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CAS Lecture 2006
Illinois State University April 25, 2006
Enlightened by lasers
Q. Charles Su
Intense Laser Physics Theory Unit
Illinois State University
Support
National Science Foundation
US Department of Energy
Research Corporation
College of Arts & Sciences
Department of Physics
Light
Newton, Edison (1879) lights up Manhattan (1882)
Laser usages
CD writer, player, laser pointer, scanner,
light knife, cosmetic treatment, laser show
What’s in a laser
active medium, stimulated emission, resonator
Maiman, Townes, MIT echo off moon
Probing matter with lasers
Ionization process, world map
Medical imaging, patent
Matter creation, Klein
Research vs education
ILP approach
In the beginning there was no light …
fire makes us happy
A very brief history of light
IN THE BEGINNING - (c 4.5 Billion BC)
THE SUN - (c 4 Billion BC)
THE EARTH - (c 4 Billion BC)
EARLY LIFE - (c 3 Billion BC)
PHOTOSYNTHESIS - (c 2 Billion BC)
FIRST MAN - (c 1 Million BC)
EARLY MAN - (c 500,000 BC)
FIRE, FLAME and TORCH - (c 400,000 BC)
PRIMITIVE LAMPS - (c 13,000 BC)
ANIMAL LAMPS - (c 5000 BC)
EARLY LIGHTING - (3000 BC)
SUNDIAL - (c 1500 BC)
OIL POTTERY LAMPS - GREEK - (600 BC)
OIL RESERVOIR LAMP - (500 BC)
ROMAN - LIFE & LIGHT - (400 BC - 80 AD)
COLOR AND MUSIC (SOUND) - (c 350 BC)
EARLY OPTICS & LENSES - (c 300 BC)
HORN LANTERN - (c 100 AD)
CANDLE - (c 400)
CAMERA OBSCURA - (c 1000)
COLORS OF THE SPECTRUM - (1666)
POLARIZATION/POLARIZED LIGHT - (1678)
PHOTOGRAPHY, EARLY - (1727)
ADDITIVE COLOR MIXING - (1769)
BETTY LAMP (& BETSY LAMP) - (1790)
FIRST - GAS LIGHTING - (1792)
INFRARED - (c 1800)
ULTRAVIOLET LIGHT (UV) - (1801)
ELECTRIC ARC LIGHT/ CARBON ARC LIGHT - (1809)
PHOTOGRAPHY, MODERN - (1826)
SPEED OF LIGHT - (1849)
SPECTROSCOPE - (c 1850)
KEROSENE LAMP - (1853)
FIRST - FOLLOWSPOT SPOTLIGHT - (c 1856)
PHOTOGRAPHY, MOTION PICTURES - EARLY - (1872)
FIRST - ELECTRIC FILAMENT (INCANDESCENT) LAMP - (1874)
EDISON LAMP - (1879)
SWAN LAMP - (1879)
FIRST - PHOTOCELL - (1880)
ELECTRICITY - (1899)
HIGH INTENSITY DISCHARGE (HID) LAMP - (1901)
MERCURY-VAPOR LAMP - (1901)
TUNGSTEN FILAMENT LAMP - (1907)
GAS FILLED LAMP - (1913)
FLASHBULB - (1930)
SODIUM LAMP - (LOW PRESSURE) - (1932)
FLUORESCENT LAMP - (1937)
PHOTOGRAPHY - POLAROID CAMERA - (1947)
FIBER OPTICS - (1955)
LASER - (1960)
HOLOGRAM/HOLOGRAPHY - (a 1960)
QUARTZ HALOGEN LAMP - (1960)
LIGHT EMITTING DIODE - (a 1965)
wave theory
Theories of light
corpuscular theory
Electromagnetic waves
Christiaan Huygens
1629–1695
photons
Sir Isaac Newton
1643 –1727
James Clerk Maxwell
1831–1879
Albert Einstein
1879–1955
Edison practically lit up the world
laying of the mains and installation of the world's first permanent, commercial central
power system in lower Manhattan, which became operative in September 1882.
Light
Newton, Edison lights (1879) up Manhattan (1882)
Laser usages
CD writer, player, laser pointer, scanner,
light knife, cosmetic treatment, laser show
What’s in a laser
active medium, stimulated emission, resonator
Maiman, Townes, MIT echo off moon
Probing matter with lasers
Ionization process, world map
Medical imaging, patent
Matter creation, Klein
Research vs education
ILP approach
Laser usages
precision
CD player
scanner
printer
power
cutting, laser surgery
temporal precision
probe fast processes
high temperature
fusion
photodynamic therapy
cheaper / safer imaging
photo density waves
In the movies
Laser shows
Light
Newton, Edison lights (1879) up Manhattan (1882)
Laser usages
CD writer, player, laser pointer, scanner,
light knife, cosmetic treatment, laser show
What’s in a laser
active medium, stimulated emission, resonator
Maiman, Townes, MIT echo off moon
Probing matter with lasers
Ionization process, world map
Medical imaging, patent
Matter creation, Klein
Research vs education
ILP approach
Active medium (hurdles in a stadium)
Hurdles ~ Atoms
Hurdle in up position
~ population inversion
Hurdle reset after fall down
~ external “pumping”
A hurdle goes down, energy releases, a pigeon flies away
pigeon ~ photon
down randomly
~ spontaneous emission of light
After many hurdles are down …
No laser
Now a pigeon with the right energy knocks down a hurdle…
+
= hurdle is down +
2 pigeons fly off exactly the same way
~ stimulated emission of light (Einstein)
Start with one pigeon 
2
64 
2048 
4
128 
4096 
8
256 
8192 
… (after 29 rounds) 
… (after 33 rounds) 
16 
512 
16384 
32 
1024 
32768 
536,870,912 > US population
8,589,934,592 > world population
all in concert with each other
~ light amplification
Let pigeons turn around in the stadium and work hard…
Then open up the stadium gate from time to time
~ Light Amplification by Stimulated Emission of Radiation
Ingredients of a laser
(1) Active medium with population inversion
(2) Stimulated emission
(3) Light amplification with resonator
Light
Newton, Edison lights (1879) up Manhattan (1882)
Laser usages
CD writer, player, laser pointer, scanner,
light knife, cosmetic treatment, laser show
What’s in a laser
active medium, stimulated emission, resonator
Maiman, Townes, MIT echo off moon
Probing matter with lasers
Ionization process, world map
Medical imaging, patent
Matter creation, Klein
Research vs education
ILP approach
Laser laboratories and how they are related to my research
Lab for Laser Energetics (U. Rochester)
Laser fusion experiments
Diagnostics
temperature and density determinations
x-ray imaging
ISU-UR collaboration through the DOE NLUF grants
Intense laser facilities around the world
Saclay-France
FOM-Holland
MPQ-Germany
SIOFM-China
U Tokyo-Japan
QOLS-UK
ATT
BrookHaven
U Michigan
ISU: Numerical/Gedanken experiments
Ultra relativistic laser experiments planed
DESY, Hamburg
GSI-Darmstadt
SLAC-Stanford
CUOS-Ann Arbor
ISU: Computer simulations, NSF grants
Bio-optical imaging research
Labs: U Penn, UC Irvine, U Mass, UI
ISU: light scattering lab and MC computations
Lund-Sweden
URC-Canada
LLL
Modeling laser action on computers
Physics and
equations
Computer
programming
Simulations of
experiments
ˆ
ˆ
b p (t)Wp (x)   d n (t)Wn (x)
̂ (x,t)  
p
n
bˆ p (t)   bˆ p' p U(t) p'   dˆ n' p U(t) n'
p'
n'
dˆ n (t)   bˆ p' n U(t) p'   dˆ n' n U(t) n'
p'
n'
U(t)=T exp{–i∫0t dt’ [ca·p–a·A(x,t’)+bc2+V(x,t’)]}
Result visualization
Explanation
More simulations
Great space for (undergraduate) student involvement
Fishing or cleaning fish ?
Laboratory experiments guide theory
Multiphoton ionization 1960s
Above threshold ionization 1979–
Higher order harmonic generation 1980s
Computer experiments predict new physics?
Atomic stabilization 1990
Cycloatom 2000
Klein paradox 2004
Bioimaging 2005
Laser
Laser-atom interaction
–
A microscopic view
Outcome 1: bound
+
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atom
+
Outcome 2: ionized
–
+
–
How does ionization vary with laser intensity ?
Computer simulation of atomic ionization
V(x)  1/ 1  x2
Model atom (Rochester model)
J. Javanainen, J.H. Eberly and Q. Su
Phys. Rev. A 38, 3430 (1988)

