FELIX’s UK User Station 1 focuses on complicated optical experiments where multiple pulses of the laser are required. By varying a few mirrors, we can drastically modify the type of experiment and information which we obtain. By using one strong pulse (the “pump”) and one weak pulse (the “probe”), we can obtain the T1 relaxation time of the states which we study. These pump-probe experiments measure only the weak probe pulse so that we can be extremely sensitive to small fluctuations.

On the other hand, by using two equally strong pulses and measuring the total effect of the two pulses, we can extract information about the energy levels and transition strengths of the states which we study. This method also lets us learn about how the donors are excited, for example allowing us to look at whether excitations happen using multiple photons.