90% Extraordinary optical transmission in the visible range through annular aperture metallic arrays

We demonstrate what we believe to be the first experimental extraordinary optical transmission (EOT) of up to 90%, thanks to a well-identified guided mode that propagates through annular apertures engraved into an optically thick silver layer. In spite of the metal losses, high transmission can be obtained by adjusting the geometrical parameters of the fabricated structure, as was already theoretically demonstrated. To our knowledge, this is the first study showing such a large transmission in the visible range.     

Tapping mode atomic force microscope combined with reflection scanning near-field optical microscope (AF/RSNOM)

A new kind of scanning probe microscope is introduced in this paper, which is a combination of atomic force microscope and reflection scanning near field optical microscopy (AF/RSNOM) with equi-amplitude tapping mode. The principle and recent experiment result of AF/RSNOM are reported. Besides convenient operation, the bi-functional probe tip of AF/RSNOM brings an even illumination for every sampling position. Experiment result and analysis show that the signal to noise ratio (SNR) of AF/RSNOM optical image is much better than that of other RSNOM without tapping working mode.     

Resolution enhancement in a light-sheet-based microscope (SPIM)

Light-sheet-based microscopy [single-plane illumination microscope (SPIM)] performs very well at low numerical apertures. It complements conventional (FM), confocal (CFM), and two-photon fluorescence microscopy (2hnu-FM) currently used in modern life sciences. Lateral and axial SPIM point spread function (PSF) extents are measured by using fluorescent beads to determine the 3D resolution. The results are compared with values derived from an analytical theory and numerical simulations. The discrepancies are found to be less than 5%. The axial extent of a SPIM-PSF (10x/0.3 W) is approximately 5.7 microm. This value is almost a factor of 2 smaller than in CFM, more than 2.5 times smaller than in FM, and more than three times smaller than in 2hnu-FM. SPIM outperforms 2hnu-FM and FM, while CFM has a better axial resolution at NAs above 0.8.     

Enhanced optical transmission through an array of compound unit with multiple concentric or eccentric annular apertures

In this paper, transmission properties through an array of compound unit with multiple concentric or eccentric annular apertures are numerically studied. It is demonstrated that the transmission of the compound structure is not a simple superposition of that of each annular aperture array but exhibit substantial changes in both the position and intensity of resonant peaks. It is also found that the gap plasmon resonance exhibit split peaks when the symmetry is broken, which can be well explained from the view of charge oscillation. These properties provide a method to achieve enhanced transmission in multi-frequencies simultaneously and are of significant applicable value to the design of tunable optical devices.     

Experimental demonstration of 10 Gbit/s transmission with an optical backplane system using optical slots

A practical optical backplane system was prepared with transmitter-receiver processing boards and an optical backplane made from polymeric-waveguide-embedded optical printed-circuit boards. Optical slots were used as connection components between the transmitter-receiver processing boards and the backplane board to permit easy and repeatable insertion and extraction of the boards with micrometer precision. We report 10 Gbit/s data transmission between an optical backplane and the transmitter-receiver processing boards.     

Electron transmission probability across CoSi2/n-Si(111) interfaces measured with a scanning tunneling microscope

In an in situ UHV study at 77 K, a scanning tunneling microscope was used in a new constant-height mode of ballistic-electron-emission microscopy to measure the electron transmission probability across epitaxial CoSi₂ films and across CoSi₂/n-Si(111) interfaces. The conventional ballistic-electron-emission microscopy, carried out in the constant-current mode, was found to give artifacts at high tip voltages (< −2 V with sample grounded), which could be eliminated in the constant-height mode with simultaneous scanning tunneling spectroscopy.     

Cs 5D_(5/2)-6F 728 nm Laser Spectroscopy with Single Pumping Laser

The sub-Doppler absorption laser spectroscopy at 728 nm transition from the 5D5/2 state to the 6 F state of cesium with linewidth near 10 MHz is first experimentally performed with indirect pumping from the ground state 6S_(1/2)to the state 7P_(3/2)by a 455.5 nm diode laser.Using a 455.5 nm diode laser as an indirect pump laser,several excited states will be populated due to spontaneous decay from the 7P state.We first implement the sub-Doppler absorption laser spectroscopy at 728 nm from the 5D_(5/2)state to the 6F state when Cs atoms within thermal glass cell decay to the 5D_(5/2) state.Due to velocity transfer effect,the hyperfine structure of 5D_(5/2)shows a mixed and complicated pattern but very clear structure when the 455.5 nm pumping laser is counter-propagating(or co-propagating)with the 728 nm probing laser.     

Nanoscale resolution in the focal plane of an optical microscope

Utilizing single fluorescent molecules as probes, we prove the ability of a far-field microscope to attain spatial resolution down to 16 nm in the focal plane, corresponding to about 1/50 of the employed wavelength. The optical bandwidth expansion by nearly an order of magnitude is realized by a saturated depletion through stimulated emission of the molecular fluorescent state. We demonstrate that en route to the molecular scale, the resolving power increases with the square root of the saturation level, which constitutes a new law regarding the resolution of an emerging class of far-field light microscopes that are not limited by diffraction.     

1 Gbit/s transmission over step-index plastic optical fiber using an optical receiver with an integrated equalizer

A single chip optical receiver with an integrated large-diameter photodiode, transimpedance amplifier, two stages active equalizer, post amplifier and 50 Ω driver is used for gigabit transmission over PMMA step plastic optical fiber (SI-POF). The large-diameter photodiode with an antireflection coating optimized for red light. The integrated equalizer enables the presented optical receiver to reach 1 Gbit/s over 50 m SI-POF at bit error ratio of 10^− 6. An error free (< 10^− 9) 1 Gbit/s data rate over 40 m standard PMMA step-index plastic optical fiber is also achieved.     

