Experimental and theoretical study of the in- fiber twist sensor based on quasi-fan Solc structure filter.

PubMed

Sun, Chunran; Wang, Muguang; Jian, Shuisheng

2017-08-21

In this paper, a novel quasi-fan Solc structure filter based on elliptical-core spun fiber for twist sensing has been experimentally investigated and theoretically analyzed. The discrete model of spun fiber has been built to analyze the transmission characteristics of proposed sensor. Both experimental and simulated results indicate that the extinction ratio of the comb spectrum based on quasi-fan Solc birefringent fiber filter varies with twist angle and agrees well with each other. Based on the intensity modulation, the proposed twist sensor exhibits a high sensitivity of 0.02219 dB/(°/m). Moreover, thanks to the invariability of the fiber birefringence and the state of polarization of the input light, the proposed twist sensor has a very low temperature and strain sensitivity, which can avoid the cross-sensitivity problem existing in most twist sensors.

Stokes parameters modulator for birefringent filters

NASA Technical Reports Server (NTRS)

Dollfus, A.

1985-01-01

The Solar Birefringent Filter (Filter Polarisiant Solaire Selectif FPSS) of Meudon Observatory is presently located at the focus of a solar refractor with a 28 cm lens directly pointed at the Sun. It produces a diffraction limited image without instrumental polarization and with a spectral resolution of 46,000 in a field of 6 arc min. diameter. The instrument is calibrated for absolute Doppler velocity measurements and is presently used for quantitative imagery of the radial velocity motions in the photosphere. The short period oscillations are recorded. Work of adapting the instrument for the imagery of the solar surface in the Stokes parameters is discussed. The first polarizer of the birefringent filter, with a reference position angle 0 deg, is associated with a fixed quarter wave plate at +45 deg. A rotating quarter wave plate is set at 0 deg and can be turned by incremented steps of exactly +45 deg. Another quarter wave plate also initially set at 0 deg is simultaneously incremented by -45 deg but only on each even step of the first plate. A complete cycle of increments produces images for each of the 6 parameters I + or - Q, I + or - U and I + or - V. These images are then subtracted by pairs to produce a full image in the three Stokes parameters Q, U and V. With proper retardation tolerance and positioning accuracy of the quarter wave plates, the cross talk between the Stokes parameters was calculated and checked to be minimal.

Liquid crystal photonic bandgap fiber components

NASA Astrophysics Data System (ADS)

Scolari, L.; Alkeskjold, T. T.; Noordegraaf, D.; Tartarini, G.; Bassi, P.; Bjarklev, A.

2007-11-01

Liquid crystal photonic bandgap fibers represent a promising platform for the design of all-in-fiber optical devices, which show a high degree of tunability and exhibit novel optical properties for the manipulation of guided light. In this review paper we present tunable fiber devices for spectral filtering, such as Gaussian filters and notch filters, and devices for polarization control and analysis, such as birefringence control devices and switchable and rotatable polarizers.

Highly efficient all-fiber tunable polarization filter using torsional acoustic wave.

PubMed

Lee, Kwang Jo; Park, Hyun Chul; Kim, Byoung Yoon

2007-09-17

We demonstrate an all-fiber tunable polarization filter with high coupling efficiency based on acousto-optic coupling between two optical polarization modes of the LP(01) mode propagating in a highly birefringent single mode optical fiber. An over-coupling between the two polarization modes is realized over the wavelength range from 1530 nm to 1610 nm using traveling torsional acoustic wave. The measured 3-dB optical bandwidth of the filter was 4.8 nm at the wavelength around 1550 nm. The details of the filter transmission and the coupling characteristics are discussed.

Design and realization of the control system for the three-channel birefringent filter

NASA Astrophysics Data System (ADS)

Zhu, Dan

2008-07-01

Space Solar Telescope is one of the large-scale scientific programs under development in China. In it, an important part is the filter, a birefringent filter with three-channels. It consists of 17 rotatable wave plates. In coordination with other mechanical and optical components, complicated and precise adjustments of their attitudes are necessary, which requests a high-accuracy control system to ensure their concertedness. The paper describes the design and realization of the control system. It mainly has a hardware plate and a software one. The former uses an industrial controller, a control card and step motors, while the latter uses the technique construction of the object oriented. That is modularization design with lengthwise dividing as per functions and breadthwise dividing as per element layers. Shift arithmetic for whole spectrum in programs is for intelligent spectral scanning. At the same time, the control information is roundly recorded in the data base of the system. Tests show that the system is characterized by high precision, good stabilization, high data safety and user-friendly interface, totally meeting the design requirements. Also discussed in this paper is some new conceivability to realize the handiness and miniaturization of the filter to fit the use in space flight in the future.

Tunable Optical Filters for Space Exploration

NASA Technical Reports Server (NTRS)

Crandall, Charles; Clark, Natalie; Davis, Patricia P.

2007-01-01

Spectrally tunable liquid crystal filters provide numerous advantages and several challenges in space applications. We discuss the tradeoffs in design elements for tunable liquid crystal birefringent filters with special consideration required for space exploration applications. In this paper we present a summary of our development of tunable filters for NASA space exploration. In particular we discuss the application of tunable liquid crystals in guidance navigation and control in space exploration programs. We present a summary of design considerations for improving speed, field of view, transmission of liquid crystal tunable filters for space exploration. In conclusion, the current state of the art of several NASA LaRC assembled filters is presented and their performance compared to the predicted spectra using our PolarTools modeling software.

Study of the spectral bandwidth of a double-pass acousto-optic system [Invited].

PubMed

Champagne, Justine; Kastelik, Jean-Claude; Dupont, Samuel; Gazalet, Joseph

2018-04-01

Acousto-optic tunable filters are known as efficient instruments for spectral and spatial filtering of light. In this paper, we analyze the bandwidth dependence of a double-pass filter. The interaction geometry chosen allows the simultaneous diffraction of the ordinary and the extraordinary optical modes by a single ultrasonic frequency. We present the main parameters of a custom device (design, optical range, driving frequency) and experimental results concerning the angular deviation of the beams including the effect of optical birefringence. The spectral resolution and the side lobes' significance are discussed. Spectral bandwidth of such a system is analyzed.

Collisions and Trapping of Time Delayed Solitons in Optical Waveguides with Orthogonally Polarized Modes

NASA Astrophysics Data System (ADS)

Zhou, Huan; Li, Jin-Hua; Chow, Kwok-Wing; Xiao, Shao-Rong; Sun, Ting-Ting

2017-04-01

The interactions and collisions of time delayed solitons in optical waveguides with orthogonally polarized modes are studied. Direct numerical simulations of the coherently coupled nonlinear Schrödinger equations are performed, and neither the high birefringence nor the low birefringence approximations are invoked. Trapping of solitary pulses occurs when the birefringence parameter is small or the four-wave mixing parameter is large. The distance before the first collision depends strongly on the initial separation of the two solitary pulses. Variational techniques are employed to calculate this distance, and results agree with those from the full simulations very well. Supported by the National Natural Science Foundation of China under Grant Nos. 11605090 and 11447113, Natural Science Foundation of Jiangsu Provincial Universities under Grant No. 14KJB140009 and the startup Foundation for Introducing Talent of Nanjing University of Information Science and Technology under Grant No. 2241131301064

Optofluidic-Tunable Color Filters And Spectroscopy Based On Liquid-Crystal Microflows

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cuennet, J. G.; Vasdekis, Andreas E.; Psaltis, D.

The integration of color filters with microfluidics has attracted substantial attention in recent years, for on-chip absorption, fluorescence, or Raman analysis. We describe such tunable filters based on the micro-flow of liquid crystals. The filter operation is based on the wavelength dependent liquid crystal birefringence that can be tuned by modifying the flow velocity field in the microchannel. The latter is possible both temporally and spatially by varying the inlet pressure and the channel geometry respectively. We explored the use of these optofluidic filters for on-chip absorption spectroscopy; by integrating the distance dependent color filter with a dye-filled micro-channel, themore » absorption spectrum of a dye could be measured. Liquid crystal microflows simplify substantially the optofluidic integration, actuation and tuning of color filters for lab-on-a-chip spectroscopic applications.« less

Spectral manipulation and complementary spectra with birefringence polarization control

NASA Astrophysics Data System (ADS)

Ding, Pan-Feng; Han, Pin

2017-03-01

A polarization control method using crystal birefringence is suggested to manipulate polychromatic light. This scheme can be used with narrower bandwidth to produce various spectral effects, such as a notch filter, a flat top, and triangle-type, nipple-type, and central-frequency-dominant distributions. A modulated spectrum with greater bandwidth can be used as an optical frequency ruler, and phenomena called complementary spectra are also proposed, where the two spectral distributions, produced by rotating the polarizer, complement each other in the sense that the peaks and valleys in one spectrum are the reverse in the other. These results benefit the controlling of the spectral shape and the measurement of an unknown optical frequency.

Survey of Hyperspectral and Multispectral Imaging Technologies (Etude sur les technologies d’imagerie hyperspectrale et multispectrale)

DTIC Science & Technology

2007-05-01

but relatively low acoustic figure of merit (the ability to couple acoustic wave to the crystal). In the infrared region TeO2 crystal (0.35 – 5.0 µm...filter. More in particular, it is based on a Lyot filter, which is a sandwich of birefringent liquid crystal, glass , quartz placed between two...variable retardance element in the sandwich composed of quartz, glass , polarizers and liquid crystal itself. To achieve the desired wavelength

Polarization-independent fiber filter with an all-polarization-maintaining fiber loop for tunable fiber lasers

NASA Astrophysics Data System (ADS)

Zhang, Jun; Wu, Weiran; Rao, Qi; Zhou, Kejiang

2018-05-01

Tunable fiber lasers are a promising light source in all-optical wavelength conversion, fiber grating sensing and optical add-drop multiplexing. In order to achieve a tunable wavelength in the output, optical filters are indispensable for the construction of tunable fiber lasers. Recently, much attention has been given to developing high-performance filters. This paper proposes an environment-insensitive filter based on a Sagnac interferometer which was designed by an all-polarization-maintaining fiber with linear birefringence. According to the Sagnac interferometer, we derived the transfer function of an environment-insensitive filter. Based on this principle, it is shown that the device is able to implement a precision filtering function that can be used in a fiber laser’s optical resonant cavity. The experiment results demonstrated the effectiveness of this structure.

Ultra-wideband microwave photonic filter with a high Q-factor using a semiconductor optical amplifier.

PubMed

Chen, Han

2017-04-01

An ultra-wideband microwave photonic filter (MPF) with a high quality (Q)-factor based on the birefringence effects in a semiconductor optical amplifier (SOA) is presented, and the theoretical fundamentals of the design are explained. The proposed MPF along orthogonal polarization in an active loop operates at up to a Ku-band and provides a tunable free spectral range from 15.44 to 19.44 GHz by controlling the SOA injection current. A prototype of the equivalent second-order infinite impulse response filter with a Q-factor over 6300 and a rejection ration exceeding 41 dB is experimentally demonstrated.

Investigation of active regions at high resolution by balloon flights of the Solar Optical Universal Polarimeter (SOUP)

NASA Technical Reports Server (NTRS)

Tarbell, T.; Frank, Z.; Gilbreth, C.; Shine, R.; Title, A.; Topka, K.; Wolfson, J.

1989-01-01

SOUP is a versatile, visible-light solar observatory, built for space or balloon flight. It is designed to study magnetic and velocity fields in the solar atmosphere with high spatial resolution and temporal uniformity, which cannot be achieved from the surface of the earth. The SOUP investigation is carried out by the Lockheed Palo Alto Research Laboratory, under contract to NASA's Marshall Space Flight Center. Co-investigators include staff members at a dozen observatories and universities in the U.S. and Europe. The primary objectives of the SOUP experiment are: to measure vector magnetic and velocity fields in the solar atmosphere with much better spatial resolution than can be achieved from the ground; to study the physical processes that store magnetic energy in active regions and the conditions that trigger its release; and to understand how magnetic flux emerges, evolves, combines, and disappears on spatial scales of 400 to 100,000 km. SOUP is designed to study intensity, magnetic, and velocity fields in the photosphere and low chromosphere with 0.5 arcsec resolution, free of atmospheric disturbances. The instrument includes: a 30 cm Cassegrain telescope; an active mirror for image stabilization; broadband film and TV cameras; a birefringent filter, tunable over 5100 to 6600 A with 0.05 A bandpass; a 35 mm film camera and a digital CCD camera behind the filter; and a high-speed digital image processor.

Investigation of active regions at high resolution by balloon flights of the Solar Optical Universal Polarimeter (SOUP)

NASA Astrophysics Data System (ADS)

Tarbell, T.; Frank, Z.; Gilbreth, C.; Shine, R.; Title, A.; Topka, K.; Wolfson, J.

SOUP is a versatile, visible-light solar observatory, built for space or balloon flight. It is designed to study magnetic and velocity fields in the solar atmosphere with high spatial resolution and temporal uniformity, which cannot be achieved from the surface of the earth. The SOUP investigation is carried out by the Lockheed Palo Alto Research Laboratory, under contract to NASA's Marshall Space Flight Center. Co-investigators include staff members at a dozen observatories and universities in the U.S. and Europe. The primary objectives of the SOUP experiment are: to measure vector magnetic and velocity fields in the solar atmosphere with much better spatial resolution than can be achieved from the ground; to study the physical processes that store magnetic energy in active regions and the conditions that trigger its release; and to understand how magnetic flux emerges, evolves, combines, and disappears on spatial scales of 400 to 100,000 km. SOUP is designed to study intensity, magnetic, and velocity fields in the photosphere and low chromosphere with 0.5 arcsec resolution, free of atmospheric disturbances. The instrument includes: a 30 cm Cassegrain telescope; an active mirror for image stabilization; broadband film and TV cameras; a birefringent filter, tunable over 5100 to 6600 A with 0.05 A bandpass; a 35 mm film camera and a digital CCD camera behind the filter; and a high-speed digital image processor.

Eternal 5D optical data storage in glass (Conference Presentation)

NASA Astrophysics Data System (ADS)

Kazansky, Peter G.; Cerkauskaite, Ausra; Drevinskas, Rokas; Zhang, Jingyu

2016-09-01

A decade ago it has been discovered that during femtosecond laser writing self-organized subwavelength structures with record small features of 20 nm, could be created in the volume of silica glass. On the macroscopic scale the self-assembled nanostructure behaves as a uniaxial optical crystal with negative birefringence. The optical anisotropy, which results from the alignment of nano-platelets, referred to as form birefringence, is of the same order of magnitude as positive birefringence in crystalline quartz. The two independent parameters describing birefringence, the slow axis orientation (4th dimension) and the strength of retardance (5th dimension), are explored for the optical encoding of information in addition to three spatial coordinates. The slow axis orientation and the retardance are independently manipulated by the polarization and intensity of the femtosecond laser beam. The data optically encoded into five dimensions is successfully retrieved by quantitative birefringence measurements. The storage allows unprecedented parameters including hundreds of terabytes per disc data capacity and thermal stability up to 1000°. Even at elevated temperatures of 160oC, the extrapolated decay time of nanogratings is comparable with the age of the Universe - 13.8 billion years. The recording of the digital documents, which will survive the human race, including the eternal copies of Universal Declaration of Human Rights, Newton's Opticks, Kings James Bible and Magna Carta, is a vital step towards an eternal archive. Additionally, a number of projects (such as Time Capsule to Mars, MoonMail, and the Google Lunar XPRIZE) could benefit from the technique's extreme durability, which fulfills a crucial requirement for storage on the Moon or Mars.

High-speed tunable microwave photonic notch filter based on phase modulator incorporated Lyot filter.

PubMed

Ge, Jia; Feng, Hanlin; Scott, Guy; Fok, Mable P

2015-01-01

A high-speed tunable microwave photonic notch filter with ultrahigh rejection ratio is presented, which is achieved by semiconductor optical amplifier (SOA)-based single-sideband modulation and optical spectral filtering with a phase modulator-incorporated Lyot (PM-Lyot) filter. By varying the birefringence of the phase modulator through electro-optic effect, electrically tuning of the microwave photonic notch filter is experimentally achieved at tens of gigahertz speed. The use of SOA-polarizer based single-sideband modulation scheme provides good sideband suppression over a wide frequency range, resulting in an ultrahigh rejection ratio of the microwave photonic notch filter. Stable filter spectrum with bandstop rejection ratio over 60 dB is observed over a frequency tuning range from 1.8 to 10 GHz. Compare with standard interferometric notch filter, narrower bandwidth and sharper notch profile are achieved with the unique PM-Lyot filter, resulting in better filter selectivity. Moreover, bandwidth tuning is also achieved through polarization adjustment inside the PM-Lyot filter, that the 10-dB filter bandwidth is tuned from 0.81 to 1.85 GHz.

Sidelobe suppression in all-fiber acousto-optic tunable filter using torsional acoustic wave.

PubMed

Lee, Kwang Jo; Hwang, In-Kag; Park, Hyun Chul; Kim, Byoung Yoon

2010-06-07

We propose two techniques to suppress intrinsic sidelobe spectra in all-fiber acousto-optic tunable filter using torsional acoustic wave. The techniques are based on either double-pass filter configuration or axial tailoring of mode coupling strength along an acousto-optic interaction region in a highly birefringent optical fiber. The sidelobe peak in the filter spectrum is experimentally suppressed from -8.3 dB to -16.4 dB by employing double-pass configuration. Axial modulation of acousto-optic coupling strength is proposed using axial variation of the fiber diameter, and the simulation results show that the maximum side peak of -9.3 dB can be reduced to -22.2dB. We also discuss the possibility of further spectral shaping of the filter based on the axial tailoring of acousto-optic coupling strength.

Liquid-crystal-based tunable plasmonic waveguide filters

NASA Astrophysics Data System (ADS)

Yin, Shengtao; Liu, Yan Jun; Xiao, Dong; He, Huilin; Luo, Dan; Jiang, Shouzhen; Dai, Haitao; Ji, Wei; Sun, Xiao Wei

2018-06-01

We propose a liquid-crystal-based tunable plasmonic waveguide filter and numerically investigate its filtering properties. The filter consists of a metal-insulator-metal waveguide with a nanocavity resonator. By filling the nanocavity with birefringent liquid crystals (LCs), we could then vary the effective refractive index of the nanocavity by controlling the alignment of the LC molecules, hence making the filter tunable. The tunable filtering properties are further analyzed in details via the temporal coupled mode theory (CMT) and the finite-difference time-domain (FDTD) method. The simulation results show that the resonant wavelengths have linear redshift as the refractive index of the nanocavity increases and the coupling efficiency is more than 65% without considering the internal loss in the nanocavity and waveguides. These achieved results by the FDTD simulations can be also accurately analyzed by CMT. The compact design of our proposed plasmonic filters is especially favorable for integration, and such filters could find many important potential applications in high-density plasmonic integration circuits.

Polarization-dependent optics using gauge-field metamaterials

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, Fu; Xiao, Shiyi; Li, Jensen, E-mail: j.li@bham.ac.uk

2015-12-14

We show that effective gauge field for photons with polarization-split dispersion surfaces, being realized using uniaxial metamaterials, can be used for polarization control with unique opportunities. The metamaterials with the proposed gauge field correspond to a special choice of eigenpolarizations on the Poincaré sphere as pseudo-spins, in contrary to those from either conventional birefringent crystals or optical active media. It gives rise to all-angle polarization control and a generic route to manipulate photon trajectories or polarizations in the pseudo-spin domain. As demonstrations, we show beam splitting (birefringent polarizer), all-angle polarization control, unidirectional polarization filter, and interferometer as various polarization controlmore » devices in the pseudo-spin domain. We expect that more polarization-dependent devices can be designed under the same framework.« less

Rocket Spectroheliograph for the Mg II Line at 2802.7 A.

PubMed

Fredga, K

1969-02-01

A rocket-borne spectroheliograph designed to take monochromatic pictures of the sun in the Mg II line at 2802.7 A is described in detail. The photographic system consists of a Questar telescope, a Solc type birefringent filter, and an automatic Robot camera. The double Solc filter has a spectral bandwidth of 3.5 A. The two units in the double filter have been thoroughly tested and are compared with theoretically calculated transmission curves. Two new types of linear film polarizers for the uv region have been tested and used in the filter. A temperature control unit was developed which stabilized the filter temperature in flight to within +/-0.2 degrees C. The instrument has been tested in vacuum and to the Aerobee 150 vibration specifications. It has been flown and successfully recovered three times and performed excellently during each fight.

Generalization of the Lyot filter and its application to snapshot spectral imaging.

PubMed

Gorman, Alistair; Fletcher-Holmes, David William; Harvey, Andrew Robert

2010-03-15

A snapshot multi-spectral imaging technique is described which employs multiple cascaded birefringent interferometers to simultaneously spectrally filter and demultiplex multiple spectral images onto a single detector array. Spectral images are recorded directly without the need for inversion and without rejection of light and so the technique offers the potential for high signal-to-noise ratio. An example of an eight-band multi-spectral movie sequence is presented; we believe this is the first such demonstration of a technique able to record multi-spectral movie sequences without the need for computer reconstruction.

Generation of supercontinuum light in micro-structured fiber and polarization study at different wavelengths

NASA Astrophysics Data System (ADS)

Valle-Atilano, F. J.; Estudillo-Ayala, J. M.; Filoteo-Razo, J. D.; Hernández-García, J. C.; Jáuregui-Vázquez, D.; Sierra-Hernández, J. M.; Rojas-Laguna, R.; Mata-Chavez, R. I.; Samano-Aguilar, L. F.

2016-09-01

In this work, we study the changes of polarization at different wavelengths in a supercontinuum source generated through a microchip laser in the IR spectrum. We use a microchip laser pulsed as pumped source, 1064 nm of wavelength, and a photonic crystal fiber by generated a supercontinuum spectrum. We twist the fiber to the purpose to induce birefringence and study the changes of the state of polarization, and through bandpass filters we observe a single wavelength of the broad spectrum obtained. Besides, ellipticity study for different filters and its relation with the supercontinuum results is discussed.

Filtering and polychromatic vision in mantis shrimps: themes in visible and ultraviolet vision.

PubMed

Cronin, Thomas W; Bok, Michael J; Marshall, N Justin; Caldwell, Roy L

2014-01-01

Stomatopod crustaceans have the most complex and diverse assortment of retinal photoreceptors of any animals, with 16 functional classes. The receptor classes are subdivided into sets responsible for ultraviolet vision, spatial vision, colour vision and polarization vision. Many of these receptor classes are spectrally tuned by filtering pigments located in photoreceptors or overlying optical elements. At visible wavelengths, carotenoproteins or similar substances are packed into vesicles used either as serial, intrarhabdomal filters or lateral filters. A single retina may contain a diversity of these filtering pigments paired with specific photoreceptors, and the pigments used vary between and within species both taxonomically and ecologically. Ultraviolet-filtering pigments in the crystalline cones serve to tune ultraviolet vision in these animals as well, and some ultraviolet receptors themselves act as birefringent filters to enable circular polarization vision. Stomatopods have reached an evolutionary extreme in their use of filter mechanisms to tune photoreception to habitat and behaviour, allowing them to extend the spectral range of their vision both deeper into the ultraviolet and further into the red.

Methods and means of laser polarimetry microscopy of optically anisotropic biological layers

NASA Astrophysics Data System (ADS)

Ushenko, A. G.; Dubolazov, A. V.; Ushenko, V. A.; Ushenko, Yu. A.; Sakhnovskiy, M. Y.; Olar, O. I.

2016-09-01

The results of optical modeling of biological tissues polycrystalline multilayer networks have been presented. Algorithms of reconstruction of parameter distributions were determined that describe the linear and circular birefringence. For the separation of the manifestations of these mechanisms we propose a method of space-frequency filtering. Criteria for differentiation of benign and malignant tissues of the women reproductive sphere were found.

Methods and means of Stokes-polarimetry microscopy of optically anisotropic biological layers

NASA Astrophysics Data System (ADS)

Ushenko, A. G.; Dubolazov, A. V.; Ushenko, V. A.; Ushenko, Yu. A.; Sakhnovskiy, M. Yu.; Sidor, M.; Prydiy, O. G.; Olar, O. I.; Lakusta, I. I.

2016-12-01

The results of optical modeling of biological tissues polycrystalline multilayer networks have been presented. Algorithms of reconstruction of parameter distributions were determined that describe the linear and circular birefringence. For the separation of the manifestations of these mechanisms we propose a method of space-frequency filtering. Criteria for differentiation of benign and malignant tissues of the women reproductive sphere were found.

Demonstration of frequency control and CW diode laser injection control of a titanium-doped sapphire ring laser with no internal optical elements

NASA Technical Reports Server (NTRS)

Bair, Clayton H.; Brockman, Philip; Hess, Robert V.; Modlin, Edward A.

1988-01-01

Theoretical and experimental frequency narrowing studies of a Ti:sapphire ring laser with no intracavity optical elements are reported. Frequency narrowing has been achieved using a birefringent filter between a partially reflecting reverse wave suppressor mirror and the ring cavity output mirror. Results of CW diode laser injection seeding are reported.

A photoelastic-modulator-based motional Stark effect polarimeter for ITER that is insensitive to polarized broadband background reflections.

PubMed

Thorman, A; Michael, C; De Bock, M; Howard, J

2016-07-01

A motional Stark effect polarimeter insensitive to polarized broadband light is proposed. Partially polarized background light is anticipated to be a significant source of systematic error for the ITER polarimeter. The proposed polarimeter is based on the standard dual photoelastic modulator approach, but with the introduction of a birefringent delay plate, it generates a sinusoidal spectral filter instead of the usual narrowband filter. The period of the filter is chosen to match the spacing of the orthogonally polarized Stark effect components, thereby increasing the effective signal level, but resulting in the destructive interference of the broadband polarized light. The theoretical response of the system to an ITER like spectrum is calculated and the broadband polarization tolerance is verified experimentally.

Frequency tuning characteristics of a Q-switched Co:MgF2 laser

NASA Technical Reports Server (NTRS)

Lovold, S.; Moulton, P. F.; Killinger, D. K.; Menyuk, N.

1985-01-01

A tunable Q-switched Co:MgF2 laser has been developed for atmospheric remote sensing applications. Frequency tuning is provided by a quartz etalon and a specially designed three-element birefringent filter covering the whole gain bandwidth of the Co:MgF2 laser. The laser has good temporal and spectral characteristics, with an emission linewidth of approximately 3 GHz (0.1 per cm).

Interrogation cradle and insertable containment fixture for detecting birefringent microcrystals in bile

DOEpatents

Darrow, Chris; Seger, Tino

2003-09-30

A transparent flow channel fluidly communicates a fluid source and a collection reservoir. An interrogating light beam passes through a first polarizer having a first plane of polarization. The flow channel is orthogonal to the light beam. The light beam passes through a fluid sample as it flows through the flow channel, and is then filtered through a second polarizer having a second plane of polarization rotated 90.degree. from the first plane of polarization. An electronic photo-detector is aligned with the light beam, and signals the presence of birefringent microcrystals in the fluid sample by generating voltage pulses. A disposable containment fixture includes the flow channel and the collection reservoir. The fixture is adapted for removable insertion into an interrogation cradle that includes optical and data processing components. The cradle rigidly positions the centerline of the flow channel orthogonal to the light beam.

Detection of birefringent microcrystals in bile

DOEpatents

Darrow, Chris; Mirhej, Andrew; Seger, Tino

2003-09-30

A transparent flow channel fluidly communicates a fluid source and a collection reservoir. A light beam passes through a first polarizer having a first plane of polarization. The flow channel is orthogonal to the light beam. The light beam passes through a fluid sample as it flows through the flow channel. The light beam is then filtered through a second polarizer having a second plane of polarization rotated 90.degree. from the first plane of polarization. The birefringence of certain crystalline materials present in the fluid sample rotates the plane of polarization of the light beam. The presence of these microcrystals thus causes a component of the beam to pass through the second polarizer and impinge an electronic photo-detector located in the path of the beam. The photo-detector signals the presence of the microcrystals by generating voltage pulses. A display device visually presents the quantitative results of the assay.

Quantum storage of heralded polarization qubits in birefringent and anisotropically absorbing materials.

PubMed

Clausen, Christoph; Bussières, Félix; Afzelius, Mikael; Gisin, Nicolas

2012-05-11

Storage of quantum information encoded into heralded single photons is an essential constituent of long-distance quantum communication based on quantum repeaters and of optical quantum information processing. The storage of photonic polarization qubits is, however, difficult because many materials are birefringent and have polarization-dependent absorption. Here we present a simple scheme that eliminates these polarization effects, and we demonstrate it by storing heralded polarization qubits into a solid-state quantum memory. The quantum memory is implemented with a biaxial yttrium orthosilicate (Y2SiO5) crystal doped with rare-earth ions. Heralded single photons generated from a filtered spontaneous parametric down-conversion source are stored, and quantum state tomography of the retrieved polarization state reveals an average fidelity of 97.5±0.4%, which is significantly higher than what is achievable with a measure-and-prepare strategy.

Towards a direct measurement of vacuum magnetic birefringence: PVLAS achievements

NASA Astrophysics Data System (ADS)

Della Valle, F.; Di Domenico, G.; Gastaldi, U.; Milotti, E.; Pengo, R.; Ruoso, G.; Zavattini, G.

2010-11-01

Nonlinear effects in vacuum have been predicted but never observed yet directly. The PVLAS collaboration has long been working on an apparatus aimed at detecting such effects by measuring vacuum magnetic birefringence. Unfortunately the sensitivity has been affected by unaccounted noise and systematics since the beginning. A new small prototype ellipsometer has been designed and characterized at the Department of Physics of the University of Ferrara, Italy entirely mounted on a single seismically isolated optical bench. With a finesse F = 414,000 and a cavity length L = 0.5 m we have reached the sensitivity of ψ=2ṡ101/√{Hz} given the laser power at the output of the ellipsometer of P = 24 mW. This record result, very close to the predicted limit, demonstrates the feasibility of reaching such sensitivities, and opens the way to designing a dedicated apparatus for a first detection of vacuum magnetic birefringence.

Wavelet analysis of polarization maps of the myocardium tissue microscopic images in the diagnosis of the causes of death

NASA Astrophysics Data System (ADS)

Ushenko, V. O.; Boichuk, T. M.; Bachinskiy, V. T.; Vanchuliak, O. Ya.; Minzer, O. P.; Dubolazov, O. V.; Marchuk, Yu. F.; Olar, O. I.

2015-08-01

The results of optical modeling of biological tissues polycrystalline multilayer networks have been presented. Algorithms of reconstruction of parameter distributions were determined that describe the linear and circular birefringence. For the separation of the manifestations of these mechanisms we propose a method of space-frequency filtering. Criteria for differentiation of benign and malignant tissues of the women reproductive sphere were found.

All-optical clock recovery, photonic balancing, and saturated asymmetric filtering for fiber optic communication systems

NASA Astrophysics Data System (ADS)

Parsons, Earl Ryan

In this dissertation I investigated a multi-channel and multi-bit rate all-optical clock recovery device. This device, a birefringent Fabry-Perot resonator, had previously been demonstrated to simultaneously recover the clock signal from 10 wavelength channels operating at 10 Gb/s and one channel at 40 Gb/s. Similar to clock signals recovered from a conventional Fabry-Perot resonator, the clock signal from the birefringent resonator suffers from a bit pattern effect. I investigated this bit pattern effect for birefringent resonators numerically and experimentally and found that the bit pattern effect is less prominent than for clock signals from a conventional Fabry-Perot resonator. I also demonstrated photonic balancing which is an all-optical alternative to electrical balanced detection for phase shift keyed signals. An RZ-DPSK data signal was demodulated using a delay interferometer. The two logically opposite outputs from the delay interferometer then counter-propagated in a saturated SOA. This process created a differential signal which used all the signal power present in two consecutive symbols. I showed that this scheme could provide an optical alternative to electrical balanced detection by reducing the required OSNR by 3 dB. I also show how this method can provide amplitude regeneration to a signal after modulation format conversion. In this case an RZ-DPSK signal was converted to an amplitude modulation signal by the delay interferometer. The resulting amplitude modulated signal is degraded by both the amplitude noise and the phase noise of the original signal. The two logically opposite outputs from the delay interferometer again counter-propagated in a saturated SOA. Through limiting amplification and noise modulation this scheme provided amplitude regeneration and improved the Q-factor of the demodulated signal by 3.5 dB. Finally I investigated how SPM provided by the SOA can provide a method to reduce the in-band noise of a communication signal. The marks, which represented data, experienced a spectral shift due to SPM while the spaces, which consisted of noise, did not. A bandpass filter placed after the SOA then selected the signal and filtered out what was originally in-band noise. The receiver sensitivity was improved by 3 dB.

Full Field Photoelastic Stress Analysis

NASA Technical Reports Server (NTRS)

Lesniak, Jon R. (Inventor)

2000-01-01

A structural specimen coated with or constructed of photoelastic material, when illuminated with circularly polarized light will, when stressed: reflect or transmit elliptically polarized light, the direction of the axes of the ellipse and variation of the elliptically light from illuminating circular light will correspond to and indicate the direction and magnitude of the shear stresses for each illuminated point on the specimen. The principles of this invention allow for several embodiments of stress analyzing apparatus, ranging from those involving multiple rotating optical elements, to those which require no moving parts at all. A simple polariscope may be constructed having two polarizing filters with a single one-quarter waveplate placed between the polarizing filters. Light is projected through the first polarizing filter and the one-quarter waveplate and is reflected from a sub-fringe birefringent coating on a structure under load. Reflected light from the structure is analyzed with a polarizing filter. The two polarizing filters and the one-quarter waveplate may be rotated together or the analyzer alone may be rotated. Computer analysis of the variation in light intensity yields shear stress magnitude and direction.

Effect of waist diameter and twist on tapered asymmetrical dual-core fiber MZI filter.

PubMed

Liu, Yan; Li, Yang; Yan, Xiaojun; Li, Weidong

2015-10-01

A compact in-fiber Mach-Zehnder interferometer (MZI) filter fabricated from custom-designed asymmetrical dual-core fiber is numerically analyzed in detail and experimentally verified. The asymmetrical dual-core fiber has core diameters and a core pitch of 6.9, 6, and 19.9 μm, respectively. The fiber tapering technique is introduced to fuse the originally uncoupled cores into strong coupling tapered regions. The length and diameter of the waist region have a close impact on the splitting ratio, which further affects the spectral properties of the MZI filter. The field evolution with varied waist parameters is characterized by the finite element method and beam propagation method. Repeatable comb filters with ∼15  dB extinction ratio are successfully achieved under the guidance of simulated optimum conditions. The twist-induced circular birefringence gives rise to a retardance that causes the spectral shifts of the MZI filter. The theoretical and experimental results confirm that the relative wavelength shift is proportional to the retardance, which follows a sinc function in the limit of a large twist rate.

High-energy vacuum birefringence and dichroism in an ultrastrong laser field

NASA Astrophysics Data System (ADS)

Meuren, Sebastian; Bragin, Sergey; Keitel, Christoph H.; di Piazza, Antonino

2017-10-01

The interaction between real photons in vacuum is a long-standing prediction of quantum electrodynamics, which has never been observed experimentally. Upcoming 10 PW laser systems like the Extreme Light Infrastructure (ELI) will provide laser pulses with unprecedented intensities. If combined with highly energetic gamma photons - obtainable via Compton backscattering from laser-wakefield accelerated electron beams - the QED critical field becomes accessible. In we have derived how a generally polarized probe photon beam is influenced by both vacuum birefringence and dichroism in a strong linearly polarized plane-wave laser field. We put forward an experimental scheme to measure these effects in the nontrivial high-energy regime, where the QED critical field is reached and the Euler-Heisenberg approximation, valid for low-frequency electromagnetic fields, breaks down. Our results suggest the feasibility of verifying/rejecting the QED prediction for vacuum birefringence/dichroism at the 3 σ confidence level on the time scale of a few days at several upcoming laser facilities. Now at Princeton University, Princeton, NJ.

Electrically tunable infrared filter based on a cascaded liquid-crystal Fabry-Perot for spectral imaging detection.

PubMed

Lin, Jiuning; Tong, Qing; Lei, Yu; Xin, Zhaowei; Wei, Dong; Zhang, Xinyu; Liao, Jing; Wang, Haiwei; Xie, Changsheng

2017-03-01

An electrically tunable infrared (IR) filter based on a key cascaded liquid-crystal Fabry-Perot (C-LC-FP) working in the wavelength range of 3-5 μm is presented. The C-LC-FP is constructed by closely stacking two FP microcavities with different depths of 12 and 15 μm and fully filled by nematic LC materials. Through continuous wavelength selection of both microcavities, radiation with a high transmittance and narrow bandwidth can pass through the filter. According to the electrically controlled birefringence characteristics of nematic LC molecules, the transmission spectrum can be shifted through applying a dual voltage signal over the C-LC-FP. Compared with common LC-FPs with a single microcavity, the C-LC-FP demonstrates better transmittance peak morphology and spectral selection performance. To be more specific, the number and the shifted scope of the IR transmission peak can be decreased and widened, respectively.

The system spatial-frequency filtering of birefringence images of human blood layers

NASA Astrophysics Data System (ADS)

Ushenko, A. G.; Boychuk, T. M.; Mincer, O. P.; Angelsky, P. O.; Bodnar, N. B.; Oleinichenko, B. P.; Bizer, L. I.

2013-09-01

Among various opticophysical methods [1 - 3] of diagnosing the structure and properties of the optical anisotropic component of various biological objects a specific trend has been singled out - multidimensional laser polarimetry of microscopic images of the biological tissues with the following statistic, correlative and fractal analysis of the coordinate distributions of the azimuths and ellipticity of polarization in approximating of linear birefringence polycrystalline protein networks [4 - 10]. At the same time, in most cases, experimental obtaining of tissue sample is a traumatic biopsy operation. In addition, the mechanisms of transformation of the state of polarization of laser radiation by means of the opticoanisotropic biological structures are more varied (optical dichroism, circular birefringence). Hereat, real polycrystalline networks can be formed by different types, both in size and optical properties of biological crystals. Finally, much more accessible for an experimental investigation are biological fluids such as blood, bile, urine, and others. Thus, further progress of laser polarimetry can be associated with the development of new methods of analysis and processing (selection) of polarization- heterogeneous images of biological tissues and fluids, taking into account a wider set of mechanisms anisotropic mechanisms. Our research is aimed at developing experimental method of the Fourier polarimetry and a spatialfrequency selection for distributions of the azimuth and the ellipticity polarization of blood plasma laser images with a view of diagnosing prostate cancer.

Core-pumped mode-locked ytterbium-doped fiber laser operating around 980 nm

NASA Astrophysics Data System (ADS)

Zhou, Yue; Dai, Yitang; Li, Jianqiang; Yin, Feifei; Dai, Jian; Zhang, Tian; Xu, Kun

2018-07-01

In this letter, we first demonstrate a core-pumped passively mode-locked all-normal-dispersion ytterbium-doped fiber oscillator based on nonlinear polarization evolution operating around 980 nm. The dissipative soliton fiber laser pulse can be compressed down to 250 fs with 1 nJ pulse energy, and the slope efficiency of the oscillator can be as high as 19%. To improve the dissipative soliton laser output spectrum smoothness, we replace the birefringent plate based intracavity filter with a diffraction-grating based filter. The output pulse duration can then be further compressed down to 180 fs with improved spectral-smoothness. These schemes have potential applications in seeding cryogenic Yb:YLF amplifiers and underwater exploration of marine resources.

Monolithically integrated active optical devices. [with application in optical communication

NASA Technical Reports Server (NTRS)

Ballantyne, J.; Wagner, D. K.; Kushner, B.; Wojtzcuk, S.

1981-01-01

Considerations relevant to the monolithic integration of optical detectors, lasers, and modulators with high speed amplifiers are discussed. Some design considerations for representative subsystems in the GaAs-AlGaAs and GaInAs-InP materials systems are described. Results of a detailed numerical design of an electro-optical birefringent filter for monolithic integration with a laser diode is described, and early experimental results on monolithic integration of broadband MESFET amplifiers with photoconductive detectors are reported.

High-Resolution Infrared Filter System for Solar Spectroscopy and Polarimetry

NASA Astrophysics Data System (ADS)

Cao, W.; Ma, J.; Wang, J.; Goode, P. R.; Wang, H.; Denker, C.

2003-05-01

We report on the design of an imaging filter system working at the near infrared (NIR) of 1.56 μ m to obtain monochromatic images and to probe weak magnetic fields in different layers of the deep photosphere with high temporal resolution and spatial resolution at Big Bear Solar Observatory (BBSO). This filter system consists of an interference filter, a birefringent filter, and a Fabry-Pérot etalon. As the narrowest filter system, the infrared Fabry-Pérot plays an important role in achieving narrow band transmission and high throughput, maintaining wavelength tuning ability, and assuring stability and reliability. In this poster, we outline a set of methods for the evaluation and calibration of the near infrared Fabry-Pérot etalon. Two-dimensional characteristic maps of the near infrared Fabry-Pérot etalon, including full-width-at-half-maximum (FWHM), effective finesse, peak transmission, along with free spectral range, flatness, roughness, stability and repeatability were obtained with lab equipments. Finally, by utilizing these results, a detailed analysis of the filter performance for the Fe I 1.5648 μ m and Fe I 1.5652 μ m Zeeman sensitive lines is presented. These results will benefit the design of NIR spectro-polarimeter of Advanced Technology Solar Telescope (ATST).

Reflective and transflective liquid crystal displays

NASA Astrophysics Data System (ADS)

Zhou, Fushan

Recently transflective liquid crystal displays (LCD) received a lot of attention. A transflective display has a transmissive mode and a reflective mode. It combines the high contrast, high brightness of the transmissive mode with energy-saving of reflective mode and has good performance in various illumination conditions. However, state-of-the-art transflective displays have problems such as different electro-optical properties, difficulty in compatibility and optimization of both modes, low efficiency of light utilization, and complexity in structure. This dissertation focuses on finding new designs of transflective displays that address those problems. One way to do this is to study film compensation of LCD. We first studied film compensation of bistable twisted nematic (BTN) LCD. Starting form the reduced (3x3) Mueller matrices, we derived and simplified the conditions that film compensated BTN can be optimized. Based on these relations, electro-optical properties of some particular configurations, and designs of transflective BTN with high brightness and contrast were given. To confirm and get a better understanding of the results, we use the Poincare sphere to analyze film compensated BTN. The key to this approach is the existence of "fixed points". Compared with the matrix approach, this approach is more simple, elegant, and efficient. We then generalized the Poincare sphere approach to a universal approach of LCD. We applied the universal approach to film compensation of ECB and IPS, and the design of achromatic birefringent filters. We also give two more new designs of transflective displays. In the first design, a dichroic mirror is used to split the visible spectrum into two parts used in transmissive and reflective modes, respectively. Both modes can be optimized. It has a simple structure and good light utilization. A design for a full-color transflective display with good performance is also given. In the second design, each pixel is divided into two sub-pixels, a transmissive one and a reflective one. By using polymer stabilization, the birefringence of the transmissive sub-pixels is twice that of the reflective ones. The display has single cell gap, low driving voltage, fast response, high contrast and brightness, and the transmissive and reflective modes are synchronized.

Testing New Physics with the Cosmic Microwave Background

NASA Astrophysics Data System (ADS)

Gluscevic, Vera

2013-01-01

In my thesis work, I have developed and applied tests of new fundamental physics that utilize high-precision CMB polarization measurements. I especially focused on a wide class of dark energy models that propose existence of new scalar fields to explain accelerated expansion of the Universe. Such fields naturally exhibit a weak interaction with photons, giving rise to "cosmic birefringence"---a rotation of the polarization plane of light traveling cosmological distances, which alters the statistics of the CMB fluctuations in the sky by inducing a characteristic B-mode polarization. A birefringent rotation of the CMB would be smoking-gun evidence that dark energy is a dynamical component rather than a cosmological constant, while its absence gives clues about the allowed regions of the parameter space for new models. I developed a full-sky formalism to search for cosmic birefringence by cross-correlating CMB temperature and polarization maps, after allowing for the rotation angle to vary across the sky. With my collaborators, I also proposed a cross-correlation of the rotation-angle estimator with the CMB temperature as a novel statistical probe which can boost signal-to-noise in the case of marginal detection and help disentangle the underlying physical models. I then investigated the degeneracy between the rotation signal and the signals from other exotic scenarios that induce a similar B-mode polarization signature, such as chiral primordial gravitational waves, and demonstrated that these effects are completely separable. Finally, I applied this formalism to WMAP-7 data and derived the first CMB constraint on the power spectrum of the birefringent-rotation angle and presented forecasts for future experiments. To demonstrate the value of this analysis method beyond the search for direction-dependent cosmic birefringence, I have also used it to probe patchy screening from the epoch of cosmic reionization with WMAP-7 data.

Birefringence of wood at terahertz frequencies

NASA Astrophysics Data System (ADS)

Todoruk, Tara M.; Schneider, Jon; Hartley, Ian D.; Reid, Matthew

2008-06-01

Fibre content of solid wood plays an important role in the wood products industry in terms of value. Additionally, fibre structure in composite wood products such as Oriented Strand Board (OSB) and paper products plays an important role in terms of strength properties. The effect of moisture content on wood properties is important in the manufacturing process and final product performance, and therefore its effect on the birefringence is of considerable interest. Since solid wood exhibits strong birefringence at terahertz frequencies, there may be potential applications of terahertz spectroscopy to fibre content and structure sensing. There are two potential sources for this strong birefringence: (i) form birefringence resulting from the porous structure of solid wood and (ii) intrinsic birefringence resulting from the dielectric properties of the material itself. In this report, the variability of birefringence within and between species, the dependence of the birefringence on moisture content and the relative contributions from form and intrinsic birefringence are examined. In order to clarify the role of these contributions to the measured birefringence, polarized terahertz reflection spectroscopy is examined and compared to the results obtained in a transmission geometry. Comparison of the birefringence measured in transmission and reflection geometries suggests that form birefringence may dominate.

A high-temperature fiber sensor using a low cost interrogation scheme.

PubMed

Barrera, David; Sales, Salvador

2013-09-04

Regenerated Fibre Bragg Gratings have the potential for high-temperature monitoring. In this paper, the inscription of Fibre Bragg Gratings (FBGs) and the later regeneration process to obtain Regenerated Fiber Bragg Gratings (RFBGs) in high-birefringence optical fiber is reported. The obtained RFBGs show two Bragg resonances corresponding to the slow and fast axis that are characterized in temperature terms. As the temperature increases the separation between the two Bragg resonances is reduced, which can be used for low cost interrogation. The proposed interrogation setup is based in the use of optical filters in order to convert the wavelength shift of each of the Bragg resonances into optical power changes. The design of the optical filters is also studied in this article. In first place, the ideal filter is calculated using a recursive method and defining the boundary conditions. This ideal filter linearizes the output of the interrogation setup but is limited by the large wavelength shift of the RFBG with temperature and the maximum attenuation. The response of modal interferometers as optical filters is also analyzed. They can be easily tuned shifting the optical spectrum. The output of the proposed interrogation scheme is simulated in these conditions improving the sensitivity.

A High-Temperature Fiber Sensor Using a Low Cost Interrogation Scheme

PubMed Central

Barrera, David; Sales, Salvador

2013-01-01

Regenerated Fibre Bragg Gratings have the potential for high-temperature monitoring. In this paper, the inscription of Fibre Bragg Gratings (FBGs) and the later regeneration process to obtain Regenerated Fiber Bragg Gratings (RFBGs) in high-birefringence optical fiber is reported. The obtained RFBGs show two Bragg resonances corresponding to the slow and fast axis that are characterized in temperature terms. As the temperature increases the separation between the two Bragg resonances is reduced, which can be used for low cost interrogation. The proposed interrogation setup is based in the use of optical filters in order to convert the wavelength shift of each of the Bragg resonances into optical power changes. The design of the optical filters is also studied in this article. In first place, the ideal filter is calculated using a recursive method and defining the boundary conditions. This ideal filter linearizes the output of the interrogation setup but is limited by the large wavelength shift of the RFBG with temperature and the maximum attenuation. The response of modal interferometers as optical filters is also analyzed. They can be easily tuned shifting the optical spectrum. The output of the proposed interrogation scheme is simulated in these conditions improving the sensitivity. PMID:24008282

Continuously wavelength-tunable passband-flattened fiber comb filter based on polarization-diversified loop structure.

PubMed

Jung, Jaehoon; Lee, Yong Wook

2017-08-16

Continuous wavelength tuning of optical comb filters, which is an essential functionality for flexible signal processing in reconfigurable optical systems, has been challenging in high order filter structures with two birefringent elements (BEs) or more due to cumbersomeness in finding a combination of waveplates and BEs and complexity in determining their individual azimuthal orientations. Here, we propose a continuously tunable polarization-independent passband-flattened fiber comb filter with two BEs using a polarization-diversified loop structure for the first time. The proposed filter consists of a polarization beam splitter and two groups of a half-wave plate, quarter-wave plate, and polarization-maintaining fiber (PMF). The azimuthal orientation of PMF in the second group is fixed as 22.5°. Orientation angle sets of the four waveplates, which can induce an arbitrary phase shift from 0 to 2π in the passband-flattened transmittance function, are found from the filter transmittance derived using Jones matrix formulation. From theoretical spectral analysis, it is confirmed that passband-flattened comb spectra can be continuously tuned. Theoretical prediction is verified by experimental demonstration. Moreover, the wavelength-dependent evolution of the output state of polarization (SOP) of each PMF is investigated on the Poincare sphere, and the relationship between wavelength tuning and SOP evolution is also discussed.

Generalized Oseen transformation for and enhancement of Bragg characteristics of electro-optic structurally chiral materials

NASA Astrophysics Data System (ADS)

Lakhtakia, Akhlesh

2006-05-01

The Oseen transformation is generalized to define a non-electro-optic structurally chiral material, wherein propagation along the axis of chirality is equivalent to that in an electro-optic SCM with local 4¯2m point group symmetry. This generalization shows that the exploitation of the Pockels effect amounts to an enhancement of the effective local birefringence, which in turn can enhance the characteristics of the circular Bragg phenomenon. Electro-optic SCMs can therefore serve as efficient and electrically controllable circular- and elliptical-polarization rejection filters.

Tunable, continuous-wave Ti:sapphire channel waveguide lasers written by femtosecond and picosecond laser pulses.

PubMed

Grivas, Christos; Corbari, Costantino; Brambilla, Gilberto; Lagoudakis, Pavlos G

2012-11-15

Fabrication and cw lasing at 798.25 nm is reported for femtosecond (fs) and picosecond (ps) laser-inscribed channel waveguides in Ti:sapphire crystals. Lasing in channels written by fs (ps) pulses was obtained above a threshold of 84 mW (189 mW) with a maximum output power and a slope efficiency of 143 mW (45 mW) and 23.5% (7.1%), respectively. The emission wavelength was tuned over a 170 nm range by using a birefringent filter in an external cavity.

Polarized Light Microscopy

NASA Technical Reports Server (NTRS)

Frandsen, Athela F.

2016-01-01

Polarized light microscopy (PLM) is a technique which employs the use of polarizing filters to obtain substantial optical property information about the material which is being observed. This information can be combined with other microscopy techniques to confirm or elucidate the identity of an unknown material, determine whether a particular contaminant is present (as with asbestos analysis), or to provide important information that can be used to refine a manufacturing or chemical process. PLM was the major microscopy technique in use for identification of materials for nearly a century since its introduction in 1834 by William Fox Talbot, as other techniques such as SEM (Scanning Electron Microscopy), FTIR (Fourier Transform Infrared spectroscopy), XPD (X-ray Powder Diffraction), and TEM (Transmission Electron Microscopy) had not yet been developed. Today, it is still the only technique approved by the Environmental Protection Agency (EPA) for asbestos analysis, and is often the technique first applied for identification of unknown materials. PLM uses different configurations in order to determine different material properties. With each configuration additional clues can be gathered, leading to a conclusion of material identity. With no polarizing filter, the microscope can be used just as a stereo optical microscope, and view qualities such as morphology, size, and number of phases. With a single polarizing filter (single polars), additional properties can be established, such as pleochroism, individual refractive indices, and dispersion staining. With two polarizing filters (crossed polars), even more can be deduced: isotropy vs. anisotropy, extinction angle, birefringence/degree of birefringence, sign of elongation, and anomalous polarization colors, among others. With the use of PLM many of these properties can be determined in a matter of seconds, even for those who are not highly trained. McCrone, a leader in the field of polarized light microscopy, often advised, If you cant determine a specific optical property of a particle after two minutes, move onto another configuration. Since optical properties can be seen so very quickly and easily under polarized light, it is only necessary to spend a maximum of two minutes on a technique to determine a particular property, though often only a few seconds are required.

Methods and means of Fourier-Stokes polarimetry and the spatial frequency filtering of phase anisotropy manifestations

NASA Astrophysics Data System (ADS)

Novakovskaya, O. Yu.; Ushenko, A. G.; Dubolazov, A. V.; Ushenko, V. A.; Ushenko, Yu. A.; Sakhnovskiy, M. Yu.; Soltys, I. V.; Zhytaryuk, V. H.; Olar, O. V.; Sidor, M.; Gorsky, M. P.

2016-12-01

The theoretical background of azimuthally stable method of Jones-matrix mapping of histological sections of biopsy of myocardium tissue on the basis of spatial frequency selection of the mechanisms of linear and circular birefringence is presented. The diagnostic application of a new correlation parameter - complex degree of mutual anisotropy - is analytically substantiated. The method of measuring coordinate distributions of complex degree of mutual anisotropy with further spatial filtration of their high- and low-frequency components is developed. The interconnections of such distributions with parameters of linear and circular birefringence of myocardium tissue histological sections are found. The comparative results of measuring the coordinate distributions of complex degree of mutual anisotropy formed by fibrillar networks of myosin fibrils of myocardium tissue of different necrotic states - dead due to coronary heart disease and acute coronary insufficiency are shown. The values and ranges of change of the statistical (moments of the 1st - 4th order) parameters of complex degree of mutual anisotropy coordinate distributions are studied. The objective criteria of differentiation of cause of death are determined.

Spectral shaping of an all-fiber torsional acousto-optic tunable filter.

PubMed

Ko, Jeakwon; Lee, Kwang Jo; Kim, Byoung Yoon

2014-12-20

Spectral shaping of an all-fiber torsional acousto-optic (AO) tunable filter is studied. The technique is based on the axial modulation of AO coupling strength along a highly birefringent optical fiber, which is achieved by tailoring the outer diameter of the fiber along its propagation axis. Two kinds of filter spectral shaping schemes-Gaussian apodization and matched filtering with triple resonance peaks-are proposed and numerically investigated under realistic experimental conditions: at the 50-cm-long AO interaction length of the fiber and at half of the original fiber diameter as the minimum thickness of the tailored fiber section. The results show that the highest peak of sidelobe spectra in filter transmission is suppressed from 11.64% to 0.54% via Gaussian modulation of the AO coupling coefficient (κ). Matched filtering with triple resonance peaks operating with a single radio frequency signal is also achieved by cosine modulation of κ, of which the modulation period determines the spectral distance between two satellite peaks located in both wings of the main resonance peak. The splitting of two satellite peaks in the filter spectra reaches 48.2 nm while the modulation period varies from 7.7 to 50 cm. The overall peak power of two satellite resonances is calculated to be 22% of the main resonance power. The results confirm the validity and practicality of our approach, and we predict robust and stable operation of the designed all-fiber torsional AO filters.

Wavelength tunability of laser based on Yb-doped YGAG ceramics

NASA Astrophysics Data System (ADS)

Šulc, Jan; Jelínková, Helena; Jambunathan, Venkatesan; Miura, Taisuke; Endo, Akira; Lucianetti, Antonio; Mocek, TomáÅ.¡

2015-02-01

The wavelength tunability of diode pumped laser based on Yb-doped mixed garnet Y3Ga2Al3O12 (Yb:YGAG) ceramics was investigated. The tested Yb:YGAG sample (10% Yb/Y) was in the form of 2mm thick plane-parallel face-polished plate (without AR coatings). A fiber (core diameter 100 μm, NA= 0.22) coupled laser diode (LIMO, LIMO35-F100-DL980-FG-E) with emission at wavelength 969 nm, was used for longitudinal Yb:YGAG pumping. The laser diode was operating in the pulsed regime (2 ms pulse length, 10 Hz repetition rate). The duty-cycle 2% ensured a low thermal load even under the maximum diode pumping power amplitude 20W (ceramics sample was only air-cooled). The 145mm long semi-hemispherical laser resonator consisted of a flat pumping mirror (HR @ 1.01 - 1.09 μm, HT @ 0.97 μm) and curved (r = 150mm) output coupler with a reflectivity of ˜ 97% @ 1.01 - 1.09 μm. Wavelength tuning of the ytterbium laser was accomplished by using a birefringent filter (single 1.5mm thick quartz plate) placed inside the optical resonator at the Brewster angle between the output coupler and the laser active medium. The laser was continuously tunable over ˜ 58nm (from 1022nm to 1080 nm) and the tuning band was mostly limited by the free spectral range of used birefringent filter. The maximum output power amplitude 3W was obtained at wavelength 1046nm for absorbed pump power amplitude 10.6W. The laser slope efficiency was 34%.

Fabrication Procedures and Birefringence Measurements for Designing Magnetically Responsive Lanthanide Ion Chelating Phospholipid Assemblies.

PubMed

Isabettini, Stéphane; Baumgartner, Mirjam E; Fischer, Peter; Windhab, Erich J; Liebi, Marianne; Kuster, Simon

2018-01-03

Bicelles are tunable disk-like polymolecular assemblies formed from a large variety of lipid mixtures. Applications range from membrane protein structural studies by nuclear magnetic resonance (NMR) to nanotechnological developments including the formation of optically active and magnetically switchable gels. Such technologies require high control of the assembly size, magnetic response and thermal resistance. Mixtures of 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) and its lanthanide ion (Ln 3+ ) chelating phospholipid conjugate, 1,2-dimyristoyl-sn-glycero-3-phospho-ethanolamine-diethylene triaminepentaacetate (DMPE-DTPA), assemble into highly magnetically responsive assemblies such as DMPC/DMPE-DTPA/Ln 3+ (molar ratio 4:1:1) bicelles. Introduction of cholesterol (Chol-OH) and steroid derivatives in the bilayer results in another set of assemblies offering unique physico-chemical properties. For a given lipid composition, the magnetic alignability is proportional to the bicelle size. The complexation of Ln 3+ results in unprecedented magnetic responses in terms of both magnitude and alignment direction. The thermo-reversible collapse of the disk-like structures into vesicles upon heating allows tailoring of the assemblies' dimensions by extrusion through membrane filters with defined pore sizes. The magnetically alignable bicelles are regenerated by cooling to 5 °C, resulting in assembly dimensions defined by the vesicle precursors. Herein, this fabrication procedure is explained and the magnetic alignability of the assemblies is quantified by birefringence measurements under a 5.5 T magnetic field. The birefringence signal, originating from the phospholipid bilayer, further enables monitoring of polymolecular changes occurring in the bilayer. This simple technique is complementary to NMR experiments that are commonly employed to characterize bicelles.

Distributed measurement of birefringence dispersion in polarization-maintaining fibers

NASA Astrophysics Data System (ADS)

Tang, Feng; Wang, Xiang-Zhao; Zhang, Yimo; Jing, Wencai

2006-12-01

A new method to measure the birefringence dispersion in high-birefringence polarization-maintaining fibers is presented using white-light interferometry. By analyzing broadening of low-coherence interferograms obtained in a scanning Michelson interferometer, the birefringence dispersion and its variation along different fiber sections are acquired with high sensitivity and accuracy. Birefringence dispersions of two PANDA fibers at their operation wavelength are measured to be 0.011 ps/(km nm) and 0.018 ps/(km nm), respectively. Distributed measurement capability of the method is also verified experimentally.

New microwave modulation LIDAR scheme for naval mine detection

NASA Astrophysics Data System (ADS)

Alem, Nour; Pellen, Fabrice; Le Jeune, Bernard

2017-10-01

In this paper, a new modulator design suited for hybrid Lidar-radar applications is proposed and implemented. This modulator delivers a stable and tunable modulated optical pulse. Modulation frequency is in the GHz range, and associated with a bandpass filtering at the detection allow detecting a target echo embedded in the backscattering noise. This principle is known as hybrid Lidar-radar. We expose in this article theoretical principle of this new modulator and its experimental implementation. As polarization filtering can be coupled with the hybrid Lidar-radar technique to further improve target return, polarimetric sensitivity of this modulator was investigated. Since, theoretical results mismatched the experimental ones, thus, further investigations were taken. Mechanical constraint induced by mirror mount caused birefringent behavior to the mirror substrate. As this effect was not homogeneously distributed in the material, we were not being able to compensate it by modelling. However, we propose an experimental approach to solve this problem.

Temperature-independent zero-birefringence polymer for liquid crystal displays

NASA Astrophysics Data System (ADS)

Shikanai, M. D.; Tagaya, A.; Koike, Y.

2016-03-01

A polymer film that shows almost no orientational birefringence even when the polymer main chain is in an oriented state and almost no temperature dependence of orientational birefringence in the temperature range from around -40 to 85 °C was prepared. This temperature range is important because it is where in-car liquid crystal displays (LCDs) are generally used; therefore, it is desirable to have constant orientational birefringence over this range. We suggest a method to compensate for the intrinsic birefringence and temperature coefficient of intrinsic birefringence of individual polymers by copolymerizing monomers of homopolymers that display opposite signs of the two parameters described above. Analysis of four types of polymers, methyl methacrylate (MMA), 2,2,2-trifluoroethyl methacrylate, benzyl methacrylate (BzMA), and phenyl methacrylate (PhMA), reveal that they possess both positive and negative signs of their temperature coefficient of intrinsic birefringence. Using this approach, we prepare P(MMA/PhMA/BzMA) (39:23:38 wt. %), which exhibits almost no intrinsic birefringence and almost no temperature dependence of intrinsic birefringence. The retardation of this polymer film when drawn uniaxially scarcely changed (between 0.3 and 0.8 nm) between 12 and 70 °C, which is small enough not to cause image degradation in LCDs.

Processing of a nine-component near-offset VSP for seismic anisotropy

DOE Office of Scientific and Technical Information (OSTI.GOV)

MacBeth, C.; Li, X.Y.; Zeng, X.

1997-03-01

A convolutional sequence of matrix operators is offered as a convenient deterministic scheme for processing a multicomponent vertical seismic profile (VSP). This sequence is applied to a nine-component near-offset VSP recorded at the Conoco borehole test facility, Kay County, Oklahoma. These data are corrected for tool spin and near-surface anisotropy together with source coupling or imbalance. After wave-field separation using a standard f-k filter, each source and receiver pair for the upgoing waves is adjusted to a common reference depth using a matrix operator based on the downgoing wavefield. The up- and downgoing waves are then processed for anisotropy bymore » a similarity transformation, to separate the qS1 and qS2 waves, from which the anisotropic properties are estimated. These estimates reveal a strong (apparent) vertical birefringence in the near-surface, but weak or moderate values for the majority of the subsurface. The target zone consists of a thin sandstone and deeper shale layer, both of which possess a strong vertical birefringence. The sandstone corresponds to a zone of known fluid flow. An observed qS2 attenuation and polarization change in the shale suggest it contains large fractures.« less

Negative birefringent polyimide films

NASA Technical Reports Server (NTRS)

Harris, Frank W. (Inventor); Cheng, Stephen Z. D. (Inventor)

1994-01-01

A negative birefringent film, useful in liquid crystal displays, and a method for controlling the negative birefringence of a polyimide film is disclosed which allows the matching of an application to a targeted amount of birefringence by controlling the degree of in-plane orientation of the polyimide by the selection of functional groups within both the diamine and dianhydride segments of the polyimide which affect the polyimide backbone chain rigidity, linearity, and symmetry. The higher the rigidity, linearity and symmetry of the polyimide backbone, the larger the value of the negative birefringence of the polyimide film.

