First realization of macroscopic Fourier ptychography for hundred-meter distance sub-diffraction imaging

Fourier ptychography (FP) imaging, drawing on the idea of synthetic aperture, has been demonstrated as a potential approach for remote sub-diffraction-limited imaging. Nevertheless, the farthest imaging distance is still limited around 10 m even though there has been a significant improvement in macroscopic FP. The most severely issue in increasing the imaging distance is FoV limitation caused by far-field condition for diffraction. Here, we propose to modify the Fourier far-field condition for rough reflective objects, aiming to overcome the small FoV limitation by using a divergent beam to illuminate objects. A joint optimization of pupil function and target image is utilized to attain the aberration-free image while estimating the pupil function simultaneously. Benefiting from the optimized reconstruction algorithm which effectively expands the camera's effective aperture, we experimentally implement several FP systems suited for imaging distance of 12 m, 90 m, and 170 m with the maximum synthetic aperture of 200 mm. The maximum imaging distance and synthetic aperture are thus improved by more than one order of magnitude of the state-of-the-art works with a fourfold improvement in the resolution. Our findings demonstrate significant potential for advancing the field of macroscopic FP, propelling it into a new stage of development

Physics-data-driven intelligent optimization for large-scale meta-devices

Meta-devices have gained significant attention and have been widely utilized in optical systems for focusing and imaging, owing to their lightweight, high-integration, and exceptional-flexibility capabilities. However, based on the assumption of local phase approximation, traditional design method neglect the local lattice coupling effect between adjacent meta-atoms, thus harming the practical performance of meta-devices. Using physics-driven or data-driven optimization algorithms can effectively solve the aforementioned problems. Nevertheless, both of the methods either involve considerable time costs or require a substantial amount of data sets. Here, we propose a physics-data-driven approach based "intelligent optimizer" that enables us to adaptively modify the sizes of the studied meta-atom according to the sizes of its surrounding ones. Such a scheme allows to mitigate the undesired local lattice coupling effect, and the proposed network model works well on thousands of datasets with a validation loss of 3*10-3. Experimental results show that the 1-mm-diameter metalens designed with the "intelligent optimizer" possesses a relative focusing efficiency of 93.4% (as compared to ideal focusing) and a Strehl ratio of 0.94. In contrast to the previous inverse design method, our method significantly boosts designing efficiency with five orders of magnitude reduction in time. Our design approach may sets a new paradigm for devising large-scale meta-devices.Comment: manuscripts:19 pages, 4 figures; Supplementary Information: 11 pages, 12 figure

Improved spatiotemporal resolution of anti-scattering super-resolution label-free microscopy via synthetic wave 3D metalens imaging

Super-resolution (SR) microscopy has dramatically enhanced our understanding of biological processes. However, scattering media in thick specimens severely limits the spatial resolution, often rendering the images unclear or indistinguishable. Additionally, live-cell imaging faces challenges in achieving high temporal resolution for fast-moving subcellular structures. Here, we present the principles of a synthetic wave microscopy (SWM) to extract three-dimensional information from thick unlabeled specimens, where photobleaching and phototoxicity are avoided. SWM exploits multiple-wave interferometry to reveal the specimen’s phase information in the area of interest, which is not affected by the scattering media in the optical path. SWM achieves ~0.42 λ/NA resolution at an imaging speed of up to 106 pixels/s. SWM proves better temporal resolution and sensitivity than the most conventional microscopes currently available while maintaining exceptional SR and anti-scattering capabilities. Penetrating through the scattering media is challenging for conventional imaging techniques. Remarkably, SWM retains its efficacy even in conditions of low signal-to-noise ratios. It facilitates the visualization of dynamic subcellular structures in live cells, encompassing tubular endoplasmic reticulum (ER), lipid droplets, mitochondria, and lysosomes

Crosstalk-free achromatic full Stokes imaging polarimetry metasurface enabled by polarization-dependent phase optimization

Imaging polarimetry is one of the most widely used analytical technologies for object detection and analysis. To date, most metasurface-based polarimetry techniques are severely limited by narrow operating bandwidths and inevitable crosstalk, leading to detrimental effects on imaging quality and measurement accuracy. Here, we propose a crosstalk-free broadband achromatic full Stokes imaging polarimeter consisting of polarization-sensitive dielectric metalenses, implemented by the principle of polarization-dependent phase optimization. Compared with the single-polarization optimization method, the average crosstalk has been reduced over three times under incident light with arbitrary polarization ranging from 9 μm to 12 μm, which guarantees the measurement of the polarization state more precisely. The experimental results indicate that the designed polarization-sensitive metalenses can effectively eliminate the chromatic aberration with polarization selectivity and negligible crosstalk. The measured average relative errors are 7.08%, 8.62%, 7.15%, and 7.59% at 9.3, 9.6, 10.3, and 10.6 μm, respectively. Simultaneously, the broadband full polarization imaging capability of the device is also verified. This work is expected to have potential applications in wavefront detection, remote sensing, light-field imaging, and so forth

