabilized liquid-crystal lens

    SciTech Connect

    Presnyakov, Vladimir V.; Galstian, Tigran V.

    2005-05-15

    A tunable focal lens using flat electro-optical liquid-crystal cell with uniform pixel-free electrodes is developed. The lenslike gradient refractive index profile is created in the cell via the spatially distributed polymer network obtained by photopolymerization using a spatially nonuniform laser beam. The conditions of the polymer network generation are optimized to improve the optical quality of the lens and its focusing properties. Low optical loss (scattering) is achieved for a focal length smoothly tunable from infinity to 0.8 m. Obtained results can be applied to develop lenses that have no moving parts and allow the electro-optical zooming.

  5. Water: Promising Opportunities For Tunable All-dielectric Electromagnetic Metamaterials

    PubMed Central

    Andryieuski, Andrei; Kuznetsova, Svetlana M.; Zhukovsky, Sergei V.; Kivshar, Yuri S.; Lavrinenko, Andrei V.

    2015-01-01

    We reveal an outstanding potential of water as an inexpensive, abundant and bio-friendly high-refractive-index material for creating tunable all-dielectric photonic structures and metamaterials. Specifically, we demonstrate thermal, mechanical and gravitational tunability of magnetic and electric resonances in a metamaterial consisting of periodically positioned water-filled reservoirs. The proposed water-based metamaterials can find applications not only as cheap and ecological microwave devices, but also in optical and terahertz metamaterials prototyping and educational lab equipment. PMID:26311410

  6. A novel tunable optical oscillator for broadband signals

    NASA Astrophysics Data System (ADS)

    Kim, Ajung; Suh, Y. K.

    2012-03-01

    A tunable optical oscillator that generates signals at the micro- to millimeter-wave band for wireless communication applications is suggested. It uses directly modulated semiconductor lasers, in which sideband modes and four-wave mixing (FWM) conjugate modes are injection locked by the simple control of the applied modulation power. The signals at 15 GHz with phase noise of below -95 dBc/Hz at an offset frequency of 100 kHz were experimentally obtained. The frequency of the generated signal is tunable, and the maximum achievable signal frequency is limited mainly by the bandwidth of the receiver.

  7. Variable bandwidth birefringent filter for tunable femtosecond lasers

    SciTech Connect

    Naganuma, K.; Lenz, G.; Ippen, E.P. )

    1992-10-01

    A design for a birefringent filter is described, which is suitable for tunable femtosecond lasers. Using a single plate, which has a steeply diving optic axis, two-octave tunability is attained with negligible deterioration of the stopband rejection. For a specific wavelength region, it means that the filter's bandwidth can be changed by a factor of four. Another characteristic of the design is that, for the same bandwidth, the proposed plate is five times thicker than a conventional plate in which the optic axis is parallel to the surface. Thus, etalon effects can be avoided. Tuning characteristics of color center lasers utilizing the new filter are also presented. 18 refs.

  8. Octave-band tunable optical vortex parametric oscillator.

    PubMed

    Abulikemu, Aizitiaili; Yusufu, Taximaiti; Mamuti, Roukuya; Araki, Shungo; Miyamoto, Katsuhiko; Omatsu, Takashige

    2016-07-11

    We developed an octave-band tunable optical vortex laser based on a 532 nm optical vortex pumped optical parametric oscillator with a simple linear-cavity configuration by employing cascaded non-critical phase-matching LiB3O5 crystals. The optical vortex output was tunable from 735 to 1903 nm. For a pump energy of 9 mJ, an optical vortex pulse energy of 0.24-2.36 mJ was obtained, corresponding to an optical-optical efficiency of 0.3-26%. PMID:27410798

