Due to rapid improvements in high-power laser performance, two-photon absorption processes have become a very useful tool for studying the molecular structures of various gases, liquids and solids. However, measurements of absolute two-photon absorption cross sections were more or less ignored ...

Two-photon excitation can excite physiological ultraviolet (UV) chromophores at visible wavelengths and holds significance for applications such as non-linear microscopy, micro-pharmacology, localized heating and tissue ablation. However, little quantitative data is available on the absolute two-photon absorption ...

Absolute two-photon absorption cross sections for various rare gas atoms and small molecules were measured by resonance ionization spectroscopy. Two-photon cross sections of various liquids and solids were obtained by the two-photon induced fluorescence method.

... Title : Two-Photon Absorption and Nonresonant Nonlinear Index of Refraction in the Intersubband Transitions in the Quantum Wells. ...

... Accession Number : ADA198860. Title : Two-Photon Absorption Characterization. Descriptive Note : Interim performance rept. ...

... Accession Number : AD0691800. Title : TWO-PHOTON ABSORPTION IN ALKALI HALIDES. CALCULATION OF NONLINEAR ...

... Keywords: Mercury cadmium telluride; Group II IV compounds; Two photon absorption; Defect characterization; Magneto optical measurements ...

... TWO PHOTON ABSORPTION, *ATOMIC SPECTROSCOPY, STEADY STATE, SODIUM, RAYLEIGH SCATTERING, RESONANCE RADIATION ...

The absorption line shape of Cs-Ar system is recorded using two-photon ionization of the system with Cs(7P) as an intermediate state. New satellite structures in the wings of Cs(7P) are observed which were not resolved in previous absorption measurements. Also the absolute absorption cross ...

... Accession Number : ADA040528. Title : Two-Photon Absorption Spectroscopy of Polyenes. Descriptive Note : Final rept. 1 Jul 73-30 Jun 76,. ...

... Accession Number : ADA207198. Title : Two-Photon Absorption Characterization of HgCdTe. Descriptive Note : Interim rept. ...

... Accession Number : ADA207197. Title : Two-Photon Absorption Characterization. Descriptive Note : Interim performance rept. 28 Aug-27 Nov ...

... Accession Number : ADA210508. Title : Two Photon Absorption Characterization. Descriptive Note : Quarterly rept. no. 6, 28 Nov 1988-27 Feb ...

... PROPERTIES, LOW TEMPERATURE, FLUORESCENCE, CHEMICAL ... QUANTUM EFFICIENCY, PHOTONS, TWO PHOTON ABSORPTION ...

... Ultrafast dynamics, such as the optical Stark effect, two photon absorption, and absorption bleaching, were readily observed. ...

Degenerate two-photon absorption (TPA) spectral properties of five AFX chromophore solutions have been studied using a single and spectrally dispersed sub-picosecond white-light continuum beam. In a specially designed optical configuration, optical pathways inside the sample solution for different spectral components of the focused continuum beam were ...

We demonstrate direct measurements of the absolute molecular two-photon absorption (TPA) cross-sections using a fluorescence technique. A theoretical model of the detected fluorescence signal generated by a femtosecond laser pulse was developed. It is shown that the onset of excited-state saturation depends on the TPA cross-section and ...

May 15, 2008 ... A new optical beam tracking approach for free-space optical communication links using two-photon absorption (TPA) in a high-bandgap detector ...

Although two-photon absorption in a semiconductor is typically a very weak effect, the rate of absorption increases dramatically when the two photons have very dissimilar wavelengths, enabling applications such as ultrafast optical sampling and room-temperature mid-infrared detection.

Intensity-induced nonlinear effects in optical window materials have been investigated at 308 nm. The absolute two-photon absorption coefficients for fused silica, CaF2, BaF2, Al2O3 and ADP crystals have been measured by using a single 120 ps, transform-limited pulse from the second harmonic of a distributed feedback (DFB) dye laser. ...

Intensity-induced nonlinear effects in optical window materials have been investigated at 308 nm. The absolute two-photon absorption coefficients for fused silica, CaF2, BaF2, Al2O3 and ADP crystals have been measured by using a single 120 ps, transform-limited pulse from the second harmonic of a distributed feedback (DFB) dye laser. ...

... determine the temperature dependence of the energy gap of various ... defects and accurately determine their activation energies, thus providing ...

... Attempts to find evidence for two photon absorption processes in several systems, including solutions of perylene in ethanol, subjected to the ...

... FINITE DIFFERENCE THEORY, TWO PHOTON ABSORPTION, OPTICAL PROCESSING, DIFFRACTION ANALYSIS, FOURIER ANALYSIS, READ ...

... ZINC OXIDES, *TWO PHOTON ABSORPTION, *OPTICAL ... BEAMS, ROOM TEMPERATURE, TRANSMITTANCE ... GAIN, TUNING, PHOTONS, MIXING ...

... The development of metal particles systems as well as conjugated organic molecules with large two-photon absorption (2PA) cross- ...

... MOBILE, MONITORS, PHOTONS, POLARIZATION, PROBES ... TIME, TRANSIENTS, TRANSPORT, TWO PHOTON ABSORPTION, CADMIUM ...

A previous study demonstrated two-photon consecutive absorption as being the most probable mechanism

... the two-photon resonance where the absorption is ... linear index of refraction as large as ... Two photon absorption and nonresonant nonlinear index of ...

... On the basis of a two photon assisted excited state absorption model we show that the excited state absorption from both the singlet and triplet ...

An extension of the J-diffusion description of rotational motion is developed for the contribution of the rotation-vibration interaction to the linewidths and lineshapes of polarized vibrational Raman scattering, two-photon absorption and two-photon-reson...

Two-photon transition rates for molecular and crystalline anthracene are calculated using Pariser's pi-electron molecular-orbital wave functions, including configuration interaction. Distinctive polarization dependences and approximate rates are obtained ...

... 8c. ADDRESS (City, State. ... FIELD GROUP SUBI-GROUP Defect characterization, Magneto-Optical nleasurelnents, 17 05 Two Photon Spectroscopy ...

