Showing papers on "Optical polarization published in 1979"
TL;DR: In twisted single-mode optical fibers the polarization of light is affected by an elastooptically induced optical activity and by a modification of any linear birefringence present.
Abstract: In twisted single-mode optical fibers the polarization of light is affected by an elastooptically induced optical activity and by a modification of any linear birefringence present. These effects are discussed theoretically and demonstrated experimentally. The activity/twist ratio is α/τ ≃ 0.13 … 0.16 universally in weakly guiding silica fibers. Twisted fibers may be used as polarization rotators. A fiber with a ±68° double twist operates as a fast/slow mode interchanger, suitable for delay equalization.
760 citations
TL;DR: Raman and Brillouin gains in fibers are a factor of 2 higher if linear polarization is maintained as mentioned in this paper.Birefringent single-mode fibers are used to demonstrate this gain difference.
Abstract: Raman and Brillouin gains in fibers are a factor of 2 higher if linear polarization is maintained. Birefringent single-mode fibers are used to demonstrate this gain difference. Threshold powers of 200 mW have been achieved in Raman oscillators.
285 citations
01 Nov 1979
TL;DR: In this paper, the authors reviewed the history and the current status of the relationship between the backscattering coefficient σ° and the wind speed u at microwave frequencies and indicated that σ lies in the vicinity of 1.4 to 2.0.
Abstract: This paper reviews the history and the current status of the relationship between the backscattering coefficient σ° and the wind-speed u at microwave frequencies. When σ° is assumed to be proportional to uγ, measurements have indicated that γ lies in the vicinity of 1.4 to 2.0. Under similar conditions with incidence angle between 30° and 80°, γ for HH polarization is usually larger than that of VV polarization and γ for upwind or downwind is larger than that of the crosswind. Better surface truth and controlled experiments are still needed to obtain a more specific value for γ under a given condition. Theoretical modeling of radar sea scatter indicates that near vertical incidence the physical optics method is applicable while for incidence angles approximately in the range 30° to 80° the return can be explained by Bragg scattering due to capillary waves when the tilting effect of the large-scale waves is also included. The methods used in extracting wind vectors from SEASAT scatterometer measurements are outlined. Areas where further experimental and theoretical studies are needed are indicated.
202 citations
TL;DR: In this paper, the behavior of light beams in nonlinear media (self-focussing of optical beams as well as self-modulation and transmission of optical pulses) is considered in the case when the nonlinear polarization contains susceptibilities of third-and fifth-order.
Abstract: The behaviour of light beams in nonlinear media (self-focussing of optical beams as well as self-modulation and transmission of optical pulses) is considered in the case when the nonlinear polarization contains susceptibilities of third- and fifth-order. The soliton solutions are obtained for the nonlinear equations deduced.
170 citations
TL;DR: In this article, the first demonstration of a guided-wave polarization independent electro-optic switch was reported, which achieved crosstalk levels below −23 dB for both switch states for arbitrary incident optical polarization.
Abstract: We report the first demonstration of a guided‐wave polarization‐independent electro‐optic switch. Using a specially designed weighted Ti‐diffused directional coupler with stepped electrodes, we have achieved crosstalk levels below −23 dB for both switch states for arbitrary incident optical polarization.
109 citations
99 citations
98 citations
TL;DR: In this article, the authors study the electromagnetic properties of plasmas allowing for the polarization effect of the vacuum induced by the presence of a strong external magnetic field. And they find that the polarization properties and transport of x-ray radiation can be severely altered by the magnetic vacuum effects.