Modeling and minimizing interference from corneal birefringence in retinal birefringence scanning for foveal fixation detection

PubMed Central

Irsch, Kristina; Gramatikov, Boris; Wu, Yi-Kai; Guyton, David

2011-01-01

Utilizing the measured corneal birefringence from a data set of 150 eyes of 75 human subjects, an algorithm and related computer program, based on Müller-Stokes matrix calculus, were developed in MATLAB for assessing the influence of corneal birefringence on retinal birefringence scanning (RBS) and for converging upon an optical/mechanical design using wave plates (“wave-plate-enhanced RBS”) that allows foveal fixation detection essentially independently of corneal birefringence. The RBS computer model, and in particular the optimization algorithm, were verified with experimental human data using an available monocular RBS-based eye fixation monitor. Fixation detection using wave-plate-enhanced RBS is adaptable to less cooperative subjects, including young children at risk for developing amblyopia. PMID:21750772

Water column profiles of particulate inorganic carbon in the northeast subarctic Pacific Ocean

NASA Astrophysics Data System (ADS)

Sutton, J. N.; Bishop, J. K.; Martinez, E. J.; Weiss, G. A.; Weiss, A.; Derr, A.; Strubhar, W.; Robert, M.; Wood, T.

2013-12-01

High resolution and real-time measurement of particulate inorganic carbon (PIC) content in seawater is necessary to improve our spatial and temporal understanding of marine carbon flux and the possible effects of ocean acidification on the biological pump. On four occasions since August 2012, we have mapped PIC distribution from surface to bottom at 26 stations along the IOS-Canada Line P transect from western Vancouver Island, BC, Canada to Ocean Station PAPA, 50N 145W using a prototype (PIC001) and a near-commercial quality (PIC008) optical birefringence sensor. The sensors are highly modified 6000m-rated WETLabs C-star transmissometers, which use a polarized laser beam and a cross-polarized receiver to measure photons emitted after passing through birefringent solids. At major stations along Line P (P2, P4, P8, P12, P16, P20, P26), one-liter rosette-collected calibration water samples were filtered through 0.45 μm Supor filters using a small-volume direct filtration system. These samples were analysed for acid-leachable particulate elements (with emphasis on Ca, Na, and Mg) by inductively coupled plasma mass spectrometry (ICPMS). ICPMS PIC was calculated as residual Ca after correction for seawater Ca using Na data. Here we report results for late summer (Aug. 2012) and winter (Feb. 2013). As expected, high levels of PIC (> 100 nmol L-1 to > 2000 nmol L-1) were found in surface waters but rapidly declined at depths greater than 200m and increased again in the nepheloid layer (>50 nmol L-1). Striking seasonal differences in PIC content and PIC profile shape were observed particularly at near shore stations P2, P4, P8 and P12. The results from this research, including sensor evolution and calibration performance, will be presented.

Arbitrary photonic wave plate operations on chip: Realizing Hadamard, Pauli-X, and rotation gates for polarisation qubits

PubMed Central

Heilmann, René; Gräfe, Markus; Nolte, Stefan; Szameit, Alexander

2014-01-01

Chip-based photonic quantum computing is an emerging technology that promises much speedup over conventional computers at small integration volumes. Particular interest is thereby given to polarisation-encoded photonic qubits, and many protocols have been developed for this encoding. However, arbitrary wave plate operation on chip are not available so far, preventing from the implementation of integrated universal quantum computing algorithms. In our work we close this gap and present Hadamard, Pauli-X, and rotation gates of high fidelity for photonic polarisation qubits on chip by employing a reorientation of the optical axis of birefringent waveguides. The optical axis of the birefringent waveguide is rotated due to the impact of an artificial stress field created by an additional modification close to the waveguide. By adjusting this length of the defect along the waveguide, the retardation between ordinary and extraordinary field components is precisely tunable including half-wave plate and quarter-wave plate operations. Our approach demonstrates the full range control of orientation and strength of the induced birefringence and thus allows arbitrary wave plate operations without affecting the degree of polarisation or introducing additional losses to the waveguides. The implemented gates are tested with classical and quantum light. PMID:24534893

In vivo polarization-sensitive optical coherence tomography of human burn scars: birefringence quantification and correspondence with histologically determined collagen density

NASA Astrophysics Data System (ADS)

Jaspers, Mariëlle E. H.; Feroldi, Fabio; Vlig, Marcel; de Boer, Johannes F.; van Zuijlen, Paul P. M.

2017-12-01

Obtaining adequate information on scar characteristics is important for monitoring their evolution and the effectiveness of clinical treatment. The aberrant type of collagen in scars may give rise to specific birefringent properties, which can be determined using polarization-sensitive optical coherence tomography (PS-OCT). The aim of this pilot study was to evaluate a method to quantify the birefringence of the scanned volume and correlate it with the collagen density as measured from histological slides. Five human burn scars were measured in vivo using a handheld probe and custom-made PS-OCT system. The local retardation caused by the tissue birefringence was extracted using the Jones formalism. To compare the samples, histograms of birefringence values of each volume were produced. After imaging, punch biopsies were harvested from the scar area of interest and sent in for histological evaluation using Herovici polychrome staining. Two-dimensional en face maps showed higher birefringence in scars compared to healthy skin. The Pearson's correlation coefficient for the collagen density as measured by histology versus the measured birefringence was calculated at r=0.80 (p=0.105). In conclusion, the custom-made PS-OCT system was capable of in vivo imaging and quantifying the birefringence of human burn scars, and a nonsignificant correlation between PS-OCT birefringence and histological collagen density was found.

Positive and negative contribution to birefringence in a family of carbonates: A Born effective charges analysis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jing, Qun; Yang, Guang; Hou, Juan

It is an important topic to investigate the birefringence and reveal the contribution from ions to birefringence because it plays an important role in nonlinear optical materials. In this paper, the birefringence of carbonates with coplanar CO{sub 3} groups were investigated using the first-principles method. The results show that the lead carbonates exhibit relative large birefringence. After detailed investigate the electronic structures, and Born effective charges, the authors find out that anisotropic electron distribution in the CO{sub 3} groups and Pb atoms give positive contribution, while the negative contribution was found from fluorine atoms, meanwhile the Ca, Mg, and Cdmore » atoms give very small contribution to birefringence. - Graphical abstract: Using the DFT and Born effective charges, the birefringence and the contribution of ions were investigated, the positive and negative contribution was found from Pb and F ions, respectively. - Highlights: • Optical properties and Born effective charges of carbonates are investigated. • Lead carbonates exhibit relative large birefringence. • Coplanar CO{sub 3} groups and Pb atoms give positive contribution. • F atoms give negative contribution. • Ca, Mg, and Cd atoms give very small contribution.« less

Competition of Faraday rotation and birefringence in femtosecond laser direct written waveguides in magneto-optical glass.

PubMed

Liu, Qiang; Gross, S; Dekker, P; Withford, M J; Steel, M J

2014-11-17

We consider the process of Faraday rotation in femtosecond laser direct-write waveguides. The birefringence commonly associated with such waveguides may be expected to impact the observable Faraday rotation. Here, we theoretically calculate and experimentally verify the competition between Faraday rotation and birefringence in two waveguides created by laser writing in a commercial magneto-optic glass. The magnetic field applied to induce Faraday rotation is nonuniform, and as a result, we find that the two effects can be clearly separated and used to accurately determine even weak birefringence. The birefringence in the waveguides was determined to be on the scale of Δn = 10(-6) to 10(-5). The reduction in Faraday rotation caused by birefringence of order Δn = 10(-6) was moderate and we obtained approximately 9° rotation in an 11 mm waveguide. In contrast, for birefringence of order 10(-5), a significant reduction in the polarization azimuth change was found and only 6° rotation was observed.

Dual function microscope for quantitative DIC and birefringence imaging

NASA Astrophysics Data System (ADS)

Li, Chengshuai; Zhu, Yizheng

2016-03-01

A spectral multiplexing interferometry (SXI) method is presented for integrated birefringence and phase gradient measurement on label-free biological specimens. With SXI, the retardation and orientation of sample birefringence are simultaneously encoded onto two separate spectral carrier waves, generated by a crystal retarder oriented at a specific angle. Thus sufficient information for birefringence determination can be obtained from a single interference spectrum, eliminating the need for multiple acquisitions with mechanical rotation or electrical modulation. In addition, with the insertion of a Nomarski prism, the setup can then acquire quantitative differential interference contrast images. Red blood cells infected by malaria parasites are imaged for birefringence retardation as well as phase gradient. The results demonstrate that the SXI approach can achieve both quantitative phase imaging and birefringence imaging with a single, high-sensitivity system.

Quantitative polarized light microscopy using spectral multiplexing interferometry.

PubMed

Li, Chengshuai; Zhu, Yizheng

2015-06-01

We propose an interferometric spectral multiplexing method for measuring birefringent specimens with simple configuration and high sensitivity. The retardation and orientation of sample birefringence are simultaneously encoded onto two spectral carrier waves, generated interferometrically by a birefringent crystal through polarization mixing. A single interference spectrum hence contains sufficient information for birefringence determination, eliminating the need for mechanical rotation or electrical modulation. The technique is analyzed theoretically and validated experimentally on cellulose film. System simplicity permits the possibility of mitigating system birefringence background. Further analysis demonstrates the technique's exquisite sensitivity as high as ∼20  pm for retardation measurement.

Thin film polarizer and color filter based on photo-polymerizable nematic liquid crystal

NASA Astrophysics Data System (ADS)

Mohammadimasoudi, Mohammad; Neyts, Kristiaan; Beeckman, Jeroen

2015-03-01

We present a method to fabricate a thin film color filter based on a mixture of photo-polymerizable liquid crystal and chiral dopant. A chiral nematic liquid crystal layer reflects light for a certain wavelength interval Δλ (= Δn.P) with the period and Δn the birefringence of the liquid crystal. The reflection band is determined by the chiral dopant concentration. The bandwidth is limited to 80nm and the reflectance is at most 50% for unpolarized incident light. The thin color filter is interesting for innovative applications like polarizer-free reflective displays, polarization-independent devices, stealth technologies, or smart switchable reflective windows to control solar light and heat. The reflected light has strong color saturation without absorption because of the sharp band edges. A thin film polarizer is developed by using a mixture of photo-polymerizable liquid crystal and color-neutral dye. The fabricated thin film absorbs light that is polarized parallel to the c axis of the LC. The obtained polarization ratio is 80% for a film of only 12 μm. The thin film polarizer and the color filter feature excellent film characteristics without domains and can be detached from the substrate which is useful for e.g. flexible substrates.

Novel birefringence interrogation for Sagnac loop interferometer sensor with unlimited linear measurement range.

PubMed

He, Haijun; Shao, Liyang; Qian, Heng; Zhang, Xinpu; Liang, Jiawei; Luo, Bin; Pan, Wei; Yan, Lianshan

2017-03-20

A novel demodulation method for Sagnac loop interferometer based sensor has been proposed and demonstrated, by unwrapping the phase changes with birefringence interrogation. A temperature sensor based on Sagnac loop interferometer has been used to verify the feasibility of the proposed method. Several tests with 40 °C temperature range have been accomplished with a great linearity of 0.9996 in full range. The proposed scheme is universal for all Sagnac loop interferometer based sensors and it has unlimited linear measurable range which overwhelming the conventional demodulation method with peak/dip tracing. Furthermore, the influence of the wavelength sampling interval and wavelength span on the demodulation error has been discussed in this work. The proposed interrogation method has a great significance for Sagnac loop interferometer sensor and it might greatly enhance the availability of this type of sensors in practical application.

Fish skin provides invisibility in open ocean (image 11)

NSF Multimedia

2017-02-10

Skin preparation from fish shows birefringence under cross polarization microscopy Skin preparation from fish shows birefringence under cross polarization microscopySkin preparation from fish shows birefringence under cross polarization microscopy Skin pr

Integrated quantitative phase and birefringence microscopy for imaging malaria-infected red blood cells.

PubMed

Li, Chengshuai; Chen, Shichao; Klemba, Michael; Zhu, Yizheng

2016-09-01

A dual-modality birefringence/phase imaging system is presented. The system features a crystal retarder that provides polarization mixing and generates two interferometric carrier waves in a single signal spectrum. The retardation and orientation of sample birefringence can then be measured simultaneously based on spectral multiplexing interferometry. Further, with the addition of a Nomarski prism, the same setup can be used for quantitative differential interference contrast (DIC) imaging. Sample phase can then be obtained with two-dimensional integration. In addition, birefringence-induced phase error can be corrected using the birefringence data. This dual-modality approach is analyzed theoretically with Jones calculus and validated experimentally with malaria-infected red blood cells. The system generates not only corrected DIC and phase images, but a birefringence map that highlights the distribution of hemozoin crystals.

On the birefringence of healthy and malaria-infected red blood cells

NASA Astrophysics Data System (ADS)

Dharmadhikari, Aditya K.; Basu, Himanish; Dharmadhikari, Jayashree A.; Sharma, Shobhona; Mathur, Deepak

2013-12-01

The birefringence of a red blood cell (RBC) is quantitatively monitored as it becomes infected by a malarial parasite. Large changes occur in the cell's refractive index at different stages of malarial infection. The observed rotation of an optically trapped, malaria-infected RBC is not a simple function of shape distortion: the malarial parasite is found to itself exercise a profound influence on the rotational dynamics by inducing stage-specific birefringence. Our measurements shed new light on the competition between shape- and form-birefringence in RBCs. We demonstrate the possibility of using birefringence to establish very early stages of infected parasites and of assessing various factors that contribute to birefringence in normal and infected cells. Our results have implications for the development and use of noninvasive techniques of quantifying changes in cell properties induced by malaria disease pathology.

Integrated quantitative phase and birefringence microscopy for imaging malaria-infected red blood cells

NASA Astrophysics Data System (ADS)

Li, Chengshuai; Chen, Shichao; Klemba, Michael; Zhu, Yizheng

2016-09-01

A dual-modality birefringence/phase imaging system is presented. The system features a crystal retarder that provides polarization mixing and generates two interferometric carrier waves in a single signal spectrum. The retardation and orientation of sample birefringence can then be measured simultaneously based on spectral multiplexing interferometry. Further, with the addition of a Nomarski prism, the same setup can be used for quantitative differential interference contrast (DIC) imaging. Sample phase can then be obtained with two-dimensional integration. In addition, birefringence-induced phase error can be corrected using the birefringence data. This dual-modality approach is analyzed theoretically with Jones calculus and validated experimentally with malaria-infected red blood cells. The system generates not only corrected DIC and phase images, but a birefringence map that highlights the distribution of hemozoin crystals.

Scleral birefringence as measured by polarization-sensitive optical coherence tomography and ocular biometric parameters of human eyes in vivo.

PubMed

Yamanari, Masahiro; Nagase, Satoko; Fukuda, Shinichi; Ishii, Kotaro; Tanaka, Ryosuke; Yasui, Takeshi; Oshika, Tetsuro; Miura, Masahiro; Yasuno, Yoshiaki

2014-05-01

The relationship between scleral birefringence and biometric parameters of human eyes in vivo is investigated. Scleral birefringence near the limbus of 21 healthy human eyes was measured using polarization-sensitive optical coherence tomography. Spherical equivalent refractive error, axial eye length, and intraocular pressure (IOP) were measured in all subjects. IOP and scleral birefringence of human eyes in vivo was found to have statistically significant correlations (r = -0.63, P = 0.002). The slope of linear regression was -2.4 × 10(-2) deg/μm/mmHg. Neither spherical equivalent refractive error nor axial eye length had significant correlations with scleral birefringence. To evaluate the direct influence of IOP to scleral birefringence, scleral birefringence of 16 ex vivo porcine eyes was measured under controlled IOP of 5-60 mmHg. In these ex vivo porcine eyes, the mean linear regression slope between controlled IOP and scleral birefringence was -9.9 × 10(-4) deg/μm/mmHg. In addition, porcine scleral collagen fibers were observed with second-harmonic-generation (SHG) microscopy. SHG images of porcine sclera, measured on the external surface at the superior side to the cornea, showed highly aligned collagen fibers parallel to the limbus. In conclusion, scleral birefringence of healthy human eyes was correlated with IOP, indicating that the ultrastructure of scleral collagen was correlated with IOP. It remains to show whether scleral collagen ultrastructure of human eyes is affected by IOP as a long-term effect.

Cancellation of birefringence in DBR laser through principal axis offset by a rotation of 90°

NASA Astrophysics Data System (ADS)

Zaini, M. K. A.; Lai, M. H.; Islam, M. R.; Lim, K. S.; Ahmad, H.

2018-04-01

The cancellation of birefringence in the distributed Bragg reflector based on 90° rotation offset method is demonstrated. It is found that the birefringence, which causes the peak bifurcation has been eliminated and a single peak is produced at each resonance in the output spectrum. This modification is an economic solution for eliminating the birefringence of the optical fibre devices.

FIBER AND INTEGRATED OPTICS. FIBER WAVEGUIDE DEVICES: Vector solitons in fiber waveguides with a random birefringence

NASA Astrophysics Data System (ADS)

Kivshar', Yu S.; Konotop, V. V.

1990-12-01

A study is made of the propagation of soliton pulses in single-mode fiber waveguides with a birefringence that gives rise to a nonlinear interaction between the polarizations and to a difference between their group velocities. It is shown that a vector soliton decays if a parameter representing the birefringence intensity exceeds a certain critical value. The case when the birefringence can be described by a random function is of special interest. It is demonstrated that fluctuations of the birefringence then split the vector solitons into separate polarizations and the characteristic distance governing such splitting is calculated analytically.

Controlling material birefringence in sapphire via self-assembled, sub-wavelength defects

NASA Astrophysics Data System (ADS)

Singh, Astha; Sharma, Geeta; Ranjan, Neeraj; Mittholiya, Kshitij; Bhatnagar, Anuj; Singh, B. P.; Mathur, Deepak; Vasa, Parinda

2018-02-01

Birefringence is the optical property of a material having a refractive index that depends on the polarization and propagation direction of light. Generally, this is an intrinsic optical property of a material and cannot be altered. Here, we report a novel technique—direct laser writing—that enables us to control the natural, material birefringence of sapphire over a broad range of wavelengths. The broadband form birefringence originating from self-assembled, periodic array of sub-wavelength (˜ 50-200 nm) defects created by laser writing, can enhance, suppress or maintain the material birefringence of sapphire without affecting its transparency range in visible or its surface quality.

Glue-induced birefringence in surface-attached FBG strain sensors

NASA Astrophysics Data System (ADS)

Helminger, Dominik; Daitche, Alexej; Roths, Johannes

2014-05-01

The influence of the gluing process on the birefringence of surface-glued FBGs that were inscribed in highly birefringence (HiBi) optical fibers of type Panda was studied by monitoring the variation of the birefringence during the gluing procedure. The isothermal curing process at 100°C of the epoxy-based adhesive is characterized by the reduction of birefringence during curing. Significant transversal strain is introduced into the fiber during the cool down period, which is due to different thermal expansion coefficients of the silica and the glue. When the slow axis of the HiBi fiber is oriented parallel to the surface, the glue-induced transversal strain reduces the birefringence of the fiber by ΔB = -6.6 10-5 and when it is perpendicular to the surface, it is increased by ΔB = 1.1 10-5. It can be estimated that for conventional FBGs in single mode fibers a glue-induced birefringence in the order of ΔB = 3.4 10-5 can be expected, which has to be taken into account if in surface-mounted FBG-based strain measurements a high accuracy has to be achieved.

Mueller matrix characterization of flexible plastic substrates

NASA Astrophysics Data System (ADS)

Hong, Nina; Synowicki, Ron A.; Hilfiker, James N.

2017-11-01

This work reports on Mueller matrix spectroscopic ellipsometry characterization of various flexible plastic substrates that are optically anisotropic with varying degrees of birefringence. The samples are divided into three groups according to the suggested characterization strategy: low birefringence, high birefringence, and twisted birefringence. The first group includes poly(methyl methacrylate) and cyclic olefin copolymer substrates. These are modeled with biaxial anisotropy for the real part of the refractive index while the imaginary part is approximated as isotropic due to small light absorption. The second group includes polyethylene terephthalate and polyethylene naphthalate substrates, which are modeled with biaxial anisotropy for both real and imaginary refractive indices. Lastly, a polyimide substrate is described as two birefringent layers with twisted in-plane orientation.

X ray, extreme and far ultraviolet optical thin films for space applications

NASA Technical Reports Server (NTRS)

Zukic, Muamer; Torr, Douglas G.; Kim, Jongmin

1993-01-01

Far and extreme ultraviolet optical thin film filters find many uses in space astronomy, space astrophysics, and space aeronomy. Spacebased spectrographs are used for studying emission and absorption features of the earth, planets, sun, stars, and the interstellar medium. Most of these spectrographs use transmission or reflection filters. This requirement has prompted a search for selective filtering coatings with high throughput in the FUV and EUV spectral region. Important progress toward the development of thin film filters with improved efficiency and stability has been made in recent years. The goal for this field is the minimization of absorption to get high throughput and enhancement of wavelength selection. The Optical Aeronomy Laboratory (OAL) at the University of Alabama in Huntsville has recently developed the technology to determine optical constants of bulk and film materials for wavelengths extending from x-rays (0.1 nm) to the FUV (200 nm), and several materials have been identified that were used for designs of various optical devices which previously have been restricted to space application in the visible and near infrared. A new design concept called the Pi-multilayer was introduced and applied to the design of optical coatings for wavelengths extending from x-rays to the FUV. Section 3 of this report explains the Pi-multilayer approach and demonstrates its application for the design and fabrication of the FUV coatings. Two layer Pi-stacks have been utilized for the design of reflection filters in the EUV wavelength range from 70 - 100 nm. In order to eliminate losses due to the low reflection of the imaging optics and increase throughput and out-of-band rejection of the EUV instrumentation we introduced a self-filtering camera concept. In the FUV region, MgF2 and LiF crystals are known to be birefringent. Transmission polarizers and quarterwave retarders made of MgF2 or LiF crystals are commercially available but the performances are poor. New techniques for the design of the EUV and FUV polarizers and quarterwave retarders are described in Section 5. X- and gamma-ray detectors rely on a measurement of the electron which is effected when a ray interacts with matter. The design of an x- and gamma-ray telescope to operate in a particular region of the spectrum is, therefore, largely dictated by the mechanism through which the rays interact. Energy selection and the focusing of the incident high energy rays can be achieved with spectrally selective high reflective multilayers. The design and spectral performance of narrowband reflective x-ray Pi-multilayers are presented in section 6.

Micromanipulation studies of chromosome movement. II. Birefringent chromosomal fibers and the mechanical attachment of chromosomes to the spindle

PubMed Central

1979-01-01

The degree of mechanical coupling of chromosomes to the spindles of Nephrotoma and Trimeratropis primary spermatocytes varies with the stage of meiosis and the birefringent retardation of the chromosomal fibers. In early prometaphase, before birefringent chromosomal fibers have formed, a bivalent can be displaced toward a spindle pole by a single, continuous pull with a microneedle. Resistance to poleward displacement increases with increased development of the chromosomal fibers, reaching a maximum at metaphase. At this stage kinetochores cannot be displaced greater than 1 micrometer toward either spindle pole, even by a force which is sufficient to displace the entire spindle within the cell. The abolition of birefringence with either colcemid or vinblastine results in the loss of chromosome-spindle attachment. In the absence of birefringent fibers a chromosome can be displaced anywhere within the cell. The photochemical inactivation of colcemid by irradiation with 366-nm light results in the reformation of birefringent chromosomal fibers and the concomitant re-establishment of chromosome attachment to the spindle. These results support the hypothesis that the birefringent chromosomal fibers anchor the chromosomes to the spindle and transmit the force for anaphase chromosome movement. PMID:479316

Detecting strain in birefringent materials using spectral polarimetry

NASA Technical Reports Server (NTRS)

Garner, Harold R. (Inventor); Ragucci, Anthony J. (Inventor); Cisar, Alan J. (Inventor); Huebschman, Michael L. (Inventor)

2010-01-01

A method, computer program product and system for analyzing multispectral images from a plurality of regions of birefringent material, such as a polymer film, using polarized light and a corresponding polar analyzer to identify differential strain in the birefringent material. For example, the birefringement material may be low-density polyethylene (LDPE), high-density polyethylene (HDPE), polypropylene, polyethylene terephthalate (PET), polyvinyl chloride (PVC), polyvinylidene chloride, polyester, nylon, or cellophane film. Optionally, the method includes generating a real-time quantitative strain map.

Corneal birefringence measured by spectrally resolved Mueller matrix ellipsometry and implications for non-invasive glucose monitoring

PubMed Central

Westphal, Peter; Kaltenbach, Johannes-Maria; Wicker, Kai

2016-01-01

A good understanding of the corneal birefringence properties is essential for polarimetric glucose monitoring in the aqueous humor of the eye. Therefore, we have measured complete 16-element Mueller matrices of single-pass transitions through nine porcine corneas in-vitro, spectrally resolved in the range 300…1000 nm. These ellipsometric measurements have been performed at several angles of incidence at the apex and partially at the periphery of the corneas. The Mueller matrices have been decomposed into linear birefringence, circular birefringence (i.e. optical rotation), depolarization, and diattenuation. We found considerable circular birefringence, strongly increasing with decreasing wavelength, for most corneas. Furthermore, the decomposition revealed significant dependence of the linear retardance (in nm) on the wavelength below 500 nm. These findings suggest that uniaxial and biaxial crystals are insufficient models for a general description of the corneal birefringence, especially in the blue and in the UV spectral range. The implications on spectral-polarimetric approaches for glucose monitoring in the eye (for diabetics) are discussed. PMID:27446644

Natural enamel caries in polarized light microscopy: differences in histopathological features derived from a qualitative versus a quantitative approach to interpret enamel birefringence.

PubMed

De Medeiros, R C G; Soares, J D; De Sousa, F B

2012-05-01

Lesion area measurement of enamel caries using polarized light microscopy (PLM) is currently performed in a large number of studies, but measurements are based mainly on a mislead qualitative interpretation of enamel birefringence in a single immersion medium. Here, five natural enamel caries lesions are analysed by microradiography and in PLM, and the differences in their histopathological features derived from a qualitative versus a quantitative interpretation of enamel birefringence are described. Enamel birefringence in different immersion media (air, water and quinoline) is interpreted by both qualitative and quantitative approaches, the former leading to an underestimation of the depth of enamel caries mainly when the criterion of validating sound enamel as a negatively birefringent area in immersion in water is used (a current common practice in dental research). Procedures to avoid the shortcomings of a qualitative interpretation of enamel birefringence are presented and discussed. © 2012 The Authors Journal of Microscopy © 2012 Royal Microscopical Society.

Tunable ultra-broadband polarization filter based on three-core resonance of the fluid-infiltrated and gold-coated photonic crystal fiber

NASA Astrophysics Data System (ADS)

Liu, Yingchao; Chen, Hailiang; Ma, Mingjian; Zhang, Wenxun; Wang, Yujun; Li, Shuguang

2018-03-01

We propose a tunable ultra-broadband polarization filter based on three-core resonance of the fluid-infiltrated and gold-coated high birefringent photonic crystal fiber (HB-PCF). Gold film was applied to the inner walls of two cladding air holes and surface plasmon polaritons were generated on its surface. The two gold-coated cladding air holes acted as two defective cores. As the phase matching condition was satisfied, light transmitted in the fiber core and coupled to the two defective cores. The three-core PCF supported three super modes in two orthogonal polarization directions. The coupling characteristics among these modes were investigated using the finite-element method. We found that the coupling wavelengths and strength between these guided modes can be tuned by altering the structural parameters of the designed HB-PCF, such as the size of the voids, thickness of the gold-films and liquid infilling pattern. Under the optimized structural parameters, a tunable broadband polarization filter was realized. For one liquid infilling pattern, we obtained a broadband polarization filter which filtered out the light in y-polarization direction at the wavelength of 1550 nm. For another liquid infilling pattern, we filtered out light in the x-polarization direction at the wavelength of 1310 nm. Our studies on the designed HB-PCF made contributions to the further devising of tunable broadband polarization filters, which are extensively used in telecommunication and sensor systems. Project supported by the National Natural Science Foundation of China (Grant Nos. 61505175 and 61475134) and the Natural Science Foundation of Hebei Province (Grant Nos. F2017203110 and F2017203193).

Optical vortex generation from a diode-pumped alexandrite laser

NASA Astrophysics Data System (ADS)

Thomas, G. M.; Minassian, A.; Damzen, M. J.

2018-04-01

We present the demonstration of an optical vortex mode directly generated from a diode-pumped alexandrite slab laser, operating in the bounce geometry. This is the first demonstration of an optical vortex mode generated from an alexandrite laser or from any other vibronic laser. An output power of 2 W for a vortex mode with a ‘topological charge’ of 1 was achieved and the laser was made to oscillate with both left- and right-handed vorticity. The laser operated at two distinct wavelengths simultaneously, 755 and 759 nm, due to birefringent filtering in the alexandrite gain medium. The result offers the prospect of broadly wavelength tunable vortex generation directly from a laser.

Passively mode-locked Nd:YVO4 laser operating at 1073 nm and 1085 nm

NASA Astrophysics Data System (ADS)

Waritanant, Tanant; Major, Arkady

2018-02-01

A passively mode-locked Nd:YVO4 laser operating at 1073 nm and 1085 nm was demonstrated with an intracavity birefringent filter as the wavelength selecting element. The average output powers achieved were 2.17 W and 2.18 W with optical-to-optical efficiency of 19.6% and 19.7%, respectively. The slope efficiencies were more than 31% at both output wavelengths. The pulse durations at the highest average output power were 10.3 ps and 8.4 ps, respectively. We believe that this is the first report of mode locking of a Nd:YVO4 laser operating at 1073 nm or 1085 nm lines.

Birefringence in anisotropic optical fibres studied by polarised light Brillouin reflectometry

DOE Office of Scientific and Technical Information (OSTI.GOV)

Smirnov, A S; Burdin, V V; Konstantinov, Yu A

2015-01-31

Modal birefringence (the difference between the effective refractive indices of orthogonal polarisation modes) is one of the key parameters of anisotropic single-mode fibres, characterising their ability to preserve a linearly polarised state of input light. This parameter is commonly measured using short pieces of fibre, but such procedures are destructive and allow the birefringence to be determined only at the ends of long fibres. In this study, polarised light Brillouin reflectometry is used to assess birefringence uniformity throughout the length of an anisotropic fibre. (optical fibres)

Note: Ultra-low birefringence dodecagonal vacuum glass cell.

PubMed

Brakhane, Stefan; Alt, Wolfgang; Meschede, Dieter; Robens, Carsten; Moon, Geol; Alberti, Andrea

2015-12-01

We report on an ultra-low birefringence dodecagonal glass cell for ultra-high vacuum applications. The epoxy-bonded trapezoidal windows of the cell are made of SF57 glass, which exhibits a very low stress-induced birefringence. We characterize the birefringence Δn of each window with the cell under vacuum conditions, obtaining values around 10(-8). After baking the cell at 150 °C, we reach a pressure below 10(-10) mbar. In addition, each window is antireflection coated on both sides, which is highly desirable for quantum optics experiments and precision measurements.

Large tuning of birefringence in two strip silicon waveguides via optomechanical motion.

PubMed

Ma, Jing; Povinelli, Michelle L

2009-09-28

We present an optomechanical method to tune phase and group birefringence in parallel silicon strip waveguides. We first calculate the deformation of suspended, parallel strip waveguides due to optical forces. We optimize the frequency and polarization of the pump light to obtain a 9 nm deformation for an optical power of 20 mW. Widely tunable phase and group birefringence can be achieved by varying the pump power, with maximum values of 0.026 and 0.13, respectively. The giant phase birefringence allows linear to circular polarization conversion within 30 microm for a pump power of 67 mW. The group birefringence gives a tunable differential group delay of 6fs between orthogonal polarizations. We also evaluate the tuning performance of waveguides with different cross sections.

In vivo detection of exercised-induced ultrastructural changes in genetically-altered murine skeletal muscle using polarization-sensitive optical coherence tomography

NASA Astrophysics Data System (ADS)

Boppart, Stephen

2006-02-01

Skeletal muscle fibers are a known source of form birefringence in biological tissue. The birefringence present in skeletal muscle is associated with the ultrastructure of individual sarcomeres, specifically the arrangement of A-bands corresponding to the thick myosin filaments. Certain structural proteins that prevent damage and maintain the structural and functional health of the muscle fiber preserve the organization of the Abands in skeletal muscle. Therefore, the level of birefringence detected can estimate the health of the muscle as well as the damage incurred during exercise. Murine skeletal muscle from both genetically-altered (mdx) and normal (wild-type) specimens were imaged in vivo with a fiber-based PSOCT imaging system to quantitatively determine the level of birefringence present in the tissue before and after exercise. The mdx muscle lacks dystrophin, a structural protein that is mutated in Duchenne muscular dystrophy in humans. Muscle from these mdx mice exhibited a marked decrease in birefringence after exercise, whereas the wild-type muscle was highly birefringent before and after exercise. The quantitative results from this tissue optics study suggest for the first time that there is a distinct relationship between the degree of birefringence detected using PS-OCT and the sarcomeric ultrastructure present within skeletal muscle.

Differential diagnosis of periapical cyst using collagen birefringence pattern of the cyst wall.

PubMed

Ji, Hyo Jin; Park, Se-Hee; Cho, Kyung-Mo; Lee, Suk Keun; Kim, Jin Woo

2017-05-01

Periapical lesions, including periapical cyst (PC), periapical granuloma (PG), and periapical abscess (PA), are frequently affected by chemical/physical damage during root canal treatment or severe bacterial infection, and thus, the differential diagnosis of periapical lesions may be difficult due to the presence of severe inflammatory reaction. The aim of this study was to make differential diagnosis among PC, PG, and PA under polarizing microscope. The collagen birefringence patterns of 319 cases of PC ( n = 122), PG ( n = 158), and PA ( n = 39) obtained using a polarizing microscope were compared. In addition, 6 cases of periodontal fibroma (PF) were used as positive controls. Collagen birefringence was condensed with a thick, linear band-like pattern in PC, but was short and irregularly scattered in PG, and scarce or absent in PA. PF showed intense collagen birefringence with a short, palisading pattern but no continuous band-like pattern. The linear band-like birefringence in PC was ascribed to pre-existing expansile tensile stress of the cyst wall. In this study all PCs ( n = 122) were distinguishable from PGs and PAs by their characteristic birefringence, despite the absence of lining epithelium ( n = 20). Therefore, the authors suggest that the presence of linear band-like collagen birefringence of the cyst wall aids the diagnostic differentiation of PC from PG and PA.

High-speed polarization sensitive optical frequency domain imaging with frequency multiplexing

PubMed Central

Yun, S.H.; Vakoc, B.J.; Shishkov, M.; Desjardins, A.E.; Park, B.H.; de Boer, J.F.; Tearney, G.J.; Bouma, B.E.

2009-01-01

Polarization sensitive optical coherence tomography (PS-OCT) provides a cross-sectional image of birefringence in biological samples that is complementary in many applications to the standard reflectance-based image. Recent ex vivo studies have demonstrated that birefringence mapping enables the characterization of collagen and smooth muscle concentration and distribution in vascular tissues. Instruments capable of applying these measurements percutaneously in vivo may provide new insights into coronary atherosclerosis and acute myocardial infarction. We have developed a polarization sensitive optical frequency domain imaging (PS-OFDI) system that enables high-speed intravascular birefringence imaging through a fiber-optic catheter. The novel design of this system utilizes frequency multiplexing to simultaneously measure reflectance of two incident polarization states, overcoming concerns regarding temporal variations of the catheter fiber birefringence and spatial variations in the birefringence of the sample. We demonstrate circular cross-sectional birefringence imaging of a human coronary artery ex vivo through a flexible fiber-optic catheter with an A-line rate of 62 kHz and a ranging depth of 6.2 mm. PMID:18542183

Optical Ptychographic Microscope for Quantitative Bio-Mechanical Imaging

NASA Astrophysics Data System (ADS)

Anthony, Nicholas; Cadenazzi, Guido; Nugent, Keith; Abbey, Brian

The role that mechanical forces play in biological processes such as cell movement and death is becoming of significant interest to further develop our understanding of the inner workings of cells. The most common method used to obtain stress information is photoelasticity which maps a samples birefringence, or its direction dependent refractive indices, using polarized light. However this method only provides qualitative data and for stress information to be useful quantitative data is required. Ptychography is a method for quantitatively determining the phase of a samples complex transmission function. The technique relies upon the collection of multiple overlapping coherent diffraction patterns from laterally displaced points on the sample. The overlap of measurement points provides complementary information that significantly aids in the reconstruction of the complex wavefield exiting the sample and allows for quantitative imaging of weakly interacting specimens. Here we describe recent advances at La Trobe University Melbourne on achieving quantitative birefringence mapping using polarized light ptychography with applications in cell mechanics. Australian Synchrotron, ARC Centre of Excellence for Advanced Molecular Imaging.

Analysis of a highly birefringent asymmetric photonic crystal fibre based on a surface plasmon resonance sensor

NASA Astrophysics Data System (ADS)

Liu, Chao; Wang, Famei; Zheng, Shijie; Sun, Tao; Lv, Jingwei; Liu, Qiang; Yang, Lin; Mu, Haiwei; Chu, Paul K.

2016-07-01

A highly birefringent photonic crystal fibre is proposed and characterized based on a surface plasmon resonance sensor. The birefringence of the sensor is numerically analyzed by the finite-element method. In the numerical simulation, the resonance wavelength can be directly positioned at this birefringence abrupt change point and the depth of the abrupt change of birefringence reflects the intensity of excited surface plasmon. Consequently, the novel approach can accurately locate the resonance peak of the system without analyzing the loss spectrum. Simulated average sensitivity is as high as 1131 nm/RIU, corresponding to a resolution of 1 × 10-4 RIU in this sensor. Therefore, results obtained via the approach not only show polarization independence and less noble metal consumption, but also reveal better performance in terms of accuracy and computation efficiency.

Influence of UV and Gamma radiations on the induced birefringence of stretched poly(vinyl) alcohol foils

NASA Astrophysics Data System (ADS)

Nechifor, Cristina-Delia; Zelinschi, Carmen Beatrice; Dorohoi, Dana-Ortansa

2014-03-01

The aim of our paper is to evidence the influence of Gamma and UV radiations on the induced birefringence of poly(vinyl alcohol) stretched foils. Thin foils of PVA were prepared and dried without modifying their surfaces. The polymeric foils were irradiated from 15 min to 6 h using UV and Gamma radiations. The induced by stretching under heating birefringence of PVA films was measured at λ = 589.3 nm with a Babinet Compensator. Physico-chemical processes (photo stabilization, photo degradation, oxidation) induced by irradiation of polymer matrix influence both the stretching degree and the anisotropy of etired foils. An increase of birefringence versus the stretching ratio of the PVA foils was evidenced for all studied samples. The dependence of the birefringence on the exposure time, stretching ratio and nature of radiation was also confirmed.

Polarization microscopy by use of digital holography: application to optical-fiber birefringence measurements.

PubMed

Colomb, Tristan; Dürr, Florian; Cuche, Etienne; Marquet, Pierre; Limberger, Hans G; Salathé, René-Paul; Depeursinge, Christian

2005-07-20

We present a digital holographic microscope that permits one to image polarization state. This technique results from the coupling of digital holographic microscopy and polarization digital holography. The interference between two orthogonally polarized reference waves and the wave transmitted by a microscopic sample, magnified by a microscope objective, is recorded on a CCD camera. The off-axis geometry permits one to reconstruct separately from this single hologram two wavefronts that are used to image the object-wave Jones vector. We applied this technique to image the birefringence of a bent fiber. To evaluate the precision of the phase-difference measurement, the birefringence induced by internal stress in an optical fiber is measured and compared to the birefringence profile captured by a standard method, which had been developed to obtain high-resolution birefringence profiles of optical fibers.

Accurate and quantitative polarization-sensitive OCT by unbiased birefringence estimator with noise-stochastic correction

NASA Astrophysics Data System (ADS)

Kasaragod, Deepa; Sugiyama, Satoshi; Ikuno, Yasushi; Alonso-Caneiro, David; Yamanari, Masahiro; Fukuda, Shinichi; Oshika, Tetsuro; Hong, Young-Joo; Li, En; Makita, Shuichi; Miura, Masahiro; Yasuno, Yoshiaki

2016-03-01

Polarization sensitive optical coherence tomography (PS-OCT) is a functional extension of OCT that contrasts the polarization properties of tissues. It has been applied to ophthalmology, cardiology, etc. Proper quantitative imaging is required for a widespread clinical utility. However, the conventional method of averaging to improve the signal to noise ratio (SNR) and the contrast of the phase retardation (or birefringence) images introduce a noise bias offset from the true value. This bias reduces the effectiveness of birefringence contrast for a quantitative study. Although coherent averaging of Jones matrix tomography has been widely utilized and has improved the image quality, the fundamental limitation of nonlinear dependency of phase retardation and birefringence to the SNR was not overcome. So the birefringence obtained by PS-OCT was still not accurate for a quantitative imaging. The nonlinear effect of SNR to phase retardation and birefringence measurement was previously formulated in detail for a Jones matrix OCT (JM-OCT) [1]. Based on this, we had developed a maximum a-posteriori (MAP) estimator and quantitative birefringence imaging was demonstrated [2]. However, this first version of estimator had a theoretical shortcoming. It did not take into account the stochastic nature of SNR of OCT signal. In this paper, we present an improved version of the MAP estimator which takes into account the stochastic property of SNR. This estimator uses a probability distribution function (PDF) of true local retardation, which is proportional to birefringence, under a specific set of measurements of the birefringence and SNR. The PDF was pre-computed by a Monte-Carlo (MC) simulation based on the mathematical model of JM-OCT before the measurement. A comparison between this new MAP estimator, our previous MAP estimator [2], and the standard mean estimator is presented. The comparisons are performed both by numerical simulation and in vivo measurements of anterior and posterior eye segment as well as in skin imaging. The new estimator shows superior performance and also shows clearer image contrast.

Note: Ultra-low birefringence dodecagonal vacuum glass cell

DOE Office of Scientific and Technical Information (OSTI.GOV)

Brakhane, Stefan, E-mail: brakhane@iap.uni-bonn.de; Alt, Wolfgang; Meschede, Dieter

We report on an ultra-low birefringence dodecagonal glass cell for ultra-high vacuum applications. The epoxy-bonded trapezoidal windows of the cell are made of SF57 glass, which exhibits a very low stress-induced birefringence. We characterize the birefringence Δn of each window with the cell under vacuum conditions, obtaining values around 10{sup −8}. After baking the cell at 150 °C, we reach a pressure below 10{sup −10} mbar. In addition, each window is antireflection coated on both sides, which is highly desirable for quantum optics experiments and precision measurements.

Influence of the composite material thermal expansion on embedded highly birefringent polymer microstructured optical fibers

NASA Astrophysics Data System (ADS)

SzelÄ g, M.; Lesiak, P.; Kuczkowski, M.; Domański, A. W.; Woliński, T. R.

2013-05-01

Results of our research on embedded highly birefringent polymer microstructured fibers are presented. A composite material sample with fibers embedded between two layers of a multi-layer composite structure is fabricated and characterized. Temperature sensitivities of the polymer fibers are measured in a free space and compared with the fibers embedded in the composite material. It appeared that highly birefringent polymer microstructured fibers exhibit a strong increase in temperature sensitivity when embedded in the composite material, which is due to the stress-induced changes in birefringence created by thermally-induced strain.

Investigation in clinical potential of polarization sensitive optical coherence tomography in laryngeal tumor model study

NASA Astrophysics Data System (ADS)

Zhou, Xin; Oak, Chulho; Ahn, Yeh-Chan; Kim, Sung Won; Tang, Shuo

2018-02-01

Polarization-sensitive optical coherence tomography (PS-OCT) is capable of measuring tissue birefringence. It has been widely applied to access the birefringence in tissues such as skin and cartilage. The vocal cord tissue consists of three anatomical layers from the surface to deep inside, the epithelium that contains almost no collagen, the lamina propria that is composed with abundant collagen, and the vocalis muscle layer. Due to the variation in the organization of collagen fibers, the different tissue layers show different tissue birefringence, which can be evaluated by PS-OCT phase retardation measurement. Furthermore, collagen fibers in healthy connective tissues are usually well organized, which provides relatively high birefringence. When the collagen organization is destroyed by diseases such as tumor, the birefringence of the tissue will decrease. In this study, a rabbit laryngeal tumor model with different stages of tumor progression is investigated ex-vivo by PS-OCT. The PS-OCT images show a gradual decrease in birefringence from normal tissue to severe tumor tissue. A phase retardation slope-based analysis is conducted to distinguish the epithelium, lamina propria, and muscle layers, respectively. The phase retardation slope quantifies the birefringence in different layers. The quantitative study provides a more detailed comparison among different stages of the rabbit laryngeal tumor model. The PS-OCT result is validated by the corresponding histology images of the same samples.

Quantification of birefringence readily measures the level of muscle damage in zebrafish

DOE Office of Scientific and Technical Information (OSTI.GOV)

Berger, Joachim, E-mail: Joachim.Berger@Monash.edu; Sztal, Tamar; Currie, Peter D.

2012-07-13

Highlights: Black-Right-Pointing-Pointer Report of an unbiased quantification of the birefringence of muscle of fish larvae. Black-Right-Pointing-Pointer Quantification method readily identifies level of overall muscle damage. Black-Right-Pointing-Pointer Compare zebrafish muscle mutants for level of phenotype severity. Black-Right-Pointing-Pointer Proposed tool to survey treatments that aim to ameliorate muscular dystrophy. -- Abstract: Muscular dystrophies are a group of genetic disorders that progressively weaken and degenerate muscle. Many zebrafish models for human muscular dystrophies have been generated and analysed, including dystrophin-deficient zebrafish mutants dmd that model Duchenne Muscular Dystrophy. Under polarised light the zebrafish muscle can be detected as a bright area in anmore » otherwise dark background. This light effect, called birefringence, results from the diffraction of polarised light through the pseudo-crystalline array of the muscle sarcomeres. Muscle damage, as seen in zebrafish models for muscular dystrophies, can readily be detected by a reduction in the birefringence. Therefore, birefringence is a very sensitive indicator of overall muscle integrity within larval zebrafish. Unbiased documentation of the birefringence followed by densitometric measurement enables the quantification of the birefringence of zebrafish larvae. Thereby, the overall level of muscle integrity can be detected, allowing the identification and categorisation of zebrafish muscle mutants. In addition, we propose that the establish protocol can be used to analyse treatments aimed at ameliorating dystrophic zebrafish models.« less

Role of the Caenorhabditis elegans multidrug resistance gene, mrp-4, in gut granule differentiation.

PubMed

Currie, Erin; King, Brian; Lawrenson, Andrea L; Schroeder, Lena K; Kershner, Aaron M; Hermann, Greg J

2007-11-01

Caenorhabditis elegans gut granules are lysosome-related organelles with birefringent contents. mrp-4, which encodes an ATP-binding cassette (ABC) transporter homologous to mammalian multidrug resistance proteins, functions in the formation of gut granule birefringence. mrp-4(-) embryos show a delayed appearance of birefringent material in the gut granule but otherwise appear to form gut granules properly. mrp-4(+) activity is required for the extracellular mislocalization of birefringent material, body-length retraction, and NaCl sensitivity, phenotypes associated with defective gut granule biogenesis exhibited by embryos lacking the activity of GLO-1/Rab38, a putative GLO-1 guanine nucleotide exchange factor GLO-4, and the AP-3 complex. Multidrug resistance protein (MRP)-4 localizes to the gut granule membrane, consistent with it playing a direct role in the transport of molecules that compose and/or facilitate the formation of birefringent crystals within the gut granule. However, MRP-4 is also present in oocytes and early embryos, and our genetic analyses indicate that its site of action in the formation of birefringent material may not be limited to just the gut granule in embryos. In a search for genes that function similarly to mrp-4(+), we identified WHT-2, another ABC transporter that acts in parallel to MRP-4 for the formation of birefringent material in the gut granule.

Differential diagnosis of periapical cyst using collagen birefringence pattern of the cyst wall

PubMed Central

2017-01-01

Objectives Periapical lesions, including periapical cyst (PC), periapical granuloma (PG), and periapical abscess (PA), are frequently affected by chemical/physical damage during root canal treatment or severe bacterial infection, and thus, the differential diagnosis of periapical lesions may be difficult due to the presence of severe inflammatory reaction. The aim of this study was to make differential diagnosis among PC, PG, and PA under polarizing microscope. Materials and Methods The collagen birefringence patterns of 319 cases of PC (n = 122), PG (n = 158), and PA (n = 39) obtained using a polarizing microscope were compared. In addition, 6 cases of periodontal fibroma (PF) were used as positive controls. Results Collagen birefringence was condensed with a thick, linear band-like pattern in PC, but was short and irregularly scattered in PG, and scarce or absent in PA. PF showed intense collagen birefringence with a short, palisading pattern but no continuous band-like pattern. The linear band-like birefringence in PC was ascribed to pre-existing expansile tensile stress of the cyst wall. Conclusions In this study all PCs (n = 122) were distinguishable from PGs and PAs by their characteristic birefringence, despite the absence of lining epithelium (n = 20). Therefore, the authors suggest that the presence of linear band-like collagen birefringence of the cyst wall aids the diagnostic differentiation of PC from PG and PA. PMID:28503476

THE CHANGING PATTERN OF BIREFRINGENCE IN PLASMODIA OF THE SLIME MOLD, PHYSARUM POLYCEPHALUM

PubMed Central

Nakajima, Hiromichi; Allen, Robert D.

1965-01-01

Plasmodia of the acellular slime mold, Physarum polycephalum, reveal a complex and changing pattern of birefringence when examined with a sensitive polarizing microscope. Positively birefringent fibrils are found throughout the ectoplasmic region of the plasmodium. In the larger strands they may be oriented parallel to the strand axis, or arranged circularly or spirally along the periphery of endoplasmic channels. Some fibrils exist for only a few minutes, others for a longer period. Some, particularly the circular fibrils, undergo changes in birefringence as they undergo cyclic deformations. In the ramifying strand region and the advancing margin there is a tendency for fibrils of various sizes to become organized into mutually orthogonal arrays. In some plasmodia the channel wall material immediately adjacent to the endoplasm has been found to be birefringent. The sign of endoplasmic birefringence is negative, and its magnitude is apparently constant over the streaming cycle. The pattern of plasmodial birefringence and its changes during the shuttle streaming cycle of Physarum are considered in the light of several models designed to explain either cytoplasmic streaming alone or the entire gamut of plasmodial motions. The results of this and other recent physical studies suggest that both streaming and the various other motions of the plasmodium may very likely be explained in terms of coordinated contractions taking place in the fibrils which are rendered visible in polarized light. PMID:14287186

Vacuum birefringence and the x-ray polarization from black-hole accretion disks

NASA Astrophysics Data System (ADS)

Caiazzo, Ilaria; Heyl, Jeremy

2018-04-01

In the next decade, x-ray polarimetry will open a new window on the high-energy Universe, as several missions that include an x-ray polarimeter are currently under development. Observations of the polarization of x rays coming from the accretion disks of stellar-mass and supermassive black holes are among the new polarimeters' major objectives. In this paper, we show that these observations can be affected by the quantum electrodynamic (QED) effect of vacuum birefringence: after an x-ray photon is emitted from the accretion disk, its polarization changes as the photon travels through the accretion disk's magnetosphere, as a result of the vacuum becoming birefringent in the presence of a magnetic field. We show that this effect can be important for black holes in the energy band of the upcoming polarimeters and has to be taken into account in a complete model of the x-ray polarization that we expect to detect from black-hole accretion disks, both for stellar mass and for supermassive black holes. We find that, for a chaotic magnetic field in the disk, QED can significantly decrease the linear polarization fraction of edge-on photons, depending on the spin of the hole and on the strength of the magnetic field. This effect can provide, for the first time, a direct way to probe the magnetic field strength close to the innermost stable orbit of black-hole accretion disks and to study the role of magnetic fields in astrophysical accretion in general.

Contribution of counterions and degree of ionization for birefringence creation and relaxation kinetics parameters of PAH/PAZO films

DOE Office of Scientific and Technical Information (OSTI.GOV)

Raposo, Maria, E-mail: mfr@fct.unl.pt; Monteiro Timóteo, Ana Rita; Ribeiro, Paulo A.

2015-09-21

Photo induced birefringent materials can be used to develop optical and conversion energy devices, and consequently, the study of the variables that influences the creation and relaxation of birefringence should be carefully analyzed. In this work, the parameters of birefringence creation and relaxation kinetics curves obtained on layer-by-layer (LBL) films, prepared from azo-polyectrolyte poly[1-[4-(3-carboxy-4 hydroxyphenylazo) benzene sulfonamido]-1,2-ethanediyl, sodium salt] (PAZO) and poly(allylamine hydrochloride)(PAH), are related with the presence of counterions and the degree of ionization of the polyelectrolytes. Those kinetics curves obtained on PAH/PAZO LBL films, prepared from PAH solutions with different pHs and maintaining the pH of PAZO solutionmore » constant at pH = 9, were analyzed taking into account the films composition which was characterized by X-ray photoelectron spectroscopy. The creation and relaxation birefringence curves are justified by two processes: one associated to local mobility of the azobenzene with a characteristic time 30 s and intensity constant and other associated with polymeric chains mobility with the characteristic time and intensity decreasing with pH. These results allow us to conclude that the birefringence creation process, associated to local mobility of azobenzenes is independent of the degree of ionization and of number of counterions or co-ions present while the birefringence creation process associated to mobility of chains have its characteristic time and intensity dependent of both degree of ionization and number of counterions. The birefringence relaxation processes are dependent of the degree of ionization. The analysis of the films composition revealed, in addition, the presence of a protonated secondary or tertiary amine revealing that PAZO may have positive charges and consequently a zwitterionic behavior.« less

Birefringent Stable Glass with Predominantly Isotropic Molecular Orientation

NASA Astrophysics Data System (ADS)

Liu, Tianyi; Exarhos, Annemarie L.; Alguire, Ethan C.; Gao, Feng; Salami-Ranjbaran, Elmira; Cheng, Kevin; Jia, Tiezheng; Subotnik, Joseph E.; Walsh, Patrick J.; Kikkawa, James M.; Fakhraai, Zahra

2017-09-01

Birefringence in stable glasses produced by physical vapor deposition often implies molecular alignment similar to liquid crystals. As such, it remains unclear whether these glasses share the same energy landscape as liquid-quenched glasses that have been aged for millions of years. Here, we produce stable glasses of 9-(3,5-di(naphthalen-1-yl)phenyl)anthracene molecules that retain three-dimensional shapes and do not preferentially align in a specific direction. Using a combination of angle- and polarization-dependent photoluminescence and ellipsometry experiments, we show that these stable glasses possess a predominantly isotropic molecular orientation while being optically birefringent. The intrinsic birefringence strongly correlates with increased density, showing that molecular ordering is not required to produce stable glasses or optical birefringence, and provides important insights into the process of stable glass formation via surface-mediated equilibration. To our knowledge, such novel amorphous packing has never been reported in the past.

Highly birefringent elliptical core photonic crystal fiber for terahertz application

NASA Astrophysics Data System (ADS)

Sultana, Jakeya; Islam, Md. Saiful; Faisal, Mohammad; Islam, Mohammad Rakibul; Ng, Brian W.-H.; Ebendorff-Heidepriem, Heike; Abbott, Derek

2018-01-01

We present a novel strategy for designing a highly birefringent photonic crystal fiber (PCF) with near zero flattened dispersion properties by applying elliptical air holes in the core area. The elliptical structure of the air holes in the porous-core region introduces asymmetry between x and y polarization modes, which consequently offers ultra-high birefringence. Also the compact geometry of the conventional hexagonal structure in the cladding confines most of the useful power. The optical properties including birefringence, dispersion, confinement loss, effective material loss (EML) and single modeness of the fiber are investigated using a full-vector finite element method. Simulation results show an ultra-high birefringence of 0 . 086 ultra-flattened near zero dispersion of 0 . 53 ± 0 . 07 ps/THz/cm in a broad frequency range. The practical implementation of the proposed fiber is feasible using existing fabrication technology and is applicable to the areas of terahertz sensing and polarization maintaining systems.

Noise stochastic corrected maximum a posteriori estimator for birefringence imaging using polarization-sensitive optical coherence tomography

PubMed Central

Kasaragod, Deepa; Makita, Shuichi; Hong, Young-Joo; Yasuno, Yoshiaki

2017-01-01

This paper presents a noise-stochastic corrected maximum a posteriori estimator for birefringence imaging using Jones matrix optical coherence tomography. The estimator described in this paper is based on the relationship between probability distribution functions of the measured birefringence and the effective signal to noise ratio (ESNR) as well as the true birefringence and the true ESNR. The Monte Carlo method is used to numerically describe this relationship and adaptive 2D kernel density estimation provides the likelihood for a posteriori estimation of the true birefringence. Improved estimation is shown for the new estimator with stochastic model of ESNR in comparison to the old estimator, both based on the Jones matrix noise model. A comparison with the mean estimator is also done. Numerical simulation validates the superiority of the new estimator. The superior performance of the new estimator was also shown by in vivo measurement of optic nerve head. PMID:28270974

Angular tuning of the magnetic birefringence in rippled cobalt films

DOE Office of Scientific and Technical Information (OSTI.GOV)

Arranz, Miguel A., E-mail: MiguelAngel.Arranz@uclm.es; Colino, José M.

We report the measurement of magnetically induced birefringence in rippled Co films. For this purpose, the magneto-optical properties of ion beam eroded ferromagnetic films were studied using Kerr magnetometry and magnetic birefringence in the transmitted light intensity. Upon sufficient ion sculpting, these ripple surface nanostructures developed a defined uniaxial anisotropy in the in-plane magnetization, finely tuning the magnetic birefringence effect. We have studied its dependence on the relative orientation between the ripple direction and the magnetic field, and found this effect to be dramatically correlated with the capability to neatly distinguish the mechanisms for the in-plane magnetization reversal, i.e., rotationmore » and nucleation. This double refraction corresponds univocally to the two magnetization axes, parallel and perpendicular to the ripples direction. We have also observed that tuned birefringence in stack assemblies of rippled Co films, which enables us to technically manipulate the number and direction of refraction axes.« less

Dodecagonal photonic quasi-crystal fiber with high birefringence.

PubMed

Cai, Weicheng; Liu, Exian; Feng, Bo; Xiao, Wei; Liu, Hongfei; Wang, Ziming; Wang, Shuo; Liang, Taiyuan; Liu, Jianqiang; Liu, Jianjun

2016-10-01

A photonic quasi-crystal fiber (PQF) with high birefringence is proposed. A dodecagonal Stampfli quasi-periodic lattice of air holes constitutes the cladding of the PQF. The PQF maintains the properties of high birefringence and single-mode operation regime in a wide wavelength range from 1.2 to 2.0 μm by optimizing the size of the air holes around the core of the PQF. A birefringence with 3.86×10^-2 can be obtained at 1.31 and 1.55 μm optical telecommunication windows. The birefringence is of the order of 10^-2, which is two orders of magnitude larger than that of the conventional polarization-maintaining fibers and hardly affected by the incident wavelength. The proposed PQF also maintains a high nonlinear coefficient and low confinement loss. Our structure and simulation results are expected to provide a valuable reference and basic data to relative fabrication and experiments.

Birefringence measurement of retinal nerve fiber layer using polarization-sensitive spectral domain optical coherence tomography with Jones matrix based analysis

NASA Astrophysics Data System (ADS)

Yamanari, Masahiro; Miura, Masahiro; Makita, Shuichi; Yatagai, Toyohiko; Yasuno, Yoshiaki

2007-02-01

Birefringence of retinal nerve fiber layer is measured by polarization-sensitive spectral domain optical coherence tomography using the B-scan-oriented polarization modulation method. Birefringence of the optical fiber and the cornea is compensated by Jones matrix based analysis. Three-dimensional phase retardation map around the optic nerve head and en-face phase retardation map of the retinal nerve fiber layer are shown. Unlike scanning laser polarimetry, our system can measure the phase retardation quantitatively without using bow-tie pattern of the birefringence in the macular region, which enables diagnosis of glaucoma even if the patients have macular disease.

Spectral contents readout of birefringent sensor

NASA Technical Reports Server (NTRS)

Redner, Alex S.

1989-01-01

The technical objective of this research program was to develop a birefringent sensor, capable of measuring strain/stress up to 2000 F and a readout system based on Spectral Contents analysis. As a result of the research work, a data acquisition system was developed, capable of measuring strain birefringence in a sensor at 2000 F, with multi-point static and dynamic capabilities. The system uses a dedicated spectral analyzer for evaluation of stress-birefringence and a PC-based readout. Several sensor methods were evaluated. Fused silica was found most satisfactory. In the final evaluation, measurements were performed up to 2000 F and the system performance exceeded expectations.

Highly sensitive distributed birefringence measurements based on a two-pulse interrogation of a dynamic Brillouin grating

NASA Astrophysics Data System (ADS)

Soto, Marcelo A.; Denisov, Andrey; Angulo-Vinuesa, Xabier; Martin-Lopez, Sonia; Thévenaz, Luc; Gonzalez-Herraez, Miguel

2017-04-01

A method for distributed birefringence measurements is proposed based on the interference pattern generated by the interrogation of a dynamic Brillouin grating (DBG) using two short consecutive optical pulses. Compared to existing DBG interrogation techniques, the method here offers an improved sensitivity to birefringence changes thanks to the interferometric effect generated by the reflections of the two pulses. Experimental results demonstrate the possibility to obtain the longitudinal birefringence profile of a 20 m-long Panda fibre with an accuracy of 10-8 using 16 averages and 30 cm spatial resolution. The method enables sub-metric and highly-accurate distributed temperature and strain sensing.

Electrical birefringence tuning of VCSELs

NASA Astrophysics Data System (ADS)

Pusch, Tobias; Lindemann, Markus; Gerhardt, Nils C.; Hofmann, Martin R.; Michalzik, Rainer

2018-02-01

The birefringence splitting B, which is the frequency difference between the two fundamental linear polarization modes in vertical-cavity surface-emitting lasers (VCSELs), is the key parameter determining the polarization dynamics of spin-VCSELs that can be much faster than the intensity dynamics. For easy handling and control, electrical tuning of B is favored. This was realized in an integrated chip by thermally induced strain via asymmetric heating with a birefringence tuning range of 45 GHz. In this paper we present our work on VCSEL structures mounted on piezoelectric transducers for strain generation. Furthermore we show a combination of both techniques, namely VCSELs with piezo-thermal birefringence tunability.

