Measurement of the induced refractive index in a photothermorefractive glass by a liquid-cell shearing interferometer

A liquid-cell shearing interferometer was developed to measure refractive-index variations (delta n) in transparent materials. The cell was filled with a liquid having a matched refractive index. The achieved resolution was better than 1/1000 of a fringe shift and resulted in a delta n measurement sensitivity down to 10(-7) for 1-mm-thick samples. A refractive-index increment in photothermorefractive glass of up to 5 x 10(-6) was observed after UV exposure at 325 nm. A refractive-index decrement of up to 1 x 10(-3) was observed after thermal development of the exposed sample. It was proved that photothermorefractive glass obeys the reciprocity law; i.e., delta n depends on the UV dosage but does not depend on the irradiance.     

Effect of terbium gallium garnet crystal orientation on the isolation ratio of a Faraday isolator at high average power

We present a comprehensive and systematic investigation of the fundamental physical limitations of Faraday isolation performance at high average powers that are due to thermally induced birefringence. First, the operation of various Faraday isolator designs by use of arbitrary orientation of cubic magneto-optic crystals is studied theoretically. It is shown that, for different Faraday isolator designs, different crystal orientations can optimize the isolation ratio. Second, thermo-optic and photoelastic constants for terbium gallium garnet crystals grown by different manufacturers were measured. Measurements of self-induced depolarization are made for various orientations of crystallographic axes. The measurements are in good agreement with our theoretical predictions. Based on our results, it is possible to select a crystal orientation that optimizes isolation performance at high average powers, resulting in a 5-dB enhancement over nonoptimized orientations.     

Visual odometry for ground vehicle applications

We present a system that estimates the motion of a stereo head, or a single moving camera, based on video input. The system operates in real time with low delay, and the motion estimates are used for navigational purposes. The front end of the system is a feature tracker. Point features are matched between pairs of frames and linked into image trajectories at video rate. Robust estimates of the camera motion are then produced from the feature tracks using a geometric hypothesize‐and‐test architecture. This generates motion estimates from visual input alone. No prior knowledge of the scene or the motion is necessary. The visual estimates can also be used in conjunction with information from other sources, such as a global positioning system, inertia sensors, wheel encoders, etc. The pose estimation method has been applied successfully to video from aerial, automotive, and handheld platforms. We focus on results obtained with a stereo head mounted on an autonomous ground vehicle. We give examples of camera trajectories estimated in real time purely from images over previously unseen distances (600 m) and periods of time. © 2006 Wiley Periodicals, Inc.     

Modulation spectroscopy study of a strained layer GaAs/GaAsP multiple quantum well structure

Using contactless electroreflectance (CER) and piezoreflectance at 300 K we have characterized a GaAs/GaAs_1?xP_x multiple quantum well (MQW) structure, “GaAs” (nominal) and GaAsP epilayers grown by chloride transport chemical vapor deposition on GaAs (001) substrates. From a detailed lineshape fit to the CER data from the epilayers we have determined the energies of the fundamental band gap and hence the phosphorous composition. The nominal “GaAs” epilayers were found to have phosphorous compositions of about 2.5–3.2%, a result of the phosphorous diffusion between growth chambers in the reactor. The GaAs_1?xP_x epilayer had x=0.29. For the GaAs_0.97P_0.03/GaAs_0.71P_0.29MQW comparison between the experimentally observed energies of a number of quantum transitions with a theoretical envelope function calculation, including the effects of strain in the barriers, made it possible to evaluate the unstrained conduction band offset parameter Q_c=0.50±0.05. Our value for this parameter is discussed in relation to other works. Atomic force microscopy was employed to investigate the surface morphology of the 230 Å GaAsP top layer of the MQW in addition to a 2000 Å GaAsP epilayer. From the absence of any cross-hatch pattern associated with misfit dislocations on the former we concluded that the GaAsP in the MQW is pseudomorphic. On the other hand the 2000 Å epilayer exhibited signs of strain relaxation.     

