1. First year talk Mark Zentile
The Slow-Light Effect
First year talk
Mark Zentile

2. 1st year talk, Mark Zentile
Project Members
Lee Weller Charles Adams Ifan Hughes
17/04/2017
1st year talk, Mark Zentile

3. 1st year talk Mark Zentile
Outline
Slow-light:
What is slow-light? What conditions are needed to see it? What are the applications?
Phase shift and absorption from the electric susceptibility.
Transmission spectra to extract key parameters for the model.
Using the our model for the electric susceptibility with Fourier analysis to model pulse propagation.
Experimental method and examples of data with theoretical predictions.
17/04/2017
1st year talk Mark Zentile

4. 1st year talk Mark Zentile
Outline
Future outlook:
Introduce the Faraday effect.
Use a Faraday signal to make a tuneable laser lock over ± 20 GHz detuning.
Harness the slow-light Faraday effect to make an optical switch.
17/04/2017
1st year talk Mark Zentile

5. 1st year talk Mark Zentile
What is ‘Slow-Light’?
17/04/2017
1st year talk Mark Zentile

6. 1st year talk Mark Zentile
What is ‘Slow-Light’?
17/04/2017
1st year talk Mark Zentile

7. 1st year talk Mark Zentile
Slow-light with EIT
17/04/2017
1st year talk Mark Zentile

8. Better interferometers
17/04/2017
1st year talk Mark Zentile

9. Image rotation  Image coding
17/04/2017
1st year talk Mark Zentile

10. 1st year talk Mark Zentile
Optical Delay Line
17/04/2017
1st year talk Mark Zentile

11. 1st year talk Mark Zentile
Optical Switch
17/04/2017
1st year talk Mark Zentile

12. 1st year talk Mark Zentile
Outline
Slow-light:
What is slow-light? What conditions are needed to see it? What are the applications?
Phase shift and absorption from the electric susceptibility.
Transmission spectra to extract key parameters for the model.
Using the our model for the electric susceptibility with Fourier analysis to model pulse propagation.
Experimental method and examples of data with theoretical predictions.
17/04/2017
1st year talk Mark Zentile

13. Complex refractive index
ABSORPTION
DISPERSION
17/04/2017
1st year talk Mark Zentile

14. 1st year talk Mark Zentile
Transmission Spectra
17/04/2017
1st year talk Mark Zentile

15. The model for the electric susceptibility
Our model has been developed over many years:
Result of solving the optical Bloch equations for a two level atom.
Accurate up to ~ 120oC
Includes:
absolute linestrengths
Doppler broadening
Temperature dependent number density.
Siddons et al. J. Phys. B: At. Mol. Opt. Phys. 41 (2008)
17/04/2017
1st year talk Mark Zentile

16. The model for the electric susceptibility
Inclusion of self-broadening:
Accurate up to ~ 360oC
Includes:
absolute linestrengths
Doppler broadening
Temperature dependent number density.
Self-broadening for binary-collision approximation
Weller et al. J. Phys. B: At. Mol. Opt. Phys. 44 (2011)
17/04/2017
1st year talk Mark Zentile

17. The model for the electric susceptibility
Inclusion of magnetic field:
Tested up to 0.6 T
Includes:
absolute linestrengths
Doppler broadening
Temperature dependent number density.
Self-broadening for binary-collision approximation
Magnetic energy level shift.
Weller et al. J. Phys. B: At. Mol. Opt. Phys. 45 (2012)
17/04/2017
1st year talk Mark Zentile

18. 1st year talk Mark Zentile
Outline
Slow-light:
What is slow-light? What conditions are needed to see it? What are the applications?
Phase shift and absorption from the electric susceptibility.
Transmission spectra to extract key parameters for the model.
Using the our model for the electric susceptibility with Fourier analysis to model pulse propagation.
Experimental method and examples of data with theoretical predictions.
17/04/2017
1st year talk Mark Zentile

19. Transmission: Extracting parameters
We want to use transmission spectra to measure experimental parameters.
Transmission  χ(ω)  dispersion  slow-light theory.
Why model transmission spectra? Can’t we just use Kramers-Kronig?
Yes, but...
17/04/2017
1st year talk Mark Zentile

20. Transmission: Extracting parameters
Rubidium 75 mm long cell, room temperature.
Excellent agreement.
One fit parameter:
Temp = (20.70 ± 0.13) oC
17/04/2017
1st year talk Mark Zentile

21. Transmission: Extracting parameters
2 mm long 98.2% 87Rb cell:
3 fit parameters:
Temp = (90.2 ± 0.1)oC
Lorentzian FWHM = 2π ∙ (165 ± 1) MHz
Very large! => Buffer gas.
Ratio of 87Rb to 85Rb = ± 0.009
17/04/2017
1st year talk Mark Zentile

22. Transmission: Extracting parameters
2 mm long 87Rb cell (high temp):
2 fit parameters:
Temp = (182.1 ± 0.4)oC
Lorentzian FWHM = 2π ∙ (170 ± 4) MHz
Very large! => Buffer gas.
17/04/2017
1st year talk Mark Zentile

23. 1st year talk Mark Zentile
Outline
Slow-light:
What is slow-light? What conditions are needed to see it? What are the applications?
Phase shift and absorption from the electric susceptibility.
Transmission spectra to extract key parameters for the model.
Using the our model for the electric susceptibility with Fourier analysis to model pulse propagation.
Experimental method and examples of data with theoretical predictions.
17/04/2017
1st year talk Mark Zentile

24. Fourier Method for pulse propagation
Electric susceptibility model is designed for monochromatic continuous wave light.
Pulses are clearly not monochromatic continuous wave light!
Solution: Use a Fourier transform to write the pulse in terms of continuous wave light.
17/04/2017
1st year talk Mark Zentile

