Vicky and Sheila showed the Quantum efficiency on PD-B of our homodyne was low in 72604 and 72973.
Today Sheila and I swapped the original S1800623 with the spare S2000862 homodyne and balanced the homodyne by adjusting the BS and PDB steering mirror to bring H1:SQZ-HD_DIFF_DC_OUTPUT to 0. Both PDs now have the same QE of >97%.
We removed the fudge factors of -1.09 and 1.11 in H1:SQZ-HD_{A,B}_DC so now these show mA. The dark noise and shot noise look similar to the old homodyne, see attached. Next week will align and match the SQZ beam to the LO. We left the original HD in SQZT7.
| Channel HD_{A,B}_DC | Ophir PM (s/n 756764, meter 751044) | QE w/Ophir (from 72604) | Thorlabs PM | QE w/Thorlabs (from 72604) | |
| PD-A | 0.486mA | 0.58mW | 97.7% | 0.560mW | 101.2% |
| PD-B | 0.486mA | 0.58mW | 97.7% | 0.563mW | 100.7% |
* Example QE calulation: Responsivity of 0.833A/W for Ophir Measurements using 0.486mA / 0.58mW. QE is 97.7% from 0.833A/W / 0.8582A/W for QE(100%) from 72604.
I accepted the SDF of the fudge factors of homodyne to go to observe.
