Aperture Optical Components Research Articles

Research on Deterministic Ring Removal Method for Full-Aperture Double-Sided Polishing of Large Aperture Optical Components

Research on Deterministic Ring Removal Method for Full-Aperture Double-Sided Polishing of Large Aperture Optical Components

Dark-field surface defects detection method for multi-surface-shape large aperture optical components

In large-scale high-power optical systems such as inertial confinement fusion systems, the design of various optical components is often larger and more complex. Therefore, determining how to ensure the quality evaluation of optical components faces new challenges. As a key evaluation step for component quality, surface defects detection needs to consider improving the detection capability for various complex surface shapes and large aperture components. Meanwhile, the accuracy level of detection does not decrease with an increase in detection aperture size. The defects that need to be detected are typically small in size and randomly distributed throughout the aperture. Comprehensive aperture-wide information is required to ensure the thorough detection of defects in the components. Therefore, it is required that the detection system maintains compatibility with multi-surface shapes while balancing detection efficiency and accuracy. Against this background, the surface defects detection technology with high compatibility is explored in this paper. The illumination system of the dark-field imaging system and a generalized scanning path search strategy is proposed. Under the condition of ensuring a detection sensitivity of 0.5 µm, surface defects detection for various types of optical components with apertures several hundred times larger than the detection field of view is achieved.

Subaperture stitching interferometry based on the combination of the phase correlation and iterative gradient methods.

Subaperture stitching interferometry (SAS) is an important method for map testing of large aperture optical components, in which a mechanical structure is often employed for the testing of each subaperture. By eliminating the phase deviation of the corresponding points in the overlapping regions of every adjacent subaperture, the whole aperture map can be obtained. Accurate subaperture positioning is an important guarantee for precise stitching. In this paper, a hybrid optimization algorithm is proposed to realize subpixel-level positioning accuracy in SAS based on the combination of the phase correlation and iterative gradient methods. The phase correlation method is adopted to calculate the pixel-level positioning deviation first, and the subpixel deviation is derived and then corrected by iterative optimization through the gradient method. The subpixel-level positioning accuracy of the proposed optimization algorithm is verified by simulations and a 76.2 mm off-axis parabolic mirror is chosen as an experimental testing sample. The surface map obtained from the proposed hybrid optimization method is consistent with the full aperture testing result, which also verifies that the proposed optimization algorithm is a powerful tool with subpixel-level positioning accuracy in SAS testing.

An Analysis on Mechanism of Civil-Military Integration Collaborative Innovation under the Traction of Large Science Project: Take the High Power Laser Facility as an Example

This paper focuses on the practice of military and civilian cooperation to develop large aperture optical components for a large scientific project—a high-powered laser facility. It expounds the mechanism of civil-military integration for collaborative innovation against the backdrop of a large scientific project, and emphasizes the key role of collaborative innovation. Actual military and civilian integration for the development of large aperture optical components as concrete practice is introduced. The practical effects of military and civilian integration are briefly described.

Numerical simulation and experimental study of surface waviness during full aperture rapid planar polishing

Surface waviness (or middle spatial frequency error) is one of the most important specifications of large aperture optical components in high-power laser systems. In this paper, the formation mechanism and the influence factors of the surface waviness of large aperture optical components finished by full aperture rapid planar polishing (RPP) process were researched. Firstly, the theoretical formula of workpiece surface figure has been derivated. Furthermore, a numerical analysis model of the surface waviness has been established using 1-D power spectral density (PSD) as evaluation criterion. At last, the surface material removal and waviness of planar optical components polished by RPP process were calculated and experimental verificated. The simulation and experimental results show that workpiece surface will appear obvious waviness (grid or annular ripples) using grid-grooved polishing plate and fixed-eccentric polishing method. By optimizing the lap groove structure parameters and polishing kinematics parameters, the waviness of the workpiece surface can be significantly reduced.

Influence of phase error of optical elements on optical path design of laser facilities

Optical path design of high power laser facilities should consider several optimization measures such as those that are related to image transmission, ghost avoidance, and stray light management. According to the diffraction optical propagation theory, we study the the influences of wavefront characteristics of large aperture optical components on optimizing the design parameters of optical path in view of increasing the output load. The results show that the arrangement interval of the last stage optical drive can be very useful in improving the output load of the laser facilities if it is controlled to be over 6 m long. In general, a large aperture optical element with a phase error peak value of 0.34 can reduce the near field beam quality of a high-power laser by about 10% and give rise to a maximum decrease of about 21% when the phase error reaches 1.36. Superposition of multiple optical elements with different phase error distribution characteristics can reduce the negative effect of the mid frequency phase error. However, the nonlinear effect of large aperture optical components can aggravate the influence of the intermediate frequency phase error on the damage resistance capacity of the device. Under the premise that the damage threshold of the large caliber optical element is limited to 20 J/cm2, the using of a laser facility with a compact optical path, with an input laser energy density controlled to be below 16.8 J/cm2, will avoid damaging the optical components efficiently. A relatively flexible optical layout can further increase the average energy density of the final output laser and is very beneficial to the enhancing of the output load capacity of the laser facility.

Stimulated rotational Raman scattering suppression by pulse stacking

Suppression of stimulated rotational Raman scattering (SRRS) is essential for the effective long-distance transmission of high-intensity laser pulses in air. In this work, a method for SRRS suppression is proposed based on the reconstruction of the initial laser pulse via subpulse stacking. The proposed method can suppress SRRS significantly and doubles the threshold distance when the initial laser pulse is stacked using 30 subpulses; this capability is attributed to the mutually perpendicular polarization directions of the adjacent subpulses. Additionally, the SRRS gain decreases even further if different phases are added to adjacent subpulses. This pulse stacking scheme also has potential for use in the suppression of other nonlinear effects, including transverse stimulated Raman scattering and transverse stimulated Brillouin scattering in large aperture optical components. There may be some difficulties in the implementation of such a scheme, and the energy losses that occur during the stacking process may even be greater than the losses due to SRRS, but we believe that the proposed method can serve as an inspiration for SRRS suppression scheme design.

Design of a large five-axis ultra-precision ion beam figuring machine: structure optimization and dynamic performance analysis

Large aperture optical components are widely used in deep space exploration and high-precision earth observation system. Ion beam figuring (IBF) is usually used as the last polishing process, and its polishing accuracy determines the optical primary mirror precision, so an IBF machine plays a very important role in the production process of large-size optics. In this paper, the state-of-the-art large-aperture IBF equipment is introduced firstly. Next, the structures, equipment parameters, and design considerations of our IBF equipment are presented. Motion accuracy and dynamic performance are the two prioritized design issues; all researches are carried out around these two issues. Then, the key design points and characteristic analyses of IBF machine are presented, including structure analysis and optimization of the vacuum chamber, the relationship analysis between the dynamic performance of the moving system and the polishing accuracy, and multi-objective optimization design and modal analysis of motion components. Finally, the dynamic characteristics and motion errors of the IBF machine are tested, and the test results show that the machine performance indexes meet the design requirements.