Phase-synchronous undersampling in nonlinear spectroscopy

We introduce the concept of phase-synchronous undersampling in nonlinear spectroscopy. The respective theory is presented and validated experimentally in a phase-modulated quantum beat experiment by sampling high phase modulation frequencies with low laser repetition rates. The advantage of undersampling in terms of signal quality and reduced acquisition time is demonstrated and breakdown conditions are identified. The presented method is particularly beneficial for experimental setups with limited signal/detection rates.