Scattering Analysis and Efficiency Optimization of Dielectric Pancharatnam-Berry-Phase Metasurfaces.

In this study, the phase modulation ability of a dielectric Pancharatnam-Berry (PB) phase metasurface, consisting of nanofins, is theoretically analyzed. It is generally considered that the optical thickness of the unit cell of a PB-phase metasurface is λ/2, i.e., a half-waveplate for polarization conversion. It is found that the λ/2 is not essential for achieving a full 2π modulation. Nevertheless, a λ/2 thickness is still needed for a high polarization conversion efficiency. Moreover, a gradient phase metasurface is designed. With the help of the particle swarm optimization (PSO) method, the wavefront errors of the gradient phase metasurface are reduced by fine-tuning the rotation angle of the nanofins. The diffraction efficiency of the gradient phase metasurface is thus improved from 73.4% to 87.3%. This design rule can be utilized to optimize the efficiency of phase-type meta-devices, such as meta-deflectors and metalenses.

Miniature Surface Plasmon Polariton Amplitude Modulator by Beat Frequency and Polarization Control.

The miniaturization of modulators keeps pace for the compact devices in optical applications. Here, we present a miniature surface plasmon polariton amplitude modulator (SPPAM) by directing and interfering surface plasmon polaritons on a nanofabricated chip. Our results show that this SPPAM enables two kinds of modulations. The first kind of modulation is controlled by encoding angular-frequency difference from a Zeeman laser, with a beat frequency of 1.66 MHz; the second of modulation is validated by periodically varying the polarization states from a polarization generator, with rotation frequencies of 0.5-10 k Hz. In addition, the normalized extinction ratio of our plasmonic structure reaches 100. Such miniaturized beat-frequency and polarization-controlled amplitude modulators open an avenue for the exploration of ultrasensitive nanosensors, nanocircuits, and other integrated nanophotonic devices.

Fully variable elliptical phase retarder composed of two linear phase retarders.

In this study, a fully variable elliptical phase retarder was developed by combining a variable linear phase retarder and a half-wave plate. All three polarization parameters of the elliptical phase retarder (elliptical phase retardation γ, azimuth angle θ, and ellipticity angle ε) were adjustable. Experimental verification was performed by measuring the polarization parameters with a polarizer-sample-analyzer polarimeter. The polarization parameters were set to γ = 120°, ε = 15°, and θ = 20°. The measurement results, γ = 119.838° ± 0.006°, ε = 14.659° ± 0.002°, and θ = 20.084° ± 0.002°, agreed with theoretical prediction.

Singular observation of the polarization-conversion effect for a gammadion-shaped metasurface.

In this article, the polarization-conversion effects of a gammadion-shaped metasurface in transmission and reflection modes are discussed. In our experiment, the polarization-conversion effect of a gammadion-shaped metasurface is investigated because of the contribution of the phase and amplitude anisotropies. According to our experimental and simulated results, the polarization property of the first-order transmitted diffraction is dominated by linear anisotropy and has weak depolarization; the first-order reflected diffraction exhibits both linear and circular anisotropies and has stronger depolarization than the transmission mode. These results are different from previously published research. The Mueller matrix ellipsometer and polar decomposition method will aid in the investigation of the polarization properties of other nanostructures.

Design of a full-dynamic-range balanced detection heterodyne gyroscope with common-path configuration.

In this article, we propose an optical heterodyne common-path gyroscope which has common-path configuration and full-dynamic range. Different from traditional non-common-path optical heterodyne technique such as Mach-Zehnder or Michelson interferometers, we use a two-frequency laser light source (TFLS) which can generate two orthogonally polarized light with a beat frequency has a common-path configuration. By use of phase measurement, this optical heterodyne gyroscope not only has the capability to overcome the drawback of the traditional interferometric fiber optic gyro: lack for full-dynamic range, but also eliminate the total polarization rotation caused by SMFs. Moreover, we also demonstrate the potential of miniaturizing this gyroscope as a chip device. Theoretically, if we assume that the wavelength of the laser light is 1550nm, the SMFs are 250m in length, and the radius of the fiber ring is 3.5cm, the bias stability is 0.872 deg/hr.

Analytical approach for unique determination of cell parameters and equivalent birefringent parameters of a generally twisted nematic liquid crystal device.

In the measurement of a twisted nematic liquid crystal device (TNLCD) by an optical apparatus, the cell parameters of the TNLCD may result in multiple solutions in the measurement that all agree with the measured data; hence manufacturers cannot find a set of correct solutions from among the ambiguous ones. With the help of the optical equivalence theorem of a unitary optical system, the ambiguity of the measured parameters of a TNLCD, including cell parameters and equivalent birefringent parameters, can be simultaneously removed by an analytical approach using a single-wavelength polarimeter. The procedure for unique determination of the cell parameters is performed using a self-consistent condition to select a set of the correct solutions from all the possible solutions. The proposed method can be applied to characterize a generally TNLCD for which the twisted angle is close to 270° and the liquid crystal phase retardation is over 2π.

