Sheila, Terry

We have swapped the input/output coupler on the H1 OPO.  The original optic was M1 from E1600051, and we have swapped it now with E1700299, which has a reflectivity of 98% for 532, so that we can use our OPO as a reference cavity.

Although this optic is M1, the mount it is on is labeled M4 because the other M1 mounts were used already.  We found that the optic was misaligned in pitch when we tried to swap it.  We measured the distance between the prompt reflection about 10mm above the leakage beam at a distance of 500mm from the cavity (we are using the 1064 beam which was aligned into the input/output coupler for the escape efficiency measurement), meaning that the beam had a 1 degree misalignment or that the mirror was pitched by +0.5 degrees compared to the original optic. 

We think the problem is the wedge of the optic.  There is an arrow on the barel which is supposed to indicate the thick part of the optic, for the original M1 that arrow is on the side of the optic farther away from the crystal, so that the wedge is horizontal.  For the new coupler, it is rotated about 45degrees clockwise from that position (the arrow is on the upper half of the barel, away from the crystal.)  Since the wedge is a half a degree this probably explains the misalignment we see. 

There is no way to adjust pitch in these mounts, but Hugh brought us some class A shims that were used for ISIs.  Hugh suggested that we place the edge of the shim half way along the front feet on the mirror holder (D1600063), so that we would be able to adjust pitch by sliding it back and forth.  We used a 5 thousandths of an inch shim and were easily able to adjust the optic pitch.  The field used for the escape efficiency measurement is again aligned to the cavity.