Ultrahigh Performance Cross-Linkable Organic Electro-Optic Material for Hybrid Modulators

Achieving both high thermal stability and high electro-optical (EO) activity has traditionally been challenging in organic EO (OEO) materials. The highest combination of thermal stability and EO performance has previously been obtained with HLD1/HLD2, which is a cross-linkable, polymer-free binary OEO material capable of achieving an EO coefficient ( r 33 ) of up to 450 pm/V when not cross-linked and >250 pm/V ( n 3 r 33 > 2000 pm/V) at 1310 nm when cross-linked to a glass transition temperature ( T g ) ∼ 175 °C. Herein, we report the design, synthesis, and evaluation of a cross-linkable chromophore system based on two higher hyperpolarizability chromophores BAH-X1 and BAH-X2, with complementary cross-linkable side chains. BAHX has ∼2 times the hyperpolarizability of HLD─based on hyper-Rayleigh scattering measurements─and ∼2 times the EO performance (maximum r 33 up to 1100 pm/V when not cross-linked and >650 pm/V, n 3 r 33 > 4500 pm/V, when cross-linked to T g ∼ 150 °C). Long-term (>2000 h) thermal stability of EO activity has been demonstrated at 85 °C under nitrogen. This high EO activity has been translated to excellent device performance in a plasmonic-organic hybrid phase modulator utilizing 2:1 BAHX, demonstrating a push–pull Mach–Zehnder modulator equivalent V π L = 38 V μm at 1550 nm.