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Published on: August 17, 2017
Rattling of Oxygen Ions in a Sub-Nanometer-Sized Cage Converts Terahertz Radiation to Visible Light
Yoshitake Toda1, Shintaro Ishiyama2,3, Eduard Khutoryan4
1Materials Research Center for Element Strategy, Tokyo Institute of Technology , 4259 Nagatsuta-cho, Midori-ku, Yokohama 226-8503, Japan.
Abstract:
A simple and robust approach to visualization of continuous wave terahertz (CW-THz) light would open up opportunities to couple physical phenomena that occur at fundamentally different energy scales. Here we demonstrate how nanoscale cages of Ca12Al14O33 crystal enable conversion of CW-THz radiation to visible light. These crystallographic cages are partially occupied with weakly bonded oxygen ions and give rise to a narrow conduction band that can be populated with localized, yet mobile electrons. CW-THz light excites a nearly stand-alone rattling motion of the encaged oxygen species, which promotes electron transfer from them to the neighboring vacant cages. When the power of CW-THz light reaches tens of watts, the coupling between forced rattling in the confined space, electronic excitation and ionization of oxygen species, and corresponding recombination processes result in emission of bright visible light.
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