Requirements on optical density and phase dispersion of imperfect band-limited occulting masks in a broadband coronagraph

We investigate the effects of the parasitic phase of imperfect band-limited occulting masks on the broadband contrast performance of a high-contrast imaging system through modeling and simulations. We also examine the effects of the phase and the optical-density dispersions of occulting masks whose parasitic phase has been compensated at the center wavelength but is nonzero at other wavelengths. Two types of occulting masks are considered: gray-scale masks such as those made on a high-energy beam-sensitive glass, and recently proposed spatially profiled metal masks, both having 1D Sinc2(linear-Sinc2) amplitude transmission coefficient (Sinc4 intensity transmittance) profiles. We determine the conditions for obtaining 1x10(-9) and 1x10(-10) contrast values with a light centered at a 785 nm wavelength and having a 10% bandwidth in a coronagraphic telescope having ideal optical surfaces but imperfect band-limited image-plane occulting masks.     

Characterization of a broadband all-optical ultrasound transducer-from optical and acoustical properties to imaging

A broadband all-optical ultrasound transducer has been designed, fabricated, and evaluated for high- frequency ultrasound imaging. The device consists of a 2-D gold nanostructure imprinted on top of a glass substrate, followed by a 3 microm PDMS layer and a 30 nm gold layer. A laser pulse at the resonance wavelength of the gold nanostructure is focused onto the surface for ultrasound generation, while the gold nanostructure, together with the 30 nm thick gold layer and the PDMS layer in between, forms an etalon for ultrasound detection, which uses a CW laser at a wavelength far from resonance as the probing beam. The center frequency of a pulse-echo signal recorded in the far field of the transducer is 40 MHz with -6 dB bandwidth of 57 MHz. The signal to noise ratio (SNR) from a 70 microm diameter transmit element combined with a 20 microm diameter receive element probing a near perfect reflector positioned 1.5 mm from the transducer surface is more than 10 dB and has the potential to be improved by at least another 40 dB. A high-frequency ultrasound array has been emulated using multiple measurements from the transducer while mechanically scanning an imaging target. Characterization of the device's optical and acoustical properties, as well as preliminary imaging results, strongly suggest that all-optical ultrasound transducers can be used to build high-frequency arrays for real-time high-resolution ultrasound imaging.     

Direct spatial resonance in the laminar boundary layer due to a rotating-disk

Numerical treatment of the linear stability equations is undertaken to investigate the occurrence of direct spatial resonance events in the boundary layer flow due to a rotating-disk. A spectral solution of the eigenvalue problem indicates that algebraic growth of the perturbations shows up, prior to the amplification of exponentially growing instability waves. This phenomenon takes place while the flow is still in the laminar state and it also tends to persist further even if the non-parallelism is taken into account. As a result, there exists the high possibility of this instability mechanism giving rise to nonlinearity and transition, long before the unboundedly growing time-amplified waves.     

Investigations of surface characterization of silicone rubber due to tracking phenomena under a.c. and d.c. voltages

In the present work, tracking phenomena has been studied with silicone rubber material under the a.c. and d.c. voltages following IEC-587 standards. The surface condition of the tracked zone was analysed using wide angle X-ray diffraction (WAXD) and thermogravimetric differential thermal analysis (TG-DTA) studies. The tracking time was different for a.c. and d.c. voltages.     

Heating of a micropolar liquid due to viscous energy dissipation in channels. 1. Poiseuille flow

An analytical study is made of the effect of the internal microstructure of a liquid on its heating due to viscous energy dissipation.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 46, No. 2, pp. 202–208, February, 1984.     

Full in-situ characterization of spatial light modulators in an optical correlator. Filter adaptation to operating curves

Abstract

In this paper we present one method for the characterization of the spatial light modulators (SLMs) of a real-time Vander Lugt type of correlator. This correlator uses two SLMs: one to introduce the scene and a second to introduce the frequency‐matched filter. The SLM characterization methods are in situ, that is in the correlator set‐up. Illumination conditions are different for each SLM, and consequently different characterization techniques must be used in each case. For the characterization of the scene SLM a diffraction method is used, while for the characterization of the filter SLM an interferometric technique is more convenient. Finally, we take into account the operating curves of scene and filter SLMs in the design of the filter in order to optimize the correlation peak.     

Investigation of surface modifications in ethylene propylene diene monomer (EPDM) rubber due to tracking under a.c. and d.c. voltages

In the present work, tracking phenomena has been studied with the ethylene propylene diene monomer (EPDM) material under the a.c. and d.c. voltages, with ammonium chloride/acid rain solution as the contaminant. It is noticed that the tracking time depends on the conductivity and flow rate of the contaminant. The physico-chemical analyses viz. wide angle X-ray diffraction (WAXD), thermo-gravimetric differential thermal analysis (TG-DTA) and the differential scanning calorimetry (DSC) studies, were carried out and it was concluded that the tracking process is a surface degradation process. The tracking time is different for a.c. and d.c. voltages.     

