Large-aperture fused silica phase optical components such as continuous phase plate (CPP) are widely used in large-scale laser devices to achieve beam homogenization and improve beam quality. However, under the action of high-energy lasers, their lower damage threshold seriously restricts their service life and increases cost of using. Compared with other fused silica components, chemical processing technology with hydrofluoric acid solution (HF) is lacking in the processing of phase components because the residual root mean square value (RMS) of phase elements is very high, and it can not guarantee this. Therefore, it is necessary to carry out research on the influence of chemical treatment on phase components. In this paper, we improved the chemical treatment process to achieve the change of residual RMS value not more than 3 nm, and improved the ability of resisting laser damage that the damage threshold of 29J/cm 2 was obtained under the test conditions 351nm@3ns. Finally, we successfully mastered the chemical control process of phase components and applied it to the CPPs as other fused quartz materials engineering production process.

Ultraintense optical vortices carrying orbital angular momentum have attracted much attention in strong-field laser physics due to their spiral phase and hollow intensity. This Letter introduces a fully continuous spiral phase plate (FC-SPP) that enables the generation of an ultraintense Laguerre-Gaussian beam. An optimization design method based on the spatial filter technique and chirp-z transform is proposed to match the polishing processing and the tightly focusing performance. To enable its use in high-power laser systems, a large-aperture (200 × 200 mm2) FC-SPP has been fabricated on a fused silica substrate through magnetorheological finishing without the use of mask techniques. The far-field phase pattern and intensity distribution based on vector diffraction calculation were compared with those of ideal spiral phase plate and fabricated FC-SPP, which confirmed the high quality of the output vortex beams and their feasibility for producing high-intensity vortices.

Focal spot with moving speed is a new concept proposed in recent years, which has many applications in physics of intense field. The current method is to control the moving speed of focal spot by chirped pulse technique and chromatic aberration focusing, which suffers from the change of frequency components with the movement of focal spot. In this paper, we propose a method to realize the colorless movement of focal spot at arbitrary speed by using two kinds of mirrors. One is an aspherical mirror with long focal depth and the other is a stepped mirror. For a specific moving speed, we derive the relationship between the surface of aspherical mirror and the wavefront of laser by the geometrical optics. The stepped mirror is used to form stepped wavefront to separate the relationship between the shape of wavefront and the direction of laser. Time-dependent simulations are carried out to verify the real focusing property after considering diffraction effects, and focal spots with moving speed of 0.5c, 2c and −c are obtained.

Magnetorheological polishing technology is a high-deterministic, high-precision optical ultra-precision processing technology, which is widely used in the polishing of large-aperture flat optical elements. The accuracy of magnetorheological removal function is a key factor that determines the accuracy and efficiency of magnetorheological polishing. In the process of making the removal function, it is easy to introduce spurious fringes when an interferometer is used for surface shape test. The spurious fringes will reduce the extraction accuracy of the removal function, and affect the certainty of magnetorheological polishing. In addition, the introduced spurious fringes contain complex mid- and high-frequency structures, which seriously affect the evaluation of the ability to remove function modification. In order to eliminate the spurious fringes, this paper proposes a method of removing the spurious fringes of the removal function based on the characteristic spectrum band-stop filter. First, the ZooMFFT algorithm is used to amplify the frequency spectrum to realize the effective identification of the spectral characteristics of the spurious fringes; secondly, a specific algorithm is used to eliminate only the frequency spectrum of the spurious fringes, completely retaining the frequency spectrum of the removal function itself, and does not change the valid shape of the removal function, making the spurious fringes are removed. And the Quad Flip operation is used in spectral filtering to improve the filtering accuracy. The magnetorheological making spot experiment uses a fused silica plate element with a diameter of 50mm. A static interferometer is used to measure the component wavefront data, and the tested result data contains obvious spurious fringes. Using the method described in this article, the spurious fringes are completely removed, and the morphological and removal efficiency of the removal function remains unchanged. Compared with the traditional frequency domain band-stop filter, the residual surface RMS of the spurious fringes separation is reduced from 5.45nm to 1.98nm; improve the extraction accuracy of the removal function. It can be effectively used to eliminate the spurious fringes of the magnetorheological removal function.

