Ultrafast Infrared-to-Visible Photon Upconversion on Plasmon/TiO₂ Solid Films.

Area of Science:

• Materials Science
• Photonics
• Nanotechnology

Background:

• Optical upconversion converts low-energy photons to higher energies.
• Existing methods like triplet-triplet annihilation operate on slower timescales.
• Semiconductors possess trap states that can be leveraged for photonic processes.

Purpose of the Study:

• To develop a solid-state thin film for efficient infrared-to-visible photon upconversion.
• To investigate the role of plasmonic nanoparticles in enhancing upconversion efficiency.
• To explore a novel three-photon absorption mechanism for upconversion.

Main Methods:

• Fabrication of a thin film comprising plasmonic nanoparticles and TiO2.
• Excitation of the material at 800 nm to induce multiphoton absorption.
• Characterization of the upconversion emission and efficiency enhancement.

Main Results:

• The plasmonic/TiO2 interface demonstrated a 20-fold increase in emission efficiency.
• The upconversion process was confirmed to be purely photonic, driven by enhanced optical absorption.
• The process occurs in the ultrafast domain (<10 ps) utilizing TiO2 trap states.

Conclusions:

• Plasmonic nanoparticles significantly enhance light absorption in TiO2 for upconversion.
• The developed thin film offers a fast and efficient solid-state solution for infrared-to-visible photon upconversion.
• This approach provides an alternative to slower molecular-based upconversion mechanisms.