Multimode Brillouin spectrum in a long tapered birefringent photonic crystal fiber.

PubMed

Tchahame, Joël Cabrel; Beugnot, Jean-Charles; Kudlinski, Alexandre; Sylvestre, Thibaut

2015-09-15

We investigate the stimulated Brillouin scattering (SBS) in a long tapered birefringent solid-core photonic crystal fiber (PCF) and compare our results with a similar but untapered PCF. It is shown that the taper generates a broadband and multipeaked Brillouin spectrum, while significantly increasing the threshold power. Furthermore, we observe that the strong fiber birefringence gives rise to a frequency shift of the Brillouin spectrum which increases along the fiber. Numerical simulations are also presented to account for the taper effect and the birefringence. Our findings open a new means to control or inhibit the SBS by tapering photonic crystal fibers.

A development of two-dimensional birefringence distribution measurement system with a sampling rate of 1.3 MHz

NASA Astrophysics Data System (ADS)

Onuma, Takashi; Otani, Yukitoshi

2014-03-01

A two-dimensional birefringence distribution measurement system with a sampling rate of 1.3 MHz is proposed. A polarization image sensor is developed as core device of the system. It is composed of a pixelated polarizer array made from photonic crystal and a parallel read out circuit with a multi-channel analog to digital converter specialized for two-dimensional polarization detection. By applying phase shifting algorism with circularly-polarized incident light, birefringence phase difference and azimuthal angle can be measured. The performance of the system is demonstrated experimentally by measuring actual birefringence distribution and polarization device such as Babinet-Soleil compensator.

Flow-induced birefringence measurement system using dual-crystal transverse electro-optic modulator for microgravity fluid physics applications

NASA Technical Reports Server (NTRS)

Mackey, Jeffrey R.

1999-01-01

We have developed a new instrument that can measure fast transient birefringence and polymer chain orientation angle in complex fluids. The instrument uses a dual-crystal transverse electro-optic modulator with the second crystal's modulation voltage applied 180 deg out of phase from that of the first crystal. In this manner, the second crystal compensates for the intrinsic static birefringence of the first crystal, and it doubles the modulation depth. By incorporating a transverse electro-optic modulator with two lithium-niobate (LiNbO3) crystals oriented orthogonal to each other with a custom-designed optical system, we have produced a very small robust instrument capable of fast transient retardation measurements. By measuring the sample thickness or optical path length through the sample, we can calculate the transient birefringence. This system can also measure dichroism. We have compared the calibration results and retardation and orientation angle measurements of this instrument with those of a photoelastic modulator (PEM) based system using a quarter wave plate and a high-precision 1/16-wave plate to simulate a birefringent sample. Transient birefringence measurements on the order of 10(exp -9) can be measured using either modulator.

In vivo thickness and birefringence determination of the human retinal nerve fiber layer using polarization-sensitive optical coherence tomography.

PubMed

Cense, B; Chen, T C; de Boer, J F

2006-01-01

Thinning of the retinal nerve fiber layer and changes in retinal nerve fiber layer birefringence may both precede clinically detectable glaucomatous vision loss. We present in vivo thickness and depth-resolved birefringence measurements of the human retinal nerve fiber layer (RNFL) by use of polarization-sensitive optical coherence tomography (PS-OCT). Using a fiber-based PS-OCT setup real-time images of the human retina in vivo were recorded, co-registered with retinal video images of the location of PS-OCT scans. PS-OCT scans around the optic nerve head (ONH) of two healthy young volunteers were made using 10 concentric circles of increasing radius. Both the mean retinal nerve fiber layer thickness and mean retinal nerve fiber birefringence for each of 48 sectors on a circle were determined. The retinal nerve fiber layer thickness and birefringence varied as a function of sector around the ONH. Measured double pass phase retardation per unit depth values around the ONH range between 0.10 and 0.35 degrees/microm. The retinal nerve fiber layer becomes thinner with increasing distance from the ONH. In contrast, the birefringence does not vary significantly with increasing distance from the ONH.

Linear Transformation of the Polarization Modes in Coiled Optical Spun-Fibers with Strong Unperturbed Linear Birefringence. I. Nonresonant Transformation

NASA Astrophysics Data System (ADS)

Malykin, G. B.; Pozdnyakova, V. I.

2018-03-01

A linear transformation of orthogonal polarization modes in coiled optical spun-fibers with strong unperturbed linear birefringence, which causes the emergence of the dependences of the integrated elliptical birefringence and the ellipticity and azimuth of the major axis of the ellipse, as well as the polarization state of radiation (PSR), on the length of optical fiber has been considered. Optical spun-fibers are subjected to a strong mechanical twisting, which is frozen into the structure of the optical fiber upon cooling, in the process of being drawn out from the workpiece. Since the values of the local polarization parameters of coiled spunwaveguides vary according to a rather complex law, the calculations were carried out by numerical modeling of the parameters of the Jones matrices. Since the rotation speed of the axes of the birefringence is constant on a relatively short segment of a coiled optical spun-fiber in the accompanying torsion (helical) coordinate system, the so-called "Ginzburg helical polarization modes" (GHPMs)—two mutually orthogonal ellipses with the opposite directions of traversal, the axis of which rotate relative to the fixed coordinate system uniformly and unidirectionally—are approximately the local normal polarization modes of such optical fiber. It has been shown that, despite the fact that the unperturbed linear birefringence of the spun-fibers significantly exceeds the linear birefringence, which is caused by the winding on a coil, the integral birefringence of an extended segment of such a fiber coincides in order of magnitude with the linear birefringence, which is caused by the winding on the coil, and the integral polarization modes tend asymptotically to circular ones. It has been also shown that the values of the circular birefringence of twisted single-mode fibers, which were calculated in a nonrotating and torsion helical coordinate systems, differ significantly. It has been shown that the polarization phenomena occur in the process of linear transformation of local polarization modes, which lead to small quasi-harmonic oscillations of the birefringence integral parameters of the optical spun-fibers, which depend on their length, and the period of these oscillations is approximately equal to half of the effective period of polarization beating.

Detection of ultrastructural changes in genetically altered and exercised skeletal muscle using PS-OCT

NASA Astrophysics Data System (ADS)

Pasquesi, James J.; Schlachter, Simon C.; Boppart, Marni D.; Chaney, Eric; Kaufman, Stephen J.; Boppart, Stephen A.

2006-02-01

Birefringence of skeletal muscle has been associated with the ultrastructure of individual sarcomeres, specifically the arrangement of A-bands corresponding to the thick myosin filaments. Murine skeletal muscle (gastrocnemius) was imaged with a fiber-based PS-OCT imaging system to determine the level of birefringence present in the tissue under various conditions. In addition to muscle controls from wild-type mice, muscle from abnormal mice included: genetically-modified (mdx) mice which model human muscular dystrophy, transgenic mice exhibiting an overexpression of integrin (α7β1), and transgenic integrin (α7β1)knockout mice. Comparisons were also made between rested and exercised muscles to determine the effects of exercise on muscle birefringence for each of these normal and abnormal conditions. The PS-OCT images revealed that the presence of birefringence was similar in the rested muscle with dystrophy-like features (i.e., lacking the structural protein dystrophin - mdx) and in the integrin (α7β1)knockout muscle when compared to the normal (wild-type) control. However, exercising these abnormal muscle tissues drastically reduced the presence of birefringence detected by the PS-OCT system. The muscle exhibiting an overexpression of integrin (α7β1) remained heavily birefringent before and after exercise, similar to the normal (wild-type) muscle. These results suggest that there is a distinct relationship between the degree of birefringence detected using PS-OCT and the sarcomeric ultrastructure present within skeletal muscle.

Liquid-Crystal-Enabled Active Plasmonics: A Review

PubMed Central

Si, Guangyuan; Zhao, Yanhui; Leong, Eunice Sok Ping; Liu, Yan Jun

2014-01-01

Liquid crystals are a promising candidate for development of active plasmonics due to their large birefringence, low driving threshold, and versatile driving methods. We review recent progress on the interdisciplinary research field of liquid crystal based plasmonics. The research scope of this field is to build the next generation of reconfigurable plasmonic devices by combining liquid crystals with plasmonic nanostructures. Various active plasmonic devices, such as switches, modulators, color filters, absorbers, have been demonstrated. This review is structured to cover active plasmonic devices from two aspects: functionalities and driven methods. We hope this review would provide basic knowledge for a new researcher to get familiar with the field, and serve as a reference for experienced researchers to keep up the current research trends. PMID:28788515

Dual light field and polarization imaging using CMOS diffractive image sensors.

PubMed

Jayasuriya, Suren; Sivaramakrishnan, Sriram; Chuang, Ellen; Guruaribam, Debashree; Wang, Albert; Molnar, Alyosha

2015-05-15

In this Letter we present, to the best of our knowledge, the first integrated CMOS image sensor that can simultaneously perform light field and polarization imaging without the use of external filters or additional optical elements. Previous work has shown how photodetectors with two stacks of integrated metal gratings above them (called angle sensitive pixels) diffract light in a Talbot pattern to capture four-dimensional light fields. We show, in addition to diffractive imaging, that these gratings polarize incoming light and characterize the response of these sensors to polarization and incidence angle. Finally, we show two applications of polarization imaging: imaging stress-induced birefringence and identifying specular reflections in scenes to improve light field algorithms for these scenes.

Microdroplet-etched highly birefringent low-loss fiber tapers.

PubMed

Mikkelsen, Jared C; Poon, Joyce K S

2012-07-01

We use hydrofluoric acid microdroplets to directly etch highly birefringent biconical fiber tapers from standard single-mode fibers. The fiber tapers have micrometer-sized cross sections, which are controlled by the etching condition. The characteristic teardrop cross section leads to a high group birefringence of B(G)≈0.017 and insertion losses <0.7 dB over waist lengths of about 2.1 mm.

NASA Tech Briefs, February 2014

NASA Technical Reports Server (NTRS)

2014-01-01

Topics include: JWST Integrated Simulation and Test (JIST) Core; Software for Non-Contact Measurement of an Individual's Heart Rate Using a Common Camera; Rapid Infrared Pixel Grating Response Testbed; Temperature Measurement and Stabilization in a Birefringent Whispering Gallery Resonator; JWST IV and V Simulation and Test (JIST) Solid State Recorder (SSR) Simulator; Development of a Precision Thermal Doubler for Deep Space; Improving Friction Stir Welds Using Laser Peening; Methodology of Evaluating Margins of Safety in Critical Brazed Joints; Interactive Inventory Monitoring; Sensor for Spatial Detection of Single-Event Effects in Semiconductor-Based Electronics; Reworked CCGA-624 Interconnect Package Reliability for Extreme Thermal Environments; Current-Controlled Output Driver for Directly Coupled Loads; Bulk Metallic Glasses and Matrix Composites as Spacecraft Shielding; Touch Temperature Coating for Electrical Equipment on Spacecraft; Li-Ion Electrolytes Containing Flame-Retardant Additives; Autonomous Robotic Manipulation (ARM); CARVE Log; Platform Perspective Toolkit; Convex Hull-Based Plume and Anomaly Detection; Pre-Filtration of GOSAT Data Using Only Level 1 Data and an Intelligent Filter to Remove Low Clouds; Affordability Comparison Tool - ACT; "Ascent - Commemorating Shuttle" for iPad; Cassini Mission App; Light-Weight Workflow Engine: A Server for Executing Generic Workflows; Model for System Engineering of the CheMin Instrument; Timeline Central Concepts; Parallel Particle Filter Toolkit; Particle Filter Simulation and Analysis Enabling Non-Traditional Navigation; Quasi-Terminator Orbits for Mapping Small Primitive Bodies; The Subgrid-Scale Scalar Variance Under Supercritical Pressure Conditions; Sliding Gait for ATHLETE Mobility; and Automated Generation of Adaptive Filter Using a Genetic Algorithm and Cyclic Rule Reduction.

Design and Performance Evaluation of Sensors and Actuators for Advanced Optical Systems

NASA Technical Reports Server (NTRS)

Clark, Natalie

2011-01-01

Current state-of-the-art commercial sensors and actuators do not meet many of NASA s next generation spacecraft and instrument needs. Nor do they satisfy the DoD needs for satellite missions, especially micro/nano satellite missions. In an effort to develop advanced optical devices and instruments that meet mission requirements, NASA Langley recently completed construction of a new cleanroom housing equipment capable of fabricating high performance active optic and adaptive optic technologies including deformable mirrors, reconfigurable lenses (both refractive and diffractive), spectrometers, spectro-polarimeters, tunable filters and many other active optic devices. In addition to performance, these advanced optic technologies offer advantages in speed, size, weight, power consumption, and radiation tolerance. The active optic devices described in this paper rely on birefringent liquid crystal materials to alter either the phase or the polarization of the incoming light. Design considerations and performance evaluation results for various NASA applications are presented. Applications presented will include large space telescopes, optical communications, spacecraft windows, coronagraphs, and star trackers. Keywords: Photonics, Adaptive Optics, Tunable Filters, MEMs., MOEMs, Coronagraph, Star Tracker

Large birefringence and polarization holographic gratings formed in photocross-linkable polymer liquid crystals comprising bistolane mesogenic side groups

NASA Astrophysics Data System (ADS)

Emoto, Akira; Matsumoto, Taro; Yamashita, Ayumi; Shioda, Tatsutoshi; Ono, Hiroshi; Kawatsuki, Nobuhiro

2009-10-01

Polarization gratings with large birefringence are formed in photoreactive polymer liquid crystals with bistolane moiety and terminal cinnamic acid moiety by the use of polarized ultraviolet interference light and subsequent annealing. The polarized ultraviolet light causes the axis-selective photoreaction between the cinnamic acid groups and subsequent annealing induce the reorientation of peripheral molecules without cross-linking along the cross-linked groups. Long bistolane mesogenic moiety exhibits large birefringence in comparison with a biphenyl mesogenic moiety, the value of the induced birefringence in the bistolane mesogenic liquid crystalline (LC) polymer is strongly dependent on both the grating constant and the wavelength of the reconstruction light.

Birefringence imaging in biological tissue using polarization sensitive optical coherent tomography

DOEpatents

De Boer, Johannes F.; Milner, Thomas E.; Nelson, J. Stuart

2001-01-01

Employing a low coherence Michelson interferometer, two dimensional images of optical birefringence in turbid samples as a function of depth are measured. Polarization sensitive detection of the signal formed by interference of backscattered light from the sample and a mirror or reference plane in the reference arm which defines a reference optical path length, give the optical phase delay between light propagating along the fast and slow axes of the birefringence sample. Images showing the change in birefringence in response to irradiation of the sample are produced as an example of the detection apparatus and methodology. The technique allow rapid, noncontact investigation of tissue or sample diagnostic imaging for various medical or materials procedures.

Polarization locked vector solitons and axis instability in optical fiber.

PubMed

Cundiff, Steven T.; Collings, Brandon C.; Bergman, Keren

2000-09-01

We experimentally observe polarization-locked vector solitons in optical fiber. Polarization locked-vector solitons use nonlinearity to preserve their polarization state despite the presence of birefringence. To achieve conditions where the delicate balance between nonlinearity and birefringence can survive, we studied the polarization evolution of the pulses circulating in a laser constructed entirely of optical fiber. We observe two distinct states with fixed polarization. This first state occurs for very small values birefringence and is elliptically polarized. We measure the relative phase between orthogonal components along the two principal axes to be +/-pi/2. The relative amplitude varies linearly with the magnitude of the birefringence. This state is a polarization locked vector soliton. The second, linearly polarized, state occurs for larger values of birefringence. The second state is due to the fast axis instability. We provide complete characterization of these states, and present a physical explanation of both of these states and the stability of the polarization locked vector solitons. (c) 2000 American Institute of Physics.

Polarization locked vector solitons and axis instability in optical fiber

NASA Astrophysics Data System (ADS)

Cundiff, Steven T.; Collings, Brandon C.; Bergman, Keren

2000-09-01

We experimentally observe polarization-locked vector solitons in optical fiber. Polarization locked-vector solitons use nonlinearity to preserve their polarization state despite the presence of birefringence. To achieve conditions where the delicate balance between nonlinearity and birefringence can survive, we studied the polarization evolution of the pulses circulating in a laser constructed entirely of optical fiber. We observe two distinct states with fixed polarization. This first state occurs for very small values birefringence and is elliptically polarized. We measure the relative phase between orthogonal components along the two principal axes to be ±π/2. The relative amplitude varies linearly with the magnitude of the birefringence. This state is a polarization locked vector soliton. The second, linearly polarized, state occurs for larger values of birefringence. The second state is due to the fast axis instability. We provide complete characterization of these states, and present a physical explanation of both of these states and the stability of the polarization locked vector solitons.

First results from the new PVLAS apparatus: A new limit on vacuum magnetic birefringence

NASA Astrophysics Data System (ADS)

Della Valle, F.; Milotti, E.; Ejlli, A.; Messineo, G.; Piemontese, L.; Zavattini, G.; Gastaldi, U.; Pengo, R.; Ruoso, G.

2014-11-01

Several groups are carrying out experiments to observe and measure vacuum magnetic birefringence, predicted by quantum electrodynamics (QED). We have started running the new PVLAS apparatus installed in Ferrara, Italy, and have measured a noise floor value for the unitary field magnetic birefringence of vacuum Δ nu(vac )=(4 ±20 )×1 0-23 T-2 (the error represents a 1 σ deviation). This measurement is compatible with zero and hence represents a new limit on vacuum magnetic birefringence deriving from nonlinear electrodynamics. This result reduces to a factor of 50 the gap to be overcome to measure for the first time the value of Δ nu(vac ,QED ) predicted by QED: Δ nu(vac ,QED )=4 ×10-24 T-2 . These birefringence measurements also yield improved model-independent bounds on the coupling constant of axion-like particles to two photons, for masses greater than 1 meV, along with a factor-2 improvement of the fractional charge limit on millicharged particles (fermions and scalars), including neutrinos.

Controlled Terahertz Birefringence in Stretched Poly(lactic acid) Films Investigated by Terahertz Time-Domain Spectroscopy and Wide-Angle X-ray Scattering.

PubMed

Iwasaki, Hotsumi; Nakamura, Madoka; Komatsubara, Nozomu; Okano, Makoto; Nakasako, Masayoshi; Sato, Harumi; Watanabe, Shinichi

2017-07-20

We report a correlation between the dielectric property and structure of stretched poly(lactic acid) (PLA) films, revealed by polarization-sensitive terahertz time-domain spectroscopy and two-dimensional (2D) wide-angle X-ray scattering (WAXS). The experiments evidence that the dielectric function of the PLA film becomes more anisotropic with increasing draw ratio (DR). This behavior is explained by a classical Lorentz oscillator model assuming polarization-dependent absorption. The birefringence can be systematically altered from 0 to 0.13 by controlling DR. The combination of terahertz spectroscopy and 2D WAXS measurement reveals a clear correlation between the birefringence in the terahertz frequency domain and the degree of orientation of the PLA molecular chains. These findings imply that the birefringence is a result of the orientation of the PLA chains with anisotropic macromolecular vibration modes. Because of a good controllability of the birefringence, polymer-based materials will provide an attractive materials system for phase retarders in the terahertz frequency range.

Optical activity via Kerr nonlinearity in a spinning chiral medium

NASA Astrophysics Data System (ADS)

Khan, Anwar Ali; Bacha, Bakht Amin; Khan, Rahmat Ali

2016-11-01

Optical activity is investigated in a chiral medium by employing the four level cascade atomic model, in which the optical responses of the atomic medium are studied with Kerr nonlinearity. Light entering into a chiral medium splits into circular birefringent beams. The angle of divergence between the circular birefringent beams and the polarization states of the two light beams is manipulated with Kerr nonlinearity. In the stationary chiral medium the angle of divergence between the circular birefringent beams is calculated to be 1.3 radian. Furthermore, circular birefringence is optically controlled in a spinning chiral medium, where the maximum rotary photon drag angle for left (right) circularly polarized beam is ±1.1 (±1.5) microradian. The change in the angle of divergence between circular birefringent beams by rotary photon drag is calculated to be 0.4 microradian. The numerical results may help to understand image designing, image coding, discovery of photonic crystals and optical sensing technology.

Mirror Birefringence in a Fabry-Perot Cavity and the Detection of Vacuum Birefringence in a Magnetic Field

NASA Technical Reports Server (NTRS)

Chui, T. C. P.; Shao, M.; Redding, D.; Gursel, Y.; Boden, A.

1995-01-01

We discuss the effect of mirror birefringence in two optical schemes designed to detect the quantum-electrodynamics (QED) predictions of vacuum birefringence under the influence of a strong magnetic field, B. Both schemes make use of a high finesse Fabry-Perot cavity (F-P) to increase the average path length of the light in the magnetic field. The first scheme, which we called the frequency scheme, is based on measurement of the beat frequency of two orthogonal polarized laser beams in the cavity. We show that mirror birefringence contributes to the detection uncertainties in first order, resulting in a high susceptibility to small thermal disturbances. We estimate that an unreasonably high thermal stability of 10-9 K is required to resolve the effect to 0.1%. In the second scheme, which we called the polarization rotation scheme, laser polarized at 45 relative to the B field is injected into the cavity.

Deep tissue volume imaging of birefringence through fibre-optic needle probes for the delineation of breast tumour

NASA Astrophysics Data System (ADS)

Villiger, Martin; Lorenser, Dirk; McLaughlin, Robert A.; Quirk, Bryden C.; Kirk, Rodney W.; Bouma, Brett E.; Sampson, David D.

2016-07-01

Identifying tumour margins during breast-conserving surgeries is a persistent challenge. We have previously developed miniature needle probes that could enable intraoperative volume imaging with optical coherence tomography. In many situations, however, scattering contrast alone is insufficient to clearly identify and delineate malignant regions. Additional polarization-sensitive measurements provide the means to assess birefringence, which is elevated in oriented collagen fibres and may offer an intrinsic biomarker to differentiate tumour from benign tissue. Here, we performed polarization-sensitive optical coherence tomography through miniature imaging needles and developed an algorithm to efficiently reconstruct images of the depth-resolved tissue birefringence free of artefacts. First ex vivo imaging of breast tumour samples revealed excellent contrast between lowly birefringent malignant regions, and stromal tissue, which is rich in oriented collagen and exhibits higher birefringence, as confirmed with co-located histology. The ability to clearly differentiate between tumour and uninvolved stroma based on intrinsic contrast could prove decisive for the intraoperative assessment of tumour margins.

Precision interferometric measurements of mirror birefringence in high-finesse optical resonators

NASA Astrophysics Data System (ADS)

Fleisher, Adam J.; Long, David A.; Liu, Qingnan; Hodges, Joseph T.

2016-01-01

High-finesse optical resonators found in ultrasensitive laser spectrometers utilize supermirrors ideally consisting of isotropic high-reflectivity coatings. Strictly speaking, however, the optical coatings are often nonuniformly stressed during the deposition process and therefore do possess some small amount of birefringence. When physically mounted the cavity mirrors can be additionally stressed in such a way that large optical birefringence is induced. Here we report a direct measurement of optical birefringence in a two-mirror Fabry-Pérot cavity with R =99.99 % by observing TEM00 mode beating during cavity decays. Experiments were performed at a wavelength of 4.53 μ m , with precision limited by both quantum and technical noise sources. We report a splitting of δν=618 (1 ) Hz, significantly less than the intrinsic cavity line width of δcav≈3 kHz. With a cavity free spectral range of 96.9 MHz, the equivalent fractional change in mirror refractive index due to birefringence is therefore Δ n /n =6.38 (1 ) ×10-6 .

Nonlinear polarization dynamics in a weakly birefringent all-normal dispersion photonic crystal fiber: toward a practical coherent fiber supercontinuum laser

PubMed Central

Tu, Haohua; Liu, Yuan; Liu, Xiaomin; Turchinovich, Dmitry; Lægsgaard, Jesper; Boppart, Stephen A.

2012-01-01

Dispersion-flattened dispersion-decreased all-normal dispersion (DFDD-ANDi) photonic crystal fibers have been identified as promising candidates for high-spectral-power coherent supercontinuum (SC) generation. However, the effects of the unintentional birefringence of the fibers on the SC generation have been ignored. This birefringence is widely present in nonlinear non-polarization maintaining fibers with a typical core size of 2 µm, presumably due to the structural symmetry breaks introduced in the fiber drawing process. We find that an intrinsic form-birefringence on the order of 10−5 profoundly affects the SC generation in a DFDD-ANDi photonic crystal fiber. Conventional simulations based on the scalar generalized nonlinear Schrödinger equation (GNLSE) fail to reproduce the prominent observed features of the SC generation in a short piece (9-cm) of this fiber. However, these features can be qualitatively or semi-quantitatively understood by the coupled GNLSE that takes into account the form-birefringence. The nonlinear polarization effects induced by the birefringence significantly distort the otherwise simple spectrotemporal field of the SC pulses. We therefore propose the fabrication of polarization-maintaining DFDD-ANDi fibers to avoid these adverse effects in pursuing a practical coherent fiber SC laser. PMID:22274457

Visualization of prostatic nerves by polarization-sensitive optical coherence tomography

PubMed Central

Yoon, Yeoreum; Jeon, Seung Hwan; Park, Yong Hyun; Jang, Won Hyuk; Lee, Ji Youl; Kim, Ki Hean

2016-01-01

Preservation of prostatic nerves is critical to recovery of a man’s sexual potency after radical prostatectomy. A real-time imaging method of prostatic nerves will be helpful for nerve-sparing radical prostatectomy (NSRP). Polarization-sensitive optical coherence tomography (PS-OCT), which provides both structural and birefringent information of tissue, was applied for detection of prostatic nerves in both rat and human prostate specimens, ex vivo. PS-OCT imaging of rat prostate specimens visualized highly scattering and birefringent fibrous structures superficially, and these birefringent structures were confirmed to be nerves by histology or multiphoton microscopy (MPM). PS-OCT could easily distinguish these birefringent structures from surrounding other tissue compartments such as prostatic glands and fats. PS-OCT imaging of human prostatectomy specimens visualized two different birefringent structures, appearing fibrous and sheet-like. The fibrous ones were confirmed to be nerves by histology, and the sheet-like ones were considered to be fascias surrounding the human prostate. PS-OCT imaging of human prostatectomy specimens along the perimeter showed spatial variation in the amount of birefringent fibrous structures which was consistent with anatomy. These results demonstrate the feasibility of PS-OCT for detection of prostatic nerves, and this study will provide a basis for intraoperative use of PS-OCT. PMID:27699090

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Science.gov Websites

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Influence of nematic range on birefringence, heat capacity and elastic modulus near a nematic-smectic-A phase transition

NASA Astrophysics Data System (ADS)

Beaubois, F.; Claverie, T.; Marcerou, J. P.; Rouillon, J. C.; Nguyen, H. T.; Garland, C. W.; Haga, H.

1997-11-01

The birefringence Δn, the specific heat Cp, and the layer compressional elastic modulus B are reported for two liquid crystals near the nematic (N) to smectic-A (SmA) phase transition. As predicted long ago by MacMillan and de Gennes [P. G. de Gennes and J. Prost, The Physics of Liquid Crystals (Clarendon, Oxford, 1993)] the coupling of the nematic orientational order parameter to the smectic-A layering order parameter can substantially alter the critical behavior near the N-SmA transition if the nematic range is small and the nematic order parameter susceptibility is large. In this paper, we present a direct experimental comparison of two compounds: 4-octyloxy-4'-cyanobiphenyl (8OCB) with a short nematic range and 4-octyloxybenzoyloxy-4'-cyanotolane (C8tolane) with a very large N range. The temperature variations of the apparent birefringence Δn and the specific heat Cp across the N-SmA phase transition show the definite influence of the proximity of the isotropic phase in the case of 8OCB while the C8tolane behaves as expected for the three-dimensional XY universality class. The elastic modulus B in the SmA phase, measured at several wave vectors by the second-sound resonance technique, was studied with high resolution as a function of temperature on approaching Tc(N-SmA). These elastic data confirm the B leveling off in both cases with an apparent breakdown of hydrodynamics in the case of the C8tolane compound.

Apparatus and method for increasing the bandwidth of a laser beam

DOEpatents

Chaffee, Paul H.

1991-01-01

A method and apparatus is disclosed that provides a laser output beam having a broad bandwidth and an intensity smooth over time. The bandwidth of the laser output can be varied easily by varying the intensity of a broadband source. The present invention includes an optical modulation apparatus comprising a narrowband laser that outputs a horizontally polarized beam (a "signal beam") and a broadband laser that outputs a vertically polarized beam (a "pump beam") whose intensity varies rapidly. The two beam are coupled into a birefringent laser material so that the respective polarizations coincide with the principal axes of the material. As the two beams travel through the material, the polarization preserving properties of the birefringent material maintain the respective polarizations of the two beam; however there is coupling between the two beams as a result of cross phase modulations, which induces a bandwidth change of the signal beam. The amount of bandwidth change is dependent upon the average intensity of the pump beam. The beams are coupled out from the birefringent material and the modulated signal beam is separated by a polarization selector. The modulated signal beam now has a wider bandwidth, and its shape remains smooth in time. This signal beam can be applied to incoherence inducing systems. The different bandwidths required by these different incoherence inducing systems can be obtained by varying the intensity of the pump beam. The United States Government has rights in this invention pursuant to Contract No. W7405-ENG-48 between the United States Department of Energy and the University of California for the operation of Lawrence Livermore National Laboratory.

Investigating compression failure mechanisms in composite laminates with a transparent fiberglass-epoxy birefringent materials

NASA Technical Reports Server (NTRS)

Shuart, M. J.; Williams, J. G.

1984-01-01

The response and failure of a + or - 45s class laminate was studied by transparent fiberglass epoxy composite birefringent material. The birefringency property allows the laminate stress distribution to be observed during the test and also after the test if permanent residual stresses occur. The location of initial laminate failure and of the subsequent failure propagation are observed through its transparency characteristics. Experimental results are presented.

ANSYS-based birefringence property analysis of side-hole fiber induced by pressure and temperature

NASA Astrophysics Data System (ADS)

Zhou, Xinbang; Gong, Zhenfeng

2018-03-01

In this paper, we theoretically investigate the influences of pressure and temperature on the birefringence property of side-hole fibers with different shapes of holes using the finite element analysis method. A physical mechanism of the birefringence of the side-hole fiber is discussed with the presence of different external pressures and temperatures. The strain field distribution and birefringence values of circular-core, rectangular-core, and triangular-core side-hole fibers are presented. Our analysis shows the triangular-core side-hole fiber has low temperature sensitivity which weakens the cross sensitivity of temperature and strain. Additionally, an optimized structure design of the side-hole fiber is presented which can be used for the sensing application.

Birefringence and dichroism of poly(vinyl-alcohol) foils containing phthalazinium ylids

NASA Astrophysics Data System (ADS)

Rogojanu, Alina; Dascalu, Carmen Felicia; Zelinschi, Beatrice Carmen; Caprosu, Maria; Dorohoi, Dana Ortansa

2011-10-01

Pure and colored with phthalazinium ylids poly(vinyl-alcohol) (PVA) foils were stretched under gentile heating. The birefringence of the thin foils was determined with a Babinet compensator standardized for yellow radiation of a Sodium lamp. The determined birefringence of the colored PVA foils is higher than that of the pure PVA foils. This fact indicates that the phthalazinium ylids facilitate the increase in the anisotropy of the stretched foils. The visible absorption electronic band of phthalazinium ylids was used to estimate the dichroic ratio and the degree of order of the ylid molecules in the stretched PVA foils. An increase in dichroism and birefringence with the degree of stretching has been evidenced for uncolored and colored PVA foils.

Birefringent Fiber Devices and Lasers

NASA Astrophysics Data System (ADS)

Theimer, James Prentice

1995-01-01

This thesis presents the results of numerical simulations of mode-locked figure eight lasers and their components: fiber amplifiers and nonlinear optical loop mirrors (NOLMs). The computations were designed to study pulse evolution in optical amplifiers and NOLMs with periodic repetition of these elements. Since fiber laser systems also include birefringent fiber, the effects of fiber birefringence was incorporated into the simulations. My studies of pulse amplification in non-birefringent amplifiers show pulse breakup when their energies exceed 4.5 fundamental soliton energies. In birefringent fibers pulse breakup is also found, but the two orthogonally polarized pulses propagate together. I find that their behavior is related to the properties of a vector soliton. I found that vector waves have close to unity transmission through a birefringent NOLM, but the pulse shape is distorted. This shape distortion reduces subsequent transmissions through the NOLM. The energy required for peak transmission of the pulse is predicted by the theory based on vector solitons. The same theory also predicted the low intensity transmission. The performance of the NOLM with birefringent fiber could not be improved by altering the polarization state of the pulse from linear polarization; the polarization controller introduced pulse distortion that resulted in excessive loss. I found an instability in the steady-state operation of the figure eight laser, which is due to pulse reshaping during propagation in the amplifier section. To remove this instability I introduced the concept of dispersion balancing; by increasing the dispersion in the amplifier section, the pulse can propagate nearly as a fundamental soliton in both the amplifier and the NOLM sections of the laser. This eliminated a major source of dispersive wave shedding and allowed the laser operation to become independent of the amplifier length. Sidebands were found on the pulse spectrum and their maxima corresponded well with the periodic resonance model.

Noninvasive assays of in vitro matured human oocytes showed insignificant correlation with fertilization and embryo development.

PubMed

Ashourzadeh, Sareh; Khalili, Mohammad Ali; Omidi, Marjan; Mahani, Seyed Nooraldin Nematollahi; Kalantar, Seyed Mehdi; Aflatoonian, Abbas; Habibzadeh, Victoria

2015-08-01

Recently, the upgrading of in vitro maturation (IVM) of human oocytes as a promising strategy has emerged in assisted reproductive technology (ART). The goal was to evaluate the correlation of the in vitro matured oocytes selected on the basis of the zona pellucida (ZP) birefringence and meiotic spindles (MS) detection with fertilization and subsequent embryo development in ICSI program. A total of 168 immature oocytes [germinal vesicle (n = 140) and metaphase I (n = 28)] obtained from patients undergoing oocytes retrieval for ICSI. After in vitro culture for 24-40 h, 112 (67 %) oocytes reached to MII stage. Using a polarized microscopy, the presence of MS and ZP birefringence were assessed in matured oocytes, followed by ICSI performance. The rates of fertilization in oocytes with spindles (51.3 %) were similar to that of the oocytes without spindles (50.7 %; P = 1.00). Moreover, the fertilization rates in high birefringence (HB) oocytes was not statistically different than oocytes with low birefringence (LB) (P = 0.44). The findings also showed that 64.9 % of the fertilized oocytes developed to embryos, in which 33.3 % were derived from spindle-detected oocytes. Regarding the ZP birefringence, 35.5 % of the embryos were derived from HB oocytes. There were insignificant relationships between the MS detection and ZP birefringence score with the rates of fertilization and embryo development in IVM oocytes.

Optical properties of extended-chain polymers under stress

NASA Astrophysics Data System (ADS)

Ramirez, Rafael G.; Eby, R. K.

1995-09-01

Birefringence and x-ray diffraction experiments have been carried out on Kevlar 49(superscript R) fibers under tensile stress to monitor structure changes under the stress field. The origin of the observed birefringence is discussed in some detail. Results from theoretical calculations using semi-empirical molecular orbital techniques are presented and contrasted to the experimental observations. The calculations involved the estimation of chain polarizability and were performed under simulated stress conditions using the AM1 Hamiltonian in MOPAC. Polarizability is then used to calculate the birefringence as a function of tensile stress, by using existing internal field theory. This theoretical approach is applied to predict the optical properties of highly oriented extended-chain polyethylene, as well as those for poly(p' phenylene therephtalamide); the latter being the base polymer in Kevlar fibers. Results reveal reasonable birefringence predictions when compared to available experimental results in the literature. Also, it is found that the contribution from orienting crystallites under the stress field, to the measured birefringence in Kevlar fibers, is only a small fraction of the total. However, the calculations predict a significant contribution from deformation (extension) at the molecular level.

Polychromatic polarization microscope: bringing colors to a colorless world.

PubMed

Shribak, Michael

2015-11-27

Interference of two combined white light beams produces Newton colors if one of the beams is retarded relative to the other by from 400 nm to 2000 nm. In this case the corresponding interfering spectral components are added as two scalars at the beam combination. If the retardance is below 400 nm the two-beam interference produces grey shades only. The interference colors are widely used for analyzing birefringent samples in mineralogy. However, many of biological structures have retardance <100 nm. Therefore, cells and tissues under a regular polarization microscope are seen as grey image, which contrast disappears at certain orientations. Here we are proposing for the first time using vector interference of polarized light in which the full spectrum colors are created at retardance of several nanometers, with the hue determined by orientation of the birefringent structure. The previously colorless birefringent images of organelles, cells, and tissues become vividly colored. This approach can open up new possibilities for the study of biological specimens with weak birefringent structures, diagnosing various diseases, imaging low birefringent crystals, and creating new methods for controlling colors of the light beam.

Narrow line width dual wavelength semiconductor optical amplifier based random fiber laser

NASA Astrophysics Data System (ADS)

Shawki, Heba A.; Kotb, Hussein E.; Khalil, Diaa

2018-02-01

A novel narrow line-width Single longitudinal mode (SLM) dual wavelength random fiber laser of 20 nm separation between wavelengths of 1530 and 1550 nm is presented. The laser is based on Rayleigh backscattering in a standard single mode fiber of 2 Km length as distributed mirrors, and a semiconductor optical amplifier (SOA) as the optical amplification medium. Two optical bandpass filters are used for the two wavelengths selectivity, and two Faraday Rotator mirrors are used to stabilize the two lasing wavelengths against fiber random birefringence. The optical signal to noise ratio (OSNR) was measured to be 38 dB. The line-width of the laser was measured to be 13.3 and 14 KHz at 1530 and 1550 nm respectively, at SOA pump current of 370 mA.

A strategy for optical properties investigation in ABe2BO3F2 (A=K, Rb, Cs) using finite field methods

NASA Astrophysics Data System (ADS)

Mushahali, Hahaer; Mu, Baoxia; Wang, Qian; Mamat, Mamatrishat; Cao, Haibin; Yang, Guang; Jing, Qun

2018-07-01

The finite-field methods can be used to intuitively learn about the optical response and find out the atomic contributions to the birefringence and SHG tensors. In this paper, the linear and second-order nonlinear optical properties of ABe2BO3F2 family (A = K, Rb, Cs) compounds are investigated using the finite-field methods within different exchange-correlation functionals. The results show that the obtained birefringence and SHG tensors are in good agreement with the experimental values. The atomic contribution to the total birefringence was further investigated using the variation of the atomic charges, and the Born effective charges. The results show that the boron-oxygen groups give main contribution to the anisotropic birefringence.

Birefringence and incipient plastic deformation in elastically overdriven [100] CaF2 under shock compression

NASA Astrophysics Data System (ADS)

Li, Y.; Zhou, X. M.; Cai, Y.; Liu, C. L.; Luo, S. N.

2018-04-01

[100] CaF2 single crystals are shock-compressed via symmetric planar impact, and the flyer plate-target interface velocity histories are measured with a laser displacement interferometry. The shock loading is slightly above the Hugoniot elastic limit to investigate incipient plasticity and its kinetics, and its effects on optical properties and deformation inhomogeneity. Fringe patterns demonstrate different features in modulation of fringe amplitude, including birefringence and complicated modulations. The birefringence is attributed to local lattice rotation accompanying incipient plasticity. Spatially resolved measurements show inhomogeneity in deformation, birefringence, and fringe pattern evolutions, most likely caused by the inhomogeneity associated with lattice rotation and dislocation slip. Transiently overdriven elastic states are observed, and the incubation time for incipient plasticity decreases inversely with increasing overdrive by the elastic shock.

Large birefringence and linear dichroism in TiS3 nanosheets.

PubMed

Papadopoulos, Nikos; Frisenda, Riccardo; Biele, Robert; Flores, Eduardo; Ares, Jose R; Sánchez, Carlos; van der Zant, Herre S J; Ferrer, Isabel J; D'Agosta, Roberto; Castellanos-Gomez, Andres

2018-06-21

TiS3 nanosheets have proven to be promising candidates for ultrathin optoelectronic devices due to their direct narrow band-gap and the strong light-matter interaction. In addition, the marked in-plane anisotropy of TiS3 is appealing for the fabrication of polarization sensitive optoelectronic devices. Herein, we study the optical contrast of TiS3 nanosheets of variable thickness on SiO2/Si substrates, from which we obtain the complex refractive index in the visible spectrum. We find that TiS3 exhibits very large birefringence, larger than that of well-known strong birefringent materials like TiO2 or calcite, and linear dichroism. These findings are in qualitative agreement with ab initio calculations that suggest an excitonic origin for the birefringence and linear dichroism of the material.

Removing left-right asymmetry in a Sagnac interferometer applied to cancel its reflectance dependence on birefringence.

PubMed

Golub, Ilya; Exir, Hourieh

2013-05-01

We present a left-right symmetry restoring method, which removes the detrimental birefringence in the single-mode fiber Sagnac interferometer, achieved with the aid of a half waveplate oriented at a specific angle. We show theoretically and demonstrate experimentally that adding a π-shift between clockwise and counterclockwise propagating, horizontally (in fiber loop plane) polarized field components, the Sagnac loop mirror's reflection becomes independent on birefringence of an element placed in the loop.

Contact stresses modeling at the Panda-type fiber single-layer winding and evaluation of their impact on the fiber optic properties

NASA Astrophysics Data System (ADS)

Lesnikova, Yu I.; Smetannikov, O. Yu; Trufanov, A. N.; Trufanov, N. A.

2017-02-01

The impact of contact transverse forces on the birefringence of the single-mode polarization-maintaining Panda-type fiber is numerically modeled. It has been established that with a single-row power winding on a cylindrical mandrel, the fiber tension at winding is the principal factor that influences birefringence. When coiling the fiber based on the local defect microbending, the birefringence at the microbending point differs from that of the free fiber by 1.3%.

Variable angle-of-incidence polarization-sensitive optical coherence tomography: its use to study the 3D collagen structure of equine articular cartilage

NASA Astrophysics Data System (ADS)

Ugryumova, Nadya; Gangnus, Sergei V.; Matcher, Stephen J.

2006-02-01

Polarization-sensitive optical coherence tomography has been used to spatially map the birefringence of equine articular cartilage. The polar orientation of the collagen fibers relative to the plane of the joint surface must be taken into account if a quantitative measurement of true birefringence is required. Using a series of images taken at different angles of illumination, we determine the fiber polar angle and true birefringence at one site on a sample of equine cartilage, on the assumption that the fibers lie within the plane of imaging. We propose a more general method based on the extended Jones matrix formalism to determine both the polar and azimuthal orientation of the collagen fibers as well as the true birefringence as functions of depth.

Precise control of photoinduced birefringence in azobenzene-containing liquid-crystalline polymers by post functionalization.

PubMed

Yu, Haifeng; Kobayashi, Takaomi; Ge, Ziyi

2009-10-19

A series of functionalized liquid-crystalline polymer materials with different degrees of functionality was synthesized by a post Sonogashira cross-coupling reaction of a polymer precursor. The post-functionalization was carried out under mild conditions and showed a high yield. Although a highly birefringent azotolane group was introduced into the polymer precursor, the photoresponse of the functionalized liquid-crystalline materials was not obviously changed. By adjusting the content of azotolane groups, precise control of the photoinduced birefringence was successfully obtained after thermal enhancement upon annealing. The present method to gain precise control of photoinduced birefringence might enable one to finely photocontrol the optical performances of materials, and may have a potential application as an advanced process for photonic materials. Copyright © 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Temperature sensibility of the birefringence properties in side-hole photonic crystal fiber filled with Indium

DOE Office of Scientific and Technical Information (OSTI.GOV)

Reyes-Vera, Erick, E-mail: erickreyes@itm.edu.co; Gómez-Cardona, Nelson D.; Facultad de Ingeniería, Instituto Tecnológico Metropolitano, A.A. 54954 Medellín

2014-11-17

We report on the temperature sensitivity of the birefringence properties of a special kind of photonic crystal fiber containing two side holes filled with Indium metal. The modulation of the fiber birefringence is accomplished through the stress field induced by the expansion of the metal. Although the fiber was made at low gas pressures during the indium infiltration process, the birefringence showed anomalous property at a relatively low temperature value, which is completely different from those reported in conventional-like fibers with two holes filled with metal. By modeling the anisotropic changes induced by the metal expansion to the refractive indexmore » within the fiber, we are able to reproduce the experimental results. Our results have practical relevance for the design of devices based on this technology.« less

Dual-wavelength polarimetric glucose sensing in the presence of birefringence and motion artifact using anterior chamber of the eye phantoms

PubMed Central

Pirnstill, Casey W.; Coté, Gerard L.

2013-01-01

Abstract. Noninvasive glucose monitoring is being investigated as a tool for effectively managing diabetes mellitus. Optical polarimetry has emerged as one such method, which can potentially be used to ascertain blood glucose levels by measuring the aqueous humor glucose levels in the anterior chamber of the eye. The key limitation for realizing this technique is the presence of sample noise due to corneal birefringence, which in the presence of motion artifact can confound the glucose signature in the aqueous humor of the eye. We present the development and characterization of a real-time, closed-loop, dual-wavelength polarimetric system for glucose monitoring using both a custom-built plastic eye phantom (in vitro) and isolated rabbit corneas (ex vivo) mounted in an artificial anterior chamber. The results show that the system can account for these noise sources and can monitor physiologic glucose levels accurately for a limited range of motion-induced birefringence. Using the dual-wavelength system in vitro and ex vivo, standard errors were 14.5  mg/dL and 22.4  mg/dL, respectively, in the presence of birefringence with motion. The results indicate that although dual-wavelength polarimetry has a limited range of compensation for motion-induced birefringence, when aligned correctly, it can minimize the effect of time-varying corneal birefringence for a range of motion larger than what has been reported in vivo. PMID:23299516

Stochastic theory of polarized light in nonlinear birefringent media: An application to optical rotation

NASA Astrophysics Data System (ADS)

Tsuchida, Satoshi; Kuratsuji, Hiroshi

2018-05-01

A stochastic theory is developed for the light transmitting the optical media exhibiting linear and nonlinear birefringence. The starting point is the two-component nonlinear Schrödinger equation (NLSE). On the basis of the ansatz of “soliton” solution for the NLSE, the evolution equation for the Stokes parameters is derived, which turns out to be the Langevin equation by taking account of randomness and dissipation inherent in the birefringent media. The Langevin equation is converted to the Fokker-Planck (FP) equation for the probability distribution by employing the technique of functional integral on the assumption of the Gaussian white noise for the random fluctuation. The specific application is considered for the optical rotation, which is described by the ellipticity (third component of the Stokes parameters) alone: (i) The asymptotic analysis is given for the functional integral, which leads to the transition rate on the Poincaré sphere. (ii) The FP equation is analyzed in the strong coupling approximation, by which the diffusive behavior is obtained for the linear and nonlinear birefringence. These would provide with a basis of statistical analysis for the polarization phenomena in nonlinear birefringent media.

Visualization of neuritic plaques in Alzheimer’s disease by polarization-sensitive optical coherence microscopy

NASA Astrophysics Data System (ADS)

Baumann, Bernhard; Woehrer, Adelheid; Ricken, Gerda; Augustin, Marco; Mitter, Christian; Pircher, Michael; Kovacs, Gabor G.; Hitzenberger, Christoph K.

2017-03-01

One major hallmark of Alzheimer’s disease (AD) and cerebral amyloid angiopathy (CAA) is the deposition of extracellular senile plaques and vessel wall deposits composed of amyloid-beta (Aβ). In AD, degeneration of neurons is preceded by the formation of Aβ plaques, which show different morphological forms. Most of them are birefringent owing to the parallel arrangement of amyloid fibrils. Here, we present polarization sensitive optical coherence microscopy (PS-OCM) for imaging mature neuritic Aβ plaques based on their birefringent properties. Formalin-fixed, post-mortem brain samples of advanced stage AD patients were investigated. In several cortical brain regions, neuritic Aβ plaques were successfully visualized in tomographic and three-dimensional (3D) images. Cortical grey matter appeared polarization preserving, whereas neuritic plaques caused increased phase retardation. Consistent with the results from PS-OCM imaging, the 3D structure of senile Aβ plaques was computationally modelled for different illumination settings and plaque sizes. Furthermore, the birefringent properties of cortical and meningeal vessel walls in CAA were investigated in selected samples. Significantly increased birefringence was found in smaller vessels. Overall, these results provide evidence that PS-OCM is able to assess amyloidosis based on intrinsic birefringent properties.

Study of the retardance of a birefringent waveplate at tilt incidence by Mueller matrix ellipsometer

NASA Astrophysics Data System (ADS)

Gu, Honggang; Chen, Xiuguo; Zhang, Chuanwei; Jiang, Hao; Liu, Shiyuan

2018-01-01

Birefringent waveplates are indispensable optical elements for polarization state modification in various optical systems. The retardance of a birefringent waveplate will change significantly when the incident angle of the light varies. Therefore, it is of great importance to study such field-of-view errors on the polarization properties, especially the retardance of a birefringent waveplate, for the performance improvement of the system. In this paper, we propose a generalized retardance formula at arbitrary incidence and azimuth for a general plane-parallel composite waveplate consisting of multiple aligned single waveplates. An efficient method and corresponding experimental set-up have been developed to characterize the retardance versus the field-of-view angle based on a constructed spectroscopic Mueller matrix ellipsometer. Both simulations and experiments on an MgF2 biplate over an incident angle of 0°-8° and an azimuthal angle of 0°-360° are presented as an example, and the dominant experimental errors are discussed and corrected. The experimental results strongly agree with the simulations with a maximum difference of 0.15° over the entire field of view, which indicates the validity and great potential of the presented method for birefringent waveplate characterization at tilt incidence.

Anisotropic properties of the enamel organic extracellular matrix.

PubMed

do Espírito Santo, Alexandre R; Novaes, Pedro D; Line, Sérgio R P

2006-05-01

Enamel biosynthesis is initiated by the secretion, processing, and self-assembly of a complex mixture of proteins. This supramolecular ensemble controls the nucleation of the crystalline mineral phase. The detection of anisotropic properties by polarizing microscopy has been extensively used to detect macromolecular organizations in ordinary histological sections. The aim of this work was to study the birefringence of enamel organic matrix during the development of rat molar and incisor teeth. Incisor and molar teeth of rats were fixed in 2% paraformaldehyde/0.5% glutaraldehyde in 0.2 M phosphate-buffered saline (PBS), pH 7.2, and decalcified in 5% nitric acid/4% formaldehyde. After paraffin embedding, 5-microm-thick sections were obtained, treated with xylene, and hydrated. Form birefringence curves were obtained after measuring optical retardations in imbibing media, with different refractive indices. Our observations showed that enamel organic matrix of rat incisor and molar teeth is strongly birefringent, presenting an ordered supramolecular structure. The birefringence starts during the early secretion phase and disappears at the maturation phase. The analysis of enamel organic matrix birefringence may be used to detect the effects of genetic and environmental factors on the supramolecular orientation of enamel matrix and their effects on the structure of mature enamel.

On the Relation Between Facular Bright Points and the Magnetic Field

NASA Astrophysics Data System (ADS)

Berger, Thomas; Shine, Richard; Tarbell, Theodore; Title, Alan; Scharmer, Goran

1994-12-01

Multi-spectral images of magnetic structures in the solar photosphere are presented. The images were obtained in the summers of 1993 and 1994 at the Swedish Solar Telescope on La Palma using the tunable birefringent Solar Optical Universal Polarimeter (SOUP filter), a 10 Angstroms wide interference filter tuned to 4304 Angstroms in the band head of the CH radical (the Fraunhofer G-band), and a 3 Angstroms wide interference filter centered on the Ca II--K absorption line. Three large format CCD cameras with shuttered exposures on the order of 10 msec and frame rates of up to 7 frames per second were used to create time series of both quiet and active region evolution. The full field--of--view is 60times 80 arcseconds (44times 58 Mm). With the best seeing, structures as small as 0.22 arcseconds (160 km) in diameter are clearly resolved. Post--processing of the images results in rigid coalignment of the image sets to an accuracy comparable to the spatial resolution. Facular bright points with mean diameters of 0.35 arcseconds (250 km) and elongated filaments with lengths on the order of arcseconds (10(3) km) are imaged with contrast values of up to 60 % by the G--band filter. Overlay of these images on contemporal Fe I 6302 Angstroms magnetograms and Ca II K images reveals that the bright points occur, without exception, on sites of magnetic flux through the photosphere. However, instances of concentrated and diffuse magnetic flux and Ca II K emission without associated bright points are common, leading to the conclusion that the presence of magnetic flux is a necessary but not sufficient condition for the occurence of resolvable facular bright points. Comparison of the G--band and continuum images shows a complex relation between structures in the two bandwidths: bright points exceeding 350 km in extent correspond to distinct bright structures in the continuum; smaller bright points show no clear relation to continuum structures. Size and contrast statistical cross--comparisons compiled from measurements of over two-thousand bright point structures are presented. Preliminary analysis of the time evolution of bright points in the G--band reveals that the dominant mode of bright point evolution is fission of larger structures into smaller ones and fusion of small structures into conglomerate structures. The characteristic time scale for the fission/fusion process is on the order of minutes.

Femtosecond laser fabrication of birefringent directional couplers as polarization beam splitters in fused silica.

PubMed

Fernandes, Luís A; Grenier, Jason R; Herman, Peter R; Aitchison, J Stewart; Marques, Paulo V S

2011-06-20

Integrated polarization beam splitters based on birefringent directional couplers are demonstrated. The devices are fabricated in bulk fused silica glass by femtosecond laser writing (300 fs, 150 nJ at 500 kHz, 522 nm). The birefringence was measured from the spectral splitting of the Bragg grating resonances associated with the vertically and horizontally polarized modes. Polarization splitting directional couplers were designed and demonstrated with 0.5 dB/cm propagation losses and -19 dB and -24 dB extinction ratios for the polarization splitting.

STUDIES ON THE ANOMALOUS VISCOSITY AND FLOW-BIREFRINGENCE OF PROTEIN SOLUTIONS

PubMed Central

Lawrence, A. S. C.; Needham, Joseph; Shen, Shih-Chang

1944-01-01

1. A coaxial viscosimeter which permits the simultaneous determination of relative and anomalous viscosity and of flow-birefringence is described. Flow-anomaly and flow-birefringence are regarded as characteristic of elongated micelles and molecules. 2. Such methods have been applied to dilute solutions of proteins. The conditions under which the coaxial (Couette) viscosimeter measures the viscosity of the bulk phase and the surface film phase respectively have been investigated and are described. 3. The general behaviour of protein solutions subjected to shear is summarised. PMID:19873384

Electro-optic imaging Fourier transform spectrometer

NASA Technical Reports Server (NTRS)

Chao, Tien-Hsin (Inventor); Znod, Hanying (Inventor)

2009-01-01

An Electro-Optic Imaging Fourier Transform Spectrometer (EOIFTS) for Hyperspectral Imaging is described. The EOIFTS includes an input polarizer, an output polarizer, and a plurality of birefringent phase elements. The relative orientations of the polarizers and birefringent phase elements can be changed mechanically or via a controller, using ferroelectric liquid crystals, to substantially measure the spectral Fourier components of light propagating through the EIOFTS. When achromatic switches are used as an integral part of the birefringent phase elements, the EIOFTS becomes suitable for broadband applications, with over 1 micron infrared bandwidth.

The effect of vacuum birefringence on the polarization of X-ray binaries and pulsars

NASA Technical Reports Server (NTRS)

Novick, R.; Weisskopf, M. C.; Angel, J. R. P.; Sutherland, P. G.

1977-01-01

In a strong magnetic field the vacuum becomes birefringent. This effect is especially important for pulsars at X-ray wavelengths. Any polarized X-ray emission from the surface of a magnetic neutron star becomes depolarized as it propagates through the magnetic field. The soft X-ray emission from AM Her, believed to be a magnetic white dwarf, may show about one radian of phase retardation. In this case, circular polarization of the X-ray flux would be a characteristic signature of vacuum birefringence.

Birefringence Polarimeter Using Dual LiNbO3 Electrooptic Crystal Modulators

NASA Astrophysics Data System (ADS)

Saitou, Takeshi; Nurdin Bin, Muhammad; Kowa, Hiroyuki; Umeda, Norihiro; Takizawa, Kuniharu; Kondoh, Eiichi; Jin, Lianhua

2012-08-01

A birefringence polarimeter that uses dual LiNbO3 electrooptic crystal modulators operating at a frequency ratio of 4:1 is described. The significance of this polarimeter is that the birefringent parameters of a sample are obtained only from the modulated polarization status. The measurement, therefore, avoids depolarization effects resulting from the sample itself and the rest of the optical system. The high speed and accuracy of this polarimeter are shown by measurements using a quarter-wave plate, a Babinet-Soleil compensator, and a phase modulator.

Harnessing energy-sharing collisions of Manakov solitons to implement universal NOR and OR logic gates

NASA Astrophysics Data System (ADS)

Vijayajayanthi, M.; Kanna, T.; Murali, K.; Lakshmanan, M.

2018-06-01

The energy-sharing collision of bright optical solitons in the Manakov system, governing pulse propagation in high birefringent fiber, is employed theoretically to realize optical logic gates. In particular, we successfully construct (theoretically) the universal NOR gate and the OR gate from the energy-sharing collisions of just four bright solitons which can be well described by the exact bright four-soliton solution of the Manakov system. This construction procedure has important merits such as realizing the two input gates with a minimal number of soliton collisions and possibilities of multistate logic. The recent experiments on Manakov solitons suggest the possibility of implementation of this theoretical construction of such gates and ultimately an all-optical computer.

Polarization independent polymer waveguide tunable receivers incorporating a micro-optic circulator

NASA Astrophysics Data System (ADS)

Wu, Xiaoping; Park, Tae-Hyun; Park, Su-Hyun; Seo, Jun-Kyu; Oh, Min-Cheol

2018-06-01

In order to simplify the receiver configuration in a wavelength division multiplexed optical fiber network, compact wavelength tunable filters have long been expected to be used as channel selectors. Bragg reflector inherently has the most suitable reflection spectrum for filtering a single wavelength from the densely multiplexed wavelength signal. Polymer has high thermo-optic coefficient and good thermal insulation property compared to the other optical waveguide materials such as silicon and silica materials. This can be used to broadly tune the reflection spectrum of Bragg reflector using a simple micro-heater. In this work, a micro-optic circulator component and a polymeric Bragg reflector device are assembled to produce a small form factor tunable receiver. Compared to the integrated-optical versions, the micro-optics are based on well-developed manufacturing processes and can achieve competitive production yields. The device exhibits high reflectivity with a flat top passband, and a polarization dependence of 0.06 nm achieved by virtue of the low birefringence of LFR polymer, which make a significant contribution to the implementation of polarization independent tunable receiver. The wavelength tuning range of 40 nm is demonstrated by using a bottom located heater with a groove for heat isolation.

Metal membrane with dimer slots as a universal polarizer

NASA Astrophysics Data System (ADS)

Zhukovsky, Sergej; Zalkovskij, Maksim; Malureanu, Radu; Kremers, Christian; Chigrin, Dmitry; Tang, Peter T.; Jepsen, Peter U.; Lavrinenko, Andrei V.

2014-03-01

In this work, we show theoretically and confirm experimentally that thin metal membranes patterned with an array of slot dimers (or their Babinet analogue with metal rods) can function as a versatile spectral and polarization filter. We present a detailed covariant multipole theory for the electromagnetic response of an arbitrary dimer based on the Green functions approach. The theory confirms that a great variety of polarization properties, such as birefringence, chirality and elliptical dichroism, can be achieved in a metal layer with such slot-dimer patterning (i.e. in a metasurface). Optical properties of the metasurface can be extensively tuned by varying the geometry (shape and dimensions) of the dimer, for example, by adjusting the sizes and mutual placement of the slots (e.g. inter-slot distance and alignment angle). Three basic shapes of dimers are analyzed: II-shaped (parallel slots), V-shaped, and T-shaped. These particular shapes of dimers are found to be sensitive to variations of the slots lengths and orientation of elements. Theoretical results are well supported by full-wave three-dimensional simulations. Our findings were verified experimentally on the metal membranes fabricated using UV lithography with subsequent Ni growth. Such metasurfaces were characterized using time-domain THz spectroscopy. The samples exhibit pronounced optical activity (500 degrees per wavelength) and high transmission: even though the slots cover only 4.3 % of the total membrane area the amplitude transmission reaches 0.67 at the resonance frequency 0.56 THz.

Wavelength dependent in-plane birefringence of transparent flexible films determined by using transmission ellipsometry

NASA Astrophysics Data System (ADS)

Yang, Sung Mo; Hong, Sera; Kim, Sang Youl

2018-05-01

We introduce a simple method to determine the in-plane birefringence of transparent flexible films by using transmission spectroscopic ellipsometry. The pseudo-ellipsometric constants which can represent their sample azimuthal angle dependent characteristics are introduced. The effect of in-plane birefringence and sample azimuthal angle on the pseudo ellipsometric constants is calculated using Jones matrix formalism, and the observed sample azimuthal angle dependence of measured pseudo-ellipsometric data is well understood. Wavelength dependence of in-plane birefringence is expressed in terms of the Sellmeier dispersion equation. The best fit pseudo-ellipsometric spectra to the measured ones at the sample azimuthal angles of every 15° from 0 to 90° are searched. The dispersion coefficients of the Sellmeier equation and the azimuthal angle of the optic axis are determined for polycarbonate (PC), poly(ethylene naphthalate) (PEN), poly(ethylene terephthalate) (PET), polyimide (PI), and colorless polyimide (CPI) films.

Pulse energy dependence of refractive index change in lithium niobium silicate glass during femtosecond laser direct writing.

PubMed

Cao, Jing; Poumellec, Bertrand; Brisset, François; Lancry, Matthieu

2018-03-19

Femtosecond laser-induced refractive index changes in lithium niobium silicate glass were explored at high repetition rate (300 fs, 500 kHz) by polarized light microscopy, full-wave retardation plate, quantitative birefringence microscopy, and digital holographic microscopy. We found three regimes on energy increase. The first one corresponds to isotropic negative refractive index change (for pulse energy ranging 0.4-0.8 μJ/pulse, 0.6 NA, 5μm/s, 650μm focusing depth in the glass). The second one (0.8-1.2 μJ/pulse) corresponds to birefringence with well-defined slow axis orientation. The third one (above 1.2 μJ/pulse) is related to birefringence direction fluctuation. Interestingly, these regimes are consistent with crystallization ones. In addition, an asymmetric orientational writing effect has been detected on birefringence. These topics extend the possibility of controlling refractive index change in multi-component glasses.

The 3-D collagen structure of equine articular cartilage, characterized using variable-angle-of-incidence polarization-sensitive optical coherence tomography

NASA Astrophysics Data System (ADS)

Ugryumova, Nadya; Gangnus, Sergei V.; Matcher, Stephen J.

