Showing papers on "Optical polarization published in 1992"

New principle for optical filters

Abstract: A theoretical characterization of the guided‐mode resonance properties of planar dielectric waveguide gratings is presented. Efficient exchange of energy between forward and backward propagating diffracted waves is shown to be possible with smooth line shapes. The linewidths of the resonances can be controlled by the grating modulation amplitude. Due to the inherent separation between the TE and TM modes associated with the waveguide grating, these elements can provide polarization separation. Applications to polarization sensitive filtering and to electro‐optic switching are suggested. The guided‐mode resonance filter represents a basic new optical element.

Polarization-sensitive low-coherence reflectometer for birefringence characterization and ranging

Abstract: We present a polarization-sensitive optical coherence-domain reflectometer capable of characterizing the phase retardation between orthogonal linear polarization modes at each reflection point in a birefringent sample. The device is insensitive to the rotation of the sample in the plane perpendicular to ranging. Phase measurement accuracy is ±0.86°, but the reflectometer can distinguish local variations in birefringence as small as 0.05° with a distance resolution of 10.8 μm and a dynamic range of 90 dB. Birefringence-sensitive ranging in a wave plate, an electro-optic modulator, and a calf coronary artery is demonstrated.

Polarization multiplexing with solitons

Abstract: It is shown both analytically and with numerical simulation, and confirmed experimentally in transmission over distances up to approximately 10000 km, that solitons maintain a high degree of polarization over an ultra-long distance transmission system consisting of birefringent dispersion-shifted fiber segments and erbium amplifiers. Based on that fact, the authors propose a polarization/time division multiplexing technique which should allow the single-wavelength bit-rate capacity of an ultra-long distance soliton transmission system to be doubled with little or no significant increase in bit error rate. >

The Hubble Space Telescope Northern-Hemisphere Grid of Stellar Polarimetric Standards

Abstract: Results are presented from a comprehensive program of optical polarimetry of strongly polarized and null-polarization standard stars. Potential sources of systematic error either instrumental in origin or due to absolute calibration are critically discussed. Although the project emphasized the requirements of a spaceborne optical-UV observatory (HST), the resulting grid of standards represents a distinct improvement over previous such tabulations and offers an opportunity to reference future multiwavelength polarimetry to a common system

Kramers-Kronig relations in nonlinear optics

Abstract: We review dispersion relations, which relate the real part of the optical susceptibility (refraction) to the imaginary part (absorption). We derive and discuss these relations as applied to nonlinear optical systems. It is shown that in the nonlinear case, for self-action effects the correct form for such dispersion relations is nondegenerate, i.e. it is necessary to use multiple frequency arguments. Nonlinear dispersion relations have been shown to be very useful as they usually only require integration over a limited frequency range (corresponding to frequencies at which the absorption changes), unlike the conventional linear Kramers-Kronig relation which requires integration over all absorbing frequencies. Furthermore, calculation of refractive index changes using dispersion relations is easier than a direct calculation of the susceptibility, as transition rates (which give absorption coefficients) are, in general, far easier to calculate than the expectation value of the optical polarization. Both resonant (generation of some excitation that is long lived compared with an optical period) and nonresonant ‘instantaneous’ optical nonlinearities are discussed, and it is shown that the nonlinear dispersion relation has a common form and can be understood in terms of the linear Kramers-Kronig relation applied to a new system consisting of the material plus some ‘perturbation’. We present several examples of the form of this external perturbation, which can be viewed as the pump in a pump-probe experiment. We discuss the two-level saturated atom model and bandfilling in semiconductors among others for the resonant case. For the nonresonant case some recent work is included where the electronic nonlinear refractive coefficient,n2, is determined from the nonlinear absorption processes of two-photon absorption, Raman transitions and the a.c. Stark effect. We also review how the dispersion relations can be extended to give alternative forms for frequency summation which, for example, allows the real and imaginary parts ofχ(2) to be related.

