I assembled the components for the optical path of the 1310nm probe:

- Fiber collimator. Output mostly p-polarized.
- Polarizing PBS. Transmission: ~90mW, Reflection ~6mW. The reflection goes to a beam dump.
- Half-Wave Plate
- Polarizing PBS rotated  so that the reflection goes upward (to a high power beam dump) and the transmission is s-polarized
- Focusing lens f=300mm
- non-polarizing BS 90(R):10(T).
- Transmitted beam (10%):
     - Gold coated mirror
     - Converging lens f=50mm
     - PD DET10N mounted on a XY lens mount
- Reflected beam (90%)
     - Gold coated prism mirror.
     - To the crossing point...

Then I aligned the beam to impinge at 0.135rad on the sample at the crossing point. The pump is at 2deg (0.035rad) to avoid the etalon effect on the thin samples, this makes the angle between the 1310nm probe and the pump 0.1rad.