Science.gov

Sample records for entanglement-preserving frequency conversion

  1. Mechanism of entanglement preservation

    SciTech Connect

    Tong Qingjun; An Junhong; Luo Honggang; Oh, C. H.

    2010-05-15

    We study the entanglement preservation of two qubits locally interacting with their reservoirs. We show that the existence of a bound state of the qubit and its reservoir and the non-Markovian effect are two essential ingredients and their interplay plays a crucial role in preserving the entanglement in the steady state. When the non-Markovian effect is neglected, the entanglement sudden death (ESD) is reproduced. On the other hand, when the non-Markovian is significantly strong but the bound state is absent, the phenomenon of the ESD and its revival is recovered. Our formulation presents a unified picture about the entanglement preservation and provides a clear clue on how to preserve the entanglement in quantum information processing.

  2. Entanglement preservation by continuous distillation

    SciTech Connect

    Mundarain, D.; Orszag, M.

    2009-05-15

    We study the two-qubit entanglement preservation for a system in the presence of independent thermal baths. We use a combination of filtering operations and distillation protocols as a series of frequent measurements on the system. It is shown that a small fraction of the total amount of available copies of the system preserves or even improves its initial entanglement during the evolution.

  3. Frequency conversion system

    NASA Technical Reports Server (NTRS)

    Sanders, Steven (Inventor); Waarts, Robert G. (Inventor)

    2001-01-01

    A frequency conversion system comprises first and second gain sources providing first and second frequency radiation outputs where the second gain source receives as input the output of the first gain source and, further, the second gain source comprises a Raman or Brillouin gain fiber for wave shifting a portion of the radiation of the first frequency output into second frequency radiation output to provided a combined output of first and second frequencies. Powers are gain enhanced by the addition of a rare earth amplifier or oscillator, or a Raman/Brillouin amplifier or oscillator between the high power source and the NFM device. Further, polarization conversion using Raman or Brillouin wavelength shifting is provided to optimize frequency conversion efficiency in the NFM device.

  4. Frequency conversion system

    NASA Technical Reports Server (NTRS)

    Sanders, Steven (Inventor); Lang, Robert J. (Inventor)

    2001-01-01

    Laser diode pumped mid-IR wavelength sources include at least one high power, near-IR wavelength, injection and/or sources wherein one or both of such sources may be tunable providing a pump wave output beam to a quasi-phase matched (QPM) nonlinear frequency mixing (NFM) device. The NFM device may be a difference frequency mixing (DFM) device or an optical parametric oscillation (OPO) device. Wavelength tuning of at least one of the sources advantageously provides the ability for optimizing pump or injection wavelengths to match the QPM properties of the NFM device enabling a broad range of mid-IR wavelength selectivity. Also, pump powers are gain enhanced by the addition of a rare earth amplifier or oscillator, or a Raman/Brillouin amplifier or oscillator between the high power source and the NFM device. Further, polarization conversion using Raman or Brillouin wavelength shifting is provided to optimize frequency conversion efficiency in the NFM device.

  5. Frequency conversion of structured light.

    PubMed

    Steinlechner, Fabian; Hermosa, Nathaniel; Pruneri, Valerio; Torres, Juan P

    2016-01-01

    Coherent frequency conversion of structured light, i.e. the ability to manipulate the carrier frequency of a wave front without distorting its spatial phase and intensity profile, provides the opportunity for numerous novel applications in photonic technology and fundamental science. In particular, frequency conversion of spatial modes carrying orbital angular momentum can be exploited in sub-wavelength resolution nano-optics and coherent imaging at a wavelength different from that used to illuminate an object. Moreover, coherent frequency conversion will be crucial for interfacing information stored in the high-dimensional spatial structure of single and entangled photons with various constituents of quantum networks. In this work, we demonstrate frequency conversion of structured light from the near infrared (803 nm) to the visible (527 nm). The conversion scheme is based on sum-frequency generation in a periodically poled lithium niobate crystal pumped with a 1540-nm Gaussian beam. We observe frequency-converted fields that exhibit a high degree of similarity with the input field and verify the coherence of the frequency-conversion process via mode projection measurements with a phase mask and a single-mode fiber. Our results demonstrate the suitability of exploiting the technique for applications in quantum information processing and coherent imaging. PMID:26875448

  6. Frequency conversion of structured light

    PubMed Central

    Steinlechner, Fabian; Hermosa, Nathaniel; Pruneri, Valerio; Torres, Juan P.

    2016-01-01

    Coherent frequency conversion of structured light, i.e. the ability to manipulate the carrier frequency of a wave front without distorting its spatial phase and intensity profile, provides the opportunity for numerous novel applications in photonic technology and fundamental science. In particular, frequency conversion of spatial modes carrying orbital angular momentum can be exploited in sub-wavelength resolution nano-optics and coherent imaging at a wavelength different from that used to illuminate an object. Moreover, coherent frequency conversion will be crucial for interfacing information stored in the high-dimensional spatial structure of single and entangled photons with various constituents of quantum networks. In this work, we demonstrate frequency conversion of structured light from the near infrared (803 nm) to the visible (527 nm). The conversion scheme is based on sum-frequency generation in a periodically poled lithium niobate crystal pumped with a 1540-nm Gaussian beam. We observe frequency-converted fields that exhibit a high degree of similarity with the input field and verify the coherence of the frequency-conversion process via mode projection measurements with a phase mask and a single-mode fiber. Our results demonstrate the suitability of exploiting the technique for applications in quantum information processing and coherent imaging. PMID:26875448

  7. Frequency conversion of structured light

    NASA Astrophysics Data System (ADS)

    Steinlechner, Fabian; Hermosa, Nathaniel; Pruneri, Valerio; Torres, Juan P.

    2016-02-01

    Coherent frequency conversion of structured light, i.e. the ability to manipulate the carrier frequency of a wave front without distorting its spatial phase and intensity profile, provides the opportunity for numerous novel applications in photonic technology and fundamental science. In particular, frequency conversion of spatial modes carrying orbital angular momentum can be exploited in sub-wavelength resolution nano-optics and coherent imaging at a wavelength different from that used to illuminate an object. Moreover, coherent frequency conversion will be crucial for interfacing information stored in the high-dimensional spatial structure of single and entangled photons with various constituents of quantum networks. In this work, we demonstrate frequency conversion of structured light from the near infrared (803 nm) to the visible (527 nm). The conversion scheme is based on sum-frequency generation in a periodically poled lithium niobate crystal pumped with a 1540-nm Gaussian beam. We observe frequency-converted fields that exhibit a high degree of similarity with the input field and verify the coherence of the frequency-conversion process via mode projection measurements with a phase mask and a single-mode fiber. Our results demonstrate the suitability of exploiting the technique for applications in quantum information processing and coherent imaging.

  8. Robust adiabatic sum frequency conversion.

    PubMed

    Suchowski, Haim; Prabhudesai, Vaibhav; Oron, Dan; Arie, Ady; Silberberg, Yaron

    2009-07-20

    We discuss theoretically and demonstrate experimentally the robustness of the adiabatic sum frequency conversion method. This technique, borrowed from an analogous scheme of robust population transfer in atomic physics and nuclear magnetic resonance, enables the achievement of nearly full frequency conversion in a sum frequency generation process for a bandwidth up to two orders of magnitude wider than in conventional conversion schemes. We show that this scheme is robust to variations in the parameters of both the nonlinear crystal and of the incoming light. These include the crystal temperature, the frequency of the incoming field, the pump intensity, the crystal length and the angle of incidence. Also, we show that this extremely broad bandwidth can be tuned to higher or lower central wavelengths by changing either the pump frequency or the crystal temperature. The detailed study of the properties of this converter is done using the Landau-Zener theory dealing with the adiabatic transitions in two level systems. PMID:19654679

  9. Power enhanced frequency conversion system

    NASA Technical Reports Server (NTRS)

    Sanders, Steven (Inventor); Lang, Robert J. (Inventor); Waarts, Robert G. (Inventor)

    2001-01-01

    A frequency conversion system includes at least one source providing a first near-IR wavelength output including a gain medium for providing high power amplification, such as double clad fiber amplifier, a double clad fiber laser or a semiconductor tapered amplifier to enhance the power output level of the near-IR wavelength output. The NFM device may be a difference frequency mixing (DFM) device or an optical parametric oscillation (OPO) device. Pump powers are gain enhanced by the addition of a rare earth amplifier or oscillator, or a Ra-man/Brillouin amplifier or oscillator between the high power source and the NFM device.

  10. Transparency in nonlinear frequency conversion

    NASA Astrophysics Data System (ADS)

    Longhi, Stefano

    2016-04-01

    Suppression of wave scattering and the realization of transparency effects in engineered optical media and surfaces have attracted great attention in the past recent years. In this work the problem of transparency is considered for optical wave propagation in a nonlinear dielectric medium with second-order χ(2 ) susceptibility. Because of nonlinear interaction, a reference signal wave at carrier frequency ω1 can exchange power, thus being amplified or attenuated, when phase-matching conditions are satisfied and frequency conversion takes place. Therefore, rather generally the medium is not transparent to the signal wave because of "scattering" in the frequency domain. Here we show that broadband transparency, corresponding to the full absence of frequency conversion in spite of phase matching, can be observed for the signal wave in the process of sum frequency generation whenever the effective susceptibility χ(2 ) along the nonlinear medium is tailored following a suitable spatial apodization profile and the power level of the pump wave is properly tuned. While broadband transparency is observed under such conditions, the nonlinear medium is not invisible owing to an additional effective dispersion for the signal wave introduced by the nonlinear interaction.

  11. Geometrical representation of sum frequency generation and adiabatic frequency conversion

    NASA Astrophysics Data System (ADS)

    Suchowski, Haim; Oron, Dan; Arie, Ady; Silberberg, Yaron

    2008-12-01

    We present a geometrical representation of the process of sum frequency generation in the undepleted pump approximation, in analogy with the known optical Bloch equations. We use this analogy to propose a technique for achieving both high efficiency and large bandwidth in sum frequency conversion using the adiabatic inversion scheme. The process is analogous with rapid adiabatic passage in NMR, and adiabatic constraints are derived in this context. This adiabatic frequency conversion scheme is realized experimentally using an aperiodically poled potassium titanyl phosphate (KTP) device, where we achieved high efficiency signal-to-idler conversion over a bandwidth of 140nm .

  12. Frequency doubling conversion efficiencies for deep space optical communications

    NASA Technical Reports Server (NTRS)

    Robinson, D. L.; Shelton, R. L.

    1987-01-01

    The theory of optical frequency doubling conversion efficiency is analyzed for the small signal input case along with the strong signal depleted input case. Angle phase matching and beam focus spot size are discussed and design trades are described which maximize conversion efficiency. Experimental conversion efficiencies from the literature, which are less than theoretical results at higher input intensities due to saturation, reconversion, and higher order processes, are applied to a case study of an optical communications link from Saturn. Double pass conversion efficiencies as high as 45 percent are expected. It is believed that even higher conversion efficiencies can be obtained using multipass conversion.

  13. Adiabatic and diabatic process of sum frequency conversion.

    PubMed

    Liqing, Ren; Yongfang, Li; Baihong, Li; Lei, Wang; Zhaohua, Wang

    2010-09-13

    Based on the dressed state formalism, we obtain the adiabatic criterion of the sum frequency conversion. We show that this constraint restricts the energy conversion between the two dressed fields, which are superpositions of the signal field and the sum frequency field. We also show that the evolution of the populations of the dressed fields, which in turn describes the conversion of light photons from the seed frequency to the sum frequency during propagation through the nonlinear crystal. Take the quasiphased matched (QPM) scheme as an example, we calculate the expected bandwidth of the frequency conversion process, and its dependence on the length of the crystal. We demonstrate that the evolutionary patterns of the sum frequency field's energy are similar to the Fresnel diffraction of a light field. We finally show that the expected bandwidth can be also deduced from the evolution of the adiabaticity of the dressed fileds. PMID:20940935

  14. Frequency conversion in free-standing periodically oriented gallium nitride

    NASA Astrophysics Data System (ADS)

    Brown, Christopher G.; Bowman, Steven R.; Hite, Jennifer K.; Freitas, Jaime A.; Kub, Francis J.; Eddy, Charles R.; Vurgaftman, Igor; Meyer, Jerry R.; Leach, Jacob H.; Udwary, Kevin

    2016-03-01

    Gallium nitride's (GaN) material properties of broadband transparency, high thermal conductivity, and wide-band gap make it a promising candidate for high-power frequency conversion devices. The strong internal polarization of GaN leads to large second-order nonlinearity, but conventional phase matching is prevented due to weak birefringence. To obtain efficient nonlinear optic frequency conversion, patterned inversion growth has been developed to induce quasiphase matching (QPM). We have fabricated and tested periodically oriented GaN (PO-GaN) devices to obtain QPM frequency conversion. This report discusses our recent measurements of second harmonic generation resonances for these devices.

  15. Nonblocking space wavelength networks with wave-mixing frequency conversion

    NASA Astrophysics Data System (ADS)

    Dasylva, Abel Clement; Montuno, Delfin Y.; Kodaypak, Prasad

    2002-06-01

    We describe what we believe to be new designs for all-optical cross connects, capable of wavelength conversion. They are based on two-dimensional, space-wavelength, Benes or Cantor topologies, and they exploit cascaded wave-mixing bulk frequency conversion. In these cross connects many channels at distinct frequencies can be simultaneously frequency translated in a common wave-mixing device, and a given lightpath may be converted many times between its input and output. The new wavelength-interchanging cross connects are nonblocking and require O{F log2 W[log2(FW)]n} wave-mixing converters, where n = 0, 1.

  16. Single-photon frequency down-conversion experiment

    SciTech Connect

    Takesue, Hiroki

    2010-07-15

    We report a single-photon frequency down-conversion experiment. Using the difference frequency generation process in a periodically poled lithium niobate waveguide, we successfully observed the phase-preserved frequency down-conversion of a coherent pulse train with an average photon number per pulse of <1, from the 0.7 {mu}m visible wavelength band to the 1.3 {mu}m telecom band. We expect this technology to become an important tool for flexible photonic quantum networking, including the realization of quantum repeater systems over optical fiber using atom-photon entanglement sources for the visible wavelength bands.

  17. Interpretation of Cluster WBD frequency conversion mode data

    NASA Astrophysics Data System (ADS)

    Pickett, J. S.; Christopher, I. W.; Kirchner, D. L.

    2014-02-01

    The Cluster wide-band data (WBD) plasma wave receiver mounted on each of the four Cluster spacecraft obtains high time resolution waveform data in the frequency range of ~70 Hz to 577 kHz. In order to make measurements above 77 kHz, it uses frequency conversion to sample the higher frequency waves at one of three different conversion frequencies (~125, 250 and 500 kHz, these frequencies being the possible options for setting the base frequency of the frequency range being sampled) in one of three different filter bandwidths (9.5, 19 and 77 kHz). Within the WBD instrument, a down-conversion technique, built around quadrature mixing, is used to convert these data to baseband (0 kHz) in order to reduce the sample rate for telemetry to the ground. We describe this down-conversion technique and illustrate it through data obtained in space. Because these down-converted data sometimes contain pulses, which can be indicative of nonlinear physical structures (e.g., electron phase-space holes and electron density enhancements and depletions), it is necessary to understand what effects mixing and down conversion have on them. We present simulations using constructed signals containing pulses, nonlinear wave packets, sinusoids and noise. We show that the pulses and impulsive wave packets, if of sufficient amplitude and of appropriate width, survive the down-conversion process, sometimes with the same pulse shape but usually with reduced amplitude, and have timescales consistent with the filter bandwidth at the base frequency. Although we cannot infer the actual timescale of the pulses and impulsive wave packets as originally recorded by the WBD instrument before mixing and down conversion, their presence indicates nonlinear processes occurring at or somewhat near the location of the measurement. Sinusoidal waves are represented in the down-conversion timescale as sinusoids of nearly the same amplitude and at frequencies adjusted down by the conversion frequency. The original

  18. Interpretation of Cluster WBD frequency conversion mode data

    NASA Astrophysics Data System (ADS)

    Pickett, J. S.; Christopher, I. W.; Kirchner, D. L.

    2013-08-01

    The Cluster Wide-Band Data (WBD) plasma wave receiver mounted on each of the four Cluster spacecraft obtains high time resolution waveform data in the frequency range of ~70 Hz to 577 kHz. In order to make measurements above 77 kHz, it uses frequency conversion to sample the higher frequency waves at one of three different conversion frequencies (~125, 250 and 500 kHz, where these frequencies are the base frequency of the frequency range being sampled) in one of three different filter bandwidths (9.5, 19 and 77 kHz). Within the WBD instrument a down conversion technique, built around quadrature mixing, is used to convert these data to baseband (0 kHz) in order to reduce the sample rate for telemetry to the ground. We describe this down conversion technique and illustrate it through data obtained in space. Because these down converted data sometimes contain pulses, which can be indicative of nonlinear physical structures (e.g., electron phase space holes and electron density enhancements and depletions), it is necessary to understand what effects mixing and down conversion have on them. We present simulations using constructed signals containing pulses, nonlinear wave packets, sinusoids and noise. We show that the pulses and impulsive wave packets, if of sufficient amplitude and of appropriate width, survive the down conversion process, sometimes with the same pulse shape but usually with reduced amplitude, and have time scales consistent with the filter bandwidth at the base frequency. Although we cannot infer the actual time scale of the pulses and impulsive wave packets as originally recorded by the WBD instrument before mixing and down conversion, their presence indicates nonlinear processes occurring at or somewhat near the location of the measurement. Sinusoidal waves are represented in the down conversion time scale as sinusoids of nearly the same amplitude and at frequencies adjusted down by the conversion frequency. The original input waveforms, regardless

  19. Resonator power to frequency conversion in a cryogenic sapphire oscillator

    NASA Astrophysics Data System (ADS)

    Nand, Nitin R.; Parker, Stephen R.; Ivanov, Eugene N.; le Floch, Jean-Michel; Hartnett, John G.; Tobar, Michael E.

    2013-07-01

    We report on the measurement and characterization of power to frequency conversion in the resonant mode of a cryogenic sapphire loaded cavity resonator, which is used as the frequency discriminating element of a loop oscillator circuit. Fluctuations of power incident on the resonator lead to changes in radiation pressure and temperature in the sapphire dielectric, both of which contribute to a shift in the resonance frequency. We measure a modulation and temperature independent radiation pressure induced power to frequency sensitivity of -0.15 Hz/mW and find that this is the primary factor limiting the stability of the resonator frequency.

  20. Mechanically Mediated Microwave Frequency Conversion in the Quantum Regime

    NASA Astrophysics Data System (ADS)

    Lecocq, F.; Clark, J. B.; Simmonds, R. W.; Aumentado, J.; Teufel, J. D.

    2016-01-01

    We report the observation of efficient and low-noise frequency conversion between two microwave modes, mediated by the motion of a mechanical resonator subjected to radiation pressure. We achieve coherent conversion of more than 1012 photons/s with a 95% efficiency and a 14 kHz bandwidth. With less than 10-1 photons.s-1.Hz-1 of added noise, this optomechanical frequency converter is suitable for quantum state transduction. We show the ability to operate this converter as a tunable beam splitter, with direct applications for photon routing and communication through complex quantum networks.

  1. Simultaneous frequency conversion, regeneration and reshaping of optical signals.

    PubMed

    McKinstrie, C J; Cargill, D S

    2012-03-26

    Nondegenerate four-wave mixing in fibers enables the tunable and low-noise frequency conversion of optical signals. This paper shows that four-wave mixing driven by pulsed pumps can also regenerate and reshape optical signal pulses arbitrarily. PMID:22453365

  2. Hybrid radio-intermediate-frequency oscillator with photonic-delay-matched frequency conversion pair.

    PubMed

    Dai, Yitang; Wang, Ruixin; Yin, Feifei; Dai, Jian; Zhou, Yue; Li, Jianqiang; Xu, Kun

    2015-06-15

    A low-phase-noise, single-loop radio-frequency (RF) oscillator is proposed and experimentally demonstrated where part of the oscillation is in intermediate-frequency (IF) domain by a pair of frequency conversions. Single-mode operation is achieved by IF filtering. The key design is the matched photonic delay between the two conversions, by which the large phase noise of the common external RF local oscillation (LO) shows no impact on the RF carrier passing through the conversion pair and the low-phase-noise oscillation is guaranteed. The phase-noise performance of the delay-matched conversion pair plus IF filtering is theoretically and experimentally studied. With the proposed scheme, we achieve 120 dBc/Hz phase noise at 10-kHz offset from 10-GHz carrier frequency through a 1-μs loop cavity. PMID:26076289

  3. High power and high SFDR frequency conversion using sum frequency generation in KTP waveguides.

    PubMed

    Barbour, Russell J; Brewer, Tyler; Barber, Zeb W

    2016-08-01

    We characterize the intermodulation distortion of high power and efficient frequency conversion of modulated optical signals based on sum frequency generation (SFG) in a periodically poled potassium titanyl phosphate (KTP) waveguide. Unwanted frequency two-tone spurs are generated near the converted signal via a three-step cascaded three-wave mixing process. Computer simulations describing the process are presented along with the experimental measurements. High-conversion efficiencies and large spur-free dynamic range of the converted optical signal are demonstrated. PMID:27472638

  4. High efficiency in mode-selective frequency conversion.

    PubMed

    Quesada, Nicolás; Sipe, J E

    2016-01-15

    Frequency conversion (FC) is an enabling process in many quantum information protocols. Recently, it has been observed that upconversion efficiencies in single-photon, mode-selective FC are limited to around 80%. In this Letter, we argue that these limits can be understood as time-ordering corrections (TOCs) that modify the joint conversion amplitude of the process. Furthermore, using a simple scaling argument, we show that recently proposed cascaded FC protocols that overcome the aforementioned limitations act as "attenuators" of the TOCs. This observation allows us to argue that very similar cascaded architectures can be used to attenuate TOCs in photon generation via spontaneous parametric downconversion. Finally, by using the Magnus expansion, we argue that the TOCs, which are usually considered detrimental for FC efficiency, can also be used to increase the efficiency of conversion in partially mode-selective FC. PMID:26766715

  5. Phase-sensitive frequency conversion of quadrature modulated signals.

    PubMed

    Webb, R P; Power, M; Manning, R J

    2013-05-20

    Two mechanisms that can make frequency conversion based on nonlinear mixing dependent on the phase of the input signal are identified. A novel phase-to-polarization converter that converts the orthogonal phase components of an input signal to two orthogonally polarized outputs is proposed. The operation of this scheme and a previously reported scheme at an increased symbol rate are simulated with semiconductor optical amplifiers (SOAs) as the nonlinear devices. Experimental results demonstrate the effectiveness of SOAs for nonlinear mixing over a wide range of wavelengths and difference frequencies and confirm the accuracy of the numerical model. PMID:23736490

  6. Frequency conversion of high-intensity, femtosecond laser pulses

    SciTech Connect

    Banks, P S

    1997-06-01

    Almost since the invention of the laser, frequency conversion of optical pulses via non- linear processes has been an area of active interest. However, third harmonic generation using ~(~1 (THG) in solids is an area that has not received much attention because of ma- terial damage limits. Recently, the short, high-intensity pulses possible with chirped-pulse amplification (CPA) laser systems allow the use of intensities on the order of 1 TW/cm2 in thin solids without damage. As a light source to examine single-crystal THG in solids and other high field inter- actions, the design and construction of a Ti:sapphire-based CPA laser system capable of ultimately producing peak powers of 100 TW is presented. Of special interest is a novel, all-reflective pulse stretcher design which can stretch a pulse temporally by a factor of 20,000. The stretcher design can also compensate for the added material dispersion due to propagation through the amplifier chain and produce transform-limited 45 fs pulses upon compression. A series of laser-pumped amplifiers brings the peak power up to the terawatt level at 10 Hz, and the design calls for additional amplifiers to bring the power level to the 100 TW level for single shot operation. The theory for frequency conversion of these short pulses is presented, focusing on conversion to the third harmonic in single crystals of BBO, KD*P, and d-LAP (deuterated I-arginine phosphate). Conversion efficiencies of up to 6% are obtained with 500 fs pulses at 1053 nm in a 3 mm thick BBO crystal at 200 GW/cm 2. Contributions to this process by unphasematched, cascaded second harmonic generation and sum frequency generation are shown to be very significant. The angular relationship between the two orders is used to measure the tensor elements of C = xt3)/4 with Crs = -1.8 x 1O-23 m2/V2 and .15Cri + .54Crs = 4.0 x 1O-23 m2/V2. Conversion efficiency in d-LAP is about 20% that in BBO and conversion efficiency in KD*P is 1% that of BBO. It is calculated

  7. Quantum frequency up-conversion of continuous variable entangled states

    SciTech Connect

    Liu, Wenyuan; Wang, Ning; Li, Zongyang; Li, Yongmin

    2015-12-07

    We demonstrate experimentally quantum frequency up-conversion of a continuous variable entangled optical field via sum-frequency-generation process. The two-color entangled state initially entangled at 806 and 1518 nm with an amplitude quadrature difference squeezing of 3.2 dB and phase quadrature sum squeezing of 3.1 dB is converted to a new entangled state at 530 and 1518 nm with the amplitude quadrature difference squeezing of 1.7 dB and phase quadrature sum squeezing of 1.8 dB. Our implementation enables the observation of entanglement between two light fields spanning approximately 1.5 octaves in optical frequency. The presented scheme is robust to the excess amplitude and phase noises of the pump field, making it a practical building block for quantum information processing and communication networks.

  8. Wavelength conversion technique for optical frequency dissemination applications.

    PubMed

    Kim, Joonyoung; Marra, Giuseppe; Wu, David S; Richardson, David J; Slavík, Radan

    2016-04-15

    We demonstrate coherent wavelength conversion capable of covering the entire C-band by modulating the incoming optical carrier with a compact Fabry-Perot cavity embedded phase modulator and by optical injection locking a semiconductor laser to a tone of the generated optical frequency comb. The phase noise of the converted optical carrier over 1 THz frequency interval is measured to be -40  dBc/Hz at 10 Hz offset and the frequency stability is better than 2×10-17 level for averaging times >1000  s, making this technique a promising solution for comparisons of state-of-the-art optical clocks over complex fiber networks. PMID:27082327

  9. Quantum frequency up-conversion of continuous variable entangled states

    NASA Astrophysics Data System (ADS)

    Liu, Wenyuan; Wang, Ning; Li, Zongyang; Li, Yongmin

    2015-12-01

    We demonstrate experimentally quantum frequency up-conversion of a continuous variable entangled optical field via sum-frequency-generation process. The two-color entangled state initially entangled at 806 and 1518 nm with an amplitude quadrature difference squeezing of 3.2 dB and phase quadrature sum squeezing of 3.1 dB is converted to a new entangled state at 530 and 1518 nm with the amplitude quadrature difference squeezing of 1.7 dB and phase quadrature sum squeezing of 1.8 dB. Our implementation enables the observation of entanglement between two light fields spanning approximately 1.5 octaves in optical frequency. The presented scheme is robust to the excess amplitude and phase noises of the pump field, making it a practical building block for quantum information processing and communication networks.

  10. Tandem filters using frequency selective surfaces for enhanced conversion efficiency in a thermophotovoltaic energy conversion system

    DOEpatents

    Dziendziel, Randolph J.; Baldasaro, Paul F.; DePoy, David M.

    2010-09-07

    This invention relates to the field of thermophotovoltaic (TPV) direct energy conversion. In particular, TPV systems use filters to minimize parasitic absorption of below bandgap energy. This invention constitutes a novel combination of front surface filters to increase TPV conversion efficiency by reflecting useless below bandgap energy while transmitting a very high percentage of the useful above bandgap energy. In particular, a frequency selective surface is used in combination with an interference filter. The frequency selective surface provides high transmission of above bandgap energy and high reflection of long wavelength below bandgap energy. The interference filter maintains high transmission of above bandgap energy and provides high reflection of short wavelength below bandgap energy and a sharp transition from high transmission to high reflection.

  11. Tandem filters using frequency selective surfaces for enhanced conversion efficiency in a thermophotovoltaic energy conversion system

    DOEpatents

    Dziendziel, Randolph J.; DePoy, David Moore; Baldasaro, Paul Francis

    2007-01-23

    This invention relates to the field of thermophotovoltaic (TPV) direct energy conversion. In particular, TPV systems use filters to minimize parasitic absorption of below bandgap energy. This invention constitutes a novel combination of front surface filters to increase TPV conversion efficiency by reflecting useless below bandgap energy while transmitting a very high percentage of the useful above bandgap energy. In particular, a frequency selective surface is used in combination with an interference filter. The frequency selective surface provides high transmission of above bandgap energy and high reflection of long wavelength below bandgap energy. The interference filter maintains high transmission of above bandgap energy and provides high reflection of short wavelength below bandgap energy and a sharp transition from high transmission to high reflection.

  12. Modeling beam propagation and frequency conversion for the beamlet laser

    SciTech Connect

    Auerbach, J.M.

    1996-06-01

    The development of the Beamlet laser has involved extensive and detailed modeling of laser performance and beam propagation to: (1) predict the performance limits of the laser, (2) select system configurations with higher performance, (3) analyze experiments and provide guidance for subsequent laser shots, and (4) design optical components and establish component manufacturing specifications. In contrast to modeling efforts of previous laser systems such as Nova, those for Beamlet include as much measured optical characterization data as possible. This article concentrates on modeling of beam propagation in the Beamlet laser system, including the frequency converter, and compares modeling predictions with experimental results for several Beamlet shots. It briefly describes the workstation-based propagation and frequency conversion codes used to accomplish modeling of the Beamlet.

  13. BBO sapphire compound for high-power frequency conversion

    NASA Astrophysics Data System (ADS)

    Rothhardt, Carolin; Rothhardt, Jan; Klenke, Arno; Peschel, Thomas; Eberhardt, Ramona; Limpert, Jens; Tünnermann, Andreas

    2015-02-01

    Lasers used for diverse applications from industry to fundamental science tend to increasing output powers. Some applications require frequency conversion via nonlinear optical crystals, which suffer from the formation of temperature gradients at high power operation which causes thermal lensing or destruction of the crystal due to tensile stresses. To avoid these unwanted effects we joined a beta barium borate (BBO) crystal with sapphire disks serving as effective heat spreaders due to their high thermal conductivity (thermal conductivity κ = 42 W/Km). Therefore, smooth and flat crystal surfaces were joined by plasma-activated bonding. The joining relies on covalent bonds, which are formed via a condensation reaction of the surfaces which are first connected by Van der Waals forces. The cleaned surfaces are activated by plasma and brought into contact, pressed together and heat treated at a temperature of about 100°C. Special attention has been paid to the cleaning of the surfaces. Therefor the surfaces have been evaluated before and after treatment by means of atomic force microscopy. A stable connection has been formed successfully, which has been tested in a proof of principle experiment and demonstrated efficient second harmonic generation at up to 253 W of input power. Compared to a bare single BBO crystal it could be shown that the temperature within the crystal compound is significantly reduced. Such hybrid structures pave the way for frequency conversion at kilowatts of average power for future high power lasers.

