Emerging electro-optic molecular crystals for optoelectronic integration

TL;DR

This paper introduces novel electro-optic molecular crystals, NDPA and derivatives, with high performance, thermal stability, and process compatibility, advancing silicon-organic hybrid optical modulators for integrated photonics.

Contribution

Discovery and characterization of new EO molecular crystals that meet high performance, stability, and fabrication requirements for optoelectronic integration.

Findings

EO performance exceeds lithium niobate

Thermal stability maintained over 1000 hours at 393 K

Crystallization into high-quality aligned thin films

Abstract

The rapid advancement of communication technology necessitates the development of hybrid optical modulators that integrate silicon photonics with electro-optic (EO) materials to enable ultrafast, low-power, and compact photonic devices. However, no existing material simultaneously meets the requirements for high EO performance, process compatibility, and thermal stability, which are essential for practical optoelectronic integration. Here, we present 4-(4'-nitrophenylazo)diphenylamine (NDPA) and its derivative, novel nonlinear optical molecular crystals discovered through materials screening incorporating crystal habit prediction. They demonstrate crystallization into high-quality aligned thin films and ultrafine silicon slot fillings through the capillary action of melts. The resulting EO performance much exceed that of conventional lithium niobate and are comparable to state-of-the-art EO polymers, with excellent thermal stability maintained for over 1000 hours at 393 K. The present EO materials satisfying all the requirements above are promising candidates for silicon-organic hybrid optical modulators, opening a significant step toward scalable and high-performance optoelectronic technologies.