Doppler Free LASER Spectroscopy It’s a headache for you And a migraine for me!
LASER Spectroscopy Setup Tunable diode LASER
LASER Spectroscopy Setup Tunable diode LASER Diffraction grating mirror Piezo-electric actuator
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)
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
Rubidium cell Probe, reference, and pump beams pass through Rubidium atoms
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
Output to Oscilloscope I made this! Mathmagical Manipulation! Probe beam Output to Oscilloscope Reference beam
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
The Statistical Doppler Effect Gaussian distribution of velocities Fast moving atoms
The Statistical Doppler Effect Gaussian distribution of velocities Fast moving atoms Slow moving (stopped) atoms
The Statistical Doppler Effect Gaussian distribution of velocities Fast moving atoms Slow moving (stopped) atoms blurring of the spectral lines
How Saturation Spectroscopy Undoes the Doppler Blurring Effects Reference beam: Passes through only Rubidium Interacts with all the atoms in its path
How Saturation Spectroscopy Undoes the Doppler Blurring Effects Reference beam: Passes through only Rubidium Interacts with all the atoms Probe beam: Passes through Rubidium
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:
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
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
The Tapered LASER Amplifier Requirements: Delicate temperature control Input beam Drives the amplifier at the given frequency
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
Partially reflective mirror Excited State Partially reflective mirror Gain Medium (semiconductor) Ground State
Gain Medium (semiconductor) Excited State Gain Medium (semiconductor) Ground State