Hokkaido University Research Profiles

Nanotechnology / Materials

New Crystal Material Converts Sunlight into Laser Light

Mikio Higuchi Specially Appointed Associate Professor

New Cr, Nd co-doped crystals for high efficiency solar-pumped lasers

The Nd:CaYAlO4 crystal exhibits a wide absorption band in the visible region and a large absorption cross section. Since the energy absorbed by chromium is transferred to neodymium, it is expected to convert solar energy to laser light with high efficiency.

Content of research

We have fabricated CaYAlO4 single crystals doped with chromium (Cr) and neodymium (Nd) using a technique called the floating zone melting method. By appropriately controlling the fabrication conditions, high-quality red transparent crystals were obtained (Fig. 1). The crystal has a very wide absorption range from the ultraviolet region to the visible region, and shows sufficient absorption even at the wavelength where the energy of sunlight is at its maximum (Fig. 2). We have also found that the absorption is 70 times or more that of conventional materials such as Cr and Nd:YAG. These properties are unique to the newly developed crystal and not found in existing materials. We have also demonstrated that neodymium can emit light upon excitation in the absorption band of chromium due to its fluorescence properties (Fig. 3). Based on this result, it is expected to convert solar energy into laser light with high efficiency.

  • Fig. 1 Cr, Nd:CaYAlO4 single crystal

  • Fig. 2 Absorption spectrum of Cr, Nd:CaYAlO4

  • Fig. 3 Fluorescence spectra of Cr, Nd:CaYAlO4

Potential for social implementation

  • ・Refining of magnesium metal
  • ・Light source for artificial photosynthesis
  • ・Highly efficient biomass use

Appealing points to industry and local governments

Although the floating zone melting technique is an excellent material exploration method, we believe that use of the pull-up method is essential for the stable production of large crystals. We are looking forward to collaborating with companies that have single crystal growth technology (especially the pull-up method). To actually apply this technology in practice, we hope to collaborate with companies that are developing laser equipment, or companies that plan to expand into the field of optical technology.