In this article, we demonstrate the feasibility of self-positioning nanoemitters onto optical waveguides by visible-light nanoscale photopolymerization. A light-sensitive material containing nanoemitters is photopolymerized at interfaces by using the evanescent field of the light propagating in photonic structures. By exploiting this method, it is possible to pattern polymeric ridges containing CdSe/ZnS nanocrystals (NCs) directly on top of optical guiding structures. Photopolymerization experiments have been performed in the case of a single ion-exchange glass waveguide (IEx WG) and of a double waveguide made of the IEx WG with a thin titanium dioxide film fabricated on top of it. Atomic force microscopy (AFM) and spectroscopy analyses highlight the reliability and reproducibility of the fabrication technique. Continuous ridges of controlled thickness have been realized on top of a single waveguide interface with thicknesses as small as 18 nm, thus thick enough to contain only a photoluminescent NC monolayer in the vertical direction. In the presence of the double waveguide (TiO2 layer on top of the IEx WG), AFM measurements reveal that the thickness of the photopolymerized ridge has a sinusoidal modulation. This is due to a light beating phenomenon theoretically predicted in the case of light propagating in coupled waveguides. In our case, the light beating can be efficiently exploited to photopolymerize ridges with modulated thickness. Overall, the flexibility of the reported nanoscale fabrication technique paves the way toward the controlled positioning of single nanoemitters in proximity of nanoantennas or other elaborate plasmonic/photonic structures.
Integrated optical devices able to control light-matter interactions on the nanoscale have attracted the attention of the scientific community in recent years. However, most of these devices are based on silicon waveguides, limiting their use for telecommunication wavelengths. In this contribution, we propose an integrated device that operates with light in the visible spectrum. The proposed device is a hybrid structure consisting of a high-refractive-index layer placed on top of an ion-exchanged glass waveguide. We demonstrate that this hybrid structure serves as an efficient light coupler for the excitation of nanoemitters. The numerical and experimental results show that the device can enhance the electromagnetic field confinement up to 11 times, allowing a higher photoluminescence signal from nanocrystals placed on its surface. The designed device opens new perspectives in the generation of new optical devices suitable for quantum information or for optical sensing.
The interplay between quantum emitters and plasmonic nanostructures can unlock unprecedented functionalities, potentially useful for novel‐concept photonics. Herein, the design and conceptual implementation of an integrated photonic–plasmonic transistor is reported. A mixed top‐down and bottom‐up nanofabrication approach is used to realize a prototype based on a nano‐guided hybrid system enabling the interaction between gold nanostructures and emitters and thus resulting in a plasmon–exciton exchange. In analogy with a classical transistor (MOSFET), gold nanotapers (NTs) are fabricated in specific positions on a TiO2 waveguide to behave as drain, source, and gate for highly localized electric near‐fields. Photopolymerization by evanescent waves is then exploited to grow a polymeric ridge containing quantum dots directly on top of the NTs. The fluorescent spectroscopy of the prototype evidences a sensitive Purcell enhancement of the emission of the quantum dots located in proximity of the apices of gold NTs. The numerical study of the hybrid system demonstrates how this enhancement is controlled to efficiently route and modulate high‐frequency optical signals in the novel photonic device.
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