Hudson, Camilla, Sheila, Vicky

Summary: Today, we mode-matched and aligned the new fiber collimator through the OPO, with >94% mode-matching into TEM00! Just as good as expected from optics lab measurements in 63389 :-)  OPO-transmitted seed beam (sqz path) is now making it out of HAM7 onto SQZT7 cameras.

Notes from today, incl. a working alignment procedure through HAM7:

• We used the filter cavity green reflection (FCGS) to align the ZM1/2/3+FC1 retroreflection back through the VIP, looking at FCGS camera/PDs on SQZT7. In practice we only adjusted ZM2 (mostly yaw) to not clipping along the ZM1/2/3+FC1 path. Also nice because FCGS is decoupled from ZM4/5.
• We locked OPOS using the thumbscrews for collimator alignment. Without locking OPOS, touching the knobs was very wobbly on the table PDs. We went back-and-forth locking/unlocking it a few times, but in the end it was fine to just lock the platform, use ZM2 to align the FC1 retro w/filter cavity green, then use ZM4 to align the seed camera/pd.
• To align mode-matching, we first loosely aligned the collimator to maximize seed reflected power on the CLF_TRIG_PD (used "H1:SQZ-SHUTTER_H_TRIGGER_OUT_DQ" for its fast refl channel).
• Then, with ~100mW seed power into the SQZT0 seed SOPO fiber, we can see seed beam transmitted past SFI1. This power level also let us loosely align collimator knobs for transmission, and we can see power on the in-vac D:QPD's too.
• We then used ZM4/5 to walk this transmitted beam onto the OPO-IR seed camera + OPO_IR_PD on SQZT7.
• We T'd off the OPO_IR_PD, and used a scope to scan the Thorlabs PZT driver to scan the OPO PZT at ~10 Hz (blue trace), and align the collimator.
  • Hudson walked the alignment using both the collimator and the first steering mirror into opo. CLF fiber mode-matching through the OPO cavity looks very good now, >94% into the fundamental mode!

Also, we've tried to resolve the polarization-dependent calibration of seed lauched power on SQZT0 today. For the waveplates between L7 and BS7, we moved the first L/4 to between BS7 and MR6, and we moved the L/4 to between MR6/7. We re-calibrated the seed launch pd (DC5), and saved its updated calibration to SDF:

• For H1:SQZ-SEED_LAUNCH_DC_VOLTS = 0.223 V @ 30dB, we measured 9.6uW on the PD, with 12.7mW going into its pickoff, BS7. To calibrate, we set Responsivity (A/W)=0.38 (up from 0.18), and beamsplitter pickoff ratio 0.075%.