suite du séminaire CPPM 5/12/2011 Morceau choisi de : FLOWER Fluctuations of the Light velOcity WhatEver the Reason François Couchot, Xavier Sarazin, Marcel Urban LAL Orsay Jérome Degert, Eric Freysz, Jean Oberlé, Marc Tondusson LOMA, Bordeaux Presented by Xavier Sarazin 9èmes Journées Phénomènes Ultra-rapides Université de Rouen Octobre 2011
Vacuum Length L (pc) Time Width rms (s) Pulsar ~kpc FWHM ~ s GRB ~ 1-10 Gpc FWHM ~ 10 ms We can improve the sensitivity using femto laser 100 fpc = 3 km FWHM ~ 6 fs Measurements of possible fluctuations of c
The FLOWER Setup Primary pulse COLA (LOMA) Ti:Sapphire Pulsed Laser 10 nJ / pulse t 0 (rms) ~ 20 fs (rms) ~ 15 nm Motor stage Diode Non linear crystal Intensity Autocorrelation R C = 1.8 m Concave Mirror M2 Planar Mirror M1 M The length of the cavity can be modified The number of round trips can be modified Input/output Hole
The number of round trips can be modified Allow measurements of different vacuum path lengths L vacuum 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 atm, L=50m, =800 15nm) ~ 60 fs General solution = k. / N N = number of round trips R C = 1.8 m Length (m) of the Herriot cell (rad) 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 R C = 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 L vacuum = 2×21×1.56 = 65.5 meters
Flower Phase 1 Herriot cell L cell ~1.55 m Can reach at least L vacuum = 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.m 1/2 0 ~ 0.2 fs.m 1/2 Better than GRB Similar 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 L cell ~ 50 m (as CALVA in LAL Orsay) ~ 50 round trips Can reach L vacuum = 5 km If 0 ~ 50 as.m 1/2, Width (rms) of initial laser pulses in ~ 2 fs in ~ 2 fs vacuum ~ 3.5 fs L vacuum =5 km out ~ 4 fs
Effet SHADOK Et si on pompait le vide ????
Effet SHADOK s s Virtual fermion antifermion pair 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 The idle pulse (circularly polarized +1) will move with a higher velocity c*
Effet SHADOK If the laser spots are focused along 1mm, it should creates an advance of the idle pulse of 1 fs Mercury Livermore (LLNL) 1 PW peak power: 15 J, 15 fs W/cm 2 maximum focused irradiance 10 Hz repetition rate 1 m If focal spot ~ 1 m 2 c/c ~ 3.10 4
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