the slow-light effect first year talk mark zentile
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The Slow-Light Effect
First year talkMark Zentile
Project Members
Lee Weller Charles Adams Ifan Hughes
19/04/23 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.
19/04/23 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.
19/04/23 1st year talk Mark Zentile
What is ‘Slow-Light’?
19/04/23 1st year talk Mark Zentile
What is ‘Slow-Light’?
19/04/23 1st year talk Mark Zentile
Slow-light with EIT
19/04/23 1st year talk Mark Zentile
Better interferometers
19/04/23 1st year talk Mark Zentile
Image rotation Image coding
19/04/23 1st year talk Mark Zentile
Optical Delay Line
19/04/23 1st year talk Mark Zentile
Optical Switch
19/04/23 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.
19/04/23 1st year talk Mark Zentile
Complex refractive index
19/04/23 1st year talk Mark Zentile
ABSORPTION DISPERSION
Transmission Spectra
19/04/23 1st year talk Mark Zentile
The model for the electric susceptibility
• Our model has been developed over many years:
19/04/23 1st year talk Mark Zentile
Siddons et al. J. Phys. B: At. Mol. Opt. Phys. 41 (2008) 155004
• Accurate up to ~ 120oC• Includes:
absolute linestrengths Doppler broadening Temperature
dependent number density.
Result of solving the optical Bloch equations for a two level atom.
The model for the electric susceptibility
• Inclusion of self-broadening:
19/04/23 1st year talk Mark Zentile
Weller et al. J. Phys. B: At. Mol. Opt. Phys. 44 (2011) 195006
• Accurate up to ~ 360oC• Includes:
absolute linestrengths Doppler broadening Temperature
dependent number density.
Self-broadening for binary-collision approximation
The model for the electric susceptibility
• Inclusion of magnetic field:
19/04/23 1st year talk Mark Zentile
Weller et al. J. Phys. B: At. Mol. Opt. Phys. 45 (2012) 055001
• 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.
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.
19/04/23 1st year talk Mark Zentile
Transmission: Extracting parameters
• We want to use transmission spectra to measure experimental parameters.– Transmission χ(ω) dispersion slow-light theory.
19/04/23 1st year talk Mark Zentile
• Why model transmission spectra? Can’t we just use Kramers-Kronig?– Yes, but...
Transmission: Extracting parameters
• Rubidium 75 mm long cell, room temperature.
19/04/23 1st year talk Mark Zentile
Excellent agreement.One fit parameter:
Temp = (20.70 ± 0.13) oC
Transmission: Extracting parameters
• 2 mm long 98.2% 87Rb cell:
19/04/23 1st year talk Mark Zentile
3 fit parameters:
Temp = (90.2 ± 0.1)oC
Lorentzian FWHM = 2π ∙ (165 ± 1) MHzVery large! => Buffer gas.
Ratio of 87Rb to 85Rb = 0.982 ± 0.009
Transmission: Extracting parameters
• 2 mm long 87Rb cell (high temp):
19/04/23 1st year talk Mark Zentile
2 fit parameters:
Temp = (182.1 ± 0.4)oC
Lorentzian FWHM = 2π ∙ (170 ± 4) MHzVery large! => Buffer gas.
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.
19/04/23 1st year talk Mark Zentile
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.
19/04/23 1st year talk Mark Zentile
Fourier Method for pulse propagation
• Fourier decomposition:
19/04/23 1st year talk Mark Zentile
Good conditions for slow-light?
19/04/23 1st year talk Mark Zentile
Rubidium at natural abundance 98.2% 87Rb
Fast-Light
19/04/23 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.
19/04/23 1st year talk Mark Zentile
Experimental Setup
19/04/23 1st year talk Mark Zentile
Advantages/disadvantages of FPD
• Works over one shot
• Slow rise time => poor resolution
• Need relatively intense pulses
=> may not be weak probe.
19/04/23 1st year talk Mark Zentile
Picture from http://www.eotech.com/product/14/2GHz_Amplified/
Advantages/disadvantages of SPCM
• Slightly better timing resolution.
• Works for much less
Intense pulses.
• Must build a pulse profile
over many repetitions.
19/04/23 1st year talk Mark Zentile
Picture from http://excelitas.com/downloads/DTS_SPCM_AQRH.pdf
Preliminary experimental data (FPD)
19/04/23 1st year talk Mark Zentile
Group refractive index of ~1000
Experimental data with theory (FPD)
19/04/23 1st year talk Mark Zentile
• 87Rb cell.•Laser locked by polarization spectroscopy.• Carrier frequency on resonant with 85Rb D1 Fg=2 Fe=2,3 transition frequency.
Pink = Measured output
Red Dashed = Theory
Reference
Experimental data with theory (SPCM)
19/04/23 1st year talk Mark Zentile
• Rb natural abundance cell.•Counted over a relatively short time
Reference
Red = Measured output
Black Dashed = Theory
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.
19/04/23 1st year talk Mark Zentile
The Faraday Effect
• Linearly polarized light can be constructed from a circularly polarized basis.
19/04/23 1st year talk Mark Zentile
The Faraday Effect
• A magnetic field breaks the degeneracy for right and left circular components
19/04/23 1st year talk Mark Zentile
The Faraday Effect
• Have already seen that the model can accurately predict Faraday rotation:
19/04/23 1st year talk Mark Zentile
Weller et al. J. Phys. B: At. Mol. Opt. Phys. 45 (2012) 055001
A Faraday signal as a laser lock
• Take inspiration from this paper. Locking off-resonance
19/04/23 1st year talk Mark Zentile
Marchant, A. L., Händel, S., Wiles, T. P., Hopkins, S. A., Adams, C. S., & Cornish, S. L. (2011). Optics letters, 36, 64-6.
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.
19/04/23 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.
19/04/23 1st year talk Mark Zentile
The Slow-light Faraday effect
19/04/23 1st year talk Mark Zentile
Large rotation with little absorption
Siddons, P., Bell, N., Cai, Y., Adams, C. S., & Hughes, I. G. (2009). Nature Photonics, 3, 225
Use optical pumping to control rotation
19/04/23 1st year talk Mark Zentile
• Can also cause a rotation by having an unbalanced distribution in the populations of the Zeeman sub-levels.
Use optical pumping to control rotation
19/04/23 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.
19/04/23 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.
19/04/23 1st year talk Mark Zentile
End
Thanks for listening.
19/04/23 1st year talk Mark Zentile
Fit with magnetic field
19/04/23 1st year talk Mark Zentile
Controlled Faraday rotation
19/04/23 1st year talk Mark Zentile
Siddons, P., Adams, C. S., & Hughes, I. G. (2010). Physical Review A, 81, 043838
Pump-Probe energy level diagram
19/04/23 1st year talk Mark Zentile
Jitter in arrival time
• FPD shows a ‘jitter’ in the arrival time and peak height.
19/04/23 1st year talk Mark Zentile
• This will broaden a photon counted pulse!
Simulating photon counting pulses
19/04/23 1st year talk Mark Zentile
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