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Transcript of Jeff Hecht, Laser Focus World - IEEE Hecht, Laser Focus World Author BEAM: ... Terahertz, far-IR...
Jeff Hecht, Laser Focus World Author BEAM: the Race to Make the Laser [email protected] http://www.jeffhecht.com
Photo courtesy of Kathleen Maiman
2 Hecht - Maiman and 50 years of lasers
50 years since May 16, 1960
Background Ted Maiman and the first laser Impact of the first laser Other lasers
He-Ne, Neodymium, CO2, Diode, etc. Developing laser applications Looking to the future
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The Starting Point -- Microwave Maser Charles Townes and James Gordon (1954)
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3-level solid-state masers - 1956 Nicolaas Bloembergen, Harvard Derrick Scovil
Ruby maser - Chihiro Kikuchi, 1957 4°K liquid helium cooling; 2.5 tons, desk-sized
Military Funding Sought more practical, compact design Army contract to Hughes Research Labs
Ted Maiman redesigned with internal magnet, liquid N2 Reduced to a few pounds
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Optical is next higher accessible frequency band Terahertz, far-IR undeveloped
Proposals Valentin Fabrikant, Russia, 1939, optical amplifier 1950s US: Robert Dicke, John von Neumann
Charles Townes starts first serious effort 1957 Examined analytically and posed physics problem
What would be needed for "optical maser" Talks with Gordon Gould about optical pumping
Gould goes off and designs laser Townes and Schawlow solve same problem
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Fabry Perot resonator (Gould)
Schawlow-Townes use same approach Both require a suitable material
Population inversion, stimulated emission
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Optically pumped metal vapor Alkali metals
Potassium, cesium, etc Lamps pump narrow
lines Very selective excitation Low power
Fairly simple physics Difficult to work with Gould, Townes
Electrically excited gas Noble gases
Helium, neon, argon Others possible
RF or DC discharge Somewhat simple physics
Spectra well known Relatively efficient Easier to work with Javan, Bennett at Bell
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Optically pumped dielectric solids Precedent in solid-state microwave masers
Ruby Rare earths
Physically complex systems Potentially simple to use Optical materials not well developed
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First QEC Sep 14-16, 1959 Most papers on microwave masers
Slow progress on He-Ne lasers at Bell Labs Slow progress on metal vapors at Columbia Schawlow says ruby won't work
3-level laser, low fluorescence efficiency ARPA-TRG program just getting started
Million dollar grant, parallel effort, mostly classified Doubts about laser
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BS EE, U of Colorado PhD, Physics, Stanford, with Willis Lamb Working at Hughes Research Laboratories
Finished ruby microwave maser Seeking new project
Optically pumping microwave maser Would reduce noise
Noise increased with temperature Became an issue with liquid nitrogen operation
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Tougher challenge than microwave maser Potentially high rewards Sought "simple, compact and rugged" material
Could ruby work? Maiman knew it from microwave maser Maiman wasn't convinced by Schawlow's analysis Where was energy going?
Measured fluorescence for himself It was near 100%
Went for optically pumped laser
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Continuous lamps Carbon arc – fumes, excess heat AH6 arc lamp (high-power projector)
Would barely provide enough energy ‘It was very hard to get excited about a marginal design’
Pulsed sources Exploding wires too messy, poor source Xenon photographic flashlamp (Leo Levitt)
Color temperature 7700° C – ruby needed 4700°C 3 coiled models readily available
Enough to demonstrate laser emission
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Maiman's group moves from Culver City to Malibu
Maiman works at home Writes paper on measurements Shows management he's doing something Avoids telling them much
Designs ruby laser Managers still in Culver City
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Stepped up flashlamp power Turned up voltage Measured spectrum Measured pulse
duration and decay Oscilloscope trace
Threshold about 950 V Worked first time Beam quality modest
New crystals improved
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Ruby Laser Impact
Proved laser was feasible First solid-state laser New approach to laser operation
Pulsed operation High gain
Well engineered and easy to replicate Small and simple Used readily available components TRG, Bell, others replicated within weeks
Made lasers accessible Ruby became first commercial laser
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Publication problems led to press conference Muddied historical record Replication was acid test of success
Observations and lessons Start with materials you know. Brilliant inventions look obvious in hindsight. Physically ‘simple’ systems can be very complex in
practice Good engineering complements good science
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Laser Boom followed
Helium-neon laser Neodymium lasers Semiconductor diode lasers Carbon dioxide lasers Ion lasers Rare-gas halide excimer lasers Many more
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Launching other laser development
Sorokin and Stevenson
IBM Watson Ur:CaF2 Sm:CaF2
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Red ruby lasers (Dec 1960)
Art Schawlow, Bell Irwin Wieder Varian
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Javan, Bennett, Herriott, Dec 1960 1.15-µm helium-neon laser, Bell Labs
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Dane Rigden, Alan White, 632.8-nm Helium-Neon Laser, Bell, 1962
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Alan White, Dane Rigden, 632.8-nm Helium-Neon Laser, Bell, 1962
What the lab really looked like
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Neodymium lasers
Nd:Ca-tungstate, pulsed then CW L. F. Johnson and Kurt Nassau, Bell 1961
Nd:glass 1961 Elias Snitzer, American Optical
Nd:YAG, 1964 Joseph E. Geusic, L. G. Van Uitert, Bell
