High-speed optical modulation based on carrier depletion in a silicon waveguide

TLDR

Fast refractive index modulation in silicon‑on‑insulator waveguides arises from electric‑field‑induced carrier depletion in a reverse‑biased pn junction. The paper presents a high‑speed, scalable silicon optical modulator that exploits the free‑carrier plasma dispersion effect. The modulator uses a travelling‑wave design in a reverse‑biased pn‑junction silicon‑on‑insulator waveguide, enabling co‑propagation of electrical and optical signals for high‑speed operation. We demonstrate a 3 dB bandwidth of ~20 GHz and data transmission up to 30 Gb/s, positioning silicon modulators as key components for next‑generation communication networks and high‑performance computing.

Abstract

We present a high-speed and highly scalable silicon optical modulator based on the free carrier plasma dispersion effect. The fast refractive index modulation of the device is due to electric-field-induced carrier depletion in a Silicon-on-Insulator waveguide containing a reverse biased pn junction. To achieve high-speed performance, a travelling-wave design is used to allow co-propagation of electrical and optical signals along the waveguide. We demonstrate high-frequency modulator optical response with 3 dB bandwidth of ~20 GHz and data transmission up to 30 Gb/s. Such high-speed data transmission capability will enable silicon modulators to be one of the key building blocks for integrated silicon photonic chips for next generation communication networks as well as future high performance computing applications.