Polarization Interferometer Research Articles

Rotation measure synthesis study and polarized properties of PSR J1745−2900 at 7 mm

We present results of interferometric polarization observations of the recently discovered magnetar J1745-2900 in the vicinity of the Galactic center. The observations were made with the Karl G. Jansky Very Large Array (VLA) on 21 February 2014 in the range 40-48 GHz. The full polarization mode and A configuration of the array were used. The average total and linearly polarized flux density of the pulsar amounts to 2.3$\pm$0.31 mJy/beam and 1.5$\pm$0.2 mJy/beam, respectively. Analysis shows a rotation measure (RM) of (-67$\pm$3)x10$^3$ rad/m$^2$, which is in a good agreement with previous measurements at longer wavelengths. These high frequency observations are sensitive to RM values of up to ~2x10$^7$ rad/m$^2$. However, application of the Faraday RM synthesis technique did not reveal other significant RM components in the pulsar emission. This supports an external nature of a single thin Faraday-rotating screen which should be located close to the Galactic center. The Faraday corrected intrinsic electric vector position angle is 16$\pm$9 deg East of North, and coincides with the position angle of the pulsar's transverse velocity. All measurements of the pulsar's RM value to date, including the one presented here, well agree within errors, which points towards a steady nature of the Faraday-rotating medium.

Coherence imaging for ion temperature and flow measurements in a low-temperature helicon plasma source

This paper describes a coherence imaging system designed for spectroscopic Doppler measurements of ion light in a low-temperature (Te < 10 eV) helicon-produced argon plasma. Observation of the very small Doppler broadening of the Ar II 488 nm emission line requires very high spectral resolution, or equivalently, very large interferometric optical path delay (comparable with the coherence length of the emission line). For these polarization interferometers, this can only be achieved using large thicknesses (100 mm) of birefringent crystal. This poses special design challenges including the application of field-widening techniques and the development of passive thermal stabilization of the optical phase offset. We discuss the measurement principles and the optical design of these systems and present measurements of the line-integrated emissivity, and ion flow and ion temperatures along with tomographic reconstructions of the local values, for a cylindrical low temperature helicon discharge in a linear magnetized device with downstream magnetic mirror. Key results reveal a hollow edge-peaked temperature profile (central temperature ∼0.1 eV) and sheared rigid-body rotational flows and axial flows which are comparable with the ion thermal speed. The emission line brightness, ion temperature and azimuthal ion flows are all found to increase with increased mirror magnetic field strength.

Hyperspectral imaging with a liquid crystal polarization interferometer.

A novel hyperspectral imaging system has been developed that takes advantage of the tunable path delay between orthogonal polarization states of a liquid crystal variable retarder. The liquid crystal is placed in the optical path of an imaging system and the path delay between the polarization states is varied, causing an interferogram to be generated simultaneously at each pixel. A data set consisting of a series of images is recorded while varying the path delay; Fourier transforming the data set with respect to the path delay yields the hyperspectral data-cube. The concept is demonstrated with a prototype imager consisting of a liquid crystal variable retarder integrated into a commercial 640x480 pixel CMOS camera. The prototype can acquire a full hyperspectral data-cube in 0.4 s, and is sensitive to light over a 400 nm to 1100 nm range with a dispersion-dependent spectral resolution of 450 cm(-1) to 660 cm(-1). Similar to Fourier transform spectroscopy, the imager is spatially and spectrally multiplexed and therefore achieves high optical throughput. Additionally, the common-path nature of the polarization interferometer yields a vibration-insensitive device. Our concept allows for the spectral resolution, imaging speed, and spatial resolution to be traded off in software to optimally address a given application. The simplicity, compactness, potential low cost, and software adaptability of the device may enable a disruptive class of hyperspectral imaging systems with a broad range of applications.

Preparation of Poincaré beams with a same-path polarization/spatial-mode interferometer

We present a same-path polarization interferometer that uses two spatial light modulators to encode the most general type of Poincaré beam. We demonstrate this design by presenting new results on the encoding of symmetric C-point polarization singularities using spatial modes with high-order topological charges. We also present new results on composite C-points. These are cases where there are multiple C-points in a single beam obtained by combining two modes with composite optical vortices in orthogonal states of polarization. The measurements show good agreement with the simulations.

