Near-infrared multiphoton absorption and third harmonic generation with CsPbBr₃ quantum dots embedded in micro-particles of metal–organic frameworks

Abstract

Materials with multiple nonlinear-optical responses have been investigated widely in recent years. Here, we report a hybrid system with both giant multiphoton absorption (MPA) and efficient third harmonic generation (THG)...

Improving Three-Photon Fluorescence of Near-Infrared Quantum Dots for Deep Brain Imaging by Suppressing Biexciton Decay

“…Three-photon fluorescence microscopy (3PFM) has emerged as a powerful tool to capture high-resolution, three-dimensional images for biomedical research, based on simultaneously absorbing three photons of low energy and emitting a single photon of high energy. , Each photon absorbed in a three-photon (3P) process has a wavelength that is roughly three times longer than that in a single-photon excitation . Therefore, long-wavelength light within the second near-infrared region (NIR-II, 1000–1700 nm) could be chosen as the excitation source of 3PFM to provide greater penetration depth, which has suppressed photon scattering and longer attenuation length in living tissues. − The best excitation wavelengths for deep brain imaging have been identified at around 1300 and 1700 nm. , In addition, the intensity of the 3P fluorescence increases cubically with the excitation intensity due to the nonlinear effect. The 3P fluorescence is confined to the area around the focal point, which significantly increases the signal-to-background ratio (SBR) of imaging .…”