Coupled localized surface plasmon resonances in periodic arrays of gold nanowires on ion-exchange waveguide technology

Abstract

Coupled localized surface plasmon resonances (LSPRs) in periodic arrays of metallic nanowires are attractive for use in sensing applications due to their light enhancement and their sensitivity to the surrounding environment. Due to the interwire coupling, they behave as plasmonic waveguides with high wavevector modes that require bulky methods for efficient excitation. In this contribution, we demonstrate the excitation of coupled LSPRs in gold nanowires with photonic modes supported by an optical waveguide made with ion exchange technology. Currently, although weakly-coupled LSPRs are experimentally demonstrated, strongly-coupled LSPRs are only demonstrated numerically due to the challenge represented by the fabrication of a high density nanowire array with current electron beam lithography. Due to their operation across the visible spectrum and its low-loss coupling to standard optical fibers, integrated nanowires on glass waveguides open new perspectives for the development of hybrid photonic-plasmonic integrated optical devices.

Coupling Light in Ion-Exchanged Waveguides by Silver Nanoparticle-Based Nanogratings: Manipulating the Refractive Index of Waveguides

“…The chemical components of the soda-lime glass (% w/w) are 66. 16 In the IE process, Ag + s in silver nitrate (AgNO 3 ) salt, mixed with sodium nitrate (NaNO 3 ) salt, replaced Na + s in soda-lime glass by a thermal process. We carried out the IE process at 350 °C for 30 min.…”

“…10−14 Ion-exchanged waveguides are also used to couple light into the photonic structure, such as plasmons in array gratings and slab. 15,16 Furthermore, ion-exchanged waveguides are intended for classical/quantum optical communications and sensing. 17,18 The refractive index of Ag + /Na + ion-exchanged glasses depends on the concentration of Ag + s introduced into the glass matrix.…”

“…The IE process increases the refractive index of the glass due to the formation of silver clusters in the glass matrix. ,, The high refractive index glasses are excellent candidates for designing solid-state lasers and creating broadband optical waveguides, which are utilized in integrated optical circuits. − Ion-exchanged waveguides are also used to couple light into the photonic structure, such as plasmons in array gratings and slab. , Furthermore, ion-exchanged waveguides are intended for classical/quantum optical communications and sensing. , …”

“…One of the significant challenges of using ion-exchanged glasses as a waveguide is coupling the light beam into the waveguides. ,, Among different coupling mechanisms, the prism coupling approach and periodic nanostructures are the most appropriate methods for coupling the light beam into ion-exchanged glasses. ,,, In the prism coupling technique, a high-index prism guides incident light into the waveguide. For this purpose, phase matching must occur between the incident wave and guided mode .…”

Towards a Glass New World: The Role of Ion-Exchange in Modern Technology

“…Furthermore, these ion-exchange optical waveguides have been used as excitation systems for surface plasmon resonance (SPR) or localized surface plasmon resonance (LSPR) in noble metal thin films or NP arrays selectively deposited on them. This approach replaced the more traditional Kretschmann configuration based on prism coupling and contributed to the realisation of hybrid-plasmonic label-free integrated optical biosensors with high performance [91][92][93][94]. Alternatively, the same noble NPs can be directly grown in the guiding structure in order to obtain LSPR optical waveguides for the detection of selected analytes by monitoring the changes in absorption spectra as a result of the chemical reaction occurred at the interface [95].…”