Calibration method for monocular laser speckle projection system.

This paper proposes a novel calibration method for the monocular laser speckle projection system. By capturing images of a calibration board with speckles under different poses, projector's optical axis is fitted and utilized to calibrate the rotation between the camera and projector. The translation is solved in closed form subsequently and projector's virtual image is recovered via homography. After calibration, the system can be regarded and operated as a binocular stereo vision system with speckle pattern. The proposed method is efficient and convenient, without need of reference image or high-precision auxiliary equipment. Validated by experiments on Astra-s and Astra-pro, it presents significant improvement in depth-estimation compared to the traditional method.

Design and Experimental Study of a Large Beam Waist Streak Tube in an ICF Experiment.

In order to realize in situ multi-frame framing, this paper designed and developed a large-waist framing converter tube. The size ratio between the waist and the object was about 1.16:1. The subsequent test results showed that the static spatial resolution of the tube could reach 10 lp/mm (@ 72.5%) under the premise of this adjustment, and the transverse magnification could reach 2.9. Once the MCP (Micro Channel Plate) traveling wave gating unit is equipped at the output end, it is expected to promote the further development of in situ multi-frame framing technology.

Secondary Amplifier Sampling Component Design of an X-ray Framing Detector Based on a Streak Tube.

The development of inertial confinement fusion (ICF) experiments necessitates the diagnostic instrument to have multiple frames with a high spatial and temporal resolution for the two-dimensional detection of the hot spot at the implosion end of the ICF. The existing sampling two-dimensional imaging technology in the world has superior performance; however, its subsequent development requires a streak tube with large lateral magnification. In this work, an electron beam separation device was designed and developed for the first time. The device can be used without changing the structure of the streak tube. It can be combined directly with the corresponding device and matched with a special control circuit. Based on the original transverse magnification, 1.77 times the secondary amplification can be achieved, which is conducive to expanding the recording range of the technology. The experimental results showed that the static spatial resolution of the streak tube after the inclusion of the device can still reach 10 lp/mm.

Experimental measurement of the meridian Petzval image plane of a streak tube.

For an electron-optical imaging system with wide beam focusing, the calculation of the field curvature can be performed only theoretically and requires the specific analytical expressions of the axial potential distribution in the streak tube and its corresponding derivatives, making the calculation cumbersome. Even when the electron trajectory is tracked using the numerical calculation method, the calculated results cannot be verified experimentally. A method for measuring the field curvature of the streak tube based on the spherical fluorescent screen is proposed for the first time, to the best of our knowledge. This method can directly measure the field curvature from the experimental image without requiring information on the internal structure of the streak tube, which is extremely useful for the design of the subsequent image reconstruction algorithm.

Simulation of the temporal resolution uniformity of a dilation framing camera.

The temporal resolution uniformity of a time-dilation framing camera is studied, and the ideal photocathode (PC) pulse curve is determined, while the temporal magnification factor is kept constant. To obtain the ideal curve, a series of linear pulses with the same slope are superposed. The variance in the temporal resolution and the number of linear pulses required are compared, while the superposition results with different slopes are used as the PC voltage. As the slope of the linear pulses decreases, the variance decreases, which means that the uniformity of the temporal resolution is improved, but the number of linear pulses required increases. In this study, linear pulses with a slope of 1 V/ps are superposed. Nine linear pulses with a front edge time of 200 ps, amplitude of 200 V, and flat top time of 1 ns are superimposed to approximate the ideal PC pulse curve with a constant temporal magnification factor of 10; the trigger times of the pulses are 0, 0, 0, 185, 200, 350, 450, 605, and 790 ps. When the superposition result is applied as the PC voltage and the measured signal is synchronized to the PC pulse at 128 ps-1 ns, the temporal resolution error is within 5%.

Dilation x-ray framing camera and its temporal resolution uniformity.

An x-ray framing camera based on pulse-dilation technology is reported. This camera first dilates the electron signal generated from a pulsed photo-cathode (PC), and then detects the dilated electron pulse by using a gated microchannel plate (MCP). While the PC is only applied with a direct current (DC) voltage, the camera's temporal resolution without pulse-dilation is about 81 ps. It is the gated MCP's temporal resolution. While an excitation pulse is applied on the PC, the electron pulse's temporal width is dilated, and the resolution is improved to 14 ps. Furthermore, the camera's temporal resolution uniformity is measured and simulated. The results show a 3.5 × drop in temporal resolution along the pulse propagation direction, due to the 5 × decrease of the PC excitation pulse gradient.