Two photon absorption spectra, detected by fluorescence, phosphorescence, and photoacoustic methods are presented for pyrazine and triazine. Vibronic assignments are made in both systems based on polarization and contour analysis. For pyrazine, origin int...

To explore the photophysics of platinum acetylide chromopores having strong two-photon absorption cross-sections, we have investigated the synthesis and spectroscopic characterization of a series of platinum acetylide complexes that feature highly &(numbe...

The effect of the non-parabolicity of the energy bands on the indirect two-photon transition is theoretically studied. An expression for the absorption coefficient valid both near and far from the energy gap is given. Numerical results, compared with rece...

This report results from a contract tasking Polish Academy of Sciences as follows: The material for real-world optical limiting applications based on RSA has to independently possess (among others) three distinct properties: large two-photon absorption cr...

The expressions describing direct and indirect two-photon absorption in crystals are given. They are valid both near and far from the energy gap. A perturbative approach through two different band models is adopted. The effects of the non-parabolicity and...

Third-order nonlinear optical spectra ?(3) of conjugated polymers are theoretically studied within the treatment of double-excitation configuration interaction for the Pariser-Parr-Pople model. We consider a realistic situation of dephasing rates being much larger than depopulation rates. It is shown that, on the low-energy side of the one-photon resonance, the absolute value ...

Fluorescent proteins with long emission wavelengths are particularly attractive for deep tissue two-photon microscopy. Surprisingly little is known about their two-photon absorption (2PA) properties. We present absolute 2PA spectra of a number of orange and red fluorescent proteins, including DsRed2, mRFP, TagRFP, and several mFruit ...

The two-photon absorption spectrum of ZnS at ET and LNT is presented. The magnitude of the nonlinear absorption cross section is discussed with respect to pumping by means of two-photon absorption and with respect to second-harmonic attenuation in ZnS. (A...

A laser two-photon excited fluorometric detector for high pressure liquid chromatography is described and characterized for the separation of the oxadiazoles PPD, PBD, and BBD. Excitation is provided by the absorption of two photons of radiation at 5145 A from an argon ion laser. The detection limits, linearity of ...

A nonresonant two-photon absorption process can be manipulated by tailoring the ultra-short laser pulse. In this paper, we theoretically demonstrate a highly selective population of two excited states in the nonresonant two-photon absorption process by rationally designing a spectral phase distribution. Our results ...

Two-photon-induced fluorescence from a soluble polythiophene containing urethane side groups has been investigated using femto-second laser pulses at 800 nm. Strong two-photon fluorescence was measured in polymer solution. The quadratic dependence of the fluorescence on the excitation laser intensity confirmed the two-photon process. The measured ...

Photochemical reactions which can be activated by the simultaneous absorption of two photons provide a means for single-step fabrication of complex 3D microstructures. These types of structures are needed for a wide range of applications, including microfluidics, electrooptics, and micro-electromechanical systems. We have shown that ...

... section. Page 10. 3.3 Coumarin 503 Coumarin 503 (also known as Coumarin 307) was studied by measurements performed ...

We experimentally demonstrate two-photon absorption with broadband down-converted light (squeezed vacuum). Although incoherent and exhibiting the statistics of a thermal noise, broadband down-converted light can induce two-photon absorption with the same sharp temporal behavior as femtosecond pulses, while ...

studies of global warming, ozone deple- tion, and impacts of meteorites. ... threshold for two-photon absorption leads to fluorophore excitation that is ...

... of Two-Photon Double-Beam Optical Bistability,. ... Descriptors : *Multiple beams(Radiation), *Quantum electronics, *Two photon absorption, *Photon ...

Quantum Entanglement Molecular Ab- sorption Spectrum Simulator (QE-MASS) is a computer program for simulating two- photon molecular-absorption spec- ...

two photon absorption of KrF laser light near 248 nm (32). The ..... The photodissociation of ozone (2,4,20) in the ultraviolet ...

It is seen that below 50 Km the laser beam in substantially absorbed by the ozone. In calculating the two photon absorption by 0, it should be kept in ...

... Title : High Rydberg States of Jet-Cooled Toluene Observed by Ultraviolet Two-Photon Absorption Spectroscopy: Ultrafast Radiationless Decay ...

... of NO2: A Molecular Beam Multiphoton Ionization Study ... spectroscopy, Molecular beams, Pulsed lasers, Two photon absorption, Energy levels ...

... donor-acceptor structural motifs exhibit exceptionally large two-photon absorption cross sections, up to roughly 400 times that of trans-stilbene. ...

... spectroscopy techniques used to characterize these materials included four-wave mixing, two photon absorption and fluorescence line narrowing. ...

The expression giving the ionisation cross-section of an atom, by an absorption process involving two photons produced from a laser beam, is derived. The non-relativistic case is considered and the dipolar approximation used. The summation over the interm...

A phthalocyanine derivative containing two-photon chromophores which are based on pyrimidine was designed and synthesized. Its light-emission property was studied in detail, and a strong energy transfer from peripheral chromophores to the phthalocyanine core was observed. The compound exhibited strong two-photon absorption responses ...

A feature associated with continuous-wave two-photon optical gain has been observed in the absorption spectrum of an ensemble of barium atoms driven by a strong near-resonant optical field. In the dressed-atom picture, the observed gain is attributable to inverted two-photon transitions with nearly resonant intermediate states. A cw ...

The rate of absorption of entangled photon pairs is linear in the photon-flux density. We demonstrate that the two-photon absorption cross section is a nonmonotonic function of the entanglement time; it vanishes for certain energy-level configurations and values of the entanglement time. This entanglement-induced two-photon ...

This investigation covers the development of nonintrusive, laser-based optical diagnostic tools for the measurement of trace amount molecular species in hostile, reactive environments such as plasmas. Two- photon laser induced fluorescence (LIF) spectroscopy is applied to obtain the temperature of atomic hydrogen and Cavity Ring-Down Spectroscopy (CRDS) to ...

... Title : Absolute Absorption Cross Section Measurements of Ozone and the Temperature Dependence at Four Reference Wavelengths Leading to ...