  14. WDM up-conversion employing frequency quadrupling in optical modulator.

    PubMed

    Shih, Po-Tsung; Lin, Chun-Ting; Jiang, Wen-Jr; Chen, Jason Jyehong; Huang, Han-Sheng; Chen, Yu-Hung; Peng, Peng-Chun; Chi, Sien

    2009-02-01

    This work presents an optical up-conversion system with frequency quadrupling for wavelength-division-multiplexing (WDM) communication systems using a dual-parallel Mach-Zehnder modulator without optical filtering. Four-channel 1.25-Gb/s wired fiber-to-the-x (FTTx) and wireless radio-over-fiber (RoF) signals are generated and transmitted simultaneously. Moreover, the decline in receiver sensitivities due to Mach-Zehnder modulator bias drifts is also investigated. Receiver power penalties of the 20-GHz up-converted WDM signals and baseband (BB) FTTx signals are less than 1 dB when bias deviation voltage is less the 20% of the half-wave voltage. After transmission over a 50-km SSMF, the receiver power penalties of both the BB and 20-GHz RF OOK signals are less than 1 dB. Notably, 60-GHz optical up-conversion can be achieved using 15-GHz radio frequency (RF) components and equipment. PMID:19189002

  15. A New Vector Frequency Modulation Method for Power Conversion Circuits

    NASA Astrophysics Data System (ADS)

    Takano, Akio

    This paper presents an excellent PWM method for power conversion circuits. The proposed method is called a Vector Frequency Modulation (VFM) in this paper. VFM does not belong to any conventional PWM methods. Although an idea of space voltage vector is employed in VFM, any traditional equations to calculate the periods of the voltage vectors are not used. The voltage vectors are classified into two groups, zero vectors and non-zero ones. Instead of the complicated equations, a very simple algorithm is employed in VFM. One vector period is fixed and the zero vectors are distributed among the non-zero vectors in the ratio determined by the command voltage or frequency. The behavior of VFM is performed in software and any modulation-wave oscillators, comparators and up-down counters are not needed. At first, a reversible chopper is modulated by VFM and a 2kW DC motor is driven by the chopper. The motor speed is regulated by modern control theory. Next, a three-phase inverter is modulated by VFM and a 2.2kW induction motor is driven by the inverter. Experimental results are shown to prove that VFM is actually useful for power conversion circuits.

  16. Non-Locus-Specific Polygenes Giving Responses to Selection for Gene Conversion Frequencies in Ascobolus Immersus

    PubMed Central

    Zwolinski, S. A.; Lamb, B. C.

    1995-01-01

    Selection for higher and lower meiotic conversion frequencies was investigated in the fungus Ascobolus immersus. Strains carrying the same known gene conversion control factors, which have major effects on conversion frequencies at their specific target locus, sometimes gave significant differences in conversion frequency. Selection for high or low conversion frequencies at the w1-78 site was practiced for five generations, giving significant responses in both directions. These responses were due to polygenes, or genes of minor effect, not to new conversion control factors of major effect. Crosses of selected strains to strains with other mutations showed that the genes' effects were not specific to w1-78, but could affect conversion frequencies of another mutation, w1-3C1, at that locus and of two other loci, w-BHj and w9, which are unlinked to w1 or to each other. The proportional changes in gene conversion frequency due to selection varied according to the locus and site involved and according to the conversion control factor alleles present. There were differences of >/=277% in conversion frequency between ``high'' and ``low'' strains. Selection for conversion frequency had little effect on other features of conversion, such as the frequency of postmeiotic segregation or the relative frequencies of conversion to mutant or wild type. PMID:7498769

  17. A Resonator for Low-Threshold Frequency Conversion

    NASA Technical Reports Server (NTRS)

    Iltchenko, Vladimir; Matsko, Andrey; Savchenkov, Anatoliy; Maleki, Lute

    2004-01-01

    A proposed toroidal or disklike dielectric optical resonator (dielectric optical cavity) would be made of an optically nonlinear material and would be optimized for use in parametric frequency conversion by imposition of a spatially periodic permanent electric polarization. The poling (see figure) would suppress dispersions caused by both the material and the geometry of the optical cavity, thereby effecting quasi-matching of the phases of high-resonance-quality (high-Q) whispering-gallery electromagnetic modes. The quasi-phase-matching of the modes would serve to maximize the interactions among them. Such a resonator might be a prototype of a family of compact, efficient nonlinear devices for operation over a broad range of optical wavelengths. A little background information is prerequisite to a meaningful description of this proposal: (1) Described in several prior NASA Tech Briefs articles, the whispering-gallery modes in a component of spheroidal, disklike, or toroidal shape are waveguide modes that propagate circumferentially and are concentrated in a narrow toroidal region centered on the equatorial plane and located near the outermost edge. (2) For the sake of completeness, it must be stated that even though optical resonators of the type considered here are solid dielectric objects and light is confined within them by total internal reflection at dielectric interfaces without need for mirrors, such components are sometimes traditionally called cavities because their effects upon the light propagating within them are similar to those of true cavities bounded by mirrors. (3) For a given set of electromagnetic modes interacting with each other in an optically nonlinear material (e.g., modes associated with the frequencies involved in a frequency-conversion scheme), the threshold power for oscillation depends on the mode volumes and the mode-overlap integral. (4) Whispering-gallery modes are attractive in nonlinear optics because they maximize the effects of

  18. WGM Resonators for Terahertz-to-Optical Frequency Conversion

    NASA Technical Reports Server (NTRS)

    Strekalov,Dmitry; Savchenkov, Anatoliy; Matsko, Andrey; Nu, Nan

    2008-01-01

    Progress has been made toward solving some practical problems in the implementation of terahertz-to-optical frequency converters utilizing whispering-gallery-mode (WGM) resonators. Such frequency converters are expected to be essential parts of non-cryogenic terahertz- radiation receivers that are, variously, under development or contemplated for a variety of applications in airborne and spaceborne instrumentation for astronomical and military uses. In most respects, the basic principles of terahertz-to-optical frequency conversion in WGM resonators are the same as those of microwave (sub-terahertz)-to-optical frequency conversion in WGM resonators, various aspects of which were discussed in the three preceeding articles. To recapitulate: In a receiver following this approach, a preamplified incoming microwave signal (in the present case, a terahertz signal) is up-converted to an optical signal by a technique that exploits the nonlinearity of the electromagnetic response of a whispering-gallery-mode (WGM) resonator made of LiNbO3 or another suitable electro-optical material. Upconversion takes place by three-wave mixing in the resonator. To ensure the required interaction among the optical and terahertz signals, the WGM resonator must be designed and fabricated to function as an electro-optical modulator while simultaneously exhibiting (1) resonance at the required microwave and optical operating frequencies and (2) phase matching among the microwave and optical signals circulating in the resonator. Downstream of the WGM resonator, the up-converted signal is processed photonically by use of a tunable optical filter or local oscillator and is then detected. The practical problems addressed in the present development effort are the following: Satisfaction of the optical and terahertz resonance-frequency requirement is a straightforward matter, inasmuch as the optical and terahertz spectra can be measured. However, satisfaction of the phase-matching requirement is

  19. Solid state frequency conversion technology for remote sensing

    SciTech Connect

    Velsko, S.P.; Webb, M.S.; Cook, W.M.; Neuman, W.A.

    1994-07-01

    Long range remote sensing from airborne or other highly mobile platforms will require high average power tunable radiation from very compact and efficient laser systems. The solid state laser pumped optical parametric oscillator (OPO) has emerged as a leading candidate for such high average power, widely tunable sources. In contrast to laboratory systems, efficiency and simplicity can be the decisive issues which determine the practicality of a particular airborne remote sensing application. The recent advent of diode laser pumped solid state lasers has produced high average power OPO pump sources which are themselves both compact and efficient. However, parametric oscillator technology which can efficiently convert the average powers provided by these pump sources remains to be demonstrated. In addition to the average power requirement, many airborne long range sensing tasks will require a high degree of frequency multiplexing to disentangle data from multiple chemical species. A key advantage in system simplicity can be obtained, for example, if a single OPO can produce easily controlled multispectral output. In this paper the authors address several topics pertaining to the conversion efficiency, power handling, and multispectral capabilities of OPOs which they are currently investigating. In Section 2, single pulse conversion efficiency issues are addressed, while average power effects are treated in Section 3. Section 4 is concerned with multispectral performance of a single OPO. The last section contains a short summary and some concluding remarks.

  20. Frequency Up-Conversion Photon-Type Terahertz Imager.

    PubMed

    Fu, Z L; Gu, L L; Guo, X G; Tan, Z Y; Wan, W J; Zhou, T; Shao, D X; Zhang, R; Cao, J C

    2016-01-01

    Terahertz imaging has many important potential applications. Due to the failure of Si readout integrated circuits (ROICs) and the thermal mismatch between the photo-detector arrays and the ROICs at temperatures below 40 K, there are big technical challenges to construct terahertz photo-type focal plane arrays. In this work, we report pixel-less photo-type terahertz imagers based on the frequency up-conversion technique. The devices are composed of terahertz quantum-well photo-detectors (QWPs) and near-infrared (NIR) light emitting diodes (LEDs) which are grown in sequence on the same substrates using molecular beam epitaxy. In such an integrated QWP-LED device, photocurrent in the QWP drives the LED to emit NIR light. By optimizing the structural parameters of the QWP-LED, the QWP part and the LED part both work well. The maximum values of the internal and external energy up-conversion efficiencies are around 20% and 0.5%. A laser spot of a homemade terahertz quantum cascade laser is imaged by the QWP-LED together with a commercial Si camera. The pixel-less imaging results show that the image blurring induced by the transverse spreading of photocurrent is negligible. The demonstrated pixel-less imaging opens a new way to realize high performance terahertz imaging devices. PMID:27147281

  1. Frequency Up-Conversion Photon-Type Terahertz Imager

    PubMed Central

    Fu, Z. L.; Gu, L. L.; Guo, X. G.; Tan, Z. Y.; Wan, W. J.; Zhou, T.; Shao, D. X.; Zhang, R.; Cao, J. C.

    2016-01-01

    Terahertz imaging has many important potential applications. Due to the failure of Si readout integrated circuits (ROICs) and the thermal mismatch between the photo-detector arrays and the ROICs at temperatures below 40 K, there are big technical challenges to construct terahertz photo-type focal plane arrays. In this work, we report pixel-less photo-type terahertz imagers based on the frequency up-conversion technique. The devices are composed of terahertz quantum-well photo-detectors (QWPs) and near-infrared (NIR) light emitting diodes (LEDs) which are grown in sequence on the same substrates using molecular beam epitaxy. In such an integrated QWP-LED device, photocurrent in the QWP drives the LED to emit NIR light. By optimizing the structural parameters of the QWP-LED, the QWP part and the LED part both work well. The maximum values of the internal and external energy up-conversion efficiencies are around 20% and 0.5%. A laser spot of a homemade terahertz quantum cascade laser is imaged by the QWP-LED together with a commercial Si camera. The pixel-less imaging results show that the image blurring induced by the transverse spreading of photocurrent is negligible. The demonstrated pixel-less imaging opens a new way to realize high performance terahertz imaging devices. PMID:27147281

  2. Frequency Up-Conversion Photon-Type Terahertz Imager

    NASA Astrophysics Data System (ADS)

    Fu, Z. L.; Gu, L. L.; Guo, X. G.; Tan, Z. Y.; Wan, W. J.; Zhou, T.; Shao, D. X.; Zhang, R.; Cao, J. C.

    2016-05-01

    Terahertz imaging has many important potential applications. Due to the failure of Si readout integrated circuits (ROICs) and the thermal mismatch between the photo-detector arrays and the ROICs at temperatures below 40 K, there are big technical challenges to construct terahertz photo-type focal plane arrays. In this work, we report pixel-less photo-type terahertz imagers based on the frequency up-conversion technique. The devices are composed of terahertz quantum-well photo-detectors (QWPs) and near-infrared (NIR) light emitting diodes (LEDs) which are grown in sequence on the same substrates using molecular beam epitaxy. In such an integrated QWP-LED device, photocurrent in the QWP drives the LED to emit NIR light. By optimizing the structural parameters of the QWP-LED, the QWP part and the LED part both work well. The maximum values of the internal and external energy up-conversion efficiencies are around 20% and 0.5%. A laser spot of a homemade terahertz quantum cascade laser is imaged by the QWP-LED together with a commercial Si camera. The pixel-less imaging results show that the image blurring induced by the transverse spreading of photocurrent is negligible. The demonstrated pixel-less imaging opens a new way to realize high performance terahertz imaging devices.

  3. Nonlinear terahertz frequency conversion via graphene microribbon array.

    PubMed

    Nasari, H; Abrishamian, M S

    2016-07-29

    By exploiting the interesting trait of graphene to have electrically tunable first- and third-order conductivities besides its capability to support plasmonic resonances at terahertz frequencies, here, through the nonlinear finite-difference time-domain numerical technique we developed, we demonstrate a noticeable improvement in the conversion efficiency of third-harmonic generation (THG) from a graphene microribbon array by more than five orders of magnitude compared to an infinite graphene sheet, under normal illumination of terahertz waves. As the Fermi level and period length of the ribbon array increase, the transmission obviously manifests a blue shift but denotes a red shift with an increase in ribbon width. The quality factor of resonance (and so the THG efficiency) also shows improvement with an increase in graphene Fermi level, carrier mobility and period length and is degraded by an increase in ribbon width. Generating new frequencies, terahertz signal processing, spectroscopy and so on are among the plethora of valuable potential applications envisioned to be developed based on the findings reported here. PMID:27306039

  4. Nonlinear terahertz frequency conversion via graphene microribbon array

    NASA Astrophysics Data System (ADS)

    Nasari, H.; Abrishamian, M. S.

    2016-07-01

    By exploiting the interesting trait of graphene to have electrically tunable first- and third-order conductivities besides its capability to support plasmonic resonances at terahertz frequencies, here, through the nonlinear finite-difference time-domain numerical technique we developed, we demonstrate a noticeable improvement in the conversion efficiency of third-harmonic generation (THG) from a graphene microribbon array by more than five orders of magnitude compared to an infinite graphene sheet, under normal illumination of terahertz waves. As the Fermi level and period length of the ribbon array increase, the transmission obviously manifests a blue shift but denotes a red shift with an increase in ribbon width. The quality factor of resonance (and so the THG efficiency) also shows improvement with an increase in graphene Fermi level, carrier mobility and period length and is degraded by an increase in ribbon width. Generating new frequencies, terahertz signal processing, spectroscopy and so on are among the plethora of valuable potential applications envisioned to be developed based on the findings reported here.

  5. Optical frequency comb based multi-band microwave frequency conversion for satellite applications.

    PubMed

    Yang, Xinwu; Xu, Kun; Yin, Jie; Dai, Yitang; Yin, Feifei; Li, Jianqiang; Lu, Hua; Liu, Tao; Ji, Yuefeng

    2014-01-13

    Based on optical frequency combs (OFC), we propose an efficient and flexible multi-band frequency conversion scheme for satellite repeater applications. The underlying principle is to mix dual coherent OFCs with one of which carrying the input signal. By optically channelizing the mixed OFCs, the converted signal in different bands can be obtained in different channels. Alternatively, the scheme can be configured to generate multi-band local oscillators (LO) for widely distribution. Moreover, the scheme realizes simultaneous inter- and intra-band frequency conversion just in a single structure and needs only three frequency-fixed microwave sources. We carry out a proof of concept experiment in which multiple LOs with 2 GHz, 10 GHz, 18 GHz, and 26 GHz are generated. A C-band signal of 6.1 GHz input to the proposed scheme is successfully converted to 4.1 GHz (C band), 3.9 GHz (C band) and 11.9 GHz (X band), etc. Compared with the back-to-back (B2B) case measured at 0 dBm input power, the proposed scheme shows a 9.3% error vector magnitude (EVM) degradation at each output channel. Furthermore, all channels satisfy the EVM limit in a very wide input power range. PMID:24515046

  6. Frequency conversion in field stabilization system for application in SC cavity of linear accelerator

    NASA Astrophysics Data System (ADS)

    Filipek, Tomasz A.

    2005-09-01

    The paper concerns frequency conversion circuits of electromagnetic field stabilization system in superconductive cavity of linear accelerator. The stabilization system consists of digital part (based on FPGA) and analog part (frequency conversions, ADC/DAC, filters). Frequency conversion circuit is analyzed. The main problem in the frequency conversion for the stabilization system are: linearity of conversion and stability. Also, second order problems are subject of analysis: control of local oscillator parameters and fluctuation of actuated signal (exposing conversion). The following work was done: analysis of individual stage parameters on field stability and external influence, simulation. The work was closed with conclusions of the major frequency conversion parameters for field stabilization. The results have been applied for field stabilization system (RF Feedback System) in TESLA Test Facility 2 and preliminary research on X-Ray Free Electron Laser.

  7. Inductive transducer for displacement-to-frequency conversion

    NASA Astrophysics Data System (ADS)

    Shakurskiy, V. K.

    1984-05-01

    A controllable three-frequency oscillator is usable as a displacement-frequency converter. Controlling such an oscillator is possible by means of nondifferential, parametric displacement transducer whose inductance forms part of the tank circuit of a tunable first amplifier (frequency F sub 10), a mixer, a tuned second amplifier (frequency F sub 20), and another mixer whose output is connected directly back to the input of the first amplifier. The other inputs of both mixers are connected to and receive signals from a quartz oscillator (frequency F sub 3). With the transducer inductance set within the middle of its range, the converter is adjusted so that F sub 10 + F sub 20 is approximately equal to F sub 3. When both amplifiers have sufficient gain to satisfy the condition of amplitude balance, then self-excited oscillations occur in the converter with frequencies F sub 1 at the output of the first amplifier and F sub 2 at the output of the second amplifier, F sub 1 + F sub 2 = F sub 3. A transducer which ensures a frequency-displacement characteristic F sub 10 (0) such that, where both frequencies F sub 1 and F sub 2 as well as thier difference are linear functions of the displacement o, was designed. The transdcuer is connected into the tank circuit of the first (transistor) amplifier. The nonlinearity of its inductance-displacement characteristic is variable.

  8. Modulation of a double-line frequency up-conversion process in cesium vapor

    NASA Astrophysics Data System (ADS)

    Gai, Baodong; Cao, Rui; Xia, Xusheng; Hu, Shu; Liu, Jinbo; Guo, Jingwei; Tan, Yannan; Liu, Wanfa; Jin, Yuqi; Sang, Fengting

    2016-06-01

    We have observed frequency up-conversion in Cs vapor. The pulsed pumping laser beam of 767.2 nm was converted to simultaneous collinear ultraviolet and blue radiation of wavelengths 387.7 and 455.6 nm, respectively (double-line frequency up-conversion). We examined properties of this up-conversion such as energy efficiency and pulse widths. An infrared laser of ~2.4 μm was successful in modulating the laser beam of the frequency up-conversion. The modulation shifts the wavelength of the blue radiation and the intensities of both the blue and ultraviolet radiation. At nanosecond grade, such modulations are expected to have applications in near-infrared up-conversion and optical communications.

  9. Dispersion of the temperature-noncritical frequency conversion and birefringence in biaxial optical crystals

    SciTech Connect

    Grechin, Sergei G; Dmitriev, Valentin G; Dyakov, Vladimir A; Pryalkin, Vladimir I

    2004-05-31

    Dispersion of the temperature-noncritical frequency conversion (phase matching) and birefringence in biaxial crystals is considered. The possibility of simultaneous realisation of these processes during SHG in a KTP crystal is discussed. (nonlinear optical phenomena)

  10. Nonlinear frequency conversion using high-quality modes in GaAs nanobeam cavities.

    PubMed

    Buckley, Sonia; Radulaski, Marina; Zhang, Jingyuan Linda; Petykiewicz, Jan; Biermann, Klaus; Vučković, Jelena

    2014-10-01

    We demonstrate the design, fabrication, and characterization of nanobeam photonic crystal cavities in (111)-GaAs with multiple high-Q modes, with large frequency separations (up to 740 nm in experiment, i.e., a factor of 1.5 and up to an octave in theory). Such structures are crucial for efficient implementation of nonlinear frequency conversion. Here, we employ them to demonstrate sum-frequency generation from 1300 and 1950 nm to 780 nm. These wavelengths are particularly interesting for quantum frequency conversion between Si vacancy centers in diamond and the fiber-optic network. PMID:25360956

  11. Negative Differential Resistance (NDR) frequency conversion with gain

    NASA Technical Reports Server (NTRS)

    Hwu, R. J.; Alm, R. W.; Lee, S. C.

    1992-01-01

    The dependence of the I-V characteristic of the negative differential resistance (NDR) devices on the power level and frequency of the rf input signal has been theoretically analyzed with a modified large- and small-signal nonlinear circuit analysis program. The NDR devices we used in this work include both the tunnel diode (without the antisymmetry in the I-V characteristic) and resonant-tunneling devices (with the antisymmetry in the I-V characteristic). Absolute negative conductance can be found from a zero-biased resonant tunneling device when the applied pump power is within a small range. This study verifies the work of Sollner et al. Variable negative conductances at the fundamental and harmonic frequencies can also be obtained from both the unbiased and biased tunnel diodes. The magnitude of the negative conductances can be adjusted by varying the pump amplitude -- a very useful circuit property. However, the voltage range over which the negative conductance occurs moves towards the more positive side of the voltage axis with increasing frequency. Furthermore, the range of the pumping amplitude to obtain negative conductance varies with the parasitics (resistance and capacitance) of the device. The theoretical observation of the dependence of the I-V characteristic of the NDR devices on the power and frequency of the applied pump signal is supported by the experimental results. In addition, novel functions of a NDR device such as self-oscillating frequency multiplier and mixer with gain have been experimentally demonstrated. The unbiased oscillator have also been successfully realized with a NDR device with an antisymmetrical I-V characteristic. Finally, the applications of these device functions will be discussed.

  12. Optical pulse frequency conversion inside transformation-optical metamaterials

    NASA Astrophysics Data System (ADS)

    Ginis, Vincent; Tassin, Philippe; Craps, Ben; Danckaert, Jan; Veretennicoff, Irina

    2012-05-01

    Based on the analogy between the Maxwell equations in complex metamaterials and the free-space Maxwell equations on the background of an arbitrary metric, transformation optics allows for the design of metamaterial devices using a geometrical perspective. This intuitive geometrical approach has already generated various novel applications within the elds of invisibility cloaking, electromagnetic beam manipulation, optical information storage, and imaging. Nevertheless, the framework of transformation optics is not limited to three-dimensional transformations and can be extended to four-dimensional metrics, which allow for the implementation of metrics that occur in general relativistic or cosmological models. This enables, for example, the implementation of black hole phenomena and space-time cloaks inside dielectrics with exotic material parameters. In this contribution, we present a time-dependent metamaterial device that mimics the cosmological redshift. Theoretically, the transformation-optical analogy requires an innite medium with a permittivity and a permeability that vary monotonically as a function of time. We demonstrate that the cosmological frequency shift can also be reproduced in more realistic devices, considering the fact that practical devices have a nite extent and bound material parameters. Indeed, our recent numerical results indicate that it is possible to alter the frequency of optical pulses in a medium with solely a modulated permittivity. Furthermore, it is shown that the overall frequency shift does not depend on the actual variation of the permittivity. The performance of a nite frequency converter is, for example, not aected by introducing the saw tooth evolution of the material parameters. Finally, we studied the eect of the introduction of realistic metamaterial losses and, surprisingly, we found a very high robustness with respect to this parameter. These results open up the possibility to fabricate this frequency converting device

  13. Orbital angular momentum light frequency conversion and interference with quasi-phase matching crystals.

    PubMed

    Zhou, Zhi-Yuan; Ding, Dong-Sheng; Jiang, Yun-Kun; Li, Yan; Shi, Shuai; Wang, Xi-Shi; Shi, Bao-Sen

    2014-08-25

    Light with helical phase structures, carrying quantized orbital angular momentum (OAM), has many applications in both classical and quantum optics, such as high-capacity optical communications and quantum information processing. Frequency conversion is a basic technique to expand the frequency range of the fundamental light. The frequency conversion of OAM-carrying light gives rise to new physics and applications such as up-conversion detection of images and generation of high dimensional OAM entanglements. Quasi-phase matching (QPM) nonlinear crystals are good candidates for frequency conversion, particularly due to their high-valued effective nonlinear coefficients and no walk-off effect. Here we report the first experimental second-harmonic generation (SHG) of an OAM-carried light with a QPM crystal, where a UV light with OAM of 100 ℏ is generated. OAM conservation is verified using a specially designed interferometer. With a pump beam carrying an OAM superposition of opposite sign, we observe interesting interference phenomena in the SHG light; specifically, a photonics gear-like structure is obtained that gives direct evidence of OAM conservation, which will be very useful for ultra-sensitive angular measurements. Besides, we also develop a theory to reveal the underlying physics of the phenomena. The methods and theoretical analysis shown here are also applicable to other frequency conversion processes, such as sum frequency generation and difference-frequency generation, and may also be generalized to the quantum regime for single photons. PMID:25321240

  14. Generation of sub-30 fs tunable infrared pulses by parametric visible-to-infrared frequency conversion

    NASA Astrophysics Data System (ADS)

    Darginavičius, J.; Tamošauskas, G.; Valiulis, G.; Piskarskas, A.; Dubietis, A.

    2012-07-01

    We propose visible-to-infrared frequency conversion method that is based on difference frequency generation and two-stage collinear optical parametric amplification in BBO crystal. The proof-of-principle experiments demonstrate efficient frequency down conversion of sub-30 fs pulses from a commercial blue-pumped noncollinear optical parametric amplifier that yields generation of sub-30-fs broadly tunable pulses in the range of 1.2 to 2.4 μm with up to 100 μJ energy.

  15. Tunable frequency-up/down conversion in gas-filled hollow-core photonic crystal fibers.

    PubMed

    Saleh, Mohammed F; Biancalana, Fabio

    2015-09-15

    Based on the interplay between photoionization and Raman effects in gas-filled photonic crystal fibers, we propose a new optical device to control frequency conversion of ultrashort pulses. By tuning the input-pulse energy, the output spectrum can be either down-converted, up-converted, or even frequency-shift compensated. For low input energies, the Raman effect is dominant and leads to a redshift that increases linearly during propagation. For larger pulse energies, photoionization starts to take over the frequency-conversion process and induces a strong blueshift. The fiber-output pressure can be used as an additional degree of freedom to control the spectrum shift. PMID:26371900

  16. Two-dimensionally tunable microwave signal generation based on optical frequency-to-time conversion.

    PubMed

    Ye, Jia; Yan, Lianshen; Pan, Wei; Luo, Bin; Zou, Xihua; Yi, Anlin; Yao, Xiaotian Steve

    2010-08-01

    We propose and experimentally demonstrate an all-fiber-based approach to generate microwave signals with tunable frequency and pulse width. The adjustable optical power spectrum can be achieved using a spectrum shaper, consisting of a variable differential-group-delay element and a bandwidth-tunable optical filter. Through the frequency-to-time conversion in the dispersive fiber, the frequency and pulse width of the obtained microwave signals can be user defined by modifying the optical spectrum shape. PMID:20680073

  17. Efficient frequency conversion of laser sources in nonlinear crystals

    NASA Technical Reports Server (NTRS)

    Byer, R. L.

    1985-01-01

    The use of nonlinear crystals to extend the frequency range of solid-state laser sources is proposed. The harmonic generation of high-average-power laser sources and CW-laser-sources nonlinear crystals is considered. The development of Nd:YAG pumped parametric oscillators and optical parametric amplifiers using LiNbO3 or AgGaS2 is studied. The LiNbO3 oscillator has tunable output over the 1.4-4.0 micron range and is applicable for remote sensing measurements of molecules and of humidity and temperature; AgGaS2 oscillators provide the potential for 3-15 micron infrared generation. Advances in material synthesis techniques related to the design and synthesis of nonlinear media are discussed. Various procedures for the synthesis of nonlinear crystals are described.

  18. Efficient and low-noise single-photon-level frequency conversion interfaces using silicon nanophotonics

    NASA Astrophysics Data System (ADS)

    Li, Qing; Davanço, Marcelo; Srinivasan, Kartik

    2016-06-01

    Optical frequency conversion has applications ranging from tunable light sources to telecommunications-band interfaces for quantum information science. Here, we demonstrate efficient, low-noise frequency conversion on a nanophotonic chip through four-wave-mixing Bragg scattering in compact (footprint <0.5 × 10–4 cm2) Si3N4 microring resonators. We investigate three frequency conversion configurations: spectral translation over a few nanometres within the 980 nm band; upconversion from 1,550 nm to 980 nm and downconversion from 980 nm to 1,550 nm. With conversion efficiencies ranging from 25% for the first process to >60% for the last two processes, a signal conversion bandwidth of >1 GHz, a required continuous-wave pump power of <60 mW and background noise levels between a few femtowatts and a few picowatts, these devices are suitable for quantum frequency conversion of single-photon states from InAs/GaAs quantum dots. Simulations based on coupled mode equations and the Lugiato–Lefever equation are used to model device performance, and show quantitative agreement with measurements.

  19. Power conversion distribution system using a resonant high-frequency AC link

    NASA Technical Reports Server (NTRS)

    Sood, P. K.; Lipo, T. A.

    1986-01-01

    Static power conversion systems based on a resonant high frequency (HF) link offers a significant reduction in the size and weight of the equipment over that achieved with conventional approaches, especially when multiple sources and loads are to be integrated. A faster system response and absence of audible noise are the other principal characteristics of such systems. A conversion configuration based on a HF link which is suitable for applications requiring distributed power is proposed.

  20. Design of diamond microcavities for single photon frequency down-conversion

    NASA Astrophysics Data System (ADS)

    Lin, Z.; Johnson, S. G.; Rodriguez, A. W.; Loncar, M.

    2015-09-01

    We propose monolithic diamond cavities that can be used to convert color-center Fock-state single photons from emission wavelengths to telecommunication bands. We present a detailed theoretical description of the conversion process, analyzing important practical concerns such as nonlinear phase shifts and frequency mismatch. Our analysis predicts sustainable power requirements ($ \\lesssim 1~\\mathrm{W}$) for a chipscale nonlinear device with high conversion efficiencies.

