Keith A. Nelson Department of Chemistry MIT - Advanced Photon … · Nonlinear optical crystals,...
Transcript of Keith A. Nelson Department of Chemistry MIT - Advanced Photon … · Nonlinear optical crystals,...
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Keith A. Nelson
Department of Chemistry
MIT
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Collective dynamics
Crystalline phase transitionsAccelerating carriers
Driving polar lattice vibrations
Driving low-frequency electronic resonances
Controlling charges and dipoles (electric & magnetic)
Measuring dynamical events involving their motions
Coherent control over collective & local structure & dynamics
K+
O2-
Nb5+
Ferroelectric
KNbO3 crystal
Ionic & polar liquids, glasses, polymers…Driving orientation, local modes, liquid rearrangements
Driving motions of charges & chemical change
Atomic & molecular transitions, charge transferRydberg transitions, ionization
Driving molecular rotations & alignment
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MD simulations of THz-driven FE domain switching: PbTiO3
w/ Andrew Rappe & Tingting Qi, U Penn
THz fields drive increasing amplitudes until switching occurs!
Collective coherent control
T. Qi et al., PRL
102, 247603 (2009)
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Sources for high THz pulse energyCommon tabletop methods
Nonlinear optical crystals, optical rectification
THz “polaritonics”
Tilted optical pulse front pumping
Plasmas, THz-IR generation
Non-tabletop methods
Synchrotron sources
E-beam fringe fields at LCLS
Nonlinear spectroscopyNonlinear vibrational & electronic responses in solids
Driving phonons & electrons
Nonlinear responses in liquids & gases
Driving molecular orientation through polarizabilities & dipoles
Prospects
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Thomas Feurer
Joshua Vaughan
Nikolay Stoyanov
David Ward
Eric Statz
Andrei Tokmakoff, MIT
Gwyn Williams, Jefferson Lab
Antoinette Taylor, LANL
X.-C. Zhang, RPI
Janos Hebling (Pecs U)
Mattias Hoffmann
Ka-Lo Yeh
Harold Hwang
Christopher Werley
Nate Brandt
Qiang Wu (Tianjin U)
Kung-Hsuan Lin
Zhao Chen
Xibin Zhou
Bradford Perkins
Christopher Tait
Stephanie Teo
Richard Averitt (Boston U)
Mengkun Liu
Robert Field (MIT)
Yan Zhou
Thanks for slides from:
Koichiro Tanaka, Kyoto U
Aaron Lindenberg, Stanford
Christoph Hauri, Paul Scherer Inst
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Difference-frequency mixing
produces THz emission
P(t)d2P/dt2
nonlinear
medium
(χ(2))
femtosecond
laser pulse
single cycle
THz pulse
100 fs laser pulse
ω>Eg(GaAs)
+
E
-
THz PULSE
j
z
Bulk GaAs
From photoconductive
antennae
ETHz~ dJ/dt = d2P/dt2
in the far field
Electron acceleration
produces THz emission
From nonlinear
crystals
Collinear or non-collinear
velocity matching...
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Optical rectification in organic crystals
THz at the focus
Opt. Lett. 37, 899 (2012)
pump
APL 99, 161116 (2011)
Recent results from Hauri Group (EPFL/PSI, Switzerland)
e.g. DAST (4-N,N-dimethylamino-4’-N’methyl
stilbazolium tosylate), OH1, DSTMS,-
strong optical χ(2) nonlinearity
low (IR, THz) absorption
high damage threshold (100 GW/cm2)
good phase matching
pump wavelength: 1.2-1.5 µm
high conversion efficiencies (≈2 %)
good focusability
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THz spot in the focusOpt. Lett. 37, 899 (2012)APL 99, 161116 (2011)
0.4 mm (FWHM)
up to 1.6 MV/cm (0.5 Tesla)
up to 20 µJ pulse energy
single-cycle pulses
CEP stabilized
excellently suited for high-field laser-matter
interaction, like THz-induced magnetic switching
(paper submitted)
Optical rectification in organic crystals
Recent results from Hauri Group (EPFL/PSI, Switzerland)