The dimethylamino nitro stilbene (DANS) molecule is studied for exploring solvent effects on two-photon absorption using the quantum mechanical/molecular mechanical (QM/MM) response theory approach, where the quantum part is represented by density functional theory. We have explored the role of geometrical change of the chromophore in solution, the importance of taking a ...

The density of neutral nitrogen atoms in a glass reactor was measured by two absolute methods: two-photon absorption laser induced fluorescence (TALIF) and catalytic probes. The source of N atoms was nitrogen plasma created in a quartz tube by surfatron microwave generator operating at 2.45 GHz and adjustable output power up to 300 W. ...

We have developed a fluorescence saturation technique for accurate measurements of the absolute molecular two-photon absorption (TPA) cross-section of fluorescent dyes. We determine the TPA crosssection both from measurements at excitation intensities well below saturation onset (in the square power-law regime) and from data obtained ...

Two-photon excitation of fluorescent proteins is an attractive approach for imaging living systems. Today researchers are eager to know which proteins are the brightest and what the best excitation wavelengths are. Here we review the two-photon absorption properties of a wide variety of fluorescent proteins, including new far-red variants, to produce a ...

The two photon excited fluorescence excitation spectrum of UF6 was observed in the region 410 to 315 nm. The spectrum was virtually indistinguishable from the one photon absorption in this region. No vibronic structure was observed in absorption or dispersed emission. These data indicate a high density of u and g ...

We report studies of collision-induced features of the 3S(1/2) yields 3P(1/2) yields 4D(3/2) two-photon absorption in atomic sodium vapor undergoing collisionss with several rare gas perturbers. The results yield the collisional redistribution function wh...

CONTENTS 1. Introduction 299 2. General Relations for Two-Photon Transitions 299 3. Experimental Technique 301 4. Two-Quantum Transitions in Molecules and Molecular Crystals 302 5. Two-Photon Absorption in Semiconductors and Ionic Crystals 308 References 318

dispersed in metha- nol and octadecene. The synthesis of CdSe quantum dots was realized accordingFrequency degenerate and nondegenerate two-photon absorption spectra of semiconductor quantum dots quantum dot sizes and size distributions, we observe that the 2PA spectra and the 2PA coefficient are size

A new spectroscopic method for monitoring Doppler-free two-photon absorption signals is analyzed. Its principle consists of high-frequency modulation of one of the incident beams and the detection of the modulation induced by two-photon absorption in the intensity of the counterpropagating beam. The predictable advantages of this ...

All-optical femtosecond switch using two-photon absorption D. D. Yavuz Department of Physics wavelength in femtosecond time scales. DOI: 10.1103/PhysRevA.74.053804 PACS number s : 42.65.Re, 42.50.Gy-optical switches with switching time in the femtosecond domain. In this paper, as an alternative to these solid

Novel donor-pi-bridge-acceptor-pi-bridge-donor (D-pi-A-pi-D)-type 1,4-diketo-3,6-diphenylpyrrolo[3,4-c]pyrrole (DPP) derivatives with end-capping diphenylamine groups have been synthesized and shown to exhibit large two-photon absorption cross-sections over a wide range of wavelengths with strong two-photon excitation red fluorescence. ...

Two-photon absorption has been observed in diacrylate mesogens for a low-power continuous laser irradiation at 632.8 nm wavelength. The two-photon absorption coefficients for the mesogens in different phases are determined, and found to be very large. In the isotropic state, the two-photon absorption coefficients ...

We study gallium arsenide (GaAs) high voltage photoconductive switches triggered by a 30 ps neodymium: yttrium aluminium garnet (Nd:YAG) laser, i.e. using photons of energy smaller than the band gap. We measure optical absorption at Brewster incidence under optical pulse excitation and determine the extrinsic one photon and intrinsic two ...

Applications of an atmospheric-pressure, nanosecond pulsed plasma jet for biomedical and dental disinfections have motivated numerous diagnostic studies in understanding of the underlying physics and chemistry during the plasma bactericidal processes. In this work, we present spectroscopic studies of a 3 cm long needle-like He-O2 plasma jet. Rotational temperature of the plasma jet was measured to ...

Absolute hydrogen atom densities in pure hydrogen capacitive discharges were measured as a function of excitation frequency (13.56, 27.12, and 40.68 MHz), nominal electrical power, and gas pressure (between 0.1 and 1 Torr). Quantitative measurements were made using two-photon absorption laser-induced fluorescence (TALIF), put on an ...

... 4401 Dayton-Xenia Road Dayton, OH 45432 ... with large two-photon absorption cross sections," Sci ... Z. Hu, D. McCord-Maughon, TC Parker, H. Rockel ...

A new method for determination of plasma parameters under atmospheric pressure conditions is formulated and applied for characterization of a radio-frequency ?-jet plasma source using He/O2 mixture. By applying absolutely calibrated optical emission spectroscopy and numerical simulation, the gas temperature in the active plasma region and plasma parameters (electron density ...

Two-photon stimulated emission depletion (STED) cross sections were determined over a broad spectral range for a novel two-photon absorbing organic molecule, representing the first such report. The synthesis, comprehensive linear photophysical, two-photon absorption (2PA), and stimulated emission properties of a ...

Magneto-Optical measurements of Hg1-xCdxTe alloys have provided a new means of studying impurities and defects in this important II-VI material. Two-photon magnetoabsorption (TMPA) has been used to accurately determine the temperature dependence of the en...

Magneto-Optical measurements of Hg(1-x)Cd(x)Te alloys have provided a new means of studying impurities and defects in this important II-VI material. Two-photon magnetoabsorption (TMPA) has been used to accurately determine the temperature dependence of th...

Physical photochromic transformations are studied in doped polymer films upon two-photon excitation. It is shown by the example of fluorescein halogen derivatives that the triplet-level population of molecules can be controlled by exciting the system by light into the T{sub 1} {yields} T{sub n} triplet - triplet absorption band of molecules. It is proposed ...