  1. Efficient and coherent frequency conversions and nonlinear interference in optical parametric and atomic Raman processes

    NASA Astrophysics Data System (ADS)

    Ding, Yu

    By implementing a parametric down-conversion process with a strong signal field injection, we demonstrate that frequency down-conversion from pump photons to idler photons can be a coherent process. Contrary to a common misconception, we show that the process can be free of quantum noise. With an interference experiment, we demonstrate that coherence is preserved in the conversion process. This technique could lead to a high-fidelity quantum state transfer from a high-frequency photon to a low-frequency photon and connect a missing link in quantum networks. Coherent and efficient nonlinear interaction and frequency conversion are of great interest in many areas of quantum optics. Traditionally, the low efficiency of Raman scattering is improved by a high-finesse optical resonator or stimulated Raman conversion. It was recently found that the atomic spin wave initially built through electromagnetically induced transparency or a weak Raman process can actively enhance the Raman frequency conversion. An experimental demonstration of an efficient Raman conversion scheme with coherent feedback of both pump and Stokes fields is presented. The temporal profile of the generated Raman pulse shows that the coherence time of the atomic spin wave is ˜1.8 ms. A laser-like power threshold is observed and its low threshold is attributed to the long coherence time of the atomic spin wave. The mechanism of the conversion enhancement process is discussed and the conversion efficiency of a single pass of the beams is compared with that of double passes. Finally, a beat signal is observed between the two Stokes fields and its Fourier transform shows that the frequency difference is caused by the AC Stark effect. Precision phase measurement is traditionally restricted by the standard quantum limit. However, this limit is not as fundamental as the Heisenberg limit and can be circumvented by use of nonclassical quantum states and structure modification of the interferometers. Several

  2. Calcium barium niobate as a functional material for broadband optical frequency conversion.

    PubMed

    Sheng, Yan; Chen, Xin; Lukasiewicz, Tadeusz; Swirkowicz, Marek; Koynov, Kaloian; Krolikowski, Wieslaw

    2014-03-15

    We demonstrate the application of as-grown calcium barium niobate (CBN) crystal with random-sized ferroelectric domains as a broadband frequency converter. The frequency conversion process is similar to broadband harmonic generation in commonly used strontium barium niobate (SBN) crystal, but results in higher conversion efficiency reflecting a larger effective nonlinear coefficient of the CBN crystal. We also analyzed the polarization properties of the emitted radiation and determined the ratio of d32 and d33 components of the second-order susceptibility tensor of the CBN crystal. PMID:24690779

  3. Note: Frequency-conversion photonic Doppler velocimetry with an inverted circulator

    SciTech Connect

    Dolan, D. H.; Ao, T.; Hernandez, O.

    2012-02-15

    Photonic Doppler velocimetry (PDV) is a fiber-based interferometer used in dynamic compression research. Conventional PDV systems are simple to construct but do not perform well in all measurement conditions, while universal PDV systems that support many different configurations are complex and expensive. A simpler approach is the use of external, inverted circulators which can be added and removed in a modular fashion. This technique permits frequency-conversion measurements with a conventional PDV system. Using a correction to remove baseline effects, frequency conversion systems can resolve low velocity transients that conventional PDV cannot.

  4. Large-alphabet time-frequency entangled quantum key distribution by means of time-to-frequency conversion

    NASA Astrophysics Data System (ADS)

    Nunn, J.; Wright, L. J.; Söller, C.; Zhang, L.; Walmsley, I. A.; Smith, B. J.

    2013-07-01

    We introduce a novel time-frequency quantum key distribution (TFQKD) scheme based on photon pairs entangled in these two conjugate degrees of freedom. The scheme uses spectral detection and phase modulation to enable measurements in the temporal basis by means of time-to-frequency conversion. This allows large-alphabet encoding to be implemented with realistic components. A general security analysis for TFQKD with binned measurements reveals a close connection with finite-dimensional QKD protocols and enables analysis of the effects of dark counts on the secure key size.

  5. A nonlinear screen as an element for sound absorption and frequency conversion systems

    NASA Astrophysics Data System (ADS)

    Rudenko, O. V.

    2016-01-01

    The paper discusses a model for a screen with dissipative and nonlinear elastic properties that can be used in acoustic sound absorption and frequency conversion systems. Calculation and estimation schemes are explained that are necessary for understanding the functional capabilities of the device. Examples of the nonlinear elements in the screen and promising applications are described.

  6. The influence of thermal deformation processes on frequency conversion in an LBO crystal

    NASA Astrophysics Data System (ADS)

    Arapov, Yu D.; Dyakov, V. A.; Grechin, S. G.; Kasyanov, I. V.

    2014-12-01

    The influence of the thermal deformation process on frequency conversion in an LBO crystal is considered. The different temperature bandwidths at the harmonic generation of YAG:Nd laser radiation were obtained experimentally three times at different types of crystal fixation.

  7. Aluminum nitride as nonlinear optical material for on-chip frequency comb generation and frequency conversion

    NASA Astrophysics Data System (ADS)

    Jung, Hojoong; Tang, Hong X.

    2016-06-01

    A number of dielectric materials have been employed for on-chip frequency comb generation. Silicon based dielectrics such as silicon dioxide (SiO2) and silicon nitride (SiN) are particularly attractive comb materials due to their low optical loss and maturity in nanofabrication. They offer third-order Kerr nonlinearity (χ(3)), but little second-order Pockels (χ(2)) effect. Materials possessing both strong χ(2) and χ(3) are desired to enable selfreferenced frequency combs and active control of comb generation. In this review, we introduce another CMOS-compatible comb material, aluminum nitride (AlN),which offers both second and third order nonlinearities. A review of the advantages of AlN as linear and nonlinear optical material will be provided, and fabrication techniques of low loss AlN waveguides from the visible to infrared (IR) region will be discussed.We will then show the frequency comb generation including IR, red, and green combs in high-Q AlN micro-rings from single CW IR laser input via combination of Kerr and Pockels nonlinearity. Finally, the fast speed on-off switching of frequency comb using the Pockels effect of AlN will be shown,which further enriches the applications of the frequency comb.

  8. Frequency and bandwidth conversion of single photons in a room-temperature diamond quantum memory.

    PubMed

    Fisher, Kent A G; England, Duncan G; MacLean, Jean-Philippe W; Bustard, Philip J; Resch, Kevin J; Sussman, Benjamin J

    2016-01-01

    The spectral manipulation of photons is essential for linking components in a quantum network. Large frequency shifts are needed for conversion between optical and telecommunication frequencies, while smaller shifts are useful for frequency-multiplexing quantum systems, in the same way that wavelength division multiplexing is used in classical communications. Here we demonstrate frequency and bandwidth conversion of single photons in a room-temperature diamond quantum memory. Heralded 723.5 nm photons, with 4.1 nm bandwidth, are stored as optical phonons in the diamond via a Raman transition. Upon retrieval from the diamond memory, the spectral shape of the photons is determined by a tunable read pulse through the reverse Raman transition. We report central frequency tunability over 4.2 times the input bandwidth, and bandwidth modulation between 0.5 and 1.9 times the input bandwidth. Our results demonstrate the potential for diamond, and Raman memories in general, as an integrated platform for photon storage and spectral conversion. PMID:27045988

  9. Frequency and bandwidth conversion of single photons in a room-temperature diamond quantum memory

    NASA Astrophysics Data System (ADS)

    Fisher, Kent A. G.; England, Duncan G.; Maclean, Jean-Philippe W.; Bustard, Philip J.; Resch, Kevin J.; Sussman, Benjamin J.

    2016-04-01

    The spectral manipulation of photons is essential for linking components in a quantum network. Large frequency shifts are needed for conversion between optical and telecommunication frequencies, while smaller shifts are useful for frequency-multiplexing quantum systems, in the same way that wavelength division multiplexing is used in classical communications. Here we demonstrate frequency and bandwidth conversion of single photons in a room-temperature diamond quantum memory. Heralded 723.5 nm photons, with 4.1 nm bandwidth, are stored as optical phonons in the diamond via a Raman transition. Upon retrieval from the diamond memory, the spectral shape of the photons is determined by a tunable read pulse through the reverse Raman transition. We report central frequency tunability over 4.2 times the input bandwidth, and bandwidth modulation between 0.5 and 1.9 times the input bandwidth. Our results demonstrate the potential for diamond, and Raman memories in general, as an integrated platform for photon storage and spectral conversion.

  10. Frequency and bandwidth conversion of single photons in a room-temperature diamond quantum memory

    PubMed Central

    Fisher, Kent A. G.; England, Duncan G.; MacLean, Jean-Philippe W.; Bustard, Philip J.; Resch, Kevin J.; Sussman, Benjamin J.

    2016-01-01

    The spectral manipulation of photons is essential for linking components in a quantum network. Large frequency shifts are needed for conversion between optical and telecommunication frequencies, while smaller shifts are useful for frequency-multiplexing quantum systems, in the same way that wavelength division multiplexing is used in classical communications. Here we demonstrate frequency and bandwidth conversion of single photons in a room-temperature diamond quantum memory. Heralded 723.5 nm photons, with 4.1 nm bandwidth, are stored as optical phonons in the diamond via a Raman transition. Upon retrieval from the diamond memory, the spectral shape of the photons is determined by a tunable read pulse through the reverse Raman transition. We report central frequency tunability over 4.2 times the input bandwidth, and bandwidth modulation between 0.5 and 1.9 times the input bandwidth. Our results demonstrate the potential for diamond, and Raman memories in general, as an integrated platform for photon storage and spectral conversion. PMID:27045988

  11. Freely designable optical frequency conversion in Raman-resonant four-wave-mixing process.

    PubMed

    Zheng, Jian; Katsuragawa, Masayuki

    2015-01-01

    Nonlinear optical processes are governed by the relative-phase relationships among the relevant electromagnetic fields in these processes. In this Report, we describe the physics of arbitrary manipulation of Raman-resonant four-wave-mixing process by artificial control of relative phases. As a typical example, we show freely designable optical-frequency conversions to extreme spectral regions, mid-infrared and vacuum-ultraviolet, with near-unity quantum efficiencies. Furthermore, we show that such optical-frequency conversions can be realized by using a surprisingly simple technology where transparent plates are placed in a nonlinear optical medium and their positions and thicknesses are adjusted precisely. In a numerical simulation assuming practically applicable parameters in detail, we demonstrate a single-frequency tunable laser that covers the whole vacuum-ultraviolet spectral range of 120 to 200 nm. PMID:25748023

  12. Ultrafast picket fence pulse trains to enhance frequency conversion of shaped inertial confinement fusion laser pulses.

    PubMed

    Rothenberg, J E

    2000-12-20

    A high-frequency train of 5-100-ps pulses (picket fence) is proposed to improve significantly the third-harmonic frequency conversion of Nd:glass lasers that are used to generate high-contrast-shaped pulses for inertial confinement fusion (ICF) targets. High conversion efficiency of the low-power foot of a shaped ICF pulse is obtained by use of a low duty cycle, multi-gigahertz train of approximately 20-ps pulses with high peak power. Even with less than 10% duty cycle, continuous illumination is maintained on the target by a combination of temporal broadening schemes. The picket fence approach is analyzed, and the practical limits are identified as applied to the National Ignition Facility laser. It is found that the higher conversion efficiency allows approximately 40% more third-harmonic energy to be delivered to the target, potentially enabling the larger drive needed for high-yield ICF target designs. In addition, the frequency conversion efficiency of these short pulses saturates much more readily, which reduces the transfer of fluctuations at the fundamental and thus greatly improves the power stability of the third harmonic. PMID:18354706

  13. Fully efficient adiabatic frequency conversion of broadband Ti:sapphire oscillator pulses.

    PubMed

    Moses, Jeffrey; Suchowski, Haim; Kärtner, Franz X

    2012-05-01

    By adiabatic difference-frequency generation in an aperiodically poled nonlinear crystal-a nonlinear optical analog of rapid adiabatic passage in a two-level atomic system-we demonstrate the conversion of a 110 nm band from an octave-spanning Ti:sapphire oscillator to the infrared, spanning 1550 to 2450 nm, with near-100% internal conversion efficiency. The experiment proves the principle of complete Landau-Zener adiabatic transfer in nonlinear optical wave mixing. Our implementation is a practical approach to the seeding of high-energy ultrabroadband optical parametric chirped pulse amplifiers. PMID:22555747

  14. Rigorous intensity and phase-shift manipulation in optical frequency conversion

    NASA Astrophysics Data System (ADS)

    Yang, Bo; Yue, Yang-Yang; Lu, Rong-Er; Hong, Xu-Hao; Zhang, Chao; Qin, Yi-Qiang; Zhu, Yong-Yuan

    2016-06-01

    A simple method is employed to investigate the nonlinear frequency conversion in optical superlattices (OSL) with pump depletion. Four rigorous phase-matching conditions for different purposes are obtained directly from the nonlinear coupled equations, and the resulting OSL domain structures are generally aperiodic rather than periodic. With this method, not only the intensity but also the phase-shift of the harmonic waves can be manipulated at will. The second-harmonic generation of Gaussian beam is further investigated. This work may provide a guidance for the practical applications of designing nonlinear optical devices with high conversion efficiency.

  15. Rigorous intensity and phase-shift manipulation in optical frequency conversion

    PubMed Central

    Yang, Bo; Yue, Yang-Yang; Lu, Rong-er; Hong, Xu-Hao; Zhang, Chao; Qin, Yi-Qiang; Zhu, Yong-Yuan

    2016-01-01

    A simple method is employed to investigate the nonlinear frequency conversion in optical superlattices (OSL) with pump depletion. Four rigorous phase-matching conditions for different purposes are obtained directly from the nonlinear coupled equations, and the resulting OSL domain structures are generally aperiodic rather than periodic. With this method, not only the intensity but also the phase-shift of the harmonic waves can be manipulated at will. The second-harmonic generation of Gaussian beam is further investigated. This work may provide a guidance for the practical applications of designing nonlinear optical devices with high conversion efficiency. PMID:27272308

  16. Rigorous intensity and phase-shift manipulation in optical frequency conversion.

    PubMed

    Yang, Bo; Yue, Yang-Yang; Lu, Rong-Er; Hong, Xu-Hao; Zhang, Chao; Qin, Yi-Qiang; Zhu, Yong-Yuan

    2016-01-01

    A simple method is employed to investigate the nonlinear frequency conversion in optical superlattices (OSL) with pump depletion. Four rigorous phase-matching conditions for different purposes are obtained directly from the nonlinear coupled equations, and the resulting OSL domain structures are generally aperiodic rather than periodic. With this method, not only the intensity but also the phase-shift of the harmonic waves can be manipulated at will. The second-harmonic generation of Gaussian beam is further investigated. This work may provide a guidance for the practical applications of designing nonlinear optical devices with high conversion efficiency. PMID:27272308

  17. Doppler frequency up conversion of electromagnetic waves in a slotline on an optically excited silicon substrate

    SciTech Connect

    Bae, Jongsuck; Xian Yuanjun; Yamada, Sho; Ishikawa, Ryo

    2009-03-02

    The Doppler frequency up conversion of microwaves in a slotline on an optically excited silicon substrate was experimentally observed. An array of 24 optical fibers with different lengths was used to effectively tilt the wave front of a 532 nm neodymium-doped yttrium aluminum garnet laser beam with a pulse duration of 33 ps. The tilted laser beam produced electron-hole surface plasma whose boundary moved at a relativistic velocity of about c/3.4 (c is the speed of light) along the slotline. The experiments showed that microwaves reflected at the moving boundary of the plasma in the slotline are converted to millimeter waves with a frequency up conversion ratio of 3.82.

  18. Schemes for realizing frequency up- and down-conversions in two-mode cavity QED

    SciTech Connect

    Zou Xubo; Dong Yuli; Guo Guangcang

    2006-02-15

    We propose experimental schemes for realizing frequency up- and down-conversion in two-mode cavity QED by considering the atom-cavity interaction in the presence of a strong driving classical field. In contrast to the recent paper based on dispersive atom-cavity interaction [Serra et al., Phys. Rev. A 71, 045802 (2005)], our scheme is based on resonant interaction of the cavity modes with a single driven three-level atom, so that the quantum dynamics operates at a high speed, which is important in view of decoherence. It is shown that, with the help of a strong driving classical field, frequency up- and down-conversion operations can be realized by initially preparing the atom in a certain state.

  19. Frequency up conversion approach to scavenge mechanical energy from an electromagnetic digital actuator

    NASA Astrophysics Data System (ADS)

    Yan, Linjuan; Badel, Adrien; Petit, Laurent; Formosa, Fabien

    2015-12-01

    This paper reports the practical design and experimental testing of a piezoelectric energy reclamation system. The presented system aims at scavenging energy from a miniaturized electromagnetic digital actuator for additional function such as obtains the discrete position information for enhanced reliability. Based on frequency up conversion technique, and the considered actuator dynamical responses, a piezoelectric energy harvester has been experimentally evaluated. In plane integration is the next step.

  20. CW, single-frequency 229nm laser source for Cd-cooling by harmonic conversion

    NASA Astrophysics Data System (ADS)

    Kaneda, Yushi; Yarborough, J. M.; Merzlyak, Yevgeny

    2015-02-01

    More than 200mW of CW 229nm for Cd atom cooling application was generated by the 4th harmonic of a single frequency optically pumped semiconductor laser using a 10-mm long, Brewster-cut BBO crystal in an external cavity. With 650mW of 458nm input, 216mW of 229nm power was observed. Conversion efficiency from 458nm to 229nm was more than 33%.

  1. Frequency up- and down-conversions in two-mode cavity quantum electrodynamics

    SciTech Connect

    Serra, R.M.; Villas-Boas, C.J.; Moussa, M.H.Y.; Almeida, N.G. de

    2005-04-01

    In this Brief Report we present a scheme for the implementation of frequency up- and down-conversion operations in two-mode cavity quantum electrodynamics (QED). This protocol for engineering bilinear two-mode interactions could enlarge perspectives for quantum-information manipulation and also be employed for fundamental tests of quantum theory in cavity QED. As an application we show how to generate a two-mode squeezed state in cavity QED (the original entangled state of Einstein, Podolsky, and Rosen)

  2. Quasi phase matching through periodic step structure: modeling of frequency conversion in consideration of heat influence

    NASA Astrophysics Data System (ADS)

    Ohfuchi, Takafumi; Hirano, Nobuyuki; Matsukawa, Hiroya; Nakayama, Koichiro; Kumagai, Hiroshi; Inoue, Norihiro; Fukuda, Naoaki; Takiya, Toshio

    2012-02-01

    Periodic inversion of spontaneous polarization in a ferroelectric substrate has realized quasi phase matching (QPM) and thereby revolutionized nonlinear optics. In this paper, we report on the heat influence on the frequency conversion in birefringence phase matching (BPM) by use of BaB2O4 (BBO) crystals as preparatory for efficient generation of the second harmonics (SHs) by QPM we suggest. Indeed, QPM is achieved normally by polarization inversion, but we suggest the periodic step structure to achieve QPM. Polarization inversion is generally formed by superimposed voltage. However, the shorter wavelength region is, the shorter inversion cycle is. Therefore, if the vacuum ultraviolet (VUV) region is treated, it becomes more difficult to form periodic inversion and the accuracy is more necessary. Accordingly, it is necessary to consider the influence of crystal's heat, caused by absorption of laser, which affects frequency conversion. We discuss validity of analytical approach about crystal's heat and frequency conversion by comparing between both results of experiment and simulation with BBO crystals.

  3. Optical frequency up-conversion of UWB monocycle pulse based on pulsed-pump fiber optical parametric amplifier

    NASA Astrophysics Data System (ADS)

    Li, Jia; Liang, Yu; Xu, Xing; Cheung, Kim K. Y.; Wong, Kenneth K. Y.

    2009-11-01

    We propose a method to realize frequency up-conversion of UWB monocycle pulse using pulsed-pump fiber optical parametric amplifier (OPA). The spectrum of the amplified signal contains many discrete frequency components which are separated by the modulation frequency of the pump. Each frequency components contain the same spectral information as that of the original signal. By selecting the first-order or higher-order frequency components of the amplified signal and beating in the photodetector, up-converted signal at different frequencies are obtained. We demonstrate frequency up-conversion of baseband UWB monocycle pulse from 3-GHz to 19-GHz in the experiment and frequency up-conversion of pseudo-random binary sequence (PRBS) signal from 3-GHz to 60-GHz in the simulation.

  4. Broadband electromagnetic power harvester from vibrations via frequency conversion by impact oscillations

    SciTech Connect

    Yuksek, N. S.; Almasri, M.; Feng, Z. C.

    2014-09-15

    In this paper, we propose an electromagnetic power harvester that uses a transformative multi-impact approach to achieve a wide bandwidth response from low frequency vibration sources through frequency-up conversion. The device consists of a pick-up coil, fixed at the free edge of a cantilever beam with high resonant frequency, and two cantilever beams with low excitation frequencies, each with an impact mass attached at its free edge. One of the two cantilevers is designed to resonate at 25 Hz, while the other resonates at 50 Hz within the range of ambient vibration frequency. When the device is subjected to a low frequency vibration, the two low-frequency cantilevers responded by vibrating at low frequencies, and thus their thick metallic masses made impacts with the high resonance frequency cantilever repeatedly at two locations. This has caused it along with the pick-up coil to oscillate, relative to the permanent magnet, with decaying amplitude at its resonance frequency, and results in a wide bandwidth response from 10 to 63 Hz at 2 g. A wide bandwidth response between 10–51 Hz and 10–58 Hz at acceleration values of 0.5 g and 2 g, respectively, were achieved by adjusting the impact cantilever frequencies closer to each other (25 Hz and 45 Hz). A maximum output power of 85 μW was achieved at 5 g at 30 Hz across a load resistor, 2.68 Ω.

  5. Piezoelectric energy harvester operated by noncontact mechanical frequency up-conversion using shell cantilever structure

    NASA Astrophysics Data System (ADS)

    Jang, Munseon; Song, Seunghwan; Park, Yong-Hee; Yun, Kwang-Seok

    2015-06-01

    In this study, we propose and demonstrate a piezoelectric energy harvester with a shell cantilever for mechanical frequency up-conversion to generate electric power in a low-frequency vibration environment. The proposed device is composed of a clamped semicylindrical shell cantilever as a driving beam and a piezoelectric cantilever attached to the proof mass of the shell cantilever as a generating beam. The shell cantilever bends downward when the external acceleration is over the threshold value for buckling transition. When the acceleration direction is reversed, the shell cantilever makes abrupt stop at its initial position, inducing impact-like force on the generating beam and resulting in free vibration at high resonance frequencies. Experimental results show that a maximum power of 101 µW at 20 Hz can be obtained.

  6. One dimensional full wave analysis of slow-to-fast mode conversion in lower hybrid frequencies

    SciTech Connect

    Jia, Guo-Zhang; Gao, Zhe

    2014-12-15

    The linear conversion from the slow wave to the fast wave in the lower hybrid range of frequencies is analyzed numerically by using the set of field equations describing waves in a cold plane-stratified plasma. The equations are solved as a two-point boundary value problem, where the polarizations of each mode are set consistently in the boundary conditions. The scattering coefficients and the field patterns are obtained for various density profiles. It is shown that, for large density scale length, the results agree well with the traditional cognitions. In contrast, the reflected component and the probable transmitted-converted component from the conversion region, which are neglected in the usual calculations, become significant when the scale length is smaller than the wavelength of the mode. The inclusion of these new components will improve the accuracy of the simulated propagation and deposition for the injected rf power when the conversion process is involved within a sharp-varying density profile. Meanwhile, the accessibility of the incident slow wave for the low frequency case is also affected by the scale length of the density profile.

  7. A small-form-factor piezoelectric vibration energy harvester using a resonant frequency-down conversion

    NASA Astrophysics Data System (ADS)

    Sun, Kyung Ho; Kim, Young-Cheol; Kim, Jae Eun

    2014-10-01

    While environmental vibrations are usually in the range of a few hundred Hertz, small-form-factor piezoelectric vibration energy harvesters will have higher resonant frequencies due to the structural size effect. To address this issue, we propose a resonant frequency-down conversion based on the theory of dynamic vibration absorber for the design of a small-form-factor piezoelectric vibration energy harvester. The proposed energy harvester consists of two frequency-tuned elastic components for lowering the first resonant frequency of an integrated system but is so configured that an energy harvesting beam component is inverted with respect to the other supporting beam component for a small form factor. Furthermore, in order to change the unwanted modal characteristic of small separation of resonant frequencies, as is the case with an inverted configuration, a proof mass on the supporting beam component is slightly shifted toward a second proof mass on the tip of the energy harvesting beam component. The proposed small-form-factor design capability was experimentally verified using a fabricated prototype with an occupation volume of 20 × 39 × 6.9 mm3, which was designed for a target frequency of as low as 100 Hz.

  8. A small-form-factor piezoelectric vibration energy harvester using a resonant frequency-down conversion

    SciTech Connect

    Sun, Kyung Ho; Kim, Young-Cheol; Kim, Jae Eun

    2014-10-15

    While environmental vibrations are usually in the range of a few hundred Hertz, small-form-factor piezoelectric vibration energy harvesters will have higher resonant frequencies due to the structural size effect. To address this issue, we propose a resonant frequency-down conversion based on the theory of dynamic vibration absorber for the design of a small-form-factor piezoelectric vibration energy harvester. The proposed energy harvester consists of two frequency-tuned elastic components for lowering the first resonant frequency of an integrated system but is so configured that an energy harvesting beam component is inverted with respect to the other supporting beam component for a small form factor. Furthermore, in order to change the unwanted modal characteristic of small separation of resonant frequencies, as is the case with an inverted configuration, a proof mass on the supporting beam component is slightly shifted toward a second proof mass on the tip of the energy harvesting beam component. The proposed small-form-factor design capability was experimentally verified using a fabricated prototype with an occupation volume of 20 × 39 × 6.9 mm{sup 3}, which was designed for a target frequency of as low as 100 Hz.

  9. Theory of mode conversion and wave damping near the ion-cyclotron frequency

    SciTech Connect

    Colestock, P.L.; Kashuba, R.J.

    1982-09-01

    Using a variational technique, a set of coupled model equations for the mode-conversion process near the ion-cyclotron frequency is derived. The system is truncated to first order in Larmor radius but includes the effects of explicit gradients and a poloidal field. From the equations a conservation rule is extracted which ensures conservation of total energy and provides an explicit expression for the wave damping in differential form. The equations are integrated numerically for the standard cases of fast waves incident from either the low- or high-field sides of the mode-conversion layer. The scaling of the damping processes is discussed and implications for current rf-heating experiments on the Princeton Large Torus are drawn.

  10. Bi-directional conversion between microwave and optical frequencies in a piezoelectric optomechanical device

    NASA Astrophysics Data System (ADS)

    Vainsencher, Amit; Satzinger, K. J.; Peairs, G. A.; Cleland, A. N.

    2016-07-01

    We describe the principles of design, fabrication, and operation of a piezoelectric optomechanical crystal with which we demonstrate bi-directional conversion of energy between microwave and optical frequencies. The optomechanical crystal has an optical mode at 1523 nm co-located with a mechanical breathing mode at 3.8 GHz, with a measured optomechanical coupling strength gom/2π of 115 kHz. The breathing mode is driven and detected by curved interdigitated transducers that couple to a Lamb mode in suspended membranes on either end of the optomechanical crystal, allowing the external piezoelectric modulation of the optical signal as well as the converse, the detection of microwave electrical signals generated by a modulated optical signal. We compare measurements to theory where appropriate.

  11. Generation of tunable few optical-cycle pulses by visible-to-infrared frequency conversion

    NASA Astrophysics Data System (ADS)

    Darginavičius, J.; Tamošauskas, G.; Piskarskas, A.; Valiulis, G.; Dubietis, A.

    2012-07-01

    We demonstrate a simple method for infrared few optical-cycle pulse generation, which is based on collinear visible-to-infrared frequency conversion and involves difference-frequency generation and subsequent two-step optical parametric amplification. The numerical simulations and experiments using BBO crystals show an efficient frequency down conversion of visible ˜20 fs pulses from a commercial blue-pumped noncollinear optical parametric amplifier yielding 1.2-2.4 μm tunable sub-100 μJ pulses with duration of 3 to 5 optical-cycles. The proposed method could be readily extended to generate few optical-cycle pulses in the mid-infrared spectral range (up to 5.5 μm) using, e.g., LiIO3 and LiNbO3 crystals, as demonstrated by the numerical simulations. In these crystals, even shorter, two-optical-cycle mid-infrared pulses could be obtained at particular wavelengths where group velocity matching between the signal and idler waves is achieved.

  12. Room temperature terahertz wave imaging at 60 fps by frequency up-conversion in DAST crystal

    NASA Astrophysics Data System (ADS)

    Fan, Shuzhen; Qi, Feng; Notake, Takashi; Nawata, Kouji; Matsukawa, Takeshi; Takida, Yuma; Minamide, Hiroaki

    2014-02-01

    Terahertz imaging has attracted a lot of interests for more than 10 years. But real time, high sensitive, low cost THz imaging in room temperature, which is widely needed by fields such as biology, biomedicine and homeland security, has not been fully developed yet. A lot of approaches have been reported on electro-optic (E-O) imaging and THz focal plane arrays with photoconductive antenna or micro-bolometer integrated. In this paper, we report high sensitive realtime THz image at 60 frames per second (fps) employing a commercial infrared camera, using nonlinear optical frequency up-conversion technology. In this system, a flash-lamp pumped nanosecond pulse green laser is used to pump two optical parametric oscillator systems with potassium titanyl phosphate crystals (KTP-OPO). One system with dual KTP crystals is used to generate infrared laser for the pumping of THz difference frequency generation (DFG) in a 4- Dimethylamino-N-Methyl-4-Stilbazolium Tosylate (DAST) crystal. The other one is for generation of pumping laser for THz frequency up-conversion in a second DAST crystal. The THz frequency can be tuned continuously from a few THz to less than 30 THz by controlling the angle of KTP crystals. The frequency up-converted image in infrared region is recorded by a commercial infrared camera working at 60 Hz. Images and videos are presented to show the feasibility of this technique and the real-time ability. Comparison with a general micro-bolometer THz camera shows the high sensitivity of this technique.

  13. Properties and Frequency Conversion of High-Brightness Diode-Laser Systems

    NASA Astrophysics Data System (ADS)

    Boller, Klaus-Jochen; Beier, Bernard; Wallenstein, Richard

    An overview of recent developments in the field of high-power, high-brightness diode-lasers, and the optically nonlinear conversion of their output into other wavelength ranges, is given. We describe the generation of continuous-wave (CW) laser beams at power levels of several hundreds of milliwatts to several watts with near-perfect spatial and spectral properties using Master-Oscillator Power-Amplifier (MOPA) systems. With single- or double-stage systems, using amplifiers of tapered or rectangular geometry, up to 2.85 W high-brightness radiation is generated at wavelengths around 810nm with AlGaAs diodes. Even higher powers, up to 5.2W of single-frequency and high spatial quality beams at 925nm, are obtained with InGaAs diodes. We describe the basic properties of the oscillators and amplifiers used. A strict proof-of-quality for the diode radiation is provided by direct and efficient nonlinear optical conversion of the diode MOPA output into other wavelength ranges. We review recent experiments with the highest power levels obtained so far by direct frequency doubling of diode radiation. In these experiments, 100mW single-frequency ultraviolet light at 403nm was generated, as well as 1W of single-frequency blue radiation at 465nm. Nonlinear conversion of diode radiation into widely tunable infrared radiation has recently yielded record values. We review the efficient generation of widely tunable single-frequency radiation in the infrared with diode-pumped Optical Parametric Oscillators (OPOs). With this system, single-frequency output radiation with powers of more than 0.5W was generated, widely tunable around wavelengths of 2.1,m and 1.65,m and with excellent spectral and spatial quality. These developments are clear indicators of recent advances in the field of high-brightness diode-MOPA systems, and may emphasize their future central importance for applications within a vast range of optical

  14. Strong Field-Induced Frequency Conversion of Laser Radiation in Plasma Plumes: Recent Achievements

    PubMed Central

    Ganeev, R. A.

