Research On Design And Fabricating Technique Of Microarray Diffractive Optical Element

Femtosecond laser processing technology is a non-contact,high-precision processing technology that rapid fabrication of complex 3D structure with great robustness,simplicity and erroneous tolerance.With the increasing demand for optical components in micro or nano scale,however,traditional techniques could no longer suffice the requirements for components with small volume,high structural complexity and processing accuracy.The advent of the photolithography technology as well as electron beam exposure technology provides new solutions for micro optical components with ultra-high precision.However,the cost-effective lithographic techniques demand the use of a specific mask during the manufacture procedure and can only fabricate two-dimensional structures,while the e-beam counterparts have a stringent requirement for vacuum environment.Thus,there has been great needs to develop a micro-processing technique that enables complex 3D microstructures fabrication with promising processing accuracy.The development of femtosecond laser processing technology provides an competitive tool for the processing of diffractive optical elements and promotes the development of the field of diffractive optical elements fabrication.Compared with other optical elements,diffractive optical elements share advantages such as high utilization rate of light energy,easy production and high efficiency.Among them,Talbot array illuminator is the typical which is diffraction-efficient and feasible for multi-functional integration.However,it's hard to process complicated multi-order phase structures using the conventional method.In order to improve the performance of optical micro-nano devices,researchers have introduced orbital angular momentum utilizing the unique characteristics of orbital angular momentum to achieve flexible functions when designing micro-nano devices.The applications of orbital angular momentum dor optical micro-nano devices have been extensively studied,among which orbital momentum beams are now widely used in the fields of optical communications,super-resolution imaging,nano-manipulation and laser processing.However,most macro and micro methods are used to generate single orbital angular momentum beam,which is not suitable for the needs of generating multi-focus and large-area array light fields.In this thesis,a galvanometer-based laser direct writing system,which can perform high-precision processing of micro-nano structures,is built up to tackle these problems.A Talbot array illuminator that can generate focusedorbital angular momentum beams is designed and constructed to generate high-quality large-area array orbital angular momentum beams,with which we successfully processed high-precision 1×1 and 3×3 Talbot array illuminators.The thesis is organized as follows:(1)In the light of fractional Talbot effect,using the detour phase encoding method,a planar optics that can generate a focused orbital angular momentum beam is designed.The device uses a detour phase encoding method to encode a specific phase distribution calculated based on the fractional Talbot effect on the tablet.Finite-difference time-domain(FDTD)method is used to simulate optical devices with square and hexagonal periodic structures.The results show that plane waves can be converted into array-type focused orbital angular momentum beams through the device.The device is easy to fabricate,easy to splice or duplicate with a high degree for integration.Meanwhile,the device can be used to generate high-quality large-area array type orbital angular momentum beams.It has good potential applications in light trapping,light manipulation,and optical processing.(2)With galvanometer laser direct writing system,which is discussed in detail in Chap 2,Talbot array illuminator could be fabricated on glass substrates,yielding 1×1and 3×3 array high-precision Talbot array illuminators.Further,the size of the primitive rectangular blocks which constitutes the Talbot array illuminator is controllable and could smoothen the edge of the primitive rectangular block thereby the accuracy of the overall Talbot structure is improved.Therefore,the device could be used to compensate the intensity loss of the convergent focus which is generally caused by the defects and low accuracy of the Talbot structures.