Nonlinear optical materials containing high boiling point solvents and efficient poling method thereof

Abstract

In general, the present invention is directed to compositions comprising electro-optical materials and high boiling point solvents that allow for improved and more efficient poling, as well as methods for poling the materials. Thus, various embodiments of the present invention provide materials with excellent electro-optical properties that can be efficiently poled for use in electro-optical devices. In various embodiments of the present invention, the materials can be applied as thin films and efficiently poled at low temperatures, typically with an applied voltage, while simultaneously exhibiting excellent macroscopic nonlinear optical properties and thermal stability.

Description

[Technical field]

[0001] The present invention is generally directed to compositions comprising electro-optic materials and high boiling point solvents that allow for improved and more efficient poling, as well as methods for poling such materials. [Background technology]

[0002] (CROSS REFERENCE TO RELATED APPLICATIONS) This application claims the benefit of U.S. Provisional Patent Application No. 63 / 264,880, filed December 3, 2021, the entire contents of which are incorporated herein by reference.

[0003] Nonlinear optical (NLO) chromophores provide electro-optical (EO) activity in poled electro-optical polymer devices. For many years, electro-optical polymers have been investigated as a replacement for inorganic materials such as lithium niobate in electro-optical devices. Electro-optical devices include, for example, external modulators for telecommunications, RF photonics, optical interconnects, etc. Polymer electro-optical materials show great potential for core applications in a wide range of next-generation systems and devices, such as phased array radar, satellite and fiber telecommunications, cable television (CATV), optical gyroscopes for aviation guidance and missile guidance applications, electronic countermeasure (ECM) systems, backplane interconnects for high-speed computing, ultrafast analog-to-digital conversion, mine detection, radio frequency photonics, spatial light modulation, and all-optical (light-switching-light) signal processing.

[0004] A large number of NLO molecules (chromophores) have been synthesized that exhibit high molecular electro-optic properties. Due to the involvement of dipoles in materials processing, the product of molecular dipole moment (μ) and hyperpolarizability (β) is often used as a measure of molecular electro-optic performance. See WO 00 / 09613 (Dalton et al., "New Class of High Hyperpolarizability Organic Chromophores and Process for Synthesizing the Same").

[0005] Nevertheless, it is possible to calculate the hyperpolarizability of a microscopic molecule (β) by comparing it to the hyperpolarizability of a macroscopic material (χ 2 ) have encountered great challenges. The molecular subcomponents (chromophores) must be incorporated into NLO materials that exhibit (i) a high degree of macroscopic nonlinearity and (ii) sufficient temporal, thermal, chemical, and photochemical stability. High electro-optic activity and the stability of the electro-optic activity, also called "temporal stability," are important for commercially viable devices. The electro-optic activity can be increased in electro-optic polymers by increasing the concentration of the nonlinear optical chromophore in the host polymer and by increasing the electro-optic properties of the chromophore. However, some techniques to increase the chromophore concentration risk decreasing the poling efficiency and temporal stability. Simultaneously solving these dual problems is considered the final obstacle to the widespread practical application of EO polymers in many devices and systems.

[0006] High material hyperpolarizability (χ 2The creation of NLO chromophores is limited by the poor social character of the NLO chromophores. Commercially available materials must incorporate the chromophores at high molecular densities with the required molecular moments statistically oriented along a single material axis. To achieve such organization, the charge-transfer (dipole) properties of the NLO chromophores are typically exploited. Here, an external electric field is applied during material processing that results in local low-energy conditions that favor non-centrosymmetric order. Unfortunately, even at moderate chromophore densities, the molecules form multi-molecular dipole-coupled aggregates (centrosymmetric) that cannot be broken up with realistic electric field energies. To overcome this difficulty, the incorporation of anti-social dipolar chromophores into cooperative material structures has typically been achieved by constructing physical barriers (e.g., anti-packing steric groups) that limit the association between nearby molecules.

[0007] Therefore, it has often been considered advantageous in the art to produce nonlinear optical chromophore-containing materials that exhibit high glass transition temperatures (Tg). Materials with high glass transition temperatures exhibit improved thermal stability and maintain macroscopic electro-optical properties to a greater extent than materials with lower glass transition temperatures. However, materials with such high glass transition temperatures require significantly higher temperatures during the poling process to achieve proper alignment. The need to use such high temperatures results in high costs and more time, resulting in what is called poling inefficiency. Summary of the Invention [Means for solving the problem]

[0008] The present invention is generally directed to compositions comprising electro-optical materials and high boiling point solvents that allow for improved and more efficient poling, as well as methods for poling the materials. Various embodiments of the present invention thus provide materials with excellent electro-optical properties that can be efficiently poled for use in electro-optical devices. In various embodiments of the present invention, the materials can be applied as thin films and efficiently poled at typically applied voltages and low temperatures while simultaneously exhibiting excellent macroscopic nonlinear optical properties and thermal stability.

