Terahertz wire-grid polarizers with micrometer-pitch Al gratings
ABSTRACT We fabricated a terahertz wire-grid polarizer consisting of a micrometer-pitch Al grating on a Si substrate by photolithography and wet etching. The ratio of TM and TE transmittances (extinction ratio) was over 35 dB at 0.5 THz. At the Brewster angle of the Si substrate, the polarization transmittance of a TM wave through the fabricated polarizer exceeded 95% and the extinction ratio was over 45 dB at approximately 1 THz. The fabricated polarizer has a higher extinction ratio than conventional free-standing terahertz wire-grid polarizers.
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ABSTRACT: In this paper, a chiral metamaterial (CMM) with triple-layer twisted split-ring resonators structure was proposed, which could exhibit a linear polarization conversion as well as asymmetric transmission only for forward and backward propagating linearly polarized waves in a broadband frequency range. The polariza- tion of broadband linearly polarized electromagnetic waves can be rotated in a speciﬁc direction by passing it through such a CMM slab with a thickness of about one-twelfth the operational center wavelength. Experiment and simulation calcula- tions are in good agreement, and the polarization conversion rate is above 90% in the frequency range of 5.5–11.1GHz. The physical mechanism of the broadband linear polarization conversion effect could be further illustrated by simulated electrical ﬁeld and surface current distributions.Journal of Electromagnetic Waves and Applications 08/2013; 27(14):1850. DOI:10.1080/09205071.2013.825891 · 1.40 Impact Factor
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ABSTRACT: We explain an istability occurring in continuously operating lasers due to moderate feedback from distant reflectors. This instability occurs despite the fact that the laser is stable with respect to small deviations from steady-state operation. It is the result of finite phase and carrier number changes caused by fluctuations in spontaneous emission. We predict several properties that agree with recent experimental observations: 1) the instability only occurs when the laser reaches a steady state that maximizes coherent feedback and laser light intensity; 2) the instability vanishes at strong feedback levels; and 3) at moderate feedback levels, the laser will be nearly stable at threshold, but unstable when operated well above threshold. The latter behavior results in a nonlinear "kinked" shape in the light versus current relation.IEEE Journal of Quantum Electronics 03/1986; 22(2-22):294 - 301. DOI:10.1109/JQE.1986.1072959 · 2.11 Impact Factor
- Journal- Ceramic Society Japan 01/2010; 118(1379):575-578. DOI:10.2109/jcersj2.118.575 · 0.85 Impact Factor