ARPES is used to map the complete electronic band structure for conductors and insulators, among others. Time- and angle-resolved photoemission spectroscopy (TR-ARPES), adds femtosecond temporal resolution, and thus also resolves elementary scattering processes in the electronic band structure.

To avoid space charge problems (electrons repealing each other), one electron or less should be produced and analyzed per laser shot. The application thus requires moderate energy high rep rate sources, and a complete measurement typically lasts 4h at 200kHz.

Amplitude range of Ytterbium lasers, such as the SatsumaX and the Tangor 100 are ideal driving sources for this application. Additional modules such as COMPRESS and HHG chamber, combined with Fastlite twinStarzz MIR OPA, are state of the arts devices allowing to build a unique TR-ARPES setup from a single supplier.

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Ultrafast structural dynamics with X-ray Diffraction

X-ray diffraction is a technique that provides information on the ultrafast dynamics of the structure of matter at the atomic scale. The sample is typically excited by a first ultrashort laser pulse in the Ultraviolet, Visible, Mid Infrared or even Terahertz, and probed by a X-ray Synchrotron or Free Electron beam, or alternatively a compact laser driven X-ray source, as presented in Secondary Sources – X-ray sources section.

When the pump and the probe are produced by two separate systems, the temporal scanning is done using electronic synchronization of the slave laser (usually the pump) with the master source (usually the probe). .

In the case of laser-based sources for pump and probe, the synchronization is inherently ultraprecise, and the scanning is achieved with a simple variable optical delay line with femtosecond precision. Amplitude proposes a broad range of solutions for the optical pump and X-ray probe and their temporal scanning : OPCPA sources pumped by Ytterbium lasers, laser drivers for laser-driven X-ray sources, photocathode lasers for FEL/synchrotron for accelerator-based X-ray sources. In each case, electronic synchronization is a key technology to ensure temporal scanning.

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Principe of sum frequency generation

The technique requires both temporal and spatial overlap of a mid-IR probe and a visible pump on the sample. A SFG signal is then generated at a frequency which is the sum of the two incident field frequencies. This converts the molecular fingerprint of interest from the mid-IR, where it is difficult to observe, to the visible where cheap, fast, convenient, and efficient detection methods are available. The SFG beam properties provide the composition, orientation distributions, and structural information of molecules at gas–solid, gas–liquid and liquid–solid interfaces.

The visible pump should be spectrally narrow to reach a sufficient spectral resolution, and thus distinguish the species’ vibrational fingerprints. However, while scanning narrow bandwidth mid-IR pulses used to be the most common modern setups are using broadband mid-IR OPA systems as a probe to cover a broad range of molecular vibrations, typically from 1000 to 4000cm-1.

Fastlite twinStarzz mid-IR OPA systems pumped by SatsumaX or Tangor are ideal tools for this application, combining high efficiency and high repetition rates to enable higher signal-to-noise ratios and shorter acquisition times. The twinStarzz unique approach allows to generate energetic and broadband mid-IR pulses with unprecedented simplicity, reliability and efficiency. The narrow bandwidth visible pump is generated via innovative second-harmonic generation (SHG) of the Ytterbium pump.

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Applications and Requirements

In order to capture ultrafast dynamics with a good temporal resolution, <100fs pulses are routinely used for 2DIR, while <20fs are common for 2DES.

• 2DES is a very powerful tool to understand the dynamics of photosynthesis and is a crucial tool to enhance current solar energy technologies.
• 2DIR is widely used in pharmaceutical studies.
• Recently, some combinations of these two techniques has even allowed to correlate electronic and nuclei dynamics (2DEV for two-dimensional electronic vibrational spectroscopy)

While Amplitude range of Ytterbium lasers, such as the SatsumaX and the Tangor100, coupled to Fastlite twinStarzz OPA are excellent candidates for this application, Fastlite Dazzler is a must-have for most setups since it drastically simplifies the generation of phase-locked pump pulses, as well as the control of delay and phase variation between them. In other words, the Dazzler immediately transform a simple pump/probe setup in a 2D spectroscopy setup.

