Two-photon excitation provides a means of activating chemical or physical processes with high spatial resolution in three dimensions and has made possible the development of three-dimensional fluorescence imaging, optical data storage, and lithographic microfabrication. These applications take advantage of the fact that the two-photon absorption probability depends quadratically on intensity, so under tight-focusing conditions, the absorption is confined at the focus to a volume of order λ3 (where λ is the laser wavelength). Any subsequent process, such as fluorescence or a photoinduced chemical reaction, is also localized in this small volume. Although three-dimensional data storage and microfabrication have been illustrated using two-photon-initiated polymerization of resins incorporating conventional ultraviolet-absorbing initiators, such photopolymer systems exhibit low photosensitivity as the initiators have small two-photon absorption cross-sections (δ). Consequently, this approach requires high laser power, and its widespread use remains impractical. Here we report on a class of π;-conjugated compounds that exhibit large δ (as high as 1, 250 × 10−50 cm4 s per photon) and enhanced two-photon sensitivity relative to ultraviolet initiators. Two-photon excitable resins based on these new initiators have been developed and used to demonstrate a scheme for three-dimensional data storage which permits fluorescent and refractive read-out, and the fabrication of three-dimensional micro-optical and micromechanical structures, including photonic-bandgap-type structures.

Two-photon polymerization initiators for three-dimensional optical data storage and microfabrication

The control of luminous radiation has extremely important implications for modern and future technologies as well as in medicine. In this Review, we detail chemical structures and their relevant photophysical features for various groups of materials, including organic dyes such as metalloporphyrins and metallophthalocyanines (and derivatives), other common organic materials, mixed metal complexes and clusters, fullerenes, dendrimeric nanocomposites, polymeric materials (organic and/or inorganic), inorganic semiconductors, and other nanoscopic materials, utilized or potentially useful for the realization of devices able to filter in a smart way an external radiation. The concept of smart is referred to the characteristic of those materials that are capable to filter the radiation in a dynamic way without the need of an ancillary system for the activation of the required transmission change. In particular, this Review gives emphasis to the nonlinear optical properties of photoactive materials for the functi...

Nonlinear Optical Materials for the Smart Filtering of Optical Radiation.

g-C3N4/carbon dot-based nanocomposites serve as efficacious photocatalysts for environmental purification and energy generation: A review

In this review, we survey the recent advances in nonlinear optics and the applications of two-dimensional (2D) materials. We briefly cover the key developments pertaining to research in the nonlinear optics of graphene, the quintessential 2D material. Subsequently, we discuss the linear and nonlinear optical properties of several other 2D layered materials, including transition metal chalcogenides, black phosphorus, hexagonal boron nitride, perovskites, and topological insulators, as well as the recent progress in hybrid nanostructures containing 2D materials, such as composites with dyes, plasmonic particles, 2D crystals, and silicon integrated structures. Finally, we highlight a few representative current applications of 2D materials to photonic and optoelectronic devices.

/pdf/nonlinear-optical-properties-and-applications-of-2d-4d2ca47k8b.pdf

Nonlinear optical properties and applications of 2D materials: theoretical and experimental aspects

Metal nanoparticles (MNPs) hold great technological promise because of the possibility of engineering their electronic and optical properties through material design. One of the effective methods to fabricate MNPs is ion implantation. In this review, recent results on the nonlinear optical properties of nanoparticles (including copper, silver, gold, and bismuth nanoparticles) doped in various bases have been discussed. Some specific optical nonlinear properties, such as nonlinear refraction, two-photon absorption, and optical limiting, for femtosecond, picosecond, and nanosecond laser pulses have also been covered. In addition to ion implantation, we have summarized several other methods for the preparation of composite materials, and Z-scan has been used to study the nonlinear optical properties of these materials.

/pdf/nonlinear-optical-properties-of-metal-nanoparticles-a-review-3s54olpzns.pdf

Nonlinear optical properties of metal nanoparticles: a review

Two cocrystals of 18-crown-6 with isophthalic acid derivatives, 5-hy­droxy­isophthalic acid and trimesic acid, have been successfully grown by the slow evaporation solution growth technique. Crystal structures of (18-crown-6)·6(5-hy­droxy­isophthalic acid)·10(H2O) (I) and (18-crown-6)·2(trimesic acid)·2(H2O) (II) elucidated by single crystal X-ray diffraction reveal that both cocrystals pack the centrosymmetric triclinic space group P{\overline 1}. The molecules are associated by strong/weak hydrogen bonds, π⋯π and H⋯H stacking interactions. Powder X-ray diffraction analyses, experimental and simulated from single-crystal diffractogram data have been matched. The vibrational patterns in FT–IR spectra are used to identify the functional groups. The band gap energy is estimated by the application of the Kubelka–Munk algorithm. Hirshfeld surfaces derived from X-ray diffraction analysis reveal the type of molecular interactions and their relative contributions. The constructed supramolecular assembly of crown ether cocrystal is thoroughly described. Both cocrystals exhibit a significant third-order nonlinear optical response and it is observed that (I) possesses a significant first-order molecular hyperpolarizability whereas it is negligible for (II).

