Showing papers on "Pulse duration published in 2010"
TL;DR: This Letter reports on the generation of 830 W compressed average power from a femtosecond fiber chirped pulse amplification (CPA) system and discusses further a scaling potential toward and beyond the kilowatt level by overcoming the current scaling limitations imposed by the transversal spatial hole burning.
Abstract: In this Letter we report on the generation of 830 W compressed average power from a femtosecond fiber chirped pulse amplification (CPA) system In the high-power operation we achieved a compressor throughput of about 90% by using high-efficiency dielectric gratings The output pulse duration of 640 fs at 78 MHz repetition rate results in a peak power of 12 MW Additionally, we discuss further a scaling potential toward and beyond the kilowatt level by overcoming the current scaling limitations imposed by the transversal spatial hole burning
559 citations
TL;DR: In this paper, the formation of nearly wavelength-sized laser-induced periodic surface structures (LIPSS) on single-crystalline silicon upon irradiation with single (N=1) and multiple (N≤1000) linearly polarized femtosecond (fs) laser pulses (pulse duration τ=130 fs, central wavelength λ=800 nm) in air is studied experimentally.
Abstract: The formation of nearly wavelength-sized laser-induced periodic surface structures (LIPSS) on single-crystalline silicon upon irradiation with single (N=1) and multiple (N≤1000) linearly polarized femtosecond (fs) laser pulses (pulse duration τ=130 fs, central wavelength λ=800 nm) in air is studied experimentally. Scanning electron microscopy (SEM) and optical microscopy are used for imaging of the ablated surface morphologies, both revealing LIPSS with periodicities close to the laser wavelength and an orientation always perpendicular to the polarization of the fs-laser beam. It is experimentally demonstrated that these LIPSS can be formed in silicon upon irradiation by single fs-laser pulses—a result that is additionally supported by a recent theoretical model. Two-dimensional Fourier transforms of the SEM images allow the detailed analysis of the distribution of the spatial frequencies of the LIPSS and indicate, at a fixed peak fluence, a monotonous decrease in their mean spatial period between ∼770 nm...
320 citations
TL;DR: In this paper, a femtosecond erbium-doped fiber-optic laser was used to produce single-cycle light pulses with a pulse duration of 4.3
Abstract: The advent of self-referenced optical frequency combs1,2 has sparked the development of novel areas in ultrafast sciences such as attosecond technology3,4 and the synthesis of arbitrary optical waveforms5,6. Few-cycle light pulses are key to these time-domain applications, driving a quest for reliable, stable and cost-efficient mode-locked laser sources with ultrahigh spectral bandwidth. Here, we present a set-up based entirely on compact erbium-doped fibre technology, which produces single cycles of light. The pulse duration of 4.3 fs is close to the shortest possible value for a data bit of information transmitted in the near-infrared regime. These results demonstrate that fundamental limits for optical telecommunications are accessible with existing fibre technology and standard free-space components. Based on a passively phase-locked superposition of a dispersive wave and a soliton from two branches of a femtosecond Er-doped fibre laser, researchers demonstrate that single cycles of light can be achieved using existing fibre technology and standard free-space components. The pulses have a pulse duration of 4.3 fs, close to the shortest possible value for a data bit of information transmitted in the near-infrared.
301 citations
Patent•
08 Jan 2010TL;DR: In this article, an electrical ablation apparatus comprises first and second electrodes, each electrode comprising a first end configured to couple an energy source and a second end configured to couple to a tissue treatment region.
Abstract: An electrical ablation apparatus comprises first and second electrodes. Each electrode comprises a first end configured to couple an energy source and a second end configured to couple to a tissue treatment region. An energy source is coupled to the first and second electrodes. The energy source is configured to deliver a first series of electrical pulses sufficient to induce cell necrosis by irreversible electroporation and a second series of electrical pulses sufficient to induce cell necrosis by thermal heating, through at least one of the first and second electrodes. The first series of electrical pulses is characterized by a first amplitude, a first pulse length, and a first frequency. The second series of electrical pulses is characterized by a second amplitude, a second pulse length, and a second frequency.
