Minimum length modulator design with a graphene-based plasmonic waveguide

Surface acoustic wave actuated plasmonic signal amplification in a plasmonic waveguide

Enhancement of nanoscale confinement in the subwavelength waveguide is a concern for advancing future photonic interconnects. Rigorous innovation of plasmonic waveguide-based structure is crucial in designing a reliable on-chip optical waveguide beyond the diffraction limit. Despite several structural modifications and architectural improvements, the plasmonic waveguide technology is far from reaching its maximum potential for mass-scale applications due to persistence issues such as insufficient confined energy and short propagation length. This work proposes a new method to amplify the propagating plasmons through an external on-chip surface acoustic signal. The gold-silicon dioxide (Au-SiO2) interface, over Lithium Niobate (LN) substrate, is used to excite propagating surface plasmons. The voltage-varying surface acoustic wave (SAW) can tune the plasmonic confinement to a desired signal energy level, enhancing and modulating the plasmonic intensity. From our experimental results, we can increase the plasmonic intensity gain of 1.08 dB by providing an external excitation in the form of SAW at a peak-to-peak potential swing of 3 V, utilizing a single chip.

GeSbSeTe-based high extinction ratio optical modulator

In this paper, a design for a high extinction ratio Mach-Zehnder optical modulator is proposed. The switchable refractive index of the germanium-antimony-selenium-tellurium (GSST) phase change material is employed to induce destructive interference between the waves passing through Mach-Zehnder interferometer (MZI) arms and to realize amplitude modulation. A novel, to the best of our knowledge, asymmetric input splitter is designed for the MZI to compensate for unwanted amplitude differences between MZI arms and increase the modulator performance. Three-dimensional finite-difference-time-domain simulations show a very high extinction ratio (ER) and low insertion loss (IL) of 45 and 2 dB, respectively, for the designed modulator at the wavelength of 1550 nm. Moreover, the ER is above 22 dB, and the IL is below 3.5 dB in the wavelength range of 1500-1600 nm. The thermal excitation process of GSST is also simulated using the finite-element method, and the speed and energy consumption of the modulator are estimated.