Showing papers on "Optical polarization published in 1983"
TL;DR: In this article, the basic birefringences that couple the two modes and change the polarization state along the fiber are reviewed, and three cases of uniform, phase-matched, and random coupling are considered.
Abstract: The polarization state of light in single-mode fibers is very sensitive to any perturbation which is not symmetric about the fiber axis. While this is a source of noise, drift, or signal fading in some applications, it can also be exploited in novel guided-wave devices. The basic birefringences that couple the two modes and change the polarization state along the fiber are reviewed. The three cases of uniform, phase-matched, and random coupling are considered. Polarization preservation in both low- and high-birefringence fibers is achieved by reducing this coupling. In addition to polarization-state changes, bireftingent fibers can quickly reduce the polarization degree of nonmonochromatic light if both modes are excited, a characteristic that greatly simplifies evaluation of the degree of polarization preservation in these fibers. Current evaluations of the birefringence and the polarization-holding ability of state-of-the-art fibers are discussed, and it is concluded that fibers with good polarization-holding properties are becoming available.
492 citations
TL;DR: In this article, it was shown that the residual polarization at the depolarizer output is proportional to the square root of the polarization-maintaining parameter h, yielding a residual polarization of about 1 percent for a fiber-optic depolariser with h = 1.1 \cdot 10^{-4} /m and a superluminescent diode.
Abstract: Fiber-optic Lyot depolarizers which are attractive for fiber-optic gyros have been studied theoretically and experimentally. It is shown that the amount of residual polarization at the depolarizer output is proportional to the square root of the polarization-maintaining parameter h , yielding a residual polarization of about 1 percent for a fiber-optic depolarizer with h = 1.1 \cdot 10^{-4} /m and a superluminescent diode.
106 citations
TL;DR: In this article, a simple analytic solution has been found for the birefringence in terms of the cross-sectional distribution of the highexpansion material used to create the thermal stress.
Abstract: Polarization-maintaining optical fibers are usually made by inducing a large anisotropic thermal stress in the core so that it appears highly birefringent. A simple analytic solution has been found for the birefringence in terms of the cross-sectional distribution of the high-expansion material used to create the thermal stress. The analysis is able to predict optimal structures which efficiently utilize the available stress and thus maximize the birefringence. It is shown that the optimum structure has a cross-sectional geometry resembling a bow-tie. Design rules are given whereby the dimensions may be chosen and these are verified in a simple experiment.
106 citations
TL;DR: In this article, the authors derived analytic output equations for the degree of polarization of light exiting a Lyot depolarizer from a coherency matrix representation, and design criteria were obtained for sources of different spectral shape.
Abstract: Analytic output equations for the degree of polarization of light exiting a Lyot depolarizer are derived from a coherency matrix representation. Design criteria are obtained for sources of different spectral shape.
93 citations
TL;DR: In this article, the radio source OV236 (1921-293) has been classified both as a quasar and a flat-spectrum radio source and its polarization and variability at 2.2 µm1 and generally featureless optical spectrum are consistent with it being a BL Lac object.
Abstract: As part of a programme of multifrequency single epoch observations of BL Lac objects and flat-spectrum radio sources we have examined the radio source OV236 (1921–293) which has been classified both as a quasar and a BL Lac object. Its polarization and variability at 2.2 µm1 and generally featureless optical spectrum are consistent with it being a BL Lac object. Wills and Wills2 measured its optical polarization, variability and emission line spectrum and find it to have a redshift z = 0.352. It is an extremely variable radio source, during the outburst reported by Dent and Balonek3 it was the brightest 10-cm quasar in the sky. The outburst was first measured at 3.3 mm and was increasingly delayed at longer wavelengths; there was also evidence for correlated optical/radio variability during this outburst4. We have obtained J, H, K, 10, 20, 800 and 1,100 µm flux measurements of 1921–293 over a period of four days from the same telescope, enabling us to present a ‘snapshot’ of its IR to millimetre spectrum. The continuum spectrum of 1921–293 is suggestive of a peak in the submillimetre region. This excess could be due to an injection of high-energy electrons into a synchrotron emitting region, although thermal emission from dust remains a possibility.
87 citations
TL;DR: The LEGS project at Brookhaven will produce a very high flux (>2×107 s-1) of background-free polarized? rays whose energy will be determined to a high accuracy (?E = 2.3 MeV) as mentioned in this paper.