A theoretical study of diffraction limit breaking via coherent control of the relative phase in coherent anti-Stokes Raman scattering microscopy.

We present a theoretical investigation of how coherent control of the relative phase in coherent anti-Stokes Raman scattering (CARS) microscopy can break the diffraction limit. In quantum theory, it is found that the relative phase of the pump and Stokes pulses can be used to periodically tune the intensity of the anti-Stokes signal. Thus, by controlling the relative phase around the center of the pump and Stokes pulses, the anti-Stokes signal can be tuned to zero in this region. In turn, the useful spot-generating anti-Stokes signal is substantially suppressed to a much smaller dimension, and scanning of the spots renders CARS images with sub-diffraction resolutions. Such super-resolutions can greatly enhance the advantage of using CARS microscopy in many potential applications.

Synchronous gating in dilation x-ray detector without 1:1 image ratio.

An x-ray detector using a pulse-dilation technology to achieve high temporal resolution is reported. The electron pulse generated from the photo-cathode (PC) is first dilated by a pulse-dilation device and then imaged onto the microchannel plate (MCP) by a magnetic lens imaging system. Finally, the dilated electron pulse is detected by a gated MCP. A resolution of 14 ps is achieved. In addition, the synchronous gating is studied in the dilation x-ray detector without a 1:1 image ratio. The results show that while the time of flight (TOF) of the electrons is identical, the MCP gating pulse can be timed relative to the PC excitation pulse to gate the dilated electron signal in a single area, and they are unsynchronized in the other area. To avoid the single area synchronization effect, the magnetic lens imaging system used in the detector should allow photoelectrons with a large energy spread to be imaged onto the MCP. This effect can also be reduced by using an MCP gating pulse with a width larger than 500 ps. Moreover, a 1:1 image ratio can avoid this effect. Furthermore, a decreasing electron TOF can eliminate the single area synchronization effect.

Kerr Nonlinearity in germanium selenide nanoflakes measured by Z-scan and spatial self-phase modulation techniques and its applications in all-optical information conversion.

Germanium selenide (GeSe) has attracted considerable research interest due to its unique photoelectric characteristics: high abundance occurrence, low toxicity, high stability, and environmentally sustainable. To the best of our knowledge, less literature is available on the nonlinear optical (NLO) properties of GeSe and on its significance of the electronic structure. In this work, the GeSe nanoflake ethanol suspensions have been studied by using liquid phase exfoliation method and then characterized by Raman, transmission electron microscopy (TEM), transmittance and atomic force microscopy (AFM). The NLO properties of GeSe suspensions with different concentration are investigated by Z-scan and spatial self-phase modulation (SSPM) methods with continuous wave laser, which are coherent with the parameter nonlinear refractive index n2 and the third order nonlinear polarizabilities χ(3). The nonlinear refractive index n2 of GeSe dispersions basically occur in the order of 10-9 cm2/W for Z-scan methods and 10-6 cm2/W for SSPM technique, whereas the third-order nonlinear polarizabilities χ(3) total are within the range of 10-6 esu for SSPM method. On the basis of these substantial characteristics of the NLO response and high stability of the 2D GeSe, we have experimentally studied the applications of the GeSe suspensions on all-optical information conversion technique.

Transparent conductive films based on quantum tunneling.

We theoretically propose an approach for designing transparent conductive films based on quantum tunneling effects. These films are constructed from insulator and metallic materials overlapped with one another. To approach the quantum tunneling regime and improve the conductivity, the thicknesses of the insulator layers should be 1 nanometer or less. The optical properties (transmittance, reflectance and admittance) are studied in detail. However, the quantum tunneling effect would have an impact on the imaginary part of the permittivity of the insulator material. Therefore, the influence of the incoming quantum tunneling effect on the transparency is also analyzed by a quantum-corrected model. Finally, we have also studied the conductivity of the films.

Femtosecond x-ray streak camera based on photoelectron filter technology for laser fusion.