A three level scheme interacting with three laser fields is considered. It is found that two competing processes contribute to the absorption/dispersion on a particular transition: (i) one-photon processes governed by the field applied to that transition, and (ii) two-photon processes governed by the two laser fields applied to two other transitions. ...

Degenerate two-photon indirect absorption in silicon is an important limiting effect on the use of silicon structures for all-optical information processing at telecommunication wavelengths. We perform a full band structure calculation to investigate two-photon indirect absorption in bulk silicon, using a ...

The polarization dependence of the two-photon absorption signal is described directly in terms of the matrix elements of the irreducible representation of the two-photon absorption tensor operator for an ensemble with cylindrical symmetry probed with identical photons of linear polarization. Nonvanishing matrix elements are easily determined from the known ...

In this article we present the study of the surface plasmon enhanced two-photon absorption of a hydrophilic stilbene derivative (trans-4,4'-diaminostilbene) in aqueous solution at different concentrations. The observed exponential growth of the effective two-photon absorption cross section [?2'(Au)] is attributed ...

Two-photon-excited fluorescence and second-harmonic generation are characterized as a function of laser pulse duration as short as sub-10-fs. A comparative study is performed where pulse duration is varied by introducing dispersion, as reported previously, and by tailoring pulse spectral width and minimizing its time-bandwidth product (transform-limited pulses). Experimental ...

... Title : Absolute Concentration Measurements of Free Radicals in Flames by Absorption Spectroscopy. Descriptive Note : Final rept. ...

The hyperfine Stark effect of 6d ,2 3/2 and 7d ,2 3/2 states of ^133Cs are studied using resonantly-enhanced laser spectroscopy. Two single-mode external-cavity diode lasers counter-propagate through a well collimated thermal beam of cesium. This interaction region is centered between two parallel field plates. The nd states are resonantly excited through the 6p ,2 1/2 intermediate state and ...

We investigate the loading rate of Yb+ ions loaded through photoionization in a radiofrequency trap. The absolute or relative number of the loaded trapped ions is measured by use of an electric resonance of the secular motion. This method is applicable even in the presence of anharmonicity. In two-color photoionization, where the first-excitation laser drives the 1S0-1P1 ...

In this paper, two-photon absorption laser induced fluorescence spectroscopy is used to follow the nitrogen atom density in flowing dielectric barrier discharges fed with pure nitrogen and operating at atmospheric pressure. Two different dielectric barrier discharge regimes are investigated: the Townsend regime, which is homogeneous although operating at ...

Subject Terms: not OZONE 'AND' .... Differential absorption lidar is a well- established technique to measure atmospheric gases, ... Incident photons from the pump laser pulse are converted into two photons, with one at the wavelength of ...

A first implementation of the single residue of the quadratic response function in the four-component Hartree-Fock approximation is presented. The implementation is based on a Kramers paired molecular orbital basis and takes full advantage of time and spatial symmetry reductions in a quaternion formulation-in analogy with the previous work on the quadratic response function [J. Chem. Phys. 121, ...

A two-photon absorption process was used to study resonance ionization spectroscopy of atoms, molecules in the gas phase, laser-induced fluorescence spectra in the condensed phase and laser induced chemical reactions in solutions. 8 refs., 1 fig., 1 tab.

A semiclassical theory for the creation of excitonic polariton states by two-photon absorption, via an intermediate exciton state, is given. A band model has been introduced which gives the dominant contribution to this process. A numerical calculation is...

This project explored structure-property relationships relevant to enhancement of two-photon absorption (2PA) in organic dendritic molecules for optical power limiting. We synthesized and studied two series of novel monodisperse dendrimers built of identi...

... where fcw is the laser photon energy and Ei is the binding or activation energy of ... For the IMA shown in Figure 3 this analysis yields 9.8 meV for ...

... the electrical and optical properties of the material. ... Particularly, we have started to study samples with x = 0.23 and ... n-HgCdTe (x=0.224) (sample * 2 ...

Two-photon absorption and emission processes make small contributions to the radiative rates in a hot plasma. In this paper these rates are calculated as a test of a new semiclassical method. The results agree closely with quantum calculations. 9 refs., 1 fig., 2 tabs.

This report summarizes a number of research programs concerned with ultrashort laser pulses and their interaction with matter. Topics discussed include second harmonic generation, parametric interactions, two photon absorption, theory of picosecond pulse ...

There has been much interest in the development of two-photon absorbing materials and many efforts to understand the nonlinear absorption properties of these dyes, but this area is still not well understood. A computational model has been developed in our...

... Shown in Figure 2 are the S1-Sn absorption spectra of AF455 in air-saturated hexane, benzene, THF, and 2-propanol upon 400 nm excitation. ...

... where Nj is the electron number density of the state j, ay,k is the absorption cross-section for ... Left side: z=O. Right side: z=1 mm. 12 Page 13. ...

"A Two-Photon Absorption Cross Section Measurement in the Gamma Band of Nitric Oxide," Optical Society of America, New Orleans, Louisiana, October l7-20, ...

We have made considerable advances in the development of optical- limiting systems based upon two-photon absorption processes. To accomplish this, it has been essential to develop an understanding of basic structure-property relationships for conjugated o...

The arc heated facility LBK in Cologne is designed to characterize thermal protection materials for re-entry vehicles in high enthalpy flow fields. Models with dimensions of 300 * 300 mm can be studied with stable flow conditions for 1800 s in the L3K. Typical model surface temperatures are 2000 K at pressure levels of up to 350 hPa and enthalpy levels up to 25 MJ/kg. Infrared thermography, ...

We report the first two-photon excited autofluorescence measurements in single cells induced by continuous wave NIR laser microbeams. In particular we demonstrate NIR-excited NAD(P)H fluorescence of motile spermatozoa in a single-beam gradient force optical trap ('optical tweezers'). In addition, two-photon NIR excited autofluorescence imaging and 'tau- ...

We report on precise two-photon ablation with 110 fs laser pulses at 1278 nm, emitted from a Cr:forsterite laser. Selective two-photon ablation of Muntjac deer chromosomes is demonstrated. The two-photon absorption at 639 nm was enhanced by using Methylene blue dye as a photosensitizer. This stain has a strong ...

