Showing papers on "Birefringence published in 1968"

Light Scattering and Birefringence Changes during Nerve Activity

Abstract: Two optical techniques—light scattering and birefringence—have been used to detect rapid structural changes accompanying the action potentials in two types of non-myelinated nerve fibre. Changes in light scattering originate from at least two different phenomena, while a large part of the birefringence change seems to be directly dependent on the potential difference across the axon membrane, and arises in radially oriented molecules associated with the membrane.

Index of Refraction of ZnO

Abstract: Measurements of the refractive indices of ZnO single crystals are extended from room down to liquid‐helium temperatures in the region between the absorption edge and 5500 A for E⊥C and E∥C. The indices are calculated from the locations of interference maxima in transmission spectra caused by multiple reflections in thin (0.4–80 μ), plane‐parallel platelets. The dispersion curves at room temperature are similar to those reported by Mollwo, but they are extended to include the optical isotropic point. At energies near absorption edge n∥ n⊥, as is found in other II‐VI materials of the wurtzite symmetry. The isotropic point and its variation with temperature was also determined by birefringence measurements.

Achromatic Wave Plates for the Visible Spectrum

Abstract: We report the experimental demonstration of an optical quarter-wave plate having a retardation of 90°±1° in the region from 4000 to 8000 A. The device is based on the synthesis procedure of Harris, Ammann, and Chang and consists of six sapphire wave plates with appropriately oriented principal axes. The device does not suffer from thermal or angular problems as do longer, narrow-band birefringent networks. Results comparing a 10-plate unit with the above 6-plate unit are given.

Quantum Field Theory of Optical Birefringence Phenomena. I. Linear and Nonlinear Optical Rotation

Abstract: A general approach to the discussion of optical birefringence phenomena is presented. It is based on the S -matrix approach to photon scattering in a nonrelativistic quantum field theoretical formalism and the Stokes operator description of polarization. The use of a canonically transformed interaction Hamiltonian in combination with diagrammatic perturbation theory enables the response of a system to electromagnetic radiation to be calculated in a straightforward and consistent manner to any order in the perturbation, and the effect of static fields is included easily. As an illustration, the angle of rotation of a beam of plane-polarized light by a solution of optically active molecules is calculated and the intensity dependence of the angle determined. The latter phenomenon should become apparent at high photon flux densities particularly when ω , the frequency of the incident light, or 2 ω are similar to electronic excitation frequencies in the optically active molecules.

Lithium Niobate: Effects of Composition on the Refractive Indices and Optical Second-Harmonic Generation

Abstract: Crystals of lithium niobate have been grown with varying amounts of Li2O, Nb2O3, and MgO present in the melt. The refractive indices have been measured and the birefringence so obtained correlated with the phase‐matching temperature for second‐harmonic generation (SHG) and with the composition. The use of optical methods is decribed for the study of compositional uniformity and a method of correcting the effects of uniform composition gradients on SHG described.

Birefringence of Sapphire, Magnesium Fluoride, and Quartz in the Vacuum Ultraviolet, and Retardation Plates

Abstract: Measurements of the birefringence of sapphire, magnesium fluoride, and synthetic quartz from 3000 A to 1500 A are reported and are followed by a discussion of the methods of achromatizing quarter-wave plates and of linearizing the path retardation of a multiwave plate against wavelength (equichromatic wave plates).

Brillouin Scattering in Birefringent Media

Abstract: The theory of Brillouin scattering is extended to incorporate birefringence. The necessary modifications to the Bragg laws are derived by the methods of physical optics. An integral equation method is used to calculate intensities of the first-order lines scattered by longitudinal and transverse acoustic waves in an infinite slab of birefringent crystal. This calculation also differs from those of previous authors in taking full account of internal reflection. Depletion of the incident beam is accounted for. No restriction is made to acoustic propagation parallel to the crystal faces. The intensity formulas for various cases of acoustic mode and incident optical polarization are found to differ in geometrical structure, and the differences can alter the intensities substantially.

Birefringence of native cellulosic fibers. I. Untreated cotton and ramie

Abstract: The Rayleigh-Gans theory of light scattering by a homogeneous cylinder has been applied to the case of scattering by a pad of fibers immersed in a liquid. The theory enables one to locate precisely the matching wavelength at which the mean refractive index of a sample of optically heterogeneous fibers coincides with that of an immersion medium. Thereby it offers a method of determining the mean refractive index. Besides, it facilitates a quantitative estimation of the variability of refractive index. The new technique has been used to study the birefringence of untreated cotton and ramie. The results are presented and discussed.