Continuous phase plate (CPP), as a key diffractive optical element, is difficult to manufacture owing to its random and small features. In this paper, a novel frequency division combined machining (FDCM) method was proposed to improve polishing efficiency of CPP by optimizing the tool influence functions (TIFs) over targeted frequency bands. In addition, the convergence rate of power spectral density (CR-PSD) was proposed to evaluate the correct ability of TIF in different frequency bands, and to determine the division frequency for the combined processing. Through simulation verification, the combined processing with optimized TIFs by FDCM enabled high precision in less total time than that with single TIF processing. The experimental results verified that the method could imprint a 300 × 300 mm CPP with residual root-mean-square 24.7 nm after approximately 6-h bonnet polishing. Comparing the focal spots of designed and fabricated CPPs, the deviation of their energy concentration within 500 microns is only 0.22%. Hence, bonnet polishing using the FDCM is a new technical option for the production of large-aperture CPPs. Furthermore, the FDCM method shows a significant increase in efficiency, and it could be a generic method for CPP processing through other technologies, including magnetorheological and ion beam finishing.

Magnetorheological polishing technology is a new type of ultra-precision processing technology. It has many advantages such as no sub-surface defects, easy realization of numerical precision control, high machining accuracy, and high polishing efficiency; and its small removal function size makes it very suitable for processing optical elements with complex geometric structures. It has been widely used in phase optical processing. In order to realize the processing of phase optical elements with a small space periodic structure, a smaller removal function is required. The traditional magnetorheological fluid circulation system structure is difficult to achieve stable control of the magnetorheological fluid flow under small flow conditions. Therefore, it is difficult to obtain a stable small size removal function. This paper analyzes the characteristics of the peristaltic pump, and aiming at the problem of strong pulse in its output flow; uses a pulsation damper and a variable-diameter back pressure pipeline to eliminate the flow pulse, realizes the stable and smooth output of the peristaltic pump flow. On this basis, this paper proposes a new type of magnetorheological fluid circulation system structure, which realizes the stable control of the flow rate under small flow rate conditions. The magnetorheological fluid flow fluctuation error of the magnetorheological fluid circulation system was from more than 25% reduced to less than 2%, realizing high stability control of magnetorheological fluid flow. Use small size removal function to process Continuous Phase Plates (CPP) with large depth and small periodic structure. The CPP is designed with a PV of 5μm and a minimum space period of 3mm. After processing, the residual error RMS of the CPP from 830nm converges to 24.5nm, realize high-precision processing of phase components with large depth and small structure.

In order to measure the aspherical transmission wavefront of large aperture optics with wedged angle, three compensators were fabricated based on theories of geometrical and diffraction optics, a single null lens and two computer-generated-holograms (CGH) by different frequecy carrier. The results show that both refraction null compensator and diffraction plate can achieve high-precision wavefront measurement of large aperture aspherical optics, the difference of wavefront measured by refraction and diffraction methods is better than 0.01λ(RMS) in the effective aperture area. Because of the measure beam deviation caused by the optic wedge, the results is very sensitive to parts position and gesture. Due to a smaller divergence angle and extra alignment/fiducial area for precision adjustment, the primary aberrations of tilted CGH measurment can get a better control than that of null compensator. Precise control or adjustment of compensator is critical for aspherical wavefront measurement. Null compensator lens can easily induce regulation error while CGH method could cause mid-frequency disturbance.

The continuous phase plate with a large wavefront gradient is used as the far-field beam shaping element in some high-power laser physics experiments. During the fabrication of continuous phase plate and before the actual use, it is necessary to measurement its wavefront to judge the fabrication quality and whether the wavefront distribution meets the requirement of use. By constructing a novel amplitude replacement phase retrieval algorithm with variable weighting factor, fast and high precision reconstruction of CPP with large wavefront gradient can be achieved. The proposed method is validated by numerical simulation and experiment.

