Showing papers on "Pulse compression published in 2013"
TL;DR: Two experiments confirming that hypocycloid Kagome-type hollow-core photonic crystal fibers (HC-PCFs) are excellent candidates for beam delivery of MW peak powers and pulse compression down to the sub-50 fs regime are presented.
Abstract: We present two experiments confirming that hypocycloid Kagome-type hollow-core photonic crystal fibers (HC-PCFs) are excellent candidates for beam delivery of MW peak powers and pulse compression down to the sub-50 fs regime. We demonstrate temporal pulse compression of a 1030-nm Yb:YAG thin disk laser providing 860 fs, 1.9 µJ pulses at 3.9 MHz. Using a single-pass grating pulse compressor, we obtained a pulse duration of 48 fs (FWHM), a spectral bandwidth of 58 nm, and an average output power of 4.2 W with an overall power efficiency into the final polarized compressed pulse of 56%. The pulse energy was 1.1 µJ. This corresponds to a peak power of more than 10 MW and a compression factor of 18 taking into account the exact temporal pulse profile measured with a SHG FROG. The compressed pulses were close to the transform limit of 44 fs. Moreover, we present transmission of up to 97 µJ pulses at 10.5 ps through 10-cm long fiber, corresponding to more than twice the critical peak power for self-focusing in silica.
102 citations
TL;DR: A new architecture for high-speed compressed sensing using chirp processing with ultrafast laser pulses, presently applied to the measurement of sparse-frequency microwave signals, is demonstrated.
Abstract: We demonstrate a new architecture for high-speed compressed sensing using chirp processing with ultrafast laser pulses, presently applied to the measurement of sparse-frequency microwave signals. We spectrally encode highly chirped ultrafast laser pulses with pseudorandom bit sequences such that every laser pulse acquires a unique spectral pattern. The pulses are partially compressed in time, extending the effective sampling rate beyond the electronic limit, and then modulated with a sparse microwave signal. Finally the pulses are fully compressed and detected, effectively integrating the measurement. We achieve 100 usable features per pattern allowing for 100 points in the reconstructed microwave spectra and experimentally demonstrate reconstruction of two- and three-tone microwave signals spanning from 900 MHz to 14.76 GHz. These spectra are reconstructed by measuring the energy of only 23 to 38 consecutive laser pulses acquired in a single shot with a 500 MHz real-time oscilloscope.
83 citations
TL;DR: A scheme for the generation of phase-coded microwave signals using an electrically tunable photonic microwave phase shifter, based on a single-sideband polarization modulator, is proposed and demonstrated.
Abstract: A scheme for the generation of phase-coded microwave signals using an electrically tunable photonic microwave phase shifter is proposed and demonstrated. The photonic phase shifter is based on a single-sideband polarization modulator (PolM), and the tuning of the phase shifter is implemented by a second PolM. By introducing an RF signal to the first PolM and an electrical coding signal to the second PolM, a phase-coded microwave signal with binary phase codes or polyphase codes is achieved. An experiment is performed. The simple and flexible operation, high coding rate, large frequency range, excellent transmission performance, and high stability of the system is confirmed.
82 citations
TL;DR: A novel scheme to compress the radiation pulse in x-ray free electron lasers is proposed not only to shorten the pulse length but also to enhance the peak power of the radiation, by inducing a periodic current enhancement with an optical laser and applying a temporal shift between the optical and electron beams.
Abstract: A novel scheme to compress the radiation pulse in x-ray free electron lasers is proposed not only to shorten the pulse length but also to enhance the peak power of the radiation, by inducing a periodic current enhancement with an optical laser and applying a temporal shift between the optical and electron beams. Calculations show that a 10-keV x-ray pulse with a peak power of 5 TW and a pulse length of 50 asec can be generated by applying this scheme to an existing x-ray free electron laser facility.
77 citations
TL;DR: It is demonstrated that a given field envelope produces a unique and unequivocal chirp-scan map and that, under some asymptotic assumptions, both the spectral amplitude and phase of the measured pulse can be retrieved analytically from only two measurements.
