110 W pulse power and 0.93J pulse energy have been obtained with direct resonant pumping of a 1.6-μm Er3+-doped bulk solid-state laser with two-dimensional stacks of 1.5μm InGaAsP∕InP diode lasers.

We report on a feature, that of hillock-shaped damage, formed on a glass surface by femtosecond pulses of t p ϭ180 fs ͓full width at half maximum ͑FWHM͒ value͔ duration produced by a recording beam focus with energy of 5 nJ/pulse at 800 nm wavelength ͑the corresponding irradiance of about 7.6 TW/cm 2 was evaluated for a 0.68 m FWHM spot size͒. Single hillocks of 40-50 nm height were recorded reproducibly in single-pulse irradiation. Surface nanopatterning over a large, curved area ͑over 200 m 2 ) can be achieved by implementing a confocal surface curvature tracking method that utilizes the reflection of a supplementary cw-laser beam. The ablation pattern achieved by this method is consistent with that of a Coulomb explosion.Femtosecond laser microfabrication is capable of recording waveguides, 1,2 three-dimensional ͑3D͒ optical memory, 3,4 and photonic crystal structures 5 in glass. In conjunction with wet etching, microchannels can be developed in glass 6 and polymers 7 that are first exposed to fs pulses. However, a large-scale ͑millimeter͒ fabrication with feature sizes of 100 nm or smaller ͑nanostructuring͒ by fs pulses has been elaborated neither on the surface nor in bulk. To further improve 3D optical memories, nanostructuring of materials is a key technology. The need for controllable nanorecording is anticipated particularly in light of the recent breakthrough in readout resolution by confocal microscopy, which reached /23Ӎ33 nm. 8 Here, we demonstrate nanostructuring of a glass surface with 100 nm resolution by single-pulse irradiation at 800 nm wavelength. Formation of hillock-shaped damage was observed. Such damage is consistent with the Coulomb explosion mechanism of dielectric ablation by ultrashort pulses. 9,10 The proposed type of nanostructuring can be used for onsurface and in-bulk recording in transparent materials.The experimental setup of fs fabrication ͑Tokyo Instru-ments͒ includes a femtosecond laser ͑Hurricane, Spectra Physics͒, upright-type optical microscope ͑Olympus MX40͒, and three-axis piezostage ͑Polytec PI͒. An electronic shutter allowed the fs shooting to be switched on and off at preprogramed moments according to the stage movement. Hereafter, the pulse energy is given at the focus, where it was controlled by attenuators built into the micromachining system. The pulse energy stability was about 3% ͑rms value͒. The laser emission at 800 nm wavelength was focused on the sample surface by a dry objective lens with a numerical aperture of NAϭ0.95 ͑Olympus͒. The focusing of the Gaussian beam would correspond to a DϭKM 2 /(2NA)Ӎ0.68 m diam spot ͓full width at half maximum ͑FWHM͒ value͔, 11 here, Kϭ1.07 is the beam's truncation factor for a truncation ratio Tϭ1.75, is the wavelength, and M 2 ϭ1.5 is the beam quality factor of femtosecond laser. The truncation ratio is defined as the Gaussian beam diameter at 1/e 2 divided by the diameter of limiting aperture, TϭD beam /D Ap . The waist length can be calculated as a doubled Rayleigh length L ϭ2 0 2 M 2 M tr 2 /Ӎ0.65 m, where 2 0 ϭ1.27 f /...

Raman microspectroscopy was applied to study the polymerization kinetics of the Langmuir-Blodgett (LB) films of 10,12-pentacosadiynoic acid (DA) adsorbed on surface enhanced Raman scattering (SERS) active Ag island films. A two-dimensional (2D) Raman microscopic image measured at 1520 cm(-1) exhibits bright and dim spots with the diameter of several hundred nanometers. Raman microscopic spectra, measured by defocusing the excitation laser light (532 nm, diameter of ca. 10 mum) on the samples at room temperature, proved the occurrence of the surface processes consisting of the formation of polydiacetylene (PDA) in the blue phase, its conversion to the red phase, and subsequent bleaching. These reactions were negligible under the same condition for the DA-LB films prepared on a smooth (i.e., SERS-inactive) Ag film, indicating that the 532-nm-induced polymerization and the bleaching process are enhanced by the SERS-active substrates. At low temperatures below -50 degrees C, the Raman microscopic measurements proved the formation of the blue phase and its conversion to the red phase with much lower reaction rates compared to the corresponding rates at room temperature. The bleaching, however, was much suppressed at the low temperatures. The kinetic analyses of the formation of the blue phase and its conversion to the red phase were performed by using the intensity changes of the Raman bands due to the blue (1477 cm(-1)) and red (1517 cm(-1)) phases as a function of the irradiation time. The results strongly suggested the existence of at least two processes taking place simultaneously on the SERS-active substrates; that is, one of the processes is a sequential reaction, DA-monomers --> PDA in the blue phase --> PDA in the red phase, and the other is another sequential reaction, DA-monomers --> PDA in the red phase --> degradation species (probably amorphous carbon). Thus, even at the low temperatures, there occurs the surface reaction consisting of the formation of PDA and its degradation. The reaction can be ascribed to a process taking place at the highly SERS-active site, which gives the bright spot (so-called "hot spot") on the 2D Raman image, as proved by the confocal Raman microscopic measurement in the following paper.

Confocal Raman microscopic measurements were performed at room temperature on the Langmuir-Blodgett (LB) monolayer of 10,12-pentacosadiynoic acid (DA) prepared on surface enhanced Raman scattering (SERS) active Ag island films, two-dimensional (2D) Raman images of which exhibit bright and dim spots on a dark background. The measurements performed by focusing the excitation laser light (488 nm) on the dark background indicate the prompt appearance of the Raman bands (1515 and 2115 cm(-1)) due to polydiacetylene (PDA) in the red phase and subsequent diminution of the Raman bands. On the other hand, the spectra observed by focusing the excitation laser spot on the dim and bright spots exhibit almost random fluctuations, giving rather narrow Raman bands in the 1620-1000 cm(-1) region, which appear and disappear temporarily with varying intensities under the continuous irradiation at 488 nm. Broad Raman bands appear around 1580 and 1360 cm(-1), which are ascribable to amorphous carbon, at a later stage of the observation, the intensities from the bright spot being more than 100 times stronger than those from the dim spot. The narrow bands are ascribed to a series of carbonaceous intermediates such as polyenes, graphite sheets with various sizes, and folded or reorganized forms of the sheets including carbon nanotubes and fullerenes, which are formed during the conversion of PDA to amorphous carbon. The random spectral fluctuation was interpreted by considering that the intermediates undergo thermally activated diffusion and get temporarily in contact with the SERS-active site, resulting in the enhancement of their Raman bands and the fluctuation.

A direct transformation of the g-BC 3 phase to a new diamond-like d-BC 3 phase was observed in a diamond-anvil cell (DAC) at high temperature, 2033 ± 241 K, and high pressure, 50 GPa. Analysis of the peak positions of the d-BC 3 , B 4 C, a-boron, and the boron-doped diamond leads to the conclusion that the positions of the peaks of the d-BC 3 are more similar to the peak pattern of the boron-doped diamond rather than that of boron carbide, a-boron.