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Cu nanoparticles supported on ZrO2 (CuNPs@ZrO2) were synthesized using a one‐step co-precipitation process, and their application in C–C coupling reactions was investigated. The catalyst was characterized using XRD, XPS, SEM, TEM, and TGA techniques. The prepared catalyst was used for the Sonogashira cross-coupling reactions of aryl bromides with phenyl-acetylene in the presence of K2CO3 in DMF at 110 °C, which resulted in substituted alkynes with good to excellent yields. The protocol was also extended for the Ullmann coupling reactions of aryl iodides under similar reaction conditions, yielding the desired products with good to excellent yields without homo-coupling. Interestingly, unlike other copper catalysts, the present catalyst worked under air and did not require an inert atmosphere to prevent alkyne. This catalytic system is versatile, tolerant, and significantly cheaper than the "traditional" Pd-catalyzed Sonogashira cross-coupling of terminal alkynes with aryl halides. The catalyst could be reused for five catalytic cycles with no significant change in the product yield. All of these characteristics make our prepared CuNPs@ZrO2 catalyst quite suitable for the gram-scale synthesis of biaryls and alkynes, with a simple workup. [ABSTRACT FROM AUTHOR]

Polyfuranic compounds produced after carbon up-gradation of 2-methylfuran by acid catalyzed C–C bond forming reactions when undergo hydro-deoxygenation produce diesel fuel. Herein, we prepared a simple and novel silica supported sulfonic acid functionalized isonicotinic acid SO3H-INA@SiO2 catalyst by treating isonicotinic acid with chlorosulphonic acid followed by heterogenization on silica. This heterogeneous solid acid catalyst was explored for the solvent free conversion of 2-methylfuran to diesel fuel precursors of C15 and C20 units via tandem ring opening followed by condensation sequence. Under optimized reaction conditions, SO3H-INA@SiO2 was able to convert, 2-methylfuran completely into condensation products such as 5,5-bis(5-methylfuran-2-yl)pentan-2-one (1) and 2,4,4-tris(5-methylfuran-2-yl)pentan-1-ol (2) with 19% and 67% yields, respectively. The heterogeneous SO3H-INA@SiO2 catalyst was successfully recycled up to six consecutive runs without loss of its activity. The SO3H-INA@SiO2 catalyst offered superior activity as compared to the commercially available -SO3H functionalized resins. Superior activity of the prepared catalyst could be attributed for its higher acidity, smaller particle size and high surface area. Structure of the prepared catalyst was confirmed by FTIR and solid state NMR. Total acidity of the prepared catalyst was determined by acid–base titration. [ABSTRACT FROM AUTHOR]

Purpose Effectual waste utilization from plant as well as marine biomass has gained tremendous importance with reference to sustainability. The valorization of marine biomass produces value added compounds containing not only C, H, O but also renewable N atom in the skeleton which widens the scope for its exploration which may prove to be economically beneficial to the society. Heterogeneous catalytic transformation of marine biomass i.e. N-acetyl glucosamine (NAG) to N-substituted aromatic heterocyclic furan derivatives is reported for the very first time. Cost effective and stable metal oxide catalysts were deployed for the transformation. Catalyst screening study showed that La2O3 was found to be an excellent catalyst for N-acetyl glucosamine (NAG) dehydration which mainly produced 3-acetamidofuran (3AF). Methods The physicochemical properties of the metal oxide catalyst were investigated by various techniques such as XRD, FTIR, MeOH-FTIR, TPD, SEM, N2 sorption studies and HR-TEM analysis for structure activity relationship. Results The effect of various reaction parameters such as catalyst concentration, reaction temperature, reaction time and solvent effect on dehydration of N-acetyl glucosamine has been studied in detail for higher yields. The results revealed that the presence of weak basic sites which are Brønsted in nature and nano pores present on the surface were responsible for improved dehydration of the chitin biomass to selectively yield 3-acetamidofuran (3AF). La2O3 catalyst showed optimum 50% 3AF yield from N-acetyl glucosamine at 180 °C in 3 h. Conclusion Efficacious exploitation of marine biomass to value added chemicals using heterogeneous catalysts can be extensively exploited. Separation of N-substituted heterocyclic aromatics is the most innovative aspect of the current study. Thus, utilization of heterogeneous catalyst and renewable biomass as a raw material indicates a transition towards more sustainable and greener approach. With reference to valorization of biomass waste towards sustainability. We report for the first time heterogeneous catalytic transformation of marine biomass i.e. N-acetyl glucosamine (NAG) over La2O3 catalyst to yield 50% 3-acetamido furan (3AF) and 20% 3-acetamido-5-acetylfuran with 100% NAG conversion. The superior performance of La2O3 catalyst was attributed to the presence of brønsted basicity and nanopores present at catalysts surface. [ABSTRACT FROM AUTHOR]

