Ultrahigh Performance Cross-Linkable Organic Electro-Optic Material for Hybrid Modulators
Huajun Xu, Delwin L. Elder, Lewis E. Johnson, Yovan de Coene, Wolfgang Heni, David Moor, Scott R. Hammond, Kevin M. O’Malley, Koen Clays, Juerg Leuthold, Larry R. Dalton, Bruce H. Robinson
Abstract
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.