Full-field characterization of a twisted nematic liquid-crystal device using equivalence theorem of a unitary optical system.

Based on the equivalence theorem of a unitary optical system, we proposed an analytical approach to characterize the cell parameters of a twisted nematic liquid-crystal device (TNLCD) with full-field resolution. The spatial distribution of three characteristic parameters of a TNLCD was measured by using a polarizer-sample-analyzer imaging polarimeter so that the untwisted phase retardation, cell thickness, and twisted angle of a TNLCD can be directly calculated through the explicit expressions as a function of the characteristic parameters. The measured results agree well with the given values. This method can be implemented for characterization of a TNLCD in the manufacturing process.

Cell parameter measurement of a twisted nematic liquid crystal device using interferometric polarimeter under normal incidence.

Five cell parameters of a twisted nematic liquid crystal device (TNLCD), namely, cell gap, pretilt angle, twisted angle, rubbing angle, and phase retardation are precisely measured by the developed amplitude-sensitive heterodyne polarimeter (ASHP) simultaneously integrated with Yeh and Gu's transfer matrix and Lien's transfer matrix. This proposed method can characterize the five cell parameters under the arrangement of a single wavelength at normal incidence. In contrast to the conventional methods on cell parameter detection either by adopting a multiple wavelength laser beam at normal incidence or by using a single wavelength laser beam under oblique incident to TNLCD, this method presents the advantage of not only having a simple setup but also the possibility to measure simultaneously five cell parameters on the characterization of TNLCD at high speed.

Kinetics of glucose mutarotation assessed by an equal-amplitude paired polarized heterodyne polarimeter.

A dual-frequency equal-amplitude paired polarization heterodyne polarimeter (DEPHP) was set up in order to precisely measure the mutarotation rate constants of D-glucose in tridistilled water. The DEPHP is based on a balanced detector detection scheme for measurement of the optical rotation angle of D-glucose/water solution during the conversion process between alpha-D-glucose and beta-D-glucose while in a nonequilibrium state. The DEPHP can perform shot-noise-limited detection, so that the total optical rotation angle together with the mutarotation rate constants of alpha-D-glucose and beta-D-glucose conversion can be measured with high sensitivity. In this experiment, the sensitivity of the optical rotation angle measurement was 8.3 x 10(-5) deg/cm, while the total (k), forward (k(1)) and reverse (k(2)) mutarotation rate constants of D-glucose were found to be k = 7.67 x 10(-5) s(-1), k(1) = 2.76 x 10(-5) s(-1), and k(2) = 4.91 x 10(-5) s(-1), respectively, in tridistilled water. Moreover, using the DEPHP, we can measure the specific rotation angles of alpha-D-glucose and beta-D-glucose in water at 632.8 nm. They were 105 degrees and 12 degrees, respectively. Finally, the detection sensitivity of the DEPHP system is also discussed.

Paired circularly polarized heterodyne ellipsometer.

We develop a paired circularly polarized heterodyne ellipsometer (PCPHE), in which a heterodyne interferometer based on a two-frequency circularly polarized laser beam is set up. It belongs to an amplitude-sensitive ellipsometer that is able to provide not only a wider dynamic range of polarization modulation frequency but also a higher detection sensitivity than that of a conventional photometric ellipsometer. A real-time and precise measurement of ellipsometric parameters, which demonstrated an accuracy of less than 1 nm on thickness measurement of SiO(2) thin film deposited on silicon substrate, can be applied with the PCPHE.

Quantitative measurement of binding kinetics in sandwich assay using a fluorescence detection fiber-optic biosensor.

Fiber-optic biosensors have been studied intensively because they are very useful and important tools for monitoring biomolecular interactions. Here we describe a fluorescence detection fiber-optic biosensor (FD-FOB) using a sandwich assay to detect antibody-antigen interaction. In addition, the quantitative measurement of binding kinetics, including the association and dissociation rate constants for immunoglobulin G (IgG)/anti-mouse IgG, is achieved, indicating 0.38 x 10(6) M(-1) s(-1) for k(a) and 3.15 x 10(-3) s(-1) for k(d). These constants are calculated from the fluorescence signals detected on fiber surface only where the excited evanescent wave can be generated. Thus, a confined fluorescence-detecting region is achieved to specifically determine the binding kinetics at the vicinity of the interface between sensing materials and uncladded fiber surface. With this FD-FOB, the mathematical deduction and experimental verification of the binding kinetics in a sandwich immunoassay provide a theoretical basis for measuring rate constants and equilibrium dissociation constants. A further measurement to study the interaction between human heart-type fatty acid-binding protein and its antibody gave the calculated kinetic constants k(a), k(d), and K(D) as 8.48 x 10(5) M(-1) s(-1), 1.7 x 10(-3) s(-1), and 2.0 nM, respectively. Our study is the first attempt to establish a theoretical basis for the florescence-sensitive immunoassay using a sandwich format. Moreover, we demonstrate that the FD-FOB as a high-throughput biosensor can provide an alternative to the chip-based biosensors to study real-time biomolecular interaction.