A femtosecond x-ray streak camera based on photoelectron filter technology is reported in this paper. Photoelectrons are collimated through the slit and channel of the photoelectron filter, so that transit time spread and space charge effect of electrons are reduced. A planar-focusing high-voltage electron-optical system is designed to match the filter. The channel length of the filter is 300 µm, and the slit width is 20 µm. The streak tube using the photoelectron filter is 273 mm in length, and the extraction field value between the Au photocathode and the filter is 10 kV/mm. An experimental platform is set up to calibrate the streak camera, which is excited by a 266 nm, 130 fs UV laser. The experimental results show that temporal resolution is 357 fs and dynamic range is 182:1 of this developed camera.

Sensitivity Enhancement of a Surface Plasmon Resonance Sensor with Platinum Diselenide.

The extraordinary optoelectronic properties of platinum diselenide (PtSe2), whose structure is similar to graphene and phosphorene, has attracted great attention in new rapidly developed two-dimensional (2D) materials beyond the other 2D material family members. We have investigated the surface plasmon resonance (SPR) sensors through PtSe2 with the transfer matrix method. The simulation results show that the anticipated PtSe2 biochemical sensors have the ability to detect analytic. It is evident that only the sensitivities of Ag or Au film biochemical sensors were observed at 118°/RIU (refractive index unit) and 130°/RIU, whereas the sensitivities of the PtSe2-based biochemical sensors reached as high as 162°/RIU (Ag film) and 165°/RIU (Au film). The diverse biosensor sensitivities with PtSe2 suggest that this kind of 2D material can adapt SPR sensor properties.

Fano Resonance in Waveguide Coupled Surface Exciton Polaritons: Theory and Application in Biosensor.

Surface exciton polaritons (SEPs) are one of the three major elementary excitations: Phonons, plasmons and excitons. They propagate along the interface of the crystal and dielectric medium. Surface exciton polaritons hold a significant position in the aspect of novel sensor and optical devices. In this article, we have realized a sharp Fano resonance (FR) by coupling the planar waveguide mode (WGM) and SEP mode with Cytop (perfluoro (1-butenyl vinyl ether)) and J-aggregate cyanine dye. After analyzing the coupling mechanism and the localized field enhancement, we then applied our structure to the imaging biosensor. It was shown that the maximum imaging sensitivity of this sensor could be as high as 5858 RIU-1, which is more than three times as much as classical FR based on metal. A biosensor with ultra-high sensitivity, simple manufacturing technique and lower cost with J-aggregate cyanine dye provides us with the most appropriate substitute for the surface plasmon resonance sensors with the noble metals and paves the way for applications in new sensing technology and biological studies.

Extreme ultraviolet spectrometer for the Shenguang III laser facility.

An extreme ultraviolet spectrometer has been developed for high-energy density physics experiments at the Shenguang-III (SG-III) laser facility. Alternative use of two different varied-line-spacing gratings covers a wavelength range of 10-260 Å. A newly developed x-ray framing camera with single wide strip line is designed to record time-gated spectra with ~70 ps temporal resolution and 20 lp/mm spatial resolution. The width of the strip line is up to 20 mm, enhancing the capability of the spatial resolving measurements. All components of the x-ray framing camera are roomed in an aluminum air box. The whole spectrometer is mounted on a diagnostic instrument manipulator at the SG-III laser facility for the first time. A new alignment method for the spectrometer based on the superimposition of two laser focal spots is developed. The approaches of the alignment including offline and online two steps are described. A carbon spectrum and an aluminum spectrum have been successfully recorded by the spectrometer using 2400 l/mm and 1200 l/mm gratings, respectively. The experimental spectral lines show that the spectral resolution of the spectrometer is about 0.2 Å and 1 Å for the 2400 l/mm and 1200 l/mm gratings, respectively. A theoretical calculation was carried out to estimate the maximum resolving power of the spectrometer.

High Quality TaS2 Nanosheet SPR Biosensors Improved Sensitivity and the Experimental Demonstration for the Detection of Hg2.

TaS2 as transition metal dichalcogenide (TMD) two-dimensional (2D) material has sufficient unstructured bonds and large inter-layer spacing, which highly supports transporting and absorbing mercury ions. The structural characterizations and simulation data show that an SPR sensor with high sensitivity can be obtained with a TaS2 material-modified sensitive layer. In this paper, the role of TaS2 nanoparticles in an SPR sensor was explored by simulation and experiment, and the TaS2 layer in an SPR sensor was characterized by SEM, elemental mapping, XPS, and other methods. The application range of structured TaS2 nanoparticles is explored, these TaS2 based sensors were applied to detect Hg2+ ions at a detection limit approaching 1 pM, and an innovative idea for designing highly sensitive detection techniques is provided.

