Research On Preparation And Application Of Periodic Ripples By The Interference Of Two Femtosecond Laser Beams

Femtosecond laser has the characteristics of ultra-short and ultra-intense,which shows the advantages of high quality and high precision in micro/nano manufacturing.At present femtosecond laser processing has been widely used in aerospace,microelectronics,biomedicine and other fields.Surface periodic nanostructures can be induced by laser excitation of plasma and surface plasmons on the material surface.In this paper,we build a femtosecond laser two-beam interference system,and study the periodic surface structure induced by femtosecond laser.The main research results are as follows:1.A new method for monitoring the co-point and co-occurrence of femtosecond laser two-beam interference experiments is introduced.The advantages of real-time monitoring of co-point and simultaneous signals by CCD camera are discussed.It is found that this method has characteristics of wide applications,convenient operation and few limitations.In the experiment of double-beam interference,the BBO crystal needs to be customized,the price is relatively expensive,and the double frequency signal is not easy to monitor,which provides a new idea for the efficient monitoring of simultaneous signals.2.The fabrication of material surface structure by 515 nm femtosecond laser has become an effective technique to change the properties of materials.In this paper,hybrid micro/nanostructures with an area of 10×10 mm²are fabricated in 30 s by using the two-beam interference of femtosecond laser combined with the cylindrical lens line scanning technique,which greatly improved the laser processing efficiency.The hybrid micro/nanostructures greatly improve the surface roughness.Under the effect of capillarity,the ablated silicon surface shows superhydrophilicity in air,and the contact angle drops from 40°to 0°.The X-ray photoelectron spectra of the silicon surface shows that the content of Si-OH and H₂O molecules increases by 22.3%and13.6%,respectively,which further improves the hydrophilicity of silicon surface.With the increase of laser fluence and the decrease of scanning speed,the contact angle of the ablated silicon surface decreases gradually.3.Regular and uniform subwavelength periodic ripples with a period of 980 nm were fabricated on silicon surface by 1030 nm femtosecond two-beam interference,which the interference period is the same as the ripples period.Based on the theory of coherent resonance-enhanced,nano-ripples with periods of 490 nm and 250 nm can be prepared on silicon surface by adjusting the laser fluence and scanning speed.Two-dimensional structures with different morphologies were prepared on the silicon surface by rotating the sample for secondary processing.