The development of organic electro-optic (EO) materials that concurrently possess a high electro-optic coefficient (r 33 ), 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 cross-linkers, thus resulting in high chromophore density (>5 × 10 20 molecules/cm 3 ) 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 the poling-induced order. With 2:1 HLD1/HLD2 (wt/wt), a maximum r 33 of 290 ± 30 pm/V was achieved in a cross-linked film. Thermal stability tests showed that after heating to 85 °C for 500 h, greater than 99% of the initial r 33 value was maintained. This combination of large EO activity, high index of refraction, and long-term alignment stability is an important breakthrough in EO materials. HLD1/HLD2 can also be poled without the subsequent cross-linking step, and even larger maximum r 33 (460 ± 30 pm/V) and n 3 r 33 figure of merit (3100 ± 200 pm/V) were achieved. Hyperpolarizabilities of HLD and control molecules were analyzed by hyper-Rayleigh scattering and computational modeling with good agreement, and they help explain the high acentric order achieved during poling.

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 (), 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 (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...

This study demonstrates enhancement of in-device electro-optic activity via a series of theory-inspired organic electro-optic (OEO) chromophores based on strong (diarylamino)phenyl electron donating moieties. These chromophores are tuned to minimize...

Organic electro-optic (EO) materials incorporated into silicon-organic hybrid and plasmonic-organic hybrid devices have enabled new records in EO modulation performance. We report a new series of nonlinear optical chromophores engineered...

Microtubules are a vital component of the cell’s cytoskeleton and their organization is crucial for healthy cell functioning. The use of label-free SH imaging of microtubules remains limited, as sensitive detection is required and the true molecular origin and main determinants required to generate SH from microtubules are not fully understood. Using advanced correlative imaging techniques, we identified the determinants of the microtubule-dependent SH signal. Microtubule polarity, number and organization determine SH signal intensity in biological samples. At the molecular level, we show that the GTP-bound tubulin dimer conformation is fundamental for microtubules to generate detectable SH signals. We show that SH imaging can be used to study the effects of microtubule-targeting drugs and proteins and to detect changes in tubulin conformations during neuronal maturation. Our data provide a means to interpret and use SH imaging to monitor changes in the microtubule network in a label-free manner.

This paper reports a multifunctional platform based on a nanocomposite hydrogel combining poly(ethylene glycol), with rhodamine B‐containing silica nanoparticles (RhB@SiO2), as temperature sensors, and gold nanorods (AuNRs) as plasmonic heaters. This composite material acts as a light‐addressable cellular matrix able to induce 3D temperature gradients locally and dynamically using the localized surface plasmon resonance (LSPR) of AuNRs under near‐infrared (NIR) laser illumination. At the same time, the temperature changes are probed locally by monitoring changes of the RhB@SiO2 NPs fluorescence. As a result of plasmonic heating, and, depending on the preparation protocol, the light‐addressable hydrogel also deforms controllably and reversibly, allowing mechanical and thermal cellular stimulation in a 3D matrix. The hydrogel deformation is quantified by means of inline holographic microscopy. This approach makes it possible to accurately and locally control and simultaneously measure temperature gradients and deformation in soft, 3D deformable materials and will enable novel platforms for studying cellular thermo‐ and mechanobiology.

Pyropheophorbide-a methyl ester (PPa-OMe) has been modified by attaching electron-donor and -acceptor groups to alter its linear and nonlinear optical properties. Regioselective bromination of the terminal vinyl position and Suzuki coupling were used to attach a 4-(N,N-diethylaminophenyl) electron-donor group. The electron-acceptor dicyanomethylene was attached at the cyclic ketone position through a Knoevenagel condensation. Four different derivatives of PPa-OMe, containing either electron-donor or electron-acceptor groups, or both, were converted to hydrophilic bis-TEG amides to generate a series of amphiphilic dyes. The absorption and emission properties of all the dyes were compared to a previously reported push-pull type porphyrin-based dye and a commercial push-pull styryl dye, FM4-64. Electrochemical measurements reveal that the electron donor group causes a greater decrease in HOMO-LUMO gap than the electron-acceptor. TD-DFT calculations on optimized geometries (DFT) of all four dyes show that the HOMO is mostly localized on the donor, 4-(N,N-diethylaminophenyl), while the LUMO is distributed around the chlorin ring and the electron-acceptor. Hyper-Rayleigh scattering experiments show that the first-order hyperpolarizabilities of the dyes increase on attaching either electron-donor or -acceptor groups, having the highest value when both the donor and acceptor groups are attached. Two-photon excited fluorescence (TPEF) and second harmonic generation (SHG) images of the bis-TEG amide attached dyes in lipid monolayer-coated droplets of water-in-oil reveal that the TPEF and SHG involve transition dipole moments in different orientations.

The molecular first hyperpolarizability (β) of bacteriorhodopsin was measured over a broad spectral range (800–1300 nm) by means of a spectral hyper-Rayleigh scattering setup. We observed that two-photon fluorescence introduced a systematic error toward overestimating the β value. Spectrally resolved hyper-Rayleigh scattering allowed us to quantify and correct for this effect, resulting in a drop to about one-half of the β value reported in the literature. Moreover, we determined the dispersion of β over the wavelength range between 800 and 1300 nm. Applications such as second harmonic generation (SHG) imaging rely on accurate molecular first hyperpolarizability values, along with information about resonance effects and wavelength-dependent photodamage. With new and more accurate measurement setups, it will be possible to gain more insight into the nonlinear optical response of bacteriorhodopsin.