[0009] Various embodiments of the present invention include compositions comprising: (i) an electro-optic material comprising a nonlinear optical chromophore; and (ii) a solvent having a boiling point of about 100° C. or greater, wherein the electro-optic material has a glass transition temperature ("Tg") of about 100° C. or greater. m " or "material glass transition temperature"), and the solvent has a glass transition temperature of the composition as a whole ("Tg c " or "composition glass transition temperature") is Tg m is present in an amount such that the

[0010] Various other embodiments of the present invention include a method comprising the steps of: (i) providing a composition comprising an electro-optic material comprising a nonlinear optical chromophore and a solvent having a boiling point of 100° C. or greater; (ii) forming a thin film of the composition on a substrate or device surface; (iii) poling the nonlinear optical chromophore in the thin film; and (iv) removing the solvent from the composition while the nonlinear optical chromophore is in the poled state to form an oriented, thermally stable electro-optic thin film, wherein the electro-optic material has a glass transition temperature (Tg) of about 100° C. or greater. m ), and the composition has a Tg m Less than the glass transition temperature (Tg c )

[0011] Various additional embodiments of the present invention can include the aforementioned compositions, in which the electro-optic material further comprises a host polymer in which the nonlinear optical chromophore can be dispersed. Various additional embodiments of the present invention can include, or can similarly include, the aforementioned compositions, in which the electro-optic material comprises a plurality of nonlinear optical chromophores and / or a plurality of host polymers. Various additional embodiments of the present invention can include, or can similarly include, electro-optic materials having material glass transition temperatures of 125° C. or higher, or 150° C. or higher, or higher. Alternatively, various additional embodiments of the present invention can include, or can similarly include, solvents having boiling points above 125° C., boiling points above 150° C., boiling points of 175° C. or higher, 200° C. or higher, 250° C. or higher, or higher.

[0012] Further embodiments of the present invention include thin films prepared using compositions or methods according to the aforementioned embodiments, and electro-optical devices comprising such thin films.

[0013] Other aspects, features and advantages will become apparent from the following disclosure, including the detailed description, the preferred embodiments, and the appended claims. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] As used herein, the singular terms "a" and "the" are synonymous with and used interchangeably with "one or more" and "at least one," unless the description and / or context clearly indicates otherwise. Thus, for example, a reference to "a polymer" or "the polymer" herein or in the appended claims can refer to a single polymer or multiple polymers. As a further example, a reference to "a solvent" or "the solvent" herein or in the appended claims can refer to a single solvent or a mixture of multiple solvents. Additionally, unless otherwise indicated, all numerical values ​​are understood to be modified by the word "about."

[0015] As used herein, the term "nonlinear optical chromophore" (NLOC) refers to a molecule or portion of a molecule that produces a nonlinear optical effect when illuminated with light. A chromophore is any molecular unit that produces a nonlinear optical effect upon interaction with light. The desired effect can occur at resonant or nonresonant wavelengths. The activity of a particular chromophore in a nonlinear optical material is manifested as a hyperpolarizability, which is directly related to the molecular dipole moment of the chromophore. Various embodiments of the NLO chromophores of the present invention are structures that are useful for producing NLO effects.

[0016] First-order hyperpolarizability (β) is one of the most common and useful NLO properties. Higher-order hyperpolarizabilities are useful in other applications, such as all-optical (light-switching-light) applications. To determine whether a material, such as a compound or polymer, contains a nonlinear optical chromophore with first-order hyperpolarizability and a sufficient value of the electro-optic coefficient (r33, which is a function of β), the following test can be performed: First, a thin film of the material is placed in an electric field to align the dipoles. This can be done, for example, by sandwiching a thin film of the material between electrodes, such as an indium-tin-oxide (ITO) substrate, a thin gold film, or a thin silver film.

[0017] A potential is then applied to the electrodes while the material is heated to near its glass transition temperature (Tg) to generate a poling field. After a suitable time, the temperature is gradually decreased while maintaining the poling field. Alternatively, the material can be poled by corona poling, where a charged needle at a suitable distance from the material film provides the poling field. In either case, dipoles in the material tend to align with the electric field.

[0018] The nonlinear optical properties of the poled material are then examined as follows: polarized light (often from a laser) is passed through the poled material and a subsequent polarizing filter to a light intensity detector. If the intensity of light received by the detector changes when the potential applied to the electrodes is changed, the material incorporates a nonlinear optical chromophore with an electro-optically varying refractive index. A more detailed discussion of techniques for measuring the electro-optic constants of poled films incorporating nonlinear optical chromophores is provided in Chia-Chi Teng, Measuring Electro-Optic Constants of a Poled Film, in Nonlinear Optics of Organic Molecules and Polymers, Chp. 7, 447-49 (Hari Singh Nalwa & Seizo Miyata eds., 1997), which is hereby incorporated by reference in its entirety. However, in the event of any disclosure or definition that conflicts with this application, the disclosure or definition in this specification shall control.