Fine roots branch orders of Abies faxoniana respond differentially to warming in a subalpine coniferous forest ecosystem

Root is an important plant organ and has high heterogeneity. Global warming could change root and affect belowground ecological processes. There is little information on how fine roots branch orders responds to global change. This study examined the growth, morphological and physiological responses of fine roots of a subalpine coniferous species to warming. We investigated biomass, average diameter, specific root length (SRL), triphenyltetrazolium chloride (TTC) reducing capacity, carbon (C), total non-structural carbon (TNC) and fractions of the primal five branch order roots of Abies faxoniana in April, August, October and December. The decrease in total fine roots biomass after a growing season was significantly greater under warming treatment compared to control, suggesting that warming could accelerate the carbon input from root to soil, but the increment depended on tree species. Warming did not affect average diameter and SRL. Responses of biomass, TTC reducing capacity, C, TNC and fractions to warming significantly differed with root order and month. Significant warming effects were only observed in C and starch concentration of the first order and also TNC and soluble sugar concentration of the first three orders. The results indicated that the lower order roots (the first three orders) were more sensitive to warming, probably because they had more frequent, intense interactions with soil and low defense capability. Thus, global warming may dramatically alter root functions such as nutrients and water uptake as well as the cycle of C and nutrients at the whole subalpine coniferous forest ecosystem

Analysis of the phenolic compounds in root exudates produced by a subalpine coniferous species as responses to experimental warming and nitrogen fertilisation

In terrestrial ecosystems, plant root exudates clearly play a crucial role in the belowground ecosystem. However, there have been few reports on root exudates from field-grown plants or mature trees in situ, especially when exposed to experimental warming. In this study, we adopted and modified a culture-based cuvette system developed especially for root exudation collection in the field to collect soluble root exudates of a subalpine coniferous species, Abies faxoniana, under experimental warming and nitrogen fertilisation treatments. We then analysed the chemical composition and relative abundance of root exudates using gas chromatography-mass spectrometry (GC-MS). The major chemical constituents of root exudates were phenols and their derivatives of all the different treatments, such as 2, 6-di-tert-butyl-4-methylphenol. Experimental warming had significant effects on the relative contents of major compounds and an increase effect on the total phenolic acid compounds. By contrast, there were small significant effects of N fertilisation on root exudation and no significant effects of the warming x N fertilisation interaction. Meanwhile, warming also markedly increased soil polyphenol oxidase activity and it may be soil ecological adjustment response to changes of root exudation under global climate warming

Meta-Optics-Empowered Switchable Integrated Mode Converter Based on the Adjoint Method

Monolithic integrated mode converters with high integration are essential to photonic integrated circuits (PICs), and they are widely used in next-generation optical communications and complex quantum systems. It is expected that PICs will become more miniaturized, multifunctional, and intelligent with the development of micro/nano-technology. The increase in design space makes it difficult to realize high-performance device design based on traditional parameter sweeping or heuristic design, especially in the optimal design of reconfigurable PIC devices. Combining the mode coupling theory and adjoint calculation method, we proposed a design method for a switchable mode converter. The device could realize the transmission of TE0 mode and the conversion from TE0 to TE1 mode with a footprint of 0.9 × 7.5 μm2 based on the phase change materials (PCMs). We also found that the mode purity could reach 78.2% in both states at the working wavelength of 1.55 μm. The designed method will provide a new impetus for programmable photonic integrated devices and find broad application prospects in communication, optical neural networks, and sensing

Metasurface spatiotemporal dynamics and asymmetric photonic spin-orbit interactions mediated vector-polarization optical chaos

10.1103/physrevresearch.3.013215Physical Review Research3101321

Meta-optics empowered vector visual cryptography for high security and rapid decryption

Usual methods for optical encryption suffer from a tradeoff between the level of security and the complexity of operation given by multiple optical measurements or digital postprocessing. Here, the authors show a multi-d.o.f. metasurface-based vector optical manipulation protocol enabling secure decryption in real time