Font Size: a A A

High Efficiency And High Resolution Femtosecond Laser Fabrication Based On Spatial Light Modulation Technique

Posted on:2017-02-05Degree:DoctorType:Dissertation
Country:ChinaCandidate:C C ZhangFull Text:PDF
GTID:1108330485453597Subject:Instrument Science and Technology
Abstract/Summary:PDF Full Text Request
Femtosecond induced two photon polymerization (TPP) is a crucial approach for making micro devices applying on optics, bioscience and microfluidic. However, its wide usage is being restricted by the low fabrication efficiency arising from the single-point scanning strategy. Conventional methods for improving efficiency is applying multi-foci parallel fabrication by microlens arrays (MLAs), spatial light modulator (SLM), or diffractive beam splitter, named as multi-point scanning strategy. But the size of foci array is limited by the view field of objective. Moreover, this strategy is only suitable for fabricating microstructure arrays with the same morphology. Hence, how to reduce the time in producing the aperiodic or large-scale structures is still a big challenge.Maskless holographic femtosecond laser patterning is a convenient technology that is able to rapidly fabricate large-scale aperiodic micro/nano structures.Firstly, a rapid method of fabricating microscope tubular structures via two-photon polymerization is presented. Novel Fresnel lens is designed and applied to modulate the light field into a uniform ring pattern with controllable diameters. Comparing with the conventional holographic processing, Fresnel lens shows higher uniformity and better flexibility, while easier to generate. This versatile method provides a powerful solution to produce tube structure array within several seconds.Secondly, for rapid fabrication of arbitrary microstructures, computer generated hologram (CGH) is loaded on SLM to project and transfer patterns into target materials. Nevertheless, there is still big difficulty in generating perfect optical field for laser patterning. The optical intensity distribution of phase modulated SLM has serious speckle noise, which will induce flawed surface. To eliminate the flawed structures, a multi-exposure approach to successively load the CGHs on SLM is proposed. Simulation result shows this approach can increase the uniformity of optical field at the defocal plane from 2% to 60%. Aperiodic microstructures with high quality were fabricated with short time. Compared with conventional single exposure CGH, the multi-exposure approach can increase the surface quality without losing efficiency. Furthermore, several kinds of Dammann gratings was realized by the multi-exposure strategy with both of high quality and short time (<1 min,95% time-saving), showing the promising prospect in rapidly fabricating and integrating various binary optical devices and their systems.Finally, a single-CGH-exposure approach based on Mixed Region Amplitude Freedom (MRAF) algorithm is proposed to realize ultrahigh throughput. The MRAF-CGH can provide patterned focal plane with high Signal to Noise Ratio (SNR), which means the focus has low speckle noise. A series of rectangles were fabricated with different parameters of MRAF to optimize the algorithm for fabrication. Numbers, letters, Olympic logo and Quick Response (QR) code are fabricated by fixed point exposure of several milliseconds, which demonstrates this approach is capable of rapidly fabricating arbitrary structures with good quality. Furthermore, trap structures, QR codes and letters e.g., "lab chip" are integrated in a channel. The trap structures covering the whole bottom of the 5000μm×170μm channel is completed to be integrated within 10 seconds, which is equivalent to the time by UV lithography.
Keywords/Search Tags:Femtosecond laser, Two-photon polymerization, Holographic fabrication, Maskless fabrication, micro/nano fabrication
PDF Full Text Request
Related items