2005-08-01

Polarization-sensitive optical coherence tomography has been used to spatially map the birefringence of equine articular cartilage. Images obtained in the vicinity of visible osteoarthritic lesions display a characteristic disruption of the regular birefringence bands shown by normal cartilage. We also note that significant (e.g. ×2) variations in the apparent birefringence of samples taken from young (18 month) animals that otherwise appear visually homogeneous are found over spatial scales of a few millimeters. We suggest that whilst some of this variation may be due to changes in the intrinsic birefringence of the tissue, the 3-D orientation of the collagen fibers relative to the plane of the joint surface should also be taken into account. We propose a method based on multiple angles of illumination to determine the polar angle of the collagen fibers.

Optical anisotropy induced by torsion stresses in LiNbO3 crystals: appearance of an optical vortex.

PubMed

Skab, Ihor; Vasylkiv, Yurij; Savaryn, Viktoriya; Vlokh, Rostyslav

2011-04-01

We report the results of studies of the torsion effect on the optical birefringence in LiNbO(3) crystals. We found that the twisting of those crystals causes a birefringence distribution revealing nontrivial peculiarities. In particular, they have a special point at the center of the cross section perpendicular to the torsion axis where the zero birefringence value occurs. It has also been ascertained that the surface of the spatial birefringence distribution has a conical shape, with the cone axis coinciding with the torsion axis. We revealed that an optical vortex, with a topological charge equal to unity, appears under the torsion of LiNbO(3) crystals. It has been shown that, in contrast to the q plate, both the efficiency of spin-orbital coupling and the orbital momentum of the emergent light can be operated by the torque moment. © 2011 Optical Society of America

Photonic switching based on the photoinduced birefringence in bacteriorhodopsin films

NASA Astrophysics Data System (ADS)

Huang, Yuhua; Wu, Shin-Tson; Zhao, Youyuan

2004-03-01

Photoinduced birefringence in bacteriorhodopsin films was investigated using pump-probe method and its application for photonic switching explored. A diode-pumped second-harmonic YAG laser was used as a pumping beam and a diode laser at λ=660 nm was used as a probing beam. The pump and probe beams overlap at the sample. Without the pumping beam, the probing light cannot transmit the analyzer to the detector. However, due to the photoinduced anisotropy, a portion of the probing light is detected when the pumping beam is present. Since λ=660 nm is far from the absorption peak (˜570 nm) of the ground state, the photoinduced birefringence predominates. Using the intensity-dependent photoinduced birefringence in a bacteriorhodopsin film, we have demonstrated a photonic switch with ˜1000:1 contrast ratio, ˜0.6 s rise time and ˜1.5 s decay time.

Birefringence imaging directly reveals architectural dynamics of filamentous actin in living growth cones.

PubMed

Katoh, K; Hammar, K; Smith, P J; Oldenbourg, R

1999-01-01

We have investigated the dynamic behavior of cytoskeletal fine structure in the lamellipodium of nerve growth cones using a new type of polarized light microscope (the Pol-Scope). Pol-Scope images display with exquisite resolution and definition birefringent fine structures, such as filaments and membranes, without having to treat the cell with exogenous dyes or fluorescent labels. Furthermore, the measured birefringence of protein fibers in the thin lamellipodial region can be interpreted in terms of the number of filaments in the bundles. We confirmed that birefringent fibers are actin-based using conventional fluorescence-labeling methods. By recording movies of time-lapsed Pol-Scope images, we analyzed the creation and dynamic composition of radial fibers, filopodia, and intrapodia in advancing growth cones. The strictly quantitative information available in time-lapsed Pol-Scope images confirms previously deduced behavior and provides new insight into the architectural dynamics of filamentous actin.

Further comments on the effects of vacuum birefringence on the polarization of X-rays emitted from magnetic neutron stars

NASA Technical Reports Server (NTRS)

Chanan, G. A.; Novick, R.; Silver, E. H.

1979-01-01

The birefringence of the vacuum in the presence of strong (of the order of 1 teragauss) magnetic fields will in general affect the polarization of X-rays propagating through these fields. Two of the four Stokes parameters will vary so rapidly with wavelength as to be 'washed out' and unobservable, but the remaining two parameters will be unaffected. These results show that one conclusion of an earlier work is incorrect: Polarized X-ray emission from the surface of a magnetic neutron star will not in general be completely depolarized by the effects of vacuum birefringence. In particular, this birefringence has no effect on the linear polarization of cyclotron emission from the poles of magnetic neutron stars, and a similar result holds for synchrotron emission. More general cases of the propagation of polarized X-rays in magnetic fields are also discussed.

Birefringence of magnesium fluoride in the vacuum ultraviolet and application to a half-waveplate.

PubMed

Ishikawa, Ryohko; Kano, Ryouhei; Bando, Takamasa; Suematsu, Yoshinori; Ishikawa, Shin-nosuke; Kubo, Masahito; Narukage, Noriyuki; Hara, Hirohisa; Tsuneta, Saku; Watanabe, Hiroko; Ichimoto, Kiyoshi; Aoki, Kunichika; Miyagawa, Kenta

2013-12-01

Spectro-polarimeteric observations in the vacuum-ultraviolet (VUV) region are expected to be developed as a new astrophysics diagnostic tool for investigating space plasmas with temperatures of >10(4)  K. Precise measurements of the difference in the extraordinary and ordinary refractive indices are required for developing accurate polarimeters, but reliable information on the birefringence in the VUV range is difficult to obtain. We have measured the birefringence of magnesium fluoride (MgF2) with an accuracy of better than ±4×10(-5) around the hydrogen Lyman-α line (121.57 nm). We show that MgF2 can be applied practically as a half-waveplate for the chromospheric Lyman-alpha spectro-polarimeter (CLASP) sounding rocket experiment and that the developed measurement method can be easily applied to other VUV birefringent materials at other wavelengths.

Gravitational birefringence and an exotic formula for redshifts

NASA Astrophysics Data System (ADS)

Duval, Christian; Pasquet, Johanna; Schücker, Thomas; Tilquin, André

2018-06-01

We compute the birefringence of light in curved Robertson-Walker spacetimes and propose an exotic formula for redshift based on the internal structure of the spinning photon. We then use the Hubble diagram of supernovae to test this formula.

Designing an Inverter-based Operational Transconductance Amplifier-capacitor Filter with Low Power Consumption for Biomedical Applications

PubMed Central

Yousefinezhad, Sajad; Kermani, Saeed; Hosseinnia, Saeed

2018-01-01

The operational transconductance amplifier-capacitor (OTA-C) filter is one of the best structures for implementing continuous-time filters. It is particularly important to design a universal OTA-C filter capable of generating the desired filter response via a single structure, thus reducing the filter circuit power consumption as well as noise and the occupied space on the electronic chip. In this study, an inverter-based universal OTA-C filter with very low power consumption and acceptable noise was designed with applications in bioelectric and biomedical equipment for recording biomedical signals. The very low power consumption of the proposed filter was achieved through introducing bias in subthreshold MOSFET transistors. The proposed filter is also capable of simultaneously receiving favorable low-, band-, and high-pass filter responses. The performance of the proposed filter was simulated and analyzed via HSPICE software (level 49) and 180 nm complementary metal-oxide-semiconductor technology. The rate of power consumption and noise obtained from simulations are 7.1 nW and 10.18 nA, respectively, so this filter has reduced noise as well as power consumption. The proposed universal OTA-C filter was designed based on the minimum number of transconductance blocks and an inverter circuit by three transconductance blocks (OTA). PMID:29535925

Designing an Inverter-based Operational Transconductance Amplifier-capacitor Filter with Low Power Consumption for Biomedical Applications.

PubMed

Yousefinezhad, Sajad; Kermani, Saeed; Hosseinnia, Saeed

2018-01-01

The operational transconductance amplifier-capacitor (OTA-C) filter is one of the best structures for implementing continuous-time filters. It is particularly important to design a universal OTA-C filter capable of generating the desired filter response via a single structure, thus reducing the filter circuit power consumption as well as noise and the occupied space on the electronic chip. In this study, an inverter-based universal OTA-C filter with very low power consumption and acceptable noise was designed with applications in bioelectric and biomedical equipment for recording biomedical signals. The very low power consumption of the proposed filter was achieved through introducing bias in subthreshold MOSFET transistors. The proposed filter is also capable of simultaneously receiving favorable low-, band-, and high-pass filter responses. The performance of the proposed filter was simulated and analyzed via HSPICE software (level 49) and 180 nm complementary metal-oxide-semiconductor technology. The rate of power consumption and noise obtained from simulations are 7.1 nW and 10.18 nA, respectively, so this filter has reduced noise as well as power consumption. The proposed universal OTA-C filter was designed based on the minimum number of transconductance blocks and an inverter circuit by three transconductance blocks (OTA).

Advanced Technologies for Structural and Functional Optical Coherence Tomography

DTIC Science & Technology

2015-01-07

vertical scale bar: 500 um. 9 OCT speckle noise can significantly affect polarimetry measurement and must be reduced for birefringence...shown in Figure 7. This technique enables more accurate polarimetry measurement and quantitative assessment of tissue birefringence. Figure 7

Quantitative polarization and flow evaluation of choroid and sclera by multifunctional Jones matrix optical coherence tomography

NASA Astrophysics Data System (ADS)

Sugiyama, S.; Hong, Y.-J.; Kasaragod, D.; Makita, S.; Miura, M.; Ikuno, Y.; Yasuno, Y.

2016-03-01

Quantitative evaluation of optical properties of choroid and sclera are performed by multifunctional optical coherence tomography. Five normal eyes, five glaucoma eyes and one choroidal atrophy eye are examined. The refractive error was found to be correlated with choroidal birefringence, polarization uniformity, and flow in addition to scleral birefringence among normal eyes. The significant differences were observed between the normal and the glaucoma eyes, as for choroidal polarization uniformity, flow and scleral birefringence. An automatic segmentation algorithm of retinal pigment epithelium and chorioscleral interface based on multifunctional signals is also presented.

Device for magneto-optic signal detection with a small crystal prism.

PubMed

Saito, K; Sato, S; Shino, K; Taniguchi, T

2000-03-10

A device made of a birefringent crystal for signal detection of magneto-optic (MO) disks is presented. The light beam from a MO disk is separated into two orthogonally polarized components at the surface of a birefringent prism. After these two components are reflected by the top and the bottom surfaces of the prism inside, at the detector they become sufficiently separated from each other for discrete detection, even though the prism is small. A method for calculating the light intensities and the positions of focused beams in a birefringent prism and the results of a fundamental experiment are presented.

Method and apparatus for measuring micro structures, anisotropy and birefringence in polymers using laser scattered light

DOEpatents

Grek, Boris; Bartolick, Joseph; Kennedy, Alan D.

2000-01-01

A method and apparatus for measuring microstructures, anistropy and birefringence in polymers using laser scattered light includes a laser which provides a beam that can be conditioned and is directed at a fiber or film which causes the beam to scatter. Backscatter light is received and processed with detectors and beam splitters to obtain data. The data is directed to a computer where it is processed to obtain information about the fiber or film, such as the birefringence and diameter. This information provides a basis for modifications to the production process to enhance the process.

Highly birefringent suspended-core photonic microcells for refractive-index sensing

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Chao; The Hong Kong Polytechnic University Shenzhen Research Institute, Shenzhen 518057; Jin, Wa

2014-08-11

An in-line photonic microcell with a highly birefringent suspended microfiber core is fabricated by locally heating and pressurizing selected air-holes of an endless single mode photonic crystal fiber. The microfiber core has rhombus-like cross-sectional geometry and could achieve a high birefringence of up to 10{sup −2}. The microfiber core is fixed at the center of the microcell by thin struts attached to an outer jacket tube, which protects and isolates the microfiber from environmental contaminations. Highly sensitive and robust refractive index sensors based on such microcells are experimentally demonstrated.

Analysis of edge birefringence.

PubMed Central

Oldenbourg, R

1991-01-01

We present an experimental and theoretical study of the phenomenon of edge birefringence that appears near boundaries of transparent objects which are observed with high extinction and high resolution polarized light microscopy. As test objects, thin flakes of isotropic KCl crystals were immersed in media of various refractive indices. The measured retardation near crystal edges increased linearly with both the crystal thickness (tested between 0.3 and 1 micron), and the difference in refractive indices n between crystal (n = 1.49) and immersion liquids (n between 1.36 and 1.62). The specific edge birefringence, i.e., the retardation per thickness and per refractive index difference, is 0.029 on the high refractive index side of the boundary and -0.015 on the low refractive index side. The transition through zero birefringence specifies the position of a boundary at a much higher precision than predicted by the diffraction limit of the optical setup. The theoretical study employs a ray tracing procedure modeling the change in phase and polarization of rays passing through the specimen. We find good agreement between the model calculations and the experimental results indicating that edge birefringence can be attributed to the change in polarization of light that is refracted and reflected by dielectric interfaces. Images FIGURE 1 FIGURE 3 FIGURE 4 PMID:1932552

Spectral interferometry for morphological imaging in in vitro fertilization (IVF) (Conference Presentation)

NASA Astrophysics Data System (ADS)

Zhu, Yizheng; Li, Chengshuai

2016-03-01

Morphological assessment of spermatozoa is of critical importance for in vitro fertilization (IVF), especially intracytoplasmic sperm injection (ICSI)-based IVF. In ICSI, a single sperm cell is selected and injected into an egg to achieve fertilization. The quality of the sperm cell is found to be highly correlated to IVF success. Sperm morphology, such as shape, head birefringence and motility, among others, are typically evaluated under a microscope. Current observation relies on conventional techniques such as differential interference contrast microscopy and polarized light microscopy. Their qualitative nature, however, limits the ability to provide accurate quantitative analysis. Here, we demonstrate quantitative morphological measurement of sperm cells using two types of spectral interferometric techniques, namely spectral modulation interferometry and spectral multiplexing interferometry. Both are based on spectral-domain low coherence interferometry, which is known for its exquisite phase determination ability. While spectral modulation interferometry encodes sample phase in a single spectrum, spectral multiplexing interferometry does so for sample birefringence. Therefore they are capable of highly sensitive phase and birefringence imaging. These features suit well in the imaging of live sperm cells, which are small, dynamic objects with only low to moderate levels of phase and birefringence contrast. We will introduce the operation of both techniques and demonstrate their application to measuring the phase and birefringence morphology of sperm cells.

Investigation of stress-induced birefringence of tissue determined with polarisation sensitive optical coherence tomography (Conference Presentation)

NASA Astrophysics Data System (ADS)

Karnowski, Karol; Li, Qingyun; Villiger, Martin; Sampson, David D.

2017-02-01

Polarisation sensitive optical coherence tomography (PS-OCT) offers additional intrinsic contrast to probe differences between healthy tissue and cancer that are often barely visible due to limited scattering contrast in an OCT image. PS-OCT reconstructs tissue birefringence from phase-sensitive measurements of orthogonal polarisation components of backscattering. In material science, polarisation has been used to study stress distribution, including the birefringence induced by stress in an otherwise isotropic material. Similar effects in biological tissues have not been well studied yet; however, may have application to tissues subjected to stress, e.g., tendons, muscles, lens, cornea or airway smooth muscle (ASM). The objective of this work is to explore stress-induced birefringence in tissue. We employ an advanced swept source-based PS-OCT system capable of measurement of tissue local polarisation properties. The sample in both cases is illuminated with orthogonal, passively depth-encoded polarisation states. Light returning from the tissue is detected via a polarisation-diversity detection module and a Mueller formalism is used to reconstruct polarisation properties (including retardation, diattenuation, and depolarisation) of the tissue. In this study, we demonstrate the measurement of stress-induced birefringence in phantoms and in soft tissues with polarisation sensitive optical coherence tomography.

High-birefringence photonic crystal fiber structures based on the binary morse-thue fractal sequence

NASA Astrophysics Data System (ADS)

Al-Muraeb, Ahmed; Abdel-Aty-Zohdy, Hoda

2016-09-01

A novel index-guiding Silica glass-core hexagonal High-Birefringence Photonic Crystal Fiber (HB-PCF) is proposed, with five rings of standard cladding air circular holes arranged in four formations inspired by the Binary Morse-Thue fractal Sequence (BMTS). The form birefringence, confinement loss, chromatic dispersion, effective mode area, and effective normalized frequency are evaluated for the four PCFs operating within (1.8 - 2 μm) eye-safe wavelength range. Modeling and analysis of the four PCF formations are performed deploying full-vector analysis in Finite Element Method (FEM) using COMSOL Multiphysics. Respecting fabrication and in light of commercial availability in designing the proposed PCF structures, a high birefringence of up to (6.549 × 10-3 at 2 μm) is achieved with dispersionfree single-mode operation. Confinement loss as low as (3.2 × 10-5 - 6.5 × 10-4 dB/m for 1.8 - 2 μm range) is achieved as well. Comparison against previously reported PCF structures reveals the desirably higher birefringence of our BMTS HB-PCF. The proposed PCFs are of vital use in various optical systems (e.g.: multi-wavelength fiber ring laser systems, and tunable lasers), catering for applications such as: optical sensing, LIDAR systems, material processing, optical signal processing, and optical communication.

Birefringence and hidden photons

NASA Astrophysics Data System (ADS)

Arza, Ariel; Gamboa, J.

2018-05-01

We study a model where photons interact with hidden photons and millicharged particles through a kinetic mixing term. Particularly, we focus on vacuum birefringence effects and we find a bound for the millicharged parameter assuming that hidden photons are a piece of the local dark matter density.

The measurement system of birefringence and Verdet constant of optical fiber

NASA Astrophysics Data System (ADS)

Huang, Yi; Chen, Li; Guo, Qiang; Pang, Fufei; Wen, Jianxiang; Shang, Yana; Wang, Tingyun

2013-12-01

The Faraday magneto-optical effect of optical fiber has many applications in monitoring magnetic field and electric current. When a linearly polarized light propagates in the direction of a magnetic field, the plane of polarization will rotate linearly proportional to the strength of the applied magnetic field, which following the relationship of θF =VBl. θF is the Faraday rotation angle, which is proportional to the magnetic flux density B and the Verdet constant V . However, when the optical fiber contains the effect of linear birefringence, the detection of Faraday rotation angle will depend on the line birefringence. In order to determine the Verdet constant of an optical fiber under a linear birefringence, the fiber birefringence needs to be accurately measured. In this work, a model is applied to analyze the polarization properties of an optical fiber by using the Jones matrix method. A measurement system based on the lock-in amplifier technology is designed to test the Verdet constant and the birefringence of optical fiber. The magnetic field is produced by a solenoid with a DC current. A tunable laser is intensity modulated with a motorized rotating chopper. The actuator supplies a signal as the phase-locked synchronization reference to the signal of the lock-in amplifier. The measurement accuracy is analyzed and the sensitivity of the system is optimized. In this measurement system, the Verdet constant of the SMF-28 fiber was measured to be 0.56±0.02 rad/T·m at 1550nm. This setup is well suitable for measuring the high signal-to-noise ratio (SNR) sensitivity for lock-in amplifier at a low magnetic field strength.

Characterizing of tissue microstructure with single-detector polarization-sensitive optical coherence tomography

NASA Astrophysics Data System (ADS)

Liu, Bin; Harman, Michelle; Giattina, Susanne; Stamper, Debra L.; Demakis, Charles; Chilek, Mark; Raby, Stephanie; Brezinski, Mark E.

2006-06-01

Assessing tissue birefringence with imaging modality polarization-sensitive optical coherence tomography (PS-OCT) could improve the characterization of in vivo tissue pathology. Among the birefringent components, collagen may provide invaluable clinical information because of its alteration in disorders ranging from myocardial infarction to arthritis. But the features required of clinical imaging modality in these areas usually include the ability to assess the parameter of interest rapidly and without extensive data analysis, the characteristics that single-detector PS-OCT demonstrates. But beyond detecting organized collagen, which has been previously demonstrated and confirmed with the appropriate histological techniques, additional information can potentially be gained with PS-OCT, including collagen type, form versus intrinsic birefringence, the collagen angle, and the presence of multiple birefringence materials. In part I, we apply the simple but powerful fast-Fourier transform (FFT) to both PS-OCT mathematical modeling and in vitro bovine meniscus for improved PS-OCT data analysis. The FFT analysis yields, in a rapid, straightforward, and easily interpreted manner, information on the presence of multiple birefringent materials, distinguishing the true anatomical structure from patterns in image resulting from alterations in the polarization state and identifying the tissue/phantom optical axes. Therefore the use of the FFT analysis of PS-OCT data provides information on tissue composition beyond identifying the presence of organized collagen in real time and directly from the image without extensive mathematical manipulation or data analysis. In part II, Helistat phantoms (collagen type I) are analyzed with the ultimate goal of improved tissue characterization. This study, along with the data in part I, advance the insights gained from PS-OCT images beyond simply determining the presence or absence of birefringence.

Electric Birefringence: A Simple Apparatus for Determining Physical Parameters of Macromolecules and Colloids.

ERIC Educational Resources Information Center

Trimm, Harold H.; And Others

1984-01-01

Describes a birefringence apparatus that can be assembled for less than $100 and can be used to measure both the dimensions and dipole moments of many macromolecules. Details are given of the construction and manipulation of the apparatus. (JN)

Transient birefringence effects in electromagnetically induced transparency

NASA Astrophysics Data System (ADS)

Parshkov, O. M.

2015-11-01

We report the results of numerical modelling of transient birefringence that arises as a result of electromagnetically induced transparency on degenerate quantum transitions between the states with J = 0, 1 and 2 in the presence of the Doppler broadening of spectral lines. It is shown that in the case of a linearly polarised control field, the effect of transient birefringence leads to a decay of the input circularly polarised probe pulse into separate linearly polarised pulses inside a medium. In the case of a circularly polarised control field, the effect of transient birefringence manifests itself in a decay of the input linearly polarised probe pulse into separate circularly polarised pulses. It is shown that the distance that a probe pulse has to pass in a medium before decaying into subpulses is considerably greater in the first case than in the second. The influence of the input probe pulse power and duration on the process of spatial separation into individual pulses inside a medium is studied. A qualitative analysis of the obtained results is presented.

High-Energy Vacuum Birefringence and Dichroism in an Ultrastrong Laser Field

NASA Astrophysics Data System (ADS)

Bragin, Sergey; Meuren, Sebastian; Keitel, Christoph H.; Di Piazza, Antonino

2017-12-01

A long-standing prediction of quantum electrodynamics, yet to be experimentally observed, is the interaction between real photons in vacuum. As a consequence of this interaction, the vacuum is expected to become birefringent and dichroic if a strong laser field polarizes its virtual particle-antiparticle dipoles. Here, we derive how a generally polarized probe photon beam is influenced by both vacuum birefringence and dichroism in a strong linearly polarized plane-wave laser field. Furthermore, we consider an experimental scheme to measure these effects in the nonperturbative high-energy regime, where the Euler-Heisenberg approximation breaks down. By employing circularly polarized high-energy probe photons, as opposed to the conventionally considered linearly polarized ones, the feasibility of quantitatively confirming the prediction of nonlinear QED for vacuum birefringence at the 5 σ confidence level on the time scale of a few days is demonstrated for upcoming 10 PW laser systems. Finally, dichroism and anomalous dispersion in vacuum are shown to be accessible at these facilities.

A bifunctional amorphous polymer exhibiting equal linear and circular photoinduced birefringences.

PubMed

Royes, Jorge; Provenzano, Clementina; Pagliusi, Pasquale; Tejedor, Rosa M; Piñol, Milagros; Oriol, Luis

2014-11-01

The large and reversible photoinduced linear and circular birefringences in azo-compounds are at the basis of the interest in these materials, which are potentially useful for several applications. Since the onset of the linear and circular anisotropies relies on orientational processes, which typically occur on the molecular and supramolecular length scale, respectively, a circular birefringence at least one order of magnitude lower than the linear one is usually observed. Here, the synthesis and characterization of an amorphous polymer with a dimeric repeating unit containing a cyanoazobenzene and a cyanobiphenyl moiety are reported, in which identical optical linear and circular birefringences are induced for proper light dose and ellipticity. A pump-probe technique and an analytical method based on the Stokes-Mueller formalism are used to investigate the photoinduced effects and to evaluate the anisotropies. The peculiar photoresponse of the polymer makes it a good candidate for applications in smart functional devices. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Noise characterization for resonantly enhanced polarimetric vacuum magnetic-birefringence experiments

NASA Astrophysics Data System (ADS)

Hartman, M. T.; Rivère, A.; Battesti, R.; Rizzo, C.

2017-12-01

In this work we present data characterizing the sensitivity of the Biréfringence Magnetique du Vide (BMV) instrument. BMV is an experiment attempting to measure vacuum magnetic birefringence (VMB) via the measurement of an ellipticity induced in a linearly polarized laser field propagating through a birefringent region of vacuum in the presence of an external magnetic field. Correlated measurements of laser noise alongside the measurement in the main detection channel allow us to separate measured sensing noise from the inherent birefringence noise of the apparatus. To this end, we model different sources of sensing noise for cavity-enhanced polarimetry experiments, such as BMV. Our goal is to determine the main sources of noise, clarifying the limiting factors of such an apparatus. We find our noise models are compatible with the measured sensitivity of BMV. In this context, we compare the phase sensitivity of separate-arm interferometers to that of a polarimetry apparatus for the discussion of current and future VMB measurements.

Distributed phase birefringence measurements based on polarization correlation in phase-sensitive optical time-domain reflectometers.

PubMed

Soto, Marcelo A; Lu, Xin; Martins, Hugo F; Gonzalez-Herraez, Miguel; Thévenaz, Luc

2015-09-21

In this paper a technique to measure the distributed birefringence profile along optical fibers is proposed and experimentally validated. The method is based on the spectral correlation between two sets of orthogonally-polarized measurements acquired using a phase-sensitive optical time-domain reflectometer (ϕOTDR). The correlation between the two measured spectra gives a resonance (correlation) peak at a frequency detuning that is proportional to the local refractive index difference between the two orthogonal polarization axes of the fiber. In this way the method enables local phase birefringence measurements at any position along optical fibers, so that any longitudinal fluctuation can be precisely evaluated with metric spatial resolution. The method has been experimentally validated by measuring fibers with low and high birefringence, such as standard single-mode fibers as well as conventional polarization-maintaining fibers. The technique has potential applications in the characterization of optical fibers for telecommunications as well as in distributed optical fiber sensing.

X-ray Birefringence: A New Strategy for Determining Molecular Orientation in Materials.

PubMed

Palmer, Benjamin A; Edwards-Gau, Gregory R; Morte-Ródenas, Anabel; Kariuki, Benson M; Lim, Gin Keat; Harris, Kenneth D M; Dolbnya, Igor P; Collins, Stephen P

2012-11-01

While the phenomenon of birefringence is well-established in the case of visible radiation and is exploited in many fields (e.g., through the use of the polarizing optical microscope), the analogous phenomenon for X-rays has been a virtually neglected topic. Here, we demonstrate the scope and potential for exploiting X-ray birefringence to determine the orientational properties of specific types of bonds in solids. Specifically, orientational characteristics of C-Br bonds in the bromocyclohexane/thiourea inclusion compound are elucidated from X-ray birefringence measurements at energies close to the bromine K-edge, revealing inter alia the changes in the orientational distribution of the C-Br bonds associated with a low-temperature order-disorder phase transition. From fitting a theoretical model to the experimental data, reliable quantitative information on the orientational properties of the C-Br bonds is determined. The experimental strategy reported here represents the basis of a new approach for gaining insights into the orientational properties of molecules in anisotropic materials.

Smectic A Filled Birefringent Elements and Fast Switching Twisted Dual Frequency Nematic Cells Used for Digital Light Deflection

NASA Technical Reports Server (NTRS)

Pishnyak, Oleg; Golovin, Andrii; Kreminskia, Liubov; Pouch, John J.; Miranda, Felix A.; Winker, Bruce K.; Lavrentovich, Oleg D.

2006-01-01

We describe the application of smectic A (SmA) liquid crystals for beam deflection. SmA materials can be used in digital beam deflectors (DBDs) as fillers for passive birefringent prisms. SmA prisms have high birefringence and can be constructed in a variety of shapes, including single prisms and prismatic blazed gratings of different angles and profiles. We address the challenges of uniform alignment of SmA, such as elimination of focal conic domains. Fast rotation of the incident light polarization in DBDs is achieved by an electrically switched 90 twisted nematic (TN) cell.

Nonlinear temperature dependence of glue-induced birefringence in polarization maintaining FBG sensors

NASA Astrophysics Data System (ADS)

Hopf, Barbara; Koch, Alexander W.; Roths, Johannes

2016-05-01

Glue-induced stresses decrease the accuracy of surface-mounted fiber Bragg gratings (FBG). Significant temperature dependent glue-induced birefringence was verified when a thermally cured epoxy-based bonding technique had been used. Determining the peak separation of two azimuthally aligned FBGs in PM fibers combined with a polarization resolved measurement set-up in a temperature range between -30°C and 150°C revealed high glue-induced stresses at low temperatures. Peak separations of about 60 pm and a nonlinear temperature dependence of the glue-induced birefringence due to stress relaxation processes and a visco-elastic behavior of the used adhesive have been shown.

Active polarisation control of a quantum cascade laser using tuneable birefringence in waveguides.

PubMed

Dhirhe, D; Slight, T J; Holmes, B M; Ironside, C N

2013-10-07

We discuss the design, modelling, fabrication and characterisation of an integrated tuneable birefringent waveguide for quantum cascade lasers. We have fabricated quantum cascade lasers operating at wavelengths around 4450 nm that include polarisation mode converters and a differential phase shift section. We employed below laser threshold electroluminescence to investigate the single pass operation of the integrated device. We use a theory based on the electro-optic properties of birefringence in quantum cascade laser waveguides combined with a Jones matrix based description to gain an understanding of the electroluminescence results. With the quantum cascade lasers operating above threshold we demonstrated polarisation control of the output.

Cavity enhanced interference of orthogonal modes in a birefringent medium

NASA Astrophysics Data System (ADS)

Kolluru, Kiran; Saha, Sudipta; Gupta, S. Dutta

2018-03-01

Interference of orthogonal modes in a birefringent crystal mediated by a rotator is known to lead to interesting physical effects (Solli et al., 2003). In this paper we show that additional feedback offered by a Fabry-Perot cavity (containing the birefringent crystal and the rotator) can lead to a novel strong interaction regime. Usual signatures of the strong interaction regime like the normal mode splitting and avoided crossings, sensitive to the rotator orientation, are reported. A high finesse cavity is shown to offer an optical setup for measuring small angles. The results are based on direct calculations of the cavity transmissions along with an analysis of its dispersion relation.

Highly tunable birefringent microstructured optical fiber.

PubMed

Kerbage, C; Steinvurzel, P; Reyes, P; Westbrook, P S; Windeler, R S; Hale, A; Eggleton, B J

2002-05-15

We demonstrate a method for introducing and dynamically tuning birefringence in a microstructured optical fiber. Waveguide asymmetry in the fiber is obtained by selective filling of air holes with polymer, and tunability is achieved by temperature tuning of the polymer's index. The fiber is tapered such that the mode field expands into the cladding and efficiently overlaps the polymer that has been infused into the air holes, ensuring enhanced tunability and low splice loss. Experimental results are compared with numerical simulations made with the beam propagation method and confirm birefringence tuning that corresponds to a phase change of 6pi for a 1-cm length of fiber.

Birefringence and vascular imaging of in vivo human skin by Jones-matrix optical coherence tomography

NASA Astrophysics Data System (ADS)

Li, En; Makita, Shuichi; Hong, Young-Joo; Kasaragod, Deepa; Yasuno, Yoshiaki

2017-02-01

A customized 1310-nm Jones-matrix optical coherence tomography (JM-OCT) for dermatological investigation was constructed and used for in vivo normal human skin tissue imaging. This system can simultaneously measure the threedimensional depth-resolved local birefringence, complex-correlation based OCT angiography (OCT-A), degree-ofpolarization- uniformity (DOPU) and scattering OCT intensity. By obtaining these optical properties of tissue, the morphology, vasculature, and collagen content of skin can be deduced and visualized. Structures in the deep layers of the epithelium were observed with depth-resolved local birefringence and polarization uniformity images. These results suggest high diagnostic and investigative potential of JM-OCT for dermatology.

Depth-resolved birefringence and differential optical axis orientation measurements with fiber-based polarization-sensitive optical coherence tomography.

PubMed

Guo, Shuguang; Zhang, Jun; Wang, Lei; Nelson, J Stuart; Chen, Zhongping

2004-09-01

Conventional polarization-sensitive optical coherence tomography (PS-OCT) can provide depth-resolved Stokes parameter measurements of light reflected from turbid media. A new algorithm that takes into account changes in the optical axis is introduced to provide depth-resolved birefringence and differential optical axis orientation images by use of fiber-based PS-OCT. Quaternion, a convenient mathematical tool, is used to represent an optical element and simplify the algorithm. Experimental results with beef tendon and rabbit tendon and muscle show that this technique has promising potential for imaging the birefringent structure of multiple-layer samples with varying optical axes.

A photoelastic modulator-based birefringence imaging microscope for measuring biological specimens

NASA Astrophysics Data System (ADS)

Freudenthal, John; Leadbetter, Andy; Wolf, Jacob; Wang, Baoliang; Segal, Solomon

2014-11-01

The photoelastic modulator (PEM) has been applied to a variety of polarimetric measurements. However, nearly all such applications use point-measurements where each point (spot) on the sample is measured one at a time. The main challenge for employing the PEM in a camera-based imaging instrument is that the PEM modulates too fast for typical cameras. The PEM modulates at tens of KHz. To capture the specific polarization information that is carried on the modulation frequency of the PEM, the camera needs to be at least ten times faster. However, the typical frame rates of common cameras are only in the tens or hundreds frames per second. In this paper, we report a PEM-camera birefringence imaging microscope. We use the so-called stroboscopic illumination method to overcome the incompatibility of the high frequency of the PEM to the relatively slow frame rate of a camera. We trigger the LED light source using a field-programmable gate array (FPGA) in synchrony with the modulation of the PEM. We show the measurement results of several standard birefringent samples as a part of the instrument calibration. Furthermore, we show results observed in two birefringent biological specimens, a human skin tissue that contains collagen and a slice of mouse brain that contains bundles of myelinated axonal fibers. Novel applications of this PEM-based birefringence imaging microscope to both research communities and industrial applications are being tested.

The interplay between viscoelastic and thermodynamic properties determines the birefringence of F-actin gels.

PubMed

Helfer, Emmanuèle; Panine, Pierre; Carlier, Marie-France; Davidson, Patrick

2005-07-01

F-actin gels of increasing concentrations (25-300 microM) display in vitro a progressive onset of birefringence due to orientational ordering of actin filaments. At F-actin concentrations <100 microM, this birefringence can be erased and restored at will by sonication and gentle flow, respectively. Hence, the orientational ordering does not result from a thermodynamic transition to a nematic phase but instead is due to mechanical stresses stored in the gels. In contrast, at F-actin concentrations > or =100 microM, gels display spontaneous birefringence recovery, at rest, which is the sign of true nematic ordering, in good agreement with statistical physics models of the isotropic/nematic transition. Well-aligned samples of F-actin gels could be produced and their small-angle x-ray scattering patterns are quite anisotropic. These patterns show no sign of filament positional short-range order and could be modeled by averaging the form factor with the Maier-Saupe nematic distribution function. The derived nematic order parameter S of the gels ranged from S = 0.7 at 300 microM to S = 0.4 at 25 microM. Both birefringence and small-angle x-ray scattering data indicate that, even in absence of cross-linking proteins, spontaneous cooperative alignment of actin filaments may arise in motile regions of living cells where F-actin concentrations can reach values of a few 100 microM.

Development of an eye-safe solid-state tunable laser transmitter in the 1.4-1.5 μm wavelength region based on Cr4+:YAG crystal for lidar applications

NASA Astrophysics Data System (ADS)

Petrova-Mayor, Anna; Wulfmeyer, Volker; Weibring, Petter

2008-04-01

An experimental optimization of the efficiency of a gain switched tunable Cr4+:YAG laser at 10 Hz is described. The thermal lensing during pulsed operation was measured. Optimal performance occurred at a crystal temperature of 34 °C and resulted in an output energy of ~7 mJ and a pulse duration of ~35 ns. Tunability in the range of 1350-1500 nm, spectral linewidth of ~200 GHz, and M2<4 are demonstrated. The main laser material parameters are estimated. Such a laser could be employed in a laboratory-based nonscanning lidar system if a narrowband birefringent filter is installed. The tunability will permit the improvement of the Cr4+:YAG transmitter for water-vapor differential absorption lidar if injection seeding is applied.

Research about the high precision temperature measurement

NASA Astrophysics Data System (ADS)

Lin, J.; Yu, J.; Zhu, X.; Zeng, Z.; Deng, Y.

2012-12-01

High precision temperature control system is one of most important support conditions for tunable birefringent filter.As the first step,we researched some high precision temperature measurement methods for it. Firstly, circuits with a 24 bit ADC as the sensor's reader were carefully designed; Secondly, an ARM porcessor is used as the centrol processing unit, it provides sufficient reading and procesing ability; Thirdly, three kinds of sensors, PT100, Dale 01T1002-5 thermistor, Wheatstone bridge(constructed by pure copper and manganin) as the senor of the temperature were tested respectively. The resolution of the measurement with these three kinds of sensors are all better than 0.001 that's enough for 0.01 stability temperature control. Comparatively, Dale 01T1002-5 thermistor could get the most accurate temperature of the key point, Wheatstone bridge could get the most accurate mean temperature of the whole layer, both of them will be used in our futrue temperature controll system.

Fibre-coupled red diode-pumped Alexandrite TEM00 laser with single and double-pass end-pumping

NASA Astrophysics Data System (ADS)

Arbabzadah, E. A.; Damzen, M. J.

2016-06-01

We report the investigation of an Alexandrite laser end-pumped by a fibre-coupled red diode laser module. Power, efficiency, spatial, spectral, and wavelength tuning performance are studied as a function of pump and laser cavity parameters. It is the first demonstration, to our knowledge, of greater than 1 W power and also highest laser slope efficiency (44.2%) in a diode-pumped Alexandrite laser with diffraction-limited TEM00 mode operation. Spatial quality was excellent with beam propagation parameter M 2 ~ 1.05. Wavelength tuning from 737-796 nm was demonstrated using an intracavity birefringent tuning filter. Using a novel double pass end-pumping scheme to get efficient absorption of both polarisation states of the scrambled fibre-delivered diode pump, a total output coupled power of 1.66 W is produced in TEM00 mode with 40% slope efficiency.

Methods and means of Fourier-Stokes polarimetry and the spatial-frequency filtering of phase anisotropy manifestations in endometriosis diagnostics

NASA Astrophysics Data System (ADS)

Ushenko, A. G.; Dubolazov, O. V.; Ushenko, Vladimir A.; Ushenko, Yu. A.; Sakhnovskiy, M. Yu.; Prydiy, O. G.; Lakusta, I. I.; Novakovskaya, O. Yu.; Melenko, S. R.

2016-12-01

This research presents investigation results of diagnostic efficiency of a new azimuthally stable Mueller-matrix method of laser autofluorescence coordinate distributions analysis of dried polycrystalline films of uterine cavity peritoneal fluid. A new model of generalized optical anisotropy of biological tissues protein networks is proposed in order to define the processes of laser autofluorescence. The influence of complex mechanisms of both phase anisotropy (linear birefringence and optical activity) and linear (circular) dichroism is taken into account. The interconnections between the azimuthally stable Mueller-matrix elements characterizing laser autofluorescence and different mechanisms of optical anisotropy are determined. The statistic analysis of coordinate distributions of such Mueller-matrix rotation invariants is proposed. Thereupon the quantitative criteria (statistic moments of the 1st to the 4th order) of differentiation of dried polycrystalline films of peritoneal fluid - group 1 (healthy donors) and group 2 (uterus endometriosis patients) are estimated.

Scalar-vector soliton fiber laser mode-locked by nonlinear polarization rotation.

PubMed

Wu, Zhichao; Liu, Deming; Fu, Songnian; Li, Lei; Tang, Ming; Zhao, Luming

2016-08-08

We report a passively mode-locked fiber laser by nonlinear polarization rotation (NPR), where both vector and scalar soliton can co-exist within the laser cavity. The mode-locked pulse evolves as a vector soliton in the strong birefringent segment and is transformed into a regular scalar soliton after the polarizer within the laser cavity. The existence of solutions in a polarization-dependent cavity comprising a periodic combination of two distinct nonlinear waves is first demonstrated and likely to be applicable to various other nonlinear systems. For very large local birefringence, our laser approaches the operation regime of vector soliton lasers, while it approaches scalar soliton fiber lasers under the condition of very small birefringence.

Three-dimensional optic axis determination using variable-incidence-angle polarization-optical coherence tomography

NASA Astrophysics Data System (ADS)

Ugryumova, Nadezhda; Gangnus, Sergei V.; Matcher, Stephen J.

2006-08-01

Polarization optical coherence tomography (PSOCT) is a powerful technique to nondestructively map the retardance and fast-axis orientation of birefringent biological tissues. Previous studies have concentrated on the case where the optic axis lies on the plane of the surface. We describe a method to determine the polar angle of the optic axis of a uniaxial birefringent tissue by making PSOCT measurements with a number of incident illumination directions. The method is validated on equine flexor tendon, yielding a variability of 4% for the true birefringence and 3% for the polar angle. We use the method to map the polar angle of fibers in the transitional region of equine cartilage.

A complex-polarization-propagator protocol for magneto-chiral axial dichroism and birefringence dispersion.

PubMed

Cukras, Janusz; Kauczor, Joanna; Norman, Patrick; Rizzo, Antonio; Rikken, Geert L J A; Coriani, Sonia

2016-05-21

A computational protocol for magneto-chiral dichroism and magneto-chiral birefringence dispersion is presented within the framework of damped response theory, also known as complex polarization propagator theory, at the level of time-dependent Hartree-Fock and time-dependent density functional theory. Magneto-chiral dichroism and magneto-chiral birefringence spectra in the (resonant) frequency region below the first ionization threshold of R-methyloxirane and l-alanine are presented and compared with the corresponding results obtained for both the electronic circular dichroism and the magnetic circular dichroism. The additional information content yielded by the magneto-chiral phenomena, as well as their potential experimental detectability for the selected species, is discussed.

Birefringence insensitive optical coherence domain reflectometry system

DOEpatents

Everett, Matthew J.; Davis, Joseph G.

2002-01-01

A birefringence insensitive fiber optic optical coherence domain reflectometry (OCDR) system is provided containing non-polarization maintaining (non-PM) fiber in the sample arm and the reference arm without suffering from signal degradation caused by birefringence. The use of non-PM fiber significantly reduces the cost of the OCDR system and provides a disposable or multiplexed section of the sample arm. The dispersion in the reference arm and sample arm of the OCDR system are matched to achieve high resolution imaging. This system is useful in medical applications or for non-medical in situ probes. The disposable section of non-PM fiber in the sample arm can be conveniently replaced when contaminated by a sample or a patient.

Polarization analysis of diamond subwavelength gratings acting as space-variant birefringent elements

NASA Astrophysics Data System (ADS)

Piron, P.; Vargas Catalan, E.; Karlsson, M.

2018-02-01

Subwavelength gratings are gratings with a period smaller than the incident wavelength. They only allow the zeroth order of diffraction, they possess form birefringence and they can be modeled as birefringent plates. In this paper, we present the first results of an experimental method designed to measure their polarization properties. The method consists in measuring the variation of the light transmitted through two linear polarizers with the subwavelength component between them for several orientations of the polarizers. In this paper, the basic principles of the method are introduced and the experimental setup is presented. Several types of components are numerically studied and the optical measurements of one component are presented.

Color changing plasmonic surfaces utilizing liquid crystal (Conference Presentation)

NASA Astrophysics Data System (ADS)

Franklin, Daniel; Wu, Shin-Tson; Chanda, Debashis

2016-09-01

Plasmonic structural color has recently garnered significant interest as an alternative to the organic dyes standard in print media and liquid crystal displays. These nanostructured metallic systems can produce diffraction limited images, be made polarization dependent, and exhibit resistance to color bleaching. Perhaps even more advantageous, their optical characteristics can also be tuned, post-fabrication, by altering the surrounding media's refractive index parallel to the local plasmonic fields. A common material with which to achieve this is liquid crystal. By reorienting the liquid crystal molecules through external electric fields, the optical resonances of the plasmonic filters can be dynamically controlled. Demonstrations of this phenomenon, however, have been limited to modest shifts in plasmon resonance. Here, we report a liquid crystal-plasmonic system with an enhanced tuning range through the use of a shallow array of nano-wells and high birefringent liquid crystal. The continuous metallic nanostructure maximizes the overlap between plasmonic fields and liquid crystal while also allowing full reorientation of the liquid crystal upon an applied electric field. Sweeping over structural dimensions and voltages results in a color palette for these dynamic reflective pixels that can further be exploited to create color tunable images. These advances make plasmonic-liquid crystal systems more attractive candidates for filter, display, and other tunable optical technologies.

Critical behavior in the vicinity of nematic to smectic A (N-SmA) phase transition of two polar-polar binary liquid crystalline systems

NASA Astrophysics Data System (ADS)

Barman, Barnali; Sarkar, Sudipta Kumar; Das, Malay Kumar

2018-01-01

Phase diagram, critical behavior and order of the nematic (N)-smectic A (SmA) phase transition of two polar-polar binary systems (i) 4-n-heptyloxy-4‧-cyanobiphenyl (7OCB) and 4-n-octyloxy-4‧-cyanobiphenyl (8OCB); (ii) 4-n-octyloxy-4‧-cyanobiphenyl (8OCB) and 4-n-nonyloxy-4‧-cyanobiphenyl (9OCB) by means of a high-resolution temperature scanning measurement of birefringence have been reported in this work. A simple power law analysis has been adopted to extract the specific heat critical exponent (α‧) at N-SmA transition from birefringence data. The α‧ for N-SmA transition indicates a uniform crossover behavior and has appeared to be non-universal in nature. With increasing concentration of the higher homologues for both the binary systems, the N-SmA transition reveals a strong tendency to be driven towards the tricritical nature. The 3D-XY limit (i.e. α‧ = -0.007) for N-SmA transition reaches at the concentration x8OCB = 0.28 corresponding to the McMillan ratio 0.914, whereas the tricritical point has been found to appear near x9OCB = 1.0 corresponding to McMillan ratio 0.992.

Quantitative analysis with advanced compensated polarized light microscopy on wavelength dependence of linear birefringence of single crystals causing arthritis

NASA Astrophysics Data System (ADS)

Takanabe, Akifumi; Tanaka, Masahito; Taniguchi, Atsuo; Yamanaka, Hisashi; Asahi, Toru

2014-07-01

To improve our ability to identify single crystals causing arthritis, we have developed a practical measurement system of polarized light microscopy called advanced compensated polarized light microscopy (A-CPLM). The A-CPLM system is constructed by employing a conventional phase retardation plate, an optical fibre and a charge-coupled device spectrometer in a polarized light microscope. We applied the A-CPLM system to measure linear birefringence (LB) in the visible region, which is an optical anisotropic property, for tiny single crystals causing arthritis, i.e. monosodium urate monohydrate (MSUM) and calcium pyrophosphate dihydrate (CPPD). The A-CPLM system performance was evaluated by comparing the obtained experimental data using the A-CPLM system with (i) literature data for a standard sample, MgF2, and (ii) experimental data obtained using an established optical method, high-accuracy universal polarimeter, for the MSUM. The A-CPLM system was found to be applicable for measuring the LB spectra of the single crystals of MSUM and CPPD, which cause arthritis, in the visible regions. We quantitatively reveal the large difference in LB between MSUM and CPPD crystals. These results demonstrate the usefulness of the A-CPLM system for distinguishing the crystals causing arthritis.

Two-photon absorption dispersion spectrometer for 1.53 μm eye-safe Doppler LIDAR.

PubMed

Vance, J D

2012-07-01

Based upon resonant two-photon absorption within a rubidium cell and 780 nm pump light, a birefringent medium for 1.530 μm is induced that changes rapidly with frequency. The birefringence is exploited to build a spectrometer that is capable of measuring the Doppler shift of scattered photons.

Digital Beam Steering Device Based on Decoupled Birefringent Prism Deflector and Polarization Rotator

NASA Technical Reports Server (NTRS)

Pishnyak, Oleg; Kreminska, Lyubov; Laventovich, Oleg D.; Pouch, John J.; Miranda, Felix A.; Winker, Bruce K.

2004-01-01

We describe digital beam deflectors (DBDs) based on liquid crystals. Each stage of the device comprises a polarization rotator and a birefringent prism deflector. The birefringent prism deflects the beam by an angle that depends on polarization of the incident beam. The prism can be made of the uniaxial smectic A (SmA) liquid crystal (LC) or a solid crystal such as yttrium orthovanadate (YVO4). SmA prisms have high birefringence and can be constructed in a variety of shapes, including single prisms and prismatic blazed gratings of different angles and profiles. We address the challenges of uniform alignment of SmA, such as elimination of focal conic domains. Rotation of linear polarization is achieved by an electrically switched twisted nematic (TN) cell. A DBD composed of N rotator-deflector pairs steers the beam into 2(sup N) directions. As an example, we describe a four-stage DBD deflecting normally incident laser beam within the range of +/- 56 mrad with 8 mrad steps. Redirection of the beam is achieved by switching the TN cells.

Determination of the space-charge field amplitude in polymeric photorefractive polymers.

PubMed

Hwang, Ui-Jung; Choi, Chil-Sung; Vuong, Nguyen Quoc; Kim, Nakjoong

2005-12-22

The space-charge field built in a polymeric photorefractive polymer was calculated by a simple method based on the oriented gas model. When anisotropic chromophores in a photorefractive polymer were exposed to an external field, they oriented preferentially to exhibit a birefringence. Then, under illumination of two coherent beams and an external field, they reoriented to form a photorefractive grating. During the formation of the grating, the chromophores were reoriented by the space-charge field as well as by the external applied field. The birefringence induced in the material by an external electric field was determined by measuring the transmittance of the sample which is placed between crossed polarizers, where birefringence depicts the orientation of the chromophores. By measuring the diffraction efficiency with a modified degenerate four-wave mixing setup, the index amplitude of the grating was determined. Finally, the space-charge field was determined by comparing the diffraction efficiency with the birefringence with respect to the applied electric field. In our study, the space-charge field was about 20% of the external applied field, which coincided with previous results obtained from our laboratory.

In vivo imaging of human burn injuries with polarization-sensitive optical coherence tomography

NASA Astrophysics Data System (ADS)

Kim, Ki Hean; Pierce, Mark C.; Maguluri, Gopi; Park, B. Hyle; Yoon, Sang June; Lydon, Martha; Sheridan, Robert; de Boer, Johannes F.

2012-06-01

The accurate determination of burn depth is critical in the clinical management of burn wounds. Polarization-sensitive optical coherence tomography (PS-OCT) has been proposed as a potentially non-invasive method for determining burn depth by measuring thermally induced changes in the structure and birefringence of skin, and has been investigated in pre-clinical burn studies with animal models and ex vivo human skin. In this study, we applied PS-OCT to the in-vivo imaging of two pediatric burn patients. Deep and superficial burned skins along with contralateral controls were imaged in 3D. The imaging size was 8 mm×6 mm×2 mm in width, length, and depth in the air respectively, and the imaging time was approximately 6 s per volume. Superficially burned skins exhibited the same layered structure as the contralateral controls, but more visible vasculature and reduced birefringence compared to the contralateral controls. In contrast, a deeply burned skin showed loss of the layered structure, almost absent vasculature, and smaller birefringence compared to superficial burns. This study suggested the vasculature and birefringence as parameters for characterizing burn wounds.

Terahertz artificial birefringence and tunable phase shifter based on dielectric metasurface with compound lattice.

PubMed

Ji, Yun-Yun; Fan, Fei; Chen, Meng; Yang, Lei; Chang, Sheng-Jiang

2017-05-15

A dielectric metasurface with line-square compound lattice structure has been fabricated and demonstrated in the terahertz (THz) regime by the THz time-domain spectroscopy and numerical simulation. A polarization dependent electromagnetically induced transparency (EIT) effect is achieved in this metasurface due to the mode coupling and interference between the resonance modes in line and square subunits of the metasurface. Accompany with the EIT effect, a large artificial birefringence effect between two orthogonal polarization states is also observed in this compound metasurface, of which birefringence is over 0.6. Furthermore, the liquid crystals are filled on the surface of this dielectric metasurface to fabricate an electrically tunable THz LC phase shifter. The experimental results show that its tunable phase shift under the biased electric field reaches 0.33π, 1.8 times higher than the bare silicon, which confirms the enhancement role of THz microstructure on the LC phase shift in the THz regime. The large birefringence phase shift of this compound metasurface and its LC tunable phase shifter will be of great significance for potential applications in THz polarization and phase devices.

A high definition Mueller polarimetric endoscope for tissue characterisation (Conference Presentation)

NASA Astrophysics Data System (ADS)

Qi, Ji; Elson, Daniel

2016-03-01

The mechanism of most medical endoscopes is based on the interaction between light and biological tissue, inclusive of absorption, elastic scattering and fluorescence. In essence, the metrics of those interactions are obtained from the fundamental properties of light as an electro-magnetic waves, namely, the radiation intensity and wavelength. As another fundamental property of light, polarisation can not only reveal tissue scattering and absorption information from a different perspective, but is also able to provide a fresh insight into directional tissue birefringence properties induced by birefringent compositions and anisotropic fibrous structures, such as collagen, elastin, muscle fibre, etc at the same time. Here we demonstrate a low cost high definition Muller polarimetric endoscope with minimal alteration of a rigid endoscope. By imaging birefringent tissue mimicking phantoms and a porcine bladder, we show that this novel endoscopic imaging modality is able to provide different information of interest from unpolarised endoscopic imaging, including linear depolarization, circular depolarization, birefringence, optic axis orientation and dichroism. This endoscope can potentially be employed for better tissue visualisation and benefit endoscopic investigations and intra-operative guidance.

Improved cutback method measuring beat-length for high-birefringence optical fiber by fitting data of photoelectric signal

NASA Astrophysics Data System (ADS)

Shi, Zhi-Dong; Lin, Jian-Qiang; Bao, Huan-Huan; Liu, Shu; Xiang, Xue-Nong

2008-03-01

A photoelectric measurement system for measuring the beat length of birefringence fiber is set up including a set of rotating-wave-plate polarimeter using single photodiode. And two improved cutback methods suitable for measuring beat-length within millimeter range of high birefringence fiber are proposed through data processing technique. The cut length needs not to be restricted shorter than one centimeter so that the auto-cleaving machine is freely used, and no need to carefully operate the manually cleaving blade with low efficiency and poor success. The first method adopts the parameter-fitting to a saw-tooth function of tried beat length by the criterion of minimum square deviations, without special limitation on the cut length. The second method adopts linear-fitting in the divided length ranges, only restrict condition is the increment between different cut lengths less than one beat-length. For a section of holey high-birefringence fiber, we do experiments respectively by the two methods. The detecting error of beat-length is discussed and the advantage is compared.

Design of high birefringence and low confinement loss photonic crystal fibers with five rings hexagonal and octagonal symmetry air-holes in fiber cladding

NASA Astrophysics Data System (ADS)

Yang, Kuang-Yu; Chau, Yuan-Fong; Huang, Yao-Wei; Yeh, Hsiao-Yu; Ping Tsai, Din

2011-05-01

We present a new cladding design for high birefringence and low confinement loss photonic crystal fibers (PCFs) using a full-vector finite element method with anisotropic perfectly matched boundary layer. Six cases of PCFs are proposed for comparison. The proposed cladding in PCFs is composed of five rings of air-holes. Air-holes on the inner two rings are arranged in a hexagonal symmetry whereas, air-holes on the outer three rings are arranged in an octagonal symmetry in fused silica. Results show that suitable design air-holes on the inner two rings will significantly increase the birefringence, whereas, elliptical holes with major axis along x-axis on the outer three rings will provide strong confinement ability. The highest modal birefringence and lowest confinement loss of our proposed case five structure at the excitation wavelength of λ = 1550 nm can be achieved at a magnitude of 0.87 × 10-2 and less than 0.01 dB/km with only five rings of air-holes in fiber cladding.

Inhibition of myosin light-chain phosphorylation inverts the birefringence response of porcine airway smooth muscle

PubMed Central

Smolensky, Alexander V; Gilbert, Susan H; Harger-Allen, Margaret; Ford, Lincoln E

2007-01-01

Muscle birefringence, caused mainly by parallel thick filaments, increases in smooth muscle during stimulation, signalling thick filament formation upon activation. The reverse occurs in skeletal muscle, where a decrease in birefringence has been correlated with crossbridge movement away from the thick filaments. When force generation by trachealis muscle was inhibited with wortmannin, which inhibits myosin light-chain phosphorylation and thick-filament formation, but not the calcium increase caused by stimulation, the birefringence response inverted, suggesting crossbridge movement similar to that of skeletal muscle. Resistance to quick stretches was much greater in stimulated muscle than in unstimulated muscle before wortmannin treatment and no different in stimulated and unstimulated muscle after force inhibition by wortmannin. Before wortmannin treatment, stimulation reduced thick-filament cross-sectional areas in electron micrographs by 44%. After force inhibition by wortmannin, filament areas were not significantly different in stimulated and unstimulated muscle and not significantly different from those of relaxed muscle without wortmannin treatment. These results suggest that myofibrillar-space calcium causes crossbridges to move away from the thick filaments without firmly attaching to thin filaments. PMID:17095560

A Mach-Zehnder interferometer based on orbital angular momentum for improved vortex coronagraph efficiency

NASA Astrophysics Data System (ADS)

Piron, P.; Delacroix, C.; Huby, E.; Mawet, D.; Karlsson, M.; Ruane, G.; Habraken, S.; Absil, O.; Surdej, J.

2015-09-01

The Annular Groove Phase Mask (AGPM) is a vectorial vortex phase mask. It acts as a half-wave plate with a radial fast axis orientation operating in the mid infrared domain. When placed at the focus of a telescope element provides a continuous helical phase ramp for an on axis sources, which creates the orbital angular momentum. Thanks to that phase, the intensity of the central source is canceled by a down-stream pupil stop, while the off axis sources are not affected. However due to experimental conditions the nulling is hardly perfect. To improve the null, a Mach-Zehnder interferometer containing Dove prisms differently oriented can be proposed to sort out light based on its orbital angular momentum (OAM). Thanks to the differential rotation of the beam, a π phase shift is achieved for the on axis light affected by a non zero OAM. Therefore the contrast between the star and its faint companion is enhanced. Nevertheless, due the Dove prisms birefringence, the performance of the interferometer is relatively poor. To solve this problem, we propose to add a birefringent wave-plate in each arm to compensate this birefringence. In this paper, we will develop the mathematical model of the wave front using the Jones formalism. The performance of the interferometer is at first computed for the simple version without the birefringent plate. Then the effect of the birefringent plate is be mathematically described and the performance is re-computed.

[Polarized light microscopy for evaluation of oocytes as a prognostic factor in the evolution of a cycle in assisted reproduction].

PubMed

González-Ortega, C; Cancino-Villarreal, P; Alonzo-Torres, V E; Martínez-Robles, I; Pérez-Peña, E; Gutiérrez-Gutiérrez, A M

2016-04-01

Identification of the best embryos to transfer is a key element for success in assisted reproduction. In the last decade, several morphological criteria of oocytes and embryos were evaluated with regard to their potential for predicting embryo viability. The introduction of polarization light microscopy systems has allowed the visualization of the meiotic spindle and the different layers of the zona pellucida in human oocytes on the basis of birefringence in a non-destructive way. Conflicting results have been reported regarding the predictive value in ICSI cycles. To assess the predictive ability of meiotic spindle and zona pellucida of human oocytes to implant by polarized microscopy in ICSI cycles. Prospective and observational clinical study. 903 oocytes from 94 ICSI cycles were analyzed with polarized microscopy. Meiotic spindle visualization and zona pellucida birefringence values by polarized microscopy were correlated with ICSI cycles results. Meiotic spindle visualization and birefringence values of zona pellucida decreased in a direct basis with increasing age. In patients aged over the 35 years, the percentage of a visible spindle and mean zona pellucida birefringence was lower than in younger patients. Fertilization rate were higher in oocytes with visible meiotic spindle (81.3% vs. 64%; p < 0.0001), as well as embryo quality (47.4% vs. 39%; p=0.01). Fertilization rate was higher in oocytes with positive values of birefringence (77.5 % vs. 68.5% p=0.005) with similar embryo quality. Conception cycles showed oocytes with higher mean value of zona birefringence and visible spindle vs. no-conception cycles (p<0.05). Polarized light microscopy improves oocyte selection, which significantly impacts in the development of embryos with greater implantation potential. The use of polarized light microscopy with sperm selection methods, blastocyst culture and deferred embryo transfers will contribute to transfer fewer embryos without diminishing rates of live birth and single embryo transfer will be more feasible.

Structure and Orientation Behavior of Highly Oriented Polymers Under Tensile and Compressive Stresses

NASA Astrophysics Data System (ADS)

Garcia-Ramirez, Rafael

The birefringence of Kevlar 49^ circler fibers has been shown to decrease with compressive strain, suggesting that structure changes under compression involve decreasing crystallite orientation. This mechanism appears to be the inverse of that occurring under tension, for which increasing crystallite orientation has been reported to occur, leading to non-linear elasticity. A contrast between the effects of both stress modes on structure (orientation) response is presented. While birefringence presents itself as a technically convenient and economically attractive technique for this type of study, caution must be exercised when interpreting results from measurements under stress. For highly crystalline fibers, experiments have led to the attribution of the observed changes in birefringence almost entirely to crystallite orientation. This study presents an analysis of the different contributions to birefringence under stress. X-ray diffraction experiments have been performed for Kevlar 49^ circler fibers under tensile stress. Results from crystal orientation cannot account for changes observed in birefringence. Moreover, they appear to account only for a small fraction of the total change. These observations suggest significant contributions from other sources. Theoretical calculations have been carried out under simulated stress conditions to quantify the effect of molecular deformation on the observed birefringence of Kevlar 49^circler fibers. The results have been obtained using semi-empirical molecular orbital calculations with the AM1 Hamiltonian in MOPAC. This analysis has been applied to poly(p^' -phenylene terephthalamide) (PPTA) and polyethylene (PE) chains. For PE, stress-free computations were performed on segments of up to 50 -(CH_2-CH _2)- units. Strains up to 1% were applied on segments of up to 40 units. For PPTA, segments of up to 5 PTA units were analyzed. Strain-free results indicate a linear dependence of molecular polarizability on chain length. The treatment yields also a linear trend for the effect of strain on the polarizability of PE segments. Thus, the calculations predict a plane in 3-D space for the dependence of molecular polarizability on both chain size and strain. The predicted molecular polarizabilities are used to evaluate the effect of stress on birefringence of the idealized polymers, by applying existing internal-field theory. Results indicate significant effects from molecules deforming under the stress field.

Investigation of Model Sunscreen Formulations Comparing the Sun Protection Factor, the Universal Sun Protection Factor and the Radical Formation Ratio.

