In-line broadband 270 degrees (3 lambda/4) chevron four-reflection wave retarders

The net differential phase shift Δt introduced between the orthogonal p and s linear polarizations after four successive total internal reflections inside an in-line chevron dual-Fresnel-rhomb retarder is a function of the first internal angle of incidence φ and prism refractive index n. Retardance of 3λ/4 (i.e., Δt=270°) is achieved with minimum angular sensitivity when φ=45° and n=1.900822. Several optical glasses with this refractive index are identified. For Schott glass SF66 the deviation of Δt from 270° is ≤4° over a wavelength range of 0.55≤λ≤1.1 μm in the visible and near-IR spectrum. For a SiC prism, whose totally reflecting surfaces are coated with an optically thick MgF2 film, Δt=270° at two wavelengths: λ1=0.707 μm and λ2=4.129 μm. This coated prism has a maximum retardance error of ≈5°over\u3ethree octaves (0.5 to 4.5μm) in the visible, near-, and mid-IR spectral range. Another mid-IR 3λ/4 retarder uses a Si prism, which is coated by an optically thick silicon oxynitride film of the proper composition, to achieve retardance that differs from 270° by \u3c0.5° over the 3-5 μm spectral range

Photopolarimeter based on planar grating diffraction

A division-of-amplitude photopolarimeter (DOAP) is described that employs a diffraction grating in the conventional spectrometer orientation with the grating grooves normal to the plane of incidence. Four coplanar diffracted orders are used for polarimetric analysis to determine all four Stokes parameters of incident light simultaneously and virtually instantaneously (with the speed being determined solely by the photodetectors and their associated electronics); a fifth order is used for alignment by autocollimation or by use of a position-sensing quadrant detector. To sensitize the instrument for the +45° and -45° azimuths of incident linearly polarized light and for the handedness of incident circular polarization (i.e., for the third and fourth Stokes parameters), we insert two linear polarizers in two diffracted orders with their transmission axes inclined at appropriate angles with respect to the plane of incidence. The calibration and testing of an instrument of this type that uses an Al-coated 600-groove/mm holographic grating at 632.8-nm wavelength are reported as an example

Broadband IR polarizing beam splitter using a subwavelength-structured one-dimensional photonic-crystal layer embedded in a high-index prism

An iterative procedure for the design of a polarizing beam splitter (PBS) that uses a form-birefringent, subwavelength-structured, one-dimensional photonic-crystal layer (SWS 1-D PCL) embedded in a high-index cubical prism is presented. The PBS is based on index matching and total transmission for the p polarization and total internal reflection for the s polarization at the prism-PCL interface at 45 degrees angle of incidence. A high extinction ratio in reflection (\u3e50 dB) over the 4-12 mu m IR spectral range is achieved using a SWS 1-D PCL of ZnTe embedded in a ZnS cube within an external field of view of +/- 6.6 degrees and in the presence of grating filling factor errors of up to +/- 10%. Comparable results, but with wider field of view, are also obtained with a Ge PCL embedded in a Si prism

Bearing Capacity of Defective Reinforced Concrete Pile in Sand-model Study

Concrete piles that were poorly constructed or analyzed in their soil analyses may have structural or geotechnical defects. To examine such defects, an experimental study was conducted to investigate how a defective reinforced concrete pile behaved. These piles were installed and subjected to a compression axial load in the sand that had relative densities of 30%,60%, and 80%. The tests were performed using four concrete model piles: one intact pile and the other three piles had a structural defect (necking) at three different positions of the pile at (0.25 L from the top, center, and 0.25 L bottom). Geotechnical defect (soft layer or debris) was studied using Styrofoam layer at various vertical distances under the pile toe with Y/D = (0, 0.5, 1 and 1.5) D. The test results showed that the bearing capacity of the structural defect was the most in the case of a neck at 0.25 L from the bottom, followed by a neck at the center, and finally a neck at 0.25 L from the top. In the case of a geotechnical defect, the bearing capacity of the pile decreased with the decrease of the vertical distance between the soft layer and the pile toe

Single-layer-coated surfaces with linearized reflectance versus angle of incidence: application to passive and active silicon rotation sensors

A transparent or absorbing substrate can be coated with a transparent thin film to produce a linear reflectanceversus- angle-of-incidence response over a certain range of angles. Linearization at and near normal incidence is a special case that leads to a maximally flat response for p-polarized, s-polarized, or unpolarized light. For midrange and high-range linearization with moderate and high slopes, respectively, the best results are obtained when the incident light is s polarized. Application to a Si substrate that is coated with a SiO2 film leads to novel passive and active reflection rotation sensors. Experimental results and an error analysis of this rotation sensor are presented

Single-layer-coated surfaces with linearized reflectance versus angle of incidence: application to passive and active silicon rotation sensors

A transparent or absorbing substrate can be coated with a transparent thin film to produce a linear reflectanceversus- angle-of-incidence response over a certain range of angles. Linearization at and near normal incidence is a special case that leads to a maximally flat response for p-polarized, s-polarized, or unpolarized light. For midrange and high-range linearization with moderate and high slopes, respectively, the best results are obtained when the incident light is s polarized. Application to a Si substrate that is coated with a SiO2 film leads to novel passive and active reflection rotation sensors. Experimental results and an error analysis of this rotation sensor are presented

Line tension and structure of smectic liquid crystal multilayers at the air-water interface

At the air/water interface, 4,-8-alkyl[1,1,-biphenyl]-4-carbonitrile (8CB) domains with different thicknesses coexist in the same Langmuir film, as multiple bilayers on a monolayer. The edge dislocation at the domain boundary leads to line tension, which determines the domain shape and dynamics. By observing the domain relaxation process starting from small distortions, we find that the line tension is linearly dependent on the thickness difference between the coexisting phases in the film. Comparisons with theoretical treatments in the literature suggest that the edge dislocation at the boundary locates near the center of the film, which means that the 8CB multilayers are almost symmetric with respect to the air/water interface.Comment: 21 pages, 6 figure