Induced free liquid surface oscillations in a visco-elastic liquid column due to angular temperature fluctuations

The response due to time-fluctuating temperature distribution applied at the free surface of a viscoelastic cylindrical liquid column with no axial dependency has been determined analytically. The amplitude of the radial- and angular velocity as well as the free liquid surface elevation has been presented as a function of the “reduced” forcing frequency of the oscillatory temperature and has numerically been evaluated for an angular temperature field proportional to sin 2φ. It was found, that visco-elasticity as described by the Maxwell model has quite some influence upon the liquid behavior. It shows for larger relaxation times besides the enlarged resonance peak additional peaks below and above resonance. This is particularly evident inside the liquid column, indicating a more pronounced elastic behavior of the liquid.     

Size effects due to Cosserat elasticity and surface damage in closed-cell polymethacrylimide foam

This article describes the experimental investigation of Cosserat (or micropolar) elasticity and surface damage effects in closed-cell polymethacrylimide foams of different densities. The method of size effects was used to find the degree of Cosserat behaviour for both cylindrical and square cross-section specimens in bending and torsion. The foams were found to behave as Cosserat materials in which slender specimens appear less stiff than thick ones, provided sufficient care is taken when machining the specimens. Surface damage caused by the machining process may cause the apparent stiffness to decrease with decreasing specimen size, giving an opposite softening size effect.     

Time-resolved spectral and spatial description of laser-induced breakdown in air as a pulsed, bright, and broadband ultraviolet-visible light source

The optical breakdown induced in air at atmospheric pressure by Nd:YAG Q-switched laser pulses is studied in terms of the spectral features of the emitted radiation in the wavelength range 180-850 nm during the first 200 ns after the laser pulse onset. During the plasma build up, radiation emission features intense, broadband, and structureless ultraviolet-visible spectra before the appearence of atomic lines on the microsecond scale. Also, the emitting plasma kernel, imaged during the buildup and decay stages in the early tens of nanoseconds, turns out to have a size of ~0.3 mm and a volume of ~0.02 mm(3). The coupling of direct emission data and broadband absorption measurements allowed us to retrieve peak values of electron temperature above 100,000 K and of an optical depth of the order of unity, under the assumptions of local thermodynamic equilibrium and a homogeneous kernel. The simultaneous occurrence of such temporal, spatial, and spectral features of the plasma kernel suggests its exploitation as a pulsed, bright, and broadband ultraviolet-visible light source.     

Structured approach to the design of a production data analysis facility. Part 1: Conceptual design and information requirements

The paper reports research into a workshop-oriented machine and inspection framework for a contemporary metalworking small manufacturing enterprise (SME) that cannot be satisfactorily achieved by the rigid scaled-down versions of software applications employed within larger companies. It identifies a structured approach to the design and conceptualization of a production data analysis framework that is supported by the use of order and manufacturing data. A major feature of the framework is its generic applicability and totally integrated approach to provide rapid manufacturing control from intelligent feedback data from the inspection and manufacturing data analysis activities of manufactured components. This production data analysis approach is formally expressed through the combined application of both the activity analysis formalism of IDEF0 and object-oriented information analysis methodology of Booch. The systematic approach employed by the integrated production data analysis framework provides both product and manufacturing process control in order to close the manufacturing feedback loop. These integrated phases are described and involve the concurrent machine operation and inspection planning, simultaneous production code generation, comparative tolerance analysis, and manufacturing data analysis of manufactured components. The final part of the paper provides a critical discussion on a number of major issues of the approach and identifies the advantages and limitations of the research.     

Tracking in a ground-to-satellite optical link: effects due to lead-ahead and aperture mismatch, including temporal tracking response

Establishing a link between a ground station and a geosynchronous orbiting satellite can be aided greatly with the use of a beacon on the satellite. A tracker, or even an adaptive optics system, can use the beacon during communication or tracking activities to correct beam pointing for atmospheric turbulence and mount jitter effects. However, the pointing lead-ahead required to illuminate the moving object and an aperture mismatch between the tracking and the pointing apertures can limit the effectiveness of the correction, as the sensed tilt will not be the same as the tilt required for optimal transmission to the satellite. We have developed an analytical model that addresses the combined impact of these tracking issues in a ground-to-satellite optical link. We present these results for different tracker/pointer configurations. By setting the low-pass cutoff frequency of the tracking servo properly, the tracking errors can be minimized. The analysis considers geosynchronous Earth orbit satellites as well as low Earth orbit satellites.     

Frequency shifts in a piezoelectric body due to a surface mass layer with consideration of the layer stiffness

Shifts of resonant frequencies of a three-dimensional piezoelectric body of an arbitrary shape due to the addition of a thin layer of mass to its surface are studied. A first-order perturbation integral is obtained for the frequency shifts. The result generalizes that of a previous paper by considering the effect of the stiffness of the mass layer, in addition to its inertial effect.     

Frequency shifts in a piezoelectric body due to small amounts of additional mass on its surface

Shifts of resonance frequencies of a three-dimensional piezoelectric body of an arbitrary shape due to the addition of a thin layer of mass to its surface are studied. A first-order perturbation integral is obtained for the frequency shifts.     