PubMed

Syring, Felicia; Weigmann, Hans-Jürgen; Schanzer, Sabine; Meinke, Martina C; Knorr, Fanny; Lademann, Jürgen

2016-01-01

In view of globally rising skin cancer rates and harmful effects exerted by sunlight throughout the ultraviolet, visible and infrared ranges, an objective, safe and comprehensive method for determining sunscreen efficacy is required in order to warrant safe sun exposure. In this study, the influence of characteristic active ingredients (chemical filters, physical filters and antioxidants) on different sunscreen indicators, including the universal sun protection factor and the radical formation ratio, was determined and compared to their influence on sun protection factor values. Spectroscopic universal sun protection factor measurements were conducted ex vivo by analyzing tape strips taken from human skin, and radical formation ratio determination was performed via electron paramagnetic resonance spectroscopy using porcine ear skin ex vivo. The sun protection factor determination was conducted according to ISO standards (ISO 24444:2010). It was shown that chemical filters provide a protective effect which was measurable by all methods examined (spectroscopy, electron paramagnetic resonance spectroscopy and erythema formation). Physical filters, when used as single active ingredients, increased protective values in universal sun protection factor and sun protection factor measurements but exhibited no significant effect on universal sun protection factor measurements when used in combination with chemical filters or antioxidants. Antioxidants were shown to increase sun protection factor values. Radical formation ratio values were shown to be influenced merely by chemical filters, leading to the conclusion that the universal sun protection factor is the most suitable efficacy indicator for the ultraviolet range. © 2015 S. Karger AG, Basel.

Flat profile laser beam shaper

DOEpatents

Johnson, Todd R.

2017-09-12

A system for shaping a beam comprises an emitter for emitting coherent electromagnetic radiation. Birefringent displacers are configured between the emitter and a target wherein the at least two birefringent displacers split the coherent electromagnetic radiation into a plurality of coherent parallel beams of electromagnetic radiation thereby producing a shaped wave front of the coherent parallel beams of electromagnetic radiation.

Induced solitons formed by cross-polarization coupling in a birefringent cavity fiber laser.

PubMed

Zhang, H; Tang, D Y; Zhao, L M; Tam, H Y

2008-10-15

We report on the experimental observation of induced solitons in a passively mode-locked fiber ring laser with a birefringence cavity. Owing to the cross coupling between the two orthogonal polarization components of the laser, it was found that if a soliton was formed along one cavity polarization axis, a weak soliton was also induced along the orthogonal polarization axis, and depending on the net cavity birefringence, the induced soliton could have either the same or different center wavelengths to that of the inducing soliton. Moreover, the induced soliton always had the same group velocity as that of the inducing soliton. They formed a vector soliton in the cavity. Numerical simulations confirmed the experimental observations.

Three-parameter error analysis method based on rotating coordinates in rotating birefringent polarizer system

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cao, Junjie; Jia, Hongzhi, E-mail: hzjia@usst.edu.cn

2015-11-15

We propose error analysis using a rotating coordinate system with three parameters of linearly polarized light—incidence angle, azimuth angle on the front surface, and angle between the incidence and vibration planes—and demonstrate the method on a rotating birefringent prism system. The transmittance and angles are calculated plane-by-plane using a birefringence ellipsoid model and the final transmitted intensity equation is deduced. The effects of oblique incidence, light interference, beam convergence, and misalignment of the rotation and prism axes are discussed. We simulate the entire error model using MATLAB and conduct experiments based on a built polarimeter. The simulation and experimental resultsmore » are consistent and demonstrate the rationality and validity of this method.« less

Optical properties of amyloid stained by Congo red: history and mechanisms.

PubMed

Howie, Alexander J; Brewer, Douglas B

2009-04-01

Amyloid stained by Congo red has striking optical properties that generally have been poorly described and inadequately explained, although they can be understood from principles of physical optics. Molecules of Congo red are orientated on amyloid fibrils, and so the dye becomes dichroic and birefringent. The birefringence varies with wavelength in accordance with a fundamental property of all light-transmitting materials called anomalous dispersion of the refractive index around an absorption peak. The combination of this and absorption of light, with modification by any additional birefringence in the optical system, explains the various colours that can be seen in Congo red-stained amyloid between crossed polariser and analyser, and also when the polariser and analyser are progressively uncrossed. These are called anomalous colours.

Birefringence dispersion compensation demodulation algorithm for polarized low-coherence interferometry.

PubMed

Wang, Shuang; Liu, Tiegen; Jiang, Junfeng; Liu, Kun; Yin, Jinde; Wu, Fan

2013-08-15

A demodulation algorithm based on the birefringence dispersion characteristics for a polarized low-coherence interferometer is proposed. With the birefringence dispersion parameter taken into account, the mathematical model of the polarized low-coherence interference fringes is established and used to extract phase shift information between the measured coherence envelope center and the zero-order fringe, which eliminates the interferometric 2 π ambiguity of locating the zero-order fringe. A pressure measurement experiment using an optical fiber Fabry-Perot pressure sensor was carried out to verify the effectiveness of the proposed algorithm. The experiment result showed that the demodulation precision was 0.077 kPa in the range of 210 kPa, which was improved by 23 times compared to the traditional envelope detection method.

Multiscale polarization diagnostics of birefringent networks in problems of necrotic changes diagnostics

NASA Astrophysics Data System (ADS)

Sakhnovskiy, M. Yu.; Ushenko, Yu. O.; Ushenko, V. O.; Besaha, R. N.; Pavlyukovich, N.; Pavlyukovich, O.

2018-01-01

The paper consists of two parts. The first part presents short theoretical basics of the method of azimuthally-invariant Mueller-matrix description of optical anisotropy of biological tissues. It was provided experimentally measured coordinate distributions of Mueller-matrix invariants (MMI) of linear and circular birefringences of skeletal muscle tissue. It was defined the values of statistic moments, which characterize the distributions of amplitudes of wavelet coefficients of MMI at different scales of scanning. The second part presents the data of statistic analysis of the distributions of amplitude of wavelet coefficients of the distributions of linear birefringence of myocardium tissue died after the infarction and ischemic heart disease. It was defined the objective criteria of differentiation of the cause of death.

Wavelet analysis of birefringence images of myocardium tissue

NASA Astrophysics Data System (ADS)

Sakhnovskiy, M. Yu.; Ushenko, Yu. O.; Kushnerik, L.; Soltys, I. V.; Pavlyukovich, N.; Pavlyukovich, O.

2018-01-01

The paper consists of two parts. The first part presents short theoretical basics of the method of azimuthally-invariant Mueller-matrix description of optical anisotropy of biological tissues. It was provided experimentally measured coordinate distributions of Mueller-matrix invariants (MMI) of linear and circular birefringences of skeletal muscle tissue. It was defined the values of statistic moments, which characterize the distributions of amplitudes of wavelet coefficients of MMI at different scales of scanning. The second part presents the data of statistic analysis of the distributions of amplitude of wavelet coefficients of the distributions of linear birefringence of myocardium tissue died after the infarction and ischemic heart disease. It was defined the objective criteria of differentiation of the cause of death.

A streaming birefringence study of the flow at the junction of the aorta and the renal arteries

NASA Astrophysics Data System (ADS)

Rankin, G. W.; Sabbah, H. N.; Stein, P. D.

1989-11-01

Streaming birefringence with an organic dye (Milling Yellow) was used to investigate the flow near the junction of the renal arteries and the descending aorta in a model of human vessels. The dye concentration was adjusted to give fluid rheological properties, typical of blood. Steady and pulsatile flow were investigated at branch-to-trunk flow ratios of 0.050 0.350. The flow ratio range over which flow separation and simple secondary flows were identified during systole near the renal ostia are reported. Streaming birefringence has the advantage of allowing visualization of the entire flow field. Also, the fluid rather than suspended particles are observed. An important disadvantage, however, is that three-dimensional flows make interpretation difficult.

Fabrication of microchannels in fused silica using femtosecond Bessel beams

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yashunin, D. A., E-mail: yashuninda@yandex.ru; Nizhny Novgorod State Technical University, 24 Minin St., Nizhny Novgorod 603950; Malkov, Yu. A.

Extended birefringent waveguiding microchannels up to 15 mm long were created inside fused silica by single-pulse irradiation with femtosecond Bessel beams. The birefringent refractive index change of 2–4 × 10{sup −4} is attributed to residual mechanical stress. The microchannels were chemically etched in KOH solution to produce 15 mm long microcapillaries with smooth walls and a high aspect ratio of 1:250. Bessel beams provide higher speed of material processing compared to conventional multipulse femtosecond laser micromachining techniques and permit simple control of the optical axis direction of the birefringent waveguides, which is important for practical applications [Corrielli et al., “Rotated waveplates inmore » integrated waveguide optics,” Nat. Commun. 5, 4249 (2014)].« less

Determination of pitch rotation in a spherical birefringent microparticle

NASA Astrophysics Data System (ADS)

Roy, Basudev; Ramaiya, Avin; Schäffer, Erik

2018-03-01

Rotational motion of a three dimensional spherical microscopic object can happen either in pitch, yaw or roll fashion. Among these, the yaw motion has been conventionally studied using the intensity of scattered light from birefringent microspheres through crossed polarizers. Up until now, however, there is no way to study the pitch motion in spherical microspheres. Here, we suggest a new method to study the pitch motion of birefringent microspheres under crossed polarizers by measuring the 2-fold asymmetry in the scattered signal either using video microscopy or with optical tweezers. We show a couple of simple examples of pitch rotation determination using video microscopy for a microsphere attached with a kinesin molecule while moving along a microtubule and of a particle diffusing freely in water.

Design for the optical retardation in broadband zero-order half-wave plates.

PubMed

Liu, Jin; Cai, Yi; Chen, Hongyi; Zeng, Xuanke; Zou, Da; Xu, Shixiang

2011-04-25

This paper presents a novel design for broadband zero-order half-wave plates to eliminate the first-order or up to second-order wavelength-dependent birefringent phase retardation (BPR) with 2 or 3 different birefringent materials. The residual BPRs of the plates increase monotonously with the wavelength deviation from a selected wavelength, so the plates are applicable to the broadband light pulses which gather most of the light energy around their central wavelengths. The model chooses the materials by the birefringent dispersion coefficient and evaluates the performances of the plates by the weighted average of the absolute value of residual BPR in order to emphasize the contributions of the incident spectral components whose possess higher energies.

Birefringence-balanced polarimetric optical fiber sensor for high-temperature measurements

NASA Technical Reports Server (NTRS)

Wang, Anbo; Wang, George Z.; Murphy, Kent A.; Claus, Richard O.

1992-01-01

A birefringence-balanced polarimetric multimode fiber temperature sensor is proposed and demonstrated. Two single-crystal sapphire rods are incorporated into the sensor head. They are connected end to end in such a way that the slow axis of the first rod is aligned with the fast axis of the second rod, referred to as the referencing rod. Since the lengths of the two rods are chosen to be almost the same, the original birefringence of the first rod is balanced by that of the second rod. A light-emitting diode serves as the light source. This sensor has been experimentally demonstrated for high-temperature measurements as high as 1500 C. A sensitivity of 5 C has been obtained.

Optical birefringence imaging of x-ray excited lithium tantalate

DOE PAGES

Durbin, S. M.; Landcastle, A.; DiChiara, A.; ...

2017-08-04

X-ray absorption in lithium tantalate induces large, long-lived (~10 -5 s) optical birefringence, visualized via scanning optical polarimetry, likely arising from electrooptic coupling to x-ray induced electric fields. Similar birefringence measured from glass, sapphire, and quartz was two orders of magnitude weaker. This suggests that x-ray excited charges preferentially create ordered, aligned dipoles within the noncentrosymmetric unit cell of ferroelectric LiTaO 3, enhancing the electric field compared to more isotropic charge distributions in the other materials. In conclusion, time-resolved measurements show a prompt response on a picosecond time scale, which along with the long decay time suggest novel approaches tomore » optical detection of x-rays using ferroelectric materials.« less

Compensation for Phase Anisotropy of a Metal Reflector

NASA Technical Reports Server (NTRS)

Hong, John

2007-01-01

A method of compensation for the polarization- dependent phase anisotropy of a metal reflector has been proposed. The essence of the method is to coat the reflector with multiple thin alternating layers of two dielectrics that have different indices of refraction, so as to introduce an opposing polarization-dependent phase anisotropy. The anisotropy in question is a phenomenon that occurs in reflection of light at other than normal incidence: For a given plane wave having components polarized parallel (p) and perpendicular (s) to the plane of incidence, the phase of s-polarized reflected light differs from the phase p-polarized light by an amount that depends on the angle of incidence and the complex index of refraction of the metal. The magnitude of the phase difference is zero at zero angle of incidence (normal incidence) and increases with the angle of incidence. This anisotropy is analogous to a phase anisotropy that occurs in propagation of light through a uniaxial dielectric crystal. In such a case, another uniaxial crystal that has the same orientation but opposite birefringence can be used to cancel the phase anisotropy. Although it would be difficult to prepare a birefringent material in a form suitable for application to the curved surface of a typical metal reflector in an optical instrument, it should be possible to effect the desired cancellation of phase anisotropy by exploiting the form birefringence of multiple thin dielectric layers. (The term "form birefringence" can be defined loosely as birefringence arising, in part, from a regular array of alternating subwavelength regions having different indices of refraction.)

Mid-infrared high birefringence As2Se3-based PCF with large nonlinearity and distinctive dispersion by using asymmetric elliptical air hole cladding

NASA Astrophysics Data System (ADS)

Hui, Zhanqiang; Yang, Min; Zhang, Youkun; Zhang, Meizhi

2018-01-01

A novel high birefringence As2Se3-based hexagonal lattice photonic crystal fiber (PCF) is proposed. In the structure, a central defect core and three kinds of elliptical air holes with different major axes length and ellipticity are introduced in the cladding. The finite difference time domain (FDTD) method with perfectly matched layer (PML) absorption boundary conditions are used to simulate the guided modes of the designed PCF. The properties of this PCF are investigated in detail including the birefringence, beat length, dispersion, nonlinearity and polarization mode dispersion in the 2-5 μm mid-infrared range. The results show that for the optimized structure parameters of Λ = 1.6μm, a = 0.4μm, b = 0.1μm, a1 = 0.6μm, b1 = 0.04μm, a2 = 0.8μm, b2 = 0.06μm, the high birefringence of 0.1192 and beat length of 41.93 μm are obtained. The maximum nonlinearity coefficient of 10,050 w-1km-1 and 15,200 w-1km-1 for x- and y-polarization modes are achieved. The distinctive dispersion is analyzed, which is all-normal in x-polarization direction while it has two zero dispersion points at 3.18 μm and 3.65 μm in y-polarization direction. The designed PCF with high birefringence, large nonlinearity and distinctive dispersion will be beneficial for mid-infrared fiber sensing, mid-infrared spectroscopy and nonlinear optics applications.

High-resolution polarization sensitive OCT for ocular imaging in rodents

NASA Astrophysics Data System (ADS)

Fialová, Stanislava; Rauscher, Sabine; Gröger, Marion; Pircher, Michael; Hitzenberger, Christoph K.; Baumann, Bernhard

2015-03-01

A new high-resolution polarization sensitive optical coherence tomography system was developed for imaging rodent retina. Various light-tissue interactions such as birefringence and depolarization can change the polarization state of light. In the eye, there are several tissues that have these properties, for example retinal pigment epithelium (depolarization) and sclera (birefringence). These layers play key roles in diseases like age-related macular degeneration or glaucoma. Animal models are an important component for understanding disease pathogenesis. The gold standard for the evaluation of preclinical experiments is histology, which is an invasive and terminal procedure. Since OCT is non-invasive, it has the potential to be an alternative to histology with the benefit of long-term study of the disease progression in the same animal. In this study, a superluminescent diode with spectrum width 100 nm and mean wavelength 840 nm is used as a light source in order to enable high axial resolution. Spectrometers are custom built to enable high imaging speed that allows acquiring 3D data sets with 1024x200x1536 voxels in 3.44 s. From the acquired data, images displaying phase retardation induced by birefringence and orientation of birefringent axis were calculated. In first measurements, we were able to identify the RPE-choroid complex (depolarization effect) and the sclera (strong birefringence) in the retina of Long-Evans and Sprague-Dawley rats. Our preliminary results demonstrate the feasibility of the system for high speed/resolution imaging of the rodent retina. This is useful for longitudinal studies of disease models of retinal disease in rats and mice

Microwave birefringent metamaterials for polarization conversion based on spoof surface plasmon polariton modes

PubMed Central

Li, Yongfeng; Zhang, Jieqiu; Ma, Hua; Wang, Jiafu; Pang, Yongqiang; Feng, Dayi; Xu, Zhuo; Qu, Shaobo

2016-01-01

We propose the design of wideband birefringent metamaterials based on spoof surface plasmon polaritons (SSPPs). Spatial k-dispersion design of SSPP modes in metamaterials is adopted to achieve high-efficiency transmission of electromagnetic waves through the metamaterial layer. By anisotropic design, the transmission phase accumulation in metamaterials can be independently modulated for x- and y-polarized components of incident waves. Since the dispersion curve of SSPPs is nonlinear, frequency-dependent phase differences can be obtained between the two orthogonal components of transmitted waves. As an example, we demonstrate a microwave birefringent metamaterials composed of fishbone structures. The full-polarization-state conversions on the zero-longitude line of Poincaré sphere can be fulfilled twice in 6–20 GHz for both linearly polarized (LP) and circularly polarized (CP) waves incidence. Besides, at a given frequency, the full-polarization-state conversion can be achieved by changing the polarization angle of the incident LP waves. Both the simulation and experiment results verify the high-efficiency polarization conversion functions of the birefringent metamaterial, including circular-to-circular, circular-to-linear(linear-to-circular), linear-to-linear polarization conversions. PMID:27698443

Recent progress in distributed fiber optic sensors.

PubMed

Bao, Xiaoyi; Chen, Liang

2012-01-01

Rayleigh, Brillouin and Raman scatterings in fibers result from the interaction of photons with local material characteristic features like density, temperature and strain. For example an acoustic/mechanical wave generates a dynamic density variation; such a variation may be affected by local temperature, strain, vibration and birefringence. By detecting changes in the amplitude, frequency and phase of light scattered along a fiber, one can realize a distributed fiber sensor for measuring localized temperature, strain, vibration and birefringence over lengths ranging from meters to one hundred kilometers. Such a measurement can be made in the time domain or frequency domain to resolve location information. With coherent detection of the scattered light one can observe changes in birefringence and beat length for fibers and devices. The progress on state of the art technology for sensing performance, in terms of spatial resolution and limitations on sensing length is reviewed. These distributed sensors can be used for disaster prevention in the civil structural monitoring of pipelines, bridges, dams and railroads. A sensor with centimeter spatial resolution and high precision measurement of temperature, strain, vibration and birefringence can find applications in aerospace smart structures, material processing, and the characterization of optical materials and devices.

Recent Progress in Distributed Fiber Optic Sensors

PubMed Central

Bao, Xiaoyi; Chen, Liang

2012-01-01

Rayleigh, Brillouin and Raman scatterings in fibers result from the interaction of photons with local material characteristic features like density, temperature and strain. For example an acoustic/mechanical wave generates a dynamic density variation; such a variation may be affected by local temperature, strain, vibration and birefringence. By detecting changes in the amplitude, frequency and phase of light scattered along a fiber, one can realize a distributed fiber sensor for measuring localized temperature, strain, vibration and birefringence over lengths ranging from meters to one hundred kilometers. Such a measurement can be made in the time domain or frequency domain to resolve location information. With coherent detection of the scattered light one can observe changes in birefringence and beat length for fibers and devices. The progress on state of the art technology for sensing performance, in terms of spatial resolution and limitations on sensing length is reviewed. These distributed sensors can be used for disaster prevention in the civil structural monitoring of pipelines, bridges, dams and railroads. A sensor with centimeter spatial resolution and high precision measurement of temperature, strain, vibration and birefringence can find applications in aerospace smart structures, material processing, and the characterization of optical materials and devices. PMID:23012508

Electrically switchable polymer liquid crystal and polymer birefringent flake in fluid host systems and optical devices utilizing same

DOEpatents

Marshall, Kenneth L.; Kosc, Tanya Z.; Jacobs, Stephen D.; Faris, Sadeg M.; Li, Le

2003-12-16

Flakes or platelets of polymer liquid crystals (PLC) or other birefringent polymers (BP) suspended in a fluid host medium constitute a system that can function as the active element in an electrically switchable optical device when the suspension is either contained between a pair of rigid substrates bearing transparent conductive coatings or dispersed as microcapsules within the body of a flexible host polymer. Optical properties of these flake materials include large effective optical path length, different polarization states and high angular sensitivity in their selective reflection or birefringence. The flakes or platelets of these devices need only a 3-20.degree. rotation about the normal to the cell surface to achieve switching characteristics obtainable with prior devices using particle rotation or translation.

Methods and means of 3D diffuse Mueller-matrix tomography of depolarizing optically anisotropic biological layers

NASA Astrophysics Data System (ADS)

Dubolazov, O. V.; Ushenko, V. O.; Trifoniuk, L.; Ushenko, Yu. O.; Zhytaryuk, V. G.; Prydiy, O. G.; Grytsyuk, M.; Kushnerik, L.; Meglinskiy, I.

2017-09-01

A new technique of Mueller-matrix mapping of polycrystalline structure of histological sections of biological tissues is suggested. The algorithms of reconstruction of distribution of parameters of linear and circular birefringence of prostate histological sections are found. The interconnections between such distributions and parameters of linear and circular birefringence of prostate tissue histological sections are defined. The comparative investigations of coordinate distributions of phase anisotropy parameters formed by fibrillar networks of prostate tissues of different pathological states (adenoma and carcinoma) are performed. The values and ranges of change of the statistical (moments of the 1st - 4th order) parameters of coordinate distributions of the value of linear and circular birefringence are defined. The objective criteria of cause of Benign and malignant conditions differentiation are determined.

Low temperature Voigt effect in the terbium gallium garnet crystal.

PubMed

Akbar, Ali; Khalid, Muhammad Waleed; Anwar, Muhammad Sabieh

2017-11-27

Magnetic linear birefringence and dichroism are investigated for the paramagnetic terbium gallium garnet (TGG) single crystal in the temperature range 8-100 K. The reciprocal nature is confirmed for the linear birefringence. Furthermore a theoretical model is validated that describes the intermixing of linear and circular birefringence. The ellipticity and rotation of the polarization ellipse are investigated in the light of these measurements. These otherwise minuscule magnetically induced effects are amplified at cryogenic temperatures and are determined by a phase-sensitive technique based on the Fourier decomposition of detected signal intensities. The correspondent measurements also allow us to determine the Curie-Weiss constant corroborating the presence of a magnetically frustrated spin system. Additionally we show how the Voigt geometry enables determining the direction of a magnetic field.

Flexible transparent aerogels as window retrofitting films and optical elements with tunable birefringence

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, Qingkun; Frazier, Allister W.; Zhao, Xinpeng

Experimental realization of optically transparent, mechanically robust and flexible aerogels has been a longstanding challenge, which limits their practical applications in energy-saving devices, such as thermally insulating films for enhancing energy efficiency of windows. The poor transparency precluded even hypothetical consideration of the possibility of birefringent aerogels. We develop birefringent and optically isotropic aerogels that combine properties of thermal super-insulation, mechanical robustness and flexibility, and transparency to visible-spectrum light. This unusual combination of physical properties is achieved by combining liquid crystalline self-organization of cellulose nanofibers with polysiloxane cross-linking and control of the nanoscale porosity to form hybrid organic-inorganic mesostructured aerogels.more » Potential applications of these inexpensive materials range from single pane window retrofitting to smart fabrics.« less

Dual-hole unit-based kagome lattice microstructure fiber for low-loss and highly birefringent terahertz guidance

NASA Astrophysics Data System (ADS)

Hasan, Md. Rabiul; Akter, Sanjida; Khatun, Tania; Rifat, Ahmmed A.; Anower, Md. Shamim

2017-04-01

A low-loss microstructure fiber is numerically investigated for convenient transmission of polarization maintaining terahertz (THz) waves. The dual-hole units (DHUs) are used inside the core of the kagome lattice microstructure to achieve high birefringence and low effective material loss (EML). It is demonstrated that by rotating the axis of orientation of the DHUs, it is possible to obtain low EML of 0.052 cm-1, low confinement loss of 0.01 cm-1, and high birefringence of 0.0354 at 0.85 THz. It is also reported that the transmission properties of the proposed microstructure fiber are varied with rotation angle, core diameter, and operating frequencies. Other guiding characteristics, such as single-mode propagation, power fraction, and dispersion, are also discussed thoroughly.

Zero-fringe demodulation method based on location-dependent birefringence dispersion in polarized low-coherence interferometry.

PubMed

Wang, Shuang; Liu, Tiegen; Jiang, Junfeng; Liu, Kun; Yin, Jinde; Qin, Zunqi; Zou, Shengliang

2014-04-01

We present a high precision and fast speed demodulation method for a polarized low-coherence interferometer with location-dependent birefringence dispersion. Based on the characteristics of location-dependent birefringence dispersion and five-step phase-shifting technology, the method accurately retrieves the peak position of zero-fringe at the central wavelength, which avoids the fringe order ambiguity. The method processes data only in the spatial domain and reduces the computational load greatly. We successfully demonstrated the effectiveness of the proposed method in an optical fiber Fabry-Perot barometric pressure sensing experiment system. Measurement precision of 0.091 kPa was realized in the pressure range of 160 kPa, and computation time was improved by 10 times compared to the traditional phase-based method that requires Fourier transform operation.

A broadband Soleil-Babinet compensator for ultrashort light pulses

NASA Astrophysics Data System (ADS)

Xu, Shixiang; Ma, Yingkun; Cai, Yi; Lu, Xiaowei; Zeng, Xuanke; Chen, Hongyi; Li, Jingzhen

2013-12-01

This letter reports a novel design for a broadband Soleil-Babinet compensator including two pairs of optical wedges plus one plate. According to our birefringent dispersion compensation model, we can eliminate the first-order birefringent phase retardation (BPR) dispersion by using three different birefringent crystals. Our results show a Soleil-Babinet compensator based on a MgF2/ADP/KDP combination can work from 0° to 360° phase compensation with the maximal residual BPR less than 6° within the spectral region from 0.65 to 0.95 μm. The residual BPR of the compensator increases monotonically with the spectral deviation from the designed central wavelength, so our compensator is very suitable to be used for broadband laser pulses with most of their energies around the central wavelengths.

Ultra-flattened nearly-zero dispersion and ultrahigh nonlinear slot silicon photonic crystal fibers with ultrahigh birefringence

NASA Astrophysics Data System (ADS)

Liao, Jianfei; Xie, Yingmao; Wang, Xinghua; Li, Dongbo; Huang, Tianye

2017-07-01

A slot silicon photonic crystal fiber (PCF) is proposed to simultaneously achieve ultrahigh birefringence, large nonlinearity and ultra-flattened nearly-zero dispersion over a wide wavelength range. By taking advantage on the slot effect, ultrahigh birefringence up to 0.0736 and ultrahigh nonlinear coefficient up to 211.48 W-1 m-1 for quasi-TE mode can be obtained at the wavelength of 1.55 μm. Moreover, ultra-flattened dispersion of 0.49 ps/(nm km) for quasi-TE mode can be achieved over a 180 nm wavelength range with low dispersion slope of 1.85 × 10-3 ps/(nm2 km) at 1.55 μm. Leveraging on these advantages, the proposed slot PCF has great potential for efficient all-optical signal processing applications.

Electro-optic study of PZT ferroelectric ceramics using modulation of reflected light

NASA Astrophysics Data System (ADS)

Kniazkov, A. V.

2016-04-01

Electro-optic coefficients of variations in the refractive index of PZT and PLZT ceramic materials induced by ac electric field are estimated using modulation of reflected light. The electro-optic coefficients of PLZT ceramics measured with the aid of conventional birefringence using the phase shift of transmitted radiation and the proposed method of birefringence using the modulation of reflected light are compared.

Measurement of optical activity of honey bee

NASA Astrophysics Data System (ADS)

Ortiz-Gutiérrez, Mauricio; Olivares-Pérez, Arturo; Salgado-Verduzco, Marco Antonio; Ibarra-Torres, Juan Carlos

2016-03-01

Optical activity of some substances, such as chiral molecules, often exhibits circular birefringence. Circular birefringence causes rotation of the vibration plane of the plane polarized light as it passes through the substance. In this work we present optical characterization of honey as function of the optical activity when it is placed in a polariscope that consists of a light source and properly arranged polarizing elements.

Wide spectral range multiple orders and half-wave achromatic phase retarders fabricated from two lithium tantalite single crystal plates

NASA Astrophysics Data System (ADS)

Emam-Ismail, M.

2015-11-01

In a broad spectral range (300-2500 nm), we report the use of channeled spectra formed from the interference of polarized white light to extract the dispersion of the phase birefringence Δnp(λ) of the x- and y-cuts of lithium tantalite (LiTaO3:LT) plates. A new method named as wavenumber difference method is used to extract the spectral behavior of the phase birefringence of the x- and y- cuts of LT plates. The correctness of the obtained birefringence data is confirmed by using Jones vector method through recalculating the plates thicknesses. The spectral variation of the phase birefringence Δnp(λ) of the x- and y-cuts of LT plates is fitted to Cauchy dispersion function with relative error for both x- and y-cuts of order 2.4×10-4. The group birefringence dispersion Δng (λ) of the x- and y-cuts of LT plates is also calculated and fitted to Ghosh dispersion function with relative error for both x- and y-cuts of order 2.83×10-4. Furthermore, the phase retardation introduced by the x- and y-cuts of LT plates is also calculated. It is found that the amount of phase retardation confirms that the x- and y-cuts of LT plates can act as a multiple order half- and quarter-wave plates working at many different wavelengths through the spectral range 300-2500 nm. For the x- and y-cuts of LT plates, a large difference between group and phase birefringence is observed at a short wavelength (λ=300 nm); while such difference progressively diminished at longer wavelength (λ=2000 nm). In the near infrared region (NIR) region (700-2500 nm), a broad spectral full width at half maximum (FWHM) is observed for either x- or y-cut of LT plate which can act as if it is working as a zero order wave plate. Finally, an achromatic half-wave plate working at 598 nm and covering a wide spectral range (300-900 nm) is demonstrated experimentally by combining both x- and y-cuts of LT plates.

Inverse thermoreversible mechanical stiffening and birefringence in methylcellulose/cellulose nanocrystal hydrogel.

PubMed

Hynninen, Ville; Hietala, Sami; McKee, Jason Robert; Murtomäki, Lasse; Rojas, Orlando J; Ikkala, Olli; Nonappa, Nonappa

2018-05-07

We show that composite hydrogels comprising methyl cellulose (MC) and cellulose nanocrystal (CNC) colloidal rods display a reversible and enhanced rheological storage modulus and optical birefringence upon heating, i.e., inverse thermoreversibility. Dynamic rheology, quantitative polarized optical microscopy (POM), isothermal titration calorimetry (ITC), circular dichroism (CD), and scanning and transmission electron microscopy (SEM and TEM) were used for characterization. The concentration of CNC in aqueous media was varied up to 3.5 wt % (i.e, keeping the concentration below the critical aq. concentration) while maintaining the MC aq. concentration at 1.0 wt %. At 20 °C, MC/CNC underwent gelation upon passing the CNC concentration of 1.5 wt %. At this point the storage modulus (G´) reached a plateau, and the birefringence underwent a stepwise increase, thus suggesting a percolative phenomenon. The storage modulus (G´) of the composite gels was an order of magnitude higher at 60 °C compared to that at 20 °C. ITC results suggested that at 60 °C, the CNC rods were entropically driven to interact with MC chains, which according to recent studies, collapse at this temperature into ring-like, colloidal-scale persistent fibrils with hollow cross-section. Consequently, the increased requirement for space and mutual alignment of components results in enhanced birefringence. At room temperature, ITC shows enthalpic binding between CNCs and MC with the latter comprising an aqueous, molecularly dispersed polymer chains that lead to looser and less birefringent material. TEM, SEM, and CD indicated CNC chiral fragments within MC/CNC composite gel. Thus, their space-filling, thermoreversible assembly within the MC network can be used to tune the rheological properties and to access liquid crystalline properties at low CNC concentrations.

Investigation of a tissue engineered tendon model by PS-OCT

NASA Astrophysics Data System (ADS)

Yang, Ying; Ahearne, Mark; Wimpenny, Ian; Guijarro-Leach, Juan; Torbet, Jim

2010-02-01

A few native tissues, such as tendon, skin and eye, possess highly organized collagenous matrices. In particular, the collagen fibers in tendon are organized into a hierarchical and unidirectional format, which gives rise to the high tissuespecific mechanical properties. This organization has been clearly revealed by a conventional polarized light microscope. The newly developed polarization-sensitive optical coherence tomography (PS-OCT) technique allows non-invasive visualization of birefringence images arising from orientated structures in a three dimensional format. Our previous studies of native tendon and tissue engineered tendon by PS-OCT demonstrate that tissue engineered tendon has a far less perfect collagen fiber organization than native tendon even under dynamic culture conditions. The purpose of this study is to use PS-OCT to assess the relationship between the degree of birefringence, collagen concentration and fiber density in model tendon tissues. The model tissue is constructed from an aligned collagen hydrogel and aligned polyester nanofibers. The effects of the diameter and density of the nanofibers and the collagen concentration in the model have been investigated. The alignment of collagen fibrils is induced by application of a high magnetic field during fibrillogenesis while aligned polyester nanofibers are manufactured using the electrospinning technique. It is found that the collagen concentration, the density and size of nanofiber bundles are the key parameters to produce birefringence in OCT images. The perfectly aligned collagen hydrogel with concentration as high as 4 mg/ml does not exhibit a birefringence image until the hydrogel has been compressed and concentrated. Aligned nanofiber bundles have demonstrated marginal birefringence in the absence of the collagen matrix. These studies enhance our understanding of how to control and optimize the parameters in tendon tissue engineering.

POLARBEAR constraints on cosmic birefringence and primordial magnetic fields

DOE PAGES

Ade, Peter A. R.; Arnold, Kam; Atlas, Matt; ...

2015-12-08

Here, we constrain anisotropic cosmic birefringence using four-point correlations of even-parity E-mode and odd-parity B-mode polarization in the cosmic microwave background measurements made by the POLARization of the Background Radiation (POLARBEAR) experiment in its first season of observations. We find that the anisotropic cosmic birefringence signal from any parity-violating processes is consistent with zero. The Faraday rotation from anisotropic cosmic birefringence can be compared with the equivalent quantity generated by primordial magnetic fields if they existed. The POLARBEAR nondetection translates into a 95% confidence level (C.L.) upper limit of 93 nanogauss (nG) on the amplitude of an equivalent primordial magneticmore » field inclusive of systematic uncertainties. This four-point correlation constraint on Faraday rotation is about 15 times tighter than the upper limit of 1380 nG inferred from constraining the contribution of Faraday rotation to two-point correlations of B-modes measured by Planck in 2015. Metric perturbations sourced by primordial magnetic fields would also contribute to the B-mode power spectrum. Using the POLARBEAR measurements of the B-mode power spectrum (two-point correlation), we set a 95% C.L. upper limit of 3.9 nG on primordial magnetic fields assuming a flat prior on the field amplitude. This limit is comparable to what was found in the Planck 2015 two-point correlation analysis with both temperature and polarization. Finally, we perform a set of systematic error tests and find no evidence for contamination. This work marks the first time that anisotropic cosmic birefringence or primordial magnetic fields have been constrained from the ground at subdegree scales.« less

Parametric resonance in quantum electrodynamics vacuum birefringence

NASA Astrophysics Data System (ADS)

Arza, Ariel; Elias, Ricardo Gabriel

2018-05-01

Vacuum magnetic birefringence is one of the most interesting nonlinear phenomena in quantum electrodynamics because it is a pure photon-photon result of the theory and it directly signalizes the violation of the classical superposition principle of electromagnetic fields in the full quantum theory. We perform analytical and numerical calculations when an electromagnetic wave interacts with an oscillating external magnetic field. We find that in an ideal cavity, when the external field frequency is around the electromagnetic wave frequency, the normal and parallel components of the wave suffer parametric resonance at different rates, producing a vacuum birefringence effect growing in time. We also study the case where there is no cavity and the oscillating magnetic field is spatially localized in a region of length L . In both cases we find also a rotation of the elliptical axis.

Birefringence profile adjustment by spatial overlap of nanogratings induced by ultra-short laser pulses inside fused silica

NASA Astrophysics Data System (ADS)

Arabanian, Atoosa Sadat; Najafi, Somayeh; Ajami, Aliasghar; Husinsky, Wolfgang; Massudi, Reza

2018-02-01

We have succeeded in realizing a method to control the spatial distribution of optical retardation as a result of nanogratings in bulk-fused silica induced by ultrashort laser pulses. A colorimetry-based retardation measurement (CBRM) based on the Michel-Levy interference color chart using a polarization microscope is used to determine the profiles of the optical retardation. Effects of the spatial overlap of written regions as well as the energy and polarization of the writing pulses on the induced retardations are studied. It has been found that the spatial overlap of lines written by pulse trains with different energies and polarizations can result in an adjustment of the induced birefringence in the overlap region. This approach offers the possibility of designing polarization-sensitive components with a desired birefringence profile.

Terahertz polarization converter based on all-dielectric high birefringence metamaterial with elliptical air holes

NASA Astrophysics Data System (ADS)

Zi, Jianchen; Xu, Quan; Wang, Qiu; Tian, Chunxiu; Li, Yanfeng; Zhang, Xixiang; Han, Jiaguang; Zhang, Weili

2018-06-01

Metamaterials have been widely applied in the polarization conversion of terahertz (THz) waves. However, common plasmonic metamaterials usually work as reflective devices and have low transmissions. All-dielectric metamaterials can overcome these shortcomings. An all-dielectric metamaterial based on silicon with elliptical air holes is reported to achieve high artificial birefringence at THz frequencies. Simulations show that with appropriate structural parameters the birefringence of the dielectric metamaterial can remain flat and is above 0.7 within a broad band. Moreover, the metamaterial can be designed as a broadband quarter wave plate. A sample metamaterial was fabricated and tested to prove the validity of the simulations, and the sample could work as a quarter wave plate at 1.76 THz. The all-dielectric metamaterial that we proposed is of great significance for high performance THz polarization converters.

A modified hexagonal photonic crystal fiber for terahertz applications

NASA Astrophysics Data System (ADS)

Islam, Md. Saiful; Sultana, Jakeya; Faisal, Mohammad; Islam, Mohammad Rakibul; Dinovitser, Alex; Ng, Brian W.-H.; Abbott, Derek

2018-05-01

We present a Zeonex based highly birefringent and dispersion flattened porous core photonic crystal fiber (PC-PCF) for polarization preserving applications in the terahertz region. In order to facilitate birefringence, an array of elliptical shaped air holes surrounded by porous cladding is introduced. The porous cladding comprises circular air-holes in a modified hexagonal arrangement. The transmission characteristics of the proposed PCF are investigated using a full-vector finite element method with perfectly matched layer (PML) absorbing boundary conditions. Simulation results show a high birefringence of 0.086 and an ultra-flattened dispersion variation of ± 0.03 ps/THz/cm at optimal design parameters. Besides, a number of other important wave-guiding properties including frequency dependence of the effective material loss (EML), confinement loss, and effective area are also investigated to assess the fiber's effectiveness as a terahertz waveguide.

Great circle solution to polarization-based quantum communication (QC) in optical fiber

DOEpatents

Nordholt, Jane Elizabeth; Peterson, Charles Glen; Newell, Raymond Thorson; Hughes, Richard John

2016-03-15

Birefringence in optical fibers is compensated by applying polarization modulation at a receiver. Polarization modulation is applied so that a transmitted optical signal has states of polarization (SOPs) that are equally spaced on the Poincare sphere. Fiber birefringence encountered in propagation between a transmitter and a receiver rotates the great circle on the Poincare sphere that represents the polarization bases used for modulation. By adjusting received polarizations, polarization components of the received optical signal can be directed to corresponding detectors for decoding, regardless of the magnitude and orientation of the fiber birefringence. A transmitter can be configured to transmit in conjugate polarization bases whose SOPs can be represented as equidistant points on a great circle so that the received SOPs are mapped to equidistant points on a great circle and routed to corresponding detectors.

Unusual electro-optical behavior in a wide-temperature BPIII cell.

PubMed

Chen, Hui-Yu; Lu, Sheng-Feng; Hsieh, Yi-Chun

2013-04-22

A low driving voltage and fast response blue phase III (BPIII) liquid-crystal device with very low dielectric anisotropy is demonstrated. To stabilize BPIII in a wide temperature range (> 15°C), a chiral molecule with good solubility was chosen. By studying field-dependent polarization state of the transmitting light, it was found that the field-induced birefringence becomes saturated in the high field. However, the transmitting intensity exhibits a tendency to increase as the electric field increases. This indicates that the electro-optical behavior in BPIII device may be from the flexoelectric effect, which induces tilted optical axis and then induces birefringence. Because the phase transition from BPIII to chiral nematic phase does not happen, the device shows no hysteresis effect and no residual birefringence, exhibits fast response, and can be a candidate for fast photonic application.

Golden spiral photonic crystal fiber: polarization and dispersion properties.

PubMed

Agrawal, Arti; Kejalakshmy, N; Chen, J; Rahman, B M A; Grattan, K T V

2008-11-15

A golden spiral photonic crystal fiber (GS-PCF) design is presented in which air holes are arranged in a spiral pattern governed by the golden ratio, where the design has been inspired by the optimal arrangement of seeds found in nature. The birefringence and polarization properties of this fiber are analyzed using a vectorial finite-element method. The fiber that is investigated shows a large modal birefringence peak value of 0.016 at an operating wavelength of 1.55 microm and exhibits highly tuneable dispersion with multiple zero dispersion wavelengths and also large normal dispersion. The GS-PCF design has identical circular air holes that potentially simplify fabrication. In light of its properties, the GS-PCF could have application as a highly birefringent fiber and in nonlinear optics, and moreover the 2D chiral nature of the pattern could yield exotic properties.

InP/ZnS quantum-dot-dispersed nematic liquid crystal illustrating characteristic birefringence and enhanced electro-optical parameters

NASA Astrophysics Data System (ADS)

Roy, Aradhana; Pathak, Govind; Herman, Jakub; Inamdar, Sanjeev R.; Srivastava, Atul; Manohar, Rajiv

2018-03-01

The present study investigates the influence of InP/ZnS core/shell QDs on various parameters of Nematic LC sample 1832A, based on 4-(4-alkyl-cyclohexyl)benzene isothiocyanates and 4-(4-alkyl-cyclohexyl)biphenyl isothiocyanates. Observations recorded consist of distinguished functioning of birefringence phenomenon along with characteristic response time measurement. Further study of rotational viscosity and splay elastic constant portrays stupendous behavior strengthening the appositeness of the composites for low-charge consumable devices. The addition of 0.2 ml of core/shell QDs producing more than two times faster response and enhanced birefringence at low-temperature range can be employed in development of thermostable photonic devices. In addition, dielectric properties comprising of relative permittivity and conductivity have been reported supporting the outcome of the investigation in applicative LC-based technologies.

The use of fractional orders in the determination of birefringence of highly dispersive materials by the channelled spectrum method

NASA Astrophysics Data System (ADS)

Nagarajan, K.; Shashidharan Nair, C. K.

2007-07-01

The channelled spectrum employing polarized light interference is a very convenient method for the study of dispersion of birefringence. However, while using this method, the absolute order of the polarized light interference fringes cannot be determined easily. Approximate methods are therefore used to estimate the order. One of the approximations is that the dispersion of birefringence across neighbouring integer order fringes is negligible. In this paper, we show how this approximation can cause errors. A modification is reported whereby the error in the determination of absolute fringe order can be reduced using fractional orders instead of integer orders. The theoretical background for this method supported with computer simulation is presented. An experimental arrangement implementing these modifications is described. This method uses a Constant Deviation Spectrometer (CDS) and a Soleil Babinet Compensator (SBC).

Polarization-maintaining fiber pulse compressor by birefringent hollow-core photonic bandgap fiber

NASA Astrophysics Data System (ADS)

Shirakawa, Akira; Tanisho, Motoyuki; Ueda, Ken-Ichi

2006-12-01

Structural birefringent properties of a hollow-core photonic-bandgap fiber were carefully investigated and applied to all-fiber chirped-pulse amplification as a compressor. The group birefringence of as high as 6.9×10-4 and the dispersion splitting by as large as 149 ps/nm/km between the two principal polarization modes were observed at 1557 nm. By launching the amplifier output to one of the polarization modes a 17-dB polarization extinction ratio was obtained without any pulse degradation originating from polarization-mode dispersion. A hybrid fiber stretcher effectively compensates the peculiar dispersion of the photonic-bandgap fiber and pedestal-free 440-fs pulses with a 1-W average power and 21-nJ pulse energy were obtained. Polarization-maintaining fiber-pigtail output of high-power femtosecond pulses is useful for various applications.

Superlattice Microstructured Optical Fiber

PubMed Central

Tse, Ming-Leung Vincent; Liu, Zhengyong; Cho, Lok-Hin; Lu, Chao; Wai, Ping-Kong Alex; Tam, Hwa-Yaw

2014-01-01

A generic three-stage stack-and-draw method is demonstrated for the fabrication of complex-microstructured optical fibers. We report the fabrication and characterization of a silica superlattice microstructured fiber with more than 800 rhomboidally arranged air-holes. A polarization-maintaining fiber with a birefringence of 8.5 × 10−4 is demonstrated. The birefringent property of the fiber is found to be highly insensitive to external environmental effects, such as pressure. PMID:28788693

Imaging Polarimetry in Age-Related Macular Degeneration

PubMed Central

Miura, Masahiro; Yamanari, Masahiro; Iwasaki, Takuya; Elsner, Ann E.; Makita, Shuichi; Yatagai, Toyohiko; Yasuno, Yoshiaki

2010-01-01

PURPOSE To evaluate the birefringence properties of eyes with age-related macular degeneration (AMD). To compare the information from two techniques—scanning laser polarimetry (GDx) and polarization-sensitive spectral-domain optical coherence tomography (OCT)—and investigate how they complement each other. METHODS The authors prospectively examined the eyes of two healthy subjects and 13 patients with exudative AMD. Using scanning laser polarimetry, they computed phase-retardation maps, average reflectance images, and depolarized light images. To obtain polarimetry information with improved axial resolution, they developed a fiber-based, polarization-sensitive, spectral-domain OCT system and measured the phase retardation associated with birefringence in the same eyes. RESULTS Both GDx and polarization-sensitive spectral-domain optical coherence tomography detected abnormal birefringence at the locus of exudative lesions. Polarization-sensitive, spectral-domain OCT showed that in the old lesions with fibrosis, phase-retardation values were significantly larger than in the new lesions (P = 0.020). Increased scattered light and altered polarization scramble were associated with portions of the lesions. CONCLUSIONS GDx and polarization-sensitive spectral-domain OCT are complementary in probing birefringence properties in exudative AMD. Polarimetry findings in exudative AMD emphasized different features and were related to the progression of the disease, potentially providing a noninvasive tool for microstructure in exudative AMD. PMID:18515594

New pediatric vision screener employing polarization-modulated, retinal-birefringence-scanning-based strabismus detection and bull's eye focus detection with an improved target system: opto-mechanical design and operation

NASA Astrophysics Data System (ADS)

Irsch, Kristina; Gramatikov, Boris I.; Wu, Yi-Kai; Guyton, David L.

2014-06-01

Amblyopia ("lazy eye") is a major public health problem, caused by misalignment of the eyes (strabismus) or defocus. If detected early in childhood, there is an excellent response to therapy, yet most children are detected too late to be treated effectively. Commercially available vision screening devices that test for amblyopia's primary causes can detect strabismus only indirectly and inaccurately via assessment of the positions of external light reflections from the cornea, but they cannot detect the anatomical feature of the eyes where fixation actually occurs (the fovea). Our laboratory has been developing technology to detect true foveal fixation, by exploiting the birefringence of the uniquely arranged Henle fibers delineating the fovea using retinal birefringence scanning (RBS), and we recently described a polarization-modulated approach to RBS that enables entirely direct and reliable detection of true foveal fixation, with greatly enhanced signal-to-noise ratio and essentially independent of corneal birefringence (a confounding variable with all polarization-sensitive ophthalmic technology). Here, we describe the design and operation of a new pediatric vision screener that employs polarization-modulated, RBS-based strabismus detection and bull's eye focus detection with an improved target system, and demonstrate the feasibility of this new approach.

The collagen structure of bovine intervertebral disc studied using polarization-sensitive optical coherence tomography

NASA Astrophysics Data System (ADS)

Matcher, Stephen J.; Winlove, C. Peter; Gangnus, Sergei V.

2004-04-01

Polarization-sensitive optical coherence tomography (PS-OCT) is used to measure the birefringence properties of bovine intervertebral disc and equine flexor tendon. For equine tendon the birefringence Dgrn is (6.0 ± 0.2) × 10-3 at a wavelength of 1.3 µm. This is somewhat larger than the values reported for bovine tendon. The surface region of the annulus fibrosus of a freshly excised intact bovine intervertebral disc displays an identical value of birefringence, Dgrn = (6.0 ± 0.6) × 10-3 at 1.3 µm. The nucleus pulposus does not display birefringence, the measured apparent value of Dgrn = (0.39 ± 0.01) × 10-3 being indistinguishable from the effects of depolarization due to multiple scattering. A clear difference is found between the depth-resolved retardance of equine tendon and that of bovine intervertebral disc. This apparently relates to the lamellar structure of the latter tissue, in which the collagen fibre orientation alternates between successive lamellae. A semi-empirical model based on Jones calculus shows that the measurements are in reasonable agreement with previous optical and x-ray data. These results imply that PS-OCT could be a useful tool to study collagen organization within the intervertebral disc in vitro and possibly in vivo and its variation with applied load and disease.

Visualizing Collagen Network Within Human and Rhesus Monkey Vocal Folds Using Polarized Light Microscopy

PubMed Central

Julias, Margaret; Riede, Tobias; Cook, Douglas

2014-01-01

Objectives Collagen fiber content and orientation affect the viscoelastic properties of the vocal folds, determining oscillation characteristics during speech and other vocalization. The investigation and reconstruction of the collagen network in vocal folds remains a challenge, because the collagen network requires at least micron-scale resolution. In this study, we used polarized light microscopy to investigate the distribution and alignment of collagen fibers within the vocal folds. Methods Data were collected in sections of human and rhesus monkey (Macaca mulatta) vocal folds cut at 3 different angles and stained with picrosirius red. Results Statistically significant differences were found between different section angles, implying that more than one section angle is required to capture the network’s complexity. In the human vocal folds, the collagen fiber distribution continuously varied across the lamina propria (medial to lateral). Distinct differences in birefringence distribution were observed between the species. For the human vocal folds, high birefringence was observed near the thyroarytenoid muscle and near the epithelium. However, in the rhesus monkey vocal folds, high birefringence was observed near the epithelium, and lower birefringence was seen near the thyroarytenoid muscle. Conclusions The differences between the collagen networks in human and rhesus monkey vocal folds provide a morphological basis for differences in viscoelastic properties between species. PMID:23534129

High-frequency polarization dynamics in spin-lasers: pushing the limits

NASA Astrophysics Data System (ADS)

Gerhardt, Nils C.; Lindemann, Markus; Pusch, Tobias; Michalzik, Rainer; Hofmann, Martin R.

2017-09-01

While the high-frequency performance of conventional lasers is limited by the coupled carrier-photon dynamics, spin-polarized lasers have a high potential to overcome this limitation and to push the direct modulation bandwidth beyond 100 GHz. The key is to utilize the ultrafast polarization dynamics in spin-polarized vertical cavity surface-emitting lasers (spin-VCSELs) which is decoupled from the intensity dynamics and its fundamental limitations. The polarization dynamics in such devices, characterized by the polarization oscillation resonance frequency, is mainly determined by the amount of birefringence in the cavity. Using an approach for manipulating the birefringence via mechanical strain we were able to increase the polarization dynamics to resonance frequencies of more than 40 GHz. Up to now these values are only limited by the setup to induce birefringence and do not reflect any fundamental limitations. Taking our record results for the birefringence-induced mode splitting of more than 250 GHz into account, the concept has the potential to provide polarization modulation in spin-VCSELs with modulation frequencies far beyond 100 GHz. This makes them ideal devices for next-generation fast optical interconnects. In this paper we present experimental results for ultrafast polarization dynamics up to 50 GHz and compare them to numerical simulations.

New pediatric vision screener employing polarization-modulated, retinal-birefringence-scanning-based strabismus detection and bull's eye focus detection with an improved target system: opto-mechanical design and operation.

PubMed

Irsch, Kristina; Gramatikov, Boris I; Wu, Yi-Kai; Guyton, David L

2014-06-01

Amblyopia ("lazy eye") is a major public health problem, caused by misalignment of the eyes (strabismus) or defocus. If detected early in childhood, there is an excellent response to therapy, yet most children are detected too late to be treated effectively. Commercially available vision screening devices that test for amblyopia's primary causes can detect strabismus only indirectly and inaccurately via assessment of the positions of external light reflections from the cornea, but they cannot detect the anatomical feature of the eyes where fixation actually occurs (the fovea). Our laboratory has been developing technology to detect true foveal fixation, by exploiting the birefringence of the uniquely arranged Henle fibers delineating the fovea using retinal birefringence scanning (RBS), and we recently described a polarization-modulated approach to RBS that enables entirely direct and reliable detection of true foveal fixation, with greatly enhanced signal-to-noise ratio and essentially independent of corneal birefringence (a confounding variable with all polarization-sensitive ophthalmic technology). Here, we describe the design and operation of a new pediatric vision screener that employs polarization-modulated, RBS-based strabismus detection and bull's eye focus detection with an improved target system, and demonstrate the feasibility of this new approach.

A simple structure of all circular-air-holes photonic crystal fiber for achieving high birefringence and low confinement loss

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chou Chau, Yuan-Fong, E-mail: chou.fong@ubd.edu.bn; Lim, Chee Ming; Yoong, Voo Nyuk

2015-12-28

We propose a simple structure of photonic crystal fibers (PCFs) with high birefringence and low confinement loss based on one rectangular centric ring of smaller circular air holes (CAHs) in the fiber core, and three rings of larger CAHs in the fiber cladding. This simple geometry (using all CAHs with two different air hole sizes) is capable of achieving a flexible control of the birefringence, B = 5.501 × 10{sup −3}, and ultra-low confinement loss, 7.30 × 10{sup −5 }dB/km, at an excitation wavelength of λ = 1550 nm. The birefringence value is ∼5.0 times greater than that obtained for conventional CAH PCF. This simple structure has the added advantagemore » from the view point of easy fabrication, robustness, and cost. A full-vector finite element method combined with anisotropic perfectly matched layers was used to analyze the various fiber structures. We have analyzed four cases of CAH PCFs, focusing on the core asymmetry design as opposed to the conventional approach of CAHs or elliptical air holes on the cladding and core. The robustness against manufacturing inaccuracies of the proposed structure has also been further investigated in this work.« less

Single-frequency, fully integrated, miniature DPSS laser based on monolithic resonator

NASA Astrophysics Data System (ADS)

Dudzik, G.; Sotor, J.; Krzempek, K.; Soboń, G.; Abramski, K. M.

2014-02-01

We present a single frequency, stable, narrow linewidth, miniature laser sources operating at 532 nm (or 1064 nm) based on a monolithic resonators. Such resonators utilize birefringent filters formed by YVO4 beam displacer and KTP or YVO4 crystals to force single frequency operation at 532 nm or 1064 nm, respectively. In both configurations Nd:YVO4 gain crystal is used. The resonators dimensions are 1x1x10.5 mm3 and 1x1x8.5 mm3 for green and infrared configurations, respectively. Presented laser devices, with total dimensions of 40x52x120 mm3, are fully equipped with driving electronics, pump diode, optical and mechanical components. The highly integrated (36x15x65 mm3) low noise driving electronics with implemented digital PID controller was designed. It provides pump current and resonator temperature stability of ±30 μA@650 mA and ±0,003ºC, respectively. The laser parameters can be set and monitored via the USB interface by external application. The developed laser construction is universal. Hence, the other wavelengths can be obtained only by replacing the monolithic resonator. The optical output powers in single frequency regime was at the level of 42 mW@532 nm and 0.5 W@1064 nm with the long-term fluctuations of ±0.85 %. The linewidth and the passive frequency stability under the free running conditions were Δν < 100 kHz and 3ṡ10-9@1 s integration time, respectively. The total electrical power supply consumption of laser module was only 4 W. Presented compact, single frequency laser operating at 532 nm and 1064 nm may be used as an excellent source for laser vibrometry, interferometry or seed laser for fiber amplifiers.

Discrete multi-wavelength tuning of a continuous wave diode-pumped Nd:GdVO4 laser

NASA Astrophysics Data System (ADS)

Nadimi, Mohammad; Waritanant, Tanant; Major, Arkady

2018-05-01

Discrete multi-wavelength operation of a diode-pumped Nd:GdVO4 laser at four different wavelengths was demonstrated using a single birefringent filter plate. The laser achieved maximum output powers of 5.92 W, 5.66 W, 5.56 W and 3.98 W at 1063.2 nm, 1070.8 nm, 1082.5 nm and 1086.2 nm wavelengths, respectively. To the best of our knowledge, apart from achieving the maximum output powers at ~1071 nm and ~1086 nm and best efficiencies at ~1071 nm, ~1083 nm and ~1086 nm wavelengths for a Nd:GdVO4 laser, this is also the largest number of wavelengths from the 4F3/2  →  4I11/2 transition that was ever obtained in a controlled manner from a single laser setup based on any of the Nd-doped laser crystals.

Asynchronous and synchronous dual-wavelength pulse generation in a passively mode-locked fiber laser with a mode-locker.

PubMed

Hu, Guoqing; Pan, Yingling; Zhao, Xin; Yin, Siyao; Zhang, Meng; Zheng, Zheng

2017-12-01

The evolution from asynchronous to synchronous dual-wavelength pulse generation in a passively mode-locked fiber laser is experimentally investigated by tailoring the intracavity dispersion. Through tuning the intracavity-loss-dependent gain profile and the birefringence-induced filter effect, asynchronous dual-wavelength soliton pulses can be generated until the intracavity anomalous dispersion is reduced to ∼8  fs/nm. The transition from asynchronous to synchronous pulse generation is then observed at an elevated pump power in the presence of residual anomalous dispersion, and it is shown that pulses are temporally synchronized at the mode-locker in the cavity. Spectral sidelobes are observed and could be attributed to the four-wave-mixing effect between dual-wavelength pulses at the carbon nanotube mode-locker. These results could provide further insight into the design and realization of such dual-wavelength ultrafast lasers for different applications such as dual-comb metrology as well as better understanding of the inter-pulse interactions in such dual-comb lasers.

Efficient continuous-wave, broadly tunable and passive Q-switching lasers based on a Tm3+:CaF2 crystal

NASA Astrophysics Data System (ADS)

Liu, Jingjing; Zhang, Cheng; Zu, Yuqian; Fan, Xiuwei; Liu, Jie; Guo, Xinsheng; Qian, Xiaobo; Su, Liangbi

2018-04-01

Laser operations in the continuous-wave as well as in the pulsed regime of a 4 at.% Tm3+:CaF2 crystal are reported. For the continuous-wave operation, a maximum average output power of 1.15 W was achieved, and the corresponding slope efficiency was more than 64%. A continuous tuning range of about 160 nm from 1877-2036 nm was achieved using a birefringent filter. Using Argentum nanorods as a saturable absorber, the significant pulsed operation of a passively Q-switched Tm3+:CaF2 laser was observed at 1935.4 nm for the first time, to the best of our knowledge. A maximum output power of 385 mW with 41.4 µJ pulse energy was obtained under an absorbed pump power of 2.04 W. The present results indicate that the Tm3+:CaF2 lasers could be promising laser sources to operate in the eye-safe spectral region.

Generation of dual-wavelength square pulse in a figure-eight erbium-doped fiber laser with ultra-large net-anomalous dispersion.

PubMed

Shao, Zhihua; Qiao, Xueguang; Rong, Qiangzhou; Su, Dan

2015-08-01

A type of wave-breaking-free mode-locked dual-wavelength square pulse was experimentally observed in a figure-eight erbium-doped fiber laser with ultra-large net-anomalous dispersion. A 2.7 km long single-mode fiber (SMF) was incorporated as a nonlinear optical loop mirror (NOLM) and provided largely nonlinear phase accumulation and anomalous dispersion, which enhanced the four-wave-mixing effect to improve the stability of the dual-wavelength operation. In the NOLM, the long SMF with small birefringence supported the Sagnac interference as a filter to manage the dual-wavelength lasing. The dual-wavelength operation was made switchable by adjusting the intra-cavity polarization loss and phase delay corresponding to two square pulses. When the pump power was increased, the duration of the square pulse increased continuously while the peak pulse power gradually decreased. This square-type pulse can potentially be utilized for signal transmission and sensing.

Third-order optical conductivity of an electron fluid

NASA Astrophysics Data System (ADS)

Sun, Zhiyuan; Basov, D. N.; Fogler, M. M.

2018-02-01

We derive the nonlinear optical conductivity of an isotropic electron fluid at frequencies below the interparticle collision rate. In this regime, governed by hydrodynamics, the conductivity acquires a universal form at any temperature, chemical potential, and spatial dimension. We show that the nonlinear response of the fluid to a uniform field is dominated by the third-order conductivity tensor σ(3 ) whose magnitude and temperature dependence differ qualitatively from those in the conventional kinetic regime of higher frequencies. We obtain explicit formulas for σ(3 ) for Dirac materials such as graphene and Weyl semimetals. We make predictions for the third-harmonic generation, renormalization of the collective-mode spectrum, and the third-order circular magnetic birefringence experiments.

Narrow bandpass steep edge optical filter for the JAST/T80 telescope instrumentation

NASA Astrophysics Data System (ADS)

Reichel, S.; Brauneck, U.; Bourquin, S.; Marín-Franch, A.

2013-09-01

The Observatorio Astrofisico de Javalambre in Spain observes with its JAST/T80 telescope galaxies in the Local Universe in a systematic study. This is accomplished with a multi-band photometric all sky survey called Javalambre Photometric Local Universe Survey (J-PLUS). A wide field camera receives the signals from universe via optical filters. In this presentation the development and design of a narrow bandpass steep edge filter with wide suppression will be shown. The filter has a full width half maximum in the range of 13-15 nm (with <1 nm tolerance) with central wavelengths in the range 350-860nm and an average transmission larger than 90% in the passband. Signals beyond the passband (blocking range) have to be suppressed down to 250nm and up to 1050nm (spectral regime), where a blocking of OD 5 (transmission < 10-5) is required. The edges have to be steep for a small transition width from 5% to 80%. The spectral requirements result in a large number of layers which are deposited with magnetron sputtering. The transmitted wavefront error of the optical filter must be less than lambda/2 over the 100mm aperture and the central wavelength uniformity must be better than +/- 0.4% over the clear aperture. The filter consists of optical filter glass and a coated substrate in order to reach the spectral requirements. The substrate is coated with more than 120 layers. The total filter thickness was specified to be 8.0mm. Results of steep edge narrow bandpass filters will be demonstrated fulfilling all these demanding requirements.

