Molecular Two-photon Absorption Cross-section Research Articles

Aggregation Enhancement on Two-Photon Optical Properties of AIE-Active D-TPE-A Molecules

We present an aggregation enhancement in two-photon-excited fluorescence (TPEF) of about 2 orders of magnitude in a series of novel noncentrosymmetric D-π-A molecules. Detailed analysis shows that their TPEF is enhanced concomitantly with both fluorescence quantum efficiency and two-photon absorptivity. These D-π-A molecules use tetraphenylethylene (TPE) as the π-bridge, giving them aggregation-induced emission characteristics. These branched or butterfly-configured molecules demonstrate two-photon absorption (TPA) transition bands similar to those in their linear absorption. The molecular TPA cross sections in the aggregation environment reach around 50–130 GM, and peak within the available wavelength range of a Ti:Sapphire femtosecond oscillator, which makes the molecules quite favorable for bioimaging applications. We observe that two-photon absorptivity increases progressively with the addition of more donor and acceptor moieties on the TPE backbone, which is presumably attributed to the improved conj...

Large Two‐Photon Absorption of Terpyridine‐Based Quadrupolar Derivatives: Towards their Applications in Optical Limiting and Biological Imaging

Developing organic chromophores with large two-photon absorption (TPA) in both organic solvents and aqueous media is crucial owing to their applications in solid-state photonic devices and biological imaging. Herein, a series of novel terpyridine-based quadrupolar derivatives have been synthesized. The influences of electron-donating group, type of conjugated bridge, as well as solvent polarity on the molecular TPA properties have been investigated in detail. In contrast to the case in organic solvents, bis(thienyl)-benzothiadiazole as a rigid conjugated bridge will completely quench molecular two-photon emission in aqueous media. However, the combination of alkylcarbazole as the donor and bis(styryl)benzene as a conjugation bridge can enlarge molecular TPA cross-sections in both organic solvent and aqueous media. The reasonable two-photon emission brightness for the organic nanoparticles of chromophores 3-5 in the aqueous media, prepared by the reprecipitation method, enables them to be used as probes for in vivo biological imaging.

3,3′-Benzene-1,4-diylbis[1-(substituted)phenylprop-2-en-1-one] derivatives: A new class of materials for third-order nonlinear optical applications

We have investigated the third-order nonlinear optical parameters of Bischalcones embedded in DMF solution and in solid PMMA matrix, by Z-scan technique using nanosecond laser pulse trains at 532 nm. Z-scan results reveal that the Bischalcones exhibits negative nonlinear refractive index as high as 10 −11 esu. The molecular two-photon absorption cross-section σ 2 ′ of Bischalcones were of the order 10 −46 cm 4 s/photon, which is nearly two orders of magnitude larger than that of Rhodamine 6G which is 10 −48 – 10 −50 cm 4 s/photon. We found that, the two-photon absorption (TPA) is the dominating nonlinear process leading to nonlinear absorption in both the cases in solution and as well as in solid medium. Based on TPA process, the Bischalcones exhibit good optical power limiting of nanosecond laser pulses at the input wavelength. The nonlinear optical parameters found to increase on enhancing the strength of the electron donor groups indicating the dependence and importance of electron donor/acceptor units on third-order nonlinear optical susceptibility χ (3).

Two-photon absorption properties of substituted porphyrins

The two-photon absorption (TPA) properties of two newly synthesized substituted porphyrins: 5,10,15,20-tetra-(4-pyrrolidinylphenyl)porphyrin (1) and 5,10,15,20-tetra-(4-diphenylamino-benzoic acid phenyl) porphyrin ester (3) were measured by the femtosecond Z-scan technique at 800 nm Ti : sapphire laser and by direct nonlinear optical transmission (NLT) using nanosecond Nd : YAG laser. The substituent effects, pumped wavelength and the environment upon the molecular TPA cross-section were investigated. It is found that the TPA cross-section for 3 is enhanced under excitation of 800 nm, relative to its precursor, 5,10,15,20-tetra(4-hydroxyphenyl) porphyrin (2), due to the former possessing extension conjugation of "D-A-core-A-D" molecular architecture. Also sample 3 obtained an increased TPA cross-section in rigid film relative to that in solution, suggesting that the enhancement is facilitated by the quasi-planar structure which allows direct interbranch conjugation throughout the molecule.

