Transient optical properties, laser induced avalanche effect, and all optical switching in molecular aggregates

Organic dyes have attracted expressive research interest in recent years due to their wide range of applications. Self-aggregation occurs in a variety of organic molecules, a phenomenon that changes the photochemical and photophysical properties of dyes. Laser beams with wavelengths of 663 nm and 532 nm were used for thermal modulation of the aggregation states of the methylene blue dye, which led to the discovery of a novel avalanche phenomena in the molecular/supramolecular level and observations of not yet reported material optical behaviors. The obtained experimental data reveals the existence of asymmetric optical responses of aggregated dyes under laser excitation with wavelengths at the monomer or at the dimer absorption bands. The observed optical behaviors, resulting from the laser modulation of the molecular aggregation states, may find applications in the field of organic electronics and devices, such as optical logical gates and optical power limiters. A dual mechanism all optical switching driven by the simultaneous action of the cooperative effects of the laser induced disruption of dimeric dye units and thermal lensing was achieved. [Display omitted] •CW laser beam modulates the aggregation state of dye molecules.•Laser beam probes the dynamics of transient dissociation of aggregated species.•Transient methylene blue dye responses to 532 nm and 663 nm high signal excitations are asymmetric.•High signal laser excitation of aggregated dyes induces avalanche phenomenon.•Avalanche phenomenon in aggregated dye switches-off the laser beam power faster than the thermal lens phenomenon alone.