Showing papers in "Optics and Laser Technology in 1986"
281 citations
TL;DR: In this paper, the behavior of a Gaussian Schell-model beam at a spherical boundary is investigated in detail, and transformation laws for its propagation parameters are obtained, which are used to extend the classic ABCD-matrix method into the context of partially coherent beams.
Abstract: The behaviour of a Gaussian Schell-model beam at a spherical boundary is investigated in detail, and transformation laws for its propagation parameters are obtained. These laws are used to extend the classic ABCD-matrix method into the context of partially coherent beams. The matrix formalism is useful in designing and analysing real optical systems, which consist of spherical boundaries and uniform media of finite thickness. Explicit relations are derived that couple the input and output beam parameters in general optical systems of that type. The closed-form imaging equations ensuing for a single thin lens are discussed as an illustrative example.
55 citations
TL;DR: The impact of incorporating fiber-optic components into well established optical techniques such as laser Doppler velocimetry, noncontact vibration measurement, holography and light scattering is discussed in the two sections of this paper as mentioned in this paper.
Abstract: The impact of incorporating fibre-optic components into well established optical techniques such as laser Doppler velocimetry, non-contact vibration measurement, holography and light scattering, is discussed in the two sections of this paper. The possibilities range from simply including a fibre ‘optic link’ in a conventional system to facilitate measurements in difficult or remote areas to the realization of entirely new optical configurations in which virtually all of the conventional optical components have been replaced by their fibre-optic equivalents. In part one, fibre properties, optical sources, directional couplers and modulators are discussed.
35 citations
TL;DR: In this paper, the influence of thermal effects arising from the pumping process on the output character of the 1.3414 μm Nd:YAP cw laser has been discussed.
Abstract: The eigen-oscillation mode of the Nd:YAP cw laser has been analysed. The influence of thermal effects arising from the pumping process on the output character of the 1.3414 μm Nd:YAP cw laser has been discussed. The crack problem of the reflective film at a 1.34 μm dielectric mirror has been solved. Based on the aforementioned work, we have been able to achieve an 82.8 W laser output at 1.3414 μm with a nearly polarized beam from a 5.8 mm diameter by 111 mm Nd:YAP rod. The overall efficiency and the slope efficiency are 1.15% and 2.02% respectively, and the fluctuation of the output power at 62 W is less than 1% during continuous operation for 45 min.
18 citations
Journal Article•
15 citations
TL;DR: In this article, a two-input real-time optical correlation using photorefractive media is discussed, where the bearing of the input arrangement on the correlator's response time to changes in input is considered.
Abstract: Two input real-time optical correlation using photorefractive media is discussed. Consideration is given to the bearing of the input arrangement on the correlator's response time to changes in input. It is demonstrated that previous correlator arrangements using photorefractive Bi 12 SiO 20 (BSO) may be adapted to improve their time response characteristics. Re-allocation of information carrying inputs leads to a two input correlator in which one input may be updated with arbitrary rapidity. The updating of the remaining input is subject to the limits imposed by the dynamics of the photorefractive effect. This is contrasted with previous correlator designs in which the updating of both inputs is subject to such dynamic limitations.
14 citations
TL;DR: In this paper, the absorption of a HeNe beam passing transversely through the plasma plume was measured using two fast response photodiodes and was repeated for sub-atmospheric pressures of air.
Abstract: Laser produced plasma plays an important role in the laser drilling of sheet metals as it can partially block and absorb the incident laser beam. A previous study of the transient properties of charged particles in the plasma plume has shown that, at low electron densities with high electron temperatures, laser drilling improves. This suggests that measurement of the absorption of the plasma plume is essential. The present study covers measurement of the absorption of a HeNe beam passing transversely through the plasma plume. The measurement was carried out using two fast response photodiodes and was repeated for sub-atmospheric pressures of air. The results obtained show that drilling is best at a pressure of 200 torr (2.7 x 104 Pa) and rapid expansion of the flares is favourable at 2 mm above the surface. Coupling of absorption and heating is also best at this pressure.
13 citations
TL;DR: In this article, the size of the echo spot on a quadrant detector is investigated and the relationships between the spot size and the shape of the tracking field of view are determined.
Abstract: The design of the size of the echo spot on a quadrant detector, a key technical problem in auto-tracking technology, is presented. The relationships between the spot size and the shape of the tracking field of view are determined, and the relationships between the spot size and the tracking sensitivity, as well as angular tracking error, are discussed. It is concluded, that to keep the spot size constant, automatic focusing of the topics is required during tracking.
11 citations
TL;DR: In this article, a CO2 gas transport laser with cylindrical geometry and two parallel electrical discharges was constructed and operated using a 600 mm diameter, 1400 mm length, 250 kg laser head and achieved more than 1.6 kW power with 2% stability and 2 mrad full angle divergence.
