suite du séminaire CPPM 5/12/2011Morceau choisi de :

FLOWERFluctuations of the Light velOcity WhatEver the Reason

François Couchot, Xavier Sarazin, Marcel UrbanLAL Orsay

Jérome Degert, Eric Freysz, Jean Oberlé, Marc TondussonLOMA, Bordeaux

Presented by Xavier Sarazin9èmes Journées Phénomènes Ultra-rapides

Université de Rouen17-19 Octobre 2011

Vacuum LengthL (pc)

Tim

e W

idth

rm

s (s

)

Pulsar ~kpcFWHM ~ s

GRB ~ 1-10 GpcFWHM ~ 10 ms

as )(50t mL

We can improve the sensitivity using femto laser

100 fpc = 3 kmFWHM ~ 6 fs

Measurements of possible fluctuations of c

The FLOWER Setup

Primary pulse

COLA (LOMA)Ti:SapphirePulsed Laser10 nJ / pulse

t0 (rms) ~ 20 fs(rms) ~ 15 nm

Motorstage

Diode

Non linearcrystal

Intensity Autocorrelation

RC = 1.8 mConcave Mirror M2Planar Mirror M1

M

The length of the cavitycan be modified

The number of round tripscan be modified

Input/output Hole

The number of round trips can be modified

Allow measurements of different vacuum path lengths Lvacuum

For a given number of round trips, the length of the cavity can be modified

The systematic due to possible mirror dispersions can be separately measured

We will first validate and calibrate the setup by filling the Herriot cell with a gas

chromatic dispersion (Argon@1 atm, L=50m,=80015nm) ~ 60 fs

General solution = k./ N N = number of round trips

RC = 1.8 mLength (m) of the Herriot cell

(r

ad)

Example with 5 round trips

Preliminary Tests in LOMA

Gold metallic concave mirror already available“Ultra high” quality

= 15 cm

Preliminar planar mirror Dedicated high quality mirror with a

hole has been purchased

Here an example with 11 round trips

Preliminary simulation for 21 round trips and RC = 1.8 m

Stable solution for = 16/21 and L = 1.56 m

By construction: the outgoing beam is similar to the incoming beam

With the available gold concave mirror, we can already reach a vacuum path length

Lvacuum = 2×21×1.56 = 65.5 meters

Flower Phase 1Herriot cell Lcell ~1.55 m Can reach at least Lvacuum = 65 m with 21 round trips

Width (rms) of COLA laser pulses ~ 20 fs

Accuracy autocorrelation measurement ~ 2 fs (width rms)

Expected sensitivity of vacuum fluctuations: 0 ~ 1 fs.m1/2

0 ~ 0.2 fs.m1/2Better than GRBSimilar to microburst from Crab pulsar

With fastest femto laser: rms ~ 2 fs

Improved accuracy of autocorrelation meas. ~ 0.5 fs (150 nm step)

Flower Phase 2

This setup allows to measure the dispersion in gas with high accuracy

Test if any discontinuity or discrete properties of the photon propagation in vacuum

Super-Flower

Herriot cell Lcell ~ 50 m (as CALVA in LAL Orsay)

~ 50 round trips

Can reach Lvacuum = 5 km

If 0 ~ 50 as.m1/2,

Width (rms) of initial laser pulses in~ 2 fs

in~ 2 fsvacuum ~ 3.5 fs

Lvacuum=5 kmout~ 4 fs

Effet SHADOK

Et si on pompait le vide ????

Effet SHADOK

s s

Virtual fermion

antifermion pair1810.31

msN

ciii

The idle pulse, circularly polarized +1, moves with a velocity c

A pump laser, circularly polarized +1, with ultra high intensity, masks some virtual pairs

Number of occupied pairs ii NNN

The idle pulse (circularly polarized +1) will move with a higher velocity c*

eiiii NN

c

NNc

64/1

1*

)/(10.264

341 mphotonsNN

N

c

c

e

Effet SHADOK

If the laser spots are focused along 1mm,

it should creates an advance of the idle pulse of 1 fs

Mercury Laser @ Livermore (LLNL)• 1 PW peak power: 15 J, 15 fs• 1023 W/cm2 maximum focused irradiance• 10 Hz repetition rate• 1 m

If focal spot ~ 1m2 c/c ~ 3.104

A mechanism has been proposed to give a finite value of the speed of light in agreement

with the observed value

This quantum vacuum description gives also the origin of and

It leads to two experimental predictions

possible fluctuations of the transit time of photons of ~ 50 as.m

a possible advance of a idle pulse of ~ 1 fs after having propagated 1 mm in a ultra

high intensity pump laser

Ultra short femto lasers seem to be the ideal tool to perform these tests

Attosecond pulses for FLOWER ?

Are FROG/RABBIT able to detect a time broadening of the XUV attosecond pulses ?

(see S. De Rossi’s talk for geometric aberrations)

CONCLUSIONS