Measurement of inhomogeneous absorptive organic media with polarization interferometric confocal microscope

Polarization interferometric confocal microscope has been developed for high-precision measurement, especially for inhomogeneous organic media doped with nonlinear chromophores. The microscope has a novel contrast-enhancing technique: suppressing the background electric field with polarization interferometer. With this technique, the microscope has allowed optical anisotropy detection in a submicron area (400 nm × 400 nm), even with a low-cost and low-power continuous-wave (CW) laser light source. In particular, the microscope clearly distinguishes between isotropic and anisotropic regions. According to polarization interferometric ellipsometry, the microscope produces inspection images showing planer distribution of the optical parameter directly.

Birefringent phase demodulator: application to wave plate characterization.

The scope of this work is to present a phase demodulator that enables the recovery of temporal phase information contained in the phase difference between two signals with different polarizations. This demodulator is a polarization interferometer that may consist only of a uniaxial crystal slab and a polarizer sheet. The phase shift between two orthogonal components of the electric field is translated into space by means of birefringent crystals, which act as demodulators or phase analyzers with great robustness. The experimental scheme utilized is based on a simple conoscopic interference setup. Each portion of the space in which the interference pattern is projected contains not only the unknown temporal phase we want to recover, but also a phase shift due to the uniaxial crystal itself. The underlying idea is developing simultaneous phase shifting with uniaxial crystals. Thus, different phase recovery techniques can be applied in order to maximize their ability to track high-speed signals. Depending on the characteristics of the fringe pattern, it will permit phase recovery via different classical procedures. In order to prove the demodulator under different experimental and signal processing schemes, we employed it for wave plate characterization. The results obtained not only allow some wave plate features such as axes determination and retardance to be characterized, but also prove the working principle and capabilities of the demodulator.

Method of Aerosol Absorption Detection with Photothermal Interferometry

The photothermal interferometry method with higher accuracy and lower uncertainty can directly measure the absorption coefficient of atmospheric aerosols and be unaffected by scattered light. With Jones matrix expression, the math expression of a special polarization interferometer is described. This paper using folded Jamin interferometer, which overcomes the influence of vibration on measuring system. Interference come from light polarization beam with two orthogonal and then combine to one beam, finally aerosol absorption induced refractive index changes can be gotten with four beam of phase orthogonal light. These kinds of styles really improve the stability of system and resolution of the system. Four-channel detections interact with interference fringes, to reduce the light intensity ‘zero drift’ effect on the system. In the laboratory, this device can be sensitivity to the refractive index of air, which have close relation with aerosol absorption index; it shows that the result principally agrees with actual value. This kind of instrument will be used to monitor ambient aerosol absorption and also be sensible for chemical component of suspended particulate matter.

Circular polarization interferometry: circularly polarized modes of cholesteric liquid crystals.

We describe a novel polarization interferometer which permits the determination of the refractive indices for circularly-polarized light. It is based on a Jamin-Lebedeff interferometer, modified with waveplates, and permits us to experimentally determine the refractive indices nL and nR of the respectively left- and right-circularly polarized modes in a cholesteric liquid crystal. Whereas optical rotation measurements only determine the circular birefringence, i.e. the difference (nL - nR), the interferometer also permits the determination of their absolute values. We report refractive indices of a cholesteric liquid crystal in the region of selective (Bragg) reflection as a function of temperature.

Structural and compositional changes in the salivary pellicle induced upon exposure to SDS and STP

Sodium dodecyl sulphate (SDS) and sodium tripolyphosphate (STP) act to remove stained pellicle from dentition and loosen deposits on tooth surfaces that may become cariogenic over time. This study investigated how SDS and STP impact the salivary pellicle adsorbed onto hydroxyapatite and silica sensors using a dual polarisation interferometer and a quartz-crystal microbalance with dissipation. After the pellicle was exposed to SDS and STP the remaining pellicle, although weaker, due to the loss of material, became less dense but with a higher elastic component; suggesting that the viscous component of the pellicle was being removed. This would imply a structural transformation from a soft but dense structured pellicle, to a more diffuse pellicle. In addition, the majority of proteins displaced by both SDS and STP were identified as being acidic in nature; implying that the negatively charged groups of SDS and STP may be responsible for the displacement of the pellicle proteins observed.

One-step Jones matrix polarization holography for extraction of spatially resolved Jones matrix of polarization-sensitive materials.