We investigated the effect of femtosecond (fs) laser ablation of enamel and dentin for different pulse wavelengths: infrared (1030 nm), green (515 nm), and ultra-violet (343 nm) and for different pulse separations to determine the optimal irradiation conditions for the precise removal of dental hard tissues with the absence of structural and compositional damage. The ablation rates and efficiencies were established for all three laser wavelengths for both enamel and dentin at room temperature without using any irrigation or cooling system, and the surfaces were assessed with optical and scanning electron microscopy, optical profilometry, and Raman spectroscopy. We demonstrated that 515 nm fs irradiation provides the highest rate and efficiency for ablation, followed by infrared. Finally, we explored the temperature variations inside the dental pulp during the laser procedures for all three wavelengths and showed that the maximum increase at the optimum conditions for both infrared and green irradiations was 5.5 °C, within the acceptable limit of temperature increase during conventional dental treatments. Ultra-violet irradiation significantly increased the internal temperature of the teeth, well above the acceptable limit, and caused severe damage to tooth structures. Thus, ultra-violet is not a compatible laser wavelength for femtosecond teeth ablation. [ABSTRACT FROM AUTHOR]

Commercial biodiesel production is becoming popular due to its sustainability and reduced greenhouse gas emissions in comparison to fossil fuels. Biodiesel production involves the co-generation of crude glycerol that is not directly viable. Valorization of glycerol is essential from techno-economic perspective to achieve goals of circular economy. In this study, the glycerol etherification was carried out using tert-butyl alcohol in presence of dodecatungstophosphoric/silica (DTP/SiO2) catalyst for production of tert-butyl glycerol ethers that can be used as fuel additives. A series of DTP/SiO2 catalysts were prepared with various compositions by impregnating heteropoly acids (HPA, H3PW12O40). The product analysis was performed to monitor mono-, di-, and tri-tert-butyl glycerol ethers. The kinetic studies were conducted based on Langmuir–Hinshelwood model. The rate constants were determined from experimental data by regression analysis. The catalysts were characterized by X-ray diffraction, SEM/EDX, and thermogravimetric analysis. Varying DTP loadings resulted in different catalytic activities. Activation energy (38.23 kJ/mol), activation enthalpy (25.94 kJ/mol), activation entropy (− 163.8 J/mol/K), and Gibbs free energy of activation (88.67 kJ/mol) were attained for DTP/SiO2 (20%) catalyst that exhibited the best selectivity for di-tert-butyl glycerol ethers. [ABSTRACT FROM AUTHOR]

The infrared transmission and reflection spectra of a series of samples of bismuth films of different thicknesses on identical single-crystal silicon substrates were measured. Transmission and reflection oscillations caused by interference on the film thickness are investigated. Properties of Si-plates are estimated. Refractive index and absorption index of bismuth are calculated. [ABSTRACT FROM AUTHOR]

In the present work, we invented a Pd nanoparticle immobilized on an amine-functionalized LDH catalyst (PdNP@NH2-LDH-Al-MCM-41) for cross-coupling reactions. The palladium was grafted onto the support by treating the Pd(OAc)2 with NH2-LDH-Al-MCM-41 in acetone at room temperature. The prepared catalyst was characterized by FT-IR, SEM, TGA, TEM, and XPS techniques. The TEM characterization of the catalyst showed the uniform distribution of PdNPs with sizes ranging from 3 to 6 nm located inside the mesoporous. The Suzuki–Miyaura cross-coupling reaction was used to demonstrate the catalytic efficiency of the prepared PdNPs@NH2-LDH-Al-MCM-41 catalyst. The prepared and analyzed catalyst showed good to excellent activity in the Suzuki–Miyaura cross-coupling reaction of various aryl bromides with different aryl boronic acids in ethanol at 80 °C. The catalyst showed TON up to ~ 47 and TOF ~ 47 h−1. The catalytic results exhibited that the catalyst is completely recoverable with simple filtration. The catalytic efficiency shows a slight decrease in activity for the Suzuki–Miyaura cross-coupling reactions even after five repeated recycles. TEM images of the freshly prepared and reused catalysts (after five catalytic cycles) showed palladium nanoparticles remain unchanged at the end of the reactions. [ABSTRACT FROM AUTHOR]

