Polarizing interferometer

In addition to interference filters, NIR manufacturers use holographic gratings (moving and fixed), interferometers, polarization interferometers, diode arrays, acoustic-optic tunable filters, as well as some specialty types. 

Ellipsometer. An instrument for determining the thickness of very thin films of monomolecular dimensions. Essentially, the instrument is a polarization interferometer that utilizes a photometer as a readout device. 

A very promising technique is the measurement of circular dichroism (and linear dichroism) by means of a polarizing interferometer (Martin and Puplett, 1969). The Martin-PupIett-interferometer uses a linear polarizer as beamsplitter. If the interferogram produced at the detector is Fourier transformed, the sine FT gives directly the circular... 

The spectrum of (-)-a-pinene as a 50 pm film of neat liquid using a Bomem spectrometer with a polarizing interferometer attachment is a composite of 60 000 VCD scans and 12 000 transmission scans and took 19.5 hours to be measured. A spectrum with comparable signal to noise ratio is shown in Fig. 6.3-9. This was measured in our laboratory with a PEM-based VCD spectrometer and is a composite of only 5000 scans (five blocks of 1024 scans each). The noise estimate shown as the upper trace is the difference between two 5000 scan VCD spectra. 

Analogous to the measurement of VCD, Polavarapu (1988) has proposed a polarizing interferometer for the measurement of ROA. 

In order to achieve better performance for the Michelson interferometer, metal meshes and wire grids have also been used as beam dividers. An especially interesting solution of this problem is the polarizing interferometer as developed by... 

There exists another way, chosen by a few manufacturers, to incorporate a delay into one of the optical paths when obtaining an interferogram. The principle relies upon the light passing through a crystal having two refractive indices, which constitutes a polarization interferometer. 

Film thicknesses were determined by the Nomarsky interference method(32) using a "Reichert Wien" polarization interferometer. 

The films were deposited by masking a portion of the glass slide so as to form a sharp step. This step was viewed under a polarization interferometer which produced a regular interference pattern with a displacement due to the difference in thickness. 

Some interferometers utilize the optical birefringence of specific crystals to produce two partial waves with mutually orthogonal polarization. The phase difference between the two waves is generated by the different refractive index for the two polarizations. An example of such a polarization interferometer is the Lyot filter [4.23] used in dye lasers to narrow the spectral linewidth (Sect. 4.2.9). 

Beom-hoan O et al (2003) Vapor sensor realized in an ultracompact polarization interferometer built of a freestanding porous-silicon form birefiingent film. Photon Technol Lett IEEE 15(6) 834-836... 

The measurements were made with a nonlinear polarization interferometer (see Fig. 3). A thermostat with the liquid crystal was placed between two crossed polarizers pi and/ 2- The beam from a helium-neon laser A = 0.638 pm), whose 2 is vanishingly small, was broadened by a telescope T and passed through polarizers into a cell with the NLC. Polarized and intensity-modulated emission from a helium-cadmium laser was also guided into the cell with the crystal whose birefringence it altered on account of conformation... 

FIG. 4. Temperature dependence of the intensity of the light passing through the polarization interferometer /,—illumination at >i = 0.44 fitn, I2—with illumination. 

In this latter regard, a considerable improvement was made in measuring fiber surface temperatures by infrared techniques [36] or with a polarizing interferometer [34]. However, even in these cases, the investigators still utilized Eq. (11-24), with its associated boundary conditions. An example was the work of Wilhelm [36], some of whose data are presented in Fig. 11-10. The curves are calculated from Eq. (11-24), and the points represent experimentally observed data. At first glance, the fit appears to be acceptable. It should be pointed out, however, that the heat-transfer coefficients used in the boundary condition (11-21) were, in essence, computed from experimental observations. In essence, then, the curves actually represent a fit of the data themselves rather than a separate theoretical solution. The trend of surface temperature change is, of course, valid. Furthermore, the plots all show a plateau (constant temperature) over a range of distances. These plateaus represent the final solidification of the fiber. For the cases studied, these occurred 8-20 cm from the spinneret face. 

Durst, F., Melling, A., and Whitelaw, J. H. (1976). Principles and Practice of Laser-Doppler Anemometry, Academic Press, London. Fran on, M., and Mallick, S. (1971). Polarization Interferometers Applications in Microscopy and Macroscopy, Wiley (Interscience), New York. 

The Martin Puplett polarizing interferometer lends itself readily to the implementation of a balanced two input - two output beam interferometer where the difference between the two beams is only the axis of polarization. This highly balanced system allows a direct interferometric ratio determination between the two inputs at both output beams separately. In the far I.R. this feature is currently exploited by Mather et al. and separately bu Gush in an attempt to measure the residual cosmic background radiation in outer space. This is believed to follow approximately a 3° K blackbody radiation distribution. The balanced dual beam eliminates the radiation contributed by the spectrometer and the actual measurement consists of a direct comparison of the space field of view with a calibrated 3°K blackbody source in the second input beam. 

Fig. 5.8.15 Simple Martin-Puplett polarization interferometer. Pi and P2 are polarizers with the wires normal to the plane of the paper. B.S. is a beamsplitter with the wires rotated at 45° with respect to that plane. R.R. are roof reflectors that rotate the plane of polarization by 90°. Symbols in the circles indicate the plane of polarization.

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