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Eleonora Rubinorelatore: Daniele Faccio
- relazione delle attività del primo anno -Università degli Studi dell’Insubria
Dottorato in Fisica XXV ciclo
Radiazione di Hawking analoga in laboratorio
PART I: • Hawking Radiation and Analogue Gravity models
• Ultrashort laser pulse filamentation
• Experiments: spontaneous and Bessel filament
PART II:
• A new mid-infrared laser source
PART III:
• Mode conversion (work in progress)
Overview
5 November 2010 Eleonora Rubino
PART I: • Hawking Radiation and Analogue Gravity models
• Ultrashort laser pulse filamentation
• Experiments: spontaneous and Bessel filament
PART II:
• A new mid-infrared laser source
PART III:
• Mode conversion (work in progress)
Overview
5 November 2010 Eleonora Rubino
Hawking radiation
Typical stellar mass black hole temperature:10 nK=> too low to be detected!
1974: S. Hawking predicted that the space-time curvature at the event horizon of a black hole is sufficient to exite photons out of the vacuum.
Hawking radiation glimpsed in artificial black hole© New Scientist, 28 September 2010
5 November 2010 Eleonora Rubino
Essential ingredient is not the astrophysical BH, but rather the space-time curvature associated to the event horizon and a quantum field...
Event horizons and analogue gravity
“The circular jump is a white hole”Jannes et al., arXiv:1010.1701v1
5 November 2010 Eleonora Rubino
“The same arguments that lead to black hole evaporation also predict a thermalspectrum of sound waves from a sonic horizon”
Unruh - 1981
physical systems analogue to black holes:
• Bose-Einstein condensates;
• Acoustic waves (phonons) in moving fluids;
• Moving refractive index perturbation (RIP) in dielectric media (Philbin et al., Science 2008: optical soliton in fiber).
faster water
slower water
Trapping RIP - phase horizon
5 November 2010 Eleonora Rubino
Travelling RIP => intense ultrashort laser pulses in a nonlinear Kerr medium:
The moving δn creates a distortion of thespace-time metric seen by light rays.- PROBE: external seed, or quantum vacuum.
• photons decelerate and are arrested at
• blue shifted frequency
white hole
n(r, t) = n0 + n2I(r, t)
Prediction of the model
5 November 2010 Eleonora Rubino
RIP steepness => blackbody temperature: T =�v2
2πc(1− vn/c)kB
dn
dx
c
n0 + δn< v <
c
n0
RIP velocity => spectral window:
Ultrashort laser pulse filamentation
5 November 2010 Eleonora Rubino
Main features:
• long propagation range of tightly focused intensity peak:
• nearly single cycle shock front:
• possibility to control v:
> pulse splitting (spontaneous filament)> cone angle (Bessel filament)
-200 -100 0 100 2000
14
7
I (TW
/cm
)2
(fs)0.1 0.4
1.98
2.05
2.02
v (1
0 m
/s)8
x (cm)
(a) (b)TL
!"#!
!"$%
!"$&
'"())))))))))'"*))))))))))'"$))))))))'"# '"$#))))))))))))))'"##))))))))))))))'"+#!"$#+
!"$+
!"$+$
!"$+,
'"%))))))))))))))))'"&)))))))))))))!!"$$&
!"$#*
!"$#%
-
./0121-345)6 78
6/8 698 6:8
input 1055 nmspontanous filament
input 800 nmspontaneus filament
input 1055 nmBessel filament, 7° cone angle
medium: Fused silica
Experiments - setup
5 November 2010 Eleonora Rubino
200 400 600 800 1000wavelength (nm)
p-e
coun
ts
0
300
600
spontaneous Raman
NBOHC !uorescence @ 650 nm
ODC !uorescence @ 470 nm
Kerr sample: 2 cm long fused silica (suprasil 311)
Hor. pol. input laser pulse, 1 ps 1055 nm Nd:glass.
Imaging of the filament at 90 degree:‣ imaging spectrometer + cooled CCD camera.
Suppression of spurious effect:
• FWM and SPM, or spectral broadening • Rayleigh scattering• Spontaneous Raman scattering • Fluorescences from glass defects
Experiments - spontaneous filament
5 November 2010 Eleonora Rubino
!"#$#%&%'$(#)*'#+)$,
*-
*.-
*/- -0.
1*2334 2%4254
*-
*.6
*7-
-
-0.
1*2334 284294
:9;%&%)<$"*2)34*=6-*************>6-***************.6-*********66-
*-
*.-
*/-
*6********?06******=06-
-0.
1*2334 2@42'4
A*2334
1 ps, 50 microJ, 10 Hz, Nd:glass laser. Spontaneous filament in 2 cm long fused silica.