Using geomagnetic birefringence to locate sources of impulsive, terrestrial VHF signals detected by satellites on orbit

NASA Astrophysics Data System (ADS)

Jacobson, Abram R.; Shao, Xuan-Min

2001-07-01

The Earth's ionosphere is magnetized by the geomagnetic field and imposes birefringent modulation on VHF radio signals propagating through the ionosphere. Satellites viewing VHF emissions from terrestrial sources receive ordinary and extraordinary modes successively from each broadband pulse emitted by the source. The birefringent intermode frequency separation can be used to determine the value of ƒce cos β, where ƒce is the electron gyrofrequency and β is the angle between the wave vector k and the geomagnetic field B at the point where the VHF ray path intersects the ionosphere. Successive receptions of multiple signals (from the same source) cause variation in ƒce cos β, and from the resulting variation in the signal intermode frequency separation the source location on Earth can be inferred. We test the method with signals emitted by the Los Alamos Portable Pulser and received by the FORTE satellite.

Optical parameters of TN display with dichroic dye

NASA Astrophysics Data System (ADS)

Olifierczuk, Marek; Zielinski, Jerzy; Perkowski, Pawel

2000-05-01

The present work contain the studies on optical parameters (contrast ratio, viewing angle, birefringence and brightness) of twisted nematic display with black dichroic dye which is designed for an application in large-area information and advertising systems. The numerical optimization of display with a dye has been done. The absorption characteristic of the dye has been obtained. Birefringence of doped mixtures (Delta) n has been measured. The contrast ratio of doped mixtures has been measured in wide temperature range from -25 degree(s)C to +70 degree(s)C. The angle characteristics of contrast ratio for +20 degree(s)C have been obtained. In the work the detailed results describing the effect of a dye on temperature dependence of birefringence and contrast ratio, moreover, the effect of dye on the viewing angle for the first and second transmission minimum will be presented. Additionally, the dielectric characteristics of different mixtures will be shown.

Spectral domain polarization-sensitive optical coherence tomography at 850 nm

NASA Astrophysics Data System (ADS)

Cense, Barry; Chen, Teresa C.; Mujat, Mircea; Joo, Chulmin; Akkin, Taner; Park, B. H.; Pierce, Mark C.; Yun, Andy; Bouma, Brett E.; Tearney, Guillermo J.; de Boer, Johannes F.

2005-04-01

Spectral-Domain Polarization-Sensitive Optical Coherence Tomography (SD-PS-OCT) is a technique developed to measure the thickness and birefringence of the nerve fiber layer in vivo as a tool for the early diagnosis of glaucoma. A clinical SD-PS-OCT system was developed and scans were made around the optic nerve head (ONH) using ten concentric circles of increasing diameter. One healthy volunteer was imaged. Retinal nerve fiber layer thickness and birefringence information was extracted from the data. Polarization-sensitive OCT images were acquired at video rate (29 frames per second (fps), 1000 A-lines / frame) and at 7 fps (1000 A-lines / frame). The last setting improved the signal to noise ratio by approximately 6 dB. Birefringence measurements on the healthy volunteer gave similar results as earlier reported values that were obtained with a time-domain setup. The measurement time was reduced from more than a minute to less than a second.

Polarization holograms in a bifunctional amorphous polymer exhibiting equal values of photoinduced linear and circular birefringences.

PubMed

Provenzano, Clementina; Pagliusi, Pasquale; Cipparrone, Gabriella; Royes, Jorge; Piñol, Milagros; Oriol, Luis

2014-10-09

Light-controlled molecular alignment is a flexible and useful strategy introducing novelty in the fields of mechanics, self-organized structuring, mass transport, optics, and photonics and addressing the development of smart optical devices. Azobenzene-containing polymers are well-known photocontrollable materials with large and reversible photoinduced optical anisotropies. The vectorial holography applied to these materials enables peculiar optical devices whose properties strongly depend on the relative values of the photoinduced birefringences. Here is reported a polarization holographic recording based on the interference of two waves with orthogonal linear polarization on a bifunctional amorphous polymer that, exceptionally, exhibits equal values of linear and circular birefringence. The peculiar photoresponse of the material coupled with the holographic technique demonstrates an optical device capable of decomposing the light into a set of orthogonally polarized linear components. The holographic structures are theoretically described by the Jones matrices method and experimentally investigated.

Hydrostatic Pressure Sensing with High Birefringence Photonic Crystal Fibers

PubMed Central

Fávero, Fernando C.; Quintero, Sully M. M.; Martelli, Cicero; Braga, Arthur M.B.; Silva, Vinícius V.; Carvalho, Isabel C. S.; Llerena, Roberth W. A.; Valente, Luiz C. G.

2010-01-01

The effect of hydrostatic pressure on the waveguiding properties of high birefringence photonic crystal fibers (HiBi PCF) is evaluated both numerically and experimentally. A fiber design presenting form birefringence induced by two enlarged holes in the innermost ring defining the fiber core is investigated. Numerical results show that modal sensitivity to the applied pressure depends on the diameters of the holes, and can be tailored by independently varying the sizes of the large or small holes. Numerical and experimental results are compared showing excellent agreement. A hydrostatic pressure sensor is proposed and demonstrated using an in-fiber modal interferometer where the two orthogonally polarized modes of a HiBi PCF generate fringes over the optical spectrum of a broad band source. From the analysis of experimental results, it is concluded that, in principle, an operating limit of 92 MPa in pressure could be achieved with 0.0003% of full scale resolution. PMID:22163435

Vacuum birefringence detection in all-optical scenarios

NASA Astrophysics Data System (ADS)

Ataman, Stefan

2018-06-01

In this paper we propose an all-optical vacuum birefringence experiment and evaluate its feasibility for various scenarios. Many petawatt-class lasers became operational and many more are expected to enter operation in the near future, therefore unprecedented electromagnetic fields (EL˜1014-1015 V/m and intensities IL˜1021-1023W/cm 2 ) will become available for experiments. In our proposal a petawatt-class laser disturbs the quantum vacuum and creates a delay in a counterpropagating probe laser beam. Placing this delayed beam in one arm of a Mach-Zehnder interferometer (MZI), allows the measurement of the vacuum refraction coefficient via a phase shift. Coherent as well as squeezed light are both considered and the minimum phase sensitivity evaluated. We show that using existing technology with some moderately optimistic assumptions, at least part of the discussed scenarios are feasible for a vacuum birefringence detection experiment.

The collagen structure of equine articular cartilage characterized using polarization-sensitive optical coherence tomography and non-linear microscopy

NASA Astrophysics Data System (ADS)

Mansfield, Jessica C.; Ugryumova, Nadya; Knapp, Karen M.; Matcher, Stephen J.

2006-09-01

Equine articular cartilage has been imaged using both polarization-sensitive optical coherence tomography (PS-OCT) and non-linear microscopy. PS-OCT has been used to spatially map the birefringence in the cartilage and we have found that in the vicinity of the lesion the images display a characteristic disruption in the regular birefringence bands shown by normal cartilage. We also note that significant (e.g. x2) variations in the apparent birefringence of samples taken from young (18 month) animals that otherwise appear visually homogeneous are found over spatial scales of a few millimeters. We have also imaged the cartilage using non-linear microscopy and compare the scans taken with second harmonic generation (SHG) light and the two photon fluorescence (TPF) light. SHG images collected using 800 nm excitation reveals the spatial distribution of collagen fibers, whilst TPF images clearly shows the distribution of intracellular and pericellular fluorophores.

Optical circulator analysis and optimization: a mini-project for physical optics

NASA Astrophysics Data System (ADS)

Wan, Zhujun

2017-08-01

One of the mini-projects for the course of physical optics is reported. The project is designed to increase comprehension on the basics and applications of polarized light and birefringent crystal. Firstly, the students are required to analyze the basic principle of an optical circulator based on birefringent crystal. Then, they need to consider the engineering optimization problems. The key tasks include analyzing the polarization transforming unit (composed of a half-waveplate and a Faraday rotator) based on Jones matrix, maximizing the walk-off angle between e-ray and o-ray in birefringent crystal, separating e-ray and o-ray symmetrically, employment of a transformed Wollaston prism for input/output coupling of optical beams to fibers. Three years' practice shows that the project is of moderate difficulty, while it covers most of the related knowledge required for the course and helps to train the engineering thinking.

Design and numerical analysis of a THz square porous-core photonic crystal fiber for low flattened dispersion, ultrahigh birefringence.

PubMed

Luo, Jianfeng; Tian, Fengjun; Qu, Hongkun; Li, Li; Zhang, Jianzhong; Yang, Xinhua; Yuan, Libo

2017-08-20

We propose a kind of square porous-core photonic crystal fiber (PCF) for polarization-maintaining terahertz (THz) wave guidance. An asymmetry is introduced by implementing rectangular array air holes in the porous core of the PCF, and ultrahigh birefringence and low effective material loss (EML) can be achieved simultaneously. The properties of THz wave propagation are analyzed numerically in detail. The numerical results indicate that the proposed fiber offers a high birefringence of 0.063 and a low EML of 0.081  cm -1 at 1 THz. Moreover, a very low flattened dispersion profile is observed over a wide frequency domain of 0.85-1.9 THz. The zero flattened dispersion can be controlled. It is predicted that this PCF would be used potentially in polarization maintaining and dispersion management of THz waves.

SOME PROPERTIES OF HYALIN

PubMed Central

Stephens, R. E.; Kane, R. E.

1970-01-01

The principal protein component of the hyaline layer of sea urchin eggs is the calcium-insoluble protein first described by Kane and Hersh. The protein hyalin is abnormally high in acidic amino acids, almost devoid of basic amino acids, and characteristically rich in valine and proline. Essentially all of the cysteine present is found in the disulfide form; no evidence points to intermolecular disulfide linkages. Hyalin from several species has a minimal subunit weight of about 100,000, though evidence exists for a particle three times this weight in urea or guanidine hydrochloride from one species. Optical rotatory dispersion measurements indicate no α-helix content, though the dispersion has unique characteristic features. Addition of small quantities of calcium causes hyalin to gel to a birefringent fibrous form. The fibrous, birefringent form of hyalin is rendered isotropic upon addition of EDTA, but the birefringence is restored with re-addition of divalent cation. PMID:4190067

Low birefringent magneto-optical waveguides fabricated via organic-inorganic sol-gel process

NASA Astrophysics Data System (ADS)

Choueikani, F.; Royer, F.; Douadi, S.; Skora, A.; Jamon, D.; Blanc, D.; Siblini, A.

2009-09-01

This paper is devoted to the study and the characterization of novel magneto-optical waveguides prepared via organic-inorganic sol-gel process. Thin silica/zirconia films doped with magnetic nanoparticles were coated on glass substrate using dip-coating technique. After annealing, samples were UV-treated. Two different techniques were used to measure their properties: m-lines spectroscopy and free space ellipsometry. Results evidence low refractive index waveguides that combine a low modal birefringence (2×10-4) with a Faraday rotation around 15 °/cm (φ = 0.1%). The low birefringence is obtained with a soft UV treatment and a graded intrinsic anisotropy is evidenced for films thicker than 5 μm. Therefore, we prove that the organic-inorganic sol-gel approach is very promising to realize magneto-optical waveguides with a non-reciprocal functionality such as TE-TM mode conversion.

Jones matrix analysis for a polarization-sensitive optical coherence tomography system using fiber-optic components.

PubMed

Park, B Hyle; Pierce, Mark C; Cense, Barry; de Boer, Johannes F

2004-11-01

We present an analysis for polarization-sensitive optical coherence tomography that facilitates the unrestricted use of fiber and fiber-optic components throughout an interferometer and yields sample birefringence, diattenuation, and relative optic axis orientation. We use a novel Jones matrix approach that compares the polarization states of light reflected from the sample surface with those reflected from within a biological sample for pairs of depth scans. The incident polarization alternated between two states that are perpendicular in a Poincaré sphere representation to ensure proper detection of tissue birefringence regardless of optical fiber contributions. The method was validated by comparing the calculated diattenuation of a polarizing sheet, chicken tendon, and muscle with that obtained by independent measurement. The relative importance of diattenuation versus birefringence to angular displacement of Stokes vectors on a Poincaré sphere was quantified.

Cognitive training transfer using a personal computer-based game: A close quarters battle case study

NASA Astrophysics Data System (ADS)

Woodman, Michael D.

In this dissertation, liquid crystal (LC) materials and devices are investigated in order to meet the challenges for photonics and displays applications. We have studied three kinds of liquid crystal materials: positive dielectric anisotropic LCs, negative dielectric anisotropic LCs, and dual-frequency LCs. For the positive dielectric anisotropic LCs, we have developed some high birefringence isothiocyanato tolane LC compounds with birefringence ˜0.4, and super high birefringence isothiocyanato biphenyl-bistolane LC compounds with birefringence as high as ˜0.7. Moreover, we have studied the photostability of several high birefringence LC compounds, mixtures, and LC alignment layers in order to determine the failure mechanism concerning the lifetime of LC devices. Although cyano and isothiocyanato LC compounds have similar absorption peaks, the isothiocyanato compounds are more stable than their cyano counterparts under the same illumination conditions. This ultraviolet-durable performance of isothiocyanato compounds originates from its molecular structure and the delocalized electron distribution. We have investigated the alignment performance of negative dielectric anisotropic LCs in homeotropic (vertical aligned, VA) LC cell. Some (2, 3) laterally difluorinated biphenyls, terphenyls and tolanes are selected for this study. Due to the strong repulsive force between LCs and alignment layer, (2,3) laterally difluorinated terphenyls and tolanes do not align well in a VA cell resulting in a poor contrast ratio for the LC panel. We have developed a novel method to suppress the light leakage at dark state. By doping positive Deltaepsilon or non-polar LC compounds or mixtures into the host negative LC mixtures, the repulsive force is reduced and the cell exhibits an excellent dark state. In addition, these dopants increase the birefringence and reduce the viscosity of the host LCs which leads to a faster response time. In this dissertation, we investigate the dielectric heating effect of dual-frequency LCs. Because the absorption peak of imaginary dielectric constant occurs at high frequency region (˜ MHz), there is a heat generated when the LC cell is operated at a high frequency voltage. We have formulated a new dual-frequency LC mixture which greatly reduces the dielectric heating effect while maintaining good physical properties. Another achievement in this thesis is that we have developed a polarization independent phase modulator by using a negative dielectric anisotropic LC gel. (Abstract shortened by UMI.)

Observation of Polarization-Locked Vector Solitons in an Optical Fiber

NASA Astrophysics Data System (ADS)

Cundiff, S. T.; Collings, B. C.; Akhmediev, N. N.; Soto-Crespo, J. M.; Bergman, K.; Knox, W. H.

1999-05-01

We observe polarization-locked vector solitons in a mode-locked fiber laser. Temporal vector solitons have components along both birefringent axes. Despite different phase velocities due to linear birefringence, the relative phase of the components is locked at +/-π/2. The value of +/-π/2 and component magnitudes agree with a simple analysis of the Kerr nonlinearity. These fragile phase-locked vector solitons have been the subject of much theoretical conjecture, but have previously eluded experimental observation.

Approximation of Viscoelastic Stresses from Newtonian Turbulent Kinematics

DTIC Science & Technology

1988-09-01

birefringence of polyethylene oxide solutions in a four roll mill. J.Poly.Sci.:Poly.Phys.Ed. 14, 1111-1119. Dandridge, A., Meeten , G.H., Layec-Raphalen, M.N...flows. Poly. Comm. 25, 144-146. Metzner, A.B., & Astarita, G . 1967 External flow of viscoelastic materials: fluid property restrictions on the use of...dumbbell model for dilute solutions. Rheol.Acta 23, 151-162. Philippoff, W. 1956 Flow-birefringence and stress. Nature 178 , 811-812. Ryskin, G . 1987a

Estimation of effective refractive index of birefringent particles using a combination of the immersion liquid method and light scattering.

PubMed

Niskanen, Ilpo; Räty, Jukka; Peiponen, Kai-Erik

2008-04-01

A method to detect the effective refractive index and concentration of birefringent pigments is suggested. The method is based on the utilization of the immersion liquid method and a multifunction spectrophotometer for the measurement of back scattered light. The method has applications in the measurement of the effective refractive index of pigments that are used, e.g., in the paper industry to improve the opacity of paper products.

In vivo glucose monitoring using dual-wavelength polarimetry to overcome corneal birefringence in the presence of motion.

PubMed

Pirnstill, Casey W; Malik, Bilal H; Gresham, Vincent C; Coté, Gerard L

2012-09-01

Over the past 35 years considerable research has been performed toward the investigation of noninvasive and minimally invasive glucose monitoring techniques. Optical polarimetry is one noninvasive technique that has shown promise as a means to ascertain blood glucose levels through measuring the glucose concentrations in the anterior chamber of the eye. However, one of the key limitations to the use of optical polarimetry as a means to noninvasively measure glucose levels is the presence of sample noise caused by motion-induced time-varying corneal birefringence. In this article our group presents, for the first time, results that show dual-wavelength polarimetry can be used to accurately detect glucose concentrations in the presence of motion-induced birefringence in vivo using New Zealand White rabbits. In total, nine animal studies (three New Zealand White rabbits across three separate days) were conducted. Using the dual-wavelength optical polarimetric approach, in vivo, an overall mean average relative difference of 4.49% (11.66 mg/dL) was achieved with 100% Zone A+B hits on a Clarke error grid, including 100% falling in Zone A. The results indicate that dual-wavelength polarimetry can effectively be used to significantly reduce the noise due to time-varying corneal birefringence in vivo, allowing the accurate measurement of glucose concentration in the aqueous humor of the eye and correlating that with blood glucose.

Exploring vacuum birefringence based on a 100 PW laser and an x-ray free electron laser beam

NASA Astrophysics Data System (ADS)

Shen, Baifei; Bu, Zhigang; Xu, Jiancai; Xu, Tongjun; Ji, Liangliang; Li, Ruxin; Xu, Zhizhan

2018-04-01

Exploring vacuum birefringence with the station of extreme light at Shanghai Coherent Light Facility is considered. Laser pulses of intensity beyond 1023 W cm-2 are capable of polarizing the vacuum due to the ultra-strong electro-magnetic fields. The subtle difference of the vacuum refractive indexes along electric and magnetic fields leads to a birefringence effect for lights propagating through. The vacuum birefringence effect can now be captured by colliding a hard x-ray free electron laser (XFEL) beam with a high-power laser. The initial XFEL beam of pure linear polarization is predicated to gain a very small ellipticity after passing through the laser stimulated vacuum. Various interaction geometries are considered, showing that the estimated ellipticity lies between 1.8 × 10-10 and 10-9 for a 100 PW laser interacting with a 12.9 keV XFEL beam, approaching the threshold for todays’ polarity detection technique. The detailed experimental set-up is designed, including the polarimeter, the focusing compound refractive lens and the optical path. When taking into account the efficiencies of the x-ray instruments, it is found that about 10 polarization-flipped x-ray photons can be detected for a single shot for our design. Considering the background noise level, accumulating runs are necessary to obtain high confident measurement.

A study of airway smooth muscle in asthmatic and non-asthmatic airways using PS-OCT (Conference Presentation)

NASA Astrophysics Data System (ADS)

Adams, David C.; Holz, Jasmin A.; Szabari, Margit V.; Hariri, Lida P.; Harris, R. Scott; Cho, Jocelyn L.; Hamilos, Daniel L.; Luster, Andrew D.; Medoff, Benjamin D.; Suter, Melissa J.

2016-03-01

Present understanding of the pathophysiological mechanisms of asthma has been severely limited by the lack of an imaging modality capable of assessing airway conditions of asthma patients in vivo. Of particular interest is the role that airway smooth muscle (ASM) plays in the development of asthma and asthma related symptoms. With standard Optical Coherence Tomography (OCT), imaging ASM is often not possible due to poor structural contrast between the muscle and surrounding tissues. A potential solution to this problem is to utilize additional optical contrast factors intrinsic to the tissue, such as birefringence. Due to its highly ordered structure, ASM is strongly birefringent. Previously, we demonstrated that Polarization Sensitive OCT(PS-OCT) has the potential to be used to visualize ASM as well as easily segment it from the surrounding (weakly) birefringent tissue by exploiting a property which allows it to discriminate the orientation of birefringent fibers. We have already validated our technology with a substantial set of histological comparisons made against data obtained ex vivo. In this work we present a comprehensive comparison of ASM distributions in asthmatic and non-asthmatic human volunteers. By isolating the ASM we parameterize its distribution in terms of both thickness and band width, calculated volumetrically over centimeters of airway. Using this data we perform analyses of the asthmatic and non-asthmatic airways using a broad number and variety and subjects.

Demonstrating ultrafast polarization dynamics in spin-VCSELs

NASA Astrophysics Data System (ADS)

Lindemann, Markus; Pusch, Tobias; Michalzik, Rainer; Gerhardt, Nils C.; Hofmann, Martin R.

2018-02-01

Vertical-cavity surface-emitting lasers (VCSELs) are used for short-haul optical data transmission with increasing bit rates. The optimization involves both enhanced device designs and the use of higher-order modulation formats. In order to improve the modulation bandwidth substantially, the presented work employs spin-pumped VCSELs (spin-VCSELs) and their polarization dynamics instead of relying on intensity-modulated devices. In spin-VCSELs, the polarization state of the emitted light is controllable via spin injection. By optical spin pumping a single-mode VCSEL is forced to emit light composed of both orthogonal linearly polarized fundamental modes. The frequencies of these two modes differ slightly by a value determined by the cavity birefringence. As a result, the circular polarization degree oscillates with their beat frequency, i.e., with the birefringence-induced mode splitting. We used this phenomenon to show so-called polarization oscillations, which are generated by pulsed spin injection. Their frequency represents the polarization dynamics resonance frequency and can be tuned over a wide range via the birefringence, nearly independent from any other laser parameter. In previous work we demonstrated a maximum birefringence-induced mode splitting of more than 250 GHz. In this work, compared to previous publications, we show an almost doubled polarization oscillation frequency of more than 80 GHz. Furthermore, we discuss concepts to achieve even higher values far above 100 GHz.

Exploiting the relationship between birefringence and force to measure airway smooth muscle contraction with PS-OCT (Conference Presentation)

NASA Astrophysics Data System (ADS)

Adams, David C.; Hariri, Lida P.; Holz, Jasmin A.; Szabari, Margit V.; Harris, R. Scott; Cho, Jocelyn L.; Hamilos, Daniel L.; Luster, Andrew D.; Medoff, Benjamin D.; Suter, Melissa J.

2016-03-01

The ability to observe airway dynamics is fundamental to forming a complete understanding of pulmonary diseases such as asthma. We have previously demonstrated that Optical Coherence Tomography (OCT) can be used to observe structural changes in the airway during bronchoconstriction, but standard OCT lacks the contrast to discriminate airway smooth muscle (ASM) bands- ASM being responsible for generating the force that drives airway constriction- from the surrounding tissue. Since ASM in general exhibits a greater degree of birefringence than the surrounding tissue, a potential solution to this problem lies in the implementation of polarization sensitivity (PS) to the OCT system. By modifying the OCT system so that it is sensitive to the birefringence of tissue under inspection, we can visualize the ASM with much greater clarity and definition. In this presentation we show that the force of contraction can be indirectly measured by an associated increase in the birefringence signal of the ASM. We validate this approach by attaching segments of swine trachea to an isometric force transducer and stimulating contraction, while simultaneously measuring the exerted force and imaging the segment with PS-OCT. We then show how our results may be used to extrapolate the force of contraction of closed airways in absence of additional measurement devices. We apply this technique to assess ASM contractility volumetrically and in vivo, in both asthmatic and non-asthmatic human volunteers.

Stable isotope ratio mass spectrometry and physical comparison for the forensic examination of grip-seal plastic bags.

PubMed

Taylor, Erica; Carter, James F; Hill, Jenny C; Morton, Carolyn; Daeid, Niamh Nic; Sleeman, Richard

2008-05-20

Plastic bags are frequently used to package drugs, explosives and other contraband. There exists, therefore, a requirement in forensic casework to compare bags found at different locations. This is currently achieved almost exclusively by the use of physical comparisons such as birefringence patterns. This paper discusses some of the advantages and shortcomings of this approach, and presents stable isotope ratio mass spectrometry (IRMS) as a supplementary tool for effecting comparisons of this nature. Carbon and hydrogen isotopic data are presented for sixteen grip-seal plastic bags from a wide range of sources, in order to demonstrate the range of values which is likely to be encountered. Both isotopic and physical comparison (specifically birefringence) techniques are then applied to the analysis of rolls of bags from different manufacturing lots from a leading manufacturer. Both approaches are able to associate bags from a common production batch. IRMS can be applied to small fragments which are not amenable to physical comparisons, and is able to discriminate bags which could be confused using birefringence patterns alone. Similarly, in certain cases birefringence patterns discriminate bags with similar isotopic compositions. The two approaches are therefore complementary. When more than one isotopically distinct region exists within a bag (e.g. the grip-seal is distinct from the body) the ability to discriminate and associate bags is greatly increased.

A scatterometry based CD metrology solution for advanced nodes, including capability of handling birefringent layers with uniaxial anisotropy

NASA Astrophysics Data System (ADS)

Ke, Chih-Ming; Hu, Jimmy; Wang, Willie; Huang, Jacky; Chung, H. L.; Liang, C. R.; Shih, Victor; Liu, H. H.; Lee, H. J.; Lin, John; Fan, Y. D.; Yen, Tony; Wright, Noelle; Alvarez Sanchez, Ruben; Coene, Wim; Noot, Marc; Yuan, Kiwi; Wang, Vivien; Bhattacharyya, Kaustuve; van der Mast, Karel

2009-03-01

A brand new CD metrology technique that can address the need for accuracy, precision and speed in near future lithography is probably one of the most challenging items. CDSEMs have served this need for a long time, however, a change of or an addition to this traditional approach is inevitable as the increase in the need for better precision (tight CDU budget) and speed (driven by the demand for increase in sampling) continues to drive the need for advanced nodes. The success of CD measurement with scatterometry remains in the capability to model the resist grating, such as, CD and shape (side wall angle), as well as the under-lying layers (thickness and material property). Things are relatively easier for the cases with isotropic under-lying layers (that consists of single refractive or absorption indices). However, a real challenge to such a technique becomes evident when one or more of the under-lying layers are anisotropic. In this technical presentation the authors would like to evaluate such CD reconstruction technology, a new scatterometry based platform under development at ASML, which can handle bi-refringent non-patterned layers with uniaxial anisotropy in the underlying stack. In the RCWA code for the bi-refringent case, the elegant formalism of the enhanced transmittance matrix can still be used. In this paper, measurement methods and data will be discussed from several complex production stacks (layers). With inclusion of the bi-refringent modeling, the in-plane and perpendicular n and k values can be treated as floating parameters for the bi-refringent layer, so that very robust CD-reconstruction is achieved with low reconstruction residuals. As a function of position over the wafer, significant variations of the perpendicular n and k values are observed, with a typical radial fingerprint on the wafer, whereas the variations in the in-plane n and k values are seen to be considerably lower.

Folded optics with birefringent reflective polarizers

NASA Astrophysics Data System (ADS)

Wong, Timothy L.; Yun, Zhisheng; Ambur, Gregg; Etter, Jo

2017-06-01

Polymeric, birefringent reflective polarizers have been used to produce compact, mid-field-of-view eyepieces and wide field-of-view optics for virtual reality (VR) head-mounted displays using the "pancake" lens configuration. Multiple configurations for pancake lens systems are discussed as are their advantages and disadvantages relative to refractive systems. Polarization control is an important consideration and the polarizing effects of different components are discussed. Designs for mid-FOV and wide FOV are presented and additional benefits of using folded optics for virtual reality systems are explored.

Polarization sensitive localization based super-resolution microscopy with a birefringent wedge

NASA Astrophysics Data System (ADS)

Sinkó, József; Gajdos, Tamás; Czvik, Elvira; Szabó, Gábor; Erdélyi, Miklós

2017-03-01

A practical method has been presented for polarization sensitive localization based super-resolution microscopy using a birefringent dual wedge. The measurement of the polarization degree at the single molecule level can reveal the chemical and physical properties of the local environment of the fluorescent dye molecule and can hence provide information about the sub-diffraction sized structure of biological samples. Polarization sensitive STORM imaging of the F-Actins proved correlation between the orientation of fluorescent dipoles and the axis of the fibril.

Method and apparatus for measuring birefringent particles

DOEpatents

Bishop, James K.; Guay, Christopher K.

2006-04-18

A method and apparatus for measuring birefringent particles is provided comprising a source lamp, a grating, a first polarizer having a first transmission axis, a sample cell and a second polarizer having a second polarization axis. The second polarizer has a second polarization axis that is set to be perpendicular to the first polarization axis, and thereby blocks linearly polarized light with the orientation of the beam of light passing through the first polarizer. The beam of light passing through the second polarizer is measured using a detector.

Stray magnetic-field response of linear birefringent optical current sensors

NASA Astrophysics Data System (ADS)

MacDougall, Trevor W.; Hutchinson, Ted F.

1995-07-01

It is well known that the line integral, describing Faraday rotation in an optical medium, reduces to zero at low frequencies for a closed path that does not encircle a current source. If the closed optical path possesses linear birefringence in addition to Faraday rotation, the cumulative effects on the state of polarization result in a response to externally located current-carrying conductors. This effect can induce a measurable error of the order of 0.3% during certain steady-state operating conditions.

Theoretical analysis of a distributed polarimetric sensor with birefringent optical fibers in noncoherent light.

PubMed

Belgnaoui, Y; Picherit, F; Turpin, M

1994-08-01

We have studied the influence of the angular rotations among four birefringent optical fibers on the performance of a system of intrinsic sensors in noncoherent light. The results obtained by the Jones formalism show that angular rotations of the order of 5 degrees are sufficient to yield the visibility required for detection of the parameters of interest. As the angular rotations come closer to 1 degrees , which is experimentally more difficult, the signal has better contrast.

Physical models of polarization mode dispersion

DOE Office of Scientific and Technical Information (OSTI.GOV)

Menyuk, C.R.; Wai, P.K.A.

The effect of randomly varying birefringence on light propagation in optical fibers is studied theoretically in the parameter regime that will be used for long-distance communications. In this regime, the birefringence is large and varies very rapidly in comparison to the nonlinear and dispersive scale lengths. We determine the polarization mode dispersion, and we show that physically realistic models yield the same result for polarization mode dispersion as earlier heuristic models that were introduced by Poole. We also prove an ergodic theorem.

The Determination of Birefringence Dispersion in Nematic Liquid Crystals by Using the S-Transform

NASA Astrophysics Data System (ADS)

Coşkun, E.; Özder, S.; Kocahan, Ö.; Köysal, O.

2007-04-01

Transmittance spectra of 5CB and ZLI-6000 coded nematic liquid crystals were acquired in the 12600-22200 cm-1 region at room temperature. The S-transform was applied to analyze the transmittance signal. Dispersion curves of the birefringence were obtained for 5CB and ZLI-6000 by this analysis and data were fitted to the Cauchy formula whereby the dispersion parameters were extracted. Results are found to be in favorable accordance with the published values.

Performance Evaluation of Axial Flow AG-1 FC and Prototype FM (High Strength) HEPA Filters - 13123

DOE Office of Scientific and Technical Information (OSTI.GOV)

Giffin, Paxton K.; Parsons, Michael S.; Wilson, John A.

High efficiency particulate air (HEPA) filters are routinely used in DOE nuclear containment activities. The Nuclear Air Cleaning Handbook (NACH) stipulates that air cleaning devices and equipment used in DOE nuclear applications must meet the American Society of Mechanical Engineers (ASME) Code on Nuclear Air and Gas Treatment (AG-1) standard. This testing activity evaluates two different axial flow HEPA filters, those from AG-1 Sections FC and FM. Section FM is under development and has not yet been added to AG-1 due to a lack of qualification data available for these filters. Section FC filters are axial flow units that utilizemore » a fibrous glass filtering medium. The section FM filters utilize a similar fibrous glass medium, but also have scrim backing. The scrim-backed filters have demonstrated the ability to endure pressure impulses capable of completely destroying FC filters. The testing activities presented herein will examine the total lifetime loading for both FC and FM filters under ambient conditions and at elevated conditions of temperature and relative humidity. Results will include loading curves, penetration curves, and testing condition parameters. These testing activities have been developed through collaborations with representatives from the National Nuclear Security Administration (NNSA), DOE Office of Environmental Management (DOE-EM), New Mexico State University, and Mississippi State University. (authors)« less

Novel Digital Signal Processing and Detection Techniques.

DTIC Science & Technology

1980-09-01

decimation and interpolation [11, 1 2]. * Submitted by: Bede Liu Department of Electrical .l Engineering and Computer Science Princeton University ...on the use of recursive filters for decimation and interpolation. 4- UNCL.ASSIFIED~ SECURITY CLASSIFICATION OF PAGEfW1,en Data Fneprd) ...filter structure for realizing low-pass filter is developed 16,7]. By employing decimation and interpolation, the filter uses only coefficients 0, +1, and

High-magnification super-resolution FINCH microscopy using birefringent crystal lens interferometers

NASA Astrophysics Data System (ADS)

Siegel, Nisan; Lupashin, Vladimir; Storrie, Brian; Brooker, Gary

2016-12-01

Fresnel incoherent correlation holography (FINCH) microscopy is a promising approach for high-resolution biological imaging but has so far been limited to use with low-magnification, low-numerical-aperture configurations. We report the use of in-line incoherent interferometers made from uniaxial birefringent α-barium borate (α-BBO) or calcite crystals that overcome the aberrations and distortions present with previous implementations that employed spatial light modulators or gradient refractive index lenses. FINCH microscopy incorporating these birefringent elements and high-numerical-aperture oil immersion objectives could outperform standard wide-field fluorescence microscopy, with, for example, a 149 nm lateral point spread function at a wavelength of 590 nm. Enhanced resolution was confirmed with sub-resolution fluorescent beads. Taking the Golgi apparatus as a biological example, three different proteins labelled with GFP and two other fluorescent dyes in HeLa cells were resolved with an image quality that is comparable to similar samples captured by structured illumination microscopy.

Polarized light imaging of birefringence and diattenuation at high resolution and high sensitivity

PubMed Central

Mehta, Shalin B.; Shribak, Michael; Oldenbourg, Rudolf

2013-01-01

Polarized light microscopy provides unique opportunities for analyzing the molecular order in man-made and natural materials, including biological structures inside living cells, tissues, and whole organisms. 20 years ago, the LC-PolScope was introduced as a modern version of the traditional polarizing microscope enhanced by liquid crystal devices for the control of polarization, and by electronic imaging and digital image processing for fast and comprehensive image acquisition and analysis. The LCPolScope is commonly used for birefringence imaging, analyzing the spatial and temporal variations of the differential phase delay in ordered and transparent materials. Here we describe an alternative use of the LC-PolScope for imaging the polarization dependent transmittance of dichroic materials. We explain the minor changes needed to convert the instrument between the two imaging modes, discuss the relationship between the quantities measured with either instrument, and touch on the physical connection between refractive index, birefringence, transmittance, diattenuation, and dichroism. PMID:24273640

Innovative application of optical techniques to comprehensive study of the etiology of osteoarthritis

NASA Astrophysics Data System (ADS)

Ugryumova, Nadya; Matcher, Stephen J.

2006-08-01

Osteoarthritis is a painful condition, causing restricted mobility in the articular joints. In this paper we present a review of different optical techniques that might be used to clarify the etiology of degeneration of connective joint tissues, such as bone and articular cartilage. Significant correlation (R2 = 0.8) between bone mineral density and scattering coefficient of cortical bone tissue are found by using Integrating Sphere Technique. Optical Coherence Tomography and Polarization-Sensitive Optical Coherence Tomography images of cartilage tissue are presented. They were performed as series of angle-dependant measurements for different location along the surface. Method for spatial mapping the birefringence of equine articular cartilage is proposed. Variations in band spacing of birefringence obtained from visually healthy and abnormal cartilage samples are compared. Visible osteoarthritic lesions are characterized by a loss of the regular birefringence bands shown by normal cartilage. We discuss the hypothesis that some of these variations may be due to changes in intrinsic structure of tissue.

Vacuum nonlinear electrodynamic polarization effects in hard emission of pulsars and magnetars

NASA Astrophysics Data System (ADS)

Denisov, V. I.; Sokolov, V. A.; Svertilov, S. I.

2017-09-01

The nonlinear electrodynamics influence of pulsar magnetic field on the electromagnetic pulse polarization is discussed from the point of observation interpretation. The calculations of pulsar magnetic field impact on the electromagnetic pulse polarization are made in such a way to make it easier to interpret these effects in space experiments. The law of hard emission pulse propagation in the pulsar magnetic field according to the vacuum (nonlinear electrodynamics is obtained. It has been shown, that due to the birefringence in the vacuum the front part of any hard emission pulse coming from a pulsar should be linearly polarized and the rest of pulse can have arbitrary polarization. The observational possibilities of vacuum birefringence are discussed. In this paper we give the estimations of detector parameters such as effective area, exposure time and necessity of polarization measurements with high accuracy. The combination of large area and extremely long exposure time gives the good opportunity to search the fine polarization effects like vacuum nonlinear electrodynamics birefringence.

A study of birefringence in the interstellar medium in the direction of the Crab Nebula

NASA Technical Reports Server (NTRS)

Martin, P. G.; Angel, J. R. P.

1974-01-01

The interstellar medium may be regarded as a weak wave plate, the linear birefringence arising from the aligned grains which produce interstellar linear polarization. Using the Crab Nebula as a background source of linearly polarized light we have investigated this birefringence by measurements of circular polarization. The circular component is found to vary with the intrinsic linear polarization in a sinusoidal fashion characteristic of a wave plate with the orientation expected from independent measurements of the interstellar linear polarization in the same direction. Measurements of the wavelength dependence, together with the sense and magnitude of the circular polarization are interpreted as evidence for the dielectric nature of the interstellar grain materials. These observations provide a firm basis for a similar interpretation of the circular polarization of reddened stars. The observations of the stars can then be used to study the grain composition and the structure of the magnetic field in many directions in the Galaxy.

Observation of ferroelastic domains in layered magnetic compounds using birefringence imaging

NASA Astrophysics Data System (ADS)

Miura, Yoko; Okumura, Kazuya; Manaka, Hirotaka

2018-03-01

The two-dimensional Heisenberg antiferromagnet (C2H5NH3)2CuCl4 is a candidate compound for the coexistence of ferroelectricity and ferroelasticity; however, the microscopic observations of multiferroic domains may still be unclear. In-plane birefringence imaging measurements were performed to observe the manner in which the ferroelectric and the ferroelastic domains change during phase transitions between 15 K and 300 K. It was found that 90° ferroelastic domains appeared in the ab-plane at 300 K. As the temperature decreased toward 15 K, each domain inverted at a certain temperature (T a) without structural or magnetic phase transitions. The value of T a was found to be significantly influenced by external stresses; therefore, birefringence imaging techniques are useful for investigating variations in ferroelastic domains with temperature. Furthermore, a structural phase transition from orthorhombic to monoclinic or triclinic occurred at 230 ~ 240 K; however, no spontaneous polarization appeared in the ab-plane over the entire investigated range.

Comparative Analysis of Hexagonal Solid Silica and Nitro-benzene Filled Hollow Core Photonic Crystal Fiber

NASA Astrophysics Data System (ADS)

Shahiruddin; Singh, Dharmendra K.; Hassan, M. A.

2018-02-01

A comparative study of five ring solid core and nitrobenzene filled hollow core liquid filled photonic crystal fiber (PCF) are presented. Considering the same structure, one is used as solid silica and another one is filled with nitrobenzene in the core. Here the paper elaborates the confinement loss, dispersion properties and birefringence of an index-guiding PCF with asymmetric cladding designed and analyzed by the finite-element method. The proposed structure shows the low confinement loss in case of solid silica, negative dispersion in nitrobenzene filled hollow core PCF and high birefringence in both the cases. The calculated values shows flat zero confinement loss in 0.7 µm to 1.54 µm range, flat zero dispersion is achieved in solid core and -2000 ps/km-nm in nitrobenzene filled hollow core PCF and high birefringence in the range of 10-3 in nitrobenzene filled hollow core PCF. Results show the relative analysis at different air fill fraction.

Detecting Casimir torque with an optically levitated nanorod

NASA Astrophysics Data System (ADS)

Xu, Zhujing; Li, Tongcang

2017-09-01

The linear momentum and angular momentum of virtual photons of quantum vacuum fluctuations can induce the Casimir force and the Casimir torque, respectively. While the Casimir force has been measured extensively, the Casimir torque has not been observed experimentally though it was predicted over 40 years ago. Here we propose to detect the Casimir torque with an optically levitated nanorod near a birefringent plate in vacuum. The axis of the nanorod tends to align with the polarization direction of the linearly polarized optical tweezer. When its axis is not parallel or perpendicular to the optical axis of the birefringent crystal, it will experience a Casimir torque that shifts its orientation slightly. We calculate the Casimir torque and Casimir force acting on a levitated nanorod near a birefringent crystal. We also investigate the effects of thermal noise and photon recoils on the torque and force detection. We prove that a levitated nanorod in vacuum will be capable of detecting the Casimir torque under realistic conditions, and will be an important tool in precision measurements.

Molecular deformation and stress-strain behavior of poly(bisphenol-A-diphenyl sulfone)

NASA Technical Reports Server (NTRS)

Hong, S.-D.; Chung, S. Y.; Fedors, R. F.

1983-01-01

The strain-birefringence response of poly(bisphenol-A-diphenyl sulfone) is found to be independent of temperature at temperatures below -100 C; at higher temperatures, the response becomes slightly dependent on temperature, with lower birefringence seen at higher temperatures. The stress-strain behavior and the stress-birefringence response both depend on temperature over the entire testing temperature range (-179 C to 150 C) studied; this dependence, however, is not pronounced. The evidence is seen as suggesting that the polymer molecules respond to deformation by undergoing conformational rearrangements; the mode of the molecular deformation remains unchanged for temperatures of -100 C or lower. At higher temperatures, the average length of the chain segments involved in the rearrangement increases. The stress-strain response is attributed mainly to chain orientation. The entropic contribution deriving from chain orientation at temperatures below -100 C is still substantial. The modest temperature dependence of the stress-strain response suggests that the energy barriers for the chain segments involved in the rearrangement are relatively low.

Recent progress of obliquely deposited thin films for industrial applications

NASA Astrophysics Data System (ADS)

Suzuki, Motofumi; Itoh, Tadayoshi; Taga, Yasunori

1999-06-01

More than 10 years ago, birefringent films of metal oxides were formed by oblique vapor deposition and investigated with a view of their application to optical retardation plates. The retardation function of the films was explained in terms of the birefringence caused by the characteristic anisotropic nanostructure inside the films. These films are now classified in the genre of the so-called sculptured thin films. However, the birefringent films thus prepared are not yet industrialized even now due to the crucial lack of the durability and the yield of products. In this review paper, we describe the present status of application process of the retardation films to the information systems such as compact disc and digital versatile disc devices with a special emphasis on the uniformity of retardation properties in a large area and the stability of the optical properties of the obliquely deposited thin films. Finally, further challenges for wide application of the obliquely deposited thin films are also discussed.

Development of orthotropic birefringent materials for photoelastic stress analysis

NASA Technical Reports Server (NTRS)

Daniel, I. M.; Niiro, T.; Koller, G. M.

1981-01-01

Materials were selected and fabrication procedures developed for orthotropic birefringent materials. An epoxy resin (Maraset 658/558 system) was selected as the matrix material. Fibers obtained from style 3733 glass cloth and type 1062 glass roving were used as reinforcement. Two different fabrication procedures were used. In the first one, layers of unidirectional fibers removed from the glass cloth were stacked, impregnated with resin, bagged and cured in the autoclave at an elevated temperature. In the second procedure, the glass roving was drywound over metal frames, impregnated with resin and cured at room temperature under pressure and vacuum in an autoclave. Unidirectional, angle-ply and quasi-isotropic laminates of two thicknesses and with embedded flaws were fabricated. The matrix and the unidirectional glass/epoxy material were fully characterized. The density, fiber volume ratio, mechanical, and optical properties were determined. The fiber volume ratio was over 0.50. Birefringent properties were in good agreement with predictions based on a stress proportioning concept and also, with one exception, with properties predicted by a finite element analysis.

Vacuum nonlinear electrodynamic polarization effects in hard emission of pulsars and magnetars

DOE Office of Scientific and Technical Information (OSTI.GOV)

Denisov, V.I.; Sokolov, V.A.; Svertilov, S.I., E-mail: vid.msu@yandex.ru, E-mail: sokolov.sev@inbox.ru, E-mail: sis@coronas.ru

The nonlinear electrodynamics influence of pulsar magnetic field on the electromagnetic pulse polarization is discussed from the point of observation interpretation. The calculations of pulsar magnetic field impact on the electromagnetic pulse polarization are made in such a way to make it easier to interpret these effects in space experiments. The law of hard emission pulse propagation in the pulsar magnetic field according to the vacuum (nonlinear electrodynamics is obtained. It has been shown, that due to the birefringence in the vacuum the front part of any hard emission pulse coming from a pulsar should be linearly polarized and themore » rest of pulse can have arbitrary polarization. The observational possibilities of vacuum birefringence are discussed. In this paper we give the estimations of detector parameters such as effective area, exposure time and necessity of polarization measurements with high accuracy. The combination of large area and extremely long exposure time gives the good opportunity to search the fine polarization effects like vacuum nonlinear electrodynamics birefringence.« less

In Vivo Glucose Monitoring Using Dual-Wavelength Polarimetry to Overcome Corneal Birefringence in the Presence of Motion

PubMed Central

Malik, Bilal H.; Gresham, Vincent C.; Coté, Gerard L.

2012-01-01

Abstract Objective Over the past 35 years considerable research has been performed toward the investigation of noninvasive and minimally invasive glucose monitoring techniques. Optical polarimetry is one noninvasive technique that has shown promise as a means to ascertain blood glucose levels through measuring the glucose concentrations in the anterior chamber of the eye. However, one of the key limitations to the use of optical polarimetry as a means to noninvasively measure glucose levels is the presence of sample noise caused by motion-induced time-varying corneal birefringence. Research Design and Methods In this article our group presents, for the first time, results that show dual-wavelength polarimetry can be used to accurately detect glucose concentrations in the presence of motion-induced birefringence in vivo using New Zealand White rabbits. Results In total, nine animal studies (three New Zealand White rabbits across three separate days) were conducted. Using the dual-wavelength optical polarimetric approach, in vivo, an overall mean average relative difference of 4.49% (11.66 mg/dL) was achieved with 100% Zone A+B hits on a Clarke error grid, including 100% falling in Zone A. Conclusions The results indicate that dual-wavelength polarimetry can effectively be used to significantly reduce the noise due to time-varying corneal birefringence in vivo, allowing the accurate measurement of glucose concentration in the aqueous humor of the eye and correlating that with blood glucose. PMID:22691020

Collagen birefringence assessment in heart chordae tendineae through PS-OCT

NASA Astrophysics Data System (ADS)

Real, Eusebio; Revuelta, José M.; González-Vargas, Nieves; Pontón, Alejandro; Calvo-Díez, Marta; López-Higuera, José M.; Conde, Olga M.

2017-02-01

Degenerative mitral regurgitation is a serious and frequent human heart valve disease. Malfunctioning of this valve brings the left-sided heart through a significant increase of pressure and volume overload. Severe degenerative mitral incompetence generally requires surgical repair or valve replacement with a bioprosthesis or mechanical heart valve. Degenerative disease affects the leaflets or/and the chordae tendineae, which link both leaflets to the papillary muscles. During mitral valve surgical repair, reconstruction of the valve leaflets, annulus and chordae are provided to prevent postoperative recurrence of valve regurgitation. The operative evaluation of the diseased and apparently normal chordae tendineae mainly depends of the surgeońs experience, without any other objective diagnosis tool. In this work, PS-OCT (Polarization Sensitive-Optical Coherence Tomography) is applied for the first time to evaluate the pathological condition of human chordae coming from the mitral valve. It consists on a prospective study to test the viability of this technique for the evaluation of the collagen core of chords. This core presents a strong birefringence due to the longitudinal and organized arrangement of its collagen bundles. Different densities and organizations of the collagen core translate into different birefringence indicators whose measurement become an objective marker of the core structure. Ex-vivo mitral degenerative chordae tendineae have been analyzed with PS-OCT. Intensity OCT is used to obtain complementary morphological information of the chords. Birefringence results correlate with the previously reported values for human tendinous tissue.

Distributed Monte Carlo Information Fusion and Distributed Particle Filtering

DTIC Science & Technology

2014-08-24

Distributed Monte Carlo Information Fusion and Distributed Particle Filtering Isaac L. Manuel and Adrian N. Bishop Australian National University and...2 20 + vit , (21) where vit is Gaussian white noise with a random variance. We initialised the filters with the state xi0 = 0.1 for all i ∈ V . This

Interferometric fiber-optic temperature sensor with spiral polarization couplers

NASA Astrophysics Data System (ADS)

Cortés, R.; Khomenko, A. V.; Starodumov, A. N.; Arzate, N.; Zenteno, L. A.

1998-09-01

A fiber optic temperature sensor, for which the changes in modal birefringence of a short section of a long birefringent fiber are monitored remotely, is described. It employs a white light interferometer, which is formed by two concatenated spiral polarization mode couplers. A new method for white light interferometer output signal processing is described which provides a high accuracy absolute temperature measurement even in discontinuous operation of the sensor. Experimental results are presented for temperature measurements over a 100°C range with resolution of 3×10 -3 °C.

Observation of polarization domain wall solitons in weakly birefringent cavity fiber lasers

NASA Astrophysics Data System (ADS)

Zhang, H.; Tang, D. Y.; Zhao, L. M.; Wu, X.

2009-08-01

We report on the experimental observation of two types of phase-locked vector soliton in weakly birefringent cavity erbium-doped fiber lasers. While a phase-locked dark-dark vector soliton was only observed in fiber lasers of positive dispersion, a phase-locked dark-bright vector soliton was obtained in fiber lasers of either positive or negative dispersion. Numerical simulations confirmed the experimental observations and further showed that the observed vector solitons are the two types of phase-locked polarization domain wall solitons theoretically predicted.

Testing chameleon theories with light propagating through a magnetic field

DOE Office of Scientific and Technical Information (OSTI.GOV)

Brax, Philippe; Bruck, Carsten van de; Davis, Anne-Christine

2007-10-15

It was recently argued that the observed PVLAS anomaly can be explained by chameleon field theories in which large deviations from Newton's law can be avoided. Here we present the predictions for the dichroism and the birefringence induced in the vacuum by a magnetic field in these models. We show that chameleon particles behave very differently from standard axionlike particles (ALPs). We find that, unlike ALPs, the chameleon particles are confined within the experimental setup. As a consequence, the birefringence is always bigger than the dichroism in PVLAS-type experiments.

Other Types Of LCDs

NASA Astrophysics Data System (ADS)

Kobayashi, Shunsuke; Mochizuki, Akihiro

The following sections are included: * INTRODUCTION * TUNABLE BIREFRINGENCE LCDs * Nematic Device with Homogeneous Alignment * Nematic Device with Homeotropic Alignment * ELECTRICALLY CONTROLLED BIREFRINGENCE EFFECT LCDs WITH A COMPENSATING CELL OR POLYMER LAYERS * Super Homeotropic LCDs * Black and White STN LCDs * Optical mode interference * Guest-host mode * Double-layered STN * Retardation film compensated STN * DUAL FREQUENCY ADDRESSING LCDs * Application for DSM LCDs * Application for TN LCDs * PI-CELL * CHOLESTERIC-NEMATIC PHASE CHANGE LCDs * Storage Mode LCDs * Stabilized Hysteresis Mode LCDs * THERMALLY ADDRESSED LCDs (CHOLESTERIC) * BISTABLE LCD * WIDE VIEWING ANGLE TN LCDs USING RETARDATION SHEETS * Type 1 Cells * Type 2 Cells * REFERENCES

Polarization-dependent diffraction in all-dielectric, twisted-band structures

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kardaś, Tomasz M.; Jagodnicka, Anna; Wasylczyk, Piotr, E-mail: pwasylcz@fuw.edu.pl

2015-11-23

We propose a concept for light polarization management: polarization-dependent diffraction in all-dielectric microstructures. Numerical simulations of light propagation show that with an appropriately configured array of twisted bands, such structures may exhibit zero birefringence and at the same time diffract two circular polarizations with different efficiencies. Non-birefringent structures as thin as 3 μm have a significant difference in diffraction efficiency for left- and right-hand circular polarizations. We identify the structural parameters of such twisted-band matrices for optimum performance as circular polarizers.

Highly birefringent polymer microstructured optical fibers embedded in composite materials

NASA Astrophysics Data System (ADS)

Lesiak, P.; SzelÄ g, M.; Kuczkowski, M.; Domański, A. W.; Woliński, T. R.

2013-05-01

Composite structures are made from two or more constituent materials with significantly different physical or chemical properties and they remain separate and distinct in a macroscopic level within the finished structure. This feature allows for introducing highly birefringent polymer microstructured optical fibers into the composite material. These new fibers can consist of only two polymer materials (PMMA and PC) with similar value of the Young modulus as the composite material so any stresses induced in the composite material can be easily measured by the proposed embedded fiber optic sensors.

Pump Spectral Bandwidth, Birefringence, and Entanglement in Type-II Parametric Down Conversion

DOE PAGES

Erenso, Daniel

2009-01-01

The twin photons produced by a type-II spontaneous parametric down conversion are well know as a potential source of photons for quantum teleportation due to the strong entanglement in polarization. This strong entanglement in polarization, however, depends on the spectral composition of the pump photon and the nature of optical isotropy of the crystal. By exact numerical calculation of the concurrence, we have shown that how pump photons spectral width and the birefringence nature of the crystal directly affect the degree of polarization entanglement of the twin photons.

Single- and dual-wavelength laser operation of a diode-pumped Nd:LaF3 single crystal around 1.05 μm and 1.32 μm

NASA Astrophysics Data System (ADS)

Xu, Bin; Huang, Xiaoxu; Lan, Jinglong; Lin, Zhi; Wang, Yi; Xu, Huiying; Cai, Zhiping; Moncorgé, Richard

2016-07-01

Calibrated room temperature polarized emission spectra recorded between 850 and 1400 nm and nearly free from any reabsorption effect are presented for the first time. A laser output power of 2.35 W is obtained at 1063.45 nm with a laser slope efficiency of about 56% by pumping an uncoated Nd:LaF3 single crystal with a fiber-coupled laser diode at 790 nm inside a standard two-mirror linear laser cavity. True dual-wavelength laser operation on two orthogonally polarized laser lines around 1040 and 1065 nm as well as continuous laser wavelength tuning around 1040 nm, 1048 nm and 1064 nm are also achieved for the first time by using either an intracavity etalon or a birefringent filter. Laser operation is finally obtained around 1330.73 nm with a maximum output power of 0.18 W and a laser slope efficiency of about 4% and simultaneous dual-wavelength laser operation at 1329.04 and 1359.67 nm is demonstrated by using a glass etalon.

Optical devices having flakes suspended in a host fluid to provide a flake/fluid system providing flakes with angularly dependent optical properties in response to an alternating current electric field due to the dielectric properties of the system

DOEpatents

Kosc, Tanya Z [Rochester, NY; Marshall, Kenneth L [Rochester, NY; Jacobs, Stephen D [Pittsford, NY

2006-05-09

Optical devices utilizing flakes (also called platelets) suspended in a host fluid have optical characteristics, such as reflective properties, which are angular dependent in response to an AC field. The reflectivity may be Bragg-like, and the characteristics are obtained through the use of flakes of liquid crystal material, such as polymer liquid crystal (PLC) materials including polymer cholesteric liquid crystal (PCLC) and polymer nematic liquid crystal (PNLC) material or birefringent polymers (BP). The host fluid may be propylene carbonate, poly(ethylene glycol) or other fluids or fluid mixtures having fluid conductivity to support conductivity in the flake/host system. AC field dependent rotation of 90.degree. can be obtained at rates and field intensities dependent upon the frequency and magnitude of the AC field. The devices are useful in providing displays, polarizers, filters, spatial light modulators and wherever switchable polarizing, reflecting, and transmission properties are desired.

X-ray topographic studies and measurement of lattice parameter differences within synthetic diamonds grown by the reconstitution technique

NASA Astrophysics Data System (ADS)

Wierzchowski, W.; Moore, M.; Makepeace, A. P. W.; Yacoot, A.

1991-10-01

A 4 x 4 x 1.5 cu mm cuboctahedral diamond and two 0.7 mm thick slabs cut from a truncated octahedral diamond grown by the reconstitution technique were studied in different double-crystal arrangements with both conventional and synchrotron X-ray sources. The back-reflection double crystal topographs of large polished 001-plane-oriented faces intersecting different growth sectors, together with cathodoluminescence patterns, allowed identification of these sectors. A double-crystal arrangement, employing the -3 2 5 quartz reflection matching the symmetrical 004 diamond reflection in CuK(alpha 1) radiation, was used for measurement of lattice parameter differences with an accuracy of one and a half parts per million. The simultaneous investigation by means of Lang projection and section topography provided complementary information about the crystallographic defects and internal structures of growth sectors. Observation of the cuboctahedral diamond with a filter of peak transmittance at 430 nm revealed a 'Maltese cross' growth feature in the central (001) growth sector, which also affected the birefringence pattern. However, this feature only very slightly affected the double-crystal topographs.

High power continuous-wave titanium:sapphire laser

DOEpatents

Erbert, G.V.; Bass, I.L.; Hackel, R.P.; Jenkins, S.L.; Kanz, V.K.; Paisner, J.A.

1993-09-21

A high-power continuous-wave laser resonator is provided, wherein first, second, third, fourth, fifth and sixth mirrors form a double-Z optical cavity. A first Ti:sapphire rod is disposed between the second and third mirrors and at the mid-point of the length of the optical cavity, and a second Ti:sapphire rod is disposed between the fourth and fifth mirrors at a quarter-length point in the optical cavity. Each Ti:sapphire rod is pumped by two counter-propagating pump beams from a pair of argon-ion lasers. For narrow band operation, a 3-plate birefringent filter and an etalon are disposed in the optical cavity so that the spectral output of the laser consists of 5 adjacent cavity modes. For increased power, seventy and eighth mirrors are disposed between the first and second mirrors to form a triple-Z optical cavity. A third Ti:sapphire rod is disposed between the seventh and eighth mirrors at the other quarter-length point in the optical cavity, and is pumped by two counter-propagating pump beams from a third pair of argon-ion lasers. 5 figures.

Universal and reusable virus deactivation system for respiratory protection

NASA Astrophysics Data System (ADS)

Quan, Fu-Shi; Rubino, Ilaria; Lee, Su-Hwa; Koch, Brendan; Choi, Hyo-Jick

2017-01-01

Aerosolized pathogens are a leading cause of respiratory infection and transmission. Currently used protective measures pose potential risk of primary/secondary infection and transmission. Here, we report the development of a universal, reusable virus deactivation system by functionalization of the main fibrous filtration unit of surgical mask with sodium chloride salt. The salt coating on the fiber surface dissolves upon exposure to virus aerosols and recrystallizes during drying, destroying the pathogens. When tested with tightly sealed sides, salt-coated filters showed remarkably higher filtration efficiency than conventional mask filtration layer, and 100% survival rate was observed in mice infected with virus penetrated through salt-coated filters. Viruses captured on salt-coated filters exhibited rapid infectivity loss compared to gradual decrease on bare filters. Salt-coated filters proved highly effective in deactivating influenza viruses regardless of subtypes and following storage in harsh environmental conditions. Our results can be applied in obtaining a broad-spectrum, airborne pathogen prevention device in preparation for epidemic and pandemic of respiratory diseases.

Universal and reusable virus deactivation system for respiratory protection

PubMed Central

Quan, Fu-Shi; Rubino, Ilaria; Lee, Su-Hwa; Koch, Brendan; Choi, Hyo-Jick

2017-01-01

Aerosolized pathogens are a leading cause of respiratory infection and transmission. Currently used protective measures pose potential risk of primary/secondary infection and transmission. Here, we report the development of a universal, reusable virus deactivation system by functionalization of the main fibrous filtration unit of surgical mask with sodium chloride salt. The salt coating on the fiber surface dissolves upon exposure to virus aerosols and recrystallizes during drying, destroying the pathogens. When tested with tightly sealed sides, salt-coated filters showed remarkably higher filtration efficiency than conventional mask filtration layer, and 100% survival rate was observed in mice infected with virus penetrated through salt-coated filters. Viruses captured on salt-coated filters exhibited rapid infectivity loss compared to gradual decrease on bare filters. Salt-coated filters proved highly effective in deactivating influenza viruses regardless of subtypes and following storage in harsh environmental conditions. Our results can be applied in obtaining a broad-spectrum, airborne pathogen prevention device in preparation for epidemic and pandemic of respiratory diseases. PMID:28051158

Tunable Universal Filter with Current Follower and Transconductance Amplifiers and Study of Parasitic Influences

NASA Astrophysics Data System (ADS)

Jeřábek, Jan; Šotner, Roman; Vrba, Kamil

2011-11-01

A universal filter with dual-output current follower (DO-CF), two transconductance amplifiers (OTAs) and two passive elements is presented in this paper. The filter is tunable, of the single-input multiple-output (SIMO) type, and operates in the current mode. Our solution utilizes a low-impedance input node and high-impedance outputs. All types of the active elements used can be realized using our UCC-N1B 0520 integrated circuit and therefore the paper contains not only simulation results that were obtained with the help of behavioral model of the UCC-N1B 0520 element, but also the characteristics that were gained by measurement with the mentioned circuit. The presented simulation and measurement results prove the quality of designed filter. Similar multi-loop structures are very-well known, but there are some drawbacks that are not discussed in similar papers. This paper also contains detailed study of parasitic influences on the filter performance.

Use of Both Cumulus Cells’ Transcriptomic Markers and Zona Pellucida Birefringence to Select Developmentally Competent Oocytes in Human Assisted Reproductive Technologies

PubMed Central

2015-01-01

Background Selection of the best oocyte for subsequent steps of fertilization and embryo transfer was shown to be the crucial step in human infertility treatment procedure. Oocyte selection using morphological criteria mainly Zona pellucida (ZP) has been the gold standard method in assisted reproductive technologies (ART) clinics, but this selection approach has limitations in terms of accuracy, objectivity and constancy. Recent studies using OMICs-based approaches have allowed the identification of key molecular markers that quantitatively and non-invasively predict the oocyte quality for higher pregnancy rates and efficient infertility treatment. These biomarkers are a valuable reinforcement of the morphological selection criteria widely used in in vitro fertilization (IVF) clinics. In this context, this study was designed to investigate the relationship between transcriptomic predictors of oocyte quality found by our group and the conventional morphological parameters of oocyte quality mainly the ZP birefringence. Results Microarray data revealed that 48 and 27 differentially expressed candidate genes in cumulus cells (CCs) were respectively overexpressed and underexpressed in the ZGP (Zona Good Pregnant) versus ZBNP (Zona Bad Non Pregnant) groups. More than 70% of previously reported transcriptomic biomarkers of oocyte developmental competence were confirmed in this study. The analysis of possible association between ZP birefringence versus molecular markers approach showed an absence of correlation between them using the current set of markers. Conclusions This study suggested a new integrative approach that matches morphological and molecular approaches used to select developmentally competent oocytes able to lead to successful pregnancy and the delivery of healthy baby. For each ZP birefringence score, oocytes displayed a particular CCs' gene expression pattern. However, no correlations were found between the 7 gene biomarkers of oocyte developmental potential and the ZP birefringence score. Further studies using larger lists of candidate markers are required to identify suitable genes that are highly correlated with the morphological criteria, and therefore able to reinforce the accuracy of oocyte selection and the effectiveness of infertility treatment. PMID:25923296

Effect of ultrasound and dexpanthenol on collagen organization in tegumentary lesions.