Structural and optical behavior due to thermal effects in end-pumped Yb:YAG disk lasers

We employ a Monte Carlo ray-tracing code along with the ANSYS package to predict the optical and structural behavior in end-pumped CW Yb:YAG disk lasers. The presence of inhomogeneous temperature, stress, and strain distributions is responsible for many deleterious effects for laser action through disk fracture, strain-induced birefringence, and thermal lensing. The thermal lensing, in turn, results in the optical phase distortion in solid-state lasers. Furthermore, the dependence of optical phase distortion on variables such as the heat transfer coefficient, the cooling fluid temperature, and crystal thickness is discussed.     

Concentration gradient immunoassay. 1. An immunoassay based on interdiffusion and surface binding in a microchannel

We describe a novel microfluidic immunoassay method based on the diffusion of a small-molecule analyte into a parallel-flowing stream containing a cognate antibody. This interdiffusion results in a steady-state gradient of antibody binding site occupancy transverse to convective flow. In contrast to the diffusion immunoassay (Hatch, A.; Kamholz, A. E.; Hawkins, K. R.; Munson, M. S.; Schilling, E. A.; Weigl, B. H.; Yager, P. Nat. Biotechnol. 2001, 19, 461-465.), this antibody occupancy gradient is interrogated by a sensor surface coated with a functional analogue of the analyte. Antibodies with at least one unoccupied binding site may specifically bind to this functionalized surface, leading to a quantifiable change in surface coverage by the antibody. SPR imaging is used to probe the spatial distribution of antibody binding to the surface and, therefore, the outcome of the assay. We show that the pattern of antibody binding to the SPR sensing surface correlates with the concentration of a model analyte (phenytoin) in the sample stream. Using an inexpensive disposable microfluidic device, we demonstrate assays for phenytoin ranging in concentration from 75 to 1000 nM in phosphate buffer. At a total volumetric flow rate of 90 nL/s, the assays are complete within 10 min. Inclusion of an additional flow stream on the side of the antibody stream opposite to that of the sample enables simultaneous calibration of the assay. This assay method is suitable for rapid quantitative detection of low molecular weight analytes for point-of-care diagnostic instrumentation.     

Non-contact measurement of surface oscillation due to Marangoni flow instability in a silicon liquid bridge by phase-shift interferometry

In order to investigate Marangoni flow instability of molten silicon, surface oscillation of a silicon liquid bridge with various aspect ratios at high Marangoni numbers, such as Ma ≥ 2400, was observed by using real-time phase-shift interferometry. By analyzing phase distribution of the phase-shift interferograms using FFT (fast Fourier transformation) and wavelet transformation, we found that two frequency bands exist in surface oscillation. Their central frequencies are 0.1–0.5 Hz for a lower band and 0.7–1.3 Hz for a higher band, respectively. Central frequency decreases with increase in aspect ratio. The lower frequency bands, which include m = 1 and m = 3 modes, appear continuously, whereas the higher frequency bands appear intermittently.     

Near-field optical properties and surface plasmon effects generated by a dielectric hole in a silver-shell nanocylinder pair

Near-field optical properties and surface plasmon effects in a silver-shell nanocylinder pair with five different dielectric holes (DHs) that interact with a transverse magnetic mode incident plane wave are simulated by use of the finite-element method, which includes the investigation of particle-particle interaction. The proposed structure exhibits a redshifted localized surface plasmon that can be tuned over an extended wavelength range by varying the dielectric constant in DHs and the thickness of the nanocylinder silver shell. The increase in the near-field intensity is attributed to a larger effective size of DH that is filled with a higher refractive medium.     

Frequency shift in signal and idler gain peaks due to nonlinear refractive index in narrow-band optical parametric oscillators

The frequency chirp in the gain spectra for the signal and idler waves in nanosecond optical parametric oscillators (OPOs) due to the nonlinear refractive index of the gain medium at the pump wavelength is discussed. Computed results for a commonly used 355 nm pumped OPO with lithium borate and beta barium borate as a gain medium show that the frequency shift remains small compared with the gain bandwith, even for a narrow-band OPO pumped above threshold.     

Development of a pulsed radio frequency glow discharge for three-dimensional elemental surface imaging. 1. Application to biopolymer analysis

Glow discharge optical emission spectrometry has cemented itself as an important surface elemental analysis technique in part because of its superb depth resolution (on the order of single nanometers). However, very few studies have explored the ability of the glow discharge to provide laterally resolved elemental information. In the present study, an end-on-viewed pulsed radio frequency glow discharge is coupled to a monochromatic imaging spectrometer to provide lateral surface imaging. The performance of the technique is demonstrated with etched copper circuits on fiber-glass substrates, and it is shown how several operating parameters including pressure, pulsed mode operation, and time-resolved detection affect the lateral surface resolution. In addition, because a pulsed radio frequency glow discharge offers elemental information on nonconducting samples, the technique is applied to the three-dimensional elemental analysis of proteins on blotting substrates. Several alternative sample types are also examined, including photographic film and glass.