Manipulating four-photon absorption of ZnO via Ga doping.

Multi-photon absorption in the second near-infrared (NIR-II) regime has attracted extensive attention due to biological imaging and frequency-upconverted lasing applications. We report the dispersion of four-photon absorption (4 PA) response in pristine and Ga-doped ZnO single crystals over the spectral range 1180-1350 nm. Femtosecond Z-scan results demonstrate that Ga doping can significantly enhance the 4 PA coefficient β of ZnO.

Synthesis, Photophysical, and Optical Limiting Properties of Twistacene-Functionalized Arenes.

To realize the relationship of structure and property, four novel twistacene-functionalized arenes, namely, 1,4-bis(2,7-di--butyl-9,14-bis(4-(-butyl)phenyl)dibenzo[,]tetracen-11-yl)buta-1,3-diyne (), 1,4-bis(3,5,10,12-tetra--butyltribenzo[,,]coronen-16-yl)buta-1,3-diyne (), 1,4-bis(2,7-di--butyl-9,14-bis(4-(-butyl)phenyl)dibenzo[,]tetracen-10-yl)buta-1,3-diyne (), 1,4-bis(3,5,10,12-tetra--butyltribenzo[,,]coronen-15-yl)buta-1,3-diyne (), linked with butadiyne as π bridges have been strategically synthesized and characterized. The nonlinear optical properties are detailly examined in solution through the open-aperture Z-scan method in a comparative manner, indicating that molecules and exhibit better nonlinear optical responses than and . Among them, and exhibit excellent optical limiting responses with limiting thresholds of 0.

Ultrafast nonlinear absorption with multiple transformations and transient dynamics of gold nanobipyramids.

The process and condition of saturable absorption (SA) and reverse saturable absorption (RSA) of ultrafast nonlinear optics in metal nanoparticles are essential for applications including light generation, amplification, modulation, and switching. Here, we first discover and explore the multiple transformations (SA-RSA-SA) of ultrafast nonlinear absorption behavior of metal nanoparticles in femtosecond pulses. Correspondingly, the energy level model and fitting formula of multiple transformations are established to illustrate the process of optical response.

Enhanced Ultrafast Broadband Reverse Saturable Absorption in Twistacenes with Enlarged π-Conjugated Central Bridge.

Optical nonlinearities of two all-carbon twistacenes, and , with the different π-conjugated central bridges were investigated. The nonlinear absorption properties of these compounds were measured using the femtosecond Z-scan with wavelengths between 650 and 900 nm. It has been found that the nonlinear absorption originated from two-photon absorption (TPA) and TPA-induced excited state absorption (ESA), wherein demonstrates higher performance than .

Enhancement of Two-Photon Absorption in Boron-Dipyrromethene (BODIPY) Derivatives.

The linear and nonlinear optical properties of two BODIPY derivatives, 1,7-Diphenyl-3,5-bis(9,9-dimethyl-9H-fluoren-2-yl)-boron-diuoride-azadipyrromethene (ZL-61) and 1,7-Diphenyl-3,5-bis(4-(1,2,2-triphenylvinyl)phenyl)-boron-diuoride-azadipyrromethene (ZL-22), were comprehensively investigated based on experimental and theoretical studies. It was found that both compounds show a strong two-photon absorption response in the near-infrared regime, and the two-photon-absorption cross-section values of ZL-61 and ZL-22 were determined to be 8321 GM and 1864 GM at 800 nm, respectively. The improvement of the two-photon absorption cross section in ZL-61 was attributed to the enhancement of the donor group, which was confirmed by transient absorption measurements and DFT calculation.

An investigation of broadband optical nonlinear absorption and transient nonlinear refraction in a fluorenone-based compound.

A novel fluorenone derivative, FO52, is designed and synthesized. The fluorenone group is introduced to provide the central π-conjugated system in the molecule and triphenylamine is substituted at both sides. Intramolecular Charge Transfer (ICT) from the terminal groups to the molecular center is confirmed DFT calculations.

Correction: D-π-A type conjugated indandione derivatives: ultrafast broadband nonlinear absorption responses and transient dynamics.

[This corrects the article DOI: 10.1039/D2RA00349J.].

D-π-A type conjugated indandione derivatives: ultrafast broadband nonlinear absorption responses and transient dynamics.

The ultrafast nonlinear optical response of two 1,3-indandione derivatives (INB3 and INT3) was systematically investigated by the femtosecond Z-scan and pump-probe technique at multiple visible and near infrared wavelengths. Both compounds show strong broadband nonlinear absorption (NLA) and different wavelength-dependent two-photon absorption (TPA) characteristics in the range of 650-1100 nm. The TPA cross section of trithiophene-based compound INT3 was found to be larger than that of triphenylamine-based compound INB3 in the red region (650-800 nm), which is attributed to its longer π-conjugated structure and better molecular planarity.

