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

We fabricate an Er 3+ /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 Er 3+ light emission. Its unique nanostructure enables efficient nanometer-range transfer of the harvested energy to the Er 3+ ions. Therefore, clear 1.54 μm Er 3+ photoluminescence (PL) is observed under excitation at any photon energy ( E exc ) from the visible to the near-UV, despite the small amount of Er 3+ ions in the layer (<2.5% of atomic monolayer). In the linear regime, the Er 3+ PL intensity can be tuned to a maximum by setting the amount of nano-Si ( Q Si ) in the layer at a suitable value, independent of E exc . In the nonlinear regime, adjustment of Q Si allows the dependence of the Er 3+ PL intensity on E exc to be tuned and achievement of nonconventional saturation properties not reported so far in Er 3+:nano-Si systems. Based on this characteristic tunability, at sufficiently low Q Si 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 Q Si 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.