  9. Tunable Weyl Points in Periodically Driven Nodal Line Semimetals.

    PubMed

    Yan, Zhongbo; Wang, Zhong

    2016-08-19

    Weyl semimetals and nodal line semimetals are characterized by linear band touching at zero-dimensional points and one-dimensional lines, respectively. We predict that a circularly polarized light drives nodal line semimetals into Weyl semimetals. The Floquet Weyl points thus obtained are tunable by the incident light, which enables investigations of them in a highly controllable manner. The transition from nodal line semimetals to Weyl semimetals is accompanied by the emergence of a large and tunable anomalous Hall conductivity. Our predictions are experimentally testable by transport measurement in film samples or by pump-probe angle-resolved photoemission spectroscopy. PMID:27588882

  10. Towards Tunable Band Gap and Tunable Dirac Point in Bilayer Graphene with Molecular Doping

    PubMed Central

    Yu, Woo Jong; Liao, Lei; Chae, Sang Hoon; Lee, Young Hee; Duan, Xiangfeng

    2011-01-01

    The bilayer graphene has attracted considerable attention for potential applications in future electronics and optoelectronics because of the feasibility to tune its band gap with a vertical displacement field to break the inversion symmetry. Surface chemical doping in bilayer graphene can induce an additional offset voltage to fundamentally affect the vertical displacement field and band-gap opening in bilayer graphene. In this study, we investigate the effect of chemical molecular doping on band-gap opening in bilayer graphene devices with single or dual gate modulation. Chemical doping with benzyl viologen molecules modulates the displacement field to allow the opening of a transport band gap and the increase of the on/off ratio in the bilayer graphene transistors. Additionally, Fermi energy level in the opened gap can be rationally controlled by the amount of molecular doping to obtain bilayer graphene transistors with tunable Dirac points, which can be readily configured into functional devices such as complementary inverters. PMID:21985035

  11. Intense, carrier frequency and bandwidth tunable quasi single-cycle pulses from an organic emitter covering the Terahertz frequency gap

    PubMed Central

    Vicario, C.; Monoszlai, B.; Jazbinsek, M.; Lee, S. -H.; Kwon, O. -P.; Hauri, C. P.

    2015-01-01

    In Terahertz (THz) science, one of the long-standing challenges has been the formation of spectrally dense, single-cycle pulses with tunable duration and spectrum across the frequency range of 0.1–15 THz (THz gap). This frequency band, lying between the electronically and optically accessible spectra hosts important molecular fingerprints and collective modes which cannot be fully controlled by present strong-field THz sources. We present a method that provides powerful single-cycle THz pulses in the THz gap with a stable absolute phase whose duration can be continuously selected between 68 fs and 1100 fs. The loss-free and chirp-free technique is based on optical rectification of a wavelength-tunable pump pulse in the organic emitter HMQ-TMS that allows for tuning of the spectral bandwidth from 1 to more than 7 octaves over the entire THz gap. The presented source tunability of the temporal carrier frequency and spectrum expands the scope of spectrally dense THz sources to time-resolved nonlinear THz spectroscopy in the entire THz gap. This opens new opportunities towards ultrafast coherent control over matter and light. PMID:26400005

  12. Intense, carrier frequency and bandwidth tunable quasi single-cycle pulses from an organic emitter covering the Terahertz frequency gap

    NASA Astrophysics Data System (ADS)

    Vicario, C.; Monoszlai, B.; Jazbinsek, M.; Lee, S.-H.; Kwon, O.-P.; Hauri, C. P.

    2015-09-01

    In Terahertz (THz) science, one of the long-standing challenges has been the formation of spectrally dense, single-cycle pulses with tunable duration and spectrum across the frequency range of 0.1-15 THz (THz gap). This frequency band, lying between the electronically and optically accessible spectra hosts important molecular fingerprints and collective modes which cannot be fully controlled by present strong-field THz sources. We present a method that provides powerful single-cycle THz pulses in the THz gap with a stable absolute phase whose duration can be continuously selected between 68 fs and 1100 fs. The loss-free and chirp-free technique is based on optical rectification of a wavelength-tunable pump pulse in the organic emitter HMQ-TMS that allows for tuning of the spectral bandwidth from 1 to more than 7 octaves over the entire THz gap. The presented source tunability of the temporal carrier frequency and spectrum expands the scope of spectrally dense THz sources to time-resolved nonlinear THz spectroscopy in the entire THz gap. This opens new opportunities towards ultrafast coherent control over matter and light.