25. Fourier Method for pulse propagation
Fourier decomposition:
17/04/2017
1st year talk Mark Zentile

26. Good conditions for slow-light?
Rubidium at natural abundance
98.2% 87Rb
17/04/2017
1st year talk Mark Zentile

27. 1st year talk Mark Zentile
Fast-Light
17/04/2017
1st year talk Mark Zentile

28. 1st year talk Mark Zentile
Outline
Slow-light:
What is slow-light? What conditions are needed to see it? What are the applications?
Phase shift and absorption from the electric susceptibility.
Transmission spectra to extract key parameters for the model.
Using the our model for the electric susceptibility with Fourier analysis to model pulse propagation.
Experimental method and examples of data with theoretical predictions.
17/04/2017
1st year talk Mark Zentile

29. 1st year talk Mark Zentile
Experimental Setup
17/04/2017
1st year talk Mark Zentile

30. Advantages/disadvantages of FPD
Works over one shot
Slow rise time => poor resolution
Need relatively intense pulses
=> may not be weak probe.
Picture from
17/04/2017
1st year talk Mark Zentile

31. Advantages/disadvantages of SPCM
Slightly better timing resolution.
Works for much less
Intense pulses.
Must build a pulse profile
over many repetitions.
Picture from
17/04/2017
1st year talk Mark Zentile

32. Preliminary experimental data (FPD)
Group refractive index of ~1000
17/04/2017
1st year talk Mark Zentile

33. Experimental data with theory (FPD)
87Rb cell.
Laser locked by polarization spectroscopy.
Carrier frequency on resonant with 85Rb D1 Fg=2  Fe=2,3 transition frequency.
Reference
Pink = Measured output
Red Dashed = Theory
17/04/2017
1st year talk Mark Zentile

34. Experimental data with theory (SPCM)
Reference
Rb natural abundance cell.
Counted over a relatively short time
Red = Measured output
Black Dashed = Theory
17/04/2017
1st year talk Mark Zentile

35. 1st year talk Mark Zentile
Outline
Future outlook:
Introduce the Faraday effect.
Use a Faraday signal to make a tuneable laser lock over ± 20 GHz detuning.
Harness the slow-light Faraday effect to make an optical switch.
17/04/2017
1st year talk Mark Zentile

36. 1st year talk Mark Zentile
The Faraday Effect
Linearly polarized light can be constructed from a circularly polarized basis.
17/04/2017
1st year talk Mark Zentile

37. 1st year talk Mark Zentile
The Faraday Effect
A magnetic field breaks the degeneracy for right and left circular components
17/04/2017
1st year talk Mark Zentile

38. 1st year talk Mark Zentile
The Faraday Effect
Have already seen that the model can accurately predict Faraday rotation:
Weller et al. J. Phys. B: At. Mol. Opt. Phys. 45 (2012)
17/04/2017
1st year talk Mark Zentile

39. A Faraday signal as a laser lock
Take inspiration from this paper. Locking off-resonance
Marchant, A. L., Händel, S., Wiles, T. P., Hopkins, S. A., Adams, C. S., & Cornish, S. L. (2011). Optics letters, 36, 64-6.
17/04/2017
1st year talk Mark Zentile

40. A Faraday signal as a laser lock
Can use our 1 mm long cell placed in a permanent magnet to achieve high magnetic fields
We will be able to lock on-resonance as well as off.
17/04/2017
1st year talk Mark Zentile

41. 1st year talk Mark Zentile
Outline
Future outlook:
Introduce the Faraday effect.
Use a Faraday signal to make a tuneable laser lock over ± 20 GHz detuning.
Harness the slow-light Faraday effect to make an optical switch.
17/04/2017
1st year talk Mark Zentile

42. The Slow-light Faraday effect
Large rotation with little absorption
Siddons, P., Bell, N., Cai, Y., Adams, C. S., & Hughes, I. G. (2009). Nature Photonics, 3, 225
17/04/2017
1st year talk Mark Zentile

43. Use optical pumping to control rotation
Can also cause a rotation by having an unbalanced distribution in the populations of the Zeeman sub-levels.
17/04/2017
1st year talk Mark Zentile

44. Use optical pumping to control rotation
17/04/2017
1st year talk Mark Zentile

45. 1st year talk Mark Zentile
Summary
Seen what slow-light is and what its applications are.
Phase shift and absorption from the electric susceptibility.
How we use transmission spectra to measure parameters for the model.
Seen how to model pulse propagation with the Fourier analysis, once χ in known.
Experimental method and examples of data with theoretical predictions.
17/04/2017
1st year talk Mark Zentile

46. 1st year talk Mark Zentile
Summary
Explained the Faraday effect.
Want to use a Faraday signal to make a tuneable laser lock.
Harness the slow-light Faraday effect to make an optical switch.
17/04/2017
1st year talk Mark Zentile

47. 1st year talk Mark Zentile
End
Thanks for listening.
17/04/2017
1st year talk Mark Zentile

48. Fit with magnetic field
17/04/2017
1st year talk Mark Zentile

49. Controlled Faraday rotation
Siddons, P., Adams, C. S., & Hughes, I. G. (2010). Physical Review A, 81,
17/04/2017
1st year talk Mark Zentile

50. Pump-Probe energy level diagram
17/04/2017
1st year talk Mark Zentile

51. 1st year talk Mark Zentile
Jitter in arrival time
FPD shows a ‘jitter’ in the arrival time and peak height.
This will broaden a photon counted pulse!
17/04/2017
1st year talk Mark Zentile

52. Simulating photon counting pulses
17/04/2017
1st year talk Mark Zentile