Polarizers wire grid

The experiments described here were performed with a Digilab FTS40 Fourier transform instrument, with a liquid nitrogen-cooled Mercury Cadmium Telluride, (MCT), detector. The instrument is provided with a computer for data acquisition, storage and mathematical treatment. P-polarized incident light was obtained by means of an A1 wire-grid polarizer supported on a BaF2 substrate. 

Samples for infra-red absorption measurement were introduced between two rubbed nylon coated calcium fluoride substrates spaced 10 pm apart. To insure proper parallel alignment, samples were cooled at 0.02° C/minute from the isotropic to the Smectic C phase. The alignment was then checked using polarizing microscopy. Polarized IR spectra (32 scans per spectrum) were obtained using an FTIR spectrometer (IFS-66 Bruker, Pillerica, MA) equipped with a wire grid polarizer at a resolution of 2 cm"1. 

Infrared spectra were taken with a Michelson-Genzel type FTIR instrument (IR/98, IBM Instruments, Inc.) equipped with a liquid nitrogen cooled HgCdTe detector. The optical attachment arrangement is shown in Fig. 2-14. The infrared radiation was p-polarized using ERS-5 wire grid polarizer. 

Figure 9.3 Wire grid polarizer for infrared radiation.

As is shown in Figure 9.3, a wire grid polarizer will attenuate light polarized parallel to the conducting wires. This is a result of attenuation of the electric field oscillating... 

The IR apparatus and dichroism methods used in this work have been previously described (11,12). In the differential dichroism experiment, the samples were stretched from both ends simultaneously at a true strain rate of approximately 30% per min. A motorized stretching jig was used which fits inside the instrument in the path of the common beam at a 45° angle. Wire grid polarizers were set at 45° in the reference and sample beams, and the instantaneous dichroic difference A A — AM — Aj was recorded with the instrument operating in constant, wave-number mode. 

The infrared spectra were recorded on a Nicolet 7199 or a Nicolet 205 Fourier transform infrared spectrometer at a resolution of 2 cm l with a total number of scans of up to 128 for low-orientation samples. The infrared beam was polarized using a SPECAC gold wire-grid polarizer. Samples, rather than polarizer, were rotated 90° in order to obtain the two polarization measurements. The dichroic ratio was calculated from the measured absorbance at the maximum of the infrared band. 

The reflective circular polarizer consists of a free-standing wire-grid polarizer parallel to and in front of a flat mirror. Half of the radiation is immediately reflected by the grid, while the other half, polarized in the orthogonal direction, is reflected by the flat mirror and delayed by X/A according to the spacing between the wire-grid polarizer and the mirror. 

Because of technological advances in this area, much higher efficiency polarizers and detector systems are available today than had been in recent years. One example of this is the commercial availability of infrared wire grid polarizers (Perkin Elmer) which is of higher efficiency in transmission and polarization than the former Brewster plate silver chloride polarizers. 

Polarization-modulation infrared reflection-absorption spectroscopy (PM-IR-RAS) spectra were recorded with a Bruker ITS 66/S Fourier transform infrared spectrometer equipped with a PMA 37 polarization modulation module and a ititrogen-cooled MCT detector. The infrared beam was first p-polarized with a ZnSe wire grid polarizer (Specac) before passing through a photoelastic modulator (Hinds Instruments, PEM-90), which modulated at a frequency of 74 kHz. A lock-in ampHfier (Stanford model SR-830) was used to obtain the PM-IRRAS spectra. The half-wave retardation frequency was set at 4000 cm . The PM-IR-RAS spectra were recorded as S= R -Rs)/(R +Rg). A total of 250 scans at a resolution of 4 cm were collected for each measurement at an angle of incidence of 82.5° with respect to the normal to the sample surface. 

A stretching device described elsewhere [67] was made by us which extended the PU samples uniformly from both ends while it was centered in the IR beam. The samples were placed at an intermediate focus in the infrared source beam at an angle of 45° to the sUts. Wire grid polarizers were placed in the sample and reference beams at a setting of 45. The entire stretching device rotated around the centre of the IR polarized beam (and the sample) to allow absorption experiments while stretching the sample both parallel and transverse to the plane of the polarized... 

Figure 9.5 Schematic illustration of the three examples of orthogonal polarization transflectors (a) cholesteric reflector, (2) birefringent interference polarizer, and (3) wire grid polarizer. Zhu 2006. Reproduced with permission from IEEE.

R. T. Perkins, D. P. Hansen, E. W. Gardner, et al.. Broadband wire grid polarizer for the visible spectrum,... 

X. J. Yu and H. S. Kwok, Optical wire-grid polarizers at oblique angles of incidence, J. Appl. Phys. 

S. H. Kim, J.-D. Park, and K.-D. Lee, Fabrication of a nano-wire grid polarizer for brightness enhancement in liquid crystal display. Nanotechnology, 17, 4436 (2006). 

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