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

Role of defects on the nonlinear optical properties of La doped Bi2WO6 nanostructures for optical device applications

N-Methylurea oxalic (NMUO) acid organic crystals were grown by solution method with slow evaporation solution technique (SEST) in aqueous solution. Using single crystal XRD (SCXRD) analysis, the structure of the crystal was determined. The powder X-ray diffraction (PXRD) study reveals that the crystallinity of the specimen. The functional groups of the title molecule were determined from FTIR and FT-Raman analyses. Optical transmittance of the crystal was studied using UV–Visible spectroscopy. The hardness of the grown crystal was found by Vickers microhardness test. The dielectric behavior of the crystal was determined at 30 oC temperature. The thermal stability of the crystal was studied by thermogravimetric analysis (TG/GTG) and differential scanning calorimetry (DSC). Zscan characterization was carried out to investigate the third-order nonlinear optical properties of the crystal.

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Growth and characterization of n-methylurea oxalic (nmuo) acid single crystal

In this paper, BaZrO3 was chemically synthesized using liquid NH3 as precipitating agent and green synthesized using Moringa oleifera (M. oleifera) leaf extract without the addition of liquid NH3. X-ray diffractograms confirmed the cubic nature of the samples with. (1 1 0) preferential growth. XPS studies ascertain the existence of Ba, Zr and O in the green synthesized sample. Decreased band gap was observed for the green synthesized sample. Ba-O stretching vibrations were observed respectively at 480 and 487 cm−1 for the chemically synthesized and green synthesized samples. The green synthesized BaZrO3 exhibits better degradation efficiency of 84.1% after 90 min against CR dye. The green synthesized BaZrO3 nanoparticles exhibited excellent antimicrobial activity against E. coli and A. terreus. The third order nonlinear absorption coefficient and susceptibility values of the green synthesized BaZrO3 were found to be equal to 3.05 × 10−6 cm/W and 4.67 × 10−8 esu, respectively. 

BaZrO3 perovskite – A UV light mediated congo red dye deactivator catalyst with good optical switching and antimicrobial abilities green synthesized using Moringa oleifera leaf extract

Laser damage threshold, hardness and third order non-linear optical analysis of potassium dihydrogen phosphate with sodium chloride

Single crystal of oxalato-bridged, Cesium-extended frame work, Cesium Hydrogen Oxalate Dihydrate (CHOD), has been synthesized by slow evaporation solution growth technique. Diffraction studies were used to identify the geometry of the atoms present in the primitive cell of the crystal. The title compound has crystallized in triclinic category-bearing space group P-1. Spectroscopic investigation of the compound was done by FTIR and FT-Raman techniques. From UV–Vis studies, optical absorption edge was ascertained as 241 nm. It has excellent optical transmission window throughout the visible region. Energy dispersive X-ray analysis (EDAX) affirms the presence of Cesium in the compound. Fluorescence decay of the molecules present in the excited state for the crystal was studied. Hirshfield surface maps intermolecular contacts present in the crystal and the contributions made by the contacts were assessed by 2D Finger print plots. Z-Scan studies ascertain the magnitude of nonlinear refractive index and nonlinear refraction.

Crystal growth, optical, spectroscopic studies, PL behaviour and Hirshfield surface analysis of a third-order nonlinear optical Cesium Hydrogen Oxalate Dihydrate (CHOD) single crystal

G. Vinitha

Papers

Role of defects on the nonlinear optical properties of La doped Bi2WO6 nanostructures for optical device applications

Growth and characterization of n-methylurea oxalic (nmuo) acid single crystal

BaZrO3 perovskite – A UV light mediated congo red dye deactivator catalyst with good optical switching and antimicrobial abilities green synthesized using Moringa oleifera leaf extract

Laser damage threshold, hardness and third order non-linear optical analysis of potassium dihydrogen phosphate with sodium chloride

Crystal growth, optical, spectroscopic studies, PL behaviour and Hirshfield surface analysis of a third-order nonlinear optical Cesium Hydrogen Oxalate Dihydrate (CHOD) single crystal