Showing papers on "Femtosecond pulse shaping published in 2010"
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: The design and performance of the Texas Petawatt Laser, which produces a 186 J 167 fs pulse based on the combination of optical parametric chirped pulse amplification (OPCPA) and mixed Nd:glass amplification, is presented.
Abstract: We present the design and performance of the Texas Petawatt Laser, which produces a 186 J167 fs pulse based on the combination of optical parametric chirped pulse amplification (OPCPA) and mixed Nd:glass amplification. OPCPA provides the majority of the gain and is used to broaden and shape the seed spectrum, while amplification in Nd:glass accounts for >99% of the final pulse energy. Compression is achieved with highly efficient multilayer dielectric gratings.
190 citations
TL;DR: The experimental results demonstrate that the passively mode-locked fiber laser operating in the anomalous regime can also realize a high-energy pulse, which is different from the conventional low-energy soliton pulse.
Abstract: We report on a long-cavity passively mode-locked fiber laser in the anomalous dispersion regime. The nonlinear polarization rotation technique is employed to achieve mode locking. The output pulse from the fiber laser has a rectangular shape and a corresponding Gaussian-shape spectral profile. Stable mode-locked pulses at a repetition rate of 278 kHz with single pulse energy as high as 715 nJ are obtained under equal bidirectional pumping power of 500 mW in cavity. The experimental results demonstrate that the passively mode-locked fiber laser operating in the anomalous regime can also realize a high-energy pulse, which is different from the conventional low-energy soliton pulse. (C) 2010 Optical Society of America
166 citations
TL;DR: In this paper, a self-referenced spectral interferometry (SFEI) method is proposed for femtosecond pulse characterization, where the reference pulse is self created from the pulse being characterized.
Abstract: A new femtosecond pulse characterization, named self-referenced spectral interferometry, is introduced. Based on linear spectral interferometry, the reference pulse is self created from the pulse being characterized. This self reference results from pulse shaping optimization and non-linear temporal filtering.
156 citations
TL;DR: Pulse generation from a ring-cavity Er:fiber laser at a repetition rate of 225 MHz and the spectral bandwidth of the pulse is 135 nm is reported.
Abstract: We report 37.4fs pulse generation from a ring-cavity Er:fiber laser at a repetition rate of 225MHz. The spectral bandwidth of the pulse is 135nm. The single-pulse energy is 0.31nJ.
124 citations
TL;DR: A new method which does not require any external delay lines and uses only a single femtosecond laser, based on the cross-correlation of an optical pulse with a subsequent pulse from the same laser, to achieve temporal delay between two optical pulses.
Abstract: Most time-resolved optical experiments rely either on external mechanical delay lines or on two synchronized femtosecond lasers to achieve a defined temporal delay between two optical pulses. Here, we present a new method which does not require any external delay lines and uses only a single femtosecond laser. It is based on the cross-correlation of an optical pulse with a subsequent pulse from the same laser. Temporal delay between these two pulses is achieved by varying the repetition rate of the laser. We validate the new scheme by a comparison with a cross-correlation measurement carried out with a conventional mechanical delay line.
117 citations
TL;DR: This Letter distributed the pulse train of a mode-locked fiber laser with femtosecond stability to different locations in the linear accelerator of the soft x-ray FEL FLASH, and succeeded in stabilizing both the arrival time and the electron bunch compression process within two magnetic chicanes.
Abstract: High-gain free-electron lasers (FELs) are capable of generating femtosecond x-ray pulses with peak brilliances many orders of magnitude higher than at other existing x-ray sources. In order to fully exploit the opportunities offered by these femtosecond light pulses in time-resolved experiments, an unprecedented synchronization accuracy is required. In this Letter, we distributed the pulse train of a mode-locked fiber laser with femtosecond stability to different locations in the linear accelerator of the soft x-ray FEL FLASH. A novel electro-optic detection scheme was applied to measure the electron bunch arrival time with an as yet unrivaled precision of 6 fs (rms). With two beam-based feedback systems we succeeded in stabilizing both the arrival time and the electron bunch compression process within two magnetic chicanes, yielding a significant reduction of the FEL pulse energy jitter.
78 citations
TL;DR: It is shown that the pulse broadening of the QD-MLL is caused by linear chirp for all values of current and voltage investigated here, resulting in a significantly increased overall mode-locking range of 101 MHz.