Spin-orbit interaction of a photon in an inhomogeneous medium

Abstract: As light propagates in an optically inhomogeneous medium, bending and twisting of the beam cause the rotation of the polarization plane. This is the well-known Rytov-Vladimirsky effect or Berry phase. Considering this effect as the result of an interaction between the spin of the photon (polarization) and its orbital motion, one can expect the reverse effect. In fact, the additional angular shift of a trajectory of the circularly polarized beam (CPB) was recently studied for the particular case of an optical fiber. In this paper the spin-orbit interaction Hamiltonian is obtained both in geometrical optics and in wave optics. We have calculated also the effect of the transverse shift of CPB under refraction on the boundary of two media. The expressions for the angular shift of a trajectory of CPB in optical fibers with two types of refractive-index profiles have been obtained. Geometrical optics expressions can be applied for the typical waveguides only at lengths less than 0.05 cm. However, using the geometric optical picture we can successfully describe statistical properties of speckle patterns of laser radiation as it propagates at a considerable distance.

Use of polarized light to discriminate short-path photons in a multiply scattering medium

Abstract: We describe a method for discriminating short- and long-path photons transmitted through a multiply scattering medium that is based on the relationship between the polarization states of the incident and forward-scattered light. Results of Monte Carlo simulations and experiments show that if the scattering anisotropy of the scatterers is sufficiently small, absorbing barriers embedded in optically dense suspensions of polystyrene spheres can be resolved with good contrast by selectively detecting a component of the scattered-light intensity that has preserved its incident circular polarization state.The principles of operation of a polarization-modulation system capable of measuring small polarization fractions are explained. Using this system we were able to measure polarized light in a depolarized background over 1000 times as large.

Nonlinear optical properties of fullerenes and charge-transfer complexes of fullerenes

Abstract: The authors present results on the second- and third-order nonlinear optical properties of fullerenes and some of their derivatives. This is part of their effort to study general nonlinear properties of clusters. Polarizability measurements in fullerenes and in N,N-diethylaniline charge transfer complexes are reported.

Noninvasive optical polarimetric glucose sensing using a true phase measurement technique

Abstract: The development and testing of a noninvasive true phase optical polarimetry sensing system to monitor in vivo glucose concentrations is described. To demonstrate the applicability of this optical sensor for glucose movement, the authors calibrate the system and then test it in vitro using both a glass test cell filled with glucose solution in the physiologic range, with a path length of 0.9 cm to approximate the 1-cm path length present in the anterior chamber of the eye, and then on an excised human eye. The technique used helium neon laser light which was coupled through a rotating linear polarizer along with two stationary linear polarizers and two detectors to produce reference and signal outputs whose amplitudes varied sinusoidally with a frequency of twice the angular velocity of the rotating polarizer, and whose phase was proportional to the rotation of the linear polarization vector passing through the glucose solution. >

Improved second-harmonic generation from Langmuir-Blodgett films of hemicyanine dyes

Abstract: THE phenomenon of second-harmonic generation (SHG), whereby a material under illumination generates light at twice the incident frequency, is finding increasing use in optical signal processing. The principal requirement for SHG is a non-centrosymmetric structure; in organic materials, this can be achieved through the use of Langmuir–Blodgett films, which offer control of structure at the molecular level. SHG has been demonstrated in films composed of hemicyanine dyes of the general formula D—C6H4— CH=CH—C5H4N+— RX-, where D is an electron donor, R is usually a hydrophobic alkyl chain and X- is a counterion such as Br- or I-. The frequency-doubling properties of these films are sensitive to the choice of donor group1,2 the extent of molecular aggregation3,4and the type of packing5–7 Mixed films, in which the dye molecules are interspersed with an inert phase, have been used to reduce aggregation and consequently enhance SHG3,8, but these films have the potential disadvantage of phase separation. Here we show that the use of an amphiphilic anion as both counterion and spacer molecule gives rise to an ordered segregation of the hemicyanine chromophores, and greatly enhanced SHG.

A survey for high optical polarization in quasars with core-dominant radio structure : is there a beamed optical continuum ?

