Emission Cross-section Spectra Research Articles

Experimental evaluation of the twofold electromagnetic enhancement theory of surface-enhanced resonance Raman scattering

We examined an electromagnetic (EM) theory of surface-enhanced resonance Raman scattering (SERRS) using single Ag nanoaggregates. The SERRS-EM theory is characterized by twofold EM enhancement induced by the coupling of plasmon resonance with both excitation and emission of Raman scattering plus fluorescence. The total emission cross-section spectra of enhanced Raman scattering and enhanced fluorescence were calculated using the following parameters: the spectrum of enhancement factor induced by plasmon resonance, resonance Raman scattering overlapped with fluorescence, and excitation wavelengths. The calculations well agreed with experimental total emission cross-section spectra, thus providing strong indications that the SERRS-EM theory is quantitatively correct.

Spectroscopic and lasing characterisation of a luminescent phenylene/bipyridine polymer

The luminescent polymer, poly[2,2′-bipyridine-5,5′-diyl-(2,5-dihexyl-1,4-phenylene)] (abbreviated PPBpy) dissolved in tetrachloroethane (TCE) and as neat film is characterised by optical absorption and emission spectroscopy. The absorption and stimulated emission cross-section spectra, the fluorescence quantum distributions, fluorescence quantum yields, degrees of fluorescence polarisation, and fluorescence lifetimes are determined. A lasing characterisation is carried out by pumping with single second harmonic pulses of a mode-locked ruby laser (wavelength 347.15 nm, duration 35 ps). The excited-state absorption at the pump-laser wavelength is determined by saturable absorption measurements. Laser oscillation of the polymer in TCE in an uncoated rectangular cell was achieved by transverse pumping using the cell windows for light feedback. From the laser threshold pump pulse energy density the effective stimulated emission cross-section at the lasing wavelength is extracted. The travelling-wave lasing behaviour of the polymer as neat film is studied by analysis of the amplification of the transverse pumped spontaneous emission. Surface emitting distributed-feedback lasing was achieved with a neat film on corrugated second-order periodic gratings.

Linear and nonlinear optical spectroscopic characterisation of triphenylamine and 1,2,3-tris(3-methylphenylphenylamino)benzene

The molecule triphenylamine (TPA) in tetrahydrofuran (THF) and the starburst triphenylamine oligomer 1,3,5-tris(3-methylphenylphenylamino)benzene (m-MTDAB) in THF and as neat film are characterized. Absorption and emission spectroscopic parameters are determined. The S 0–S 1 transition is found to be weak (nπ * transition) with small fluorescence quantum yield and efficient non-radiative decay (singlet–triplet intersystem crossing). The S 0–S 1 absorption cross-section spectra in the tails of the broad first absorption bands of the compounds are separated out by radiative lifetime determination and applying the mirror-image relation between absorption and emission. Excimer formation is observed for m-MTDAB neat films, its photo-dynamics is studied, and monomer and excimer stimulated emission cross-section spectra are extracted. Reverse saturable absorption is observed for TPA and m-MTDAB in picosecond laser nonlinear transmission measurements (laser duration 35 ps, laser wavelength 347.15 nm) and the responsible excited-state absorption cross-sections are determined. A new method is developed to calculate the excited-state absorption cross-section spectra of the samples in the fluorescence spectral region by amplification/attenuation of spontaneous emission measurements. The excited-state absorption is found to be larger than the stimulated emission for TPA in THF and for m-MTDAB films excluding their lasing ability. For m-MTDAB in THF the stimulated emission is found to be slightly larger than the excited-state absorption at the wavelength position of peak fluorescence emission.

