After 30 years since the discovery of the intrinsic orbital angular momentum (OAM) possessed by certain beams, a plethora of applications have been developed in diverse fields such as communications, astrophysics, and biochemistry. Meanwhile, injecting high-order harmonics (HOH) into krypton amplifier plasmas has emerged as a promising alternative to Free Electron Lasers (FEL) for generating table-top, XUV coherent radiation sources. This work brings together these two concepts and asks the following question: what happens when an HOH with OAM is injected into a plasma? Does the amplified beam retain the same OAM, or is this property affected? Understanding the OAM response to this process lays the foundation for new applications. Simulations using the 3D, time-dependent, Maxwell-Bloch code Dagon show that OAM is conserved in low-density plasmas. However, at higher densities, although the OAM is still preserved, the density profiles leave increasing footprints in phase patterns in the form of phase jumps curvature. Finally, a study has been conducted for a plasma with a waveguide, further supporting the potential of OAM for plasma diagnosis.
Optical field ionized (OFI) plasma amplifiers have recently demonstrated sub-picosecond pulses when seeded with high order harmonics. In addition to this, the intensity and phase profile of the amplified harmonic beams carry information about possible plasma inhomogeneities (electron density, lasing ion abundance) that may appear in the amplifier. 1D and 3D modelling has played a fundamental role in these results and it will be required to support present and future experiments. This modelling involves different physical processes and time-scales, from the nanoseconds (hydrodynamics) to the picoseconds (atomic physics) and femtoseconds (dynamics of the amplified beam). Here we briefly present the different codes that have been coupled to fully model this process, from the creation of the plasma to the amplification of XUV and soft X-rays and show how this framework can be applied to study the impact of plasma inhomogeneities in the intensity and phase profile of the amplified beam.
X-ray microscopy has proven its advantages for resolving nanoscale objects. High Harmonic Generation (HHG) sources allow performing nanoimaging experiments at the lab scale and their femtosecond pulse duration and synchrony to an optical laser renders them useful for studying dynamic processes. HHG sources regularly provide high average photon flux but relatively low single-shot flux limiting time-resolved applications to adiabatic processes. Here, we show that soft X-ray lasers (SXRL) in turn provide high flux due to an X-ray lasing transition, but the coherence of an SXRL operating in the amplified-spontaneous-emission scheme is limited. The coherence properties of an SXRL seeded by an HHG source can be significantly improved allowing single-shot nanoscale imaging. In combination with ptychography, source properties are measured with high fidelity. This is applied to study the plasma dynamics of SXRL amplification in unprecedented quality.
In this paper we present the modelling work currently performed at the Instituto de Fusión Nuclear “Guillermo Velarde” (Universidad Politécnica de Madrid) in the field of plasma amplifiers of UV, XUV and soft X-ray radiation. Hydrodynamic simulations are performed with ARWEN. The amplification of radiation is studied with 1D (DeepOne), and 3D (Dagon) Maxwell-Bloch codes. Results on hydrodynamic modelling of QSS and OFI soft X-ray lasers, characterization of plasma waveguides and amplification of harmonics in plasmas will be presented.
We evaluated the capabilities of an intense ultrafast high-harmonic seeded soft X-ray laser at 32.8 nm wavelength regarding single-shot lensless imaging and ptychography. Additionally the wave front at the exit of the laser plasma amplifier is monitored in amplitude and phase using high resolution ptychography and backpropagation techniques.Characterizing the laser plasma amplifier performance depending on the arrival time of the seed pulse with respect to pump pulses provides insight into the light plasma interaction in the soft X-ray range.
The amplification of UV radiation and high order harmonics (HOH) in plasmas is a subject of raising interest
due to its different potential applications in several fields like environment and security (detection at distance),
biology, materials science and industry (3D imaging) and atomic and plasma physics (pump-probe experiments).
In order to develop these sources, it is necessary to properly understand the amplification process. Being the
plasma an inhomogeneous medium which changes with time, it is desirable to have a full time-dependent 3D
description of the interaction of UV and XUV radiation with plasmas. For these reasons, at the Instituto de
Fusi´on Nuclear we have developed DAGON, a 3D Maxwell-Bloch code capable of studying the full spationtemporal
structure of the amplification process abovementioned.
