Valedictory Lecture by David Hanna Vale University of

Valedictory Lecture by David Hanna Vale! University of Southampton November 9 2007

The Fighting Temeraire, tugged to her Last Berth to be broken up, 1838 J. M. W. Turner

Theodore "Ted" Maiman (1927 -2007)

From Big Bang to the LASER: some historical highlights Years ago § Big Bang 13. 7± 0. 2 Gyr § First stars 12. 5 Gyr § Our sun (solar system) 4. 5 Gyr § First life on earth 3. 5 Gyr § Cambrian explosion (proper vision evolved) § Homo Sapiens evolved § Cave painters at work 530 Myr 100 kyr 30 kyr

From Big Bang to the LASER: some historical highlights Years ago § Big Bang 13. 7± 0. 2 Gyr § First stars 12. 5 Gyr § Our sun (solar system) 4. 5 Gyr § First life on earth 3. 5 Gyr § Cambrian explosion (proper vision evolved) § Homo Sapiens evolved § Cave painters at work § Astronomers and physicists evolve 530 Myr 100 kyr 30 kyr

Astronomers & physicists grapple with the nature of light Rømer 1676 Observing Jupiter’s moons, revealed light to have finite velocity Young 1801 Measured light wavelength; calculated frequency n Maxwell 1862 Electromagnetism: LIGHT is an electromagnetic wave Planck 1900 Birth of quantum theory Einstein 1905 Special theory of relativity, based on invariance of “c” 1905 Postulated particle of light, of energy hn 1916 Introduced the process of stimulated emission 1960 Created first laser light Maiman

Astronomers & physicists grapple with the nature of light Rømer 1676 Observing Jupiter’s moons, revealed light to have finite velocity Young 1801 Measured light wavelength; calculated frequency n Maxwell 1862 Electromagnetism: LIGHT is an electromagnetic wave Planck 1900 Birth of quantum theory Einstein 1905 Special theory of relativity, based on invariance of “c” 1905 Postulated particle of light, of energy hn 1916 Introduced the process of stimulated emission 1960 Created first laser light Maiman

Ole Rømer (1644 -1710) Speed of light measurement 1676

Astronomers & physicists grapple with the nature of light Rømer 1676 Observing Jupiter’s moons, revealed light to have finite velocity Young 1801 Measured light wavelength; calculated frequency n Maxwell 1862 Electromagnetism: LIGHT is an electromagnetic wave Planck 1900 Birth of quantum theory Einstein 1905 Special theory of relativity, based on invariance of “c” 1905 Postulated particle of light, of energy hn 1916 Introduced the process of stimulated emission 1960 Created first laser light Maiman

Thomas Young (1773 -1829) Double slit experiment 1801 On the Theory of Light and Colours Philosophical Transactions of the Royal Society of London Vol 92(1802) 12 -48

wavelength frequency velocity

Thomas Young (1773 -1829) Double slit experiment 1801 On the Theory of Light and Colours Philosophical Transactions of the Royal Society of London Vol 92(1802) 12 -48 “The absolute frequency expressed in numbers is too great to be distinctly conceived. . . ”

Velocity of light, and the metre Measure l and f: hence calculate velocity of light In 1983 c defined as 299792458 m/s Metre defined as distance travelled by light in vacuum in 1/299792458 seconds “. . . and let’s all go home early” John Hall

Astronomers & physicists grapple with the nature of light Rømer 1676 Observing Jupiter’s moons, revealed light to have finite velocity Young 1801 Measured light wavelength; calculated frequency n Maxwell 1862 Electromagnetism: LIGHT is electromagnetic wave Planck 1900 Birth of quantum theory Einstein 1905 Special theory of relativity, based on invariance of “c” 1905 Postulated particle of light, of energy hn 1916 Introduced the process of stimulated emission 1960 Created first laser light Maiman

James Clerk Maxwell (1831 -1879) War es ein Gott, der diese Zeichen schrieb? (Was it a god who wrote these signs? ) Boltzmann, 1891, quoting from Goethe’s Faust

Heinrich Rudolf Hertz (1857 - 1894)

Astronomers & physicists grapple with the nature of light Rømer 1676 Observing Jupiter’s moons, revealed light to have finite velocity Young 1801 Measured light wavelength; calculated frequency n Maxwell 1862 Electromagnetism: LIGHT is an electromagnetic wave. Planck 1900 Birth of quantum theory Einstein 1905 Special theory of relativity, based on invariance of “c” 1905 Postulated particle of light, of energy hn 1916 Introduced the process of stimulated emission 1960 Created first laser light Maiman

Max Planck (1858 -1947) “Black-body” radiation law

Astronomers & physicists grapple with the nature of light Rømer 1676 Observing Jupiter’s moons, revealed light to have finite velocity Young 1801 Measured light wavelength; calculated frequency n Maxwell 1862 Electromagnetism: LIGHT is an electromagnetic wave Planck 1900 Birth of quantum theory Einstein 1905 Special theory of relativity, based on invariance of “c” 1905 Postulated particle of light, of energy hn 1916 Introduced the process of stimulated emission 1960 Created first laser light Maiman

Albert Einstein (1879 -1955)

Astronomers & physicists grapple with the nature of light Rømer 1676 Observing Jupiter’s moons, revealed light to have finite velocity Young 1801 Measured light wavelength; calculated frequency n Maxwell 1862 Electromagnetism: LIGHT is an electromagnetic wave Planck 1900 Birth of quantum theory Einstein 1905 Special theory of relativity, based on invariance of “c” 1905 Postulated particle of light, of energy hn 1916 Introduced the process of stimulated emission 1960 Created first laser light Maiman

