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Tomohiro Shirai

Bio: Tomohiro Shirai is an academic researcher from National Institute of Advanced Industrial Science and Technology. The author has contributed to research in topics: Coherence (physics) & Coherence theory. The author has an hindex of 22, co-authored 79 publications receiving 1785 citations. Previous affiliations of Tomohiro Shirai include Hokkaido University & University of Auckland.


Papers
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Journal ArticleDOI
TL;DR: It is found that in atmospheric turbulence the relative spreading of higher-order modes is smaller than that of lower- order modes, whereas the relative spread of all order modes is the same as in free space.
Abstract: The spreading of partially coherent beams propagating through atmospheric turbulence is studied by use of the coherent-mode representation of the beams. Specifically, we consider partially coherent Gaussian Schell-model beams entering the atmosphere, and we examine the spreading of each coherent mode, represented by a Hermite-Gaussian function, on propagation. We find that in atmospheric turbulence the relative spreading of higher-order modes is smaller than that of lower-order modes, whereas the relative spreading of all order modes is the same as in free space. This modal behavior successfully explains why under certain circumstances partially coherent beams are less affected by atmospheric turbulence than are fully spatially coherent laser beams.

290 citations

Journal ArticleDOI
TL;DR: In this article, the authors present a sufficient condition for building cross-spectral density matrices in such a way that non-negative definiteness is automatically satisfied for an electromagnetic stochastic beam.
Abstract: For an electromagnetic stochastic beam, the choice of the mathematical structure of the cross-spectral density matrix is limited by the constraint of non-negative definiteness. We present a sufficient condition for building these matrices in such a way that this constraint is automatically satisfied. This allows us to put into evidence that electromagnetic beams can exhibit very peculiar correlation properties, some of which would not be encountered in scalar treatments. These results are illustrated by means of a number of examples.

157 citations

Journal ArticleDOI
TL;DR: In this article, a method of generating an electromagnetic Gaussian Schell-model source from two coherent linearly polarized plane waves is described, which involves two mutually correlated phase-only liquid-crystal spatial light modulators placed in the arms of a Mach-Zehnder interferometer.
Abstract: A method of generating an electromagnetic Gaussian Schell-model source from two coherent linearly polarized plane waves is described. This method involves two mutually correlated phase-only liquid-crystal spatial light modulators placed in the arms of a Mach–Zehnder interferometer. The sources produced by this method can be used to generate a wide class of electromagnetic beams with prescribed coherence and polarization properties.

130 citations

Journal ArticleDOI
TL;DR: It is shown that some partially coherent Gaussian Shell-model beams may generate, in free space, the same angular distribution of radiant intensity as a fully coherent laser beam even if the beams propagate in atmospheric turbulence, irrespective of the particular model of turbulence used.
Abstract: It is known that some partially coherent Gaussian Schell-model beams may generate, in free space, the same angular distribution of radiant intensity as a fully coherent laser beam. We show that this result also holds even if the beams propagate in atmospheric turbulence, irrespective of the particular model of turbulence used. The result is illustrated by an example.

113 citations

Journal ArticleDOI
TL;DR: The spectral degree of coherence and of polarization of some model electromagnetic beams modulated by a polarization-dependent phase-modulating device, such as a liquid-crystal spatial light modulator, acting as a random phase screen are examined on the basis of the recent theory formulated in terms of the 2 x 2 cross-spectral density matrix of the beam.
Abstract: The spectral degree of coherence and of polarization of some model electromagnetic beams modulated by a polarization-dependent phase-modulating device, such as a liquid-crystal spatial light modulator, acting as a random phase screen are examined on the basis of the recent theory formulated in terms of the 2 x 2 cross-spectral density matrix of the beam. The phase-modulating device is assumed to have strong polarization dependence that modulates only one of the orthogonal components of the electric vector, and the phase of the phase-modulating device is assumed to be a random function of position imitating a random phase screen and is assumed to obey Gaussian statistics with zero mean. The propagation of the modulated beam is also examined to show how the spectral degrees of coherence and of polarization of the beam change on propagation, even in free space. The results are illustrated by numerical examples.

82 citations


Cited by
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Journal Article
TL;DR: In this article, the diffraction tomography theorem is adapted to one-dimensional length measurement and the resulting spectral interferometry technique is described and the first length measurements using this technique on a model eye and on a human eye in vivo are presented.
Abstract: The diffraction tomography theorem is adapted to one-dimensional length measurement. The resulting spectral interferometry technique is described and the first length measurements using this technique on a model eye and on a human eye in vivo are presented.

1,237 citations

Journal ArticleDOI
TL;DR: The last volume of the Progress in Optics series as discussed by the authors contains seven chapters on widely diverging topics, written by well-known authorities in their fields, including laser selective photophysics and photochemistry, laser phase profile generation, laser beamforming, and laser laser light emission from high-current surface spark discharges.
Abstract: Have you ever felt that the very title, Progress in Optics, conjured an image in your mind? Don’t you see a row of handsomely printed books, bearing the editorial stamp of one of the most brilliant members of the optics community, and chronicling the field of optics since the invention of the laser? If so, you are certain to move the bookend to make room for Volume 16, the latest of this series. It contains seven chapters on widely diverging topics, written by well-known authorities in their fields. These are: 1) Laser Selective Photophysics and Photochemistry by V. S. Letokhov, 2) Recent Advances in Phase Profiles (sic) Generation by J. J. Clair and C. I. Abitbol, 3 ) Computer-Generated Holograms: Techniques and Applications by W.-H. Lee, 4) Speckle Interferometry by A. E. Ennos, 5 ) Deformation Invariant, Space-Variant Optical Pattern Recognition by D. Casasent and D. Psaltis, 6) Light Emission from High-Current Surface-Spark Discharges by R. E. Beverly, and 7) Semiclassical Radiation Theory within a QuantumMechanical Framework by I. R. Senitzkt. The breadth of topic matter spanned by these chapters makes it impossible, for this reviewer at least, to pass judgement on the comprehensiveness, relevance, and completeness of every chapter. With an editorial board as prominent as that of Progress in Optics, however, it seems hardly likely that such comments should be necessary. It should certainly be possible to take the authority of each author as credible. The only remaining judgment to be made on these chapters is their readability. In short, what are they like to read? The first sentence of the first chapter greets the eye with an obvious typographical error: “The creation of coherent laser light source, that have tunable radiation, opened the . . . .” Two pages later we find: “When two types of atoms or molecules of different isotopic composition ( A and B ) have even one spectral line that does not overlap with others, it is pos-

1,071 citations

Journal ArticleDOI
TL;DR: It is found that after a long propagation distance a dark hollow beam of circular or noncircular eventually becomes a circular Gaussian beam (without dark hollow) in a turbulent atmosphere, which is much different from its propagation properties in free space.
Abstract: Propagation of a dark hollow beam (DHB) of circular, elliptical or rectangular symmetry in a turbulent atmosphere is investigated. Analytical formulas for the average intensity of various DHBs prop ...

256 citations

01 Jan 1973
TL;DR: In this article, the Planck's radiation law and the Einstein coefficients were used to describe the atom-radiation interaction and the quantum mechanics of optical fluctuations and coherence, respectively.
Abstract: Preface 1. Planck's radiation law and the Einstein coefficients 2. Quantum mechanics of the atom-radiation interaction 3. Classical theory of optical fluctuations and coherence 4. Quantization of the radiation field 5. Single-mode quantum optics 6. Multimode and continuous-mode quantum optics 7. Optical generation, attenuation and amplification 8. Resonance fluorescence and light scattering 9. Nonlinear quantum optics Index

248 citations