Giant nonlinear optical responses from photon-avalanching nanoparticles.

Area of Science:

• Nonlinear optics
• Nanotechnology
• Biophotonics

Background:

• Avalanche phenomena, driven by nonlinear dynamics, amplify small perturbations into large responses.
• Photon avalanching is crucial for technologies like optical imaging and upconverted lasing.
• Previous observations were limited to bulk materials, restricting practical applications.

Purpose of the Study:

• To realize photon avalanching in single nanostructures at room temperature.
• To demonstrate the application of these nanostructures in super-resolution imaging.
• To explore their potential in biological imaging within transparent near-infrared windows.

Main Methods:

• Fabrication of thulium-doped (Tm3+) upconverting nanocrystals.
• Characterization of photon avalanching phenomena, including excitation-power thresholds and excited-state absorption.
• Implementation of photon-avalanche single-beam super-resolution imaging using scanning confocal microscopy.

Main Results:

• Achieved room-temperature photon avalanching in single nanocrystals (avalanching nanoparticles, ANPs).
• Observed nonlinear emission scaling with the 26th power of pump intensity above threshold.
• Demonstrated sub-70-nanometre resolution imaging with ANPs, requiring lower excitation intensities.

Conclusions:

• Single nanostructure photon avalanching is feasible and offers significant advantages.
• ANPs enable efficient super-resolution imaging with high resolution and low light levels.
• Their properties suggest broad utility in sub-wavelength imaging and sensing applications.