Pound-Drever-Hall Driving Circuit.

See this publication from my lab group for a detailed explanation. The just of the circuit is a tunable VCO generating a signal that is both sent out to the optics setup and an internal mixer via a phase shifter. Then the optics produce a signal with modulation driven by this VCO, which is also directed to the mixer. This produces a homodyne measurement proportional to the detuning of an optical cavity. Feedback is then used to maintain the cavity length at resonance.

From earlier prototypes I built an enclosed unit for producing these signals. It's mostly just some AC/DC converted and voltage regulators to generate the relevent levels, and a combination of modular RF components from minicircuits. This design was then followed up an a single PCB designed by an other student under my supervision.