Ultrahigh Electro-optic Coefficients, High Index of Refraction, and Long-term Stability from Diels-Alder Crosslinkable Binary Molecular Glasses

The development of organic electro-optic (EO) materials that concurrently possess a high electro-optic coefficient (r33), high index of refraction, and long-term or high temperature stability of chromophore alignment, has been a crucial goal. To address this challenge, we developed a crosslinkable EO system consisting of two chromophores, HLD1 and HLD2, which can be electric field poled and then thermally crosslinked in situ to form a stable EO material. This approach avoids the necessity for nonlinear optically inactive materials such as polymers or small molecule crosslinkers, thus resulting in high chromophore density (> 5 × 1020 molecules/cm3) and high index of refraction (n = 1.89 at 1310 nm) for HLD1/HLD2. Different ratios of HLD1 and HLD2 were evaluated to optimize poling efficiency and thermal stability of poling-induced order. With 2:1 HLD1:HLD2 (wt:wt), a maximum r33 of 290 ± 30 pm/V was achieved in a crosslinked film. Thermal stability tests showed that after heating to 85 °C for 500 h, greater...