Control of emission interval and timing in triggered periodic superradiance

To achieve more controllable development of coherence in solids, we investigated the effect of a trigger laser tuned to the superradiance (SR) transition wavelength on periodic SR observed in an Er:YSO crystal. For period control, applying the trigger laser reduced both the SR period and its variance, demonstrating enhanced controllability of coherence development dynamics. As the trigger laser power increased, both the period and the number of emitted SR photons decreased while maintaining a proportional relationship. This behavior is explained by a reduced SR threshold under a constant excitation rate and is reproduced by numerical simulations based on the Maxwell–Bloch equations. For timing control, we found that SR could be triggered even when the excitation laser alone was insufficient. This enabled us to control the emission timing of SR using short trigger pulses and provided a device capable of generating SR at desired timing.