Interaction with laser
Solve: Schrödinger
equation
Pick a laser intensity I
Current QM state  future state  
Compute ionization for each state
Gedanken experiment on computer:
Ionization beyond 1016 W/cm2
ionization
all ionized
100%
IN
weak
0
?
strong
super
strong
laser intensity
10 –6
P(t)
10 –4
P(t)
I2
P(t)
I3
P(t)
I4
I
N
T
E
N
S
I
T
Y
Ionization
Suppression!
I4
I > 1016 W/cm2
P(t)
I5
P(t)
I6
10 0
Ionization P(T)
I1
L
A
S
E
R
P(T, I)
P(t)
10 -1
4
5
1st 6
recovery7
2nd
3rd
3
2
1
-2
0
10Laser
10
10I2
intensity,
I (a.u.)
P(t)
I7
Su, Eberly, Javanainen PRL, 64, 862, ’90
Laser intensity
Electron spatial density
stabilization
Outcome 3:
stabilized
ionization
Outcome 2:
ionized
atom
0
Outcome 1:
bound
space
Su, Laser Phys. 3, 241 (1993)
Gavrila, Atoms in Intense Fields (1992)
+
–
–
+
+
–
Computer prediction: Stabilization
Normally
+
–
Increased intensity increases ionization
more chance for electron to pick up energy around nucleus
At super-strong fields
Laser also distorts electron orbits
reduces the chance of interaction with nucleus
+
Other theoretical studies and experimental evidence
Kulander et al, Atoms in Intense Laser Fields Ed Gavrila, (1992)
Keitel and Knight, Phys. Rev. A 51,1420 (1995)
van Druten, et al Phys. Rev. A 55 622(1997)
Longhi, et al, Phys. Rev. Lett. 94, 073002 (2005)
–
Stabilization and recoveries of ionization
10 0
P(T, I)
1st
recovery
10 -1
10 -2
10 0
I (a.u.)
2nd
3rd
10 2
S
nl=S
Su, Irving*, Johnson*, Eberly, J. Phys. B 29, 5755 (1996)
Su, Irving*, Eberly, Laser Phys. 7, 568 (1997)
Users of the Rochester model atom
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> 128 groups in 23 countries
Light
Newton, Edison lights (1879) up Manhattan (1882)
Laser usages
CD writer, player, laser pointer, scanner,
light knife, cosmetic treatment, laser show
What’s in a laser
active medium, stimulated emission, resonator
Maiman, Townes, MIT echo off moon
Probing matter with lasers
Ionization process, world map
Medical imaging, patent
Matter creation, Klein
Research vs education
ILP approach
Dream: to build an imaging device …
safer than x-ray CT
cheaper than MRI
better resolved than ultrasound
Possible solution: IR laser based imaging
Imaging schemes
shadow-gram (like x-ray, CAT)
x-ray
shadow
reflection-gram (like ultra-sound)
ultrasound
scatter-gram (infrared lasers)
laser
Forward problems (predict the future)
medium —> scattered light
Inverse problems (predict the past)
medium <— scattered light
Light-medium interaction computer simulations
FFT on the grid method
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Pane of glass
Wanare, Su and Grobe, PRE 62, 8705 (2000)
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Random medium
X-rays vs laser light
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Monte Carlo Simulation
S. L. Jacques and L.-H. Wang, in Optical Thermal Response of Laser Irradiated Tissue,
edited by A. J. Welch and M. J. C. van Gemert (Plenum Press, New York, 1995), pp. 73-100.
Complication of laser-based image reconstruction
• X-ray
• Laser
Modulation of light induces beam narrowing
=0
 0
wide beam
narrow beam
Transverse light beam waist 
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Intensity I()



