A family of multi-heterocycle donor–acceptor–donor (DAD) telechelic conjugated oligomers designed for two-photon absorption (2PA) and emission in the near-infrared (near-IR) were prepared, relationship between their spectral, structural, electrochemical properties investigated. These oligomers, based on electron-rich thiophene, phenylene, 3,4-ethylenedioxythiophene (EDOT) units as donors along with electron-deficient benzothiadiazole or its derivative acceptors, have been characterized...

We present first- and second-order Raman spectra of boron-doped multiwalled carbon nanotubes. The intensities are analyzed as a function the nominal boron concentration. both D mode high-energy in first-order increase with increasing concentration, if normalized respect to mode. interpret this result an indication that nanotubes is defect-induced similar way Based on result, we provide preliminary quantitative relation between concentration intensity ratios.

Carbon disulfide is the most popular material for applications of nonlinear optical (NLO) liquids, and frequently used as a reference standard NLO measurements. Although it has been subject many investigations, determination third-order nonlinearity CS2 incomplete. This in part because several strong mechanisms refraction (NLR), leading to complex pulse width dependence. We expand upon recently developed beam deflection technique, which we apply, along with degenerate four-wave mixing...

Large-scale and vertically aligned nitrogen-doped carbon nanotubes were synthesized by pyrolysis of pyridine with ferrocene as the catalysts under either pure NH3 or a mixture argon atmosphere using injection chemical vapor deposition method. Nitrogen content ranges from 4.8 at. % to 8.8 changes function growth temperature flow rate NH3. not only increases nitrogen but also proportion pyridine-like N doping in nanotubes. It suggests that concentration environments could be controlled changing

Optical spectra of two families symmetrical polymethine dyes, bearing a positive and negative charge, are analyzed based on an essential-state model recently developed for quadrupolar dyes. The accounts molecular vibrations polar solvation reproduces the anomalous evolution with solvent polarity experimental absorption band shapes. Fluorescence excited-state well-described within same model, which also quantitatively recent observation intense two-photon toward (two-photon forbidden) lowest...

Two-photon absorption (2PA) spectra with pairs of extremely nondegenerate photons are measured in several direct-gap semiconductors (GaAs, CdTe, ZnO, ZnS and ZnSe) using picosecond or femtosecond pulses. In ZnSe, a ratio energies ~12, we obtain 270-fold enhancement 2PA when comparing to the corresponding degenerate coefficient at average photon energy (ηω1 + ηω2)/2. This corresponds pump 8% bandgap. coefficients as large 1 cm/MW measured. Thus, by two widely different wavelengths able access...

The two-photon absorption, 2PA, cross sections of PbS quantum dots, QDs, are theoretically and experimentally investigated shown to be enhanced with increasing confinement. This is in contrast our previous results for CdSe CdTe QDs where the reduced density states dominated resulted a decrease 2PA QD size. Qualitatively this trend can understood by highly symmetric distribution conduction valence band that an accumulation allowed transitions certain spectral regions. We also measure...

Light can be confined transversely and delivered axially in a waveguide. However, waveguides are lossy static structures whose modal characteristics fundamentally determined by the boundary conditions, thus cannot readily changed post-fabrication. Here we show that unpatterned planar optical films exploited for low-loss two-dimensional waveguiding using `space-time' wave packets, which unique family of one-dimensional propagation-invariant pulsed beams. We observe `hybrid guided' space-time...

A series of 1,7-bis(arylethynyl)-N,N'-bis[2,6-diisopropylphenyl]perylene-3,4:9,10-bis(dicarboximide)s has been obtained from Sonogashira coupling the 1,7-dibromoperylene-3,4:9,10-bis(dicarboximide) with p-substituted phenylacetylenes in which p-substituents include pi-donors (dialkylamino, diarylamino, p-(diarylamino)phenyl, alkoxy) and pi-acceptors (diarylboryl, p-(diarylboryl)phenyl). The bis(arylethynyl)-substituted chromophores all show two reversible molecular reductions are slightly...

A chromophore in which zinc porphyrin donors are linked through their meso positions by ethynyl bridges to a bis(indolinylidenemethyl) squaraine core has been synthesized using Sonogashira coupling. The exhibits two-photon absorption spectrum characterized peak cross section of 11,000 GM and, more unusually, also large >780 over photon-wavelength window 750 nm width.

