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Confocal nonlinear optical imaging on hexagonal boron nitride nanosheets

Lee, G and Jyothsna, KM and Park, J and Lee, JD and Raghunathan, V and Kim, H (2023) Confocal nonlinear optical imaging on hexagonal boron nitride nanosheets. In: PhotoniX, 4 (1).

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Official URL: https://doi.org/10.1186/s43074-023-00103-6


Optical microscopy with optimal axial resolution is critical for precise visualization of two-dimensional flat-top structures. Here, we present sub-diffraction-limited ultrafast imaging of hexagonal boron nitride (hBN) nanosheets using a confocal focus-engineered coherent anti-Stokes Raman scattering (cFE-CARS) microscopic system. By incorporating a pinhole with a diameter of approximately 30 μm, we effectively minimized the intensity of side lobes induced by circular partial pi-phase shift in the wavefront (diameter, d0) of the probe beam, as well as nonresonant background CARS intensities. Using axial-resolution-improved cFE-CARS (acFE-CARS), the achieved axial resolution is 350 nm, exhibiting a 4.3-folded increase in the signal-to-noise ratio compared to the previous case with 0.58 d0 phase mask. This improvement can be accomplished by using a phase mask of 0.24 d0. Additionally, we employed nondegenerate phase matching with three temporally separable incident beams, which facilitated cross-sectional visualization of highly-sample-specific and vibration-sensitive signals in a pump-probe fashion with subpicosecond time resolution. Our observations reveal time-dependent CARS dephasing in hBN nanosheets, induced by Raman-free induction decay (0.66 ps) in the 1373 cm�1 mode. © 2023, Chinese Society for Optical Engineering.

Item Type: Journal Article
Publication: PhotoniX
Publisher: Springer
Additional Information: The copyright for this article belongs to the Authors.
Keywords: Coherent scattering; Diffraction; III-V semiconductors; Nanosheets; Near field scanning optical microscopy; Nitrides; Nonlinear optics; Optical data storage; Probes; Raman scattering; Raman spectroscopy; Signal to noise ratio; Visualization, 2d material; Boron nitride nanosheets; Coherent anti-stokes Raman spectroscopy; Diffraction limited; Hexagonal boron nitride nanosheet; Nonlinear optical microscopy; Phonon dynamics; Sub-diffraction; Sub-diffraction-limited nonlinear optical microscopy; Ultrafast phonon dynamic; Ultrafast phonons, Phase matching
Department/Centre: Division of Electrical Sciences > Electrical Communication Engineering
Date Deposited: 08 Nov 2023 06:06
Last Modified: 08 Nov 2023 06:06
URI: https://eprints.iisc.ac.in/id/eprint/83014

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