Showing papers in "Optics and Laser Technology in 1981"
36 citations
IBM1
TL;DR: In this article, a large number of nonlinear organic materials have been investigated by second-harmonic generation (SHG) in powders, including several urea derivatives, sterically perturbed anilines and pyridines, and substituted stilbenes.
Abstract: A large number of non-linear organic materials have been investigated by second-harmonic generation (SHG) in powders. The materials studied include several urea derivatives, sterically perturbed anilines and pyridines, and substituted stilbenes. Several compounds have been found with both a very large second-order non-linearity and a high optical damage threshold. Many compounds, even though known to possess large molecular hyperpolarizabilities, showed no detectable SHG, indicating a centrosymmetric crystal point group. The results are interpreted in terms of bond configuration, charge transfer and crystal structure. The use of good non-linear organic materials in integrated non-linear optics is discussed.
33 citations
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TL;DR: Fibre optic sensors are being developed which have significant potential for sensing a variety of physical variables such as acoustic pressures, magnetic fields, temperature, acceleration and rate of rotation as discussed by the authors. But they are not suitable for all applications.
Abstract: Fibre optic sensors are being developed which have significant potential for sensing a variety of physical variables. These include acoustic pressures, magnetic fields, temperature, acceleration and rate of rotation. This paper concentrates mainly on acoustic sensors which use fibre optic interferometers sensitive to acoustic fields. The influence of various noise sources on the detection processes is described. Techniques for varying the acoustic and magnetic sensitivity of optical fibres are discussed and some advantages associated with the geometric versatility of their sensors considered. Several non-interferometric acoustic sensors which are amplitude sensitive to acoustic fields are discussed. Finally a brief account of fibre optic magnetic sensors and accelerometers is given.
29 citations
TL;DR: A brief description of the principle of Schlieren photography is given in this paper, followed by a review of variations in the technique and a bibliography is presented which includes references to all the important system modifications and spans a wide range of applications.
Abstract: A brief description of the principle of Schlieren photography is given, followed by a review of variations in the technique. A bibliography is presented which includes references to all the important system modifications and spans a wide range of applications.
26 citations
TL;DR: In this paper, the relationship between the microstructure and the d c and optical properties of composites is discussed, focusing on two unique characteristics of metal-insulator composites: the percolation threshold and optical dielectric anomaly.
Abstract: This paper reviews some of the recent progress in understanding the relationship between the microstructure and the d c and optical properties of composites By focusing on two unique characteristics of metal-insulator composites — the percolation threshold and the optical dielectric anomaly — it is demonstrated that the concept of a ‘structural unit’ arises naturally as a means for incorporating the microstructural information in the calculation of the effective dielectric function ϵ for an inhomogeneous system A theory based on a statistical consideration of two types of structural unit is shown to result in values for ϵ in excellent agreement with observed data
17 citations
TL;DR: The development of the moire method in its technical means and practical application to anthropological and medical studies and emphasis is placed on references in various fields of human biology.
Abstract: This paper reviews the development of the moire method in its technical means and practical application to anthropological and medical studies. Emphasis is placed on references in various fields of human biology.
13 citations
TL;DR: In this paper, a modified laser range-finder system using a simplified slope method is described, and the accuracy of this two-point method is analyzed for several atmospheric conditions, including weather conditions.
Abstract: Careful measurement of slant range visibility is becoming more important for safe and regular aircraft landing operation. Measurements are necessary under conditions of less than 1500 m visibility up to altitudes of about 100 m. Discussions of the use of laser radar systems to measure the optical properties of the atmosphere have been published. For practical applications such an expensive system was not useful. This paper describes a modified laser range-finder system which uses a simplified slope method. The accuracy of this two-point method is analyzed for several atmospheric conditions. Measurements with a described prototype system are presented.
13 citations
11 citations
TL;DR: In this article, an edge interference filter (19 alternating layers of SiO 2 and TiO 2 ) for a beam incident at 20° from glass realized through tradeoff between acceptable insertion loss and desired crosstalk attenuation is presented.
Abstract: The theory for realizing edge interference filters, exhibiting minimum polarization at the wavelengths to be separated, despite oblique beam incidence, is extended to versions for any angle. An edge filter (19 alternating layers of SiO 2 and TiO 2 ) for a beam incident at 20° from glass realized through tradeoff between acceptable insertion loss and desired crosstalk attenuation is presented. Due to its steep edge, it is capable of separating the emissions of two led's at close wavelengths. Whereas the reflectance for the wavelength to be passed is almost zero, that for the wavelength to be reflected is almost complete.
11 citations
10 citations
TL;DR: In this article, the active stabilization of a cw CO2 laser is described, where the servo control system uses frequency stabilization at the maximum of the power profile, and the results obtained by this servo-control system are presented.
Abstract: The active stabilization of a cw CO2 laser is described. The servo control system uses frequency stabilization at the maximum of the power profile. Description of the high voltage current regulated supply is given together with details and diagrams of the electronics. The results obtained by this servo-control system are presented.
TL;DR: In this paper, it has been found that optical waveguide effects caused by the refractive index gradient affected the biascope pattern but, provided that stress birefringence was distinguished, by analyser rotation, from intrinsic refractive indices differences between guided modes, and that the bireringence and refraction index values were dissimilar, surface stress determination was possible.
Abstract: The introduction of gas lasers has greatly increased the number of biascope applications. It has been found that optical waveguide effects caused by the refractive index gradient affected the biascope pattern but, provided that stress birefringence was distinguished, by analyser rotation, from intrinsic refractive index differences between guided modes, and that the birefringence and refractive index values were dissimilar, surface stress determination was possible. Birefringence and refraction patterns were recorded and compared for a variety of glasses.