Amplification by stimulated emission Photon energy hn = E 2 – E 1 Energy E 2 Absorption Energy E 1 Spontaneous emission Stimulated emission Emitted photon identical to incident photon: AMPLIFICATION OF LIGHT

Prokhorov, Townes and Basov Nobel prize for physics 1964 “… maser-laser principle”

Theodore "Ted" Maiman (1927 -2007)

Laser oscillation Input Amplification of an input beam Amplification of spontaneous emitted light Amplification plus feedback: oscillation builds up a directional output - Laser Beam

Taming the laser: the pursuit of perfection Gain medium Mirror Temporal shaping Spectral filter to shape spectrum, eg to discriminate against unwanted frequencies Spatial filter to discriminate against excessive divergence

Figures of merit for light sources Brightness Spectral Brightness ≡ ≡ Power [Beam diameter x Beam divergence]2 Power [Diameter x divergence]2 [Spectral Bandwidth]

Brightness of some typical sources W/m 2/sr Tungsten lamp, visible light 105 50 W diode bar 1010 1 m. W laser pointer * 3 x 109 1 W Ar laser (488 nm) * 4. 5 x 1012 1 k. W laser @1µm * 1015 1 MW laser @1µm * 1018 30 fs, 1 m. J @0. 8µm * 5 x 1022 45 TW @0. 8µm * 7 x 1025 * assumed diffraction limited

Coherent X-ray generation

The birth of nonlinear optics Peter Alden Franken (1928 -1999) LASER SECOND HARMONIC ω 2ω (Red) Quartz (UV) Laser field E is strong enough to modify response of medium Response a. E + b. E 2 + c. E 3 + … Nonlinear response

One minute guide to Optical Parametric Amplification ω ω 2ω Second harmonic generation ω1 ω2 ω3 = ω1 + ω2 Sum frequency generation ω3 ω1 ω2 Parametric generation and AMPLIFICATION ω1, ω2 are amplified in presence of strong pump field at frequency ω3 Any pair ω1, ω2 that add to ω3 can be amplified ω3 ω1 ω2 OPTICAL PARAMETRIC OSCILLATOR Frequencies ω1, ω2 are tunable, but always add up to ω3

The laser: ‘a solution in search of a problem’! § Cutting, drilling, welding, scribing, marking chip repair, printing, lithography § Laser gyros, sensors, pollution monitors, bar-code readers DVDs, displays, entertainment § Microscopy, surgery, corneal sculpting, optical coherence tomography Optoelectronics forecast: $1012 global market by 2015

The laser: ‘a solution in search of a problem’! § Optical communications § Military/defence § Machine tool control § Isotope separation § Surveying, ranging, LIDAR, Doppler speed monitoring § Security, forensic § Laser fusion, energy § Cytometry

Semiconductor diode laser

Optical materials and structures § Laser materials § Semiconductor laser, quantum wells, wires, dots § Nonlinear optical materials § Optical fibres, waveguides § Bragg gratings for fibre, waveguides, semiconductors § Photonic bandgap materials, holey fibres § Metamaterials § Negative refractive index materials § Liquid crystals § LEDs, poly. LEDs

The laser as a scientific tool § § § Ultrafast time resolution Laser fusion Laser particle accelerator Gravity wave observatory Laser guide star for astronomy Optical clocks, frequency standards Quantum computing Tests of QED, General relativity Coherent control Atom interferometry Cold atoms, Bose-Einstein condensates

Fast flash photography

Short pulse generation with lasers Pulse of time duration T secs requires a spectral bandwidth of at least 1/T Hz, hence also carrier frequency of at least 1/THz Pulse duration Required bandwidth 10 -9 s, 1 ns (nanosecond) 109 Hz, 1 GHz (Gigahertz) 10 -12 s, 1 ps (picosecond) 1012 Hz, 1 THz (Terahertz) 10 -15 s 1 fs (femtosecond) 1015 Hz, 1 PHz (Petahertz) 10 -18 s, 1 as (attosecond) 1018 Hz, 1 EHz (Exahertz) Shortest pulse (as of 2007), ~80 as

Electric field of optical pulse displayed on an “attosecond oscilloscope”

Laser fusion - Nova

Petawatt lasers

Gravity wave observatory – Virgo F 1

LISA

Laser guide star

Manipulation of atoms § Atom cooling, trapping, guiding § Bose-Einstein condensation § Atom interferometers § Coherent control of atoms

Coherent control of atoms Optical pulses Atom state 2 |1 |1 + a |2 |2 1 Atom phase |1

Kathleen Puech, Rudiger Paschotta, Paul Suni, Markus Pollnau, Dave Shepherd, David Cotter, Andy Clarkson, Richard Wyatt, Mike Percival, Ralf Koch, Sylvain Girard, Martin O’Connor, Helen Pask, Jose Sais, Michael Yuratich, Joseph Koo, Simon Mussett, Dave Arnold, Barry Luther-Davies, Vikram Rampal, Andy Turner , Richard Wyatt, Leslie Laycock, Pertti Karkkainen, Walter Tuttlebee, Craig Sawyers, Andy Berry, David Hearn, David Pratt, Ian Carr, Marco Pacheco, Ian Alcock, David Pointer, Ken Ure, Andrew Kazer, Leigh Bromley, Ian Perry, Andy Guy, Michael Ibison, Matthew Mc. Carthy, Colin Mackechnie, Martin Milton, Tony Neilson, Stuart Butterworth, Valerio Pruneri, Kevin Martin, Paul Hardman, Christoph Bollig, Nick Moore, Graham Friel, Rob Hayward, Malcolm Watson, David Brink