Abstract: 129 new optical linear polarization measurements of 84 quasars (defined as starlike on Sky Survey prints) are presented. 23 new highly polarized objects (p > 3%) were discovered, of which 14 are known to have broad emission lines. This represents a significant increase in the numbers of these objects that were known. With the addition of data from the literature, our measurements constitute well-defined samples of flat-spectrum core-dominant radio quasars brighter than about 18 mag, one selected from the list published by Perley (1982, AJ, 87), and another from that by Kuhr et al. (1981)

Fabrication of GaAs quantum wires on epitaxially grown V grooves by metal‐organic chemical‐vapor deposition

Abstract: Successful fabrication of thin GaAs quantum wires (120–200 A)×(200–300 A) by a novel metal‐organic chemical‐vapor‐deposition growth technique is reported. The GaAs quantum wires were grown on a V groove formed by two GaAs triangular prisms which were selectively grown on SiO2 masked substrates. The V groove has a very sharp corner at the bottom, which results in reduction of the effective width of the quantum wire structures. The measurement of photoluminescence and photoluminescence excitation spectra with polarization dependence indicate the existence of the quantized state in the quantum wires.

Angle measurement based on the internal-reflection effect: a new method

Abstract: We describe a new method of angle measurement that is based on the internal-reflection effect at an air-glass boundary. The method uses a differential detection scheme to largely reduce the inherent nonlinearity of the reflectance versus the angle of incidence in internal reflection. With nonlinearity reduced, the displacement of the angle of incidence can be determined accurately by measuring the reflectance. The resolution and measurement range are determined by the initial angle of incidence, the polarization state of the light, and the number of reflections. Compared with interferometers and autocollimators, this method has the advantage of a simple sensor design for applications ranging from a wide measurement range to extremely high resolution. Other advantages are compact size, simple structure, and low cost. A theoretical analysis of the method and some experimental results of a prototype sensor are presented. The possible applications of the method are also discussed.

Antiphase dynamics and polarization effects in the Nd-doped fiber laser.

Abstract: The response of an Nd-doped optical fiber laser to modulation of the pump power reveals that the polarization of the laser light plays an important role in the linear and nonlinear dynamics of this laser. Experiments have been carried out under pulsed or sinusoidal modulation of the pump power as well as in the continuous-wave regime. Most of the observed phenomena may be interpreted in the framework of a theory of the two-mode laser in which each mode is associated with one polarization eigenstate of the laser. Effects such as the appearance of slow modes and antiphase behavior have also been observed. A model of a two-mode laser including spontaneous emission is theoretically and numerically analyzed. It reproduces well most of the experimental findings.

Dispersion and radiation loss characteristics of antiresonant reflecting optical waveguides-numerical results and analytical expressions

Abstract: Propagation characteristics of novel single-mode slab waveguides, ARROW (antiresonant reflecting optical waveguides), ARROW-B, and their modified configurations, are investigated. The dispersion and radiation loss characteristics, field profile, confinement factor, and spot size of these ARROW-type waveguides are analyzed in detail by a mode analysis method using the system interference matrix. Approximate expressions for these characteristics are obtained in simple forms, which provide useful suggestions for the design of these waveguides. Possible combinations of materials and design conditions of ARROW-type waveguides are discussed on the basis of these results. >

Critical analysis of the empirical tests of local hidden-variable theories

Abstract: A local hidden-variable model is exhibited for the experiments by Aspect, Grangier, and Roger [Phys. Rev. Lett. 47, 460 (1981); 49, 91 (1982)] and Aspect, Dalibard, and Roger [Phys. Rev. Lett. 49, 1804 (1982)] measuring polarization correlation of optical-photon pairs. The model agrees with quantum-mechanical predictions for all measurable quantities even with ideal polarizers and detectors, and emphasizes the need of a high degree of directional correlation, besides the correlation of spin (or polarization or other quantities), in any test of locality. It is proved that homogeneous inequalities, involving only coincidence detection rates, cannot discriminate between quantum mechanics and local theories, which invalidates all previously used empirical tests. The role of supplementary assumptions, like the so-called no enhancement, for the derivation of Bell's inequalities is discussed. Finally it is conjectured that quantum mechanics might be compatible with local realism, if we assume that not all self-adjoint operators represent observables and not all density operators represent states.

Photoinduced birefringence in optical fibers: a comparative study of low-birefringence and high-birefringence fibers.

Abstract: A study of photoinduced birefringence in bow-tie (stress-induced) high-birefringence (Hi-Bi) and low-birefringence (Lo-Bi) germanosilicate optical fibers is conducted by using 532-nm light. The study reveals that Hi-Bi fibers are insensitive to light polarized along the fast axis, in contrast to Lo-Bi fibers, which are photosensitive along both axes. The induced birefringence in Lo-Bi fibers is reversible, whereas the change in Hi-Bi fibers is permanent. The sign of the induced birefringence is established experimentally for the first time to our knowledge, and the significance of the results to models based on stress and/or glass defects is briefly discussed.