    2013-01-01

    New findings in plasma harmonics studies using strong laser fields are reviewed. We discuss recent achievements in the growth of the efficiency of coherent extreme ultraviolet (XUV) radiation sources based on frequency conversion of the ultrashort pulses in the laser-produced plasmas, which allowed for the spectral and structural studies of matter through the high-order harmonic generation (HHG) spectroscopy. These studies showed that plasma HHG can open new opportunities in many unexpected areas of laser-matter interaction. Besides being considered as an alternative method for generation of coherent XUV radiation, it can be used as a powerful tool for various spectroscopic and analytical applications. PMID:23864818

  15. Low-noise quantum frequency down-conversion of indistinguishable photons (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Kambs, Benjamin; Kettler, Jan; Bock, Matthias; Becker, Jonas; Arend, Carsten; Jetter, Michael; Michler, Peter; Becher, Christoph

    2016-04-01

    Single-photon sources based on quantum dots have been shown to exhibit almost ideal properties such as high brightness and purity in terms of clear anti-bunching as well as high two-photon interference visibilities of the emitted photons, making them promising candidates for different quantum information applications such as quantum computing, quantum communication and quantum teleportation. However, as most single-photon sources also quantum dots typically emit light at wavelengths of electronic transitions within the visible or the near infrared range. In order to establish quantum networks with remote building blocks, low-loss single photons at telecom wavelengths are preferable, though. Despite recent progress on emitters of telecom-photons, the most efficient single-photon sources still work at shorter wavelengths. On that matter, quantum frequency down-conversion, being a nonlinear optical process, has been used in recent years to alter the wavelength of single photons to the telecom wavelength range while conserving their nonclassical properties. Characteristics such as lifetime, first-order coherence, anti-bunching and entanglement have been shown to be conserved or even improved due to background suppression during the conversion process, while the conservation of indistinguishability was yet to be shown. Here we present our experimental results on quantum frequency down-conversion of single photons emitted by an InAs/GaAs quantum dot at 903.6 nm following a pulsed excitation of a p-shell exciton at 884 nm. The emitted fluorescence photons are mixed with a strong pump-field at 2155 nm inside a periodically poled lithium niobate ridge waveguide and converted to 1557 nm. Common issues of a large background due to Raman-scattered pump-light photons spectrally overlapping with the converted single photons could largely be avoided, as the pump-wavelength was chosen to be fairly longer than the target wavelength. Additional narrowband spectral filtering at the

  16. Quantum frequency conversion and strong coupling of photonic modes using four-wave mixing in integrated microresonators

    NASA Astrophysics Data System (ADS)

    Vernon, Z.; Liscidini, M.; Sipe, J. E.

    2016-08-01

    Single-photon-level quantum frequency conversion has recently been demonstrated using silicon nitride microring resonators. The resonance enhancement offered by such systems enables high-efficiency translation of quantum states of light across wide frequency ranges at subwatt pump powers. We present a detailed theoretical analysis of the conversion dynamics in these systems and show that they are capable of converting single- and multiphoton quantum states. Analytic formulas for the conversion efficiency, spectral conversion probability density, and pump-power requirements are derived which are in good agreement with previous theoretical and experimental results. We show that with only modest improvement to the state of the art, efficiencies exceeding 95% are achievable using less than 100 mW of pump power. At the critical driving strength that yields maximum conversion efficiency, the spectral conversion probability density is shown to exhibit a flat-topped peak, indicating a range of insensitivity to the spectrum of a single-photon input. Two alternate theoretical approaches are presented to study the conversion dynamics: a dressed-mode approach that yields a better intuitive picture of the conversion process, and a study of the temporal dynamics of the participating modes in the resonator, which uncovers a regime of Rabi-like coherent oscillations of single photons between two different frequency modes. This oscillatory regime arises from the strong coupling of distinct frequency modes mediated by coherent pumps.

  17. Spike train generation and current-to-frequency conversion in silicon diodes

    NASA Technical Reports Server (NTRS)

    Coon, D. D.; Perera, A. G. U.

    1989-01-01

    A device physics model is developed to analyze spontaneous neuron-like spike train generation in current driven silicon p(+)-n-n(+) devices in cryogenic environments. The model is shown to explain the very high dynamic range (0 to the 7th) current-to-frequency conversion and experimental features of the spike train frequency as a function of input current. The devices are interesting components for implementation of parallel asynchronous processing adjacent to cryogenically cooled focal planes because of their extremely low current and power requirements, their electronic simplicity, and their pulse coding capability, and could be used to form the hardware basis for neural networks which employ biologically plausible means of information coding.

  18. Comment on "Mode Conversion of Waves In The Ion-Cyclotron Frequency Range in Magnetospheric Plasmas"

    SciTech Connect

    Kim, Eun; Johnson, J. R.

    2014-02-01

    Recently, Kazakov and Fulop [1] studied mode conversion (MC) at the ion-ion hybrid (IIH) resonance in planetary magnetospheric plasmas by simplifying the dispersion relation of the fast wave (FW) modes to describe a cutoff-resonance (CR) pair near the IIH resonance, which can be reduced to a Budden problem. They suggested that when the IIH resonance frequency (ωS) approaches the crossover frequency (ωcr), and the parallel wavenumber (k∥) is close to the critical wavenumber k* ∥(ωS = ωcr), MC can be efficient for arbitrary heavy ion density ratios. In this Comment, we argue that (a) the FW dispersion relation cannot be simplified to the CR pair especially near ωcr because in many parameter regimes there is a cutoff-resonance-cutoff (CRC) triplet that completely changes the wave absorption; and (b) the maximum MC efficiency does not always occur near k∥ ≈ k*∥∥.

  19. Nonlinear optical frequency conversion of an amplified Fourier Domain Mode Locked (FDML) laser.

    PubMed

    Leonhardt, Rainer; Biedermann, Benjamin R; Wieser, Wolfgang; Huber, Robert

    2009-09-14

    We report on the highly efficient non-linear optical frequency conversion of the wavelength swept output from a Fourier Domain Mode Locked (FDML) laser. Different concepts for power scaling of FDML lasers by post-amplification with active fibers are presented. A two-stage post-amplification of an FDML laser with an amplification factor of 300 up to a peak power of 1.5 W is used to supply sufficient power levels for non-linear conversion. Using a single-mode dispersion shifted fiber (DSF), we convert this amplified output that covers the region between 1541 nm and 1545 nm to a wavelength range from 1572 nm to 1663 nm via modulation instability (MI). For this four wave mixing process we observe an efficiency of approximately 40%. The anti-Stokes signal between 1435 nm and 1516 nm was observed with lower conversion efficiency. In addition to shifting the wavelength, the effect of MI also enables a substantial increase in the wavelength sweep rate of the FDML laser by a factor of approximately 50 to 0.55 nm/ns. PMID:19770897

  20. Wavelength conversion through soliton self-frequency shift in tellurite microstructured fiber with picosecond pump pulse

    NASA Astrophysics Data System (ADS)

    Bi, Wanjun; Li, Xia; Xing, Zhaojun; Zhou, Qinling; Fang, Yongzheng; Gao, Weiqing; Xiong, Liangming; Hu, Lili; Liao, Meisong

    2016-01-01

    Wavelength conversion to the wavelength range that is not covered by commercially available lasers could be accomplished through the soliton self-frequency shift (SSFS) effect. In this study, the phenomenon of SSFS pumped by a picosecond-order pulse in a tellurite microstructured fiber is investigated both theoretically and experimentally. The balance between the dispersion and the nonlinearity achieved by a 1958 nm pump laser induces a distinct SSFS effect. Attributed to the large spectral distance between the pump pulse and the fiber zero-dispersion wavelength, the SSFS is not cancelled due to energy shedding from the soliton to the dispersive wave. Details about the physical mechanisms behind this phenomenon and the variations of the wavelength shift, the conversion efficiency are revealed based on numerical simulations. Owing to the large soliton number N, the pulse width of the first split fundamental soliton is approximately 40 fs, producing a pulse compression factor of ˜38, much higher than that pumped by a femtosecond pulse. Experiments were also conducted to confirm the validity of the simulation results. By varying the pump power, a continuous soliton shift from 1990 nm to 2264 nm was generated. The generation of SSFS in tellurite microstructured fibers with picosecond pump pulse can provide a new approach for wavelength conversion in the mid-infrared range and could be useful in medical and some other areas.

  1. High-frequency mode conversion technique for stiff lesion detection with magnetic resonance elastography (MRE).

    PubMed

    Mariappan, Yogesh K; Glaser, Kevin J; Manduca, Armando; Romano, Anthony J; Venkatesh, Sudhakar K; Yin, Meng; Ehman, Richard L

    2009-12-01

    A novel imaging technique is described in which the mode conversion of longitudinal waves is used for the qualitative detection of stiff lesions within soft tissue using magnetic resonance elastography (MRE) methods. Due to the viscoelastic nature of tissue, high-frequency shear waves attenuate rapidly in soft tissues but much less in stiff tissues. By introducing minimally-attenuating longitudinal waves at a significantly high frequency into tissue, shear waves produced at interfaces by mode conversion will be detectable in stiff regions, but will be significantly attenuated and thus not detectable in the surrounding soft tissue. This contrast can be used to detect the presence of stiff tissue. The proposed technique is shown to readily depict hard regions (mimicking tumors) present in tissue-simulating phantoms and ex vivo breast tissue. In vivo feasibility is demonstrated on a patient with liver metastases in whom the tumors are readily distinguished. Preliminary evidence also suggests that quantitative stiffness measurements of stiff regions obtained with this technique are more accurate than those from conventional MRE because of the short shear wavelengths. This rapid, qualitative technique may lend itself to applications in which the localization of stiff, suspicious neoplasms is coupled with more sensitive techniques for thorough characterization. PMID:19859936

  2. Inherited differences in crossing over and gene conversion frequencies between wild strains of Sordaria fimicola from "Evolution Canyon".

    PubMed Central

    Saleem, M; Lamb, B C; Nevo, E

    2001-01-01

    Recombination generates new combinations of existing genetic variation and therefore may be important in adaptation and evolution. We investigated whether there was natural genetic variation for recombination frequencies and whether any such variation was environment related and possibly adaptive. Crossing over and gene conversion frequencies often differed significantly in a consistent direction between wild strains of the fungus Sordaria fimicola isolated from a harsher or a milder microscale environment in "Evolution Canyon," Israel. First- and second-generation descendants from selfing the original strains from the harsher, more variable, south-facing slope had higher frequencies of crossing over in locus-centromere intervals and of gene conversion than those from the lusher north-facing slopes. There were some significant differences between strains within slopes, but these were less marked than between slopes. Such inherited variation could provide a basis for natural selection for optimum recombination frequencies in each environment. There were no significant differences in meiotic hybrid DNA correction frequencies between strains from the different slopes. The conversion analysis was made using only conversions to wild type, because estimations of conversion to mutant were affected by a high frequency of spontaneous mutation. There was no polarized segregation of chromosomes at meiosis I or of chromatids at meiosis II. PMID:11779798

  3. High voltage-power frequency electrical heating in-situ conversion technology of oil shale

    NASA Astrophysics Data System (ADS)

    Sun, Youhong; Yang, Yang; Lopatin, Vladimir; Guo, Wei; Liu, Baochang; Yu, Ping; Gao, Ke; Ma, Yinlong

    2014-05-01

    With the depletion of conventional energy sources,oil shale has got much attention as a new type of energy resource,which is rich and widespread in the world.The conventional utilization of oil shale is mainly focused on resorting to produce shale oil and fuel gas with low extraction efficiency about one in a million due to many shortcomings and limitations.And the in-situ conversion of oil shale,more environmentally friendly,is still in the experimental stage.High voltage-power frequency electrical heating in-situ conversion of oil shale is a new type of in-situ pyrolysis technology.The main equipment includes a high voltage-power frequency generator and interior reactor. The high voltage-power frequency generator can provide a voltage between 220-8000 V which can be adjusted in real time according to the actual situation.Firstly,high voltage is used to breakdown the oil shale to form a dendritic crack between two electrodes providing a conductive channel inside the oil shale rock.And then the power frequency(220V) is used to generate the electric current for heating the internal surface of conductive channel,so that the energy can be transmitted to the surrounding oil shale.When the temperature reaches 350 degree,the oil shale begins to pyrolysis.In addition,the temperature in the conductive channel can be extremely high with high voltage,which makes the internal surface of conductive channel graphitization and improves its heat conduction performance.This technology can successfully make the oil shale pyrolysis, based on a lot of lab experiments,and also produce the combustible shale oil and fuel gas.Compared to other in-situ conversion technology,this method has the following advantages: high speed of heating oil shale,the equipment underground is simple,and easy to operate;it can proceed without the limitation of shale thickness, and can be used especially in the thin oil shale reservoir;the heating channel is parallel to the oil shale layers,which has more

  4. Nanolaminated Permalloy Core for High-Flux, High-Frequency Ultracompact Power Conversion

    SciTech Connect

    Kim, J; Kim, M; Galle, P; Herrault, F; Shafer, R; Park, JY; Allen, MG

    2013-09-01

    Metallic magnetic materials have desirable magnetic properties, including high permeability, and high saturation flux density, when compared with their ferrite counterparts. However, eddy-current losses preclude their use in many switching converter applications, due to the challenge of simultaneously achieving sufficiently thin laminations such that eddy currents are suppressed (e.g., 500 nm-1 mu m for megahertz frequencies), while simultaneously achieving overall core thicknesses such that substantial power can be handled. A CMOS-compatible fabrication process based on robot-assisted sequential electrodeposition followed by selective chemical etching has been developed for the realization of a core of substantial overall thickness (tens to hundreds of micrometers) comprised of multiple, stacked permalloy (Ni80Fe20) nanolaminations. Tests of toroidal inductors with nanolaminated cores showed negligible eddy-current loss relative to total core loss even at a peak flux density of 0.5 T in the megahertz frequency range. To illustrate the use of these cores, a buck power converter topology is implemented with switching frequencies of 1-2 MHz. Power conversion efficiency greater than 85% with peak operating flux density of 0.3-0.5 T in the core and converter output power level exceeding 5 W was achieved.

  5. Frequency conversion of radiation of IR molecular gas lasers in nonlinear crystals (A review)

    NASA Astrophysics Data System (ADS)

    Ionin, A. A.; Kinyaevskiy, I. O.; Klimachev, Yu. M.; Kotkov, A. A.

    2015-09-01

    The solution of problems related, e.g., to transport of laser radiation in the atmosphere requires availability of a broadband IR laser source operating in the transparency windows of the atmosphere. In this review, we present the results of an investigation of the properties of a hybrid laser system consisting of molecular gas pump lasers and a solid-state laser frequency converter based on nonlinear crystals. We demonstrate broadening and enrichment of spectrum of radiation of the pump laser by means of sum- and difference-frequency generation. In particular, by using a relatively simple laser system consisting of gas-discharge CO and CO2 lasers, radiation tunable over a large number of spectral lines in a broad range of wavelength from 2.5 to 16.6 µm (more than two and a half octaves), which includes two transparency windows of the atmosphere, is obtained. Thus, the possibility of exploring the IR spectral range by means of hybrid laser systems based on frequency conversion of radiation of molecular gas lasers is demonstrated.

  6. Temporal mode sorting using dual-stage quantum frequency conversion by asymmetric Bragg scattering.

    PubMed

    Christensen, Jesper B; Reddy, Dileep V; McKinstrie, C J; Rottwitt, K; Raymer, M G

    2015-09-01

    The temporal shape of single photons provides a high-dimensional basis of temporal modes, and can therefore support quantum computing schemes that go beyond the qubit. However, the lack of linear optical components to act as quantum gates has made it challenging to efficiently address specific temporal-mode components from an arbitrary superposition. Recent progress towards realizing such a "quantum pulse gate," has been proposed using nonlinear optical signal processing to add coherently the effect of multiple stages of quantum frequency conversion. This scheme, called temporal-mode interferometry [D. V. Reddy, Phys. Rev. A 91, 012323 (2015)], has been shown in the case of three-wave mixing to promise near-unity mode-sorting efficiency. Here we demonstrate that it is also possible to achieve high mode-sorting efficiency using four-wave mixing, if one pump pulse is long and the other short - a configuration we call asymmetrically-pumped Bragg scattering. PMID:26368430

  7. A scalable multipass laser cavity based on injection by frequency conversion for noncollective Thomson scattering

    SciTech Connect

    Schaeffer, D. B.; Constantin, C. G.; Everson, E. T.; Van Compernolle, B.; Kugland, N. L.; Niemann, C.; Ebbers, C. A.; Glenzer, S. H.

    2010-10-15

    A scalable setup using injection by frequency conversion to establish a multipassing cavity for noncollective Thomson scattering on low density plasmas is presented. The cavity is shown to support >10 passes through the target volume with a 400% increase in energy on target versus a single-pass setup. Rayleigh scattering experiments were performed and demonstrate the viability of the cell to study low density plasmas of the order of 10{sup 12}-10{sup 13} cm{sup -3}. A high-repetition, low-energy, single-pass Thomson scattering setup was also performed on the University of California, Los Angeles Large Plasma Device and shows that the multipass cavity could have a significant advantage over the high-repetition approach due to the cavity setup's inherently higher signal per shot.

  8. A scalable multipass laser cavity based on injection by frequency conversion for noncollective Thomson scattering.

    PubMed

    Schaeffer, D B; Kugland, N L; Constantin, C G; Everson, E T; Van Compernolle, B; Ebbers, C A; Glenzer, S H; Niemann, C

    2010-10-01

    A scalable setup using injection by frequency conversion to establish a multipassing cavity for noncollective Thomson scattering on low density plasmas is presented. The cavity is shown to support >10 passes through the target volume with a 400% increase in energy on target versus a single-pass setup. Rayleigh scattering experiments were performed and demonstrate the viability of the cell to study low density plasmas of the order of 10(12)-10(13) cm(-3). A high-repetition, low-energy, single-pass Thomson scattering setup was also performed on the University of California, Los Angeles Large Plasma Device and shows that the multipass cavity could have a significant advantage over the high-repetition approach due to the cavity setup's inherently higher signal per shot. PMID:21033873

  9. On the propagation and mode conversion of auroral medium frequency bursts

    NASA Astrophysics Data System (ADS)

    Broughton, M. C.; LaBelle, J.; Kim, E.-H.; Yoon, P. H.; Johnson, J. R.; Cairns, I. H.

    2016-02-01

    Auroral medium frequency (MF) bursts are broadband, impulsive radio emissions associated with local substorm onsets. MF bursts consist of a characteristic fine structure whereby the higher frequencies arrive 10-100 ms before the lower frequencies. LaBelle (2011a) proposed that MF bursts originate as Langmuir/Z mode waves on the topside of the ionosphere that mode-convert to LO mode waves and propagate to ground level, with the fine structure resulting by propagation delays due to the topside ionospheric density profile. We investigate three aspects of this mechanism. First, full-wave calculations are used to simulate the MF burst fine structure using a realistic ionospheric density profile. The delay between the highest and lowest frequencies is 21 ms. This value is smaller than the experimentally determined delays of ˜100 ms presented in Bunch and LaBelle (2009), but differences between the topside electron number density profile used in the simulations and the number density profile during disturbed conditions make comparisons only approximate. Second, the Landau damping of Langmuir/Z mode waves on the topside ionosphere is calculated, assuming the electron distribution function consists of a cold background population (ne0) and a warm secondary population (nse). The Landau damping is small when nse/ne0 = 0.04% (consistent with Maggs and Lotko (1981)) but is significant when nse/ne0 > 0.4%. Finally, full-wave calculations are used to determine the mode conversion efficiency from Langmuir/Z mode waves to LO mode waves. These imply that waves would suffer an attenuation of wave energy density of approximately 5-10% if they are generated with their wave vectors in a narrow cone centered around the local magnetic field. Taken together, these calculations suggest that for small values of nse/ne0 <0.4%, the mechanism proposed by LaBelle (2011a) is a plausible explanation for the origin of MF bursts.

  10. Nanophotonics and nanochemistry: controlling the excitation dynamics for frequency up- and down-conversion in lanthanide-doped nanoparticles.

    PubMed

    Chen, Guanying; Yang, Chunhui; Prasad, Paras N

    2013-07-16

    Nanophotonics is an emerging science dealing with the interaction of light and matter on a nanometer scale and holds promise to produce new generation nanophosphors with highly efficient frequency conversion of infrared (IR) light. Scientists can control the excitation dynamics by using nanochemistry to produce hierarchically built nanostructures and tailor their interfaces. These nanophosphors can either perform frequency up-conversion from IR to visible or ultraviolet (UV) or down-conversion, which results in the IR light being further red shifted. Nanophotonics and nanochemistry open up numerous opportunities for these photon converters, including in high contrast bioimaging, photodynamic therapy, drug release and gene delivery, nanothermometry, and solar cells. Applications of these nanophosphors in these directions derive from three main stimuli. Light excitation and emission within the near-infrared (NIR) "optical transparency window" of tissues is ideal for high contrast in vitro and in vivo imaging. This is due to low natural florescence, reduced scattering background, and deep penetration in tissues. Secondly, the naked eye is highly sensitive in the visible range, but it has no response to IR light. Therefore, many scientists have interest in the frequency up-conversion of IR wavelengths for security and display applications. Lastly, frequency up-conversion can convert IR photons to higher energy photons, which can then readily be absorbed by solar materials. Current solar devices do not use abundant IR light that comprises almost half of solar energy. In this Account, we present our recent work on nanophotonic control of frequency up- and down-conversion in fluoride nanophosphors, and their biophotonic and nanophotonic applications. Through nanoscopic control of phonon dynamics, electronic energy transfer, local crystal field, and surface-induced non-radiative processes, we were able to produce new generation nanophosphors with highly efficient frequency

  11. High-fidelity frequency down-conversion of visible entangled photon pairs with superconducting single-photon detectors

    SciTech Connect

    Ikuta, Rikizo; Kato, Hiroshi; Kusaka, Yoshiaki; Yamamoto, Takashi; Imoto, Nobuyuki; Miki, Shigehito; Yamashita, Taro; Terai, Hirotaka; Wang, Zhen; Fujiwara, Mikio; Sasaki, Masahide; Koashi, Masato

    2014-12-04

    We experimentally demonstrate a high-fidelity visible-to-telecommunicationwavelength conversion of a photon by using a solid-state-based difference frequency generation. In the experiment, one half of a pico-second visible entangled photon pair at 780 nm is converted to a 1522-nm photon. Using superconducting single-photon detectors with low dark count rates and small timing jitters, we observed a fidelity of 0.93±0.04 after the wavelength conversion.

  12. Efficient frequency conversion by stimulated Raman scattering in a sodium nitrate aqueous solution

    SciTech Connect

    Ganot, Yuval E-mail: ibar@bgu.ac.il; Bar, Ilana E-mail: ibar@bgu.ac.il

    2015-09-28

    Frequency conversion of laser beams, based on stimulated Raman scattering (SRS) is an appealing technique for generating radiation at new wavelengths. Here, we investigated experimentally the SRS due to a single pass of a collimated frequency-doubled Nd:YAG laser beam (532 nm) through a saturated aqueous solution of sodium nitrate (NaNO{sub 3}), filling a 50 cm long cell. These experiments resulted in simultaneous generation of 1st (564 nm) and 2nd (599 nm) Stokes beams, corresponding to the symmetric stretching mode of the nitrate ion, ν{sub 1}(NO{sub 3}{sup −}), with 40 and 12 mJ/pulse maximal converted energies, equivalent to 12% and 4% efficiencies, respectively, for a 340 mJ/pulse pump energy. The results indicate that the pump and SRS beams were thermally defocused and that four-wave mixing was responsible for the second order Stokes process onset.

  13. Graphene-channel FETs for photonic frequency double-mixing conversion over the sub-THz band

    NASA Astrophysics Data System (ADS)

    Kawasaki, Tetsuya; Sugawara, Kenta; Dobroiu, Adrian; Eto, Takanori; Kurita, Yuki; Kojima, Kazuki; Yabe, Yuhei; Sugiyama, Hiroki; Watanabe, Takayuki; Suemitsu, Tetsuya; Ryzhii, Victor; Iwatsuki, Katsumi; Fukada, Youichi; Kani, Jun-ichi; Terada, Jun; Yoshimoto, Naoto; Kawahara, Kenji; Ago, Hiroki; Otsuji, Taiichi

    2015-01-01

    We report on photonic frequency double-mixing conversion utilizing a graphene-channel FET (G-FET). Optoelectronic properties of graphene are exploited to perform single-chip photonic double-mixing functionality, which is greatly advantageous in future broadband technological conversion between optical fiber and sub-terahertz wireless communications. A 1 GHz modulation signal on a 125 GHz carrier is electrically input to the gate, whereas a 1.58 μm dual wavelength CW laser beam having a frequency difference of 112.5 GHz impinges on the G-FET. The G-FET works as a photomixer generating a 112.5 GHz local signal which is then electrically mixed to the 1 GHz modulated 125 GHz carrier signal, resulting in the down-conversion of the 1 GHz signal to a 12.5 GHz intermediate frequency (IF) signal.

  14. Power scalable semiconductor disk lasers for frequency conversion and mode-locking

    SciTech Connect

    Okhotnikov, O G

    2008-12-31

    The semiconductor disk laser, a relatively novel type of light oscillators, is now under intensive development. These lasers produce an excellent beam quality in conjunction with a scalable output power. This paper presents recent achievements in power scalability, mode-locking and frequency conversion with optically-pumped semiconductor disk lasers. A novel concept for power scaling described here allows the thermal load of the gain material to be reduced, increasing the threshold of rollover and extending the capability for boosting the output power without degradation in the beam quality. The proposed technique is based on the multiple gain scheme. The total power of over 8 W was achieved in dual-gain configuration, while one-gain lasers could produce separately up to 4 W, limited by the thermal rollover of the output characteristics. The results show that the reduced thermal load to a gain element in a dual-gain cavity allows extending the range of usable pump powers boosting the laser output. Orange-red radiation required for a number of challenging applications can be produced through frequency-doubling using a GaInNAs/GaAs laser. Using such a disk laser operating at a fundamental wavelength of 1224 nm, we demonstrate an output power of 2.68 W in the visible region with an optical-to-optical conversion efficiency of 7.4%. The frequency-converted signal could be launched into a single-mode optical fibre with 70%-78% coupling efficiency, demonstrating good beam quality for the visible radiation. Using a Fabry-Perot glass etalon, the emission wavelength could be tuned over an 8-nm spectral range. We report on optically-pumped disk lasers passively mode-locked with a semiconductor saturable-absorber mirror. The potential of harmonic mode-locking in producing pulse trains at multigigahertz repetition rates has been explored. The mode-locked disk laser is investigated for different designs of the gain medium that allow bistable mode-locking to be controlled. An

  15. Warm white LED light by frequency down-conversion of mixed yellow and red Lumogen

    NASA Astrophysics Data System (ADS)

    Mosca, Mauro; Caruso, Fulvio; Zambito, Leandro; Seminara, Biagio; Macaluso, Roberto; Calı, Claudio; Feltin, Eric

    2013-05-01

    This work reports on the benefits and promising opportunities offered by white LED hybrid technology, based on a mixing perylene-based dyes in order to obtain a warm white light for frequency-down conversion. In a standard Ce:YAG-based white LED, the white light appears cold due to the weakness of red wavelength components in the emission spectrum. In order to obtain a warmer white, one possible solution is to add a red phosphor to the yellow one to move the chromatic coordinates properly, though the luminous efficiency drastically decreases due to the increased light absorption of the coating layer. It is generally believed that the low efficiency of warm white LEDs is the main issue today for LED-based lighting. Using photoluminescence of Lumogen® F Yellow 083, a perylene-based polymer dye commercialized by BASF, and adding a small quantity of another perylene-based dye, Lumogen® F Red 305 (BASF), we obtained high-efficiency warm white LEDs by yellow and red conversion from a standard 450 nm GaN/InGaN royal blue LED. Different weight proportions of dyes were dissolved in solutions with equal amounts of poly-methyl-methacrylate (PMMA) in ethyl acetate, then the LEDs were dip-coated in each solution and optically characterized. Record values of 8.03 lm of luminous flux and 116.11 lm/W of optical efficiency were achieved. Finally, the effects of both driving current, and pump wavelength on LED performances - such as chromatic coordinates, correlated color temperature, color rendering index (CRI), and optical efficiency - were investigated.

  16. Group velocity mismatch-absent nonlinear frequency conversions for mid-infrared femtosecond pulses generation

    PubMed Central

    Zhong, Haizhe; Zhang, Lifu; Li, Ying; Fan, Dianyuan

    2015-01-01

    A novel group velocity mismatch (GVM) absent scheme for nonlinear optical parametric procedure in mid-infrared was developed with type-I quasi phase matching by use of an off-digital nonlinear optical coefficient d31. This was achieved by matching of the group velocities of the pump and the signal waves, while the phase velocities were quasi phase matched. The system employs MgO-doped periodically poled LiNbO3 as the nonlinear medium. Desired group-velocity dispersion would be obtained via appropriately temperature regulation. To demonstrate its potential applications in ultrafast mid-infrared pulses generation, aiming at a typical mid-infrared wavelength of ~3.2 μm, design examples of two basic nonlinear frequency conversion procedures are studied for both the narrow-band seeding mid-IR optical parametric amplification (OPA) and the synchronously pumped femtosecond optical parametric oscillation (SPOPO). Compared with the conventional scheme of type-0 QPM, the quantum-efficiency can be more than doubled with nearly unlimited bandwidth. The proposed GVM- absent phase matching design may provide a promising route to efficient and broadband sub-100 fs mid-infrared ultrafast pulses generation without group-velocity walk-off. PMID:26099837

  17. Observation of ion-cyclotron-frequency mode-conversion flow drive in tokamak plasmas.

    PubMed

    Lin, Y; Rice, J E; Wukitch, S J; Greenwald, M J; Hubbard, A E; Ince-Cushman, A; Lin, L; Porkolab, M; Reinke, M L; Tsujii, N

    2008-12-01

    Strong toroidal flow (Vphi) and poloidal flow (Vtheta) have been observed in D-3He plasmas with ion cyclotron range of frequencies (ICRF) mode-conversion (MC) heating on the Alcator C-Mod tokamak. The toroidal flow scales with the rf power Prf (up to 30 km/s per MW), and is significantly larger than that in ICRF minority heated plasmas at the same rf power or stored energy. The central Vphi responds to Prf faster than the outer regions, and the Vphi(r) profile is broadly peaked for r/a < or =0.5. Localized (0.3 < or = r/a < or =0.5) Vtheta appears when Prf > or =1.5 MW and increases with power (up to 0.7 km/s per MW). The experimental evidence together with numerical wave modeling suggests a local flow drive source due to the interaction between the MC ion cyclotron wave and 3He ions. PMID:19113561

  18. Pulsed Tm-doped fiber lasers for mid-IR frequency conversion

    NASA Astrophysics Data System (ADS)

    Creeden, Daniel; Budni, Peter A.; Ketteridge, Peter A.

