Fengqi Guo

Optical limiting of pentaazadentate complexes in solution for nanosecond pulses

Passive optical limiters are significant for protecting sensors and human eyes from high intensity laser. The selection of materials is still the key point for optical power limiters. The optical limiting perfor- mances have been measured for six new pentaazadentate metal com- plexes with initial linear transmission of 0.90 i na2m mcell in chloroform at 532 nm with 8 ns pulses, in which the reverse saturable absorption from the triplet!triplet excited state is responsible for the optical limiting. The optical limiting thresholds at T/T050.5 are 139 mJ/cm 2 , 350 mJ/cm 2 and 420 mJ/cm 2 for ((PMC-NO2)Cd)Cl, ((PMC-Np)Cd)Cl and ((PMC)Sm)Cl, respectively. The lowest nonlinear transmittance for ((PMC-NO2)Cd)Cl is 10%, while the incident maximum fluence reaches to 600 mJ/cm 2 . The ratios of T0 /Tlim are estimated at 2.3 to 9.0. The limiting thresholds are strongly influenced by the nature of the substitu- ents on the benzene ring and the heavy atom effect. Electron withdraw- ing groups of the complexes can enhance the limiting capability, and the heavy atom effect facilitates the decreasing of the limiting threshold.

Optical limiting behaviors of penta-azadentate metal complexes for nanosecond laser

Pentaazadentate metal complexes are a macrocyclic ligand containing 22 (pi) -electrons, which coordinate with numerous metal ions to form near coplanar configurations with excellent thermal and light stabilities. A more extended optical window between Soret (420 nm) and Q (760 nm) band in visible region provides a condition for requiring high transmittances at low incident light intensity and they are of also large third- order nonlinear optical susceptibilities comparing with porphyrins and phthalocyanines metal complexes. The third- order optical susceptibilities (chi) (3)1111 are determined at 647 nm in methanol by pump-probed procedure and the molecular second hyperpolarizabilities (gamma) 1111 which are of approximately 10-31 esu are also obtained. Optical limiting based on reverse saturable absorption are observed for ns pulses laser. The optical limiting behaviors may be alternated by introduce different substituents onto the benzene ring or/and different metal ion into the center of macrocylic ligands The limiting threshold at T/T0 equals 0.5 is 131 mJ/cm2 for complex [(PL- NO2)Cd]Cl, the corresponding clamped energy is 34 mJ/cm2. The optical limiting performance may be influenced by solution concentrations.

Excited State Absorption Cross-Sections of a Novel Terpyridyl Platinum (II) Complex

The absorption cross-sections of the singlet and triplet excited states of a novel terpyridyl platinum (II) complex have been measured using Z-scans at picosecond and nanosecond pulse widths and a variety of pulse energies.

Wavelength dispersion of two-photon absorption and two-photon-induced fluorescence of stilbazolium derivatives

Organic materials with large two-photon absorption are desired for numerous photonics applications, such as optical limiting,upconversion lasing, three-dimensional data storage,and photodynamic therapy. Stilbazolium derivatives are interesting two-photon absorbers for these applications. In this work,the nonlinear transmissivities of trans -4-[4-(dimethylamino)styryl ]-1-methylpyridinium iodide (DASPI),trans -4-(4-aminostyryl)-1-methylpyridinium iodide (ASPI),trans -4-[2-(1-methylpyrryl)vinyl ]-1-methylpyridinium iodide (MPVPI),trans -4-(2-pyrrylvinyl)-1-methylpyridinium iodide (PVPI),and trans -4-styryl-1-methylpyridinium iodide (SPI)at 800,850,900,950 and 1000 nm have been studied respectively using 21 ps laser pulses. The two-photon induced fluorescence of these compounds at 872,900,and 940 nm has also been investigated.All of these compounds exhibit two-photon absorption and two-photon induced up-converted fluorescence in the near-IR wavelengths,and the two-photon absorption cross section and two-photon induced fluorescence intensity vary with the wavelength and with the chemical structure changes. These preliminary results suggest that it is possible to increase the two-photon absorption cross-sections by proper structure modifications

Nonlinear optical properties and optical limiting performances of penta-azadentate metal complexes in solution

The passive optical limiters are of significant for protecting sensors and human eyes from high intensity laser. The selection of materials is still one of the key for optical power limiters. The nonlinear optical properties of pentaazadentate metal complexes (PMC) were measured, the third-order optical nonlinear polarizabilities of 1.19~3.38x10-13esu were obtained, from which the molecular second order hyperpolarizabilities of 8.0x10-32~2.83x10-31esu were calculated. The optical limiting performances for PMC have been studied at 532nm for 8ns and 35ps pulses by using nonlinear absorption technique, in which the reverse saturable absorptions in the T1 and S1 states were responsible for the optical limitings. Experimental results demonstrated that the peripheral substituents and center metal ions influenced the third-order optical nonlinearities and the optical limiting performances of PMC.

Optical limiting of penta-azadentate complexes in solution for picosecond pulses

The passive optical limiters are of significant for protecting sensors and human eyes from high intensity laser. The selection of materials is still the key point for optical power limiters. The optical limiting performances for five new pentaazadentate metal complexes with transmission of 0.45 - 0.70 in a 1 cm cell in tetrahydrofuran have been measured at 532 nm with 35 ps pulses, in which the reverse saturable absorption from the singletyieldssinglet excited state is responsible for the optical limiting. The optical limiting thresholds of pentaazadentate and benzopentaazadentate cadmium complexes at T/To equals 0.5 are 44 mJ/cm2 and 146 mJ/cm2 respectively, the lowest nonlinear transmittance for pentaazadentate complex I is 7.7%, while the incident maximum fluence reaches to 881 mJ/cm2. The bounds of figure of merit-like are estimated at 1.7 - 8.7. The limiting thresholds are strongly influenced by the nature of the substituents on the benzene ring. Electron withdrawing groups of the complexes can enhance the limiting capability, while the effect of heavy atom acts opposite roles. The optical limiting abilities are compared with C60, tetra- phenyl-tetrabenzoporophyrin-zinc and octanoxyl- phthalocyanine free base at same conditions. The sequence of the limiting capability is pentaazadentate cadmium complex >C60 > tetra-phenyl-tetrabenzoporphyrin-zinc > octanoxyl-phthalocyanine free base.