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High-Repetition-Rate and High-Beam-Quality Laser Pulses with 1.5MW Peak Power Generation from a Two-Stage Nd:YVO <sub/>4</sub> Amplifier <sup>*</sup>
摘要： We develop a two-stage end-pumped Nd:YVO4 amplifier seeded by a passively Q-switched microchip laser. An average output power of 13.5 W with repetition rate up to 7 kHz and pulse duration of ～1.24 ns is obtained, corresponding to a pump extraction efficiency of 16.1% (19.5% for the second stage) and peak power of ～1.5 MW. The beam quality factors at maximum output power are measured to be ?? 2 ?? = 1.56 and ?? 2 ?? = 1.48. We introduce an analytical model to estimate gain and beam quality after amplification. This model focuses on the influence of ratio of seed spot radius to pump spot radius when designing an amplifier. Moreover, our experiments reveal that the re-imaging system in the double-pass configuration can be used to enhance the beam quality.
关键词： peak power,high-beam-quality,Nd:YVO4 amplifier,high-repetition-rate,laser pulses
更新于2025-09-12 10:27:22
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - High Efficiency, High Energy Few-Cycle Driver at 1-μm
摘要： The recent development of high repetition rate lasers based on ytterbium-doped fiber amplifiers (YDFA), has paved the way to increase the repetition rate (>100 kHz) of coherent extreme ultra violet (XUV) sources generated by high harmonic generation (HHG). High repetition rate HHG driver comes with several advantages, such as increased photon flux [1], reduction of the acquisition time in coincidence experiments to study molecular dynamics such as COLTRIMS, and the possibility to study the electronic structure of matter via photoemission spectroscopy and microscopy, where low doses are needed to avoid space-charge effects [2]. Up to now, the overall majority of HHG studies and applications has been restricted to the low repetition rates of Ti:sapphire lasers. Commonly, Ti:sapphire lasers delivers 20 fs pulses at a central wavelength λ = 800 nm, with pulse energies up to hundreds of mJ. However, the average power of these laser systems cannot easily be scaled beyond 10 W, restricting HHG at low repetition rates (up to 10 kHz). Currently, the most mature and powerful ultrafast source technology is undoubtedly ytterbium-based systems, with average power levels beyond 1 kW [3] and numerous industrial applications. However, the long pulse duration of around >200 fs delivered by YDFA sources limits their relevance to this application field. Therefore, nonlinear compression setups have been used successfully to reduce the pulse duration and obtain XUV photon flux among the highest ever reported for HHG-based sources [1]. However, to reach sub-3 cycles regime (< 10 fs at 1030 nm), which is typically required in combination with gating techniques to obtain isolated attosecond pulses, two stages of compression must usually be implemented [4]. This reduces the energy efficiency of the systems dedicated to attosecond physics to typically less than 30% of the overall YDA energy. Here, we demonstrate a two-cycle-source based on a high-energy femtosecond YDFA followed by a hybrid two-stage nonlinear compression setup. The association of a multipass cell-based stage and large-diameter capillary stage provides a compression factor of 48 with an overall transmission of 61%. This source is, to the best of our knowledge, the most efficient few cycle, high energy and high repetition rate laser demonstrated to date. It is very compact with an overall footprint of 1.8 m × 1.0 m and provides a stable train of few-cycle pulses at a central wavelength of 1030 nm that has been continuously characterized over more than 8h. The delivered 6.8 fs (see Fig. 1) 140 μJ pulses at 150 kHz repetition rate, corresponding to 21 W average power, are ideally suited to drive high-photon flux XUV sources [5] through HHG. The described laser system is robust, compact, and power efficient, making it an ideal driver laser for application-ready high flux XUV and attosecond sources.
关键词： attosecond pulses,high harmonic generation,ytterbium-doped fiber amplifiers,extreme ultra violet,high repetition rate lasers
更新于2025-09-12 10:27:22
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Dispersive Fourier Transform Based Single-Shot CEP Drift Measurement at Arbitrary Repetition Rate
摘要： In recent years attosecond science motivated the development of laser systems, which provide millijoule energy level few-cycle pulses. These experiments rely on a field with stable amplitude and carrier envelope phase (CEP) to provide reproducible results [1]. As a consequence, diagnostic devices, which are capable of single-shot CEP measurement and pulse tagging, became a must-have equipment in today’s laser systems. The self-referenced interferometry such as f-to-2f [2] are one of the most typical way to characterize the shift of the CEP in a single-shot manner. The highest achievable recording rate is mostly limited by the measurement times of the optical spectroscopes, which can only reach 10 kHz even with fast detector array. Dispersive Fourier Transform (DFT) [3,4] can be used to bypass this limitation, so single-shot recordings of the output signal of an f-to-2f interferometer becomes possible even at high repetition rates. The method depends on an optical element with enough dispersion to stretch to pulse duration up to the nanosecond range. Therefore, the spectral modulation pattern containing the encoded CEP appears in the temporal domain, which allows for tracking with a relatively slow photodetector. To demonstrate the validity and performance of this concept, a CEP drift measurement was performed on the state-of-the-art mid-infrared (MIR) laser system at ELI-ALPS [5], which provides mid-IR laser pulses at 100 kHz. As a comparison, an alternative measurement was performed in parallel with a grating spectrometer (Fringeezz, Fastlite) [6] at 10 kHz sampling rate. The two recorded signals were synchronized and a decimated 10 kHz subset was extracted, where correlation between measurements is the highest. One of the main limitation of the DFT method originates from the time jitter between the output of the laser and the TTL signal used for triggering. This time jitter changes the time delay of the modulation pattern, creating an additional noise source for the measured relative CEP value. In order to perform truly time jitter-free single-shot CEP drift measurement, an additional CEP independent spectral modulation was introduced, which can be used to determine the noise originating from the jitter. The jitter-free decimated dataset against the grating spectrometer measurement is displayed on Fig. 1. The calculated CEP noises are summarized in Table 1. These values agree within the limit of the uncertainty of these measurements, validating that this new CEP drift measurement method is easily scalable to arbitrary repetition rates.