We propose, for the first time to our knowledge, a method for realizing one-step measurement of two-dimensional Jones matrix parameters of polarization-sensitive materials. This method could be called one-step Jones matrix polarization holography (JMPH). Our theoretical analysis and the experimental results demonstrate that a double-source polarization interferometer combined with angular multiplexing holography make it possible to realize one-step holographic measurements of four spatially resolved Jones matrix parameters. Compared with the existing methods, our one-step JMPH has a simpler optical arrangement and easier measuring procedure. We believe that it will provide a new approach for development of an integrated system suitable for measuring, in real-time, a Jones matrix or transmittance matrix, as well as dynamic polarization imaging.

Characterization of spatial polarization fluctuations in scattered field

We extend the concept of Poincare vector correlations for the characterization of spatial polarization fluctuations of scattered fields. Spatial (rather than temporal) dynamics of polarization in the scattered field is investigated experimentally by detecting instantaneous polarization with a specially designed polarization interferometer. Use of the Poincare-vector correlation in characterization is demonstrated by determining polarization dynamics of three different cases of scattered fields. This confirms usefulness of the proposed technique in diagnosis of scatterers. Under the condition of spatial ergodicity and Gaussian statistics of the scattered field, we replace the ensemble average of the instantaneous field with the space average, and estimate generalized Stokes parameters (GSPs) of the polarization speckles. Results of GSPs are used to obtain spatial correlation of the Poincare vectors.

A source of polarization-entangled photon pairs interfacing quantum memories with telecom photons

We present a source of polarization-entangled photon pairs suitable for the implementation of long-distance quantum communication protocols using quantum memories. Photon pairs with wavelengths 883 nm and 1338 nm are produced by coherently pumping two periodically poled nonlinear waveguides embedded in the arms of a polarization interferometer. Subsequent spectral filtering reduces the bandwidth of the photons to 240 MHz. The bandwidth is well-matched to a quantum memory based on an Nd:YSO crystal, to which, in addition, the center frequency of the 883 nm photons is actively stabilized. A theoretical model that includes the effect of the filtering is presented and accurately fits the measured correlation functions of the generated photons. The model can also be used as a way to properly assess the properties of the source. The quality of the entanglement is revealed by a visibility of in a Bell-type experiment and through the violation of a Bell inequality.

Temporally flat top pulse generation from gain switched semiconductor lasers based on a polarization interferometer with variable transfer function

We propose the use of a polarization based interferometer with variable transfer function for the generation of temporally flat top pulses from gain switched single mode semiconductor lasers. The main advantage of the presented technique is its flexibility in terms of input pulse characteristics, as pulse duration, spectral bandwidth and operating wavelength. Theoretical predictions and experimental demonstrations are presented and the proposed technique is applied to two different semiconductor laser sources emitting in the 1550nm region. Flat top pulses are successfully obtained with input seed pulses with duration ranging from 40ps to 100ps.

Real-time edge detection by cyclic-path polarization interferometer

In a triangular path cyclic interferometer employing a polarizing beam splitter (PBS), the two counterpropagating beams are orthogonally polarized. A sample placed almost equidistant from the PBS is imaged by a lens placed in the path of the emerging beams so that two defocused images of the sample are recorded on a CCD. Using a linear polarizer in the path of the orthogonally polarized imaging beams, it is possible to achieve amplitude subtraction between the two images, resulting in an edge-enhanced image of the sample. The proposed real-time edge-enhancement technique is experimentally demonstrated.

Photoinduced Orientation of Photoresponsive Polymers with N-Benzylideneaniline Derivative Side Groups

Axis-selective photoreaction, photoinduced orientation, and formation of surface relief (SR) gratings of liquid crystalline polymethacrylates comprised of N-benzylideneaniline (NBA) derivative side groups are explored. Irradiating with linearly polarized (LP) 313 nm light generates molecular reorientation of the NBA side groups based on the axis-selective trans–cis–trans photoisomerization and photocleavage of the NBA groups. The in-plane order parameter (S) and birefringence (Δn) are ∼0.53 and ∼0.16, respectively. Furthermore, thermally stimulated amplification of the photoinduced optical anisotropy occurs upon exposing films to LP 313 nm light and subsequently annealing in the liquid crystalline temperature range of the material. The amplified S and Δn values are ∼0.71 and ∼0.21, respectively. Finally, polarization holography using 325 nm He–Cd laser beams with various interferometric polarization conditions demonstrates the formation of SR gratings with a molecularly oriented structure based on the per...

