查看更多>>摘要：? 2021Dynamically structural color has great attraction and practicability in display. By introducing a phase change material Sb2S3 (SS23), which exhibits significantly different optical properties in different crystalline states, we have theoretically studied the active gamut regulation using symmetric optical microcavities. When SS23 is embedded in the oxide layer of the traditional symmetric optical microcavity, the high order resonance is suppressed, resulting in a wide color gamut. Moreover, switching SS23 from the amorphous state to the crystalline state also produces resonant damping, resulting in a high purity transmission color, further increasing the gamut to 128% of sRGB. The influence of incident angle and machining error on the color gamut when SS23 is crystal state is also investigated in CIE 1931 chromaticity diagram. Our work provides a way to achieve dynamic gamut modulation using optical microcavity.
查看更多>>摘要：? 2021 Elsevier B.V.In this study, we present an alternative method to measure the optical phase of transparent objects using two coupled interferometers. The first system comprises a polarized Mach–Zehnder interferometer (PMZI) that generates an interference pattern with crossed circular polarization. The second component is a compact rectangular Sagnac system (CRSS), which functions as a replicator and generates two interferograms. Because the trajectories of the two replicas are cyclical and collinear in the CRSS, no aberrations are produced; moreover, a controllable lateral displacement is achieved to separate the two replicas. By placing a mask with two linear polarizers at the output of the coupled system, a controllable phase shift is produced on each replicated interferogram. The results achieved with static transparent objects and a time-varying test are shown, demonstrating the feasibility of our proposed method.
查看更多>>摘要：? 2021We have proposed a scheme to control the soliton molecule (SM) dynamics in a mode-locked laser. The SMs in the mode-locked laser can be controlled by the complex second-order group-velocity dispersion β?k. The real and imaginary parts of β?k determines the balance of the dispersion and nonlinearity and the balance of dispersive losses and gain, respectively. The experimental observations show that the imaginary part of β?k makes it possible to tailor the temporal separation of the SMs. The proposed scheme can help us create multiple SMs with the scheduled values of temporal separation.
查看更多>>摘要：? 2021 Elsevier B.V.A cesium/oxygen activation experiment was conducted on a gallium-arsenide-based electron-injection cathode in an ultra-high vacuum system connected to a spectral response measuring instrument. Before activation, high-temperature cleaning was performed at 650 °C to obtain an atomically clean surface. The cathode surface impurities before and after the experiment were characterized by X-ray photoelectron spectroscopy. Because of the cathode Ti/Pt/Au electrode properties, the sample could not be cleaned chemically. High-temperature cathode treatment before activation could not remove the oxides completely, which led to a low cathode emission capacity in the photocurrent and spectral response. The experimental quantum efficiency curve was fitted by a two-minima diffusion model, and parameters, such as the electron diffusion length and escape probability, which characterize the cathode performance, were calculated. According to the fitting results, the residual impurities on the cathode surface and the thin emitter layer resulted in a low probability of electron escape, which resulted in a low quantum efficiency.
查看更多>>摘要：? 2021Network virtualization can enhance the flexibility of Internet infrastructure resources and the scalability of the substrate elastic optical networks (EONs) through the coexistence of multiple virtual optical networks supporting different services. Traditional virtual optical network embedding mostly assumed fixed embedding, that is, once a virtual optical network (VON) is embedded, the network resources allocated to it are almost unchanged during its lifetime. However, the actual traffic demand on a VON usually changes over time. To address the problems of high bandwidth blocking probability and low spectrum utilization caused by the mismatch between the resources allocated and the required resources during the virtual optical network embedding of the time-varying traffic in the elastic optical networks (EONs), we propose a virtual optical network embedding algorithm of the time-varying traffic (TVT-VONE). Firstly, in the node embedding stage, a node weight value measurement is designed based on the attributes of virtual nodes and physical nodes. Secondly, in the virtual optical link embedding stage, a measurement formula for path spectrum resource richness is designed to decrease link embedding failure due to insufficient spectrum resources on the path. Finally, in order to adapt to the characteristics of dynamic changes in bandwidth requirements of time-varying traffic, we design a resource-aware virtual network reconfiguration strategy when the spectrum resources of traffic required do not match the resources allocated to the changed traffic. Simulation results show that the proposed algorithm can effectively reduce the bandwidth blocking probability of VON requests and improve spectrum utilization of EONs.