Abstract: A complete characterization of pulse shape and phase of a 1.3 µm, monolithic-two-section, quantum-dot mode-locked laser (QD-MLL) at a repetition rate of 40 GHz is presented, based on frequency resolved optical gating. We show that the pulse broadening of the QD-MLL is caused by linear chirp for all values of current and voltage investigated here. The chirp increases with the current at the gain section, whereas larger bias at the absorber section leads to less chirp and therefore to shorter pulses. Pulse broadening is observed at very high bias, likely due to the quantum confined stark effect. Passive- and hybrid-QD-MLL pulses are directly compared. Improved pulse intensity profiles are found for hybrid mode locking. Via linear chirp compensation pulse widths down to 700 fs can be achieved independent of current and bias, resulting in a significantly increased overall mode-locking range of 101 MHz. The suitability of QD-MLL chirp compensated pulse combs for optical communication up to 160 Gbit/s using optical-time-division multiplexing are demonstrated by eye diagrams and autocorrelation measurements.
77 citations
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
76 citations
TL;DR: In this article, the authors showed that molecular orientation can be controlled by sequential three-photon Raman excitations with time-delayed dual-color ultrashort laser pulses.
Abstract: We show that molecular orientation can be controlled by sequential three-photon Raman excitations with time-delayed dual-color ultrashort laser pulses. The field-free molecular orientation created by a dual-color ultrashort laser pulse can be significantly enhanced or completely suppressed when another in-phase or antiphase dual-color ultrashort laser pulse is applied at its full revival time. By applying the second dual-color ultrashort laser pulse at the half-revival time, the odd and even rotational wave packets for the impulsive molecular orientation can be promoted and depressed by changing its carrier-envelope phase.
74 citations
TL;DR: In this paper, the authors presented a method to generate an extremely short unipolar half-cycle pulse based on resonant propagation of a fewcycle pulse through asymmetrical media with periodic subwavelength structure.
Abstract: We present a method to generate an extremely short unipolar half-cycle pulse based on resonant propagation of a few-cycle pulse through asymmetrical media with periodic subwavelength structure. Moreover, single- and few-cycle gap solitons with different frequencies are found to split from one incident few-cycle ultrashort pulse. These solitons with various frequencies provide evidence for the generation of different parametric waves during the strong light-matter coupling in asymmetrical media under the extreme nonlinear optics condition. Because of the pulse self-shaping process during the course of resonant propagation, the generated low-frequency sideband and another broadband continuum sideband ranging from the visible to the near-infrared regime couple together, which results in the generation of the subfemtosecond unipolar half-cycle pulse. A time-frequency analysis is preformed which corroborates the mechanism. The generated unipolar half-cycle pulse might be utilized to control and probe the ultrafast electronic dynamics.
TL;DR: It is found that intensity clamping during filamentation effect still play a role even under strong external focusing, and the electron density in some interaction zones is higher than 3 × 10(19) cm(-3), which indicates that each air molecule there is ionized.
Abstract: The propagation of tightly focused femtosecond laser pulse with numerical aperture of 012 in air is investigated experimentally The formation and evolution of the filament bunch are recorded by time-resolved shadowgraph with laser energy from 24 mJ to 47 mJ The distribution of electron density in breakdown area is retrieved using Nomarski interferometer It is found that intensity clamping during filamentation effect still play a role even under strong external focusing The electron density in some interaction zones is higher than 3×1019 cm-3, which indicates that each air molecule there is ionized
TL;DR: High-energy ultrashort pulse generation from an all-normal-dispersion large-mode-area fiber laser is reported by exploiting an efficient combination of nonlinear polarization evolution (NPE) and a semiconductor-based saturable absorber mode-locking mechanism.
Abstract: We report on high-energy ultrashort pulse generation from an all-normal-dispersion large-mode-area fiber laser by exploiting an efficient combination of nonlinear polarization evolution (NPE) and a semiconductor-based saturable absorber mode-locking mechanism. The watt-level laser directly emits chirped pulses with a duration of 1 ps and 163 nJ of pulse energy. These can be compressed to 77 fs, generating megawatt-level peak power. Intracavity dynamics are discussed by numerical simulation, and the intracavity pulse evolution reveals that NPE plays a key role in pulse shaping.
TL;DR: Pulses with an energy of 3.3 nJ and a bandwidth-limited pulse duration of 195 fs could be amplified to 151 nJ, which corresponds to an average power of 5.7 W at 37.6 MHz pulse repetition rate.