Abstract: We investigate a variant of the d-scan technique, an intuitive pulse characterization method for retrieving the spectral phase of ultrashort laser pulses. In this variant a ramp of quadratic spectral phases is applied to the input pulses and the second harmonic spectra of the resulting pulses are measured for each chirp value. We demonstrate that a given field envelope produces a unique and unequivocal chirp-scan map and that, under some asymptotic assumptions, both the spectral amplitude and phase of the measured pulse can be retrieved analytically from only two measurements. An iterative algorithm can exploit the redundancy of the information contained in the chirp-scan map to discard experimental noise, artifacts, calibration errors and improve the reconstruction of both the spectral intensity and phase. This technique is compared to two reference characterization techniques (FROG and SRSI). Finally, we perform d-scan measurements with a simple grating-pair compressor.
75 citations
TL;DR: In this article, the authors demonstrate temporal pulse compression in gas-filled kagome hollow-core photonic crystal fiber (PCF) using two different approaches: fiber-mirror compression based on self-phase modulation under normal dispersion, and soliton effect self-compression under anomalous dispersion with a decreasing pressure gradient.
Abstract: We demonstrate temporal pulse compression in gas-filled kagome hollow-core photonic crystal fiber (PCF) using two different approaches: fiber-mirror compression based on self-phase modulation under normal dispersion, and soliton effect self-compression under anomalous dispersion with a decreasing pressure gradient. In the first, efficient compression to near-transform-limited pulses from 103 to 10.6 fs was achieved at output energies of 10.3 μJ. In the second, compression from 24 to 6.8 fs was achieved at output energies of 6.6 μJ, also with near-transform-limited pulse shapes. The results illustrate the potential of kagome-PCF for postprocessing the output of fiber lasers. We also show that, using a negative pressure gradient, ultrashort pulses can be delivered directly into vacuum.
73 citations
TL;DR: In this paper, a phase-coded or frequency-chirped microwave waveform with a tunable microwave carrier frequency using a frequency-tunable optoelectronic oscillator (OEO) is proposed and experimentally demonstrated.
Abstract: Photonic generation of a phase-coded or frequency-chirped microwave waveform with a tunable microwave carrier frequency using a frequency-tunable optoelectronic oscillator (OEO) is proposed and experimentally demonstrated, for the first time to the best of our knowledge. In the proposed system, the tunable OEO has functions to generate a frequency-tunable microwave signal and to output an optical sideband. The optical sideband and a portion of the light wave from the OEO laser source are sent to a polarization modulator (PolM), with their polarization directions aligned with the two principal axes of the PolM. An electrical signal is applied to the PolM, and two complementary phase-coded or frequency-chirped light waves are generated which are converted to an electrical signal by beating the light waves at a high-speed photodetector. The key significance of the technique is that a phase-coded or frequency-chirped microwave waveform with a tunable microwave carrier frequency and a reconfigurable phase-coding or frequency-chirping pattern can be generated without using a separate microwave source. The technique is experimentally verified. The generation of a binary- and a polyphase-coded microwave waveform with a microwave carrier frequency at 10 and 15 GHz is demonstrated. The generation of a linearly frequency-chirped microwave waveform with a chip rate of 20.98 GHz/ns at a 10-GHz carrier frequency and 22.5 GHz/ns at a 15-GHz carrier frequency is also achieved.
69 citations
TL;DR: Based on the heterodyne beating between the pre-chirped optical pulse and the continuous wave light in a wideband photodetector, linearly chirped microwave pulse, which yields a large time-bandwidth product (TBWP) of 106 and high compression ratio of 160, is generated in this experiment.