Abstract: We study the electromagnetic properties of plasmas allowing for the polarization effect of the vacuum induced by the presence of a strong external magnetic field. Adopting the cold-plasma polarization tensor to account for the electron component, we find that the polarization properties and transport of x-ray radiation can be severely altered by the magnetic vacuum effects. The effect becomes important at relatively high frequencies, $\frac{\ensuremath{\omega}}{{\ensuremath{\omega}}_{p}}\ensuremath{\gtrsim}{(\frac{15\ensuremath{\pi}}{\ensuremath{\alpha}})}^{\frac{1}{2}}$ $\frac{{B}_{c}}{B}$ where ${\ensuremath{\omega}}_{p}={(4\ensuremath{\pi}{n}_{e}\frac{{e}^{2}}{m})}^{\frac{1}{2}}$ is the plasma frequency of the electron component, $\ensuremath{\alpha}$ is the fine-structure constant, and ${B}_{c}=\frac{{m}^{2}{c}^{3}}{e\ensuremath{\hbar}}\ensuremath{\simeq}4.4\ifmmode\times\else\texttimes\fi{}{10}^{13}$ G is the electrodynamic critical field. For typical pulsar magnetic fields, $B\ensuremath{\sim}0.1$ ${B}_{c}$, and x-ray frequencies, this condition is satisfied even for relatively high plasma densities ${n}_{e}\ensuremath{\sim}{10}^{23}$ ${\mathrm{cm}}^{\ensuremath{-}3}$. Whenever the above inequality is fulfilled the vacuum effect dominates the polarization properties of the normal modes of the medium, giving rise to a significant change in the medium opacity. The Thomson, bremsstrahlung, and cyclotron opacities are thus significantly altered from their usual cold-plasma values. The largest departures are found in the vicinity of the electron gyrofrequency, where the vacuum induces a strongly anisotropic resonant behavior on the ordinary mode (which is nonresonant in the usual cold-plasma circumstances). This property may be significant in analyzing the polarization and spectral character of the cyclotron feature in Hercules X-1 and other accreting x-ray pulsars.
66 citations
TL;DR: In this paper, the authors constructed the first all-fiber interferometric sensor system and performed preliminary studies on the effects of birefringence in these interferometers.
Abstract: In a conventional circular cross‐section single‐mode fiber, built‐in and induced birefringences remove the degeneracy and make the fiber a two‐Eigenmode system. We have constructed the first all‐fiber interferometric sensor system and have performed preliminary studies on the effects of birefringence in these interferometers. Theoretical analysis and experimental data supporting this analysis are presented for the 3‐dB coupler and all‐fiber interferometer sensor.
64 citations
TL;DR: In this article, the angular distribution of the returned energy was investigated as a function of time and height, and it was shown that the higher layers exhibit scatter from a much larger range of off-vertical angles, and the power returned from them varies less in time than for the lower layers.
Abstract: Radio pulses have been used as a probe to investigate scattering characteristics of ionospheric irregularities in the D - region at a frequency of 1.98 MHz, at Adelaide, South Australia (35/sup 0/S). The angular distribution of the returned energy was investigated as a function of time and height. Distinct layers of strong scatter have frequently been detected, the heights of which differ on different days. The layers appear to be of two distinct types - those occurring above 80 km and those below - the two groups having different temporal and angular characteristics. The higher layers exhibit scatter from a much larger range of off-vertical angles, and the power returned from them varies less in time than for the lower layers, which tend to show short 'bursts' of scatter.
TL;DR: In this paper, it was shown that the nonlinear electric polarization density that is third order in the propagating electric fields in the guide medium generates the replica by the process of four-wave mixing.
Abstract: We show that one can generate the time-reversed replica of an "input" monochromatic, image-bearing beam by coupling it into a waveguide where it interacts with counterpropagating multimode "pump" waves of the same frequency. The nonlinear electric polarization density that is third order in the propagating electric fields in the guide medium generates the replica by the process of "four-wave mixing." We show also that the input beam can serve simultaneously as its own pump beam. If the frequency ν of the backward pump beam is different from the frequency ω to of the input beam, then the "phase-conjugate" to the input is generated at the entrance plane to the guide, and this radiates a replica of the input field, magnified by \omega/
u , back along the input beam. The pump power required per resolution element to phase-conjugate a beam in a waveguide is orders-of-magnitude less than for the corresponding process with free (unguided) waves interacting in an infinite medium. Unlike the requirements for free waves, the pump waves do not need to be well aligned or single-mode to produce high fidelity in the replication process. Neither does the guiding structure or enclosed medium have to be precise in dimension or uniformity; the main requirements on the guiding structure being that it not attenuate the waves too heavily. Formulas are derived for the replication efficiency and fidelity in the various guided configurations. We also show how the process can be used: 1) to make a narrowband optical filter with a large acceptance solid angle; 2) to perform image-frequency conversion; 3) to obtain Raman and two-photon spectra of small samples; and 4) to achieve broadband optical amplification. We examine the conditions under which phase conjugation and these applications can be performed at several frequencies simultaneously. Limitations placed by the power-dependence of propagation constants are derived.
