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.

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

Second-order nonlinear optical (NLO) materials have been investigated for decades driven by the application requirements of electro-optic modulators for optical communication, optical switches, sensors, terahertz generation and detection. The prominent advantages of organic NLO materials are ultra-fast response and structural versatility, which gives the materials large NLO activity, good processability and other necessary properties for specific applications via suitable molecular engineering. In this review, historic and recent studies of organic dipolar chromophores in acentric alignment affording macroscopic anisotropy are overviewed. In particular, recent marked progress in the development of acentric bulky materials, including isolating chromophores to prevent centrosymmetric alignment, is focused on. We also review fascinating methods for the ordered alignment of chromophores, which include supramolecular interaction, light fields, electric fields and so on. It is hoped that better chromophore molecular structures and film construction techniques can be devised using suitable NLO films to achieve higher performances in optoelectronic devices.

Molecular engineering of organic chromophores and polymers for enhanced bulk second-order optical nonlinearity

We have developed an efficient synthetic platform for the preparation of a new class of high performance thermosets based on the 1,3-dipolar cycloaddition of a bifunctional sydnone with a trifunctional alkyne. These processable materials possess outstanding thermal stability, with Td5% of 520 °C and a weight loss of <0.1% per day at 225 °C (both in air). Key to this performance is the stability of the starting functional groups that allows for reactive B-staging via simple thermal activation to give fully aromatic and highly cross-linked polypyrazole-based thermosets.

Fully Aromatic High Performance Thermoset via Sydnone-Alkyne Cycloaddition.

The interest of the scientific community in sydnones and sydnone imines, the most known mesoionic compounds, is grounded on their unusual molecular structures, specific physical and biological properties, and chemical behavior. This nonexhaustive review highlights the achievements in sydnone and sydnone imine chemistry reported since 1998 and covers the preparations of these mesoionic compounds, their functionalization both at the 1,3,4-oxadiazoline ring and in side chains (including that one at N6 of sydnone imines), the ring-opening processes, and [3 + 2]-cycloaddition reactions where sydnones and sydnone imines act as the 1,3-dipoles. Special attention is paid to 4-lithio and 4-halogeno derivatives that have manifested themselves as the key intermediate compounds for preparations of a variety of sydnone and sydnone imine derivatives. Biological and some other applications of sydnone and sydnone imines are only slightly mentioned in this review.

Recent developments in the chemistry of sydnones and sydnone imines

Spontaneous thermal crosslinking of a sydnone-containing side-chain polymer with maleimides through a convergent [3 + 2] dual cycloaddition/cycloreversion process for electro-optics

A new approach to polymer cross-linking is investigated using a cascading cycloreversion of a maleimide-furan adduct and a double 1,3-dipolar cycloaddition between a sydnone and maleimide. The cross-linking proceeds quantitatively above 63 °C, despite the polymer possessing no observable glass transition temperature. The resulting polymer network possesses a high thermal stability (>300 °C) due to the irreversibility of the sydnone-maleimide cycloaddition, which releases CO2 during the cross-linking, driving the reaction. The rigid three-dimensional structure of the bis-maleimide-sydnone cycloadduct produced local free volumes in films, decreasing the dielectric constant of the material.

Cascading retro-Diels-Alder cycloreversion and sydnone-maleimide based double 1,3-dipolar cycloaddition for quantitative thermal cross-linking of an amorphous polymer solid

Wei Huang

Papers

Spontaneous thermal crosslinking of a sydnone-containing side-chain polymer with maleimides through a convergent [3 + 2] dual cycloaddition/cycloreversion process for electro-optics

Cascading retro-Diels-Alder cycloreversion and sydnone-maleimide based double 1,3-dipolar cycloaddition for quantitative thermal cross-linking of an amorphous polymer solid