Combination of femtosecond Kerr, two photon absorption, and impulsive stimulated Raman scattering (ISRS) experiments have been carried out to investigate the effect of pulse energy and crystal temperature on the generation of coherent polaritons and phonons in <110> cut ZnTe single crystals of three different resistivities. We ...

. The 775 nm pulses excited the sample by one-photon absorption, whereas 1550 mn pulses (fundamental beamITuNS Two-photon'spin'injectionin semiconductors RD.R Bhat, P.Nemec, Y.Kerachian, J.E. Sipe and A polarization of electrons photogenerated in bulk GaAs by two-photon absorption of circularly polarized light

It has been conjectured that atomic oxygen and ozone can have a great influence on the plasma oxidation of ultrathin aluminum for magnetic tunnel junctions. In order to measure the density of O and ozone, two-photon absorption laser induced fluorescence measurements are performed in the dc glow plasma that is used for the oxidation process. It was found ...

It has been conjectured that atomic oxygen and ozone can have a great influence on the plasma oxidation of ultrathin aluminum for magnetic tunnel junctions. In order to measure the density of O and ozone, two-photon absorption laser induced fluorescence measurements are performed in the dc glow plasma that is used for the oxidation process. It was found ...

We report on the experimental-theoretical analysis of degenerated two-photon absorption circular-linear dichroism (2PA-CLD) in (S)-(-)-1,1'-bi(2-naphthol) and (R)-(+)-1,1'-bi(2-naphthol) dissolved in THF. 2PA-CLD reveals similarities and differences between optical polarization states for the different enantiomers. These results unveil the potential ...

Two-photon excitation (TPE) and second harmonic generation (SHG) have been studied in phenanthrene crystals at low temperatures (2 to 6K) in order to investigate mechanisms of two-photon absorption (TPA), the relationship between TPE and SHG, and polariton effects. The transition studied is of special interest because it is both one- and two-photon allowed ...

We report here the synthesis and characterization of a new type of non-ionic blue fluorescent water-soluble chromophores specifically designed for two-photon absorption microscopy. The water solubility is induced by introduction of short oligo(ethylene glycol) monomethyl ether moieties. This work has led to low molecular weight dyes with efficient ...

... Title : High Resolution Absolute Absorption Cross Sections of NO2 at 295, 573, and 673K at Visible Wavelengths: Comprehensive Data Tables. ...

We report the photochemistry and development of a fluorescence readout-based, nonlinear absorption, three-dimensional optical data storage system. In this system, writing was achieved by acid generation upon two-photon absorption (2PA) of a photoacid generator (PAG; at 710 or 730 nm). Readout was then performed by interrogating ...

BackgroundTwo-photon dual-color imaging of tissues and cells labeled with fluorescent proteins (FPs) is challenging because most two-photon microscopes only provide one laser excitation wavelength at a time. At present, methods for two-photon dual-color imaging are limited due to the requirement of large differences in Stokes shifts between the FPs used ...

Multiphoton excitation of exogenous dyes and endogenous biochemical species has been used extensively for tissue diagnosis by fluorescence spectroscopy. Unfortunately, the majority of endogenous biochemical chromophores have low quantum yields, less than 0.2, therefore determining two-photon cross sections of weakly luminescencing molecules is difficult using ...

Intensities of translational lattice mode absorptions of alpha phase solid molecular nitrogen in far

Two-photon absorption spectrum of aniline is recorded using thermal lens effect with optical parametric oscillator as the pump source. Studies show that the two-photon absorption spectrum observed corresponds to 1A1 --> 1B2 transition of aniline.

Linear spectral properties, including excitation anisotropy, of pseudoisocyanine or 1,1?-diethyl-2,2?-cyanine iodide (PIC) J-aggregates in aqueous solutions with J-band position at 573 nm were investigated. Two-photon absorption of PIC J-aggregates and monomer molecules was studied using an open aperture Z-scan technique. A strong enhancement of the ...

Two-photon absorption (2PA) measurements in ADP and in KD(asterisk)P are reported on in some detail. Measurements of nonlinear absorption in these materials and measurements of linear and nonlinear absorption at the second harmonic frequency are presented and discussed. Effects of 2PA on second harmonic generation, ...

The design and synthesis of symmetrical and unsymmetrical heptamethine cyanines is reported. These chromophores present significant two-photon cross section in the 1400-1600 nm spectral range. In addition, they display optical power limiting (OPL) properties. OPL curves were interpreted on the basis of two-photon absorption (2PA) followed by excited state ...

Many chromophores with a large two-photon absorptive cross section are hybrid materials where the two-photon absorption (TPA) is coupled to an excited-state absorption (ESA). We develop a numerical technique to investigate hybrid two-photon processes in nonlinear absorbers. Our numerical method ...

... DIOXIDE, *INFRARED SPECTRA, GASES, ABSORPTION, HEAT OF REACTION, DETERMINATION, CHEMICAL EQUILIBRIUM, LIQUIDS ...

Epilayers of packaged indium gallium nitride light-emitting diodes (LED's) are characterized by optical-beam-induced current (OBIC) and photoluminescence laser-scanning microscopy through two-photon excitation. Light scattering and absorption in the packaging material and the p-doped top layer of the LED's are greatly reduced as a result of employing a ...

Two-photon fluorescence was observed for 18 organic dyes in a polymethyl methacrylate (PMMA) matrix excited by a femtosecond Ti:sapphire laser. The product of the cross section for two-photon absorption by the quantum yield of fluorescence (two-photon fluorescence cross section) is estimated by comparing it with fluorescence of ...

One-photon ionization studies of solute molecules in a liquid medium are limited by the absorption of the host medium. A laser two-photon ionization (TPI) technique using a frequency tunable dye laser has been developed, whereby the photoionization threshold of a solute molecule was determined from the induced conductivity in the liquid medium under study ...

This paper describes measurements of the beam polarization and quantum efficiency for photoemission using two-photon excitation from unstrained bulk GaAs illuminated with pulsed, high intensity 1560nm laser light. Quantum efficiency is linearly proportional to 1560nm peak laser intensity, which was varied in three independent ways, indicating that the emitted electrons are ...