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http://www.rpi.edu/~zhangxc
All-Air THz Photonics
Laser pulse
100 fs, 0.8 mJ
800 nm, 1 kHzDetector
BBO
Plasma
Filter
Si filterTHz
HV
J. Dai, et al., PRL 97, 103903 (2006).
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ω
2ω
BBO crystal
THz generation mechanism:
ω
e- e- e- e- e-
e- e- e-
THz
Current surge
THz generation
Directional quasi-
DC current
10
K. Y. Kim et al., Nature
Photonics 2, 605 (2008).
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Cross-correlation
with 45 fs 3 µm in InSb
Pulse duration < 100 fs
P.B. Andersen & A. Tokmakoff,
Opt. Lett. 35, 1962 (2010)
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Reflection directs THz into
far field
From electron
accelerator
Electron acceleration
produces THz emission
From electron beam
near field
e- -> 100 MeV, so γ=200
THz
ρ
Gwyn Williams, Jefferson Lab Aaron Lindenberg, Stanford/LCLS
Daranciang et al., APL 99, 141117 (2011)Carr et al., Nature 420, 153 (2002)
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Conventional NLO crystal
Collinear velocity matching
Optical pump
ZnTeTOP VIEW
THz
Equal refractive index values
⇒ Equal velocities
Optical & THz pulses
copropagate through crystal
gr
vis THz
gr ph
vis THz
n n=
=v v
High-dielectric NLO crystal
Collinear velocity matching is not possible
,gr grgr grgr grgr grTHz vis THz visTHz vis THz visTHz vis THz visTHz vis THz visn >>n v <<vn >>n v <<vn >>n v <<vn >>n v <<vph
Optical pump
THz THzLiNbO3TOP VIEW
γγγγ
cos
cos
gr
vis THz
gr ph
vis THz
n nγ
γ
=
=v v
Cerenkov condition:
THz velocity << optical velocity
THz pulses propagate
mostly laterally through crystal
ZnTe, GaP, GaSe, etc.
So LiNbO3 can’t velocity match collinearly
But it has a very high figure of merit!
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THz phonon-polariton generation in LiNbO3 slabs
The large index mismatch
between THz and optical light
leads to Cherenkov radiation: the
THz propagates mostly
perpendicular to optical pulse
THz
800 nm
LiNbO3
Iopt(x) ETHz(x)
Optical Intensity
envelope → THz
E-field waveform ⇒
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Polar lattice vibrational mode
“Soft” mode in FE phase transitions
⇒ high ε
K+
O2-
Nb5+
Ferroelectric
KNbO3 crystal
2
12
2
0 212
0
1( )
/
TOw b
bc
µε∞
+ Γ + =
∇ − = −
r r r r&& &
rr r &&&
Q Q Q E
A A Q
ISRS
Laser Field2
0
1( ) ( )
2
NE t
M w
αε
∂+
∂
r
r
F+
THz phonon coordinate THz Field
electronic nonlinearity – neglected!
