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

*NH

VT

Dartmouth

An Ivy League School in New England

Maine

Boston

Dartmouth College

4000 undergraduates (# men = # women)

Graduate school in the sciencesMedical school (1797 – fourth oldest)

Tuck Business School (1900 – the first)

Thayer School of Engineering – (1867)the oldest engineering graduate school

Thayer School of Engineering

• 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• 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. Femto-second 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-to-wavelength conversion for communication systems. (Faculty contact: Garmire, Osterberg)

Source: http://engineering.dartmouth.edu/research/by-discipline/electrical.html

Other optics at ThayerMagneto-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 nano-textured 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 researchPhotodynamic 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 LegacyLasers that are everywhere

eg. the laser pointer

Laser Printer

http://library.thinkquest.org/C0115420/Cyber-club%20800x600/Gif/pics2/Laser%20Printer.gif

Laserdiode

CD/DVD Players

Laser diode

Lens

CD

The Internet

Laser Diode

Optical Fiber

MultipleOptical Fibers

Laser light is focusedinto a single fiber

Laser scansacross bar code. Reflected light, modulatedby the bar code,is detected, anddata is entered in a computer.

Handscanner

Product ScannersSupermarkets

Photo-Detector

Hologram for Security Credit Card, ID Cards, Advertising

November, 1985

LASIK procedure

Laser re-shapes cornea after flap (conjunctiva) is lifted

Laser Light

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

http://www.thetech.org/exhibits/online/lasers/Basics/images/albert.gif

http://www.physics.ubc.ca/~outreach/phys420/p420_95/mark/h2.gif

Stimulatedemission

Spontaneous emissionAbsorption

Einstein, 1916

photon

ground state

excited state

More light leaves than came in

Charles Townes and the Maser(with post-doc Jim Gordon) about 1953

http://globetrotter.berkeley.edu/people/Townes/images/maser.jpg

Maser

Townes

Gordon

Maser requires gain and feedback

Gain requiresStimulated emission

MicrowaveAmplification byStimulatedEmission ofRadiation Result: Oscillation

Oscillation from gain and feedbackExample: sound systems

Speaker

Microphone

Amplifier

Feedback Gain

Result: a shriek!!

The Laser Idea (1958) Charles Townes and Art Schawlow

Townes

Schawlow

ArgonLaserBeam

Atoms as gainmedium

Mirrors for feedback

~ 1963

gain

The First Ruby Laser: 1960Ted Maiman at Hughes Aircraft

http://www.ieee-virtual-museum.org/media/bW8Jx8FS8nF2.jpg

Ruby

Flash Lamp

Gain: ruby rod excited by light from a helical flash lampMirrors: silver films on the end of the ruby rod

The First Gas Laser – Helium/Neon(Inventors: Javan, Bennett and Herriott)

Gain: helium-neongas discharge

Mirrors:Special high-reflectivitymulti-layer films

1961

What do today’s lasers look like?They can be small …

http://upload.wikimedia.org/wikipedia/en/thumb/b/bd/Laser_diode_chip.jpg/300px-Laser_diode_chip.jpg

Laser diodes are tiny chips of semiconductor

The laser diode chip

A commercial package

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

Lawrence Livermore National Laboratories

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

A person

Capabilities of Lasersgain + feedback = stimulated emission

Coherent (All photons behave in an identical manner)directionalfocus to small pointinterfere

Ultra-stable single frequency or color (1 part in 1015)Ultra-high speed communications 1012 bpsUltra-long distance communications (to the moon)Ultra-short pulses 3 attoseconds 10-15 secUltra-high power (for 10-12 s) >1018 WUltra-small size 10-12 cm3

Coherence

Time’s SquareNew Year’s Eve

U.S. Soldiers, World War II

http://www.trumanlibrary.org/photographs/58-790-38.jpg

http://www.mistyvisions.com/images/nyc.jpg

All stimulated emission photons are identical, like soldiers

Spontaneous emission photons are random

speckle

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

Hole Size ~50 µmHuman

Hair

Sizes to scale

Hole size ~ 2 µm

OpticalFiber

Interference

Miniature Commercial Interferometers

www.armstrongoptical.co.ukReflective surface

Measurement of distance, motion, non-destructive testingNon-contact measurement

Ultrastable: LIGO Interferometerfor measuring gravity waves

http://www.phys.lsu.edu/dept/gifs/LIGO.gif

near Baton-Rouge Louisana – two arms, each 2.5 mi long

Monochromatic: Ring Laser Gyro Sagnac Effect

One gyro Honeywell’s 3-gyro system

Clockwise vs. CounterclockwiseFrequency Difference determines rotation

Interference: Holograms

Research at MIT: 1962-1966

Townes moved to MIT in the fall, 1961Existing 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

 fy.chalmers.se/.../Photonic/information.html

Electron orbitals distort nonlinearly -- non-linear polarization

00

21 22

1 + 2

Light Pulse

Electrical Signal

0 - 0

6943 A7670 A

SRS Laser

Representation of the spectrumEnergy difference between photons is given up to molecular vibrations

LL -

MIT Laser Laboratory, 1962-65

Stimulated Raman Scattering

My PhD research: Nonlinear Optics Stimulated Raman Scattering

A nonlinear processthat introduces

new wavelengths byinvolving

molecular vibrations

Two Laser Photons

Stokes Anti-Stokes

Anti-Stokes radiates in ringsdriven by Stokes in corresp. ring

Molecular vibration + Laser anti-Stokes

Laser beam

Stokes beam

L - L +

L L

Laser Stokes + molecular vibration

First explanation of multi-photon processes inStimulated Raman Scattering.