Experimental study of annular bright field (ABF) imaging using aberration-corrected scanning transmission electron microscopy (STEM)

Experimental parameters used in the annular bright field (ABF) imaging method were tested using images simulated with the multislice method. Images simulated under identical conditions were found to agree well with experimental images. The ABF technique was shown to be relatively insensitive to the sample thickness and the defocus. In experimental ABF images, atomic columns exhibited dark contrast over a wide range of specimen thickness and defocus values, from 10 to 70 nm and ?20 to +20 nm, respectively. A series of diffraction patterns at atomic columns, obtained using the diffraction imaging method, exhibited higher intensities in their central regions (0–11 mrad) for light elements and in their peripheral regions (11–22 mrad) for heavy elements. The results indicated that the contrast of light elements is enhanced by subtraction of the central region of the transmitted beam, since this is blocked by a circular mask in the ABF-STEM technique. Thus, the overall contrast of light elements is greatly improved, allowing them to be clearly visualized.     

Measuring 0.1-nm motion in 1 ms in an optical microscope with differential back-focal-plane detection

Back-focal-plane detection of micrometer-sized beads offers subnanometer resolution for single-molecule, optical trapping experiments. However, laser beam-pointing instability and mechanical drift of the microscope limit the resolution of optical-trapping experiments. By combining two infrared lasers with improved differential beam-pointing stability (< or = 0.05 microrad), we simultaneously measure and subtract the motion of the microscope stage, leading to a resolution of <0.1 nm in 1 ms and stability of 0.5 nm over 60 s. Repeated steps of 0.4 nm at 1 Hz are resolved with a signal-to-noise ratio of 25.     

Propagation of Bessel-modulated Gaussian beams through a paraxial ABCD optical system with an annular aperture

Based on the generalized Collins diffraction integral and the expansion of the hard aperture function into a finite sum of complex Gaussian functions, the approximate analytical expressions of Bessel-Gaussian beams and QBG beams passing through a paraxial ABCD optical system with an annual aperture are derived. As special cases, the corresponding closed-forms for the unaperture or circular aperture or circular black screen cases are also given. The results provide more convenience for studying their propagation and transformation than the usual way by using diffraction integral formula directly. Numerical examples are given to illustrate the propagation properties of Bessel-Gaussian and QBG beams.     

Propagation characteristics of linearly polarized Bessel-Gaussian beams through an annular apertured paraxial ABCD optical system

By means of Collins diffraction integral formula in the paraxial approximation and based on the fact that a hard aperture function can be expanded into a finite sum of complex Gaussian functions, an approximate analytical expression for linearly polarized Bessel-Gaussian beams passing through a paraxial ABCD optical system with an annular aperture has been derived. The results provide more convenient for studying their propagation and transformation than the usual way by using diffraction integral directly. By using the analytical expression and the diffraction integral formula some numerical simulations are done to illustrate for the propagation characteristics of a linearly polarized Bessel-Gaussian beam through an optical system with an annular aperture.     

Investigating carbonization and graphitization using electron energy loss spectroscopy (EELS) in the transmission electron microscope (TEM)

Electron energy loss spectroscopy (EELS) in the transmission electron microscope (TEM) is explored as a useful characterization technique in the study of carbonization and graphitization of organic precursors. A model series of carbon materials was prepared from highly graphitizable petroleum pitch heat treated in the range 200–2730°C. Initial characterization was performed using the established techniques of X-ray diffraction (XRD), He pycnometry, TEM, electron diffraction and high-resolution lattice imaging (HREM). EELS in the TEM was then examined. Two routes are presented to quantify the change in the proportion of sp ² type hybridization accompanying the heat treatment as the material transforms to the graphitic state. Both routes suggest an initial relative sp ² content of ～70%, rapidly increasing to ～90% during mesophase development and carbonization, and then slowly increasing to 100% during graphitization. The peak position of the bulk valence plasmon (π?+?σ) is shown to be an excellent measure of the degree of graphitic character, and its fundamental dependence upon sample density (ρ) is confirmed. The appearance and definition of features within the core loss region representing the density of unoccupied σ* states are demonstrated to be an excellent measure of the extent of order. Finally, a method is established by which to extract the C–C bond length from core loss EELS spectra with an accuracy of ±0.1?pm. This method suggests an average bond length of 1.44?Å in samples with low heat treatment temperatures, decreasing to the theoretical length of 1.42?Å as both the heteroatom content and proportion of non-sp ²-type hybridized carbon atoms decrease.     

光学偶极阱中铷原子5S_(1/2)及5P_(3/2)态的AC Stark频移

基于二能级模型和多能级模型,分析计算了由强聚焦高斯光束形成的光学偶极阱中87Rb原子5S1/2态和5P3/2态的AC Stark频移。基于多能级模型,针对在852 nm高斯激光束强聚焦所形成的87Rb原子远失谐光学偶极阱中进行偏振梯度冷却的情形,计算了冷却循环跃迁(5S1/2F=2-5P3/2F′=3)的频移量,结果显示频移对molasses冷却过程产生了重要的影响。同时,计算了5S1/2|F=2,mF=±2〉态和5P3/2|F′=3,mF=±3〉态的AC Stark频移随光学偶极阱激光波长的变化情况,发现在红失谐情况下,对于87Rb原子5S1/2-5P3/2态跃迁不存在魔数波长。