Department of Experimental Physics Physics http://physics.ttk.pte.hu Prospects of THz Pulse Generation with mJ- L l E d 100 MV/ El t i Fi ld Level Energy and 100 MV/cm Electric Field JA Fülöp 1,2, * Z Ollmann 3 L Pálfalvi 3 G Almási 1,3 J .A. Fülöp , Z. Ollmann , L. Pálfalvi , G. Almási , J. Hebling 1,3 1 High-Field THz Research Group HAS Hungary High Field THz Research Group , HAS, Hungary 2 Attosecond Light Pulse Source of the Extreme Light Infrastructure, Hungary 3 Department of Experimental Physics, University of Pécs, Hungary *e mail: fulop@fizika ttk pte hu e-mail: fulop@fizika.ttk.pte .hu Workshop on THz Sources for Time Resolved Studies of Matter, ANL, Argonne, July 30-31, 2012
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Department of ExperimentalPhysicsPhysics
http://physics.ttk.pte.hu
Prospects of THz Pulse Generation with mJ-L l E d 100 MV/ El t i Fi ldLevel Energy and 100 MV/cm Electric Field
J A Fülöp1,2,* Z Ollmann3 L Pálfalvi3 G Almási1,3J.A. Fülöp , , , Z. Ollmann , L. Pálfalvi , G. Almási , ,J. Hebling1,3
1High-Field THz Research Group HAS HungaryHigh Field THz Research Group, HAS, Hungary2Attosecond Light Pulse Source of the Extreme Light Infrastructure, Hungary
3Department of Experimental Physics, University of Pécs, Hungary
Workshop on THz Sources for Time Resolved Studies of Matter, ANL, Argonne, July 30-31, 2012
Applications of High-Energy THz Pulses
0,6
0,8
1,01,0
ampl
itude
(a. u
.)
.)
Emax
0 1 2 30,0
0,2
0,4
0 0
0,5
Spe
ctra
l a
Frequency (THz)
tric
field
(a. u
.
-0,5
0,0El
ect
Linear THz spectroscopy (E ≈ 100 V/cm → 10 fJ pulse energy)
-2 0 2 4 6 8time (ps)
Linear THz spectroscopy (Emax ≈ 100 V/cm → 10 fJ pulse energy) graphene, nanotubes, molecular magnets, etc.
N li TH t (E 100 kV/ J l )Nonlinear THz spectroscopy (Emax ≈ 100 kV/cm → µJ pulse energy)THz pump – THz probe measurements of dynamics (Hoffmann et al., PRB, 2009)
Manipulation and acceleration of charged particlesManipulation and acceleration of charged particles(Emax ≈ 100 MV/cm → 10 mJ pulse energy)VUV–XUV pulse generation by Thomson-scattering, X-ray free electron laser, …
Optical Rectification
[ ][ ]2
THz2
232
22eff
2THz
THz 44sinh2
THz
LLeILd L α
εωη α ⋅⋅= −
Conversionefficiency
[ ]THz3
THz2
0 4Lcnnv αεdepends on:
THz frequency: 2THzTHz ωη ∝
h
Material parameters → FOM
THzTHzη
phTHz
grvis vv =Phase matching → velocity matching:
L << 12222 ILdeffω
η eff LdFOM
22
Figure of merit (FOM):
αTHzL << 1 320 cnn THzv
ffTHz ε
η =
228 Ideffω
THzv
ffNA nn
FOM 2=
24 ffdαTHzL >> 1 322
0
8cnn
d
THzTHzv
effTHz αε
ωη = 22
4
THzTHzv
effA nn
dFOM
α=
Materials for Optical Rectification
Material deff( /V) ( 1)
FOM*( 2 2/V2)
grnmn800 THn
grmn μ55.1
THzα(pm/V) (cm-1) (pm2cm2/V2)
CdTe 81.8 3.24 2.81 4.8 11.0
nm800 THzn μ
GaAs 65.6 4.18 3.59 3.56 0.5 4.21
G P 24 8 3 67 3 34 3 16 0 2 0 72GaP 24.8 3.67 3.34 3.16 0.2 0.72
ZnTe 68.5 3.13 3.17 2.81 1.3 7.27
GaSe 28.0 3.13 3.27 2.82 0.5 1.18
sLiNbO3sLN 100K
168 2.25 4.96 2.18 174.8
18.248.6sLN 100K 8 8 6
DAST 615 3.39 2.58 2.25 50 41.5
Velocity matching condition: THzgrNIR
phTHz
grNIR nnvv =⇒=
* for L = 2 mm
Tilted-Pulse-Front Pumping (TPFP)
phTHz
grvis cos vv =⋅ γ
~100 fs typicalHebling et al., Opt. Express, 2002
Tilted-Pulse-Front Pumping vs. Line Focusing
Stepanov et al., Opt. Express, 2005 Hoffmann & Fülöp, J. Phys. D, 2011
THz Pulse Generation by Optical Rectification in LiNbO Using Tilted Pulse Front Pumping
Large nonlinear coefficient (deff = 168 pm/V)
LiNbO3 Using Tilted Pulse Front Pumping
Velocity matching by tilting the pump pulse front