    2009-02-01

    Fiber lasers are an ideal pump source for nonlinear frequency conversion because they have the capability to generate short pulses with high peak-powers and excellent beam quality. Thulium-doped silica fibers allow for pulse generation and amplification in the 2-micron spectral band. This opens the door to a variety of nonlinear crystals, such as ZnGeP2 (ZGP) and orientation patterned GaAs (OPGaAs), which cannot be pumped by Yb- or Er-doped fiber laser directly due to high losses in the near-IR band. These crystals combine low losses with high nonlinearities and transparency for efficient nonlinear mid-IR converters. Using such nonlinear crystals and a pulsed Tm-doped master oscillator fiber amplifier (MOFA), we have demonstrated efficient mid-IR generation with watts of output power in the 3-5μm region. The Tm-doped MOFA is capable of generating from 10 to 100W of average output power at a variety of repetition rates (10kHz - >500kHz) and pulse widths (10ns - >100ns). Total mid-IR power is only limited by thermal effects in the nonlinear materials. The use of Tm-doped fiber-pumped OPOs shows the path toward compact, efficient, and lightweight mid-IR laser systems.

  19. The principle of frequency interaction and photoelectric conversion of the mass wave

    NASA Astrophysics Data System (ADS)

    Cao, Dayong

    2007-08-01

    The experiment results show that human consciousness can change photoelectric signals such as Voc and Isc of solar cell at isolation air. First in the world, consciousness signal is able to be recorded through the experiment. (It succeed in 10,22,2002) Consciousness augment or reduce the Voc to the slow wave like the ERP of the brain wave. Photoelectrical signal converts to slow fluctuation signal without characteristics of sine fluctuation, Which proves that there is a "cause and effect" relationship between alterations of consciousness (active) and photoelectrical signal (passive); Under the standard limit optical source (AM1.5), consciousness changes a normal photoelectric signal above threshold value of I-V tester. The experiment proves that consciousness signal is a kind of unknown physical signal. With a characteristic of slow fluctuation, mass wave of the light is different from the Einstein's light quantum (energy wave). Frequency interaction principle of it and its photoelectric conversion equation are being put forward. It is rife hold true. Consequently, it is discovered that consciousness signal with a slow weak wave has such high power. Mass energy space and time system theory and Quantum microcosmics space and time are being put forward. It give a support to new Mass wave. Consciousness can produces the consciousness signal with the mass wave and use it to act on photoelectric system. The system magnifies it. Consciousness is independent and self-determined while brain signal is passive and driven. Consciousness is spiritual and Intelligence while brain signal is physical, corporality and mechanic.

  20. Particle simulations of mode conversion between slow mode and fast mode in lower hybrid range of frequencies

    NASA Astrophysics Data System (ADS)

    Jia, Guozhang; Xiang, Nong; Wang, Xueyi; Huang, Yueheng; Lin, Yu

    2016-01-01

    The propagation and mode conversion of lower hybrid waves in an inhomogeneous plasma are investigated by using the nonlinear δf algorithm in a two-dimensional particle-in-cell simulation code based on the gyrokinetic electron and fully kinetic ion (GeFi) scheme [Lin et al., Plasma Phys. Controlled Fusion 47, 657 (2005)]. The characteristics of the simulated waves, such as wavelength, frequency, phase, and group velocities, agree well with the linear theoretical analysis. It is shown that a significant reflection component emerges in the conversion process between the slow mode and the fast mode when the scale length of the density variation is comparable to the local wavelength. The dependences of the reflection coefficient on the scale length of the density variation are compared with the results based on the linear full wave model for cold plasmas. It is indicated that the mode conversion for the waves with a frequency of 2.45 GHz (ω ˜ 3ωLH, where ωLH represents the lower hybrid resonance) and within Tokamak relevant amplitudes can be well described in the linear scheme. As the frequency decreases, the modification due to the nonlinear term becomes important. For the low-frequency waves (ω ˜ 1.3ωLH), the generations of the high harmonic modes and sidebands through nonlinear mode-mode coupling provide new power channels and thus could reduce the reflection significantly.

  1. Modeling of large aperture third harmonic frequency conversion of high power Nd:glass laser systems

    SciTech Connect

    Henesian, M.A.; Wegner, P.J.; Speck, D.R.; Bibeau, C.; Ehrlich, R.B.; Laumann, C.W.; Lawson, J.K.; Weiland, T.L.

    1991-03-13

    To provide high-energy, high-power beams at short wavelengths for inertial-confinement-fusion experiments, we routinely convert the 1.053-{mu}m output of the Nova, Nd:phosphate-glass, laser system to its third-harmonic wavelength. We describe performance and conversion efficiency modeling of the 3 {times} 3 arrays potassium-dihydrogen-phosphate crystal plates used for type II/type II phase-matched harmonic conversion of Nova 0.74-m diameter beams, and an alternate type I/type II phase-matching configuration that improves the third-harmonic conversion efficiency. These arrays provide energy conversion of up to 65% and intensity conversion to 70%. 19 refs., 11 figs.

  2. Coherent optical frequency-combs-based wideband signal channelization and analog to digital conversion

    NASA Astrophysics Data System (ADS)

    Yin, Feifei; Dai, Yitang; Li, Jianqiang; Xu, Kun

    2014-11-01

    We demonstrate a photonic-assisted broadband radio frequency (RF) channelization scheme based on dual coherent optical frequency combs (OFCs). The advantages include coarse optical alignment requirement, ideal rectangular frequency response in each channel without any ultra-narrow optical filters, and digitalized output for further processing. Meanwhile, the channel frequency response and crosstalk of the scheme are also evaluated experimentally.

  3. 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

  4. Estimation of frequency conversion efficiency of THz devices using a ballistic electron wave swing circuit model

    NASA Astrophysics Data System (ADS)

    Schildbach, Christian; Ong, Duu Sheng; Hartnagel, Hans; Schmidt, Lorenz-Peter

    2016-06-01

    The ballistic electron wave swing device has previously been presented as a possible candidate for a simple power conversion technique to the THz -domain. This paper gives a simulative estimation of the power conversion efficiency. The harmonic balance simulations use an equivalent circuit model, which is also derived in this work from a mechanical model. To verify the validity of the circuit model, current waveforms are compared to Monte Carlo simulations of identical setups. Model parameters are given for a wide range of device configurations. The device configuration exhibiting the most conforming waveform is used further for determining the best conversion efficiency. The corresponding simulation setup is described. Simulation results implying a conversion efficiency of about 22% are presented.

  5. High Conversion Efficiency and Power Stability of 532 nm Generation from an External Frequency Doubling Cavity

    NASA Astrophysics Data System (ADS)

    Zhao, Yang; Lin, Bai-Ke; Li, Ye; Zhang, Hong-Xi; Cao, Jian-Ping; Fang, Zhan-Jun; Li, Tian-Chu; Zang, Er-Jun

    2012-09-01

    We present a high-efficiency 532 nm green light conversion from an external cavity-enhanced second harmonic generation (SHG) with a periodically poled KTP crystal (PPKTP). The cavity is a bow-tie ring configuration with a unitized structure. When the impedance matching is optimized, the coupling efficiency of the fundamental is as high as 95%. Taking into account both the high power output of the second harmonic and the stability of the system, we obtain over 500 mW green passing through the output cavity mirror, corresponding to a net conversion efficiency higher than 75.2%. Under these operating conditions, the power stability is better than ±0.25% during 5 h. It is the highest conversion efficiency and power stability ever produced in the bow-tie ring cavity with PPKTP for 532 nm generation.

  6. Soft Magnetic Materials in High-Frequency, High-Power Conversion Applications

    NASA Astrophysics Data System (ADS)

    Leary, Alex M.; Ohodnicki, Paul R.; McHenry, Michael E.

    2012-07-01

    Advanced soft magnetic materials are needed to match high-power density and switching frequencies made possible by advances in wide band-gap semiconductors. Magnetics capable of operating at higher operating frequencies have the potential to greatly reduce the size of megawatt level power electronics. In this article, we examine the role of soft magnetic materials in high-frequency power applications and we discuss current material's limitations and highlight emerging trends in soft magnetic material design for high-frequency and power applications using the materials paradigm of synthesis → structure → property → performance relationships.

  7. A short report on voltage-to-frequency conversion for HISTRAP RF system tuning control loops

    SciTech Connect

    Hasanul Basher, A.M.

    1991-09-01

    One of the requirements of the HISTRAP RF accelerating system is that the frequency of the accelerating voltage for the cavity must keep in step with the change in the magnetic field. As the energy of the particle increases, the magnetic field is increased to keep the radius of the particle orbit constant. At the same time, the frequency of the electric field must be changed to insure that it is synchronized with the angular movement of the particle. So we need to generate the frequency of the accelerating voltage in relation to the magnetic field. The frequency generation can be accomplished in two stages. The first stage of frequency generation consists of measuring the magnetic field in terms of voltage which is already developed. The second stage is to convert this voltage into frequency. Final frequency precision can be achieved by deriving a frequency-correcting signal from the beam position. This project is concerned with generating the frequency from the analog voltage. The speed of response required will place very stringent requirements on both hardware and software. Technology is available to carry out this task. A hardware configuration has been established and software has been developed. In the following section, we describe the implementation strategy, the hardware configuration, and the desired specifications. Next, we present the software developed, results obtained, along with capabilities and limitations of the system. Finally, we suggest alternate solutions to overcome some of the limitations toward meeting our goal. In the appendices, we include program listings.

  8. Soft Magnetic Materials in High-Frequency, High-Power Conversion Applications

    SciTech Connect

    Leary, AM; Ohodnicki, PR; McHenry, ME

    2012-07-04

    Advanced soft magnetic materials are needed to match high-power density and switching frequencies made possible by advances in wide band-gap semiconductors. Magnetics capable of operating at higher operating frequencies have the potential to greatly reduce the size of megawatt level power electronics. In this article, we examine the role of soft magnetic materials in high-frequency power applications and we discuss current material's limitations and highlight emerging trends in soft magnetic material design for high-frequency and power applications using the materials paradigm of synthesis -> structure -> property -> performance relationships.

  9. Design and characterisation of a piezoelectric knee-joint energy harvester with frequency up-conversion through magnetic plucking

    NASA Astrophysics Data System (ADS)

    Kuang, Yang; Yang, Zhihao; Zhu, Meiling

    2016-08-01

    Piezoelectric energy harvesting from human motion is challenging because of the low energy conversion efficiency at a low-frequency excitation. Previous studies by the present authors showed that mechanical plucking of a piezoelectric bimorph cantilever was able to provide frequency up-conversion from a few hertz to the resonance frequency of the cantilever, and that a piezoelectric knee-joint energy harvester (KEH) based on this mechanism was able to generate sufficient energy to power a wireless sensor node. However, the direct contact between the bimorph and the plectra leads to reduced longevity and considerable noise. To address these limitations, this paper introduces a magnetic plucking mechanism to replace the mechanical plucking in the KEH, where primary magnets (PM) actuated by knee-joint motion excite the bimorphs through a secondary magnet (SM) fixed on the bimorphs tip and so achieve frequency up-conversion. The key parameters of the new KEH that affect the energy output of a plucked bimorph were investigated. It was found that the bimorph plucked by a repulsive magnetic force produced a higher energy output than an attractive force. The energy output peaked at 32 PMs and increased with a decreasing gap between PM and SM as well as an increasing rotation speed of the PMs. Based on these investigations, a KEH with high energy output was prototyped, which featured 8 piezoelectric bimorphs plucked by 32 PMs through repulsive magnetic forces. The gap between PM and SM was set to 1.5 mm with a consideration on both the energy output and longevity of the bimorphs. When actuated by knee-joint motion of 0.9 Hz, the KEH produced an average power output of 5.8 mW with a life time >7.3 h (about 3.8 × 105 plucking excitations).

  10. Frequency of Use Leads to Automaticity of Production: Evidence from Repair in Conversation

    ERIC Educational Resources Information Center

    Kapatsinski, Vsevolod

    2010-01-01

    In spontaneous speech, speakers sometimes replace a word they have just produced or started producing by another word. The present study reports that in these replacement repairs, low-frequency replaced words are more likely to be interrupted prior to completion than high-frequency words, providing support to the hypothesis that the production of…

  11. Nanosecond-laser-induced damage in potassium titanyl phosphate: pure 532 nm pumping and frequency conversion situations

    SciTech Connect

    Wagner, Frank R.; Hildenbrand, Anne; Natoli, Jean-Yves; Commandre, Mireille

    2011-08-01

    Nanosecond-laser-induced damage measurements in the bulk of KTiOPO{sub 4} (KTP) crystals are reported using incident 532 nm light or using incident 1064 nm light, which pumps more or less efficient second harmonic generation. No damage threshold fatigue effect is observed with pure 532 nm irradiation. The damage threshold of Z-polarized light is higher than the one for X- or Y-polarized light. During frequency doubling, the damage threshold was found to be lower than for pure 1064 or 532 nm irradiation. More data to quantify the cooperative damage mechanism were generated by performing fluence ramp experiments with varying conditions and monitoring the conversion efficiency. All damage thresholds plotted against the conversion efficiency align close to a characteristic curve.

  12. Low phase noise microwave extraction from femtosecond laser by frequency conversion pair and IF-domain processing.

    PubMed

    Dai, Yitang; Cen, Qizhuang; Wang, Lei; Zhou, Yue; Yin, Feifei; Dai, Jian; Li, Jianqiang; Xu, Kun

    2015-12-14

    Extraction of a microwave component from a low-time-jitter femtosecond pulse train has been attractive for current generation of spectrally pure microwave. In order to avoid the transfer from the optical amplitude noise to microwave phase noise (AM-PM), we propose to down-convert the target component to intermediate frequency (IF) before the opto-electronic conversion. Due to the much lower carrier frequency, the AM-PM is greatly suppressed. The target is then recovered by up-conversion with the same microwave local oscillation (LO). As long as the time delay of the second LO matches that of the IF carrier, the phase noise of the LO shows no impact on the extraction process. The residual noise of the proposed extraction is analyzed in theory, which is also experimentally demonstrated as averagely around -155 dBc/Hz under offset frequency larger than 1 kHz when 10-GHz tone is extracted from a home-made femtosecond fiber laser. Large tunable extraction from 1 GHz to 10 GHz is also reported. PMID:26698985

  13. Optical NRZ-to-RZ format conversion based on frequency chirp linearization and spectrum slicing

    NASA Astrophysics Data System (ADS)

    Wang, Dong; Huo, Li; Chen, Xin; Jiang, Xiangyu; Lou, Caiyun

    2015-12-01

    A flexible optical NRZ-to-RZ format converter based on a time lens followed by optical filtering is proposed and demonstrated experimentally. After frequency chirp linearization, 9-tone ultra-flat optical frequency comb of 25-GHz frequency spacing within 1 dB power variation is obtained. By changing the shape of the following optical band-pass filter, 3.4-ps Nyquist-shaped RZ signal and 3.7-ps Gaussian-shaped RZ signal are both achieved. The sensitivity improvements at a bit error rate of 10-9 are 3.3 dB and 1.7 dB, respectively.

  14. Effect of pulse to pulse variation of divergence, pointing and amplitude of copper vapor laser radiations on their second harmonic and sum frequency conversion

    NASA Astrophysics Data System (ADS)

    Prakash, Om; Mahakud, Ramakanta; Nakhe, Shankar V.; Dixit, Sudhir K.

    2013-09-01

    This paper presents the effect of single pulse stability of divergence angle, beam pointing angle and amplitude of green and yellow radiation pulses of an unstable resonator copper vapor laser (CVL) oscillator in the sum frequency (SF) mixing and second harmonic (SH). The conversion efficiency of sum frequency generation was lower compared to second harmonic processes despite larger fundamental power being used in sum frequency experiments. However the net UV power obtained at the sum frequency was higher than both of the second harmonic UV frequencies. Lower sum frequency generation (SFG) conversion efficiency compared to second harmonic generation (SHG) of individual CVL radiation is attributed to difference in single pulse stability of beam pointing, divergence and amplitude fluctuation of both CVL radiations in addition to commonly known fact of spatio-temporal mis-match. At the same fundamental input power, higher SH conversion efficiency of yellow compared to green is attributed to its better single pulse stability of beam pointing and divergence.

  15. Systems for controlling the intensity variations in a laser beam and for frequency conversion thereof

    DOEpatents

    Skupsky, Stanley; Craxton, R. Stephen; Soures, John

    1990-01-01

    In order to control the intensity of a laser beam so that its intensity varies uniformly and provides uniform illumination of a target, such as a laser fusion target, a broad bandwidth laser pulse is spectrally dispersed spatially so that the frequency components thereof are spread apart. A disperser (grating) provides an output beam which varies spatially in wavelength in at least one direction transverse to the direction of propagation of the beam. Temporal spread (time delay) across the beam is corrected by using a phase delay device (a time delay compensation echelon). The dispersed beam may be amplified with laser amplifiers and frequency converted (doubled, tripled or quadrupled in frequency) with nonlinear optical elements (birefringent crystals). The spectral variation across the beam is compensated by varying the angle of incidence on one of the crystals with respect to the crystal optical axis utilizing a lens which diverges the beam. Another lens after the frequency converter may be used to recollimate the beam. The frequency converted beam is recombined so that portions of different frequency interfere and, unlike interference between waves of the same wavelength, there results an intensity pattern with rapid temoral oscillations which average out rapidly in time thereby producing uniform illumination on target. A distributed phase plate (also known as a random phase mask), through which the spectrally dispersed beam is passed and then focused on a target, is used to provide the interference pattern which becomes nearly modulation free and uniform in intensity in the direction of the spectral variation.

  16. Systems for controlling the intensity variations in a laser beam and for frequency conversion thereof

    DOEpatents

    Skupsky, S.; Craxton, R.S.; Soures, J.

    1990-10-02

    In order to control the intensity of a laser beam so that its intensity varies uniformly and provides uniform illumination of a target, such as a laser fusion target, a broad bandwidth laser pulse is spectrally dispersed spatially so that the frequency components thereof are spread apart. A disperser (grating) provides an output beam which varies spatially in wavelength in at least one direction transverse to the direction of propagation of the beam. Temporal spread (time delay) across the beam is corrected by using a phase delay device (a time delay compensation echelon). The dispersed beam may be amplified with laser amplifiers and frequency converted (doubled, tripled or quadrupled in frequency) with nonlinear optical elements (birefringent crystals). The spectral variation across the beam is compensated by varying the angle of incidence on one of the crystals with respect to the crystal optical axis utilizing a lens which diverges the beam. Another lens after the frequency converter may be used to recollimate the beam. The frequency converted beam is recombined so that portions of different frequency interfere and, unlike interference between waves of the same wavelength, there results an intensity pattern with rapid temporal oscillations which average out rapidly in time thereby producing uniform illumination on target. A distributed phase plate (also known as a random phase mask), through which the spectrally dispersed beam is passed and then focused on a target, is used to provide the interference pattern which becomes nearly modulation free and uniform in intensity in the direction of the spectral variation. 16 figs.

  17. Frequency up-conversion of optical microwaves for multichannel optical microwave system on a WDM network

    NASA Astrophysics Data System (ADS)

    Shin, Myunghun; Kumar, Prem

    2012-07-01

    We propose a multichannel optical microwave system employing a frequency up-converting optoelectronic oscillator (FU-OEO) [FU-OEO: frequency up-converting optoelectronic oscillator] as a low-phase noise local oscillator (LO) and a multichannel frequency up-converter. Employing the FU-OEO, we demonstrated an optical microwave system capable of 16 optical microwave links in the C-band on a WDM network; the generated optical microwaves were distributed to their designated remote stations according to the channel wavelength. When the FU-OEO was used as the system LO, the phase noise of the optical microwaves was under -80 dBc/Hz at a 10 kHz offset from a 20 GHz carrier frequency. As a frequency up-converter, the FU-OEO simultaneously up-converted all optical data channels at a 1.25 Gbps data rate for optical microwaves in the 20 GHz band of an optical carrier suppression mode having almost 100% modulation depth. The overall system performance was verified by measuring the bit error rates (BER) of the data recovered from optical microwaves received through single-mode fibers. The measured BER indicated that the system can transmit over 50 km with a power penalty of less than 1 dB. This method can be useful for high-frequency applications where the generation and transmission of optical microwaves are greatly restricted by optical or electrical bandwidths.

  18. Frequency conversion of molecular gas lasers in PbIn6Te10 crystal within mid-IR range.

    PubMed

    Ionin, A A; Kinyaevskiy, I O; Klimachev, Y M; Kotkov, A A; Badikov, V V; Mitin, K V

    2016-05-15

    PbIn6Te10 is a new mid-infrared (IR) nonlinear crystal with a very wide transparency range from 1.7 up to 31 μm. Calculated phase-matching angles show possibility of frequency conversion throughout the transparency range. Sum frequency generation of multiline carbon monoxide (CO) laser and difference frequency generation when mixing CO and carbon dioxide laser radiation were experimentally studied. Laser-induced damage threshold and frequency conversion efficiency under multiline CO laser pumping were measured. PMID:27177010

  19. Multipass configuration to achieve high-frequency conversion in Li2B4O7 crystals

    NASA Astrophysics Data System (ADS)

    Chatterjee, Udit; Gangopadhyay, Sudipta; Ghosh, Chittaranjan; Bhar, Gopal C.

    2005-02-01

    A multipass configuration for second-harmonic generation of Nd:YAG laser radiation is demonstrated to produce, for the first time to the authors' knowledge in twin lithium tetraborate crystals, as much as 21% conversion efficiency even though the effective nonlinear coefficient of the crystal is as low as 1/6th that of KDP. Apart from crystals that have large walk-off angles, low effective nonlinear coefficients, or both, the simple experimental setup would also be quite suitable for those crystals, especially infrared crystals, that have large effective nonlinear coefficients but low laser damage thresholds.

  20. Multipass configuration to achieve high-frequency conversion in Li2B4O7 crystals.

    PubMed

    Chatterjee, Udit; Gangopadhyay, Sudipta; Ghosh, Chittaranjan; Bhar, Gopal C

    2005-02-10

    A multipass configuration for second-harmonic generation of Nd:YAG laser radiation is demonstrated to produce, for the first time to the authors' knowledge in twin lithium tetraborate crystals, as much as 21% conversion efficiency even though the effective nonlinear coefficient of the crystal is as low as 1/6th that of KDP. Apart from crystals that have large walk-off angles, low effective nonlinear coefficients, or both, the simple experimental setup would also be quite suitable for those crystals, especially infrared crystals, that have large effective nonlinear coefficients but low laser damage thresholds. PMID:15751864

  1. Cavity piezomechanical strong coupling and frequency conversion on an aluminum nitride chip

    NASA Astrophysics Data System (ADS)

    Zou, Chang-Ling; Han, Xu; Jiang, Liang; Tang, Hong X.

    2016-07-01

    Schemes to achieve strong coupling between mechanical modes of aluminum nitride microstructures and microwave cavity modes due to the piezoelectric effect are proposed. We show that the strong-coupling regime is feasible for an on-chip aluminum nitride device that is either enclosed by a three-dimensional microwave cavity or integrated with a superconducting coplanar resonator. Combining with optomechanics, the piezomechanical strong coupling permits coherent conversion between microwave and optical modes with high efficiency. Hence, the piezomechanical system will be an efficient transducer for applications in hybrid quantum systems.

  2. Local oscillator free all optical OOK signal frequency up conversion enabled by injection locking of Fabry-Pérot laser

    NASA Astrophysics Data System (ADS)

    Han, Bing-chen; Yu, Jin-long; Wang, Wen-rui; Wang, Ju; Shi, Yun-long

    2014-08-01

    We demonstrate an all optical up-conversion system by injecting low bitrates baseband OOK signal directly into a conventional Fabry-Pérot laser diode (FP-LD). Radio frequency (RF) carrier is generated due to period-one (P1) oscillation state of nonlinear dynamics system (NDS) in the FP-LD with the injection of external optical signal. No extra high speed and expensive local oscillator is required for the up-conversion. Based on this approach, we experimentally achieved the up-conversion of 2 Gbps RZ-OOK baseband signal to 12 GHz and 14.28 GHz RF carriers, and 2.5 Gbps NRZ-OOK baseband signal to 10 GHz, 18.2 GHz and 20.88 GHz RF carriers respectively. The obtained 20.88 GHz RF carriers have a signal to side mode suppression ratio of 29 dB, and phase noise of -84.2 dBc/Hz@10 kHz.

  3. Effect of bandwidth on beam smoothing and frequency conversion at the third harmonic of the Nova laser

    SciTech Connect

    Pennington, D.M.; Henesian, M.A.; Dixit, S.N.; Powell, H.T.; Thompson, C.E.; Weiland, T.L.

    1993-05-01

    We present the results of experiments performed on the Nova laser system to determine the effect of bandwidth on third harmonic (3{omega}) frequency conversion and beam smoothing by spectral dispersion (SSD). Our experiments utilized a wide bandwidth fiber optic cross-phase modulated (XPM) source and a narrower bandwidth microwave modulated (FM) source, each centered at 1053 nm (1{omega}). The FM source produced {approximately}2 cm{sup {minus}1} of bandwidth, modulated at 3 GHz; the XPM bandwidth was varied from 5 to 15 cm{sup {minus}1}, modulated by the temporally noisy output of a multimode Nd:glass laser ({le} 500 GHz). The FM beam showed no evidence of self-phase modulation in the laser chain produced by intensity fluctuations, and 1{omega} bandwidth was tripled upon conversion to 3{omega} (2--6 cm{sup {minus}1}). The 1{omega} XPM bandwidth increased by {ge} 25% due to self-phase modulation in the laser chain (16--22 cm{sup {minus}1}) due to it`s relative noisy temporal structure. Over 50% of the 1{omega} XPM bandwidth was transferred to the 3{omega} beam (22--36 cm{sup {minus}1}), yielding 0.13% bandwidth at 3{omega}. The maximum intrinsic narrowband 3{omega} frequency conversion obtained using a type-II/type-II KDP crystal array was 62%. The intrinsic efficiency obtained at the Nova 10-beam chamber is typically > 65%. We have developed broadband frequency conversion codes and broadband pulse simulations to model our results, and have obtained good agreement with experiment. Using a random phase plate without bandwidth, we obtained a smoothing level, {sigma}/I {approximately} 0.79, defined by the rms variance normalized with respect to the average intensity. This is less than the theoretically expected value of 1 for an ideal speckle pattern, and could be evidence of polarization smoothing as a result of focus lens birefringence. With spectral dispersion and RPP we demonstrated an excellent level of smoothing with the XPM source.

  4. Non-Markovian environments and entanglement preservation

    NASA Astrophysics Data System (ADS)

    Tan, Jackson; Kyaw, Thi Ha; Yeo, Ye

    2010-06-01

    Using the Shabani-Lidar post-Markovian master equation, we derive non-Markovian generalizations of important quantum decohering operations on single qubits. When environmental memory effects are being taken into account, both single-qubit coherence and two-qubit entanglement may be preserved over a longer period of time, in contrast to the corresponding situations where these are totally neglected. We argue that recognizing the fact that every environment is inherently non-Markovian could be the key to the resolution of the issue of entanglement sudden death.

  5. Non-Markovian environments and entanglement preservation

    SciTech Connect

    Tan, Jackson; Kyaw, Thi Ha; Yeo, Ye

    2010-06-15

    Using the Shabani-Lidar post-Markovian master equation, we derive non-Markovian generalizations of important quantum decohering operations on single qubits. When environmental memory effects are being taken into account, both single-qubit coherence and two-qubit entanglement may be preserved over a longer period of time, in contrast to the corresponding situations where these are totally neglected. We argue that recognizing the fact that every environment is inherently non-Markovian could be the key to the resolution of the issue of entanglement sudden death.

  6. Shaping pulses using frequency conversion with a modulated picosecond free electron laser

    SciTech Connect

    Hooper, B.A.; Madey, J.M.J.

    1995-12-31

    Computer simulations and experiments indicate that we can shape the infrared picosecond pulses of the Mark III FEL in amplitude, frequency, and phase. Strongly modulated fundamental and second harmonic pulses have been generated by operating the Mark III FEL in the regime of strong sideband growth. In this paper, we present the results of simulations and experiments for second harmonic generation with fundamental inputs from 2 to 3 {mu}m.

  7. Empirical conversion of the vertical profile of reflectivity from Ku-band to S-band frequency

    NASA Astrophysics Data System (ADS)

    Cao, Qing; Hong, Yang; Qi, Youcun; Wen, Yixin; Zhang, Jian; Gourley, Jonathan J.; Liao, Liang

    2013-02-01

    ABSTRACT This paper presents an empirical method for converting reflectivity from Ku-band (13.8 GHz) to S-band (2.8 GHz) for several hydrometeor species, which facilitates the incorporation of Tropical Rainfall Measuring Mission (TRMM) Precipitation Radar (PR) measurements into quantitative precipitation estimation (QPE) products from the U.S. Next-Generation Radar (NEXRAD). The development of empirical dual-frequency relations is based on theoretical simulations, which have assumed appropriate scattering and microphysical models for liquid and solid hydrometeors (raindrops, snow, and ice/hail). Particle phase, shape, orientation, and density (especially for snow particles) have been considered in applying the T-matrix method to compute the scattering amplitudes. Gamma particle size distribution (PSD) is utilized to model the microphysical properties in the ice region, melting layer, and raining region of precipitating clouds. The variability of PSD parameters is considered to study the characteristics of dual-frequency reflectivity, especially the variations in radar dual-frequency ratio (DFR). The empirical relations between DFR and Ku-band reflectivity have been derived for particles in different regions within the vertical structure of precipitating clouds. The reflectivity conversion using the proposed empirical relations has been tested using real data collected by TRMM-PR and a prototype polarimetric WSR-88D (Weather Surveillance Radar 88 Doppler) radar, KOUN. The processing and analysis of collocated data demonstrate the validity of the proposed empirical relations and substantiate their practical significance for reflectivity conversion, which is essential to the TRMM-based vertical profile of reflectivity correction approach in improving NEXRAD-based QPE.

  8. High-frequency thermal-electrical cycles for pyroelectric energy conversion

    SciTech Connect

    Bhatia, Bikram; Damodaran, Anoop R.; Cho, Hanna; Martin, Lane W.; King, William P.

    2014-11-21

    We report thermal to electrical energy conversion from a 150 nm thick BaTiO{sub 3} film using pyroelectric cycles at 1 kHz. A microfabricated platform enables temperature and electric field control with temporal resolution near 1 μs. The rapid electric field changes as high as 11 × 10{sup 5 }kV/cm-s, and temperature change rates as high as 6 × 10{sup 5 }K/s allow exploration of pyroelectric cycles in a previously unexplored operating regime. We investigated the effect of phase difference between electric field and temperature cycles, and electric field and temperature change rates on the electrical energy generated from thermal-electrical cycles based on the pyroelectric Ericsson cycle. Complete thermodynamic cycles are possible up to the highest cycle rates tested here, and the energy density varies significantly with phase shifts between temperature and electric field waveforms. This work could facilitate the design and operation of pyroelectric cycles at high cycle rates, and aid in the design of new pyroelectric systems.

  9. Sorting photon wave packets using temporal-mode interferometry based on multiple-stage quantum frequency conversion

    NASA Astrophysics Data System (ADS)

    Reddy, D. V.; Raymer, M. G.; McKinstrie, C. J.

