分类: 光学 >> 量子光学 提交时间: 2023-02-19
摘要: Two-photon photopolymerization (TPP) has recently become a popular method for the fabrication of three-dimensional (3D) micro- and nanostructures. The reproduction fidelity of the designed micro- and nanostructures is influenced by experimental writing conditions, including laser power, exposure time, etc. To determine the appropriate writing parameters, characterization of morphological features and surface roughness during the experiment is needed. Traditional characterization methods for TPP, e.g., scanning electron microscopy and atomic force microscopy, have limited speed and cannot study internal structures without invasive approaches. Optical diffraction tomography (ODT) is an emerging label-free 3D imaging technique based on reconstructing the object's 3D refractive index (RI) distribution with diffraction-limited resolution. Here, we propose a non-invasive solution to fully characterize the TPP-fabricated structures using a high-speed ODT technique, which can eliminate the need for complex sample preparation, such as fluorescence labelling or metal-coating, and achieve a full 3D measurement time of 6 ms. By visualizing and studying different TPP-fabricated structures, including embedded spirals and cubes, via the ODT system, the fabrication quality, including 3D morphological features, exposure levels, and surface roughness, can be examined quantitatively. The results suggest our method can effectively improve the fabrication quality and reproducibility of TPP, generating impacts on the nanofabrication community.
分类: 光学 >> 量子光学 提交时间: 2023-02-19
摘要: The physical properties of two-dimensional (2D) materials may drastically vary with their thickness profiles. Current thickness profiling methods for 2D material (e.g., atomic force microscopy and ellipsometry) are limited in measurement throughput and accuracy. Here we present a novel high-speed and high-precision thickness profiling method, termed Transmission-Matrix Quantitative Phase Profilometry (TM-QPP). In TM-QPP, picometer-level optical pathlength sensitivity is enabled by extending the photon shot-noise limit of a high sensitivity common-path interferometric microscopy technique, while accurate thickness determination is realized by developing a transmission-matrix model that accounts for multiple refractions and reflections of light at sample interfaces. Using TM-QPP, the exact thickness profiles of monolayer and few-layered 2D materials (e.g., MoS2, MoSe2 and WSe2) are mapped over a wide field of view within seconds in a contact-free manner. Notably, TM-QPP is also capable of spatially resolving the number of layers of few-layered 2D materials.
分类: 光学 >> 量子光学 提交时间: 2023-02-19
摘要: Polarization light microscopes are powerful tools for probing molecular order and orientation in birefringent materials. While a multitude of polarization light microscopy techniques are often used to access steady-state properties of birefringent samples, quantitative measurements of the molecular orientation dynamics on the millisecond time scale have remained a challenge. We propose polarized shearing interference microscopy (PSIM), a single-shot quantitative polarization imaging method, for extracting the retardance and orientation angle of the laser beam transmitting through optically anisotropic specimens with complex structures. The measurement accuracy and imaging performances of PSIM are validated by imaging a rotating wave plate and a bovine tendon specimen. We demonstrate that PSIM can quantify the dynamics of a flowing lyotropic chromonic liquid crystal in a microfluidic channel at an imaging speed of 506 frames per second (only limited by the camera frame rate), with a field-of-view of up to $350\times350 \mu m^2$ and a diffraction-limit spatial resolution of $\sim 2\mu m$. We envision that PSIM will find a broad range of applications in quantitative material characterization under dynamical conditions.
分类: 光学 >> 量子光学 提交时间: 2023-02-19
摘要: Three-dimensional (3D) image cytometers may significantly improve the cell analysis accuracy to facilitate biological discoveries and clinical diagnosis, but their development is curbed by the low imaging throughput. Here we report SIngle-frame LAbel-free Cell Tomography (SILACT) with diffraction-limited resolution and unprecedented imaging speed of over 10,000 volumes/second. SILACT is built on a unique interferometric microscope with angle-multiplexing illumination and a pre-trained physics-incorporating Deep Neural Network for efficient 3D Refractive Index (RI) reconstruction, from which 3D morphological and biophysical parameters of cells are extracted. With microfluidics and a high-speed camera, SILACT is capable of imaging over 20,000 cells/second and distinguishing different cell species during rapid measurements of large cell quantities, as well as visualizing shear-induced 3D transient deformation of red blood cells on a sub-millisecond scale.