Terahertz transmission characteristics of double wire-grid polarizer on low-loss polyethylene substrate

We fabricated a double metallic wire-grid polarizer consisting of micrometer-pitch Cu grating on both sides of low-loss polyethylene substrate by simple electroplating and lithography micro-processing techniques. The performance of transmission was measured using a terahertz (THz) time domain spectroscopy system. The mixed polarization effects of surface plasmon polaritons in an azimuthally rotated grating were investigated. The polarization dependence of both amplitude and phase shift on frequency was demonstrated in the wide range of 0.1?C3 THz, and the extinction ratio is over 22 dB.     

Common-path double-pass optical interferometry using a wire-grid polarizer as a reference mirror

A novel common-path double-pass optical interferometer that employs a wire-grid polarizer (WGP) as a reference mirror is presented. When a laser beam polarized at 45° relative to the wire grid is incident on the WGP, the polarization component parallel to the grid direction (s-polarized beam) is reflected and is used as a reference beam. The perpendicular component (p-polarized beam) passes through the WGP coupled with a quarter-wave plate and serves as a probe beam, with its polarization transformed as p, right-circular, s, left-circular, and p, to irradiate the sample surface twice in order to double the phase change due to displacement of the sample. This beam is then retransmitted through the WGP, where it recombines and interferes with the reference beam. Preliminary experiments demonstrate that the WGP performs successfully as a reference mirror, and that the interferometer has a potential displacement sensitivity as low as 0.1 nm.     

Terahertz broadband polarizer using bilayer subwavelength metal wire-grid structure on polyimide film

A terahertz(THz) broadband polarizer using bilayer subwavelength metal wire-grid structure on both sides of polyimide film is simulated by the finite-difference time-domain method. We analyze the effect of film thickness, material loss, and lateral shift between two metallic gratings on the performance of the THz polarizer. Bilayer wire-grid polarizers are fabricated by a simple way of laser induced and non-electrolytic plating with copper. The THz time-domain spectroscopy measurements show that in 0.2–1.6 THz frequency range, the extinction ratio is better than 45 d B, the average extinction ratio reaches 53 d B, and the transmittance exceeds 67%, which shows great advantage over conventional single wire-grid THz polarizer.     

Efficient diffractive optical elements in chalcogenide glass layers fabricated by direct DUV laser writing

Direct laser writing with high power densities at a wavelength of 244 nm is applied to the patterning of surface relief diffractive optical elements (DOEs) with submicron features in thin chalcogenide layers of different compositions. The topology of created features in dependence on exposure conditions is investigated. Potential and limitations of this technique for the fabrication of efficient DOEs for applications from the visible to the near infrared spectral region are discussed on the basis of examples.     

Current-voltage characteristics of diodes based on a four-component chalcogenide glass

An experimental study was made of film diodes based on a chalcogenide glass with symmetric and asymmetric electrodes and with two lower symmetric electrodes. Film diodes with aluminum electrodes can be used as varistors. The electrodes affect the shape of the current-voltage characteristics. Diodes having two lower electrodes have a longer useful lifetime than do those having an upper electrode and a lower one. Generation in the negative-resistance region is described.Translated from Izvestiya VUZ. Fizika, No. 12, pp. 30–33, December, 1969.The author thanks P. T. Oreshkin for constant interest in this study.     

Heat action of pumping radiation on a chalcogenide glass microcylinder

The character of the intensity distribution inside a cylindrical microparticle of chalcogenide glass is established to be nonuniform and determined by the cylinder radius. Depending on the microcylinder radius, regions of maximal intensities of the internal field are located in the illuminated or shadow parts of the cylinder (or in both the parts simultaneously) near the surface of the cylindrical particle and can exceed the incident radiation intensity by a factor of 2–4 as R < 2 μm. Heating occurs first in the shadow part of the microcylinders, then in both parts simultaneously, and then only in the illuminated part of the cylinders near their surface. This depends on the microcylinder radii and is caused by the manifestation of optical properties of the microcylinder substance and by the action of the heat transfer mechanism.     

Surface-relief gratings with high spatial frequency fabricated using direct glass imprinting process

Surface-relief gratings with high spatial frequencies were first fabricated using a direct imprinting process with a glassy carbon mold at the softening temperature of phosphate glass. A grating with maximum height of 730 nm and 500 nm period was formed on the glass surface by the pressing at the softening temperature of glass under constant pressure of 0.4 kN/cm(2). Phase retardation of 0.1 lambda was observed between TE-polarized and TM-polarized light at 600 nm wavelength.     

Fabrication of a side-polished fiber polarizer with a biref ringent polymer overlay

The fabrication of an in-line fiber polarizer consisting of a side-polished fiber (SPF) with a birefringent polymer thin-film overlay, polyvinyl carbazole, is described. Typical devices had <0.5 -dB insertion loss and extinction ratios of ~36 dB. A weakly coupled waveguide model that accurately describes these SPF-thin-film overlay devices and guides in their fabrication is also presented.     

