Large aperture off-axis Fresnel lens will play an important role in the future 10 m scale aperture transmission space telescope system. Improving diffraction efficiency and wavefront image quality is always the goal of engineering applications. A 4-level off-axis fresnel lens with Ф350 mm effective aperture was fabricated through overlay etching technique by laser direct writing system. The wavefront aberration characteristics of the off-axis Fresnel lens at 632.8 nm wavelength are analyzed and discussed in detail, and the large aperture off-axis Fresnel lenses wavefront aberration measurement scheme, including a high-precision plane reflector, measured LAOFL, CGH, interferometer and laser tracker to compensate for certain low-order aberrations caused by LAOFL imperfect imaging, is proposed. Wavefront aberration of 0.020 λ(1/50 λ) RMS was achieved. This work presented the best results to our knowledge among the same field with similar aperture in open publications and provided a strong foundation for the future 10 m scale aperture transmission space telescope system.

Reactive ion etching (RIE) is a promising material removal method for processing membrane diffractive optical elements and fabrication of meter-scale aperture optical substrates because of its high-efficiency parallel processing and low surface damage. However, the non-uniformity of the etching rate in the existing RIE technology will obviously reduce the machining accuracy of diffractive elements, deteriorate the diffraction efficiency and weaken the surface convergence rate of optical substrates. In the etching process of the polyimide (PI) membrane, additional electrodes were introduced for the first time to achieve the modulation of the plasma sheath properties on the same spatial surface, thus changing the etch rate distribution. Using the additional electrode, a periodic profile structure similar to the additional electrode was successfully processed on the surface of a 200-mm diameter PI membrane substrate by a single etching iteration. By combining etching experiments with plasma discharge simulations, it is demonstrated that additional electrodes can affect the material removal distribution, and the reasons for this are analyzed and discussed. This work demonstrates the feasibility of etching rate distribution modulation based on additional electrodes, and lays a foundation for realizing tailored material removal distribution and improving etching uniformity in the future.

A quartz sub-mirror was figure-corrected in a parallel removal process for the first time. An Reactive Ion Figuring (RIF) process with a simple and universal masking method was demonstrated, and the 350-mm quartz sub-mirror was figure-corrected from the initial figure error of ~23 nm RMS to the final figure error of ~8 nm RMS in total effective figuring time of ~52 minutes after 4 iterations, which exhibited the actual potential of RIF on the figure-correction of quartz optical elements and the possibility on applying RIF to meet the requirement of mass production for sub-mirrors of transmissive diffractive segmented telescopes.

In the process of plasma figure correction for a quartz sub-mirror, the plasma parallel removal process and ink masking layer are combined for the first time. A universal plasma figure correction method based on multiple distributed material removal functions is demonstrated, and its technological characteristics are analyzed. Through this method, the processing time is independent of the workpiece aperture, which saves time for the material removal function to scan along the trajectory. After seven iterations, the form error of the quartz element is converged from the initial figure error of ~114 nm RMS to a figure error of ~28 nm RMS, which shows the practical potential of the plasma figure correction method based on multiple distributed material removal functions in optical element manufacturing and the possibility of becoming a new stage process in the optical manufacturing chain.

Diffractive optical elements are gradually replacing some conventional optical elements and becoming a key component of optical systems due to their unique phase modulation function. However, the imaging performance will be reduced due to the fact that this single-sided microstructured lens still produces chromatic aberration. Therefore, the key issue for the application of diffractive optical elements in optical systems is the reduction of chromatic aberration, and diffractive lenses with double-sided microstructures are proposed as a solution. This research describes the design and analysis of a 70-mm-diameter, 296-mm-focal-length double-sided microstructured hybrid-order monolithic imaging diffractive lens operating in the mid-wave infrared region (3.7–4.7 μm). The design minimizes chromatic aberration by up to 30 times compared to a standard harmonic diffractive lens and improves the image performance of a single-lens optical system operating in the infrared range. Experiments indicate that this design is capable of achieving single-lens imaging with high sensitivity for optical systems with a measured NETD ≤ 50 mK. The analysis of the experiments yielded suggestions for future research.