Frequency Upconversion Fluorescence Research Articles

Intense frequency upconversion fluorescence emission of Er 3+/Yb 3+-codoped oxychloride germanate glass

Structural and frequency upconversion fluorescence properties of Er 3+/Yb 3+-codoped oxychloride germanate glasses have been investigated. The Raman spectrum investigation indicates that PbCl 2 plays an important role in the formation of glass network and has an important influence on the upconversion luminescence. Intense green and red emissions centered at 525, 546 and 657 nm, corresponding to the transitions 2H 11/2 → 4I 15/2, 4S 3/2 → 4I 15/2 and 4F 9/2 → 4I 15/2, respectively, were observed at room temperature. The possible upconversion mechanism was also estimated and evaluated. Intense upconversion luminescence indicates that Er 3+/Yb 3+-codoped oxychloride germanate glass is a promising laser material.

Observation of upconversion fluorescence and stimulated emission based on three-photon absorption

The observations of three-photon-induced frequency-upconversion fluorescence and the highly directional stimulated visible emission in two dyes, 4-[p-(dicyanoethylamino) styryl]-N-methylpyridinium iodide (abbreviated as CEASP) and the complex of CEASP and Ce(NO3) (abbreviated as CEASP-Ce), are reported. The photographs of the forward amplified spontaneous emissions spots, pumped by an optical parametric oscillator idler with a pulse width of 8 ns and a wavelength of 1.3 μ m, are shown. The upconversion fluorescence produced both in dimethyl formamide solution and 2-hydroxyethyl methacrylate (HEMA) polymer spans from green to red, with a cubic dependence on the pump light intensity. The experimental results imply that the existence of the lanthanide ion Ce3 + sensitizes the nonlinear absorption and emission.

Frequency Upconversion Fluorescence Emission ofEr3+-Doped Oxychloride Germanate Glass

Frequency upconversion fluorescence property of Er3+-dopedoxychloride germanate glass is investigated. Intense green and redemissions centred at 525, 546, and 657 nm, corresponding to thetransitions 2H11/2→4I15/2,4S3/2→4I15/2, and 4F9/2→4I15/2,respectively, were simultaneously observed at room temperature. Thequadratic dependence of the 525, 546, and 657 nm emissions onexcitation power indicates that a two-photon absorption process occursunder 975 nm laser diode (LD) excitation. The Raman spectruminvestigation indicates that oxychloride germanate glass has the maximumphonon energy at ~805 cm−1. The thermal stability of thisoxychloride germanate glass is evaluated by differential scanningcalorimetry, and thermal stability factor ΔT (ΔT = Tx−Tg) is 187 degrees C. Intense upconversion luminescence and goodthermal stability indicate that Er3+-doped oxychloride germanateglass is a promising upconversion laser material.

Three-photon-absorption induced fluorescence and optical limiting properties of a new organic compound

Three-photon-absorption-induced frequency up-conversion fluorescence emission has been observed in a solution of 4-2-(7-(4-amido styrene)-9,9-di(2-ethyl hexyl)-9H-fluorene-2-) ethylene) aniline (BASF) in N,N-dimethylformamide(DMF), pumped with 38ps Q-switched 1064nm laser pulses. The spectral peak of the observed fluorescence emission is located in the 456—775nm range, and the intensity dependence of the visible emission on the IR excitation obeys the cubic law. At higher solute concentration and moderate IR excitation intensity levels, obvious optical limitation behavior has been observed due to three-photon-absorption. The measured nonlinear absorption coefficient and the molecular three-photon-absorption cross section are 4.34×10-20cm3/Ｗ2 and 2.4×10-39cm6/Ｗ2, respectively.

Two-photon absorption properties of hyperbranched conjugated polymers with triphenylamine as the core

Two new hyperbranched phenylene vinylenes (HPVs) with triphenylamine as the core, 2,5-dihexyloxyl substituted phenylene vinylene as the connecting unit, and electron-donating triphenylamine or electron-deficient nitrobenzene as the different terminal groups were synthesized by modified Wittig polymerization reaction. Their one- and two-photon absorption (TPA) properties have been investigated. The two-photon absorption cross sections of the two polymers were performed by open-aperture Z-scan experiment using 120 femtosecond (fs) pulse, and their TPA cross section were determined to be 1.43 and 0.64×10 −20 cm 4/GW per repeating unit at 800 nm, respectively. In chloroform, HPVs exhibit intense frequency up-converted fluorescence under the excitation of 120 fs pulses at 800 nm with the peaks located at 544 and 554 nm, respectively.

Linear and tri-branched copolymers for two-photon absorption and two-photon fluorescent materials

The one- and two-photon properties of linear (M2) and tri-branched (M3) copolymers with triphenylamine and cyano groups in the main chain were experimentally investigated. Open-aperture z-scan experiments were performed with 1 kHz, 120 fs, and 800 nm Ti:sapphire laser pulses to measure the two-photon absorption cross sections. The two-photon cross sections of M2 and M3 were determined to be 0.304 and 1.441×10−20cm4/Gw per repeating unit, respectively. In a CHCl3 solution, M2 and M3 emit strong frequency up-converted fluorescence under the excitation of 120 fs pulses at 800 nm with the peaks located at 561 and 542 nm.