Abstract: Collisions of light photons with relativistic electrons have previously been used to produce polarized ?-ray beams with modest (~10%) resolution, but relatively low intensity. In contrast, the LEGS project (Laser+Electron Gamma Source) at Brookhaven will produce a very high flux (>2×107 s-1) of background-free polarized ? rays whose energy will be determined to a high accuracy (?E =2.3 MeV). Initially, 300(420) MeV ? rays will be produced by backscattering UV light from the new 2.5(3.0) GeV X-ray storage ring of the National Synchrotron Light Source (NSLS). The LEGS facility will operate as one of many passive users of the NSLS. In a later stage of the project, a Free Electron Laser is expected to extend the ?-ray energy up to 700 MeV.
79 citations
TL;DR: In this article, an integrated planar antenna-mixer structure for use at millimeterwave frequencies is described, and a simple but accurate theory of the slot-ring antenna is applied to several experimental devices.
Abstract: An integrated planar antenna-mixer structure for use at millimeterwave frequencies is described. A simple but accurate theory of the slot-ring antenna is applied to several experimental devices. Mixer conversion loss of about 6.5 dB was obtained from an X-band model. Measured radiation patterns of structures designed for 65 GHz agree reasonably well with theory.
76 citations
TL;DR: A heterodyne interferometric system based on optical polarization is described, which uses a simple rotating analyzer as the frequency shifter and the theory and the potential errors are analyzed.
Abstract: A heterodyne interferometric system based on optical polarization is described. The method uses a simple rotating analyzer as the frequency shifter. The theory and the potential errors of the system are analyzed.
73 citations
TL;DR: In this article, it was shown that the Seyfert 1 galaxy NGC4151 is parallel to the associated radio axis, and that the alignment effects can be interpreted as being due to thin and thick scattering disks, respectively, surrounding the continuum sources.
Abstract: Optical polarization position angles tend to align with large-scale radio structure in low polarization quasars1, and they tend to align with or be perpendicular to the radio structure in radio galaxies2. In some cases active object emission lines are polarized like the continuum, so the polarization is probably caused by scattering (ref. 3 and R.R.J.A., in preparation). Thus, the polarization alignments indicate the geometrical distribution of scatterers in those cases and so provide information on the matter distribution in the innermost regions. In a new interpretation of the polarization of the Seyfert 2 galaxy NGC1068 (ref. 4), it is noted that the optical polarization of that object is perpendicular to the inner radio contours, while the polarization of the Seyfert 1 galaxy NGC4151 is parallel to the associated radio axis. It is speculated that these are prototypical of two polarization classes of Seyferts analogous to the perpendicular and parallel radio galaxy groups. I show here that this is indeed the case: all Seyfert 1 galaxies in this sample have roughly parallel polarization and all Seyfert 2 galaxies have roughly perpendicular polarizations. These alignment effects can be interpreted as being due to thin and thick scattering disks, respectively, surrounding the continuum sources. This would represent a fundamental difference between the two types of Seyfert galaxies.
72 citations
58 citations
TL;DR: In this article, the reduction of the degree of polarization of broadband light due to propagation in ordinary single-mode fiber is examined theoretically and experimentally, and a model for one discrete mode-coupling center and extending it qualitatively to include multiple centers is developed.
Abstract: The reduction of the degree of polarization of broad-band light due to propagation in ordinary single-mode fiber is examined theoretically and experimentally. Previous work is extended to account for polarization-mode coupling along the fiber by developing a model for one discrete mode-coupling center and extending it qualitatively to include multiple centers. The existence of nonzero degree of polarization in long lengths of fiber is shown to be due to mode coupling at particular positions along the fiber and the degree of polarization is shown to be related to the degree of coherence associated with the mode-coupling site. The experimental results generally support the model developed.
TL;DR: The invariants of nonlinear wave equations suggest an existence of mutual eigenarrangements of polarization with different relevant eigennonreciprocities, and a nonreciprocal spectroscopy of the anisotropic nonlinear susceptibility may be developed.
Abstract: It is shown that the magnitude of nonlinear nonreciprocity, self-induced by counterpropagating laser beams, is related to the anisotropic properties of the nonlinear third-order susceptibility (resulting in the light-induced birefringence and gyrotropy) and therefore is sensitive to the mutual arrangement of polarization of both of the beams. The invariants of nonlinear wave equations suggest an existence of mutual eigenarrangements of polarization with different relevant eigennonreciprocities. By using this effect, a nonreciprocal spectroscopy of the anisotropic nonlinear susceptibility may be developed.
TL;DR: The geometric ray tracing theory for the scattering of light by hexagonal cylinders to cubes and parallelepipeds is modified for the interpretation of observed scattering and polarization data from planetary atmospheres and for the physical understanding of the transfer of radiation in an atmosphere containing nonspherical particles.