Large third-order nonlinear optical response of porphyrin J-aggregates oriented in self-assembled thin films

The preparation and characterization of a self-assembled material showing a high nonlinear response and good photostability to ultrashort laser pulses is presented. The material is built by alternate deposition of tetrakis(4-sulfonatophenyl)porphyrin diacid (H4TPPS2−) and poly(diallyldimethylammonium chloride) (PDDA) forming electrostatically self-assembled multilayers (ESAMs). UV-visible absorption and emission experiments show that in this matrix H4TPPS2− is present mainly in its J-aggregated form. Furthermore, linear dichroism experiments on a 3 bilayer film show a preferential alignment of the porphyrin aggregate with the J-band transition dipole moment parallel to the film surface. The two photon absorption (TPA) properties of these films are investigated with the Z-scan technique at 806 nm, employing 130 fs pulses. The samples exhibit strong nonlinearities with a very large two-photon absorption coefficient βTPA of 50 cm GW−1. The origin of this large response is investigated. It has been already demonstrated that aggregation enhances the molecular TPA cross section of H4TPPS2− from 30 to 1000 GM in water solution thanks to cooperative effects. In a 20 bilayer film a further increase by a factor of 1.7 is observed and explained in terms of preferential alignment of J-aggregates in the multilayers.

Upconversion fluorescence and optical power limiting effects based on the two- and three-photon absorption process of a new organic dye BPAS.

A new organic dye, trans-4, 4'-bis(pyrrolidingl) stilbene (BPAS), with large two-photon absorption (TPA) and three-photon absorption (3PA) has been synthesized. The molecular TPA cross section sigma2' at 550-670 nm and the 3PA cross section sigma3' at 720-1000 nm have been measured. The biggest sigma2' and sigma3' was 5.77 x 10(-47) cm4s/photon and 27 x 10(-75) cm6 s2 at 600 and 980 nm, respectively. In the experiment process we found that the strongest TPA wavelength is not at two times of the strongest linear absorption wavelength, but there is some blue shift. The 3PA-induced optical power-limiting properties have also been illustrated at 980 nm.

Two-photon pumped upconversion and nonlinear optical properties of a new lasing dye: HMASPS

Two-photon pumped frequency upconversion optical properties and two-photon absorption (TPA) induced nonlinear absorption of a new dye, trans-4-[p-(N-hydroxyethyl-N-methylamino)styryl]-N-methylpyridinium ptoluene sulfonate (abbreviated to HMASPS) have been experimentally investigated. This new dye exhibits strong superradiation properties when the pumping power is above its threshold. The superradiation upconversion efficiency from 900 to 1150 nm and the nonlinear absorption from 720 to 1100 nm have been measured. The largest effective molecular TPA cross-section was measured to be 44.3 × 10−48 cm4·s·photon−1at 920 nm. At 1064 nm, it was 2.77 × 10−48 cm4·s·photon−1, much smaller than that at 920 nm. The highest conversion efficiency is 7% at 990 nm, whereas 4.2% at 1064 nm.

Two-Photon Absorption and Optical Power Limiting Based on New Organic Dyes

Two new organic dye samples J and L with a large two-photon absorption(TPA) cross section have been reported. The linear absorption spectra showthat there is no linear absorption at the wavelength from 650 to 1200 nm.The molecular TPA cross section was measured to be ashigh as 2.59×10-47 cm4·s and 2.98×10-47 cm4·s at 1064 nm for samples J andL, respectively. The input-output curves indicate that there is a clearoptical power limiting behaviour when the input intensity is higher than0.4 GW/cm2. Furthermore, the basic theory of the TPA process has beendiscussed.

