Doctorant: Limin Meng Directrice: Annie Klisnick

Etude expérimentale et simulation numérique des lasers XUV transitoires en mode ASE et injecté

Experimental study and numerical simulations of transient XUV lasers in ASE and seeded mode

1 What is XUV laser?

XUV (Extreme ultraviolet) laser is the coherent radiation whose wavelength is in the X-ray range(3nm-50nm).

XUV

y

x

z

Target(Ti, Mo, Ag….)

Pre-Laser

Plasma

Pump laser

HOH

2 production of transient XUV laser

1 ） ionization-pre pulse irradiate in normal direction,

2 ） Pump-interval hundreds ps, grazing incidence pumping (GRIP)

3a ） production of ASE XUV laser-Amplitude Spontaneous Emission (ASE mode) 3b ） production of seeded XUV laser-high order harmonics (HOH) seed

ASE XRL

Seeded XUV

3 My topic---measure the temporal coherence and the spectral line width of the XUV laser

In many application, we need short pulse duration. Such as production of plasma, and the detection of fast process.

The duration of current XUV lasers is limited to ~1ps, due to a very narrow bandwidth (Δλ/λ 10∼ -5)

Our goal is to find strategies to enlarge the bandwidth and reach duration of a few 100 fs

4 How to measure the bandwith of the XUV laser —the variable path difference interferometer

Interferometer—view outside

Lc is the coherent length that we can calculate directly from the experiment results.

Interference field

Interferometer—principle shown

mobile dihedron

fixed tilted dihedron

XUV Laser Beam

Z

CCD

cc Lc 112

4 the work I have done 1 --Measurement of the Temporal Coherence of a

Seeded GRIP Transient Mo XUV Laser

Far field footprint

Detected fringesExperiment performed at CSU (USA)Results are submitted to Optics Letters

Main conclusion: the coherence length is about 400um, corresponding to a linewidth of about 3mÅ; spectral narrowing when the length of the plasma amplifier is increased.—agreement with simulation

-100 0 100 200 300 400 500 600 700 8000,0

0,2

0,4

0,6

0,8

1,0

Vis

ibil

ity

Path difference (um)

average

exponential fitting

the work I have done 2–- Measurement of the Temporal Coherence and the

duration of a ASE Transient Mo XUV Laser In the second year, I have done a new experiment, which is performed at LASERIX! We are now analysing the data. Some example of the images and the preliminary results are shown below

XUV laser duration vs pump pulse duration

0

1

2

3

4

5

6

7

0 2 4 6 8 10

pump pulse duration(ps)

XU

V la

se

r p

uls

e

du

rati

on

(ps

)

0.75 ps

8 ps4 ps

1.5 ps

5 What I Will do

The goal is to define the effect of several

parameters to the linewidth:

atomic number the electron density

----Preparing new experiment at Laserix

----compare the results with numerical simulation

Thank you for your attention!