Abstract: The aim of this work is to report the achievement of a light weight, compact, high power CO2 laser which can be used in industry. The construction and operation of a CO2 gas transport laser with cylindrical geometry and two parallel electrical discharges are presented. Using a 600 mm diameter, 1400 mm length, 250 kg laser head, we have obtained more than 1.6 kW laser power with 2% stability and 2 mrad full angle divergence. For comparison the results are presented for one electrical discharge laser.
10 citations
TL;DR: In this article, an iterative method is presented which can uniformly distribute the Fourier transformed amplitudes of an original object, which is effective in making phase quantized holograms whose amplitudes have constant values, and further, it is effective for such imaging systems where the decreased spectral information is desirable for transmission and storage.
Abstract: An iterative method is presented which can uniformly distribute the Fourier transformed amplitudes of an original object. The method is effective in making phase quantized holograms whose amplitudes have constant values, and further, it is effective for such imaging systems where the decreased spectral information is desirable for transmission and storage. The hologram is produced by iterations of the Fourier transform and inverse Fourier transform operations. The image quality depends upon the number of iterations, however, a great many iterations will not necessarily lead to a marked improvement in the image quality because a rapid improvement is often achieved by only a few iterative operations. From our experiments, the iterative operations have made remarkable improvements in reconstructed images. The proposed method is also suitable for other types of holograms and for applications in imaging systems.
10 citations
TL;DR: In this article, the authors describe an acousto-optical Bragg deflector integrated onto a silicon substrate to have a good performance and quite high deflection efficiency, which is achieved by diminishing the influence of acoustic propagation losses.
Abstract: Technical solutions are described which allow the 500 MHz acousto-optical Bragg deflector integrated onto a silicon substrate to have a good performance and quite high deflection efficiency. This is achieved by diminishing the influence of acoustic propagation losses. As a consequence, is it possible to implement a large bandwidth acousto-optical rf spectrum analyser using fully planar technology.
TL;DR: In this article, the influence on image quality of a finite aperture due to low-contrast response is discussed taking into account the average exposure level of holograms, and the reconstructed image plane is computed taking into consideration both finite and infinite hologram apertures.
Abstract: Irradiance distributions in the reconstructed image plane are computed taking into consideration both finite and infinite hologram apertures. The influence on image quality of a finite aperture due to low-contrast response is discussed taking into account the average exposure level of holograms.
TL;DR: In this article, the light intensity transmission of GaAlAs strip waveguides is sensitively dependent on the strength of the electric field inside the waveguide, when the photon energy is close to the band gap (Franz-Keldysh effect).
Abstract: The light intensity transmission of GaAlAs strip waveguides is sensitively dependent on the strength of the electric field inside the waveguide, when the photon energy is close to the band gap (Franz-Keldysh effect). In a waveguide embedded in a pn-junction the transmitted light itself induces the field changes through the photoelectric effect. This photo-induced Franz-Keldysh effect causes a non-linear intensity transmission of the waveguide. Light power levels far below 1 mW are sufficient to give strong non-linearities. Possible application schemes for modulation and all-optical switching in integrated optics and optoelectronics are discussed.
TL;DR: In this article, the fabrication of an all-fibre Lyot depolarizer was reported, operating in the 850 nm region with the lowest residual polarization known to date of more than 22 dB down on a 100% polarized input.
Abstract: The fabrication of an all-fibre Lyot depolarizer is reported, operating in the 850 nm region with the lowest residual polarization known to date of more than 22 dB down on a 100% polarized input.
TL;DR: In this article, the anti-Stokes spectrum was used to extend the operating range of the Raman spectrometer, to study photodegradable samples and for the analysis of samples which exhibit strong fluorescence.
Abstract: The Raman spectrum of any molecule consists of two mirror-image signals, th e Stokes and anti-Stokes Raman spectra. In most cases, unless highly specific sampling conditions are used, the anti-Stokes signal is much weaker than that of the Stokes. The recent application of intensified diode array detectors to Raman spectroscopy has produced a marked increase in the sensitivity of the technique which makes a study of the anti-Stokes spectrum potentially more rewarding than it has been to date. The present study has shown that, although of limited use for general purposes, there are some specific instances where the anti-Stokes spectrum can be of considerable practical use. Such applications are to extend the operating range of the Raman spectrometer, to study photodegradable samples and for the analysis of samples which exhibit strong fluorescence.
TL;DR: In this paper, the first results on the use of a flexible fiber-optic cable (based on KRS-5 fibre) for the transmission of CO laser power to the operating zone for the coagulation and destruction of biological tissue are presented.
Abstract: The first results on the use of a flexible fibre-optic cable (based on KRS-5 fibre) for the transmission of CO laser power to the operating zone for the coagulation and destruction of biological tissue are presented.
TL;DR: The intensity distribution through the thickness of the illuminating light sheet is deliberately graded, allowing the shape of the object to be recovered more accurately by interpolation of the sampled image.
