Lasers and optics

In our experiments we use two diode lasers. These lasers are diode lasers with an output power of about 40 mW at the frequency of 1083.034 nm that we use. The beam of the laser is about 1cm in height by 0.5cm in width. For the collimator it would be optimal if all four beams entering the collimator have the same $s_0$. Especially each pair of laser beams should have the same $s_0$. If this is not the case, an atom moving parallel with the collimator axis will have a higher chance to absorb a photon from the laser with a higher intensity than to absorb a photon from the laser beam with a lower intensity. This would cause a net force that would give the atoms a velocity component perpendicular to the central axis of the setup. With use of a power meter we have measured the intensities of the four beams. The four beams are created by splitting the initial beam into two beams with use of a beam splitter. The two beams are both split into two beams with two other beam splitters. The intensity of the two beams leaving a beam splitter can be adjusted by slightly rotating the beam splitter cube. In this way we have created four laser beams with the following intensities: in the horizontal direction, both laser beams have $s_0 = 154$, and in the vertical direction, the laser beams have $s_0 = 123$ and $s_0 = 126$. It is important to first make sure that the intensities of the pairs of beams are equal, since rotating or translating the beam splitter cubes obviously alters the path of the light.

The glass plate that splits off a small percentage of the beam for the stabilization unit (see sec. 2.7.2) is placed in front of the first beam splitter, and gives a loss in intensity of 20%. This is due to the fact that the glass plate is not coated for light of a wavelength of 1083 nm, like all the other mirrors, beam splitter cubes and windows. The value of $s_0$ of the beam used for the laser stabilization unit is $s_0 = 4$.