Signal Boosting in Plasmonic Waveguides by Interdigital Transducer-Generated Surface Acoustic Waves

Plasmonic waveguides have emerged as a key component in integrated photonics, enabling strong light confinement at subwavelength scales [1]. However, the efficient utilization of plasmonic waveguides is often hindered by weak signal intensities along the propagation path, limiting their effectiveness in practical applications [1]. Conventional plasmonic structures, such as V-grooves, wedges, ring resonators, and nanowires, provide high confinement but lack mechanisms to dynamically amplify the plasmonic signal [2]. This challenge has driven the need for innovative strategies to boost signal intensity within these waveguides. To address this limitation, we propose a novel method to enhance plasmonic signal intensity by utilizing on-chip surface acoustic waves (SAWs) generated by interdigital transducers (IDTs) [3]. The device comprises a plasmonic waveguide integrated with two IDTs, fabricated using a Til Au metal stack on a patterned SiO<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf>/Si layer deposited on a lithium niobate (LN) substrate, as depicted in Fig. 1(a). Surface plasmon polaritons (SPPs) are excited using white light, while SAWs are produced by applying an AC signal to the IDTs. The interaction between the SAWs and SPPs dynamically modulates and amplifies the plasmonic signal, leading to a significant boost in intensity. This study demonstrates that the coupling of SAWs with SPPs offers a promising route for on-chip signal amplification in plasmonic waveguides. The enhanced plasmonic intensity was characterized through spectral and temporal measurements using a spectrometer and an oscilloscope, as shown in Fig. 1(b).