Two-photon absorption and frequency-upconversion properties of a new organic dye HMASPS

Two-photon absorption (TPA) and frequencyupconversion properties of a new upconversion laser dyetrans-4-[p-(N-hydroxyethyl-N-methyl-amino)styryl]-N-methylpyridinium toluene-p-sulfonate (abbreviated to HMASPS) were reported in this note. The linear absorption, TPA, single-photon induced fluorescence, TPA induced fluorescence and TPA induced upconverted lasing spectra of HMASPS solution in dimethyl formamide (abbreviated to DMF) were measured at room temperature. The red shift for the central wavelength of TPA induced fluorescence peak, which was compared with that of the single-photon induced fluorescence peak, and the blue shift for that of TPA induced upconverted lasing compared with that of TPA induced fluorescence, were explained by using re-absorption effect. TPA peak was at 930 nm. There is an 11 nm blue shift for two-photon energy of TPA peak compared with the linear absorption peak. The molecular TPA cross-section σ2 9′ at 1064 nm was measured to be 6.0×10−48 cm4 · s/photon by using the open aperture Z-scanning system. The highest upconversion efficiency was measured to be 8.4% at 1064 nm.

Nonlinear optical properties of a new two-photon-absorption organic dye: HEASPS

Trans-4-[p-(N-hydroxyethyl-N-ethylamino)styryl]-N-methylpyridinium p-toluene sulfonate (abbreviated as HEASPS) is a two-photon-absorption (TPA) dye newly synthesized by our research group. It possesses a much larger TPA cross-section and much stronger upconversion fluorescence emission than those of common organic dyes (such as rhodamine) when excited with near-infrared (IR) radiation. TPA spectrum and upconversion efficiency spectrum of HEASPS solution at different wavelengths have been measured. The largest molecular TPA cross-section σ2 ′ is measured to be 2.06×10-47 cm4 s/photon at 930 nm. At 1064 nm, σ2 ′ is 2.71×10-48 cm4 s/photon, which is only one-ninth of that at 930 nm. The upconverted lasing efficiency spectrum has been measured at different wavelengths. The highest efficiency is 5.1% at 1020 nm, whereas it is 3.5% at 1064 nm. Its optical-power-limiting properties at 930 nm have also been illustrated.

Two-photon absorption and nonlinear optical properties of a new organic dye PSPI

Trans-4-[ p-(pyrrolidinyl)styryl]- N-methylpyridinium iodide (abbreviated as PSPI thereafter) is a two-photon absorption (TPA) dye newly synthesized by our research group. It possesses much larger TPA cross-section and much stronger upconversion fluorescence emission than those of common organic dye (such as rhodamine) when excited with near infrared (IR) radiation. TPA spectrum and upconversion efficiency spectrum of HEASPI solution at various wavelengths were measured. There is 34 nm blue shift for the central wavelength of the TPA induced absorption peak compared with two times of the linear absorption peak. The biggest molecular TPA cross-section σ 2 ′ is 2.85×10 −47 cm 4 s/photon at 930 nm. At 1064 nm, σ 2 ′ is 3.12×10 −48 cm 4 s/photon. The highest efficiency is 3.9% at 1010 nm, whereas 2.9% at 1064 nm. Its optical power limiting properties at 930 nm have also been illustrated.

Two-photon Absorption and Nonlinear Optical Properties of a New Organic Dye Trans-4-[p-(N-hydroxyethyl-N-methylamino)styryl]-N-methylpyridinium p-toluene Sulfonate

