Chien-Ming, Yu-Hang, and Aritomi

Yesterday we adjusted the BS horizontal angle to make the LO beam reach the DC balance at homodyne detector. We measured the CMRR, it is better than 80 dB at 1 kHz.

However, in this case, if we let that BAB and LO have a good overlapping, we need to change the optical set up of BAB a lot.

So today we keep the BAB beam in its original condition and adjust the BS angle to make the BAB beam reach the DC balance at homodyne. Then we adjust the LO beam to achieve a good overlapping with BAB beam. In this case, when the BAB is DC balanced, the homodyne DC offset of the LO shows -10mV.

We repeatedly adjust the BS angle and the alignment of both beams a little bit, finally, we make the LO beam become DC balanced and the DC Offset of BAB is 2.4 mV.