There has been a lot of interest in utilizing remote sensing images to anticipate landslides. We propose a novel framework for automatic landslide detection and landslide region localization from the input remote sensing image. The framework consists of pre-processing, dynamic segmentation, automatic feature extraction, classification, and localization. The pre-processing is the integrated step that performs atmospheric corrections, geometric corrections, and unnecessary region removal with denoising using 2D median filtering. The pre-processed image is then segmented using the dynamic segmentation approach to extract the Region of Interest (ROI). We propose lightweight Convolutional Neural Network (CNN) layers for automatic feature extraction and scaling using the ResNet50 model. The CNN layers are designed systematically for automatic feature extraction to improve accuracy and reduce computational requirements. The Long-Term Short Memory (LSTM), Artificial Neural Network (ANN), and Support Vector Machine (SVM) classifiers are designed to perform the landslide prediction. If landslides are forecast, the post-processing stages are intended to identify potential landslide locations. The experimental results show that the proposed CNN-LSTM model outperformed the existing solutions in terms of accuracy, F1 score, precision, and recall rates. The experimental outcomes reveal that the proposed model improves the overall prediction accuracy by 2% and reduces the computational complexity by 35% compared to state-of-the-art methods. [ABSTRACT FROM AUTHOR]

We explore femtosecond laser cleaning of materials used in the construction of historic monuments, such as stone and steel covered in typical contaminants caused by harsh environments that may be found in urban areas. We address the cleaning of these materials from a conservation perspective, taking as examples the preservation and cleaning of iconic structures such as the steel and the granite of the Sydney Harbour Bridge, Hawkesbury sandstone, a popular building material of a variety of monuments in Sydney (Australia), Makrana marble taken from the Soami Bagh Samadh temple of Agra in India, and also graffiti removal. We demonstrate that femtosecond laser pulses can clean a range of different contaminants such as biofilm, environmental soiling, rust, and spray paints, while preserving the integrity of the underlying substrates. Femtosecond laser cleaning is a fast and effective method and a safer alternative to lasers with longer pulse durations for the preservation of historic monuments. [ABSTRACT FROM AUTHOR]

An efficient and convenient method for synthesis of 7,10,11,12-tetrahydrobenzo[c]acridin-8(9H)-one derivatives using Cu/MCM-41 (20 mg) as heterogeneous catalyst. The advantages have an excellent product yield within a short time and easy work-up procedure, and the products have directly recrystallized from hot methanol with cost-effective catalyst. One-pot three-component reaction from aromatic aldehydes, cyclic 1,3-dicarbonyl compounds, and 1-naphthyl amine has been carried under ethanol as a solvent with reflux condition. Moreover, the catalyst can be recovered conveniently and reused efficiently, and recyclable. [ABSTRACT FROM AUTHOR]

The agricultural sector is the backbone of the Indian economy, where precision agriculture is playing a vital role in boosting productivity. The soil chemical parameters play an important role in precision agriculture. Analysis and prediction of micronutrient of the soil chemical parameters are highly insisted upon by farmers and agriculture researchers. The soil nutrients parameters can be analyzed from multispectral data through ISO cluster unsupervised classification. Understanding the nutrient level of soil is highly recommended for farming; early understanding may help to improve soil fertility and fully meet productivity requirements. This paper addresses the soil nutrients analysis by the regression method and its spectral indexed based on the prediction model by Iterative Self-Organizing (ISO) cluster unsupervised classification algorithm. Therefore, for this study, the Baggi, Ibrahimpur, Wai, Mogra, and Bori (for validation) villages were selected. These villages are located in the Amravati district and fall under Maharashtra provenance of India. From the study area, three soil nutrients parameters such as P, Fe, pH indices-based data were acquired from the spectral calculation of Sentinel-2 and Landsat-8 bands. The P, Fe and pH indices were calculated from the yellowness index (YI), ferrous oxide index, and carbonate level. The ISO cluster unsupervised mechanism has been used for prediction of soil chemical parameter indices out of 100 samples. The study regions recognition rate is 97% for P, 94.05% for Fe, and 69% for pH. During the validation process, four villages' results were used for the identification of soil nutrient parameters for Bori village. The results of the study area can be helpful for the development of the planning of soil fertility in the agriculture fields and effectively increase the crop yield production in the semi-arid region. [ABSTRACT FROM AUTHOR]

