Monolithic silicon nitride electro-optic modulator enabled by optically-assisted poling

TL;DR

This paper demonstrates optically-assisted poling of silicon nitride microring resonators to induce a significant second-order nonlinearity, enabling high-speed electro-optic modulation without high-temperature processing, advancing integrated photonics.

Contribution

First demonstration of optically-assisted poling in silicon nitride microrings to achieve effective EO modulation, eliminating the need for high-temperature device processing.

Findings

Effective second-order nonlinearity of 1.2 pm/V achieved.

EO bandwidth of 4 GHz demonstrated.

Poling process simplifies fabrication and enhances device performance.

Abstract

Electro-optic (EO) modulation is a key functionality to have on-chip. However, achieving a notable linear EO effect in stoichiometric silicon nitride has been a persistent challenge due to the material's intrinsic properties. Recent advancements revealed that the displacement of thermally excited charge carriers under a high electric field induces a second-order nonlinearity in silicon nitride, thus enabling the linear EO effect in this platform regardless of the material's inversion symmetry. In this work, we show for the first time optically-assisted poling of a silicon nitride microring resonator, removing the need for high-temperature processing of the device. The optical stimulation of charges avoids the technical constraints due to elevated temperature. By optimizing the poling process, we experimentally obtain a long-term effective second-order nonlinearity of 1.2 pm/V. Additionally, we measure the high-speed EO response of the modulator, showing a bandwidth of 4 GHz, only limited by the quality factor of the microring resonator. This work goes towards the implementation of monolithic, compact silicon nitride EO modulators, a necessary component for high-density integrated optical signal processing.