Abstract: We report on chirped-pulse amplification of an ultrafast thulium-doped fiber laser. Pulses with an energy of 3.3nJ and a bandwidth-limited pulse duration of 195fs could be amplified to 151nJ, which corresponds to an average power of 5.7W at 37.6MHz pulse repetition rate. The maximum output power was limited by the available pump power. The pulses could be dechirped to a duration of 258fs.
TL;DR: It is demonstrated for the first time the application of a self-diffraction process in a bulk Kerr medium to improve the temporal, spectral, and spatial qualities of femtosecond laser pulses.
Abstract: We demonstrated for the first time the application of a self-diffraction (SD) process in a bulk Kerr medium to improve the temporal, spectral, and spatial qualities of femtosecond laser pulses. A proof-of-principle experiment succeeded in improving the temporal contrast of a femtosecond pulse by four orders of magnitude even in the picosecond region using a 0.5-mm-thick fused silica glass plate by this technique. The energy conversion efficiency from the incident pulses to the two first-order SD signals is about 12%. By the SD process, a laser pulse with smoother spectral shape, higher beam quality, and shorter pulse duration than those of the input pulse was generated. This technique is expected to be used to design background-free petawatt laser system in the future.
TL;DR: Numerical simulations reveal that pulse shaping is dominated by the amplitude modulation and spectral filtering provided by a resonant semiconductor saturable absorber, leading to pulse peak powers as high as 1.9 MW.
Abstract: We report the generation of high-energy high-peak power pulses in an all-normal dispersion fiber laser featuring large-mode-area photonic crystal fibers. The self-starting chirped-pulse fiber oscillator delivers 11W of average power at 15.5MHz repetition rate, resulting in 710nJ of pulse energy. The output pulses are dechirped outside the cavity from 7ps to nearly transform-limited duration of 300fs, leading to pulse peak powers as high as 1.9MW. Numerical simulations reveal that pulse shaping is dominated by the amplitude modulation and spectral filtering provided by a resonant semiconductor saturable absorber.
TL;DR: This pulse energy is a 1-order-of-magnitude improvement compared with previous sub-100-fs sources in this wavelength range and the duration measurements are achieved by pump-probe ionization of Xe gas providing the cross correlation between the fifth harmonic and the fundamental.
Abstract: We report on the generation of femtosecond pulses at 160 nm with energies up to 240 nJ at 1 kHz repetition rate and sub-50-fs pulse duration. This pulse energy is a 1-order-of-magnitude improvement compared with previous sub-100-fs sources in this wavelength range. The pulses are generated by four-wave difference-frequency mixing process between the fundamental of a Ti:sapphire laser and its third harmonic in argon. Pulse duration measurements are achieved by pump–probe ionization of Xe gas providing the cross correlation between the fifth harmonic and the fundamental.
TL;DR: Gain-switched by a 1.914-µm Tm:YLF crystal laser, a two-stage Tm(3+) fiber laser has been achieved 100-W level ~2- pulsed laser output with a slope efficiency of ~52% and further scaling the pulse energy and average power from such kind of gain- Switched fiber lasers was discussed.
Abstract: Gain-switched by a 1.914-µm Tm:YLF crystal laser, a two-stage Tm(3+) fiber laser has been achieved 100-W level ~2-µm pulsed laser output with a slope efficiency of ~52%. With the 6-m length of Tm fiber, the laser wavelength was centered at 2020 nm with a bandwidth of ~25 nm. Based on an acousto-optic switch, the pulse repetition rate can be modulated from 500 Hz to 50 kHz, and the laser pulse width can be tuned between 75 ns and ~1 µs. The maximum pulse energy was over 10 mJ, and the maximum pulse peak power was 138 kW. By using the fiber-coiling-induced mode-filtering effect, laser beam quality of M2 = 1.01 was obtained. Further scaling the pulse energy and average power from such kind of gain-switched fiber lasers was also discussed.
TL;DR: It is shown that multiple-pulse excitation improves the signal-to-noise ratio through an accumulated energy deposition effect and is invaluable for photoacoustic measurements that require ultrashort laser pulses with minimized pulse energy to avoid laser damage.
