A Charles Townes Legacy
Elsa Garmire
Sydney E. Junkins Professor
of Engineering Sciences
Thayer School of Engineering
Dartmouth College
Townes’ PhD student (1962-1965)
Dartmouth College
An Ivy League School in New England
Maine
Dartmouth
NH
*
VT
Boston
Dartmouth College
4000 undergraduates (# men = # women)
Graduate school in the sciences
Medical school (1797 – fourth oldest)
Tuck Business School (1900 – the first)
Thayer School of Engineering – (1867)
the oldest engineering graduate school
Thayer School of Engineering
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No separate departments
Synergy across expertise from different engineering disciplines
Teamwork and entrepreneurship are encouraged
Opportunity to take courses with Tuck Business School professors
Opportunity for collaborative research with Dartmouth Medical School
Opportunity for collaborative research with the Science Departments
Graduate Enrollment: 47 PhD students
20 MS students (with research thesis)
60 Masters in Engineering Management (with industrial project)
• Undergraduate Enrollment: 112 juniors and seniors
• 44 Bachelor in Engineering students (5th year for ABET credit)
Thayer School Impact Areas
• Engineering in Medicine
Addresses today's technology-driven healthcare system. Advances
depend in the technical side of patient care. Collaboration between
Dartmouth engineers, medical researchers, and clinicians speeds
testing and implementation of technological advances.
• Energy Technologies
Crucial to the future stability of human society. Research includes a
range of projects—from biomass processing to power electronics
optimization. Investigators synthesize ideas and expertise from
biochemical and chemical, electrical, and materials engineering as
well as physics, chemistry, and microbiology.
• Complex Systems
Systems permeate technology in the 21st century. The goal is to
analyze and design complex systems so that their behavior can be
predicted and controlled. Dartmouth engineers are working together
to meet the challenges of large, complex engineered systems such
as computer networks, social networks, smart robots, living cells,
energy infrastructure, and the near-Earth space environment.
Source: http://engineering.dartmouth.edu/research/index.html
Optics and Lasers at Thayer
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Instrumentation  A new type of non-contact optical sensor of
vibration and other motion detection. New designs for free space
optical communications, both for transmission through the atmosphere
and through water. Active and passive waveguides for optical signal
processing, telecommunications, optical data storage, and other
applications. Fiber optics devices such as tunable filters and fiber
lasers. (Faculty contact: Garmire)
Femtosecond pulses being transmitted through water sustain much
less loss than longer pulses, particularly at long distances. Femtosecond pulses are used to create terahertz radiation, whose
transmission through a variety of media is being investigated.
(Faculty contacts: Osterberg, Garmire)
Nonlinear optical studies investigate second- and third-order nonlinear
effects in optical glass fibers, thin films, and semiconductor structures.
A novel project is ultrafast pulse shaping of wavelets for high
bandwidth fiber-optic free-space systems. Nonlinear devices are being
investigated for high-speed image processing and for time-towavelength conversion for communication systems.
(Faculty contact: Garmire, Osterberg)
Source: http://engineering.dartmouth.edu/research/by-discipline/electrical.html
Other optics at Thayer
Magneto-optics: production and studies of magnetic vortex states in ring
structures, and the coupling between them. Thin dielectric films enhance the
magneto-optic Kerr effect signal. Interactions of proximal rings and
symmetry effects. (Faculty contact: Gibson)
Nanophotonics: interaction of light with sub-micron structures and nanotextured materials. Molecular Imprint Polymers (MIPS) with surface plasmon
resonance and capacitive measurements for chemical sensing. Applications
include the detection of pollutants, chemical residues and biological
compounds indicative of early-stage cancer. ZnO nanopillars for photonic
bandgap engineered devices. (Faculty contact: Gibson)
Microelectromechanical Systems (MEMS) -- includes modeling, fabrication,
and testing of the following:
– untethered mobile micro-robots, and interactions between small swarms
of micro-robots;
– stress engineering of out-of-plane electromechanical structures such
as microturbines;
– integrated micro-inductors for power electronics;
– high sensitivity optical sensors;
– binary optical devices.