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Laser Solutions for THz-TDS

As mentioned in Secondary Sources – Terahertz Generation section, depending on the pulse energy and spectral range used, different lasers and conversion processes can be used.  Amplitude proposes a broad range of solutions :

• For broadband Terahertz generation with two-color filamentation, ultrashort TiSa lasers have been widely used, and now post-compressed Ytterbium lasers bring increasing interest.
• For optical rectification in organic crystals, Ytterbium lasers are usually preferred.
• For organic crystals MIR OPCPA sources are the best option.

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Ultrafast Lasers for Compact High-Brightness Sources

It has been rapidly identified in laboratories that ultrafast lasers have the ability to overcome those limitations thanks to a new physical process. A high-intensity beam focused on a solid target produces a hot plasma in a very confined space. The electrons present in the plasma are then converted into X-rays when they hit the target, like in conventional tubes, but with a much higher intensity when the correct laser parameters are selected.

This laser-based technique allows, among other things:

• Achievement of significantly greater brightness sources than X-ray tubes,
• Much higher spatial resolution together with a reduced deposited dose,
• Greater access for all to trustworthy results from synchrotron sources.

We are convinced that this new X-ray source will revolutionize the world of medical imaging, by giving access to high-resolution images in hospitals in the coming years.

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Rayleigh and Raman scattering techniques use laser light to probe combustion processes. The scattered signal provides information about the molecular composition, temperature, and flow properties, enabling detailed analysis of combustion dynamics.

Thomson scattering for plasma diagnostics

Plasma is a state of matter characterized by the presence of a significant portion of charged particles in any combination of ions or electrons. It is mainly characterized by the density, temperature, and distribution in space of each charged particle composing the plasma.

Plasma Diagnostics: Thomson Scattering

Thomson scattering consists in illuminating a plasma with a laser, and analyze the scattered light in order to retrieve the temperature and density of electrons.

Structure Diagnostics: X-ray Diffraction and Absorption

When matter is placed in extreme conditions (e.g., high pressure or temperature), X-ray sources are used to analyze its properties:

• X-ray diffraction (XRD): reveals the structural evolution of the material.
• X-ray absorption spectroscopy: provides information on the local atomic environment. Techniques include:
  • XANES (X-ray Absorption Near Edge Structure) for electronic and chemical state information.
  • XAFS (X-ray Absorption Fine Structure) for detailed atomic-scale structural information.

Amplitude’s high-energy ultrafast lasers, from Ti:Sapphire systems to Ytterbium platforms, provide the required stability, pulse shaping, and precision to drive advanced diagnostics in combustion science, plasma physics, and extreme matter studies.

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Compression and Ignition Strategies

The inertial confinement fusion (ICF) consists in concentrating high energy laser beams in few nanosecond time scale on a spherical fuel target in order to adiabatically compress and heat the target, and use additional laser beams to ignite the nuclear fusion process. The ultimate goal is to produce energy in power plants, called Inertial Fusion Energy (IFE). This requires to provide laser beams with sufficient total average power and wallplug efficiency to produce significant and rewardable power production to the grid.

Even if compression and ignition strategies still vary among the experts of the community,  there is a common need for kJ-class lasers, operating either at few shots/min for the exploratory research phase, and then at high repetition rate (typically 10Hz) and high wallplug efficiency for the exploitation phase.

For compression, one of the key technical aspects is the ability of shaping the temporal profile of the laser pulses in order to optimize the compression process. This feature is ensured thanks to a flexible seeder routinely used in Amplitude nanosecond lasers (Intrepid-Agilite).

For ignition, one of the strategies consists in producing protons that will penetrate the compressed target and ignite the fusion process. As mentioned in Secondary Sources section, the proton generation relies on the quality of the temporal contrast of the laser driver.

Amplitude is the leader in the field of high energy nanosecond lasers, with significant achievements over the last decade, mainly for the pumping of high intensity lasers at high repetition rate. This unique know-how is a key starting point for the fast development of solutions addressing inertial fusion challenges.

Moreover, our long experience in high contrast lasers places Amplitude at the forefront of the fusion adventure.

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