Resonantly enhanced terahertz four-wave mixing in fluorides.

Converting a THz signal into the optical domain is of great interest for THz sensing and spectroscopy. Here intense broadband THz pulses with a central frequency of Ω are mixed with an optical pump at ω, and a signal is observed at a wavelength of ω = 2(ω - Δω) - Ω with the detuning ω - Δω being due to pump pulse spectral broadening. The observed THz-four-wave mixing (FWM) signal close to 400 nm is shown to result from a resonantly amplified four-wave mixing in CaF, BaF, and MgF.

Bond Polarizability as a Probe of Local Crystal Fields in Hybrid Lead-Halide Perovskites.

A rotating organic cation and a dynamically disordered soft inorganic cage are the hallmark features of organic-inorganic lead-halide perovskites. Understanding the interplay between these two subsystems is a challenging problem, but it is this coupling that is widely conjectured to be responsible for the unique behavior of photocarriers in these materials. In this work, we use the fact that the polarizability of the organic cation strongly depends on the ambient electrostatic environment to put the molecule forward as a sensitive probe of the local crystal fields inside the lattice cell.

Spin-Electric Coupling in Lead Halide Perovskites.

Lead halide perovskites enjoy a number of remarkable optoelectronic properties. To explain their origin, it is necessary to study how electromagnetic fields interact with these systems. We address this problem here by studying two classical quantities: Faraday rotation and the complex refractive index in a paradigmatic perovskite CH_{3}NH_{3}PbBr_{3} in a broad wavelength range.

Two-color symmetry breaking in laser-based secondary neutral mass spectrometry.

Rationale: An alternative method of analysis for laser-based secondary neutral mass spectrometry is introduced.

Methods: By mixing a fundamental 1240 nm wavelength of the near-infrared laser field with an intensity of 1 × 10  W/cm with its second harmonic generation wavelength of 620 nm, control is attained over the ion yield in secondary neutral mass spectrometry for a native silver surface and a surface covered with silver nanoparticles.

Results: The ion yields of selected species in the mass spectra, such as a C H O surfactant fragment ion and the Ag ion, are enhanced or suppressed by a factor of 8 or 23, respectively, in comparison with single color post-ionization.

Effect of Iodination on the Photophysics of the Laser Borane -BH: Generation of Efficient Photosensitizers of Oxygen.

Treatment of the laser borane -BH (compound ) with iodine in ethanol gives the monoiodinated derivative 7-I--BH (compound ) in 67% yield, or, by reaction with iodine or ICl in the presence of AlCl in dichloromethane, the diiodinated derivative 4,4'-I--BH (compound ) in 85% yield. On excitation with 360 nm light, both compounds and give strong green phosphorescent emissions (λ = 525 nm, Φ = 0.41 and λ = 545 nm, Φ = 0.

Linear and Multi-Photon Fluorescence of Thiophene Based Copolymer with Electron-Accepting Side Chains.

A novel copolymer poly(thiophene-2,5-diyl-2,5-di-n-octyloxycarbonyl-1,4-phenylene), denoted as P33, is introduced as potential material for photovoltaics, polymer light-emitting diodes, and/or organic transistors. P33 dissolved in chloroform is investigated by steady-state absorption, linear/non-linear fluorescence spectroscopies and time-resolved fluorescence spectroscopy. Molar extinction coefficient, fluorescence quantum yield, and singlet fluorescence lifetime of P33 are determined to be 18,315 M cm, 0.

Nonphasematched broadband THz amplification and reshaping in a dispersive chi(3) medium.

We theoretically investigate non-phasematched broadband THz amplification in dispersive chi(3) media. A short 100 fs pump pulse is interacting with a temporally matched second harmonic pulse and a weak THz signal through the four wave mixing process and a significant broadband THz amplification and reshaping is observed. The pulse evolution dynamics is explored by numerically solving a set of generalized Nonlinear Schroedinger equations.

Adaptive Control of Ion Yield in Femtosecond Laser Post-ionization for Secondary Ion Mass Spectrometry.