273 citations
TL;DR: In this paper, a supercontinuum (SC) generation in all-normal dispersion photonic crystal fiber under high energy femtosecond pumping is numerically investigated, and it is shown that coherent octave spanning SC spectra with flatness of better than ± 1 dB can be achieved over the entire bandwidth.
Abstract: Supercontinuum (SC) generation in all-normal dispersion photonic crystal fiber under high energy femtosecond pumping is numerically investigated. It is shown that coherent octave spanning SC spectra with flatness of better than ±1 dB can be achieved over the entire bandwidth. A single pulse is maintained in the time domain, which may be externally compressed to the sub-10 fs regime even by simple linear chirp elimination. The single optical cycle limit is approached for full phase compensation, leading to peak power spectral densities of multiple kilowatts/nanometer. The generated SC is therefore ideal for applications which require high broadband spectral power densities as well as a defined pulse profile in the time domain. The properties of the generated SC are shown to be independent of the input pulse duration.
267 citations
TL;DR: There has been a long-standing, ongoing effort in the field to reduce the pulse duration and increase the power of these lasers to continue to empower existing and new applications.
Abstract: Ultrashort lasers provide an important tool to probe the dynamics of physical systems at very short time-scales, allowing for improved understanding of the performance of many devices and phenomena used in science, technology, and medicine. In addition ultrashort pulses also provide a high peak intensity and a broad optical spectrum, which opens even more applications such as material processing, nonlinear optics, attosecond science, and metrology. There has been a long-standing, ongoing effort in the field to reduce the pulse duration and increase the power of these lasers to continue to empower existing and new applications. After 1990, new techniques such as semiconductor saturable absorber mirrors (SESAMs) and Kerr-lens mode locking (KLM) allowed for the generation of stable pulse trains from diode-pumped solid-state lasers for the first time, and enabled the performance of such lasers to improve by several orders of magnitude with regards to pulse duration, pulse energy and pulse repetition rates. This invited review article gives a broad overview and includes some personal accounts of the key events during the last 20 years, which made ultrafast solid-state lasers a success story. Ultrafast Ti:sapphire, diode-pumped solid-state, and novel semiconductor laser oscillators will be reviewed. The perspective for the near future indicates continued significant progress in the field.
210 citations
TL;DR: The proposed method enables the requirements for the pump pulse duration to be relaxed but also to reduce ionization of the harmonic medium, which opens the door to create an intense isolated attosecond pulse using a conventional femtosecond laser system.
Abstract: We propose and demonstrate the generation of a continuum high-order harmonic spectrum by mixing multicycle two-color (TC) laser fields with the aim of obtaining an intense isolated attosecond pulse. By optimizing the wavelength of a supplementary infrared pulse in a TC field, a continuum harmonic spectrum was created around the cutoff region without carrier-envelope phase stabilization. The obtained harmonic spectra clearly show the possibility of generating isolated attosecond pulses from a multicycle TC laser field, which is generated by an 800 nm, 30 fs pulse mixed with a 1300 nm, 40 fs pulse. Our proposed method enables us not only to relax the requirements for the pump pulse duration but also to reduce ionization of the harmonic medium. This concept opens the door to create an intense isolated attosecond pulse using a conventional femtosecond laser system.
204 citations
TL;DR: In this paper, the effect of laser power, pulse duration and overlapping factor on the tensile strength of a keyhole welding of low carbon steel to 5754 aluminum alloy was investigated.
203 citations
TL;DR: In this paper, a 355 nm pulsed Nd:YAG laser with a pulse duration of 6 ns focussed onto a copper solid sample in air at atmospheric pressure is studied spectroscopically, and the temperature and electron density characterizing the plasma are measured by time-resolved spectroscopy of neutral atom and ion line emissions in the time window of 300-2000 ns.
