Kazuaki Sajiki

Detection of Neutral Species in Silane Plasma Using Coherent Anti-Stokes Raman Spectroscopy

Coherent Anti-Stokes Raman Spectroscopy (CARS) has been employed for the first time to investigate silane (SiH4) glow-discharge plasma. By measuring ν1 vibrational line of silane as a function of position between the two electrodes, spatial distribution of silane (number density) in the (bulk) plasma has been determined for various gas pressures. It has been demonstrated that CARS is an excellent diagnostic tool for a chemically-active plasma such as silane-based glow discharge.

High repetition rate, wide-aperture KrF lasers for subpicosecond amplification

A high repetition rate, wide-aperture KrF laser with a magnetic switch has been developed. A dynamic response and a core loss of several magnetic materials were measured, resulting in a loss as low as 0.45 J/pulse for a voltage risetime of approximately 100 ns. A maximum output energy of 2.5 J in 20 ns (FWHM) was obtained with a total efficiency of 2.5% at 20 Hz. The cross section of the output beam was 65*50 mm/sup 2/. Spectral, spatial, and temporal profiles of gain and absorption coefficients were also measured, resulting in a peak gain of 8.5%/cm. An output energy of 410 mJ was extracted in 280 fs with two beams by using this laser as an amplifier. >

HIGH-REPETITION-RATE HIGH-AVERAGE-POWER 300-FS KRF/TI:SAPPHIRE HYBRID LASER

We have developed a 1-kHz KrF/Ti:sapphire hybrid laser system. Average power was 7 W at 248 nm with a pulse width of 300 fs. A kilohertz Ti:sapphire regenerative amplifier at a wavelength of 745 nm is also described.

Hall coefficients in the superconductor‐insulator transition of Bi2+xSr2−xCuOy: Measurement of Hall‐bar shaped single crystals fabricated by excimer‐laser cutting

Hall coefficients and resistivities of a series of Bi2+xSr2−xCuOy single crystals were measured to investigate the relation between the carrier concentration and the disorder of the system in the superconductor‐insulator transition. Excimer‐laser cutting technique was applied to fabricate the Hall‐bar shaped samples in order to determine precisely the transport properties of the single crystals. The Hall coefficients were found to be independent of the temperature, which suggests Coulomb interaction was negligible in the localized regime of Bi2+xSr2−xCuOy. We found the Ioffe–Legel condition kFl∼1 laid around n0∼8×1020 cm−3 in this system, and the carriers in the localized regime were essentially ‘‘metallic.’’

UV pre-ionized wide-aperture XeCl laser using magnetic pulse compression

To provide a spatially homogeneous and sufficiently high-voltage discharge, the laser described here used LC inversion and two-stage magnetic pulse compression in the excitation circuit and used UV radiation for pre-ionization. It also employed one commercial thyratron as a high-voltage switch. Evaluation of the dynamic magnetic characteristics of four magnetic materials in a magnetic pulse compression circuit showed that the Fe-based nanocrystalline soft magnetic alloy was the best core material for a compact switch with low core loss. At a 10 Hz repetition rate the maximum output energy obtained in a 80/spl times/60 nm discharge cross section and in 70 ns pulses (FWHM) was 6.2 J.

Scaling behavior of the surface roughness in the crystallization process :transformation of polycrystalline Si from amorphous Si

We made polycrystalline silicon (poly-Si) thin films from amorphous silicon (a-Si) thin films by the excimer-laser crystallization method. And we have investigated the surface roughness in the process from a-Si to poly-Si crystallized gradually by changing the energy density E of the excimer-laser. By using atomic force microscopy (AFM), the surface width W(L, E) is estimated as the root mean square (rms) value of the roughness, where L is the length scale, E the energy density of the excimer-laser. We discovered a new scaling law in the crystallization process. We observed W (L, E) ~ L α (L ≪ L x ), and the saturation width W sat (E) scaled with E as W sat (E) ~ E β* (L ≫ L x ), where L x is the crossover length, the roughness exponent α = 0.88 ± 0.10, and the exponent β* = 1.37 ± 0.10, respectively.

High-power high beam quality ArF laser

A high power injection-locked ArF excimer laser system for advanced material processing and machining is presented. The spectrally narrowed oscillator produced seed laser pulses with a spectral bandwidth of less than 0.8 pm (FWHM). The wide aperture discharge pumped amplifier produced 1.3 J output energy in oscillator operation. Stable output energy was obtained with the injection timing between -5 ns and 5 ns and with the injection energy density of more than 1 mJ/cm2.