This paper proposes a modified Shack-Hartmann wavefront sensor for phase retrieval. The sensor is revamped by placing a detector at a defocused plane before the focal plane of the lenslet array of the Shack-Hartmann sensor. The algorithm for phase retrieval is an optimization with initial Zernike coefficients calculated by the conventional phase reconstruction of the Shack-Hartmann sensor. Numerical simulations show that the proposed sensor permits sensitive, accurate phase retrieval. Furthermore, experiments tested the feasibility of phase retrieval using the proposed sensor. The surface irregularity for a flat mirror was measured by the proposed method and a Veeco interferometer, respectively. The irregularity for the mirror measured by the proposed method is in very good agreement with that measured using the Veeco interferometer.

Mitigating leaks through permeable defects by stacking graphene layers would greatly reduce the molecular permeance through porous graphene membranes for gas separation. We propose a multilayer graphene membrane with conical nanopores which instead presents an ultrahigh molecular permeance even higher than those of single-layer graphene membranes. Comparison with existing experimental data also shows that such membranes present an excellent separation performance in the aspect of molecular permeance. The highly permeable conical nanopore is particularly promising for the strongly adsorbed gases on the graphene surface, such as CO 2 and H 2 S. The underlying mechanisms are revealed by using molecular dynamics simulations, including (1) a large permeable area in the penetration side and (2) low permeation resistance caused by molecular bouncing in the nanopore for finding a possibility of permeation. The proposed conical nanopore can not only improve the molecular permeance through the defect-free and easy-fabricated multilayer graphene membranes but also provide a good example for the applications involving molecular permeation through nanopores.

Based on the dynamic characteristics of human eye aberration, a microadaptive optics retina imaging system set is established for real-time wavefront measurement and correction. This paper analyzes the working principles of a 127-unit Hartmann-Shack wavefront sensor and a 37-channel micromachine membrane deformable mirror adopted in the system. The proposed system achieves wavefront reconstruction through the adaptive centroid detection method and the mode reconstruction algorithm of Zernike polynomials, so that human eye aberration can be measured accurately. Meanwhile, according to the adaptive optics aberration correction control model, a closed-loop iterative aberration correction algorithm based on Smith control is presented to realize efficient and real-time correction of human eye aberration with different characteristics, and characteristics of the time domain of the system are also optimized. According to the experiment results tested on a USAF 1951 standard resolution target and a living human retina (subject ZHY), the resolution of the system can reach 3.6 LP/mm, and the human eye wavefront aberration of 0.728λ (λ=785 nm) can be corrected to 0.081λ in root mean square (RMS) so as to achieve the diffraction limit (Strehl ratio is 0.866), then high-resolution retina images are obtained.

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