Phase unwrapping for 2-D blind deconvolution of ultrasound images

In most approaches to the problem of two-dimensional homomorphic deconvolution of ultrasound images, the estimation of a corresponding point-spread function (PSF) is necessarily the first stage in the process of image restoration. This estimation is usually performed in the Fourier domain by either successive or simultaneous estimation of the amplitude and phase of the Fourier transform (FT) of the PSE This paper addresses the problem of recovering the FT-phase of the PSF, which is an important reconstruction problem by itself. The purpose of this paper is twofold. First, it provides a theoretical framework, establishing that the FT-phase of the PSF can be effectively estimated by a proper smoothing of the FT-phase of the appropriate radio-frequency (RF) image. Second, it presents a novel approach to the estimation of the FT-phase of the PSF, by solving a continuous Poisson equation over a predefined smooth subspace, in contrast to the discrete Poisson equation solver used for the classical least mean squares phase unwrapping algorithms, followed by a smoothing procedure. The proposed approach is possible due to the distinct properties of the FT-phases, among which the most important property is the availability of precise values of their partial derivatives. This property overcomes the main disadvantage of the discrete schemes, which routinely use wrapped (principal) values of the phase in order to approximate its partial derivatives. Since such an approximation is feasible subject to the restriction that the partial phase differences do not exceed pi in absolute value, the discrete schemes perform satisfactory only for few practical situations. The proposed approach is shown to be independent of this restriction and, thus, it performs for a wider class of the phases with significantly lower errors. The main advantages of the novel method over the algorithms based on discrete schemes are demonstrated in a series of computer simulations and for in vivo measurements.     

DVR3D: a program suite for the calculation of rotation-vibration spectra of triatomic molecules

The DVR3D program suite calculates energy levels, wavefunctions, and where appropriate dipole transition moments, for rotating and vibrating triatomic molecules. Potential energy and, where necessary, dipole surfaces must be provided. Expectation values of geometrically defined functions can be calculated, a feature which is particularly useful for fitting potential energy surfaces. The programs use an exact (within the Born-Oppenheimer approximation) Hamiltonian and offer a choice of Jacobi or Radau internal coordinates and several body-fixed axes. Rotationally excited states are treated using an efficient two-step algorithm. The programs uses a Discrete Variable Representation (DVR) based on Gauss-Jacobi and Gauss-Laguerre quadrature for all 3 internal coordinates and thus yields a fully point-wise representation of the wavefunctions. The vibrational step uses successive diagonalisation and truncation which is implemented for a number of possible coordinate orderings. The rotational, expectation value and transition dipole programs exploit the savings offered by performing integrals on a DVR grid. The new version has been rewritten in FORTRAN 90 to exploit the dynamic array allocations and the algorithm for dipole and spectra calculations have been substantially improved. New modules allow the z-axis to be embedded perpendicular to the plane of the molecule and for the calculation of expectation values.

Program summary

Title of the program: DVR3D suiteCatalogue number: ADTIProgram summary URL:http://cpc.cs.qub.ac.uk/summaries/ADTIProgram obtainable from: CPC Program Library, Queen's University of Belfast, N. IrelandProgramming language: Fortran 90No. of lines in distributed program, including test data, etc.: 61 574No. of bytes in distributed program, including test data, etc.: 972 404Distribution format: tar.gz

New version summary

Title of program: DVR3DRJZCatalogue number: ADTBProgram summary URL:http://cpc.cs.qub.ac.uk/summaries/ADTBProgram obtainable from: CPC Program Library, Queen's University of Belfast, N. IrelandReference in CPC to previous version: 86 (1995) 175Catalogue identifier of previous version: ADAKAuthors of previous version: J. Tennyson, J.R. Henderson and N.G. FultonDoes the new version supersede the original program?: DVR3DRJZ supersedes DVR3DRJComputer: PC running LinuxInstallation: desktopOther machines on which program tested: Compaq running True64 Unix; SGI Origin 2000, Sunfire V750 and V880 systems running SunOS, IBM p690 Regatta running AIXProgramming language used in the new version: Fortran 90Memory required to execute: case dependentNo. of lines in distributed program, including test data, etc.: 4203No. of bytes in distributed program, including test data, etc.: 30 087Has code been vectorised or parallelised?: The code has been extensively vectorised. A parallel version of the code, PDVR3D has been developed [1], contact the first author for detailsAdditional keywords: perpendicular embeddingDistribution format: gzNature of physical problem: DVR3DRJZ calculates the bound vibrational or Coriolis decoupled rotational-vibrational states of a triatomic system in body-fixed Jacobi (scattering) or Radau coordinates [2]Method of solution: All coordinates are treated in a discrete variable representation (DVR). The angular coordinate uses a DVR based on (associated) Legendre polynomials and the radial coordinates utilise a DVR based on either Morse oscillator-like or spherical oscillator functions. Intermediate diagonalisation and truncation is performed on the hierarchical expression of the Hamiltonian operator to yield the final secular problem. DVR3DRJ provides the vibrational wavefunctions necessary for ROTLEV3, ROLEV3B or ROTLEV3Z to calculate rotationally excited states, DIPOLE3 to calculate rotational-vibrational transition strengths and XPECT3 to compute expectation valuesRestrictions on the complexity of the problem: (1) The size of the final Hamiltonian matrix that can practically be diagonalised. (2) The order of integration in the radial coordinates that can be dealt with within the machine exponent range. Some adjustment in the code may be necessary when large order Gauss-Laguerre quadrature is usedTypical running time: Case dependent but usually dominated by the final (3D) matrix diagonalisation. The test runs take minutes on a fast PCUnusual features of the program: A user supplied subroutine containing the potential energy as an analytic function is a program requirementReferences:

[1]

H.Y. Mussa, J. Tennyson, Comput. Phys. Commun. 128 (2000) 434.

[2]

J. Tennyson, B.T. Sutcliffe, Internat. J. Quantum Chem. 42 (1992) 941.

New version summary

Title of program: ROTLEV3Catalogue number: ADTCProgram summary URL:http://cpc.cs.qub.ac.uk/summaries/ADTCProgram obtainable from: CPC Program Library, Queen's University of Belfast, N. IrelandReference in CPC to previous version: 86 (1995) 175Catalogue identifier of previous version: ADALAuthors of previous version: J. Tennyson, J.R. Henderson and N.G. FultonDoes the new version supersede the original program?: YesComputer: PC running LinuxInstallation: desktopOther machines on which program tested: Compaq running True64 Unix; SGI Origin 2000, Sunfire V750 and V880 systems running SunOSProgramming language used: Fortran 90High speed storage required: case dependentNo. of lines in distributed program, including test data, etc.: 1514No. of bytes in distributed program, including test data, etc.: 12 652Has code been vectorised or parallelised?: The code has been extensively vectorised. A parallel version of the code, PROTLEV3 has been developed [1], contact the first author for detailsDistribution format: gzNature of physical problem: ROTLEV3 performs the second step in a two-step variational calculation for the bound rotational-vibrational levels of a triatomic system represented in either Jacobi or unsymmetrised Radau coordinatesMethod of solution: A basis is constructed from the solutions of the Coriolis decoupled problem provided by DVR3DRJZ. The angular coordinate is transformed back to a basis set representation. The sparse Hamiltonian matrix can be diagonalised iteratively or in coreRestrictions on the complexity of the problem: The size of matrix that can practically be diagonalisedTypical running time: Case dependent. The sample data takes less than a minute on a fast PCUnusual features of the program: Most data is read directly from DVR3DRJZ. ROTLEV3 can provide data to drive DIPOLE3 and/or XPECT3References: [1] H.Y. Mussa, J. Tennyson, Comput. Phys. Commun. 128 (2000) 434.

New version summary

Title of program: ROTLEV3BCatalogue number: ADTDProgram summary URL:http://cpc.cs.qub.ac.uk/summaries/ADTDProgram obtainable from: CPC Program Library, Queen's University of Belfast, N. IrelandReference in CPC to previous version: 86 (1995) 175Catalogue identifier of previous version: ADAMAuthors of previous version: J. Tennyson, J.R. Henderson and N.G. FultonDoes the new version supersede the original program?: YesComputer: PC running LinuxInstallation: desktopOther machines on which program tested: Compaq running True64 Unix, Sunfire V750 and V880 systems running SunOSProgramming language used: Fortran 90High speed storage required: case dependentNo. of lines in distributed program, including test data, etc.: 2215No. of bytes in distributed program, including test data, etc.: 16 595Has code been vectorised or parallelised?: The code has been extensively vectorised. A parallel version of the code, PROTLEV3B has been developed [1], contact the first author for detailsDistribution format: gzNature of physical problem: ROTLEV3B performs the second step in a two-step variational calculation for the bound rotational-vibrational levels of a triatomic system represented by symmetrised Radau coordinates using a bisector embedding [2]Method of solution: A basis is constructed from the solutions of the Coriolis decoupled problem provided by DVR3DRJZ. The problem is constructed entirely within the DVR. The Hamiltonian matrix can be diagonalised iteratively or in coreRestrictions on the complexity of the problem: The size of matrix that can practically be diagonalisedTypical running time: Case dependent. The sample data takes a few minutes on a fast PCUnusual features of the program: Most data is read directly from DVR3DRJZ. ROTLEV3B can provide data to drive DIPOLE3 and/or XPECT3References:

[1]

H.Y. Mussa, J. Tennyson, Comput. Phys. Commun. 128 (2000) 434.

