Showing papers in "Journal of Modern Optics in 1989"
TL;DR: In this article, the physics of laser plasma interactions were studied and discussed in the context of particle physics and laser plasminar simulations, and the results were presented in the Journal of Modern Optics: Vol. 36, No. 3, No.
Abstract: (1989). The Physics of Laser Plasma Interactions. Journal of Modern Optics: Vol. 36, No. 3, pp. 417-418.
626 citations
TL;DR: In this paper, it was shown that the number-phase commutator differs from that originally postulated by Dirac and this difference allows consistent use of the commutators for inherently quantum states.
Abstract: It has long been believed that no Hermitian optical phase operator exists. However, such an operator can be constructed from the phase states. We demonstrate that its properties are precisely in accord with the results of semiclassical and phenomenological approaches when such approximate methods are valid. We find that the number-phase commutator differs from that originally postulated by Dirac. This difference allows the consistent use of the commutator for inherently quantum states. It also leads to the correct periodic phase behaviour of the Poisson bracket in the classical regime.
447 citations
TL;DR: In this paper, the structural invariants of the field of isophotes on lambertian surfaces of arbitrary shape under arbitrary illumination were identified and an attempt was made to identify several such invariants.
Abstract: An attempt is made to identify the structural invariants of the field of isophotes on lambertian surfaces of arbitrary shape under arbitrary illumination. It is a priori clear that such invariants play an important part in the perception of solid shape by means of chiaroscuro. We have found several such invariants. The topological structure of the field of isophotes is determined by the collection of nested, closed parabolic curves on the surface. An important class of stationary points of the field clings to these parabolic lines. The isophotes cut the parabolic lines at a constant angle, irrespective of the location of the light sources. For certain canonical surface undulations the field of isophotes is explicitly given.
253 citations
TL;DR: In this article, the temporal correlation of speckle patterns produced when a specimen is illuminated with a laser beam is analyzed by using statistical processing of the digital speckles applied to the computation of correlation coefficients.
Abstract: A biological activity phenomenon, the cyclose that occurs in citrus fruits or in seaweed, is analysed by using the temporal correlation of speckle patterns produced when a specimen is illuminated with a laser beam. The experimental verification of the phenomenon as well as a theoretical model of the distribution of the elementary moving particles are given. Specific statistical processing of the digital speckle is applied to the computation of correlation coefficients. Experimental results are given for three kinds of biological samples.
194 citations
TL;DR: In this article, the influence of the finite size of an incident beam upon both the anomalous-reflection spectrum and the shape of the energy distribution in a reflected beam was investigated.
Abstract: The paper is concerned with the influence of the finite size of an incident beam upon both the anomalous-reflection spectrum and the shape of the energy distribution in a reflected beam. It is proved experimentally that the use of corrugated waveguides as a laser-resonator selective mirror improves the spatial coherence of radiation.
186 citations
TL;DR: In this paper, the influence of coherent noise and chromatic errors on the performance of array generators is investigated, and different systems for array generation are classified and compared with respect to their relevant parameters.
Abstract: An array generator is an optical system that splits an incoming beam of light into an array of many ‘beamlets’. Such a multiple beam-splitting system is necessary in optical data processing, where two-dimensional arrays of optical modulators, optical logic devices or optically bistable devices have to be read out optically or have to be provided with power-supply or bias beams. Other applications include multiple imaging and space-variant processing. The number of beams within an array has to be adapted to the size of the array of optical devices, also the modal shape of each single beam has to be adapted to the acceptable modes for the individual devices. Different systems for array generation are classified and compared with respect to their relevant parameters. Methods for modal adaptation are described. The influence of coherent noise and of chromatic errors is investigated. Non-Cartesian and irregular array generators are proposed.
174 citations
TL;DR: In this paper, the distribution and moments of the depth reached by a photon, conditional on its having reached the surface at a (dimensionless) distance, ϱ, from the point of entry of the beam into the tissue, are derived.
Abstract: We derive some statistical properties of photons emitted from bulk tissue that has been irradiated by a continuous beam of laser light. The properties include the distribution and moments of the depth reached by a photon, conditional on its having reached the surface at a (dimensionless) distance, ϱ, from the point of entry of the beam into the tissue. Theoretical predictions are made on the basis of a lattice random-walk model and are checked by simulations of the light penetration problem for a more realistic continuum model.