Fs pulses drive lattice through impulsive stimulated Raman scattering
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THz optic phonon-polariton modes in FE crystals
-5 0 5 10 15 20 25 30 35
Probe beam 1 mm away
from excitation beams
Probe beam overlaps
excitation beams
LiTaO3 ISRS Data
(b)
(a)
inte
nsi
ty(a
u)
time (ps)
Polaritons can be used as THz signals
Terahertz “Polaritonics” platform possible
0 2000 4000 6000 8000 10000 12000 14000 160000
1
2
3
4
5
6LiTaO
3 phonon-polariton dispersion curve
fre
qu
en
cy (
TH
z)
polariton wavevector (cm-1)
Coupled lattice vibrational/electromagnetic modes
~ 0.1-10 THz frequencies, 5-500 µm wavelengths in FE crystals
Polaritons move through host crystal at light-like speeds
Four-wave mixing data FWM results with many wavevectors
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Direct x-ray probing of polariton lattice displacements
Fs x-rays achievable through tabletop laser system
Polaritons & polariton-induced structural change may be monitored
Fs x-ray pulse used for time-resolved diffraction
X-ray
Probe
Optical
Pump
006 x-ray diffraction
c
a
b
Derived from LBL synchrotron source
Nature 442, 664 (2006)
Collaborators: A. Cavalleri, S. Wall, C. Simpson, M.Rini, R.W. Schoenlein
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Complete temporal and spatial evolution monitored
ProbePulse
ExcitationPulses
Sample
1.3 ps
Lateral propagation makes THz wave
accessible to further optical inputs
T. Feurer et al., Annu. Rev.
Mater. Res. 37, 317 (2007)
Optical pump
THz THz LiNbO3TOP VIEW
γγγγ
CCD camera
Optical probe & imaging
Enables real-space polariton imaging
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The movies
Samples: LiTaO3, LiNbO3 crystals Polariton speed ≈ c/6 = 50 µm/ps
Length scale ~ 1-2 mm, Temporal range ~ 20-40 ps
Crossed
beams
Round spotRing of light
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The movies
Line source
Single crystal
Line source
Two crystals
Samples: LiTaO3, LiNbO3 crystals Polariton speed ≈ c/6 = 50 µm/ps
Length scale ~ 1-2 mm, Temporal range ~ 20-40 ps
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sample
blue
filter
dichroic
mirrorcylindrical lens
f1
f1
f2
f2
razor
bladediffracted
lightphase
plate
camera
30 µmλ/4
phase plate High sensitivity
In focus
Quantitative
C.Werley et al.,
JOSA B (in press)
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Polaritonic structures & devices
Integrated THz functionalities
Air
All LiNbO3 channels are 200-300 µm wide
LiNbO3
Polaritonic waveguide splitter, interferometer, resonator, 90º bend
LiTaO3
Air
Air
Polaritonic grating5 mm x 4 mm crystal, 250 µm thickNature Materials 1, 95 (2002)
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WaveguideFocusing reflector
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Spatiotemporal
polariton imaging
THz “movies” yield complete spatial & temporal evolution
ProbePulse
ExcitationPulses
Sample
THz amplification,
phased array generation
Programmable
Spatiotemporal
Fs Pulse Shaper
Input:
Single beam,
Single fs pulse
Output:
Many beams,
Many fs pulsesSample
Spatiotemporal THz
coherent control
Integrated THz
functional elementsfabricated by fs laser machining
LiNbO3Air Air
AirLiNbO3
T. Feurer et al., Annu. Rev.
Mater. Res. 37, 317 (2007)
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Through spatiotemporal fs pulse shaping
SLMgrating gratinglens lens
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Timed/phased array generation
4 spots
Tilt down
40 spots
Tilt up
8 spots
Focus
8 spots
Focus
Tilt down
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Horizontal array
Cylindrically focused “line” sources
Linear temporal sweep
Coherent THz amplification
T. Feurer et al., Science 299, 374 (2003)
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Spatiotemporal control over THz field
Annu. Rev. Mater. Res.
37, 317 (2007) Optical pumps
With reconfigurable spatiotemporal fs pulse shaping
With non-reconfigurable echelon structurelens LiNbO3
THz
echelon
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Grating introduces tilt
Lens adjusts tile angle
Crystal in image planeLiNbO3 prism
Tilted pulse front: Simple, compact setup
Pyroelectric
detector
Imaging lens
λ/2
Pumplaser
Grating
2 mm
sLN
THz
Works well at Hz-KHz-MHz rep rates
J. Hebling et al., Opt.
Exp. 10, 1161 (2002)
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-2 0 2 4-1.0
-0.5
0.0
0.5
1.0
0 1 2 30.0
0.2
0.4
0.6
0.8
1.0
Frequency (THz)
Ele
ctr
ic fie
ld s
tre
ng
ht (a
. u
.)
