Nanoscale Field Effect Optical Modulators Based on Depletion of Epsilon-Near-Zero Films

TL;DR

This paper introduces nanoscale optical modulators using epsilon-near-zero films that leverage field effect depletion to control light attenuation, enabling efficient on-chip optical communication.

Contribution

It presents a novel design of field effect electro-absorption modulators with ENZ films integrated into waveguides, demonstrating significant modulation with low insertion loss.

Findings

Achieved up to 3.44 dB extinction ratio in silicon waveguides.

Achieved up to 7.86 dB extinction ratio in plasmonic waveguides.

Demonstrated low insertion loss suitable for integrated photonics.

Abstract

The field effect in metal-oxide-semiconductor (MOS) capacitors plays a key role in field-effect transistors (FETs), which are the fundamental building blocks of modern digital integrated circuits. Recent works show that the field effect can also be used to make optical/plasmonic modulators. In this paper, we report field effect electro-absorption modulators (FEOMs) each made of an ultrathin epsilon-near-zero (ENZ) film, as the active material, sandwiched in a silicon or plasmonic waveguide. Without a bias, the ENZ film maximizes the attenuation of the waveguides and the modulators work at the OFF state; contrariwise, depletion of the carriers in the ENZ film greatly reduces the attenuation and the modulators work at the ON state. The double capacitor gating scheme is used to enhance the modulation by the field effect. According to our simulation, extinction ratio up to 3.44 dB can be achieved in a 500-nm long Si waveguide with insertion loss only 0.71 dB (85.0%); extinction ratio up to 7.86 dB can be achieved in a 200-nm long plasmonic waveguide with insertion loss 1.11 dB (77.5%). The proposed modulators may find important applications in future on-chip or chip-to-chip optical interconnection.