Microsphere Photonic Superlens for a Highly Emissive Flexible Upconversion-Nanoparticle-Embedded Film

Abstract

Increasing upconversion luminescence (UCL) to overcome the intrinsically low conversion efficiency of upconversion nanoparticles (UCNPs) poses a fundamental challenge. Photonic nanostructures are the efficient approaches for UCL enhancement by tailoring the local electromagnetic fields. Unfortunately, such nanostructures are sensitive to environmental conditions, and the regulation strength is varied in flexible applications. Here, we report giant UCL enhancement from a flexible UCNP-embedded film coupled with a microsphere photonic superlens (MPS), by which the enhancement ratio of UCL is over 10 4 -fold under 808 nm excitation down to 0.72 mW. The enhancement pathways of MPS-enhanced UCL are attributed to Mie-resonant nanofocusing for high excitationphoton density, optical whispering-gallery modes (WGMs) for fast radiative decay, and the directional antenna effect for far-field emission confinement. The contribution of optical resonance in the MPS to suppressing the phonon-induced nonradiative transition and thermal quenching is experimentally validated. The UCL quantum yield is therefore improved by 3-fold to 4.20% under 120 mW/cm 2 near-infrared excitation, consistent with the enhancement ratio via the Purcell effect of WGMs. Furthermore, the MPS demonstrates the robust optical regulation capability toward flexible applications, opening up new opportunities for facilitating multiphoton upconversion in wearable optoelectrical devices for nanoimaging, biosensing, and energy conversion in the future.

Enhancement of Valley Polarization in Monolayer WSe2 Coupled with Microsphere‐Cavity‐Array

“…The circularly‐polarized photons carrying the valley information are emitted from the bottom ML‐TMDCs, in which the chiral photons are amplified by the lower MCA via Purcell effect of WGMs and confined within a narrow emission divergence owing to the directional antenna effect. [ 53 ] The upper MCA collected and focused the chiral light onto the top ML‐TMDCs to generate the certain valley excitons. Figure 6b demonstrates the process of ML‐TMDCs interlayer communication of valley information by circularly‐polarized photons.…”

Multifunctional Laser-Induced Bubble Microresonator for Upconversion Emission Enhancement

“…Such microspheres can support optical whispering gallery modes (WGMs), as these allow for total internal reflection and trapping of photons thereby amplifying the intensity of the emission from nanomaterials . Recently, Yan et al developed a highly refractive microsphere photonic superlens array integrated with a flexible UCNP-embedded film which enhanced the upconversion emissions by 10 4 -fold in an all-dielectric microstructure . This enhancement was attributed to optical WGMs, Mie-resonant nanofocusing, and a directional antenna effect.…”

“…22 Recently, Yan et al developed a highly refractive microsphere photonic superlens array integrated with a flexible UCNPembedded film which enhanced the upconversion emissions by 10 4 -fold in an all-dielectric microstructure. 23 ment was attributed to optical WGMs, Mie-resonant nanofocusing, and a directional antenna effect. These reports highlight the role of UCNPs in dry environments suitable for photonic applications.…”

Augmented Fluorescence Signaling on a Single BaTiO3 Microbead Optical Booster toward High-Sensitive Biosensing

“…Herein, we have developed a single BaTiO 3 microbead (BTM) optical booster that enables augmented fluorescence signaling toward highly sensitive determination of both protein and nucleic acid biomarkers. Different from the conventional single microbead-based methods in which the single microbead acts solely as the reaction carrier, this BTM optical booster exhibits appealing optical enhancing properties that can facilitate light focusing, confinement, and scattering on the microscale. − Specifically, after the target-molecule-actuated fluorescence deposition on the single BTM, the high refractive index of BaTiO 3 allows for the whispering gallery mode (WGM) by confining the reflection of incident light inside the BTM to continuously excite the target-induced fluorescence molecules enriched on its surface. Meanwhile, the BTM can also act as a microlens to increase the fluorescence collection efficiency.…”