查看更多>>摘要：? 2021 Elsevier B.V.With a SiC plane mirror, we demonstrated the double-pass amplification of gain saturated 46.9 nm laser pumped by capillary discharge. In comparison with the single-pass amplified 46.9 nm laser, the amplitude of the double-pass laser pulse increased about 2.4 times, and the FHWM of the double-pass laser pulse broadened about 0.9 ns. In addition, the single-pass and the double-pass amplified laser spots have similar spatial distributions and peak-to-peak divergences. The double-pass 46.9 nm laser has good practicability because the SiC mirror is hardly damaged by the plasma.
查看更多>>摘要：? 2021 Elsevier B.V.With the rapid advances in terahertz technologies, the research on sensing applications implemented by terahertz metasurface has attracted significant attention. In this work, we experimentally demonstrated a silicon-based metasurface, which offers the capability for pesticide residue sensing. The spectral characteristics of the resonance peak at about 0.89 THz exhibit a good linear correlation with both benomyl and tricyclazole solutions concentrations. The correlation coefficient reaches 0.995 and 0.972, and the sensitivity is 0.0017 ppm ?1 and 0.0015 ppm ?1, respectively. In addition, the effects of analytes on spectra were analyzed by numerical simulation. These results provided a promising sensing platform for biochemical sensing application and feasible strategy to achieving rapid primary screening and quantitative analysis of the analyte.
查看更多>>摘要：? 2021 Elsevier B.V.In this study, the nonlinear optical response of the MoTe2 quantum dots (QDs) dispersion was measured by the method of spatial self-phase modulation (SSPM). Using this method, the nonlinear refractive index (n2) of the MoTe2 QDs dispersion is calculated to be 3.6569 × 10?5 cm2W?1 and 1.0288 × 10?5 cm2W?1 at λ=457nm and 532 nm, respectively. Moreover, the relative change of nonlinear refractive index (Δn2/n2) of the MoTe2 QDs caused by distortion was discussed. The results show that the value of Δn2/n2 can be regulated from 0.2 to 0.8 by changing the incident intensity at λ=457nm, and the adjustable range of 0.1–0.7 for Δn2/n2 at λ=532nm. Taking advantage of the strong nonlinear effect, we further experimentally design an all-optical switching based on MoTe2 QDs dispersion that to manipulate a signal light (λ=532nm) by a controlling light (λ=457nm) with the method of spatial cross-phase modulation (SXPM). This investigation unambiguously demonstrates that MoTe2 QDs has potential application in optoelectronic devices, especially in all-optical switching.
查看更多>>摘要：? 2021 Elsevier B.V.We propose two designs of plasmonic enhancement using metamaterial nanograting (MNG) for color filters. MNGs are composed of metal–insulator–metal and metal–air–metal layers denoted as MNG-1 and MNG-2, respectively. MNGs exhibit polarization-dependent, high color purity, and wide color gamut characteristics. According to the surface plasmon (SP) theory, MNG-1 shows all colors filtering in the whole visible spectrum by changing the thickness of metal and insulator layers. While MNG-2 exhibits tunable color filtering characteristic by dynamically changing the distance between two metal layers. MNG-2 also exhibits tunable dual-resonance when exposed on the ambient with different refraction index. These high color purity and wide color gamut characteristics open the avenue of ultrahigh resolution imaging, visual anti-counterfeiting, and environmental sensing applications.
查看更多>>摘要：? 2021 Elsevier B.V.Simultaneous monitoring of pressure and temperature in the skull cavity, kidneys, and cardiovascular organs and sites is urgently needed during clinical consultation and minimum invasive procedures. In this paper, the pressure/temperature fiber Fabry–Perot composite sensor fabricated by the micro electro mechanical system (MEMS) technology was studied. A variable step size fast Fourier transform-Minimum Mean Square-Error (FFT-MMSE) cavity length demodulation algorithm was proposed. This improved the demodulation accuracy and the rate of the cavity length signal. The experimental results showed that the optical fiber Fabry–Perot composite sensor had good response characteristics for pressure and temperature. It could maintain good linearity in the pressure measurement range of 0～14 kPa and the temperature measurement range of 35～50 °C. The pressure sensitivity was 9.811 nm/kPa, the temperature sensitivity was 1.707 nm/°C, and the temperature cross-sensitivity was 27.6 Pa/°C. The sensor has the characteristics of small size, fast response speed, high sensitivity, and strong stability. So it has great application potential in the field of biological medicine.