Snitzer 1964 made coiled fiber amplifier to place on linear lamp
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Semiconductor diode lasers
Robert Hall et al, GE R&D Labs 1962 Homostructure GaAs diode laser Pulsed and cryogenically cooled
Fenner, Hall and Kingsley
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Kumar Patel, CO2 laser, Bell Labs, 1964
1967 photo, higher power CO2
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Bill Bridges, Ar-Ion Laser, Hughes 1964 Developed CW with Gene Gordon, Ed Labuda, Bell Labs
1969 photo
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Rare-gas halide "excimer" lasers-mid 1970s
Stuart Searles, Gary Hart, Nick Djeu NRL J. J. Ewing and Charles Brau, Avco Everett Earl Ault, Mani Bhaumik, Northrop Gary Tisone and A.K. Hays, Sandia
Tisone and Hays ArF e-beam pump
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First wave of small companies TRG, defense research Trion Instruments, ruby lasers
Ann Arbor, spinoff of U of Michigan Korad, ruby lasers
Maiman, spinoff of Hughes Spectra-Physics, helium-neon
Silicon valley, spinoff of Varian Optics Technology, ruby, He-Ne
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Hughes Aircraft – copies of Maiman's Raytheon – industrial lasers American Optical - glass lasers RCA – gas, diodes Perkin-Elmer (He-Ne with Spectra) Martin-Marietta General Electric (mostly research) IBM (mostly research) Westinghouse (mostly research)
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July 7, 1960 Hughes press conference Increasing number of available
communications channels – fiber optics True amplification of light – fiber amplifiers Probing matter for basic research - many Concentrating light for industry, chemistry and
medicine – many examples High-power beams for space communications
– not there yet
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"A solution looking for a problem." Irnee D'Haenens, assistant to Ted Maiman
Pulsed ruby lasers Non-contact materials working, hole drilling Dermatology, ophthalmology (detached retina)
CW helium-neon lasers Measurement and alignment Communications, information processing
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3D Holography
Emmett Leith and Juris Upatnieks 1964 Courtesy Juris Upatnieks
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Diode lasers Ranging Directly modulated communications
CO2 lasers CW cutting Laser surgery
Ion lasers Visible displays, UV sources, info-tech
Neodymium lasers Metal working, CW or higher rep rate
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Laser Light Shows and Displays
Laserium Courtesy of Ivan Dryer
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Government: $150 million Military equipment (rangefinder/designators) 'Energy' research (laser fusion, isotopes) Other (R&D, equipment)
Civilian: $120 million Industrial Measurement Medicine Information handling
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Emerging applications 1975
Inside a supermarket scanner Auto underbody welding @ Ford
40 Hecht - Maiman and 50 years of lasers
From fusion to fiber
LLNL Argus Laser 1976 Early fiber system 1979
41 Hecht - Maiman and 50 years of lasers
Laser videodisk MCA, Philips, Thomson-CSF 12-inch disk, one hour per side He-Ne player (cheap mass-produced tubes) Led to CDs, other optical disks
Supermarket scanners UPC recently adopted
Printed bar codes He-Ne reader in checkout counter Slowed by safety concerns, economy Took off circa 1980
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Initially driven by fiber communications Bell Labs million-hour GaAs laser 1977 Shift to InGaAsP for longer links, higher speed
Mass production for CD players Started as $1000 toy for audiophiles Quickly gained market leverage Used GaAs lasers developed for telecom Spinoffs in computer data storage, CD-ROM
Diode laser printers for PCs Scaled down from high-speed mainframe laser printers
based on gas lasers
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MCI network early 1980s, long-haul Submarine cables, TAT-8 - 1988
Revolution in global phone network Early 1990s developments
Erbium-doped fiber amplifiers WDM becomes practical – huge capacity
Internet and World Wide Web Bubble madness
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Laser refractive surgery ArF lasers, LASIK, etc.
Excimer lasers become photolithography source for semiconductor fab KrF 248 nm ArF 193 nm
Laser skin resurfacing and hair removal Various lasers
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Second diode laser revolution Red diodes High-power pump lasers Blue diode lasers Telecommunications lasers
Diode-pumped solid-state laser revolution Fiber lasers, rods, slabs
Ultrafast laser revolution Femtosecond pulses, Titanium-sapphire Frequency combs
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Alfred Leitenstorfer U. Konstanz Nature Photonics
(doi: 10.1038/NPHOTON.2009.258)
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High efficiency, high-power solid state lasers Thin disk lasers Fiber lasers Direct diodes Seriously high powers – 100 kW class
Wavelengths on demand Nonlinear optics, tunability, new materials OPSLs/VECSELs (thin-disk semiconductors)
Ultrashort pulse lasers Femtosecond frequency combs High intensity pulses
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Metamaterials Nanophotonics Plasmonics Photonic crystals Microstructured optical fibers Open new possibilities
New classes of optical properties Better confinement of light Stronger interactions
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Linac Coherent Light Source Free-electron laser 0.15-1.5 nm
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Higher speed telecommunications Expanded backbone, 100-Gbit/s line rate IP-TV fiber to the home
Expansion of medical diagnostics Individually tailored medicine
Consumer products Laser nano-projectors Higher-efficiency fluorescent lighting Think convenient, efficient and fun
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Advances in direct diode technology Beam combination Wavelength shifting
Synergies with new photonics technology Metamaterials, photonic crystals Nanophotonics, plasmonics
Social/economic/commercial priorities Energy efficiency, production, conservation China, India, Developing countries
The Unexpected