Optical properties and frequency upconversion fluorescence in a Tm3+ -doped alkali niobium tellurite glass

Optical spectroscopic properties of Tm3+-doped 60TeO2−10GeO2−10K2O−10Li2O−10Nb2O5 glass are reported. The absorption spectra were obtained and radiative parameters were determined using the Judd–Ofelt theory. Characteristics of excited states were studied in two sets of experiments. Excitation at 360 nm originates a relatively narrow band emission at 450 nm attributed to transition D21→3F4 of the Tm3+ ion with photon energy larger than the band-gap energy of the glass matrix. Excitation at 655 nm originates a frequency upconverted emission at 450 nm (1D2→3F4) and emission at 790 nm (3H4→3H6). The radiative lifetimes of levels D21 and H43 were measured and the differences between their experimental values and the theoretical predictions are understood as due to the contribution of energy transfer among Tm3+ ions.

Thermal effect on upconversion fluorescence emission in Er-doped chalcogenide glasses under anti-Stokes, Stokes and resonant excitation

Abstract We investigate thermal effects upon infrared to visible frequency upconversion fluorescence emission in Er3+-doped chalcogenide glasses, pumped under anti-Stokes, Stokes and resonant excitation. The upconversion emission signals is found to decrease with increasing temperature in the range of 23–200 °C. The observed thermal effect is modeled by conventional rate equations considering a temperature-dependent effective absorption cross-section for the 4 I 15/2 → 4 I 9/2 and 4 I 11/2 → 4 F 3/2 , 4F5/2 erbium transitions. The temperature dependence is mainly attributed the nonradiative decays. This model accurately reproduces the experimental results.

Thermal effects on light emission in Yb3+-sensitized rare-earth doped optical glasses

The temperature effect upon infrared-to-visible frequency upconversion fluorescence emission in off-resonance infrared excited Yb3+-sensitized rare-earth doped optical glasses is theoretically and experimentally investigated. We have examined samples of Er3+/Yb3+-codoped Ga2S3:La2O3 chalcogenide glasses and germanosilicate optical fibers, and Ga2O3:La2O3 chalcogenide and fluoroindate glasses codoped with Pr3+/Yb3+, excited off-resonance at 1.064mum. The experimental results revealed thermal induced enhancement in the visible upconversion emission intensity as the samples temperatures were increased within the range of 20°C to 260°C. The fluorescence emission enhancement is attributed to the temperature dependent multiphonon-assisted anti-Stokes excitation process of the ytterbium-sensitizer. A theoretical approach that takes into account a sensitizer temperature dependent effective absorption cross-section, which depends upon the phonon occupation number in the host matrices, has proven to agree very well with the experimental data. As beneficial applications of the thermal enhancement, a temperature tunable amplifier and a fiber laser with improved power performance are presented.

Two-Photon Absorption and Fluorescence of a Novel CompoundTrans-1,3,5-tri-(4-N,N-Dimethylaminobenzylstyryl)-Acetylacetone

Large two-photon absorption cross section of a novel compoundtrans-1,3,5-tri-(4-N,N-dimethylaminobenzylstyryl)-acetylacetone ismeasured to be σ2 = 8.4×10-20 cm4/GW orσ2' = 1.594×10-47 cm4/(photon·s) by using a 1064 nmNd:YAG laser with 35 ps pulse width based on the intensity-dependenttransmissivity measurement. The frequency upconversion fluorescence isobserved by two-photon laser pumping.This material is an idealcandidate for optical limiting and upconversion fluorescence.

Up-conversion luminescence from neodymium ion implantation silicon

Strong ultra-violet and visible frequency up-conversion fluorescence spectroscopy in neodymium-ion implantation single crystalline silicon at the excitation wavelengths of 625, 650, 675 and 700 nm, was experimentally investigated. The PL intensity increased with the increase in the excitation wavelength and ion fluence. The photoluminescence excitation (PLE) spectrum in the wavelength range of 500–770 nm was also studied. For 700-nm pumping, a mechanism of two-photon absorption and radiation transition process was proposed.

Thermal effect on multiphonon-assisted anti-Stokes excited upconversion fluorescence emission in Yb 3+ -sensitized Er 3+ -doped optical fiber

The temperature effect upon infrared-to-visible frequency upconversion fluorescence emission in Yb3+-sensitized Er3+-doped germanosilicate optical fibers excited with cw radiation at 1.064 μm is investigated. The experimental results revealed an eightfold enhancement in the visible upconversion emission intensity as the fiber temperature was increased from 17 °C to 180 °C. The fluorescence emission enhancement is attributed to the temperature-dependent multiphonon-assisted anti-Stokes excitation process of the ytterbium sensitizer. A theoretical approach that takes into account a sensitizer absorption cross-section, which depends on the phonon occupation number, has proven to agree very well with the experimental data

Frequency-upconverted organic crystal

The fluorescent characteristics of Troger's base have been investigated experimentally. A one-photon-induced fluorescent spectrum was observed, and the peak wavelength was at 337 nm with a full width at half-maximum of ~85nm . The violet radiation of the Troger's base crystal could result from the pi(*) -pi transition of the benzenoid pi bond. Two-photon-pumped frequency-upconverted fluorescence was obtained, which is a wideband emission with the main peak wavelength at 337 nm and a subordinate peak. Donor groups and acceptor groups of electrons in the aromatic rings strengthen the two-photon-pumped frequency-upconverted fluorescence.

