Saifollah Rasouli - Academia.edu (original) (raw)

Papers by Saifollah Rasouli

In this work, by using a local reciprocal vector concept, we introduce a considerable number of q... more In this work, by using a local reciprocal vector concept, we introduce a considerable number of quasi-periodic structures where each of them is constructed by a set of curved lines with varying period. By using a simple and very comprehensive recently proposed method, formulations and characterizations of the various moiré patterns of different pairs of curved line quasi-periodic structures are presented. Some advantages of the concept of local reciprocal vector in the area of curved line quasi-periodic structures are clarified.

Optics in Atmospheric Propagation and Adaptive Systems IX, 2006

Europhysics Letters, Aug 1, 2009

We investigate the induced geodesic deviation equations in the brane world models, in which all t... more We investigate the induced geodesic deviation equations in the brane world models, in which all the matter forces except gravity are confined on the 3-brane. Also, the Newtonian limit of induced geodesic deviation equation is studied. We show that in the first Randall-Sundrum model the Bohr-Sommerfeld quantization rule is as a result of consistency between the geodesic and geodesic deviation equations. This indicates that the path of test particle is made up of integral multiples of a fundamental Compton-type unit of length h/mc.

One of the solutions of the Helmholtz Equation is the vortex beam. In the recent decades, product... more One of the solutions of the Helmholtz Equation is the vortex beam. In the recent decades, production and applications of this type of beams have found serious attentions. Determination of the vortex beam topological charge and its sign are very important issue. Odd number of reflections of the vortex beam changes its vorticity. In this paper, we used a q-plate (QP) to generate a vortex beam from a plane wave of a He-Ne laser beam. A two-channel moiré based wave-front sensor is used to measure wave-front gradient of the vortex beam. In two different arrangements the vortex beam posses odd and even number of reflections, respectively, and from the moiré patterns deformation, value and sign of the topological charge were determined.

Use of Fourier frequency domain is one of the usual methods for studying moiré pattern. In this m... more Use of Fourier frequency domain is one of the usual methods for studying moiré pattern. In this method, spatial frequency spectrum of the moiré pattern instead of its intensity profile is used. Comparing with other methods, this method is very simple. In this work, we present a formulation for the moiré pattern of superimposing two linear l-fork gratings using reciprocal vector approach. For this kind of moiré pattern some applications are presented such as 2D displacement measurement. In addition, effect of changing relative angle of the grating lines is investigated and we find that it is possible to extract the topological defects of the gratings by the moiré technique. Finally, we introduced a simple way for variable frequency l-fork shape patterns generation by superimposing of two rotating l-fork gratings.

One of the solutions of the Helmholtz equation is the vortex beams. In the recent decades, produc... more One of the solutions of the Helmholtz equation is the vortex beams. In the recent decades, production and applications of these types of beams have found serious attentions. Determination of the vortex beam topological charge and its sign are very important issues. Odd number of reflections of the vortex beam changes its vorticity. In this paper, we have used a q-plate to generate a vortex beam from a plane wave of a He-Ne laser beam and a two-channel moiré based wavefront sensor is used to measure wavefront gradient of the vortex beam. In two different arrangements the vortex beam experience odd and even number of reflections, respectively, and from the moiré pattern deformations the topological charge of the vortex beam and its sign are determined.

When a light beam passes through a strongly atmospheric turbulence, phase singularities appear in... more When a light beam passes through a strongly atmospheric turbulence, phase singularities appear in some points of the wave front surface. For reconstruction of these beams or extracting topological charge of a pure Laguerre-Gaussian beam, it is needed to determine the center of the vorticities. In this work, we introduce a new method for this purpose by use of the wavefront slope value data. For a case, center of vortex beam and the selected origin for the coordinate system match together, the variance of determined topological charge to be minimized. Wavefront slops can be extracted with a wavefront sensor like a two-channel moiré based wavefront sensor. In experiment, lens phase function or a white noise are added to an azimuthally dependence phase of an incident beam. This is done by use of diffraction of a plane wave from a LCD, which is used as a spatial phase modulator. In addition, we used amplitude forked grating and allow passing diffracted beam through a turbulent medium. Then, we determined centers of these beams and noted some considerations for this process.

Moiré pattern of two superimposed Fresnel zone plates (ZP) is used for displacement measurement. ... more Moiré pattern of two superimposed Fresnel zone plates (ZP) is used for displacement measurement. In addition, spiral ZP is an elementary tool to generate vortex beam by diffraction of a plane wave. In this work, firstly, we introduce a great family of ZPs consisting topological defects that we named L-fork ZPs. Spiral ZP is an special form of the L-fork ZPs, in which the topological defect is located at the center of the plate. We investigated moiré pattern of two ZPs consisting topological defects in several cases using reciprocal vector approach. We show that the resulting moiré pattern has three general forms: large scale l-fork ZP pattern, propeller like pattern, and large scale linear l-fork grating pattern. This formulation can be used for superimposed gratings characterization, displacement measurements, generating variable frequency l-fork, or generating and measuring characteristics of Laguerre-Gaussian beams.