Time (ps)
x 200
1 kHz
Sp
ectr
al a
mp
litu
ide
(a
. u
.)
10 HzTHz Pulse Energy: 10 µµµµJEnergy efficiency: ~ 10-3
Photon efficiency: 100%
Peak power: 5.0 MW
Average power: 100 µW
Terahertz peak intensity
10 MW/cm2
Field strength: 750 kV/cm
0 1 2 3 4 5 6 7 8 9 10
-0.3
-0.2
-0.1
0.0
0.1
0.2
0.3
0.5 1.0 1.5 2.0 2.5 3.0 3.5
0.002
0.004
0.006
0.008
0.010
am
plit
ud
e
freq (THz)
time (ps)
J. Hebling et al. APL
90 171121 (2007)
1 kHzTHz Pulse Energy: > 2.5 µµµµJTHz Av. Power: > 2.5 mW
Peak power: 2.5 MW
Energy efficiency: 4 x 10-4
Photon efficiency: 15 %
Field strength: 150 kV/cm
1 MHz
THz Av. Power: > 0.25 mW
THz Pulse Energy: > 2.5 nJ
Pump: Yb fiber laser/amp
Energy efficiency: 1.8 x 10-5
Photon efficiency: ½ %
Suitable for practical applications
0 1 2 3
1E-3
0.01
0.1
0 2 4 6 8 10
-5
0
5
10
Am
plit
ude (
a. u.)
Frequency (THz)
Time (ps)
Ele
ctr
ic fie
ld s
tre
ng
th (
a. u
.)
0 2 4 6 8 10Time (ps)
Frequency (THz)
THz Pulse Energy: THz Pulse Energy: 7 µµµµJ
M. Hoffmann et al., APL
93, 141107 (2008)Yeh et al., Opt. Commun.
13, 3567 (2008)
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Chirp-and-delay optical pump yields tunable THz frequency
Multi-µµµµJ multiple-cycle pulse energies
Z. Chen, X. Zhou, C.A. Werley, KAN, Appl. Phys. Lett. 99, 071102 (2011)
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Beam profile with pyroelectric camera (Spiricon Pyrocam III)
Focusing with an aspheric lens
100 mm pixel size
2.5 mJ THz pulse energy, 1 kHz rep rate
2 mm
Excellent for imaging, spectroscopy, other applications
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ETHz ~ 1.2 MV/cm BTHz ~ 0.4 Tesla
H. Hirori, K. Tanaka et al., Appl. Phys. Lett., 98, 091106, 2011 .
33
3
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Microjoule level pulses ⇒⇒⇒⇒ THz nonlinear spectroscopy
Nonlinear THz transmission, self-phase modulation
THz-induced ionization, fluorescence
THz pump – optical probe
THz pump – THz probe
THz nonlinear spectroscopy measurements conducted
Nonlinear vibrational & electronic responses studied
Solid-state vibrational & electronic responses
Phase transitions, chemical reactions
Liquid-state molecular alignment
Gas-phase molecular orientation, ionization
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THz Transmission Spectrometer
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THz Pump – THz Probe Capabilities
Also THz pump – Optical probeMeasure optical birefringence, SHG,…
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Collinear pump & probe pulses
EO readout of transmitted pump & probe fields
-8 -6 -4 -2 0 2 4 6
-2
-1
0
1
2
3
4
Ele
ctr
ic fie
ld s
tre
ng
th (
a. u
.)
