Nutsinee Terry Daniel

We were finally able to lock the OPO in air. We took the output of the common mode board and send it to the laser PZT via a Thorlabs PZT driver (gain of 15).  The ugf we achieved is 10kHz. With all 3 boosts engaged the lock is reasonably tight. The attached screenshot shows the CMB settings.

The noise spectrum indicates a strong acoustic peak around 1.1kHz that needs a large driving range.

We also measured the transfer function from the OPO PZT to the laser PZT. The first resonance is at ~6.0 kHz as expected—confirming that the 1.1kHz peak is not an inline resonance.

Some of the problems we encountered along the way:

• The 4kHz low pass filter in the CMB common path is flawed by design and was operating as a voltage follower.
• The Thorlabs PZT driver doesn't accept a negative input voltage even if the offset is set to 50V.