Heterogeneous catalysis has been utilized in number of efficient reactions with higher selectivity of the product, more stable, reusable and easy for separation as compared to homogeneous catalysts. Generally, heterogeneous catalysts are prepared by using mesoporous materials, microporous materials, metal oxides and metal organic framework. The mesoporous materials have small particle size and high surface area as compared to the microporous materials. The adsorbent mesoporous materials have highly efficient for the therapeutic applications in chemistry hence it has best as compared to other heterogeneous materials. Herein, we have reported synthesis of 1,4-dihydropyridines and polyhydroquinolines at solvent free and environmental benign condition in the presence of Zn/MCM-41 catalyst. The present protocol gives excellent yield (89–96%) of the product within short reaction time by easy work up procedure and no need of further purification of product. The catalyst was characterized by XRD diffractometer, SEM, EDAX, TGA-DTA, BET surface area analysis and FT-IR Spectroscopy. The synthesized organic compounds were characterized by FT-IR, 1H NMR, 13C NMR, LC–MS spectrometry. [ABSTRACT FROM AUTHOR]

A simple and efficient protocol for the ligand-free Mizoroki–Heck coupling reaction of various aryl bromides with different olefins has been reported by using in situ generated PdNPs of size 5–10 nm in aqueous solution of bio-surfactant. The bio-surfactant used in this study is a saponin extract of the seeds of pericarps (pods) of the Acacia concinna plant. The in situ generated PdNPs have been characterized by various techniques such as HRTEM, EDS and XPS. The influence of various parameters such as the nature and amount of bases, the nature of Pd precatalysts as well as the effect of temperature has been investigated on Mizoroki–Heck coupling reaction. The generated PdNPs significantly coupled the various aryl bromides with different olefins in aqueous extract of the seeds of pericarps (pods) of the Acacia concinna plant at 100 °C. [ABSTRACT FROM AUTHOR]

In this report, we documented novel strategy for the synthesis of bioactive polysubstituted 2-amino-4H-chromine derivatives under a heterogeneous Al-MCM-41-LDH@APTES (ALAM) catalysis. A synthetic procedure is developed to prepare Al-MCM-41-LDH@APTES (ALAM) heterogeneous basic catalysts. Mesoporous Al-MCM-41 is functionalized by known grafting chemistry via layered double hydroxide (LDH) nanosheets and (3-aminopropyl)triethoxysilane (APTES) moiety as a basic organocatalyst. The resulting catalysts contain amino group functionality on the external surface as well as inside the layers and the basicity can be tuned by the loading of APTES. The samples were fully characterized by 29Si and 13C CP/MAS NMR, infrared absorption spectroscopy, TEM, XPS, EDX, TGA, XRD, CO2-TPD, N2 adsorption isotherms measurements, and they were successfully examined for the cascade type Knoevenagel–Michael addition reactions. The product yields associated with these substrates were optimized, and key reaction parameters affecting the yields were identified. The present catalytic method is simple and robust for diversity oriented synthesis which proceeds good to excellent yields without generating any hazards waste. The broad substrate scope, excellent functional group compatibility makes this protocol highly useful towards synthesis of polysubstituted α-cyanoacrylates, α-cyanoacrylonitriles and 2-amino-4H-chromenes with an electron-donating or electron-withdrawing group. We have also successfully established a flow reaction system, gram-scale synthesis as well as catalyst recyclability up to six catalytic cycles without appreciable loss of its activity. [ABSTRACT FROM AUTHOR]

In this paper we show that laser beams containing phase singularity can be used for trapping and guiding light-absorbing particles in air. The experiments were performed with agglomerates of carbon nanoparticles with the size in the range 0.1–10 μm; the typical cw laser power was of a few mW. The stability of open-air three-dimensional trapping was within ±2 μm in both the transverse and the longitudinal directions. The particle position on the beams axis within the trap can be controlled by changing the relative intensity of two beams. The distinguishing feature of the trapping strategy is that particles are trapped at the intensity minimum of the beam, thus with minimum heating and intervention into the particle properties, which is important for direct studies of particle properties and for air-trapping of living cells. [ABSTRACT FROM AUTHOR]