Secondary ion mass spectrometry is an excellent technique of analytical chemistry, where primary ions sputter a solid sample generating the secondary ions which are determined. Although the ion yield is inherently low, it can be enhanced by using a post-ionization of sputtered neutral species. Our novel approach integrates this technique with a near infrared femtosecond laser post-ionization based on an adaptive control through a laser pulse shaper.

Surface Nanostructures Composed of Thiolated Cyclodextrin/Au and Fe Species: Gas- and Liquid-Phase Preparation.

Supramolecular surface nanostructures have application potential as functional devices. The complex combination of thiolated cyclodextrin, chemisorbed on an Au surface (Au-S-CD), with deposited Fe species is studied by secondary ion mass spectrometry. The Fe species are prepared by pulsed laser ablation in water and thermal effusion in vacuum.

Preparation of Cyclodextrin-Iron Species in Water by Laser Ablation: Secondary Ion Mass Spectrometry.

Supramolecular complexes between cyclodextrin and iron species are studied by using secondary ion mass spectrometry. The iron species are prepared by pulsed-laser ablation of bulk iron in water; this gives Fe(+) (56 m/z) and Fex Oy (+) (x, y=1-7) species. Cyclodextrin is added to the water either before or after the laser ablation.

Intense Cr:forsterite-laser-based supercontinuum source.

Supercontinuum pulses covering the range from 1100 to 1700 nm with energies >1.0  mJ and excellent beam quality are generated via nonlinear spectral broadening of Cr:forsterite (1240 nm, 110 fs) pulses in pressurized molecular nitrogen. Our spectra, which extend over more than half an octave, offer an attractive alternative to intense few-cycle pulse synthesis in the 1-2 μm range and lend themselves as an important add-on to Cr:forsterite laser technologies.

Fluorescence dynamics of coumarin C522 as a function of micelle confinement along with cyclodextrin supramolecular complex formation.

Our aim is to doubly confine a molecule of coumarin C522 in a host-guest supramolecular complex with β-cyclodextrin in a reverse sodium dioctyl sulfosuccinate (AOT) micelle using nonpolar n-heptane and polar water solvents. Varying the volumes of coumarin C522 and β-cyclodextrin dissolved in water allows us to control the water-pool diameters of the reverse micelle in n-heptane with values of w=3, 5, 10, 20, and 40, where w is the ratio of water concentration to AOT concentration in n-heptane. To study the fluorescence dynamics of coumarin C522, the spectral steady-state and time-resolved dependences are compared for the two systems coumarin C522(water)/AOT(n-heptane), denoted C522/micelle, and coumarin C522/β-cyclodextrin(water)/AOT(n-heptane), referred to as C522/CD/micelle.

Infrared femtosecond laser preionization in secondary ion mass spectrometry of silver surface.

An alternative secondary ion mass spectrometry utilizing laser preionization is introduced. The native Ag sample surface is first irradiated with laser pulse (100 fs duration, 10(10)-10(11) W/cm(2) intensity, 1240 nm wavelength) and subsequently bombarded with primary ions (Bi(3)(+), 10 ns duration, 25 keV energy). Multiple correlation patterns are observed in the mass spectra, confirming the mutual laser-secondary ion mass spectrometry (SIMS) interplay in the preionization mechanism.

Chemical imaging of cardiac cell and tissue by using secondary ion mass spectrometry.

Purpose: Identification and localization of biomolecules in cells and tissue samples are important for understanding of subcellular structures and can be helpful in biomedical and pharmaceutical research.

Procedures: Isolated cardiac cells and tissue of rats are studied by using time-of-flight secondary ion mass spectrometry. This technique provides chemical composition of cardiac cell membrane and tissue surface in native form.

Highly birefringent silicate glass photonic-crystal fiber with polarization-controlled frequency-shifted output: A promising fiber light source for nonlinear Raman microspectroscopy.

A highly birefringent silicate glass photonic-crystal fiber (PCF) is employed for polarization-controlled nonlinear-optical frequency conversion of femtosecond Cr: forsterite laser pulses with a central wavelength of 1.24 mum to the 530--720-nm wavelength range through soliton dispersion-wave emission. The fiber exhibits a modal birefringence of 1.