Probe delay (ps)
Probe
Pump
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THz 1 0.5 THz
THz 2 0.5 THz
LiNbO3
crystal
Anharmonic
lattice vibrations
Crossed THz pump beams induce
anharmonic lattice vibrations
Start toward collective coherent control
J. Hebling et al., IEEE J.
Sel. Top. QE 14, 345 (2008)
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3
1.2
1.0
0.8
0.6
0.4
0.2
0.0
-0.2
Am
plit
ude (
a.u
.)
43210-1Time (ps)
0.6
0.4
0.2
0.0
Im[P
(ω)/
E(ω
)]
2.01.00.0Frequency (THz)
X0.5
E0 (80 kV)
E0/2
E0/4
E0/8
EXPERIMENT
S
THEORY
d 2q
dt2+ Γ
dq
dt+ω0
2q+ aq3 = AE t( )
I. Katayama K. Tanaka et al., Phys. Rev. Lett., 108, 097401 (2012)
3000
2000
1000
0
-1000Die
lectr
ic c
on
sta
nt
2.52.01.51.00.50.0
Frequency (THz)
Imaginary Part
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3High T: instantaneous response Lower T: Soft mode 2x ω
Still lower T: Rise then decay Lowest T: Slowest decay
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Moderate T: Mode softening Moderate T dependence
Soft mode & polar nanoregion response
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Overall hot electron relaxation dynamics
Bulk Ge & GaAs crystals
Phys. Rev. B 79, 161201 (R) (2009)
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THz pump – THz probe electron dynamics
InSb impact ionization & THz-induced tunneling
THz fields pull weakly bound electrons out of conduction band
Accelerated carriers ionize additional electrons
THz fields can release weakly bound electrons generally
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THz pump – THz probe electron & lattice dynamics
Temporal and spectral resolution reveal buildup of carriers, relaxation into phonon manifold
Difference phonon absorption at 1.2 THz due to carrier equilibration with lattice phonons
JOSA B 26, A29-A34 (2009)
PRB 79, 161201 (R) (2009)
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H. Hirori, K. Tanaka et al., Phys. Rev. B, 81, 081305(R), 2010
45
THz off (-1.8 ps)
THz on (0 ps)
(c)
∆t=tTHz-toptMQWs
(a)
THz pump
Optical probe
2.962.922.882.84
Energy (eV)
∆OD
(d)
0.4
0.2
0.0
-0.2
-0.4
Inte
nsity (
arb
. units)
210Frequency (THz)
86420Energy (meV)
-2
-1
0
1
100 0
ETHz (kV/cm)
(b)
THz off (-1.8 ps)
THz on (0 ps)
(c)
∆t=tTHz-toptMQWs
(a)
THz pump
Optical probe
2.962.922.882.84
Energy (eV)
∆OD
(d)
0.4
0.2
0.0
-0.2
-0.4
Inte
nsity (
arb
. units)
210Frequency (THz)
86420Energy (meV)
-2
-1
0
1
100 0
ETHz (kV/cm)
(b)
exciton
electron
hole
Field ionization of
excitons (instantanious)
Dynamical Franz-Keldysh
effect in band to band
transition
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H. Hirori, K. Tanaka et al., Nature Comm. 2, 594, 2011
46
Impact ionization
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Ef = -270 meV (Hole Doped CVD)
CVD graphene• Linear electronic dispersion
• Massless (or very low mass) carriers
• Limited mobility (~2500 cm2V-1s-1)
• Large sizes (macroscopic meter size
sheets!)
