Optical Intensity Variations Research Articles

Statistical Prediction of Micro-Arcing in Radio-Frequency Plasmas for Manufacture of Semiconductor Device

A hard-arcing precursor that causes charging damage to semiconductor devices was found. The micro-arcing that occurs during the plasma etch process was statistically classified based on the optical intensity variation by using high-speed optical sensing. According to the level of effect on semiconductor device failure, the micro-arcing was categorized into soft-arcing I (8–11σ), soft-arcing II (11–15σ), and hard-arcing (over 15σ). Experimental results suggest that a sufficiently large increase in soft-arcing is directly associated with the occurrence of hard-arcing. By using this characteristic and based on a Gaussian distribution, hard-arcing was statistically predicted within 12 wafers. A mathematical model is also proposed to explain the same. This is the first control system capable of predicting and effectively restraining micro-arcing during the plasma process.

Plasmonic Nanopore for Electrical Profiling of Optical Intensity Landscapes

We present a novel method for sensitive mapping of optical intensity distributions at subdiffraction-limited resolution. This is achieved with a novel device, a plasmonic nanopore, which combines a plasmonic bowtie nanoantenna with a 10 nm-in-diameter solid-state nanopore. Variations in the local optical intensity modulate the plasmonic heating, which we measure electrically through changes in the ionic conductance of the nanopore. We demonstrate the method by profiling the focal volume of a 10 mW laser beam that is tightly focused by a high-numerical-aperture microscope objective. The results show a complex three-dimensional intensity distribution that closely matches predictions obtained by theoretical calculations of the optical system. In addition to laser profiling, the ionic conductance of a nanopore is also shown to provide quantitative estimates of the temperature in the proximity of single plasmonic nanostructures.

Experimental determination of effective electro-optic coefficient and electric screening field factor in the electrically induced birefringent Bi12TiO20 crystal by using an oblique incidence setup

We present an alternative procedure to determine the effective electro-optic coefficient (reff) and the electric screening field factor by measuring the optical intensity variation induced by an applied electric field (EApp), which is transmitted through an undoped photorefractive Bi12TiO20 (BTO) crystal in an oblique incidence setup. The transmitted intensity variation (TIV) was modeled taking into account the transmission coefficients for the polarization plane parallel and perpendicular to the incidence plane, as well as the birefringence induced by the EApp, which changes the components of the polarization vector of the light beam. The measurements were performed with infrared radiation at 780nm and provided reff=5.5±0.2pm/V. It allowed us to conclude, with support of results from the literature, that the region without dispersion of the electro-optic coefficient in the BTO crystal ranges from 510nm to at least 780nm. The procedure proposed here can be used for distinct wavelengths and seems to be suitable for other electrically induced birefringent materials.

Near-Field Optical Imaging of a Porous Au Film: Influences of Topographic Artifacts and Surface Plasmons

In this work, near-field scanning optical microscopy is employed to study a porous Au film and the direct observation of topographic artifacts and surface plasmon influences is revealed. Under tip illumination, topographic artifacts are found to be present in a reflection mode optical image but not in a transmission mode image. A simple algorithm is used for filtering the topographic artifacts and extracting a correct near-field optical image approximately. On the other hand, surface plasmon influences are present in both modes. By using three exciting wavelengths of 488, 647.1, and 520.8 nm, it is confirmed that a suitable wavelength should be chosen for avoiding the surface plasmon interference in a near-field optical investigation of morphological or material dielectric contrast. Finally, plasmonic or nonplasmonic regions on the porous Au film can be identified from the observed optical intensity variation in the optical images obtained at incident polarizations of 0°, 90°, and 45°.

팔라듐이 코팅된 단일모드 광섬유 센서를 이용한 수소 경보 시스템 구현

In this paper, a study on a portable hydrogen alarm system based on the palladium coated single mode fiber sensor has been reported. The fabricated hydrogen sensor exhibited 0.14 dB, 0.41 dB and 0.54 dB optical intensity variation when it was exposed by the nitrogen and hydrogen mixed gas containing 0.5 %, 1 % and 4 % of the hydrogen concentration, respectively. The fabricated sensor exhibited 20 second of response time and 120 second of recovery time for 4 % hydrogen containing gas. The fiber optics layout and software algorithm for detection of hydrogen leakage have been presented. The implanted portable hydrogen alarm system successfully generated an alarm signal when a 4 % hydrogen containing gas was leaked out.

