2. Doppler Free LASER Spectroscopy
It’s a headache for you
And a migraine for me!

3. LASER Spectroscopy Setup
Tunable diode LASER

5. LASER Spectroscopy Setup
Tunable diode LASER
Diffraction grating mirror
Piezo-electric actuator

7. LASER Spectroscopy Setup
Tunable diode LASER
Diffraction grating mirror
Piezo-electric actuator
Miscellaneous Optics
Beam-splitter – splits LASER beam into two probe beams (weak) and a pump beam (strong)

9. LASER Spectroscopy Tunable diode LASER Miscellaneous Optics
Diffraction grating mirror
Piezo-electric actuator
Miscellaneous Optics
Beam-splitter – splits LASER beam into two probe beams (weak) and a pump beam (strong)
Mirrors – reflect stronger pump beam to counter-propagate against probe beam

11. Rubidium cell
Probe, reference, and pump beams pass through Rubidium atoms

13. Photodiode differential amplifier
Rubidium cell
Probe, reference, and pump beams pass through Rubidium atoms
Photodiode differential amplifier
Subtracts the two signals from the reference and probe beams

15. Output to Oscilloscope
I made this!
Mathmagical
Manipulation!
Probe beam
Output to Oscilloscope
Reference beam

16. Photodiode differential amplifier
Rubidium cell
Probe, reference, and pump beams pass through Rubidium atoms
Photodiode differential amplifier
Subtracts the two signals from the reference and probe beams
Oscilloscope
Creates a real-time plot of “absorption” vs. frequency

18. The Statistical Doppler Effect
Gaussian distribution of velocities
Fast moving atoms

20. The Statistical Doppler Effect
Gaussian distribution of velocities
Fast moving atoms
Slow moving (stopped) atoms

22. The Statistical Doppler Effect
Gaussian distribution of velocities
Fast moving atoms
Slow moving (stopped) atoms
blurring of the spectral lines

25. How Saturation Spectroscopy Undoes the Doppler Blurring Effects
Reference beam:
Passes through only Rubidium
Interacts with all the atoms in its path

27. How Saturation Spectroscopy Undoes the Doppler Blurring Effects
Reference beam:
Passes through only Rubidium
Interacts with all the atoms
Probe beam:
Passes through Rubidium

30. How Saturation Spectroscopy Undoes the Doppler Blurring Effects
Reference beam:
Passes through only Rubidium
Interacts with all the atoms
Probe beam:
Passes through Rubidium
and “pump beam”
Pump beam:

32. How Saturation Spectroscopy Undoes the Doppler Blurring Effects
Reference beam:
Passes through only Rubidium
Interacts with all the atoms
Probe beam:
Passes through Rubidium
and “pump beam”
Pump beam:
Counter-propagates through probe beam and excites the
atoms in its path
Ignores “stationary” atoms at transition frequency because
they are already excited by the pump beam

37. Application
Use the LASER, which is now accurately locked on a precise frequency, to trap atoms
Instead of using multiple LASERs, feed the locked LASER beam into a tapered amplifier

38. The Tapered LASER Amplifier
Requirements:
Delicate temperature control
Input beam
Drives the amplifier at the given frequency

39. I made this too! Temperature measuring device (thermistor)
Thermal Electric cooler
LASER diode current supply
Amplification Process
Unthinkably powerful output beam
Super stable seed beam
LASER diode chip

40. Partially reflective mirror
Excited State
Partially reflective mirror
Gain Medium (semiconductor)
Ground State

41. Gain Medium (semiconductor)
Excited State
Gain Medium (semiconductor)
Ground State