Enhancing Upconversion Performance via Thermoplasmonic Remote Heating and Its Application to All-Photonic Logic Gates

Solid-state triplet–triplet annihilation-based upconversion (TTA-UC) systems, where the sensitizer and emitter are dispersed in polymer host matrices, are advantageous in terms of ease of preparation and practical robustness. However, their performance is often hampered by low energy-transfer efficiency between TTA-UC components compared to solution-state TTA-UC systems. In this study, we present a technique for remotely manipulating TTA-UC performance by highly leveraging the photothermal conversion effect (thermoplasmonic effect) of plasmonic metal nanoparticles. This is achieved through the development of thin solid films for TTA-UC combined with anisotropic plasmonic gold nanoparticles. The upconversion (UC) emission was enhanced by up to 58 times by simultaneously irradiating with near-infrared light for the thermoplasmonic effect, in addition to conventional excitation light. The enhancement is attributed to a substantial increase in the energy-transfer efficiency between TTA-UC components induced by an increase in mobility in the polymer host matrix via the thermoplasmonic effect. This UC emission enhancement is, in principle, applicable to various TTA-UC systems and has been experimentally demonstrated to further enhance the UC emission through synergies with the near-field effects of plasmonic metal nanoparticles. These results support the excellent versatility of thermoplasmonic TTA-UC systems. Furthermore, we demonstrate that these distinctive UC emission properties can function as all-photonic logic gates, which are key components in next-generation optical computing systems. The system exhibited a substantial enhancement of UC emission, accompanied by a slight reduction in sensitizer phosphorescence by the two excitation light sources as inputs, resulting in simultaneous operations of multiple logic gates, consisting of "AND," "YES," and "INHIBIT."