Traditional optical processing technology is limited by factors such as the geometric size and stability of the removal function of the processing equipment, and it is very difficult to process optical elements with complex structures with large depths and small periods. In particular, the high-efficiency and high-precision processing of optical elements with complex structures whose depth is micron-level and space period is millimeter-level has always been a technical difficulty. This paper proposes a method for processing optical components with complex structures based on magnetorheological polishing technology, focusing on solving the traditional magnetorheological polishing technology small size removal function generation and stable control problems, and obtaining small size removal with stable removal efficiency and morphology function. The magnetorheological fluid circulation system is a key component of the magnetorheological polishing machine. The structure of traditional magnetorheological fluid circulation system is difficult to match the stable transmission of magnetorheological fluid under small flow conditions. This paper proposes a method of dual peristaltic pump & pulsation damper combined with variable-diameter back pressure pipeline to achieve the stability of magnetorheological fluid control. The flow fluctuation error of magnetorheological fluid is reduced from 10-40ml/min to 1-5ml/min. The diameter of the polishing wheel of the machine is 20mm and the flow rate of the magnetorheological fluid is 200ml/min. A two-dimensional sinusoidal surface processing was performed using magnetorheological machine. Sinusoidal surface design PV=1.0λ (λ=632.8nm), RMS=159.5nm, the space period is 3mm, the element size is 50mm×50mm. The width of removal function is 1.33mm, FWHH (Full Width at Half Height) is 0.98mm, and volume removal rate is 0.004mm 3/min. After the element is completed, the residual RMS is reduced from the original 159.5nm to 15.7nm, and its convergence rate is 90.1%, with high convergence accuracy. The experimental results show that the configuration of the magnetorheological fluid circulation system proposed in this paper realizes the generation and stable control of the small size removal function and finally realize the fabricating of phase components with a minimum space period of 3mm.

The fully continuous spiral phase plate (SPP) has been used more and more widely in high-power laser and other fields. Its unique jump cross section structure with a width of only a few millimeters puts forward extremely high requirements for wavefront measurement. In this paper, a defocus multi-intensity phase retrieval algorithm based on weighted GS for wavefront measurement of SPP is proposed, and the influence of phase retrieval test error on measurement accuracy is analyzed. Finally, a phase retrieval test platform is established, and the high-precision phase retrieval measurement of the SPP wavefront is realized.

For lens-free imaging technology based on axial multi-plane phase retrieval, the test parameters have a very important impact on the image reconstruction speed and quality. The deviations between the actual position of the recorded diffraction intensity pattern and the set position in the reconstruction algorithm will also affect the image reconstruction quality. We analyzed the influence of test parameters and deviations on the reconstruction accuracy and proposed a method to correct the position mismatch of the intensity image. The effectiveness of the method is verified by simulation and experiment.

Due to the characteristics of large depth, small period and high steepness, phase optical elements with complex structure need to use a small size removal function in magnetorheological processing, and use very small line spacing and step size values when planning the polishing path，so the dwell time matrix is very large, and the dwell time calculation speed is slow; besides, because of the complicated phase optical profile, it is difficult to achieve high-precision convergence of the dwell time. This paper proposes a fast and high-precision numerical iterative dwell time algorithm for complex structure phase optical elements. this paper proposes the concept of the dwell point matrix, which realizes the methods of the FFT convolution multi-core parallel algorithm to calculate the dwell time in the entire iterative calculation process. Also, to achieve high-precision convergence of the dwell time calculation, this paper proposes a calculation rule based on machine dynamic performance matching, when calculating the dwell time, the speed, acceleration, and speed smoothness of the machine were matched with the performance of the magnetorheological machine, which improves the stability of the machine. A large-diameter Continuous Phase Plate (CPP) is processed on a magnetorheological machine. The shape of the CPP contains a random structure of various periods. The initial RMS = 228.07nm, the CPP data matrix size is 2424 × 2424, and the line spacing is 0.6mm, the dwell time is calculated using the algorithm described in this article, the entire calculation process takes only 4.2 seconds, the calculation speed is about 3 times faster than the traditional iterative methods, the CPP residual error RMS converges to 10.2nm; After the CPP processing is completed, the CPP actual residual error RMS is reduced from the original 228.07nm to 15.6nm, and its convergence rate is 93.1%, which shows that the algorithm has high calculation efficiency and convergence accuracy.

