Yasunori Arima

Crystallization of amorphous Si on a glass substrate through nucleation by Si+ ion implantation

Crystallization of amorphous Si films on a glass substrate by Si+ implantation (acceleration energy: 180 keV, beam current density: 10 μA/cm, ion dose: 1×1017 ions/cm2) was performed without external heating of the substrate. Transmission electron microscopy images of the crystallized specimens lead to the following conclusions: (1) crystallization was achieved through bulk nucleation by Si+ implantation, which is a low temperature and rapid process compared with the ordinary thermal process, (2) the crystallization is strongly related to the ion‐solid interaction, not due to ‘‘pure’’ thermal annealing by ion beam heating.

Ion implantation for large-area optoelectronics on glass substrates

Abstract The authors have investigated the possibility of large-area optoelectronics on glass substrates fabricated by ion implantation, particularly AM-LCD (active-matrix liquid crystal display) and highly intelligent functional devices. Basic knowledge and technologies have been obtained for the formation of SiON- and PSG-layer underneath the glass surfaces by ion implantation. These layers can prevent sodium diffusion into the optoelectronic devices fabricated on glass substrates. Planarization of glass surfaces by ion implantation and the crystallization of amorphous Si by ion implantation without external heating are also discussed.

Grain‐size distribution in ion‐irradiated amorphous Si films on glass substrates

Amorphous Si films containing crystal seeds can be converted to a polycrystal by an ion beam with heating at 350 °C on silica glass substrates, and the density of the crystal grain is almost the same as that of the initial seed. However, the size and density of the crystal seed decrease when the ion irradiation is performed without external heating. The average grain size in the completely crystallized film can be controlled by decreasing the crystal seed density before crystallization. The growth process of crystal grains (average grain diameter R and standard deviation σR) is reported and the gradient ΔσR/ΔR is estimated to be about 0.15. A model calculation is performed to estimate the gradient on the assumption that the growth rate is governed by the plane (111) crystallization and the calculated value is 0.05.

Optical device fabrication using femtosecond laser processing with glass-hologram

Using femtosecond laser processing with glass-hologram, fabrication of 1cm-long straight waveguide and X-coupler is reported in this paper. We design and fabricate 4-level glass-hologram which generates 1cm-long straight line intensity. We fabricate 1cm-long waveguides inside fused silica at one shot exposure with the glass-hologram. We investigate the waveguide performance of near field pattern and propagation loss at wavelength of 1550nm. The near field pattern is almost circular shape. The propagation loss at 1550nm is estimated to be < 1.0 dB/cm. As an example of an optical device consisting of straight waveguides, we fabricate X-coupler or 2x2 coupler using straight line waveguides, and observe the output power ratio depending on crossing angle.

Curved-waveguide fabrication using femtosecond laser processing with glass hologram

We report on a curved waveguide fabrication using femtosecond laser processing with a glass hologram. We design and produce a glass hologram that transforms femtosecond laser beam into a half-ring beam. The half-ring beam generated by the glass hologram is patterned inside fused silica with one laser shot. The guided light whose bending radius is larger than 1mm is observed at wavelength of 635nm. As a simple application, a directional coupler consisting of a straight-line waveguide and a half-ring waveguide is fabricated by two laser shots. Its basic functionality as a coupler is confirmed. We also develop a hologram that simultaneously produces a straight-line and a half-ring. Using it, we demonstrate a directional coupler fabrication inside crown glass with one laser shot.