We present an experimental and theoretical investigation of the linear nonlinear optical properties a series acceptor-pi-acceptor symmetrical anionic polymethine dyes with diethylamino-coumarin-dioxaborine terminal groups different conjugation lengths. Two-photon absorption (2PA) cross sections (delta(2PA)) are enhanced increase pi-conjugation length in investigated dyes. 2PA spectra for all consist two well-separated bands. The first band, located within telecommunications window, occurs...

We present a technique in which small solute nonlinearities may be extracted from large solvent signals by performing simultaneous Z-scans on two samples (solvent and solution). By using dual-arm Z-scan apparatus with identical arms, fitting error determining the nonlinearity is reduced because irradiance fluctuations are correlated for both solution measurements. To verify sensitivity of this technique, dispersion nonlinear refraction squaraine molecule measured. Utilizing allows effects n2...

The photophysical properties of two pairs squaraine molecules where oxygen atoms in a bridge are replaced with sulfur investigated. This substitution leads to an inversion the lowest singlet π−π* electronic transition by n−π* transition, effectively reducing energy difference between and triplet states significantly increasing intersystem crossing efficiency without use "heavy atoms". Experimental results, agreement quantum chemical calculations, show near-unity values for yield generation...

Polymethine dyes (PDs) with absorption bands in the near-infrared region undergo symmetry breaking polar solvents. To investigate how affects nonlinear optical responses of PDs, an extensive and challenging experimental characterization a cationic 2-azaazulene polymethine dye, including linear absorption, fluorescence, two-photon excited-state has been performed two solvents different polarity. Based on this set data, three-electronic-state model, accounting for coupling electronic degrees...

The Michigan Infrared Combiner (MIRC) has been designed for two primary goals: 1) imaging with all six CHARA telescopes simultaneously in the near-infrared, 2) direct detection of "hot Jupiter" exoplanets using precision closure phases. In September 2005, MIRC was commissioned on-sky at Array on Mt. Wilson, CA, successfully combining light from 4 simultaneously. After a brief overview features and design philosophy, we provide detailed description key components present results laboratory...

Employing methods developed for the control of shape and size in silver nanoparticles, we have compared optical properties nanorods, nanoprisms, nanodisks, nanospheres. Solutions these particles show distinct surface plasmon resonant absorption signatures that are directly correlated with symmetries their morphology. Nonlinear behavior suspensions nanostructures, nanosecond pulses at 532 1064 nm, been to resonances determined by size.

Single-crystal aluminum-gallium oxide films have been grown by molecular beam epitaxy in the corundum phase. Films of (Al(1-x)Ga(x))(2)O(3) alloys doped with neodymium favorable properties for solid-state waveguide lasers, including a high-thermal-conductivity sapphire substrate and dominant emission peak 1090-1096 nm wavelength range. The position is linearly correlated to unit cell volume, which dependent on film composition stress. Varying Ga-Al alloy during growth will enable fabrication...

A detailed experimental and theoretical study of the linear nonlinear absorption a series asymmetrical D–π–A cyanine dyes with same trimethylindolin donor (D) diethylamino-coumarin-dioxaborine acceptor (A) terminal groups different conjugation lengths, is presented. Strong solvatochromic behavior affecting fluorescence quantum yields, lifetimes, properties observed due to presence permanent ground state dipole moments. Detailed studies lifetime dynamics are performed by direct...

The time dynamics of the photoexcited carriers and carrier-multiplication efficiencies in PbS quantum dots (QDs) are investigated. In particular, we report on carrier dynamics, including multiplication, as a function QD size compare them to bulk value. We show that intraband 1$P$\ensuremath{\rightarrow}1$S$ decay becomes faster for smaller QDs, agreement with absence phonon bottleneck. Furthermore, QDs decreases, energy threshold multiplication shifts from value higher energies. However,...

The influence of quantum confinement on the one- and two-photon absorption spectra (1PA 2PA) PbS PbSe semiconductor dots (QDs) is investigated. results show 2PA peaks at energies where only 1PA transitions are predicted by often used isotropic k·p four-band envelope function formalism. first experimentally identified peak coincides with energy one photon allowed transition. This cannot be explained band anisotropy, verifying that inversion symmetry wave functions broken relaxation parity...

Two different approaches to increase intersystem crossing rates in polymethine-like molecules are presented: traditional heavy-atom substitution and molecular levels engineering. Linear nonlinear optical properties of a series polymethine dyes with Br- Se-atom substitution, new squaraine molecules, where one or two oxygen atoms bridge replaced sulfur atoms, investigated. A consequence the oxygen-to-sulfur squaraines is inversion their lowest-lying ππ* nπ* states leading significant reduction...