TL;DR: In this article, an apparatus for scanning the output radiation from a 5 W argon ion gas laser across a sample surface has been developed, where a microprocessor was used to control the x and y axis reflectors.
Abstract: An apparatus for scanning the output radiation from a 5 W argon ion gas laser across a sample surface has been developed. A microprocessor was used to control the x and y axis reflectors. Laser scanning of a sample in six different patterns, and any combinations of these patterns, has been achieved. Scan rates of up to 33.6 degrees per second with a resolution of 0.034 degrees per step have been obtained. The benefits and limitations of such a system are discussed.
TL;DR: In this article, the velocity and direction of small dust particles charged in the high electric field of a model electrostatic precipitator were measured using a laser Doppler velocimetry.
Abstract: As a preliminary study for the collection of dust particles in an electrostatic precipitator, laser Doppler velocimetry has been used to measure the velocity of small dust particles charged in the high electric field of a model electrostatic precipitator. A differential optical system is adopted for the velocimeter. The period-measuring system is used to analyse Doppler beat signals and to obtain velocity data from them. By means of the laser Doppler velocimeter, the dynamic behaviour of the velocity and direction of moving dust particles is fully revealed as a function of the applied electric voltage in the entire collecting space of the model electrostatic precipitator, and is shown in vectorial flow diagrams of particle velocity.
TL;DR: In this paper, the system capabilities for concentration measurements in initially laminar and turbulent free jets are shown in a cw laser Raman spectroscopy system with a single-dimensional laser array.
Abstract: Experimental fluid dynamic studies have been performed using cw laser Raman spectroscopy. The system capabilities for concentration measurements are shown in initially laminar and turbulent free jets.
TL;DR: In this paper, the properties and main design features of a small, cataphoretic HeSe+ laser are described, and the length of the active laser region can be reduced to 100 mm without appreciable loss in single pass gain by reduction of the capillary diameter to 1 mm.
Abstract: The properties and main design features of a small, cataphoretic HeSe+ laser are described. By improving both the He buffer gas containment and the Se vapour deposition, laser life can be increased considerably to several thousand hours. The length of the active laser region can be reduced to 100 mm without appreciable loss in single pass gain by reduction of the capillary diameter to 1 mm. Up to 3 mW laser power in six blue-green and green Sell lines can be extracted from this small active volume. By synchronizing the spontaneous discharge striations in the He-Se vapour mixture, laser noise is reduced to less than 3% r m s. A few potential applications for this type of laser are listed to encourage commercial interest.
TL;DR: In this article, a technique for measuring the form of small objects is presented, which is similar to conventional Moire contouring but, by combining the advantages of light and electron optics, the problem of obtaining a large depth of field and high resolution is overcome.
Abstract: A technique for measuring the form of small objects is presented. The process is similar to conventional Moire contouring but, by combining the advantages of light and electron optics, the problem of obtaining a large depth of field and high resolution is overcome. The technique is applied to the measurement of a Rockwell diamond indenter, using a scanning electron microscope to form height contours over a field diameter of 800 μm and to a depth of 200 μm. Qualitative results are presented and the expected accuracy of subsequent microprocessor aided, quantitative metrology is predicted.
TL;DR: The properties of a hybrid scanning, optical-electronic image processor are described, pointing out its ability to enhance the flexibility of optical processors while retaining, to a large extent, their advantage of speed.
Abstract: The properties of a hybrid scanning, optical-electronic image processor are described, pointing out its ability to enhance the flexibility of optical processors while retaining, to a large extent, their advantage of speed. Some experimental results demonstrating the advantage of a scanning optical recognition system are given.
TL;DR: In this article, a polarization interferometer is described which has prisms made of Iceland spar and of glass, and the refractive index of glass is approximately equal to that of the Iceland spar for the ordinary beam.
Abstract: A polarization interferometer is described which has prisms made of Iceland spar and of glass. The refractive index of glass is approximately equal to that of Iceland spar for the ordinary beam. Interferograms are presented showing the supersonic flow around a sphere and the flow behind a shock wave diffracting around the edge of a nozzle.
TL;DR: In this article, the principle of a new technique to vary continuously the duration of a laser pulse using an electro-optical modulator is described, and an experiment using a ruby laser demonstrates the validity of the idea.
Abstract: The principle of a new technique to vary continuously the duration of a laser pulse using an electro-optical modulator is described. An experiment using a ruby laser demonstrates the validity of the idea.
TL;DR: In this paper, a very sensitive interferometric technique is presented, which allows direct measurement of optical and thermal properties, up to 10-7 K-1 for some liquids, particularly for water and deuterium oxide.
Abstract: A very sensitive interferometric technique is presented. It allows direct measurement of optical and thermal properties. The experimental set-up is very simple and acts essentially as an unfocused Fabry-Perot interferometer giving rise only to a central fringe. Measurement of ( ∂n ∂T ) p up to 10-7 K-1 is possible. Determination of ( ∂n ∂T ) p for some liquids, particularly for water and deuterium oxide, has been already performed and others, for ionic crystals, are under way.
TL;DR: In this article, an actively Q-controlled and mode-locked Nd: YAG laser system is described, which uses three Pockels cells to obtain several modes of operation.
Abstract: An actively Q-controlled and mode-locked Nd: YAG laser system is described It uses three Pockels cells to obtain several modes of operation. Single output pulses in the range from 100 ps to 50 ns can be reliably generated. A repetition rate of 10 Hz and jitter in pulse appearance of better than ±50 ns was obtained. The amplified pulse energy was in the range 10–50 mJ.
TL;DR: A simple technique to reduce the noise levels of retrieved images and its application in high density optical information storage is described.
Abstract: Now that crystals are being considered suitable for high density optical information storage, it is important to reduce the noise levels of retrieved images. The paper describes a simple technique to bring this about.