MEMS device fabrication takes place in Thayer School's microengineering
lab, a Class 100 clean room facility. (Faculty contact: Levey)
Biomedical Imaging Research at Thayer
Fluorescence imaging to track molecular signals and tags in tissue, especially cancer tumors
in vivo and vascular diseases. Also coupled to magnetic resonance imaging and computed
tomography imaging. Evaluating their response to therapy. (Faculty contact: Pogue)
Dynamic multimodal imaging (DMI), a framework for reconstructing images of neural and
vascular dynamics in the human brain. DMI combines concurrently recorded data from
multiple imaging modalities such as electroencephalography, near-infrared spectroscopy,
and functional magnetic resonance imaging. (Faculty contact: Diamond)
Image-guided neurosurgery gives the surgeon the ability to track instruments in reference to
subsurface anatomical structures. Using clinical brain displacement data, a computational
technique is being developed to model the brain deformation that typically occurs during
neurosurgery. The resulting deformation predictions are then used to update the patient's
preoperative magnetic resonance images seen by the surgeon during the procedure.
(Faculty contact: Paulsen)
Near-infrared imaging (NIR) to quantify blood and water concentrations in tissue, as well as
structural and functional parameters. NIR spectroscopy can be combined into standard
imaging systems to provide additional information for breast cancer detection and
diagnosis. Work is ongoing to improve techniques for better image reconstruction, display
and integration with magnetic resonance imaging (MRI) and computed tomography (CT)
imaging. (Faculty contacts: Pogue, Paulsen, Jiang)
Non-linear image reconstruction techniques: Excitation-induced measurements from each
instrument are compared with calculations to compute images. As images are updated in a
non-linear iterative process, important features become more apparent. The computational
core of the breast imaging project works synergistically to improve our fundamental
understanding of these mathematical systems to improve overall image quality and
resolution. These processes have been developed for both 2D and 3D geometries in each
modality and are being expanded to exploit emerging parallel computing capabilities.
(Faculty contacts: Paulsen, Meaney)
Other lasers and optics biomedical research
Photodynamic therapy for cancer, age-related blindness, pre-malignant
transformation or psoriasis. Administration of a photosensitizing agent, together
with the application of moderate intensity light activates the molecules to
produce local doses of singlet oxygen. Developing dosimetry instrumentation
and software, fluorescence tomography imaging to sense drug localization, and
assaying treatment effects in experimental cancers. (Faculty contacts: Pogue,
Hoopes)
Therapy monitoring using imaging modalities. These include:
– near-infrared imaging of brain tissue;
– near-infrared spectroscopy for diagnosing peripheral vascular disease;
– electrical impedance spectroscopy for radiation therapy monitoring;
– magnetic resonance elastography for detecting brain or prostate lesions; to
follow the progression of diabetic damage in the foot;
– microwave imaging spectroscopy for hyperthermia therapy monitoring, brain
imaging, and detection of early-stage osteoporosis.
(Faculty contacts: Paulsen, Meaney)
Clinical optical-electric probes are being developed for noninvasive simultaneous
measurement of blood oxygenation and electrical potential changes associated
with brain activity. (Faculty contact: Diamond)
Label free genome sequencing to "read" the sequence in a single DNA molecule
in a massively-parallel fashion. The technology combines concepts of single
nucleotide addition sequencing, near field optics, single molecule force
spectroscopy, and microfluidics. (Faculty contact: Shubitidze)
A Townes Legacy
Lasers that are everywhere
eg. the laser pointer
Laser Printer
Laser
diode
http://library.thinkquest.org/C0115420/Cyber-club%20800x600/Gif/pics2/Laser%20Printer.gif
CD/DVD Players
Laser diode
Lens
CD
The Internet
Optical Fiber
Multiple
Optical
Fibers
Laser Diode
Laser light is focused
into a single fiber
Product Scanners
Supermarkets
Laser scans
across bar
code. Reflected
light, modulated
by the bar code,
is detected, and
data is entered
in a computer.