Abstract: Plasma produced by a 355 nm pulsed Nd:YAG laser with a pulse duration of 6 ns focussed onto a copper solid sample in air at atmospheric pressure is studied spectroscopically. The temperature and electron density characterizing the plasma are measured by time-resolved spectroscopy of neutral atom and ion line emissions in the time window of 300-2000 ns. An echelle spectrograph coupled with a gated intensified charge coupled detector is used to record the plasma emissions. The temperature is obtained using the Boltzmann plot method and the electron density is determined using the Saha-Boltzmann equation method. Both parameters are studied as a function of delay time with respect to the onset of the laser pulse. The results are discussed. The time window where the plasma is optically thin and is also in local thermodynamic equilibrium (LTE), necessary for the laser-induced breakdown spectroscopy (LIBS) analysis of samples, is deduced from the temporal evolution of the intensity ratio of two Cu I lines. It is found to be 700-1000 ns.
134 citations
TL;DR: The pulses used were based on the frequency offset correction inversion technique, as well as time dilation of functions, but the RF amplitude, frequency sweep, and gradient functions were all generated using a genetic algorithm with an evaluation function that took into account both the desired inversion profile and the transmit field inhomogeneity.
Abstract: The radiofrequency (RF) transmit field is severely inhomogeneous at ultrahigh field due to both RF penetration and RF coil design issues. This particularly impairs image quality for sequences that use inversion pulses such as magnetization prepared rapid acquisition gradient echo and limits the use of quantitative arterial spin labeling sequences such as flow-attenuated inversion recovery. Here we have used a search algorithm to produce inversion pulses tailored to take into account the heterogeneity of the RF transmit field at 7 T. This created a slice selective inversion pulse that worked well (good slice profile and uniform inversion) over the range of RF amplitudes typically obtained in the head at 7 T while still maintaining an experimentally achievable pulse length and pulse amplitude in the brain at 7 T. The pulses used were based on the frequency offset correction inversion technique, as well as time dilation of functions, but the RF amplitude, frequency sweep, and gradient functions were all generated using a genetic algorithm with an evaluation function that took into account both the desired inversion profile and the transmit field inhomogeneity.
131 citations
TL;DR: The power scaling concept of the MIXSEL is demonstrated using optimized quantum dot saturable absorbers in an antiresonant structure design combined with an improved thermal management by wafer removal and mounting of the 8-µm thick MixSEL structure directly onto a CVD-diamond heat spreader.
Abstract: High-power ultrafast lasers are important for numerous industrial and scientific applications. Current multi-watt systems, however, are based on relatively complex laser concepts, for example using additional intracavity elements for pulse formation. Moving towards a higher level of integration would reduce complexity, packaging, and manufacturing cost, which are important requirements for mass production. Semiconductor lasers are well established for such applications, and optically-pumped vertical external cavity surface emitting lasers (VECSELs) are most promising for higher power applications, generating the highest power in fundamental transverse mode (>20 W) to date. Ultrashort pulses have been demonstrated using passive modelocking with a semiconductor saturable absorber mirror (SESAM), achieving for example 2.1-W average power, sub-100-fs pulse duration, and 50-GHz pulse repetition rate. Previously the integration of both the gain and absorber elements into a single wafer was demonstrated with the MIXSEL (modelocked integrated external-cavity surface emitting laser) but with limited average output power (<200 mW). We have demonstrated the power scaling concept of the MIXSEL using optimized quantum dot saturable absorbers in an antiresonant structure design combined with an improved thermal management by wafer removal and mounting of the 8-µm thick MIXSEL structure directly onto a CVD-diamond heat spreader. The simple straight cavity with only two components has generated 28-ps pulses at 2.5-GHz repetition rate and an average output power of 6.4 W, which is higher than for any other modelocked semiconductor laser.
TL;DR: In this article, spherical silicon nanoparticles were prepared by laser ablation of a single crystal Si wafer immersed in 95% ethanol with a pulse duration shorter than the time of electron−phonon relaxation (from 35 to 900 fs).
