Dynamic hydrophobicity of water droplets on the line-patterned hydrophobic surfaces

Static and dynamic hydrophobicities of water droplet on a patterned surface prepared using fluoroalkylsilanes with different molecular chain lengths were investigated. Contact angles on the patterned surfaces well agreed with values predicted using Cassie’s theory. On the same line width ratio, total retention force was governed by the fluoroalkylsilane with slow-sliding acceleration. The total retention force decreased with the decreasing width ratio of silane with slow-sliding acceleration on the surface. These results imply that the sliding acceleration of water droplets on a hydrophobic surface depends both on chemical composition and patterning structure.     

The chemisorption of pentacene on Si(0 0 1)-2 × 1

Adsorption structures of the pentacene (C₂₂H₁₄) molecule on the clean Si(0 0 1)-2 × 1 surface were investigated by scanning tunneling microscopy (STM) in conjunction with density functional theory calculations and STM image simulations. The pentacene molecules were found to adsorb on four major sites and four minor sites. The adsorption structures of the pentacene molecules at the four major sites were determined by comparison between the experimental and the simulated STM images. Three out of the four theoretically identified adsorption structures are different from the previously proposed adsorption structures. They involve six to eight Si-C covalent chemical bonds. The adsorption energies of the major four structures are calculated to be in the range 67-128 kcal/mol. It was also found that the pentacene molecule hardly hopped on the surface when applying pulse bias voltages on the molecule, but was mostly decomposed.     

Simultaneous observation of CO isotopomer absorption by broadband difference-frequency generation using a direct-bonded quasi-phase-matched LiNbO3 waveguide

Rovibration absorption lines both of 12CO and 13CO are observed simultaneously with the output of a 2 microm broadband difference frequency generated in a direct-bonded quasi-phase-matched LiNbO3 waveguide, which is a 50 mm device with a single quasi-phase-matching period that is operated at a constant temperature. The wavelength conversion efficiency and the difference-frequency generation bandwidth reach 100%/W and 100 nm, respectively. The idler output bandwidth in the 2 microm region is obtained by group-velocity matching or phase-mismatch minimization when a 0.94 microm pump laser diode and a 1.55 microm tunable signal source are used.     

Strong resonance enhancement of a single harmonic generated in the extreme ultraviolet range

We report the demonstration of strong resonance enhancement of a single high-order harmonic in the extreme ultraviolet (XUV) region generated from the interaction of a femtosecond pulse with low-ionized In ablation. A strong 13th harmonic (61.2 nm) of Ti:sapphire laser radiation with output intensity almost two orders of magnitude higher than neighboring harmonics was observed in these studies. The high conversion efficiency of the 13th harmonic (8 x 10(-5)) is attributed to multiple collisions of electron trajectories with the origin due to multiphoton resonance with the In ion.     

Single-transverse-mode output from a fiber laser based on multimode interference

An alternative original approach to achieve single-transverse-mode laser emissions from multimode (MM) active fibers is demonstrated. The fiber cavity is constructed by simply splicing a conventional passive single-mode fiber (SMF-28) onto a few centimeters-long active MM fiber section whose length is precisely controlled. Owing to the self-imaging property of multimode interference (MMI) in the MM fiber, diffraction-limited laser output is obtained from the end of the SMF-28, and the MMI fiber laser is nearly as efficient as the corresponding MM fiber laser. Moreover, because of the spectral filtering effect during in-phase MMI, the bandwidth of the MMI fiber laser is below 0.5 nm.     

Origin of ion beam mixing effects on morphological features in solid-phase titanium silicide formation

The origin of the ion beam mixing effect, which causes the formation of smooth silicide films, is investigated for the Ti/Si solid-phase silicidation reaction. Ge ion beam mixing of a conventional Ti/c-Si structure with an oxide-contaminated interface shows an obvious effect when the implant conditions are such that the Ti/Si interface is amorphized. On the other hand, silicidation without ion mixing for Ti/a-Si and Ti/c-Si structures with oxide-free interfaces, prepared by sequential deposition in UHV, results in smooth and rough film surfaces, respectively. This strongly suggests that the ion beam mixing effect primarily comes from the amorphization of the Si substrate surface rather than the destruction of the interfacial oxide film.     

Unequally spaced multiple mid-infrared wavelength generation using an engineered quasi-phase-matching device

We propose a novel quasi-phase-matched (QPM) device that can generate unequally spaced multiple wavelengths. Unequally spaced multiple QPM peaks can be obtained by employing the optimized phase modulation of a periodic domain structure. We fabricated a LiNbO3 waveguide device for 3.2-3.4 microm band difference frequency generation based on the design. Using the multiple mid-infrared outputs, we demonstrate the detection of multiple hydrocarbon gases, namely, methane, ethylene, and ethane.     

Widely tunable narrowband soliton source generation in tellurite microstructured fibers

We demonstrate widely tunable soliton and dispersive wave source generation in a highly nonlinear tellurite microstructured fiber pumped by a 1550 nm femtosecond fiber laser. The spectral range covered by the soliton and dispersive wave source is as wide as 1100 nm from 1150 to 2250 nm. It is shown that the spectral linewidth of the soliton and dispersive wave can be controlled by changing the length of the tellurite microstructured fiber easily owing to the dispersion-induced pulse broadening effects. This light source using tellurite microstructured fiber could open wide applications.     

Development and test of SEOP neutron spin filter in Japan

We have begun the development of an in-situ spin-exchange optical pumping (SEOP) system aiming to use it as a neutron spin filter for incident beam polarization at the Japan Proton Accelerator Research Complex (J-PARC). To use it, it is recommended that the optics be adjusted easily, have high stability, and have a small size. In this paper we improved our previous SEOP system aiming to use it in J-PARC and performed a neutron beam test at the JRR-3 NOP beamline to see the performance of the neutron spin filter (NSF). The polarization of the ³He gas reached 73%. This paper gives the present status of the development of in-situ SEOP system in J-PARC.