Photo-Detector
Hand
scanner
Hologram for Security
Credit Card, ID Cards, Advertising
November, 1985
LASIK procedure
Laser Light
Laser re-shapes cornea after flap (conjunctiva) is lifted
History:
From Quantum Electronics to Laser
• Combine physics of “quantum” with
electrical engineering of “electronics”
• Developed after WWII
• Microwave devices, originating from radar
• Charles Townes: designed/built radars
then studied microwave spectroscopy
Stimulated Emission: the source of gain
Einstein, 1916
Absorption
Spontaneous emission
excited state
photon
ground state
Stimulated
emission
More light
leaves than
came in
http://www.thetech.org/exhibits/online/lasers/Basics/images/albert.gif
http://www.physics.ubc.ca/~outreach/phys420/p420_95/mark/h2.gif
Charles Townes and the Maser
(with post-doc Jim Gordon) about 1953
Townes
Gordon
Maser
Microwave
Amplification by
Stimulated
Emission of
Radiation
Maser requires
gain and feedback
Gain requires
Stimulated emission
Result: Oscillation
http://globetrotter.berkeley.edu/people/Townes/images/maser.jpg
Oscillation from gain and feedback
Example: sound systems
Speaker
Feedback
Microphone
Gain
Amplifier
Result: a shriek!!
The Laser Idea (1958)
Charles Townes and Art Schawlow
Atoms
as gain
medium
gain
Mirrors for feedback
Townes
Schawlow
~ 1963
Argon
Laser
Beam
The First Ruby Laser: 1960
Ted Maiman at Hughes Aircraft
Flash Lamp
Ruby
Gain: ruby rod excited by light from a helical flash lamp
Mirrors: silver films on the end of the ruby rod
http://www.ieee-virtual-museum.org/media/bW8Jx8FS8nF2.jpg
The First Gas Laser – Helium/Neon
(Inventors: Javan, Bennett and Herriott)
1961
Gain: helium-neon
gas discharge
Mirrors:
Special
high-reflectivity
multi-layer films
What do today’s lasers look like?
They can be small …
Laser diodes are tiny chips of semiconductor
A
commercial
package
http://upload.wikimedia.org/wikipedia/en/thumb/b/bd/
Laser_diode_chip.jpg/300px-Laser_diode_chip.jpg
The laser diode chip
Used in CD players,
laser printers, and
fiber optic systems
They can be large:
National Ignition Facility
The world’s largest laser, being built now
A person
View of Laser Bay 1 from the transport spatial filter, containing 96 laser beams.
In all, 192 beams of beampath are complete: 1.8 Million Joules of light.
To ignite nuclear fusion
Lawrence Livermore National Laboratories
Capabilities of Lasers
gain + feedback = stimulated emission
Coherent (All photons behave in an identical manner)
directional
focus to small point
interfere
Ultra-stable single frequency or color (1 part in 1015)
Ultra-high speed communications
1012 bps
Ultra-long distance communications (to the moon)
Ultra-short pulses 3 attoseconds
10-15 sec
Ultra-high power (for 10-12 s)
>1018 W
Ultra-small size
10-12 cm3
Coherence
All stimulated emission photons are identical, like soldiers
Spontaneous emission photons
are random
U.S. Soldiers, World War II
http://www.trumanlibrary.org/photographs/58-790-38.jpg
speckle
Time’s Square
New Year’s Eve
http://www.mistyvisions.com/images/nyc.jpg
Directional: Laser beams reach
the moon and back
Time delay
of pulses
gives distance
Lasers beams
travel
in straight lines
Focus to a small point: Lasers drill
holes smaller than human hair
Human
Hair
Hole Size ~50 µm
Sizes to scale
Optical
Fiber
Hole size ~ 2 µm
Interference
Miniature
Commercial Interferometers
www.armstrongoptical.co.uk
Reflective surface
Measurement of distance, motion, non-destructive testing
Non-contact measurement
Ultrastable: LIGO Interferometer
for measuring gravity waves
near Baton-Rouge Louisana – two arms, each 2.5 mi long
http://www.phys.lsu.edu/dept/gifs/LIGO.gif
Monochromatic:
Ring Laser Gyro Sagnac Effect
One gyro
Honeywell’s 3-gyro system
Clockwise vs. Counterclockwise
Frequency Difference determines rotation
Interference: Holograms
Research at MIT: 1962-1966
Townes moved to MIT in the fall, 1961
Existing lasers: Ruby laser (pulsed, high
power), HeNe (continuous, monochromatic,
invisible)
Fundamental research: Michelson-Morley
experiment with HeNe (looking for aether).
