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Abstract:
We report on the design, implementation, and
characterization of fully digital control loops for laser frequency
stabilization, differential phase-locking, and performance optimization
of the optical metrology system on-board the LISA
Pathfinder space mission. The optical metrology system consists
of a laser with modulator, four Mach–Zehnder interferometers,
a phase-meter and a digital processing unit for data analysis.
The digital loop design has the advantage of easy and flexible
controller implementation and loop calibration, automated and
flexible locking and resetting, and improved performance over
analog circuitry. Using the practical ability of our system to
modulate the laser frequency allows us to accurately determine
the open-loop transfer function and other system properties.
Various noise sources and their impact on system performance
are investigated in detail.
