Eigendecomposition-free inverse design of meta-optics devices.

The inverse design of meta-optics has received much attention in recent years. In this paper, we propose a GPU-friendly inverse design framework based on improved eigendecomposition-free rigorous diffraction interface theory, which offers up to 16.2 × speedup over the traditional inverse design based on rigorous coupled-wave analysis. We further improve the framework's flexibility by introducing a hybrid parameterization combining neural-implicit and traditional shape optimization. We demonstrate the effectiveness of our framework through intricate tasks, including the inverse design of reconfigurable free-form meta-atoms.

Multiple intra-articular injections of autologous stromal vascular fractions for the treatment of multicompartmental osteoarthritis in both the tibiofemoral and patellofemoral joint: a single-blind randomized controlled study.

BACKGROUND: Multicompartmental osteoarthritis (MOA) in both tibiofemoral and patellofemoral joints is a more commonly occurring, but neglected, clinical condition, and we examined the short-term safety and efficacy of autologous stromal vascular fractions (SVFs) for MOA using a single-blind, prospective, randomized, placebo-controlled trial. METHODS: Seventy MOA patients were recruited and randomly assigned to the SVF group and hyaluronic acid (HA) group (control group). The scores of visual analog scale, the Western Ontario and McMaster University Osteoarthritis Index, and the Samsung Medical Center patellofemoral scoring system were assessed and compared between the two groups 3, 6 and 12 months after treatment. RESULTS: The SVF group had significantly better visual analog scale scores than the HA group at 6 and 12 months after treatment and had better Western Ontario and McMaster University Osteoarthritis Index scores than the HA group only at 6 months after treatment. For Samsung Medical Center patellofemoral scoring system of the patellofemoral joint, the SVF group had significantly better scores than the control group at all postoperative time points. The proportion of patients whose visual analog scale and Western Ontario and McMaster University Osteoarthritis Index scores were above the minimal clinically important improvement was higher in the SVF group than in the HA group in the majority of assessments. The improvement of bone marrow by SVF treatment was significantly better than that of the HA group as observed by pre- and postoperative Magnetic resonance imaging (MRI). CONCLUSIONS: Multiple intra-articular injection of autologous SVF reduces pain and improves function in the short term in patients with early or midstage MOA. However, there was heterogeneity in the improvement of overall knee and isolated patellofemoral joint after treatment.

Four-channel joint-polarization-frequency-multiplexing encryption meta-hologram based on dual-band polarization multiplexing meta-atoms.

Holography is an advanced imaging technology where image information can be reconstructed without a lens. Recently, multiplexing techniques have been widely adapted to realize multiple holographic images or functionalities in a meta-hologram. In this work, a reflective four-channel meta-hologram is proposed to further increase the channel capacity by simultaneously implementing frequency and polarization multiplexing. Compared to the single multiplexing technique, the number of channels achieves a multiplicative growth of the two multiplexing techniques, as well as allowing meta-devices to possess cryptographic characteristics. Specifically, spin-selective functionalities for circular polarizations can be achieved at lower frequency, while different functionalities can be obtained at higher frequency under different linearly polarized incidences. As an illustrative example, a four-channel joint-polarization-frequency-multiplexing meta-hologram is designed, fabricated, and characterized. The measured results agree well with the numerically calculated and full-wave simulated ones, which provides the proposed method with great potential in numerous opportunities such as multi-channel imaging and information encryption technology.

Broadband high-efficiency polarization-encoded meta-holograms based on 3-bit spin-decoupled reflective meta-atoms.

Metasurfaces are engineered planar surfaces consisting of arrays of resonators for tailoring the electromagnetic wavefronts in a desirable way. However, the spin-locked issue of the geometric metasurfaces hinders simultaneous manipulation of both spins. In this work, a spin-decoupled information metasurface composed of simple C-shaped resonators is proposed to realize two different information channels under the orthogonal circularly polarized (CP) incidences. Based on the encoded digit '0' or '1', the diffusion scattering or a holographic image could be realized under the CP excitation in a broadband frequency range from 9 to 12 GHz. As an illustrative example, a 3-bit polarization-encoded meta-hologram is designed, fabricated, and characterized. The measured results agree very well with the numerical results, which gives the proposed method great potential in numerous applications such as holographic displays and information processing.

Dual-channel geometric meta-holograms with complex-amplitude modulation based on bi-spectral single-substrate-layer meta-atoms.

Metasurfaces with complex-amplitude modulation are superior in power regulation and hologram imaging resolution compared with those with phase-only modulation. Nevertheless, a single-cell metasurface with multi-band independent phase and amplitude controls is still a great challenge for the circularly polarized incidences. In this work, we propose and design a single-substrate-layer single-cell metasurface with independent complex-amplitude modulations at two discrete frequencies. Based on this emerging technique, a bi-spectral meta-hologram is designed and verified by both full-wave simulations and experiments, which could reconstruct two Chinese characters at the imaging plane at two frequencies. The proposed method shows great potential in multifunctional meta-devices with enhanced performance.

