Participant: Marco and Yuhang

After lock coherent control PLL with a 7MHz frequency offset with the main laser, we tried to demodulate the OPO reflection signal with 14MHz. And the OPO transmission is going to the homodyne detector. Then there is demodulation of 7MHz(7MHz local oscillator was connected). 

After the demodulation of each signal, we make them go through the filter separately. And then goes to the green phase shifter and the infrared phase shifter separately. After close these two loops, we can basically lock them.

We scanned the green and infrared phase. The error signal for the green phase is around 70mV p-p while 700mV p-p for IR(green power now is 50mW). This may be the reason why we can lock the IR phase much better.

I measured the optical-mechanical transfer function of green phase part. It shows wired behavior. However, we checked together and the measurement strategy looks reasonable. The result is shown in the attached picture and should be further investigated.