Rare Earth-Ion/Nanosilicon Ultrathin Layer: A Versatile Nanohybrid Light-Emitting Building Block for Active Optical Metamaterials

Abstract

We fabricate an Er3+/nano-Si ultrathin (≈ 4 nm) layer and explore its optical response from the near-UV to the near-IR, in the linear and nonlinear regimes. This nanohybrid layer combines the tunable broad-band light harvesting properties of nano-Si with the robust and sharp Er3+ light emission. Its unique nanostructure enables efficient nanometer-range transfer of the harvested energy to the Er3+ ions. Therefore, clear 1.54 μm Er3+ photoluminescence (PL) is observed under excitation at any photon energy (Eexc) from the visible to the near-UV, despite the small amount of Er3+ ions in the layer (<2.5% of atomic monolayer). In the linear regime, the Er3+ PL intensity can be tuned to a maximum by setting the amount of nano-Si (QSi) in the layer at a suitable value, independent of Eexc. In the nonlinear regime, adjustment of QSi allows the dependence of the Er3+ PL intensity on Eexc to be tuned and achievement of nonconventional saturation properties not reported so far in Er3+:nano-Si systems. Based on this characteristic tunability, at sufficiently low QSi the nanohybrid layer is an ideal candidate for efficient near-IR emission under intense near UV–visible broad-band excitation. Furthermore, the nanohybrid layers with high enough QSi show an interesting potential for the optical modulation of the PL intensity by using UV light in a pump–probe configuration. Therefore, this nanohybrid layer is an outstanding candidate as a pure-color light-emitting building block for the development of advanced multiscale active optical metamaterials.