  13. Fully-tunable microwave photonic filter with complex coefficients using tunable delay lines based on frequency-time conversions.

    PubMed

    Mokhtari, Arash; Preußler, Stefan; Jamshidi, Kambiz; Akbari, Mahmood; Schneider, Thomas

    2012-09-24

    A fully electrically tunable microwave photonic filter is realized by the implementation of delay lines based on frequency-time conversion. The frequency response and free spectral range (FSR) of the filter can be engineered by a simple electrical tuning of the delay lines. The method has the capability of being integrated on a silicon photonic platform. In the experiment, a 2-tap tunable microwave photonic filter with a 3-dB bandwidth of 2.55 GHz, a FSR of 4.016 GHz, a FSR maximum tuning range from -354 MHz to 354 MHz and a full FSR translation range is achieved. PMID:23037423

  14. Widely tunable Tm-doped mode-locked all-fiber laser

    PubMed Central

    Yan, Zhiyu; Sun, Biao; Li, Xiaohui; Luo, Jiaqi; Shum, Perry Ping; Yu, Xia; Zhang, Ying; Wang, Qi Jie

    2016-01-01

    We demonstrated a widely tunable Tm-doped mode-locked all-fiber laser, with the widest tunable range of 136 nm, from 1842 to 1978 nm. Nonlinear polarization evolution (NPE) technique is employed to enable mode-locking and the wavelength-tunable operation. The widely tunable range attributes to the NPE-induced transmission modulation and bidirectional pumping mechanism. Such kind of tunable mode-locked laser can find various applications in optical communications, spectroscopy, time-resolved measurement, and among others. PMID:27263655

  15. Tunable 1550nm VCSELs using high-contrast grating for next-generation networks

    NASA Astrophysics Data System (ADS)

    Chase, Christopher; Rao, Yi; Huang, Michael; Chang-Hasnain, Connie

    2013-12-01

    We demonstrate wavelength-tunable SFF transceivers operating at 1550 nm using a tunable VCSEL with a high contrast grating (HCG) as the output mirror. Tunable HCG VCSELs with a ~25 nm mechanical tuning range and over 2 mW output power were realized. Error-free operation of an optical link using directly-modulated tunable HCG VCSELs transmitting at 1.25 Gbps over 18 channels spaced by 100 GHz and transmitted over 20 km of single mode fiber is demonstrated, showing the suitability of the HCG tunable VCSEL as a low cost source for next generation DWDM communications systems in access networks and data centers.

  16. Widely tunable Tm-doped mode-locked all-fiber laser.

    PubMed

    Yan, Zhiyu; Sun, Biao; Li, Xiaohui; Luo, Jiaqi; Shum, Perry Ping; Yu, Xia; Zhang, Ying; Wang, Qi Jie

    2016-01-01

    We demonstrated a widely tunable Tm-doped mode-locked all-fiber laser, with the widest tunable range of 136 nm, from 1842 to 1978 nm. Nonlinear polarization evolution (NPE) technique is employed to enable mode-locking and the wavelength-tunable operation. The widely tunable range attributes to the NPE-induced transmission modulation and bidirectional pumping mechanism. Such kind of tunable mode-locked laser can find various applications in optical communications, spectroscopy, time-resolved measurement, and among others. PMID:27263655

  17. Widely tunable Tm-doped mode-locked all-fiber laser

    NASA Astrophysics Data System (ADS)

    Yan, Zhiyu; Sun, Biao; Li, Xiaohui; Luo, Jiaqi; Shum, Perry Ping; Yu, Xia; Zhang, Ying; Wang, Qi Jie

    2016-06-01

    We demonstrated a widely tunable Tm-doped mode-locked all-fiber laser, with the widest tunable range of 136 nm, from 1842 to 1978 nm. Nonlinear polarization evolution (NPE) technique is employed to enable mode-locking and the wavelength-tunable operation. The widely tunable range attributes to the NPE-induced transmission modulation and bidirectional pumping mechanism. Such kind of tunable mode-locked laser can find various applications in optical communications, spectroscopy, time-resolved measurement, and among others.

