Electro‐Optic Activity in Excess of 1000 pm V⁻¹ Achieved via Theory‐Guided Organic Chromophore Design

Abstract

artificial intelligence/machine learning (AI/ML), cloud-based services, telemedicine, and autonomous vehicles, as well as, demands from remote work due to the COVID-19 pandemic. To keep pace with demand for optical and wireless communications, there is an urgent need for electro-optic modulators with large bandwidths, high power-efficiency, and micrometer-scale footprints that enable dense chip-scale integration with complementary metal-oxide-semiconductor electronics. [1][2][3][4] Significant improvements in device performance have been made by silicon-organic hybrid [5][6][7][8][9][10][11][12][13][14] and plasmonicorganic hybrid. [1,[15][16][17][18][19][20][21][22][23][24][25][26][27] Pockels effect modulators, which have proven to be effective photonic platforms for both analog and digital applications.Achieving groundbreaking performance requires synergistic innovation from rational design of organic electrooptic (OEO) materials to device engineering and advancements in communication systems. [20,[28][29][30] As the active component for the Pockels effect, OEO materials, using conjugated π-electron systems, deliver large EO coefficients > 300 pm V −1 (>10× lithium niobate), low dielectric constant (static ε < 7), and femtosecond (<30 fs) response times. [28] Large EO coefficients (r 33 ) of organic material require a combination of high chromophore hyperpolarizability (β), electric field poling-induced acentric order of the chromophores (<cos 3 θ>), and chromophore number density (ρ N ). Furthermore, the EO modulator operating voltage is strongly dependent on the refractive index of the material (n) at the operational wavelength: The half-wave voltage-length parameter V π L for an EO modulator is inversely proportional to n 3 r 33 . Furthermore, n increases with β and ρ N . [28,29] The past two decades of research and development have demonstrated many effective molecular engineering strategies to increase ρ N <cos 3 θ> (increasing ρ N by eliminating the inactive polymer host, while maintaining good poling efficiency). These strategies include side-chain engineering, site-isolation, self-assembly, multi-chromophore dendrimers, chromophore blending, and control of chromophore shape. [31][32][33][34][35][36][37][38][39][40][41] These strategies, led to materials with enhanced r 33 (300-550 pm V −1 at 1310 nm wavelength), [31,35,36,[42][43][44][45][46] which is a large improvement over lithium niobate (≈30 pm V −1 ), High performance organic electro-optic (OEO) materials enable ultrahigh bandwidth, small footprint, and extremely low drive voltage in silicon-organic hybrid and plasmonic-organic hybrid photonic devices. However, practical OEO materials under device-relevant conditions are generally limited to performance of ≈300 pm V −1 (10× the EO response of lithium niobate). By means of theory-guided design, a new series of OEO chromophores is demonstrated, based on strong bis(4-dialkylaminophenyl)phenylamino electron donating groups, capable of EO coefficients (r 33 ) in excess of 1000 pm V −1 . Density functi...

Methacrylic copolymers with quinoxaline chromophores in the side chain exhibiting quadratic nonlinear optical response

“…38 The study of the temporal and thermal stability of quadratic NLO response was performed by the example of P1Ch( 6) and P2Ch(6) copolymers. After storing the samples at room temperature for 3 months the measurements demonstrated almost no change in d 33 value; the heating of the samples at 50 C during 100 h also did not result in essential decrease of the NLO coefficient: 100% and 97% of the response retained for P1Ch(6) and P2Ch (6), what is better than for PMMA/AEEA-VQV-TCF and PMMA-based composite material with DBA-VQV-TCF Ar chromophoresguests. 49 The subsequent heating at 65 C during 100 h has shown that 90% and 85% of the initial NLO response retained for P1Ch(6) and P2Ch(6); the corresponding estimation for PMMA/AEEA-VQV-TCF gives 80%.…”

“…The development of organic polymer materials exhibiting quadratic nonlinear optical (NLO) response to the applied electric field during last several decades is at the forefront of research activities in the field of new functional materials, in particular, those for use in photonics and optoelectronics due to their advantages in comparison with the traditionally used inorganic materials. [1][2][3][4][5][6] High quadratic electric susceptibility, fast response, and other attractive features of these materials, together with virtually endless possibilities of structural modifications make them extremely attractive for the applications in photonic devices, such as the frequency converters, high-speed electro-optic (EO) modulators, and switches. [1][2][3]6 Polymer materials with NLO chromophores in the side chain possess a number of recognized advantages over guest-host chromophore-containing materials, the most important being enhanced NLO coefficients, improved thermal stability and temporal stability of the quadratic NLO response.…”

“…[1][2][3][4][5][6] High quadratic electric susceptibility, fast response, and other attractive features of these materials, together with virtually endless possibilities of structural modifications make them extremely attractive for the applications in photonic devices, such as the frequency converters, high-speed electro-optic (EO) modulators, and switches. [1][2][3]6 Polymer materials with NLO chromophores in the side chain possess a number of recognized advantages over guest-host chromophore-containing materials, the most important being enhanced NLO coefficients, improved thermal stability and temporal stability of the quadratic NLO response. 1,3,5 These polymers permit achieving a higher chromophore concentration without crystallization or phase separation due to the reduced probability of interchromophore interactions resulting in the decrease of nonlinearity.…”

Design and synthesis of chromophores with enhanced electro-optic activities in both bulk and plasmonic–organic hybrid devices

“…[34][35][36] In past a decade, EO performance has been improved via strategies such as siteisolation, self-assembly, chromophore blending, and charge blocking layers (CBLs) to enhance the r N hcos 3 yi value of bulk materials. 26,28,31,33,[37][38][39][40][41][42][43][44][45][46][47][48][49] Recent work 50,51 has also shown substantial increases in hyperpolarizability due to theoryguided design, after years of little increase in b of reported chromophores.…”

“…28 The best r 33 value (1100 AE 100 pm V À1 ) of BAH13 was achieved by using HfO 2 as CBL, which is comparable to the performance of BAY1 but with greatly decreased absorption at communication wavelengths. 50…”