[0019] The relationship between a change in applied potential and the change in refractive index of a material is expressed as the EO coefficient, r33. This effect is commonly referred to as the electro-optic effect (EO effect). Devices that contain materials whose refractive index changes in response to changes in applied potential are called electro-optic (EO) devices.

[0020] Second-order hyperpolarizability (γ) or third-order susceptibility (χ (3)) is a common measure of third-order NLO activity. There are several ways to measure these properties, but the degenerate four-wave mixing (DFWM) method is very common. See CW Thiel, "For-wave Mixing and Its Applications", http: / / www.physics.montana.edu.students.thiel.docs / FWMixing.pdf, which is incorporated herein by reference in its entirety. A method for evaluating the third-order NLO properties of thin films known in the art as the degenerate four-wave mixing (DFWM) method can be used, see US Patent Publication No. 2012 / 0267583, which is incorporated herein by reference in its entirety. In FIG. 4 of US Patent Publication No. 2012 / 0267583, beams 1 and 2 are picosecond coherent pulses that are absorbed in an NLO film deposited on a glass substrate. Beam 3 is a weaker, slightly delayed beam with the same wavelength as beams 1 and 2. Beam 4 is the result of wave mixing diffracted off the transient holographic grating produced by the interference of Beam 1 and Beam 2 in the NLO material of the film. Beam 3 can be a "control" beam at telecommunications wavelengths that produces a "signal" beam at a frequency not absorbed by the NLO material.

[0021] Compositions suitable for use in various embodiments of the present invention include an electro-optic material and a solvent having a boiling point equal to or greater than 100° C. Electro-optic materials suitable for use include at least one nonlinear optical chromophore and may further include a host polymer.

[0022] Nonlinear optical chromophores suitable for use in accordance with various embodiments of the present invention include those having the general formula (I): D-Π-A (I) wherein D represents an electron donating organic group; A represents an electron accepting organic group having an electron affinity greater than that of D; and π represents a π-bridge between A and D. The terms electron donating group (donor or "D"), π-bridge (bridging group or "π"), and electron accepting group (acceptor or "A"), as well as general synthetic methods for forming D-π-A chromophores, are known in the art and are described, for example, in U.S. Pat. Nos. 5,670,000, 5,670,091, 5,679,763, 6,090,332, 6,716,995, 6,716,995, and U.S. Patent Application No. 17 / 358,960, filed June 25, 2021, which are incorporated herein by reference in their entireties.

[0023] An acceptor is an atom or group of atoms with a low reduction potential that can accept electrons from a donor through a π bridge. Because the acceptor (A) has a larger electron affinity than the donor (D), at least in the absence of an external electric field, the chromophore is generally polarized in the ground state, with a relatively high electron density on the acceptor (A). Typically, the acceptor group contains at least one electronegative heteroatom that is part of a π bond (double or triple bond), and a resonance structure can be drawn in which the electron pair of the π bond is transferred to the heteroatom, simultaneously reducing the multiplicity of the π bond (i.e., the double bond is formally converted to a single bond or the triple bond is formally converted to a double bond) and the heteroatom acquires a formal negative charge. The heteroatom may be part of a heterocycle. Exemplary acceptor groups include, but are not limited to, -NO2, -CN, -CHO, COR, CO2R, -PO(OR)3, -SOR, -S2R, and -S3R, where R is alkyl, aryl, or heteroaryl. The total number of heteroatoms and carbons in the acceptor group is about 30, and the acceptor group may be further substituted with alkyl, aryl, and / or heteroaryl.

[0024] Suitable electron accepting groups "A" (also referred to in the literature as electron withdrawing groups) for nonlinear optical chromophores that can be used in accordance with various embodiments of the present invention include those described in U.S. Patent Application Publication Nos. 2007 / 0260062, 2007 / 0260063, 2008 / 0009620, 2008 / 0139812, 2009 / 0005561, and 2012 / 0267583 (collectively the "prior published documents"), which are incorporated herein by reference in their entireties, and in U.S. Patent Nos. 6,584,266, 6,392, 6,413, 6,512, 6,522, 6,536, 6,540, 6,552, 6,562, 6,572, 6,582, 6,592, 6,671, 6,711, 6,722, 6,736, 6,742, 6,752, 6,762, 6,826, 6,912, 6,922, 6,932, 6,822, 6,912, 6,922, 6,932, 6,742, 6,822, 6,93 ... Nos. 3,190, 6,448,416, 6,44,830, 6,514,434, 5,044,725, 4,795,664, 5,247,042, 5,196,509, 4,810,338, 4,936,645, 4,767,169, 5,326,661, 5,187,234, 5,170,461, 5,133,037, 5,106,211, and 5,006,285.