The resonant and non-resonant two-photon single ionization processes of He were investigated using intense free electron laser light in the extreme ultraviolet (XUV) region (53.4�61.4 nm) covering the 1s�2p and 1s�3p resonant transitions of He. On the basis of the dependences of the yield of He+ on the XUV light-field intensity at 53.4, 58.4, 56.0 and 61.4 nm, the ...

Identifying strong and fast nonlinearities for today's photonic applications is an ongoing effort. Materials and devices are typically sought to achieve increasing nonlinear interactions. We report large enhancement of two-photon absorption through intrinsic resonances using extremely non-degenerate photon pairs. We experimentally demonstrate two-photon ...

Photoinduced nonlinear optical phenomena in amorphous As2Te3-CaCl2-PbCl2 glasses have been studied using experimental and theoretical quantum chemical and molecular-dynamics methods. Especially photoinduced two-photon absorption (TPA) and second-harmonic generation (SHG) were measured in the IR region from 5.5-21 ?m. CO laser (?=5.5 ?m) and parametrically ...

A single CW infrared laser beam can simultaneously trap and excite an individual colloidal quantum dot. Though the laser light is relatively weak, the excitation occurs through two-photon absorption. This finding eliminates the demand for an excitation light source in addition to a trapping laser in nanoscale experiments with simultaneous ...

The fluorescence properties of a new two-photon absorption chromophore in dimethyl formamide, methanol, acetone, benzyl alcohol, methylene chloride and chloroform are reported. The lifetime, intensity and central wavelength of the fluorescence signal vary significantly in different solvents. The fluorescence properties are explained by using the twisted ...

The two-photon absorption cross section of the efficient red laser dye 6-(Cyclohexylamino)-3-triflurometyl-1H-phenalen-1-one (phenalemine 512) in ethanol and polymethyl methacrylate excited by nanosecond pulses from a 1064-nm Nd:YAG laser is measured by the method of two-quantum standard. Lasing in phenalemine 512 is obtained upon two-photon excitation of ...

We report on the use of interferometric autocorrelation measurements to investigate the non-linear absorption processes evident in single InGaN/GaN quantum dots. The near quadratic excitation intensity dependence of the photoluminescence signal in conjunction with the asymmetric collinear autocorrelation trace unambiguously confirms the process as being one involving ...

Observation of two-photon excitation (760 nm) and emission of two responsive water soluble europium complexes is reported with cross-sections of up to 2 GM. Two-photon excitation spectra have also been measured, acquisition being achieved by the use of a cavity-dumped mode locked Ti-sapphire laser. Time-gated detection is used to differentiate the ligand fluorescence and metal ...

The transitional behavior of the two-photon Kerr effect between the self-Kerr and cross-Kerr cases is investigated. To this end, we have developed a semiclassical method for evaluating the two-photon Kerr effect that is applicable to any two-photon input state. It is revealed that the maximum Kerr effect is obtained when the second photon is input with a delay time that ...

Extended bis(donor)-substituted squaraine chromophores exhibit very high two-photon cross-sections (as high as 33 000 GM) in the near-IR; these can be attributed to the combination of large transition dipoles with small detuning energies. The modulus of the third-order nonlinear optical susceptibility at 1.3 mum has been found to be 7.0 x 10-11 esu for one of these ...

We investigate the excitation of an atom or molecule via two-photon absorption induced by an ultrashort laser pulse in the perturbative intensity regime. We show that the probability for a resonant transition, i.e., with an intermediate state within the spectral width of the pulse, can be reduced to zero by pulses having a {theta}-phase step at a certain ...

At room temperature, multiphoton absorption- (MPA-) induced photoluminescence in ZnO strongly driven by a femtosecond (fs) near-infrared laser is studied. Two-photon absorption and three-photon absorption are proved to be responsible for the intense luminescence, when the wavelength of the fs excitation laser is ...

Theoretical and experimental investigations were made of the dependence of the absorption of infrared radiation by ozone on the intensity of such radiation in the range from 1 kW/cm2 to 3 GW/cm2. The nonlinear absorption spectra of ozone were recorded by switching between the CO2 laser emission lines in the range 970-1090 cm?1. A comparison of the theory ...

Recently, transmission Raman spectroscopy has been shown to be a valuable tool in the volumetric quantification of pharmaceutical formulations. In this work a Monte Carlo simulation and experimental study are performed to elucidate the dependence of the Raman signal on depth from the viewpoint of probing pharmaceutical tablets and powders in this experimental configuration. The transmission Raman ...

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 ...

To explore the photophysics of platinum acetylide chromophores with strong two-photon absorption cross-sections, we have investigated the synthesis and spectroscopic characterization of a series of platinum acetylide complexes that feature highly pi-conjugated ligands substituted with pi-donor or -acceptor moieties. The molecules (numbered 1-4) considered ...

Two photon absorption cross-sections and fluorescence dynamics of Riboflavin, Fluorescein 548, Coumarin 519 and Quinizarin adsorbed onto reactive (TiO2) and non-reactive (ZrO2) semiconductor nanoparticles have been investigated. These dye molecules are chosen because of their inherently different anchoring groups with which they can ...

We have studied two-photon absorption in solids theoretically and experimentally. We have shown that it is possible to use accurate band structure techniques to compute two-photon absorption spectra within 15% of measured values in a wide band-gap material, ZnS. The empirical pseudopotential technique that we used ...

In this paper, the authors measured two-photon-absorption spectra of GaAs/Al{sub 0.4}Ga{sub 0.6}As quantum-well structures in a static electric field for photon energies near half the band gap energy, and found drastic field-induced-changes in the spectra. The two-photon-absorption peak at half the energy of the lowest light-hole exciton is induced by the ...

The two-photon absorption of few-electron ions has been studied by using second-order perturbation theory and Dirac's relativistic equation. Within this framework, the general expressions for the excitation cross sections and rates are derived including a full account of the higher-order multipole terms in the expansion of the electron-photon interaction. While these ...