First explanation of anti-Stokes and several orders of Stokes

First explanation of angularemission of anti-Stokes

Proof of coherent molecular vibration theory:Chiao, Stoicheff and Townes: SRS in calcite

My Experimental SRS Data in Liquids

Agrees with theory

Most ofmy results“Stokes”

“Anti-Stokes”

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 ScatteringAppl Phys. Lett. August, 1964 experiments in liquids

SBSSeveralorders observed

Q-switchgain mirror SBS

Laser

Fabry-Perot Interferogram

NonlinearRefractiveIndexEnablesLight to Form its Own Waveguide

SpatialSoliton

ThresholdPower isRequired.

Self-trapping of Optical Beams

Laser

IncreasingLaserPower

No Pinhole

Garmire, et. al. PRL, 1966

Self-trapping

How they looked then (1966)

Charles Townes Frances Townes

Elsa, Gordon and Lisa Garmirethe 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

• How do we measure them?– Collide two pulses in two-photon fluorescent medium

• How do we expect them to behave in nonlinear optics?– Harmonic pulses longer in time

Yariv

Comly

Yariv, Laussade

Integrated Optics (~1970)

Equivalent to integrated electronicsOn one chip: laser, detector, modulator, switch

Uses waveguides

Modulator:

Turns light on

and off

with voltage

VInput Light Output Light

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

http://www.alpeslasers.ch/technology/dfb_pict_b.jpg

Corrugation replaces end mirrors

Caltech: A. Yariv et al.

Regular Laser

Laser ArtLaserium: laser light show

Laser Light Wall

Caltech Moon Landing Celebration

LaserBeacon

On TV at art opening, 1970

LASER IMAGESShow of photographsand light boxHollywood, 1969

Experiments in Art and TechnologyPepsi-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

Susan Allen

GraduateStudent

~ 1982

Lithium Niobate Modulators

http://fibers.org/objects/news/6/11/1/FSErnd1_10-04.jpg

Pencil

Early modulators were long

Lithium Niobate Crystal sliced into wafers & polished

Today’sTinyModulator

Titanium in-diffusion

Hybrid Optical Control: Optical Bistability Optically Addressed Switch

Laserinput

output

amplifierdetector

Beam splitter

J. MarburgerS. D. Allen

V

Input light

Output light

Hysteresis

Distributed Feedback Bistability

Recent results from Japan (2004)

. http://mizumoto-www.pe.titech.ac.jp/img/

Control signal can change the direction of the output signal

Input

Output A

Low intensity light reflects -- high intensity goes through

Output B

H. Winful, J. Marburger

All-Optical Bistability

Nonlinear Fabry-Perot in Semiconductors

Thin sandwich of semiconductor between mirrors as “bread”

InAs C. D. Poole

in

out

USC Laboratory with Researchers

Alan KostRandy Swimm

~ 1988

Semiconductor Quantum WellsNonlinear Optical Properties

GaAs

AlGaAs

Pump-Probe Experiments

Kost, Dapkus, et al.

Quantum Well Hetero-n-i-p-i’sfor sensitive nonlinearities

Band diagram

Experimental Results

Kost, Dapkus

mW optical power levels

Some of my USC Students

Nan Marie Jokerst

Ramadas Pillai

Boo Gyoun Kim

The USC Research Group

~ 1990

me

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:

Former Post-Docs now faculty members:Susan D. Allen, VP for Research & Academic Affairs, Arkansas State Ping Tong Ho, University of Maryland, ProfessorAlan Kost, University of Arizona, Associate Professor

Herbert Winful, University of Michigan, Arthur Thurnau Prof.Professor of the Year, EECS (twice)State of Michigan Teaching Excellence Fellow: OSA, IEEE, APS

Nan Marie Jokerst, Duke University. J.A. Jones Distinguished ProfessorBest Teacher in EECS Fellow: OSA, IEEE

•SongSil Univ. Korea•Chaio Tung Univ. Taiwan•Japanese Defense Academy•Frederick Institute ofTechnology,Cyprus

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 Indian-American 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 yearOriginal 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

• Katherine Liu Herbert Winful• Nan Marie Jokerst Keith Wilson• Mei Yang Wayne Richardson• Jean Yang Antonio Mendez• Grace Huang

• Susan Allen 13 out of 45: ~1/3• Kate Zachrewska• Cao Mingcui• Patricia Berghold

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)

YAG laser

Scanning mirrorcontrol

patented

Pattern Recognitionand Computer Controller

Camera

Photo-refractive Four-wave Mixing

Converts image from one laser beam to anotherCan convert color, or direction, or incoherent to coherentUsed for image processing – correlationRequires semiconductor quantum wellsCompetition from computers Akheel Abeeluck

Referenceless Optical Detectionof Surface Vibrations

Philip Heinz

Detector

Spatially moving speckle

Mirror

HeNe laser Detector

Elements

Four-point Photoconductive Detector

Detector Array Summing Electronics

Jon Bessette: Researching ways to extend the idea to higher frequencies

Philip Heinz

Research Now Underway

Optical Beam Propagation with Spatial Phase Jumps

Phase 0

Phase 0Phase

Phase Gaussian Beam

At 175 metersAshifi Gogo

My Family in October, 2005Charles Townes’ 90th Birthday

My Family in October, 2005Charles Townes’ 90th Birthday

A Townes’ LegacyLasers, 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 ResearchScience 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