PubMed

Guimarães, Gustavo N; Pires-De-Campos, Maria S M; Leonardi, Gislaine R; Dib-Giusti, Helena H K; Polacow, Maria L O

2011-01-01

To analyze the effect of ultrasound (US), dexpanthenol (d-P) and a combination of these treatments (US+d-P) on collagen fiber organization in tegumentary lesions in rats by birefringence analysis. Wistar rats (50) were anesthetized (Thionembutal - Sodic = 50 mg/Kg), 1 cm² of dorsal region skin was removed, and the animals were divided into five groups: control (C), gel (G), US (3 MHz, 0.1 W/cm2, 1 minute, continuous), d-P (10%) and US+d-P. After daily treatment for 7 and 14 days, 6 µm thick sections of lesioned areas were stained in picrosirius and measurements of the collagen birefringent area (µm²) were obtained using polarized light microscopy (Zeiss Axiolab-ZEISS- Germany) with histological image analysis software (KS 400 2.0 - Kontrol Eletronics, Munique, Germany). The means were compared by ANOVA followed by the Tukey test (p<0.05). The US+d-P group showed a significantly greater (p ≤ 0.001) birefringent area (1586.43±162.14) than the other experimental groups: C (139.36±35.35), US (317.55±129.9) and d-P (192.41±3657) by the 7th day of treatment, indicating acceleration of the wound healing process. By the 14th day of treatment, the US+d-P, US and d-P groups presented greater birefringence than the control group, but did not differ from each other. The combination of treatments (US+d-P) accelerated collagen fiber synthesis and organization in the early stages of cutaneous repair.

Retinal nerve fiber layer measurements by scanning laser polarimetry with enhanced corneal compensation in healthy subjects.

PubMed

Rao, Harsha L; Venkatesh, Chirravuri R; Vidyasagar, Kelli; Yadav, Ravi K; Addepalli, Uday K; Jude, Aarthi; Senthil, Sirisha; Garudadri, Chandra S

2014-12-01

To evaluate the (i) effects of biological (age and axial length) and instrument-related [typical scan score (TSS) and corneal birefringence] parameters on the retinal nerve fiber layer (RNFL) measurements and (ii) repeatability of RNFL measurements with the enhanced corneal compensation (ECC) protocol of scanning laser polarimetry (SLP) in healthy subjects. In a cross-sectional study, 140 eyes of 73 healthy subjects underwent RNFL imaging with the ECC protocol of SLP. Linear mixed modeling methods were used to evaluate the effects of age, axial length, TSS, and corneal birefringence on RNFL measurements. One randomly selected eye of 48 subjects from the cohort underwent 3 serial scans during the same session to determine the repeatability. Age significantly influenced all RNFL measurements. RNFL measurements decreased by 1 µm for every decade increase in age. TSS affected the overall average RNFL measurement (β=-0.62, P=0.003), whereas residual anterior segment retardance affected the superior quadrant measurement (β=1.14, P=0.01). Axial length and corneal birefringence measurements did not influence RNFL measurements. Repeatability, as assessed by the coefficient of variation, ranged between 1.7% for the overall average RNFL measurement and 11.4% for th nerve fiber indicator. Age significantly affected all RNFL measurements with the ECC protocol of SLP, whereas TSS and residual anterior segment retardance affected the overall average and the superior average RNFL measurements, respectively. Axial length and corneal birefringence measurements did not influence any RNFL measurements. RNFL measurements had good intrasession repeatability. These results are important while evaluating the change in structural measurements over time in glaucoma patients.

Assessment of coronary plaque collagen with polarization sensitive optical coherence tomography (PS-OCT)

NASA Astrophysics Data System (ADS)

Giattina, Susanne D.; Courtney, Brian K.; Herz, Paul R.; Harman, Michelle; Shortkroff, Sonya; Stamper, Debra L.; Liu, Bin; Fujimoto, James G.; Brezinski, Mark E.

2006-02-01

Current evidence indicates that most plaques classified as vulnerable or ruptured plaques do not lead to unstable angina or myocardial infarction. Improved methods are needed to risk stratify plaques to identify those which lead to most acute coronary syndromes. Collagen depletion in the intima overlying lipid collections appears to be a critical component of unstable plaques. In this study, we use polarization sensitive optical coherence tomography (PS-OCT) for the assessment of coronary plaque collagen. Collagen is birefringent, meaning that different polarization states travel through it at different velocities. Changes in PS-OCT images are a measure of tissue birefringence. Twenty-two coronary artery segments were imaged with PS-OCT and analyzed by picrosirius staining (a measure of collagen intensity and fiber size) and trichrome blue. The regression plot between PS-OCT changes and measured collagen yielded a correlation coefficient value of 0.475 (p<0.002). Good correlation was noted between two blinded investigators both with respect to PS-OCT measurements as well as luminosity as assessed by picrosirius. The predictive value of a PS-OCT measurement of negligible birefringence (less than 33% change) for minimal collagen was 93% while the predictive value of high birefringence (greater than 66% change) for high collagen concentrations was 89%. The effect of fiber type (chemical composition) was minimal relative to the effect due to fiber concentration. The capability of PS-OCT to assess plaque collagen content, in addition to its ability to generate high resolution structural assessments, make it a potentially powerful technology for identifying high risk plaques.

Butterfly scale form birefringence related to photonics.

PubMed

Vidal, Benedicto de Campos

2011-12-01

Wings of the butterflies Morpho aega and Eryphanis reevesi were investigated in the present study by fluorescence, polarization and infra-red (IR) spectroscopic microscopy with the aim of identifying the oriented organization of their components and morphological details of their substructures. These wings were found to exhibit a strong iridescent glow depending on the angle of the incident light; their isolated scales exhibited blue fluorescence. Parallel columns or ridges extend from the pad and sockets to the dented apical scale's region, and they are perpendicular to the ribs that connect the columnar ridges. The scales reveal linear dichroism (LD) visually, when attached on the wing matrix or isolated on slides. The LD was inferred to be textural and positive and was also demonstrated with IR microscopy. The scale columns and ribs are birefringent structures. Images obtained before and after birefringence compensation allowed a detailed study of the scale morphology. Form and intrinsic birefringence findings here estimated and discussed in the context of nonlinear optical properties, bring to the level of morphology the state of molecular order and periodicity of the wing structure. FT-IR absorption peaks were found at wavenumbers which correspond to symmetric and asymmetric (-N-H) stretching, symmetric (-C-H) stretching, amide I (-CO) stretching, amide II(-N-H), and β-linking. Based on LD results obtained with polarized IR the molecular vibrations of the wing scales of M. aega and E. reevesi are assumed to be oriented with respect to the long axis of these structures. Copyright © 2011 Elsevier Ltd. All rights reserved.

Highly-nonlinear polarization-maintaining As2Se3-based photonic quasi-crystal fiber for supercontinuum generation

NASA Astrophysics Data System (ADS)

Zhao, Tongtong; Lian, Zhenggang; Benson, Trevor; Wang, Xin; Zhang, Wan; Lou, Shuqin

2017-11-01

We propose an As2Se3-based photonic quasi-crystal fiber (PQF) with high nonlinearity and birefringence. By optimizing the structure parameters, a nonlinear coefficient up to 2079 W-1km-1 can be achieved at the wavelength of 2 μm; the birefringence reaches up to the order of 10-2 due to the introduction of large circular air holes in the cladding. Using an optical pulse with a peak power of 6 kW, a pulse width of 150 fs, and a central wavelength of 2.94 μm as the pump pulse, a mid-infrared polarized supercontinuum is obtained by using a 15 mm long PQF. The spectral width for x- and y-polarizations covers 1 μm-10.2 μm and 1 μm-12.5 μm, respectively. The polarization state can be well maintained when the incident angle of the input pulse changes within ±2°. The proposed PQF, with high nonlinear coefficient and birefringence, has potential applications in mid-infrared polarization-maintaining supercontinuum generation.

Fully vectorial laser resonator modeling of continuous-wave solid-state lasers including rate equations, thermal lensing and stress-induced birefringence.

PubMed

Asoubar, Daniel; Wyrowski, Frank

2015-07-27

The computer-aided design of high quality mono-mode, continuous-wave solid-state lasers requires fast, flexible and accurate simulation algorithms. Therefore in this work a model for the calculation of the transversal dominant mode structure is introduced. It is based on the generalization of the scalar Fox and Li algorithm to a fully-vectorial light representation. To provide a flexible modeling concept of different resonator geometries containing various optical elements, rigorous and approximative solutions of Maxwell's equations are combined in different subdomains of the resonator. This approach allows the simulation of plenty of different passive intracavity components as well as active media. For the numerically efficient simulation of nonlinear gain, thermal lensing and stress-induced birefringence effects in solid-state active crystals a semi-analytical vectorial beam propagation method is discussed in detail. As a numerical example the beam quality and output power of a flash-lamp-pumped Nd:YAG laser are improved. To that end we compensate the influence of stress-induced birefringence and thermal lensing by an aspherical mirror and a 90° quartz polarization rotator.

Two-dimensional magneto-optical light modulation in EuTiO3

NASA Astrophysics Data System (ADS)

Bussmann-Holder, Annette; Roleder, Krystian; Stuhlhofer, Benjamin; Logvenov, Gennady; Simon, Arndt; KöHler, Jürgen

EuTiO3 is antiferromagnetic at low temperature, namely below TN = 5.7K. In the high temperature paramagnetic phase the strongly nonlinear coupling between the lattice and the nomnially silent Eu 4f7 spins induces magnetic correlations which become apparent in muon spin rotation experiments and more recently in birefringence measurments in an external magnetic field. It is shown here, that high quality films of insulating EuTiO3 deposited on a thin SrTiO3 substrate are versatile tools for light modulation. The operating temperature is close to room temperature and admits multiple device engineering. By using small magnetic fields the birefringence of the samples can be switched off and on. Similarly, rotation of the sample in the field can modify its birefringence Δn. In addition, Δn can be increased by a factor of 4 in very modest fields with simultaneously enhancing the operating temperature by almost 100K. The results can be understood in terms of paramagnon phonon interaction where spin activity is achieved via the local spin-phonon double-well potential.

Fourier analysis for hydrostatic pressure sensing in a polarization-maintaining photonic crystal fiber.

PubMed

Childs, Paul; Wong, Allan C L; Fu, H Y; Liao, Yanbiao; Tam, Hwayaw; Lu, Chao; Wai, P K A

2010-12-20

We measured the hydrostatic pressure dependence of the birefringence and birefringent dispersion of a Sagnac interferometric sensor incorporating a length of highly birefringent photonic crystal fiber using Fourier analysis. Sensitivity of both the phase and chirp spectra to hydrostatic pressure is demonstrated. Using this analysis, phase-based measurements showed a good linearity with an effective sensitivity of 9.45 nm/MPa and an accuracy of ±7.8 kPa using wavelength-encoded data and an effective sensitivity of -55.7 cm(-1)/MPa and an accuracy of ±4.4 kPa using wavenumber-encoded data. Chirp-based measurements, though nonlinear in response, showed an improvement in accuracy at certain pressure ranges with an accuracy of ±5.5 kPa for the full range of measured pressures using wavelength-encoded data and dropping to within ±2.5 kPa in the range of 0.17 to 0.4 MPa using wavenumber-encoded data. Improvements of the accuracy demonstrated the usefulness of implementing chirp-based analysis for sensing purposes.

Reduced thermal sensitivity of hybrid air-core photonic band-gap fiber ring resonator

NASA Astrophysics Data System (ADS)

Feng, Li-shuang; Wang, Kai; Jiao, Hong-chen; Wang, Jun-jie; Liu, Dan-ni; Yang, Zhao-hua

2018-01-01

A novel hybrid air-core photonic band-gap fiber (PBF) ring resonator with twin 90° polarization-axis rotated splices is proposed and demonstrated. Frist, we measure the temperature dependent birefringence coefficient of air-core PBF and Panda fiber. Experimental results show that the relative temperature dependent birefringence coefficient of air-core PBF is 1.42×10-8/°C, which is typically 16 times less than that of Panda fiber. Then, we extract the geometry profile of air-core PBF from scanning electron microscope (SEM) images. Numerical modal is built to distinguish the fast axis and slow axis in the fiber. By precisely setting the length difference in air-core PBF and Panda fiber between two 90° polarization-axis rotated splicing points, the hybrid air-core PBF ring resonator is constructed, and the finesse of the resonator is 8.4. Environmental birefringence variation induced by temperature change can be well compensated, and experimental results show an 18-fold reduction in thermal sensitivity, compared with resonator with twin 0° polarization-axis rotated splices.

Elliptical As2Se3 filled core ultra-high-nonlinearity and polarization-maintaining photonic crystal fiber with double hexagonal lattice cladding

NASA Astrophysics Data System (ADS)

Li, Feng; He, Menghui; Zhang, Xuedian; Chang, Min; Wu, Zhizheng; Liu, Zheng; Chen, Hua

2018-05-01

A high birefringence and ultra-high nonlinearity photonic crystal fiber (PCF) is proposed, which is composed of an elliptical As2Se3-doped core and an inner cladding with hexagonal lattice. Optical properties of the PCF are simulated by the full-vector finite element method. The simulation results show that the high birefringence of ∼0.33, ultra-high-nonlinearity coefficient of 300757 W-1km-1 and the low confinement loss can be achieved in the proposed PCF simultaneously at the wavelength of 1.55 μm. Furthermore, by comparison with the other two materials (80PbO•20Ga2O3, As2S3) filled in the core, the As2Se3-doped PCF is found to have the highest birefringence and nonlinearity due to its higher refractive index and nonlinear refractive index. The flattened dispersion feature, as well as the low confinement loss of the proposed PCF structure make it suitable as a wide range of applications, such as the coherent optical communications, polarization-maintaining and nonlinear optics, etc.

Polarization sensitive optical coherence tomography in equine bone

NASA Astrophysics Data System (ADS)

Jacobs, J. W.; Matcher, S. J.

2009-02-01

Optical coherence tomography (OCT) has been used to image equine bone samples. OCT and polarization sensitive OCT (PS-OCT) images of equine bone samples, before and after demineralization, are presented. Using a novel approach, taking a series of images at different angles of illumination, the polar angle and true birefringence of collagen within the tissue is determined, at one site in the sample. The images were taken before and after the bones were passed through a demineralization process. The images show an improvement in depth penetration after demineralization allowing better visualization of the internal structure of the bone and the optical orientation of the collagen. A quantitative measurement of true birefringence has been made of the bone; true birefringence was shown to be 1.9x10-3 before demineralization increasing to 2.7x10-3 after demineralization. However, determined collagen fiber orientation remains the same before and after demineralization. The study of bone is extensive within the field of tissue engineering where an understanding of the internal structures is essential. OCT in bone, and improved depth penetration through demineralization, offers a useful approach to bone analysis.

Theory and application of laser ultrasonic shear wave birefringence measurements to the determination of microstructure orientation in transversely isotropic, polycrystalline graphite materials

DOE PAGES

Zeng, Fan W.; Contescu, Cristian I.; Gallego, Nidia C.; ...

2016-12-18

Laser ultrasonic line source methods have been used to study elastic anisotropy in nuclear graphites by measuring shear wave birefringence. Depending on the manufacturing processes used during production, nuclear graphites can exhibit various degrees of material anisotropy related to preferred crystallite orientation and to microcracking. In this paper, laser ultrasonic line source measurements of shear wave birefringence on NBG-25 have been performed to assess elastic anisotropy. Laser line sources allow specific polarizations for shear waves to be transmitted – the corresponding wavespeeds can be used to compute bulk, elastic moduli that serve to quantify anisotropy. These modulus values can bemore » interpreted using physical property models based on orientation distribution coefficients and microcrack-modified, single crystal moduli to represent the combined effects of crystallite orientation and microcracking on material anisotropy. Finally, ultrasonic results are compared to and contrasted with measurements of anisotropy based on the coefficient of thermal expansion to show the relationship of results from these techniques.« less

[INVITED] Magnetic field vector sensor by a nonadiabatic tapered Hi-Bi fiber and ferrofluid nanoparticles

NASA Astrophysics Data System (ADS)

Layeghi, Azam; Latifi, Hamid

2018-06-01

A magnetic field vector sensor based on super-paramagnetic fluid and tapered Hi-Bi fiber (THB) in fiber loop mirror (FLM) is proposed. A two-dimensional detection of external magnetic field (EMF) is experimentally demonstrated and theoretically simulated by Jones matrix to analyze the physical operation in detail. A birefringence is obtained due to magnetic fluid (MF) in applied EMF. By surrounding the THB with MF, a tunable birefringence of MF affect the transmission of the sensor. Slow and fast axes of this obtained birefringence are determined by the direction of applied EMF. In this way, the transmission response of the sensor is depended on the angle between the EMF orientation and the main axes of polarization maintaining fiber (PMF) in FLM. The wavelength shift and intensity shift versus EMF orientation show a sinusoidal behavior, while the applied EMF is constant. Also, the changes in the intensity of EMF in a certain direction results in wavelength shift in the sensor spectrum. The maximum wavelength sensitivity of 214 pm/mT is observed.

Development and characterization of orthotropic-birefringent materials

NASA Technical Reports Server (NTRS)

Daniel, I. M.; Koller, G. M.; Niiro, T.

1984-01-01

Materials were selected and fabrication procedures developed for orthotropic birefringent materials. An epoxy resin (Maraset 658/558 system) was selected as the matrix material. Fibers obtained from style 3733 glass cloth and type 1062 glass roving were used as reinforcement. Two different fabrication procedures were used. In the first one, layers of unidirectional fibers removed from the glass cloth were stacked, impregnated with resin, bagged and cured in the autoclave at an elevated temperature. In the second procedure, the glass roving was drywound over metal frames, impregnated with resin and cured at room temperature under pressure and vacuum in an autoclave. Unidirectional, angle-ply and quasi-isotropic laminates of two thicknesses and with embedded flaws were fabricated. The matrix and the unidirectional glass/epoxy material were fully characterized. The density, fiber volume ratio, mechanical, and optical properties were determined. The fiber volume ratio was over 0.50. Birefringent properties were in good agreement with predictions based on a stress proportioning concept and also, with one exception, with properties predicted by a finite element analysis. Previously announced in STAR as N81-26183

Functional organization of mitotic microtubules. Physical chemistry of the in vivo equilibrium system.

PubMed Central

Inoué, S; Fuseler, J; Salmon, E D; Ellis, G W

1975-01-01

Equilibrium between mitotic microtubules and tubulin is analyzed, using birefringence of mitotic spindle to measure microtubule concentration in vivo. A newly designed temperature-controlled slide and miniature, thermostated hydrostatic pressure chamber permit rapid alteration of temperature and of pressure. Stress birefringence of the windows is minimized, and a system for rapid recording of compensation is incorporated, so that birefringence can be measured to 0.1 nm retardation every few seconds. Both temperature and pressure data yield thermodynamic values (delta H similar to 35 kcal/mol, delta S similar to 120 entropy units [eu], delta V similar to 400 ml/mol of subunit polymerized) consistent with the explanation that polymerization of tubulin is entropy driven and mediated by hydrophobic interactions. Kinetic data suggest pseudo-zero-order polymerization and depolymerization following rapid temperature shifts, and a pseudo-first-order depolymerization during anaphase at constant temperature. The equilibrium properties of the in vivo mitotic microtubules are compared with properties of isolated brain tubules. Images FIGURE 1 FIGURE 2 FIGURE 5 FIGURE 12 FIGURE 13 FIGURE 14 FIGURE 19 PMID:1139037

Photopatterned surface relief gratings in azobenzene-amorphous polycarbonate thin films

NASA Astrophysics Data System (ADS)

Vollmann, Morten; Getek, Peter; Olear, Kellie; Combs, Cody; Campos, Benjamin; Witkowski, Edmund; Cain, Erin; McGee, David

Photoinduced orientation of azobenzene chromophores in polymeric host materials has been broadly explored for optical processing applications. Illumination of the chromophore with polarized light rotates the trans isomer perpendicular to the polarization, resulting in spatially modulated birefringence. The photoinduced anisotropy may also drive mass transport, with surface relief patterns being observed in a wide variety of systems. Here we report photoinduced birefringence in a guest-host system of Disperse Red 1- amorphous polycarbonate (DR1-APC). Birefringence was induced with a 490 nm laser and probed at 633 nm, with typical values of Δn = 0.01 in 2 micron thick films. Illumination of DR1-APC with intensity and/or polarization gratings also resulted in sinusoidal surface relief patterns with periodicity 1- 3 micron as controlled by the interbeam crossing angle of the 490 nm writing beams; the surface modulation was +/- 20 nm as measured by atomic force microscopy. Photopatterned DR1-APC is advantageous for applications given the ease of thin-film fabrication and the high glass transition temperature of APC, resulting in robust optically-induced surface gratings. We acknowledge support from NSF-DMR Award No. 1138416.

Effect of birefringence of lens material on polarization status and optical imaging characteristics

NASA Astrophysics Data System (ADS)

Kim, Wan-Chin; Park, No-Cheol

2018-04-01

In most cases of molding with glass or optical polymers, it is expected that there will be birefringence caused by the internal mechanical stresses remaining in the molding material. The distribution of the residual stress can be annealed by slow cooling, but this approach is disadvantageous with respect to the shape accuracy and manufacturing time. In this study, we propose an analytical model to calculate the diffracted field near the focal plane by considering two primary parameters, the orientation angle of the fast axis and the path difference. In order to verify the reliability of the analytical model, we compared the measured beam spot of the F-theta lens of the laser scanning unit (LSU) with the analytical result. In addition, we analyzed the calculated result from the perspective of the polarization status in the exit pupil. The proposed analysis method can be applied to enhance the image quality for cases in which birefringence occurs in a lens material by suitably modeling the amplitude and phase of the incident light flux.

Annealing of linear birefringence in single-mode fiber coils - Application to optical fiber current sensors

NASA Technical Reports Server (NTRS)

Tang, Dingding; Rose, A. H.; Day, G. W.; Etzel, Shelley M.

1991-01-01

Annealing procedures that greatly reduce linear birefringence in single-mode fiber coils are described. These procedures have been successfully applied to coils ranging from 5 mm to 10 cm in diameter and up to 200 or more turns. They involve temperature cycles that last 3-4 days and reach maximum temperatures of about 850 C. The residual birefringence and induced loss are minimized by proper selection of fiber. The primary application of these coils is optical fiber current sensors, where they yield small sensors that are more stable than those achieved by other techniques. A current sensor with a temperature stability of 8.4 x 10 to the -5th/K over the range from -75 to 145 C has been demonstrated. This is approximately 20 percent greater than the temperature dependence of the Verdet constant. Packaging degrades the stability, but a packaged sensor coil with a temperature stability of about 1.6 + 10 to the -4th/K over the range from -20 to 120 C has also been demonstrated.

A review of the generalized uncertainty principle.

PubMed

Tawfik, Abdel Nasser; Diab, Abdel Magied

2015-12-01

Based on string theory, black hole physics, doubly special relativity and some 'thought' experiments, minimal distance and/or maximum momentum are proposed. As alternatives to the generalized uncertainty principle (GUP), the modified dispersion relation, the space noncommutativity, the Lorentz invariance violation, and the quantum-gravity-induced birefringence effects are summarized. The origin of minimal measurable quantities and the different GUP approaches are reviewed and the corresponding observations are analysed. Bounds on the GUP parameter are discussed and implemented in the understanding of recent PLANCK observations of cosmic inflation. The higher-order GUP approaches predict minimal length uncertainty with and without maximum momenta. Possible arguments against the GUP are discussed; for instance, the concern about its compatibility with the equivalence principles, the universality of gravitational redshift and the free fall and law of reciprocal action are addressed.

Parallel Photonic Quantum Computation Assisted by Quantum Dots in One-Side Optical Microcavities

PubMed Central

Luo, Ming-Xing; Wang, Xiaojun

2014-01-01

Universal quantum logic gates are important elements for a quantum computer. In contrast to previous constructions on one degree of freedom (DOF) of quantum systems, we investigate the possibility of parallel quantum computations dependent on two DOFs of photon systems. We construct deterministic hyper-controlled-not (hyper-CNOT) gates operating on the spatial-mode and the polarization DOFs of two-photon or one-photon systems by exploring the giant optical circular birefringence induced by quantum-dot spins in one-sided optical microcavities. These hyper-CNOT gates show that the quantum states of two DOFs can be viewed as independent qubits without requiring auxiliary DOFs in theory. This result can reduce the quantum resources by half for quantum applications with large qubit systems, such as the quantum Shor algorithm. PMID:25030424

Parallel photonic quantum computation assisted by quantum dots in one-side optical microcavities.

PubMed

Luo, Ming-Xing; Wang, Xiaojun

2014-07-17

Universal quantum logic gates are important elements for a quantum computer. In contrast to previous constructions on one degree of freedom (DOF) of quantum systems, we investigate the possibility of parallel quantum computations dependent on two DOFs of photon systems. We construct deterministic hyper-controlled-not (hyper-CNOT) gates operating on the spatial-mode and the polarization DOFs of two-photon or one-photon systems by exploring the giant optical circular birefringence induced by quantum-dot spins in one-sided optical microcavities. These hyper-CNOT gates show that the quantum states of two DOFs can be viewed as independent qubits without requiring auxiliary DOFs in theory. This result can reduce the quantum resources by half for quantum applications with large qubit systems, such as the quantum Shor algorithm.

Versatile tunable current-mode universal biquadratic filter using MO-DVCCs and MOSFET-based electronic resistors.

PubMed

Chen, Hua-Pin

2014-01-01

This paper presents a versatile tunable current-mode universal biquadratic filter with four-input and three-output employing only two multioutput differential voltage current conveyors (MO-DVCCs), two grounded capacitors, and a well-known method for replacement of three grounded resistors by MOSFET-based electronic resistors. The proposed configuration exhibits high-output impedance which is important for easy cascading in the current-mode operations. The proposed circuit can be used as either a two-input three-output circuit or a three-input single-output circuit. In the operation of two-input three-output circuit, the bandpass, highpass, and bandreject filtering responses can be realized simultaneously while the allpass filtering response can be easily obtained by connecting appropriated output current directly without using additional stages. In the operation of three-input single-output circuit, all five generic filtering functions can be easily realized by selecting different three-input current signals. The filter permits orthogonal controllability of the quality factor and resonance angular frequency, and no inverting-type input current signals are imposed. All the passive and active sensitivities are low. Postlayout simulations were carried out to verify the functionality of the design.

Versatile Tunable Current-Mode Universal Biquadratic Filter Using MO-DVCCs and MOSFET-Based Electronic Resistors

PubMed Central

2014-01-01

This paper presents a versatile tunable current-mode universal biquadratic filter with four-input and three-output employing only two multioutput differential voltage current conveyors (MO-DVCCs), two grounded capacitors, and a well-known method for replacement of three grounded resistors by MOSFET-based electronic resistors. The proposed configuration exhibits high-output impedance which is important for easy cascading in the current-mode operations. The proposed circuit can be used as either a two-input three-output circuit or a three-input single-output circuit. In the operation of two-input three-output circuit, the bandpass, highpass, and bandreject filtering responses can be realized simultaneously while the allpass filtering response can be easily obtained by connecting appropriated output current directly without using additional stages. In the operation of three-input single-output circuit, all five generic filtering functions can be easily realized by selecting different three-input current signals. The filter permits orthogonal controllability of the quality factor and resonance angular frequency, and no inverting-type input current signals are imposed. All the passive and active sensitivities are low. Postlayout simulations were carried out to verify the functionality of the design. PMID:24982963

Vector solitons in a laser passively mode-locked by single-wall carbon nanotubes

NASA Astrophysics Data System (ADS)

Wong, Jia Haur; Wu, Kan; Liu, Huan Huan; Ouyang, Chunmei; Wang, Honghai; Aditya, Sheel; Shum, Ping; Fu, Songnian; Kelleher, E. J. R.; Chernov, A.; Obraztsova, E. D.

2011-04-01

Polarization Rotation Locked Vector Solitons (PRLVSs) are experimentally observed for the first time in a fiber ring laser passively mode-locked by a single-wall carbon nanotube (SWCNT) saturable absorber. Period-doubling of these solitons at certain birefringence values has also been observed. We show that fine adjustment to the intracavity birefringence can swing the PRLVSs from period-doubled to period-one state without simultaneous reduction in the pump strength. The timing jitter for both states has also been measured experimentally and discussed analytically using the theoretical framework provided by the Haus model.

Imaging polarimetry in patients with neovascular age-related macular degeneration

PubMed Central

Elsner, Ann E.; Weber, Anke; Cheney, Michael C.; VanNasdale, Dean A.; Miura, Masahiro

2007-01-01

Imaging polarimetry was used to examine different components of neovascular membranes in age-related macular degeneration. Retinal images were acquired with a scanning laser polarimeter. An innovative pseudo-color scale, based on cardinal directions of color, displayed two types of image information: relative phases and magnitudes of birefringence. Membranes had relative phase changes that did not correspond to anatomical structures in reflectance images. Further, membrane borders in depolarized light images had significantly higher contrasts than those in reflectance images. The retinal birefringence in neovascular membranes indicates optical activity consistent with molecular changes rather than merely geometrical changes. PMID:17429494

Terahertz birefringence of potassium niobate crystals

NASA Astrophysics Data System (ADS)

Antsygin, V. D.; Mamrashev, A. A.; Nikolaev, N. A.

2018-03-01

We present terahertz optical properties (refractive indices and absorption coefficients) of potassium niobate crystals measured by time-domain spectroscopy in the range of 0.2-2.0 THz. We observe average refractive indices nx = 5.25, ny = 4.8, nz = 5.9 for corresponding optical axes X, Y, Z with the large birefringence of Δn = nz - ny = 1.1. We report rising absorption coefficient at higher frequencies (α ∼ 50 cm-1 at 1 THz for all three axes) while the dichroism is not pronounced. Somewhat higher absorption compared to the previous results could be attributed to some polydomain structure remaining in the crystal.

Structure of dysprosium(111) dl-tartrate dimer in aqueous solution

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chevela, V.V.; Vulfson, S.G.; Salnikov, Y.I.

1994-10-01

The paramagnetic birefringence method was supplemented by numerical simulation to determine the molar paramagnetic-birefringence constant of the dysprosium dl-tartrate dimer Dy{sub 2}(d-L)(l-L){sup 2-} (I), where d-L{sup 4-} and l-L{sup 4-} are the deprotonated d- and l-tartaric acid molecules, respectively. The structure of the ligand and hydration surroundings of I was modeled by molecular mechanic calculations (the Dashevskii-Pylamovatyi model). It is shown that adequate results can be obtained only if one takes into account the coordination of I to the Na{sup +} ion.

Simultaneous measurement of dynamic strain and temperature distribution using high birefringence PANDA fiber Bragg grating

NASA Astrophysics Data System (ADS)

Zhu, Mengshi; Murayama, Hideaki

2017-04-01

New approach in simultaneous measurement of dynamic strain and temperature has been done by using a high birefringence PANDA fiber Bragg grating sensor. By this technique, we have succeeded in discriminating dynamic strain and temperature distribution at the sampling rate of 800 Hz and the spatial resolution of 1 mm. The dynamic distribution of strain and temperature were measured with the deviation of 5mm spatially. In addition, we have designed an experimental setup by which we can apply quantitative dynamic strain and temperature distribution to the fiber under testing without bounding it to a specimen.

Shot-noise-limited measurement of sub-parts-per-trillion birefringence phase shift in a high-finesse cavity

DOE Office of Scientific and Technical Information (OSTI.GOV)

Durand, Mathieu; Morville, Jerome; Romanini, Daniele

2010-09-15

We report on a promising approach to high-sensitivity anisotropy measurements using a high-finesse cavity locked by optical feedback to a diode laser. We provide a simple and effective way to decouple the weak anisotropy of interest from the inherent mirror's birefringence whose drift may be identified as the key limiting parameter in cavity-based techniques. We demonstrate a shot-noise-limited phase shift resolution previously inaccessible in an optical cavity, readily achieving the state-of-the-art level of 3x10{sup -13} rad.

Soliton-dark pulse pair formation in birefringent cavity fiber lasers through cross phase coupling.

PubMed

Shao, Guodong; Song, Yufeng; Zhao, Luming; Shen, Deyuan; Tang, Dingyuan

2015-10-05

We report on the experimental observation of soliton-dark pulse pair formation in a birefringent cavity fiber laser. Temporal cavity solitons are formed in one polarization mode of the cavity. It is observed that associated with each of the cavity solitons a dark pulse is induced on the CW background of the orthogonal polarization mode. We show that the dark pulse formation is a result of the incoherent cross polarization coupling between the soliton and the CW beam and has a mechanism similar to that of the polarization domain formation observed in the fiber lasers.

Few-cycle solitons in the medium with permanent dipole moment under conditions of the induced birefringence

NASA Astrophysics Data System (ADS)

Sazonov, S. V.

2016-12-01

Propagation of electromagnetic pulse in the birefringent medium consisting of symmetric and asymmetrical molecules is investigated. Stationary quantum states of asymmetrical molecules have the permanent dipole moment. Under considered conditions the ordinary pulse component excites quantum transitions between stationary states. The extraordinary component, besides, causes a dynamic chirp of frequencies of these transitions. The new solitonic modes of propagation of the half- and single-period pulses are found. The solitonic mechanism of simultaneous generation of the second and zero harmonics in the modes of "bright" and "dark" solitons is analyzed.

Photonic-chip-based all-optical ultra-wideband pulse generation via XPM and birefringence in a chalcogenide waveguide.

PubMed

Tan, Kang; Marpaung, David; Pant, Ravi; Gao, Feng; Li, Enbang; Wang, Jian; Choi, Duk-Yong; Madden, Steve; Luther-Davies, Barry; Sun, Junqiang; Eggleton, Benjamin J

2013-01-28

We report a photonic-chip-based scheme for all-optical ultra-wideband (UWB) pulse generation using a novel all-optical differentiator that exploits cross-phase modulation and birefringence in an As₂S₃ chalcogenide rib waveguide. Polarity-switchable UWB monocycles and doublets were simultaneously obtained with single optical carrier operation. Moreover, transmission over 40-km fiber of the generated UWB doublets is demonstrated with good dispersion tolerance. These results indicate that the proposed approach has potential applications in multi-shape, multi-modulation and long-distance UWB-over-fiber communication systems.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kuzmina, M S; Khazanov, E A

The problem on laser radiation propagation in a birefringent medium is solved with the allowance made for thermally induced linear birefringence under the conditions of cubic nonlinearity. It is shown that at high average and peak radiation powers the degree of isolation in a Faraday isolator noticeably reduces due to the cubic nonlinearity: by more than an order of magnitude when the B-integral is equal to unity. This effect is substantial for pulses with the energy of 0.2 – 3 J, duration of 10 ps to 4 ns and pulse repetition rate of 0.2 – 40 kHz. (components of lasermore » devices)« less

Video image processing greatly enhances contrast, quality, and speed in polarization-based microscopy

PubMed Central

1981-01-01

Video cameras with contrast and black level controls can yield polarized light and differential interference contrast microscope images with unprecedented image quality, resolution, and recording speed. The theoretical basis and practical aspects of video polarization and differential interference contrast microscopy are discussed and several applications in cell biology are illustrated. These include: birefringence of cortical structures and beating cilia in Stentor, birefringence of rotating flagella on a single bacterium, growth and morphogenesis of echinoderm skeletal spicules in culture, ciliary and electrical activity in a balancing organ of a nudibranch snail, and acrosomal reaction in activated sperm. PMID:6788777

Casimir effect and graphene: Tunability, scalability, Casimir rotor

NASA Astrophysics Data System (ADS)

Martinez, J. C.; Chen, X.; Jalil, M. B. A.

2018-01-01

We study the combined effects of separated parallel disks, birefringence and surface currents on the Casimir force and torque. All three contribute to the Casimir force and surface currents from graphene permit tuning and switching from attraction to repulsion thus allowing for an oscillating Casimir force which can be relevant to parametric amplification applications. Only the latter two contribute to the Casimir torque and their combined effect can enhance the torque by at least tenfold (possibly more) compared to that due to birefringence alone, a hint at a scalable Casimir torque. We also consider a feasible non-contact rotor.

Crystalline folliculitis revealed by non-aqueous staining technique.

PubMed

Siscos, Spyros Michael; Tran, Chi; Fischer, Ryan; Fraga, Garth

2017-07-15

Necrotizing infundibular crystalline folliculitis (NICF) is a rare superficial folliculitis characterized by expansive deposits of birefringent crystallized lipid. We report a case of NICF in a transplant patient presenting with folliculocentric acneiform papules across the lateral face and neck. Biopsy demonstrated intrafollicular crystalline deposits within an intact epidermis. Diagnostic crystals were identified using a non-aqueous histologic technique involving thick unstained sections. To our knowledge, this is the first report of NICF in a transplant patient. Our case suggests NICF is a follicular disorder and highlights a technique that may prevent loss of birefringent crystals and assist in facilitating accurate diagnosis.

Generating polarization-entangled photon pairs using cross-spliced birefringent fibers.

PubMed

Meyer-Scott, Evan; Roy, Vincent; Bourgoin, Jean-Philippe; Higgins, Brendon L; Shalm, Lynden K; Jennewein, Thomas

2013-03-11

We demonstrate a novel polarization-entangled photon-pair source based on standard birefringent polarization-maintaining optical fiber. The source consists of two stretches of fiber spliced together with perpendicular polarization axes, and has the potential to be fully fiber-based, with all bulk optics replaced with in-fiber equivalents. By modelling the temporal walk-off in the fibers, we implement compensation necessary for the photon creation processes in the two stretches of fiber to be indistinguishable. Our source subsequently produces a high quality entangled state having (92.2 ± 0.2) % fidelity with a maximally entangled Bell state.

Persistence of bone collagen cross-links in skeletons of the Nuraghi population living in Sardinia 1500-1200 B.C

NASA Technical Reports Server (NTRS)

Wojtowicz, A.; Yamauchi, M.; Montella, A.; Bandiera, P.; Sotowski, R.; Ostrowski, K.

1999-01-01

Bone collagen has a specific molecular ultrastructure which can be proved by birefringence. This protein, forming the main organic component of bone tissue, is known to survive millennia in paleontological bones and teeth. Birefringence of bone collagen obtained from the skeletons of the Nuraghi population living in Sardinia c-ca 1500 years B.C. was found previously by the use of polarizing microscopy [1]. In this paper, using high pressure liquid chromatography (HPLC) techniques, we show the existence of bone collagen cross-links preserved in Nuraghi skeletons after more than 3000 years.

(Full field) optical coherence tomography and applications

NASA Astrophysics Data System (ADS)

Buchroithner, Boris; Hannesschläger, Günther; Leiss-Holzinger, Elisabeth; Prylepa, Andrii; Heise, Bettina

2018-03-01

This paper illustrates specific features and use of optical coherence tomography (OCT) in the raster-scanning and in comparison in the full field version of this imaging technique. Cases for nondestructive testing are discussed alongside other application schemes. In particular monitoring time-dependent processes and probing of birefringent specimens are considered here. In the context of polymer testing birefringence mapping may often provide information about internal strain and stress states. Recent results obtained with conventional raster-scanning OCT systems, with (dual and single-shot) full field OCT configurations, and with polarization-sensitive versions of (full field) OCT are presented here.

HYBRID SILICON-ON-SAPPHIRE/SCALED CMOS INTERFERENCE MITIGATION FRONT END BASED ON SIMULTANEOUS NOISE CANCELLATION, ACTIVE-INTERFERENCE CANCELLATION AND N-PATH-MIXER FILTERING

DTIC Science & Technology

2017-04-01

INTERFERENCE-CANCELLATION AND N-PATH-MIXER FILTERING Harish Krishnaswamy, Negar Reiskarimian, and Linxiao Zhang Columbia University APRIL 2017 Final...INTERFERENCE-CANCELLATION AND N- PATH-MIXER FILTERING 5a. CONTRACT NUMBER FA8650-14-1-7414 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 61101E/62716E 6...techniques for developing interference mitigation technology (IMT) enabling frequency-agile, reconfigurable filter -less receivers. Wideband noise

Frequency Agile Microwave Photonic Notch Filter in a Photonic Chip

DTIC Science & Technology

2016-10-21

AFRL-AFOSR-JP-TR-2016-0087 Frequency Agile Microwave Photonic Notch Filter in a Photonic Chip Benjamin Eggleton UNIVERSITY OF SYDNEY Final Report 10...REPORT TYPE      Final 3.  DATES COVERED (From - To)      14 May 2014 to 13 May 2016 4.  TITLE AND SUBTITLE Frequency Agile Microwave Photonic Notch Filter ...primary objective is to explore a novel class microwave photonic (MWP) notch filter with a very narrow isolation bandwidth, an ultrahigh stopband

J-PLUS: The Javalambre Photometric Local Universe Survey

NASA Astrophysics Data System (ADS)

Cenarro, Javier; Marin-Franch, Antonio; Moles, Mariano; Cristobal-Hornillos, David; Mendes de Oliveira, Claudia; Sodre, Laerte

2015-08-01

The Javalambre-Photometric Local Universe Survey, J-PLUS (www.j-plus.es), is defined to observe 8500 deg2 of the sky visible from the Javalambre Observatory (Teruel, Spain) with the panoramic camera T80Cam at the JAST/T80 telescope, using a set of 12 broad, intermediate and narrow band optical filters. The Project is particularly designed to carry out the photometric calibration of J-PAS (http://j-pas.org). For this reason, some J-PLUS filters are located at key stellar spectral features that allow to retrieve very accurate spectral energy distributions for more than 5 millions of stars in our Galaxy. Beyond the calibration goals, the unusually large FOV of T80Cam, 2deg2, together with the unique width and location of some filters, turn the J-PLUS Project into a powerful 3D view of the nearby Universe, mapping more than 20 millions of galaxies with reliable distance determinations and a similar number of stars of the Milky Way halo. At a rate of 100 gigabytes of data per night, J-PLUS will provide unprecedented multi-color images of the Universe to address a wide variety of astrophysical questions related with cosmology, large scale structure, galaxy clusters, 2D stellar populations and star formation studies in galaxies, the discovery of high redshift galaxies at specific redshift slices, quasars, supernovae, Milky Way science and structure, and minor bodies in the Solar System. In addition, the repetition of the whole area over time in certain filters will allow to face variability studies in the time domain.Complementing J-PLUS, a replica of the JAST/T80 telescope, T80Cam and the J-PLUS filters have been installed at the CTIO, allowing to extend the project to the Southern Hemisphere. J-PLUS together with the southern extension, S-PLUS, constitute an All-sky Photometric Local Universe Survey whose details and scientific applications are the bulk of the present talk.

A THERMODYNAMIC ANALYSIS OF MITOTIC SPINDLE EQUILIBRIUM AT ACTIVE METAPHASE

PubMed Central

Stephens, R. E.

1973-01-01

The mitotic apparatus of first-division metaphase eggs of the sea urchin Strongylocentrotus drobachiensis was observed by means of polarization microscopy under controlled temperature conditions. Eggs were fertilized and grown at two temperature extremes in order to produce two different sizes of available spindle pool. Slow division time allowed successive samples of such cells to be observed at the same point in metaphase but at different equilibrium temperatures, yielding curves of metaphase equilibrium birefringence vs. observational temperature. Using the plateau value of birefringence at higher temperatures as a measure of total available spindle pool and the observed birefringence at lower temperatures as a measure of polymerized material at equilibrium, the spindle protein association was evaluated according to the method of Inoué. Both pool conditions produced linear van't Hoff functions. Analysis of these functions yielded enthalpy and entropy changes of +55–65 kcal/mol and +197–233 entropy units (eu), respectively. These values for active mitotic metaphase are quite comparable to those obtained by Inoué and co-workers for arrested meiotic metaphase cells. When other equilibrium treatments were considered, the best fit to the experimental data was still that of Inoué, a treatment which theoretically involves first-order polymerization and dissociation kinetics. Treatment of metaphase cells with D2O by direct immersion drove the equilibrium to completion regardless of temperature, attaining or exceeding a birefringence value equal to the cell's characteristic pool size; perfusion with D2O appeared to erase the original temperature-determined pool size differences for the two growth conditions, attaining a maximum value characteristic of the larger pool condition. These data confirm Inoué's earlier contention that D2O treatment can modify the available spindle pool. PMID:4734864

The study of optical properties and proteoglycan content of tendons by PS-OCT

NASA Astrophysics Data System (ADS)

Yang, Ying; Rupani, Asha; Weightman, Alan; Wimpenny, Ian; Bagnaninchi, Pierre; Ahearne, Mark

2011-03-01

Tendons are load-bearing collagenous tissues consisting mainly of type I collagen and various proteoglycans (PGs) including decorin and versican. It is widely accepted that highly orientated collagen fibers in tendons a play critical role for transferring tensile stress and demonstrate birefringent optical properties. However, the influence that proteoglycans have on the optical properties of tendons is yet to be fully elucidated. Tendinopathy (defined as a syndrome of tendon pain, tenderness and swelling that affects the normal function of the tissue) is a common disease associated with sporting injuries or degeneration. PG's are the essential components of the tendon extracellular matrix; changes in their quantities and compositions have been associated with tendinopathy. In this study, polarization sensitive optical coherence tomography (PS-OCT) has been used to reveal the relationship between proteoglycan content/location and birefringent properties of tendons. Tendons dissected from freshly slaughtered chickens were imaged at regular intervals by PS-OCT and polarizing light microscope during the extraction of PGs or glycosaminoglycans using established protocols (guanidine hydrochloride (GuHCl) or proteinase K solution). The macroscopic and microscopic time lapsed images are complimentary; mutually demonstrating that there was a higher concentration of PG's in the outer sheath region than in the fascicles; and the integrity of the sheath affected extraction process and the OCT birefringence bands. Extraction of PGs using GuHCl disturbed the organization of local collagen bundles, which corresponded to a reduction in the frequency of birefringence bands and the band width by PS-OCT. The feature of OCT penetration depth helped us to define the heterogeneous distribution of PG's in tendon, which was complimented by polarizing light microscopy. The results provide new insight of tendon structure and also demonstrate a great potential for using PS-OCT as a diagnostic tool to examine tendon pathology.

Detailed analysis of evolution of the state of polarization in all-fiber polarization transformers.

PubMed

Zhu, Xiushan; Jain, Ravinder K

2006-10-30

We present a detailed analysis of key attributes and performance characteristics of controllably-spun birefringent-fiber-based all-fiber waveplates or "all fiber polarization transformers" (AFPTs), first proposed and demonstrated by Huang [11]; these AFPTs consist essentially of a long carefully-designed "spin-twisted" high-birefringence fiber, fabricated by slowly varying the spin rate of a birefringent fiber preform (either from very fast to very slow or vice versa) while the fiber is being drawn. The evolution of the eigenstate from a linear polarization state to a circular polarization state, induced by slow variation of the intrinsic structure from linear anisotropy at the unspun end to circular anisotropy at the fast-spun end, enables the AFPT to behave like an all-fiber quarter-wave plate independent of the wavelength of operation. Power coupling between local eigenstates causes unique evolution of the polarization state along the fiber, and has been studied to gain insight into - as well as to understand detailed characteristics of -- the polarization transformation behavior. This has been graphically illustrated via plots of the relative power in these local eigenstates as a function of distance along the length of the fiber and plots of the extinction ratio of the output state of polarization (SOP) as a function of distance and the normalized spin rate. Deeper understanding of such polarization transformers has been further elucidated by quantitative calculations related to two crucial requirements for fabricating practical AFPT devices. Our calculations have also indicated that the polarization mode dispersion behaviour of the AFPT is much smaller than that of the original birefringent fiber. Finally, a specific AFPT was experimentally investigated at two widely-separated wavelengths (1310 nm and 1550 nm) of interest in telecommunications systems applications, further demonstrating and elucidating the broadband character of such AFPTs.

Detection of oral early cancerous lesion by using polarization-sensitive optical coherence tomography: mice model

NASA Astrophysics Data System (ADS)

Lee, Hong-Yi; Chen, Ping-Hsien; Lee, Tzu-Han; Chang, Kuo-Wei; Kuo, Wen-Chuan

2018-02-01

Oral cancer is the 11th most common cancer worldwide, especially in a male adult. The median age of death in oral cancer was 55 years, 10-20 years earlier than other cancers. Presently, oral cancer is often found in late stage, because the lesion is often flat in early stage and is difficult to diagnose under traditional white light imaging. The only definitive method for determining cancer is an invasive biopsy and then using histology examination. How to detect precancerous lesions or early malignant lesions is an important issue for improving prognosis of oral cancer. Optical coherence tomography (OCT) is a new optical tool for diagnosing early malignant lesions in the skin or gastrointestinal tract recently. Here we report a new method for detecting precancerous or early malignant oral lesions by using swept source polarization-sensitive optical coherence tomography (PS-OCT) with center-wavelength 1310 nm, bandwidth 110 nm and 100 kHz swept rate. We used all single-mode fiber design to detect the change of birefringence information in the epithelium structure. This system has an advantage that enables measurement of backscattered intensity and birefringence simultaneously with only one A-scan per transverse location. In preliminary result, we computed the slope of the every A-scan signal in tissue part using a linear-curve fitting in backscattered intensity and birefringence on the enface. In this research, we used an oral cancer mice model for observing the change of structure and birefringence properties in different stages of oral cancer mice. We presented the parametric enface imaging that can detect the early oral malignant lesions.

Effect of production variables on microbiological removal in locally-produced ceramic filters for household water treatment.

PubMed

Lantagne, Daniele; Klarman, Molly; Mayer, Ally; Preston, Kelsey; Napotnik, Julie; Jellison, Kristen

2010-06-01

Diarrhoeal diseases cause an estimated 1.87 million child deaths per year. Point-of-use filtration using locally made ceramic filters improves microbiological quality of stored drinking water and prevents diarrhoeal disease. Scaling-up ceramic filtration is inhibited by lack of universal quality control standards. We investigated filter production variables to determine their affect on microbiological removal during 5-6 weeks of simulated normal use. Decreases in the clay:sawdust ratio and changes in the burnable decreased effectiveness of the filter. Method of silver application and shape of filter did not impact filter effectiveness. A maximum flow rate of 1.7 l(-hr) was established as a potential quality control measure for one particular filter to ensure 99% (2- log(10)) removal of total coliforms. Further research is indicated to determine additional production variables associated with filter effectiveness and develop standardized filter production procedures prior to scaling-up.

Graphene-Based Filters and Supercapacitors for Space and Aeronautical Applications

NASA Technical Reports Server (NTRS)

Calle, Carlos I.

2015-01-01

Overview of the capabilities of graphene for selective filters and for energy storage with a general description of the work being done at NASA Kennedy Space Center in collaboration with the University of California Los Angeles for space and aeronautical applications.

Analytical modeling of polarization transformation of laser radiation of various spectral ranges by birefringent structures

NASA Astrophysics Data System (ADS)

Motrich, A. V.; Ushenko, O. G.

2018-01-01

The results of statistical dependence and correlation structures of two-dimensional Mueller matrix elements in various spectral regions of laser radiation by changes in the distribution of orientations of optical axes and birefringence of protein crystals. Namely, a two-wave ("red-blue") approach - layer of biological tissues irradiated by He-Ne laser (λ1 = 0,63μm ) and He-Cd laser (λ1 = 0,41μm )was used Conducted analysis of polarimetric sensitivity was made, a state of polarization points that contain volumetric structures of biological objects to spectral region of laser radiation was detected.

Planar Poincare chart - A planar graphic representation of the state of light polarization

NASA Technical Reports Server (NTRS)

Tedjojuwono, Ken K.; Hunter, William W., Jr.; Ocheltree, Stewart L.

1989-01-01

The planar Poincare chart, which represents the complete planar equivalence of the Poincare sphere, is proposed. The four sets of basic lines are drawn on two separate charts for the generalization and convenience of reading the scale. The chart indicates the rotation of the principal axes of linear birefringent material. The relationships between parameters of the two charts are given as 2xi-2phi (orientation angle of the major axis-ellipticity angle) pair and 2alpha-delta (angle of amplitude ratio-phase difference angle) pair. The results are useful for designing and analyzing polarization properties of optical components with birefringent properties.

Radially polarized and passively Q-switched Yb-doped fiber laser based on intracavity birefringent mode discrimination

NASA Astrophysics Data System (ADS)

Sun, Xuehuan; Wu, Yongxiao; Chen, Sanbin; Li, Jianlang

2018-05-01

In this paper, we demonstrated a passive Q-switched ytterbium-doped fiber laser with radially polarized beam emission by using a c-cut YVO4 birefringent crystal as the intracavity polarization discriminator, and a Cr4+:YAG crystal as the saturable absorber and output coupler. The maximum averaged laser power reached 3.89 W with a high slope efficiency of 66.5%. The laser pulse had a peak power of 161 W, 160 ns duration, and 151 kHz repetition rate at the absorbed pump power of 6.48 W. Such a radially polarized pulse would facilitate numerous applications.

The structure of polarization maps of skin histological sections in the Fourier domain for the tasks of benign and malignant formations differentiation

NASA Astrophysics Data System (ADS)

Ushenko, V. A.; Dubolazov, A. V.; Savich, V. O.; Novakovskaya, O. Y.; Olar, O. V.; Marchuk, Y. F.

2015-02-01

The optical model of birefringent networks of biological tissues is presented. The technique of Fourier polarimetry for selection of manifestations of linear and circular birefringence of protein fibrils is suggested. The results of investigations of statistical (statistical moments of the 1st-4th orders), correlation (dispersion and excess of autocorrelation functions) and scalar-self-similar (logarithmic dependencies of power spectra) structure of Fourier spectra of polarization azimuths distribution of laser images of skin samples are presented. The criteria of differentiation of postoperative biopsy of benign (keratoma) and malignant (adenocarcinoma) skin tumors are determined.

Experiment to measure vacuum birefringence: Conceptual design

NASA Astrophysics Data System (ADS)

Mueller, Guido; Tanner, David; Doebrich, Babette; Poeld, Jan; Lindner, Axel; Willke, Benno

2016-03-01

Vacuum birefringence is another lingering challenge which will soon become accessible to experimental verification. The effect was first calculated by Euler and Heisenberg in 1936 and is these days described as a one-loop correction to the differential index of refraction between light which is polarized parallel and perpendicular to an external magnetic field. Our plan is to realize (and slightly modify) an idea which was originally published by Hall, Ye, and Ma using advanced LIGO and LISA technology and the infrastructure of the ALPS light-shining-through-walls experiment following the ALPS IIc science run. This work is supported by the Deutsche Forschungsgemeinschaft and the Heising-Simons Foundation.

FIBER AND INTEGRATED OPTICS: Radio-frequency electrooptic modulation in optical fibers

NASA Astrophysics Data System (ADS)

Bulyuk, A. N.

1992-10-01

The electrooptic interaction in single-mode optical fibers with both linear and circular birefringe is analyzed. In most cases, a large interaction length imposes a limit on the modulation frequency. A circular birefringence in an optical fiber may lead to an effective coupling of polarization normal modes if a phase-matching condition is satisfied. Through an appropriate choice of polarization states of the light at the entrance and exit of the device, one can achieve a polarization modulation or a frequency shift of the light. There are possible applications in rf polarization modulators, devices for shifting the frequency of light, and detectors of electromagnetic fields.

High-sensitivity temperature sensor based on highly-birefringent microfiber

NASA Astrophysics Data System (ADS)

Sun, Li-Peng; Li, Jie; Jin, Long; Gao, Shuai; Tian, Zhuang; Ran, Yang; Guan, Bai-Ou

2013-09-01

We demonstrate an ultrasensitive temperature sensor by sealing a highly-birefringent microfiber into an alcoholinfiltrated copper capillary. With a Sagnac loop configuration, the interferometric spectrum is strongly dependent on the external refractive index (RI) with sensitivity of 36800nm/RIU around RI=1.356. As mainly derived from the ultrahigh RI sensitivity, the temperature response can reach as high as -14.72 nm/°C in the range of 30.9-36.9 °C. The measured response time is ~8s, as determined by the heat-conducting characteristic of the device and the diameter of the copper capillary. Our sensor is featured with low cost, easy fabrication and robustness.

Material parameters that determine the surface accuracy of large astronomical mirrors

NASA Astrophysics Data System (ADS)

Amur, G. I.

1983-03-01

The design and manufacture of large astronomical mirrors are examined from both theoretical and practical perspectives. The effects of birefringence, tool-load relief, cord position, and temperature gradient on the surface quality are assessed quantitatively and discussed in terms of material choice and fabrication technique. It is shown that a single cord positioned horizontally produces only minimum image distortion. Formulas for calculating the deformation of the wave front by the mirror surface due to birefringence difference, the optimum load relief, and the deformation temperature, are presented. Graphs of important relationships and a table listing the diameters and surface parameters of recently built large telescopes are provided.

Birefringence in a chiral medium, via temporal cloaking

NASA Astrophysics Data System (ADS)

Khan, Humayun; Haneef, Muhammad

2017-05-01

This paper reports theoretical investigation of birefringence in a chiral medium for the creation of temporal cloaking. The chiral medium splits the input probe beam into left/right circular polarized beams. These left/right circular polarized beams are then controlled and modified within the chiral medium. The left circular polarized beam delays by 24 ns whereas the right circular polarized beam advances by  -23 ns at a control field of rabbi frequency 6γ . This opens a 47 ns time gap for temporal cloaking to hide information without noise corruption and energy loss. The results have potential applications in communication devices for secure propagation of light pulse.

Optical Properties of TGS Crystal with L-Valine Admixture

DOE Office of Scientific and Technical Information (OSTI.GOV)

Stadnyk, V. Yo., E-mail: vasylstadnyk@ukr.net; Romanyuk, N. A.; Kiryk, Yu. I.

2010-11-15

The thermal expansion and temperature and the spectral dependences of the refractive indices and birefringence of triglycine sulphate (TGS) crystals with a 5% L-valine admixture have been investigated. It is established that the introduction of L-valine weakens the temperature dependence of the refractive indices and the birefringence and thermal expansion of TGS crystals. The parameters of the Sellmeier formula, refractions, and electronic polarizabilities are calculated. The changes observed may be related to the increase in hardness of admixture-containing crystals, the decrease in the spontaneous polarization, the replacement of the refraction components of the valine bond, or the spontaneous electro-optic effect.

Phase diagram of tetradecyltrimethylammonium bromide (TTAB) + water + octanol system with application of mechanical deformation

NASA Astrophysics Data System (ADS)

Yavuz, Aykut Evren; Masalci, Özgür; Kazanci, Nadide

2014-11-01

Morphological properties of tetradecyltrimethylammonium bromide (TTAB) + water + octanol system in different concentrations have been studied. In the process, isotropic phase (L1) and nematic calamitic (NC), nematic discotic (ND), hexagonal E and lamellar D anizotropic mesophases have been determined by polarizing microscopy method and partial ternary phase diagram of the system set up. Textural properties of the anisotropic mesophases of the system have been discussed and their birefringence values measured. Mechanical deformation has been applied to the mesophases. The textural properties and the birefringence values have been observed to be changed by the deformation, after and before which changes have been compared.

Polarization mode control of long-wavelength VCSELs by intracavity patterning

DOE PAGES

Long, Christopher Michael; Mickovic, Zlatko; Dwir, Benjamin; ...

2016-04-26

Polarization mode control is enhanced in wafer-fused vertical-cavity surface-emitting lasers emitting at 1310 nm wavelength by etching two symmetrically arranged arcs above the gain structure within the laser cavity. The intracavity patterning introduces birefringence and dichroism, which discriminates between the two polarization states of the fundamental transverse modes. We find that the cavity modifications define the polarization angle at threshold with respect to the crystal axes, and increase the gain anisotropy and birefringence on average, leading to an increase in the polarization switching current. As a result, experimental measurements are explained using the spin-flip model of VCSEL polarization dynamics.

Optical assessment of tissue anisotropy in ex vivo distended rat bladders

NASA Astrophysics Data System (ADS)

Alali, Sanaz; Aitken, Karen J.; Shröder, Annette; Bagli, Darius J.; Alex Vitkin, I.

2012-08-01

Microstructural remodelling in epithelial layers of various hollow organs, including changes in tissue anisotropy, are known to occur under mechanical distension and during disease processes. In this paper, we analyze how bladder distension alters wall anisotropy using polarized light imaging (followed by Mueller matrix decomposition). Optical retardance values of different regions of normal rat bladders under different distension pressures are derived. Then optical coherence tomography is used to measure local bladder wall thicknesses, enabling the calculation of the tissue birefringence maps as a measure of the tissue anisotropy. Selected two-photon microscopy is also performed to better understand the compositional origins of the obtained anisotropy results. The dome region of the bladder shows maximum birefringence when the bladder is distended to high pressures, whereas the ventral remains roughly isotropic during distension. In addition, the average anisotropy direction is longitudinal, along the urethra to dome. The derived wall anisotropy trends are based on birefringence as an intrinsic property of the tissue organization independent of its thickness, to aid in understanding the structure-functions relation in healthy bladders. These new insights into the wall microstructure of ex vivo distending bladders may help improve the functionality of the artificially engineered bladder tissues.

Circularly polarized light to study linear magneto-optics for ferrofluids: θ-scan technique

NASA Astrophysics Data System (ADS)

Meng, Xiangshen; Huang, Yan; He, Zhenghong; Lin, Yueqiang; Liu, Xiaodong; Li, Decai; Li, Jian; Qiu, Xiaoyan

2018-06-01

Circularly polarized light can be divided into two vertically linearly polarized light beams with  ±π/2 phase differences. In the presence of an external magnetic field, when circularly polarized light travels through a ferrofluid film, whose thickness is no more than that of λ/4 plate, magneto-optical, magnetic birefringence and dichroism effects cause the transmitted light to behave as elliptically polarized light. Using angular scan by a continuously rotating polarizer as analyzer, the angular (θ) distribution curve of relative intensity (T) corresponding to elliptically polarized light can be measured. From the T  ‑  θ curve having ellipsometry, the parameters such as the ratio of short to long axis, and angular orientation of the long axis to the vertical field direction can be obtained. Thus, magnetic birefringence and dichroism can be probed simultaneously by measuring magneto-optical, positive or negative birefringence and dichroism features from the transmission mode. The proposed method is called θ-scan technique, and can accurately determine sample stability, magnetic field direction, and cancel intrinsic light source ellipticity. This study may be helpful to further research done to ferrofluids and other similar colloidal samples with anisotropic optics.