()
()

Distance from
optical axis 
Pulse width () shrinks with increasing frequency 
ISU filed patent application in 2005
Beyond theory: experiment?
Output
Fiber
z
Input
Laser
Laboratory measurements for on axis light intensity
S. Campbell, A. O’Connell, S. Menon, Q. Su and R. Grobe, PRE, submitted
experiment
Log(N)
8
simulation
theory I
theory II
8
z=0cm
6
4
z=10cm
4
0
z=5cm
2
-0.6
0
10
20
-0.4
-0.2
0
y [cm]
30
0.2
0.4
z [cm]
0.6
40
Light
Newton, Edison lights (1879) up Manhattan (1882)
Laser usages
CD writer, player, laser pointer, scanner,
light knife, cosmetic treatment, laser show
What’s in a laser
active medium, stimulated emission, resonator
Maiman, Townes, MIT echo off moon
Probing matter with lasers
Ionization process, world map
Medical imaging, patent
Matter creation, Klein
Research vs education
ILP approach
Matter creation from light?
E = mc2
Light = electron + positron
Laser intensity > 1026
Mourou, Yanovsky
Opt. Ph. News 15, 40 (2004)
Popular science articles on matter creation from light
“Conjuring matter from light”
Science, Aug, 29, 1997
“Real photons create matter”
Physics News, Sept. 18, 1997
“Light work”
New Scientist, Sept. 27, 1997
“Boom! From light comes matter”
Photonics Spectra, Nov. 1997
“Matter from light”
CERN Courier, Nov. 1997
“E=mc2, really”
Scientific American, Dec. 1997
“Let there be matter”
Discover, Dec. 1997
“Gamma rays create matter by plowing into laser light”
Phys. Today, Feb 1998
Wave or particle description of matter ?
Traditional wave view
Dirac Equation (1928)
deals with physics after creation
(no creation)
Particle view
Quantum Field Theory (1940s)
deals with # of creation
(no wave nature)
?????????????
Computational QFT
Phys. Rev. Lett. (2004)
wave nature during creation
(new framework)
What are these nice graphs?
Solution of the field operator for e– and e+
ˆ (x,t)
ˆ (x,t)= [ c a·p–a·A+bc2+V ] 
Dirac equation for field it 
Solution
ˆ (t)W (x)   dˆ  (t)W (x) where
ˆ
b