Refractive Indices of NaNO 2 and Anisotropic Polarizability of NO 2

Abstract: The method of minimum deviation was employed to measure the temperature dependence and the dispersion of principal indices of refraction of NaNO 2 crystal. Their room temperature values have been found to be n a =1.3455, n b =1.4125 and n c =1.6547. The temperature dependence of the birefringence were measured by a Berek compensator. Slight anomalies were found at the transition point. The anisotropic electronic polarizability of a nitrite ion was calculated from the experimental data of refractive indices based on the point-dipole approximation and has been found to be 2.240, 2.716 and 4.610A 3 along the a , b and c axis, respectively, at room temperature. It was concluded that the large optical anisotropy in this substance mainly arises from the polarizability anisotropy of the nitrite ion.

Determination of polyolefin film properties from refractive index measurements. II. Birefringence

Abstract: The use of refractive index data for studying changes in oriented polyolefin films has been demonstrated Application of this technique to oriented polypropylene and polyethylene films showed that the birefringence is a linear function of the refractive index in the direction of maximum orientation By utilizing refractive index, density, and crystallinity data the crystalline refractive indices nc and (na + nb)/2 and polarizabilities α∥ and α⊥ could be estimated for polypropylene and polyethylene

Electrical and hydrodynamical properties of polypeptides in solution. I. Poly(L-glutamic acid) in methanol-water mixtures

Abstract: The electric birefringence of poly(L-glutamic acid) (PLGA) in methanol–water mixtures has been measured by the use of the rectangular pulse technique at 25°C. The permanent dipole moment, the anisotropy of electrical polarizability, and the optical anisotropy factor of PLGA in solution were obtained from the dependence of the steady-state birefringence on the electric field strength. Further, the mean length of PLGA in solution was calculated by a parameter method developed for analyzing the decay curve of electric birefringence. The permanent dipole moment per unit length obtained from these studies was 2.96, 2.48, 2.30, 2.66 D/A in pure methanol, 10, 30, and 50 vol-% water, respectively. The increase of water content caused the decrease of the mean length and broadened the length distribution of PLGA. These results are discussed in relation to the viscosity and the electrical conductivity of PLGA solutions.

Quantum Field Theory of Optical Birefringence Phenomena. II. Birefringence Induced by Static and Optical Electric Fields

Abstract: The scattering matrix technique in conjunction with the Stokes's operator formalism for characterizing the polarization of a light beam which was developed in a previous paper (Atkins & Barron 1968) is applied to the description of the optical birefringence induced in fluid materials by electrical fields. The fields considered are both static (the Kerr effect), arise from a second, intense light beam (the optical Kerr effect) or from the measuring beam itself. The last phenomenon causes the polarization ellipse to rotate and affects the angle of rotation induced by optically active molecules.

Frequency stabilized laser

Abstract: THE INVENTION IS A FREQUENCY STABILIZED LASER IN WHICH AN ACTIVE LASER ELEMENT AND A BIREFRINGENT PLATE ARE DISPOSED WITHIN A REGENERATIVE CAVITY IN A REGENERATIVE PATH DEFINED BETWEEN TWO END REFLECTORS TO PRODUCE A DUAL POLARIZED OUTPUT BEAM THE ACTIVE LASER ELEMENT IS EXCITED BY PLUMP ENERGY AND A PORTION OF THE LASER OUTPUT BEAM IS DIVERTED BY A BEAM SPLITTER TO A WOLLASTON PRISM WHERE IT IS SEPARATED AC- CORDING TO POLARIZATION INTO TWO BEAMS EACH OF THESE BEAMS IS DIRECTED TO AN OPTICAL DETECTOR WHICH DETECTS THE AMPLITUDE OF THE INCIDENT BEAM AT ITS OWN PARTICULAR FREQUENCY OF OSCILLATION THE AMPLITUDES OF THE TWO BEAMS ARE COMPARED BY A COMPARATOR THAT PRODUCES AN ERROR SIGNAL WHICH DRIVES A FREQUENCY ADJUSTMENT ELEMENT COUPLED TO THE LASER

Transient electric birefringence studies of T2 bacteriophage and T2 ghost.

Abstract: The transient electric birefringence behavior of bacteriophage T2 and the T2 ghost or protein coal was studied. The field free relaxation measurements show both the intact virus and its ghost to have two rotary diffusion coefficients. These coefficients have values of 555 ± 54 and 111 ± 22 sec.−1 for the intact virus and 688 ± 89 and 161 ± 29 sec.−l for the ghost. The equivalent ellipsoids for the fast and slow relaxation coefficients were obtained by use of Perrin's equation and were related to the bacteriophage structure in terms of a possible extension of the tail fibers or an enlargement of the head structure. The saturation of the specific birefringence of the phage and the ghost when compared with the specific birefringence of the free nucleic acid gave an average optical orientation of 10 to 18% of the nucleic acid parallel to the main axis of the phage. The analysis of the birefringence versus applied field strength in the Kerr region gave the following values for the anisotropy of the polarixability. αe,33 – αe,11 and intrinsic dipole, μ, of both phage and ghost : for T2 phage αe,33 – αe,11 = 5.0 × 10−14 cm.3 and μ = 64,400 Debyes; for T2 ghost αe,33 – αe,11 = 7.9 × 10−14cm.3 and μ = 57,200 Debyes. The high intrinsic dipole for phage and ghost is interpreted as to be associated with the mechanisms of the virus for attachment, to the host cell wall.