Abstract: Based on the heterodyne beating between the pre-chirped optical pulse and the continuous wave (CW) light in a wideband photodetector (PD), linearly chirped microwave pulse with time duration of 32ns and bandwidth of 33GHz, which yields a large time-bandwidth product (TBWP) of 106 and high compression ratio of 160, is generated in our experiment Dispersion compensation fiber (DCF) with uniform response across broad bandwidth is used for providing the original linear chirp in our method, which shows the promise to generate linearly chirped microwave pulse with bandwidth of up to THz The flexibility of the center frequency and the stability of the time-frequency performance are demonstrated by generating different types of linearly chirped microwave pulses The range resolution of our generated microwave pulse is also verified by off-line processing
67 citations
TL;DR: Large-scale gratings with conformal coating have been installed successfully in the 500 TW Scarlet laser system and it was confirmed by electromagnetic field modeling using the finite element method, which showed that non-conformal coating morphology gives rise to significant local field enhancement near groove edges, lowering the diffraction efficiency and increasing Joule heating.
Abstract: Laser-induced femtosecond damage thresholds of Au and Ag coated pulse compression gratings were measured using 800 nm laser pulses ranging in duration from 30 to 200 fs. These gratings differ from conventional metal-on-photoresist pulse compression gratings in that the gratings patterns are generated by etching the fused silica substrate directly. After etching, the metal overcoating was optimized based on diffraction efficiency and damage threshold considerations. The experiment on these gratings was performed under vacuum for single-shot damage. Single-shot damage threshold, where there is a 0% probability of damage, was determined to be within a 400–800 mJ/cm2 range. The damage threshold exhibited no clear dependence on pulse width, but showed clear dependence on gold overcoat surface morphology. This was confirmed by electromagnetic field modeling using the finite element method, which showed that non-conformal coating morphology gives rise to significant local field enhancement near groove edges, lowering the diffraction efficiency and increasing Joule heating. Large-scale gratings with conformal coating have been installed successfully in the 500 TW Scarlet laser system.
66 citations
TL;DR: In this article, the authors use an in-situ photo-triggered streak camera to track the time of arrival of each electron pulse and correct for the timing jitter in the radio frequency synchronization.
Abstract: We demonstrate a method of time-stamping Radio Frequency compressed electron bunches for Ultrafast Electron Diffraction experiments in the sub-pC regime. We use an in-situ ultra-stable photo-triggered streak camera to directly track the time of arrival of each electron pulse and correct for the timing jitter in the radio frequency synchronization. We show that we can correct for timing jitter down to 30 fs root-mean-square with minimal distortion to the diffraction patterns, and performed a proof-of-principle experiment by measuring the ultrafast electron-phonon coupling dynamics of silicon.
66 citations
TL;DR: This work considers optical pulse propagation in an Erbium doped inhomogeneous lossy optical fiber with time dependent phase modulation and discusses various soliton dynamics such as periodic distributed amplification, pulse compression etc.
TL;DR: A high-performance photonic sweeping- frequencies (chirped) radio-frequency (RF) generator has been demonstrated and the high-repeatability in sweeping frequency has been verified by analyzing tens of repetitive chirped waveforms.
Abstract: A high-performance photonic sweeping-frequency (chirped) radio-frequency (RF) generator has been demonstrated. By use of a novel wavelength sweeping distributed-feedback (DFB) laser, which is operated based on the linewidth enhancement effect, a fixed wavelength narrow-linewidth DFB laser, and a wideband (dc to 50 GHz) photodiode module for the hetero-dyne beating RF signal generation, a very clear chirped RF waveform can be captured by a fast real-time scope. A very-high frequency sweeping rate (10.3 GHz/μs) with an ultra-wide RF frequency sweeping range (~40 GHz) have been demonstrated. The high-repeatability (~97%) in sweeping frequency has been verified by analyzing tens of repetitive chirped waveforms.
TL;DR: This research considers an advanced pulse compression noise (APCN) radar waveform possessing salient features from linear-FM (LFM) and noise waveforms and demonstrates the low probability of interception (LPI) characteristic of the APCN waveform for different κ values.
Abstract: This research considers an advanced pulse compression noise (APCN) radar waveform possessing salient features from linear-FM (LFM) and noise waveforms. A cross-correlation model considering several chirp waveform profiles is used to simulate the output of a passive electronic intelligence (ELINT) intercept-receiver. By doing so we are able to demonstrate the low probability of interception (LPI) characteristic of the APCN waveform for different κ values.
