real-time-label-free-imaging-quantitative-analysis-macrophage

Real-Time Label-Free Imaging and Quantitative Analysis of Macrophage Morphodynamics Using Optical Diffraction Tomography

This study establishes a label-free optical diffraction tomography (ODT)-based workflow for live-cell imaging and analysis to observe time-dependent ...

Peking University

Broadband light trapping and field localization is highly desired in enhanced light-matter interaction, especially in harmonic generations. However, due to the limited resonant bandwidth, most periodic plasmonic nanostructures cannot cover both fundamental excitation wavelength and harmonic generation wavelength simultaneously. Therefore, most previously reported plasmonic nonlinear optical processes are low in conversion efficiency. Here, we report a strong enhancement of second harmonic generation based on a three-layered super absorbing metasurface structure consisting of a dielectric spacer layer sandwiched by an array of random metallic nanoantennas and a metal ground plate. Intriguingly, the strong light trapping band (e.g. >80%) was realized throughout the entire visible to near-infrared spectral regime (i.e., from 435 nm to 1100 nm), enabling plasmonically enhanced surface harmonic generation and frequency mixing across a broad range of excitation wavelengths, which cannot be achieved with narrow band periodic plasmonic structures. By introducing hybrid random antenna arrays with small metallic nanoparticles and ultra-thin nonlinear optical films (e.g. TiO) into the nanogaps, the nonlinear optical process can be further enhanced. This broadband light-trapping metastructure shows its potential as a building block for emerging nonlinear optical meta-atoms.

Ultra-broadband enhancement of nonlinear optical processes from randomly patterned super absorbing metasurfaces.

Ultrahigh-resolution optical strain sensors provide powerful tools in various scientific and engineering fields, ranging from long-baseline interferometers to civil and aerospace industries. Here we demonstrate an ultrahigh-resolution fibre strain sensing method by directly detecting the time-of-flight (TOF) change of the optical pulse train generated from a free-running passively mode-locked laser (MLL) frequency comb. We achieved a local strain resolution of 18 pε/Hz and 1.9 pε/Hz at 1 Hz and 3 kHz, respectively, with large dynamic range of >154 dB at 3 kHz. For remote-point sensing at 1-km distance, 80 pε/Hz (at 1 Hz) and 2.2 pε/Hz (at 3 kHz) resolution is demonstrated. While attaining both ultrahigh resolution and large dynamic range, the demonstrated method can be readily extended for multiple-point sensing as well by taking advantage of the broad optical comb spectra. These advantages may allow various applications of this sensor in geophysical science, structural health monitoring, and underwater science.

Ultrasensitive, high-dynamic-range and broadband strain sensing by time-of-flight detection with femtosecond-laser frequency combs.

Birefringence-involved phase matching is demonstrated to be a novel mechanism to generate transform limited solitary pulses in an ultrafast mode-locking fiber laser cavity with normal dispersion.

New soliton dynamics revealed in the normal dispersion region.

The noninvasive two-photon excitation autofluorescence imaging of cellular and subcellular structure and dynamics in live tissue could provide critical  information for biomedical studies. However, the two-photon microscopy of short-wavelength endogenous fluorophores, such as tryptophan and hemoglobin, is extremely limited due to the lack of suitable imaging techniques. In this study, we developed a short-wavelength excitation time- and spectrum-resolved two-photon microscopy system. A 520-nm femtosecond fiber laser was used as the excitation source, and a time-correlated single-photon counting module connected with a spectrograph was used to provide time- and spectrum-resolved detection capability. The system was specially designed for measuring ultraviolet and violet-blue fluorescence signals and thus was very suitable for imaging short-wavelength endogenous fluorophores. Using the system, we systematically compared the fluorescence spectra and fluorescence lifetimes of short-wavelength endogenous fluorophores, including the fluorescent molecules tyrosine, tryptophan, serotonin (5-HT), niacin (vitamin B3), pyridoxine (vitamin B6), and NADH and the protein group (keratin, elastin, and hemoglobin). Then, high-resolution three-dimensional (3D) label-free imaging of different biological tissues, including rat esophageal tissue, rat oral cheek tissue, and mouse ear skin, was performed  or . Finally, we conducted time-lapse imaging of leukocyte migration in the lipopolysaccharide injection immunization model and a mechanical trauma immunization model. The results indicate that the system can specifically characterize short-wavelength endogenous fluorophores and provide noninvasive label-free 3D visualization of fine structures and dynamics in biological systems. The microscopy system developed here can empower more flexible imaging of endogenous fluorophores and provide a novel method for the 3D monitoring of biological events in their native environment.

Short-wavelength excitation two-photon intravital microscopy of endogenous fluorophores.

Because of the lack of spatiotemporal characterization techniques, it has been of great challenge to investigate the crystallization of nanocrystals. With a high-speed structured illumination super-resolution fluorescence microscopy (SIM), we hereby report an in situ fluorescence imaging technique to monitor the crystallization of perovskite nanocrystals at single-particle level. By correlating the fluorescence intensity with particle size, we illustrate the coupled nucleation-and-growth of perovskite nanocrystals in polymer matrix. The temporal fluorescence intensity analysis of individual nanocrystals reveals the diffusion-controlled growth process with a fast growth at the beginning followed by a slow growth. The analysis of ensemble nanocrystals illustrates the evolution of nucleation rate with the change of precursor concentrations. We further analyze the Gibbs free energy fluctuation of couple nucleation-and-growth. The growth free energy dominates in the continuous nucleation of perovskite nanocrystals, which accounts for the narrow size distribution. In comparison with LaMer model, the coupled nucleation-and-growth provides an alternative model to fabricate narrow sized nanocrystals.

Article	Year
Ultra-broadband enhancement of nonlinear optical processes from randomly patterned super absorbing metasurfaces. Scientific reports\| PubMed ID: 28659592	2017
Ultrasensitive, high-dynamic-range and broadband strain sensing by time-of-flight detection with femtosecond-laser frequency combs. Scientific reports\| PubMed ID: 29042647	2017
New soliton dynamics revealed in the normal dispersion region. Light, science & applications\| PubMed ID: 35322807	2022
Short-wavelength excitation two-photon intravital microscopy of endogenous fluorophores. Biomedical optics express\| PubMed ID: 37497479	2023
Single particle fluorescence imaging of perovskite nanocrystal crystallization for illustrating coupled nucleation-and-growth. Nature communications\| PubMed ID: 40593586	2025

Ke-bin Shi

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