Deterministic, analytically complete measurement of polarization-dependent transmission through optical devices

Abstract: Polarization dependence of the loss or gain of an optical device has been difficult to measure in a consistent and reproducible manner because it has been necessary to search for the extrema of transmission over a two-dimensional polarization space. It is shown that the global variation of the transmission through any linear, time-invariant optical device, over all states of polarization, can be found in a strictly deterministic, analytically complete manner by measuring the polarization responses to only three input polarizations. A series of fast, automated measurements of two test devices yielded standard deviations of 0.017 and 0.033 dB and agreement with manual measurements. >

High-spatial-frequency binary and multilevel stairstep gratings: polarization-selective mirrors and broadband antireflection surfaces.

Abstract: High-spatial-frequency, surface-relief binary gratings have been shown to have diffraction properties that are similar to homogeneous layers of equivalent refractive indices, which depend on the grating characteristics, angle of incidence, and polarization. Thus these gratings in the long-wavelength limit could be used as equivalent thin-film coatings. Because of their polarization discrimination these gratings can function as polarization-selective mirrors. A procedure for designing these gratings to be antireflective for one polarization (TE or TM) and to maximize their reflectivity for the orthogonal polarization (TM or TE) is presented. Multilevel stairstep gratings can similarly exhibit characteristics that resemble those of multilayer antireflection coatings (quarter-wave impedance transformers), thus permitting a broader wavelength bandpass. A systematic procedure for designing multilevel stairstepgratings to operate as multilayer thin-film antireflection surfaces is presented. These design methods are valid for both TE and TM polarizations and for any angle of incidence. Example designs are presented, and the rigorous coupled-wave diffraction analysis is used to evaluate the performance of these gratings as functions of the ratio of their period to the incident wavelength. Comparisons are included with homogeneous layers that are equivalent to the gratings in the long-wavelength limit.

Single-polarisation fibre amplifier

Abstract: A novel single-polarisation fibre amplifier design is presented. The use of a Faraday mirror in a double-pass design yields optical gain with high efficiency, without spatial hole burning and independent of gain-fibre birefringence. An amplifier, tunable polarised laser, and a high-power polarised super-fluorescent source are demonstrated.

On the Deterministic and Non-deterministic Mueller Matrix

Abstract: The Mueller matrices of the passive systems are investigated. If a system is deterministic, the corresponding Mueller matrix can be decomposed as a product of two special matrices, one of which preserves the polarization degree of the input light, and the other has its internal structure determined by certain characteristic quantities. We found that the mapping nature of a deterministic system may be described by these characteristic quantities. To study the non-deterministic system, we propose a diagonalization procedure that involves deterministic Mueller matrices. The result of its application to certain experimentally measured Mueller matrices clearly shows that there must be some fundamental restrictions on the validity of the Stokes-Mueller calculus.

The structure of magnetic fields in dark clouds: Infrared polarimetry in B216-217

Abstract: A near-infrared polarization map of background starlight seen through the B216-217 dark cloud in Taurus is presented. The mean direction and dispersion in direction of the polarization vectors observed in the near-infrared are indistinguishable from the direction and dispersion of optical polarization vectors around the periphery of the dark cloud. Measurements of J- and K-magnitudes of the stars observed in the near-infrared imply a range of extinctions 1 ≤ A V ≤ 10 mag, while the mean A V for the stars whose polarization has been measured optically is ≤1 mag

Polarimetry and spectrophotometry of the QSO IRAS 13349 + 2438 and the unification of active galaxies

Abstract: We have made new observations of the bright (V=14.7) infrared-selected QSO IRAS 13349+2438 (Beichman et al.), which provide important clues about the structure of the inner few parsecs of active galactic nuclei (AGNs). The principal observational facts are as follows: 1. There is high linear optical polarization, increasing with decreasing wavelength from 1.4% at 2.2 μm (K-band) to 8% at 0.36 μm (U-band). 2. The position angle of polarization is independent of wavelength in the optical region and is aligned with the direction of elongation of the r-band optical image, presumably the major axis of the host galaxy