116 citations
92 citations
TL;DR: In this paper, a theoretical analysis of an optical processing system for time-space shaping of short light pulses is presented, which consists of two gratings with a 4-f Fourier processing system placed between them.
Abstract: A theoretical analysis of an optical processing system for time-space shaping of short light pulses is presented. The optical scheme considered consists of two gratings with a 4-f Fourier-processing system placed between them. Using an expansion of the field over a set of temporal and spatial modes, we find an expression for the output field as a function of the input field and of the system parameters. Our approach allows the solving of the inverse problem: a determination of the filter function, which will give a preliminary designed output pulse shape. The formalism developed could be applied in the description of other similar systems.
71 citations
TL;DR: In this paper, the anomalous light reflection from waveguides with two corrugated boundaries is considered and it is shown theoretically and experimentally that these structures can form the basis for a highly efficient unidirectional grating coupler for slab waveguide.
Abstract: Waveguide structures with two corrugated interfaces are considered. It is shown theoretically and experimentally that these structures can form the basis for a highly-efficient unidirectional grating coupler for slab waveguides. The anomalous light reflection from waveguides with two corrugated boundaries is also considered. The possibility of using corrugated waveguides for frequency stabilization of a semiconductor laser is demonstrated.
TL;DR: In this paper, a simple optical system for synthesizing two-dimensional planar sources having a wide variety of one-dimensional spectral degrees of coherence is analyzed, where a pupil mask acting on the dispersed image of a polychromatic incoherent slit is used to control the spectral degree of coherent of the source.
Abstract: A simple optical system for synthesizing two-dimensional planar sources having a wide variety of one-dimensional spectral degrees of coherence is analysed. A pupil-mask acting on the dispersed image of a polychromatic incoherent slit is used to control the spectral degree of coherence of the source. Examples of sources exhibiting interesting spectral shifts and modulations in the far field are shown.
TL;DR: In this article, the density correlation function p(x) varies like x D − 3 as x → 0, where D is the fractal dimension, and the theory predicts that for clusters with D 2 both scattering and absorption decay as N → ∞ after reaching a maximum.
Abstract: Fractal aggregates such as soot particles are modelled as connected clusters of N spherules of radius a and complex refractive index µ, whose density correlation function p(x) varies like x D − 3 as x → 0, where D is the fractal dimension. They scatter scalar or vector waves of wavelength 2π/k where ka ≪ 1. Multiple scattering effects are included using a mean field theory. Optical cross-sections are derived in terms of N D ka and µ using an analytic form for p(x). The theory predicts that for clusters with D 2 both scattering and absorption decay as N → ∞ after reaching a maximum.
TL;DR: A Fourier filtration algorithm has been applied to speckled fringe patterns, as obtained with the electronic speckle pattern interferometer, which facilitates the computer interferometric analysis of such fringe patterns.
Abstract: A Fourier filtration algorithm has been applied to speckled fringe patterns, as obtained with the electronic speckle pattern interferometer. The Fourier power spectrum components found are then conveniently manipulated to extract noise that is inherent to the speckled fringes, thus rendering holographic-quality displays. The use of this technique facilitates the computer interferometric analysis of such fringe patterns. Some examples of the phase fringes and the corresponding object displacements obtained using this method are shown.
TL;DR: In this paper, the effects associated with small particles were investigated and the effects of optical effects on small particles on small-particle optical effects were discussed. Journal of Modern Optics: Vol. 36, No. 9, No 2, pp. 1275-1276
Abstract: (1989). Optical Effects Associated with Small Particles. Journal of Modern Optics: Vol. 36, No. 9, pp. 1275-1276.
TL;DR: In this article, the effect of non-uniform pump and laser beam profile on relaxation oscillation frequency and slope efficiency for a longitudinally-pumped four-level laser was analyzed.
Abstract: Measurement of relaxation oscillation frequency can provide a convenient means for measurement of laser resonator losses. Expressions are derived which take account of the effect of non-uniform pump and laser beam profile on relaxation oscillation frequency and slope efficiency for a longitudinally-pumped four-level laser. Significant departures from plane-wave calculations are found. It is also shown that by combining a measurement of slope efficiency and relaxation oscillation frequency, the loss can be deduced without detailed knowledge of the pump beam profile. Experimental results supporting these calculations are described.
