The performance and limitations of FPGA-based digital servos for atomic, molecular, and optical physics experiments

Area of Science:

• Atomic, Molecular, and Optical (AMO) Physics
• Control Systems Engineering

Background:

• High-bandwidth feedback control is crucial for precision laser manipulation in AMO physics.
• Traditional analog servos face limitations in flexibility and performance for complex control tasks.

Purpose of the Study:

• To evaluate the performance, advantages, and limitations of Field Programmable Gate Array (FPGA)-based digital servos for laser control.
• To compare FPGA digital servo performance against state-of-the-art analog servos in experimental settings.
• To explore advanced control functionalities offered by digital servo implementations.

Main Methods:

• Implementation of two digital servos using low and mid-range FPGA development platforms.
• Benchmark testing of digital servos for noise, bandwidth, and dynamic range.
• Comparative analysis against a commercial analog servo for laser intensity stabilization.
• Application of advanced filtering techniques, including three-pole and phase-compensated two-pole filters.

Main Results:

• FPGA digital servos achieved feedback bandwidths of 2.5 MHz, limited by signal latency.
• Demonstrated superior control capabilities beyond analog servos, including resonance suppression.
• Performance benchmarks for noise, bandwidth, and dynamic range were established.
• Identified specific advantages and limitations of the FPGA-servo implementation.

Conclusions:

• FPGA-based digital servos provide a viable and high-performance alternative to analog servos for laser control in AMO physics.
• Digital servos offer enhanced control features and flexibility, enabling improved experimental precision.
• Further development and consideration of design subtleties are important for optimizing FPGA servo applications.