    2015-01-01

    All classical and quantum technologies that encode in and retrieve information from optical fields rely on the ability to selectively manipulate orthogonal field modes of light. Such manipulation can be achieved with high selectivity for polarization modes and transverse-spatial modes. For the time-frequency degree of freedom, this could efficiently be achieved for a limited choice of approximately orthogonal modes, i.e., nonoverlapping bins in time or frequency. We recently proposed a method that surmounts the selectivity barrier for sorting arbitrary orthogonal temporal modes [Opt. Lett. 39, 2924 (2014)., 10.1364/OL.39.002924] using cascaded interferometric quantum frequency conversion in nonlinear optical media. We call this method temporal-mode interferometry, as it has a close resemblance to the well-known separated-fields atomic interferometry method introduced by Ramsey. The method has important implications for quantum memories, quantum dense coding, quantum teleportation, and quantum key distribution. Here we explore the inner workings of the method in detail, and extend it to multiple stages with a concurrent asymptotic convergence of temporal-mode selectivity to unity. We also complete our analysis of pump-chirp compensation to counter pump-induced nonlinear phase modulation in four-wave mixing implementations.

  10. Multiwavelength green-yellow laser based on a Nd:YAG laser with nonlinear frequency conversion in a LBO crystal.

    PubMed

    Wang, Zhichao; Yang, Feng; Xie, Shiyong; Xu, Yiting; Xu, Jialin; Bo, Yong; Peng, Qinjun; Zhang, Jingyuan; Cui, Dafu; Xu, Zuyan

    2012-06-20

    We demonstrate a multiwavelength laser in the green-yellow region by means of a diode-pumped neodymium-doped yttrium aluminum garnet laser. This laser system combines a homemade 1074 nm and 1112 nm dual-wavelength laser with extracavity second harmonic generation (SHG) or sum-frequency generation in a lithium triborate crystal to generate visible output at any one of three wavelengths, 537 nm, 546 nm, and 556 nm, by simple temperature tuning, which has an important application in detecting carbon monoxide. The maximum average output power at the three wavelengths (537 nm, 546 nm, and 556 nm) was obtained to be 10.5 W, 0.5 W, and 8.5 W, respectively. The maximum SHG conversion efficiency from the infrared to the visible spectral region was about 51%. PMID:22722297

  11. Broadband frequency conversion and shaping of single photons emitted from a nonlinear cavity.

    PubMed

    McCutcheon, Murray W; Chang, Darrick E; Zhang, Yinan; Lukin, Mikhail D; Loncar, Marko

    2009-12-01

    Much recent effort has focused on coupling individual quantum emitters to optical microcavities in order to produce single photons on demand, enable single-photon optical switching, and implement functional nodes of a quantum network. Techniques to control the bandwidth and frequency of the outgoing single photons are of practical importance, allowing direct emission into telecommunications wavelengths and "hybrid" quantum networks incorporating different emitters. Here, we describe an integrated approach involving a quantum emitter coupled to a nonlinear optical resonator, in which the emission wavelength and pulse shape are controlled using the intra-cavity nonlinearity. Our scheme is general in nature, and demonstrates how the photonic environment of a quantum emitter can be tailored to determine the emission properties. As specific examples, we discuss a high Q-factor, TE-TM double-mode photonic crystal cavity design that allows for direct generation of single photons at telecom wavelengths (1425 nm) starting from an InAs/GaAs quantum dot with a 950 nm transition wavelength, and a scheme for direct optical coupling between such a quantum dot and a diamond nitrogen-vacancy center at 637 nm. PMID:20052195

  12. Targeted high and low speech frequency bands to right and left ears respectively improve task performance and perceived sociability in dyadic conversations.

    PubMed

    Gregory, Stanford W; Kalkhoff, Will; Harkness, Sarah K; Paull, Jessica L

    2009-07-01

    Past research shows that the lower nonverbal frequencies of the human voice, beneath .5 kHz, transmit an acoustic signal promoting social convergence and status accommodation between human interlocutors. We conducted a laboratory experiment and a validation study to explore the possible communications benefits of targeting the low-frequency band to the left ears of human participants and the high-frequency band to the right ears. We compare this "Enhanced" condition with two other conditions: a "Confounded" condition, in which the low-frequency band was targeted to participants' right ears and the higher-frequency band to their left ears; and a Control condition, in which the entire unaltered frequency band was targeted to both ears. For the duration of their interaction, experiment participants engaged in dyadic conversations while attempting to complete a task via an audio-visual communication system. Our results show that both the speed and accuracy of task completion were significantly improved in the Enhanced condition. In the second validation study, groups of participants rated the quality of videotaped conversations from the experiment using a semantic differential instrument. The Enhanced condition conversations were rated significantly more affectively favourable than either the unaltered Control or Confounded condition conversations. Overall, our results exhibit potential for enhancing two-way electronic communications and improving task performances in media environments. PMID:19031308

  13. Frequency domain near-infrared multiwavelength imager design using high-speed, direct analog-to-digital conversion

    NASA Astrophysics Data System (ADS)

    Zimmermann, Bernhard B.; Fang, Qianqian; Boas, David A.; Carp, Stefan A.

    2016-01-01

    Frequency domain near-infrared spectroscopy (FD-NIRS) has proven to be a reliable method for quantification of tissue absolute optical properties. We present a full-sampling direct analog-to-digital conversion FD-NIR imager. While we developed this instrument with a focus on high-speed optical breast tomographic imaging, the proposed design is suitable for a wide-range of biophotonic applications where fast, accurate quantification of absolute optical properties is needed. Simultaneous dual wavelength operation at 685 and 830 nm is achieved by concurrent 67.5 and 75 MHz frequency modulation of each laser source, respectively, followed by digitization using a high-speed (180 MS/s) 16-bit A/D converter and hybrid FPGA-assisted demodulation. The instrument supports 25 source locations and features 20 concurrently operating detectors. The noise floor of the instrument was measured at <1.4 pW/√Hz, and a dynamic range of 115+ dB, corresponding to nearly six orders of magnitude, has been demonstrated. Titration experiments consisting of 200 different absorption and scattering values were conducted to demonstrate accurate optical property quantification over the entire range of physiologically expected values.

  14. New Crystalline Materials for Nonlinear Frequency Conversion, Electro-Optic Modulation, and Mid-Infrared Gain Media

    SciTech Connect

    Adams, J

    2002-08-09

    New crystalline materials were investigated for applications in frequency conversion of near-infrared wavelengths and as gain media for tunable mid-infrared solid-state lasers. GaCa{sub 4}O(BO{sub 3}){sub 3} (GdCOB), YCa{sub 4}O(BO{sub 3}){sub 3} (YCOB), LaCa{sub 4}O(BO{sub 3}){sub 3} (LaCOB), and Gd{sub 0.275}Y{sub 0.725}Ca{sub 4}O(BO{sub 3}){sub 3} were characterized for frequency conversion of 1 {micro}m lasers. For type I doubling at 1064 nm, LaCOB, GdCOB, and YCOB were found to have effective coupling coefficients (d{sub eff}) of 0.52 {+-} 0.05, 0.78 {+-} 0.06, and 1.12 {+-} 0.07 pm/V, respectively. LaCOB was measured to have angular and thermal sensitivities of 1224 {+-} 184 (cm-rad){sup -1} and < 0.10 (cm-{sup o}C){sup -1}, respectively. The effective coupling coefficient for type II noncritically phasematched (NCPM) doubling at 1064 nm in Gd{sub 0.275}Y{sub 0.725}Ca{sub 4}O(BO{sub 3}){sub 3} was measured to be 0.37 {+-} 0.04 pm/V. We predict LaCOB to have a type I NCPM fundamental wavelength of 1042 {+-} 1.5 nm. Due to its low angular and thermal sensitivities for doubling near 1047 nm, LaCOB has potential for frequency doubling of high-average power Nd:LiYF{sub 4} and Yb:Sr{sub 5}(P0{sub 4}){sub 3}F lasers. LaCOB, GdCOB, and YCOB were also investigated for optical parametric oscillator applications and we determined that they may have potential in a Ti:sapphire pumped oscillator. The effective linear electro-optic coefficients (r{sub eff}) were measured along dielectric directions in YCOB and a maximum r{sub eff} of 10.8 pm/V was found. For a crystal with a 5:1 aspect ratio, the corresponding half-wave voltage at 1064 nm would be 19.6 kV. Therefore a Pockels cell composed of two YCOB crystals with 5:1 aspect ratios would have a required half-wave voltage <10 kV. Moderate coupling coefficients (3 x KH{sub 2}PO{sub 4}), low thermal sensitivities, ease of growth to large sizes, non-hygroscopicity, and favorable polishing and coating characteristics make La

  15. Efficiency of non-linear frequency conversion of double-scale pico-femtosecond pulses of passively mode-locked fiber laser.

    PubMed

    Smirnov, Sergey V; Kobtsev, Sergey M; Kukarin, Sergey V

    2014-01-13

    For the first time we report the results of both numerical simulation and experimental observation of second-harmonic generation as an example of non-linear frequency conversion of pulses generated by passively mode-locked fiber master oscillator in different regimes including conventional (stable) and double-scale (partially coherent and noise-like) ones. We show that non-linear frequency conversion efficiency of double-scale pulses is slightly higher than that of conventional picosecond laser pulses with the same energy and duration despite strong phase fluctuations of double-scale pulses. PMID:24515065

  16. Cascade photonic integrated circuit architecture for electro-optic in-phase quadrature/single sideband modulation or frequency conversion.

    PubMed

    Hasan, Mehedi; Hall, Trevor

    2015-11-01

    A photonic integrated circuit architecture for implementing frequency upconversion is proposed. The circuit consists of a 1×2 splitter and 2×1 combiner interconnected by two stages of differentially driven phase modulators having 2×2 multimode interference coupler between the stages. A transfer matrix approach is used to model the operation of the architecture. The predictions of the model are validated by simulations performed using an industry standard software tool. The intrinsic conversion efficiency of the proposed design is improved by 6 dB over the alternative functionally equivalent circuit based on dual parallel Mach-Zehnder modulators known in the prior art. A two-tone analysis is presented to study the linearity of the proposed circuit, and a comparison is provided over the alternative. The proposed circuit is suitable for integration in any platform that offers linear electro-optic phase modulation such as LiNbO(3), silicon, III-V, or hybrid technology. PMID:26512513

  17. Phase discrimination and simultaneous frequency conversion of the orthogonal components of an optical signal by four-wave mixing in an SOA.

    PubMed

    Webb, R P; Dailey, J M; Manning, R J; Ellis, A D

    2011-10-10

    Simultaneous conversion of the two orthogonal phase components of an optical input to different output frequencies has been demonstrated by simulation and experiment. A single stage of four-wave mixing between the input signal and four pumps derived from a frequency comb was employed. The nonlinear device was a semiconductor optical amplifier, which provided overall signal gain and sufficient contrast for phase sensitive signal processing. The decomposition of a quadrature phase-shift keyed signal into a pair of binary phase-shift keyed outputs at different frequencies was also demonstrated by simulation. PMID:21997012

  18. Homo and heteroepitaxial growth and study of orientation-patterned GaP for nonlinear frequency conversion devices

    NASA Astrophysics Data System (ADS)

    Tassev, V. L.; Vangala, S.; Peterson, R.; Kimani, M.; Snure, M.; Markov, I.

    2016-03-01

    Frequency conversion in orientation-patterned quasi-phase matched materials is a leading approach for generating tunable mid- and long-wave coherent IR radiation for a wide variety of applications. A number of nonlinear optical materials are currently under intensive investigation. Due to their unique properties, chiefly wide IR transparency and high nonlinear susceptibility, GaAs and GaP are among the most promising. Compared to GaAs, GaP has the advantage of having higher thermal conductivity and significantly lower 2PA in the convenient pumping range of 1- 1.7 μm. HVPE growth of OPGaP, however, has encountered certain challenges: low quality and high price of commercially available GaP wafers; and strong parasitic nucleation during HVPE growth that reduces growth rate and aggravates layer quality, often leading to pattern overgrowth. Lessons learned from growing OPGaAs were not entirely helpful, leaving us to alternative solutions for both homoepitaxial growth and template preparation. We report repeatable one-step HVPE growth of up to 400 μm thick OPGaP with excellent domain fidelity deposited for first time on OPGaAs templates. The templates were prepared by wafer fusion bonding or MBE assisted polarity inversion technique. A close to equilibrium growth at such a large lattice mismatch (-3.6%) is itself noteworthy, especially when previously reported attempts (growth of OPZnSe on OPGaAs templates) at much smaller mismatch (+0.3%) have produced limited results. Combining the advantages of the two most promising materials, GaAs and GaP, is a solution that will accelerate the development of high power, tunable laser sources for the mid- and long-wave IR, and THz region.

  19. Nonlinear frequency up-conversion of femtosecond pulses from an erbium fibre laser to the range of 0.8 - 1 {mu}m in silica fibres

    SciTech Connect

    Anashkina, E A; Andrianov, A V; Kim, A V

    2013-03-31

    We consider different mechanisms of nonlinear frequency up-conversion of femtosecond pulses emitted by an erbium fibre system ({lambda} = 1.5 {mu}m) to the range of 0.8 - 1.2 {mu}m in nonlinear silica fibres. The generation efficiency and the centre frequencies of dispersive waves are found as functions of the parameters of the fibre and the input pulse. Simple analytical estimates are obtained for the spectral distribution of the intensity and the frequency shift of a wave packet in the region of normal dispersion during the emission of a high-order soliton under phase matching conditions. In the geometrical optics approximation the frequency shifts are estimated in the interaction of dispersive waves with solitons in various regimes. (extreme light fields and their applications)

  20. Conversion of oscillation frequency at the front of an electromagnetic shock wave in a coaxial line with a gas-discharge tube

    NASA Astrophysics Data System (ADS)

    Parshin, V. N.; Kataev, I. G.

    1989-01-01

    An analysis is made of oscillation-frequency conversion at an electromagnetic shock front in a circular gas-filled waveguide with insulated walls. The study is performed in the linear approximation, with allowance for the dispersion of the moving plasma formed in the shock wave fields as well as for the dispersion of the waveguide itself. Two possible cases of interaction between microwave oscillations and the shock wave are identified: subluminal and superluminal.

  1. Performance of smoothing by spectral dispersion (SSD) with frequency conversion on the Beamlet Laser for the National Ignition Facility

    SciTech Connect

    Rothenberg, J.E.; Morgan, B.; Wegner, P.; Weiland, T.W.

    1997-11-04

    Simulations and ongoing measurements indicate that SSD results in small degradation to the near field beam quality. The measured effect of SSD bandwidth on conversion to the third harmonic and smoothing of the target illumination will also be described.

  2. Application of frequency conversion of starlight to high-resolution imaging interferometry. On-sky sensitivity test of a single arm of the interferometer

    NASA Astrophysics Data System (ADS)

    Ceus, D.; Reynaud, F.; Woillez, J.; Lai, O.; Delage, L.; Grossard, L.; Baudoin, R.; Gomes, J.-T.; Bouyeron, L.; Herrmann, H.; Sohler, W.

    2012-11-01

    We investigate the sensitivity of frequency conversion of starlight using a non-linear optical sum frequency process. This study is being carried out in the context of future applications of optical interferometry dedicated to high-resolution imaging. We have implemented a complete experimental chain from telescope to detector. The starlight frequency is shifted from the infrared to the visible using an optically non-linear crystal. To fulfil the requirements of interferometry, our experimental setup uses spatially single-mode and polarization maintaining components. Due to the small size of the collecting aperture (8 inches Celestron C8) with a 3 nm spectral bandwidth, on-sky tests were performed on bright stars in the H band. The detection was achieved in a true photon counting operation, using synchronous detection. Betelgeuse (HMag =-3.9), Antares (HMag =-3.6) and Pollux (HMag =-1) were successfully converted and detected in visible light. Despite the low transmission of our experiment, our results prove that the efficiency of frequency conversion offers sufficient sensitivity for future interferometric applications.

  3. Impact of BaB2O4 growth method on frequency conversion to the deep ultra-violet

    NASA Astrophysics Data System (ADS)

    Deyra, L.; Maillard, A.; Maillard, R.; Sangla, D.; Salin, F.; Balembois, F.; Kokh, A. E.; Georges, P.

    2015-12-01

    In this article, we report how the growth method used for barium beta-borate β-BaB2O4 (BBO) impacts its high power second harmonic generation properties in the deep-UV. We compared a BBO crystal grown by flux (Top Seeded Solution Growth or TSSG) and a BBO crystal grown by the Czochralski (CZ) method. We first characterized their transparency properties, then we measured their single-pass second harmonic conversion efficiencies with both a low average power and a high average power nanosecond pulsed lasers. We show that both crystals have comparable linear absorption and conversion efficiencies at low power, whereas in a high power experiment, the CZ-grown BBO yields higher conversion efficiency than the TSSG grown BBO. With a 30 W, 150 kHz, 8 ns green laser, the use of a CZ BBO led at best to a 40% increase in available average output power at 257 nm.

  4. Frequency up-conversion of a high-power microwave pulse propagating in a self-generated plasma

    NASA Technical Reports Server (NTRS)

    Kuo, S. P.; Ren, A.

    1992-01-01

    In the study of the propagation of a high-power microwave pulse, one of the main concerns is how to minimize the energy loss of the pulse before reaching the destination. A frequency autoconversion process that can lead to reflectionless propagation of powerful electromagnetic pulses in self-generated plasmas is studied. The theory shows that, under the proper condition, the carrier frequency omega of the pulse shifts upward during the growth of local plasma frequency omega(pe). Thus, the self-generated plasma remains underdense to the pulse. A chamber experiment to demonstrate the frequency autoconversion during the pulse propagation through the self-generated plasma is conducted. The detected frequency shift is compared with the theoretical result calculated by using the measured electron density distribution along the propagation path of the pulse. Good agreement is obtained.

  5. The Mercury Laser System: An Average power, gas-cooled, Yb:S-FAP based system with frequency conversion and wavefront correction

    SciTech Connect

    Bibeau, C; Bayramian, A; Armstrong, P; Ault, E; Beach, R; Benapfl, M; Campbell, R; Dawson, J; Ebbers, C; Freitas, B; Kent, R; Liao, Z; Ladran, T; Menapace, J; Molander, B; Moses, E; Oberhelman, S; Payne, S; Peterson, N; Schaffers, K; Stolz, C; Sutton, S; Tassano, J; Telford, S; Utterback, E; Randles, M

    2005-08-31

    We report on the operation of the Mercury laser with fourteen 4 x 6 cm{sup 2} Yb:S-FAP amplifier slabs pumped by eight 100 kW peak power diode arrays. The system was continuously run at 55 J and 10 Hz for several hours, (2 x 10{sup 5} cumulative shots) with over 80% of the energy in a 6 times diffraction limited spot at 1.047 um. Improved optical quality was achieved in Yb:S-FAP amplifiers with magneto-rheological finishing, a deterministic polishing method. In addition, average power frequency conversion employing YCOB was demonstrated at 50% conversion efficiency or 22.6 J at 10 Hz.

  6. Real-time terahertz wave imaging by nonlinear optical frequency up-conversion in a 4-dimethylamino-N'-methyl-4'-stilbazolium tosylate crystal

    NASA Astrophysics Data System (ADS)

    Fan, Shuzhen; Qi, Feng; Notake, Takashi; Nawata, Kouji; Matsukawa, Takeshi; Takida, Yuma; Minamide, Hiroaki

    2014-03-01

    Real-time terahertz (THz) wave imaging has wide applications in areas such as security, industry, biology, medicine, pharmacy, and arts. In this letter, we report on real-time room-temperature THz imaging by nonlinear optical frequency up-conversion in organic 4-dimethylamino-N'-methyl-4'-stilbazolium tosylate crystal. The active projection-imaging system consisted of (1) THz wave generation, (2) THz-near-infrared hybrid optics, (3) THz wave up-conversion, and (4) an InGaAs camera working at 60 frames per second. The pumping laser system consisted of two optical parametric oscillators pumped by a nano-second frequency-doubled Nd:YAG laser. THz-wave images of handmade samples at 19.3 THz were taken, and videos of a sample moving and a ruler stuck with a black polyethylene film moving were supplied online to show real-time ability. Thanks to the high speed and high responsivity of this technology, real-time THz imaging with a higher signal-to-noise ratio than a commercially available THz micro-bolometer camera was proven to be feasible. By changing the phase-matching condition, i.e., by changing the wavelength of the pumping laser, we suggest THz imaging with a narrow THz frequency band of interest in a wide range from approximately 2 to 30 THz is possible.

  7. Generating Periodic Terahertz Structures in a Relativistic Electron Beam through Frequency Down-Conversion of Optical Lasers

    SciTech Connect

    Dunning, Michael

    2012-07-19

    We report generation of density modulation at terahertz (THz) frequencies in a relativistic electron beam through laser modulation of the beam longitudinal phase space. We show that by modulating the energy distribution of the beam with two lasers, density modulation at the difference frequency of the two lasers can be generated after the beam passes through a chicane. In this experiment, density modulation around 10 THz was generated by down-converting the frequencies of an 800 nm laser and a 1550 nm laser. The central frequency of the density modulation can be tuned by varying the laser wavelengths, beam energy chirp, or momentum compaction of the chicane. This technique can be applied to accelerator-based light sources for generation of coherent THz radiation and marks a significant advance toward tunable narrow-band THz sources.

  8. Mode-locked Yb:YAG thin-disk oscillator with 41 µJ pulse energy at 145 W average infrared power and high power frequency conversion.

    PubMed

    Bauer, Dominik; Zawischa, Ivo; Sutter, Dirk H; Killi, Alexander; Dekorsy, Thomas

    2012-04-23

    We demonstrate the generation of 1.1 ps pulses containing more than 41 µJ of energy directly out of an Yb:YAG thin-disk without any additional amplification stages. The laser oscillator operates in ambient atmosphere with a 3.5 MHz repetition rate and 145 W of average output power at a fundamental wavelength of 1030 nm. An average output power of 91.5 W at 515 nm was obtained by frequency doubling with a conversion efficiency exceeding 65%. Third harmonic generation resulted in 34 W at 343 nm at 34% efficiency. PMID:22535061

  9. Autler-Townes splitting via frequency up-conversion at ultralow-power levels in cold 87Rb atoms using an optical nanofiber

    NASA Astrophysics Data System (ADS)

    Kumar, Ravi; Gokhroo, Vandna; Deasy, Kieran; Chormaic, Síle Nic

    2015-05-01

    The tight confinement of the evanescent light field around the waist of an optical nanofiber makes it a suitable tool for studying nonlinear optics in atomic media. Here, we use an optical nanofiber embedded in a cloud of laser-cooled 87Rb for near-infrared frequency up-conversion via a resonant two-photon process. Sub-nW powers of the two-photon radiation, at 780 and 776 nm, copropagate through the optical nanofiber and the generation of 420 nm photons is observed. A measurement of the Autler-Townes splitting provides a direct measurement of the Rabi frequency of the 780 nm transition. Through this method, dephasings of the system can be studied. In this work, the optical nanofiber is used as an excitation and detection tool simultaneously, and it highlights some of the advantages of using fully fibered systems for nonlinear optics with atoms.

  10. Optical frequency up-conversion by supercontinuum-free widely-tunable fiber-optic Cherenkov radiation

    PubMed Central

    Tu, Haohua; Boppart, Stephen A.

    2010-01-01

    Spectrally-isolated narrowband Cherenkov radiation from commercial nonlinear photonic crystal fibers is demonstrated as an ultrafast optical source with a visible tuning range of 485–690 nm, which complementarily extends the near-infrared tuning range of 690–1020 nm from the corresponding femtosecond Ti:sapphire pump laser. Pump-to-signal conversion efficiency routinely surpasses 10%, enabling multimilliwatt visible output across the entire tuning range. Appropriate selection of fiber parameters and pumping conditions efficiently suppresses the supercontinuum generation typically associated with Cherenkov radiation. PMID:19506636

  11. Noncritically phase-matched sum frequency generation and image up-conversion in KNbO/sub 3/ crystals

    SciTech Connect

    Baumert, J.; Guenter, P.

    1987-03-09

    Tunable and continuous wave (cw) near infrared up-conversion into the dark blue wavelength range (410--465 nm) has been achieved in KNbO/sub 3/ crystals using the nonlinear optical coefficient d/sub 32/ (..omega../sub 1/+..omega../sub 2/; ..omega../sub 1/,..omega../sub 2/) = 20.4 pm/V. High efficiencies have been reached due to the large nonlinearity and the possibility of temperature-tuned noncritical 90/sup 0/ phase matching. Using a neodymium:yttrium aluminum garnet laser (1064.2 nm) as the signal source and a krypton laser (676.4 nm) as the pump source, a sum signal (413.6 nm) power of over 0.1 mW was reached at a pump power of only 26.2 mW. cw image up-conversion into the blue wavelength range has been demonstrated using a noncritically phase-matched configuration in the same crystals at T = -4 /sup 0/C.

  12. Frequency down-conversion of solid-state laser sources to the mid-infrared spectral range using non-oxide nonlinear crystals

    NASA Astrophysics Data System (ADS)

    Petrov, Valentin

    2015-07-01

    The development of parametric devices down-converting the laser frequency to the mid-infrared (3-30 μm) based on non-oxide nonlinear optical crystals is reviewed. Such devices, pumped by solid-state laser systems operating in the near-infrared, fill in this spectral gap where no such lasers exist, on practically all time scales, from continuous-wave to femtosecond regime. All important results obtained so far with difference-frequency generation, optical parametric oscillation, generation and amplification are presented in a comparative manner, illustrating examples of recent achievements are given in more detail, and some special issues such as continuum and frequency comb generation or pulse shaping are also discussed. The vital element in any frequency-conversion process is the nonlinear optical crystal and this represents one of the major limitations for achieving high energies and average powers in the mid-infrared although the broad spectral tunability seems not to be a problem. Hence, an overview of the available non-oxide nonlinear optical materials, emphasizing new developments such as wide band-gap, engineered (mixed), and quasi-phase-matched crystals, is also included.

  13. Anisotropic nanolaminated CoNiFe cores integrated into microinductors for high-frequency dc-dc power conversion

    NASA Astrophysics Data System (ADS)

    Kim, Jooncheol; Kim, Minsoo; Kim, Jung-Kwun; Herrault, Florian; Allen, Mark G.

    2015-11-01

    This paper presents a rectangular, anisotropic nanolaminated CoNiFe core that possesses a magnetically hard axis in the long geometric axis direction. Previously, we have developed nanolaminated cores comprising tens to hundreds of layers of 300-1000 nm thick metallic alloys (i.e. Ni80Fe20 or Co44Ni37Fe19) based on sequential electrodeposition, demonstrating suppressed eddy-current losses at MHz frequencies. In this work, magnetic anisotropy was induced to the nanolaminated CoNiFe cores by applying an external magnetic field (50-100 mT) during CoNiFe film electrodeposition. The fabricated cores comprised tens to hundreds of layers of 500-1000 nm thick CoNiFe laminations that have the hard-axis magnetic property. Packaged in a 22-turn solenoid test inductor, the anisotropic core showed 10% increased effective permeability and 25% reduced core power losses at MHz operation frequency, compared to an isotropic core of the identical geometry. Operating the anisotropic nanolaminated CoNiFe core in a step-down dc-dc converter (15 V input to 5 V output) demonstrated 81% converter efficiency at a switching frequency of 1.1 MHz and output power of 6.5 W. A solenoid microinductor with microfabricated windings integrated with the anisotropic nanolaminated CoNiFe core was fabricated, demonstrating a constant inductance of 600 nH up to 10 MHz and peak quality factor exceeding 20 at 4 MHz. The performance of the microinductor with the anisotropic nanolaminated CoNiFe core is compared with other previously reported microinductors.

  14. High frequency transformerless electronics ballast using double inductor-capacitor resonant power conversion for gas discharge lamps

    SciTech Connect

    Lai, J.S.

    1995-06-20

    A novel high frequency LCLC double resonant electronic ballast has been developed for gas discharge lamp applications. The ballast consists of a half-bridge inverter which switches at zero voltage crossing and an LCLC resonant circuit which converts a low ac voltage to a high ac voltage. The LCLC resonant circuit has two LC stages. The first LC stage produces a high voltage before the lamp is ignited. The second LC stage limits lamp current with the circuit inductance after the lamp is ignited. In another embodiment a filament power supply is provided for soft start up and for dimming the lamp. The filament power supply is a secondary of the second resonant inductor. 27 figs.

  15. High power coupled midinfrared free-electron-laser oscillator scheme as a driver for up-frequency conversion processes in the x-ray region

    NASA Astrophysics Data System (ADS)

    Tecimer, M.

    2012-02-01

    In this paper we present a high-gain free-electron-laser (FEL) oscillator scheme composed of two oscillators that are ideally coupled unidirectionally, with the coupled signal power flowing from the master to the amplifier oscillator. Electron bunches driving the oscillators are in perfect synchronization with the optical pulses building up within the respective cavities. The scheme is applied to a 100 MeV range superconducting energy recovery linac FEL. The computed mJ level, ultrashort pulse (<10cycles) output in the midinfrared region indicates the potential of the proposed FEL oscillator scheme in driving up-frequency conversion processes in the x-ray region, enabling tunable, high average brightness, attosecond scale coherent soft/hard x-ray sources.

  16. Measuring solid-state quantum yields: The conversion of a frequency-doubled Nd:YAG diode laser pointer module into a viable light source.

    PubMed

    Daglen, Bevin C; Harris, John D; Dax, Clifford D; Tyler, David R

    2007-07-01

    This article outlines the difficulties associated with measuring quantum yields for solid-state samples using a high-pressure mercury arc lamp as the irradiation source. Details are given for the conversion of an inexpensive frequency-doubled neodymium-doped yttrium aluminum garnet (Nd:YAG) diode laser pointer module into a viable irradiation source. The modified Nd:YAG laser was incorporated into a computer-controlled system, which allowed for the simultaneous irradiation and spectroscopic monitoring of the sample. The data obtained with the Nd:YAG diode laser system show far less scatter than data obtained with a high-pressure Hg arc lamp, and consequently the degradation rates obtained with the laser system could be calculated with far greater accuracy. PMID:17672778

  17. Alignment and maintenance free all-fiber laser source for CARS microscopy based on frequency conversion by four-wave-mixing

    NASA Astrophysics Data System (ADS)

    Baumgartl, Martin; Chemnitz, Mario; Jauregui, Cesar; Meyer, Tobias; Dietzek, Benjamin; Popp, Jürgen; Limpert, Jens; Tünnermann, Andreas

    2012-01-01

    In this contribution we report on a novel approach for pump and stokes pulse generation in extremely compact all-fiber systems using parametric frequency conversion (four-wave-mixing) in photonic-crystal fibers. Representing a completely alignment-free approach, the all-fiber ytterbium-based short-pulse laser system provides intrinsically synchronized tunable two-color picosecond pulses emitted from a single fiber end. The system was designed to address important CH-stretch vibrational resonances. Strong CARS signals are generated and proved by spectroscopic experiments, tuning the laser over the resonance of toluene at 3050cm-1. Furthermore the whole laser setup with a footprint of only 30x30cm2 is mounted on a home-built laser-scanning-microscope and CARS imaging capabilities are verified. The compact turn-key system represents a significant advance for CARS microscopy to enter real-world, in particular bio-medical, applications.

