Aritomi and Yuhang

According to elog 1659, the simulation result of beam size and gouy phase for AA system is shown in the attached figure 1. We could see that there is only 1000mm lens and QPD1 is located close to beam waist while QPD2 is located far from beam waist.

The measurement was done recently to check the real beam size. The measured points and beam diameter is shown in the attached figure 2. The measurement done for QPD1 (9 points) is indicated by 'cross' wihle the measurement done for QPD2 (3 points) is indicated by 'point' 21,22,23.

Since the beam size should be symmetric for two path after BS, the 'cross' and 'point' can be imagined to be located in a single beam. These measured ponits are fit with gaussian beam as shown in figure 3. The measurement done for QPD1 and 2 seems to have a wrong distance, we will check that.