Comparison of two absorption imaging methods to detect cold atoms in magnetic trap

Two methods of absorption imaging to detect cold atoms in a magnetic trap are implemented for a high-precision cold atom interferometer.In the first method,a probe laser which is in resonance with a cycle transition frequency is used to evaluate the quantity and distribution of the atom sample.In the second method,the probe laser is tuned to an open transition frequency,which stimulates a few and constant number of photons per atom.This method has a shorter interaction time and results in absorption images which are not affected by the magnetic field and the light field.We make a comparison of performance between these two imaging methods in the sense of parameters such as pulse duration,light intensity,and magnetic field strength.The experimental results show that the second method is more reliable when detecting the quantity and density profiles of the atoms.These results fit well to the theoretical analysis.

Near-Infrared Absorption Imaging and Processing Technologies Based on Gold Nanorods

Noble metal nanoparticles with localized surface plasmon resonance （LSPR） properties are widely used as optical sensors in biochemical detection and medical diagnosis. In this paper, we propose an effective determination method to measure the LSPR absorption intensity of gold nanorods （GNRs）. A near-infrared （NIR） imaging system is established, and an NIR absorption image of the multiple samples of the colloidal GNRs is captured. Then, the LSPR absorption intensities of these samples are obtained by calculating the average grayscale of the target areas based on the NIR image processing technology. By using this method, the LSPR absorption intensities of the multiple samples are determined all at once, and their accuracy is as high as that obtained by using spectrophotometry. These results suggest that this method is an efficient multi-channel determination technique with high-throughput sensing applications.

Synthesis, Crystal Structure, Two-photon Absorption and Biological Imaging Application of a Water Soluble Carbazole Quaternary Ammonium Compound

A novel carbazole quaternary ammonium compound（abbreviated as T_2） had been synthesized and characterized by ~1H NMR, ^（13）C NMR and Mass spectrometry. The single-crystal structure has been determined by X-ray single-crystal diffraction. The electrochemical and two-photon absorption properties of T_2 were systematically studied by cyclic voltammetry and Z-scan determination methods, respectively. The results suggested that T_2 had a good oxidation-reduction and excellent nonlinear optical property. The two-photon absorption（TPA） value has a maximum corresponding to cross section σ = 7963.3 GM（Goeppert-Mayer units） at 700 nm, indicating potential applications in nonlinear optical materials. Furthermore, attributing to the excellent water solubility and low cytotoxicity, the compound was explored on its primary application in biological imaging.

Fringe removal algorithms for atomic absorption images:A survey

The fringe noises disrupt the precise measurement of the atom distribution in the process of the absorption images.The fringe removal algorithms have been proposed to reconstruct the ideal reference images of the absorption images to remove the fringe noises.However,the focus of these fringe removal algorithms is the association of the fringe removal performance with the physical systems,leaving the gap to analyze the workflows of different fringe removal algorithms.This survey reviews the fringe removal algorithms and classifies them into two categories:the imagedecomposition based methods and the deep-learning based methods.Then this survey draws the workflow details of two classical fringe removal algorithms,and conducts experiments on the abs DL ultracold image dataset.Experiments show that the singular value decomposition(SVD)method achieves outstanding performance,and the U-net method succeeds in implying the image inpainting idea.The main contribution of this survey is the interpretation of the fringe removal algorithms,which may help readers have a better understanding of the research status.

Direct loading of atoms from a macroscopic quadrupole magnetic trap into a microchip trap

We demonstrate the direct loading of cold atoms into a microchip 2-mm Z-trap, where the evaporative cooling can be performed efficiently, from a macroscopic quadrupole magnetic trap with a high loading efficiency. The macroscopic quadrupole magnetic trap potential is designed to be moveable by controlling the currents of the two pairs of anti-Helrnholtz coils. The cold atoms are initially prepared in a standard six-beam magneto-optical trap and loaded into the macroscopic quadrupole magnetic trap, and then transported to the atom chip surface by moving the macroscopic trap potential. By means of a three-dimensional absorption imaging system, we are able to optimize the position alignment of the atom cloud in the macroscopic trap and the microchip Z-shaped wire. Consequently, with a proper magnetic transfer scheme, we load the cold atoms into the microchip Z-trap directly and efficiently. The loading efficiency is measured to be about 50%. This approach can be used to generate appropriate ultracold atoms sources, for example, for a magnetically guided atom interferometer based on atom chip.

X-ray diffraction enhanced imaging study of intraocular tumors in human beings

Diffraction enhanced imaging （DEI） with edge enhancement is suitable for the observation of weakly absorbing objects. The potential ability of the DEI was explored for displaying the microanatomy and pathology of human eyeball in this work. The images of surgical specimens from malignant intraocular tumor of hospitalized patients were taken using the hard X-rays from the topography station of Beamline 4W1A at Beijing Synchrotron Radiation Facility （BSRF）. The obtained radiographic images were analyzed in correlation with those of pathology. The results show that the anatomic and pathologic details of intraocular tumors in human beings can be observed clearly by DEI for the first time, with good visualization of the microscopic details of eyeball ring such as sclera, choroids and other details of intraocular organelles. And the best resolution of DEI images reaches up to the magnitude of several tens of μm. The results suggest that it is capable of exhibiting clearly the details of intraocular tumor using DEI method.