Nanohole processing of silicon substrate using surface plasmon polaritons of nano gold excited by femtosecond laser is described in comparison with the nanohole processing with transparent polystyrene (PS) nanoparticle template. Gold particles with diameters of 40, 80, or 200 nm are spin coated on the substrate, and a 100 fs, 820 nm laser pulse is used to irradiate the samples. The produced holes are analyzed by scanning electron microscopy and atomic force microscopy. A theoretical analysis of the experimental results is conducted by FDTD (Finite Difference Time Domain) simulation. The dependence of the laser fluence and particle size on the nanohole properties is studied. The nanohole profiles correspond to the field distributions on the Si substrate at low fluence region. A highest electric field enhancement factor of about 26 is obtained for gold particles with a diameter of 200 nm.
We have demonstrated the nanostructure fabrication on the Si surface by a 150 fs, 800 nm femtosecond laser pulse. The nanohole size of about 100 nm can be formed presumably by a near-field optical enhancement effect induced by the particle illumination. The nanohole size is nearly independent of the irradiated pulse number. It is found that the optical enhancement factor was about 7 in this experiment. The hexagonally arrayed nanoholes were fabricated. The diameter of the fabricated nanohole was about 90 nm and the depth was about 9 nm. In addition, using the double pulse fs laser, we demonstrated a low-loss waveguide fabrication in fused silica. A low-optical-loss waveguide is fabricated under the conditions that the first pulse energy and teh second pulse energy in the double pulse mode are 30 jJ and 160 jJ, respectively, nad the pulse time interval is 3 ps. The weak first pulse would act as a pre-conditioner of the fused silica and then the second subsequent pulse effectively induces the uniform refractive index change. This new femtosecond double pulse fabrication technique will be very promising for low-loss photonic device fabrication for photonic networks.
We report a nanohole array fabrication with a particle light enhancement effect using a femtosecond laser pulse. Two-dimensional (2-D) arrayed polystyrene (PS) nanoparticles are deposited on silicon (Si) substrates. Polystyrene spherical particles with diameters of 200, 450, and 820 nm are used. We investigated the fabricated nanohole profiles in terms of the particles diameter and irradiated laser fluence. The morphology of the nanoholes is characterized by scanning electron microscopy (SEM) and atomic force microscopy (AFM). The nanohole diameter and depth became larger and deeper as the diameter of used particle or the irradiated laser fluence is increased. The intensity enhancement factor is obtained from the experimental data by comparing the nanohole depths to the ablation rate of the Si surface without particles. The enhanced light intensity between a PS particle and a Si substrate is calculated by the finite difference time domain (FDTD) method. The calculated optical enhancement factor is consistent with the experimental value.
We will report on nanostructure fabrication on silicon (Si) substrate by 800 nm femtosecond laser pulses. Spherical alumina particles were placed on the substrate surface. After femtosecond laser irradiation at below-ablation-threshold fluences, we have successfully observed the nanoholes formation with around 100 nm in diameter using scanning electron microscope (SEM) and atomic force microscope (AFM). The dependence of nanohole formation on the laser fluence and laser pulse number was investigated. The mechanism for the nanohole drilling is the near-field optical enhancement effect induced by interaction between local surface plasmon on the particles surface and surface plasmon polariton on the Si substrate surface.
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