Abstract: The application of light sectioning to the accurate measurement of a rail cross-section, from a train moving at high speed, is described. The intensity distribution through the thickness of the illuminating light sheet is deliberately graded, allowing the shape of the object to be recovered more accurately by interpolation of the sampled image. Rail profiles are extracted with a definition approximately ten-times better than that of the sampled image.
TL;DR: In this article, an electro-optical feedback control system was built to lock the output of a pulsed or cw laser to within 5 mA of a wavelength reference.
Abstract: An electro-optical feedback control system has been built to lock the output of a pulsed or cw laser to within 5 mA of a wavelength reference. The system senses wavelength changes by detecting movement in an etalon fringe pattern. The laser wavelength is adjusted by angle-tuning an intra-cavity etalon. System performance is evaluated using a tunable and narrow linewidth XeCl-Pb vapour laser system.
TL;DR: In this paper, a short discussion of the technique is presented and its experimental application is described where the difference interferogram is automatically evaluated, where the experimental results show that it can be used to compare large volume production lamps with a master lamp.
Abstract: Total bulb fill pressure and density changes inside incandescent lamps can be studied by holographic interferometry. The main drawback stems from the fact that such techniques only provide information concerning the integral refractive index changes in response to a given electrical load. Difference hologram interferometry results in a direct comparison of any one of the large volume production lamps with a master lamp. A short discussion of the technique is presented and its experimental application is described where the difference interferogram is evaluated automatically.
TL;DR: In this article, the transmission characteristics of a new mixed birefringent filter are investigated and the performance of this filter is better because of the more effective suppression of side peaks.
Abstract: Birefringent filters can be used for tuning lasers, with some advantages over prisms, gratings and tilted etalons. In this paper the transmission characteristics of a new mixed birefringent filter are investigated. The term ‘mixed’ is used because both circular birefringence and linear birefringence have been utilized in the fabrication of this filter. It has a loss-less core, formed by a cascaded system of alternate rotators and retarders, and a linear polarizer at each end. The performance of this filter is better because of the more effective suppression of side peaks. Unlike previous birefringent filters, this one may be used inside a linear resonator.
TL;DR: In this paper, a method for tomographic flow visualization by means of the scattering of a plane laser light sheet is described, which allows three-dimensional visualization, particularly in internal flows.
Abstract: A previous article described a method for tomographic flow visualization by means of the scattering of a plane laser light sheet. This paper shows recent improvements of such a method using two-dimensional sweeps of a pencil laser, which allows three-dimensional visualization, particularly in internal flows.
TL;DR: In this article, the value of using rotation prisms in series to obtain a stationary image of a rotating object was investigated, and it was concluded that a small number of series prisms can be used to advantage, but that the number should be kept small.
Abstract: This paper considers the value of using rotation prisms in series to obtain a stationary image of a rotating object. It addresses the photometric problem which accompanies the use of reflection rotators, and concludes that a small number of series prisms can be used to advantage, but that the number should be kept small.
TL;DR: In this article, the leakage flow through building parts was simulated in laboratory conditions, and was visualized by means of holographic interferometry, and the subject of a forthcoming paper is to investigate leakage flow in the winter time under real conditions.
Abstract: The leakage flow through building parts was simulated in laboratory conditions, and was visualized by means of holographic interferometry. The subject of a forthcoming paper is to investigate the leakage flow in the winter time under real conditions.
TL;DR: In this paper, the general equations of a multipass system using mirrors of different radii are reported, and a geometrical calculation of the fundamental gaussian mode for the open resonator can be obtained.
Abstract: The general equations of a multipass system using mirrors of different radii are reported. By using these solutions, a geometrical calculation of the fundamental gaussian mode for the open resonator can be obtained. This result is equal to that obtained taking account of diffraction effects.
TL;DR: In this article, a single mode 3 dB fused coupler, to be used as a redundant laser combiner in the submerged repeater of an undersea optical fiber transmission system, is described.
Abstract: A single mode 3 dB fused coupler, to be used as a redundant laser combiner in the submerged repeater of an undersea optical fibre transmission system, is described. The fabrication and package design of the component for this high reliability application is discussed, and the results of a wide range of environmental tests are given.
TL;DR: In this paper, the optical system of an electro-optical distance meter is described and the impact of the measuring conditions is dealt with, and the method of analysis involving numerical calculations is given and the results for three typical cases are shown.
Abstract: Vignetting in the optical system of an electro-optical distance meter is described, and the impact of the measuring conditions is dealt with. The method of analysis, involving numerical calculations, is given and the results for three typical cases are shown.
TL;DR: In this article, a white light source and based on the self correlation effect of a group of moving particles, a method is proposed for measuring the velocity and acceleration of the particles.
Abstract: By using a white light source and based on the self correlation effect of a group of moving particles, a method is proposed for measuring the velocity and acceleration of the particles. This velocity can be colour coded. A simple theoretical analysis is given and a simulation experiment is presented. The method is simple and economic.