Non-chromium Cu:Al nano catalyst prepared by simultaneous co-precipitation and digestion method without any template or stabilizer, showed three times higher activity than the bulk Cu–Cr catalyst for hydrogenolysis of glycerol in both isopropanol and water solvents, with the selectivity to 1,2-Propanediol (1,2-PDO) as high as 91% at 493 K and H2 pressure of 7 MPa in 5 h. XRD pattern showed the presence of Cu+ species in the activated Cu:Al nano catalyst. Although Cu+ is catalytically inactive in glycerol hydrogenolysis reaction, the presence of Cu+ helps to stabilize the particle size in a narrow range of 7–11 nm by inhibiting the sintering of copper particles under reaction conditions. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

The effects of acidity and variation in concentration of acid sites of dodecatungstophosphoric acid (DTP), supported DTP and montmorillonite-K catalysts were studied for various organic reactions such as the hydroxyalkylation of phenols to bisphenols, intramolecular rearrangement of benzyl phenyl ether (BPE) to 2-benzyl phenol (2-BP) and selective cleavage of tert-butyldimethylsilyl (TBDMS) ether into the corresponding alcohol. Both dodecatungstophosphoric acid (DTP) impregnated on silica (SiO2) and montmorillonite catalysts showed the highest catalyst activity with 90-95% selectivity to bisphenol for the hydroxyalkylation of phenols to give bisphenol. Temperature Programmed Desorption (TPD) of ammonia and activity results of various catalysts showed that an appropriate combination of both strong and weak acidic sites in the catalyst was highly desirable for high bisphenol selectivity. A 10% DTP/SiO2 catalyst was found to be highly selective for the cleavage of TBDMS ether into the corresponding alcohol at room temperature giving a high TON of 9.5 x 105 even after the 4th recycle. DTP was also found to be a promising solid acid catalyst for the intramolecular rearrangement of BPE giving 2-BP. [ABSTRACT FROM AUTHOR]

Thin films of Ge–As–Se chalcogenide glasses have been deposited by thermal evaporation from bulk material and submitted to thermal treatments. The linear refractive index and optical band-gap for as-deposited and annealed films have been analyzed as function of the deposition parameters, chemical composition and mean coordination number (MCN). The chemical composition of the films was found to be directly affected by deposition rate, with low rates producing films with elevated Ge and reduced As content, whilst at high rates the Ge content was generally reduced and As levels increased compared with the bulk starting material. As a result films with close to the same stoichiometry as the bulk glass could be obtained by choosing appropriate deposition conditions. As-deposited films with MCN in between 2.44 and 2.55 showed refractive indices and optical band-gaps very close to those of the bulk glass whereas outside this range the film indices were higher and the optical gaps lower than those of the bulk glass. Upon annealing at close to their glass transition temperature, high MCN films evolved such that their indices and band-gaps approached the bulk glass values whereas at low MCN films resulted in no changes to the film properties. [ABSTRACT FROM AUTHOR]

Liquid phase oxidation of p-cresol was carried out over a Co-saponite catalyst in a temperature and pressure range of 333–393 K and 20–827 kPa, respectively in n-propanol. Co-saponites with varying cobalt content (5–30%) were prepared and screened among which 13% Co-saponite gave the highest conversion of 92% of p-cresol with 92% selectivity to p-hydroxybenzaldehyde without formation of any non-oxidation products. [ABSTRACT FROM AUTHOR]

The hydrogenation behavior of tetralin in the presence and absence of benzothiophene was studied over a charcoal-supported rhodium catalyst in supercritical carbon dioxide solvent. The catalyst activity, as well as cis-decalin selectivity, decreased in the presence of benzothiophene. [ABSTRACT FROM AUTHOR]

We study experimentally the formation of refractive index voxels (volume elements) in photorefractive LiNbO3 and LiTaO3 crystals illuminated with high irradiance femtosecond laser pulses. We used 150 fs pulses at 800 nm wavelength (energy 6–50 nJ) tightly focused inside the crystals in a single shot regime. This resulted in a formation of a micrometer size region of elevated refractive index, which may be used as memory bits in information storage/retrieval application. The maximum refractive index change of 5×10−4 was recorded in undoped LiNbO3 at an average light intensity of ∼TW/cm2 that is close to the breakdown threshold. A simple setup for photorefractive recording and in situ monitoring of the refractive index changes has been proposed. [ABSTRACT FROM AUTHOR]

