There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

Femtosecond filamentation in transparent media

인공고관절의 세라믹 볼 헤드의 기계적 안정성 평가를 위한 3 차원 유한요소 해석

Ion acceleration driven by superintense laser pulses is attracting an impressive and steadily increasing effort. Motivations can be found in the applicative potential and in the perspective to investigate novel regimes as available laser intensities will be increasing. Experiments have demonstrated, over a wide range of laser and target parameters, the generation of multi-MeV proton and ion beams with unique properties such as ultrashort duration, high brilliance, and low emittance. An overview is given of the state of the art of ion acceleration by laser pulses as well as an outlook on its future development and perspectives. The main features observed in the experiments, the observed scaling with laser and plasma parameters, and the main models used both to interpret experimental data and to suggest new research directions are described.

/pdf/ion-acceleration-by-superintense-laser-plasma-interaction-2jqzeizem7.pdf

Ion acceleration by superintense laser-plasma interaction

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-

Progress in optics

Catastrophic self-focusing is a main obstacle for increasing the throughput in transparent optical materials. Here we show that collapse can be suppressed by a focusing index profile.

Collapse suppression by a positive index profile

This study analyzes numerically supercontinuum generation for the three laser wavelengths of 248 nm, 800 nm and 1550 nm, on the basis of different nonlinear Schrodinger-like equations for the electric field envelope involving or not space-time focusing and self-steepening operators. A numerical analysis of the unidirectional propagation equation is also performed, avoiding any Taylor expansion of the dispersion relation. Several photo-ionization models, fixing the level of the filament intensity in the range of 10 to 100 TW/cm2, are investigated. Finally, emphasis is given on long-range propagation over several meters in air.

Supercontinuum generation of femtosecond filaments at different laser wavelengths in air

Here we discuss a second optical system that clearly features rogue waves, namely the spatial fluence distribution in multifilament beam profiles. Given the formal analogy between one-dimensional fiber solitons and the spatial two-dimensional filament strings, the appearance of rogue waves may not appear overly surprising at first sight. We will show, however, that there are marked differences in the driver mechanism between both optical systems. In particular, while shot-to-shot energy fluctuations on the input beam are considered the driver for rogue wave dynamics in fibers, the formal equivalent of shot-to-shot beam profile variations does not seem to play any role in our system. Instead, mechanical turbulence inside the filament cell appears to act as the trigger mechanism. Refractive index fluctuations inside the cell then act to steer individual filaments into each other, which gives rise to short lived mergers. These filament mergers constitute the rogue waves in our two-dimensional system.

Rogue waves in the beam profiles of multifilaments

Research on intense terahertz (THz) electromagnetic sources has received an increasing attention owing to numerous applications, for example, in time-domain spectroscopy, biomedical imaging or security screening. Here, THz emission in gases via ionizing multi-color femtosecond pulses is analyzed by means of semi-analytical models and finite-difference-time-domain simulations in 1D and 2D geometries. We find the emission in backward direction having a much smaller spectral bandwidth than in forward direction and explain this by interference effects. Forward THz radiation is generated predominantly at the ionization front and thus almost not affected by the opacity of the plasma, in excellent agreement with results obtained from a unidirectional pulse propagation model. Moreover, we show that produced THz signals interact with free electron trajectories and
thus influence significantly further THz generation upon propagation, i.e., make the process inherently nonlocal. This self-action plays a key role in the observed strong spectral broadening of the generated THz field in forward direction. Diffraction limits the achievable THz bandwidth by efficiently depleting the low frequency amplitudes in the propagating field.

THz and far-infrared radiation from ionizing multi-color pulses

We present the first example of stable rotating two-soliton bound states in nonlinear optical media with nonlocal response. We show that, in contrast to media with local response, nonlocality opens possibilities to generate stable azimuthons.

Stable rotating dipole solitons in nonlocal media

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