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

Atomic layer deposition: an overview.

A topical review of numerical and experimental studies of supercontinuum generation in photonic crystal fiber is presented over the full range of experimentally reported parameters, from the femtosecond to the continuous-wave regime. Results from numerical simulations are used to discuss the temporal and spectral characteristics of the supercontinuum, and to interpret the physics of the underlying spectral broadening processes. Particular attention is given to the case of supercontinuum generation seeded by femtosecond pulses in the anomalous group velocity dispersion regime of photonic crystal fiber, where the processes of soliton fission, stimulated Raman scattering, and dispersive wave generation are reviewed in detail. The corresponding intensity and phase stability properties of the supercontinuum spectra generated under different conditions are also discussed.

Supercontinuum generation in photonic crystal fiber

Dielectric-barrier discharges (silent discharges) are used on a large industrial scale. They combine the advantages of non-equilibrium plasma properties with the ease of atmospheric-pressure operation. A prominent feature is the simple scalability from small laboratory reactors to large industrial installations with megawatt input powers. Efficient and cost-effective all-solid-state power supplies are available. The preferred frequency range lies between 1 kHz and 10 MHz, the preferred pressure range between 10 kPa and 500 kPa. Industrial applications include ozone generation, pollution control, surface treatment, high power CO2 lasers, ultraviolet excimer lamps, excimer based mercury-free fluorescent lamps, and flat large-area plasma displays. Depending on the application and the operating conditions the discharge can have pronounced filamentary structure or fairly diffuse appearance. History, discharge physics, and plasma chemistry of dielectric-barrier discharges and their applications are discussed in detail.

https://www3.nd.edu/~sst/teaching/AME60637/reading/2003_PCPP_Kogelschatz_dbd_review.pdf

Dielectric-barrier Discharges: Their History, Discharge Physics, and Industrial Applications

Atomic layer deposition(ALD), a chemical vapor deposition technique based on sequential self-terminating gas–solid reactions, has for about four decades been applied for manufacturing conformal inorganic material layers with thickness down to the nanometer range. Despite the numerous successful applications of material growth by ALD, many physicochemical processes that control ALD growth are not yet sufficiently understood. To increase understanding of ALD processes, overviews are needed not only of the existing ALD processes and their applications, but also of the knowledge of the surface chemistry of specific ALD processes. This work aims to start the overviews on specific ALD processes by reviewing the experimental information available on the surface chemistry of the trimethylaluminum/water process. This process is generally known as a rather ideal ALD process, and plenty of information is available on its surface chemistry. This in-depth summary of the surface chemistry of one representative ALD process aims also to provide a view on the current status of understanding the surface chemistry of ALD, in general. The review starts by describing the basic characteristics of ALD, discussing the history of ALD—including the question who made the first ALD experiments—and giving an overview of the two-reactant ALD processes investigated to date. Second, the basic concepts related to the surface chemistry of ALD are described from a generic viewpoint applicable to all ALD processes based on compound reactants. This description includes physicochemical requirements for self-terminating reactions,reaction kinetics, typical chemisorption mechanisms, factors causing saturation, reasons for growth of less than a monolayer per cycle, effect of the temperature and number of cycles on the growth per cycle (GPC), and the growth mode. A comparison is made of three models available for estimating the sterically allowed value of GPC in ALD. Third, the experimental information on the surface chemistry in the trimethylaluminum/water ALD process are reviewed using the concepts developed in the second part of this review. The results are reviewed critically, with an aim to combine the information obtained in different types of investigations, such as growth experiments on flat substrates and reaction chemistry investigation on high-surface-area materials. Although the surface chemistry of the trimethylaluminum/water ALD process is rather well understood, systematic investigations of the reaction kinetics and the growth mode on different substrates are still missing. The last part of the review is devoted to discussing issues which may hamper surface chemistry investigations of ALD, such as problematic historical assumptions, nonstandard terminology, and the effect of experimental conditions on the surface chemistry of ALD. I hope that this review can help the newcomer get acquainted with the exciting and challenging field of surface chemistry of ALD and can serve as a useful guide for the specialist towards the fifth decade of ALD research.

Surface chemistry of atomic layer deposition: A case study for the trimethylaluminum/water process

Femtosecond infrared pulses from an ultrashort high‐peak‐power Ti:sapphire laser were successfully utilized for ablation of polymer films such as polytetrafluoroethylene, tetrafluoro‐ ethylene‐hexafluoropropylene copolymer, and polyimide. Good agreement between experimental data and calculations from a model suggested that simultaneous absorption of three photons for polyimide and five photons for tetrafluoroethylene‐hexafluoropropylene copolymer predominated over the other absorptive channels and that such a multiphoton absorption was induced efficiently.

Ablation of polymer films by a femtosecond high-peak-power Ti:sapphire laser at 798 nm

We report the first observation of amplification of spontaneous emission on the Lyman-\ensuremath{\alpha} transition of hydrogenlike lithium ions by optical-field-induced ionization. Using a subpicosecond KrF laser (0.5 ps, 50 mJ) focused at ${10}^{17}$ W/${\mathrm{cm}}^{2}$, singly ionized lithium ions have been further ionized to fully stripped states, resulting in the population inversion with respect to the ground state of the hydrogenic ions. A small signal gain coefficient of 20 ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}1}$ was obtained.

Soft-x-ray amplification of the Lyman-α transition by optical-field-induced ionization

We report the first observation of high-order harmonic waves from rare-gas-like ions excited by a subpicosecond KrF excimer laser At an intensity of ${10}^{15}$ W/${\mathrm{cm}}^{2}$, the highest orders of observed harmonics are the ninth (276 nm) in ${\mathrm{Li}}^{+}$, the eleventh (226 nm) in ${\mathrm{Na}}^{+}$, and the thirteenth (191 nm) in ${\mathrm{K}}^{+}$ The advantage of such ions as nonlinear media for extreme ultraviolet generation is discussed in relation to ionization potentials

Generation of high-order harmonics using laser-produced rare-gas-like ions.

We have investigated the high-order harmonic generation of a subpicosecond KrF laser (248 nm) using nine ionic species in laser-produced plasmas. The highest order of the 21 st harmonic (11.8 nm) has been observed in a lead plasma. The maximum observed harmonic orders in various ions and neutral rare gases are found to be proportional to the ionization potentials of these species. We have obtained superior results for the high-order harmonic generation by using ions compared to using neutral rare gases, and have demonstrated the advantages of using ions as nonlinear media to generate extreme ultraviolet radiation

High-order harmonic generation in laser-produced ions

Twenty bilayers of titanium oxide and aluminum oxide with the layer-pair thickness of 443 nm on a silicon substrate were fabricated for novel multilayer reflectors at water-window wavelengths by an atomic layer deposition method of controlled growth with sequential surface chemical reactions The high reflectance of over 30% at a wavelength of 2734 nm and an incident angle of 718° from the normal incidence was demonstrated experimentally The full width at half-maximum of the reflectances at 2734 nm was 00381 nm, which corresponds to Δλ/λ=14%

Koichi Toyoda

Papers

Ablation of polymer films by a femtosecond high-peak-power Ti:sapphire laser at 798 nm

Soft-x-ray amplification of the Lyman-α transition by optical-field-induced ionization

Generation of high-order harmonics using laser-produced rare-gas-like ions.

High-order harmonic generation in laser-produced ions

Titanium oxide/aluminum oxide multilayer reflectors for "water-window" wavelengths