An Elimination Method of Temperature-Induced Linear Birefringence in a Stray Current Sensor

PubMed Central

Xu, Shaoyi; Li, Wei; Xing, Fangfang; Wang, Yuqiao; Wang, Ruilin; Wang, Xianghui

2017-01-01

In this work, an elimination method of the temperature-induced linear birefringence (TILB) in a stray current sensor is proposed using the cylindrical spiral fiber (CSF), which produces a large amount of circular birefringence to eliminate the TILB based on geometric rotation effect. First, the differential equations that indicate the polarization evolution of the CSF element are derived, and the output error model is built based on the Jones matrix calculus. Then, an accurate search method is proposed to obtain the key parameters of the CSF, including the length of the cylindrical silica rod and the number of the curve spirals. The optimized results are 302 mm and 11, respectively. Moreover, an effective factor is proposed to analyze the elimination of the TILB, which should be greater than 7.42 to achieve the output error requirement that is not greater than 0.5%. Finally, temperature experiments are conducted to verify the feasibility of the elimination method. The results indicate that the output error caused by the TILB can be controlled less than 0.43% based on this elimination method within the range from −20 °C to 40 °C. PMID:28282953

Polarization Converter with Controllable Birefringence Based on Hybrid All-Dielectric-Graphene Metasurface

NASA Astrophysics Data System (ADS)

Owiti, Edgar O.; Yang, Hanning; Liu, Peng; Ominde, Calvine F.; Sun, Xiudong

2018-02-01

Previous studies on hybrid dielectric-graphene metasurfaces have been used to implement induced transparency devices, while exhibiting high Q-factors based on trapped magnetic resonances. Typically, the transparency windows are single wavelength and less appropriate for polarization conversion structures. In this work, a quarter-wave plate based on a hybrid silicon-graphene metasurface with controllable birefringence is numerically designed. The phenomena of trapped magnetic mode resonance and high Q-factors are modulated by inserting graphene between silicon and silica. This results in a broader transmission wavelength in comparison to the all-dielectric structure without graphene. The birefringence tunability is based on the dimensions of silicon and the Fermi energy of graphene. Consequently, a linear-to-circular polarization conversion is achieved at a high degree of 96%, in the near-infrared. Moreover, the polarization state of the scattered light is switchable between right and left hand circular polarizations, based on an external gate biasing voltage. Unlike in plasmonic metasurfaces, these achievements demonstrate an efficient structure that is free from radiative and ohmic losses. Furthermore, the ultrathin thickness and the compactness of the structure are demonstrated as key components in realizing integrable and CMOS compatible photonic sensors.

Investigations on birefringence effects in polymer optical fiber Bragg gratings

NASA Astrophysics Data System (ADS)

Hu, X.; Sáez-Rodríguez, D.; Bang, O.; Webb, D. J.; Caucheteur, C.

2014-05-01

Step-index polymer optical fiber Bragg gratings (POFBGs) and microstructured polymer optical fiber Bragg gratings (mPOFBGs) present several attractive features, especially for sensing purposes. In comparison to FBGs written in silica fibers, they are more sensitive to temperature and pressure because of the larger thermo-optic coefficient and smaller Young's modulus of polymer materials. (M)POFBGs are most often photowritten in poly(methylmethacrylate) (PMMA) materials using a continuous-wave 325 nm HeCd laser. For the first time to the best of our knowledge, we study photoinduced birefringence effects in (m)POFBGs. To achieve this, highly reflective gratings were inscribed with the phase mask technique. They were then monitored in transmission with polarized light. For this, (m)POF sections a few cm in length containing the gratings were glued to angled silica fibers. Polarization dependent loss (PDL) and differential group delay (DGD) were computed from the Jones matrix eigenanalysis using an optical vector analyser. Maximum values exceeding several dB and a few picoseconds were obtained for the PDL and DGD, respectively. The response to lateral force was finally investigated. As it induces birefringence in addition to the photo-induced one, an increase of the PDL and DGD values were noticed.

A novel Zeonex based oligoporous-core photonic crystal fiber for polarization preserving terahertz applications

NASA Astrophysics Data System (ADS)

Islam, Md. Saiful; Sultana, Jakeya; Dinovitser, Alex; Ng, Brian W.-H.; Abbott, Derek

2018-04-01

A novel waveguide consisting of oligo-porous core photonic crystal fiber (PCF) with a kagome lattice cladding has been designed for highly birefringent and near zero dispersion flattened applications of terahertz waves. The wave guiding properties of the designed PCF including birefringence, dispersion, effective material loss (EML), core power fraction, confinement loss, and modal effective area are investigated using a full vector Finite Element Method (FEM) with Perfectly Matched Layer (PML) absorbing boundary condition. Simulation results demonstrate that an ultra-high birefringence of 0.079, low EML of 0.05 cm-1, higher core power fraction of 44% and negligible confinement loss of 7 . 24 × 10-7 cm-1 can be achieved at 1 THz. Furthermore, for the y-polarization mode a near zero flattened dispersion of 0 . 49 ± 0 . 05 ps/THz/cm is achieved within a broad frequency range of 0.8-1.7 THz. The fabrication of the proposed fiber is feasible using the existing fabrication technology. Due to favorable wave-guiding properties, the proposed fiber has potential for terahertz imaging, sensing and polarization maintaining applications in the terahertz frequency range.

Polarization Converter with Controllable Birefringence Based on Hybrid All-Dielectric-Graphene Metasurface.

PubMed

Owiti, Edgar O; Yang, Hanning; Liu, Peng; Ominde, Calvine F; Sun, Xiudong

2018-02-03

Previous studies on hybrid dielectric-graphene metasurfaces have been used to implement induced transparency devices, while exhibiting high Q-factors based on trapped magnetic resonances. Typically, the transparency windows are single wavelength and less appropriate for polarization conversion structures. In this work, a quarter-wave plate based on a hybrid silicon-graphene metasurface with controllable birefringence is numerically designed. The phenomena of trapped magnetic mode resonance and high Q-factors are modulated by inserting graphene between silicon and silica. This results in a broader transmission wavelength in comparison to the all-dielectric structure without graphene. The birefringence tunability is based on the dimensions of silicon and the Fermi energy of graphene. Consequently, a linear-to-circular polarization conversion is achieved at a high degree of 96%, in the near-infrared. Moreover, the polarization state of the scattered light is switchable between right and left hand circular polarizations, based on an external gate biasing voltage. Unlike in plasmonic metasurfaces, these achievements demonstrate an efficient structure that is free from radiative and ohmic losses. Furthermore, the ultrathin thickness and the compactness of the structure are demonstrated as key components in realizing integrable and CMOS compatible photonic sensors.

Optical properties of large amyloid spherulites

NASA Astrophysics Data System (ADS)

Smith, Michael; Sharp, James

2012-02-01

Amyloid Spherulites, consisting of a central core surrounded by radially oriented birefringent fibres (known as amyloid fibrils), have been found to occur in certain pathologies, such as Alzheimer's disease. Typically ˜5 30 m in diameter they can be observed by optical microscopy and easily distinguished by their characteristic maltese cross pattern, seen when viewed under crossed polarisers. Here we report the existence of much larger amyloid spherulites formed from bovine insulin, which grow under a particular set of conditions (10 mgml-1 BPI, pH ˜2.8, T ˜67^oC, 25mM NaCl) to diameters of up to ˜500 m. These huge spherulites when viewed under crossed polarisers in addition to the maltese cross feature beautiful coloured rings which change with the size and density of the spherulite. Such rings have been observed in other systems such as fish eye lenses and nematic liquid crystal drops and appear to be related to the rather unusual radially oriented birefringence of their internal structure. Using a ray tracing technique we model the optical path of rays through these spherulites. Taking into account refraction and the radially oriented birefringence of the amyloid fibrils, we elucidate the origin of these beautiful patterns.

Characterization of light scattering in nematic droplet-polymer films

NASA Astrophysics Data System (ADS)

Kinugasa, Naoki; Yano, Yuichi; Takigawa, Akio; Kawahara, Hideo

1992-06-01

The optical properties of nematic droplet-polymer films were studied both in the on and off state using Lambert-Beer''s law to characterize their scattering phenomena. For the preparation of the devices, NCAP process was employed with the different diameter, distribution, shape, and density of nematic droplets. Their cell thickness and refractive indices concerning the birefringence of liquid crystals were also controlled. The results showed that the scattering phenomena of nematic droplet-polymer films were likely caused by two types of features. One, related to the surface area of nematic droplets, was the difference of the refractive indices in the interface between liquid crystals and polymer matrix. The other, related to the liquid crystal volume inside the nematic droplets, was the birefringence of liquid crystals. Considering such relations, the extinction coefficient of Lambert-Beer''s law could be described by the sum of the area in the interface multiplied by the difference of the refractive indices between two materials and the liquid crystal volume multiplied by their birefringence. Furthermore, it was found their parallel transmittance in the off state and haze ratio in the on state were well characterized by such extinction coefficient of Lambert-Beer''s law.

Torque Induced on Lipid Microtubules with Optical Tweezers

NASA Astrophysics Data System (ADS)

wichean, T. Na; Charrunchon, S.; Pattanaporkratana, A.; Limtrakul, J.; Chattham, N.

2017-09-01

Chiral Phospholipids are found self-assembled into cylindrical tubules of 500 nm in diameter by helical winding of bilayer stripes under cooling in ethanol and water solution. Theoretical prediction and experimental evidence reported so far confirmed the modulated tilt direction in a helical striped pattern of the tubules. This molecular orientation morphology results in optically birefringent tubules. We investigate an individual lipid microtubule under a single optical trap of 532 nm linearly polarized laser. Spontaneous rotation of a lipid tubule induced by radiation torque was observed with only one sense of rotation caused by chirality of a lipid tubule. Rotation discontinued once the high refractive index axis of a lipid tubule aligned with a polarization axis of the laser. We further explored a lipid tubule under circularly polarized optical trap. It was found that a lipid tubule was continuously rotated confirming the tubule birefringent property. We modified the shape of optical trap by cylindrical lens obtaining an elliptical profile optical trap. A lipid tubule can be aligned along the elongated length of optical trap. We reported an investigation of competition between polarized light torque on a birefringent lipid tubule versus torque from intensity gradient of an elongated optical trap.

Optical anomalies in Biological media; Using naturally occurring birefringence and radiance dependent nonlinear optics to our advantage in the laser treatment of arrhythmias.

NASA Astrophysics Data System (ADS)

Splinter, Robert; Svenson, Robert H.; Sosa, Eduardo; Buchele d'Avila, Andre Luiz; Scanavacca, Mauricio; Pruitt, Ernest; Kasell, Jackie H.

2003-02-01

When irradiating particular biological media in general there will be a range of optical properties to deal with, with respect to the irradiating wavelength, and the respective tissues that make up the organ under treatment or being imaged. In addition to this we saw changing optical properties under influence of denaturization, dehydration and carbonization. We also observed optical nonlinearities that are irradiance dependent, in addition to the birefringence which affects the light distribution throughout the tissue differently than the polarization birefringence used in optical polarization microscopy. In the treatment of ventricular tachycardia with laser photocoagulation the success of the procedure depends on whether sufficient energy has been directed to the relevant region of the myocardium to ablate the entire arrhythmogenic focus. A new high power diode laser operating in the near infrared was used in an animal infarct model and in human arrhythmia ablation. The light distribution measured for Chagasic heart tissues at the diode laser wavelength demonstrated the key potential to create controlled deep photocoagulation lesions. From our observations we may conclude that the diode laser - catheter combination offers significant potential for the elimination of arrhythmia's resulting from Chagas disease.

Orthogonality-breaking sensing model based on the instantaneous Stokes vector and the Mueller calculus

NASA Astrophysics Data System (ADS)

Ortega-Quijano, Noé; Fade, Julien; Roche, Muriel; Parnet, François; Alouini, Mehdi

2016-04-01

Polarimetric sensing by orthogonality breaking has been recently proposed as an alternative technique for performing direct and fast polarimetric measurements using a specific dual-frequency dual-polarization (DFDP) source. Based on the instantaneous Stokes-Mueller formalism to describe the high-frequency evolution of the DFDP beam intensity, we thoroughly analyze the interaction of such a beam with birefringent, dichroic and depolarizing samples. This allows us to confirm that orthogonality breaking is produced by the sample diattenuation, whereas this technique is immune to both birefringence and diagonal depolarization. We further analyze the robustness of this technique when polarimetric sensing is performed through a birefringent waveguide, and the optimal DFDP source configuration for fiber-based endoscopic measurements is subsequently identified. Finally, we consider a stochastic depolarization model based on an ensemble of random linear diattenuators, which makes it possible to understand the progressive vanishing of the detected orthogonality breaking signal as the spatial heterogeneity of the sample increases, thus confirming the insensitivity of this method to diagonal depolarization. The fact that the orthogonality breaking signal is exclusively due to the sample dichroism is an advantageous feature for the precise decoupled characterization of such an anisotropic parameter in samples showing several simultaneous effects.

Effect of grain size on optical transmittance of birefringent polycrystalline ceramics

NASA Astrophysics Data System (ADS)

Wen, Tzu-Chien

Polycrystalline ceramics are increasingly used for fabricating windows and domes for the mid infra-red regime (3-5 mum) due to their superior durability as compared to glass and the lower cost of their fabrication and finishing relative to single crystals without significant compromise in optical properties. Due to the noncubic structure, MgF2 and Al2O3 are birefringent ceramics. Birefringence causes scatter of light at the grain boundaries and diminishes in-line transmittance and optical performance. This dissertation presents experimental results and analyses of the grain-size and wavelength dependence of the in-line transmittance of polycrystalline MgF2 and Al2O3. Chapter 2 presents experimental results and analyses of light transmission in polycrystalline MgF2 as a function of the mean grain size at different wavelengths. The scattering coefficient of polycrystalline MgF 2 increased linearly with the mean grain size and inversely with the square of the wavelength of light. These trends are consistent with theoretical models based on both a limiting form of the Raleigh-Gans-Debye theory of particle scattering and light retardation theories that take refractive-index variations along the light path. Chapter 3 investigates the applicability of particle light scattering theories to light attenuation in birefringent polycrystalline ceramics by measuring light transmittance in a model two-phase system. The system consisted of microspheres of silica dispersed in a solution of glycerol in water. It was found that RGD theory showed the systematic deviation for higher particle volume fraction (φ > 0.2) and larger particle size (d p > 1 mum). This result suggested that light scattering models based on single particle scattering are unlikely to provide viable physical explanation for the effect of grain size on light transmittance in birefringent polycrystalline ceramics due to the high volume fraction in dense polycrystalline ceramics. Chapter 4 analyses light transmission properties of polycrystalline Al 2O3 using theories of wave propagation in random media. Fully dense polycrystalline Al2O3 was fabricated using a pressure filtration method. By obtaining the Delta n2 measured from EBSD, the wave retardation theories of Raman and Viswanathan and Kahan et al. provided upper and lower bounds for the theoretical predictions of light transmittance as a function of mean intercept length.

Localization Methods for a Mobile Robot in Urban Environments

DTIC Science & Technology

2004-10-04

Columbia University, Department of Computer Science, 2001. [30] R. Brown and P. Hwang , Introduction to random signals and applied Kalman filtering, 3rd...sensor. An extended Kalman filter integrates the sensor data and keeps track of the uncertainty associated with it. The second method is based on...errors+ compass/GPS errors corrected odometry pose odometry error estimates zk zk h(x)~ h(x)~ Kalman Filter zk Fig. 4. A diagram of the extended

Enabling technologies for fiber optic sensing

NASA Astrophysics Data System (ADS)

Ibrahim, Selwan K.; Farnan, Martin; Karabacak, Devrez M.; Singer, Johannes M.

2016-04-01

In order for fiber optic sensors to compete with electrical sensors, several critical parameters need to be addressed such as performance, cost, size, reliability, etc. Relying on technologies developed in different industrial sectors helps to achieve this goal in a more efficient and cost effective way. FAZ Technology has developed a tunable laser based optical interrogator based on technologies developed in the telecommunication sector and optical transducer/sensors based on components sourced from the automotive market. Combining Fiber Bragg Grating (FBG) sensing technology with the above, high speed, high precision, reliable quasi distributed optical sensing systems for temperature, pressure, acoustics, acceleration, etc. has been developed. Careful design needs to be considered to filter out any sources of measurement drifts/errors due to different effects e.g. polarization and birefringence, coating imperfections, sensor packaging etc. Also to achieve high speed and high performance optical sensing systems, combining and synchronizing multiple optical interrogators similar to what has been used with computer/processors to deliver super computing power is an attractive solution. This path can be achieved by using photonic integrated circuit (PIC) technology which opens the doors to scaling up and delivering powerful optical sensing systems in an efficient and cost effective way.

New thermotropic chiral nematic polymers. 3. Copolymers containing a cyanobiphenyl group and (S)-(-)-1-phenylethanol or (S)-(-)-1-phenylethylamine

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mastrangelo, J.C.; Chen, S.H.

Thermotropic chiral nematics in thin films on the order of 10 [mu]m possess a unique optical property, selective wavelength reflection, that forms the basis of a number of potential applications including circular polarizers, notch filters, beamsplitters, and so on. Instead of low molar mass chiral nematics, thermotropic copolymers have been actively pursued as an alternative in view of the possibility of achieving long-term mesophase stability and optical characteristics desired for passive device applications. Cyanobiphenyl is a relatively high birefringent group which is known to contribute to the formation of low molar mass liquid crystals; it was found to exhibit amore » nematic mesophase between the glass transition and clearing temperatures in side-chain polyacrylates with spacer lengths in the 2-6 range. However, there exists only one report on the formation of a chiral nematic copolymer with cholesterol as the chiral moiety. Since several chiral building blocks other than cholesterol have been found to possess strong helical twisting powers with selected nematogenic monomers, it would be of interest to explore a cyanobiphenyl group as a building block for the synthesis of new chiral nematic copolymers.« less

Plasma photonics in ICF & HED conditions

NASA Astrophysics Data System (ADS)

Michel, Pierre; Turnbull, David; Divol, Laurent; Pollock, Bradley; Chen, Cecilia Y.; Tubman, Eleanor; Goyon, Clement S.; Moody, John D.

2015-11-01

Interactions between multiple high-energy laser beams and plasma can be used to imprint refractive micro-structures in plasmas via the lasers' ponderomotive force. For example, Inertial confinement fusion (ICF) experiments at the National Ignition Facility already rely on the use of plasma gratings to redirect laser light inside an ICF target and tune the symmetry of the imploded core. More recently, we proposed new concepts of plasma polarizer and waveplate, based on two-wave mixing schemes and laser-induced plasma birefringence. In this talk, we will present new experimental results showing the first demonstration of a fully tunable plasma waveplate, which achieved near-perfect circular laser polarization. We will discuss further prospects for novel ``plasma photonics'' concepts based on two- and four-wave mixing, such as optical switches, bandpass filters, anti-reflection blockers etc. These might find applications in ICF and HED experiments by allowing to manipulate the lasers directly in-situ (i.e. inside the targets), as well as for the design of high power laser systems. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

On the Recommender System for University Library

ERIC Educational Resources Information Center

Fu, Shunkai; Zhang, Yao; Seinminn

2013-01-01

Libraries are important to universities, and they have two primary features: readers as well as collections are highly professional. In this study, based on the experimental study with five millions of users' borrowing records, our discussion covers: (1) the necessity of recommender system for university libraries; (2) collaborative filtering (CF)…

Field testing of a low-cost retrofit filter berm to treat stormwater runoff contaminants.

DOT National Transportation Integrated Search

2008-09-01

The goal of this cooperative effort between MaineDOT and the University of New Hampshire was to test a low-cost : retrofit filter berm that would reduce non-point pollution from highway runoff. The retrofit berm would be easy to : construct using rea...

The Zeeman effect or linear birefringence? VLA polarimetric spectral line observations of H2O masers

NASA Astrophysics Data System (ADS)

Zhao, Jun-Hui; Goss, W. M.; Diamond, P.

We present line profiles of the four Stokes parameters of H2O masers at 22 GHz observed with the VLA in full polarimetric spectral line mode. With careful calibration, the instrumental effects such as linear leakage and the difference of antenna gain between RCP and LCP, can be minimized. Our measurements show a few percent linear polarization. Weak circular polarization was detected at a level of 0.1 percent of the peak intensity. A large uncertainty in the measurements of weak circular polarization is caused by telescope pointing errors. The observed polarization of H2O masers can be interpreted as either the Zeeman effect or linear birefringence.

Local birefringence of the anterior segment of the human eye in a single capture with a full range polarisation-sensitive optical coherence tomography

NASA Astrophysics Data System (ADS)

Li, Qingyun; Karnowski, Karol; Villiger, Martin; Sampson, David D.

2017-04-01

A fibre-based full-range polarisation-sensitive optical coherence tomography system is developed to enable complete capture of the structural and birefringence properties of the anterior segment of the human eye in a single acquisition. The system uses a wavelength swept source centered at 1.3 μm, passively depth-encoded, orthogonal polarisation states in the illumination path and polarisation-diversity detection. Off-pivot galvanometer scanning is used to extend the imaging range and compensate for sensitivity drop-off. A Mueller matrix-based method is used to analyse data. We demonstrate the performance of the system and discuss issues relating to its optimisation.

Scattering of a cross-polarized linear wave by a soliton at an optical event horizon in a birefringent nanophotonic waveguide.

PubMed

Ciret, Charles; Gorza, Simon-Pierre

2016-06-15

The scattering of a linear wave on an optical event horizon, induced by a cross-polarized soliton, is experimentally and numerically investigated in integrated structures. The experiments are performed in a dispersion-engineered birefringent silicon nanophotonic waveguide. In stark contrast with copolarized waves, the large difference between the group velocity of the two cross-polarized waves enables a frequency conversion almost independent of the soliton wavelength. It is shown that the generated idler is only shifted by 10 nm around 1550 nm over a pump tuning range of 350 nm. Simulations using two coupled full vectorial nonlinear Schrödinger equations fully support the experimental results.

Transparent EuTiO3 films: a possible two-dimensional magneto-optical device

NASA Astrophysics Data System (ADS)

Bussmann-Holder, Annette; Roleder, Krystian; Stuhlhofer, Benjamin; Logvenov, Gennady; Lazar, Iwona; Soszyński, Andrzej; Koperski, Janusz; Simon, Arndt; Köhler, Jürgen

2017-01-01

The magneto-optical activity of high quality transparent thin films of insulating EuTiO3 (ETO) deposited on a thin SrTiO3 (STO) substrate, both being non-magnetic materials, are demonstrated to be a versatile tool for light modulation. The operating temperature is close to room temperature and allows for multiple device engineering. By using small magnetic fields birefringence of the samples can be switched off and on. Similarly, rotation of the sample in the field can modify its birefringence Δn. In addition, Δn can be increased by a factor of 4 in very modest fields with simultaneously enhancing the operating temperature by almost 100 K.

Chirped fiber Bragg grating written in highly birefringent fiber in simultaneous strain and temperature monitoring.

PubMed

Bieda, Marcin S; Sobotka, Piotr; Woliński, Tomasz R

2017-02-20

A new sensor configuration is proposed for simultaneous strain and temperature monitoring in a composite material that is based on a chirped fiber Bragg grating (CFBG) written in a highly birefringent (HB) polarization-maintaining fiber. The sensor is designed in the reflective configuration in which the CFBG acts both as a reflector and a sensing element. Since CFBG and HB fiber induce changes in the state of polarization (SOP), interference between polarization modes in the reflected spectrum is observed and analyzed. We used a simple readout setup to enable fast, linear operation of strain sensing as well simultaneous strain and temperature measurements in the composite.

An integrated study of seismic anisotropy and the natural fracture system at the Conoco Borehole Test Facility, Kay County, Oklahoma

DOE Office of Scientific and Technical Information (OSTI.GOV)

Queen, J.H.; Rizer, W.D.

1990-07-10

A significant body of published work has developed establishing fracture-related seismic anisotropy as an observable effect. To further the understanding of seismic birefringence techniques in characterizing natural fracture systems at depth, an integrated program of seismic and geologic measurements has been conducted at Conoco's Borehole Test Facility in Kay County, Oklahoma. Birefringence parameters inferred from the seismic data are consistent with a vertical fracture model of density 0.04 striking east-northeast. That direction is subparallel to a fracture set mapped both on the surface and from subsurface data, to the in situ maximum horizontal stress, and to the inferred microfabric.

Mapping of polycrystalline films of biological fluids utilizing the Jones-matrix formalism

NASA Astrophysics Data System (ADS)

Ushenko, Vladimir A.; Dubolazov, Alexander V.; Pidkamin, Leonid Y.; Sakchnovsky, Michael Yu; Bodnar, Anna B.; Ushenko, Yuriy A.; Ushenko, Alexander G.; Bykov, Alexander; Meglinski, Igor

2018-02-01

Utilizing a polarized light approach, we reconstruct the spatial distribution of birefringence and optical activity in polycrystalline films of biological fluids. The Jones-matrix formalism is used for an accessible quantitative description of these types of optical anisotropy. We demonstrate that differentiation of polycrystalline films of biological fluids can be performed based on a statistical analysis of the distribution of rotation angles and phase shifts associated with the optical activity and birefringence, respectively. Finally, practical operational characteristics, such as sensitivity, specificity and accuracy of the Jones-matrix reconstruction of optical anisotropy, were identified with special emphasis on biomedical application, specifically for differentiation of bile films taken from healthy donors and from patients with cholelithiasis.

The collagen structure of equine articular cartilage, characterized using polarization-sensitive optical coherence tomography

NASA Astrophysics Data System (ADS)

Ugryumova, Nadya; Attenburrow, Don P.; Winlove, C. Peter; Matcher, Stephen J.

2005-08-01

Optical coherence tomography and polarization-sensitive optical coherence tomography images of equine articular cartilage are presented. Measurements were made on intact joint surfaces. Significant (e.g. × 2) variations in the intrinsic birefringence were found over spatial scales of a few millimetres, even on samples taken from young (18 month) animals that appeared visually homogeneous. A comparison of data obtained on a control tissue (equine flexor tendon) further suggests that significant variations in the orientation of the collagen fibres relative to the plane of the joint surface exist. Images of visually damaged cartilage tissue show characteristic features both in terms of the distribution of optical scatterers and of the birefringent components.

Polarization-sensitive optical coherence tomography-based imaging, parameterization, and quantification of human cartilage degeneration

NASA Astrophysics Data System (ADS)

Brill, Nicolai; Wirtz, Mathias; Merhof, Dorit; Tingart, Markus; Jahr, Holger; Truhn, Daniel; Schmitt, Robert; Nebelung, Sven

2016-07-01

Polarization-sensitive optical coherence tomography (PS-OCT) is a light-based, high-resolution, real-time, noninvasive, and nondestructive imaging modality yielding quasimicroscopic cross-sectional images of cartilage. As yet, comprehensive parameterization and quantification of birefringence and tissue properties have not been performed on human cartilage. PS-OCT and algorithm-based image analysis were used to objectively grade human cartilage degeneration in terms of surface irregularity, tissue homogeneity, signal attenuation, as well as birefringence coefficient and band width, height, depth, and number. Degeneration-dependent changes were noted for the former three parameters exclusively, thereby questioning the diagnostic value of PS-OCT in the assessment of human cartilage degeneration.

Structural, spectral and birefringence studies of semiorganic nonlinear optical single crystal: Calcium5-sulfosalicylate

NASA Astrophysics Data System (ADS)

Shalini, D.; Kalainathan, S.; Ambika, V. Revathi; Hema, N.; Jayalakshmi, D.

2017-11-01

Semi-organic nonlinear optical crystal Calcium5-Sulfosalicylate (CA5SS) was grown by slow evaporation solution growth technique. The cell parameters and molecular structure of the grown crystal were studied by single crystal x-ray diffraction analysis. The presence of various functional groups of the grown crystal was confirmed using Fourier transform infrared (FT-IR), Fourier transform Raman (FT-Raman) analysis. UV-Visible spectrum shows that CA5SS crystals have high transmittance in the range of 330-900 nm. The refractive index, birefringence and transient photoluminescence properties of the grown crystal were analyzed. The frequency doubling of the grown crystal (CA5SS) were studied and compared with that of KDP.

Fine tuning of the dichroic behavior of Bragg reflectors based on anisotropically nanostructured silicon

NASA Astrophysics Data System (ADS)

Diener, J.; Künzner, N.; Kovalev, D.; Gross, E.; Koch, F.; Fujii, M.

2003-05-01

Electro-chemical etching of heavily doped, (110) oriented, p+ (boron) doped silicon wafers results in porous silicon (PSi) layers which exhibit a strong in-plane anisotropy of the refractive index (birefringence). Single- and multiple layers of anisotropically nanostructured silicon (Si) have been fabricated and studied by polarization-resolved reflection and transmission measurements. Dielectric stacks of birefringent PSi acting as distributed Bragg reflectors have two distinct reflection bands depending on the polarization of the incident linearly polarized light. This effect is caused by a three-dimensional (in plane and in-depth) variation of the refraction index. The possibility of fine tuning the two orthogonally polarized reflection bands and their spectral splitting is demonstrated.

Exceptionally large magneto-optical response in dispersions of plate-like nanocrystallites and magnetic nanoparticles

NASA Astrophysics Data System (ADS)

May, Kathrin; Eremin, Alexey; Stannarius, Ralf; Szabó, Balázs; Börzsönyi, Tamás; Appel, Ingo; Behrens, Silke; Klein, Susanne

2017-06-01

We introduce a binary colloidal system with an exceptionally strong magneto-optical response. Its induced optical birefringence at even low magnetic fields (in the mT range) reaches a value with the same order of magnitude as that of nematic liquid crystals. This system is based on a binary mixture of plate-like, non-magnetic pigment nanoparticles and a small volume fraction (< 1 v %) of spherical magnetic nanoparticles. In the field-free state, the suspension is isotropic. Birefringence is caused by an alignment of the pigment platelets, commanded by shape-anisotropic agglomerates of the magnetic nanoparticles in an external magnetic field. We give a semiquantitative discussion about this.

THE ROLE OF THREE CYTOPLASMIC FIBERS IN BHK-21 CELL MOTILITY

PubMed Central

Goldman, Robert D.

1971-01-01

Microtubule breakdown in the presence of 5 or 40 µg/ml of colchicine is observed in BHK-21/C13 fibroblast-like cells. Several morphological and physiological effects are noted in the absence of microtubules: (a) the cells transform from fibroblast-like to epithelial-like cells; (b) the normal pattern of intracellular birefringence changes and a juxtanuclear cap of birefringent filaments is formed; (c) time-lapse cinematography demonstrates that cell locomotion is inhibited in colchicine-treated cells, even though membrane ruffling persists. The results are discussed in terms of the specific roles of microtubules in cultured cell motility and possible functional relationships of the three types of cytoplasmic fibers seen in BHK-21 cells. PMID:4942774

Wide-field imaging of birefringent synovial fluid crystals using lens-free polarized microscopy for gout diagnosis

NASA Astrophysics Data System (ADS)

Zhang, Yibo; Lee, Seung Yoon Celine; Zhang, Yun; Furst, Daniel; Fitzgerald, John; Ozcan, Aydogan

2016-06-01

Gout is a form of crystal arthropathy where monosodium urate (MSU) crystals deposit and elicit inflammation in a joint. Diagnosis of gout relies on identification of MSU crystals under a compensated polarized light microscope (CPLM) in synovial fluid aspirated from the patient’s joint. The detection of MSU crystals by optical microscopy is enhanced by their birefringent properties. However, CPLM partially suffers from the high-cost and bulkiness of conventional lens-based microscopy, and its relatively small field-of-view (FOV) limits the efficiency and accuracy of gout diagnosis. Here we present a lens-free polarized microscope which adopts a novel differential and angle-mismatched polarizing optical design achieving wide-field and high-resolution holographic imaging of birefringent objects with a color contrast similar to that of a standard CPLM. The performance of this computational polarization microscope is validated by imaging MSU crystals made from a gout patient’s tophus and steroid crystals used as negative control. This lens-free polarized microscope, with its wide FOV (>20 mm2), cost-effectiveness and field-portability, can significantly improve the efficiency and accuracy of gout diagnosis, reduce costs, and can be deployed even at the point-of-care and in resource-limited clinical settings.

Optical-strain characteristics of anisotropic polymer films fabricated from a liquid crystal diacrylate

NASA Astrophysics Data System (ADS)

Escuti, Michael J.; Cairns, Darran R.; Crawford, Gregory P.

2004-03-01

The optomechanical characteristics of oriented polymer films made from a photopolymerizable liquid crystal diacrylate (BASF LC242) were examined, with general implications for oriented films of similar materials being used and considered for display-component applications. The birefringence of these uniaxial films before and after polymerization was determined by measuring the retardation between crossed polarizers, (resulting in Δn=0.142±0.002 at 633 nm for the cured polymer films). Optical-strain characteristics were also determined by measuring the transmittance of the films between crossed polarizers at two wavelengths (612 and 633 nm) during the application of a monotonically increasing tensile strain. Under the conservative assumption that Poisson's ratio is constant for the relatively small strains in our experiment, we develop a strained-waveplate model to detect changes in birefringence directly from the modulation in transmittance with increasing strain. We show that strain applied along the axis of the polymer chains did not substantially affect the birefringence, and strain applied perpendicularly caused only a slight decrease (˜1% decrease for 10% strain). These results highlight the robustness of fully polymerized reactive mesogen optical films to withstand the moderate strains anticipated during manufacturing processes and in-service deformation caused by bending or impact.

Phase and birefringence aberration correction

DOEpatents

Bowers, Mark; Hankla, Allen

1996-01-01

A Brillouin enhanced four wave mixing phase conjugate mirror corrects phase aberrations of a coherent electromagnetic beam and birefringence induced upon that beam. The stimulated Brillouin scattering (SBS) phase conjugation technique is augmented to include Brillouin enhanced four wave mixing (BEFWM). A seed beam is generated by a main oscillator which arrives at the phase conjugate cell before the signal beams in order to initiate the Brillouin effect. The signal beam which is being amplified through the amplifier chain is split into two perpendicularly polarized beams. One of the two beams is chosen to be the same polarization as some component of the seed beam, the other orthogonal to the first. The polarization of the orthogonal beam is then rotated 90.degree. such that it is parallel to the other signal beam. The three beams are then focused into cell containing a medium capable of Brillouin excitation. The two signal beams are focused such that they cross the seed beam path before their respective beam waists in order to achieve BEFWM or the two signal beams are focused to a point or points contained within the focused cone angle of the seed beam to achieve seeded SBS, and thus negate the effects of all birefringent and material aberrations in the system.

Phase and birefringence aberration correction

DOEpatents

Bowers, M.; Hankla, A.

1996-07-09

A Brillouin enhanced four wave mixing phase conjugate mirror corrects phase aberrations of a coherent electromagnetic beam and birefringence induced upon that beam. The stimulated Brillouin scattering (SBS) phase conjugation technique is augmented to include Brillouin enhanced four wave mixing (BEFWM). A seed beam is generated by a main oscillator which arrives at the phase conjugate cell before the signal beams in order to initiate the Brillouin effect. The signal beam which is being amplified through the amplifier chain is split into two perpendicularly polarized beams. One of the two beams is chosen to be the same polarization as some component of the seed beam, the other orthogonal to the first. The polarization of the orthogonal beam is then rotated 90{degree} such that it is parallel to the other signal beam. The three beams are then focused into cell containing a medium capable of Brillouin excitation. The two signal beams are focused such that they cross the seed beam path before their respective beam waists in order to achieve BEFWM or the two signal beams are focused to a point or points contained within the focused cone angle of the seed beam to achieve seeded SBS, and thus negate the effects of all birefringent and material aberrations in the system. 5 figs.

Needle-based polarization-sensitive OCT of breast tumor (Conference Presentation)

NASA Astrophysics Data System (ADS)

Villiger, Martin; Lorenser, Dirk; McLaughlin, Robert A.; Quirk, Bryden C.; Kirk, Rodney W.; Bouma, Brett E.; Sampson, David D.

2016-03-01

OCT imaging through miniature needle probes has extended the range of OCT and enabled structural imaging deep inside breast tissue, with the potential to assist in the intraoperative assessment of tumor margins. However, in many situations, scattering contrast alone is insufficient to clearly identify and delineate malignant areas. Here, we present a portable, depth-encoded polarization-sensitive OCT system, connected to a miniature needle probe. From the measured polarization states we constructed the tissue Mueller matrix at each sample location and improved the accuracy of the measured polarization states through incoherent averaging before retrieving the depth-resolved tissue birefringence. With the Mueller matrix at hand, additional polarization properties such as depolarization are readily available. We then imaged freshly excised breast tissue from a patient undergoing lumpectomy. The reconstructed local retardation highlighted regions of connective tissue, which exhibited birefringence due to the abundance of collagen fibers, and offered excellent contrast to areas of malignant tissue, which exhibited less birefringence due to their different tissue composition. Results were validated against co-located histology sections. The combination of needle-based imaging with the complementary contrast provided by polarization-sensitive analysis offers a powerful instrument for advanced tissue imaging and has potential to aid in the assessment of tumor margins during the resection of breast cancer.

Correlation of collagen synthesis with polarization-sensitive optical coherence tomography imaging of in vitro human atherosclerosis

NASA Astrophysics Data System (ADS)

Kuo, Wen-Chuan; Shyu, Jeou-Jong; Chou, Nai-Kuan; Lai, Chih-Ming; Tien, En-Kuang; Huang, Huan-Jang; Chou, Chien; Jan, Gwo-Jen

2005-04-01

Atherosclerosis is unquestionably the leading cause of morbidity and mortality in developed countries. In the mean time, the worldwide importance of acute vascular syndromes is increasing. Because collagen fiber is a critical component of atherosclerotic lesions; it constitutes up to 60% of the total atherosclerotic plaque protein. The uncontrolled collagen accumulation leads to arterial stenosis, whereas excessive collagen breakdown weakens plaques thereby making them prone to rupture finally. Thus, in this study, we present the first application, to our knowledge, of using polarization-sensitive optical coherence tomography (PS-OCT) in human atherosclerosis. We demonstrate this technique for imaging of intensity, birefringence, and fast-axis orientation simultaneously in atherosclerotic plaques. This in vitro study suggests that the birefringence change in plaque is due to the prominent deposition of collagen according to the correlation of PS-OCT images with histological counterpart. Moreover, we can acquire quantitative criteria based on the change of polarization of incident beam to estimate whether the collagen synthesized is "too much" or "not enough". Thus by combining of high resolution intensity imaging and birefringence detection makes PS-OCT could be a potentially powerful tool for early assessment of atherosclerosis appearance and the prediction of plaque rupture in clinic.

Stromal characterization and comparison of odontogenic cysts and odontogenic tumors using picrosirius red stain and polarizing microscopy: A retrospective and histochemical study.

PubMed

Jahagirdar, P B; Kale, A D; Hallikerimath, S

2015-01-01

Odontogenic lesions represent a range of conditions, the features of which probably depend on the stage of induction towards tooth formation reached prior to neoplastic or hamartomatous proliferation. It has been also suggested that inductive changes may allow progression from one type of odontogenic tumor to another. The epithelium also plays an important role in the pathogenesis of these lesions; even stroma is likely to play an equally important role in the pathogenesis and biological behavior. So, this study was performed to investigate, compare, and correlate different types of collagen fibers in odontogenic cysts and odontogenic tumors. Thirty each pre-diagnosed odontogenic cysts and tumors were histochemically analyzed using a special stain (Picrosirius red stain) and polarizing microscopy. Seven cases (99%) of inflammatory cysts exhibited predominantly greenish-yellow birefringence indicating procollagen, intermediate, or pathologic collagen fibers suggestive of loosely packed collagen fibers. Predominant yellowish-orange birefringence exhibited by 21 cases (99%) of developmental cysts was comparable to the yellowish-orange and orangish-red to red birefringence exhibited by odontogenic tumors suggesting tightly packed fibers. The Picrosirius red stain in conjunction with polarizing microscopy serves as a specific and sensitive tool in characterizing collagen fibers in odontogenic cysts and odontogenic tumor.

Polarization properties of amyloid-beta plaques in Alzheimer's disease (Conference Presentation)

NASA Astrophysics Data System (ADS)

Baumann, Bernhard; Wöhrer, Adelheid; Ricken, Gerda; Pircher, Michael; Kovacs, Gabor G.; Hitzenberger, Christoph K.

2016-03-01

In histopathological practice, birefringence is used for the identification of amyloidosis in numerous tissues. Amyloid birefringence is caused by the parallel arrangement of fibrous protein aggregates. Since neurodegenerative processes in Alzheimer's disease (AD) are also linked to the formation of amyloid-beta (Aβ) plaques, optical methods sensitive to birefringence may act as non-invasive tools for Aβ identification. At last year's Photonics West, we demonstrated polarization-sensitive optical coherence tomography (PS-OCT) imaging of ex vivo cerebral tissue of advanced stage AD patients. PS-OCT provides volumetric, structural imaging based on both backscatter contrast and tissue polarization properties. In this presentation, we report on polarization-sensitive neuroimaging along with numerical simulations of three-dimensional Aβ plaques. High speed PS-OCT imaging was performed using a spectral domain approach based on polarization maintaining fiber optics. The sample beam was interfaced to a confocal scanning microscope arrangement. Formalin-fixed tissue samples as well as thin histological sections were imaged. For comparison to the PS-OCT results, ray propagation through plaques was modeled using Jones analysis and various illumination geometries and plaque sizes. Characteristic polarization patterns were found. The results of this study may not only help to understand PS-OCT imaging of neuritic Aβ plaques but may also have implications for polarization-sensitive imaging of other fibrillary structures.

Differentiating characteristic microstructural features of cancerous tissues using Mueller matrix microscope.

PubMed

Wang, Ye; He, Honghui; Chang, Jintao; Zeng, Nan; Liu, Shaoxiong; Li, Migao; Ma, Hui

2015-12-01

Polarized light imaging can provide rich microstructural information of samples, and has been applied to the detections of various abnormal tissues. In this paper, we report a polarized light microscope based on Mueller matrix imaging by adding the polarization state generator and analyzer (PSG and PSA) to a commercial transmission optical microscope. The maximum errors for the absolute values of Mueller matrix elements are reduced to 0.01 after calibration. This Mueller matrix microscope has been used to examine human cervical and liver cancerous tissues with fibrosis. Images of the transformed Mueller matrix parameters provide quantitative assessment on the characteristic features of the pathological tissues. Contrast mechanism of the experimental results are backed up by Monte Carlo simulations based on the sphere-cylinder birefringence model, which reveal the relationship between the pathological features in the cancerous tissues at the cellular level and the polarization parameters. Both the experimental and simulated data indicate that the microscopic transformed Mueller matrix parameters can distinguish the breaking down of birefringent normal tissues for cervical cancer, or the formation of birefringent surrounding structures accompanying the inflammatory reaction for liver cancer. With its simple structure, fast measurement and high precision, polarized light microscope based on Mueller matrix shows a good diagnosis application prospect. Copyright © 2015 Elsevier Ltd. All rights reserved.

Wide-field imaging of birefringent synovial fluid crystals using lens-free polarized microscopy for gout diagnosis

PubMed Central

Zhang, Yibo; Lee, Seung Yoon Celine; Zhang, Yun; Furst, Daniel; Fitzgerald, John; Ozcan, Aydogan

2016-01-01

Gout is a form of crystal arthropathy where monosodium urate (MSU) crystals deposit and elicit inflammation in a joint. Diagnosis of gout relies on identification of MSU crystals under a compensated polarized light microscope (CPLM) in synovial fluid aspirated from the patient’s joint. The detection of MSU crystals by optical microscopy is enhanced by their birefringent properties. However, CPLM partially suffers from the high-cost and bulkiness of conventional lens-based microscopy, and its relatively small field-of-view (FOV) limits the efficiency and accuracy of gout diagnosis. Here we present a lens-free polarized microscope which adopts a novel differential and angle-mismatched polarizing optical design achieving wide-field and high-resolution holographic imaging of birefringent objects with a color contrast similar to that of a standard CPLM. The performance of this computational polarization microscope is validated by imaging MSU crystals made from a gout patient’s tophus and steroid crystals used as negative control. This lens-free polarized microscope, with its wide FOV (>20 mm2), cost-effectiveness and field-portability, can significantly improve the efficiency and accuracy of gout diagnosis, reduce costs, and can be deployed even at the point-of-care and in resource-limited clinical settings. PMID:27356625

Discrepancies between descriptions and illustrations of colours in Congo red-stained amyloid, and explanation of discrepant colours.

PubMed

Howie, Alexander J; Owen-Casey, Mared P

2010-09-01

Congo red-stained sections of amyloid may show various colours between crossed polariser and analyser. The aims were to see how papers described the colours, to compare descriptions with illustrations, and to explain the colours. In 160 papers on Congo red-stained amyloid, the commonest descriptions were 'green birefringence' and 'apple-green birefringence'. In 191 figures in 82 papers, 59 (31%) showed a pure green colour, 62 (32%) showed green and yellow or blue and yellow, 38 (20%) showed green and a colour other than yellow, mostly red, and 32 (17%) showed other colours. Discrepancies between colours reported and illustrated were noted in 127 figures (66%). Most (77) were between green alone in descriptions and green and another colour in figures, and 30 were between green in descriptions and no green at all in figures. Pure green can be seen in ideal conditions, but more often there are green and yellow, explained by strain birefringence, and green and red or other combinations, explained by uncrossing of polariser and analyser. These other anomalous colours are just as characteristic of amyloid as the pure green colour. Many papers on Congo red-stained amyloid appear to describe what is expected theoretically rather than what is actually seen.

Stagnation point flow of wormlike micellar solutions in a microfluidic cross-slot device: effects of surfactant concentration and ionic environment.

PubMed

Haward, Simon J; McKinley, Gareth H

2012-03-01

We employ the techniques of microparticle image velocimetry and full-field birefringence microscopy combined with mechanical measurements of the pressure drop to perform a detailed characterization of the extensional rheology and elastic flow instabilities observed for a range of wormlike micellar solutions flowing through a microfluidic cross-slot device. As the flow rate through the device is increased, the flow first bifurcates from a steady symmetric to a steady asymmetric configuration characterized by a birefringent strand of highly aligned micellar chains oriented along the shear-free centerline of the flow field. At higher flow rates the flow becomes three dimensional and time dependent and is characterized by aperiodic spatiotemporal fluctuations of the birefringent strand. The extensional properties and critical conditions for the onset of flow instabilities in the fluids are highly dependent on the fluid formulation (surfactant concentration and ionic strength) and the resulting changes in the linear viscoelasticity and nonlinear shear rheology of the fluids. By combining the measurements of critical conditions for the flow transitions with the viscometric material properties and the degree of shear-thinning characterizing each test fluid, it is possible to construct a stability diagram for viscoelastic flow of complex fluids in the cross-slot geometry.

A Jones matrix formalism for simulating three-dimensional polarized light imaging of brain tissue.

PubMed

Menzel, M; Michielsen, K; De Raedt, H; Reckfort, J; Amunts, K; Axer, M

2015-10-06

The neuroimaging technique three-dimensional polarized light imaging (3D-PLI) provides a high-resolution reconstruction of nerve fibres in human post-mortem brains. The orientations of the fibres are derived from birefringence measurements of histological brain sections assuming that the nerve fibres—consisting of an axon and a surrounding myelin sheath—are uniaxial birefringent and that the measured optic axis is oriented in the direction of the nerve fibres (macroscopic model). Although experimental studies support this assumption, the molecular structure of the myelin sheath suggests that the birefringence of a nerve fibre can be described more precisely by multiple optic axes oriented radially around the fibre axis (microscopic model). In this paper, we compare the use of the macroscopic and the microscopic model for simulating 3D-PLI by means of the Jones matrix formalism. The simulations show that the macroscopic model ensures a reliable estimation of the fibre orientations as long as the polarimeter does not resolve structures smaller than the diameter of single fibres. In the case of fibre bundles, polarimeters with even higher resolutions can be used without losing reliability. When taking the myelin density into account, the derived fibre orientations are considerably improved. © 2015 The Author(s).

University Research--Reaching Out to the Community.

ERIC Educational Resources Information Center

Coleman, Elizabeth

1994-01-01

Describes three programs that are a result of a bead filtering system used for aquaculture developed in a university setting. Two of the programs described are career-training experiments for high school and junior high school students. (LZ)

Physics Notes

ERIC Educational Resources Information Center

School Science Review, 1972

1972-01-01

Short articles describe a method of introducing the study of simple harmonic motion, and suggest models that are analogues for impedence matching, electrical transformers, and birefringent crystals. (AL)

Evanescent-wave and ambient chiral sensing by signal-reversing cavity ringdown polarimetry.

PubMed

Sofikitis, Dimitris; Bougas, Lykourgos; Katsoprinakis, Georgios E; Spiliotis, Alexandros K; Loppinet, Benoit; Rakitzis, T Peter

2014-10-02

Detecting and quantifying chirality is important in fields ranging from analytical and biological chemistry to pharmacology and fundamental physics: it can aid drug design and synthesis, contribute to protein structure determination, and help detect parity violation of the weak force. Recent developments employ microwaves, femtosecond pulses, superchiral light or photoionization to determine chirality, yet the most widely used methods remain the traditional methods of measuring circular dichroism and optical rotation. However, these signals are typically very weak against larger time-dependent backgrounds. Cavity-enhanced optical methods can be used to amplify weak signals by passing them repeatedly through an optical cavity, and two-mirror cavities achieving up to 10(5) cavity passes have enabled absorption and birefringence measurements with record sensitivities. But chiral signals cancel when passing back and forth through a cavity, while the ubiquitous spurious linear birefringence background is enhanced. Even when intracavity optics overcome these problems, absolute chirality measurements remain difficult and sometimes impossible. Here we use a pulsed-laser bowtie cavity ringdown polarimeter with counter-propagating beams to enhance chiral signals by a factor equal to the number of cavity passes (typically >10(3)); to suppress the effects of linear birefringence by means of a large induced intracavity Faraday rotation; and to effect rapid signal reversals by reversing the Faraday rotation and subtracting signals from the counter-propagating beams. These features allow absolute chiral signal measurements in environments where background subtraction is not feasible: we determine optical rotation from α-pinene vapour in open air, and from maltodextrin and fructose solutions in the evanescent wave produced by total internal reflection at a prism surface. The limits of the present polarimeter, when using a continuous-wave laser locked to a stable, high-finesse cavity, should match the sensitivity of linear birefringence measurements (3 × 10(-13) radians), which is several orders of magnitude more sensitive than current chiral detection limits and is expected to transform chiral sensing in many fields.

Self-Calibration of BICEP1 Three-Year Data and Constraints on Astrophysical Polarization Rotation

NASA Technical Reports Server (NTRS)

Kaufman, J. P.; Miller, N. J.; Shimon, M.; Barkats, D.; Bischoff, C.; Buder, I.; Keating, B. G.; Kovac, J. M.; Ade, P. A. R.; Aikin, R.;

On-sky tests of a polarization grating for visible astronomy

NASA Astrophysics Data System (ADS)

Millar-Blanchaer, Maxwell A.; Moon, Dae-Sik; Graham, James R.; Williams, Michael

2016-08-01

Polarization gratings (PGs) are a type of diffraction grating that take advantage of birefringent liquid crystal polymers to simultaneously act as a polarizing beam splitter and as a spectral dispersive element. Furthermore, PGs are capable of providing high diffraction efficiency (>90%) over a very broad wavelength range. These properties make PGs ideal for spectropolarimetry and/or high throughput, broad wavelength observations for a range of astronomical objects. Here we report on the design and on-sky testing of a prototype spectropolarimeter instrument that employs a PG optimized for operation from 500 nm to 900 nm. The prototype was mounted on a 16-inch telescope at the University of Toronto, where we carried out observations of the polarized twilight sky, a polarized standard star and two spectroscopic standard stars. Using these observations we demonstrate the PG's ability to measure linear polarization fraction and position angle, as well as recover spectra from astronomical objects.

Universal filtered multi-carrier system for asynchronous uplink transmission in optical access network

NASA Astrophysics Data System (ADS)

Kang, Soo-Min; Kim, Chang-Hun; Han, Sang-Kook

2016-02-01

In passive optical network (PON), orthogonal frequency division multiplexing (OFDM) has been studied actively due to its advantages such as high spectra efficiency (SE), dynamic resource allocation in time or frequency domain, and dispersion robustness. However, orthogonal frequency division multiple access (OFDMA)-PON requires tight synchronization among multiple access signals. If not, frequency orthogonality could not be maintained. Also its sidelobe causes inter-channel interference (ICI) to adjacent channel. To prevent ICI caused by high sidelobes, guard band (GB) is usually used which degrades SE. Thus, OFDMA-PON is not suitable for asynchronous uplink transmission in optical access network. In this paper, we propose intensity modulation/direct detection (IM/DD) based universal filtered multi-carrier (UFMC) PON for asynchronous multiple access. The UFMC uses subband filtering to subsets of subcarriers. Since it reduces sidelobe of each subband by applying subband filtering, it could achieve better performance compared to OFDM. For the experimental demonstration, different sample delay was applied to subbands to implement asynchronous transmission condition. As a result, time synchronization robustness of UFMC was verified in asynchronous multiple access system.

Combining Multiple Types of Intelligence to Generate Probability Maps of Moving Targets

DTIC Science & Technology

2013-09-01

normalization coefficient k similar to Demspter-Shafer’s combination rule. d. Mass Mean This rule of combination is the most straightforward one... coefficient , we can state that without normalizing, the updated distribution is: fupdate t   qk k t M 1 qk n k t M        (3.3) 36...Lawrence, KS. Chen, Z. (2003). Bayesian filtering: From Kalman filters to particle filters and beyond. Technical report, McMaster University. Dempster

Intermediate-Band Photometric Luminosity Descrimination for M Stars

NASA Astrophysics Data System (ADS)

Robertson, T. H.; Furiak, N. M.

1995-12-01

Synthetic photometry has been used to design an intermediate-band filter to be used with CCD cameras to facilitate the luminosity classification of M stars. Spectrophotometric data published by Gunn & Stryker (1983) were used to test various bandwidths and centers. Based on these calculations an intermediate-band filter has been purchased. This filter is being used in conjunction with standard BVRI filters to test its effectiveness in luminosity classification of M stars having a wide range of temperatures and different chemical compositions. The results of the theoretical calculations, filter design specifications and preliminary results of the testing program are presented. This research is supported in part by funds provided by Ball State University, The Fund for Astrophysical Research and the Indiana Academy of Science.

DNA accumulation on ventilation system filters in university buildings in Singapore

PubMed Central

Luhung, Irvan; Wu, Yan; Xu, Siyu; Yamamoto, Naomichi; Nazaroff, William W.

2017-01-01

Introduction Biological particles deposit on air handling system filters as they process air. This study reports and interprets abundance and diversity information regarding biomass accumulation on ordinarily used filters acquired from several locations in a university environment. Methods DNA-based analysis was applied both to quantify (via DNA fluorometry and qPCR) and to characterize (via high-throughput sequencing) the microbial material on filters, which mainly processed recirculated indoor air. Results were interpreted in relation to building occupancy and ventilation system operational parameters. Results Based on accumulated biomass, average DNA concentrations per AHU filter surface area across nine indoor locations after twelve weeks of filter use were in the respective ranges 1.1 to 41 ng per cm2 for total DNA, 0.02 to 3.3 ng per cm2 for bacterial DNA and 0.2 to 2.0 ng DNA per cm2 for fungal DNA. The most abundant genera detected on the AHU filter samples were Clostridium, Streptophyta, Bacillus, Acinetobacter and Ktedonobacter for bacteria and Aspergillus, Cladosporium, Nigrospora, Rigidoporus and Lentinus for fungi. Conditional indoor airborne DNA concentrations (median (range)) were estimated to be 13 (2.6–107) pg/m3 for total DNA, 0.4 (0.05–8.4) pg/m3 for bacterial DNA and 2.3 (1.0–5.1) pg/m3 for fungal DNA. Conclusion Conditional airborne concentrations and the relative abundances of selected groups of genera correlate well with occupancy level. Bacterial DNA was found to be more responsive than fungal DNA to differences in occupancy level and indoor environmental conditions. PMID:29023520

Adaptive Combinatorial Multimodal Sensing Physics & Methods

DTIC Science & Technology

2012-03-07

group on doped Q-dot studies • NRL: support in-house polarimetry filter research effort • DARPA: coordinate w/Nibir Dhar in sensors -- their...International: • National Cheng Kung University, Taiwan: CNTs • Taras Shevchenko University, Kiev, Ukraine: polarimetry Coordination/Conferences

Versatile current-mode universal biquadratic filter using DO-CCIIs

NASA Astrophysics Data System (ADS)

Chen, Hua-Pin

2013-07-01

In this article, a new three-input and three-output versatile current-mode universal biquadratic filter is proposed. The circuit employs three dual-output current conveyors (DO-CCIIs) as active elements together with three grounded resistors and two grounded capacitors. The proposed configuration exhibits low-input impedance and high-output impedance which is important for easy cascading in the current-mode operations. It can be used as either a single-input and three-output or three-input and two-output circuit. In the operation of single-input and three-output circuit, the lowpass, bandpass and bandreject can be realised simultaneously, while the highpass filtering response can be easily obtained by connecting appropriated output current directly without using addition stages. In the operation of three-input and two-output circuit, all five generic filtering functions can be easily realised by selecting different three input current signals. The filter permits orthogonal controllability of the quality factor and resonance angular frequency, and no component matching conditions or inverting-type input current signals are imposed. All the passive and active sensitivities are low. HSPICE simulation results based on using TSMC 0.18 µm 1P6M CMOS process technology and supply voltages ±0.9 V to verify the theoretical analysis.

Singular structure of Mueller matrices images of biological crystal networks for diagnostic human tissues pathological changes

NASA Astrophysics Data System (ADS)

Sakhnovskiy, M. Y.; Ushenko, V. A.

2013-09-01

The process of converting of laser radiation by optically anisotropic crystals of biological networks are singular in the sense of total (simultaneous) of mechanisms of orientation and phase (birefringence) anisotropy the formation of polarization-inhomogeneous field of scattered radiation. This work is aimed at developing a method of polarization selection mechanisms of blood plasma polycrystalline networks anisotropy. The relationship between statistics, correlation and fractal parameters of polarization-inhomogeneous images of blood plasma and by linear dichroism and linear birefringence of polycrystalline networks albumin and globulin was found. The criteria of differentiation and diagnostic images of polarization-inhomogeneous plasma samples of the control group (donor) and a group of patients with malignant changes of breast tissue was identified.

The sign of the polarizability anisotropy of polar molecules is obtained from the terahertz Kerr effect

NASA Astrophysics Data System (ADS)

Kampfrath, Tobias; Wolf, Martin; Sajadi, Mohsen

2018-01-01

The terahertz Kerr effect (TKE) of polar molecular vapors is reported. The birefringence signal of fluoroform appears with opposite polarity compared to acetonitrile and water. This behavior is a hallmark of the opposite sign of a new molecular polarizability anisotropy ΔαTKE =αzz - (αxx +αyy) / 2 , with αzz being the polarizability along the permanent dipole moment. As the excitation of the rotational states orients the permanent dipoles along the terahertz electric field, the orientation is translated into an optical birefringence proportional to ΔαTKE . Thus, the sign of ΔαTKE is imprinted onto the TKE signal, providing novel insights into the polarizability tensor of water.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Abe, T., E-mail: kikutani.t.aa@m.titech.ac.jp; Takarada, W., E-mail: kikutani.t.aa@m.titech.ac.jp; Kikutani, T., E-mail: kikutani.t.aa@m.titech.ac.jp

Effect of pre-annealing on stress and birefringence behavior of poly(ethylene naphthalate) (PEN) films during stretching and relaxation processes was investigated. Amorphous and non-oriented PEN films were pre-annealed under the conditions of different temperatures and periods. The pre-annealed films were stretched uniaxially or equi-biaxially and then relaxed at fixed length. It was found that pre-annealing did not cause any notable change for the initial behavior of refractive indices variation, whereas the behaviors after necking were significantly affected. Through the comparison between in-plane and out-of-plane birefringence and the analysis of wide-angle x-ray diffraction patterns of drawn films of both stretching modes, itmore » was confirmed that the orientation of naphthalene ring in the film plane was enhanced by pre-annealing.« less

Stimulated Brillouin scattering in highly birefringent multimode tapered chalcogenide photonic crystal fiber for distributed optical sensors (Retraction Notice)

NASA Astrophysics Data System (ADS)

Baili, Amira; Cherif, Rim; Zghal, Mourad

2016-09-01

This paper, originally published on September 15, 2016, was retracted from the SPIE Digital Library on October 5, 2016, due to a high degree of similarity between specific portions of the text of the paper to the following publications: J. Tchahame, J. Beugnot, A. Kudlinski, and T. Sylvestre, "Multimode Brillouin spectrum in a long tapered birefringent photonic crystal fiber," Opt. Lett. 40, 4281-4284 (2015). doi: 10.1364/OL.40.004281 W. W. Ke, X. J. Wang and X. Tang, "Stimulated Brillouin Scattering Model in Multi-Mode Fiber Lasers," in IEEE Journal of Selected Topics in Quantum Electronics, vol. 20, no. 5, pp. 305-314, Sept.-Oct. 2014. doi: 10.1109/JSTQE.2014.2303256.

Polarization-interference mapping of biological fluids polycrystalline films in differentiation of weak changes of optical anisotropy

NASA Astrophysics Data System (ADS)

Ushenko, V. O.; Vanchuliak, O.; Sakhnovskiy, M. Y.; Dubolazov, O. V.; Grygoryshyn, P.; Soltys, I. V.; Olar, O. V.; Antoniv, A.

2017-09-01

The theoretical background of the azimuthally stable method of polarization-interference mapping of the histological sections of the biopsy of the prostate tissue on the basis of the spatial frequency selection of the mechanisms of linear and circular birefringence is presented. The diagnostic application of a new correlation parameter - complex degree of mutual anisotropy - is analytically substantiated. The method of measuring coordinate distributions of complex degree of mutual anisotropy with further spatial filtration of their high- and low-frequency components is developed. The interconnections of such distributions with parameters of linear and circular birefringence of prostate tissue histological sections are found. The objective criteria of differentiation of benign and malignant conditions of prostate tissue are determined.

Refractive index and birefringence of 2H silicon carbide

NASA Technical Reports Server (NTRS)

Powell, J. A.

1972-01-01

The refractive indices of 2H SiC were measured over the wavelength range 435.8 to 650.9 nm by the method of minimum deviation. At the wavelength lambda = 546.1 nm, the ordinary index n sub 0 was 2.6480 and the extraordinary index n sub e was 2.7237. The estimated error (standard deviation) in the measured values is 0.0006 for n sub 0 and 0.0009 for n sub e. The experimental data were curve fitted to the Cauchy equation for the index of refraction as a function of wavelength. The birefringence of 2H SiC was found to vary from 0.0719 at lambda = 650.9 nm to 0.0846 at lambda = 435.8 nm.