Femtosecond Laser-induced Nano Phase Change By Spatial Light Modulation

Indium Tin Oxide(ITO),as an n-type semiconductor material,holds a significant position in scientific research and industrial applications.ITO is transparent in the visible light range and possesses good conductivity.More importantly,ITO exhibits near-zero dielectric constant(ENZ)characteristics in the near-infrared region,opening new possibilities for the development of nonlinear optical devices and microelectronic devices,among others.In the process of fabricating nonlinear optical devices and microelectronic devices,the technology for manufacturing sub-micrometer patterned ITO structures is particularly crucial.Therefore,developing flexible and efficient manufacturing technologies is important for advancing the application of ITO in various advanced devices.With the rapid development of manufacturing technologies,femtosecond laser processing technology based on spatial light field modulation,which combines the advantages of high processing precision and efficiency,has been widely applied in many fields such as metasurface processing,3D printing,and microchannel processing.This paper introduces the femtosecond laser-induced nano-phase transformation of ITO films based on spatial light field modulation,including:Firstly,this paper achieved the transformation from the amorphous phase to the crystalline phase of ITO in nano-regions.By focusing femtosecond laser through a high numerical aperture lens on the surface of the ITO film,and utilizing the difference in etching rate between amorphous ITO and crystalline ITO,the amorphous parts were removed through selective etching with hydrofluoric acid,while the crystalline parts were retained on the glass substrate,forming the desired pattern.This process is similar to the working principle of negative photoresist,but this paper substitutes the traditional photolithography steps requiring a mask with direct writing by femtosecond laser,significantly enhancing the flexibility and efficiency of processing.By precisely adjusting the laser power,this paper was able to manufacture nano-lines with widths ranging from 190 nanometers to 1 micrometer,demonstrating the process’ s flexibility in feature size and also showcasing the technology’s application in fabricating microoptical elements,including Fresnel zone plates and two-dimensional Dammann gratings.Secondly,this paper enhanced the efficiency of femtosecond laser nano-phase transformation processing through studying spatial light field modulation technology.Considering the relatively low efficiency of the laser single-point scanning processing mode,this paper adopted laser beam splitting technology to enhance processing efficiency.The paper detailed the beam splitting algorithm and constructed a laser processing system based on a liquid crystal spatial modulator.By loading holograms on the liquid crystal spatial light modulator,a beam-splitting light field with high uniformity was achieved.Additionally,a vector integral algorithm was used to simulate the light field intensity distribution under different light field controls and compare it with the actual light field.Eventually,this technology was applied to ITO nano-phase transformation processing,successfully manufacturing multiple parallel nano-lines in a single scan using 1 × 3 and 1 × 4 beam-splitting light fields.Not only did this significantly improve processing efficiency,but it also provided an effective way to manufacture complex nano-structures.Further,this paper constructed and explored the electrical properties of the nanolines.By constructing four parallel nano-lines and growing aluminum electrodes on their ends,the current-voltage and current-time characteristic curves were measured using a four-probe instrument.The test results showed that these nano-lines exhibited good conductivity,with the total resistance of the four parallel nano-lines being approximately 470 ohms,which is significant for studying the application of ITO nanolines in electronic devices.In summary,this paper studied the femtosecond laser nano-phase transformation process on ITO films,achieved efficient patterned ITO film processing using beamsplitting technology based on light field modulation,and tested and characterized the resistance of ITO nano-lines.The universality and flexibility of this processing technology offer tremendous potential for future broader semiconductor material processing.With further development and optimization of the technology,this method is expected to play a role in the manufacture of optoelectronic devices,nanotechnology,and other fields.