  18. Photonic generation of bipolar direct-sequence UWB signals based on optical spectral shaping and incoherent frequency-to-time conversion

    NASA Astrophysics Data System (ADS)

    Mu, Hongqian; Wang, Muguang; Ye, Jun; Jian, Shuisheng

    2016-06-01

    A novel technology to obtain binary phase-coded ultrawideband (UWB) signals for direct-sequence spread-spectrum communication systems is investigated by using a cost-effective incoherent source. The bipolar encoding is performed based on an all-fiber spectrum shaper composed of two FBG arrays to tailor the optical spectrum, and a section of single-mode fiber to achieve incoherent frequency-to-time conversion. We demonstrate a 1.325-Gb/s UWB encoding system by the use of binary spreading codes of 4-chip length via computer simulations. The proposed bipolar UWB encoding technology can be applied to high-speed UWB-over-fiber communication systems.

  19. High efficiency on-chip three wave parametric frequency conversion and its applications in both classical and quantum optics

    NASA Astrophysics Data System (ADS)

    Guo, Xiang; Zou, Changling; Schuck, Carsten; Jung, Hojoong; Cheng, Risheng; Tang, Hong X.

    Second order nonlinearity (?(2)) is one of the most widely explored properties in photonics. Integrating nonlinear devices on a photonic chip attracts more and more attention due to the devices' small foot-print and large scalability. However, ?(2) nonlinearity in a scalable platform is normally believed to be weak due to difficulties in finding a suitable material with both high nonlinearity and compatibility with advanced nanofabrication technologies. Aluminum nitride is newly developed as a material combining such two properties: high nonlinearity in low-loss, small foot-print waveguide circuits. In experiment, we fabricate microring resonator devices supporting both telecom and visible modes and achieve exceptionally large second harmonic generation efficiency. High quality photon pair generation is further demonstrated with a generation rate of 3 MHz/mW for degenerate photon pair and 5.8 MHz/mW for non-degenerate photon pair. Furthermore, the strong nonlinearity results in coherent interaction between two spectraly far-away modes which manifest as a nonlinear optic induced transparency and efficient frequency converter. We envision more interesting and important applications in the AlN platform combining its outstanding linear and nonlinear properties.

  20. Tunable error-free optical frequency conversion of a 4ps optical short pulse over 25 nm by four-wave mixing in a polarisation-maintaining optical fibre

    NASA Astrophysics Data System (ADS)

    Morioka, T.; Kawanishi, S.; Saruwatari, M.

    1994-05-01

    Error-free, tunable optical frequency conversion of a transform-limited 4.0 ps optical pulse signalis demonstrated at 6.3 Gbit/s using four-wave mixing in a polarization-maintaining optical fibre. The process generates 4.0-4.6 ps pulses over a 25nm range with time-bandwidth products of 0.31-0.43 and conversion power penalties of less than 1.5 dB.

  1. Validation of full-wave simulations for mode conversion of waves in the ion cyclotron range of frequencies with phase contrast imaging in Alcator C-Mod

    SciTech Connect

    Tsujii, N.; Porkolab, M.; Bonoli, P. T.; Edlund, E. M.; Ennever, P. C.; Lin, Y.; Wright, J. C.; Wukitch, S. J.; Jaeger, E. F.; Green, D. L.; Harvey, R. W.

    2015-08-15

    Mode conversion of fast waves in the ion cyclotron range of frequencies (ICRF) is known to result in current drive and flow drive under optimised conditions, which may be utilized to control plasma profiles and improve fusion plasma performance. To describe these processes accurately in a realistic toroidal geometry, numerical simulations are essential. Quantitative comparison of these simulations and the actual experimental measurements is important to validate their predictions and to evaluate their limitations. The phase contrast imaging (PCI) diagnostic has been used to directly detect the ICRF waves in the Alcator C-Mod tokamak. The measurements have been compared with full-wave simulations through a synthetic diagnostic technique. Recently, the frequency response of the PCI detector array on Alcator C-Mod was recalibrated, which greatly improved the comparison between the measurements and the simulations. In this study, mode converted waves for D-{sup 3}He and D-H plasmas with various ion species compositions were re-analyzed with the new calibration. For the minority heating cases, self-consistent electric fields and a minority ion distribution function were simulated by iterating a full-wave code and a Fokker-Planck code. The simulated mode converted wave intensity was in quite reasonable agreement with the measurements close to the antenna, but discrepancies remain for comparison at larger distances.

  2. Validation of full-wave simulations for mode conversion of waves in the ion cyclotron range of frequencies with phase contrast imaging in Alcator C-Mod

    NASA Astrophysics Data System (ADS)

    Tsujii, N.; Porkolab, M.; Bonoli, P. T.; Edlund, E. M.; Ennever, P. C.; Lin, Y.; Wright, J. C.; Wukitch, S. J.; Jaeger, E. F.; Green, D. L.; Harvey, R. W.

    2015-08-01

    Mode conversion of fast waves in the ion cyclotron range of frequencies (ICRF) is known to result in current drive and flow drive under optimised conditions, which may be utilized to control plasma profiles and improve fusion plasma performance. To describe these processes accurately in a realistic toroidal geometry, numerical simulations are essential. Quantitative comparison of these simulations and the actual experimental measurements is important to validate their predictions and to evaluate their limitations. The phase contrast imaging (PCI) diagnostic has been used to directly detect the ICRF waves in the Alcator C-Mod tokamak. The measurements have been compared with full-wave simulations through a synthetic diagnostic technique. Recently, the frequency response of the PCI detector array on Alcator C-Mod was recalibrated, which greatly improved the comparison between the measurements and the simulations. In this study, mode converted waves for D-3He and D-H plasmas with various ion species compositions were re-analyzed with the new calibration. For the minority heating cases, self-consistent electric fields and a minority ion distribution function were simulated by iterating a full-wave code and a Fokker-Planck code. The simulated mode converted wave intensity was in quite reasonable agreement with the measurements close to the antenna, but discrepancies remain for comparison at larger distances.

  3. Interplay between random laser performance and self-frequency conversions in NdxY1.00-xAl3(BO3)4 nanocrystals powders

    NASA Astrophysics Data System (ADS)

    Carreño, Sandra J. M.; Moura, André L.; Pincheira, Pablo I. R.; Fabris, Zanine V.; Maia, Lauro J. Q.; Gomes, Anderson S. L.; de Araújo, Cid B.

    2016-04-01

    Random Laser emission at 1.06 μm, self-second-harmonic generation at 0.53 μm and self-sum-frequency generation at 0.46 μm were investigated in NdxY1.00-xAl3(BO3)4 nanocrystalline powders, for 0.05 ⩽ x ⩽ 1.00, excited by a pulsed laser operating at 808 nm, focusing on the interplay between the RL performance and the second-order nonlinear processes. The RL performance, characterized by a figure-of-merit relating the laser slope efficiency and the excitation pulse energy threshold, improved as x increased up to 1.00 while the efficiency of the self-frequency conversion processes reduced for increasing x because of distortions introduced in the crystalline structure of the grains. The RL wavelength was also dependent on the Nd3+ concentration and presented a redshift from 1061.9 nm to 1063.5 nm for increasing values of x.

  4. Laser-induced breakdown and damage generation by nonlinear frequency conversion in ferroelectric crystals: Experiment and theory

    SciTech Connect

    Louchev, Oleg A.; Saito, Norihito; Wada, Satoshi; Hatano, Hideki; Kitamura, Kenji

    2013-11-28

    Using our experimental data for ns pulsed second harmonic generation (SHG) by periodically poled stoichiometric LiTaO{sub 3} (PPSLT) crystals, we consider in detail the mechanism underlying laser-induced damage in ferroelectric crystals. This mechanism involves generation and heating of free electrons, providing an effective kinetic pathway for electric breakdown and crystal damage in ns pulsed operation via combined two-photon absorption (TPA) and induced pyroelectric field. In particular, a temperature increase in the lattice of ≈1 K induced initially by ns SHG and TPA at the rear of operating PPSLT crystal is found to induce a gradient of spontaneous polarization generating a pyroelectric field of ≈10 kV/cm, accelerating free electrons generated by TPA to an energy of ≈10 eV, followed by impact ionization and crystal damage. Under the damage threshold for ns operation, the impact ionization does not lead to the avalanche-like increase of free electron density, in contrast to the case of shorter ps and fs pulses. However, the total number of collisions by free electrons, ≈10{sup 18} cm{sup −3} (generated during the pulse and accelerated to the energy of ≈10 eV), can produce widespread structural defects, which by entrapping electrons dramatically increase linear absorption for both harmonics in subsequent pulses, creating a positive feedback for crystal lattice heating, pyroelectric field and crystal damage. Under pulse repetition, defect generation starting from the rear of the crystal can propagate towards its center and front side producing damage tracks along the laser beam and stopping SHG. Theoretical analysis leads to numerical estimates and analytical approximation for the threshold laser fluence for onset of this damage mechanism, which agree well with our (i) experiments for the input 1064 nm radiation in 6.8 kHz pulsed SHG by PPSLT crystal, (ii) pulsed low frequency 532 nm radiation transmission experiments, and also (iii) with the data

  5. Conversion of power and frequency

    SciTech Connect

    Ruggiero, A.G.; Wei, J.

    1992-05-01

    This paper deals with a novel idea to excite electrons to radiate energy in the short (millimeter) wavelength range. A short electron bunch is made to travel along the axis of a waveguide where a TM electromagnetic wave is also traveling and causes the beam to perform transverse oscillations. The electrons radiate energy as a consequence of the oscillations. It is found that a convenient mode of operation is to drive the waveguide in proximity of the cut-off.

  6. Conversion of power and frequency

    SciTech Connect

    Ruggiero, A.G.; Wei, J.

    1992-01-01

    This paper deals with a novel idea to excite electrons to radiate energy in the short (millimeter) wavelength range. A short electron bunch is made to travel along the axis of a waveguide where a TM electromagnetic wave is also traveling and causes the beam to perform transverse oscillations. The electrons radiate energy as a consequence of the oscillations. It is found that a convenient mode of operation is to drive the waveguide in proximity of the cut-off.

  7. RETRACTED — Studies on the effect of instability of divergence, pointing and amplitude of green and yellow radiation pulses of copper vapour laser in second harmonic and sum frequency conversion

    NASA Astrophysics Data System (ADS)

    Prakash, Om; Mahakud, Ramakanta; Nakhe, Shankar V.; Dixit, Sudhir K.

    2013-02-01

    This paper presents the effect of single pulse stability of divergence angle, beam pointing angle and amplitude of green and yellow radiation pulses of an unstable resonator copper vapour laser (CVL) oscillator in the sum frequency mixing and second harmonic. The conversion efficiency of sum frequency generation was lower compared to second harmonic processes despite larger fundamental power being used in sum frequency experiments. However the net UV power obtained at the sum frequency was higher than both of the second harmonic UV frequencies. Lower SFG conversion efficiency (12.4%—271 nm) compared to SHG (16.7%—255 nm, 14.5%—289 nm) of individual CVL radiations is attributed to difference in single pulse stability of beam pointing, divergence and amplitude fluctuation of both CVL radiations in addition to commonly known fact of spatio-temporal mis-match. At the same fundamental input power (2.7 W), higher SH conversion efficiency of yellow (12.7%) compared to green (11.0%) is attributed to its better single pulse stability of beam pointing and divergence.

  8. Observation of frequency up-conversion in the propagation of a high-power microwave pulse in a self-generated plasma

    NASA Technical Reports Server (NTRS)

    Kuo, S. P.; Zhang, Y. S.; Ren, A.

    1990-01-01

    A chamber experiment is conducted to study the propagation of a high-power microwave pulse. The results show that the pulse is experiencing frequency up-shift while ionizing the background air if the initial carrier frequency of the pulse is higher than the electron plasma frequency at the incident boundary. Such a frequency autoconversion process may lead to reflectionless propagation of a high-power microwave pulse through the atmosphere.

  9. Frequency mixer having ferromagnetic film

    DOEpatents

    Khitun, Alexander; Roshchin, Igor V.; Galatsis, Kosmas; Bao, Mingqiang; Wang, Kang L.

    2016-03-29

    A frequency conversion device, which may include a radiofrequency (RF) mixer device, includes a substrate and a ferromagnetic film disposed over a surface of the substrate. An insulator is disposed over the ferromagnetic film and at least one microstrip antenna is disposed over the insulator. The ferromagnetic film provides a non-linear response to the frequency conversion device. The frequency conversion device may be used for signal mixing and amplification. The frequency conversion device may also be used in data encryption applications.

  10. Group velocity effects in broadband frequency conversion on OMEGA. 1998 summer research program for high school juniors at the University of Rochester`s Laboratory for Laser Energetics: Student research reports

    SciTech Connect

    Grossman, P.

    1999-03-01

    The powerful lasers needed for ICF can only produce light in the infrared wavelengths. However, the one micron wavelength produced by the neodymium glass that powers OMEGA and other lasers used for fusion research does not efficiently compress the fuel pellet. This happens because the infrared light is not well absorbed by the target, and because of the creation of suprathermal electrons. These suprathermal electrons preheat the fuel, adding extra resistance to compression. To eliminate these problems associated with longer wavelengths of light, the process of frequency converting the laser beam was invented. This process efficiently converts the initial beam to a beam which has three times the frequency and one third the wavelength. The third-harmonic beam, in the UV range, has a better absorption rate. The PV-WAVE computer program that the author has written has shown that increasing the frequency of SSD (Smoothing by Spectral Dispersion) on OMEGA to approximately 10 GHz as planned will not hurt the third harmonic generation conversion efficiency significantly. The increased bandwidth and increased frequency of SSD will make the laser beams that strike the target on OMEGA much smoother and more uniform than ever before. Therefore it is both safe and advisable to add a second tripler crystal to the OMEGA system and decrease the SSD time cycle to around 100 picoseconds. Since the conversion efficiency remains high up to approximately 30 GHz, more experiments on OMEGA may be carried out with even higher modulation frequencies. These modifications to the existing OMEGA laser should make target irradiation more uniform, leading to more uniform compression and hopefully, a higher energy yield.

  11. Frequency up-conversion in nonpolar a-plane GaN/AlGaN based multiple quantum wells optimized for applications with silicon solar cells

    NASA Astrophysics Data System (ADS)

    Radosavljević, S.; Radovanović, J.; Milanović, V.; Tomić, S.

    2014-07-01

    We have described a method for structural parameters optimization of GaN/AlGaN multiple quantum well based up-converter for silicon solar cells. It involves a systematic tuning of individual step quantum wells by use of the genetic algorithm for global optimization. In quantum well structures, the up-conversion process can be achieved by utilizing nonlinear optical effects based on intersubband transitions. Both single and double step quantum wells have been tested in order to maximize the second order susceptibility derived from the density matrix formalism. The results obtained for single step wells proved slightly better and have been further pursued to obtain a more complex design, optimized for conversion of an entire range of incident photon energies.

  12. Frequency up-conversion in nonpolar a-plane GaN/AlGaN based multiple quantum wells optimized for applications with silicon solar cells

    SciTech Connect

    Radosavljević, S.; Radovanović, J. Milanović, V.; Tomić, S.

    2014-07-21

    We have described a method for structural parameters optimization of GaN/AlGaN multiple quantum well based up-converter for silicon solar cells. It involves a systematic tuning of individual step quantum wells by use of the genetic algorithm for global optimization. In quantum well structures, the up-conversion process can be achieved by utilizing nonlinear optical effects based on intersubband transitions. Both single and double step quantum wells have been tested in order to maximize the second order susceptibility derived from the density matrix formalism. The results obtained for single step wells proved slightly better and have been further pursued to obtain a more complex design, optimized for conversion of an entire range of incident photon energies.

  13. High power UV generation at 355 nm by means of extracavity frequency conversion of a high repetition rate Innoslab MOPA system

    NASA Astrophysics Data System (ADS)

    Gronloh, Bastian; Höfer, Marco; Wester, Rolf; Hoffmann, Hans-Dieter

    2009-02-01

    An Innoslab based Nd:YV04 MOPA system with pulse energy of 7.25 mJ at 40 kHz repetition rate and pulse duration of 11.4 ns has been used for third harmonics generation in Lithium Triborate (LBO) crystals. We report UV pulses of 8.9 ns duration at pulse energy of 1.65 mJ, which means an average power of 66 W. We have been able to show UV beam qualities (M2) of 1.7/2.4 (stable/instable direction with 90/10 knife edge method), while IR beam quality is 1.8/5.2. A sinc2-shape transversal distribution of beam intensity has been used in instable direction of the Innoslab MOPA system for conversion. Due to high average power and short pulse length at 355 nm the laser meets the demands for high-throughput micro material processing as stereolithography or edge isolation of solar cells. The thermal dependence of the conversion efficiency (due to heating power of the beam) has been investigated theoretically, using a time resolved numerical simulation model for the nonlinear process in both LBO crystals. Scaling effects of the absorption coefficients of LBO and the pulse power on the conversion efficiency are presented in this article.

  14. Digital optical conversion module

    DOEpatents

    Kotter, Dale K.; Rankin, Richard A.

    1991-02-26

    A digital optical conversion module used to convert an analog signal to a computer compatible digital signal including a voltage-to-frequency converter, frequency offset response circuitry, and an electrical-to-optical converter. Also used in conjunction with the digital optical conversion module is an optical link and an interface at the computer for converting the optical signal back to an electrical signal. Suitable for use in hostile environments having high levels of electromagnetic interference, the conversion module retains high resolution of the analog signal while eliminating the potential for errors due to noise and interference. The module can be used to link analog output scientific equipment such as an electrometer used with a mass spectrometer to a computer.

  15. Digital optical conversion module

    DOEpatents

    Kotter, D.K.; Rankin, R.A.

    1988-07-19

    A digital optical conversion module used to convert an analog signal to a computer compatible digital signal including a voltage-to-frequency converter, frequency offset response circuitry, and an electrical-to-optical converter. Also used in conjunction with the digital optical conversion module is an optical link and an interface at the computer for converting the optical signal back to an electrical signal. Suitable for use in hostile environments having high levels of electromagnetic interference, the conversion module retains high resolution of the analog signal while eliminating the potential for errors due to noise and interference. The module can be used to link analog output scientific equipment such as an electrometer used with a mass spectrometer to a computer. 2 figs.

  16. Digital optical conversion module

    NASA Astrophysics Data System (ADS)

    Kotter, Dale K.; Rankin, Richard A.

    1988-07-01

    A digital optical conversion module is used to convert an analog signal to a computer compatible digital signal including a voltage-to-frequency converter, frequency offset response circuitry, and an electrical-to-optical converter. Also used in conjunction with the digital optical conversion module is an optical link and an interface at the computer for converting the optical signal back to an electrical signal. Suitable for use in hostile environments having high levels of electromagnetic interference, the conversion module retains high resolution of the analog signal while eliminating the potential for errors due to noise and interference. The module can be used to link analog output scientific equipment such as an electrometer used with a mass spectrometer to a computer.

  17. Matched cascade of bandgap-shift and frequency-conversion using stimulated Raman scattering in a tapered hollow-core photonic crystal fibre.

    PubMed

    Beaudou, B; Couny, F; Wang, Y Y; Light, P S; Wheeler, N V; Gérôme, F; Benabid, F

    2010-06-01

    We report on a novel means which lifts the restriction of the limited optical bandwidth of photonic bandgap hollow-core photonic crystal fiber on generating high order stimulated Raman scattering in gaseous media. This is based on H(2)-filled tapered HC-PCF in which the taper slope is matched with the effective length of Raman process. Raman orders outside the input-bandwidth of the HC-PCF are observed with more than 80% quantum-conversion using a compact, low-power 1064 nm microchip laser. The technique opens prospects for efficient sources in spectral regions that are poorly covered by currently existing lasers such as mid-IR. PMID:20588364

  18. High resolution A/D conversion based on piecewise conversion at lower resolution

    DOEpatents

    Terwilliger, Steve

    2012-06-05

    Piecewise conversion of an analog input signal is performed utilizing a plurality of relatively lower bit resolution A/D conversions. The results of this piecewise conversion are interpreted to achieve a relatively higher bit resolution A/D conversion without sampling frequency penalty.

  19. Phase-matched frequency conversion below 150 nm in KBe2BO3F2.

    PubMed

    Nakazato, Tomoharu; Ito, Isao; Kobayashi, Yohei; Wang, Xiaoyang; Chen, Chuangtian; Watanabe, Shuntaro

    2016-07-25

    Sum frequency mixing has been demonstrated below 150 nm in KBeBO3F2 by using the fundamental with its fourth harmonic of a 6 kHz Ti: sapphire laser system. The wavelength of 149.8 nm is the shortest ever obtained to our knowledge by phase matching in nonlinear crystals. The output powers were 3.6 μW at 149.8 nm and 110 μW at 154.0 nm, respectively. The phase matching angles measured from 149.8 to 158.1 nm are larger by 3-4 degrees than those expected from the existing Sellmeier equation. The measured transmission spectra of KBeBO3F2 crystals support the generation of coherent radiation below 150 nm. PMID:27464165

  20. Bridging a few terahertz to tens of terahertz: Inspection on a cost-effective, room-temperature operated measurement system based on frequency conversion via 4-dimethylamino-N'-methyl-4'-stilbazolium tosylate crystal

    NASA Astrophysics Data System (ADS)

    Qi, Feng; Nawata, Kouji; Hayashi, Shin'ichiro; Notake, Takashi; Matsukawa, Takeshi; Minamide, Hiroaki

    2014-01-01

    Based on experimental studies, we inspected the feasibility of a frequency conversion system, including both terahertz (THz) generation and detection, by using 4-dimethylamino-N'-methy-4'-stilbazolium tosylate crystal for wideband measurement. At 27 THz, more than five orders dynamic range in power have been obtained. Compared with typical pyroelectric detectors, it is four orders better in terms of sensitivity. Power calibration has been implemented and the minimum detectable pulse energy is 3 fJ, with a corresponding noise equivalent power of 22 pW/Hz1/2. For broadband operation, we have achieved good signal level downwards to 2.5 THz. Such a system can be an excellent complement to classical time-domain spectroscopy systems.

  1. Metric Conversion

    Atmospheric Science Data Center

    2013-03-12

    ... 1,000,000 1,000,000 micrometers nano- 1,000,000,000 1,000,000,000 nanometers ... conversions, see the National Institute of Standards and Technology (NIST) Special Publications: NIST Guide to SI Units: ...

  2. Conversation Classes.

    ERIC Educational Resources Information Center

    Xia, Jiang

    1998-01-01

    Describes an activity for use in the conversational English-as-a-foreign-language classroom. The activity involves having each student say one or two sentences that continues a story being made up as the activity goes along. Students were positive about the activity, because saying only one or two sentences helped them not to feel pressured or…

  3. Conversational sensemaking

    NASA Astrophysics Data System (ADS)

    Preece, Alun; Webberley, Will; Braines, Dave

    2015-05-01

    Recent advances in natural language question-answering systems and context-aware mobile apps create opportunities for improved sensemaking in a tactical setting. Users equipped with mobile devices act as both sensors (able to acquire information) and effectors (able to act in situ), operating alone or in collectives. The currently- dominant technical approaches follow either a pull model (e.g. Apple's Siri or IBM's Watson which respond to users' natural language queries) or a push model (e.g. Google's Now which sends notifications to a user based on their context). There is growing recognition that users need more flexible styles of conversational interaction, where they are able to freely ask or tell, be asked or told, seek explanations and clarifications. Ideally such conversations should involve a mix of human and machine agents, able to collaborate in collective sensemaking activities with as few barriers as possible. Desirable capabilities include adding new knowledge, collaboratively building models, invoking specific services, and drawing inferences. As a step towards this goal, we collect evidence from a number of recent pilot studies including natural experiments (e.g. situation awareness in the context of organised protests) and synthetic experiments (e.g. human and machine agents collaborating in information seeking and spot reporting). We identify some principles and areas of future research for "conversational sensemaking".

  4. Conversational sensing

    NASA Astrophysics Data System (ADS)

    Preece, Alun; Gwilliams, Chris; Parizas, Christos; Pizzocaro, Diego; Bakdash, Jonathan Z.; Braines, Dave

    2014-05-01

    Recent developments in sensing technologies, mobile devices and context-aware user interfaces have made it pos- sible to represent information fusion and situational awareness for Intelligence, Surveillance and Reconnaissance (ISR) activities as a conversational process among actors at or near the tactical edges of a network. Motivated by use cases in the domain of Company Intelligence Support Team (CoIST) tasks, this paper presents an approach to information collection, fusion and sense-making based on the use of natural language (NL) and controlled nat- ural language (CNL) to support richer forms of human-machine interaction. The approach uses a conversational protocol to facilitate a ow of collaborative messages from NL to CNL and back again in support of interactions such as: turning eyewitness reports from human observers into actionable information (from both soldier and civilian sources); fusing information from humans and physical sensors (with associated quality metadata); and assisting human analysts to make the best use of available sensing assets in an area of interest (governed by man- agement and security policies). CNL is used as a common formal knowledge representation for both machine and human agents to support reasoning, semantic information fusion and generation of rationale for inferences, in ways that remain transparent to human users. Examples are provided of various alternative styles for user feedback, including NL, CNL and graphical feedback. A pilot experiment with human subjects shows that a prototype conversational agent is able to gather usable CNL information from untrained human subjects.

  5. AD Conversion Revisited in the Frequency Domain

    NASA Astrophysics Data System (ADS)

    Chikada, Y.

    2010-12-01

    The output of a quantizer is shown in the form of a sum of harmonics and inter-modulations, whose coefficient is also shown in an analytical form using Kummer confluent hypergeometric functions of the first kind. Methods to reduce quantization noise are also discussed.

  6. [An effect enhancement mechanism of up-conversion luminescence--up-conversion sensitization].

    PubMed

    Meng, C; Meng, G; Song, Z

    2001-04-01

    The research of frequency up-conversion has been developed greatly in recent ten years. In order to achieve its applications, it needs to enhance the up-conversion efficiency further greatly, which is the core problem of up-conversion. Because of the specialty of Yb3+ ion energy level, Yb3+ can greatly enhance up-conversion luminescence of co-doped rare earth ion activator through energy transfer. Meanwhile it may not cause the obvious fluorescence quenching. Thus it is very significance to investigate up-conversion sensitization which Yb3+ ion acts as a sensitizer. It is more important that it is quite urgent to combine up-conversion efficiency and material property to develop up-conversion. This paper reviews the proposing and developing process of up-conversion sensitization. The achievement of up-conversion sensitization field especial the originate fruit in indirect up-conversion sensitization obtained by China are introduce emphatically. PMID:12947606

  7. Mid-IR Kerr-lens mode-locked polycrystalline Cr:ZnS and Cr:ZnSe lasers with intracavity frequency conversion via random quasi-phase-matching

    NASA Astrophysics Data System (ADS)

    Vasilyev, Sergey; Moskalev, Igor; Mirov, Mike; Smolski, Viktor; Mirov, Sergey; Gapontsev, Valentin

    2016-03-01

    Cr2+ doped ZnS and ZnSe possess a unique blend of physical, spectroscopic, and technological parameters. These laser materials feature ultra-broadband gain in 1.9 - 3.3 μm mid-IR range, low saturation intensities, and large pump absorption coefficients. The II-VI semiconductor hosts provide a low phonon cut-off, broad IR transparency, and high second and third order nonlinearity. Cr:ZnS and Cr:ZnSe are available in polycrystalline form: the material consists of a multitude of microscopic single-crystal grains with a broad distribution of grain sizes and orientations, which results in random quasi-phase-matching (RQPM). The distinctive features of RQPM are a linear dependence of the conversion yield with length of the medium and ultra-wide bandwidth of three-wave mixing. We review resent experimental results on optically pumped mid-IR ultrafast lasers based on polycrystalline Cr:ZnS and Cr:ZnSe. We demonstrate that Kerrlens mode-locking of polycrystalline Cr:ZnS and Cr:ZnSe lasers allow for generation of few-cycle mid-IR pulses with MW-level peak power. This opens several avenues for efficient nonlinear frequency conversion of short optical pulses directly in the laser gain medium via RQPM process. We implemented Kerr-lens mode-locked Cr:ZnS oscillators, which feature high power (up to 0.25 W), spectrally broad (up to 22 THz) second harmonic generation (SHG) in the laser medium. We also demonstrate simple and robust ultrafast source based on single-pass continuously pumped polycrystalline Cr:ZnS laser amplifier: mid-IR pulses with 6.8 W average power and the spectrum spanning 2.0-2.6 μm as well as SHG pulses with 0.52 W average power and 1.05 - 1.25 μm spectral span were obtained.

  8. Converse Piezoelectricity

    NASA Astrophysics Data System (ADS)

    Springborg, Michael; Kirtman, Bernard

    2013-03-01

    Piezoelectricity results from a coupling between responses to mechanical and electric perturbations and leads to changes in the polarization due to strain or stress or, alternatively, the occurrence of strain as a function of an applied external, electrostatic field (i.e., converse piezoelectricity). Theoretical studies of those properties for extended systems require accordingly that their dipole moment or polarization can be calculated. However, whereas the definition of the operator for the dipole moment for any finite system is trivial, it is only within the last 2 decades that the expressions for the equivalent operator in the independent-particle approximation for the infinite and periodic system have been presented. Here, we demonstrate that the so called branch dependence of the polarization for the infinite, periodic system is related to physical observables in contrast to what often is assumed. This is related to the finding that converse piezoelectric properties depend both on the surfaces of the samples of interest even for samples with size well above the thermodynamic limit. However, we shall demonstrate that these properties can be calculated without explicitly taking the surfaces into account. Both the foundations and results for real system shall be presented.

  9. Energy conversion

    SciTech Connect

    Woodall, J.M.

    1982-02-16

    Energy conversion capable of receiving input energy in thermal or radiant form at a variable rate and releasing energy in thermal, radiant or electrical form independent of rate is accomplished by providing a buffer member of a material that has three criteria: a melting temperature above 1300/sup degree/ K, a thermal conductance greater than 0.1 in calories per square centimeter per centimeter per degree per second and a latent heat of fusion of the order of 1 kilocalorie per mole. The converter can absorb energy of multiple types, store it and then release it in a form compatible with the prospective use. Sunlight of daylight duration and varying intensity is converted to steady 24 hour a day electrical output.

