Microfabrication is required to process glass materials in order to locally assign the desired optical properties. The authors have proposed a new microfabrication technique to form a metal sphere and manipulate the sphere inside glass. When a continuous-wave (CW) laser was illuminated from the glass side to a metal attached to the glass, a metal sphere was formed. The metal sphere was moved towards a light source with laser illumination in the glass. When the sphere migrates, it is accompanied by the diffusion of submicron metal particles. Hence, this technique allows the creation of doped regions of fine particles in the shape of a sphere’s trajectory. Controlling the shape of the particle-doped area to transform into arbitrary shapes enables the design of more flexible optical devices. The Soret effect could be one of the keys to satisfying these requirements. The Soret effect is a material transport phenomenon driven by temperature gradients in multiple components. However, to the best of our knowledge, there have been no studies on the Soret effect on metal particles in glass. Herein, we show that iron particles are transported inside silica glass as a result of temperature gradient. Metal-sphere migration produces a local particle-doped area in the glass. A temperature gradient was formed by laser heating the sphere under conditions that prevented it from moving. In situ observations revealed that particles migrated toward the metal sphere at a maximum speed of 0.56 μm/s.
Ultrashort-pulsed laser illumination focused inside a diamond converts sp3-bonded diamond to sp2-bonded amorphous carbon in the vicinity of the focal point and changes the color to black. A wire-shaped modified region is fabricated by scanning the laser focus toward the laser source in the diamond. Volumetric expansion by converting diamond to amorphous carbon forms cracks around the modified region. In this study, diamond slicing was attempted by using cracks formed around the modified region. A near-infrared picosecond laser was focused inside a high-temperature, high-pressure diamond. The cracks fabricated under various laser conditions were observed. The plane crack was formed by lining up the wire-shaped modified regions next to each one. During the fabrication, a high-speed polarization camera was used to observe the stress distribution around the modified region and in the adjacent wire-shaped modified region. The crack propagation was estimated by observing the stress distribution in situ. The kerf loss in the slicing process was estimated by observing the cross section of the cracks from multiple directions. These results demonstrate that plane cracks suitable for slicing the diamond were fabricated. Diamond separation was performed by applying an external force to the plane cracks.
Metal doping in glass can change the properties of glass. A metal foil placed in direct contact with one side of the glass substrate. Continuous-wave (CW) laser illumination can implant metal spheres by heating the metal foil. In this study, the laser heating conditions required to implant metal spheres into glass are investigated experimentally and theoretically. The temperature of the glass exceeded the temperature threshold of laser absorption when the metal sphere was implanted. In addition, sphere implantation speed increased with the laser power density. The metal sphere was implanted at speeds of 20 to 50 mm/s.
The authors reported that laser illumination to a metal sphere in glass migrated the metal sphere toward the light source. The migration was caused by interfacial tension gradient. In this presentation, we demonstrate the metal sphere separation by the two laser beam illumination from opposite direction. The metal sphere separation was not explained by the interfacial gradient and suggested the existence of pulling force to the light source side.
We have reported that laser-induced metal particle migration in glass. Laser illumination heated a metal particle in glass. The surrounding glass of the metal particle was also heated and softened; hence, the metal particle migrated in the glass. The temperature gradient caused the driving force. The interfacial tension between the glass and the metal particle was varied by the temperature. The temperature nonuniformity caused the interfacial tension nonuniformity and metal particle migration. In this presentation, we demonstrated metal particle migration by the surface heating of the glass with a CO2 laser. Heating of glass surface moved metal particle located 200 μm below the surface. The particle was moved out of the glass after 400 s illumination. The migration speed was 0.3~0.7 μm/s.
We proposed a technique to manipulate a metal particle in glass optically. The glass in the neighborhood of the laserheated
metal particle softened; hence, the metal particle migrated in the glass. In our numerical calculation, the
temperature difference in the metal particle generated the inhomogeneous distribution of the interfacial tension between
melted metal particle and softened glass. The inhomogeneous distribution generated driving force. In this presentation,
the experimental temperature measurement by using emitted light of the migrating metal particle in glass was discussed.
The temperature was approximately 2400 K and corresponded with the numerical calculated temperature reported before.
In this study, a statistical analysis was carried out about influences of energy variance, pre-pulse and post-pulse setting to the main pulse on the melt zone. In the experiment, laser beams were irradiated on the plates of aluminum alloy by two spots, and then, depth and width of melt were measured. Thus, the fluctuation in the dimensions measured was analyzed using statistical methods.
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