Simon, Pengbo

We remove the first PBS of the FI because it will block the reflective beam, so we put another PBS behind the first HWP, then remeasure the beam waist.  

The result shows the waist is about 0.03529 mm at Z_position = 59.96 mm, which is good, our next step will be to recover the birefringence measurement system and test the performance of the new system.