Self-Induced Transparency

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Self-Induced Transparency

• By Christine Tsai
• Physics 138 Presentation

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Outline

• Introduction
• Features
• Experiments
• Conclusion

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Introduction

• Two-level system
• Absorption
• Spontaneous emission
• Stimulated emission

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Absorption
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Spontaneous Emission
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Stimulated Emission
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For Self-Induced Transparency

• No (small) spontaneous emission
• Resonant light pulse

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• So if we shine a light pulse onto an absorptive
  medium, well get a population of excited atoms.

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What you will needLight Pulse and Absorber
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(No Transcript)
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Outline

• Introduction
• Features
• Experiments
• Conclusion

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3 Main Features

• Loss-less propagation
• Pulse reshaping
• Pulse delay

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Feature 1Loss-less Propagation

• Energy is conserved
• Einput Eoutput
• No spontaneous decay
• Spontaneous decay can go in any direction, so
  usually E is lost from the beam.
• ?R gtgt 1/?
• ?R Rabi frequency of input pulse
• ? life time of atom in excited state

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Feature 2Pulse Reshaping

• Area Theorem

dA(z)/dz -?/2 sinA(z)
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Feature 2Pulse Reshaping

• The output pulse may be reshaped by the medium if
  the input pulse is not SYMMETRIC HYPERBOLIC
  SECANT.

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Feature 3Pulse Delay

• As light pulse passed through the absorber, it is
  delayed.
• Delay time is
• ?delay (L/v) (L/c)
• L length of absorber
• v velocity of pulse
• c speed of light

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Outline

• Introduction
• Features
• Experiments
• Conclusion

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Experiments

• Experiments on Self-induced transparency have
  been performed by many physicists. And they have
  confirmed that the effect exists.
• Some people who have done the experiment
• McCall and Hahn
• Gibbs and Slusher

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McCall and Hahn

• Used a Q-switched liquid-nitrogen-cooled ruby
  laser to create short input pulse.
• Used a liquid-helium-cooled ruby rod as the
  absorber.
• Result

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Gibbs and Slusher

• Used Hg II laser for input pulses.
• Used dilute Rb vapor as absorber.
• Result

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• More Results from Gibbs and Slusher

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Outline

• Introduction
• Features
• Experiments
• Conclusion

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Conclusion

• Self-induced transparency works!