Study Of Micro-scale Gratings Fabrication Method Using Laser And Its Applications

With the development and application of micro-electronic mechanical system, micromechanics have drawn great attention from related researchers. Optical measurement methods are widely used in different fields’ material or structural deformation measurements due to the advantages like non-contact, full field and high precision, etc. Grating as an important deformation measurement sensing element, its fabrication has been great concern. Therefore, it is the important problems that how to locate the measurement area accurately and fast fabricate gratings. Different fabrications of gratings have different advantages and limitations. Lasers have been widely used for micro-scale processing owing to a very high instantaneous power and small heat-affected zone. Compared with other fabrications of gratings, laser can fabricate micro- gratings on the surface of the specimen without a mask and other processes. The fabrication of area can be adjusted and located accurately.Fabrication of micro-scale grating by nanosecond laser and femtosecond laser were systematic studied in this thesis. The main contents are listed as follows:(1) Two important micro-scale gratings methods named Geometric Phase Analysis(GPA) method and SEM moiré are studied. Structural characterization of large-area grating can be used by those methods on different frequencies. A characterization method based on the two-dimensional Fourier transform and phase analysis was deduced and simulated. In SEM moiré method, the relationship between the magnification and the frequency of reference gratings was presented.(2) Fabrication of micro-scale gratings by nanosecond laser is studied. Firstly, the parameters of basic line etching were studied. Secondly, the processing conditions of different materials were analyzed. Finally, the ablation thresholds of different materials were obtained. The film deposition on a specimen was suggested before laser processing. The selective problem of laser relative to the material was solved. The relationship between the fluence and distance was studied. The fabrication of micro-scale gratings by nanosecond laser was further analyzed. The frequency of 10 lines / mm parallel and orthogonal gratings were fabricated on aluminum film. The structure and pitch of grating are stability. It can be used for optical measurement.(3) Fabrication of micro-scale gratings by femtosecond laser is studied. Fabrication of micro-scale gratings by femtosecond laser system in the surface of the quartz glass samples was experimentally investigated. The basic parameters of points and lines by femtosecond laser system were studied and analyzed. Through the analysis the mechanism, the frequency of 500 lines / mm grating was fabricated. The grating maximum error of 0.95% was obtained by characterization analysis. Finally, according to SEM moiré, it can be used to characterize grating structure and deformation measurement.(4) Micro-scale gratings were fabricated on coated specimens by nanosecond. The parallel tensile experiment and the V- shaped crack experiment were carried out successfully. The verification tests prove that the applicability of the proposed fabrication method for the micro-scale gratings in optical measurement methods and the micro-scale gratings can be fabricated on an area of interest for deformation measurement.