Nonlinear Optics with the ruby laser
Lasers enabled Nonlinear Optics
>Second Harmonic Generation<
Laser beam enters a crystal of ADP
as red light and emerges as blue
Electron orbitals distort nonlinearly -- non-linear polarization
fy.chalmers.se/.../Photonic/information.html
2w0
w0
w1 + w2
2w1
2w2
Light Pulse
Electrical Signal
w0 - w0
7670 A
6943 A
SRS
wL - W
Laser
wL
Representation of the spectrum
Energy difference between photons
is given up to molecular vibrations W
MIT Laser Laboratory, 1962-65
Stimulated Raman Scattering
My PhD research: Nonlinear Optics
Stimulated Raman Scattering
Laser  Stokes + molecular vibration
Stokes beam
A nonlinear process
that introduces
new wavelengths by
involving
molecular vibrations
wL + W
wL - W
Laser beam
Anti-Stokes
Stokes
Two Laser Photons
wL
wL
Molecular vibration + Laser  anti-Stokes Anti-Stokes radiates in rings
driven by Stokes in corresp. ring
First explanation of
multi-photon processes in
Stimulated Raman
Scattering.
First explanation of antiStokes and several orders of
Stokes
First explanation of angular
emission of anti-Stokes
Proof of coherent molecular vibration theory:
Chiao, Stoicheff and Townes: SRS in calcite
My Experimental SRS Data in Liquids
“Stokes”
“Anti-Stokes”
Most of
my results
Agrees
with theory
Ultimately explained by the presence of self-trapping
Townes’ New Idea:
Stimulated Brillouin Scattering
Experiments in quartz with Chiao and Stoicheff (PRL May 1964)
My Data on Stimulated Brillouin Scattering
Appl Phys. Lett. August, 1964 experiments in liquids
Q-switch
gain
mirror
Fabry-Perot
Interferogram
Laser
SBS
SBS
Several
orders
observed
Nonlinear
Refractive
Index
Enables
Light to
Form its
Own
Waveguide
Spatial
Soliton
Threshold
Power is
Required.
Self-trapping of Optical Beams
Laser
Increasing
Laser
Power
Selftrapping
No Pinhole
Garmire, et. al. PRL, 1966
How they looked then (1966)
Charles Townes
Frances Townes
Elsa, Gordon and Lisa Garmire
the Townes’ horse and buggy
1966
1966-1974: Research in
Amnon Yariv’s Caltech Laboratory
Ultra-short Pulses (1966-1970)
Picoseconds
• How do we generate them?
– Nonlinear absorption in laser cavity: theory
Yariv
• How do we measure them?
– Collide two pulses in two-photon fluorescent medium
Yariv, Laussade
• How do we expect them to behave in nonlinear
optics?
– Harmonic pulses longer in time
Comly
Integrated Optics (~1970)
Equivalent to integrated electronics
On one chip: laser, detector, modulator, switch
Uses waveguides
Input Light
V
Output Light
Modulator:
Turns light on
and off
with voltage
Yariv, Hall
Semiconductor Waveguides
• Ion Implantation
– First demonstration
– First use for waveguide couplers
– First use for rib waveguides
• Zinc Diffusion
– First demonstration
• Epitaxy (growing one layer on another)
– First demonstration:
DFB lasers
Distributed Feedback Lasers
Regular Laser
http://www.alpeslasers.ch/technology/dfb_pict_b.jpg
Corrugation replaces end mirrors
Caltech: A. Yariv et al.
