Procedure

The manual mostly explains what the optics table will look like and what data to take and how. The video recording of the experiment is pretty thorough and has lots of useful tips. Please watch that after you’ve read the manual but before you read much more of this document. Here are some extra guidelines that may be helpful:

1. Getting the laser beam through the Rubidium cell can be difficult. Take your time and do your best to identify the beam trajectory using the laser card.
2. The photodiodes have a resistor setting on the back that acts as a gain setting.  The photodiodes have a maximum output of 10 V, so you will need to set the resistor such that the current output across the resistor is in that range.  If the voltage is always near zero, then change the resistor setting.  If the voltage is always 10 V, even as you pass an attenuator in front of the beam, then change the resistor setting.
3. It can be difficult to get the entire Doppler-broadened spectrum in one ramp of the laser current.  Get as much as you can and be ready to label the peaks in your spectrum.
4. You will zoom in on one of the Doppler-broadened peaks to detect the hyperfine structure.  Be sure to keep track of which isotope peak you are using.
5. Don’t change the sweep frequency as you zoom in from Doppler-broadened to saturated absorption. You want to be using the same time for the sweep for all your data so you can compare your results. If you absolutely have to change the frequency, record the frequency of the current sweep before you change it.
6. To see the hyperfine structure, you will need to decrease the amplitude of the sweep while adjusting the DC offset to keep the peaks centered in the sweep.  Be mindful that you don’t lose the peaks to a mode hop.
7. When doing the saturated absorption experiment, it can be very difficult to align the two detectors and the 50/50 beam splitter.  The mount for the 50/50 can get in the way.  Take your time and use the laser card to make sure the two beams come through.  This may be an iterative process as you align the beams.
8. If any alignment step is taking longer than about 15 minutes, please get the attention of a lab technician or TA.  You are not supposed to struggle so hard that you leave without any data.