An Au–Ag hybrid nanoparticle array with dense hotspots was constructed through a low-cost route for SERS detection with high sensitivity and stability.

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Vertically coupled plasmonic structures have been widely used in optical applications due to its enhanced electromagnetic fields in the gaps between metallic nanostructures. In this paper, a large-scale vertically coupled structure composed of the Ag triangle array (AgTA) on Ag grating separated by a nanometric dielectric layer is fabricated by nanosphere lithography incorporated with photolithography. Thanks to the effective surface plasmon polaritons excitation on the Ag grating, a significant surface enhanced Raman spectroscopy (SERS) effect arises from a strongly enhanced local electric field within the tiny gaps between the AgTA and Ag grating, which is verified by experiment and theoretical simulations. The as-proposed SERS substrate exhibits a nice uniformity with the relative standard deviation of about 10.5%, leading to excellent reliability for Raman detection. The simple fabrication of the large-area, productive, and inexpensive vertically coupled plasmonic structure can be a potential candidate for SERS applications.

Random lasers are generated by multiple light scattering in disordered optically gain medium, which are fundamentally different from conventional lasers. Control of emission properties, especially emission wavelength for random lasers is still challenging due to absence of optical cavity. Although plasmonic random lasers exhibit well‐controlled properties, most of studies on plasmonic random lasers to date are still focused on scattering amplification by disorder metal nanoparticles. Here, a tunable random laser based on emitters of Nile red/poly‐methyl methacrylate (PMMA) coupled to plasmonic resonant nanocavities of silver nanorod arrays is presented. The plasmonic random laser has very strong and narrow emission peaks and a very low lasing threshold of 22.8 µJ, resulting from plasmon resonance energy transfer (PRET), the enhanced absorption, scattering, and excitation rates of Nile red/PMMA due to strong localized electric fields in the nanocavities, and enhanced multiple light scattering from the disorder–order hybrid silver nanorod arrays. Furthermore, the lasing wavelength can be tuned in a wide range from 623 to 654 nm by different order harmonic modes of the plasmonic resonant nanocavities. This work not only provides a new strategy to design tunable random lasers, but also opens up their potential applications in medicine and sensing.