Exciton dynamics as a function of excitation intensity and double-pulse excitation in cyanine molecule thin films: Toward low-power optical switches

Exciton decay dynamics can be optically controlled by changing the excitation conditions, particularly, the excitation intensity. In this study, we report how the exciton dynamics in cyanine thin films depend on the excitation intensity and sequence. The excitons in these films have two decay components, and the ratio of the population of the fast decay component to the total population depends on the excitation intensity. Conversely, sequential excitation by a second optical pulse does not alter this ratio. Although the total excitation power is comparable, the change in the dynamics by the second pulse is different from the simple increase in the excitation power. Therefore, the sequential excitation by the second pulse can be a key point for realizing low-power optical switches.