A probe of the radiation field magnetic component based on octahedral Yb3+ in the CaNbGa garnet – CNGG – single crystal

Abstract

In a disordered Yb³⁺-doped CaNbGa garnet – CNGG – single crystal, it is shown that octahedral Yb centers exist up to a solubility limit of about 5 × 10¹⁸ cm⁻³ in addition to the well known dodecahedral Yb which incorporates to a much larger density ∼10²¹ cm⁻³. Despite the low density of the octahedral Yb, the presence of a symmetry center for this garnet site forbids electric dipole (ED) transitions, thus magnetic dipole (MD) spectroscopic contributions are observed with an intensity similar to that of ED ones. Because of the easy growth of this garnet, the potential application of these two contributions for probing the magnetic field component radiated by plasmonic structures is discussed on the basis of time-resolved spectroscopy, since ED Yb³⁺ photoluminescence is about one order of magnitude faster than MD ²F_5/2 → ²F_7/2 (ΔJ = +1) emissions for the 0.3 at%Yb:CNGG crystal. Channels appropriated for room temperature operation can be excited at λ_EXC = 960.3 nm, while sensed at λ_EMI = 1022 nm for the short-lived ED reference channel and λ_EMI = 998, 1011, 1068 or 1080 nm for the long-lived MD signal channel.