[0025] In nonlinear optical chromophores suitable for use in accordance with various embodiments of the present invention, suitable electron accepting groups have the general formula (I a ):

[0026] [ka]

[0027] (In the formula, R 2 and R 3 are each independently H, substituted or unsubstituted C1-C 10 Alkyl, substituted or unsubstituted C2-C10 Alkenyl, substituted or unsubstituted C2-C 10 Alkynyl, substituted or unsubstituted aryl, substituted or unsubstituted alkylaryl, substituted or unsubstituted carbocyclic groups, substituted or unsubstituted heterocyclic groups, substituted or unsubstituted cyclohexyl, and (CH2) n -O-(CH2) n where n is 1 to 10. As used herein, the following symbols represent a point of attachment to another portion of a larger molecular structure.

[0028] [ka]

[0029] In various preferred embodiments, R 2 and R 3 One or both of R represent halogen substituted moieties. Halogen substitution may refer to mono-, di-, tri- and higher degrees of substitution. In various embodiments, R 2 and R 3 One of R represents a halogen substituted alkyl moiety and the other represents an aromatic moiety. 2 and R 3 one represents a halogen substituted aromatic moiety and the other represents an alkyl moiety. In various embodiments, the electron accepting group can be:

[0030] [ka]

[0031] In various embodiments, the electron accepting group can be:

[0032] [ka]

[0033] In various embodiments, the electron accepting group can be:

[0034] [ka]

[0035] The donor includes an atom or group of atoms with a low oxidation potential that can donate electrons to the acceptor "A" through a π bridge. Since the donor (D) has a smaller electron affinity than the acceptor (A), the chromophore is generally polarized in the ground state and has a relatively low electron density on the donor (D), at least in the absence of an external electric field. Typically, the donor group includes at least one heteroatom having an unshared electron pair that can be conjugated with the p orbital of the atom directly bonded to the heteroatom, and a resonance structure can be drawn in which the unshared electron pair is transferred to a bond with the p orbital of the atom directly bonded to the heteroatom to formally increase the bond multiplicity between the heteroatom and the atom directly bonded to the heteroatom (i.e., a single bond is formally converted to a double bond or a double bond is formally converted to a triple bond), so that the heteroatom formally gains a positive charge. The p orbital of the atom directly bonded to the heteroatom may be vacant or may be part of a multiple bond with another atom other than the heteroatom. The heteroatom may be a substituent of an atom having a pi bond or may be within a heterocycle. Exemplary donor groups are R2N-, and R n X 1 - (wherein R is alkyl, aryl or heteroaryl; and X 1 is O, S, P, Se or Te, and n is 1 or 2. The total number of heteroatoms and carbons in the donor group can be about 30, and the donor group can be further substituted with alkyl, aryl or heteroaryl.

[0036] Suitable electron donating groups "D" for nonlinear optical chromophores that can be used in accordance with various embodiments of the present invention include those described in U.S. Patent Application Publication Nos. 2007 / 0260062, 2007 / 0260063, 2008 / 0009620, 2008 / 0139812, 2009 / 0005561, and 2012 / 0267583 (collectively, the "Prior Published Documents"), which are incorporated herein by reference in their entireties, and in U.S. Patent Nos. 6,584,266, 6,393,190, 6,448,416, and 6,44,830, which are incorporated herein by reference in their entireties. Nos. 6,514,434, 5,044,725, 4,795,664, 5,247,042, 5,196,509, 4,810,338, 4,936,645, 4,767,169, 5,326,661, 5,187,234, 5,170,461, 5,133,037, 5,106,211, and 5,006,285, as well as those described in U.S. Patent Application Serial No. 17 / 358,960, filed June 25, 2021, the entirety of which is incorporated herein by reference.

[0037] In various embodiments, the electron donating group can include quinolinyl groups, which may be substituted or unsubstituted, including hydro and alkyl substituents, aryl substituents, and combinations thereof.Such quinolinyl groups can have one or more diamondoid groups covalently bonded thereto.For example, the electron donating group can include alkoxyphenyl-substituted quinolones, such as:

[0038] [ka]

[0039] Or, for example, the electron donating group can include an aromatic nitrogen-containing group such as:

[0040] [ka]

[0041] A "π-bridge" includes an atom or group of atoms through which electrons can be delocalized from an electron donor (defined above) to an electron acceptor (defined above) via orbitals of atoms in the bridge. Such groups are very well known in the art. Typically, the orbitals are located between doubly bonded carbon atoms (sp 2 ) or p orbitals on triple bonded carbon atoms (sp). Additionally, the orbitals may be p orbitals on atoms such as boron or nitrogen. Additionally, the orbitals may be p, d or f organometallic or hybrid organometallic orbitals. In this specification, the bridge atoms containing the orbitals where the electrons are delocalized are referred to as "critical atoms". The number of critical atoms in the bridge is 1 to about 30. The critical atoms may be substituted with organic or inorganic groups. The substituents are selected with a view to improving the solubility of the chromophore in the polymer matrix, improving the stability of the chromophore, or for another purpose.

