Modified Double Slit Interferometer for Shock Wave Investigations

Camera positioning units for surveillance applications are often mounted on mobile supports or vehicles. In such circumstances, the motion of the supporting base affects the camera field of view, thus making the task of pointing and tracking a specific target problematic, especially when using low cost devices that are usually not equipped with rapid actuators and fast video processing units. Visual tracking capabilities can be improved if the camera field of view is preliminarily stabilized against the movements of the base. Although some cameras available on the market are already equipped with an optical image stabilization (OIS) system, implemented either in the camera lenses or in the image sensor, these are usually too expensive to be installed on low-end positioning devices. A cheaper approach to image stabilization consists of stabilizing the camera motion using the motors of the positioning unit and the inertial measurements provided by a low-cost MEMS Inertial Measurement Unit (IMU). This paper explores the feasibility of applying such image stabilization system to a low cost pan-tilt-zoom (PTZ) camera positioning unit driven by hybrid stepper motors (HSMs), in order to aid the task of pointing and tracking of a specific target on the camera image plane. In the proposed solution, a two-level cascaded control structure, consisting of inner inertial stabilizing control loop and an outer visual servoing control loop, is used to control the PTZ unit. Several tests are carried out on a real device mounted on a moving table actuated by a 6 degrees-of-freedom pneumatic hexapod. Realistic motions are recreated by using the data recordings taken aboard of a patrolling ship.

The Mach-Zehnder interferometer is a fundamental tool for measuring phase shifts between two light paths, serving as a crucial prototype for achieving high-precision measurements in various scientific and technological applications. In this study, we analyze different models for estimating relative phase shift in a general two-arm Mach-Zehnder interferometer. We demonstrated that single- parameter estimation models can be reduced from the two-parameter estimation model by imposing appropriate constraints on the parameter space. To make quantum Fisher information of the single- parameter estimation models meaningful, the corresponding constraints must be guaranteed in the experiment implementation. Furthermore, we apply the quantum Fisher information approach to analyze the Mach-Zehnder interferometer with the an input state composed of a displaced squeezed vacuum state and a coherent state, providing insights into the precision limits of such configurations.

Dephosphophosphorylase was isolated from swine kidney by a procedure involving precipitation with acetone and ethanol in the presence of glycogen, ammonium sulfate fractionation and chromatography on DEAE‐cellulose. The enzyme was purified about 15000‐fold to a final specific activity of 30 μmol glucose‐1‐phosphate formed from glycogen and inorganic phosphate per min per mg protein at 26°C. Yields of 20% of the activity present in crude extracts were obtained by this method. The purified enzyme could be completely converted to a phosphorylated form by incubation with ATP, magnesium ion and a partially purified soluble protein kinase which was isolated from the same crude kidney extracts. The final specific activity of phosphophosphorylase isolated by the same procedure was about 70 μmol glucose‐1‐phosphate formed from glycogen and inorganic phosphate per min per mg protein at 26°C.Ultracentrifugation and polyacrylamide‐gel electrophoresis studies with the purified enzymes indicated that the preparations were homogeneous. Molecular weight determination by Sephadex G‐200 and Sepharose 6‐B column chromatography revealed V0/Ve ratios which corresponded to a molecular weight of 190000 ± 5000 for both of the enzyme preparations. Sucrose‐density centrifugation further confirmed that both forms of kidney phosphorylase had similar molecular weights of about 190000 ± 10000 and s20,w values of from 8.1 to 8.3 S. The s20,w values obtained in ultracentrifugation studies, 8.3 to 8.4 S, agreed reasonably well with those obtained by sucrose density centrifugation. The molecular weights of the two forms of the enzyme calculated from this data and a diffusion coefficient of 0.4 μm2/s which was determined by exclusion chromatography and a partial specific volume of 0.735 cm3/g was 195000 ± 5000 in each case. When the enzymes were subjected to polyacrylamide‐gel electrophoresis in the presence of sodium dodecyl‐sulfate a single sharp protein band was observed. These studies showed that both forms of the enzyme contained two identical subunits with molecular weights of 95000.Some of the kinetic and allosteric properties of the phospho and dephospho‐forms of purified kidney phosphorylase were examined and compared. The Km of the phosphorylated form of the enzyme for Pi was 2.8 mM compared to 100 mM for the dephospho‐form in the presence of 0.2 mg glycogen and 2 mM AMP. The corresponding values for glycogen at about 4 mM Pi were 1.4 mM and 20 mM for the phospho and dephospho‐forms, respectively. The apparent Km values for Pi or glycogen varied as a function of the other substrate for the dephospho‐enzyme. This effect was not observed with the phospho‐enzyme. The dephospho‐form of kidney phosphorylase required AMP for activity and protamine also stimulated the activity of this form of the enzyme. Glucose (0.5 mM) inhibited the activity of kidney dephosphophosphorylase.A protein kinase isolated from crude kidney extracts converted the dephospho‐form of the enzyme to a phosphorylated form in the presence of ATP and magnesium. About two equivalents of phosphate were transferred from ATP to the phosphorylated form of the enzyme during this conversion.