Design of broadband and wide-field-of-view metalenses.

In this Letter, we adapt the direct search method to metasurface optimization. We show that the direct search algorithm, when coupled with deep learning techniques for free-form meta-atom generation, offers a computationally efficient optimization approach for metasurface optics. As an example, we apply the approach to optimization of achromatic metalenses. Taking advantage of the diverse dispersion responses of free-form meta-atoms, metalenses designed using this approach exhibit superior broadband performances compared to their multilevel diffractive counterparts. We further demonstrate an achromatic and wide-field-of-view metalens design.

Large-area optical metasurface fabrication using nanostencil lithography.

We demonstrate a large-area fabrication process for optical metasurfaces utilizing reusable SiN on Si nanostencils. To improve the yield of the nanostencil fabrication, we partially etch the front-side SiN layer to transfer the metasurface pattern from the resist to the nanostencil membrane, preserving the integrity of the membrane during the subsequent potassium hydroxide etch. To enhance the reliability and resolution of metasurface fabrication using the nanostencil, we spin coat a sacrificial layer of resist to precisely determine the gap between the nanostencil and the metasurface substrate for the subsequent liftoff. 1.5 mm diameter PbTe meta-lenses on ${\rm{Ca}}{{\rm{F}}_2}$ fabricated using nanostencils show diffraction-limited focusing and focusing efficiencies of 42% for a 2 mm focal length lens and 53% for a 4 mm focal length lens. The nanostencils can also be cleaned using chemical cleaning methods for reuse.

Ceramide synthases: insights into the expression and prognosis of lung cancer.

CerSs (ceramide synthases), a group of enzymes that catalyze the formation of ceramides from sphingoid base and acyl-CoA substrates. As far, six types of CerSs (CerS1-CerS6) have been found in mammals. Each of these enzymes have unique characteristics, but maybe more noteworthy is the ability of individual CerS isoform to produce a ceramide with a characteristic acyl chain distribution. As key regulators of sphingolipid metabolism, CerSs highlight their unique characteristics and have emerging roles in regulating programmed cell death, cancer and many other aspects of biology. However, the role of CerSs in lung cancer has not been fully elucidated. In this study, there was no significant change in the sequence or copy number of CerSs gene, which could explain the stability of malignant tumor development through COSMIC database. In addition, gene expression in lung cancer was examined using the OncomineTM database, and the prognostic value of each gene in non-small cell lung cancer (NSCLC) was analyzed by Kaplan-Meier analysis. The results showed that high mRNA expression levels of CerS2, CerS3, CerS4 and CerS5 in all NSCLC patients were associated with improved prognosis. Among them, CerS2 and CerS5 are also highly expressed in adenocarcinoma (Ade), but not in squamous cell carcinoma (SCC). In contrast, high or low expression of CerS1 and CerS6 no difference was observed in patients with NSCLC, Ade and SCC. Integrated the data of this study suggested that these CerSs may be a potential tumor markers or drug target of new research direction.

Single-Element Diffraction-Limited Fisheye Metalens.

Wide field-of-view (FOV) optical functionality is crucial for implementation of advanced imaging and image projection devices. Conventionally, wide FOV operation is attained with complicated assembly of multiple optical elements known as "fisheye lenses". Here we present a novel metalens design capable of performing diffraction-limited focusing and imaging over an unprecedented near 180° angular FOV. The lens is monolithically integrated on a one-piece flat substrate and involves only a single layer of metasurface that corrects third-order Seidel aberrations including coma, astigmatism, and field curvature. The metalens further features a planar focal surface, which enables considerably simplified system architectures for applications in imaging and projection. We fabricated the metalens using Huygens meta-atoms operating at 5.2 µm wavelength and experimentally demonstrated aberration-free focusing and imaging over the entire FOV. The design concept is generic and can be readily adapted to different meta-atom geometries and wavelength ranges to meet diverse application demands.

Full control of dual-band vortex beams using a high-efficiency single-layer bi-spectral 2-bit coding metasurface.

Vortex beams (VBs) carrying orbital angular moment (OAM) modes have been proven to be promising resources for increasing communication capacity. Although considerable attention has been paid on metasurface-based VB generators due to the unprecedented advantages of metasurface, most applications are usually limited at a single band with a fixed OAM mode. In this work, an emerging dual-band reflection-type coding metasurface is proposed to mitigate these issues by newly engineered meta-atoms, which could achieve independent 2-bit phase modulations at two frequency bands. The proposed coding metasurface could efficiently realize and fully control dual-band VBs carrying frequency selective OAM modes under the linearly polarized incidence. As the first illustrative example, a dual-band VB generator with normal beam direction is fabricated and characterized at two widely used communication bands (Ku and Ka bands). Moreover, by encoding proper coding sequences, versatile beams carrying frequency selective OAM modes can be achieved. Therefore, by adding a gradient phase sequence to the first VB generator, the second one is designed to steer the generated beams to a preset direction, which could enable diverse scenarios. The measurement results of both VB generators agree very well with the numerical ones, validating the full control capability of the proposed approach.