Conditional integration of Incoherent Scattering in relation to flickering aurora

In this report we present incoherent scatter radar (ISR) observations of ionospheric response to precipitation causing flickering aurora. Flickering aurora is caused by electron precipitation with modulations at frequencies higher than 5 Hz. To resolve the variation at these short time‐scales with ISR we have integrated together pulses at the same phase of the optical intensity variation observed with high‐speed narrow field‐of‐view imaging in white light to determine the intensity variation in the field aligned direction, which is also the direction of the beam of the EISCAT Svalbard Radar (ESR). Further we show that the 3% modulation in ISR back‐scattered power can be explained with electron heating by temporally modulated electron precipitation and electron cooling in collisions with ions and neutrals.

The Secret World of Shrimps: Polarisation Vision at Its Best

BackgroundAnimal vision spans a great range of complexity, with systems evolving to detect variations in light intensity, distribution, colour, and polarisation. Polarisation vision systems studied to date detect one to four channels of linear polarisation, combining them in opponent pairs to provide intensity-independent operation. Circular polarisation vision has never been seen, and is widely believed to play no part in animal vision.Methodology/Principal FindingsPolarisation is fully measured via Stokes' parameters—obtained by combined linear and circular polarisation measurements. Optimal polarisation vision is the ability to see Stokes' parameters: here we show that the crustacean Gonodactylus smithii measures the exact components required.Conclusions/SignificanceThis vision provides optimal contrast-enhancement and precise determination of polarisation with no confusion states or neutral points—significant advantages. Linear and circular polarisation each give partial information about the polarisation of light—but the combination of the two, as we will show here, results in optimal polarisation vision. We suggest that linear and circular polarisation vision not be regarded as different modalities, since both are necessary for optimal polarisation vision; their combination renders polarisation vision independent of strongly linearly or circularly polarised features in the animal's environment.

Nontarget Image-Based Technique for Small Cable Vibration Measurement

In this paper, a proof-of-concept image-based technique is proposed for measuring small cable vibration. The technique analyzes an image sequence of a vibrating cable segment captured by a camera. An optical flow method is used to calculate variation of optical intensity of an arbitrary selected region of interest ROI on the cable image sequence. The obtained optical flow vector provides the direction of vibration for the ROI on the cable segment, which then can be used to estimate displacement of the ROI on the image plane. Furthermore, actual displacement of the ROI can be extracted when some conditions are met. The proposed technique is validated both in the laboratory using a rigid pipe and in the field on a small pedestrian bridge cable. Results show that the technique is able to measure the pipe motion and the cable vibration accurately. The proposed technique requires only one commercial camera, and no prior camera calibration is needed. In addition, the use of an optical flow method eliminates the need to attach any target to the cable and makes the technique very easy to implement. Despite these advantages, the technique still needs further development before it can be applied to long-span bridge cables.

High-speed all-optical differentiator based on a semiconductor optical amplifier and an optical filter

We demonstrate a novel all-optical differentiator that carries out the first-order temporal derivation of optical intensity variation at high speed. It consists of a semiconductor optical amplifier (SOA) and an optical filter (OF) serving as an optical phase modulator and a frequency discriminator, respectively. A polarity-reversed derivative pair with a certain bias can be obtained by locating the probe wavelength at the positive or negative slope of the OF. Differentiations of super-Gaussian and Gaussian signals are obtained at various data rates. Defined as the mean absolute deviation of the measured result from the ideal result, total average errors of less than 0.12 are observed in all cases. Input power dynamics as well as control wavelength dependence are investigated and show that the cross-gain modulation in the SOA is detrimental to the differentiation performance.

