Research On Femtosecond Laser Induced Micro-Nano Structures With Wide Spectral Absorption Properties On Material Surface

Femtosecond laser has a broad applied prospects in the field of micro-nano machining because of its short pulse width and high peak power, Femtosecond laser interaction with metal or semiconductor, by controlling the appropriate experimental conditions, can produce micro-nano structures that have strong absorption through wide spectrum region, and these structures are directly generated on the sample surface. These micro-nano structures have characteristics of anti-shedding, high temperature stability and environmental friendliness comparing with coated materials. It has great potential value in the field of stray light shielding of the optical system, solar-driven thermoelectric generator, aircraft stealth and so on.This thesis experimentally research on femtosecond laser induced micro-nano structures of strong absorption through wide spectrum on the surface of aluminum, titanium and silicon. Depending on the different materials properties, different experimental conditions are used. In our experiments, the surface reflectance of aluminum and titanium are below10%from ultraviolet to near infrared (0.38μm-2.3μm). and the reflectance of silicon from0.35μm to1μm is also below10%. The reflectance of aluminum and titanium are significantly reduced comparing to the untreated samples. In addition, the reflectance of femtosecond laser-treated aluminum is also less than20%at the mid-infrared band(8-24.5μm). Using scanning electron microscope (SEM), some gratings with periodic of hundred microns we founded, laser-induced periodic surface structure (LIPSSs) and random nano-structures densely covered on the grating surface are also founded. Based on morphology characteristics of the samples, a numerical model is established, numerical calculations are well done using FDTD Solutions software, and absorption mechanism is systematically studied combining with the simulated result.