TL;DR: In this article, the least absolute error (L1 norm) is used to define both the data and model error in the objective functional, which is more immune to noise when compared to the usual L2 one, especially when the data are contaminated by discrepant sample values.
Abstract: In order to perform a good pulse compression, the conventional spike deconvolution method requires that the wavelet is stationary. However, this requirement is never reached since the seismic wave always suffers high‐frequency attenuation and dispersion as it propagates in real materials. Due to this issue, the data need to pass through some kind of inverse‐Q filter. Most methods attempt to correct the attenuation effect by applying greater gains for high‐frequency components of the signal. The problem with this procedure is that it generally boosts high‐frequency noise. In order to deal with this problem, we present a new inversion method designed to estimate the reflectivity function in attenuating media. The key feature of the proposed method is the use of the least absolute error (L1 norm) to define both the data and model error in the objective functional. The L1 norm is more immune to noise when compared to the usual L2 one, especially when the data are contaminated by discrepant sample values. It also favours sparse reflectivity when used to define the model error in regularization of the inverse problem and also increases the resolution, since an efficient pulse compression is attained. Tests on synthetic and real data demonstrate the efficacy of the method in raising the resolution of the seismic signal without boosting its noise component.
TL;DR: A compact, transportable, and dual-polarization X-band weather radar was developed at the Advanced Radar Research Center of the University of Oklahoma using a software-defined radio (SDR) approach for waveform versatility and the mitigation of blind range.
Abstract: In this paper, a compact, transportable, and dual-polarization X-band weather radar was developed at the Advanced Radar Research Center of the University of Oklahoma. The radar was designed using a software-defined radio (SDR) approach for waveform versatility. One of the key innovations in this paper is the combination of SDR design and the mitigation of blind range, which is inherent in pulse compression radars, using a time-frequency multiplexed waveform while compression is performed in pure software architecture. Internally, this radar has been referred to as the PX-1000. It is primarily used as a platform for waveform studies and various signal processing techniques, such as pulse compression, polarimetric signal processing, refractivity retrieval, and support of various field campaigns. The radar system has been completed and is operational. It has two identical and independent power amplifiers, one for each polarization. The system also features a 1.2-m parabolic reflector dish with dual-polarization feed, which provides a 1.8 ° beamwidth. A majority of the components are housed above the turntable of an azimuth-over-elevation pedestal. We also took this opportunity to design and develop a new software suite that includes signal processing, system control, and graphical user interface. The raw I/Q time series can be recorded and streamed out of the radar system in real time. In this paper, a detailed description of the radar and some experimental data will be presented.
TL;DR: In this article, a novel method for generating octave-spanning supercontinua and few-cycle pulses in the important mid-IR wavelength range is discussed. But the technique relies on strongly phase-mismatched cascaded second-harmonic generation (SHG) in nonlinear frequency conversion crystals, where no phase matching can be achieved but as a compensation the largest quadratic nonlinearities are exploited.
Abstract: We discuss a novel method for generating octave-spanning supercontinua and few-cycle pulses in the important mid-IR wavelength range. The technique relies on strongly phase-mismatched cascaded second-harmonic generation (SHG) in mid-IR nonlinear frequency conversion crystals. Importantly we here investigate the so-called noncritical SHG case, where no phase matching can be achieved but as a compensation the largest quadratic nonlinearities are exploited. A self-defocusing temporal soliton can be excited if the cascading nonlinearity is larger than the competing material self-focusing nonlinearity, and we define a suitable figure of merit to screen a wide range of mid-IR dielectric and semiconductor materials with large effective second-order nonlinearities deff. The best candidates have simultaneously a large bandgap and a large deff. We show selected realistic numerical examples using one of the promising crystals: in one case soliton pulse compression from 50 fs to 15 fs (1.5 cycles) at 3.0 μm is achieved, and at the same time a 3-cycle dispersive wave at 5.0 μm is formed that can be isolated using a long-pass filter. In another example we show that extremely broadband supercontinua can form spanning the near-IR to the end of the mid-IR (nearly 4 octaves).