• Fairly high doping from etching and
possibly impurities
Exfoliated Graphene• Linear electronic dispersion
• Massless (or very low mass) carriers
• High mobility (>104 cm2V-1s-1)
• Small size (due to difficulties in
exfoliation technique)
• Low intrinsic carrier concentration
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arXiv:1101.4985v1
Intraband Drude conductivity
• When Temp increases, weak effects
on conductivity (increase) and
transmission (decrease)
•When τ decreases, strong effects on
conductivity (decreases) and
transmission (increases) – Suggested
by theoretical results from Bao
0.5 0.7 0.9 1.1 1.3 1.570
80
90
100
110
390 µJ/cm2
220 µJ/cm2
135 µJ/cm2
25 µJ/cm2
0.4 µJ/cm2
Tra
nsm
issio
n (
%)
Frequency (THz)
Induced transparency
as fluence increases
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Nonlinear THz Responses in CVD GrapheneHole-doped graphene
Saturation of THz absorption
THz field drives carriers & impact ionization
arXiv:1101.4985v1 cond-mat.mtrl.-sci] 26 Jan 2011
Low-power
absorption
High-power
saturation
0.5 0.7 0.9 1.1 1.3 1.570
80
90
100
110
390 µJ/cm2
220 µJ/cm2
135 µJ/cm2
25 µJ/cm2
0.4 µJ/cm2
Tra
nsm
issio
n (
%)
Frequency (THz)
Time-dependent absorption recovery
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530 GHz, on resonance
60 µm
l
Collaboration w/ R. Averitt group, Boston U
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530 GHz, on resonance60 µm
l
Low-order mode
Field enhancement
Nano-gap THz field enhancement: work by Dai-Sik Kim and by Thomas Feurer
C.A. Werley et al, Optics Express 20, 8551-8567 (2012)
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Metamaterials: Tailored electromagnetic responses
Padilla, et. al. PRB 75, 041102® (2007)
• Engineered resonant
structures
• Specific EM responses
• Depends strongly on
materials used
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Metamaterial responses are highly sensitive to the substrate
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Nonlinear metamaterial responses in n-doped GaAs:
Electron acceleration at moderate fieldsne = 1 x 1016 cm-3
No metamaterial response
in unexcited system due to
substrate conductivity σ
Unexcited system
THz excitation reduces σσσσMM resonance appears!
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Metamaterial response enhances THz field
and sensitizes THz measurement
Eg = 1.4 eV
1 THz = 4 meV
Nonlinear metamaterial responses in n-doped GaAs:
Impact ionization at high fields
Strong THz field is enhanced at induced MM resonance!
MV/cm fields ⇒⇒⇒⇒ impact ionization ⇒⇒⇒⇒ increases σσσσMM resonance is suppressed!
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Huge conductivity change suggests THz sensing applications!
Nonlinear metamaterial responses in SI GaAs:
Tunneling & impact ionization increase σne = 2 x 106 cm-3
Metamaterial response in
unexcited system due to low
substrate conductivity σ
Strong THz field is enhanced
MV/cm fields ⇒⇒⇒⇒ impact ionization
⇒⇒⇒⇒ increases σ σ σ σ by 108!
MM resonance is suppressed!
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Damage along field lines
Pattern resembles dielectric breakdown
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Pads for electrical contact
Active area
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V. Eyert, Ann. Phys. (Leipzig) 11 650-702 (2002)
L.A. Ladd, W. Paul, Solid State Commun. 7 425-428 (1969)
M. M. Qazilbash et al., Phys. Rev. B 77, 115121 (2008),
Low temperature
Monoclinic structure
Insulating: σ < 10-2(Ωcm)-1
am
bm
cm
High temperature
Rutile structure
Metallic: σ > 103(Ωcm)-1
aR
bR
cR
Tc=340K
w/ Mengkun Liu & Rick Averitt,
Boston University
Nature 487, 345–348
(11 July 2012)
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2
0.4 THz metamaterial
resonance
Metallic VO2 shorts gaps
THz resonance disappears
at high T in metallic
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25 µJ/cm2
70 µJ/cm2
160 µJ/cm2
230 µJ/cm2
320 µJ/cm2
2
THz resonance
disappears at high
THz fluence
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T = 325 KMeasurement Simulation
2
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Poole-Frenkel ionization and carrier heating in VO2
Two-temperature model
- conductivity
E - THz electric field
Ce, Ci – electron/lattice specific heat
Te, Ti – electron/lattice temperature
G - electron-phonon coupling
coefficient
• With P-F , ΔT ~ 20 K
• With = 10 (Ω∙cm)-1, ΔT <1 K
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THz-induced damage in VO2:
Damage patterns and the Poole-Frenkel mechanism
Damage along equipotential lines
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First time
Partial decomposition of TNT!
