# Coupling-enhanced Dual ITO Layer Electro-absorption Modulator in Silicon Photonics

## TL;DR

This paper presents a compact, broadband electro-absorption modulator in silicon photonics, using a novel dual-gated ITO structure to enhance coupling and achieve high performance without resonances.

## Contribution

The work introduces a heterogeneously integrated dual-gated ITO absorber at a silicon directional coupler for improved electro-optic modulation in a compact form.

## Key findings

- Achieved 2 dB extinction ratio with a 4 μm device at 4 V bias.
- Demonstrated broadband operation across the entire C-band.
- Enabled high-performance modulation without optical resonances.

## Abstract

Electro-optic signal modulation provides a key functionality in modern technology and information networks. Photonic integration has enabled not only miniaturizing photonic components, but also provided performance improvements due to co-design addressing both electrical and optical device rules. However, the millimeter-to-centimeter large footprint of many foundry-ready photonic electro-optic modulators significantly limits on-chip scaling density. To address these limitations, here we experimentally demonstrate a coupling-enhanced electro-absorption modulator by heterogeneously integrating a novel dual-gated indium-tin-oxide (ITO) phase-shifting tunable absorber placed at a silicon directional coupler region. Our experimental modulator shows a 2 dB extinction ratio for a just 4 um short device at 4 volt bias. Since no material nor optical resonances are deployed, this device shows spectrally broadband operation as demonstrated here across the entire C-band. In conclusion we demonstrate a modulator utilizing strong index-change from both real and imaginary part of active material enabling compact and high-performing modulators using semiconductor foundry-near materials.

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Source: https://tomesphere.com/paper/1907.10756