Anisotropic behavior of random lasing in a highly concentrated dye solution

Area of Science:

• Optics and Photonics
• Materials Science

Background:

• Diffusive random lasers (DRLs) offer unique emission properties.
• High concentrations of dyes like Rhodamine 6G (Rd6G) can lead to molecular aggregation (monomers and dimers).
• Molecular aggregation influences the optical properties of the gain medium.

Purpose of the Study:

• To investigate the angular dependence of diffusive random laser (DRL) emission.
• To understand the role of molecular aggregation and scattering in Rd6G solutions.
• To explore the impact of Förster resonance energy transfer (FRET) and anisotropic inner filter effect (IFE) on RL emission.

Main Methods:

• Excitation of highly concentrated Rhodamine 6G solutions.
• Analysis of emission spectra and angular dependence.
• Enhanced backscattering (EBS) tests to confirm scattering.
• Assessment of Förster resonance energy transfer (FRET) and inner filter effect (IFE).

Main Results:

• Dimerization at high concentrations causes random fluctuations in the dielectric constant.
• Aggregated dye molecules induce multiple scattering events, confirmed by EBS.
• Scattering feedback and FRET enable random laser (RL) spikes over dimeric fluorescence.
• RL emission exhibits strong angular dependence due to anisotropic IFE.

Conclusions:

• Molecular aggregation significantly impacts DRL emission characteristics.
• The observed angular dependence is crucial for understanding light-matter interactions in aggregated media.
• Findings are important for optical characterization of media with significant fluorophore aggregation.