In this paper, we have used a LCD as spatial light modulator to generate simple or composite Lagu... more In this paper, we have used a LCD as spatial light modulator to generate simple or composite Laguerre-Gaussian beams from a plane wave of a He-Ne laser beam. Moiré Deflectometry is used to measure gradients of wave-front of the vortex beam. Integral along a given closed path of gradients used to measure topological charge of the beam. We show that the sum of topological charges of all beams results overall topological charge of the composite beam. Also, the intensity and phase distribution of such beams were simulated. Comparing results of the numerical simulation and experimental results demonstrate that moiré deflectometry can be used to determine topological charge of a beam with an adequate accuracy.

Inducing cubic spatial phase is an essential prerequisite for generation of optical Airy beams. T... more Inducing cubic spatial phase is an essential prerequisite for generation of optical Airy beams. The best approach to generate such a phase distribution is to tune the optical aberrations in a set of tilted cylindrical telescopic systems. This method is capable of producing tunable continuous cubic phase without wavelength and intensity limitations. Despite the tunablity, such a cubic phase inducing system is very sensitive to its alignment and therefore effective quadratic and quantic phases may also be generated simultaneously. In this work, we employed a wavefront sensing technique based on moiré deflectometry to perform a quantitative measurement of the polynomial phase values for various tilt angles in a 1-D cylindrical telescopic system.

Optics Communications

This is an erratum to the paper [K. Jamshidi-Ghaleh, N. Mansour, Opt. Commun. 234 (2004) 419], in... more This is an erratum to the paper [K. Jamshidi-Ghaleh, N. Mansour, Opt. Commun. 234 (2004) 419], in which a new method for measuring the nonlinear refractive index of materials using the moiré deflectometry is reported. The paper was published with an error in Eq. (4) and it has propagated through the paper.

Optics in Atmospheric Propagation and Adaptive Systems XII, 2009

A wavefront sensor which takes advantage of the moire deflectometry has been constructed for meas... more A wavefront sensor which takes advantage of the moire deflectometry has been constructed for measuring atmosphere induced wavefront distortions. In this sensor a collimated laser beam propagates through turbulent atmosphere, then a beam splitter splits it into two beams and the beams pass through a pair of moire deflectometers. Directions of the grating's rulings are parallel in each moire deflectometer

Optical Measurement Systems for Industrial Inspection IV, 2005

Specification of vibrational modes and amplitudes of structures are crucial issues in civil and m... more Specification of vibrational modes and amplitudes of structures are crucial issues in civil and mechanical engineering. Several techniques have been used for this kind of studies, including holographic interferometry, speckle interferometry and moire technique. But, for large-scale structures modal analysis technique is usually used. In this work we have used time averaging moire technique to study in plane vibrations of

Classical and Quantum Gravity, 2014

Optics Letters, 2008

When a slightly divergent laser beam passes through a turbulent ground level atmosphere and strik... more When a slightly divergent laser beam passes through a turbulent ground level atmosphere and strikes a linear grating, fluctuating self-images are formed at Talbot distances. By superimposing a similar grating on one of the self-images, even for the case of parallel gratings' lines, fluctuating moiré fringes are formed owing to the beam divergence. Recording the successive moiré patterns by a CCD camera and feeding them to a computer, after filtering the higher spatial frequencies, produces highly magnified fluctuations of the laser beam. Using moiré fringe fluctuations we have calculated the fluctuations of the angle of arrival and the atmospheric refractive index structure constant. The implementation of the technique is straightforward, a telescope is not required, fluctuations can be magnified more than ten times, and the precision of the technique is similar to that reported in our previous work.

Optics Letters, 2010

An instrument has been built for the study of the atmospheric turbulence by measuring the fluctua... more An instrument has been built for the study of the atmospheric turbulence by measuring the fluctuation of the angle of arrival across a telescope aperture using moiré deflectometry. A slightly divergent laser beam passes through a turbulent ground level atmosphere and enters the telescope aperture. The laser beam is recollimated behind the telescope's focal point by means of a collimator. The collimated beam passes through a moiré deflectometer. The fluctuating self-image of the first grating is formed on the second grating of the moiré deflectometer and fluctuating moiré fringes are formed. Using moiré fringe fluctuations we have calculated the fluctuations of the angle of arrival, the Fried's parameter r(0), and the atmospheric refractive index structure constant. Because of the magnifications of the telescope and moiré deflectometry, the precision of the technique can potentially be 1 order of magnitude more precise than previous methods.

