Random Lasing at Localization Transition in a Colloidal Suspension (TiO₂@Silica)

Area of Science:

• Photonics
• Condensed Matter Physics
• Materials Science

Background:

• Anderson localization of light and random lasing are key research areas with potential applications.
• Disordered scattering media are crucial for studying these phenomena.

Purpose of the Study:

• Investigate random laser action at the localization transition.
• Characterize the behavior of light in a colloidal suspension of core-shell nanoparticles.

Main Methods:

• Utilized a colloidal suspension of TiO2@Silica core-shell nanoparticles in Rhodamine 6G ethanol solution.
• Measured random laser emission by collecting light from both the back and front of the samples.
• Employed the fraction of absorbed pumping method to analyze light confinement.

Main Results:

• Observed classical superfluorescence with linear dependence on pumping fluence (back collection).
• Detected absorption and emission saturation under frontal collection.
• Identified narrow, equally intense peaks on the superfluorescence band, indicating suppressed mode interactions.
• Determined that these localized modes are confined to a shallow region near the pumping border.

Conclusions:

• The study demonstrates distinct behaviors of random lasing in disordered media at the localization transition.
• Localized modes exhibit unique characteristics, including reduced linewidth and surface confinement.
• Findings contribute to understanding light-matter interactions in strongly disordered systems and potential applications in photonics.