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Ion beam sputtering is widely utilized in the area of ultra-high precision fabrication, coating, and discovering the microworld. A pulsed ion beam (PIB) can achieve higher material removal resolution while maintaining traditional ion beam removal performance and macro removal efficiency. In this paper, a 0.01 s pulse width beam is used to sputter atom layer deposition (ALD) coated samples. The nano-scale phenomenon is observed by high-resolution TEM. The results show that when the cumulative sputtering time is less than 1.7 s, the sputtering removal of solid by ion beam is accompanied by a nonlinear effect. Furthermore, the shortest time (0.05 s) and lowest thickness (0.35 nm) necessary to remove a uniform layer of material were established. The definition of its nonlinear effect under a very small removal amount guides industrial ultra-high precision machining. It reveals that PIB not only has high removal resolution on nanoscale, but can also realize high volume removal efficiency and large processing diameter at the same time. These features make PIB promising in the manufacturing of high power/energy laser optics, lithography objective lens, MEMS, and other ultra-high precision elements. [ABSTRACT FROM AUTHOR]

Freeform optical surfaces are advantageous to optical designers, as they provide additional degrees of freedom for optimization. The loss of rotational symmetry, however, makes measurement of freeforms more challenging. Herein, advances in interferometric areal measurement of freeform optical surfaces, including null tests, non‐null tests, near‐null tests, and adaptive null tests, are reviewed. Some new developments, in the Hartmann test, deflectometry, and phase retrieval, as representatives of non‐interferometric areal measurement, are then presented. Overall, the focus is on single‐point‐probe‐based profilometry categorized into coordinate measurements and slope‐ or curvature‐based measurements. Innovative measurement technology is trying to bridge the gap between high accuracy and high dynamic range as freeform optical surfaces are finding more applications in visible and shorter‐wavelength optics. [ABSTRACT FROM AUTHOR]

The magnetorheological (MR) repair method can effectively repair the small-scale damage of fused silica optics and further improve the laser-induced damage threshold of fused silica optics. However, at present, the rules of MR repair of small-scale damage of fused silica are not clear and cannot provide further guidance for the repair process. In this paper, the fused silica damage samples were repaired layer by layer by the MR method. The number and size changes of all the surface damage, the morphology, the fluorescence area distribution, and photothermal-absorption value of a single typical small-scale damage were measured. Through dark field scattering imaging, it is found that when the repair depth is 5 μm, the repair completion rate of damage with a transverse size less than 50 μm can reach 44%, and the repair efficiency decreases gradually with the repair process. Focusing on the whole repair process of a single typical, small-scale damage—due to the flexible shear removal mechanism of the MR method—the repair process of damage can be divided into three stages, which as a whole is a top-down, from outside to inside process. The first stage is the process of removing the surface of the damage layer by layer. In this process, MR fluid will introduce pollution to the inside of the damage. In the second stage, MR fluid begins to repair the inside of the damage. In the third stage, the MR ribbon completely covers the inside of the damage, and the repair effect is the most obvious. The measurement results of photothermal absorption and fluorescence area distribution of damage confirm this process. The photothermal absorption value and fluorescence area distribution of damage do not simply decrease with the repair process. On the contrary, they gradually increase first, and then decrease significantly when the damage depth reaches less than 1 μm. As the thickness of the MR ribbon is 1 μm, the reduction in the photothermal absorption value and fluorescence area of the damage is due to the process of repairing the inside of the damage. The results show that the absorbent impurities inside the small-scale damage of fused silica are the main factor affecting the performance. The key to repairing the small-scale damage of fused silica by the MR method is that the damaged interior must be repaired effectively. This paper outlines the MR repair method of small-scale damage of fused silica, which is of great significance to optimize the MR repair process. [ABSTRACT FROM AUTHOR]