  18. Exploiting dimensionality and defect mitigation to create tunable microwave dielectrics.

    PubMed

    Lee, Che-Hui; Orloff, Nathan D; Birol, Turan; Zhu, Ye; Goian, Veronica; Rocas, Eduard; Haislmaier, Ryan; Vlahos, Eftihia; Mundy, Julia A; Kourkoutis, Lena F; Nie, Yuefeng; Biegalski, Michael D; Zhang, Jingshu; Bernhagen, Margitta; Benedek, Nicole A; Kim, Yongsam; Brock, Joel D; Uecker, Reinhard; Xi, X X; Gopalan, Venkatraman; Nuzhnyy, Dmitry; Kamba, Stanislav; Muller, David A; Takeuchi, Ichiro; Booth, James C; Fennie, Craig J; Schlom, Darrell G

    2013-10-24

    The miniaturization and integration of frequency-agile microwave circuits--relevant to electronically tunable filters, antennas, resonators and phase shifters--with microelectronics offers tantalizing device possibilities, yet requires thin films whose dielectric constant at gigahertz frequencies can be tuned by applying a quasi-static electric field. Appropriate systems such as BaxSr1-xTiO3 have a paraelectric-ferroelectric transition just below ambient temperature, providing high tunability. Unfortunately, such films suffer significant losses arising from defects. Recognizing that progress is stymied by dielectric loss, we start with a system with exceptionally low loss--Srn+1TinO3n+1 phases--in which (SrO)2 crystallographic shear planes provide an alternative to the formation of point defects for accommodating non-stoichiometry. Here we report the experimental realization of a highly tunable ground state arising from the emergence of a local ferroelectric instability in biaxially strained Srn+1TinO3n+1 phases with n ≥ 3 at frequencies up to 125 GHz. In contrast to traditional methods of modifying ferroelectrics-doping or strain-in this unique system an increase in the separation between the (SrO)2 planes, which can be achieved by changing n, bolsters the local ferroelectric instability. This new control parameter, n, can be exploited to achieve a figure of merit at room temperature that rivals all known tunable microwave dielectrics. PMID:24132232

  19. 40nm tunable multi-wavelength fiber laser

    NASA Astrophysics Data System (ADS)

    Jia, Qingsong; Wang, Tianshu; Zhang, Peng; Dong, Keyan; Jiang, Huilin

    2014-12-01

    A Brillouin-Erbium multi-wavelength tunable fiber laser at C-band is demostrated. A 10 km long singlemode fiber(SMF), a 6 m long Erbium-doped fiber, two couplers, a wavelength division multiplexer, a isolator, an optical circulator, a 980nm pump laser and a narrow linewidth tunable laser are included in the structure. A segment of 10 km-long single-mode fiber (SMF) between the two ports of a 1×2 coupler is used as Brillouin gain. Ebiumdoped fiber amplifier (EDFA) consists of a segment of 6m er-doped fiber pumped by 980nm laser dioder . A narrow linewidth tunable laser from 1527 to 1607 nm as Brillouin bump, At the Brillouin pump power of 8mW and the 980 nm pump power of 400 mw, 16 output channels with 0.08 nm spacing and tuning range of 40 nm from 1527 nm to 1567 nm are achieved. We realize the tunable output of wavelength by adjusting the 980 nm pump power and the Brillouin pump wavelength. Stability of the multiwavelength fiber laser is also observed.

  20. SPECTRAL MEASUREMENTS OF GASEOUS SULFURIC ACID USING TUNABLE DIODE LASERS

    EPA Science Inventory

    Using a tunable diode laser spectrometer with a spectral resolution of about 10 to the -4 power/cm, the important central portions of the two infrared absorption bands of H2SO4 at 8.2 micrometers (1222/cm) and 11.3 micrometers (880/cm) have been scanned at low pressure (approxima...