Fabrication of wire-grid polarizers and dependence of submillimeter-wave optical performance on pitch uniformity

We describe a device for fabricating high-precision free-standing grids of fine wire, suitable for use as polarizing elements for radiation at millimeter and submillimeter wavelengths. Computer control of the winding process makes changing grid parameters particularly convenient and flexible. We present measurements of the mechanical uniformity and of the optical performance of wire grid polarizers made with 25 m and 10 m diameter wire. The flexibility of computer control is exploited to introduce a known degree of randomness in the grid pitch (center-to-center wire spacing), allowing the dependence of polarizer quality on uniformity to be quantified. This information allows prediction of the fabrication tolerances required for polarizers to be used at very high frequencies.     

Fabrication of microfluidics structures on different glasses by simplified imprinting technique

Imprinting technique is an efficient method for fabricating microstructures for microfluidics and lab-on-chip applications. However such technique is not commonly used for glass based microstructures fabrication. In this study, microstructures were transferred completely and successfully from a nickel alloy stamp to different glasses such as sodalime glass, Pyrex glass, SGBN glass and magneto optical glasses, using imprinting technique. Furthermore, the traditional vacuum hot press for imprinting was replaced with the conventional electric furnace which increases the cost efficiency and simplicity greatly. Using specific mold in the conventional furnace, the mass production of microstructured glass chips can be realized.     

Fabrication and characterization of Ge20Sb15S65 chalcogenide glass for photonic crystal fibers

Chalcogenide glasses are known for their high transparency in the mid-infrared (IR) range, which includes two atmospheric windows that lie from 3 to 5 μm and 8 to 12 μm, respectively. Chalcogenide photonic crystal fibers have numerous potential applications in the field of IR, such as spectroscopy, microscopy, astronomy, biology, and sensing. In this paper, Ge₂₀Sb₁₅S₆₅ chalcogenide glass was fabricated and systematically studied. Chalcogenide glass has high transmission property (>70 %), good thermal stability, and good mechanical stability. The glass transition temperature T _g is 296 °C, and no exothermic peak was associated with crystallization up to 500 °C, which indicates its suitability for fiber drawing. As a result of its excellent mechanical properties, preforms with a variety of geometrical patterns were fabricated by using mechanical drilling. The near-field intensity distribution image of the drawn fiber shows a strong light propagation confinement.     

Demonstration of chalcogenide glass racetrack microresonators

We have demonstrated what we believe to be the first chalcogenide glass racetrack microresonator using a complementary metal-oxide semiconductor-compatible lift-off technique with thermally evaporated As(2)S(3) films. The device simultaneously features a small footprint of 0.012 mm x 0.012 mm, a cavity Q (quality factor) of 10,000, and an extinction ratio of 32 dB. These resonators exhibit a very high sensitivity to refractive index changes with a demonstrated detection capability of Dn(As(2)S(3)=(4.5 x 10(-6)+/-10%) refractive index unit. The resonators were applied to derive a photorefractive response of As(2)S(3) to lambda=550 nm light. The resonator devices are a versatile platform for both sensing and glass material property investigation.     

Thermo-mechanical dynamics of nanoimprinting anti-reflective structures onto small-core mid-IR chalcogenide fibers [Invited]

Thermal nanoimprinting is a fast and versatile method for transferring the anti-reflective properties of subwavelength nanostructures onto the surface of highly reflective substrates, such as chalcogenide glass optical fiber end faces. In this paper, the technique is explored experimentally on a range of different types of commercial and custom-drawn optical fibers to evaluate the influence of geometric design, core/cladding material, and thermo-mechanical properties. Up to32.4% increased transmission and 88.3% total transmission are demonstrated in the 2–4.3 μm band using a mid-infrared(IR) supercontinuum laser.     

剪切液晶散射偏光玻璃的研制与应用

介绍了聚合物分散液晶、剪切液晶、散射偏光片以及透明投影屏幕等概念。实验制备了剪切液晶散射偏光玻璃样品,样品由两张玻璃夹层聚合物分散液晶膜在紫外光固化过程中施加剪切应力制成。实验给出了样品偏光显微镜照片和透光率以及雾度随透光轴与入射偏振光偏振方向夹角的变化曲线。剪切液晶散射偏光玻璃外观半透明,存在透光轴。散射偏光玻璃与吸收偏光片组合具有调光窗功能,与单片液晶投影机或单片硅上液晶投影机配套还能用作背投影成像效果十分清晰的透明投影屏幕。     

Large core, multimode, chalcogenide glass fibre coupler by side-polishing

A novel method for obtaining a multimode optical coupler in chalcogenide glass fibre is described. The fibres used had a large $\text{ Ge }_{17}\text{ As }_{18}\text{ Se }_{65}$ Ge 17 As 18 Se 65 core comprising about 74 % of the total cross-sectional area with an optical cladding of $\text{ Ge }_{17}\text{ As }_{18}\text{ Se }_{62}\text{ S }_{3}$ Ge 17 As 18 Se 62 S 3 . A single arc-shaped U-groove was formed in each of two silicate glass blocks. A length of fibre was embedded into each groove and glued in place. The centre of each fibre length was subsequently side-polished. Finally two such embedded fibres were glued together in close contact to form the coupler, whilst monitoring the coupling ratio at the output.