Bachelor defense by Gro G. Grandahl

Generation of 866 nm laser light - and stability characterization

For a laser to be able to drive an atomic transition of a Ca+ ion of linewidth 1.5 MHz, it must be tuned to the frequency of the transition, and it must not deviate more than the linewidth from this frequency. This thesis prepares and characterizes a continuous wave (CW) laser to be used for driving the mentioned transition. The light emitted by the CW laser was sent through different optical components, fiber-coupled, and sent to a wavemeter, to the main experiment, as well as to a distinct setup allowing it to interfere with light from a frequency comb. This created a beat note which was recorded using a spectrum analyzer. Although the laser has yet to be tuned to the exact frequency of the atomic transition, the measured beat note together with the less precise frequency reading from the wavemeter, allowed for a sub-MHz determination of the frequency of the laser. Then, two similar measurements were conducted, differing by the laser being locked to a wavemeter in one but not the other. The stability of the frequency of the CW laser was then quantified using the Allan deviation, and it was shown that when locked to the wavemeter, the frequency deviation is within the linewidth of the atomic transition during measuring times within two hours. This thesis concludes that the laser only remains to be tuned to the correct frequency, before it is ready to drive the atomic transition.