In the interference test process of a parallel flat optical element, the light beam after multiple reflections on the front and rear surfaces of the element with the wavefront to be measured often cause multi-surface interference, forming spurious fringes on the interferogram, which will introduce large errors to the wavefront measurement. Spurious fringes mainly have a great impact on the parameters such as wavefront gradient root mean square (GRMS) and mid-spatial-frequency power spectral density (PSD). The RMS value of the wavefront containing spurious fringes is generally significantly larger than the true value, which will affect the accurate measurement and evaluation of the wavefront quality of optical components. Existing spurious fringes suppression methods often have the disadvantages of multiple adjustment steps in the test process or high hardware requirements, and it is difficult to match the requirements for rapid and high-efficiency test of high-precision optical flat components. This paper proposes a method for removing spurious fringes in interference test based on characteristic spectrum band-stop filter, which can achieve accurate removal of spurious fringes. First, by using the ZoomFFT algorithm to zoom up the spectrum of the wavefront data points, the effective identification of the spectral characteristics of the spurious fringe is realized; then the band-stop filter in a specific area is used according to the spectral characteristics of the spurious fringes, only the frequency spectrum of the spurious fringes is removed, and the wavefront data of the component to be tested is completely retained without changing its own shape; the Quad-Flip operation and error function filter window are used for spectrum filtering, which effectively reduces Gibb's noise in the frequency domain due to the sudden truncation of the input data edge during FFT transformation. The transmitted wavefront of a fused silica element with a diameter of Φ100mm was tested on the ZYGO static interferometer, and the test results contained a large number of spurious fringes. After processing by this method, the spurious fringes were removed. The mid-spatial-frequency wavefront RMS of the component is reduced from 5.365nm to 3.678nm. The method does not need to add additional hardware and tedious measurement and adjustment operations, the calculation is fast, and the spurious fringes removal is accurate.

Continuous phase plate (CPP) is the vital diffractive optical element in large laser devices. It is extremely difficult to manufacture owing to its random and small feature structures. Bonnet polishing (BP) has obvious advantage of high efficiency, and is widely uesd in manufacturing process of large optics. In the paper, BP techniques have been developed to manufacture CPP. Firstly, the relationship between the process parameters and tool influence functions (TIFs) has been analyzed, and the adjustable ranges of TIF size and efficiency have been determined. Then, a surface topography simulation model has been established to forecast CPP residual errors. Based on the model, the influence of TIF size on the processing precision and efficiency of CPP has been simulated and analyzed; meanwhile the optimized TIFs have been determined. Finally, an experiment has been carried out by a 300mmx300mm CPP element. The result has shown that the residual root-mean-square (RMS) of CPP is 26 nm. Based on the optimized TIFs of BP, it has been realized the high-efficient and high-precision processing of CPP in this paper, and a new technical reference for the CPP manufacturing has been provided simultaneously.

Spiral phase plate (SPP) for generating vortex hollow beams has high efficiency in various applications. However, it is difficult to obtain an ideal spiral phase plate because of its continuous-varying helical phase and discontinued phase step. This paper describes the demonstration of continuous spiral phase plate using filter methods. The numerical simulations indicate that different filter method including spatial domain filter, frequency domain filter has unique impact on surface topography of SPP and optical vortex characteristics. The experimental results reveal that the spatial Gaussian filter method for smoothing SPP is suitable for Computer Controlled Optical Surfacing (CCOS) technique and obtains good optical properties.

