17' Coherent and Incoherent Control

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17. Coherent and Incoherent Control

• Coherent Control attempts to control a chemical
  reaction with light, usually a cleverly shaped
  ultrashort laser pulse.
• Why its hard IVR.
• Using shaped pulses and an iterative approach.
• Incoherent Control is just my term for laser
  machining, in which we only care how intense the
  pulse is.
• Extreme conditions at the focus of a fs pulse.

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Coherent Control

• Chemical reactions proceed in a manner
  determined by the molecular Hamiltonian.
• What if wed like to change this and make
  different products?
• Bring in a light frequency to excite a bond wed
  like to break. But its not so easy! Theres a
  lot more to it.
• A long-held dream of chemists. Its now coming
  true. Shaped ultrashort pulses are the key.

Coherent control slides thanks to Gustav Gerber,
University of Wurzberg, Germany
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Excite one bond
A few fs later, the entire molecule is vibrating.
IVR occurs on a few-fs time scale, so long pulses
excite entire molecule, and the weakest bond
breaks.
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More Coherent Control
Reaction Under Study
Shaped Pulse
CO2
CCl4
CCl2O
Murnane and Kapteyn, University of Colorado
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Incoherent control Laser machining
A simple apparatus!
Slides thanks to Eric Mazur, Harvard University
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Ultrafast machining set up
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A Femtosecond-Pulse Drilled Hole
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Things can get mighty hot at the focus of even a
fairly low-energy fs pulse!
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Not to mention the pressure
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Youd be better off inside the sun.
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The size of the hole is determined by the pulse
energy and the number of shots.
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Damage mechanisms
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Applications of ultrafast machining
Encoding of information on a microscale
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Applications of ultrafast machining
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Applications of ultrafast machining
Waveguide machining