Ultra-fast silicon electro-optic modulator based on ITO-integrated directional coupler

Abstract

An optical modulator is a very essential component in optoelectronic communication system as it generates an optical data stream out of an applied electric signal. Designing devices with subwavelength dimensions turned out to be a challenge constrained by the ‘diffraction limit’. Plasmonic-based devices had overcome this issue, reaching miniature footprint but introducing high propagation losses. Alternative materials such as conducting transparent oxides (TCOs) act as an optical dielectric material with an excess of free carriers. By adjusting the gating potential on such materials, an epsilon-near-zero state can be reached and the material exhibits a metal-like behavior, in terms of the optical losses. A very popular TCO material is indium tin oxide (ITO). In this work, ITO is utilized in electro-optic modulator design based on a directional coupler device with a slot waveguide platform. The design introduces an ITO/HfO2 combination in the coupler section waveguide. An extinction ratio more than 9 dB and an insertion loss less than 0.9 dB are achieved at a telecommunication standard wavelength of 1.55 μm. Additionally, an average energy per bit (E) of 4.355 fJ/bit as well as an operating bandwidth up to 1 THz, under optimal conditions, are attained.

Effects of Nb concentration on Nb-doped anatase TiO2: DFT + U calculations

“…Transparent conducting oxide (TCO) plays significant roles in various fields including sensors, heat mirrors, displays, active energy generation and optoelectronic devices, etc [1][2][3][4]. In different TCO materials, Sn-doped In 2 O 3 (ITO) is widely applied thanks to its excellent electrical and optical properties [5].…”

Design of low power silicon electro optic modulators based on hybrid plasmonic ring resonator

“…ITO's unique epsilon-near-zero (ENZ) conditions and electrical conductivity have made it suitable for optical modulators [33,34]. The hybrid plasmonic modulators with a vertical [11,34,35] or horizontal [36,37] structure are designed and investigated [34,[38][39][40][41].…”

Silicon ring resonator electro-optical modulator utilizing epsilon-near-zero characteristics of indium tin oxide

“…However, high propagation losses of metals are considered a drawback to plasmonic-based optical devices. Recently, modulators that utilize transparent conducting oxide (TCO) materials [21][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36] as the EO active layer have concerned a lot of research. Latterly, one of the most commonly used CMOS-compatible TCOs is indium tin oxide (ITO).…”

“…The carriers' accumulation rate is very fast so that the modulation speed is limited solely by the RC delay [36]. In the past few years, integrating ITO with silicon EO modulators has received a great attention because of its electrically-induced ENZ characteristics [30][31][32][33][34][35].…”