Optical polarization division multiplexing at 4 Gb/s

Abstract: An optical polarization multiplexing system using BPSK coherent heterodyne detection to transmit 4 Gb/s over a 45-km standard single-mode fiber optical link at a receiver sensitivity of -35 dBm is described. The 4-Gb/s system has a potential receiver sensitivity of -40 dBm while using 2-Gb/s baseband electronics. >

Ultrafast polarisation-independent all-optical switching using a polarisation diversity scheme in the nonlinear optical loop mirror

Abstract: Polarisation-independent 32 to 8 Gbit/s demultiplexing in the nonlinear optical loop mirror is successfully demonstrated using a novel polarisation diversity scheme in which two independent switching operations are performed along the two principal axes of a polarisation-maintaining fibre loop. The variation of the switched signal powers is measured to be less than 1 dB as the input polarisation direction is varied over 180°.

Adiabatic 3-dB couplers, filters, and multiplexers made with silica waveguides on silicon

Abstract: The performance of adiabatic 3-dB couplers and V-branches is reported. These devices are broadband and divide power equally. They have no observable polarization dependence. Typical excess losses relative to a straight waveguide is 0.1-0.2 dB for the 3-dB couplers and about 0.4 dB for the V-branches. Fiber to fiber insertion loss of 0.31 dB was measured for a 2.5-cm straight waveguide. The devices were used to fabricate transmission filters peaked at 1.55 mu m and power combiners having two channels at 1.48 and 1.55 mu m. The device fabrication was improved by use of a flowable top cladding layer containing boron and phosphorous which easily filled-in between closely spaced waveguides. >

Method and apparatus for measuring polarization mode dispersion in optical devices

Abstract: An instrument includes a polarized optical source for producing three sequential predetermined states of polarization of a light beam at each of at least two wavelengths, as well as an optical polarization meter for measuring the polarization of a portion of the light beam at each wavelength transmitted by or reflected from an optical network by splitting it into four beams, passing three of the beams through optical elements, measuring the transmitted intensity of all four beams, and calculating Stokes parameters. The three sequential predetermined states of polarization at each wavelength yield three corresponding Jones input vectors at each wavelength, and the Stokes parameters for the responses of the optical network are converted to three Jones output vectors at each wavelength. A Jones matrix for the optical network to within a complex constant is then computed from the Jones input and output vectors at each wavelength. Polarization mode dispersion in the optical network is determined from these matrices.

The first spectropolarimetric study of the wavelength dependence of interstellar polarization in the ultraviolet

Abstract: The first UV spectropolarimetry along six lines of sight with significant interstellar polarization is reported The observations were obtained with the Wisconsin Ultraviolet Photo-Polarimeter Experiment (WUPPE) during the Astro-1 mission HD 37903, HD 62542 and HD 99264 show a wavelength dependence which follows the Serkowski relation extrapolated into the UV HD 25443 and Alpha Cam have UV polarization well in excess of the Serkowski extrapolation HD 197770 clearly shows a polarization bump which closely matches the 2175 A extinction feature This bump polarization can be fitted by small aligned graphite disks The differences along various lines of sight might be the result of differences in the environments which affect the size and alignment of the grains

The optical polarizations of high- and intermediate-redshift radio galaxies

Abstract: Optical polarization measurements are presented for 12 high- and intermediate-redshift radio galaxies (0.2 0.5 objects with good polarization measurements have their integrated light polarized at the 5-20 per cent level. This result, and the fact that the polarization is frequently oriented perpendicular to the radio axis, suggests that a large fraction of the UV continuum has been scattered out of radiation beams from the AGN by dust or electrons in the high-redshift host galaxies. In contrast, it is found that none of the intermediate-redshift (0.2 5 per cent level

Shaping of clean, femtosecond pulses at 1.053 μm for chirped-pulse amplification

Abstract: We report the generation of 200-fs optical pulses at 1.053 μm using two stages of fiber-grating compressors. The usual intensity background associated with this compression technique has been reduced to less than 10−7 of the peak intensity by using nonlinear birefringence in the second fiber. These pulses are used at the front end of our chirped-pulse amplification terawatt Nd:glass laser system.