Two-photon excitation (TPE) and second harmonic generation (SHG) data associated with the 31475-cm/sup -1/ ..cap alpha..-exciton of high-purity strain-free mounted sublimation crystals of naphthalene are reported. The marked temperature dependence of the TPE/SHG branching ratio for several phase-matching conditions is in accord with the polariton model. The branching ratio ...

We report the observation of interband two-photon absorption (TPA) saturation in cadmium sulfide nanocrystals (CdS NCs) under intense femtosecond laser excitation with 1.6-eV photon energy. The observation has been compared to interband TPA saturation in bulk CdS under the same experimental conditions. By using both Z-scan technique and transient ...

Cold atmospheric pressure plasma jets promise high potential for temperature sensitive surface treatments in biomedicine, see e.g. Stoffels et al. (2006). Stable homogeneous low temperature plasma operation is achieved by using helium feed gas and applying radio frequency excitation. Small admixtures of molecular oxygen to the feed gas lead to the efficient generation of highly reactive oxygen ...

THe emission spectrum of Xe2+Cl- in HCl plus Xe doped crystalline CO, excited by 308 nm laser, are firstly observed. The cooperative charge transfer absorptions: HCl plus Xe plus 2 hv yields [Xe+(HCL)-] is demonstrated, and the four-body, two-photon cooperative absorption cross section at 308 nm is 5 multiplied by 10-42 cm4s.

Herein we report on the full experimental measurement of the two-photon absorption circular dichroism spectra of (S)-(-)-1,1'-bi(2-naphthol) and (R)-(+)-1,1'-bi(2-naphthol), their analysis, and theoretical support. The finding of new nonlinear optical fingerprints in chiral molecules offers new opportunities in the recognition and understanding of optically active systems in ...

The two-photon absorption spectrum of single crystal cadmium sulfide was measured at liquid nitrogen temperature. Excitation to final states in the region 2.5 to 3.5 eV was achieved using a neodymium-glass laser and a tunable visible light source similar ...

Nonlinear absorption measurements were performed on fluorophosphate glasses with high concentrations of tungsten oxide. Large two-photon absorption coefficients, alpha2, were determined at 660 nm using nanosecond laser pulses. It was observed that alpha2 increases for increasing tungsten oxide concentrations and, hence, the optical ...

We have measured the temperature dependence of the intensity of the lowest energy two-photon absorption line in poly(di-n-hexylsilane) and find that it does not change between ambient temperature and 14 K. The line width decreases by about a factor of three.

Colloidal CdSe quantum dots (QDs), whose surface traps are controlled with the purification process, are measured with a Z-scan technique using an 80 femtosecond pulse duration laser source. Their two-photon absorption coefficient and refractive index are decreased more than one order of magnitude with the increase of the density of surface traps, indicating that the surface ...

We show that ringlike localized gain landscapes imprinted in focusing cubic (Kerr) nonlinear media with strong two-photon absorption support new types of stable higher-order vortex solitons containing multiple phase singularities nested inside a single core. The phase singularities are found to rotate around the center of the gain landscape, with the ...

A series of three-coordinate octupolar compounds with varied centers (boron, aluminum, and nitrogen), which exhibit very large effective two-photon absorption cross sections have been theoretically studied. The ground state geometries and electronic structures are obtained using the density functional theory with the B3LYP functional and 6-31G(d) basis ...

A series of three-coordinate octupolar compounds with varied centers (boron, aluminum, and nitrogen), which exhibit very large effective two-photon absorption cross sections have been theoretically studied. The ground state geometries and electronic structures are obtained using the density functional theory with the B3LYP functional and 6-31G(d) basis ...

Multielectron ionization of colloidal CdSe quantum dots under intense femtosecond UV excitation has been studied. By directly probing the absorption from the ionized electron, quantitative measurements of the yield and dynamics of the ionization have been made as a function of excitation fluence and variations of size and potential structure of quantum dots. The results have ...

A comprehensive photophysical study of the linear and nonlinear absorption properties has been carried out on two series of two-photon absorbing dyes to gain insight into how structure-property relationships influence observed nonlinear absorption. The ma...

The two-photon absorption spectrum of KI has been measured to 7.5 eV. The region studied spans the spectral range in which all the prominent one-photon absorption peaks reside. Our two-photon data exhibit two noticeable peaks at 7.21 and 7.375 eV. (Author...

The project has considered several aspects of the optical properties of lanthanide (rare-earth) doped crystals and glasses at near ultraviolet wavelengths. These include two-photon absorption, excited state absorption, excited-state photoionization and co...

The project has considered several aspects of the optical properties of lanthanide (rare-earth) doped crystals and glasses at near ultraviolet wavelengths. These include two-photon absorption, excited state absorption, excited-state photoionization and co...

The process of two photon absorption between two bound states through a repulsive intermediate state has been investigated by 2+1 multiphoton ionization of molecular chlorine. In these experiments, the first photon goes into a fairly strong repulsive cont...

In this work, we present the design and construction of a femtosecond laser pulse autocorrelator, based on the two-photon absorption process in a light emitting diode (LED). Compared with traditional autocorrelators based on nonlinear crystals, this autocorrelator has the advantages of lower cost and greater ease of alignment. The intensity and interferometric autocorrelation ...

Since its inception more than 15 years ago, two-photon laser scanning microscopy (2PLSM) has found widespread use in biological and medical research. Two-photon microscopy is based on simultaneous absorption of two photons by fluorophores and subsequent fluorescence emission, a process which ...

An important ingredient in improving Multi Photon Laser Scanning Microscopy, MPLSM, is the development of efficient two-photon fluorescent (TPF) probes. We previously reported on a new class of TPF probes, specifically designed in order to maximize their efficiency in potential MPLSM applications. The fluorophores are based on a tetraketo derivative (TK) with a symmetric ...

ZnO nanoparticles have attracted increased attention due to its large exciton binding energy. Moreover it has enhanced nonlinear optical properties due to its noncentrosymmetric crystal structure which results in a second order nonlinearity. The presence of oxygen vacancy and modified surface states also yields third order nonlinearity such as two photon ...

