As a new lightweight material, Carbon Fiber-reinforced polymer (CFRP) has been widely used in various fields, but its difficult-to-machine characteristic also severely restricts its application. In this paper, femtosecond laser with center wavelength of 400nm and 800nm was used for multi-pass scanning processing of CFRP to study the relationship between laser wavelength and processing quality and processing efficiency, and try to obtain smaller heat affected zone (HAZ). The experimental results show that when the experimental conditions are the same, the HAZ obtained by femtosecond laser processing of CFRP with the wavelength of 400 nm is about half that of the wavelength of 800 nm, and the minimum can reach 1.5μm, but the width of slit is smaller than that obtained by femtosecond laser processing with the wavelength of 800 nm. Therefore, reducing the wavelength of femtosecond laser can effectively reduce the HAZ, but at the same time, it will also reduce the processing efficiency.
Graphene has emerged excellent electronic, optical and mechanical properties as a layered semiconductor, and opening its bandgap through modulation further expands its practical applications. Direct laser writing has been widely used in material modulation, owing to its high precision, convenient local processing capacity. As an important factor, laser parameters play a crucial role in the ablation of materials. In this paper, the influence of laser parameters on the ablation was investigated by adjusting the energy and numbers of laser pulse. The saturation of ablation was found in the case of 500 pulses, and the ablation threshold of graphene paper was calculated to be 0.2 J/cm2. The results above have a positive effect on the modulation and the further devices fabrication of graphene paper.
Recently, the application of femtosecond laser ablation of nickel to prepare super-hydrophobic structures in marine anticorrosion has become more and more mature, but the processing efficiency is slow, which limits its large-scale application. In this study, a method for improving the efficiency of ablating nickel through multiple scanning of femtosecond lasers single pulse is proposed. The experimental results show that when the total processing time is the same, the higher scanning speed and more scanning times will promote the increase of the groove depth formed by the ablated nickel compared with the low scanning speed. This phenomenon has been verified under three different laser fluences. Compared with 25 um/s, the ablation efficiency is increased by 42.6%, 48.2% and 55.4% when scanning speed is 200 um/s, respectively. The difference in ablation efficiency in the experiment is related to the fact that femtosecond laser ablation of nickel will change the physical and chemical properties of the bottom of the material.
Coherent anti-Stokes Raman scattering (CARS) microscopy is an attractive technique for label-free biochemical-specific characterization of biological specimens. However, it has very low sensitivity in monitoring and imaging molecules present in extremely low concentrations or at fast speeds. To improve this sensitivity, especially for multiplex CARS, the intensity of the pump beam and broadband Stokes beam should be enhanced simultaneously. Therefore, the gold shell particle and gold surface are demonstrated to enhance the forward and backward CARS, respectively. Results show that a signal enhancement factor of ∼25,000 can be achieved for the gold surface and an even higher enhancement factor can be achieved for the gold shell particles. Thus, we can obtain an enhanced CARS signal in a broad spectral range, which will substantially improve the detection sensitivity of hyperspectral CARS spectroscopy and imaging.
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