Spectroscopic and travelling-wave lasing characterisation of tetraphenylbenzidine and di-naphtalenyl-diphenylbenzidine

The organic light emitting diode (OLED) hole transport molecules N,N,N’,N’-tetraphenylbenzidine (TPB, triphenylamine dimer TAD or TPD) and N,N’-bis(2-naphtalenyl)-N,N’-bis(phenylbenzidine) (β-NPB, naphtyl-diphenylamine dimer β-NPD), dissolved in tetrahydrofuran (THF) and as neat film, are characterized by optical absorption and emission spectroscopy. The absorption and stimulated emission cross-section spectra, the fluorescence quantum distributions, fluorescence quantum yields, degrees of fluorescence polarization, and fluorescence lifetimes are determined. The lasing behaviour is studied by picosecond laser pulse excitation (excitation wavelength 347.15 nm, pulse duration 35 ps). The excited-state absorption at the pump laser wavelength is determined by saturable absorption measurement. Low-Q laser oscillation of TPB in THF is achieved by transverse pumping of the dye in a cell. The excited-state absorption of TPB in THF at the laser wavelength is extracted from the laser threshold. In TPB neat films, wave-guided travelling-wave lasing was obtained. No laser action was achieved for β-NPB because of small S1-S0 stimulated emission cross-section, and the presence of excited-state absorption in the fluorescence wavelength region. The TPB and β-NPB results are compared with the corresponding spectroscopic and lasing behaviour of the related methyl-substituted triphenylamine dimers, 3-methyl-TPD and 4-methyl-TPD, which are well established OLED hole transport materials.

Spectroscopic and lasing characterisation of a dicarbazovinylene-MEH-benzene dye

The dye 1,4-bis(9-ethyl-3-carbazovinylene)-2-methoxy-5-(2′-ethyl-hexyloxy)-benzene (abbreviated 2CzV-MEH-B) dissolved in tetrahydrofuran (THF) and as neat film is characterised by optical absorption and emission spectroscopy. The absorption and stimulated emission cross-section spectra, the fluorescence quantum distributions, fluorescence quantum yields, degrees of fluorescence polarisation, and fluorescence lifetimes are determined. A lasing characterisation is carried out by pumping with single second harmonic pulses of a mode-locked ruby laser (wavelength 347.15 nm, pulse duration 35 ps). The excited-state absorption at the pump laser wavelength is determined by saturable absorption measurements. Laser oscillation of the dye in THF in a rectangular cell is achieved by transverse pumping using the uncoated cell windows for light feedback. From the emission behaviour around threshold the excited-state absorption cross-section spectrum in the laser active spectral region is extracted. The wave-guided travelling-wave lasing behaviour of the dye as neat film is studied by analysis of the amplification of the transverse pumped spontaneous emission. Surface emitting distributed-feedback lasing was achieved with a neat film on corrugated second-order periodic gratings.

Spectral kinetic properties of Yb3+:Na4Y6F22 and Yb3+:LiLuF4 crystals

Yb3+ (2.7 at.%):Na4Y6F22 and Yb3+(1 at.%):LiLuF4 crystals were grown by the Bridgman-Stockbarger method. We measured the temperature dependences of the thermal conductivity of the crystals and the absorption spectra. We determined the radiative lifetime of the Yb3+ ion in these crystals (1.94 msec and 2.13 msec) and calculated the stimulated emission cross section spectra.

Absorption and fluorescence spectroscopic characterisation of a phenothiazine–flavin dyad

The phenothiazine–phenylene–isoalloxazine dyad, 3-methyl-10-[4-(10-heptyl-10 H-phenothiazin-3-yl)-phenyl]-10 H-benzo[ g]pteridine-2,4-dione, dissolved in either dichloromethane or acetonitrile is characterized by absorption and emission spectroscopy. Absorption cross-section spectra, stimulated emission cross-section spectra, fluorescence quantum distributions, fluorescence quantum yields, and degrees of fluorescence polarisation are determined. The fluorescence decay is determined by time-resolved measurements. The dye photo-stability is investigated by observation of absorption spectral changes due to prolonged blue-light excitation. The absorption spectrum of the dyad resembles the superposition of the absorption of the isoalloxazine (flavin) moiety and of the phenylphenothiazine moiety. Photo-excitation of the flavin moiety causes fluorescence quenching by ground-state reductive electron transfer from phenylphenothiazine to isoalloxazine followed by charge recombination. Photo-excitation of the phenothiazine moiety causes (i) efficient excited-state oxidative electron transfer from phenothiazine to isoalloxazine with successive recombination, and (ii) moderate energy transfer followed by ground-state phenothiazine electron transfer and recombination.