Instantaneous phase-stepping interferometry based on a pixelated micro-polarizer array

Intra-Tissue Refractive Index Shaping (IRIS) uses a 405 nm femtosecond laser focused into the stromal region of the cornea to induce a local refractive index change through multiphoton absorption. This refractive index change can be tailored through scanning of the focal region and variations in laser power to create refractive structures, such as gradient index lenses for visual refractive correction. Previously, IRIS was used to create 2.5 mm wide, square, -1 D cylindrical refractive structures in living cats. In the present work, we first wrote 400 mu m wide bars of refractive index change at varying powers in enucleated cat globes using a custom flexure-based scanning system. The cornea and surrounding sclera were then removed and mounted into a wet cell. The induced optical phase change was measured with a Mach-Zehnder Interferometer (MZI), and appeared as fringe displacement, whose magnitude was proportional to the refractive index change. The interferograms produced by the MZI were analyzed with a Fourier Transform based algorithm in order to extract the phase change. This provided a phase change versus laser power calibration, which was then used to design the scanning and laser power distribution required to create -1.5 D cylindrical Fresnel lenses in cat cornea covering an area 6 mm in diameter. This prescription was inscribed into the corneas of one eye each of two living cats, under surgical anesthesia. It was then verified in vivo by contrasting wavefront aberration measurements collected pre-IRIS with those obtained over six months post-IRIS using a Shack-Hartmann wavefront sensor.

Analysis of the rotation of the polarisation direction in a cylindrical liquid crystal lens where the direction of the incident linear polarisation is not parallel to the axis of the cylindrical lens

We propose a light delivery system to the near-field transducer (NFT) of a heat-assisted magnetic recording (HAMR) head using a Mach–Zehnder interferometer (MZI) waveguide arrangement with a transverse electric (TE) mode coupled to the planar waveguide from a single mode fiber. The proposed design offers great flexibility in the coupling of light to the NFT in order to match the desired radiation pattern of the antenna and thus to optimize the energy transfer. Furthermore, it allows excitation of particular surface plasmon (SP) resonances of the transducer (quadrupole or higher) by controlling the coupling angle and the phase of the two beams of light. The optimum phase shift between the TE waveguide modes incident on the NFT can be achieved either statically by making one of the MZI arms longer/shorter compared with the other one, or dynamically by changing the mode effective index of the MZI waveguide arm through electro-optic or thermo-optic modulation. In addition, the proposed MZI waveguide arrangement enables easier coupling from a laser with coupling losses from laser to MZI waveguide being below 3 dB and the design enables an arrangement of the NFT placed either on the top of the waveguide at the termination side of the MZI or between the rib and the ridge at the maximum of the electric field of the waveguide, which maximizes the SP resonance enhancement of the NFT. Another advantage is that the magnetic-write pole, in our design, can be easily integrated on the same chip, preferably above the center of the MZI, between the two arms of the interferometer and away from the propagating mode, thus avoiding blocking of the light path.

<div class="htmlview paragraph">The paper presents new data to document the effective test area in a model ¾ open jet wind tunnel with a long test section using drag measurements. The drag on MIRA Pickup models (up to 20% blockage) was tested and found to be virtually independent of blockage when tested in a non-resonant test section with L/D ratio of about 8. An analysis of these test results is presented to predict the required test section L/D as a function of blockage. In addition, the effects of plenum dimensions are presented. Based on these results, the test sections of present open jet test sections have a limited range for testing models without corrections for the effects of blockage, model location, and test section length. A longer test section enables direct measurement of drag even with high blockage models. Testing with higher blockage can mean lower test facility costs.</div> <div class="htmlview paragraph">The test section design technology described in this report is the subject of a pending patent application.</div>

Image rectification for prism-based stereoscopic optical systems

Electrically tunable optical fiber device based on hollow-core fiber infiltrated with liquid crystal

