Huidan Zeng

Nonlinear absorption and optical limiting in gold-precipitated glasses induced by a femtosecond laser

Nonlinear absorptions of Au nanoparticles precipitated silicate glasses by irradiation of a focused femtosecond pulsed laser were investigated using Z-scan technique with 8 ns pulses at 532 nm. Optical limiting (OL) effects in such glasses have been also measured. It is observed that the behaviors of transition from saturable absorption to reverse saturable absorption and the OL performances for different samples are significantly different, which depend drastically on the irradiation power density of the femtosecond laser used for the Au nanoparticles precipitation in the glass. Strong nonlinear absorptions in these samples are mainly attributed to the surface plasmon resonance (SPR) and free carrier absorptions of the precipitated Au nanoparticles.

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.

Metal nanoparticle precipitation in periodic arrays in Au2O-doped glass by two interfered femtosecond laser pulses

We report on the precipitation control of Au nanoparticles in periodic arrays in silicate glass. Au2O-doped glass samples were first irradiated by two 800 nm interfered femtosecond laser pulses at room temperature and then heat treated at 550u200a°C for the Au nanoparticle precipitation in the laser irradiation areas. One-dimensional periodic arrays of the Au nanoparticles were controlled by changing the pulse energy and the incident angle between the interfered laser pulses. The smallest dimension in the obtained arrays was a width of 300 nm. The mechanism of the metal nanoparticle precipitation by this technique was discussed. Only two pulses are required to encode these periodic microstructures, which are applicable to emerging nanostructure devices such as optical memory with ultrahigh storage density, micrograting with high diffractive efficiency and integrative micro-optical switches.

The effect of femtosecond laser irradiation conditions on precipitation of silver nanoparticles in silicate glasses

We report the effect of femtosecond laser irradiation conditions on precipitation of silver nanoparticles in silicate glasses. Absorption spectra show that the intensity of the absorption peak due to the surface plasmon resonance of silver nanoparticles increases with increase of the light intensity of the laser beam, beam diameter in the focal plane, Rayleigh length of the focusing lens and shot number of the laser pulse. The position of the surface plasmon resonance peak remains constant regardless of the variation of the irradiation conditions. The influences of laser irradiation conditions on the size and spatial distribution of silver nanoparticles are discussed.

Laser-controlled precipitation of gold nanoparticles in silicate glasses

We report on the observation of space-selective precipitation of gold nanoparticles in Au 2 O-doped silicate glass by a method of irradiation with an 800-nm femtosecond laser and further heat treatment. The irradiated region of the glass first became gray in color after irradiation with the femtosecond laser and then turned red after further heat treatment at around 520 °C, indicating that gold nanoparticles have precipitated in the irradiated region of the glass. A possible mechanism has been suggested that the Au + ions in the region irradiated are reduced to Au° atoms by the femtosecond laser, and then the Au 0 atoms accumulate to form gold nanoparticles with the glass sample heat treated. The observed phenomenon should have potential applications in the fabrication of ultrafast all-optical switches.

Nonlinear absorption and optical limiting properties in sol-gel solidified gold nanorods

The Optical nonlinearities and optical limiting (OL) properties of Sol-gel solidified gold nanorods were investigated by using Z-scan technique and OL measurement, respectively, with nanosecond pulses at 532nm. The experimental results show that their strong nonlinear optical performances depend on the sizes of nanorods. The surface plasmon absorption is the main mechanism.

Space-selective precipitation of silver nanoparticles in AG2O-doped silicate glass by irradiation of femtosecond laser

We report on the observation of space-selective precipitation of silver nanoparticles in the Ag2O doped silicate glass in a method of irradiation with an 800nm femtosecond laser and then heat-treatment. The irradiated portion of the glass first became gray in color after irradiation of the femtosecond laser and then turned into yellow after further heat-treatment at around 400 °C. An absorption peak at 402 nm observed in the absorption spectra of the irradiated and heat-treated glass indicates that silver nanoparticles have precipitated in the irradiated region of the glass. A possible mechanism has been suggested that the Ag+ ions in the region irradiated are first reduced to Ag atoms by femtosecond laser through multiphoton absorption and then accumulate to form silver nanoparticles when glass sample was heat-treated. The observed phenomenon should have potential applications in fabrication of ultrafast all-optical switch.

Dependence of femtosecond laser irradiation and heat treatment on gold nanoparticle precipitation in silicate glass

Three-dimensionally manipulated gold nanoparticles were precipitated in silicate glass containing gold ions by irradiation with femtosecond pulsed laser and successive heat treatment. Influence of the heat treatment conditions on the gold nanoparticles precipitation behaviors was investigated. For the tested silicate glass, the treatment temperature threshold of irradiated area for color appearance was obviously lower than that of non-irradiated area. Along with increasing the treatment temperature from such threshold, the irradiated area turned to be colorful. And finally the whole glass became multicolored corresponding to a certain high temperature. Absorption spectrum measurement indicated that, under the given irradiation condition, the sizes of Au nanoparticles were obviously affected by the heat treatment temperature.

Nonlinear response properties of femtosecond-laser-induced microstructures containing gold nanoparticles inside silicate glass

Nonlinear optical properties of femtosecond laser-induced micro-structures containing gold nanoparticles in silicate glasses were investigated by using Z-scan technique with 8ns pulses at 532nm. Optical limiting effects of such structures were also measured. The experimental results were found to be significantly variable for the microstructures under different induction conditions. Strong optical nonlinearities in these yielded structures can be attributed to the surface plasmon absorption of gold nanoparticles precipitated in glasses. These microstructures exhibiting large optical nonlinearities are inferred to be useful for the fabrication of integrated ultrafast optical switching and laser protection devices.