arXiv subjects

Shupei Lin

Publications and source records attributed to Shupei Lin.

4 recordsLinked to original sources

arXiv2025

Photothermal Fourier-plane Phase Synchronization for Interferometric Scattering Microscopy

We introduce and experimentally implement Fourier-plane phase synchronization for optical microscopy, and demonstrate its performance with interferometric scattering microscopy. By combining a photothermal phase plate and laser beam scanning, we realize a synchronized phase for all scattering components on the Fourier plane of high numerical-aperture microscopes, where the evanescent waves and optical aberration normally produce highly inhomogeneous phase distributions. We achieve an almost perfect point spread function, exhibiting a tighter focus with 50\% enhancement of the signal and ideal circular symmetry. Particularly, by synchronizing the phase to $\pi/2$, we demonstrate the background speckles exhibit an anti-symmetric dependence on axial defocus, enabling the effective suppression of the speckles via defocus integration and thus the detection of 10 nm particles immobilized on the substrate. The concept and technique of seamless dynamic phase control on the Fourier plane constitute a key asset for modern optical microscopy.

physics.optics↗

arXiv2024

Defocus-integration Interferometric Scattering Microscopy for Speckle Suppression and Enhancing Nanoparticle Detection on Substrate

Direct optical detection and imaging of single nanoparticles on substrate in wide field underpin vast applications across different research fields. However, the speckles originating from the unavoidable random surface undulations of the substrate ultimately limit the size of the decipherable nanoparticles by the current optical techniques, including the ultrasensitive interferometric scattering microscopy (iSCAT). Here we report a defocus-integration iSCAT to suppress the speckle noise and to enhance the detection and imaging of single nanoparticles on ultra-flat glass substrate and silicon wafer. In particular, we discover distinct symmetry properties of the scattering phase between the nanoparticle and the surface undulations that cause the speckles. Consequently, we develop the defocus-integration technique to suppress the speckles.We experimentally achieve an enhancement of the signal to noise ratio by 6.9 dB for the nanoparticle detection. We demonstrate that the technique is generally applicable for nanoparticles of various materials and for both low and high refractive-index substrates.

physics.optics↗

arXiv2022

Optical Fingerprint of Flat Substrate Surface and Marker-free Lateral Displacement Detection with Angstrom-level Precision

We report that flat substrates such as glass coverslips with surface roughness well below 0.5 nm feature notable speckle patterns when observed with high-sensitivity interference microscopy. We uncover that these speckle patterns unambiguously originate from the subnanometer surface undulations, and develop an intuitive model to illustrate how subnanometer non-resonant dielectric features could generate pronounced interference contrast in the far field. We introduce the concept of optical fingerprint for the deterministic speckle pattern associated with a particular substrate surface area and intentionally enhance the speckle amplitudes for potential applications. We demonstrate such optical fingerprints can be leveraged for reproducible position identification and marker-free lateral displacement detection with an experimental precision of 0.22 nm. The reproducible position identification allows us to detect new nanoscopic features developed during laborious processes performed outside of the microscope. The demonstrated capability for ultrasensitive displacement detection may find applications in the semiconductor industry and super-resolution optical microscopy.

physics.optics↗

arXiv2020

Multiscale Modeling and Analysis for High-fidelity Interferometric Scattering Microscopy

Interferometric scattering microscopy (iSCAT), as an ultrasensitive fluorescence-free imaging modality, has recently gain enormous attention and been rapidly developing from demonstration of principle to quantitative sensing. Here we report on a theoretical and experimental study for iSCAT with samples having structural dimensions that differ by 4-5 orders of magnitude. In particular, we demonstrate and intuitively explain the profound effects of sub-nanometer surface roughness of a glass coverslip and of a mica surface on the absolute signal and the shape of the point spread function of a gold nanoparticle. These quantities significantly affect the accuracies for determining the target size and position in all three dimensions. Moreover, we investigate a sample system mimicking a gold nanoparticle in a simplified cell environment and show position-dependent and even asymmetric point spread function of the nanoparticle. The multiscale study will facilitate the development of high fidelity iSCAT in real applications.

physics.optics↗