(x,t)


p
p
n
n
p
bˆ p (t)   bˆ p' p U(t) p'  dˆ n' p U(t) n'
p'

n

dˆ n (t)   bˆ p' n U(t) p'   dˆ n' n U(t) n'
n'
p'
n'
U(t)=T exp{–i∫0t dt’ [ca·p–a·A(x,t’)+bc2+V(x,t’)]}
Krekora, Su, Grobe, PRL 92, 040406 (2004) ; PRL 93, 043004 (2004)
Braun, Su, Grobe, PRA 59, 604 (1999)
C.H. Keitel, Cont. Phys. 42, 353 (2001)
A.D. Bandrauk, H. Shen J. Phys. A, 7147 (1994)
From quantum field theory to quantum mechanics
F(x,y,t) = <0||

vacuum
state
ˆ


(+)(x,t)
positive
frequency
part
ˆ c(+)(y,t) || F(t=0)>

charge
conjugation
initial
state
S.S. Schweber, “An introduction to relativistic quantum field theory”
The space-time resolved pair creation
energy
e–
e+
Sample projects that employed the new CQFT method
(1) Space time resolved pair creation
(2) Klein paradox, 70 years old
Phys. Rev. Lett. 92, 040406 (2004)
Phys. Rev. A 72, 064103 (2005)
(3) Localization and Zitterbewegung
Phys. Rev. Lett. 93, 043004 (2004)
(4) Entanglement
J. Mod. Opt. 52, 489 (2005)
(5) Modified Schwinger formula
Las. Phys. 15, 282 (2005)
(6) Supercritical bound states
Phys. Rev. Lett. 95, 070403 (2005)
(7) Interpretational difficulty in QED
Phys. Rev. A, 73, 022114 (2006)
Experimental verification?
Time dependent colliding ions
(existing)
Static supercritical field
Experimental plans:
CUOS Ann Arbor, Michigan
DESY Hamburg, Germany
GSI
SLAC
Darmstadt, Germany
Stanford, California
Laser fields lead to new unions of
Particle
Gravitational
Atomic
Plasma
Astro-physics
Cosmology
Enlightened ?
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Light
Newton, Edison lights (1879) up Manhattan (1882)
Laser usages
CD writer, player, laser pointer, scanner,
light knife, cosmetic treatment, laser show
What’s in a laser
active medium, stimulated emission, resonator
Maiman, Townes, MIT echo off moon
Probing matter with lasers
Ionization process, world map
Medical imaging, patent
Matter creation, Klein
Research vs education
ILP approach
Graduate or Undergraduate
US, best graduate school system in the world
> 50% Nobel in Science after WWII
good research-industry relation
What about our pre-graduate education
Cuts in education funding
Flat science funding
Math/Science not “cool” in school
Do we need to change the perception?
Undergraduate physics research at ISU
Large number of students
Large number faculty mentors
National awards
Show cased at conferences
Center or Research and Education on Nanostructures
Center for Research and Instruction in Space Physics
Intense Laser Physics Theory Unit
Surface Science Lab
Polarized Electron Lab
Atomic Structure
Statistical Mechanics
Nonlinear Dynamics
Mathematical Physics
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Undergraduate research at ILP
Our approach
Start early
Small group collaboration
Project design, execution, completion
Know physics, math, programming
Use intuition, catch misconception
Communicate result with others
Thanks to funding agencies
Big thanks to colleagues past and present
Support from CAS, RSP, Honors Program
Physics faculty colleagues
Postdoctoral fellows
All 35 undergraduate students
Especially Prof. Grobe for collaborations
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Thanks to Alex,
Christina, and Jean!
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Thanks for attending
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