[Shalika, Marc]

Our polarization camera's aperture is 3 mm and required divergence of beam is 2°. We investigated that the telescope had beam divergence of 0.038°. But, the issue was that beam waist was exceeding (almost) the 3 mm aperture. See plot 1 to see evolution of beam after the lens. The position of lens was 0.21 and 0.253 m from laser. 

For modification, BSN11 was removed from the path, and the beam was measured after the lens using beam profiler, both before and after modification. 

The lens position was modified to tune the beam waist at a far distance of around 1.3 m after the telescope. See plot 2 of beam evolution after the telescope modification. For optimal modification a reference point was set around 1 m after the lens. The beam waist before modification was around 3.2 mm. The lens position were tuned to reduce the waist. The position was finalised when the waist was around 8.5 mm at 1 m. After this modification, the beam profiler was used to obtain the plot 2. The lens of f = -50mm is kept at almost 0.3 cm after the faraday isolator. The lens of f = 75mm is kept within 25mm after the 1st lens. 

After this, we placed back the BSN11 and the position was tuned to obatin the beam back on the polarization camera. 

Also, the characterisitcs of BSN11 were evaluated(The arrow on the optics points toward the coating). The reflection of this had two beams.

incident: 39 +/-0.1 mW

reflected: 4+/-0.1 mW

reflection without 2nd beam: 3.7 mW

transmission: 34.5+-/0.1 mW

With optimal beam parameters we will proceed to use the setup for polarization generation and other future experiments.