Supramolecular cocrystals of O-H...O hydrogen-bonded 18-crown-6 with isophthalic acid derivatives: Hirshfeld surface analysis and third-order nonlinear optical properties.

Optical Limiting Characteristics of Core-Shell Nanoparticles

l-Alanine dl-mandelic acid hemihydrate (LADLMAH) an organic nonlinear optical chromophore crystal was synthesized using water as solvent and the crystals were grown by a slow solvent evaporation method. The single crystal X-ray diffraction study reveals that the crystals possess to triclinic system with acentric space group P1. The coordination of different moieties present in the compound and molecular structure were elucidated by vibrational and NMR spectroscopic studies. The lower cut-off wavelength is observed down to 258 nm and direct optical band gap was calculated as 5.20 eV. Second harmonic generation was confirmed by Kurtz–Perry powder method. Discrete thermodynamic properties were carried out by TG–DTA techniques. A multiple shot laser technique was adopted to investigate the surface laser damage of the crystal. The microhardness test was carried out employing one of the as-grown hard crystals and there by hardness number (Hv) and Meyer’s index (n) were assessed. The dielectric behaviour of the grown crystal was studied for different temperatures at different frequencies. The third-order optical nonlinearity parameters of LADLMAH were investigated in detail using a Z-scan technique with Nd:YAG laser at 532 nm.

Growth and characterization of a nonlinear optical material: l -alanine dl -mandelic acid hemihydrate

A new third order nonlinear optical single crystal of Morpholin-4-ium hydrogen tartrate has been grown by the slow evaporation method. The lattice parameters and crystalline purity of this orthorhombic crystal were measured by single crystal X-ray diffraction and powder X-diffraction technique respectively. The optimized geometry shows that the morpholinium ring exist in a chair form where tartrate anions are linked via N H⋯O hydrogen bonds, forming chains. These chains are linked via N H⋯O and O H⋯O hydrogen bonds, involving the morpholinium cation. The vibrational spectral investigation predicts that the red shifting of O H and N H stretching wavenumbers are due to O H⋯O and N H⋯O intermolecular interactions, respectively which are also evident form NBO analysis. The photoluminescence spectrum shows luminescence at the blue region with an appreciable lifetime leading to applications in blue OLEDs. Third order nonlinear optical properties like self-defocusing, saturable absorption and optical limiting at 532 nm are identified by Z-scan analysis. The laser damage threshold (LDT) energy have been measured by using Nd:YAG laser of wavelength 532 nm. The field dependent nature of first and second order hyperpolarizabilities and luminescence properties suggest that MHT crystal is a potential candidate for OLED and nonlinear optical applications.

Growth of Morpholin-4-ium hydrogen tartrate single crystal for optical limiting application

This paper summarizes the synthesis, growth and the effect of the
position of the substituent in the thienyl ring and also the properties of the
grown chalcone crystals, 2-CTP and 3-CTP. The formation of compound is
confirmed by the re- corded H1NMR spectra. A FT-IR spectrum confirms the presence of all
functional groups in both of the crystals. Single crystal XRD reports that even
though these two compounds crystallize in monoclinic crystal system, 2-CTP has
centro- symmetric P21/c space group and 3-CTP has
non-centrosymmetric space group P21. Thermal properties of grown
crys- tals analyzed by TG/DTA study explain that the 3-CTP compound is
slightly more stable than 2-CTP. The transparency of these isomers in the vis-IR
region has been studied. Second and third order nonlinear optical properties of
3-CTP and 2-CTP crystals have been investigated by powder SHG and Z-scan
technique respectively.

/pdf/effect-of-substituent-position-on-the-properties-of-chalcone-3o6a97y4qm.pdf

G. Vinitha

Papers

Supramolecular cocrystals of O-H...O hydrogen-bonded 18-crown-6 with isophthalic acid derivatives: Hirshfeld surface analysis and third-order nonlinear optical properties.

Optical Limiting Characteristics of Core-Shell Nanoparticles

Growth and characterization of a nonlinear optical material: l -alanine dl -mandelic acid hemihydrate

Growth of Morpholin-4-ium hydrogen tartrate single crystal for optical limiting application

Effect of Substituent Position on the Properties of Chalcone Isomer Single Crystals