Synthesis of Optical Quality Proustite and Pyrargyrite

Abstract: THE compounds silver orthothioarsenite, Ag3AsS3, and silver orthothioantimonite, Ag3SbS3, occur in nature as small imperfect crystals and have been given the mineral names proustite and pyrargyrite, respectively. Harker1 determined their structures and assigned them to the space group R3c. They are non-centrosymmetric uniaxial crystals with a large refractive index, large negative birefringence (n0–ne>0.2) and transmission over a wide spectral range (0.6–13 µm). They also exhibit semiconducting, photoconducting and piezoelectric properties.

Optical anisotropy of synthetic polynucleotides. I. Flow birefringence and pi-electron polarizability of bases.

Abstract: Birefringence of poly-A, poly-U, and double-stranded poly-AU are investigated experimentally as well as theoretically. Single-stranded poly-A, at low ionic strength, exhibits a strong negative birefringence indicating that, adenine molecules are stacked regularly with their planes along the transverse direction. On the addition of Mg or Mn ions, the birefringence decreases markedly. Poly-U has no noticeable birefringence indicating that poly-U has a contracted configuration in solution. On mixing poly-A and poly-U with 10–3M MgCl2, the birefringence increases markedly, but the change in the chain configuration seems less pronounced. The polarizability of adenine and uracyl are ejaculated using the simple Ifiuckel scheme. The calculation shows that the π-electron polarizability normal to the base plane is zero. Therefore, the negative birefringence is probably due to the lack of π-electron polarizability in the direction normal to the base plane and accordingly no π-electron polarizability along the major helix axis. Conversely, the negative birefringence is an indiaction of base stacking.

New Type of Birefringent Filter

Abstract: A new type of birefringent filter is proposed which uses a single birefringent plate placed between two Faraday-rotation elements within the cavity of a Fabry–Perot interferometer. The interferometer is placed between crossed polarizers whose axes are parallel to the principal directions of the plate. Such an instrument, called a gyromagnetic polarizing interferometer (GYMPI), has an instrumental function which is essentially an Airy function whose finesse is approximately equal to the reflective finesse of the etalon. The argument of the Airy function is the birefringent phase shift of the retardation plate rather than the phase shift of transit between the mirrors. Thus the passband of the filter has that relative independence of angle of incidence that characterizes all birefringent filters. The instrument is readily tunable over a free spectral range by making the retarder a Soliel compensator or incorporating an electro-optic element. This advantage, along with the greater versatility and lower cost of construction, should make the instrument of interest despite the low peak transmittance which is the order of the reciprocal of twice the reflective finesse. The optimum of Faraday rotation is only a few degrees which means that the magnetic-field requirements are not severe.

Birefringent display systems

Abstract: OPTICAL ELEMENTS FOR DISPLAY AND THE LIKE, UTILIZING A MATERIAL CAPABLE OF EXHIBITING OPTICAL BIREFRINGENCE WHEN PLACED UNDER STRESS OR STRAIN, PROVIDED WITH DIFFERENT ARRANGEMENTS FOR LOCALLY PLACING THE MATERIAL UNDER STRESS BY MEANS OF ELECTROSTRICTION, MAGNETOSTRICTION, HEAT DISTORTION, ETC., SUCH THAT THE STRESSED PORTIONS OF THE MATERIAL ACTS AS VARIABLE RETARDATION PLATE OR VARIABLE POLARIZER AND DISPLAY A DIFFERENT COLOR FROM THE COLOR DISPLAYED BY UNSTRESSED PORTIONS WHEN POLARIZED LIGHT IS PASSED THROUGH THE MATERIAL AND OBSERVED THROUGH AN ANALYZER.

Sampling system utilizing electrooptic techniques

Abstract: A sampling system is described which utilizes electrooptic techniques for sampling an electrical signal. Short duration light pulses are polarized and directed through a crystal exhibiting either a linear or longitudinal electrooptic effect or through a liquid showing a large Kerr effect, located in traveling wave relationship with a terminated transmission line structure. The group velocity of the polarized light, that is, the velocity of a light pulse, or the velocity, of the modulation envelope of a modulated light beam, along the electrooptic crystal and the phase velocity of the electrical signal along the transmission line structure are in synchronism. Due to electrically induced birefringence, the state of polarization of the light pulse is altered according to the electrical field intensity to which the electrooptic crystal is subjected by that portion of the electrical signal traveling coincidentally along the transmission line structure. Consequently, the transmission of the light pulse by a crossed analyzer placed at the output of the electrooptic crystal varies in response to the coincidental portion of the electrical signal. The energy of the light pulse emanating from the analyzer is detected and directed to a utilization of circuit, for example, the hold and display circuitry of a sampling oscilloscope.