  10. Conversion of Questionnaire Data

    SciTech Connect

    Powell, Danny H; Elwood Jr, Robert H

    2011-01-01

    During the survey, respondents are asked to provide qualitative answers (well, adequate, needs improvement) on how well material control and accountability (MC&A) functions are being performed. These responses can be used to develop failure probabilities for basic events performed during routine operation of the MC&A systems. The failure frequencies for individual events may be used to estimate total system effectiveness using a fault tree in a probabilistic risk analysis (PRA). Numeric risk values are required for the PRA fault tree calculations that are performed to evaluate system effectiveness. So, the performance ratings in the questionnaire must be converted to relative risk values for all of the basic MC&A tasks performed in the facility. If a specific material protection, control, and accountability (MPC&A) task is being performed at the 'perfect' level, the task is considered to have a near zero risk of failure. If the task is performed at a less than perfect level, the deficiency in performance represents some risk of failure for the event. As the degree of deficiency in performance increases, the risk of failure increases. If a task that should be performed is not being performed, that task is in a state of failure. The failure probabilities of all basic events contribute to the total system risk. Conversion of questionnaire MPC&A system performance data to numeric values is a separate function from the process of completing the questionnaire. When specific questions in the questionnaire are answered, the focus is on correctly assessing and reporting, in an adjectival manner, the actual performance of the related MC&A function. Prior to conversion, consideration should not be given to the numeric value that will be assigned during the conversion process. In the conversion process, adjectival responses to questions on system performance are quantified based on a log normal scale typically used in human error analysis (see A.D. Swain and H.E. Guttmann

  11. Mode conversion in ITER

    NASA Astrophysics Data System (ADS)

    Jaeger, E. F.; Berry, L. A.; Myra, J. R.

    2006-10-01

    Fast magnetosonic waves in the ion cyclotron range of frequencies (ICRF) can convert to much shorter wavelength modes such as ion Bernstein waves (IBW) and ion cyclotron waves (ICW) [1]. These modes are potentially useful for plasma control through the generation of localized currents and sheared flows. As part of the SciDAC Center for Simulation of Wave-Plasma Interactions project, the AORSA global-wave solver [2] has been ported to the new, dual-core Cray XT-3 (Jaguar) at ORNL where it demonstrates excellent scaling with the number of processors. Preliminary calculations using 4096 processors have allowed the first full-wave simulations of mode conversion in ITER. Mode conversion from the fast wave to the ICW is observed in mixtures of deuterium, tritium and helium3 at 53 MHz. The resulting flow velocity and electric field shear will be calculated. [1] F.W. Perkins, Nucl. Fusion 17, 1197 (1977). [2] E.F. Jaeger, L.A. Berry, J.R. Myra, et al., Phys. Rev. Lett. 90, 195001-1 (2003).

  12. Document Conversion Methodology.

    ERIC Educational Resources Information Center

    Bovee, Donna

    1990-01-01

    Discusses digital imaging technology and examines document database conversion considerations. Two types of document imaging systems are described: (1) a work in process system, and (2) a storage and retrieval system. Conversion methodology is outlined, and a document conversion scenario is presented as a practical guide to conversion. (LRW)

  13. Pashto Conversation Manual and Pashto Conversation Tapescript.

    ERIC Educational Resources Information Center

    Tegey, Habibullah; Robson, Barbara

    This conversation manual and tapescript are part of a set of materials that have been developed to teach oral and written Afghan Pashto to English speakers. In addition to the conversation manual and tapescript, the set consists of a beginning textbook, an intermediate textbook, a reader, and a set of taped lessons that correlate with the…

  14. Biotechnology of biomass conversion

    SciTech Connect

    Wayman, M.; Parekh, S.R.

    1990-01-01

    This book covers: An introduction to biomass crops; The microbiology of fermentation processes; The production of ethanol from biomass crops, such as sugar cane and rubbers; The energy of biomass conversion; and The economics of biomass conversion.

  15. Frequency-Shift Hearing Aid

    NASA Technical Reports Server (NTRS)

    Weinstein, Leonard M.

    1994-01-01

    Proposed hearing aid maps spectrum of speech into band of lower frequencies at which ear remains sensitive. By redirecting normal speech frequencies into frequency band from 100 to 1,500 Hz, hearing aid allows people to understand normal conversation, including telephone calls. Principle operation of hearing aid adapted to other uses such as, clearing up noisy telephone or radio communication. In addition, loud-speakers more easily understood in presence of high background noise.

  16. Direct Conversion of Energy.

    ERIC Educational Resources Information Center

    Corliss, William R.

    This publication is one of a series of information booklets for the general public published by the United States Atomic Energy Commission. Direct energy conversion involves energy transformation without moving parts. The concepts of direct and dynamic energy conversion plus the laws governing energy conversion are investigated. Among the topics…

  17. Frequency-bin entangled photons

    SciTech Connect

    Olislager, L.; Emplit, P.; Nguyen, A. T.; Massar, S.; Merolla, J.-M.; Huy, K. Phan

    2010-07-15

    A monochromatic laser pumping a parametric down-conversion crystal generates frequency-entangled photon pairs. We study this experimentally by addressing such frequency-entangled photons at telecommunication wavelengths (around 1550 nm) with fiber-optics components such as electro-optic phase modulators and narrow-band frequency filters. The theory underlying our approach uses the notion of frequency-bin entanglement. Our results show that the phase modulators address coherently up to eleven frequency bins, leading to an interference pattern which can violate by more than five standard deviations a Bell inequality adapted to our setup.

  18. Iterated multidimensional wave conversion

    NASA Astrophysics Data System (ADS)

    Brizard, A. J.; Tracy, E. R.; Johnston, D.; Kaufman, A. N.; Richardson, A. S.; Zobin, N.

    2011-12-01

    Mode conversion can occur repeatedly in a two-dimensional cavity (e.g., the poloidal cross section of an axisymmetric tokamak). We report on two novel concepts that allow for a complete and global visualization of the ray evolution under iterated conversions. First, iterated conversion is discussed in terms of ray-induced maps from the two-dimensional conversion surface to itself (which can be visualized in terms of three-dimensional rooms). Second, the two-dimensional conversion surface is shown to possess a symplectic structure derived from Dirac constraints associated with the two dispersion surfaces of the interacting waves.

  19. Effects of conversation interference on annoyance due to aircraft noise

    NASA Technical Reports Server (NTRS)

    Key, K. F.; Powell, C. A.

    1980-01-01

    The annoyance and interference effects of aircraft flyover noise on face to face conversation were investigated. Twenty 5 minute sessions, each composed of three flyovers, were presented to each of 20 pairs of female subjects in a simulated living room. Flyovers varied in peak noise level (55-79 dB, A-weighted) and spectrum (low or high frequency components). Subjects engaged in conversation for 10 sessions and in reverie for the other 10 sessions, and completed subjective ratings following every session. Annoyance was affected by noise level, but was not significantly different for the two activities of reverie and conversation. A noise level of 77 db was found unacceptable for conversation by 50 percent of the subjects. Conversation interference was assessed by incidence of increased vocal effort and/or interruption of conversation during flyovers. Although conversation interference increased with noise level, the conversation interference measures did not improve prediction of individual annoyance judgments.

  20. Frequency curves

    USGS Publications Warehouse

    Riggs, H.C.

    1968-01-01

    This manual describes graphical and mathematical procedures for preparing frequency curves from samples of hydrologic data. It also discusses the theory of frequency curves, compares advantages of graphical and mathematical fitting, suggests methods of describing graphically defined frequency curves analytically, and emphasizes the correct interpretations of a frequency curve.

  1. Enhanced 2 μm broad-band emission and NIR to visible frequency up-conversion from Ho3+/Yb3+ co-doped Bi2O3-GeO2-ZnO glasses.

    PubMed

    Biswas, Kaushik; Sontakke, Atul D; Sen, R; Annapurna, K

    2013-08-01

    In this work, a new and non-conventional oxide glass composition based on Bi2O3-GeO2-ZnO system has been formulated with an aim to realize low phonon oxide glass and elucidate its performance when co-doped with Ho(3+)/Yb(3+) for the energy transfer based NIR emission at 2 μm from Ho(3+) ions under Yb(3+) excitation. The glass with 1.0 mol% Ho2O3 and 0.5 mol% Yb2O3 has exhibited maximum energy transfer rate (3602 s(-1)) and energy transfer efficiency (65.92%). Important radiative properties have been predicted for emission transitions of Ho(3+) ions using intensity parameters derived from measured absorption spectra using standard Judd-Ofelt theory. At lower acceptor ion concentration (0.1 mol%), an efficient NIR to visible up-conversion emission has been observed based on two photon absorption process which has found to be reduced significantly at higher Ho(3+) concentrations with simultaneous enhancement in 2 μm emission. Hence, this newly developed glass codoped with Yb(3+)/Ho(3+) is promising glass for sensitized 2 μm emission applications as broad band tunable lasers because of the combination of low phonon energy (707 cm(-1)), high energy transfer efficiency, moderately high emission cross-section (5.33×10(-21) cm(2)) and larger effective half-width of the emission band value of 169 nm. PMID:23685797

  2. [Cutaneous allergen test in children: frequency of conversion of prick-test reactions, IgE concentrations in serum and course of the disease in young asthmatics during or without treatment with "Dinatrium cromoglicicum" inhalation (author's transl)].

    PubMed

    Arndt, M

    1975-11-01

    Among 62 children with asthma or/and hay fever 32 were treated symptomatically. 30 were treated with DNCG inhalations. 22 asthmatics with proved inhalation-allergy responded well or very well to DNCG inhalations, 3 others only fairly. Of 5 patients without proved allergy 4 showed a fair response, 1 none. In group I (without DNCG) 4 out of 20 negative prick-tests became definitely positive at a follow-up examination, in group II (with DNCG) 9 out of 14. The follow-up examinations tended to be done during a time when symptoms were reduced or absent. In group II there were 7 of 9 children with good effect of DNCG. IgE assays in serum were clearly lower in "non-allergics" than in sensitized patients. The IgE was raised only in children where the follow-up showed a positive reaction. One might assume that when the clinical symptoms improve, IgE or mediator substances in the tissues, particularly in mast cells, are accumulated so that cutaneous skin-reactions now become clearly positive. IgE concentration in serum did not show correlated changes. Assessment of the clinical course of the illness apart, conversion of prick testing might indicate protective action of DNCG inhalations in bronchial asthma due to inhalation allergy. PMID:814366

  3. Conversing with Computers

    NASA Technical Reports Server (NTRS)

    2004-01-01

    I/NET, Inc., is making the dream of natural human-computer conversation a practical reality. Through a combination of advanced artificial intelligence research and practical software design, I/NET has taken the complexity out of developing advanced, natural language interfaces. Conversational capabilities like pronoun resolution, anaphora and ellipsis processing, and dialog management that were once available only in the laboratory can now be brought to any application with any speech recognition system using I/NET s conversational engine middleware.

  4. Oxidative methane conversion in dielectric barrier discharge

    NASA Astrophysics Data System (ADS)

    Krawczyk, Krzysztof; Młotek, Michał; Ulejczyk, Bogdan; Pryciak, Krzysztof; Schmidt-Szałowski, Krzysztof

    2013-02-01

    A dielectric barrier discharge was used for the oxidative coupling of methane (OCM) with oxygen at the pressure of 1.2 bar. A dielectric barrier discharge (DBD) reactor was powered at the frequency of about 6 kHz. Molar ratio CH4/O2 in the inlet gas containing 50% or 25% of argon was 3, 6 and 12. The effects of temperature (110, 150 and 340 ◦C), gas flow rate, molar ratio of methane to oxygen on the overall methane and oxygen conversion and methane conversion to methanol, ethanol, hydrocarbons, carbon oxides and water were studied. In the studied system the increase of the temperature decreases the conversion of methane to methanol. The increase of the molar ratio of methane to oxygen increased the methane conversion to hydrocarbons and strongly decreased the methane conversion to alcohols. The conversion of methane to hydrocarbons increased and the conversion of methane to methanol decreased with the decrease of the gas flow rate from 2 to 1 NL/h. Contribution to the Topical Issue "13th International Symposium on High Pressure Low Temperature Plasma Chemistry (Hakone XIII)", Edited by Nicolas Gherardi, Henryca Danuta Stryczewska and Yvan Ségui.

  5. 0.5W CW single frequency blue at 486 nm via SHG with net conversion of 81.5% from the NIR using a 30mm PPMgO:SLT crystal in a resonant cavity

    NASA Astrophysics Data System (ADS)

    Khademian, Ali; Jadhav, Shilpa; Shiner, David

    2015-02-01

    A single frequency fiber Bragg grating (FBG) stabilized laser at 972 nm is coupled into a doubling ring cavity with an optical length of 138 mm, a 91% input coupler, a 30 mm long Brewster cut magnesium doped periodically poled lithium tantalate (PPMgO:SLT) crystal and a high reflector. The cavity buildup is 37 and loss is 0.63%. The cavity is monitored, controlled and locked with a single chip processor. With IR power of 572 mW in the input fiber, 466 mW blue output is obtained, giving 81.5% net efficiency. The blue and IR beams are separated by refraction at the crystal's Brewster surface with negligible loss and without the need for dichroic optics.

  6. Mid-infrared frequency combs

    NASA Astrophysics Data System (ADS)

    Schliesser, Albert; Picqué, Nathalie; Hänsch, Theodor W.

    2012-07-01

    Laser frequency combs are coherent light sources that emit a broad spectrum of discrete, evenly spaced narrow lines whose absolute frequency can be measured to within the accuracy of an atomic clock. Their development in the near-infrared and visible domains has revolutionized frequency metrology while also providing numerous unexpected opportunities in other fields such as astronomy and attosecond science. Researchers are now exploring how to extend frequency comb techniques to the mid-infrared spectral region. Versatile mid-infrared frequency comb generators based on novel laser gain media, nonlinear frequency conversion or microresonators promise to significantly expand the applications of frequency combs. In particular, novel approaches to molecular spectroscopy in the 'fingerprint region', with dramatically improved precision, sensitivity, recording time and/or spectral bandwidth may lead to new discoveries in the various fields relevant to molecular science.

  7. NUCLEAR CONVERSION APPARATUS

    DOEpatents

    Seaborg, G.T.

    1960-09-13

    A nuclear conversion apparatus is described which comprises a body of neutron moderator, tubes extending therethrough, uranium in the tubes, a fluid- circulating system associated with the tubes, a thorium-containing fluid coolant in the system and tubes, and means for withdrawing the fluid from the system and replacing it in the system whereby thorium conversion products may be recovered.

  8. Common conversion factors.

    PubMed

    2001-05-01

    This appendix presents tables of some of the more common conversion factors for units of measure used throughout Current Protocols manuals, as well as prefixes indicating powers of ten for SI units. Another table gives conversions between temperatures on the Celsius (Centigrade) and Fahrenheit scales. PMID:18770653

  9. Marathi Conversational Situations.

    ERIC Educational Resources Information Center

    Berntsen, Maxine; Nimbkar, Jai

    This volume is an elementary Marathi conversation text for adult learners of Marathi, both foreign and Indian. Designed to be used in conjunction with "Marathi Structural Patterns. Book One," the volume presents over 80 conversations that include material required in everyday situations. Each section contains basic and more difficult…

  10. Energy conversion alternatives study

    NASA Technical Reports Server (NTRS)

    Shure, L. T.

    1979-01-01

    Comparison of coal based energy systems is given. Study identifies and compares various advanced energy conversion systems using coal or coal derived fuels for baselaoad electric power generation. Energy Conversion Alternatives Study (ECAS) reports provede government, industry, and general public with technically consistent basis for comparison of system's options of interest for fossilfired electric-utility application.

  11. Assessment through Conversation.

    ERIC Educational Resources Information Center

    Fu, Danling; Lamme, Linda L.

    2002-01-01

    Presents conversations with parents, teachers, and children around portfolios that provide a better picture of a child's growth and understanding than standardized test scores ever can. Concludes that the involvement of students, teachers, and parents in conversation about children's literacy development brings the potential of a common vision and…

  12. Changing Our Conversations

    ERIC Educational Resources Information Center

    Porto, Mark

    2007-01-01

    In this article, a principal is inspired to change the conversations with students and staff members from discipline and deficit to hope and planning for future achievement. He wants conversations to be more about academic goals and decision making and less about discipline and random acceptance of postsecondary plans. He has asked all staff…

  13. Potassium plasma cell facilitates thermionic energy conversion process

    NASA Technical Reports Server (NTRS)

    Richards, H. K.

    1967-01-01

    Thermionic energy converter converts nuclear generated heat directly into high frequency and direct current output. It consists of a potassium plasma cell, a tantalum emitter, and a silver plated copper collector. This conversion process eliminates the steam interface usually required between the atomic heat source and the electrical conversion system.

  14. Frequency Combs

    NASA Astrophysics Data System (ADS)

    Hänsch, Theodor W.; Picqué, Nathalie

    Much of modern research in the field of atomic, molecular, and optical science relies on lasers, which were invented some 50 years ago and perfected in five decades of intense research and development. Today, lasers and photonic technologies impact most fields of science and they have become indispensible in our daily lives. Laser frequency combs were conceived a decade ago as tools for the precision spectroscopy of atomic hydrogen. Through the development of optical frequency comb techniques, technique a setup of the size 1 ×1 m2, good for precision measurements of any frequency, and even commercially available, has replaced the elaborate previous frequency-chain schemes for optical frequency measurements, which only worked for selected frequencies. A true revolution in optical frequency measurements has occurred, paving the way for the creation of all-optical clocks clock with a precision that might approach 10-18. A decade later, frequency combs are now common equipment in all frequency metrology-oriented laboratories. They are also becoming enabling tools for an increasing number of applications, from the calibration of astronomical spectrographs to molecular spectroscopy. This chapter first describes the principle of an optical frequency comb synthesizer. Some of the key technologies to generate such a frequency comb are then presented. Finally, a non-exhaustive overview of the growing applications is given.

  15. Postoperative conversion disorder.

    PubMed

    Afolabi, Kola; Ali, Sameer; Gahtan, Vivian; Gorji, Reza; Li, Fenghua; Nussmeier, Nancy A

    2016-05-01

    Conversion disorder is a psychiatric disorder in which psychological stress causes neurologic deficits. A 28-year-old female surgical patient had uneventful general anesthesia and emergence but developed conversion disorder 1 hour postoperatively. She reported difficulty speaking, right-hand numbness and weakness, and right-leg paralysis. Neurologic examination and imaging revealed no neuronal damage, herniation, hemorrhage, or stroke. The patient mentioned failing examinations the day before surgery and discontinuing her prescribed antidepressant medication, leading us to diagnose conversion disorder, with eventual confirmation by neuroimaging and follow-up examinations. PMID:27041258

  16. Responsive Teaching through Conversation

    ERIC Educational Resources Information Center

    Dozier, Cheryl; Garnett, Susan; Tabatabai, Simeen

    2011-01-01

    Conversations are the heart of responsive teaching. By talking with struggling learners, teachers can find out about their interests in order to design effective, personalized instruction; build relationships; work through complexities in teaching and learning; and celebrate successes.

  17. Structured luminescence conversion layer

    DOEpatents

    Berben, Dirk; Antoniadis, Homer; Jermann, Frank; Krummacher, Benjamin Claus; Von Malm, Norwin; Zachau, Martin

    2012-12-11

    An apparatus device such as a light source is disclosed which has an OLED device and a structured luminescence conversion layer deposited on the substrate or transparent electrode of said OLED device and on the exterior of said OLED device. The structured luminescence conversion layer contains regions such as color-changing and non-color-changing regions with particular shapes arranged in a particular pattern.

  18. Conversion of solar energy

    NASA Astrophysics Data System (ADS)

    Semenov, N. N.; Shilov, A. E.

    The papers presented in this volume provide an overview of current theoretical and experimental research related to the conversion and practical utilization of solar energy. Topics discussed include semiconductor photovoltaic cells, orbital solar power stations, chemical and biological methods of solar energy conversion, and solar energy applications. Papers are included on new theoretical models of solar cells and prospects for increasing their efficiency, metrology and optical studies of solar cells, and some problems related to the thermally induced deformations of large space structures.

  19. Conversational Flow Promotes Solidarity

    PubMed Central

    Koudenburg, Namkje; Postmes, Tom; Gordijn, Ernestine H.

    2013-01-01

    Social interaction is fundamental to the development of various aspects of “we-ness”. Previous research has focused on the role the content of interaction plays in establishing feelings of unity, belongingness and shared reality (a cluster of variables referred to as solidarity here). The present paper is less concerned with content, but focuses on the form of social interaction. We propose that the degree to which conversations flow smoothly or not is, of itself, a cue to solidarity. We test this hypothesis in samples of unacquainted and acquainted dyads who communicate via headsets. Conversational flow is disrupted by introducing a delay in the auditory feedback (vs. no delay). Results of three studies show that smoothly coordinated conversations (compared with disrupted conversations and a control condition) increase feelings of belonging and perceptions of group entitativity, independently of conversation content. These effects are driven by the subjective experience of conversational flow. Our data suggest that this process occurs largely beyond individuals' control. We conclude that the form of social interaction is a powerful cue for inferring group solidarity. Implications for the impact of modern communication technology on developing a shared social identity are discussed. PMID:24265683

  20. Astrophysicists' conversational connections on Twitter.

    PubMed

    Holmberg, Kim; Bowman, Timothy D; Haustein, Stefanie; Peters, Isabella

    2014-01-01

    Because Twitter and other social media are increasingly used for analyses based on altmetrics, this research sought to understand what contexts, affordance use, and social activities influence the tweeting behavior of astrophysicists. Thus, the presented study has been guided by three research questions that consider the influence of astrophysicists' activities (i.e., publishing and tweeting frequency) and of their tweet construction and affordance use (i.e. use of hashtags, language, and emotions) on the conversational connections they have on Twitter. We found that astrophysicists communicate with a variety of user types (e.g. colleagues, science communicators, other researchers, and educators) and that in the ego networks of the astrophysicists clear groups consisting of users with different professional roles can be distinguished. Interestingly, the analysis of noun phrases and hashtags showed that when the astrophysicists address the different groups of very different professional composition they use very similar terminology, but that they do not talk to each other (i.e. mentioning other user names in tweets). The results also showed that in those areas of the ego networks that tweeted more the sentiment of the tweets tended to be closer to neutral, connecting frequent tweeting with information sharing activities rather than conversations or expressing opinions. PMID:25153196

  1. Astrophysicists’ Conversational Connections on Twitter

    PubMed Central

    Holmberg, Kim; Bowman, Timothy D.; Haustein, Stefanie; Peters, Isabella

    2014-01-01

    Because Twitter and other social media are increasingly used for analyses based on altmetrics, this research sought to understand what contexts, affordance use, and social activities influence the tweeting behavior of astrophysicists. Thus, the presented study has been guided by three research questions that consider the influence of astrophysicists’ activities (i.e., publishing and tweeting frequency) and of their tweet construction and affordance use (i.e. use of hashtags, language, and emotions) on the conversational connections they have on Twitter. We found that astrophysicists communicate with a variety of user types (e.g. colleagues, science communicators, other researchers, and educators) and that in the ego networks of the astrophysicists clear groups consisting of users with different professional roles can be distinguished. Interestingly, the analysis of noun phrases and hashtags showed that when the astrophysicists address the different groups of very different professional composition they use very similar terminology, but that they do not talk to each other (i.e. mentioning other user names in tweets). The results also showed that in those areas of the ego networks that tweeted more the sentiment of the tweets tended to be closer to neutral, connecting frequent tweeting with information sharing activities rather than conversations or expressing opinions. PMID:25153196

  2. Isomolybdate conversion coatings

    NASA Technical Reports Server (NTRS)

    Minevski, Zoran (Inventor); Maxey, Jason (Inventor); Nelson, Carl (Inventor); Eylem, Cahit (Inventor)

    2002-01-01

    A conversion coating solution and process forms a stable and corrosion-resistant layer on metal substrates or layers or, more preferably, on a boehmite layer or other base conversion coating. The conversion coating process involves contacting the substrate, layer or coating with an aqueous alkali metal isomolybdate solution in order to convert the surface of the substrate, layer or coating to a stable conversion coating. The aqueous alkali metal molybdates are selected from sodium molybdate (Na.sub.2 MoO.sub.4), lithium molybdate (Li.sub.2 MoO.sub.4), potassium molybdate (K.sub.2 MoO.sub.4), or combinations thereof, with the most preferred alkali metal molybdate being sodium molybdate. The concentration of alkali metal molybdates in the solution is preferably less than 5% by weight. In addition to the alkali metal molybdates, the conversion coating solution may include alkaline metal passivators selected from lithium nitrate (LiNO.sub.3), sodium nitrate (NaNO.sub.3), ammonia nitrate (NH.sub.4 NO.sub.3), and combinations thereof; lithium chloride, potassium hexafluorozirconate (K.sub.2 ZrF.sub.6) or potassium hexafluorotitanate (K.sub.2 TiF.sub.6).

  3. Laser energy conversion

    NASA Technical Reports Server (NTRS)

    Jalufka, N. W.

    1989-01-01

    The conversion of laser energy to other, more useful, forms is an important element of any space power transmission system employing lasers. In general the user, at the receiving sight, will require the energy in a form other than laser radiation. In particular, conversion to rocket power and electricity are considered to be two major areas where one must consider various conversion techniques. Three systems (photovoltaic cells, MHD generators, and gas turbines) have been identified as the laser-to-electricity conversion systems that appear to meet most of the criteria for a space-based system. The laser thruster also shows considerable promise as a space propulsion system. At this time one cannot predict which of the three laser-to-electric converters will be best suited to particular mission needs. All three systems have some particular advantages, as well as disadvantages. It would be prudent to continue research on all three systems, as well as the laser rocket thruster. Research on novel energy conversion systems, such as the optical rectenna and the reverse free-electron laser, should continue due to their potential for high payoff.

  4. Volterra series modeling of power conversion systems

    SciTech Connect

    Tymerski, R. )

    1991-10-01

    This paper reports that the nonlinear control-to-output response of pulse-width modulated (PWM) conversion system is modeled via the Volterra functional series. The determination of the Volterra kernels in the transform domain is performed on a simplified state space model of the converter. The dominant component of various harmonic and intermodulation distortion frequency products in the output spectrum are derived and are expressed in terms of these kernels. Experimental results are presented confirming the modeling procedure.

  5. Direct conversion technology

    NASA Technical Reports Server (NTRS)

    Massier, Paul F.; Bankston, C. P.; Williams, R.; Underwood, M.; Jeffries-Nakamura, B.; Fabris, G.

    1989-01-01

    The overall objective of the Direct Conversion Technology task is to develop an experimentally verified technology base for promising direct conversion systems that have potential application for energy conservation in the end-use sectors. This report contains progress of research on the Alkali Metal Thermal-to-Electric Converter (AMTEC), and on the Two-Phase Liquid-Metal Magnetohydrodynamic Electrical Generator (LMMHD) for the period January 1, 1989 through December 31, 1989. Research on these concepts was initiated during October 1987. Reports prepared on previous occasions contain discussions on the following other direct conversion concepts: thermoelectric, pyroelectric, thermionic, thermophotovoltaic, thermoacoustic, thermomagnetic, thermoelastic (nitinol heat engines); and also, more complete discussions of AMTEC and LMMHD systems.

  6. Direct conversion technology

    SciTech Connect

    Massier, P.F.; Back, L.H.; Ryan, M.A.; Fabris, G.

    1992-01-07

    The overall objective of the Direct Conversion Technology task is to develop an experimentally verified technology base for promising direct conversion systems that have potential application for energy conservation in the end-use sectors. This report contains progress of research on the Alkali Metal Thermal-to-Electric Converter (AMTEC) and on the Two-Phase Liquid-Metal MHD Electrical Generator (LMMHD) for the period January 1, 1991 through December 31, 1991. Research on AMTEC and on LMMHD was initiated during October 1987. Reports prepared on previous occasions (Refs. 1--5) contain descriptive and performance discussions of the following direct conversion concepts: thermoelectric, pyroelectric, thermionic, thermophotovoltaic, thermoacoustic, thermomagnetic, thermoelastic (Nitionol heat engine); and also, more complete descriptive discussions of AMTEC and LMMHD systems.

  7. Direct conversion technology

    NASA Astrophysics Data System (ADS)

    Massier, Paul F.; Bankston, C. P.; Williams, R.; Underwood, M.; Jeffries-Nakamura, B.; Fabris, G.

    1989-12-01

    The overall objective of the Direct Conversion Technology task is to develop an experimentally verified technology base for promising direct conversion systems that have potential application for energy conservation in the end-use sectors. This report contains progress of research on the Alkali Metal Thermal-to-Electric Converter (AMTEC), and on the Two-Phase Liquid-Metal Magnetohydrodynamic Electrical Generator (LMMHD) for the period January 1, 1989 through December 31, 1989. Research on these concepts was initiated during October 1987. Reports prepared on previous occasions contain discussions on the following other direct conversion concepts: thermoelectric, pyroelectric, thermionic, thermophotovoltaic, thermoacoustic, thermomagnetic, thermoelastic (nitinol heat engines); and also, more complete discussions of AMTEC and LMMHD systems.

  8. Predictability of Conversation Partners

    NASA Astrophysics Data System (ADS)

    Takaguchi, Taro; Nakamura, Mitsuhiro; Sato, Nobuo; Yano, Kazuo; Masuda, Naoki

    2011-08-01

    Recent developments in sensing technologies have enabled us to examine the nature of human social behavior in greater detail. By applying an information-theoretic method to the spatiotemporal data of cell-phone locations, [C. Song , ScienceSCIEAS0036-8075 327, 1018 (2010)] found that human mobility patterns are remarkably predictable. Inspired by their work, we address a similar predictability question in a different kind of human social activity: conversation events. The predictability in the sequence of one’s conversation partners is defined as the degree to which one’s next conversation partner can be predicted given the current partner. We quantify this predictability by using the mutual information. We examine the predictability of conversation events for each individual using the longitudinal data of face-to-face interactions collected from two company offices in Japan. Each subject wears a name tag equipped with an infrared sensor node, and conversation events are marked when signals are exchanged between sensor nodes in close proximity. We find that the conversation events are predictable to a certain extent; knowing the current partner decreases the uncertainty about the next partner by 28.4% on average. Much of the predictability is explained by long-tailed distributions of interevent intervals. However, a predictability also exists in the data, apart from the contribution of their long-tailed nature. In addition, an individual’s predictability is correlated with the position of the individual in the static social network derived from the data. Individuals confined in a community—in the sense of an abundance of surrounding triangles—tend to have low predictability, and those bridging different communities tend to have high predictability.

  9. Direct Conversion Technology

    SciTech Connect

    Back, L.H.; Fabris, G.; Ryan, M.A.

    1992-07-01

    The overall objective of the Direct Conversion Technology task is to develop an experimentally verified technology base for promising direct conversion systems that have potential application for energy conservation in the end-use sectors. Initially, two systems were selected for exploratory research and advanced development. These are Alkali Metal Thermal-to-Electric Converter (AMTEC) and Two-Phase Liquid Metal MD Generator (LMMHD). This report describes progress that has been made during the first six months of 1992 on research activities associated with these two systems. (GHH)

  10. Accessory apartment conversion programs.

    PubMed

    Retsinas, J; Retsinas, N P

    1991-01-01

    In recent years, state housing finance agencies have joined with state units on aging to develop programs to help the frail, elderly homeowner. Under an accessory apartment conversion program, a low-income homeowner will borrow money at a reduced interest rate to underwrite conversion of excess space into a rental apartment. The tenant will provide additional income as well as, ideally, certain kinds of personal assistance and a friendly presence. To date, few elderly clients have used this option. The initial rationale for the program is explained as are plausible reasons for the fact that it has not met expectations. PMID:10186784