Femtojoule electro-optic modulation using a silicon–organic hybrid device

Abstract

Energy-efficient electro-optic modulators are at the heart of short-reach optical interconnects, and silicon photonics is considered the leading technology for realizing such devices. However, the performance of all-silicon devices is limited by intrinsic material properties. In particular, the absence of linear electro-optic effects in silicon renders the integration of energy-efficient photonic–electronic interfaces challenging. Silicon–organic hybrid (SOH) integration can overcome these limitations by combining nanophotonic silicon waveguides with organic cladding materials, thereby offering the prospect of designing optical properties by molecular engineering. In this paper, we demonstrate an SOH Mach–Zehnder modulator with unprecedented efficiency: the 1-mm-long device consumes only 0.7 fJ bit−1 to generate a 12.5 Gbit s−1 data stream with a bit-error ratio below the threshold for hard-decision forward-error correction. This power consumption represents the lowest value demonstrated for a non-resonant Mach–Zehnder modulator in any material system. It is enabled by a novel class of organic electro-optic materials that are designed for high chromophore density and enhanced molecular orientation. The device features an electro-optic coefficient of r33≈180 pm V−1 and can be operated at data rates of up to 40 Gbit s−1. Scientists have demonstrated a hybrid silicon–organic electro-optic modulator that consumes just 0.7 fJ of energy per processed data bit. Such highly energy efficient optical modulators are needed for the short-reach, high-density data interconnects of the future. The 1-mm-long device is based on a Mach–Zehnder interferometer design and is compatible with data rates of up to 40 Gbit s−1. The modulator realizes a subfemtojoule efficiency by employing silicon slot waveguides filled with a highly nonlinear organic material called DLD164, which has a very large electro-optic coefficient of 180 pm V−1. The researchers, who are from Europe, the USA and China, claim that the modulator has the lowest power consumption demonstrated to date for a non-resonant Mach–Zehnder modulator realized in any material system.