TL;DR: The M-type asteroids are not reproduced by silicate rocks in any surface textures; nor do they correspond to metallic fractures as mentioned in this paper, but they fit with powders of 20 to 40-μm diameter fragments of metals.
TL;DR: In this paper, the 6th, 7th and 8th harmonics of cyclotron absorption in a magnetic field of ∼3×107 G were identified for the first time in this object in the optical spectrum during the bright phases with high circular polarisation.
Abstract: VV Puppis is an AM Herculis type binary system exhibiting variable circular and linear polarisation1. In its ‘normal’ state, the optical light curve shows a slow rise to maximum (mmax∼15–16) and a rapid drop to minimum (mmin∼17.5–18) where it remains for ∼60% of its 100-min period2–4. However, the system has also been observed in faint inactive states5 (mmin∼mmax∼15). Only a few spectroscopic observations of VV Pup have been published and these show a continuous spectrum with emission lines of hydrogen and helium superimposed. We present here spectrophotometric observations obtained on 2 February 1979. Broad absorption features are seen for the first time in this object in the optical spectrum during the bright phases with high circular polarisation. We suggest that these features be identified with the 6th, 7th and 8th harmonics of cyclotron absorption in a magnetic field of ∼3×107 G.
TL;DR: In this paper, the authors show how coupling of light energy can take place between ordinary and extraordinary polarizations at the isotropic point by application of a dc electric field, and they conclude that this type of filter can, in principle, accommodate a 2π field with less than 20 percent increase in passband over that of the narrow-field condition.
Abstract: A new optical filter, first demonstrated more than a decade ago and recently extended to other frequencies and materials, is based on the accidental isotropy of refractive indexes that occurs in certain uniaxial semiconductors near the band edge. This paper shows how coupling of light energy can take place between ordinary and extraordinary polarizations at the isotropic point by application of a dc electric field. When placed between crossed polarizers, these materials can thus act as narrow-band filters. The field-of-view characteristics have been analyzed; and it is concluded that this type of filter can, in principle, accommodate a 2π field with less than 20 percent increase in passband over that of the narrow-field condition. It is noted, in particular, that AgGaS 2 exhibits the required change of sign of its birefringence at a wavelength of 4970 A (blue-green), with a rate of change that could provide a passband of only 0.2 A in a 1 cm sample.
TL;DR: In this article, coherent Raman-induced Kerr effect was used to obtain the Brillouin spectrum of CS2 for acoustic phonon excitations, where the nonlinear polarization in this case is so large that the effects of Stokes gain and anti-Stokes loss must be included in the theoretical interpretation of the spectrum.
Abstract: We have established the viability of coherent Raman techniques in the study of acoustic phonon excitations. Using the Raman‐induced Kerr effect scheme, we have obtained the Brillouin spectrum of CS2. The nonlinear polarization in this case is so large that the effects of Stokes gain and anti‐Stokes loss must be included in the theoretical interpretation of the spectrum.
TL;DR: The soft X-ray source H 2155-304 has been precisely located with the HEAO 1 scanning modulation collimator, and identified with an object of bolometric magnitude approximately 14 as mentioned in this paper.
Abstract: The soft X-ray source H 2155-304 has been precisely located with the HEAO 1 scanning modulation collimator, and identified with an object of bolometric magnitude approximately 14. The linear polarization, variability, spectrum, and diffuse image of the optical flux, together with the positional coincidence of the radio source PKS 2155-304, indicate that this object is a new member of the BL Lacertae class. Its characteristics are compared with those of other X-ray-emitting BL Lacertae objects, particularly Mrk 421.
TL;DR: In this paper, the feasibility of Doppler-free polarization spectroscopy with a train of ultrashort pulses from a synchronously pumped mode-locked dye laser was demonstrated.
Abstract: We have demonstrated the feasibility of Doppler-free polarization spectroscopy with a train of ultrashort pulses from a synchronously pumped mode-locked dye laser. The sensitivity of the method is compared with saturation spectroscopy with a single-mode laser.
TL;DR: In this article, a sharp zero-phonon line emission at 682.8 nm is observed in yellow-colored CaO crystals and it is concluded that the emission is due to a photoexcited triplet state of an orthorhombic $I$ center.
