From the previous alog post, Sheila measured a power drop across BL2 lens.
Here I modeled the loss of the 700um beam waist across the 2.5mm BL2 lens aperture.
The expression for the transmitted power obtained by modifying the Gaussian beam equation to include a displacement d2 = dx2 + dy2 is shown here.
And here's the contour plot for the loss (1-T) across the lens aperture for a beam transversing across various spots on the lens.
Me and Sheila are checking on the geometry of the setup.
The BM3 mirror mount IXM100.2 has a 100 pitch screw adjustment ( correspond to 100 turn per inch translation), and the beam appeared to be clipped symmetrically for 1/8 rev. For the mirror mount of 1.87" width, this correspond to a mirror rotation of 1.3mrad.
The distance between BM3 and BL2 is 148mm, from the mirror rotation, the IR beam angular deflection is 2.6mrad, this implies an aperture size of 0.4mm. Something is not right, and it's a mystery that requires more investigation.