Abstract: Purpose: The purpose of this work is to demonstrate that higher amplitude of ultrashort laser induced photoacoustic signal can be achieved by multiple-pulse excitation when the temporal duration of the pulse train is less than the minimum of the medium’s thermal relaxation time and stress relaxation time. Thus, improved signal-to-noise ratio can thus be attained through multiple-pulse excitation while minimizing the energy of each pulse.
Methods: The authors used a Michelson interferometer together with a picoseconds laser system to introduce two 6 ps pulses separated by a controllable delay by introducing a path length difference between the two arms of the interferometer. The authors then employed a series of three interferometers to create a pulse train consisting of eight pulses. The average pulse energy was 11 nJ and the temporal span of the pulse train was less than 1 ns.
Results: The detected peak-to-peak amplitude of the multiple-pulse induced photoacoustic waves were linearly dependent on the number of pulses in the pulse train and such a linearity held for different optical absorption coefficients. The signal-to-noise ratio improved when the number of pulses increased. Moreover, nonlinear effects were not detected and no photoacoustic saturation effect was observed.
Conclusions: The authors have shown that multiple-pulse excitation improves the signal-to-noise ratio through an accumulated energy deposition effect. This method is invaluable for photoacoustic measurements that require ultrashort laser pulses with minimized pulse energy to avoid laser damage.
TL;DR: The measured pulse duration decreases linearly with increasing length and density of the plasma, in quantitative agreement with the intensity-dependent group velocity variation in the plasma wave.
Abstract: We present complete experimental characterization of the temporal shape of an intense ultrashort 200-TW laser pulse driving a laser wakefield. The phase of the pulse was uniquely measured by using (second-order) frequency-resolved optical gating. The pulses are asymmetrically compressed and exhibit a positive chirp consistent with the expected asymmetric self-phase-modulation due to photon acceleration or deceleration in a relativistic plasma wave. The measured pulse duration decreases linearly with increasing length and density of the plasma, in quantitative agreement with the intensity-dependent group velocity variation in the plasma wave.
TL;DR: Using high-intensity femtosecond laser pulses for surface structuring, technologically important metallic light absorbers (dark Au, W, and Ti alloy) with absorption of about 85-95% over a broad spectrum were used in this article.
Abstract: Using high-intensity femtosecond laser pulses for surface structuring, technologically important metallic light absorbers (dark Au, W, and Ti alloy) with absorption of about 85–95% over a broad wav...
TL;DR: In this article, a photonic generation of power-efficient ultra wideband (UWB) pulse by incoherent summation of two asymmetric monocycle pulses with inverted polarities is experimentally demonstrated.
Abstract: A novel photonic generation of power-efficient ultra-wideband (UWB) pulse by incoherent summation of two asymmetric monocycle pulses with inverted polarities is experimentally demonstrated. The principles of multiple cross-phase modulations in a highly nonlinear fiber and multiple phase modulation to intensity modulation conversions in a commercially available arrayed-waveguide grating are used. The combined UWB pulse exploiting spectral efficiency of 50.59% in experiment is fully compliant with the Federal Communications Commission (FCC) spectral mask without power attenuation. The FCC-compliant UWB pulse gains larger than 11.5- and 6-dB improvement against monocycle and doublet pulses after power attenuation to respect the FCC spectral mask, respectively. Such a power-efficient UWB pulse with pulse duration of approximately 320 ps has potential to achieve high-speed transmission without pulse overlapping and obvious distortion.
TL;DR: In this paper, the authors demonstrate high-order harmonic generation in a wave form synthesized by a multicycle 800-nm chirped laser pulse and a chirp-free laser pulse.
Abstract: We demonstrate high-order harmonic generation in a wave form synthesized by a multicycle 800-nm chirped laser pulse and a chirp-free laser pulse. Compared with the case of using only a chirped pulse, both the harmonic cutoff and the extreme ultraviolet supercontinuum can be extended when a weak chirp-free pulse is combined with the chirped pulse. When chirp-free pulse intensity grows, the cutoff energy and bandwidth of the supercontinuum grow as well. It is found that the broad supercontinuum can be achieved for a driving pulse with long duration even though the driving pulse reaches 10 optical cycles. An isolated attosecond pulse with duration of about 59 as is obtained, and after appropriate phase compensation with a duration of about $11$ as. In addition, by performing time-frequency analyses and the classical trajectory simulation, the difference in supercontinuum generation between the preceding wave form and a similar wave form synthesized by an $800$-nm fundamental pulse and a $1600$-nm subharmonic pulse is investigated.