Dual-frequency heterodyne ellipsometer for characterizing generalized elliptically birefringent media.

This research proposed a dual-frequency heterodyne ellipsometer (DHE) in which a dual-frequency collinearly polarized laser beam with equal amplitude and zero phase difference between p- and s-polarizations is setup. It is based on the polarizer-sample-analyzer, PSA configuration of the conventional ellipsometer. DHE enables to characterize a generalized elliptical phase retarder by treating it as the combination of a linear phase retarder and a polarization rotator. The method for measuring elliptical birefringence of an elliptical phase retarder based on the equivalence theorem of an unitary optical system was derived and the experimental verification by use of DHE was demonstrated too. The experimental results show the capability of DHE on characterization of a generalized phase retardation plate accurately.

Requirement of inducible nitric-oxide synthase in lipopolysaccharide-mediated Src induction and macrophage migration.

Previously, we have demonstrated the induction of Src in lipopolysaccharide (LPS)-stimulated macrophages. In this study, we observed that pharmacological blockade or knockout of inducible nitric-oxide synthase (iNOS) reduced LPS-mediated Src induction and macrophage migration. Either SNAP (a NO donor) or 8-Br-cGMP (a cGMP analogue) could rescue these defects in iNOS-null macrophages, which indicated the participation of NO/cGMP in LPS-elicited Src expression and mobilization. In addition, Src family kinase (SFK)-specific inhibitor, PP2, inhibited SNAP- and 8-Br-cGMP-evoked motility implicating the involvement of SFKs downstream of NO/cGMP. Analysis of the expression of SFKs indicated LPS dramatically induced Src, which could be attributable to the increased level of the src transcript. Attenuation of Src by src-specific siRNA reduced LPS- and SNAP-evoked mobilization in Raw264.7 macrophages, and reintroduction of avian Src could rescue their motility. Furthermore, LPS-mediated Src induction led to increased FAK Pi-Tyr-397 and Pi-Tyr-861, which was also iNOS-dependent. With these findings, we concluded that iNOS was important for LPS-mediated macrophage locomotion and Src was a critical player in this process.

High speed interferometric ellipsometer.

A novel high speed interferometric ellipsometer (HSIE) is proposed and demonstrated. It is based on a novel differential-phase decoder which is able to convert the phase modulation into amplitude modulation in a polarized heterodyne interferometer. Not only high detection sensitivity but also fast response ability on ellipsometric parameters (EP) measurements based on amplitude-sensitive method is constructed whereas different amplitudes with respect to P and S polarized heterodyne signals in this phase to amplitude modulation conversion is discussed. The ability of HSIE was verified by testing a quarter wave plate while a real time differential-phase detection of a liquid crystal device versus applied voltage by using HSIE was demonstrated too. These results confirm that HSIE is able to characterize the optical property of specimen in terms of EP at high speed and high detection sensitivity experimentally.

Degrees of polarization and coherence of paired linear polarized laser beam by scattering glass plates measured using optical coherent ellipsometer.

An accurate optical coherent ellipsometer (OCE) is proposed and setup in which a two-frequency paired linear polarized laser beam is integrated with a common-path heterodyne interferometer. This OCE is able to precisely measure the optical properties of scattering specimen by measuring ellipsometric parameters (Psi, Delta). In the mean time the degree of polarization P, and degree of coherence Chi of incident two-frequency linear polarized laser beam are measured too. In the experiment, both smooth and ground BK7 glass plates were tested in which the optical parameters (Psi, Delta, P, Chi ) were obtained precisely. Comparing with conventional ellipsometers, OCE can characterize scattering specimen precisely and excludes the scattering effect.

Fiber optic biosensor for the detection of C-reactive protein and the study of protein binding kinetics.

Application of a fiber optic biosensor (FOB) to the real-time investigation of the interaction kinetics between FITC-conjugated monoclonal sheep anti-human C-reactive protein (CRP) antibody and CRP isoforms on the surface of optical fiber is described. Recently, both the native pentameric CRP (pCRP), an acute phase protein belonging to pentraxin family, and an isoform of pCRP, modified CRP (mCRP), have been suggested to have proinflammation effects on vascular cells in acute myocardial infarction (AMI). In current studies, we generate mCRP from pCRP, and use several methods including fluorescence spectral properties, circular dichroism, analytical ultracentrifuge, and Western blotting to demonstrate their differences in physical and chemical properties as well as the purity of pCRP and mCRP. In addition, we design and implement an FOB to study the real-time qualitative and quantitative biomolecular recognition of CRP isoforms. Specifically, the association and dissociation rate constants of the reaction between FITC-conjugated monoclonal sheep anti-human CRP antibody and the pCRP and mCRP are determined. The feasibility of our current approach to measure the association and dissociation rate constants of the reaction between tested CRP isoforms was successfully demonstrated.