High-Power Laser Performance of ${\hbox {Yb:}}{\hbox {YAl}}_{3}({\hbox {BO}}_{3})_{4}$ Crystals Cut Along the Crystallographic Axes

High-power continuous-wave laser operation near 1 mum was demonstrated at room temperature with c-cut and a-cut Yb:YAl <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> (BO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> ) <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> crystals end-pumped by a fiber-coupled diode laser. Using a 2-mm-thick c-cut crystal, 10.6 W of output power was generated with an optical-to-optical efficiency of 65% and a slope efficiency of 72%. The complex polarization state of the generated laser radiation was also studied. With a 2-mm-thick a-cut crystal, sigma-polarized laser oscillation was obtained, producing a maximum output power of 8.1 W; the optical-to-optical and slope efficiencies were 56% and 61%, respectively. Complete absorption and emission cross section spectra of the Yb:YAl <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> (BO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> ) <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> crystal were also derived, revealing very strong anisotropy of the spectroscopic properties

Absorption and emission spectroscopic characterisation of a pyrene-flavin dyad

The pyrene-flavin (isoalloxazine) dyad, PFD {C 44H 31N 5O 5; CA Index name: 1-pyrenepropanoic acid, α-[[4,10-dihydro-2,4-dioxo-10-phenylbenzo[g]pteridin-3(2H)-yl)acetyl]amino]-, phenylmethyl ester, (αR)–(9Cl); CA Registry number: 618907-57-6}, dissolved in either dichloromethane or acetonitrile is characterized by absorption and emission spectroscopy. Absorption cross-section spectra, stimulated emission cross-section spectra, fluorescence quantum distributions, quantum yields, and degrees of fluorescence polarisation are determined. The fluorescence decay after femtosecond pulse excitation is determined by fluorescence up-conversion. The ground-state absorption recovery is determined by picosecond pump and probe transmission measurements. The dye photo-stability is investigated by observation of absorption spectral changes due to prolonged blue-light excitation. The absorption spectrum of PFD dyad resembles the superposition of the absorption of isoalloxazine (flavin) and 1-methylpyrene. Long-wavelength photo-excitation of the flavin moiety causes fluorescence quenching by ground-state electron transfer from pyrene to isoalloxazine. Short-wavelength photo-excitation of the pyrene moiety causes (i) excited-state electron transfer from pyrene to isoalloxazine, and (ii) Förster-type energy transfer from pyrene to flavin followed by ground-state electron transfer from pyrene to flavin.

Photophysical characterization of pyrromethene 597 laser dye in silicon-containing organic matrices

Samples of dipyrromethene-BF2 dye PM597 incorporated in copolymers of 3-(trimethoxysilyl)propyl methacrylate (TMSPMA) with methyl methacrylate (MMA) and 2-hydroxyethylmethacrylate (HEMA), and in terpolymers of MMA, HEMA and TMSPMA are characterized. The absorption cross-section spectra, stimulated emission cross-section spectra, and the excited-state absorption cross-section at 527 nm are determined. The fluorescence quantum distributions and fluorescence lifetimes are measured. The photo-degradation is studied under cw laser excitation conditions and quantum yields of photo-degradation are extracted. PM597 solid state samples are compared with PM597 in liquid ethyl acetate solution. The fluorescence quantum yield of PM597 is higher in doped samples (around 70%) compared to PM597 in ethyl acetate (43%). The excited-state absorption cross-section was found to be negligibly small. The photo-stability is considerably larger in the polymeric samples compared to the liquid solutions.

Absorption and emission spectroscopic characterization of platinum-octaethyl-porphyrin (PtOEP)

The absorption and emission spectroscopic behaviour of the platinum complexed porphyrin PtOEP (platinum-octaethyl-porphyrin) is studied at room temperature. Liquid solutions, doped films, and a neat film are investigated. The absorption cross-section spectra including singlet–triplet absorption, the triplet–singlet stimulated emission cross-section spectra, the phosphorescence quantum distributions, the phosphorescence quantum yields, and the phosphorescence signal decays are determined. In the neat film a red-shifted phosphorescent excimer emission is observed. In diluted solid solution (polystyrene and dicarbazole-biphenyl films) as well as in de-aerated liquid solutions (tetrahydrofuran, toluene, chloroform) high phosphorescence quantum yields are obtained. In air-saturated liquid solutions, the phosphorescence efficiency is reduced by oxygen quenching. At intense short-pulse laser excitation the phosphorescence lifetime is shortened by triplet–triplet annihilation. No amplification of spontaneous emission was observed.