[0042] Suitable bridging groups (Π) for the nonlinear optical chromophores according to general formula (I) include those described in U.S. Pat. Nos. 6,584,266, 6,393,190, 6,448,416, 6,44,830, and 6,514,434, the entireties of which are hereby incorporated by reference.

[0043] In various embodiments, the bridging group (Π) of the nonlinear optical chromophore according to general formula (I) is represented by the general formula (II a ):

[0044] [ka]

[0045] (wherein X represents a substituted or unsubstituted, branched or unbranched C2-C4 diyl moiety; each of a and b independently represents an integer of 0 to 3; and z represents an integer of 1 to 3). a In various embodiments where a or b in formula (I) is 1, the carbon-carbon double bond in formula (I) can be replaced with a carbon-carbon triple bond. Alternatively, in various embodiments, the bridging group (Π) for the nonlinear optical chromophore according to formula (I) can be replaced with a carbon-carbon triple bond. b ) can contain:

[0046] [ka]

[0047] wherein X represents a substituted or unsubstituted, branched or unbranched C2-C4 diyl moiety. The diamondoid group or groups may include a group having the general formula (II a ) or (II b In various embodiments where the diamondoid group is covalently linked to a bridging group according to the formula (I), the diamondoid group or groups may be bonded, for example, to the sulfur or oxygen atoms of a thiophene group, or may be bonded to one or more carbon atoms in X via ether or thioether bonds.

[0048] In various embodiments, the bridging group (Π) of the nonlinear optical chromophore according to general formula (I) is represented by the general formula (II c ) can contain:

[0049] [ka]

[0050] wherein each Y independently represents a diamondoid-containing group covalently bonded to a bridging group through any of the various linking groups described herein and below, including but not limited to ether and thioether bonds; or each Y independently represents hydrogen, an alkyl group, an aryl group, an alkyl or aryl group linked by sulfur or oxygen, or a C1-C4 substituent that may be branched or unbranched and may optionally contain heteroatoms; each of a and b independently represents an integer from 0 to 3; z independently represents an integer from 1 to 3; each of the arcs A independently represents a substituted or unsubstituted C2-C4 alkyl group that, together with the carbon bearing the Y substituent and its two adjacent carbon atoms, forms a cyclic group. The substituted or unsubstituted C2-C4 alkyl groups that make up the arc A may include 1 to 4 hydrogen substituents, each of which may be a substituted or unsubstituted C1-C4 alkyl group. 10 Alkyl, substituted or unsubstituted C2-C 10 Alkenyl, substituted or unsubstituted C2-C 10 Alkynyl, substituted or unsubstituted aryl, substituted or unsubstituted alkylaryl, substituted or unsubstituted carbocyclic groups, substituted or unsubstituted heterocyclic groups, substituted or unsubstituted cyclohexyl, and (CH2) n -O-(CH2) n In various embodiments, z represents 1. In various embodiments, the electron donating or electron accepting group may include one or more covalently bonded diamondoid groups and may be represented by the general formula II c Y may represent any of the substituents described above. In various embodiments, the chromophore may include one or more covalently linked diamondoid groups, preferably electron donating groups including adamantyl groups, and the bridging group may be represented by the general formula II c The compound may include an isophorone group according to the formula: where Y represents an aryl thioether substituent.

[0051] In various embodiments, the bridging group (Π) of the nonlinear optical chromophore according to general formula (I) is a group represented by the general formula (II d ) can contain:

[0052] [ka]

[0053] wherein each Y independently represents a diamondoid-containing group covalently bonded to a bridging group through any of the various linking groups described herein and below, including, but not limited to, ether and thioether bonds; or each Y independently represents a hydrogen, an alkyl group, an aryl group, a sulfur- or oxygen-linked alkyl or aryl group, an aryl group bonded directly through a carbon-carbon bond (which may optionally bear a diamondoid group) (e.g., adamantly anisole), a halogen, a halogenated alkyl group, a halogenated aryl group, or a branched or unbranched, optionally heteroatom-containing C1-C4 substituent; each of a and b independently represents an integer from 0 to 3; and z represents an integer from 1 to 3. In various embodiments, the electron donating or electron accepting group may include one or more covalently bonded diamondoid groups and may be represented by a group having the general formula II: d Y may represent any of the substituents described above. In various embodiments, the chromophore may include one or more covalently linked diamondoid groups, preferably electron donating groups including adamantyl, and the bridging group may be represented by the general formula II d Alternatively, in various embodiments, the isophorone group may be according to the general formula II: d Each of the geminal methyl groups on the isophorone bridging group is independently a substituted or unsubstituted C1-C 10 Alkyl, substituted or unsubstituted C2-C 10 Alkenyl, substituted or unsubstituted C2-C 10Alkynyl, substituted or unsubstituted aryl, substituted or unsubstituted alkylaryl, substituted or unsubstituted carbocyclic groups, substituted or unsubstituted heterocyclic groups, substituted or unsubstituted cyclohexyl, halogens, halogenated alkyl groups (e.g., -CF3), halogenated aryl and heteroaryl groups (e.g., pentafluorothiophenol), and (CH2) n -O-(CH2) n (wherein n is 1 to 10).