Structural characterisation of parotid and whole mouth salivary pellicles adsorbed onto DPI and QCMD hydroxyapatite sensors

In this study we investigated the differences in the properties of pellicles formed from stimulated parotid saliva (PS), which contains little or no mucin; and stimulated whole mouth saliva (WMS), which contains mainly two types of mucin: MUC5B and MUC7. By contacting WMS and PS with quartz-crystal microbalance with dissipation monitoring (QCM-D) and dual polarisation interferometer (DPI) hydroxyapatite (the main component of enamel) coated sensors, we observed the formation and structure of the respective salivary pellicles. As this was the first time that DPI hydroxyapatite sensors have been used to measure salivary pellicle adsorption; the techniques combined allowed us to measure the hydrated mass, dry mass, thickness and viscoelastic properties of the pellicle; but also to record the density of the PS and WMS formed pellicles. Subsequently, the PS pellicle was shown to form a denser layer than WMS pellicle; which would suggest that the proteins present in PS are also responsible for forming the dense basal layer of the acquired enamel pellicle. Whereas proteins present in the WMS are more likely to help form the softer outer layer of the pellicle. The data presented help to further define the mechanisms leading to the multi-layered structure of the salivary pellicle and demonstrate that salivary composition has an important effect on the structural properties of the adsorbed pellicle.

Photon-number squeezing with a noisy femtosecond fiber laser amplifier source using a collinear balanced detection technique

We experimentally demonstrate photon-number squeezing at 1.55 μm using a noisy erbium-doped fiber amplifier (EDFA). We employ a collinear balanced detection (CBD) technique, where the intensity noise at a specific radio frequency is canceled between two pulse trains. In spite of substantially large excess noise (>10 dB) in an EDFA due to amplified spontaneous emission, we successfully cancel the intensity noise and achieve a shot noise limit at a specific radio frequency with the CBD technique. We exploit two sets of fiber polarization interferometers to generate squeezed light and observe a maximal photon-number squeezing of -2.6 dB.

Accurate determination of the Freédericksz transition threshold using a method based upon precise fluctuation measurements

In this paper, we describe an accurate method for determining the critical threshold of the Fréedericksz transition driven by an electric field. It is based on the measurement of the amplitude of the molecule fluctuations as a function of the voltage difference applied to a planar nematic cell. The precise measurement of the director fluctuations of the liquid crystal is made possible by the use of a very precise and sensitive polarization interferometer. The great advantage of the method is that it does not depend on complex fits as it is usually done in literature.

Testing Leggett's inequality using Aharonov-Casher effect.

Bell's inequality is established based on local realism. The violation of Bell's inequality by quantum mechanics implies either locality or realism or both are untenable. Leggett's inequality is derived based on nonlocal realism. The violation of Leggett's inequality implies that quantum mechanics is neither local realistic nor nonlocal realistic. The incompatibility of nonlocal realism and quantum mechanics has been currently confirmed by photon experiments. In our work, we propose to test Leggett's inequality using the Aharonov-Casher effect. In our scheme, four entangled particles emitted from two sources manifest a two-qubit-typed correlation that may result in the violation of the Leggett inequality, while satisfying the no-signaling condition for spacelike separation. Our scheme is tolerant to some local inaccuracies due to the topological nature of the Aharonov-Casher phase. The experimental implementation of our scheme can be possibly realized by a calcium atomic polarization interferometer experiment.

Local Oscillator Free Frequency Up-Conversion at Millimeter-Wave Band

We have demonstrated all-optical frequency upconversion at millimeter-wave band without using local oscillators. By launching a low bit rate signal into a Fabry-Perot laser diode (FP-LD), a microwave subcarrier is generated based on the four wavelength mixing and injection mode locking. Due to the dynamic charge carrier density response during the injection locking, the wavelength of the leading part of the subcarrier will be red-shifted while that of the falling part will be blue-shifted. By compensating the generated chirp with a suitable negative dispersion device, the time-domain pulses will be compressed and the second harmonic of the subcarrier will be generated. A polarization interferometer is used to further suppress the foundational frequency. In our experiment, a subcarrier of 30.8 and 34.8 GHz is obtained by launching a 2.5-Gb/s NRZ signal into the FP-LD. We also show that the photonic frequency upconversion can go up to ~60 GHz with the proposed scheme.