Cause of transient decay background after green repump pulse

Identify the physical origin of the weak, approximately 100 microsecond decaying background signal observed after the green repump pulse during spin-pumping measurements and ascertain whether it arises from acousto-optic modulator transients or other optical or sample-related processes.

Background

During spin-relaxation measurements with near-axis magnetic field alignment, the authors observed an unexpected transient background following the green repump step. This background complicates the analysis and necessitated increased separation between pulses and post-processing subtraction using a bi-exponential fit.

Understanding the origin of this transient is crucial for improving measurement fidelity, minimizing systematic errors in spin-relaxation time extraction, and ensuring robust operation across different cooldowns and alignment conditions.

References

We note that the green repump AOM began to exhibit an unknown transient behavior which results in a weak background signal decaying over 100 µs after the end of the pulse.

— A scalable gallium-phosphide-on-diamond spin-photon interface  (2601.04733 - Yama et al., 8 Jan 2026) in Section SI.3, Subsubsection "Near-axis field"