Heterogeneously Integrated ITO Plasmonic Mach-Zehnder Interferometric Modulator on SOI

TL;DR

This paper presents a compact, broadband, GHz-fast ITO-based Mach-Zehnder interferometric modulator integrated on silicon, achieving high efficiency and enabling dense, high-speed photonic circuits for next-generation on-chip networks.

Contribution

The authors demonstrate a heterogeneously integrated ITO plasmonic phase-shifter on silicon that is spectrally broadband, GHz-fast, and highly efficient, advancing integrated photonics technology.

Findings

Achieved a VpL of 95 V·μm for the modulator.

Operates broadband across the entire telecommunication C-band.

Demonstrated sub-wavelength, high-speed modulation in silicon photonics.

Abstract

Densely integrated active photonics is key for next generation on-chip networks for addressing both footprint and energy budget concerns. However, the weak light-matter interaction in traditional active Silicon optoelectronics mandates rather sizable device lengths. The ideal active material choice should avail high index modulation while being easily integrated into Silicon photonics platforms. Indium tin oxide (ITO) offers such functionalities and has shown promising modulation capacity recently. Interestingly, the nanometer-thin unity-strong index modulation of ITO synergistically combines the high group-index in hybrid plasmonic with nanoscale optical modes. Following this design paradigm, here, we demonstrate a spectrally broadband, GHz-fast Mach-Zehnder interferometric modulator, exhibiting a high efficiency signified by a miniscule VpL of 95 Vum, deploying an one-micrometer compact electrostatically tunable plasmonic phase-shifter, based on heterogeneously integrated ITO thin films into silicon photonics. Furthermore we show, that this device paradigm enables spectrally broadband operation across the entire telecommunication near infrared C-band. Such sub-wavelength short efficient and fast modulators monolithically integrated into Silicon platform open up new possibilities for high-density photonic circuitry, which is critical for high interconnect density of photonic neural networks or applications in GHz-fast optical phased-arrays, for example.