[2]

J. Tennyson, B.T. Sutcliffe, Internat. J. Quantum Chem. 42 (1992) 941.

Program summary

Title of program: ROTLEV3ZCatalogue number: ADTEProgram summary URL:http://cpc.cs.qub.ac.uk/summaries/ADTEProgram obtainable from: CPC Program Library, Queen's University of Belfast, N. IrelandComputer: PC running LinuxInstallation: desktopOther machines on which program tested: Compaq running True64 Unix, Sunfire V750 and V880 systems running SunOSProgramming language used: Fortran 90High speed storage required: case dependentNo. of lines in distributed program, including test data, etc.: 2919No. of bytes in distributed program, including test data, etc.: 17 241Keywords: rotationally excited state, Coriolis coupling, secondary variational method, sparse matrix, vectorised, perpendicular embedding, Radau coordinatesHas code been vectorised or parallelised?: The code has been extensively vectorisedDistribution format: gzNature of physical problem: ROTLEV3Z performs the second step in a two-step variational calculation for the bound rotational-vibrational levels of a triatomic system represented by symmetrised Radau coordinates using a perpendicular embedding [1]Method of solution: A basis is constructed from the solutions of the Coriolis decoupled problem provided by DVR3DRJZ. The problem is constructed entirely within the DVR. The Hamiltonian matrix is diagonalised in coreRestrictions on the complexity of the problem: The size of matrix that can practically be diagonalisedTypical running time: Case dependent. The sample data takes a few minutes on a fast PCUnusual features of the program: Most data is read directly from DVR3DRJZReferences: [1] M.A. Kostin, O.L. Polyansky, J.Tennyson, J. Chem. Phys. 116 (2002) 7564.

New version summary

Title of program: DIPOLE3Catalogue number: ADTFProgram summary URL:http://cpc.cs.qub.ac.uk/summaries/ADTFProgram obtainable from: CPC Program Library, Queen's University of Belfast, N. IrelandReference in CPC to previous version: 86 (1995) 175Catalogue identifier of previous version: ADANAuthors of previous version: J. Tennyson, J.R. Henderson and N.G. FultonDoes the new version supersede the original program?: YesComputer: PC running LinuxInstallation: desktopOther machines on which program tested: Compaq running True64 Unix; SGI Origin 2000; sunfire V750 and V880 systemsProgramming language used: Fortran 90High speed storage required: case dependentNo. of lines in distributed program, including test data, etc.: 1921No. of bytes in distributed program, including test data, etc.: 15 685Has code been vectorised or parallelised?: The code has been extensively vectorised. Commands to parallelise the code using OpenMP are included in the sourceDistribution format: gzNature of physical problem: DIPOLE3 calculates dipole transition intensities between previously calculated wavefunction for both rotational and rotational-vibrational transitionsMethod of solution: Integrals over dipole surfaces are constructed using a DVR in all three coordinates, this requires a transformation of the angular wavefunctions. Wavefunctions generated by DVR3DRJZ and ROTLEV3 or ROTLEV3B are then used to give transition intensities for individual pairs of statesRestrictions on the complexity of the problem: The complexity of the problem that can be solved by DVR3DRJZ, ROTLEV3 or ROTLEV3BTypical running time: Case dependent. The test data takes a few seconds on a fast PCUnusual features of the program: Most data is read directly from DVR3DRJZ and ROTLEV3 or ROTLEV3B. DIPOLE provides data to drive SPECTRA