Abstract: Spherical silicon nanoparticles were prepared by laser ablation of a single crystal Si wafer immersed in 95% ethanol with a pulse duration shorter than the time of electron−phonon relaxation (from 35 to 900 fs). The size distribution depends on the pulse duration as well as the width of the size distribution, which increases with the increase of the laser pulse duration. High resolution transmission electron microscopy performed on 20−40 nm particles showed polycrystalline particles made up mainly of silicon (α-Si) crystallites with the diamond structure and in some cases cubic silicon carbide (SiC) inclusions. Electron energy loss spectroscopy data on the large particles are very similar to bulk Si. Raman analysis extended to small frequencies showed a downshift and an asymmetrical broadening of the first-order Si optical peak with respect to bulk Si in good agreement with a spatial confinement in 5−10 nm crystallites. The photoluminescence spectra present a maximum of emission band at about 640 nm.
TL;DR: A general numerical approach is described that allows obtaining model sets of temporal pulse shapes of free-electron lasers operating in the self-amplified spontaneous emission mode that satisfy statistical criteria of FEL light predicted by established FEL theory.
Abstract: A general numerical approach is described that allows obtaining model sets of temporal pulse shapes of free-electron lasers (FELs) operating in the self-amplified spontaneous emission mode. Based on a random partial-coherence approach, sets of pulse shapes can be calculated that satisfy statistical criteria of FEL light predicted by established FEL theory. Importantly, the numerically retrieved sets of pulses reproduce the experimentally accessible FEL light characteristics as measured at the Free-electron LASer at Hamburg (FLASH), such as the average spectrum, single-shot spectral shape, and pulse duration. The high-precision agreement with the experimental average spectral shape, without further knowledge of FEL machine parameters, makes this approach a convenient tool for the analysis and theoretical modeling of nonlinear optical or pump–probe experiments with FEL light.
TL;DR: Results demonstrate a significant dependence of the growth parameters on laser pulse duration at 351 nm from 1 ns to 15 ns, including the observation of a dominant exponential versus linear, multiple-shot growth behavior for long and short pulses, respectively.
Abstract: The growth behavior of laser-induced damage sites is affected by a large number of laser parameters as well as site morphology. Here we investigate the effects of pulse duration on the growth rate of damage sites located on the exit surface of fused silica optics. Results demonstrate a significant dependence of the growth parameters on laser pulse duration at 351 nm from 1 ns to 15 ns, including the observation of a dominant exponential versus linear, multiple-shot growth behavior for long and short pulses, respectively. These salient behaviors are tied to the damage morphology and suggest a shift in the fundamental growth mechanisms for pulses in the 1-5 ns range.
TL;DR: In this paper, the pulse amplitude needed to reverse the magnetization was shown to be inversely proportional to the pulse duration, consistent with a macrospin spin transfer model, but the amplitude amplitude duration depends on the applied field much more strongly than predicted by the zero temperature macrospin model.
Abstract: Spin-transfer switching with short current pulses has been studied in spin-valve nanopillars with perpendicularly magnetized free and reference layers. Magnetization switching with current pulses as short as 300 ps is demonstrated. The pulse amplitude needed to reverse the magnetization is shown to be inversely proportional to the pulse duration, consistent with a macrospin spin-transfer model. However, the pulse amplitude duration switching boundary depends on the applied field much more strongly than predicted by the zero temperature macrospin model. The results also demonstrate that there is an optimal pulse length that minimizes the energy required to reverse the magnetization.
TL;DR: A simple model is developed that accounts for the long pulse duration, the triangular shape of the current pulse and the increase in the standard deviation of the pulse duration with increasing protein size, which is in general agreement with results obtained from other investigations of protein adsorption to surfaces.
