Search results for "harmonic"
showing 10 items of 984 documents
Third-order nonlinear optical effects of silver nanoparticles and third harmonic generation from their plasma plumes
2021
Abstract We investigated the third-order nonlinear optical (NLO) properties of the silver (Ag) nanoparticles (NPs) of various sizes, which were produced by disintegration of commercially available 20 and 100 nm NPs in different solvents. It is observed that NPs with the sizes less or greater than 30 nm possess saturable absorption or reverse saturable absorption (or two-photon absorption), respectively. The NPs suspensions show a self-focusing effect. In addition, the third harmonic generation from the plasma plumes produced by nanosecond laser ablation of bulk Ag and Ag NPs of 100 nm and 20 nm sizes is reported. The third harmonic efficiency from the plasmas containing NPs was higher compa…
Luminescence properties of KNbO3 crystals
1997
Thermostimulated luminescence, X-ray-induced luminescence, photostimulated luminescence as well as the time-resolved luminescence and absorption after pulsed electron beam irradiation were studied in KNbO3 crystals at 80–400 K. A correlation between defects causing the luminescence and blue-light-induced IR absorption effects supressing the second harmonic generation efficiency in KNbO3 is discussed.
Phonons in YBa2Cu3O7?x crystals with site-selective oxygen isotope substitution: Frequencies, normal vectors, non-linear properties
1995
Lattice vibrations of YBa2Cu3O7−x crystals with a site-selective isotope substitution18O→16O are investigated theoretically. It is shown that shifts of the frequencies of A1g oxygen vibrations due to this substitution are smaller than under complete one. However, phonon bands and normal vectors are changed much stronger, especially in the case when apical oxygens are substituted. On the basis of the presented analysis anharmonic properties and transition temperatures of the selectively substituted crystals are also briefly discussed.
Features of randomized electric-field assisted domain inversion in lithium tantalate
2011
We report on bulk and guided-wave second-harmonic generation via random Quasi-Phase-Matching in Lithium Tantalate. By acquiring the far-field profiles at several wavelengths, we extract statistical information on the distribution of the quadratic nonlinearity as well as its average period, both at the surface and in the bulk of the sample. By investigating the distribution in the two regions we demonstrate a non-invasive approach to the study of poling dynamics.
Quadratic nonlinear optical parameters of 7% MgO-doped LiNbO3 crystal
2016
International audience; Pure and 7% MgO-doped lithium niobate (LiNbO3) single crystals were grown by the Czochralski technique. The shift of optical absorption edge in 7% MgO-doped crystal in direction of shorter wavelength compared to undoped crystal was observed. The second harmonic generation measurements of 7% MgO-doped LiNbO3 crystal were performed at room temperature by means of the rotational Maker fringe technique using Nd:YAG laser generating at 1064 nm in picoseconds regime. Experimentally obtained value of nonlinear optical coefficient d33 for 7% MgO-doped LiNbO3 was found to be less than for undoped crystal but higher than for 5% MgO-doped. I-type phase-matched second harmonic g…
Surface plasmon subwavelength optics.
2003
International audience; Surface plasmons are waves that propagate along the surface of a conductor. By altering the structure of a metal's surface, the properties of surface plasmons- in particular their interaction with light-can be tailored, which offers the potential for developing new types of photonic device. This could lead to miniaturized photonic circuits with length scales that are much smaller than those currently achieved. Surface plasmons are being explored for their potential in subwavelength optics, data storage, light generation, microscopy and bio-photonics.
Influence of corona poling procedures on linear and non-linear optical properties of polymer materials containing indandione derivatives as a cromoph…
2008
SHG efficiency of the poled guest - host polymer system is proportional to the concentration and orientation degree of NLO active molecules (chromophores). Corona poling realized at elevated temperatures could cause concentration decrease of NLO- active molecules due to centrosymmetric crystallization. Our studies showed that number density of crystallites is depending on orientation procedure. To obtain the best orientation procedure for guest - host systems containing four different chromophores based on dimethylaminobenzylidene 1, 3 - indandione we have compared optical images and SHG efficiency of corona poled films. According to our observations external poling electric field applied f…
Raman studies of isotope effects in Si and GaAs
1999
Abstract We have measured by Raman scattering changes of the optic phonon energy and line width in Si and GaAs with isotopic composition. The phonon energies of isotopically pure samples show the expected dependence on the average atomic mass in Si and the reduced mass in GaAs, respectively, as well as small anharmonic contributions. In isotopically disordered samples we find frequency shifts of 1.15(20) cm−1 for 28Si0.530Si0.5 and 0.31(20) cm−1 for the TO phonon of natGaAs, induced by mass disorder which also contributes to the line broadening. We give theoretical estimates of these effects.
Graphene in strong laser field: experiment and theory
2015
The interaction of graphene nanoparticles and strong 64 fs pulses is examined. We demonstrate high-order harmonic generation in the plasma contained in crumpled sheets of graphene. The morphological studies of the debris of ablated graphene, application of single-color and two-color pumps of graphene-containing plasma, and theoretical consideration of the high-order harmonic generation in this medium are presented.
Second-harmonic Generation Microscopy of Carbon Nanotubes
2012
We image an individual single-walled carbon nanotube (SWNT) by second-harmonic generation (SHG) and transmission electron microscopy and propose that SHG microscopy could be used to probe the handedness of chiral SWNTs.