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.

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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.

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Nonlinear optical properties of metal nanoparticles: a review

Zinc-doped manganese ferrites synthesized by chemical co-precipitation technique showed significant linear and nonlinear optical properties and have been utilized to realize optoelectronic device applications. Mn1−xZnxFe2O4 (0 ≤ x ≤ 0.25) nanoparticles were characterized by various spectroscopic and microscopic techniques along with Z-scan studies. The formation of a single phase cubic spinel structure is confirmed from XRD analysis, whereas the FTIR spectra indicated corresponding bond formations between the ions. The micrographs of doped and undoped samples show a clear difference in morphology. The absence of additional/impure peaks in EDX spectra confirms phase purity. The optical band gap decreases with increasing Zn2+ ion concentration, which indicates the blue shift. In PL spectra, the peak at 386 nm is attributed to the defects which are originated because of oxygen vacancies. Calculated nonlinear parameters such as nonlinear absorption coefficient (β), nonlinear refractive index (n2), real and imaginary parts of third order nonlinear susceptibility (χ3) of doped systems are found to be enhanced compared with pure ferrite. Limiting threshold values indicate that the Zn2+ doped manganese spinel ferrites are one of the efficient materials for broadband optical limiting applications.

Effect of Zn2+ ions on third order nonlinear optical behavior and power limiting properties of manganese ferrite nanoparticles

Role of surface defects in the third order nonlinear optical properties of pristine NiO and Cr doped NiO nanostructures

Growth and characterization of organic 4-methyl-2-nitroaniline single crystals for nonlinear optical applications

Structural, multichannel sensing and optical properties of 2-aminopyridinium diphenylacetate diphenylacetic acid crystal

Structural characterization, computational and biological studies of a new third order NLO (1:1) organic adduct: 2-Aminopyrimidine: 3-nitrophthalic acid

G. Vinitha

Papers

Effect of Zn2+ ions on third order nonlinear optical behavior and power limiting properties of manganese ferrite nanoparticles

Role of surface defects in the third order nonlinear optical properties of pristine NiO and Cr doped NiO nanostructures

Growth and characterization of organic 4-methyl-2-nitroaniline single crystals for nonlinear optical applications

Structural, multichannel sensing and optical properties of 2-aminopyridinium diphenylacetate diphenylacetic acid crystal

Structural characterization, computational and biological studies of a new third order NLO (1:1) organic adduct: 2-Aminopyrimidine: 3-nitrophthalic acid