The optical limiting performance of platinum nanoparticle protected by C60 derivative in chloroform, ethanol and dimethylformamide (DMF) was measured with 532nm, 8ns duration laser pulses. Experiments showed that the optical limiting is solvent-dependent. The origins and solvent effect of the optical limiting were analyzed. It was proposed that the absorption-induced scattering is the main mechanism causing the optical limiting behavior and solvent effect.
We investigate the formation of ripple and nanohole induced by femtosecond laser pulses on the surface of silicon. Periodic ripples aligned perpendicular to the direction of laser polarization has been observed. The period of the periodic ripples decreases with the increasing pulse number. Particularly aperiodic ripples with orientation parallel to the laser polarization are formed depend on the number of laser pulses and energy. The nanohole arrays are formed on the overlapped areas of periodic and aperiodic ripples. The interference between the surface scattered or excited wave and the laser itself is proposed to explain the decrease of ripple period.
In this paper, we demonstrated the fabrication of laser-induced holes in the gold film of 50nm thickness using 120fs laser pulses at 800nm wavelength in air environment. The surface morphologies¬microstructures and diameters of holes were characterized using atomic force microscopy (AFM). It was found that, there are two kinds of thresholds of laser fluence for the formation of holes. And the diameters of holes were influenced by pulse energy and shot numbers. Based on the investigation above, the origin of the holes was discussed.
The propagation and split of the filamentation of femtosecond pulses in air have been paid much attention since last a few years. However, most research works are performed with few considerations of the turbulence effects of atmosphere due to the difficulties of utilizing analytical solutions and experiment conditions. In this work, we will attempt to introduce a kind of numerical simulation method to analyze the transmission features of femtosecond laser pulses in air or in the turbulent air, namely, it is called multi-phase screen method (MPSM) which use phase screen to simulate atmospheric turbulence. In this presentation, the main laser parameters are as follows: 85 fs pulse-width, 0.8cm radius of the beam, the two kinds of 160GW and 1.0 TW peak-power operating at 800 nm. Then utilizing the structure of Vortex soliton to control the filamentation is proposed. In our cases, four Gaussian pulses with a difference of π/2 in the phase of each adjacent beam as a ring to control the filamentation by utilizing its characteristics of the vortex soliton. Some results show that the coupling and interaction among four Gaussian pulses cause the rotational transfer of the energy of the four beams. Finally, we obtain the transmission features of the beams propagating in the turbulent air with different intensities by the MPSM.
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.