Infrared to visible up-conversion fluorescence spectroscopy in Er 3+-doped chalcogenide glass

Infrared to visible frequency up-conversion fluorescence spectroscopy in erbium-doped chalcogenide glass samples excited at 1.06 and 1.54 μm, is experimentally investigated. For 1.06 μm pumping, two-photon absorption and phonon-assisted energy transfer account for the excitation of the 2H 11/2, 4S 3/2 and 4F 9/2 emitting levels, yielding intense green emission at 530 and 555 nm and low intensity light at 670 nm, respectively. For excitation at 1.54 μm, much higher up-conversion efficiencies were obtained with the red emission signal around 670 nm presenting higher intensity than the green fluorescence signals. At this excitation wavelength the population of the 2H 11/2, 4S 3/2 and 4F 9/2 excited-state emitting levels is accomplished via energy-transfer and phonon-assisted decays. Saturation of the up-conversion efficiency for 1.54 μm pumping was also observed.

Optical limiting effect in a two-photon absorption dye doped solid matrix

We recently reported a new lasing dye, trans-4-[p-(N-ethyl-N-hydroxylethylamino)styryl]-N-methylpyridinium tetraphenylborate (ASPT), which has also been shown to possess a strong two-photon absorption (TPA) and subsequent frequency upconversion fluorescence behavior when excited with near infrared laser radiation. Based on the TPA mechanism, a highly efficient optical limiting performance has been demonstrated in a 2 cm long ASPT-doped epoxy rod pumped with 1.06 μm Q-switched laser pulses at 50–250 MW/cm2 intensity levels. The measured nonlinear absorption coefficient reached 6 cm/GW for the tested sample of dopant concentration d0=4×10−3 M/L. The molecular TPA cross section of ASPT in the epoxy matrix is estimated as σ2=2.5×10−18 cm4/GW or σ2′=4.7×10−46 cm4/photon/s, respectively. Two-photon pumped cavity lasing is also observed in an ASPT-doped polymer rod.

Preparation and optical properties of transparent glass-ceramics containing β-PbF2:Tm3+

Transparent glass ceramics containing β-PbF2:Tm3+ crystallites have been prepared by heat treatment of glasses in GeO2-PbO-PbF2-TmF3 system. Average crystallite size of β-PbF2 evaluated from the full width at half maximum of x-ray diffraction lines varies from about 16 to 20 nm as the heat treatment temperature increases from 340 to 400 °C when 50GeO2⋅40PbO⋅10PbF2⋅1TmF3 glass is heat treated. The glass ceramics containing β-PbF2:Tm3+ of 16 nm is transparent in the visible region. The incorporation of Tm3+ into β-PbF2 crystalline phase has been demonstrated from the linewidth and peak position of optical absorption spectrum. Frequency upconversion fluorescence has been observed for the transparent glass ceramics at room temperature. The upconversion fluorescence intensities due to the 1D2→3H6 and 1D2→3F4 transitions are higher for the transparent glass ceramics than for the glass. This phenomenon is explainable by assuming that the multiphonon relaxation rate of the 3H4 state is smaller in the glass ceramics than in the glass.

Three-photon-absorption-induced fluorescence and optical limiting effects in an organic compound

Three-photon-absorption-induced frequency-upconversion f luorescence emission has been observed in a solution of 2,5-benzothiazole 3,4-didecyloxy thiophene (BBTDOT) in tetrahydrofuran, pumped with 10-ns Q-switched 1.06-microm laser pulses. The spectral peak of the observed fluorescence emission is located in the 450-480-nm range, and the intensity dependence of the visible emission on the IR excitation obeys the cubic law. At a higher solute concentration (0.18 M/L) and moderate IR excitation intensity levels (50-200 MW/cm(2)), obvious optical limiting behavior has been observed as a result of three-photon absorption. The measured nonlinear absorption coeff icient and the corresponding molecular three-photon-absorption cross section are gamma= 2.7 x 10(-18) cm(3)/W(2) and sigma'(3) = 8.8 x 10(-76) cm(6) s(2), respectively.

Excited-state absorption mechanisms in red-laser-pumped uv and blue upconversions in Tm3+-doped fluoroaluminate glass.

The mechanism of red-pumped frequency-upconversion fluorescence observed in the uv and blue ranges of frequencies for a Tm 3+ -doped fluoroaluminate glass was investigated by single-wavelength pumping of a tunable 4-(dicyanomethylene)-2-methyl-6-(p-dimethyl-amino-styryl)-4H-pyran dye laser. It was found that the dependences of fluorescence intensity on the incident excitation power were quadratic both for the 0.36- and 0.45-μm emissions, which originate from 1 D 2 , and for the 0.48-μm emission from 1 G 4 , indicating two-step excitation mechanisms