New version summary

Title of program: SPECTRACatalogue number: ADTGProgram summary URL:http://cpc.cs.qub.ac.uk/summaries/ADTGProgram obtainable from: CPC Program Library, Queen's University of Belfast, N. IrelandComputer: PC running LinuxInstallation: desktopOther machines on which program tested: Compaq running True64 UnixReference in CPC to previous version: 75 (1993) 339Catalogue identifier of previous version: ACNBAuthors of previous version: J. Tennyson, S. Miller and C.R. Le SueurDoes the new version supersede the original program?: YesProgramming language used: Fortran 90High speed storage required: case dependentNo. of lines in distributed program, including test data, etc.: 1037No. of bytes in distributed program, including test data, etc.: 9159Has code been vectorised or parallelised?: As execution times are very short this is usually not importantDistribution format: gzNature of physical problem: SPECTRA generates synthetic, frequency ordered spectra as a function of temperature. Absolute intensities can be calculated if the necessary data to calculate the partition function is suppliedMethod of solution: Transitions are sorted by frequency and weighted using Boltzmann statisticsRestrictions on the complexity of the problem: The complexity of problem that can be solved by other programs in the suiteTypical running time: Case dependent, but very small for sample dataUnusual features of the program: Most data is read directly from DIPOLE3. Some data from DVR3DRJZ and ROTLEV3 or ROTLEV3B may also be required

Program summary

Title of program: XPECT3Catalogue number: ADTHProgram summary URL:http://cpc.cs.qub.ac.uk/summaries/ADTHProgram obtainable from: CPC Program Library, Queen's University of Belfast, N. IrelandComputer: PC running LinuxInstallation: desktopOther machines on which program tested: Compaq running True64 UnixProgramming language used: Fortran 90High speed storage required: case dependentNo. of lines in distributed program, including test data, etc.: 1214No. of bytes in distributed program, including test data, etc.: 9361Distribution format: gzKeywords: Expectation values, Hellmann-Feynman theorem, potential fittingHas code been vectorised or parallelised?: The code has been extensively vectorisedNature of physical problem: XPECT3 calculates expectation of geometrically defined operators using previously calculated wavefunctionsMethod of solution: Integrals over the user defined surfaces are constructed using a DVR in all three coordinates. Wavefunctions generated by DVR3DRJZ and ROTLEV3 or ROTLEV3B are then used to give expectation values for each stateRestrictions on the complexity of the problem: The complexity of problem that can be solved by DVR3DRJZ, ROTLEV3 or ROTLEV3BTypical running time: Case dependent. The test data takes a few seconds on a fast PCUnusual features of the program: Most data is read directly from DVR3DRJZ and ROTLEV3 or ROTLEV3B.     

Single-material inhomogeneous optical filters based on microstructural gradients in plasma-deposited silicon nitride

Transparent hydrogenated amorphous silicon nitride (SiNx:H) coatings were prepared by dual-mode microwave-radio-frequency plasma-enhanced chemical vapor deposition. By controlling the effects of plasma density and ion energy on the film growth, it was possible to modify the microstructure of the coatings and hence the refractive index n. Using this method, we were able to vary n from 1.6 to 2.0, at 550 nm, by adjusting the power levels of the radio-frequency and microwave components while keeping the gas composition (SiH4, N2) and pressure constant. An inhomogeneous bandpass filter with a controlled refractive-index depth profile was fabricated, and its optical performance was compared with that of its multilayer counterpart. Besides the attractive optical features of such single-material rugate filters, we found that the mechanical resistance of inhomogeneous films is superior to that of multilayer systems.     

Laser excess noise reduction in optical phase-shift measurements

We describe an optical detection scheme that reduces laser excess noise in measurements of small optical phase shifts. The scheme improves the sensitivity of the balanced differential detection. Analysis of the scheme and comparison with the conventional detection are presented. The scheme is applied in electro-optic probing of electrical signals in integrated circuits, where the excess laser noise is reduced by approximately 20 dB.     

Thermal patterns in evaporating liquid

In this paper, some of the preparatory experiments of the ESA sponsored space program CIMEX-1 are presented. A liquid layer of variable thickness is subject to a flow of inert gas. The non-uniform evaporation induced by the gas flow creates a temperature gradient parallel to the interface triggering in that way thermocapillary convection. The combined action of evaporation, thermocapillarity and gravity has been not completely clarified both theoretically and experimentally. The experiment presented in this work concerns a liquid layer of ethanol of 2.2 mm thickness in presence of a mass flow of Nitrogen whose intensity varies in the range of hundreds of milliliter per minute. The experiments were performed at an initial liquid temperature of 21°C. The patterns observed are strongly dependent on the flow rate of inert gas. A change in the instability patterns has been observed for a gas flow of about 1.7 l/min.