Research On Integrated Micro-optical Devices And Systems Based On Femtosecond Laser Direct Writing

Traditional and non-integrated macro-optical systems are composed of macrosized optical devices,which have problems such as bulky system,huge volume,high energy consumption and low degree of freedom in design,and have been unable to achieve the further development of modern information technology.In contrast,microoptical devices and systems with small size,light weight,low energy consumption,low cost,and high design freedom can realize many functions that are difficult to be achieved by traditional optical devices.Therefore,micro-optical devices and systems have great advantages in the fields of imaging,sensing,communication,information processing and computing,and are an inevitable trend in the development of optoelectronic instruments and systems in the future.Up to now,the theory of micro-optics is being continuously improved and updated,and various micro-optical devices and systems with different functions are being continuously developed.However,there are still some challenges and problems in the further development of micro-optical devices and systems,mainly manifesting requirements for the superior processing technologies for the fabrication of true 3D micro-optical devices with flexible design,smooth surface,and free surface shape at the microscale.Traditional processing technologies are still difficult to meet the processing needs of high-quality micro-optic devices.Therefore,this paper aims to solve the problems of simple structure,single function,poor working performance,difficulty in system integration,and low integration level of existing micro-optical devices and systems caused by insufficient processing capability of traditional processing technology.On this basis,a pre-compensation correction technology and a definition,reinforcement,solidification(DRS)scanning strategy were proposed,which can expand the range of femtosecond laser direct writing and improve the processing efficiency,making it possible to rapidly fabricate high-precision and cross-scale complex true 3D micro-optical devices.Based on the proposed pre-compensation correction technology and DRS scanning strategy,we designed and fabricated highquality non-diffraction and self-healing micro Bessel vortex beam generators,enriching the types and functions of micro-optics;The broadband and high-efficiency microdiffractive optical elements were proposed and fabricated,improving the broadband performance of micro-optical devices and systems;Furthermore,the solution for the incompatibility between the miniature curved compound eye and the flat detector was proposed,realizing the optoelectronic integration of the micro compound eye and miniature photosensitive chip,solving the key problems in system integration,and effectively improving the system integration degree.The main research work and results are listed as follows:1.Expansion of range and improvement of processing efficiency for femtosecond laser direct writing.For the miniaturization and integration of optical devices,the requirements for processing technology are increasing.Traditional processing technologies such as mask lithography,particle beam lithography,and nano-imprinting still have complex processes,high costs,and difficulty in true 3D processing and monolithic integration of multiple devices.We established an effective precompensation correction model based on the galvanometer-based femtosecond laser direct writing system.By performing software pre-compensation correction on the processing data,the adverse effects of the off-axis optical aberration of the system on the processing were effectively eliminated.Through theoretical simulation and experimental verification,under the premise of ensuring the processing accuracy,an improvement in the effective processing range from 100 ?m to 550 ?m was achieved and a high-quality continuous surface Fresnel lens with a diameter of 550 ?m was fabricated in one step.In addition,a DRS scanning strategy was proposed to solve the problems of poor mechanical strength and low processing efficiency caused by femtosecond laser near-threshold point-by-point scanning processing.The proposed DRS scanning strategy can improve the processing efficiency by two orders of magnitude under the premise of ensuring the processing accuracy and can realize the high-precision and rapid preparation of any complex 3D micro-optical devices and systems.Our improvement in processing technology provides a strong technical guarantee for the preparation of micro-optical devices and systems.2.Functional micro-Bessel vortex beam generators.Aiming at the problems of simple structure,single function,and difficulty in introducing high-quality novel light fields into integrated optical systems caused by the insufficient capacity of traditional processing technology,we designed functional micro high-order Bessel beam generators and multi-orbit angular momentum beam generators by combining logarithmic axicons and spiral phase plates.The designed complex 3D continuous surface micro-optical devices can be fabricated in one step by femtosecond laser direct writing technology.The device with a diameter and height of only 100 ?m and 1.266?m can be integrated into various micro-optical systems.Through theoretical simulation and experimental verification,the fabricated micro-optics can effectively generate high-quality non-diffraction self-healing micro-sized Bessel vortex beams and multi-orbital angular momentum beams.The designed and prepared functional microBessel vortex beam generator solves the problems of difficulty in beam generation,complex methods,large device size,and difficulty in being applicable to integrated optical systems,further enriching the types and functions of existing micro-optical devices.3.High-performance broadband micro diffractive optical elements.Aiming at the problems of poor performance,narrow bandwidth,and low broadband diffraction efficiency of traditional micro-diffractive optical elements,we proposed a general broadband and high-efficiency micro-diffractive optical element architecture,which is of great significance for the construction of broadband micro-optical systems.The multi-layer diffractive structure of the device was fabricated and integrated in one step by femtosecond laser direct writing technology,avoiding the micro-alignment error problem.At the same time,the microfluidic channel was used to introduce the refractive index matching liquid.The dispersion and refractive index matching of solid materials and liquid materials under broadband and the design of multi-layer diffraction structure were utilized to make the device maintain a stable phase shift under broadband,and finally,the first-order diffraction efficiency in the visible band was maintained above80%.The proposed broadband diffractive architecture can achieve the broadband and high-efficiency working goals of most micro-diffractive optical elements.As a proofof-concept,we designed and fabricated micro-diffractive gratings,micro-diffractive lenses,and micro-orbital angular momentum beam generators based on the proposed broadband diffractive architecture via femtosecond laser direct writing.The fabricated devices have good surface morphology,conform to the designed cross-sectional profile,and exhibit good broadband operating characteristics.4.Photoelectric integrated miniature artificial compound eye camera.Aiming at the problem that the curved focal plane and image plane of the traditional miniature curved artificial compound eye are incompatible with commercial flat detectors,and it is difficult to achieve optoelectronic integration,we proposed a design scheme of a defocus-free artificial compound eye with designable ommatidium surface and focal depth.The large-size 3D curved compound eye with a special ommatidium surface was rapidly fabricated by the improved femtosecond laser direct writing technology based on pre-compensation correction and DRS scanning strategy.The prepared defocus-free compound eye had superior processing quality and optical properties conforming to the design,solving the defocusing problem of the micro-curved compound eye.Using the designed and fabricated defocus-free artificial compound eye lens as an optical component and a micro-CMOS photosensitive chip(Omnivision 9734)as an electrical component for optoelectronic integration,the currently smallest and lightest microartificial compound eye camera with independent imaging of ommatidia was prepared.Furthermore,we also realized real-time reconstruction of the movement trajectories of the macroscopic moving target beetle and the microscopic moving target paramecium by using the multi-eye vision of the compound-eye camera.The designed and fabricated miniature artificial compound eye camera solved some key problems in the system integration of micro-optical devices and is of great significance for realizing the system integration of micro-optical devices and improving the degree of system integration.In summary,under the background of the insufficient processing capability of traditional micro/nano processing technology,this paper improves the traditional femtosecond laser direct writing technology,proposes a pre-compensation correction technology and a DRS scanning strategy,and realizes the simultaneous improvement of processing range and processing efficiency.The improvement can realize the highprecision and rapid preparation of complex 3D surface micro-optical devices and systems.Moreover,the present work performed in-depth study on the design,fabrication,and characterization of micro-optic devices and systems,supplementing micro-optic devices' function,enhancing micro-optic devices' broadband performance,and solving some key problems in the integration of micro-optic devices.Our work has important implications for building fully functional,superior-performance,and highintegration micro-optics devices and systems in the future.