Abstract: We have been investigating an electrochemical single-molecule counting experiment called nanopore resistive-pulse sensing. The sensor element is a conically shaped gold nanotube embedded in a thin polymeric membrane. We have been especially interested in counting protein molecules using these nanotube sensors. This is accomplished by placing the nanotube membrane between two electrolyte solutions, applying a transmembrane potential difference, and measuring the resulting ionic current flowing through the nanopore. In simplest terms, when a protein molecule enters and translocates the nanopore, it transiently blocks the ion current, resulting in a downward current pulse. We have found that the duration of such current-pulses are many orders of magnitude longer than the electrophoretic transport time of the protein through the nanotube detection zone. We develop here a simple model that accounts for this key, and previously explained, observation. This model assumes that the protein molecule engages in repeated adsorption/desorption events to/from the nanotube walls as it translocates through the detection zone. This model not only accounts for the long pulse duration but also for the triangular shape of the current pulse and the increase in the standard deviation of the pulse duration with increasing protein size. Furthermore, the results of our analyses are in general agreement with results obtained from other investigations of protein adsorption to surfaces. This includes the observations that smaller proteins stick more readily to the surface but remain adsorbed for shorter times than larger proteins. In addition, the sticking probabilities calculated from our data are in general agreement with results obtained from other methods.
TL;DR: In this paper, the authors proposed and realized passive Q-switched cladding pumped Er-doped fiber laser with a saturable absorber based on Tm-Doped fiber.
Abstract: For the first time we have suggested and realized passive Q-switched cladding pumped Er-doped fiber laser with a saturable absorber based on Tm-doped fiber. The pulse duration was of 100 ns, the pulse energy – 0.35 mJ, the peak power – 3.5 kW while the average power is less than 1 W. The laser is perspective for technology processes and medicine.
TL;DR: In this paper, an analytical solution to the cubic-quintic Ginzbug-Landau equation is derived for dissipative optical solitons, where the energy does not scale inversely with the pulse duration, and in addition there is an upper limit to the energy.
Abstract: Soliton area theorems express the pulse energy as a function of the pulse shape and the system parameters. From an analytical solution to the cubic-quintic Ginzbug-Landau equation, we derive an area theorem for dissipative optical solitons. In contrast to area theorems for conservative optical solitons, the energy does not scale inversely with the pulse duration, and in addition there is an upper limit to the energy. Energy quantization explains the existence of, and conditions for, multiple-pulse solutions. The theoretical predictions are confirmed with numerical simulations and experiments in the context of dissipative soliton fiber lasers.
TL;DR: In this article, a pulsed neodymium:yttrium aluminum garnet laser weld was used to examine the influence of the pulse energy in the characteristics of the weld fillet.
TL;DR: In this paper, a modulation cavity is inserted between the slow wave structure to decrease the energy spread of modulated beam electrons, and an extraction cavity is employed at the end of the slow-wave structure to further recover energy from the electron beam.
Abstract: Efficient generation regime with a high power output has been experimentally realized in a klystron-like relativistic backward wave oscillator, in which a modulation cavity is inserted between the slow wave structure to decrease the energy spread of modulated beam electrons, and an extraction cavity is employed at the end of the slow wave structure to further recover energy from the electron beam. At a guiding magnetic field of 2.2 T, a microwave pulse with power of 6.5 GW, frequency of 4.26 GHz, pulse duration of 38 ns, and efficiency of 36% was generated when the diode voltage was 1.1 MV, and diode current was 16.4 kA. When the diode voltage was 820 kV, efficiency up to 47% with microwave power 4.4 GW was also realized experimentally.
TL;DR: A passive optical resonator is used to enhance the power of a pulsed 78 MHz repetition rate Yb laser providing 200 fs pulses and limitations relating to the achievable time-averaged and peak power are found, which are distinguished by varying the duration of the input pulses.
Abstract: A passive optical resonator is used to enhance the power of a pulsed 78MHz repetition rate Yb laser providing 200fs pulses. We find limitations relating to the achievable time-averaged and peak power, which we distinguish by varying the duration of the input pulses. An intracavity average power of 18kW is generated with close to Fourier-limited pulses of 10W average power. Beyond this power level, intensity-related effects lead to resonator instabilities, which can be removed by chirping the seed laser pulses. By extending the pulse duration in this way to 2ps, we could obtain 72kW of intracavity circulating power with 50W of input power.
TL;DR: This work introduces simplified representations of a number of shaped pulses, commonly used in biomolecular NMR spectroscopy, consisting in a suite of free evolution delays and ideal rf pulses, that reproduce astonishingly well the effect on a scalar-coupled hetero-nuclear two-spin system.