Device for determining birefringence

Abstract: A DEVICE FOR ELECTRICALLY AND DIRECTLY INDICATING THE BIREFRINGENCE OF A TRANSPARENT MATERIAL WHICH UTILIZES AN ELECTRO OPTICAL SENSOR HAVING A COMBINATION OF POLARIZERS, BIREFRINGENT PLATES AND PHOTOCELLS TO PRODUCE VOLTAGES FUNCTIONALLY DEPENDENT UPON THE BIREFRINGENCE OF THE TRANSPARENT MATERIAL. DIFFERENCE AMPLIFIERS AND A CATHODE RAY TUBE OR SERVO SYSTEM ANALYZE THE PHOTOCELL PRODUCED VOLTAGES TO GIVE A DIRECT INDICATION OF THE BIREFRINGENCE OF THE TEST MATERIAL.

Modified Forms for Glan–Thompson and Rochon Prisms*†

Abstract: Many of the commonly used types of polarizers and polarizing beam splitters consist of two appropriately oriented birefringent crystals (of the same material) which are cemented together. This paper describes modified forms of Glan–Thompson and Rochon prisms in which one of the two calcite (or quartz) halves is replaced by an isotropic material such as glass. In addition to a saving of calcite, these devices have other advantages which add to their usefulness. Two types of modified Glan–Thompson prisms and two types of modified Rochon prisms are described. The modified Glan–Thompson prisms behave as Glan–Thompson prisms for light entering one end, and as Rochon prisms for light entering the other end. The modified Rochon prisms, on the other hand, behave like Rochon prisms regardless of which end light enters. Several commercially available glasses are listed which can be used with calcite or quartz in these devices.

Optical activity and molecular dissymmetry

Abstract: Summary The rotation of the plane of linearly polarized light by an optically-active medium arises from a difference between the refractive indices of the medium for left- and right-circularly polarized light. The circular birefringence is related to a circular dichroism, which is exhibited by all molecules which are not superposable on their mirror image and exist as laevo- and dextro-rotatory isomers. The circular dichroism of a dissymmetric molecule in a particular absorption region originates from an electronic transition with collinear electric and magnetic dipole moments, corresponding to the displacement of a molecular valency electron through a helical path by the absorption of radiation. The right- or left-handed form of the helical path depends upon the molecular structure, and the absolute stereochemical configuration of dissymmetric molecules may be determined by comparing their circular dichroism spectra with the calculated rotational strengths. In addition the polarization direction of an el...

Relaxation characteristics and intrinsic birefringence and viscosity of polystyrene solutions for a wide range of molecular weights

Abstract: A comparison is made between measurements on polystyrene solutions and the relaxation characteristics and intrinsic birefringence and viscosity given by the theory for the flexible Gaussian chain of variable number of segments and with internal viscosity and internal hydrodynamic interaction. This is done in order to determine the applicability of the theory to polymers over a wide range of molecular weights, including the low molecular weight range in which there may be conflict with the theoretical assumption of chains having a large number of segments. The longest, terminal relaxation time and the number of chain segments are determined from measurements of the frequency dependence of oscillatory flow birefringence while the intrinsic birefringence and viscosity are determined from steady flow measurements. The range of molecular weights studied is from approximately 900 at 106. It is found that the segment weight is approximately 1000 and the number of segments is in direct proportion to the molecular weight for the range from 1 to 1000 segments. The terminal relaxation time has a molecular weight dependence of the type given by the theory but with better agreement for higher molecular weights. While the measured dependences of the intrinsic viscosity and birefringence are in agreement with theory for molecular weights greater than 5 × 104, they deviate significantly for molecular weights below 1 × 104. The ratio of the intrinsic birefringence to intrinsic viscosity, which in theory is a constant independent of molecular weight, is found to change at the lower molecular weights.

Magnetic birefringence in thin ferromagnetic films

Abstract: Intensity variations observed in light (λsimilar, equals0·95 μm) transmitted normally by thin magnetic films of Fe, Ni-Fe (81-19) and Co with uniaxial anisotropy when switched along their hard direction, are attributed directly to magnetic birefringence. The intensity changes are of the order of one part in 103. Theoretical considerations enable the form of the intensity variations to be predicted, and show that measurement of their magnitude for a particular optical configuration leads to the magnitude of the complex magneto-optic parameter.