To develop this innovative memory storage technique, the team incorporated rare earth elements, also known as lanthanides, into a crystal. They specifically used praseodymium and an yttrium oxide crystal, though the process they developed can be applied to a variety of materials, utilizing the powerful and flexible optical properties of rare earth elements.
As França further explains, rare earth elements exhibit specific electronic transitions that allow for the selection of precise laser excitation wavelengths for optical control, ranging from UV to near-infrared regimes.