TL;DR: In this paper, an attosecond-precision ultrafast photonics based on ultra-low timing jitter optical pulse trains from mode-locked lasers is discussed. But the authors focus on the application of optical pulse train for high-resolution sampling and analog-to-digital conversion.
Abstract: We review our recent progress toward attosecond-precision ultrafast photonics based on ultra-low timing jitter optical pulse trains from mode-locked lasers. In femtosecond mode-locked lasers, the concentration of a large number of photons in an extremely short pulse duration enables the scaling of timing jitter into the attosecond regime. To characterize such jitter levels, we developed new attosecond-resolution measurement techniques and show that standard fiber lasers can achieve sub-fs high-frequency jitter. By leveraging the ultra-low jitter of free-running mode-locked lasers, we pursued high-precision optical-optical and optical-microwave synchronization techniques. Optical signals spanning 1.5 octaves were synthesized by attosecond-precision timing and phase synchronization of two independent mode-locked lasers. High-stability microwave signals were also synthesized from mode-locked lasers with drift-free sub-10-fs precision. We further demonstrated the attosecond-precision distribution of optical pulse trains to remote locations via timing-stabilized fiber links. Finally, the application of optical pulse trains for high-resolution sampling and analog-to-digital conversion is discussed.
TL;DR: The mechanism and intrinsic conditions of high-energy wave-breaking-free pulse generation in fiber laser mode-locked by a nonlinear polarization rotation technique are investigated numerically and experimentally in this paper.
Abstract: The mechanism and intrinsic conditions of high-energy wave-breaking-free pulse generation in fiber lasers mode-locked by a nonlinear polarization rotation technique are investigated numerically and experimentally. Both numerical and experimental results show that the pulses along the two orthogonal polarization axes of the fiber have a large difference in pulse energy. The numerical simulations show that the ratio of the energy of two components is limited and ranges from about 8 to about 65. The slope of the instantaneous frequency at the central position of the pulse decreases rapidly with the increase of the pulse duration and energy, whereas the slope at the pulse edge changes slightly. The accumulation of instantaneous frequency throughout the pulse width approaches a constant in a higher pulse energy regime. Understanding the mechanism and intrinsic conditions of the wave-breaking-free pulse generation could be useful in generating high-energy pulses delivered from fiber lasers.
TL;DR: In this paper, the authors proposed a scheme for detecting a concealed source of ionizing radiation by observing the occurrence of breakdown in atmospheric air by an electromagnetic wave whose electric field surpasses the breakdown field in a limited volume.
Abstract: A scheme is proposed for detecting a concealed source of ionizing radiation by observing the occurrence of breakdown in atmospheric air by an electromagnetic wave whose electric field surpasses the breakdown field in a limited volume. The volume is chosen to be smaller than the reciprocal of the naturally occurring concentration of free electrons. The pulse duration of the electromagnetic wave must exceed the avalanche breakdown time (10–200 ns) and could profitably be as long as the statistical lag time in ambient air (typically, microseconds). Candidate pulsed electromagnetic sources over a wavelength range, 3 mm>λ>10.6 μm, are evaluated. Suitable candidate sources are found to be a 670 GHz gyrotron oscillator with 200 kW, 10 μs output pulses and a Transversely Excited Atmospheric-Pressure (TEA) CO2 laser with 30 MW, 100 ns output pulses. A system based on 670 GHz gyrotron would have superior sensitivity. A system based on the TEA CO2 laser could have a longer range >100 m.
TL;DR: In this paper, the beam waist size and the pulse duration can be optimized for maximal acceleration, and it is shown that an electron can effectively reach the high-intensity optical cycles of this particular beam and be optimally accelerated without the necessity of being released by photoionization near the pulse peak.