• The phenomena of laser energy deposition and light-field enhancement caused by ripple structures was cleared through FEM simulation. • A combined technique of low–stress CCOS and IBF was used to polishing ripple–structure optical surface, and its suitability was verified for fused silica laser optics. • The changes of anti-laser damage characteristics at different processing stage were studied. The correlation between processing parameters, photo-thermal absorption, laser induced damage threshold was cleared. In AMRF (arrayed magnetorheological finishing) process of fused silica laser optics, ripple structures would generate on the optical surface. The ripple structures could cause nonlinear self-focusing and localized energy deposition, finally induced laser damage. In this work, the removal of ripple structures and the improvement of anti-laser damage characteristics were studied. First, the heat deposition and light-field enhancement induced by ripple structures were analyzed by finite element simulation method, and the negative impact of ripple structures was clarified. Then, the ripple-structure surface was polished by a combined technique of low-stress CCOS (computer control optical surfacing) and ion beam finishing (IBF). After the combined polishing process, the ripple structures and the hydrolyzed layer on the surface were removed, the photo-thermal absorption decreased from 0.736 ppm to 0.124 ppm, and the laser induced damage threshold (LIDT) increased from 6.3 J/cm2 to 7.4 J/cm2. In this work, the combined technique was able to remove the ripple structures while maintaining the processing efficiency, and it also could improve the anti-laser damage characteristics of the optics. The relative research results had important reference value for ultra-precision manufacturing of large-aperture laser optics. [ABSTRACT FROM AUTHOR]

• A PSD (Power Spectral Density) analysis method based on the contour of removal function was proposed for AMRF technique. • A new polishing path called "non-equal-interval parallel raster path" customized for AMRF technique was proposed and applied to control mid-spatial-frequency ripple error. • Simulation and actual experiment verified the effects of analysis method and polishing path. With the continuous development of high-power laser systems, laser optics gradually changed towards large-aperture, high-quality. To adapt to the fabrication of large-aperture laser optics, a new-type array magnetorheological finishing (AMRF) technique was developed and had made initial progress. However, AMRF technique would introduce more obvious ripple structures (such as 1 mm−1 of spatial frequency) compared to original MRF technique while adopting conventional raster path, and the ripple structures might affect laser beam transmission. For the further application of AMRF technique, the formation mechanism of ripple structures was studied, and a method based on the contour of removal function was proposed to analyze the changes of spatial frequency and evaluate the effect of different polishing paths. According to the analysis method, non-equal-interval parallel raster path was chosen and applied into AMRF process, along with maintaining efficiency while controlling ripple structures. In general, this work could provide a valuable support for the AMRF process of large-aperture laser optics and had a certain significance for the high-power laser system. [ABSTRACT FROM AUTHOR]

• The development of new-type arrayed MRF equipment was conducted through theoretical analysis, simulation and experiment. • High removal efficiency of 2.03 × 107 μm3/min and stability better than 5 % were achieved. • Actual experiment verified the effects of arrayed MRF equipment. Along with the continuous development of optical systems, the fabrication of optics gradually moved towards large aperture and high quality. To meet the requirements of optical systems, advanced technologies represented by magnetorheological finishing (MRF) were applied in the processing of optics. According to the background of high-efficiency processing, this work focused on the design of arrayed magnetorheological equipment, including magnetic field theoretical analysis, magnetic field simulation, equipment construction, removal function preparation and stability test. Through the study, arrayed MR (magnetorheological) equipment was preliminarily built and the removal function was prepared. The volume removal rate of arrayed removal function was 2.03 μm3/min after detection, which was 1.35 times of electromagnetic equipment under the same process parameters, and the stability of the removal function was better than 5 %. The results of two-dimensional removal experiment also verified that arrayed MR equipment could significantly improve materials removal efficiency. Based on the experimental results in this work, it is believed that arrayed MR equipment have certain advantages in the improvement of processing efficiency and surface quality, and it could meet the requirement of optical processing at the present stage. The relevant design theories and methods could provide reference to the follow-up research. [ABSTRACT FROM AUTHOR]

In recent years, monolithic multisurface optics with high-order aspheric surfaces and free-form surfaces have become a research hotspot. However, the high-precision shape and position error detection and high-efficiency compensation processing are the challenges faced by monolithic multisurface optics. In this paper, the shape and position error detection and compensation processing methods of monolithic multisurface optics are researched. Firstly, the highly accurate measurement of tool radius and highly accurate centering are realized by in situ interferometry. Moreover, the shape and position detection CGH is designed. Finally, the high-precision in situ detection and compensation turning experiments of monolithic multisurface optics are carried out, and the high-precision and high-efficiency processing are realized. • Highly accurate measurement of tool radius with in situ interferometry. • Highly accurate alignment by in situ interferometry. • High-precision in situ detection and compensation turning of the monolithic multisurface optics. • Separation of clamping error. [ABSTRACT FROM AUTHOR]