[0054] For example, the bridging group (π) of the nonlinear optical chromophore according to general formula (I) can include:

[0055] [ka]

[0056] Examples of chromophores suitable for use in accordance with various embodiments can include the following, in addition to all of the chromophores disclosed in the references incorporated herein by reference:

[0057] [ka]

[0058] [ka]

[0059] The compositions according to various embodiments of the present invention may further include a host polymer, also referred to as a matrix material, and may incorporate one or more nonlinear optical chromophores into the host polymer. Suitable matrix materials may include polymers such as, for example, poly(methyl methacrylate) (PMMA); polyimide; polyamic acid; polystyrene; poly(urethane) (PU); amorphous polycarbonate (APC). In various embodiments, the matrix material may include, for example, poly(methyl methacrylate) having a molecular weight of about 120,000 and a glass transition temperature Tg of about 100-165°C, or APC having a Tg of about 150-220°C.

[0060] In general, the nonlinear optical chromophore can be incorporated into the matrix material in virtually any amount, or can be used in the absence of a matrix material (i.e., "neat" or 100% chromophore). For example, suitable electro-optical materials can include the nonlinear optical chromophore in an amount of about 1% to 90% by weight, based on the total combined weight of the nonlinear optical chromophore and matrix material. In various embodiments, suitable electro-optical materials can include the nonlinear optical chromophore in an amount of about 2% to 80% by weight, based on the total combined weight of the nonlinear optical chromophore and matrix material. In various embodiments, suitable electro-optical materials can include the nonlinear optical chromophore in an amount of about 3% to 75% by weight, based on the total combined weight of the nonlinear optical chromophore and matrix material. For example, one or more chromophores can be combined with an amorphous polycarbonate or mixture of matrix materials in a ratio of 70% chromophore / 30% matrix material by weight. In various embodiments, the chromophore can be crosslinked with the matrix material or other polymers.

[0061] Solvents suitable for use in various embodiments of the present invention include high boiling point solvents. As used herein, "high boiling point solvent" refers to a solvent having a boiling point (at 1 atmosphere) of 100°C or higher. In various embodiments, suitable solvents have boiling points of 110°C or higher, 120°C or higher, 130°C or higher, 140°C or higher, 150°C or higher, 160°C or higher, 170°C or higher, 180°C or higher, 190°C or higher, 200°C or higher, 210°C or higher, 220°C or higher, 230°C or higher, 240°C or higher, and 250°C or higher. Solvents suitable for use in various embodiments of the present invention, when added to the materials forming the compositions of the present invention, have a composition glass transition temperature (Tg c ) the material's glass transition temperature (Tg m In various embodiments, a suitable solvent, when added to the materials forming the composition of the present invention, can reduce the glass transition temperature (Tg c ) is the material glass transition temperature (Tg m In various embodiments, a suitable solvent, when added to the materials forming the composition of the present invention, can reduce the composition glass transition temperature (Tg c ) is the material glass transition temperature (Tg m ) at least 20°C lower than the material glass transition temperature (Tg m ) at least 30°C lower than the material glass transition temperature (Tg m ) and the material glass transition temperature (Tg m ) can be reduced to a value at least 50°C lower than that.

[0062] Solvents suitable for use in various embodiments can include solvents that can form homogeneous solutions of the electro-optical material and are generally high boiling, relatively non-polar, and aprotic. Suitable solvents include, for example, N-methylpyrrolidone, dimethylsulfoxide, carbonates such as ethylene carbonate and propylene carbonate, and glycol ethers such as diethylene glycol dibutyl ether. Solvents that are considered "polar" such as DMSO can be used and are considered relatively non-polar as long as they can dissolve both polar and non-polar solutes. In various embodiments, a suitable high boiling solvent can include diethylene glycol dibutyl ether. In various embodiments, the high boiling solvent can be used in a mixture with a co-solvent that does not have a high boiling point.