Abstract: In this paper, the geometric ray tracing theory for the scattering of light by hexagonal cylinders to cubes and parallelepipeds has been modified. Effects of the real and imaginary parts of the refractive index and aspect ratio of the particle on the scattering phase function and the degree of linear polarization are investigated. Causes of the physical features in the scattering polarization patterns are identified in terms of the scattering contribution due to geometric reflections and refractions. The single-scattering phase function and polarization data presented in this paper should be of some use for the interpretation of observed scattering and polarization data from planetary atmospheres and for the physical understanding of the transfer of radiation in an atmosphere containing nonspherical particles.
TL;DR: In this paper, high-resolution photometry is presented for outbursts of the quasi-stellar object QSO 1156+295 in 1981 and 1982, showing variations on time scales of weeks to about half an hour.
Abstract: Photometric observations are presented for outbursts of the quasi-stellar object QSO 1156+295 in 1981 and 1982. High time resolution photometry is included showing variations on time scales of weeks to about half an hour. Data from early plate material show that the object may have been quite bright at the beginning of this century but was quite faint and probably inactive between about 1950 and the beginning of recent activity in 1977-1979. Some results of optical linear polarization are discussed. In examining spectrophotometric results, broadband spectra show very little change in spectral shape during changes in continuum brightness. High resolution spectra (0.1-A FWHM) show no evidence for the Mg II 2798-A absorption sometimes seen in optically violent variables and other QSOs. The radio flux density variations at several frequencies are documented and discussed and compared with the optical light curve. Models for 1156+295 are discussed including variability time scales, and the observed energy output is compared with a magnetic accretion disk model proposed by Shields and Wheeler (1976). Results are summarized and the different sizes of active and inactive regions of the object are compared.
TL;DR: In this article, the theory for understanding fibres composed of highly birefringent material is presented and one of the two possible polarisation states of the fundamental mode can be made leaky, suggesting a novel single-mode single-polarisation fibre design.
Abstract: The theory for understanding fibres composed of ‘highly’ birefringent material is presented. One of the two possible polarisation states of the fundamental mode can be made leaky, suggesting a novel single-mode single-polarisation fibre design. No leakage occurs in planar waveguides constructed similarly from the identical material.
TL;DR: In this article, the bend radius and orientation of the fiber in the bend considerably affect the single-polarisation operation of bow-tie fibres, and the effect of bend radius on the singlepolarization operation was investigated.
Abstract: Experimental results are presented which show how both bend radius and the orientation of the fibre in the bend considerably affect the single-polarisation operation of bow-tie fibres.
TL;DR: A new technique for measuring the polarization mode coupling of a polarization-maintaining optical fiber is proposed that uses a modified optical time-domain reflectometry in which two kinds of backscattered signals coming through each principal axis of the fiber are utilized.
Abstract: A new technique for measuring the polarization mode coupling of a polarization-maintaining optical fiber has been proposed that uses a modified optical time-domain reflectometry in which two kinds of backscattered signals coming through each principal axis of the fiber are utilized. This technique shows how the mode coupling occurs along the fiber. The extinction ratio evaluated by the present technique is in good agreement with that obtained by a conventional technique (within ±0.5 dB).
TL;DR: In this article, a new preform fabrication technique for realising long lengths of polarisation-maintaining optical fibres is described, which produces stress-induced birefringent fibres with symmetry and uniformity along the length in the stress-applying parts.
Abstract: A new preform fabrication technique for realising long lengths of polarisation-maintaining optical fibres is described. The technique is shown to produce stress-induced birefringent fibres with symmetry and uniformity along the length in the stress-applying parts. The resultant 8.3 km-long fibre whose relative refractive-index difference is 0.6% has been obtained with a crosstalk of −23 dB at 1.15 μm wavelength, where the loss is 1.7 dB/km.
TL;DR: In this article, a quasi-optical and wide-angle (of incidence) polarization rotator is described and analyzed for a dually polarized multibeam satellite ground station antenna employing a linear array feed.
Abstract: A quasi-optical and wide-angle (of incidence) polarization rotator is described and analyzed. It consists of three or more parallel, equispaced wire-grid polarizers whose wires are oriented in different directions. With the proper choice of the number of grids, their spacings, and their relative orientations, such a polarization rotator is capable of operating over a broad frequency band and a wide range of angles of incidence. A seven-grid 90\deg polarization rotator was designed to operate over a 42 percent relative bandwidth for a \pm 60\deg range of angles of incidence with less than 0.1 dB transmission loss. Various designs based upon our analysis are given. The impetus for this work is the specific application of this polarizer in a dually polarized multibeam satellite ground station antenna employing a linear array feed. The design of a seven-grid polarization rotator for the ground station antenna is presented.
TL;DR: In this article, the coupling characteristics for each polarization are strongly dependent on the mode confinement, and hence on the modes dispersion, and also vary differently with changes in mode dispersion.