This paper presents experimental and theoretical results on the temperature-dependent optical response of a single crystal of bismuth to excitation by femtosecond laser pulses. We demonstrate that the measured damping rate of the transient reflectivity oscillations relates to the lifetime of optical phonons. The lifetime is the inverse rate of the decay of optical phonons into two acoustic phonons. This lifetime also indicates the approach to the vibration instability (catastrophe) threshold that manifests the beginning of the disordering of a solid crystal and transition to a liquid state. We observe the red shift of phonon frequency, which increases with the rise of the initial lattice temperature. The red shift is different from the previously observed red shift proportional to the electron temperature, and thus to the excitation laser fluence. The coherent phonon excitation process imprinted into the initial change in the reflectivity and the following reflectivity oscillations allowed us to uncover the temporal phonon history preceding the structural transformation of solid Bi. [ABSTRACT FROM AUTHOR]

Differential scanning calorimetry (DSC) was performed at different heating rates under non-isothermal conditions to probe the glass transition kinetics of several Ge–As–Se glasses with different chemical compositions. The change of the glass transition temperature T g with the heating rate and composition was investigated and the activation energy of the glass transition was estimated. The fragility index was calculated and the correlation to the mean coordination number of Ge–As–Se glasses was discussed. [ABSTRACT FROM AUTHOR]

Catalytic hydrogenation of naphthalene to decalin was studied over a carbon-supported rhodium catalyst in supercritical carbon dioxide solvent at 333 K, and the results were compared with those in an organic solvent. cis-, trans-Decalin and tetralin were formed from the beginning of the reaction in supercritical carbon dioxide. Higher concentration of hydrogen in carbon dioxide solvent and on the active site, and also the suppression of desorption of partially hydrogenated tetralin molecules from the active site would be responsible for higher selectivity to cis-decalin in supercritical carbon dioxide than that in an organic solvent. [ABSTRACT FROM AUTHOR]

We have built a mode-locked Nd:YVO4 laser with a very long resonator which produces an average power of 50 W in 13-ps pulses at 1064 nm and was designed for applications in micro-machining, the deposition of optical thin films, and the growth of nano-clusters in the laser-ablated plumes. By operating the laser at very low mode-locking repetition rates (1.5 MHz, 2.6 MHz, and 4.1 MHz), high pulse power is available in a near diffraction limited beam, allowing focused intensities to exceed 1012 W/cm2 and permitting efficient evaporation of difficult materials such as Si. The high power also allows conversion into the second harmonic at 532 nm with an efficiency exceeding 80%. Measurements of the ablation mass in experiments with metals show a 30–100 times increase in the ablation rate compared to the conventional low-repetition-rate ns-range lasers. [ABSTRACT FROM AUTHOR]

Swift excitation of transparent dielectrics by ultrashort and highly intense laser pulse leads to ultra-fast re-structuring of the electronic landscape and generates many transient material states, which are continuously reshaped in accord with the changing pulse intensity. These unconventional transient material states, which exhibit simultaneously both dielectric and metallic properties, we termed here as the ‘Die-Met’ states. The excited material is transparent and conductive at the same time. The real part of permittivity of the excited material changes from positive to negative values with the increase of excitation, which affects strongly the interaction process during the laser pulse. When the incident field has a component along the permittivity gradient, the amplitude of the field increases resonantly near the point of zero permittivity, which dramatically changes the interaction mode and increases absorption in a way that is similar to the resonant absorption in plasma. The complex 3D structure of the permittivity makes a transparent part of the excited dielectric (at ε0 > εre > 0) optically active. The electro-magnetic wave gets a twisted trajectory and accrues the geometric phase while passing through such a medium. Both the phase and the rotation of the polarisation plane depend on the 3D permittivity structure. Measuring the transmission, polarisation and the phase of the probe beam allows one to quantitatively identify these new transient states. We discuss the revelations of this effect in different experimental situations and their possible applications. [ABSTRACT FROM AUTHOR]

We study experimentally the formation of refractive index voxels (volume elements) in photorefractive LiNbO3 and LiTaO3 crystals illuminated with high irradiance femtosecond laser pulses. We used 150 fs pulses at 800 nm wavelength (energy 6–50 nJ) tightly focused inside the crystals in a single shot regime. This resulted in a formation of a micrometer size region of elevated refractive index, which may be used as memory bits in information storage/retrieval application. The maximum refractive index change of 5×10−4 was recorded in undoped LiNbO3 at an average light intensity of ∼TW/cm2 that is close to the breakdown threshold. A simple setup for photorefractive recording and in situ monitoring of the refractive index changes has been proposed. [ABSTRACT FROM AUTHOR]