Ulf Leonhardt

from Wikipedia, the free encyclopedia
Ulf Leonhardt

Ulf Leonhardt (born October 9, 1965 in Schlema ) is a German physicist who deals with metamaterials , optical analogues to black holes and other optical phenomena as well as quantum levitation .

Life

Ulf Leonhardt studied at the Friedrich Schiller University in Jena (diploma 1990), the Lomonossow University in Moscow and at the Humboldt University in Berlin , where he received his doctorate in 1993 with the thesis Quantum theory of simple optical instruments , the Tiburtius -Prize from the Berlin Senate. In 1994/5 he was a member of the research group Non-Classical Radiation of the Max Planck Society in Berlin. In 1995/96 he was a visiting scientist at the Oregon Center for Optics in Eugene (Oregon) . 1996 to 1998 he completed his habilitation at the University of Ulm ( quantum mechanical state measurement ). From 1998 to 2000 he was at the Royal Technical University of Stockholm . From 2000 to 2012 Leonhardt was Professor of Theoretical Physics at the University of St. Andrews in Scotland . Since autumn 2012 he has been a professor at the Weizmann Institute for Science in Israel.

Leonhardt received the Otto Hahn Medal from the Max Planck Society and the Wolfson Research Merit Award from the Royal Society . In 2006 he received the Scientific American 50 Award for his work on invisibility phenomena in optics . Ulf Leonhardt has been a member of the Royal Society of Edinburgh since March 2009 .

plant

Leonhardt attracted attention with his suggestion to construct analogues of black holes from gravitational physics in optics by using special optical materials and geometries. Analogues of black holes in wave phenomena were previously proposed by William Unruh (in the acoustic field) and independently of Grigori Volovik and Matt Visser. There are also simple hydrodynamic examples, such as hydraulic jumps : a water jet hits a flat plane perpendicularly, where the water first flows smoothly outwards and waves only form from a certain radius after the flow speed has fallen below the wave speed of the water (analogue a "white hole"). Leonhardt realized this in optical fibers . In order to construct event horizons in analogy to black holes, the speed of light in the medium, which depends on the refractive index and is frequency-dependent, must fall below the speed of signal propagation in the medium, which occurs with the so-called group speed . Laser light pulses in fiber optics increase the refractive index ( Kerr effect ) through non-linear optical effects . If a leading light pulse is caught up with subsequent pulses of different frequencies and thus different local speeds of light, this increase in the refractive index acts like an event horizon - corresponding to a black hole at the front of the generating pulse and a white hole at the rear end. The analogues of Hawking radiation were also observed by Leonhardt and his co-workers in these experiments . It also occurs continuously with the laser pulses used for communication purposes in fiber optics, but is of negligible magnitude for all practical purposes.

In 2006 he developed theoretical ideas to make objects invisible, again using special materials and geometries (which Leonhardt constructed with the help of conforming images ), which function similarly to mirages (" Fata Morgana "), where a background view due to the changed light refraction conditions obscures an object in the foreground in heated air. John Pendry made similar suggestions at the same time . First experiments on this were carried out by David Smith ( Duke University ) and colleagues using man-made metamaterials. They generate an “invisibility effect” - but only for small frequency ranges (in this case in the microwave range).

In 2007 he theoretically showed that when using special materials, the Casimir effect between two conductor plates, which is normally attractive and is based on the changed boundary conditions for quantum fluctuations in the vacuum, could be made repulsive (levitation). According to Leonhardt, the materials required for this and placed between the circuit boards have a negative refractive index (instead of the usual positive ones as in glass or water).

Fonts

  • Essential quantum optics - from quantum measurements to black holes , Cambridge University Press 2010, ISBN 0521145058
  • Measuring the quantum state of light , Cambridge Studies in Modern Optics, Cambridge University Press 1997
  • Slow Light in Grigori Volovik, Matt Visser, Mario Novello (editors): Artificial Black Holes , World Scientific 2002
  • Black Holes in the Laboratory , Physics in Our Time, 2009, Issue 2

Web links

Notes and individual references

  1. ↑ Thomas G. Philbin, Chris Kuklewicz, Scott Robertson, Stephen Hill, Friedrich König, Ulf Leonhardt: Fiber-Optical Analog of the Event Horizon . In: Science . tape 319 , no. 5868 , March 7, 2008, p. 1367-1370 , doi : 10.1126 / science.1153625 , PMID 18323448 .
  2. ^ Ulf Leonhardt: Notes on conformal invisibility devices . In: New Journal of Physics . tape 8 , no. 7 , July 2006, p. 118-118 , doi : 10.1088 / 1367-2630 / 8/7/118 .
  3. ^ Ulf Leonhardt: Optical Conformal Mapping . In: Science . tape 312 , no. 5781 , June 23, 2006, p. 1777-1780 , doi : 10.1126 / science.1126493 , PMID 16728596 .
  4. ↑ Awatif Hendi, Julian Henn, Ulf Leonhardt: Ambiguities in the Scattering Tomography for Central potential . In: Physical Review Letters . tape 97 , no. 7 , August 14, 2006, p. 073902 , doi : 10.1103 / PhysRevLett.97.073902 .
  5. ↑ David Smith et al. a., Science Express, October 19, 2006
  6. ↑ Ulf Leonhardt, Thomas G. Philbin: Quantum levitation by left-handed metamaterials . In: New Journal of Physics . tape 9 , no. 8 , August 2007, p. 254-254 , doi : 10.1088 / 1367-2630 / 9/8/254 .
  7. ↑ Theoretically proposed by the Russian physicist Wesselago in 1968. John Pendry made suggestions for implementation using metamaterials in 1999; they were first implemented in 2001 in David Smith's group.
personal data
SURNAME Leonhardt, Ulf
BRIEF DESCRIPTION German physicist, university professor in St. Andrews
DATE OF BIRTH October 9, 1965
PLACE OF BIRTH Schlema