Spectral line variability amplitudes in active galactic nuclei

We present the results of a long-term variability campaign of very broad-line AGNs with line widths broader than FWHM > 5000 km s-1. The main goal of our investigation was to study whether the widths of the optical broad emission lines are correlated with the optical intensity variations on timescales of years. Our AGN sample consisted of 10 objects. We detected a significant correlation between optical continuum variability amplitudes and Hβ emission line widths (FWHM) and, to a lesser degree, between Hβ line intensity variations and Hβ equivalent widths. We add the spectroscopic data of variable AGNs from the literature to supplement our sample. The AGNs from other optical variability campaigns with different line-widths helped to improve the statistical significance of our very broad-line AGN sample. After including the data on 35 additional galaxies, the correlation between optical continuum variability amplitudes and Hβ emission line widths becomes even more significant and the probability that this is a random correlation drops to 0.7 percent.

Optical interference induced by deposited wall-film in inductively coupled plasmas

Temporal periodic variation and long-time decrease of optical emission intensity collected by a spectrometer in an inductively coupled CH4/N2 plasma, which deposits a film of growing thickness on the chamber wall, are measured. The periodic variation is interpreted as a result of the interference between the light reflected from the film surface and that which re-emerged from the surface after being reflected by the chamber wall. The re-emerged light is attenuated due to absorption by the film and thus leads to the long-time decrease of the intensity. The periodic variation of the line intensities, however, can be used for in situ film thickness monitoring.

Lithium niobate electro-optic sensor for examining conductive patterns on display panels

The fabrication of an electric field detector using an electro- optic LiNbO3 (LN) single crystal is studied for an application to check the electric field of a conductively patterned panel. When this electric field detector moves on the surface of the panel, a constant air gap, which is close enough for the given field intensity and resolution, must be main- tained so as not to damage the surface patterns. For the effective detec- tion of electric field change in this air gap state, an LN single crystal is selected because of its relatively high electro-optic coefficient, transmit- tance, and low dielectric constant. X-cut LN and Z-cut LN structures are selected to estimate the applicability of LN by simulation on the optical intensity variation and electric field distribution of various structures. At an air gap of 10 mm in the Z-cut LN structure, Vp is about 100 to 150 V and optical intensity variation with unit voltage (Q) is 6.7%/V larger than that of the X-cut LN structure. From these characteristics, the Z-cut LN structure proves to be applicable for the electric field detector because the variation of optical intensity (0.8 mW) is sufficient in the ac driving voltage region (620 V) of a real system. © 2003 Society of Photo-Optical

Understanding solar flares from opticalobservations: How do particle beams affect the lower atmosphere?

Abstract During the impulsive phase of solar flares, both hard X-ray (HXR) and optical emissions exhibit fast temporal fluctuations detectable down to sub-second scales. This is usually ascribed to the propagation of beams of accelerated particles and to the dissipation of their energy in lower layers of the solar atmosphere. Although it is rather difficult to prove a temporal correlation between HXR and optical intensity variations, we discuss here some previous results and recent attempts. Namely in coordination with RHESSI observations, several ground-based observatories started to detect fast optical variations in the Hα line. In addition to this, we also mention a possibility of using some other diagnostically important lines. The proper interpretation of coordinated HXR and optical observations further requires robust tools for radiation-hydrodynamical (RHD) forward modeling. We briefly describe a new ‘hybrid’ code which consists of RHD part and particle-simulation part. Short-duration heating due to beam pulses is modeled which allows us to predict temporal fluctuations of HXR and selected optical and UV lines formed in chromospheric layers and in the transition region. Particularly the line asymmetries originating in a highly dynamical lower atmosphere of the flare can be used to diagnose the response of these layers to particle beams.

Performance analyses of flowing chemical oxygen-iodine laser.

A modified simplified rate-equation model that utilizes the Voigt profile function and another gain saturation model deduced from the kinetic equations are presented for performance analyses of a flowing chemical oxygen-iodine laser. Both models are adapted to both the condition of homogeneous broadening and that of inhomogeneous broadening being of importance and the condition of inhomogeneous broadening being predominant. Effects of temperature and iodine density on the output power and on variations of output power, optical intensity, and saturation intensity with flow distance are presented as well. There are differences between results of two models, but both qualitatively agree with known results.

