Switching nonlinear signals

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Switching nonlinear signals
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Light in matter
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Spectroscopic transitions
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Fluorescence
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Fluorescence microscopy
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Switching fluorescence off
Stimulated emission
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Useful!
Prof. Stephan Hell, Göttingen
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STED microscopy
Prof. Stephan Hell, Göttingen
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Nonlinearities
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Coherent nonlinear signals
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Coherent nonlinear signals
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CARS microscopy
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CARS microscopy
100 ?m
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Switching?
CARS
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Messy business!
CSRS
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Even messier!
a total of 28 different interactions between the
colors are present!
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How does the signal grow?
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Coupled equations
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Phase matching
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Depletion
CARS intensity
z
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Phase-matching in microscopy
1 ?m
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Controlled depletion?
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Switching with an external field
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Vibrational oscillators
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Switching in practice
Rel. CARS intensity
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Fun with switching
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What have we learned?
A very weak external field can be used to switch
off coherent nonlinear signals