Dual‐band circular‐polarization filter for obliquely incident light

Abstract

Chiral sculptured thin films of zinc selenide with different helical periods were deposited on both sides of a glass slide using the serial bideposition technique in order to fabricate a dual‐band circular‐polarization filter polarizer that exhibits two distinct circular Bragg regimes for a wide range (about 45°) of the angle of incidence. This device can be angle tuned within a ±8% spectral range. © 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 58:2381–2384, 2016

Temperature‐mediated excitation of defect modes in a periodic structure at terahertz frequencies

“…The most common and simple multilayers are periodic structures made as a cascade of unit cells consisting of two layers with high ( n H ) and low ( n L ) refractive index. These structures are used in controlling the propagation of the electromagnetic field because these types of multilayers exhibit a photonic bandgap 17,18 . They are generally referred as 1D photonic crystal and have been extensively studied in the last two decades 19‐22 …”

“…These structures are used in controlling the propagation of the electromagnetic field because these types of multilayers exhibit a photonic bandgap. 17,18 They are generally referred as 1D photonic crystal and have been extensively studied in the last two decades. [19][20][21][22] If the periodicity is broken by inserting-after a certain number of cells-a "defect"layer of a material different than those that form the unit cell, a defect mode appears within the forbidden band.…”

Chiral sculptured thin films for circular polarization of mid-wavelength infrared light

“…arXiv:1806.00986v1 [physics.optics] 4 Jun 2018 the circular Bragg phenomenon is the formation of a light pipe that bleeds energy backward inside the SCM under appropriate conditions [6,7].The center wavelength λ Br 0 of the circular Bragg regime depends on P . Typically, λ Br 0 /P > 1 for normal incidence because all eigenvalues of the relative permittivity dyadics of CLCs and CSTFs exceed unity, and the ratio L/P has to be in the neighborhood of 10 or higher for adequately strong manifestation of the circular Bragg phenomenon [5,8].Both CLCs [9,10,11,12] and CSTFs [13,14,15,16] have been demonstrated to serve as circular-polarization filters in the visible and the near-infrared (NIR) regimes, because CLCs with P 700 nm [17,18,19] and CSTFs with P ≤ 800 nm [14,15,20] are commonplace. CLCs with periods as large as about 6000 nm have been reported [21], to our knowledge.…”

“…Therefore, with the aim of developing MWIR circular-polarization filters, we decided to fabricate CSTFs with P as high as 5880 nm. Zinc selenide (ZnSe) was chosen because its bulk refractive index varies quite slowly with λ 0 in the MWIR regime [26] and because it is easy to deposit CSTFs [20,28] of this material by oblique-angle thermal evaporation [29,30]. The ratio L/P was kept as large as practicable with our thermal evaporation system that was designed for CSTFs to function in the visible regime and is definitely suboptimal for industrial use to fabricate very thick CSTFs needed for the longer wavelengths in the MWIR regime.…”

“…Both CLCs [9,10,11,12] and CSTFs [13,14,15,16] have been demonstrated to serve as circular-polarization filters in the visible and the near-infrared (NIR) regimes, because CLCs with P 700 nm [17,18,19] and CSTFs with P ≤ 800 nm [14,15,20] are commonplace. CLCs with periods as large as about 6000 nm have been reported [21], to our knowledge.…”