TL;DR: In this paper, the authors investigated the nonlinear propagation of femtosecond laser filaments created at central wavelengths between 0.8 and 8 µm in a pressurized argon gas.
Abstract: We investigate the nonlinear propagation of femtosecond laser filaments created at central wavelengths between 0.8 and 8 $\ensuremath{\mu}$m in a pressurized argon gas. Attention is paid to spectral broadenings and self-compression of mid-infrared pulses. It is shown that the longer the central wavelength is, the more efficient the pulse compression is. Three key mechanisms entering the spectral dynamics, i.e., low-order-harmonic generation, four-wave mixing, and self-steepening, are discussed.
TL;DR: This work numerically investigates self-frequency blueshifting of a fundamental soliton in a gas-filled hollow-core photonic crystal fiber and proposes a device that enables frequency shifting over an octave and pulse compression from 30 fs down to 2.3 fs.
Abstract: We numerically investigate self-frequency blueshifting of a fundamental soliton in a gas-filled hollow-core photonic crystal fiber. Because of the changing underlying soliton parameters, the blueshift gives rise to adiabatic soliton compression. Based on these features, we propose a device that enables frequency shifting over an octave and pulse compression from 30 fs down to 2.3 fs.
TL;DR: In this article, a Hilbert transform-based matched filtering method was used for the detection of subsurface features lying deep inside a glass fiber-reinforced plastic test sample, and the results obtained from this pulse compression approach are less affected by random noise generated inside the test sample during experimentation as well as the variations of surface emissivity over the test samples.
Abstract: Among various widely used thermal non-destructive testing methods, non-stationary thermal non-destructive testing modalities have proved to be an indispensable approach for the inspection and evaluation of various solid materials. These techniques facilitate the use of low peak power heat sources in a moderate time compared with the conventional widely used pulsed and sinusoidal modulated (lock-in) thermographic techniques. In this reported work, Barker non-stationary excitation followed by Hilbert transform-based matched filtering for the detection of subsurface features lying deep inside a glass fibre-reinforced plastic test sample is incorporated. Results obtained from this pulse compression approach are less affected by random noise generated inside the test sample during experimentation as well as the variations of surface emissivity over the test sample. A comparison has been carried out among the amplitude, time delay and phase images obtained for the experimentally matched filter data.
TL;DR: The robust and simple pumping scheme based on a commercially available multimode diode laser makes this laser attractive for future frequency comb metrology applications.
Abstract: A high-power gigahertz SESAM modelocked Yb:KGW laser is pumped with a commercial multimode diode laser and enables a strong frequency comb offset beat signal without additional amplification or pulse compression. The ultrafast Yb:KGW solid-state laser oscillator generates 125-fs pulses at an average power of 3.4 W and a repetition rate of 1.06 GHz with a record-high peak power of 22.7 kW. An octave-spanning frequency comb was generated with a 1-m long highly nonlinear photonic crystal fiber (PCF) launching only 900 mW of the total average power with a PCF coupling efficiency of 70%. The frequency comb offset was successfully detected with a carrier-envelope offset (CEO) frequency beat signal of 30-dB signal-to-noise ratio for a resolution bandwidth of 100 kHz. The robust and simple pumping scheme based on a commercially available multimode diode laser makes this laser attractive for future frequency comb metrology applications.
TL;DR: A novel photonic approach to generating widely tunable and background-free binary phase-coded radio-frequency (RF) pulses by cascading a polarization modulator and a phase modulator using an optical carrier and two sidebands with orthogonal polarization states.
