Tunable Broadband Terahertz Metamaterial Absorber Based on Vanadium Dioxide and Graphene.

We propose a dynamically tunable ultra-broadband terahertz metamaterial absorber, which was based on graphene and vanadium oxide (VO2) and numerically demonstrated. The excellent absorption bandwidth almost entirely greater than 90% was as wide as 6.35 THz from 2.30 to 8.65 THz under normal incidence. By changing the conductivity of VO2 from 20 S/m to 3 × 105 S/m, the absorption intensity could be dynamically tuned from 6% to 99%. The physical mechanism of the ultra-wideband absorption is discussed based on the interference cancelation, impedance matching theory, and field distributions, and the influences of the structural parameters on absorption are also discussed. According to the symmetric configuration, the absorption spectra of the considered polarizations were very close to each other, resulting in a polarization-insensitive structure. Such a tunable ultra-broadband absorber may have promising potential in the applications of modulating, cloaking, switching, and imaging technology.

Orientation-dependent fiber-optic inclinometer based on core-offset michelson interferometer.

An in-fiber Michelson interferometer (MI)-based inclinometer, which consists of misalignment-spliced fiber with end coating, is proposed and experimentally demonstrated. The incident light divided at the misalignment-spliced joint is reflected at the end coating, and then re-coupled into the fiber core. Due to the phase difference between the core mode and the [Formula: see text] cladding mode, a typical MI is formed. The fiber near the misalignment-spliced joint is inserted in two capillary quartz tubes. The tilt of the capillary quartz tube leads to a significant deformation and curvature of the misalignment-spliced joint, which causes the wavelength and intensity of the MI spectrum to change. The experimental results indicate a good response within the angle range of 0°-50°. Both the wavelength modulation and intensity modulation are realized, with sensitivities of 0.55 nm/deg and 0.17 dB/deg, respectively. Moreover, the sensor shows a strong orientation dependence due to the asymmetric structure in the misalignment-spliced joint.