Review of Interface Passivation of Perovskite Layer.

Perovskite solar cells (PSCs) are the most promising substitute for silicon-based solar cells. However, their power conversion efficiency and stability must be improved. The recombination probability of the photogenerated carriers at each interface in a PSC is much greater than that of the bulk phase. The interface of a perovskite polycrystalline film is considered to be a defect-rich area, which is the main factor limiting the efficiency of a PSC. This review introduces and summarizes practical interface engineering techniques for improving the efficiency and stability of organic-inorganic lead halide PSCs. First, the effect of defects at the interface of the PSCs, the energy level alignment, and the chemical reactions on the efficiency of a PSC are summarized. Subsequently, the latest developments pertaining to a modification of the perovskite layers with different materials are discussed. Finally, the prospect of achieving an efficient PSC with long-term stability through the use of interface engineering is presented.

Atomic Force Microscope Study of Ag-Conduct Polymer Hybrid Films: Evidence for Light-Induced Charge Separation.

Scanning Kelvin probe microscopy (SKPM), electrostatic force microscopy (EFM) are used to study the microscopic processes of the photo-induced charge separation at the interface of Ag and conductive polymers, i.e., poly[2,6-(4,4-bis-(2-ethylhexyl)-4H-cyclopenta[2,1-b;3,4-b']dithiophene)-alt-4,7-(2,1,3-benzothiadiazole)] (PCPDTBT) and poly(3-hexylthiophene-2,5-diyl) (P3HT). They are also widely used in order to directly observe the charge distribution and dynamic changes at the interfaces in nanostructures, owing to their high sensitivity. Using SKPM, it is proved that the charge of the photo-induced polymer PCPDTBT is transferred to Ag nanoparticles (NPs). The surface charge of the Ag-induced NPs is quantified while using EFM, and it is determined that the charge is injected into the polymer P3HT from the Ag NPs. We expect that this technology will provide guidance to facilitate the separation and transfer of the interfacial charges in the composite material systems and it will be applicable to various photovoltaic material systems.

Nonlinear optical response, all optical switching, and all optical information conversion in NbSe2 nanosheets based on spatial self-phase modulation.

An efficient liquid phase exfoliation method has been developed for the preparation of high quality NbSe2 nanosheets. The pure nonlinear optical properties of these nanosheets have been investigated using three different wavelength continuous wave (CW) lasers. The spatial self-phase modulation (SSPM) effect can be observed clearly in solution dispersions of (NbSe2). The experimental data show that the diffraction is caused by the third-order optical nonlinearity of NbSe2. The third-order nonlinearity susceptibility χ(3) of NbSe2 is about 10-9 e.s.u. by analyzing the experimental results. The relaxation time in the dynamic relaxation is about 1.38 s, 1.58 s, and 1.15 s for 532 nm, 671 nm, and 457 nm, respectively. In addition, the realization of all-optical switching based on SSPM, particularly two-color intrachromatic coherence, indicates that the generation of electron coherence is a universal characteristic of layered quantum materials. All optical information conversion based on the SSPM is also confirmed experimentally. Our experimental results have simple potential application prospects for NbSe2 based on its nonlinear optical response.

Observation of electron beam moiré fringes in an image conversion tube.

An image conversion tube with a magnetic lens was designed to observe electron beam moiré fringes. Electron beam moiré fringes result from the interference between the photocathode and the anode meshes. The photocathode had a strip line structure with a spatial frequency of 10L/mm. The anode mesh had a fixed spatial frequency of 10L/mm, and could be rotated around the axis of the image tube. The changes to the fringe direction and the spacing as a function of the rotation angle between the photocathode and the anode mesh were examined. The experimental results agreed with the theoretical analysis. Moiré fringes with a modulation of ~20% were obtained using a 3keV electron beam.

Note: Non-gain microchannel plate gated framing camera.

An x-ray framing camera using a non-gain microchannel plate (MCP) is reported in this article. The advantage of the non-gain MCP is the less transit time spread. The non-gain MCP gated framing camera has four microstrip line cathodes with 6 mm in width. The time domain reflectometry curves of the four microstrip lines are measured, which show that the characteristic impedance of each microstrip line is about 17 Ω. While the photocathode is driven by the gating electrical pulse with width of 125 ps and amplitude of -1.48 kV with -400 V bias, the measured exposure time of this camera is about 72 ps.