Abstract: We present a novel photonic approach to generating widely tunable and background-free binary phase-coded radio-frequency (RF) pulses by cascading a polarization modulator (PolM) and a phase modulator (PM). The PolM is used to produce an optical carrier and two sidebands with orthogonal polarization states. The phase shift θ between the optical carrier and the sidebands is controlled by the electrical driving signal applied to the PM. For θ>π/2 or <π/2, the phase of the detected RF signal is 0 or π, respectively. For θ=π/2, there is no RF signal recovered in the photodiode (PD). In this way, binary phase-coded RF pulses can be generated, while the optical power launched to the PD keeps constant. The proposed technique is therefore background free by eliminating the baseband frequency components. Moreover, the carrier frequency of the RF pulses is widely tunable and the π phase shift of the RF signal is independent of the amplitude of the electrical driving signal. The proposed scheme is theoretically analyzed and experimentally verified.
TL;DR: A nonlinear preshaper that optimizes initial pulses for self-similar evolution in a next fiber amplifier that consists of a pair of gratings and a segment of single-mode fiber (SMF).
Abstract: We report on a nonlinear preshaper that optimizes initial pulses for self-similar evolution in a next fiber amplifier. It consists of a pair of gratings and a segment of single-mode fiber (SMF). The grating pair provides negative chirp to make the pulses preshaped temporally and spectrally in the SMF. With this optimization, the self-similar amplification can be realized in a 2.2 m Yb-doped fiber in a large range of pump power. After amplification, the pulse can be dechirped to transform-limited pulses with ∼60 fs pulse duration.
TL;DR: In this article, the authors identify the physical scenarios of nonlinear spatiotemporal dynamics of extreme-power laser fields enabling compression of a broad-beam ultrafast multipetawatt laser output to sub-exawatt few-cycle light pulses focusable to pulse intensities up to 10 25 W/cm 2.
TL;DR: An efficient pulse compression method of chirp-coded excitation, in which the pulse compression is conducted with complex baseband data after downsampling, to lower the computational complexity.
Abstract: Coded excitation can improve the SNR in medical ultrasound imaging. In coded excitation, pulse compression is applied to compress the elongated coded signals into a short pulse, which typically requires high computational complexity, i.e., a compression filter with a few hundred coefficients. In this paper, we propose an efficient pulse compression method of chirp-coded excitation, in which the pulse compression is conducted with complex baseband data after downsampling, to lower the computational complexity. In the proposed method, although compression is conducted with the complex data, the L-fold downsampling is applied for reducing both data rates and the number of compression filter coefficients; thus, total computational complexity is reduced to the order of 1/L2. The proposed method was evaluated with simulation and phantom experiments. From the simulation and experiment results, the proposed pulse compression method produced similar axial resolution compared with the conventional pulse compression method with negligible errors, i.e., >36 dB in signal-to-error ratio (SER). These results indicate that the proposed method can maintain the performance of pulse compression of chirp-coded excitation while substantially reducing computational complexity.
TL;DR: It is demonstrated theoretically that chirped dynamic gratings can be created in optical fibers through stimulated Brillouin scattering with frequency-chirped "signal" and "write" pulses, providing a method to regenerate stored pulses and enhance signal levels for communications applications.
Abstract: We demonstrate theoretically that chirped dynamic gratings can be created in optical fibers through stimulated Brillouin scattering with frequency-chirped “signal” and “write” pulses. When the grating is interrogated with a third pulse of the opposite chirp, a compressed signal pulse is retrieved. This provides a method to regenerate stored pulses and enhance signal levels for communications applications.
TL;DR: In this paper, the role of MI and self-Raman self-scattering has been discussed and a new method for increasing the pulse train repetition rate through frequency modulation of the seed wave has been proposed.
Abstract: Optical pulse generation and compression have been numerically studied in anomalous dispersion decreasing fibers. We show that evolution of modulation instability (MI) observed with chirped wave packets in tapered fibers produces the mechanism for generation of ultrashort pulses with high repetition rates. The role of MI and Raman self-scattering has been also discussed. The simulations show that pulse chirping enhances self-Raman scattering at early stages of pulse propagation and improves compression of the generated pulses. It is also shown that the presence of amplitude and frequency modulation of the seed wave provide essential impact on the pulse train formation. The new method for increasing the pulse train repetition rate through frequency modulation of the seed wave has been proposed.
