I optimized mode matching from BAB to OPO yesterday, as reported in elog2896. In this elog, I suspected that the BAB OPO transmission may dependend on the alignment condition of BAB to OPO. To check this BAB OPO transmission, we can utilize AMC, which is a reference we have for both LO and squeezing (BAB OPO transmission represents squeezing since they are both resonant inside OPO).

The setting for BAB resonant inside OPO is: OPO temperature 7.164, p-pol PLL frequency 300MHz (60MHz is sent to ADF4002 from the second channel CH1 of AD9959). The lock of OPO was not just flicking a switch as usual, which has already been reported to Pierre and we are waiting for his help. Now the lock of OPO is done by firstly manually moving high voltage driver offset to make OPO on resonance. Secondly, put servo operation mode to 'MAN & LOCK'. Finally, flipping SIGN switch to trigger servo lock. Make sure the loop sign is 'INV' but not 'NON INV'.

After optimizing just alignment of BAB OPO transmission to AMC, I got a mode matching of 98.5%. The check of AMC transmission PD signal while PZT scanned is shown in figure 1, 2, 3, and 4. The 98.5% matching is calculated from these figures.

We should note that the higher order mode position is very different from a characterization done last time in elog1867. Also, at that moment, the BAB OPO tranmission matching to AMC is about 99.6%.