Abstract: In the past few years, there has been a growing interest for direct-field electron acceleration with ultra-intense and ultrafast radially polarized laser beams. This particular acceleration scheme offers the possibility of producing highly collimated mono-energetic relativistic attosecond electron pulses from an initial cloud of free electrons that could be produced by ionizing a nanoparticle. In this paper, we describe how electron energy scales with laser power and we explain how the beam waist size and the pulse duration can be optimized for maximal acceleration. The main conclusion of our work is that an electron can effectively reach the high-intensity optical cycles of this particular beam and be optimally accelerated without the necessity of being released by photoionization near the pulse peak.
TL;DR: In this paper, the authors employ coherent x-ray diffraction imaging (CXDI) using the free-electron laser (FEL) to image non-crystalline, biological specimens at unprecedented resolutions.
Abstract: Coherent x-ray imaging represents a new window to imaging non- crystalline, biological specimens at unprecedented resolutions. The advent of free-electron lasers (FEL) allows extremely high flux densities to be delivered to a specimen resulting in stronger scattered signal from these samples to be measured. In the best case scenario, the diffraction pattern is measured before the sample is destroyed by these intense pulses, as the processes involved in radiation damage may be substantially slower than the pulse duration. In this case, the scattered signal can be interpreted and reconstructed to yield a faithful image of the sample at a resolution beyond the conventional radiation damage limit. We employ coherent x-ray diffraction imaging (CXDI) using the free-electron
TL;DR: In this paper, a nanosecond (ns) pulse generator which has a 5 ns pulse duration in output pulsed voltage is developed, and NO-removal experiments using ns pulsed discharge were conducted.
Abstract: Pulsed streamer discharge plasmas, one type of nonthermal plasma, have been used to treat exhaust gases. Since a pulsewidth of applied voltage has a strong influence on the energy efficiency of the removal of pollutants, the development of a short-pulse generator is of paramount importance for practical applications. In this paper, a nanosecond (ns) pulse generator which has a 5-ns pulse duration in output pulsed voltage is developed, and NO-removal experiments using ns pulsed discharge were conducted. The experimental results of the NO removal showed 100% of NO-removal ratio at 7 pps of pulse repetition rate and the extremely high energy efficiency, which is 0.43 mol/kWh (12.9 g-NO/kWh) for NO removal (initial NO concentration = 200 ppm; gas flow = 2.0 l/min ). The result of deriving energy efficiency for NO removal indicated that the ns pulsed discharge has great advantage in energy efficiency for NO removal to the conventional discharge methods. By this research, the utility of the ns pulse plasma process was proven, and the influence of shorter pulse duration on NO-removal energy efficiency was confirmed.
TL;DR: In this paper, Stokes et al. demonstrated quasi continuous-wave (qCW) yellow emission (pulse duration 5 ms, repetition rate 20 Hz) at 559 nm through intracavity sum frequency generation (SFG) of Stokes and fundamental fields in Nd:YVO4 diode pumped self-Raman laser for the first time.
Abstract: Quasi continuous-wave (qCW) yellow emission (pulse duration 5 ms, repetition rate 20 Hz) at 559 nm is demonstrated through intracavity sum frequency generation (SFG) of Stokes and fundamental fields in Nd:YVO4 diode pumped self-Raman laser for the first time. Average in pulse output power at 559 nm was 0.47 W for 22 W of pump power, which corresponds to 2.1% of diode-to-yellow efficiency. The pulsed mode of operation was due to diode pump modulation and was used to reduce thermal stress of the crystal.
TL;DR: Ultrafast terahertz emission from two-color generated laser plasma gas targets is studied using air and the noble gases as the generation media using a simple one dimensional transient photocurrent ionization model showing good agreement with experiments.
Abstract: Ultrafast terahertz emission from two-color generated laser plasma gas targets is studied using air and the noble gases (neon, argon, krypton, and xenon) as the generation media Terahertz output pulse energy and power spectra are measured as function of gas species, gas pressure, and input pulse energy up to 6 mJ per pulse using a 40-fs 1-kHz Ti:sapphire laser system as the drive source Terahertz pulse energies approaching 1 μJ per pulse with spectral content out to 40 THz and pulse duration of 35 fs is reported A simple one dimensional transient photocurrent ionization model is used to calculate the spectra showing good agreement with experiments