TL;DR: In this paper, the effects of the pulse repetition rate of input power on the physical and chemical properties of pulsed discharges in water were investigated using point-to-plane electrode geometry.
Abstract: A repetitive pulsed-power modulator, which employs a magnetic pulse compression circuit with a high-speed thyristor switch, was used to study the effects of the pulse repetition rate of input power on the physical and chemical properties of pulsed discharges in water. Positive high-voltage pulses of 20 kV with repetition rates of up to 1 kHz were used to generate a discharge in water using the point-to-plane electrode geometry. By varying the pulse repetition rate, two distinct modes of the discharge plasma were formed in water. The first mode was characterized by the formation of a corona-like discharge propagating through water in the form of streamer channels. The second mode was formed typically above 500 Hz, when the formation of streamer channels in water was suppressed and all plasmas occurred inside a spheroidal aggregate of very fine gas bubbles surrounding the tip of the high-voltage electrode. The production of hydrogen peroxide, degradation of organic dye Acid Orange 7 (AO7) and inactivation of bacteria Escherichia coli by the discharge in water were studied under different discharge plasma modes in dependence on the pulse repetition rate of input power. The efficiency of both chemical and biocidal processes induced by the plasma in water decreased significantly with pulse repetition rates above 500 Hz.
TL;DR: The nonlinear pulse compression of temporally divided pulses, which is presented in a proof-of-principle experiment, holds promise for overcoming fundamental limitations of the pulse peak power that lead to destruction of the fiber or ionization limitations in high-energy hollow-core compression.
Abstract: We report on the nonlinear pulse compression of temporally divided pulses, which is presented in a proof-of-principle experiment. A single 320 fs pulse is divided into four replicas, spectrally broadened in a solid-core fiber, and subsequently recombined. This approach makes it possible to reduce the nonlinearities in the fiber and therefore to use total input peak power of about 13.3 MW, which is more than three times higher than the self-focusing threshold. Finally, the combined output pulse could be compressed to sub-100 fs pulse duration. This general and universal approach holds promise for overcoming fundamental limitations of the pulse peak power that lead to destruction of the fiber or ionization limitations in high-energy hollow-core compression.
TL;DR: The carrier-envelope phase (CEP) stability of hollow-fiber compression for high-energy few-cycle pulse generation and the onset of an ionization-induced CEP instability is observed, which saturates beyond input pulse energies of 1.25 mJ.
Abstract: We investigated the carrier-envelope phase (CEP) stability of hollow-fiber compression for high-energy few-cycle pulse generation. Saturation of the output pulse energy is observed at 0.6 mJ for a 260 μm inner-diameter, 1 m long fiber, statically filled with neon. The pressure is adjusted to achieve output spectra supporting sub-4-fs pulses. The maximum output pulse energy can be increased to 0.8 mJ by either differential pumping (DP) or circularly polarized input pulses. We observe the onset of an ionization-induced CEP instability, which saturates beyond input pulse energies of 1.25 mJ. There is no significant difference in the CEP stability with DP compared to static-fill.
TL;DR: Passive spatial and temporal coherent combining schemes are implemented to scale the output energy of a nonlinear temporal compression setup and it is demonstrated the output of a high-energy fiber chirped-pulse amplifier can be compressed using self-phase modulation in a large-mode-area rod-type fiber at peak-power levels well beyond the self-focusing power.
Abstract: Passive spatial and temporal coherent combining schemes are implemented to scale the output energy of a nonlinear temporal compression setup. By generating 32 replicas of the incident femtosecond pulses, the output of a high-energy fiber chirped-pulse amplifier can be compressed using self-phase modulation in a large-mode-area rod-type fiber at peak-power levels well beyond the self-focusing power. We demonstrate the generation of 71 fs 7.5 μJ pulses at 100 kHz repetition rate, corresponding to a peak power of 86 MW.