[0063] The electro-optic material can be dispersed in a suitable solvent in virtually any amount to provide a uniform solution and suitable properties for thin film formation. For example, the solids content of the electro-optic material in the solvent in the various embodiments described herein can be adjusted depending on the desired film thickness and the spin speed of the spin-coating apparatus. As is known in the art, a less viscous solution generally results in a thinner spin-coated film. In various embodiments, the solids content of the electro-optic material in the solvent can be from about 1% to about 25%. In various embodiments, the solids content of the electro-optic material in the solvent can be from about 2% to about 20%. In various embodiments, the solids content of the electro-optic material in the solvent can be from about 5% to about 15%.

[0064] Methods according to various embodiments of the present invention include providing a composition as described herein, forming a thin film comprising the composition, poling the thin film, and drying the thin film (i.e., removing the solvent).

[0065] Suitable thin films can be formed on substrates using, for example, a spin-coating process or inkjet printing. Suitable substrates can include surfaces coated with indium tin oxide (ITO), conductive materials, silicon, semiconductors, etc. Thin films can be formed with various thicknesses ranging from submicrons to several microns. Prior to the poling step, the thin films can be soft-baked, for example, at 60° C. for about 1 minute.

[0066] Thin films made according to various method embodiments disclosed herein can be poled by applying a suitable voltage across the material at a suitable temperature. Electrodes can be formed or placed on opposing sides of the thin film, or above and below the thin film in various devices and structures, in such a manner that a suitable voltage can be applied across the thin film. The electrodes can be formed of gold, for example. A suitable voltage can be from about 50 V / μm to about 150 V / μm. A suitable temperature for poling the thin film is generally below the glass transition temperature of the composition, but high enough to allow for the alignment of the nonlinear optical chromophores in the material. Thus, for example, if the glass transition temperature of the composition is 125° C., suitable poling temperatures can include temperatures from about 100° C. to just below about 125° C.

[0067] After poling the thin film, the thin film according to various embodiments described herein can be dried or densified by removing the remaining solvent while maintaining the electric field of the applied voltage. Generally, the solvent is selected from those having a temperature above the glass transition temperature Tg of the thin film. m Drying or solvent removal can be accomplished, for example, by slowly increasing the temperature slightly while maintaining the poling field until the solvent is removed, and then cooling. Drying or solvent removal can be accomplished, for example, by cooling to a low temperature while maintaining the poling field applied so that depoling does not occur at a substantial rate, and then applying a vacuum to remove the solvent.

[0068] Thin films according to various embodiments herein can be incorporated into a variety of devices, including electro-optical devices having open-top or coplanar designs, and devices having permeable layers, openings, etc., to allow solvent to escape after poling. Examples of open-top devices are described in the art, including the following documents, which are hereby incorporated by reference in their entireties: Qiu, F. et al., "A hybrid electro-optic polymer and TiO2 double-slot waveguide modulator", SCI. REP. 5, 8561 (2015); Shi, S. and Prather, D., "Ultrabroadband Electro-Optic Modulator Based on Hybrid Silicon-Polymer Dual Vertical Slot Waveguide", ADVANCES IN OPTOELECTRONICS Volume 2011, Article ID 714895, 6 pages; Qui, F. et al., "Plate-slot polymer waveguide modulator on silicon-on-insulator", OPT.EXPRESS 26, 11213-11221 (2018); Enami, Y. et al., "Electro-optic polymer / TiO2 multilayer slot waveguide modulators", APPLIED PHYSICS LETTERS 101, 123509 (2012); and Lee, E. et al., "Coplanar Electrode Polymer Modulator Incorporating Fluorinated Polyimide Backbone Electro-Optic Polymer", PHOTONICS 7, no.4: 100 (2020).

[0069] The present invention will now be described in further detail with reference to the following non-limiting examples. EXAMPLES

[0070] (Composition example 1) An electro-optic material was formed by adding 70% by weight of the nonlinear optical chromophore shown below to amorphous polycarbonate (APC180).

[0071] [ka]

[0072] The electro-optic material was combined with an 80:20 mixture of dibromomethane:diethylene glycol dibutyl ether as a solvent. The composition was spin-coated onto ITO-coated glass and baked under nitrogen at 60° C. for 1 minute.

[0073] (Composition example 2) An electro-optic material was formed by adding 70% by weight of the nonlinear optical chromophore shown below to amorphous polycarbonate (APC180).

[0074] [ka]

[0075] The electro-optic material was combined with an 80:20 mixture of dibromomethane:diethylene glycol dibutyl ether as a solvent. The composition was spin-coated onto ITO-coated glass and baked under nitrogen at 60° C. for 1 minute.

[0076] (Comparative composition example 1) Similarly, an electro-optical material was prepared by adding 70% by weight of the nonlinear optical chromophore used in Composition Example 1 to APC180. This composition was spin-coated on an ITO-coated glass and baked under nitrogen at 150° C. for 30 minutes.