Tuning Nonlinear Optical Behavior by Incorporation of the Chalcogenophene into Twistacenes.

Four chalcogenophene-fused acenes containing O, S, Se, or Te, respectively, were presented, and the chalcogenophene effect on linear and nonlinear optics was systematically investigated. Their excited-state absorption performance and two-photon absorption (TPA) capacity could be modulated by the incorporating chalcogen atoms. The experimental results showed that the heavy chalcogen facilitated the intersystem crossing resulting in the presence of the triplet state absorption for and , and the TPA capacity gradually increased with the atomic size of the chalcogens.

Anthracene derivatives as broadband nonlinear optical materials: nonlinear absorption and excited-state dynamics analysis.

Two anthracene derivatives, AN-1 and AN-2, with different π-bridge lengths were designed and synthesized to investigate their optical nonlinearities. The nonlinear absorption (NLA) properties of both derivatives were measured the femtosecond Z-scan technique with the wavelength range from 532 nm to 800 nm. The reverse saturable absorption (RSA) of both compounds results from two-photon absorption induced excited-state absorption (TPA-ESA).

Ultrafast broadband nonlinear optical properties and excited-state dynamics of two bis-chalcone derivatives.

The development of organic nonlinear optical (NLO) chromophores is vital for various fields such as two-photon biomedical imaging, optical limiting, In this work, two bis-chalcone molecules 1,4-bis[3-(2,4-dimethoxyphenyl)-2-acryloyl]benzene (C1) and 4,4'-bis[3-(2,4-bimethoxy phenyl)-2-acryloyl]biphenyl (C2) were synthesized and characterized. The excited-state dynamics of these two chromophores were studied using femtosecond transient absorption (TA) measurements. And their broadband nonlinear absorption properties and optical limiting (OL) response were investigated by femtosecond open-aperture Z-scan and intensity-dependent transmittance measurements in the wavelength range from 515 nm to 800 nm, respectively.

Synthesis, self-assembly and nonlinear optical activity of selenium-annulated perylene diimide.

A novel Se-annulated perylene diimide derivative tethered with polyhedral oligosilsesquioxane (POSS) nanoparticles (POSS-2SePDI-POSS) was designed and prepared. The introduction of selenium atoms endows POSS-2SePDI-POSS with significant fluorescence quenching but enhanced excited-state absorption. As a result, POSS-2SePDI-POSS exhibits a distinct reverse saturable absorption characteristic, suggesting its potential application in optical limiting.

Morphology-dependent third-order optical nonlinearity of a 2D Co-based metal-organic framework with a porphyrinic skeleton.

A two-dimensional (2D) Co-based metal-organic framework (MOF) with porphyrinic skeleton forms crystalline plates, flower-shaped clusters, and ultrathin films under optimized conditions, including the use of polyvinylpyrrolidone (PVP) as a surfactant. Ultrathin films demonstrate the best solution-based third-order nonlinear optical properties, featuring a nonlinear transmittance (T) value of 0.54, absorption coefficient (α2) of 9.

Polyhedral oligosilsesquioxane tethered perylene diimide for application in optical limiting and rapid detection of fluoride ions.

A novel perylene diimide derivative equipped with polyhedral oligosilsesquioxane nanocages (POSS-AMPDI) was designed and synthesized for application in optical limiting. Moreover, due to the dual mechanisms of POSS collapse and intermolecular proton transfer, POSS-AMPDI exhibits high sensitivity and rapid selectivity to fluoride ions, with a detection limit as low as 1.64 × 10-8 M.

Rectangle and [2]catenane from cluster modular construction.

Reaction of [Et4N][Tp*WS3] (1) with [Cu(MeCN)4]PF6, CsCl, isonicotinic acid and CuCN, and treatment of [Et4N][Tp*WS3(CuCl)3] (2)/[Et4N][{Tp*WS3Cu3Cl}2(μ-Cl)2(μ4-Cl)] (3) with AgOTf and bpp (Tp* = hydridotris(3,5-dimethylpyrazol-1-yl)borate; bpp = 1,3-di(4-pyridyl)propane) give rise to [Et4N]2[{Tp*WS3Cu3(CN)0.5}2(μ-Cl)2(μ4-Cl)]2(PF6)2 (4) and [(Tp*WS3Cu3)2(μ3-Cl)2(bpp)3]2(OTf)4 (5), respectively. Compounds 4 and 5 feature cluster-based rectangle and [2]catenane architecture, and both exhibit enhanced third-order nonlinear optical responses relative to those of 1.