Abstract: Measurements are described on Z-LiNbO 3 , single-mode, channel waveguide directional couplers for the TE- and TM-mode polarizations at 0.83- and 1.3-μm wavelengths. The coupling characteristics for each polarization are strongly dependent on the mode confinement, and, hence, on the mode dispersion, and also vary differently with changes in mode dispersion. With particular waveguide fabrication parameters, the TE- and TM-mode coupling coefficients are equal for any waveguide spacing; for other fabrication conditions, the coupling coefficients are always unequal or equal at only one spacing. Theoretical calculations, based on experimentally determined diffusion parameters, follow the trend of measured values in most cases and correctly predict the effect on the coupling characteristics of changes in waveguide fabrication.
TL;DR: The recent progress of coherent optical fibre communication systems is reviewed, and system constituent technologies, such as coherent optical modulation-demodulation, optical direct amplification for repeaters and single polarization fibre transmission are outlined.
Abstract: The recent progress of coherent optical fibre communication systems is reviewed. System constituent technologies, such as coherent optical modulation-demodulation, optical direct amplification for repeaters and single polarization fibre transmission are outlined. Several important optical device technologies, such as frequency stabilization of semiconductor lasers, AM and FM quantum noise and their reduction, and integrated opto-electronic devices, are also described. Finally, on the basis of the current state of the art in these technological areas, the expected system performance and future problems are discussed.
TL;DR: In this paper, a 4-m yttrium-iron-garnet film at 9.4 GHz was used to detect light scattering from parametrically excited magnons.
Abstract: Brillouin light scattering has been observed from parametrically excited magnons by parallel pumping in a 4-\ensuremath{\mu}m yttrium-iron-garnet film at 9.4 GHz. Scattering from the spin waves could be observed continuously from the thermal level through the nonlinear region of parametrically excited magnons. Magnons with small wave vectors propagating perpendicular to the static field are seen to have the lowest critical field as predicted theoretically. The spectra of these parametric excitations show a pronounced structure.
TL;DR: In this article, a low-loss single-polarization fiber with stress-induced birefringence has been fabricated using VAD single-mode fiber preforms.
Abstract: Low-loss single-polarization fibers with stress-induced birefringence have been fabricated using VAD single-mode fiber preforms. Design criteria have also been clarified with due regard to optimum fiber structure that reduces transmission loss and increases birefringence. As a result of these criteria, the minimum loss of 0.4 dB/km at 1.54 μm, and the birefringence B s of 1.2 \times 10^{-4} at 1.15 μm was obtained. It has been shown that a large refractive-index difference between the core and the cladding Δ, as well as large birefringence, are very effective to stabilize the state of polarization. In a 5-km-long fiber with \Delta = 0.8 percent and B_{s}= 1.2 \times 10^{-4} , crosstalk lower than -20 dB has been obtained.
TL;DR: In this article, the authors report on changes in magnetization when Cd$(n) is subject to optical pumping and the Faraday rotation of a second beam is used as a monitor.
Abstract: This Letter reports on changes in magnetization when Cd${\mathrm{Cr}}_{2}$${\mathrm{Se}}_{4}$ is subject to optical pumping. The Faraday rotation of a second beam was used as a monitor. Circularly polarized pumping was found an order of magnitude more effective than unpolarized pumping. Models using magnetic coupling mechanics of first and second order in the exchange energy, respectively, account quite well for the observations.
TL;DR: Controlled bleaching of the iodine dichromophore from iodine-polyvinyl alcohol polarizers has been demonstrated to result in a dramatic increase in transmission.
Abstract: Controlled bleaching of the iodine dichromophore from iodine-polyvinyl alcohol polarizers has been demonstrated to result in a dramatic increase in transmission. Internal transmission of 95% for linearly polarized light has been observed in the spectral range of 5000–6000 A. Degradation of polarizer extinction is most severe at shorter wavelengths; however, the transmittance for the crossed polarization remains <0.1% through much of the visible spectrum.
TL;DR: In this article, the polarization noise, originating from the combination of single mode fibres and diffraction gratings, is investigated experimentally and a drastic deterioration of the signal/noise ratio is observed, which is even more severe than modal noise with multimode fibres.
Abstract: Fluctuations of the state of polarization in single mode fibres due to environmental conditions such as vibrations cause intensity noise if elements with polarization-dependent loss are inserted into the fibre system. Diffraction gratings, which are key elements for wavelength division multiplex-single mode fibre systems, exhibit a strong polarization dependence of loss. The polarization noise, originating from the combination of single mode fibres and diffraction gratings, is investigated experimentally. A drastic deterioration of the signal/noise ratio is observed, which is even more severe than modal noise with multimode fibres. Depolarizing devices, which reduce this kind of noise sufficiently, are presented and examined.