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.
"Thus, the effective manipulation of EM wave polarization is highly desirable, which has become an important research topic for long time. Conventionally, optical gratings and dichroic crystals can be used to manipulate polarization, which require a system much thicker than wavelength and is also inconvenient for low-frequency applications .  Over the past decade, metamaterials (MMs) concept have been proposed and investigated widely due to exotic properties, and have opened a new way to manipulate polarizations. "
[Show abstract][Hide abstract] 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 · 0.73 Impact Factor
"First wire grid polarizers for the IR spectral region were demonstrated by Bird and Parrish  in 1960. Subsequent work in the past years showed polarizers for the terahertz , IR , visible , and UV  spectral ranges. Decreasing the operation wavelength requires smaller grating periods. "
[Show abstract][Hide abstract] ABSTRACT: ABSTRACT: In this work, an effective multistep process toward fabrication of an iridium wire grid polarizer for UV applications involving a frequency doubling process based on ultrafast electron beam lithography and atomic layer deposition is presented. The choice of iridium as grating material is based on its good optical properties and a superior oxidation resistance. Furthermore, atomic layer deposition of iridium allows a precise adjustment of the structural parameters of the grating much better than other deposition techniques like sputtering for example. At the target wavelength of 250 nm, a transmission of about 45% and an extinction ratio of 87 are achieved.
Nanoscale Research Letters 10/2011; 6(1):558. DOI:10.1186/1556-276X-6-558 · 2.78 Impact Factor
[Show abstract][Hide abstract] 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.
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