Volumetric bubble display with a gold-nanoparticle-containing glycerin screen.

A key issue in the development of volumetric bubble displays whose voxels are femtosecond laser-excited bubbles is to enlarge the size of displayed graphics. In our previous research in which used glycerin as a screen, this size was less than several millimeters. To increase the size, it is important to reduce the excitation energy, because increasing the display size leads results in a larger focus volume due to the use of laser scanning optics with a low numerical aperture and requires more laser energy to excite the material. The use of gold nanoparticles in glycerin has been proposed as one way of reducing the excitation energy, because such materials are commercially available with controlled shapes, and consequently a controlled absorption spectrum. It was found that glycerin containing gold nanoparticles (GNPs), including gold nanospheres (GNSs) and gold nanorods (GNRs), reduced the pulse energy required for bubble generation compared with the use of pure glycerin. Larger GNSs resulted in a smaller threshold energy and, in particular, GNRs resulted in a threshold energy one-quarter that of pure glycerin. It was also found that the density had almost no effect on the threshold energy, but did affect the bubble generation probability. Finally, it was demonstrated that the bubble graphics with a size on the order of centimeters were rendered in GNR-containing glycerin.