Apparatus:

The experimental set up included a diode laser which was connected to both a current and a temperature control device. The temperature and the current controls were used to adjust the wavelength of the laser. The laser beam passed through a glass plate. Approximately 10% of the beam was reflected off the front face of the plate to a gold mirror. The 10% beam reflected off the mirror and passed through the rubidium cell on to a photo diode. This beam was the probe beam for the experiment. The other 90% of the beam passed through the glass plate and on to a gold mirror where it was reflected to another mirror. After being reflected twice, the 90% beam passed through the rubidium cell in the opposite direction of the 10% beam. The 90% beam was the pump beam for the experiment. This set-up is known as a Lamb Dip apparatus. A photo diode was connected to an oscilloscope where the output signal could be monitored. In order to make graphs of the data, the photo diode was connected to a signal interface which was in turn connected to a computer. A program called Science Workshop was used to collect the data from the photo diode.

Alterations were made to the set-up shown above during different parts of the experiment. To initially tune the diode laser to the desired wavelength, a detector for the Wavemeter Junior was used and the pump beam blocked. The probe beam traveled into the photo diode and the wavelength of the beam could be read from the Wavemeter Junior.

After the laser was tuned to the appropriate wavelength, the pump beam was blocked again so that a graph of the fine structure absorption spectrum could be generated without the hyperfine structure peaks. We did this so we could compare the fine structure and the hyperfine structure spectra.

During all other parts of the lab the set-up was as shown in the apparatus diagram above.

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