Olivier Delmas

Q-switched laser-assisted grazing incidence pumping (QAGRIP) for efficient soft x-ray laser generation.

We have investigated a new scheme for laser plasma transient collisional soft x-ray lasers based on the use of an additional laser to produce the preplasma. Soft x-ray emission measurements made for different solid targets are presented and discussed. A significant enhancement of the SXRL emission as compared to double-pulse single-beam grazing incidence (DGRIP) using the same pump laser is reported for 13.9- and 32.6-nm SXRL wavelengths.

Gain dynamics in quickly ionized plasma for seeded operated soft x-ray lasers

Harmonic seeded operation of a neon-like titanium plasma-based soft x-ray laser is described. The plasma amplifier is pumped with a variation of the grazing incidence technique involving a fast and localized ionization step. We discuss its effect on gain dynamics by measuring the amplifying factor as a function of the delay between pump pulse and harmonic seed. Two different regimes are pointed out, following the pumping scheme used. For one of them, a delay in the gain generation compared with the pumping laser pulse is observed.

One long and two short pumping pulses control for plasma x-ray amplifier optimization

Development of efficient soft x-ray laser plasma amplifiers adapted to seeded operation, requires a better control over amplifier transverse spatial extent, brilliance control and gain lifetime. Here it is shown that pumping the plasma amplifier with one long and two short pump pulses (1L2S) provides advantages in terms of control for the specified parameters in the case of Ni-like Ag x-ray laser. Also, significant tunability of the gain lifetime in the 1L2S pumping scheme for Ne-like Ti x-ray laser is observed. Direct harmonics seeding and chirped harmonics seeding amplification approaches may benefit from the control of the gain lifetime, in terms of better use of the pump energy and as a way to reduce the amplified spontaneous emission in x-ray lasers.

Diagnosis of energy transport in iron buried layer targets using an extreme ultraviolet laser

We demonstrate the use of extreme ultra-violet (EUV) laboratory lasers in probing energy transport in laser irradiated solid targets. EUV transmission through targets containing a thin layer of iron (50 nm) encased in plastic (CH) after irradiation by a short pulse (35 fs) laser focussed to irradiances 3 × 1016 Wcm−2 is measured. Heating of the iron layer gives rise to a rapid decrease in EUV opacity and an increase in the transmission of the 13.9 nm laser radiation as the iron ionizes to Fe5+ and above where the ion ionisation energy is greater than the EUV probe photon energy (89 eV). A one dimensional hydrodynamic fluid code HYADES has been used to simulate the temporal variation in EUV transmission (wavelength 13.9 nm) using IMP opacity values for the iron layer and the simulated transmissions are compared to measured transmission values. When a deliberate pre-pulse is used to preform an expanding plastic plasma, it is found that radiation is important in the heating of the iron layer while for pre-pu...

Transient Collisionally Excited X-ray Lasers Pumped with One Long and Two Short Pulses

X-ray laser simulations based on Ehybrid code have shown that enhanced plasma x-ray laser emission can be achieved mastering the ionization dynamics and plasma temperature using one long and two short pulses (Ursescu and Ionel, J Optoelectron Adv Mat 12:48–51, 2010). In parallel, two simple methods to generate multiple short pulses for pumping x-ray lasers were reported in conjunction with x-ray laser developments. Five to ten fold enhancement in the emission of the silver x-ray laser was demonstrated using the newly developed pump methods, when compared with the traditional one, based on a long pulse followed by one short pump pulse. An overview of these recent experiments will be presented. The possible implementation of these novel x-ray laser pumping methods at Extreme Light Infrastructure—Nuclear Physics facility will be discussed.

Seeded Operation of a Ne-like Titanium Soft X-Ray Laser

Seeded operation of a Neon-like Titanium plasma-based soft x-ray laser is described. The plasma amplifier is pumped using a variation of the classical grazing incidence pumping technique, combining a long low energy pulse followed by a main short pulse. Because the preformed plasma is underionized, a part of the main short pulse energy is used to ionized it to the lasing stage. Consequences of this feature on seeded laser properties are discussed.

Diagnosis of Radiation Heating in Iron Buried Layer Targets

Extreme ultra-violet (EUV) laboratory lasers can be used to probe energy transport in laser irradiated solid targets. We report on a recent experiment undertaken at LASERIX whereby the heating of laser-irradiated targets containing a thin layer of iron (50 nm) encased in plastic (CH) was diagnosed using EUV laser (13.9 nm) back-lighter probing. The heating laser pulse duration was 35fs with focal irradiances of \(3 \times 10^{16}\)Wcm\(^{-2}\) and a deliberate prepulse 20 ps before the main pulse at irradiances of \(3 \times 10^{15}\)Wcm\(^{-2}\). A one dimensional hydrodynamic fluid code HYADES has been used to simulate the temporal variation in EUV transmission using IMP opacity values for the iron layer and the simulated transmissions compared to measured transmission values. When a deliberate prepulse is used to preform an expanding plastic plasma, it is found that radiation heating is dominant in the heating of the iron layer giving rise to a rapid decrease in EUV opacity and an increase in the transmission of the 13.9nm laser radiation as the iron ionizes to Fe\(^{5+}\) and above.

High Harmonic Generation Driven by Two Quasi-collinear Pulses

We have investigated the high harmonic generation driven by two quasi-collinear IR pulses separated by picosecond delay. Experiments were performed at the LASERIX facility using 50 fs pulses at 800 nm with energy up to 25 mJ. We have studied the generation of two high harmonic pulses from the same medium. In particular, we show how the ratio in energy of each pulse can be used to balance the perturbation induced by the first pulse in the generating gas.

Regenerative Laser Cavity Tuning for Efficient Soft-X-Ray Laser Operation

The influence of temporal pump laser profile on the Soft X-ray laser (SXRL) efficiency is investigated in double grazing incidence pumping (DGRIP) transient collisional scheme. We have demonstrated a simple method that allows to produce and control one or several small prepulses and the ASE level of the pump laser beam by modifying the regenerative amplifier parameters. By changing the temporal structure of the pump beam we observed both an increase of the SXRL energy and an improvement of the target lifetime. Measurements made for different configurations are presented and discussed.

Harmonic Generation and Soft-X-Ray Laser with LASERIX: Source Development, Applications and Advanced Diagnosis

The LASERIX facility has restarted operation in the middle of the year 2010. Since then, important work has been achieved on the XUV sources performance, reliability and stability, which lead to the construction of two beamlines. The first one is based on transient collisional soft X-ray laser. In the second one, the high order harmonic generation process is used to convert infrared laser into coherent XUV radiations. Characteristics and some recent works on both of them will be presented. Besides, a complete setup for pump-probe experiments has been developed and successfully tested. Some examples involving this device and dealing with plasma opacity, radiobiology and nanomagnetism will be presented. We will conclude this paper by a discussion on how application experiments can be turned into valuable diagnostics for XUV sources.