Selective Plasmon Enhancement of the 1.08 μm Nd³⁺ Laser Stark Transition by Tailoring Ag Nanoparticles Chains on a PPLN Y-cut

Abstract

Selective photoluminescence enhancement of the specific Nd(3+) Stark transition for which laser gain has been obtained in Nd(3+)/LiNbO3 is demonstrated by means of plasmonic resonances with the appropriate symmetry configuration. By using the nonpolar Y-cut of a periodically poled LiNbO3 crystal as platform for photoreduction of metallic nanostructures, periodically distributed chains of Ag nanoparticles oriented parallel to the ferroelectric c-axis are obtained. This alternative metallic nanostructure configuration supports the resonance between the localized surface plasmon and exclusively the π-polarized Stark laser line of Nd(3+) ions at 1.08 μm, while maintaining the remaining crystal field transitions unchanged. The work provides the experimental proof on how plasmonic-based optical antennas can be used to influence selectively rare earth optical Stark transitions to improve the performance of solid state laser gain media.

Hybrid Plasmonic–Ferroelectric Architectures for Lasing and SHG Processes at the Nanoscale

“…More detail on the size distribution and interparticle distances for that system can be found in reference . Here, it is worth noting the possibility of fabricating similar metallic arrangements on Nd 3+ :PPLN crystals using a nonpolar surface as a platform . In particular, the formation of metallic nanostructures on a Y‐cut Nd 3+ :PPLN substrate was demonstrated, showing that the metallic deposition was not necessarily linked to the persistence of spontaneous polarization, but to the presence of surface charge.…”

“…d) PFM image of a periodically poled LiNbO 3 crystal (left panel) and the corresponding SEM image of Ag nanoparticle chains formed at the domain walls after the photodeposition process. Adapted with permission . Copyright 2013, American Chemical Society.…”

“…The amplitude of the near field profiles computed at the NIR region differ by almost two orders of magnitude when comparing the radiated field parallel or perpendicular to the chain axis (Figure c). The near field enhancement and the radiative character of the longitudinal modes, make linear chains of interacting NPs an interesting plasmonic system for the enhancement and polarization control of different optical processes …”

“…Therefore, another interesting outcome of combining metallic nanostructures with RE 3+ doped ferroelectric substrates is the possibility of inducing a selective enhancement of RE 3+ Stark transitions with specific polarization character by taking advantage of the anisotropic response of metallic arrangements. In this regard, two different strategies have been adopted: i) the use of linear chains of interacting NPs with anisotropic optical response due to the presence of the longitudinal and transversal modes, and ii) the use of morphologically isotropic Ag‐DPNs, which generates anisotropic near field polarization components …”

“…Accordingly, the deposition of Ag NP chains on the Y‐cut Nd 3+ doped LiNbO 3 , (see Figure b), gives rise to the selective plasmonic enhancement of the π emission line. Note that, for this geometrical configuration the linear chains are oriented parallel to the optical axis, so that the excitation of the longitudinal plasmonic mode produces the specific enhancement of the π‐polarized optical transitions, whereas the transverse plasmonic mode interacts with the Nd 3+ transitions with σ character …”