Here we report graphene systems' nano-Raman hyperspectral imaging based on tip-enhanced Raman scattering (TERS). The vibrational and electronic structures are modulated within the graphene-related materials, leading to nano-scale changes in the behavior of electrons and phonons that can be used for spectral imaging. Furthermore, we utilize a He-focused ion beam to do nanolithography on graphene. We then show that the tiny features on graphene made by the He-focused ion beam can only be visualized under nanometer-scaled spectroscopy imaging. We have also imaged low-angle reconstructed twisted bilayer graphene, and our observations highlight the relevance of solitons and topological points for the structures' vibrational and electronic properties, relevant in the context of twistronics.
A visible fiber Bragg grating (Vis-FBG) with wavelength peak centered at 673.07 nm was inscribed in a multimode fiber designed for infrared (IR) operation using a femtosecond (fs) laser emitting at 248 nm. The fiber cladding is removed by chemical etching in hydrofluoric acid solution (40%). The sensor refractive index response is determined by dipping the sensor into diluted glycerin solution at different concentrations with refractive index range from 1.3328 to 1.4607. The Vis-FBG performance is compared with an IR etched FBG (EFBG) with similar diameter. The sensitivity found for the Vis-FBG sensor is 15.71nm/RIU with a 6.34 x 10-3 RIU resolution for a refractive index of 1.4607.
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