查看更多>>摘要：? 2021 Elsevier B.V.An intriguing method of propelling stainless steel (SS, metallic) microsphere by employing the nanosecond laser pulses output from the end face of the fiber was demonstrated, in order to investigate the interaction of nanosecond laser pulses with metal microsphere. Using a two-dimensional model of the shock wave acting on the metal microsphere, the propagation characteristics of shock wave such as propagation distance and pressure have been calculated. Experimentally, we observed that the propulsion efficiency is dependent on the laser pulse energy and the gap distance. The momentum coupling coefficient and the energy coupling efficiency of SS microsphere were analyzed, which showed that metal microsphere has the high propulsion efficiency. In addition, an experiment was performed to remove the SS contamination particles on the surface of the microstructure. Compared with conventional technology, this new method has advantages of high controllability, directional and non-contact, and can be used for the removal of metal pollution particles and the manipulation of metal micromachines.
查看更多>>摘要：? 2021 Elsevier B.V.In view of the complexity of the traditional calibration methods for the line structured light measurement system, this paper proposes a direct system calibration method and corresponds to a direct calibration model. This method adopts a planar target to create the feature lines and uses the moving distance of linear guide as constraints, which can determine the mathematical relationship between the pixel and world coordinates directly. Compared with traditional calibration models, the proposed model does not need to consider the spatial structure of this system and calibrate each component separately, which simplifies the calibration process and reduces accumulative errors. Furthermore, the target used in this approach can be an ordinary plane, which avoids the difficulty of manufacturing special targets. Experimental results show that the root mean square error (RMSE) is 0.0238 mm and the mean absolute error (MAE) is 0.0255 mm, which can be used for industrial measurement more effectively.
查看更多>>摘要：? 2021We disclose a simple procedure for phase binary coding, any input picture, under noncoherent illumination. The procedure employs two suitably snapshots of the same input picture. At the first snapshot, the input is noncoherently illuminated with a binary pattern. At the second snapshot, the same input picture is also noncoherently illuminated, but now with the complementary pattern. Then, the two recorded snapshots are digitally subtracted. Next, as an extension of our proposal, we unveil the design of a circularly symmetric, noncoherent bandpass filtering.
查看更多>>摘要：? 2021 Elsevier B.V.Erbium-doped optical waveguide amplifier (EDWA) is an important building block for conventional and integrated optical communication and light signal processing systems. In recent years remarkable advancement has been achieved for EDWA to meet the demand for silicon photonic chips and integrated photonic circuits. However, in the currently demonstrated EDWAs all the laser pumping sources are external or off-chip, which not only limits the application field of EDWA, complicates the amplification scheme, but also does not fulfill the expectation of monolithic integration. In this work we propose a design of EDWA using high-gain Er-doped Al2O3 waveguide, low-loss silicon-on-insulator (SOI) waveguide, and on-chip integrated semiconductor laser pumping source. The 1550 nm signal light and 1480 nm pump light are transmitted and combined in SOI waveguide and coupled into the EDWA waveguide embedded in the adjacent layer. The 1480 nm pump light is coupled into the SOI waveguide from a bonded hybrid III–V semiconductor laser. The pump and signal waveguide building scheme, the coupling method and structure, and the integration process of laser pumping source are shown and simulated. The system performance was evaluated by using the device's structure parameters and Er3+ rate equation model. More than 1 dB/cm net gain and up to 35 dB maximum net gain can be achieved at about 100 mW pump power. It indicates that such an on-chip integration design is feasible and fully on-chip integrated optical waveguide amplifier could be achieved.
查看更多>>摘要：? 2021 Elsevier B.V.We demonstrated an all-fiber Er-doped Mamyshev oscillator with short pulse-duration and low mode-locking threshold based on an external seed. In experiments, the proposed laser generated stable pulses with 5.45 MHz repetition rate and 47.4 nm bandwidth at 10-dB. The pulse duration is 83 fs, which is the first time to our knowledge, that the sub-90 fs pulse output was observed directly from the Mamyshev oscillator output coupler (OC) without extra compression. Incorporating suitable setting of the cavity structure, the mode-locking operation could be achieved easily along with the two pumps beyond mode-locking threshold of 33.9 mW and 28.8 mW, respectively. To our knowledge, this is by far the shortest pulse duration and lowest mode-locking threshold Er-doped Mamyshev oscillator. The experimental results suggest that the proposed laser shows potential applications in laser communication and biosensing fields.
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