Hiroshi Wakatsuki

Laser trapping of deformable objects

We report the trapping and manipulation of bubbles in viscous glass melts through the use of a laser. This phenomenon is observed in bubbles tens of micrometers in diameter under illumination by low numerical aperture (NA = 0.55). Once the bubble was centered on the optical axis, it was trapped and followed a lateral relocation of the laser beam. This phenomenon is explained by modifications of the bubbles shape induced by axial heating and a decrease in surface tension. It is shown that formation of a concave dimple on the bubbles front surface explains the observed laser trapping and manipulation. This mechanism of laser trapping is expected to take place in other deformable materials and can also be used to remove bubbles from melts or liquids. For this technique to be effective, the alteration of the bubbles shape should be faster than its expulsion out of the lasers point of focus.

Crack-Free High-Aspect-Ratio Drilling of Glasses by 1 µm Yttrium Aluminum Garnet Laser and Translucent Adhesive Tape

We have succeeded in drilling a crack-free high-aspect-ratio hole through glass using a YAG laser of 1 µm wavelength, 5 ns pulse width and 30–630 mJ/pulse. The hole is 25.5 mm long with 500 µm radius and no crack is observed even under atmospheric conditions. This success is due to the use of a translucent adhesive tape pasted on the glass surface in which the temperature is controlled and thermal stress is reduced. Computer simulation revealed the mechanism of the phenomena.

Visualization of Micro-scale Surface Forming Process by Infrared Pulse Laser Heating

In this paper, surface forming process on glass plate was studied by using pulsed CO2 laser irradiation. The process was visualized by a high speed camera. Surface forming process of humped lens-like surface that had 470 μm in diameter and 18.3 μm in height and ablated surface that had 522 μm in diameter and 3.2 μm in depth were visualized. In comparatively high laser intensity the center of lens-like surface ablate and the surface get dented.