Laser Art
Laser
Beacon
Laserium: laser light show
Laser Light Wall
Caltech Moon Landing Celebration
On TV at art opening, 1970
LASER IMAGES
Show of photographs
and light box
Hollywood, 1969
Experiments in Art and Technology
Pepsi-Cola Pavilion, Expo ’70, Japan
Moved to USC in 1975
Infrared Waveguides with Mike Bass
Infrared light from CO2 lasers cuts materials
Wouldn’t a fiber for this laser be nice?
Our solution: hollow metal waveguide
Rectangular cross-section
Low-loss, flexible in one dimension
A typical USC laser laboratory
Graduate
Student
Susan Allen
~ 1982
Lithium Niobate Modulators
Lithium Niobate Crystal
sliced into wafers & polished
Early modulators were long
Today’s
Tiny
Modulator
Pencil
http://fibers.org/objects/news/6/11/1/FSErnd1_10-04.jpg
Titanium in-diffusion
Hybrid Optical Control: Optical Bistability
Optically Addressed Switch
Laser
input
Beam splitter
output
V
detector
amplifier
Hysteresis
J. Marburger
S. D. Allen
Output
light
Input light
Distributed Feedback Bistability
H. Winful, J. Marburger
Output A
Input
Output B
Low intensity light reflects -- high intensity goes through
Control signal can change the direction of the output signal
.
http://mizumoto-www.pe.titech.ac.jp/img/
Recent results from Japan (2004)
All-Optical Bistability
Nonlinear Fabry-Perot in Semiconductors
Thin sandwich of semiconductor between mirrors as “bread”
InAs
in
out
C. D. Poole
USC Laboratory with Researchers
Alan Kost
Randy Swimm
~ 1988
Semiconductor Quantum Wells
Nonlinear Optical Properties
GaAs
Pump-Probe
Experiments
AlGaAs
Kost, Dapkus, et al.
Quantum Well Hetero-n-i-p-i’s
for sensitive nonlinearities
mW optical power levels
Band diagram
Kost, Dapkus
Experimental Results
Some of my USC Students
Nan Marie Jokerst
Ramadas Pillai
Boo Gyoun Kim
The USC Research Group
me
~ 1990
Marla, Lisa, Elsa, Bob, 1979
One of the Advantages of being a
Researcher
1982
My students are Townes’ “grand-students”
Where are they now?
Former Students now faculty members:
Herbert Winful, University of Michigan, Arthur Thurnau Prof.
Professor of the Year, EECS (twice)
State of Michigan Teaching Excellence
Fellow: OSA, IEEE, APS
•SongSil Univ. Korea
Nan Marie Jokerst, Duke University. •Chaio Tung Univ. Taiwan
J.A. Jones Distinguished Professor
•Japanese Defense
Best Teacher in EECS
Academy
Fellow: OSA, IEEE
•Frederick Institute of
Technology,Cyprus
Former Post-Docs now faculty members:
Susan D. Allen, VP for Research & Academic Affairs, Arkansas State
Ping Tong Ho, University of Maryland, Professor
Alan Kost, University of Arizona, Associate Professor
9 professors
Where are Townes’ grand-students now?
•
Started companies
– C. Poole, Eigenlight, CTO (10,000 Sq. ft. manufacturing) OSA Fellow
– R. Pillai, Nuphoton, President, $3.4 M annual sales (14th largest IndianAmerican manufacturer)
– R. Logan, Phasebridge, President ($2 M annual sales)
– E. Park, LuxN, CTO (36 employees, bought out)
– D. Magharefteh, Azna Inc. Chief Technology Officer
– J. Millerd, 4D Technology Corp., CTO (R&D 100, NASA awards)
•
Key positions in companies
–
–
–
–
–
T. Hasenberg, JDS Uniphase, Director of Wafer Fabrication.
K. Tatah, Cray Inc. Lead Optical Engineer
R. Kuroda, XCOM Wireless, Vice President of Engineering
S. Koehler, Phasebridge, VP of Strategic & Product Marketing
M. Jupina (MBA), Checkpoint Technologies, Sales & Marketing Manager
Total financial impact: ~ $15 M per year
Original government investment: $5 M.