Nonlinear optical characterization of cluster dynamic in water in oil microemulsion by a pump probe laser beam technique.

We present a new pump probe laser beams configuration for the nonlinear optical characterization of microemulsions. We detect the variation of the on-axis optical intensity of the probe beam as generated by the concentration profile induced in an optically thin film of microemulsion by the pump beam. A mathematical model has been introduced to describe the phenomenon. The technique allows the determination of both Kerr-like optical nonlinearity and time constants and, therefore, it gives information both on cluster dimension and their shape. We discuss its application to WAD (water/AOT/decane, where AOT denotes sodium-bis-di-ethyl-sulfosuccinate) with the application of a strong electric field of optical source. Comparison between theoretical predictions and experimental results confirms the presence of giant optical nonlinearity in the absence of turbidity divergence. Chainlike shape of clusters, of the kind already reported with the application of strong electric field, could justify this result.

430 光強度分布X線マスクによる微細3次元加工の検討(OS 材料の超精密加工・マイクロ加工)

The X ray mask used in the present LIGA process has the uniform thickness of an absorber. Therefore, the resist patterning is the structure of the same depth form, and the fabrication of 3-dimensional microstructure is difficult. In this paper,we propose the procedure of 3-D micro processing by X-ray mask with optical intensity variation.

Study of the stability of optical parametric amplification

Numerical simulation and analysis of the output stability of optical parametric amplification process versus pump intensity variations are presented. It is shown that there exists an optimal working point where excellent stability can be achieved by properly balancing relevant system parameters within certain ranges of pump variations.

Expansion of the luminous region of the lightning return stroke channel

We developed a high‐speed line‐scanning camera (HSLSC) for measuring the radial variation of optical intensity of lightning channels. With this system we succeeded in obtaining a few examples of data for natural lightning. From these data we found that the luminous region of return stroke channels may expand with a velocity of more than 105 m/s during the initial stage and then reach the maximum diameter of several tens of meters after about 100 μs from the initiation of the return stroke and finally decrease with time. This suggests the occurrence of lateral discharges along the lightning channel during the propagation of return strokes.

Contact printing of Bragg gratings in optical fibers: rigorous diffraction analysis

The fabrication of Bragg gratings inside the core of single-mode optical fibers has been greatly simplified by the application of contact printing [Appl. Phys. Lett. 62, 1035 (1993)]. According to this technique, the fiber is placed in proximity to an appropriate phase grating, which is illuminated with nominally monochromatic UV light. The transmitted light is redistributed into an ideally sinusoidal variation of optical intensity (more properly, irradiance), which is imprinted into the core as a result of photoinduced refractive index changes. In accordance with normal practice in this field, intensity is used instead of optical intensity throughout the text. The main advantage of such a writing method, apart from its simplicity, is that the illumination source need not be highly coherent. Rigorous analysis of this method is given with a new phase grating design.

Poling temperature dependence of optical second-harmonic intensity of MgO–ZnO–TeO2 glasses

Poling temperature variation of optical second-harmonic intensity induced by electrical poling has been examined for 30ZnO⋅70TeO2, 5MgO⋅25ZnO⋅70TeO2, and 10MgO⋅20ZnO⋅70TeO2 glasses. The Maker fringe pattern of these glasses indicates that the orientation of electric dipoles presumably due to TeO4 trigonal bipyramids and TeO3 trigonal pyramids is not restricted within the glass surface but extends into the inside of bulk glass. The poling temperature dependence of second-harmonic intensity manifests a maximum in all the glasses. There exists a tendency that the poling temperature which corresponds to the maximum of second-harmonic intensity is higher in the glass with higher glass transition temperature. This fact suggests that the orientation of tellurite structural units occurs as a result of the structural relaxation of tellurite network at around the glass transition temperature.