Erbium doped phospho-tellurite glasses for 1.5μm optical amplifiers

Abstract Erbium doped phospho-tellurite glasses with the alkali ions sodium and lithium is made and their optical and physical properties are studied. Glasses with high glass transition temperature and phonon energy which are suitable for fabrication of integrated optical amplifiers and lasers is obtained. From the optical absorption spectra the Judd–Ofelt parameters (Ωt) and their radiative lifetimes are calculated. Absorption and emission cross-section spectra of the glasses for the transitions between 4I13/2 and 4I15/2 levels are reported.

Absorption and emission spectroscopic characterization of 10-phenyl-isoalloxazine derivatives

The flavoquinone dyes 10-phenyl-isoalloxazine-3-acetic acid ethyl ester ( 1) and 10-(4-bromo-phenyl)-3-methyl-isoalloxazine ( 2) in dichloromethane, acetonitrile, and methanol are characterized by absorption and emission spectroscopy. Absorption cross-section spectra, stimulated emission cross-section spectra, fluorescence quantum distributions, quantum yields, lifetimes, and degrees of fluorescence polarization are determined. The blue-light photo-degradation of the dyes is studied. Mass spectroscopic measurements reveal the formation of phenyl-benzo-pteridine (isoalloxazine) derivatives, tetraaza-benzo-aceanthrylene derivatives, dihydro-quinooxaline derivatives, and pyrazino-carbazole derivatives. An enhancement of photo-degradation is observed by the formed photo-fragments.

Spectroscopic properties of Er 3+ doped phospho-tellurite glasses

Erbium doped phospho-tellurite glasses of molar compositions 50TeO 2 30P 2O 5 19Na 2O 1Er 2O 3 and 45TeO 2 35P 2O 5 19Na 2O 1Er 2O 3 are made and their optical and physical properties are studied in comparison to erbium doped sodium-tellurite glass. Differential scanning calorimetry shows an increase in the glass transition temperature with the addition of P 2O 5. From the infrared transmittance spectra we found that the maximum phonon energy of the phospho-tellurite glasses is also high ( ∼ 1290 cm - 1 ) . Optical absorption spectra of the phospho-tellurite glasses shows a blue shift in the absorption edge comparing to the sample without phosphate. From the optical absorption spectra the Judd–Ofelt parameters ( Ω t ) , transition probabilities, branching ratios of various transitions and their radiative lifetimes are calculated. The absorption and emission cross-section spectrum of the I 15 / 2 4 to I 13 / 2 4 transition of erbium in tellurite glass with 30% P 2O 5 shows almost equal bandwidth and peak cross-sections as in sodium-tellurite glass.

Spectroscopic properties of Er3+ ions in transparent oxyfluoride glass ceramics containingCaF2 nano-crystals

In this paper, the spectroscopic properties ofEr3+-doped oxyfluoride glassceramics containing CaF2 nano-crystals are systematically investigated. X-ray diffraction (XRD) andtransmission electron microscope (TEM) experiments confirmed the formation ofCaF2 nano-crystals in the glassy matrix. Based on the Judd–Ofelt theory, the intensity parametersΩ2,4,6,spontaneous emission probability, radiative life, radiative quantum efficiency, width of the emissionline, stimulated emission cross-section and gain spectrum were evaluated, and the effect ofEr3+ doping concentration on the spectroscopic properties of the transition is discussed. For glass ceramics, intense red and weak green up-conversionluminescence were observed and ascribed to two-photon absorption processes.