Where are other of his grand-students?
• Small start-ups and sole proprietorships
– W. Richardson, Qusemde, CTO. (3 employees)
(after research scientist at Stanford)
– K. Liu, All-optronics, President (3 employees)
– G. Hauser. Sole proprietor, microscopes
– J. Menders, IPITEK, Principal Investigator
– D. Tsou, consultant
• Government Service
–
–
–
–
A. Partovi (MBA), The Science Foundation of Ireland, Research Advisor
C. Mueller, Aerospace Corporation, 20-yr award; NASA awardee, 2003
M. Chang, Aerospace Corporation
K. Wilson, Jet Propulsion Laboratories
• Other
– T. Papaiannou, Cedars Sinai Hospital
– Erich Ippen, Industrial Light and Magic
– M. Yang, retired (raising two children)
My women/minority
students & post-docs
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•
•
•
•
•
•
•
•
Katherine Liu
Nan Marie Jokerst
Mei Yang
Jean Yang
Grace Huang
Susan Allen
Kate Zachrewska
Cao Mingcui
Patricia Berghold
Herbert Winful
Keith Wilson
Wayne Richardson
Antonio Mendez
13 out of 45: ~1/3
Where are my Dartmouth
graduates now?
• Ergun Canoglu (PhD, USC), LuxN, Principal Engineer
• Akheel Abeeluck (PhD), Directed Energy Solutions,
Principal Investigator
• Brian West (MS), Post-doc, University of Toronto
• J. Halbrooks (MS), Engineer, Mathsoft
• Philip Heinz (PhD), Prismark Partners
At Dartmouth:
Lasers to Remove Graffiti
(continued from USC)
Camera
Pattern Recognition
and Computer Controller
YAG laser
Scanning mirror
control
patented
Photo-refractive Four-wave Mixing
Converts image from one laser beam to another
Can convert color, or direction, or incoherent to coherent
Used for image processing – correlation
Requires semiconductor quantum wells
Akheel Abeeluck
Competition from computers
Referenceless Optical Detection
of Surface Vibrations
Spatially moving speckle
Detector
HeNe
laser
Mirror
Philip Heinz
Detector
Elements
Four-point Photoconductive
Detector
Detector Array
Philip Heinz
Summing Electronics
Jon Bessette: Researching ways to extend
the idea to higher frequencies
Research Now Underway
Optical Beam Propagation
with Spatial Phase Jumps
Gaussian Beam
Ashifi Gogo
Phase 0
Phase p
Phase p
Phase 0
At 175 meters
harles Townes’ 90 Birthday
My Family in October, 2005
Charles Townes’ 90th Birthday
A Townes’ Legacy
Lasers, which are ubiquitous
• Lasers differ in type, capabilities, and size
• Lasers are a fundamentally new technology, operating
on a different principle from anything before.
• Government’s investment in my research pays off
annually with my former students.
• These students are Townes’ “grand-students.”
• Who could have imagined the science and the
applications?
Eleven Nobel Prize years – 24 individuals more each year
Laser Research
Science or Engineering?
• The laser was a paradigm shift:
nothing like it before
• The maser had no practical application
• No clear path from laser to application
• There is a continuum between science
and engineering.
– New technology requires new science
– New technology enables new science
Scientific Advances using Lasers
•
•
•
•
•
•
•
•
•
4 degree black body radiation
High resolution spectroscopy
Femtosecond chemistry
Biology: confocal microscope
Bose Einstein Condensation
Combustion analysis
Aerodynamics
Atomic Force Microscopy (AFM)
Michelson-Morley Experiment: no ether
Eleven Nobel Prize years – more each year
24 individuals – more each year
Applications
• Lasers and Processing
– LASIK, Surgery, Coagulation
– Manufacturing: cutting, welding, heat treating
– Materials processing: selective reactions
• Lasers and Information
– CD players, laser printers, internet, cell
phones
• Lasers and measurement
– Surveying, distance, level line, specialty tools