We used a variety of picosecond transient and cw spectroscopies to investigate the linear and nonlinear optical properties of films of PPE/PPV copolymer semiconductor. The spectroscopies used include absorption, electro-absorption (EA) and two-photon-absorption (TPA). In addition to the odd parity excitons at ca. 3.0 eV, we also found ...

Secondary cataracts are quite often observed after implantation of polymeric intraocular lenses. The reason for this complication is that lens epithelial cells remain in the capsular bag when the natural lens is removed. They begin proliferation and cause secondary cataracts. It is not desireable to add cell toxic agents at the time of the implantation because wound healing is negatively affected. ...

A series of star-shaped octupolar triazatruxenes (TATs, 1-6) with intramolecular "push-pull" structure were synthesized and their photophysical properties have been systematically investigated. These chromophores showed obvious solvatochromic effect, i.e., significant bathochromic shift of the emission spectra and larger Stokes shifts were observed in more polar solvents mainly due to photoinduced ...

Advancement over the past decade of materials based on two-photon absorption has been phenomenal; yet, a need for greater understanding of multi-photon processes remains. Questions of design to maximize two-photon absorbance cross-sections and quantum yields have been addressed quantitatively. However, effects of the chemical environment on the ...

Organic compounds that undergo strong nonlinear, multiphoton absorption have been gaining greater interest, mainly in the developing fields of multiphoton fluorescence imaging, optical data storage, 3-D microfabrication, and photodynamic therapy. Systematic studies have shown that conjugated organic molecules with large delocalized ? electron systems show very large nonlinear ...

We analyze in this paper the process of double-electron ejection through two-photon absorption from the fundamental state of helium. We focus on the case of photon energies close to 2 a.u., which marks the threshold between direct and sequential double-ionization regimes. We demonstrate the crucial role of two-photon excitation-plus-ionization process of ...

We study the photon correlation properties of broadband parametric down-converted light. The measurement of the photon correlation is carried out thanks to a modified Hanbury Brown-Twiss interferometer based on two photon absorption in GaAs detector. Since this method is not affected by the phase matching conditions of the detecting ...

Photocurrent spectroscopy has been carried out on single CdS nanosheet devices in the metal-semiconductor-metal configuration with both Schottky and Ohmic contacts. Spatial imaging of the photocurrent shows that the photosensitive regions are localized at the reverse biased contact for Schottky type contacts and uniformly distributed throughout the nanosheet for Ohmic contacts. Photocurrent ...

A scheme of optical polarization modulation of a linearly polarized infrared probe field is studied in a degenerate four-level Yb atomic system. We have observed an anomalous transmission spectra of two circular polarization components of the probe field exhibiting an enhanced two-photon absorption and a three-photon gain with comparable magnitude, leading ...

In this paper, we study theoretically and experimentally the coherent control of non-resonant two-photon transition in a molecular system (Perylene dissolved in chloroform solution) by shaping the femtosecond pulses with simple phase patterns (cosinusoidal and ? phase step-function shape). The control efficiency of the two-photon transition probability is correlated with both ...

Energy migration between chromophores plays a prominent role in a range of energy harvesting assemblies. Recent advances in the design and production of light-harvesting polymers have led to the synthesis of novel two-photon absorbing dendrimers. To construct increasingly efficient multifunctional macromolecules of this type, understanding the inherent optical processes and ...

We report energy-transferring organically modified silica nanoparticles for two-photon photodynamic therapy. These nanoparticles co-encapsulate two-photon fluorescent dye nanoaggregates as an energy up-converting donor and a photosensitizing PDT drug as an acceptor. They combine two features: i) aggregation-enhanced two-photon ...

The optical absorption spectra of the glasses with composition xBi(2)O(3) . (30 - x)R2O . 70B(2)O(3) (R=Li, Na, K) and xBi(2)O(3) . (70 - x)B2O3 . 30Li(2)O (0 less than or equal to x less than or equal to 20) have been recorded in the wavelength range 350-650 nm. The glass samples were prepared by the normal melt-quench technique. The fundamental ...

Red upconversion luminescence (UCL) is observed using an 800 nm femtosecond laser to irradiate a Eu3+-doped LiNbO3 single crystal. Power-dependent and polarization-dependent experiments demonstrate that the red UCL originates from Eu3+ two-photon simultaneous absorption rather than second harmonic generation of nonlinear optical crystal followed by ...

In this letter, laser micronanofabrication via two-photon absorption initiated isomerization was proposed and explored. Experimentally a cis-form rich poly[2,5-dihexyloxy-1,4-phenylene] vinylene)-alt-(2,5-diphenyl-1,4-phenylene vinylene)] (DPO-PPV) was used as the precursory material, which underwent pinpoint molecular conformational change upon the ...

We study the steady optical response of a five-level atomic system in the parametric region where resonant two-photon transitions are much stronger than far-detuned single-photon transitions. We find that the concurrent absorption of two weak probe fields can be well suppressed in a narrow spectral region to attain electromagnetically induced transparency ...

The two photon absorption spectrum at the intrinsic absorption edge of ZnO is measured with various directions and modes of polarization of the incident light beams. Several peaks are observed, corresponding to the 2 P 0,�1-exciton states of the 3 series A, B, C (which occur on account of the threefold upper ...

A version of the one-photon probing of optical properties of semiconductors is presented under conditions when a high-power pump pulse excites biexcitons from the ground state of a crystal due to two-photon absorption. The existence of a Lorentzian absorption peak is predicted and the quasi-polariton dispersion law is found in the region where a real ...

Nonlinear optical effects can be enhanced in tapered optical fibers with diameters less than the wavelength of the propagating light. Here we report on the observation of two-photon absorption using tapered fibers in rubidium vapor at power levels of less than 150 nW. Transit-time broadening produces two-photon absorption spectra with ...

We investigate the connections between two field-enhanced phenomena of gold nanoparticles: multiphoton-absorption-induced luminescence (MAIL) and metal-enhanced multiphoton absorption polymerization (MEMAP). We observe a strong correlation between the nanoparticles and aggregates that have high efficiency for each process. The results of our studies ...