We proposed a multilayer infrared metamaterial absorber with metal-insulator-metal (MIM) stacks and patterned nanostructured surfaces for ultra-broadband infrared applications. Chromium (Cr) and silicon dioxide (SiO2) were designated as the main materials of the absorber considering assessing the real functionalities of several metals and insulator materials in the structure. Furthermore, the electromagnetic field distribution shows that the stacks of different MIMs above the structure excite absorption peaks in distinct wavelength ranges, and the absorption range can be enlarged by manipulating structural parameters. The average absorptivity is higher than 80% throughout a wide wavelength range of 780 nm to 5500 nm, according to results of numerical simulation. The absorption spectrum encompasses the entire near-infrared and mid-infrared range, and it has promising applications in spectral sensing, infrared light sources, and detectors.
In this paper, a surface plasmon waveguide structure consisting of annular gap and metal-insulator-metal waveguides is proposed, and its spectral characteristics are analyzed and studied. The results show that this waveguide structure has good performance in narrowband filtering in sub-wavelength band, and the central wavelength of the transmission peak is linearly related to the angle of the annular with notch. The results are of great significance for the application of filtering structures in highly integrated photonic circuits.
This paper illustrates the principle of several common distributed fiber sensing techniques, especially Brillouin optical time domain reflectometry (BOTDR) and optical time domain reflectometry (OTDR). By measuring the frequency shift of spontaneous Brillouin scattering light in fiber, BOTDR could simultaneously monitor both strain and temperature with a high spatial resolution. But the spontaneous Brillouin scattering signal is so weak that it has a high demand of the laser generator and the signal-to-noise ratio of the whole system. Therefore, the BOTDR system is usually too complex, expensive and difficult to be widely used. Unlike BOTDR, OTDR utilizes Rayleigh scattering to measure the loss of fiber. Rayleigh scattering signal is much stronger than spontaneous Brillouin scattering signal, thus OTDR system has the advantages of high sensitivity, long distance and relatively low price. These advantages make OTDR very suitable for wide application in the field of slope monitoring, especially in remote areas where the geographical environment is complex and are difficult for staff to stay.
This paper designed and implemented a slope monitoring and warning system based on the technology of optical time domain reflectometry(OTDR). The test result shows that the system has high sensitivity, strong real-time and provides user friendly interface.
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