In this work, by using a local reciprocal vector concept, we introduce a considerable number of q... more In this work, by using a local reciprocal vector concept, we introduce a considerable number of quasi-periodic structures where each of them is constructed by a set of curved lines with varying period. By using a simple and very comprehensive recently proposed method, formulations and characterizations of the various moiré patterns of different pairs of curved line quasi-periodic structures are presented. Some advantages of the concept of local reciprocal vector in the area of curved line quasi-periodic structures are clarified.

Optics in Atmospheric Propagation and Adaptive Systems IX, 2006

Europhysics Letters, Aug 1, 2009

We investigate the induced geodesic deviation equations in the brane world models, in which all t... more We investigate the induced geodesic deviation equations in the brane world models, in which all the matter forces except gravity are confined on the 3-brane. Also, the Newtonian limit of induced geodesic deviation equation is studied. We show that in the first Randall-Sundrum model the Bohr-Sommerfeld quantization rule is as a result of consistency between the geodesic and geodesic deviation equations. This indicates that the path of test particle is made up of integral multiples of a fundamental Compton-type unit of length h/mc.

One of the solutions of the Helmholtz Equation is the vortex beam. In the recent decades, product... more One of the solutions of the Helmholtz Equation is the vortex beam. In the recent decades, production and applications of this type of beams have found serious attentions. Determination of the vortex beam topological charge and its sign are very important issue. Odd number of reflections of the vortex beam changes its vorticity. In this paper, we used a q-plate (QP) to generate a vortex beam from a plane wave of a He-Ne laser beam. A two-channel moiré based wave-front sensor is used to measure wave-front gradient of the vortex beam. In two different arrangements the vortex beam posses odd and even number of reflections, respectively, and from the moiré patterns deformation, value and sign of the topological charge were determined.

Use of Fourier frequency domain is one of the usual methods for studying moiré pattern. In this m... more Use of Fourier frequency domain is one of the usual methods for studying moiré pattern. In this method, spatial frequency spectrum of the moiré pattern instead of its intensity profile is used. Comparing with other methods, this method is very simple. In this work, we present a formulation for the moiré pattern of superimposing two linear l-fork gratings using reciprocal vector approach. For this kind of moiré pattern some applications are presented such as 2D displacement measurement. In addition, effect of changing relative angle of the grating lines is investigated and we find that it is possible to extract the topological defects of the gratings by the moiré technique. Finally, we introduced a simple way for variable frequency l-fork shape patterns generation by superimposing of two rotating l-fork gratings.

One of the solutions of the Helmholtz equation is the vortex beams. In the recent decades, produc... more One of the solutions of the Helmholtz equation is the vortex beams. In the recent decades, production and applications of these types of beams have found serious attentions. Determination of the vortex beam topological charge and its sign are very important issues. Odd number of reflections of the vortex beam changes its vorticity. In this paper, we have used a q-plate to generate a vortex beam from a plane wave of a He-Ne laser beam and a two-channel moiré based wavefront sensor is used to measure wavefront gradient of the vortex beam. In two different arrangements the vortex beam experience odd and even number of reflections, respectively, and from the moiré pattern deformations the topological charge of the vortex beam and its sign are determined.

When a light beam passes through a strongly atmospheric turbulence, phase singularities appear in... more When a light beam passes through a strongly atmospheric turbulence, phase singularities appear in some points of the wave front surface. For reconstruction of these beams or extracting topological charge of a pure Laguerre-Gaussian beam, it is needed to determine the center of the vorticities. In this work, we introduce a new method for this purpose by use of the wavefront slope value data. For a case, center of vortex beam and the selected origin for the coordinate system match together, the variance of determined topological charge to be minimized. Wavefront slops can be extracted with a wavefront sensor like a two-channel moiré based wavefront sensor. In experiment, lens phase function or a white noise are added to an azimuthally dependence phase of an incident beam. This is done by use of diffraction of a plane wave from a LCD, which is used as a spatial phase modulator. In addition, we used amplitude forked grating and allow passing diffracted beam through a turbulent medium. Then, we determined centers of these beams and noted some considerations for this process.

Moiré pattern of two superimposed Fresnel zone plates (ZP) is used for displacement measurement. ... more Moiré pattern of two superimposed Fresnel zone plates (ZP) is used for displacement measurement. In addition, spiral ZP is an elementary tool to generate vortex beam by diffraction of a plane wave. In this work, firstly, we introduce a great family of ZPs consisting topological defects that we named L-fork ZPs. Spiral ZP is an special form of the L-fork ZPs, in which the topological defect is located at the center of the plate. We investigated moiré pattern of two ZPs consisting topological defects in several cases using reciprocal vector approach. We show that the resulting moiré pattern has three general forms: large scale l-fork ZP pattern, propeller like pattern, and large scale linear l-fork grating pattern. This formulation can be used for superimposed gratings characterization, displacement measurements, generating variable frequency l-fork, or generating and measuring characteristics of Laguerre-Gaussian beams.