Metamaterial-enhanced chemical decomposition
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InntEttRdtntn
t
20
2
0 )'()'(')( +≈−+= ∫∞−
0 5 10 15 20 25 30
0
2
4
6
8
10
12
14
16
18
20
22
24
39 K
77 K
150 K
297 K
TH
z K
err
effe
ct sig
na
l (a
rbitra
ry u
nits)
time (ps)
KTN relaxor
ferroelectric crystal
Hoffmann, et. al., APL (2009)
THz pulse drives polarizability anisotropies, induces birefringence
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0 5 10 15 20 25 30
-2
0
2
sig
na
l (u
V)
time (ps)
Nonlinear signal in air!
What from??
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Sharly Fleischer
w/ Yan Zhou & Robert W. Field
Orientation and Alignment of Gas Phase
Molecules by Single Cycle THz Pulses
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Revival Revival
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rev
revrev
time (ps)
EO sampling, OCS 250torr
ReflectionsReflections
S. Fleischer et. al. PRL 107, 163603 (2011)
Macroscopic dipole
cosdE
dt
θ∝
H. Harde, S. Keiding, and D.
Grischkowsky, PRL 66, 1834 (1991)
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Time (ps)
revT
rev
revT
Population
Transferred
To higher J’s
Alignment of OCS, 350 torr, 300K
Measured through Kerr effect (optical birefringence)
S. Fleischer, Y. Zhou, R.W. Field, KAN, PRL 107, 163603 (2011)
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Two delayed THz pulses 350 torr OCS
1/2
13/2
Small second pulse induces
large second revivals!
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33ps
16.5ps
Time (ps)
16.5ps
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J=0J=1
J=2
J=3
J=4
2B
4B
6B
10B
6B
10B
14B
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J J11
22
33
44
55
12
23
34
45
21
32
43
54
13
24
3531
42
53
14
25
41
52
15
51
J J J
2
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020
40
6080
1
2
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Time (ps)
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1
3
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Multiple-cycle waveform can be tuned to specific water lines
Waveform can be optimized for energetic material response
Can saturate water absorption lines
Simulation ⇒ enhanced propagation in air!
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Strong THz sources
Tabletop sources provide high THz pulse energies, high THz field
amplitudes
Enable versatile nonlinear spectroscopy at low and high order
Nonlinear THz spectroscopy
Can be declared a subfield!
Nonlinear responses observed in solid, liquid, gas, plasma phases
Electronic, magnetic, vibrational, rotational responses
Collective structural and localized chemical rearrangements
Prospects
Nonlinear THz spectroscopy is just beginning
Multidimensional, high-order, multispectral spectroscopy
THz coherent control over molecular & collective responses
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Thomas Feurer
Joshua Vaughan
Nikolay Stoyanov
David Ward
Eric Statz
Andrei Tokmakoff, MIT
Gwyn Williams, Jefferson Lab
Antoinette Taylor, LANL
X.-C. Zhang, RPI
Janos Hebling (Pecs U)
Mattias Hoffmann
Ka-Lo Yeh
Harold Hwang
Christopher Werley
Nate Brandt
Qiang Wu (Tianjin U)
Kung-Hsuan Lin
Zhao Chen
Xibin Zhou
Bradford Perkins
Christopher Tait
Stephanie Teo
Richard Averitt (Boston U)
Robert Field (MIT)
Thanks for slides from:
Koichiro Tanaka, Kyoto U
Aaron Lindenberg, Stanford
Christoph Hauri, Paul Scherer Inst