Multimodal laser-scanning nonlinear optical microscope with a rapid broadband Fourier-transform coherent Raman modality

Imaging and component analysis of pumpkin stem tissue with simultaneous SF-CARS and TPEF microscopy

A multimodal nonlinear optical imaging platform based on a single femtosecond oscillator is built for simultaneous TPEF and SF-CARS imaging. TPEF microscopy and SF-CARS microscopy is utilized for mapping the distribution of the lignin component and the polysaccharide component, respectively. Visualization of vessel structure is realized. And the relative distribution of lignin and polysaccharide of vessel structure is mapped. Two pumpkin stem tissue areas with different degrees of lignification are observed with simultaneous TPEF and SF-CARS imaging, and two types of cell walls are identified. The different distribution patterns of lignin and polysaccharide in these two types of cell walls, induced by different degrees of lignification, are analyzed in detail.

In Situ Kinetic Observations on Crystal Nucleation and Growth

Nucleation and growth are critical steps in crystallization, which plays an important role in determining crystal structure, size, morphology, and purity. Therefore, understanding the mechanisms of nucleation and growth is crucial to realize the controllable fabrication of crystalline products with desired and reproducible properties. Based on classical models, the initial crystal nucleus is formed by the spontaneous aggregation of ions, atoms, or molecules, and crystal growth is dependent on the monomer's diffusion and the surface reaction. Recently, numerous in situ investigations on crystallization dynamics have uncovered the existence of nonclassical mechanisms. This review provides a summary and highlights the in situ studies of crystal nucleation and growth, with a particular emphasis on the state-of-the-art research progress since the year 2016, and includes technological advances, atomic-scale observations, substrate- and temperature-dependent nucleation and growth, and the progress achieved in the various materials: metals, alloys, metallic compounds, colloids, and proteins. Finally, the forthcoming opportunities and challenges in this fascinating field are discussed.

Broadband complementary vibrational spectroscopy with cascaded intra-pulse difference frequency generation

One of the essential goals of molecular spectroscopy is to measure all fundamental molecular vibrations simultaneously. To this end, one needs to measure broadband infrared (IR) absorption and Raman scattering spectra, which provide complementary vibrational information. A recently demonstrated technique called complementary vibrational spectroscopy (CVS) enables simultaneous measurements of IR and Raman spectra with a single device based on a single laser source. However, the spectral coverage was limited to ∼1000cm^-1, which partially covers the spectral regions of the fundamental vibrations. In this work, we demonstrate a simple method to expand the spectral bandwidth of the CVS with a cascaded intra-pulse difference-frequency generation (IDFG). Using the system, we measure broadband CVS spectra of organic liquids spanning over 2000cm^-1, more than double the previous study.