One promising way to reach ultra-short soft X-ray lasers is to guide an intense infrared pulse through a plasma channel generated in a high pressure gas. However, in such a case, strong non-linear effects, as overionizationinduced refraction and self-focusing, hinder the propagation of the laser beam and thus the creation of the lasing ion and the population inversion. Using a particle-in-cell (PIC) code and a ray-tracing model, we demonstrate that a stable self-regulation mechanism between self-focusing and overionization appears, which enables guiding the infrared beam over several milimetres, well beyond the saturation length for amplification of the soft X-ray laser.
X-ray free-electron lasers (FELs) are powerful tools for probing matter properties down to sub-nanometer scales with femtosecond time resolution, allowing a growing number of physical, chemical, biological and medical investigations to be carried out. FELs operating in seeding mode intrinsically present enhanced temporal coherence properties with respect to those relying on the self-amplified spontaneous emission (SASE) process. They are however limited, for the moment, to extreme ultraviolet (XUV) wavelengths, or in some cases to soft X-rays, and durations of tens of femtoseconds. We studied how these limits can be overcome by means of X-ray chirped pulse amplification, inspired by infrared lasers.
As a matter of fact, the use of a seed enables a fine control of the chirp and a spectro-temporal shaping of the FEL emission. Moreover, ultrashort wavelengths can be envisaged through schemes of high-gain harmonic generation and echo-enabled harmonic generation. We will present FEL simulations coupled with the study of a compressor in conical diffraction geometry.
Ultra-intense X-ray sources have opened new avenues by creating new states of matter or probing and imaging living or inert matter. Free-electron lasers have a strong leadership by delivering pulses combining femtosecond duration and 10s of microJoules to milliJoule energy. However, these sources remain highly expensive limiting their number to a few worldwide. In parallel, laser-pumped soft X-ray lasers hold outstanding promises having demonstrated the most energetic monochromatic soft x-ray pulse and being intrinsically fully synchronized with any secondary source of the pump laser. Since the first successful demonstration of amplification of a high harmonic pulse in a plasma from gas in 2003 and from solid in 2008, we have developed an extensive numerical study. 2D hydrodynamic simulations showed that optimized Transient Collisional Excitation plasma amplifiers, may store up to 0.4 mJ in the population inversion. If carefully seeded, pulses of 80 fs and 20 μJ might be generated with table-top lasers (10J). As the energy extracted is far from the milliJoule requirements of most exciting applications, we studied the seminal experiment of Ditmire et al who seeded a plasma emitting milliJoules in the form of Amplified Spontaneous Emission (ASE).We retrieved and explained for the first time the experimental result (ASE 1,000 times stronger than amplified seed). We thus proposed and fully modeled the transposition of the so-called Chirped Pulse Amplification (CPA) in the soft X-ray range, showing that 6 mJ, 200 fs, fully coherent soft X-ray pulse is accessible with compact pump lasers.
An experiment was set up to measure the wavefront of an injection-seeded soft x-ray laser based on a solid-target plasma amplifier. The 43rd harmonic signal from a Ti:Sa laser was used to seed a molybdenum plasma amplifier operating in the λ=18.9 nm line of Ni-like Mo. A Hartmann wavefront senor with an accuracy of λ/32 rms at this wavelength was employed to measure the wavefront of both the high harmonics seed and the seeded soft x-ray lasers. A significant improvement in wavefront aberration from 0.51±0.04λ rms to 0.25±0.03λ rms was observed as a function of plasma column length. The variation of wavefront characteristic by the time delay between the injection of the seed and the peak of soft x-ray amplifier pump was studied in this paper.
Plasma-based seeded soft x-ray lasers (PBSXRL) have the potential to generate high-energy, fully coherent,
short pulse beam. Nowadays, PBSXRL have demonstrated experimentally 1 μJ, 1 ps (1 MW) fully coherent,
aberration-free pulses. Nevertheless, most exciting applications (as single-shot coherent imaging) require pulses
shorter than 200 fs and energy ranging from 10 μJ to several miliJoules. In this chapter we will review the
theoretical modelling tools and the results obtained related to this source.