TL;DR: In this article, a reconfigurable optical pulse generator based on the creation of a high-quality flat continuum that covers the C-band, followed by the tailoring of the spectral amplitude and phase of the continuum using a commercially available programmable optical processor, provides an arbitrary picosecond pulse shape or width.
Abstract: This paper demonstrates a reconfigurable optical pulse generator based on the creation of a high-quality flat continuum that covers the C-band, followed by the tailoring of the spectral amplitude and phase of the continuum using a commercially available reconfigurable programmable optical processor in order to provide an arbitrary picosecond pulse shape or width. The highly efficient continuum is achieved by seeding a highly nonlinear fiber with transform-limited 4 ps parabolic-shaped pulses. A 20 nm 3 dB continuum at the very high repetition rate of 40 GHz is generated. Fourier-domain pulse shaping techniques are then applied to this continuum via the programmable optical processor to generate any arbitrary pulse shape. We present two specific pulse shaping examples suitable for a variety of high-bit-rate applications. The first example shows the improvement in pulse quality using tailored compression techniques over conventional methods and the second example presents multiwavelength pulse generation, which demonstrates the flexibility and range of pulse shapes that can be achieved using this system. Experimental findings are supported with theoretical results.
TL;DR: Self-compression of the generated deep-UV pulse in air has been demonstrated to produce sub-10fsdeep-UV pulses with excellent temporal and spectral profiles for ultrafast spectroscopy in the deep UV.
Abstract: We propose and demonstrate experimentally a novel way of generating sub-10fs deep-UV pulses. The technique is based on chirped-pulse four-wave mixing induced by a broadband near-IR (NIR) pulse and a near-UV pulse. The broadband IR pulse is prepared by preliminarily broadening the spectral width of an NIR pulse by self-phase modulation. The positively chirped broadband IR pulse is suitable for generating a negatively chirped deep-UV pulse, which can be compressed by normal group-velocity dispersion in a transparent medium. Self-compression of the generated deep-UV pulse in air has been demonstrated to produce sub-10fs deep-UV pulses with excellent temporal and spectral profiles for ultrafast spectroscopy in the deep UV.
TL;DR: In this paper, the dispersion management of the chirped pulse amplification in order to minimize the pulse duration and thus to maximize the intensity available for experiments is discussed, and a detailed description of the stretcher and compressor design with a novel alignment routine is given.
Abstract: At the Institute of Optics and Quantum Electronics in Jena, Germany, the currently most powerful diode-pumped solid-state laser system with 25-TW peak power Polaris is in operation. In this paper we give an overview about the dispersion management of the chirped pulse amplification in order to minimize the pulse duration and thus to maximize the intensity available for experiments. A detailed description of the stretcher and compressor design with a novel alignment routine is given as well as measurements for the pulse duration and the temporal contrast. The far field measurement of the beam focussed by an off-axis parabola yields a nearly diffraction limited focal spot.
TL;DR: The design and performance of a high power femtosecond laser source near 1 micron wavelength which is generated from an octave-spanning supercontinuum (SC) pumped by an Er-doped mode-locked laser is reported.
Abstract: We report the design and performance of a high power femtosecond laser source near 1 micron wavelength which is generated from an octave-spanning supercontinuum (SC) pumped by an Er-doped mode-locked laser. The laser system delivers >5W average power at 35MHz repetition rate and 135 fs pulse duration.
TL;DR: In this paper, the optoelectronic switching of silicon semiconductor devices embedded in a frozen wave generator is described in the linear regime, which enables temporal and spectral pulse shaping.
Abstract: This letter describes subnanosecond electric pulse generation and shaping. The optoelectronic switching of silicon semiconductor devices embedded in a frozen wave generator is obtained in the linear regime. Control of the switching delay time, combined with power modulation of the optical gating signals, enables temporal and spectral pulse shaping. In this way, monocycle nanosecond and/or picosecond pulses with balanced or unbalanced positive and negative components and square electrical pulses with adjustable duration are obtained.
TL;DR: The theoretical model that explains the experimental results and predicts new possibilities to control terahertz pulse parameters is developed.
Abstract: We examine the conical terahertz emission from the superluminous ionization front created in air by an axicon-focused femtosecond laser pulse. We develop the theoretical model that explains the experimental results and predicts new possibilities to control terahertz pulse parameters.