[0077] (Comparative composition example 2) Similarly, an electro-optical material was prepared by adding 70% by weight of the nonlinear optical chromophore used in Composition Example 2 to APC180. This composition was spin-coated on an ITO-coated glass and baked under nitrogen at 150° C. for 30 minutes.

[0078] The thin films prepared in each of the Examples and Comparative Examples were poled and the r33 values ​​at 1310 nm were measured. The results are shown in Table 1 below.

[0079] [Table 1]

[0080] As shown in Table 1, the poling temperatures of the thin films prepared from both Composition Example 1 and Composition Example 2 were significantly lower than the poling temperatures of the thin films prepared from Comparative Composition Example 1 and Comparative Composition Example 2. Furthermore, the r33 values ​​at 1310 nm were significantly larger in the examples of the present invention.

[0081] It will be appreciated by those skilled in the art that changes could be made to the embodiments described above without departing from the broad inventive concept thereof. It is understood, therefore, that the invention is not limited to the particular embodiments disclosed, but is intended to cover modifications within the spirit and scope of the invention as defined by the appended claims.

Claims

1. 1. A composition comprising an electro-optic material comprising a nonlinear optical chromophore, The nonlinear optical chromophore has the general formula (I): D-Pi-A (I) (wherein D represents an electron-donating organic group; A represents an electron-accepting organic group having an electron affinity greater than that of D; and Π represents a Π-bridge between A and D). and the organic electron-donating group is a substituted or unsubstituted tetrahydroquinoline group, The electro-optical material has a glass transition temperature (Tg) of about 100° C. or higher. m ) the composition further comprises a solvent having a boiling point of about 100° C. or greater; The solvent is selected from the group consisting of a solvent having a glass transition temperature (Tg c ) is Tg m The composition is characterized in that the amount of

2. 10. The composition of claim 1, wherein the electro-optic material further comprises a host polymer in which the nonlinear optical chromophore is dispersed.

3. The electro-optical material has a glass transition temperature (Tg) of about 150° C. or higher. m 2. The composition of claim 1, wherein the hydroxyl group is hydroxypropyl methylcellulose.

4. The electro-optical material has a glass transition temperature (Tg) of about 180° C. or higher. m 2. The composition of claim 1, wherein the hydroxyl group is hydroxypropyl methylcellulose.

5. 10. The composition of claim 1, wherein the solvent has a boiling point of about 150°C or higher.

6. 10. The composition of claim 1, wherein the solvent has a boiling point of about 250°C or greater.

7. The glass transition temperature (Tg c ) is Tg m 2. The composition of claim 1, wherein the temperature is at least 10°C lower than the reference temperature.

8. The glass transition temperature (Tg c ) is Tg m 2. The composition of claim 1, wherein the temperature is at least 25°C lower than the reference temperature.

9. The glass transition temperature (Tg c ) is Tg m 2. The composition of claim 1, wherein the temperature is at least 50°C lower than the

10. 3. The composition of claim 2, wherein the host polymer comprises an amorphous polycarbonate.

11. 10. The composition of claim 1, wherein the solvent comprises diethylene glycol dibutyl ether.

12. The host polymer comprises an amorphous polycarbonate, the solvent comprises diethylene glycol dibutyl ether, and the Tg m The composition according to claim 2, wherein the temperature is 150°C or higher.

13. providing a composition comprising an electro-optic material comprising a nonlinear optical chromophore and a solvent having a boiling point of 100°C or greater, wherein the electro-optic material has a glass transition temperature (Tg) of about 100°C or greater; m ), and the composition has a Tg m A glass transition temperature (Tg c ) a step of preparing a thin film of the composition on a substrate; poling the nonlinear optical chromophore in the thin film; removing the solvent from the composition while the nonlinear optical chromophore is in a poled state to form an oriented, thermally stable electro-optic thin film; A method comprising:

14. 14. The method of claim 13, wherein the thin film is prepared by a technique selected from the group consisting of spin coating and inkjet printing.

15. 14. The method of claim 13, wherein the electro-optic material further comprises a host polymer.

16. The host polymer comprises an amorphous polycarbonate, the solvent comprises diethylene glycol dibutyl ether, and the Tg m The method according to claim 15, characterized in that the temperature is 150°C or higher.

17. 17. The method of claim 16, wherein the thin film is prepared by a technique selected from the group consisting of spin coating and inkjet printing.

18. A thin film prepared by the method of claim 13.

19. 14. An electro-optical device comprising a thin film prepared by the method of claim 13.

20. Electro-optical materials containing nonlinear optical chromophores, said electro-optical materials having a glass transition temperature (Tg) of about 100° C. or higher. m an electro-optical material having a solvent selected from the group consisting of N-methylpyrrolidinone, dimethyl sulfoxide (DMSO), and glycol ethers; A composition comprising: The solvent is selected from the group consisting of a solvent having a glass transition temperature (Tg c ) is Tg m The composition is characterized in that the amount of