Streamer discharges in water, which are a pre-breakdown phenomenon caused by underwater discharge, have gained attention because of the development of plasma-based technologies for water purification and medical treatment. In this study, a single-shot pulsed negative high voltage of –18 to –21 kV with a rise time of 100 ns was applied to a needle electrode in ultrapure water, and streamers were continuously imaged using an optical system combining a high-speed video camera, a streak camera, and an ultra-high-speed camera with a microscope lens. These observations were synchronized with the applied voltage and the discharge current to investigate the effect of the discharge on streamer propagation. Negative streamers propagated with a velocity of 820 ± 50 m/s in the presence of pulsed currents, and 100 ± 20 m/s when pulsed currents were absent. The streak camera detected light emission when the pulsed currents appeared, and it was also observed that 1480 m/s pressure waves were generated during streamer propagation. Furthermore, we developed a simple new method of imaging weak density changes similar to those detected using the Schlieren method or Mach–Zehnder interferometer. This method simply involves inserting a pair of polarizing plates on the optical axis, so that the pressure waves can also be imaged in two-dimensional photographs. Our results indicated that the pressure waves were generated from the propagating streamer head when the pulsed currents appeared in the waveform. Analysis of temporal resolution with nano-second order clarified that the branching phenomenon occurred at different times resulting in the branching streamer propagation with different directions.

Electro-optic materials play an essential role in telecommunications. In active devices like Mach–Zehnder modulators, typically the diagonal Pockels coefficients are employed to induce an optical phase shift through electrical tuning of the refractive index along an optic axis. On the other hand, waveguide polarization rotators are usually passive devices where asymmetric structures or specially designed couplers are used. In this Letter, we exploit off diagonal Pockels coefficients to demonstrate an active straight waveguide polarization rotator using a c-axis single crystal thin film barium titanate (BTO)-on-insulator, with a maximum power conversion of ∼30% from the input TE (or TM) mode into its orthogonal mode observed. The device is switched on or off through an applied voltage and is demonstrated in a simple straight waveguide. A TM output extinction ratio of 26.1 dB is achieved in the device with a TE input. The r51 value in the BTO thin film is estimated to be around 600 pm/V. This work adds a different polarization rotation scheme to the active photonics family.

An unsensitive-bending Mach-Zehnder interferometer (MZI) structure is proposed to detect the Clostridium alpha toxin by using single-mode fiber dislocation fusion. A standard single-mode fiber (SMF) is offset laterally and spliced between two SMFs to form the U-shaped microcavity in the middle, which is used for sensing. The MZI structure is encapsulated with capillary tube and injected with pure water, and the temperature sensitivity is tested in the temperature range of 26–50 °C. The temperature sensitivity of MZI is 0.78nm/°C, which ensures its practicability in the environment of temperature fluctuation. The axial tension and radial strain of MZI structure are measured. The weight range of the load is 10 to 60g. The experimental results show that the sensitivity of axial tension is −30.43 nm/N and the sensitivity of radial pressure is only −1.54 nm/N. The sensitivity of axial tension is about 20 times of radial pressure sensitivity. In the subsequent sensing experiments, axial fixation is needed to ensure the stability of MZI, the effect of radial pressure can be ignored under certain circumstances. Finally, the bending insensitive interferometer is used to detect the Clostridium alpha toxin, The sensing properties of MZI structure at concentrations of 2 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sup> , 2– <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</sup> , 2– <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> , 2– <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> were studied. When the concentration is 2 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sup> , the peak wavelength shift of the transmission spectrum can reach to 4.25 nm. Therefore, the proposed unsensitive-bending sensor has the advantages of high refractive index sensitivity, small size and low cost, which has a good prospect in biosensor applications.

A simple and practical photonic approach for microwave instantaneous frequency measurement has been proposed and experimentally demonstrated. The unknown microwave signal with its frequency to be measured is carrier-suppressed modulated on the lightwave by a Mach-Zehnder modulator biased at the minimum point. And thanks to the inherent complementary transmission responses of the Mach-Zehnder interferometer (MZI), the fixed relationship between the amplitude comparison function and microwave frequency to be measured is established. By monitoring and processing the optical powers of the two output ports of the MZI, the frequency of the microwave signal could be easily estimated. The proposed scheme is experimentally verified and has many advantages, such as simple structure, low cost, fast response, practical prospect, tunable measurement range, and high resolution.

Simultaneous measurement three parameters of temperature, strain, and curvature by thin-core fiber based-Mach-Zehnder interferometer