Photophysical characterisation of some dipyrromethene dyes in ethyl acetate and covalently bound to poly(methyl methacrylate)

Abstract Analogues of the dipyrromethene-BF 2 dye PM567 modified at the 8-position by acetoxymethyl (P1Ac), s -acetoxypentyl (P5Ac), and p -acetoxymethylphenyl (PAr1Ac) groups are studied in ethyl acetate solution. PM567 modified at the 8-position by methacryloyloxymethyl (P1MA), s -methacryloyloxypentyl (P5MA), and p -methacryloyloxymethylphenyl (PAr1MA) groups have been copolymerized with methyl methacrylate (MMA), and these solid samples are also studied. The absorption cross-section and stimulated emission cross-section spectra are determined. The fluorescence quantum distributions and fluorescence lifetimes are measured. Saturable absorption measurements with picosecond laser excitation are carried out for excited-state absorption cross-section determination at the excitation wavelength. The photo-degradation of the dyes is studied under cw laser excitation conditions and quantum yields of photo-degradation are extracted.

Absorption and emission spectroscopic characterization of Ir(ppy)3

Abstract The absorption and emission spectroscopic behaviour of cyclometalated fac -tris(2-phenylpyridine) iridium(III) [Ir(ppy) 3 ] is studied at room temperature. Liquid solutions, doped films, and neat films are investigated. The absorption cross-section spectra including singlet–triplet absorption, the triplet–singlet stimulated emission cross-section spectra, the phosphorescence quantum distributions, the phosphorescence quantum yields and the phosphorescence signal decays are determined. In neat films fluorescence self-quenching occurs, in diluted solid solution (polystyrene and dicarbazole-biphenyl films) as well as deaerated liquid solution (toluene) high phosphorescence quantum yields are obtained, and in air-saturated liquid solutions (chloroform, toluene, tetrahydrofuran) the phosphorescence efficiency is reduced by triplet oxygen quenching. At intense short-pulse laser excitation the phosphorescence lifetime is shortened by triplet–triplet annihilation. No amplification of spontaneous emission in the phosphorescence spectral region was observed indicating higher excited-state absorption than stimulated emission.

Spectroscopic characterization ofEr3+ transitionsin Bi4Si3O12

A systematic investigation of optical absorption and luminescence is presented forEr3+ ionsin the Bi4Si3O12 crystal. The intrinsic emission of this crystal gives rise to a radiative energy transfer among the host latticeand Er3+ ions. Measured oscillator strengths for seven different transitions from the ground state toexcited state manifolds compare favourably with the electric dipole oscillator strengthscalculated from the Judd–Ofelt formalism. Radiative lifetimes of the former seven excitedstates were determined from calculated spontaneous emission probabilities. The ratio of the excited state absorption oscillator strength to the ground state absorption oscillator strength turned out to be similar to those found for materials pumpedefficiently at 4I11/2 level excitation wavelengths. The stimulated emission cross section and gain spectra weredetermined for the transition of special interest for laser application.

Integral Method o Reciprocity in the Spectroscopy of Laser Crystals with Impurity Centers

A new method of determining the stimulated emission cross-section spectra from the absorption cross-section spectra, which we call the integral method of reciprocity, is suggested it does not require knowledge of the structure of the impurity-center electron levels. Based on this method, formulas for calculating the radiation lifetime of impurity centers in crystals have been derived. The effectiveness of the integral method of reciprocity was demonstrated in determining the stimulated emission cross sections and radiation lifetime of an ytterbium ion in the laser crystals Yb3+:KYW and Yb3+:KGW.

Absorption and emission spectroscopic characterisation of F 3 - colour centers in a LiF crystal

For a LiF crystal containing F3 (R1, R2), F2, F3 +, F4 (N1, N2), F3 -, and F2 - colour centers the absorption and emission spectroscopic behaviour of the F3 - centers is studied. The absorption cross-section spectrum and the number density of F3 - centers are extracted from saturable absorption and transmission measurements. Additionally fluorescence quantum distribution measurements and fluorescence lifetime measurements are carried out to determine the stimulated emission cross-section spectrum and the fluorescence quantum yield of the F3 - centers. Fluorescence excitation spectroscopy reveals the presence of an absorption band with its absorption peak around 700 nm (called R′ 1 band) in addition to the ground-state to first excited-state F3 - center absorption band centered at 800 nm (called R′ 2).