Optimizing the precision of the acquired optical tweezers stiffness with the FPGA-based PID algorithm

The stiffness of an optical tweezer is one of the most crucial parameters in virtually all related quantization experiments. Due to the limitation of instruments and the uncertainty of the measurement, the acquisition of the stiffness often takes place in a prolonged period and or requires additional data processing. Here, we demonstrate that with a PID power locking system made from a feedback loop consisting of a Field-Programmable Gate Array (FPGA) and Acoustic Optical Modulator (AOM), the stiffness calculated from the Quadrant Photodetector (QPD) signal shows a significantly reduced uncertainty compared to that of the unlocked situation, resulting in a much-reduced measurement time and an improved accuracy.