Counting Atoms

After last changing of temperature, the absorption dissappered and I was trying to look for it on different temperatures. However, it wasn’t succesfull and the absorption is still lost.

I adjusted the horizontal tilt slightly today and found the absorption.  It was mode hopping terribly however so I tried adjusting the vertical tilt to get a better lock.  After this I could no longer find the absorption, and my laser is reading was much different wavelength.  I am having some difficulty getting back to 811 nm.  Next time I will readjust the vertical tilt in case I did a poor job the first time.

By changing the current, I found the absorption. However, I couldn’t get closer when I was lowering the amplitude of piezo-changer of position of grating and after a  specific value the absorption disappeared. I changed the temperature by the smallest step as I could and continue in finding the wavelength.

This is my first time down here since the break.  My laser was not lined up very well with the optical fiber coupler, so I tuned it to maximize output.  I then put it through the lit krypton tube, but unfortunately it was not on the absorption line.  Even at several different temperatures I could not find absorption.  It is at 811.65 nm.  I checked the vertical tilt on the grating by finding the lazing threshold, and found that it is still very good (~51mA).  Can you think of any solution other than adjusting the grating to find the absorption?  If the laser hasn’t changed, its grating should be perfect still.

Today, I installed a Krypton tube and tweaked the beam into a detector after the tube. I put the lens into the path, so the end of a beam is focused into the center of detector/sensor. My laser was already on the wavelength between 811.28-30, according to current. Miracle happened and when I lit the cathode tube, by changing current only, I reached the absorption. The signal was symmetrically changing about the peak of the function that changes the wavelength and it was nice broad curve that went from maximum to zero and then was rising up again. However, when I installed a lid on a laser, absorption disappeared. But I am very near and the wavelength was exactly 811.29 in my case.

The branch that leads to Fabry - Perot was totally out of tune. I rebuilt it, so now, the observation of the modes of the laser is possible.

I set up the branch to the Fabry-perot today. I can see the modes of laser now, but it needs to maximize the output. The laser seem stable at 811.3 so I hope that finding the absorption will not be that tough.

The wavemeter worked today but it showed the wavelength of 805 nm. Though, I had to readjust the grating  and the lens in the laser, as the beam was diverging. Because of this the angles of beams changed so much that I had to make all the system completely from the beginning. I set up a branch for the meter and the laser is now on the frequency of 811.34 nm. Next time, I will be adjusting the branch to Fabry - Perrot.

I set up a laser grating so I am sure that the back reflection is maximum and I got stimulated emission for a minimal current. I did iterative processes of setting up geometrical paths so now, I am able to measure the wavelength in the one branch and to observe modes on intereferometer, or send a beam throw crypton test tube. For now, I need to adjust a grating for a proper wavelength and I need Chad to log-in to lab computer so I can use the software of BristolMeter.

I tuned the laser again to maximize absorption and minimize mode hopping.  Just in case it shifts again and I have to tune it again, I will wait to run the laser through the AOM system again.  Despite my efforts, I couldn’t get saturated absorption in the krypton cell.  I think I will need another person helping me for this, as I cannot see the oscilloscope from where the krypton tube is.  It should be close though.  Also, the wavemeter wasn’t working today.  The computer is running slow so it could just be that the computer needs to be restarted.