Keith A. Nelson

Department of Chemistry

MIT

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

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)

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

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

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...

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

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)

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).

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).

Cross-correlation

with 45 fs 3 µm in InSb

Pulse duration < 100 fs

P.B. Andersen & A. Tokmakoff,

Opt. Lett. 35, 1962 (2010)

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)

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!

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 ⇒

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

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

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

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

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

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

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)

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)

WaveguideFocusing reflector

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)

Through spatiotemporal fs pulse shaping

SLMgrating gratinglens lens

Timed/phased array generation

4 spots

Tilt down

40 spots

Tilt up

8 spots

Focus

8 spots

Focus

Tilt down

Horizontal array

Cylindrically focused “line” sources

Linear temporal sweep

Coherent THz amplification

T. Feurer et al., Science 299, 374 (2003)

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

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)

-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)

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)

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

ETHz ~ 1.2 MV/cm BTHz ~ 0.4 Tesla

H. Hirori, K. Tanaka et al., Appl. Phys. Lett., 98, 091106, 2011 .

33

3

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

THz Transmission Spectrometer

THz Pump – THz Probe Capabilities

Also THz pump – Optical probeMeasure optical birefringence, SHG,…

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

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)

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

3High T: instantaneous response Lower T: Soft mode 2x ω

Still lower T: Rise then decay Lowest T: Slowest decay

Moderate T: Mode softening Moderate T dependence

Soft mode & polar nanoregion response

Overall hot electron relaxation dynamics

Bulk Ge & GaAs crystals

Phys. Rev. B 79, 161201 (R) (2009)

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

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)

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

H. Hirori, K. Tanaka et al., Nature Comm. 2, 594, 2011

46

Impact ionization

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

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

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

530 GHz, on resonance

60 µm

l

Collaboration w/ R. Averitt group, Boston U

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)

Metamaterials: Tailored electromagnetic responses

Padilla, et. al. PRB 75, 041102® (2007)

• Engineered resonant

structures

• Specific EM responses

• Depends strongly on

materials used

Metamaterial responses are highly sensitive to the substrate

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!

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!

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!

Damage along field lines

Pattern resembles dielectric breakdown

Pads for electrical contact

Active area

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)

2

0.4 THz metamaterial

resonance

Metallic VO2 shorts gaps

THz resonance disappears

at high T in metallic

25 µJ/cm2

70 µJ/cm2

160 µJ/cm2

230 µJ/cm2

320 µJ/cm2

2

THz resonance

disappears at high

THz fluence

T = 325 KMeasurement Simulation

2

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

THz-induced damage in VO2:

Damage patterns and the Poole-Frenkel mechanism

Damage along equipotential lines

First time

Partial decomposition of TNT!

Metamaterial-enhanced chemical decomposition

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

0 5 10 15 20 25 30

-2

0

2

sig

na

l (u

V)

time (ps)

Nonlinear signal in air!

What from??

Sharly Fleischer

w/ Yan Zhou & Robert W. Field

Orientation and Alignment of Gas Phase

Molecules by Single Cycle THz Pulses

Revival Revival

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)

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)

Two delayed THz pulses 350 torr OCS

1/2

13/2

Small second pulse induces

large second revivals!

33ps

16.5ps

Time (ps)

16.5ps

J=0J=1

J=2

J=3

J=4

2B

4B

6B

10B

6B

10B

14B

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

020

40

6080

1

2

Time (ps)

1

3

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!

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

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