90° acquisitions, integrated over 3600 laser shots. 0.1 photons/pulse
c
n0 + δn< v <
c
n0
-200 -100 0 100 2000
14
7
I (TW
/cm
)2
(fs)0.1 0.4
1.98
2.05
2.02
v (1
0 m
/s)
8
x (cm)
(a) (b)TL
varying trailing pulse group velocity
Experiments - Bessel filament
5 November 2010 Eleonora Rubino
n2 = 2.8± 0.5× 10−16 cm2/W
n2 = 3× 10−16 cm2/W
fit slope:
in fused silica:
Kerr effect:
Hawking radiation from ultrashort laser pulse filamentsF. Belgiorno, S.L. Cacciatori, M. Clerici, V. Gorini, G. Ortenzi, L. Rizzi, E. Rubino, V.G. Sala, D. Faccio
Phys. Rev. Lett., in press.
vB =vGcos θ
θ = 7 deg
slightly superluminal RIP velocity:
5 November 2010 Eleonora Rubino
PART I: • Hawking Radiation and Analogue Gravity models
• Ultrashort laser pulse filamentation
• Experiments: spontaneous and Bessel filament
PART II:
• A new mid-infrared laser source
PART III:
• Mode conversion (work in progress)
Overview
5 November 2010 Eleonora Rubino
PART I: • Hawking Radiation and Analogue Gravity models
• Ultrashort laser pulse filamentation
• Experiments: spontaneous and Bessel filament
PART II:
• A new mid-infrared laser source (LaserLab project - Vilnius University)
PART III:
• Mode conversion (work in progress)
Overview
5 November 2010 Eleonora Rubino
MIR - justification
5 November 2010 Eleonora Rubino
• ultrafast IR spectroscopy• biomedicine• laser-matter interaction• high harmonic generation - attosecond science• analogue Hawking radiation
✓ 2nd order nonlinear optics:• NOPAs in KTP, BIBO, PPSLT…
✓ 3rd order nonlinear optics:• gases: FWOPA in filamentation and guided-wave regime• solids: FWOPA in the visible and UV range…
MIR - four-wave optical parametric amplifier
5 November 2010 Eleonora Rubino
(nm)0.4 0.6 0.8 1.0 1.2 1.4
2
4
6
8
Ext
.
(d
eg
)p
m
(b)
signal
near-IR idler
pump
diagnostics
30 fs, 4.8 J seed pulse (TOPAS white)
130 fs, 1.8 mJ
pump pulse
(Ti:Sapph.)
1 mm
fused silica
f
TF10, 60°
TF5, 60°
prisms pair
compressorAl(a)
pm 1 f2
fs
fp
@ Vilnius University, Laserlab project in collaboration with prof. A. Dubietis
Single-pass FWOPA in bulk fused silica:
➡ pump: 800 nm (1.8 mJ, 130 fs, Ti:sapph)
➡ seed: 550-650 nm (4.8 microJ, 30 fs, TOPAS white)
➡ IR idler: 1000-1500 nm
Diagnostics: - spectrum (fiber spectrometer QE65000 Ocean Optics);- spatial profile (InGaAs CMOS camera - Xenics, Xeva 202):- temporal profile (autocorrelator).
MIR - experimental results
5 November 2010 Eleonora Rubino
500 550 600 650 700 750(nm)
(a)
0.6-0.6
-0.6
0.6
0
0
x (mm)
y (m
m)
(d)
0
0.5
1
40-40 0time delay (fs)
(c)
1.0 1.1 1.2 1.3 1.4 1.5 1.60
1
0.5
I (a.
u.)
(m)
(b)
0
1
0.5
I (a.
u.)
1
0.5
I (a.
u.)
visible seed pulse
infrared idler pulse
temporal and spatial profile after compressor stage
‣ 20 microJ, sub-30-fs across the whole range
‣ 17.6 fs FWHM at 1200 nm
‣ 1% pump-to-idler conversion efficiency
Generation of broadly tunable sub-30-fs infrared pulses by four-wave optical parametric amplificationE. Rubino, J. Darginavicius, D. Faccio, P. Di Trapani, A. Piskarskas and A. Dubietis
Opt. Lett., Submitted.
5 November 2010 Eleonora Rubino
PART I: • Hawking Radiation and Analogue Gravity models
• Ultrashort laser pulse filamentation
• Experiments: spontaneous and Bessel filament
PART II:
• A new mid-infrared laser source
PART III:
• Mode conversion (work in progress)
Overview
5 November 2010 Eleonora Rubino
PART I: • Hawking Radiation and Analogue Gravity models
• Ultrashort laser pulse filamentation
• Experiments: spontaneous and Bessel filament
PART II:
• A new mid-infrared laser source
PART III:
• Mode conversion (work in progress)
Overview
5 November 2010 Eleonora Rubino
Mode conversion
5 November 2010 Eleonora Rubino
input = 1 mode(seed)
ω+
ω−
ωin
output = 2 modes
• Co-moving Ref. Frame: 1 positive mode, 1 negative mode
• Lab Ref. Frame: 2 blue-shifted real modes!
The 2 mode-converted waves are generated at the phase horizon:
travellingRIP
δn
t-x diagram
ω� = 0→ → v = c/nv� = 0
Mode conversion - numerics
5 November 2010 Eleonora Rubino
1D code: linear propagation of the field.
Intrinsic numerical dispersion (grid resolution):
labco-moving
P
N
N
P
c/vin
in
ph
ω� = 0
ω� − k� n− ω
Mode conversion - numerics
5 November 2010 Eleonora Rubino
P
Nin
v = 0.996c
τ = 5 cycles FWHM
λin = 4µm
δn = 2.39× 10−3
Mode conversion - numerics
5 November 2010 Eleonora Rubino
spectrum
in
field evolution
P
N
5 November 2010 Eleonora Rubino