TL;DR: In this paper, the angular dependence of the reflectivity of a ferroelectric liquid crystal (FLC) cell fabricated from glass pyramids with 60° evaporated SiO aligning layers was investigated.
Abstract: By observing the angular dependence of the reflectivity of a ferroelectric liquid crystal (FLC) cell fabricated from glass pyramids with 60° evaporated SiO aligning layers it has been possible to sensitively probe the configuration of the optical dielectric tensor in the FLC layer. It is found that the optical data can best be explained by a uniaxial slab twisted from the alignment axis; this is consistent with the recently proposed chevron structure.
TL;DR: In this paper, the influence of the initial states of the atom on the squeezing of light is investigated in detail, and it is shown that in the intensity-dependent coupling Jaynes-Cummings model with the coherent radiation field light squeezing exhibits periodical revivals.
Abstract: We have found that in the intensity-dependent-coupling Jaynes-Cummings model with the coherent radiation field light squeezing exhibits periodical revivals. The influence of the initial states of the atom on the squeezing of light is investigated in detail.
TL;DR: In this article, the effects of coherence between the states of a two-level atom on the phenomenon of collapses and revivals in an undamped binomial state of the electromagnetic field are investigated.
Abstract: The effects of the coherence between the states of a two-level atom on the phenomenon of collapses and revivals in an undamped binomial state of the electromagnetic field are investigated. It is found that the Rabi oscillations exhibit qualitatively different behaviour for different phases of coherence between the levels. This behaviour in the binomial state of the field is in contrast with that in a coherent state field, in which case the Rabi oscillations are qualitatively the same for all values of the coherence between the two atomic levels.
TL;DR: In this paper, the authors discuss the instability and chaos in Quantum Optics, and propose a method to solve the problem of quantum instability and Chaos in quantum Optics (COCO).
Abstract: (1989). Instabilities and Chaos in Quantum Optics. Journal of Modern Optics: Vol. 36, No. 1, pp. 149-149.
TL;DR: In this paper, photoacoustic and Photothermal Phenomena are discussed. But their focus is on the photo-acoustic properties rather than the photothermal properties of the image itself.
Abstract: (1989). Photoacoustic and Photothermal Phenomena. Journal of Modern Optics: Vol. 36, No. 6, pp. 809-809.
TL;DR: In this article, the authors present several perturbative approaches to the Jaynes-Cummings model of optical resonance with the counter-rotating terms included, and they find that there exists a hitherto overlooked phase-dependence of the atomic inversion which is due to an interference between the rotating wave and counterrotating contributions.
Abstract: We present several perturbative approaches to the Jaynes-Cummings model of optical resonance with the counter-rotating terms included. We find that there exists a hitherto overlooked phase-dependence of the atomic inversion which is due to an interference between the rotating wave and counter-rotating contributions.
TL;DR: In this article, the active correction of a 1 m test mirror was described in detail and a residual aberration term was found which still required correction in order to achieve the aim of the experiment: removal of all systematic defects leaving only statistical or highfrequency noise.
Abstract: In ‘Active Optics II’, the active correction of a 1 m test mirror was described in detail. A residual aberration term was found which still required correction in order to achieve the aim of the experiment: removal of all systematic defects leaving only statistical or high-frequency noise. The present paper describes the interferometric confirmation of the term and this final correction stage of the 1 m experiment.
TL;DR: In this paper, the effects of optical depth, beam focusing and nonperturbative atomic response on the spectrum of optical harmonics generated by an intense beam of laser radiation (up to 1014W cm−2) in a small volume of atomic vapour were discussed.
Abstract: We discuss effects of optical depth, beam focusing and non-perturbative atomic response on the spectrum of optical harmonics generated by an intense beam of laser radiation (up to 1014W cm−2) in a small volume of atomic vapour. We find remarkable enhancement of high harmonics at intensities beyond the perturbative limit.
TL;DR: In this paper, surface plasmon-polaritons (SPP) have been excited on evaporated films of the transition metals nickel, palladium and platinum using the Otto geometry and a He/Ne laser operating at 3·391 μm.