Trans-4-[p-(N-hydroxyethyl-N-methylamino)styryl]-N-methylpyridinium p-toluene sulfonate (abbreviated as HMASPS) is a newly synthesized dye that possesses a much greater two-photon-absorption (TPA) cross-section and much stronger upconversion fluorescence emission than common dyes (such as rhodamine) when excited with near infrared laser radiation. TPA induced upconverted lasing has been obtained in HMASPS solution in dim eth ylformamide (abbreviated as DMF) pumped by near infrared laser beam from 900 to 1150 nm. The central wavelength and bandwidth of the lasing are 626 nm and 26 nm. The upconversion efficiencies of 1cm-path HMASPS solution in DMF at 0.05 mol/l concentration at different wavelengths from 900 to 1150 nm were measured. The net upconversion efficiency from the absorbed pump energy to the upconverted lasing output was 14% at the pump energy level of 2.04 mJ when the pump laser beam was provided by Nd:YAG laser. The molecular TPA cross-section at 1064 nm was σ2=6.0×10-48 cm4·s/photon measured by using an open aperture Z-scan system. The linear absorption, single-photon induced fluorescence, two-photon induced fluorescence and two-photon induced upconverted lasing properties have also been studied in this paper.

Two‐Photon Absorption and Excited‐State Refractions in Anthraquinone Dyes

AbstractWe examine the nonlinear optical properties of solutions of 9,10‐anthraquinone, 1,4‐dihydroxy‐anthraquinone, 5,8‐dichloro‐1,4‐dihydroxy‐anthraquinone and 1,4‐bisethylamino‐anthraquinone by means of the intensity‐dependent transmission and the Z‐scan method with 532 nm 8 ns pulses. The results demonstrated that the 9,10‐anthraquinone displayed a two‐photon absorption (TPA) character. The molecular TPA cross section of this compound is estimated as σ2 = 7.22 × 10−19 cm4/GW or σ2 = 26.96 × 10−48 cm4/photon/s, respectively, and an essential state of ‘m1Ag’, which should be located near the 2ω virtual transition state, is predicted. On the other hand, the effective excited‐state nonlinear refractive coefficients n2eff of these anthraquinones are found to be ∼10−10 esu, which are comparable with those highly conjugated planar molecules of tetrabenzporphyrins and phthalocyanines.

Nonlinear optical properties of a new chromophore

Strong two-photon-absorption (TPA) based nonlinear optical properties of a new chromophore, N, N-diphenyl-7-[2-(4-pyridinyl) ethenyl]-9,9-di-n-decyl-fluoren-2-amine (AF-50) has been experimentally studied. Under excitation with 10-Hz, ∼8-ns, and ∼800-nm laser pulses, the TPA cross section and the TPA-induced frequency-upconverted emission spectra are measured for AF-50 solutions in various solvents. The most attractive feature of this chromophore is its remarkably high value of the molecular TPA cross section (∼78×10-20 cm2/GW in benzene solution). Based on this feature, superior optical power limiting and stabilization performance has been demonstrated in a 1-cm-long AF-50 solution sample with concentration of d0=0.045 M/L. The nonlinear transmission of the measured sample decreased from ∼0.93 to ∼0.3 when the input-beam intensity increased from ∼10 MW/cm2 to ∼360 MW/cm2; the relative intensity fluctuation of the output laser pulses was reduced to one third of that of the input laser beam.

Efficient, two-photon pumped green upconverted cavity lasing in a new dye

Two-photon pumped green cavity lasing has been observed in a solution of a new dye in N,N-dimethyl formamide (DMF). The dye, 4-[N-(2-hydroxyethyl)-N-(methyl) amino phenyl]-4′-(6-hydroxyhexyl sulfonyl) stilbene, abbreviated as APSS, shows a strong two-photon absorption induced fluorescence when excited at 800 nm. The molecular two-photon absorption cross section was measured to be σ 2 = 1.5 × 10 −19 cm 4/GW or σ′ 2 = 3.8 × 10 −47 cm 4/photon/s, and is 1 to 2 orders of magnitude higher than Rhodamine 6G. The peak of the lasing spectrum was around 555 nm, and is to the best of our knowledge, the shortest wavelength obtained from a two-photon pumped dye laser. The conversion efficiency from the absorbed pump energy to the lasing output energy was as high as 2.8%. The absorption and the fluorescence spectra of the new dye, along with the spectral and temporal behavior of the two-photon pumped lasing output is presented.

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.