Hebling et al Opt E press 2002phgr Hebling et al., Opt. Express, 2002
Highest THz pulse energy from a table-top source0 25 μJ Stepanov et al Opt Express 2005
phTHz
grvis cos vv =⋅ γ
0.25 μJ Stepanov et al., Opt. Express, 200510 μJ Yeh et al., Appl. Phys. Lett., 200750 μJ Stepanov et al., Appl. Phys. B, 2010
125 J Fülö t l O t L tt 2012125 μJ Fülöp et al., Opt. Lett., 2012
Further increase of THz energy is in sightti l diti – optimal conditions
(pump pulse duration & wavelength, crystal temperature & length)Fülöp et al., Opt. Express, 2011
– by increasing the pumped area in optimized setupsPálfalvi et al., Appl. Phys. Lett., 2008Fülöp et al., Opt. Express, 2010
Effective Interaction Length
-20 -10 0 10 20
Pump propagation distance, ζ [mm]
ps]
εdnPulse front tilt:
2
dura
tion,
τ [p (a)
λελγddtan
gnn
−=
1
Pum
p pu
lse
d
2Ld
materialdispersion
angular dispersionLiNbO3
[%]
0 τ0 = 50 fsτ = 350 fs
P
GVD parameter:
dispersiondispersionLiNbO3λp = 800 nm
Fp = 5.1 mJ/cm2
Ωpm = 1 THz
( )⎥⎦
⎤⎢⎣
⎡−⎟
⎠⎞
⎜⎝⎛==
−
2
221
λλελ
λ dnd
ddn
cdvd
D g
4
(b) Ln ef
ficie
ncy
[ τ0 350 fs τ0 = 600 fs
⎦⎣ ⎠⎝ λλλ ddcd2
(b) Leff
Hz
gene
ratio
n
Martínez et al JOSA A 1984-5 0 5
0
THz propagation distance, z [mm]
TH
Martínez et al., JOSA A, 1984Hebling, Opt. Quantum Electron., 1996Fülöp et al., Opt. Express, 2010
10 MV/cm level using imagingIp, max = 40 GW/cm2 → 10 MV/cm level using imaging
→ 100 MV/cm level using focusing
Optimization of the Pump Pulse Length
Frequency at the spectral peak
1,5 LiNbO3
L ≤ 10 mm 300 K 100 K 10 K
0 [T
Hz] Ip, max = 40 GW/cm2
lp = 1064 nm1,0
uenc
y, Ω
0
Phase matching adjusted to the
0,5
peak
freq
u
spectral peak
0 200 400 600 800 1000
p
pump pulse duration [fs]
New Appilcation Possibilities for THz Pulses with High Electric Field
TH
High Electric Field
THz beam
AccelerationAccelerationPlettner et al., Phys. Rev. Spec. Top. – Accel. and Beams 9, 111301 (2006)
Beam deflection, focusingPl tt t l Ph R S T A l d B 12 101302 (2009)
1 GV/m = 10 MV/cm peak field strength is needed
Plettner et al., Phys. Rev. Spec. Top. – Accel. and Beams 12, 101302 (2009)
New Appilcation Possibilities for THz Pulses with High Electric Field High Electric Field
Enhancement of HHGEnhancement of HHGE. Balogh et al., PRB, 2011K. Kovács et al., PRL, 2012
Longitudinal compression of electron bunches→ single-cycle MIR…XUV pulse generationHebling et al., arXiv:1109.6852Hebling et al., presentation on Monday
Electron undulationH bli t l Xi 1109 6852Hebling et al., arXiv:1109.6852
1 MV/cm field and 0 1% efficiency reached by applying our above results1 MV/cm field and 0.1% efficiency reached by applying our above resultsHirori et al., Appl. Phys. Lett., 2011
Design of Contact Grating on LiNbO3
Contact grating for THz generation proposed:
Index matching by glass:
R f ti i d t hi li id (RIML)
Pálfalvi et al., APL, 2008
Nagashima et al., Japan J. Appl. Phys., 2010
Oll t l APB b itt dRefractive index matching liquid (RIML):
Pump: 1.5 µm wavelength, 5 cm beam diameter→ THz energy = 2.2 mJgy→ THz intensity = 630 GW/cm2 (focused)→ THz field ≈ 20 MV/cm (focused)
Summary
Single-cycle THz pulse generation with 100 MV/cm field and ~10 mJ energy is feasible around ~1 THzf b OR d b ffi i t DPSS lfrequency by OR pumped by efficient DPSS lasers
→ nonlinear THz spectroscopy→ manipulation of electrons and ions
1 10 1001
pump pulse energy [mJ]
p
Acknowledgement: Hungarian Scientific Research Fund (OTKA), grant numbers 78262 and 101846, SROP-4.2.1.B-10/2/KONV-2010-0002, and hELIos ELI_09-01-2010-0013.