Guangyu Fang

Optical nonlinearities of space selectively precipitated Au nanoparticles inside glasses

Optical nonlinearities of Au nanoparticles precipitated inside glasses induced by irradiation of a focused femtosecond laser were investigated using Z-scan technique with 8 ns pulses at 532 nm. The transformation behaviors both from self-defocusing to self-focusing and from saturable absorption to reverse saturable absorption were observed in the glass samples, which depend drastically on the irradiation power density of the femtosecond laser used. The optical nonlinearities were analyzed in detail and proved numerically by the excited-state theory of conduction band electrons.

Excited-state absorption and optical-limiting properties of organometallic fullerene–C60 derivatives

Singlet excited-state absorption properties and optical limiting behaviors of organochromium and organomolybdenum C60 derivatives (C89H24CrO3P2 and C89H24MoO3P2) were studied by using a double frequency ns/ps Nd:YAG pulse laser system at wavelength of 532 nm and pulse width 21 ps. The experimental results demonstrated that the optical limiting behavior of organochromium C60 derivative is better than both organomolybdenum C60 derivative and fullerene–C60 itself. The experimental results agree well with the singlet excited-state absorption theory.

Optical limiting properties of phthalocyanine-fullerene derivatives

The solubility of fullerene (C60) is improved by combining it with an alkyl group of substituted copper (II) phthalocyanine (CuPc) through Diels–Alder reaction. Optical limiting properties of this compound were investigated by using a double frequency Nd:YAG laser system at a wavelength of 532 nm with pulse duration of 45 ps. The results show that there are two separated conjugation systems in this kind of molecule. Both of them independently contribute to the reverse saturable absorption. Broadband optical limiting materials might be designed based on the combination of various optical limiting molecules through covalent bonds. Phase separation problems existing in the mixture of various materials can be avoided.

Optical nonlinearity and optical limiting properties of new metal cluster [WOS3Cu3I(2-MePy)3]

Abstract Optical limiting property of the new cluster [WOS 3 Cu 3 I(2-MePy) 3 ] is studied. The comparison of the optical limiting performance of this compound with that of C 60 fullerene has demonstrated to be superior to the C 60 fullerene. The optical limiting behavior of the cluster can be attributed to the excited-state absorption, which is measured by using Z -scan technique.

Z-scan of excited-state nonlinear materials with reverse saturable absorption

Abstract The nonlinear refraction property of excited-state nonlinear optical materials was studied based on rate-equation theory. The effects of the ratios of excited-state absorption cross section and refrangibility to those of ground state upon their nonlinear refraction properties were analyzed. The nonlinear optical properties of ( m -MeC 6 H 4 ) 5 C 60 H-toluene solution were investigated by using Z -scan method with 8 ns 532 nm laser pulses. The solution was proved to possess strong nonlinear absorption and weak nonlinear refraction.

Two interesting heterobimetallic compounds [MOS3Cu3(4-pic)6]·Br (M=Mo, W) with cationic cluster: synthesis, structural characterization, non-linear response and large optical limiting properties

Abstract Two heterobimetallic cluster compounds [MOS 3 Cu 3 (4-pic) 6 ]·Br (M=Mo, W) with cationic cluster skeleton and halide anion Br − synthesized by the reaction of (NH 4 ) 2 MOS 3 , CuBr and 4-picoline (4-pic) are presented. Their structures have been crystallographically determined and such nest-shaped cationic clusters, obtained for the first time, are interesting in comparison with the analogical nest-shaped clusters with a neutral skeleton or anionic skeleton. The non-linear optical (NLO) properties of these two clusters are investigated with an 8 ns pulsed laser at 532 nm. These two clusters exhibit large optical limiting abilities with limiting thresholds F th =0.18 J cm −2 ( 1 ) and F th =0.15 J cm −2 ( 2 ), respectively. Both compounds show strong third-order NLO absorption effects ( α 2 -value of 1.6×10 −10 m W −1 ( 1 ), 2.8×10 −10 m W −1 ( 2 )) and self-focusing performance ( n 2 -value of 4.56×10 −11 esu ( 1 ), 4.62×10 −11 esu ( 2 )) in 3.86×10 −4 mol dm −3 ( 1 ) and 8.89×10 −4 mol dm −3 ( 2 ) DMF solution separately. The corresponding effective NLO susceptibilities χ (3) are 5.4×10 −12 esu ( 1 ) and 5.5×10 −12 esu ( 2 ) while the corresponding hyperpolarizabilities ( γ ( 1 ) =2.51×10 −31 esu and γ ( 2 ) =1.03×10 −31 esu) are also reported.

Large picosecond optical limiting properties of a novel planar cluster [WS4Cu4I2(py)6] for picosecond laser pulse

Abstract Large optical limiting response of a novel pentanuclear planar metal cluster [WS 4 Cu 4 I 2 (py) 6 ] were studied by using a double-frequency ns/ps Nd:YAG pulse laser system at wavelength of 532 nm and pulse width of 40 ps. The optical limiting results were discussed based on non-linear absorption theory. The non-linear absorption performance of the metal cluster is better than that of fullerene-C 60 .

Signs alteration of nonlinear refraction of cubane-like shaped clusters from nanosecond to picosecond pulses

Abstract The excited-state nonlinear refraction of a novel cubane-like shaped metal cluster MoOS 3 ICu 3 (2-Mepy) 3 in DMF solution is studied by using Z -scan measurement technique with laser pulses of 10 ns and 40 ps pulse width at the wavelength of 532 nm, respectively. For picosecond pulses the compound possesses a self-focusing property, the positive nonlinear refraction is attributed to population transitions among singlet states, while for nanosecond pulses it exhibits a self-defocusing property and the negative nonlinear refraction is attributed to population relaxing to triplet states.

Excited state optical nonlinearity of cubane-like shaped clusters

Abstract Nonlinear absorption and refraction of novel cubane-like shaped metal clusters WOS 3 Cu 3 I(2-Mepy) 3 (I) and MoOS 3 Cu 3 I(2-Mepy) 3 (II) in DMF solution are studied by using Z -scan measurement technique with laser pulses of 10 ns pulse-width at the wavelength of 532 nm. The compound (I) possesses a self-focusing property, while compound (II) exhibits a self-defocusing property. The refractive nonlinearity of the cluster can be attributed to the excited-state nonlinear refraction effect. A theoretical model of the excited-state refraction is presented to analyze the experimental results. The theoretical results are in good agreement with the experimental data. The condition of the sign change of nonlinear refraction is also studied.

Nonlinear optical and optical limiting properties of a novel cluster [WS4Cu4I2(py)6]

Abstract The optical nonlinearity of a new pentanuclear cluster WS 4 Cu 4 I 2 (py) 6 was investigated by using the Z-scan method. The cluster has a strong nonlinear absorption and self-focusing property. The optical limiting power of the cluster in DMF was stronger than that of C60–toluene and the reported cluster with the same structure and skeleton atoms but different peripherical ligands. The experimental results were analyzed based on the rate-equation theory.