In this paper, we have used a LCD as spatial light modulator to generate simple or composite Lagu... more In this paper, we have used a LCD as spatial light modulator to generate simple or composite Laguerre-Gaussian beams from a plane wave of a He-Ne laser beam. Moiré Deflectometry is used to measure gradients of wave-front of the vortex beam. Integral along a given closed path of gradients used to measure topological charge of the beam. We show that the sum of topological charges of all beams results overall topological charge of the composite beam. Also, the intensity and phase distribution of such beams were simulated. Comparing results of the numerical simulation and experimental results demonstrate that moiré deflectometry can be used to determine topological charge of a beam with an adequate accuracy.

Inducing cubic spatial phase is an essential prerequisite for generation of optical Airy beams. T... more Inducing cubic spatial phase is an essential prerequisite for generation of optical Airy beams. The best approach to generate such a phase distribution is to tune the optical aberrations in a set of tilted cylindrical telescopic systems. This method is capable of producing tunable continuous cubic phase without wavelength and intensity limitations. Despite the tunablity, such a cubic phase inducing system is very sensitive to its alignment and therefore effective quadratic and quantic phases may also be generated simultaneously. In this work, we employed a wavefront sensing technique based on moiré deflectometry to perform a quantitative measurement of the polynomial phase values for various tilt angles in a 1-D cylindrical telescopic system.

Optics Communications

This is an erratum to the paper [K. Jamshidi-Ghaleh, N. Mansour, Opt. Commun. 234 (2004) 419], in... more This is an erratum to the paper [K. Jamshidi-Ghaleh, N. Mansour, Opt. Commun. 234 (2004) 419], in which a new method for measuring the nonlinear refractive index of materials using the moiré deflectometry is reported. The paper was published with an error in Eq. (4) and it has propagated through the paper.

Optics in Atmospheric Propagation and Adaptive Systems XII, 2009

A wavefront sensor which takes advantage of the moire deflectometry has been constructed for meas... more A wavefront sensor which takes advantage of the moire deflectometry has been constructed for measuring atmosphere induced wavefront distortions. In this sensor a collimated laser beam propagates through turbulent atmosphere, then a beam splitter splits it into two beams and the beams pass through a pair of moire deflectometers. Directions of the grating's rulings are parallel in each moire deflectometer

Optical Measurement Systems for Industrial Inspection IV, 2005

Specification of vibrational modes and amplitudes of structures are crucial issues in civil and m... more Specification of vibrational modes and amplitudes of structures are crucial issues in civil and mechanical engineering. Several techniques have been used for this kind of studies, including holographic interferometry, speckle interferometry and moire technique. But, for large-scale structures modal analysis technique is usually used. In this work we have used time averaging moire technique to study in plane vibrations of

Classical and Quantum Gravity, 2014

Optics Letters, 2008

When a slightly divergent laser beam passes through a turbulent ground level atmosphere and strik... more When a slightly divergent laser beam passes through a turbulent ground level atmosphere and strikes a linear grating, fluctuating self-images are formed at Talbot distances. By superimposing a similar grating on one of the self-images, even for the case of parallel gratings' lines, fluctuating moiré fringes are formed owing to the beam divergence. Recording the successive moiré patterns by a CCD camera and feeding them to a computer, after filtering the higher spatial frequencies, produces highly magnified fluctuations of the laser beam. Using moiré fringe fluctuations we have calculated the fluctuations of the angle of arrival and the atmospheric refractive index structure constant. The implementation of the technique is straightforward, a telescope is not required, fluctuations can be magnified more than ten times, and the precision of the technique is similar to that reported in our previous work.

Optics Letters, 2010

An instrument has been built for the study of the atmospheric turbulence by measuring the fluctua... more An instrument has been built for the study of the atmospheric turbulence by measuring the fluctuation of the angle of arrival across a telescope aperture using moiré deflectometry. A slightly divergent laser beam passes through a turbulent ground level atmosphere and enters the telescope aperture. The laser beam is recollimated behind the telescope's focal point by means of a collimator. The collimated beam passes through a moiré deflectometer. The fluctuating self-image of the first grating is formed on the second grating of the moiré deflectometer and fluctuating moiré fringes are formed. Using moiré fringe fluctuations we have calculated the fluctuations of the angle of arrival, the Fried's parameter r(0), and the atmospheric refractive index structure constant. Because of the magnifications of the telescope and moiré deflectometry, the precision of the technique can potentially be 1 order of magnitude more precise than previous methods.