Ultra-compact and broadband electro-absorption modulator using an epsilon-near-zero conductive oxide

Transparent conductive oxides have emerged as a new type of plasmonic material and demonstrated unique electro-optic（E-O） modulation capabilities for next-generation photonic devices. In this paper, we report an ultra-compact, broadband electro-absorption（EA） modulator using an epsilon-near-zero（ENZ） indium-tin oxide（ITO）. The device is fabricated on a standard silicon-on-insulator platform through the integration with a 3 μm long, 300 nm wide gold plasmonic slot waveguide. The active E-O modulation region consists of a metal–HfO;–ITO capacitor that can electrically switch the ITO into ENZ with ultra-high modulation strengths of 2.62 and 1.5 dB/μm in simulation and experiment, respectively. The EA modulator also demonstrated a uniform E-O modulation with 70 nm optical bandwidth from 1530 to 1600 nm wavelength.