Slow Light in Crystals

Transcription

1 With Department of Physics & Astronomy Faculty of Science Utrecht University Photon Physics Course 2007

2 Outline Introduction 1 Introduction Slow Light Electromagnetically Induced Transparency 2 CPO Phenomenon Setup Results 3 Saturable Absorption Saturable Absorption Simulations Comparison

3 Slow Light Electromagnetically Induced Transparency Group Velocity leading to : v g = v g ω k, c n ω + ω n. ω Kramers Kronig relation A change of absorption over a small spectrum range must be accompanied by a similar change in refractive index.

4 Slow Light Electromagnetically Induced Transparency Rephrased To create slow light; we must change the absorption over a small frequency range.

5 Slow Light Electromagnetically Induced Transparency Rephrased To create slow light; we must change the absorption over a small frequency range. Most commonly used method Electromagnetically Induced Transparency.

6 Slow Light Electromagnetically Induced Transparency Rephrased To create slow light; we must change the absorption over a small frequency range. Most commonly used method Electromagnetically Induced Transparency. Thanks to Thomas You know all about EIT, right?

7 Slow Light Electromagnetically Induced Transparency Electromagnetically Induced Transparency EIT Summary

8 Research for this Talk CPO Phenomenon Setup Results This talk is about "". Research was done at the Institute of Optics in Rochester, NY, USA by Bigelow, Lepeshkin and Boyd. They published papers about it in Science and Physical Review Letters.

9 CPO Phenomenon Setup Results A light beam is amplitude modulated This creates side bands Take one side band as probe Electrons start to oscillate at the modulation frequency Susceptibility oscillates at modulation frequency This creates a new side band on the pump, at same frequency New side band added to the probe Reduced absorption

10 The Setup Introduction CPO Phenomenon Setup Results

11 Ruby Energy Levels CPO Phenomenon Setup Results Figure: Ruby Energy level diagram

12 Results Introduction CPO Phenomenon Setup Results

13 Critics Introduction Saturable Absorption Saturable Absorption Simulations Comparison According to Zapasskii & Kozlov, and Selden, all measured phenomena can be easily explained by the model for a two-level saturable absorber. Of which Ruby is a well-known example.

14 Saturable absorption of a pulse Saturable Absorption Saturable Absorption Simulations Comparison

15 Saturable absorption of a pulse Saturable Absorption Saturable Absorption Simulations Comparison

16 Calculate the Sat. absorber model Saturable Absorption Saturable Absorption Simulations Comparison

17 Saturable Absorption Saturable Absorption Simulations Comparison Reasons to go for the Saturable Absorber Model Totally predicts the measurements, but much simpler. Bigelows model is too simplified by taking only one wanted sideband. Pulseshape should be heavily distorted. Laser spectral width must be extremely small (37 Hz for Ruby), to detect the CPO hole in the spectrum. A CPO hole could only increase the width of the pulse, but it is shortened. No-one has succeeded in slowing the pulse down beyond the temporal length of the pulse.

18 Summary Introduction Saturable Absorption Saturable Absorption Simulations Comparison Summary Bigelow et al probably did not create slow light, but measured well-known behaviour of a saturable absorber. Suggestion Additional measurements must be performed to positively identify slow light by CPO. An easy way is taking a medium that is long enough to move the pulse beyond the pulselength.