Abstract: In yellow-colored CaO crystals a sharp zero-phonon line emission at 682.8 nm is observed. From optically-detected-magnetic-resonance experiments conducted at 1.3 K and at low- and high-magnetic-field strengths, it is concluded that the emission is due to a photo-excited triplet state of an orthorhombic $I$ center. Optical polarization, spin alignment, and spin coherence decay phenomena were studied, the latter by means of techniques for the optical detection of spin echoes and spin locking, in order to determine the radiative and nonradiative properties of the triplet sublevels. The triplet state is assocaited with a $1s2p$ excited state of two electrons captured in two nearest-neighbor oxygen-anion vacancies (an ${{F}_{2}}^{2+}$ center) with possibly a ${\mathrm{Ca}}^{2+}$ vacancy nearby for charge compensation (i.e., an ${{F}_{2}}^{2+}\ensuremath{-}{V}^{2\ensuremath{-}}$ center). The observed linear dichroism in the excitation microwave double-resonance spectra is considered in connection with the mechanism for the triplet-state production. It is discussed briefly why the lowest ${(1s)}^{2}$ triplet state, which is predicted in the $M$-center model, could not be observed.
TL;DR: In this paper, the authors studied the properties of isolated and coupled optical rib waveguides (RWG) as a function of rib height and width in GaAs layers on AlGaAs for TE-like and TM-like polarizations.
Abstract: We have studied the properties of isolated and coupled optical rib waveguides (RWG) as a function of rib height and width in GaAs layers on AlGaAs for TE‐like and TM‐like polarizations. We compare mode shape parameters for isolated RWG to the coupling constant, K, obtained from distributed couplers. The effective index model accurately describes the mode distributions and the coupling constant for single‐mode RWG. The model also gives an accurate estimate for anodic oxide loaded strip waveguides. In this model, the relative lateral difference in the effective dielectric constant, Δx, is determined by the depth characteristics (the rib height, layer thicknesses, and compositions) and the free‐space wavelength. The lateral confinement of guided modes and K are then determined by Δx, the effective dielectric constant, the waveguide width, the waveguide spacing, and the free‐space wavelength. At λ?1.06 μm, ribs of height h?0.05 μm on GaAs waveguiding layers of thickness t?0.75 μm with underlying Al0.1Ga0.9As ...
TL;DR: In this paper, the polarizer and analyzer are arranged at appropriate angles with respect to the crystallographic axes of an electrooptic crystal to achieve controllable multistable operations.
Abstract: Optical multistable operations are controllably accomplished in the mirrorless electrooptic device with feedback by arranging the polarizer and/or analyzer at appropriate angles with respect to the crystallographic axes of an electrooptic crystal. Moreover, different operating characteristics in two optical output powers with orthogonal polarizations separated from each other by an analyzer are examined theoretically and experimentally.
TL;DR: In this article, the photoferroelectric effect was used to store nonvolatile gray-scale images in lead lanthanum zirconate titanate (PLZT) ceramics.
Abstract: A recently discovered photoferroelectric (PFE) effect in which the electric-field-induced antiferroelectric (AFE)-to-ferroelectric (FE) phase transition is photoinhibited is used to store nonvolatile gray-scale images in lead lanthanum zirconate titanate (PLZT) ceramics. Stored images exhibit exceptionally high contrast and approximately linear gray-scale reproduction. Images are stored as spatial variations of the volume ratio of FE phase to the initial AFE phase. Localized variations of the ratio of FE to AFE phase produce related variations in light scattering. In the materials studied, the scattering effect partially depolarizes transmitted visible light, and the stored image can be viewed directly or projected onto a screen using crossed linear polarizers.
TL;DR: In this article, the X-ray source 2A 0311-227 has been precisely positioned by using the HEAO 1 scanning modulation collimator, resulting in an optical candidate with a B magnitude of about 15.
Abstract: The X-ray source 2A 0311-227 has been precisely positioned by using the HEAO 1 scanning modulation collimator, resulting in an optical candidate with a B magnitude of about 15. Medium-resolution optical spectra of this star show remarkable similarity to the spectrum of AM Her, a short-period binary containing a magnetic white dwarf. The Balmer decrement in 2A 0311-227 is also similar to that in AM Her and may likewise be attributed to collisional excitation in a plasma with an electron density of the order of 10 to the 13th per cu cm.