We present an experimental design to independently pump two soft X-ray laser media suitable for a seed-amplifier
configuration. Both the seed and the amplifier target are operated in the TCE scheme utilizing the DGRIP technique with
its intrinsic travelling wave excitation. Controlled injection of the seed X-ray laser into the amplifier medium is realized
via a spherical XUV mirror. The experimental design is perfectly appropriate for benchmarking combined simulations of
the ARWEN and DeepOne code. A first experiment at the PHELIX laser utilizing this scheme has been conducted,
demonstrating signs of amplification and allowing for the direct measurement of the gain life time of a Ni-like silver
SXRL.
Seeding plasma-based soft-x-ray lasers (PBSXR) with high order harmonics (HOH) is a promising way to obtain
fully coherent, short (hundreds of femtoseconds), tens of microJoules pulses. Nevertheless, up to date only 1
μJ, 1 ps pulses have been demonstrated seeding plasmas created from gas targets and solid targets. As the
amplification process couples plasma hydrodynamics, atomic processes and the propagation of electromagnetic
fields, a careful optimization of seed and amplifier properties is essential to reach multi-microJoule, hundreds
of fs regime. Recent papers showed that short and wide (up to 1 mm) plasmas present an optimal gain
zone and up to 20 μJ could be extracted when seeding. Nevertheless, the temporal duration and profile of the
output beam is still not optimal. Simulations show that the HOH is weakly amplified whereas most of the
energy is within a long (several picoseconds) wake induced by the HOH. In addition to this, these simulation
pointed out the presence of deleterious Amplified Spontaneous Emission (ASE). In order to obtain intense pulses
useful for practical applications is crucial to reduce the duration to hundreds of fs and obtain ASE-suppressed,
structure-free (ideally only an amplified HOH) pulses. Using the 1D Bloch-Maxwell code DeepOne we will show
that fully coherent, wake and ASE-suppressed, 15 μJ, 120 fs pulse can be obtained when optimizing at the same
time both the seed and the plasma conditions.
By seeding amplifying plasmas pumped with the so-called Transient collisionnal excitation scheme, the amplified pulse
seems to be limited to an energy of several 10's of μJ. Aiming to attain several mJ, we study the seeding of plasma
pumped by long laser pulse. Thanks to our time-dependant Maxwell-Bloch code, we demonstrate that direct seeding with
femtosecond pulse is inefficient. We also study the amplification of pulse train with the drawback of re-synchronizing
the pulses. We proposed and studied the amplification of high harmonic seed stretched by a grating pair, amplified
finally compressed. We consider off-axis diffraction on the gratings for maximizing their efficiency. Considering the
phase deformation induced by the amplification and the spectral narrowing the final pulse is 230 fs in duration and 5 mJ.
Seeding plasma-based soft x-ray laser (SXRL) demonstrated diffraction-limited, fully coherent in space and in time
beam but with energy not exceeding 1 μJ per pulse. Quasi-steady-state (QSS) plasmas demonstrated to be able to store
high amount of energy and then amplify incoherent SXRL up to several mJ. Using 1D time-dependant Bloch-Maxwell
model including amplification of noise, we demonstrated that femtosecond HHG cannot be efficiently amplified in QSS
plasmas. However, using Chirped Pulse Amplification concept on HHG seed allows to extract most of the stored energy,
reaching up to 5 mJ in fully coherent 130 fs pulses. Original pump-probe experiments will be proposed thanks to the
high laser energy available in ELI facilities.
Plasma-based seeded soft x-ray lasers have the potential to generate high-energy, highly coherent, short pulse beam. Due to their high density, plasmas created by interaction of intense laser with solid target should store the highest amount of energy density among all plasma amplifiers. However, to-date output energy from seeded
solid amplifiers remains as low as 60 nJ. We demonstrated that careful tailoring of the plasma shape is crucial for extracting energy stored in the plasma. With 1 mm wide plasma, energy as high as 22 μJ in sub-ps pulse is achievable. With such tailored plasma, gain and pumping efficiency has been increased by nearly a factor of 10 as compared to the narrower plasma amplifiers studied previously and here.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.