Abstract: Surface plasmon-polaritons (SPP) have been excited on evaporated films of the transition metals nickel, palladium and platinum. Using the Otto geometry and a He/Ne laser operating at 3·391 μm we report the first characterisations of these metals using this technique. Adjusting the air-gap over the range 4 to 15 μm has allowed observation of > 95% coupling of p-polarised (TM) radiation to the SPP and precise quantification of the optical dielectric constants of the metal films. The relatively large imaginary components so obtained mean that these materials may not readily be used in the Kretschmann geometry at this wavelength. By contrast the SPP resonances observed using the Otto geometry are sharp and open up potential for catalytic studies with SPP excitation on these metals.
TL;DR: In this article, a non-perturbative approach based on the direct numerical solution of the time-dependent Schrodinger wave equation is described, and the results of this theory are presented, including evidence for a plateau of high-order harmonic peak intensities.
Abstract: We present theoretical work on high-order harmonic generation accompanying multiphoton ionization of atoms in intense laser fields. We first review some elements of the theory of harmonic generation, particularly the limitations imposed by perturbation theory and some aspects of phase-matching at high pump intensities. A new non-perturbative approach to the theory based on the direct numerical solution of the time-dependent Schrodinger wave equation is described. Selected results of this theory are presented, including: (a) evidence for a plateau of high-order harmonic peak intensities and a relatively abrupt cut-off of this plateau, closely similar to what has been reported experimentally in noble gas atoms, (b) specific predictions for harmonic production by H, He and Xe atoms, and (c) analytical and numerical evidence for the correlation of harmonic production spectra with above-threshold photoelectron spectra under certain circumstances.
TL;DR: In this article, the rates for the absorption of radiation by complex systems are calculated for the most general elliptically polarized light, and the results are presented through generalized B-coefficients, which are basically functions of the absorbing molecules, the coherence and intensity dependency of the rates being factored out.
Abstract: The rates for the absorption of radiation by complex systems are calculated for the most general elliptically polarized light. Absorption is considered from intense beams where multiphoton processes are important so that the mechanism must be considered in the nonlinear regime. The results are presented through generalized B-coefficients, which are basically functions of the absorbing molecules, the coherence and intensity dependency of the rates being factored out. The present calculations extend our previous ones in so far as the emphasis is on the effects of the ellipticity of the light beam. Extensive results are given for two- and three-photon absorption rates for molecules with both permanent and transition electric dipole, magnetic dipole and electric quadrupole moments being effective. Special consideration is given to chiroptical effects, both where these are due to orientational dependence of the molecule with respect to the light beam and where these are due to the intrinsic structure ...
TL;DR: In this paper, the authors describe a number of multiplexing techniques which may be used for fiber-optic sensors in which the sensing element is a ring resonator, which can be used to yield a sensor of increased sensitivity over that obtainable with a two-beam interferometer.
Abstract: We describe a number of multiplexing techniques which may be used for fibre-optic sensors in which the sensing element is a ring resonator. The basic optical unit comprises a sensing ring resonator connected to a second interrogating ring resonator of nearly equal length, and illuminated by a source of short coherence length. A number of such units may be combined to form an array, using coherence multiplexing techniques. Using such an arrangement, the high finesse of the ring resonator may be exploited to yield a sensor of increased sensitivity over that obtainable with a two-beam interferometer. When a high-coherence source is used, then multiplexing may be accomplished using frequency-division techniques. However, in this case, the resonators must have low finesse, in order to avoid cross-talk. We also show that when a source of moderate coherence length is used, it is possible to use both frequency division and coherence multiplexing simultaneously, with the potential of realizing a large sen...
TL;DR: In this article, a simple kinetic model was presented which describes the temporal behaviour of an Er:YAG laser pulse and predicts c.w. operation up to 40Hz with 4W average power.
Abstract: A simple kinetic model is presented which describes the temporal behaviour of an Er:YAG laser pulse and predicts c.w. operation. The use of transfer dye to selectively pump the erbium ions, and suitable optimisation of laser cavity parameters has allowed operation up to 40Hz with 4W average power. 10W at 100Hz is predicted.
TL;DR: The aberrations and apodization of microscope objectives have been measured by observation of the defocus signal in a confocal interference microscope system as mentioned in this paper, and quantitative information is given about the imaging performance of the lenses in situ in the optical system.
Abstract: The aberrations and apodization of microscope objectives have been measured by observation of the defocus signal in a confocal interference microscope system. Phase distortions can be measured to approximately λ/100, and quantitative information is given about the imaging performance of the lenses in situ in the optical system.