查看更多>>摘要：? 2021 Elsevier B.V.Based on the radiation pattern of a spatial uniform magnetic current line source (UMLS) antenna, we propose a method for creating a spatial optical tube with a variable length and arbitrary orientation for a 4π focusing system. A virtual spatial UMLS antenna situated at the foci of two high numerical aperture objectives is used to obtain the required illumination at the entrance pupil plane. Numerical results demonstrate that the length of the created optical tube is approximately equal to that of the UMLS antenna. Its orientation is consistent with that of the line source. Its polarization is pure azimuthal, and the transverse size of the optical tube shell and the dark tunnel is uniform over the entire depth of focus. This optical tube can be customized according to application requirements. The generated optical tube can be used for such applications as arbitrary orientation particle trapping and guiding, micromanipulation, and optical microscopy.
查看更多>>摘要：? 2021 Elsevier B.V.Perspective projection model is the common measurement method for laser sensor to calculate the 3D coordinates of spatial points. However, the error of mathematical model is introduced, which inevitably decrease the measurement accuracy of laser sensor. In order to improve the accuracy, an optimization measurement method is proposed in this paper. Firstly, the structural design and measurement principle of laser sensor is developed. Secondly, the error propagation model is established, and the effect of the structural parameters in perspective projection model is probed in detail. Next, an optimization measurement method is presented by adjusting the structural parameters, which is the projection angle of laser beam in measurement coordinate system. Finally, the effectiveness of the proposed optimization method is evaluated by the simulative and practical experiments. The experiment results show that the maximum error can be reduced to 0.589 mm with optimization from 1.090 mm of previous method. Enough theoretical research is offered for optimization design of measurement model of the laser sensor.
查看更多>>摘要：? 2021 The Author(s)A bridge architecture enabling seamless wireless interconnection within an optical fiber link is studied. Optical baseband data is remodulated by local oscillators using two stages to allow efficient and cost-effective upconversion. Proof-of-concept experiments show the feasibility of the approach. Direct operation with standard optical signals and ease of integration in the conventional optical fiber infrastructure define the transparency property of this subsystem, which represents a potential solution to restore data traffic in scenarios where fiber deployment is uneconomical or a disaster has taken place.
查看更多>>摘要：? 2021 Elsevier B.V.A novel transparent Pr3+, Ce3+ co-doped terbium gallium garnet (Pr,Ce:Tb3Ga5O12, Pr,Ce:TGG) single crystal was grown by the Czochralski technique. Its transmittance is about 80% in 600～1300 nm wavelength range except for special absorption peaks. The Verdet constants (V) of Pr,Ce:TGG crystal at 532 nm and 632.8 nm are ?230 and ?153 rad T?1 m?1, which are both larger than those of terbium gallium garnet (Tb3Ga5O12, TGG) crystal. The thermal conductivity of Pr,Ce:TGG crystal is 3.35 W m?1 K?1 at 300 K. Bulk laser induced damage threshold (LIDT) of Pr,Ce:TGG crystal was measured to be 15 J cm?2 by R-on-1 test. The results show that Pr,Ce:TGG crystal as magneto-optical material has potential ability to be used in optical isolators.
查看更多>>摘要：? 2021 Elsevier B.V.We show that de-focused single particle micrographs recorded using a cryo-electron microscope (cryoEM) system may be processed like a Fresnel zone in-line hologram to obtain physically meaningful quantitative phase maps associated with individual particles. In particular, a region-of-interest (ROI) of the de-focused micrograph surrounding a particle can be numerically back-propagated, in order to determine accurate de-focus information for single particles based on the sparsity-of-gradient merit function. Further with the knowledge of de-focus information, an iterative Fresnel zone phase retrieval algorithm using image sparsity constraints can accurately estimate the quantitative phase information associated with a single particle. The proposed methodology which can correct for both de-focus and spherical aberrations is a deviation from the image processing chain currently used in single particle cryoEM reconstructions. Our illustrations as presented here suggest that the phase retrieval approach applies uniformly to de-focused image data recorded using the traditional CCD detectors as well as the newer direct electron detectors.
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