关键词： high repetition rate,mid-infrared laser system,Dispersive Fourier Transform,CEP drift measurement,single-shot
更新于2025-09-12 10:27:22
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - High Repetition Rate, Wavelength-Tunable Mid-IR Source Driven by ps-Pulses from a Ho:YLF Amplifier at 2 μm
摘要： The generation of ultrashort pulses in the mid-infrared (mid-IR) spectral region is highly demanded for a multitude of applications such as spectroscopy, materials processing, or biomolecular and chemical sensing. For many of the aforementioned applications a high pulse repetition frequency (PRF) is desirable, since it reduces measurement time and improves spectroscopic signal-to-noise ratio. However, most of the ultrafast mid-IR sources are limited to a PRF below 10 kHz as they rely on regenerative amplifier-based pump sources for optical parametric chirped pulse amplification (OPCPA) [1-3]. The herein applied Pockels cell represents a bottleneck for PRF tuning usually below 10 kHz. Just recently, we presented a 2-μm, sub-10 ps pulse laser system with millijoule-level pulse energy, which is in principle not limited by the PRF [4]. This laser system benefits from its simplified, compact CPA-free architecture and high efficiency. In this contribution we use a similar laser system as front-end to pump nonlinear ZnGeP2 (ZGP) crystals in order to approach the wavelength range between 2.5 and 9 μm. This compact mid-IR source benefits from the broad spectral and PRF tunability as well as a remarkably simple experimental scheme.
关键词： ultrashort pulses,ZnGeP2 crystals,wavelength-tunable,mid-IR,high repetition rate,Ho:YLF amplifier
更新于2025-09-11 14:15:04
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A multihertz, kiloelectronvolt pulsed proton source from a laser irradiated continuous hydrogen cluster target
摘要： A high-repetition rate laser-driven proton source from a continuously operating cryogenic hydrogen cluster target is presented. We demonstrate a debris-free, Coulomb-explosion based acceleration in the 10s of kilo-electron-volt range with a stability of about 10% in a 5 Hz operation. This acceleration mechanism, delivering short pulse proton bursts, represents an ideal acceleration scheme for various applications, for example, in materials science or as an injector source in conventional accelerators. Furthermore, the proton energy can be tuned by varying the laser and/or cluster parameters. 3D numerical particle-in-cell simulations and an analytical model support the experimental results and reveal great potential for further studies, scaling up the proton energies, which can be realized with a simple modification of the target.
关键词： high-repetition rate,laser-driven proton source,Coulomb-explosion,particle-in-cell simulations,cryogenic hydrogen cluster target
更新于2025-09-11 14:15:04
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Implementation of a pulse-type laser detection and ranging system based on heterodyne detection for long-range measurement with high repetition rate
摘要： This paper presents the implementation of a pulse-type LAser Detection And Ranging (LADAR) system based on heterodyne detection for long-range measurement. A pulse-type LADAR based on an intensity direct-detection is certainly simple and mature, but it requires a high peak-power laser and a low-noise avalanche photodiode for long-range measurement, which restricts the scope of the application due to the weight, power consumption, and cost of the laser and the photodetector. In this work, heterodyne detection using a PIN photodiode is implemented to increase receiver sensitivity instead of using a low-noise avalanche photodiode. An optical phase-locked loop is adopted to generate an optical local oscillator signal for heterodyne detection. The proposed heterodyne detection scheme achieves a minimum detectable signal level of ?52.6 dBm at a bandwidth of 1.2 GHz, and it is adopted in a pulse-type LADAR system for long-range measurement. The pulse-type LADAR system can measure a distance of 2.77 km at a repetition rate of 40 kHz, and it demonstrates great advantages for realizing real-time 3D imaging for long-range measurement with a high frame rate.
关键词： LADAR,optical phase-locked loop,long-range measurement,heterodyne detection,high repetition rate
更新于2025-09-11 14:15:04
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Nonlinear energy chirp compensation with corrugated structures
摘要： Herein, a feasible method is proposed to compensate the high-order effect during bunch length compression, thereby enhancing the peak current of a high-repetition-rate X-ray free-electron laser source. In the proposed method, the corrugated structure is inserted downstream of the high-order harmonic cavities to function as a passive linearizer and enhance the longitudinal pro?le of the electron beam. Three-dimensional simulations are performed to analyze the evolution of the longitudinal phase space, and the results demonstrate that the pro?le of the electron beam is improved and the peak current can be easily optimized to over 2 kA with a bunch charge of 100 pC.
关键词： Corrugated structure,High-repetition-rate FEL,Nonlinear energy chirp
更新于2025-09-10 09:29:36