为了利用磁流变加工实现对大口径平面光学元件波前中频误差的控制,研究了磁流变抛光去除函数的频谱误差校正能力和磁流变加工残余误差抑制方法。首先,比较了模拟加工前后元件中频功率谱密度（PSD1）误差和元件PSD曲线的变化,分析了磁流变去除函数的可修正频谱误差范围。然后,利用均匀去除方法分析了加工深度、加工轨迹间距和去除函数尺寸等磁流变加工参数对中频PSD2误差的影响,提出了抑制中频PSD2误差的方法。最后,对一块400mm×400mm口径平面元件的频谱误差进行了磁流变加工控制实验。实验显示:3次迭代加工后,该元件的波前PV由加工前的0.6λ收敛至0.1λ,中频PSD1误差由5.57nm收敛至1.36nm,PSD2由0.95nm变化至0.88nm。结果表明:通过优化磁流变加工参数并合理选择加工策略,可实现磁流变加工对大口径平面光学元件中频误差的收敛控制。

最小空间周期是连续位相板（CPP）设计和加工过程中的重要特征参数。根据惯性约束聚变大型激光驱动装置的需求,建立不同空间周期的CPP设计与分析方法,研究了不同最小空间周期对磁流变加工和焦斑性能的影响。结果表明,磁流变加工的去除函数尺寸直接与CPP的最小空间周期成线性关系,而加工去除量与最小空间周期的平方根成线性关系,最小周期越大,加工越容易,但加工量越大;焦斑整形性能受最小空间周期的影响小,能量集中度差异小于0.2%,但焦斑顶部均匀性随着最小空间周期变小而变好,5 mm最小周期CPP的焦斑顶部不均匀比15 mm的CPP小3.5%。因此,设计时应尽量减小最小空间周期,但选取的最小空间周期不能大于加工设备的约束条件。

为了提高惯性约束聚变(ICF)激光装置中连续相位板(CPP)的焦斑性能,建立了波前畸变下连续相位板焦斑的理论计算和分析模型,并根据CPP使用条件搭建了三倍频大口径CPP远场离线测试系统.对加工330 mm×330 mm口径的CPP和波前畸变元件进行了理论计算和离线测试实验的对比研究.理论计算和实测的焦斑形貌、参数数值均非常一致,验证了计算模型的正确性和实验系统的可靠性.理论和实验结果一致表明,波前畸变对CPP焦斑性能的影响非常严重,当弥散斑为0.5倍CPP焦斑时,畸变量已对CPP焦斑形貌产生了很大影响,能量利用率下降值大于4％,焦斑半径增大超过20μm,陡边阶数下降1.3阶,不均匀性均方根(RMS)值下降6％,旁瓣份额增长超过0.5％.

建立了包括非热稳定热力学模型、光学传输模型、能量转换模型及非稳腔模型的综合理论分析平台.理论分析得到以下主要结论:谐振腔长度变化对光束质量及光光效率的影响不大,对于给定的增益,激光最佳效率和光束质量分别对应不同的非稳腔放大率.提出非稳腔腔内相位板补偿介质静态畸变提高光束质量的技术措施,并开展实验验证,光束质量由补偿前的5.48倍衍射极限提升到补偿后的2.46倍,输出功率为12.1 kW.

This paper analyzes characteristics of wavefront and light intensity of large-aperture continuous phase plates(CPPs) fabricated by magnetorheological finishing(MRF). Three groups of CPPs fabricated by different processing parameters such as scanning intervals and scanning offsets are compared, and the influence of mid-frequency error introduced by MRF on CPPs wavefront and light intensity are analyzed as well. Total analysis indicates that the performance of CPP is poor when scanning interval is 2 mm and scanning offsets are 0.1-0.3 mm; The iteration fabrication efficiency is higher when scanning interval is 2 mm and scanning offsets are 0.4-0.5 mm compared with that when scanning interval is 1 mm and scanning offsets are 0.1-0.3 mm, and the mid-frequency error is improved as well. Further analysis indicates that mid-frequency error introduced by MRF has a greater impact on CPPs wavefront gradient, near-field and side lobe.