One compound approach combining factor-analytic model with AMMI and GGE biplot to improve multi-environment trials analysis

To improve multi-environmental trial(MET)analysis,a compound method—which combines factor analytic(FA)model with additive main effect and multiplicative interaction(AMMI)and genotype main effect plus genotype-by-environment interaction(GGE)biplot—was conducted in this study.The diameter at breast height of 36 open-pollinated(OP)families of Pinus taeda at six sites in South China was used as a raw dataset.The best linear unbiased prediction(BLUP)data of all individual trees in each site was obtained by fitting the spatial effects with the FA method from raw data.The raw data and BLUP data were analyzed and compared by using the AMMI and GGE biplot.BLUP results showed that the six sites were heterogeneous and spatial variation could be effectively fitted by spatial analysis with the FA method.AMMI analysis identified that two datasets had highly significant effects on the site,family,and their interactions,while BLUP data had a smaller residual error,but higher variation explaining ability and more credible stability than raw data.GGE biplot results revealed that raw data and BLUP data had different results in mega-environment delineation,test-environment evaluation,and genotype evaluation.In addition,BLUP data results were more reasonable due to the stronger analytical ability of the first two principal components.Our study suggests that the compound method combing the FA method with the AMMI and GGE biplot could improve the analysis result of MET data in Pinus teada as it was more reliable than direct AMMI and GGE biplot analysis on raw data.

Metasurface array for single-shot spectroscopic ellipsometry

Spectroscopic ellipsometry is a potent method that is widely adopted for the measurement of thin film thickness and refractive index.Most conventional ellipsometers utilize mechanically rotating polarizers and grating-based spectrometers for spectropolarimetric detection.Here,we demonstrated a compact metasurface array-based spectroscopic ellipsometry system that allows single-shot spectropolarimetric detection and accurate determination of thin film properties without any mechanical movement.The silicon-based metasurface array with a highly anisotropic and diverse spectral response is combined with iterative optimization to reconstruct the full Stokes polarization spectrum of the light reflected by the thin film with high fidelity.Subsequently,the film thickness and refractive index can be determined by fitting the measurement results to a proper material model with high accuracy.Our approach opens up a new pathway towards a compact and robust spectroscopic ellipsometry system for the high throughput measurement of thin film properties.

High-Efficiency Dynamic Terahertz Deflector Utilizing a Mechanically Tunable Metasurface

Terahertz (THz) wave manipulation, especially the beam deflection, plays an essential role in various applications, such as next-generation communication, space exploration, and high-resolution imaging. Current THz optical components and devices are hampered by their large bulk sizes and passive responses, limiting the development of high-performance, miniaturized THz microsystems. Tunable metasurfaces offer a powerful dynamic optical platform for controlling the propagation of electromagnetic waves. In this article, we presented a mechanically tunable metasurface (MTM), which can achieve terahertz beam deflection and vary the intensity of the anomalous reflected terahertz wave by changing the air gap between the metallic resonator (MR) array with phase discontinuities and Au ground plane. The absence of lossy spacer materials substantially enhances deflection efficiency. The device was fabricated by a combination of the surface and bulk-micromachining processes. The THz beam steering capability was characterized using terahertz time domain spectroscopy. When the air gap is 50 μm, the maximum deflection coefficient reaches 0.60 at 0.61 THz with a deflection angle of ~44.5°, consistent with theoretical predictions. We further established an electrically tunable miniaturized THz device for dynamic beam steering by introducing a micro voice coil motor to control the air gap continuously. It is shown that our designed MTM demonstrates a high modulation depth of deflection coefficient (~ 62.5%) in the target steered angle at the operating frequency. Our results showcase the potential of the proposed MTM as a platform for high-efficiency THz beam manipulation.

Intracavity spatiotemporal metasurfaces

Optical metasurfaces are endowed with unparallel flexibility to manipulate the light field with a subwavelength spatial resolution.Coupling metasurfaces to materials with strong optical nonlinearity may allow ultrafast spatiotemporal light field modulation.However,most metasurfaces demonstrated thus far are linear devices.Here,we experimentally demonstrate simultaneous spatiotemporal laser mode control using a single-layer plasmonic metasurface strongly coupled to an epsilon-near-zero(ENZ)material within a fiber laser cavity.While the geometric phase of the metasurface is utilized to convert the laser’s transverse mode from a Gaussian beam to a vortex beam carrying orbital angular momentum,the giant nonlinear saturable absorption of the ENZ material enables pulsed laser generation via the Q-switching process.The direct integration of a spatiotemporal metasurface in a laser cavity may pave the way for the development of miniaturized laser sources with tailored spatial and temporal profiles,which can be useful for numerous applications,such as superresolution imaging,high-density optical storage,and three-dimensional laser lithography.

Metasurface designed with quantitative field distributions

A new method for designing metasurfaces has been proposed and demonstrated,which allows for the generation of precise quantitative field distributions.This unique approach involves combining a tandem neural network with an iterative algorithm to optimize the metasurface design,enabling accurate control over the intensity and polarization of the resulting field.This strategy is both efficient and robust and has the potential to accelerate the development of metasurface devices with complex functionalities.

Optical meta-waveguides for integrated photonics and beyond

The growing maturity of nanofabrication has ushered massive sophisticated optical structures available on a photonic chip.The integration of subwavelength-structured metasurfaces and metamaterials on the canonical building block of optical waveguides is gradually reshaping the landscape of photonic integrated circuits,giving rise to numerous metawaveguides with unprecedented strength in controlling guided electromagnetic waves.Here,we review recent advances in meta-structured waveguides that synergize various functional subwavelength photonic architectures with diverse waveguide platforms,such as dielectric or plasmonic waveguides and optical fibers.Foundational results and representative applications are comprehensively summarized.Brief physical models with explicit design tutorials,either physical intuition-based design methods or computer algorithms-based inverse designs,are cataloged as well.We highlight how meta-optics can infuse new degrees of freedom to waveguide-based devices and systems,by enhancing light-matter interaction strength to drastically boost device performance,or offering a versatile designer media for manipulating light in nanoscale to enable novel functionalities.We further discuss current challenges and outline emerging opportunities of this vibrant field for various applications in photonic integrated circuits,biomedical sensing,artificial intelligence and beyond.

Broadband terahertz wave generation from an epsilon-near-zero material

Broadband light sources emitting in the terahertz spectral range are highly desired for applications such as noninvasive imaging and spectroscopy.Conventionally,THz pulses are generated by optical rectification in bulk nonlinear crystals with millimetre thickness,with the bandwidth limited by the phase-matching condition.Here we demonstrate broadband THz emission via surface optical rectification from a simple,commercially available 19nmthick indium tin oxide(ITO)thin film.We show an enhancement of the generated THz signal when the pump laser is tuned around the epsilon-near-zero(ENZ)region of ITO due to the pump laser field enhancement associated with the ENZ effect.The bandwidth of the THz signal generated from the ITO film can be over 3 THz,unrestricted by the phasematching condition.This work offers a new possibility for broadband THz generation in a subwavelength thin film made of an ENZ material,with emerging physics not found in existing nonlinear crystals.

Synthetic aperture metalens

Metalenses are ultrathin optical elements that can focus light using densely arranged subwavelength structures.Due to their minimal form factor,they have been considered promising for imaging applications that require extreme system size,weight,and power,such as in consumer electronics and remote sensing.However,as a major impediment prohibiting the wide adoption of the metalens technology,the aperture size,and consequently the imaging resolution,of a metalens are often limited by lithography processes that are not scalable.Here,we propose to adopt a synthetic aperture approach to alleviate the issue,and experimentally demonstrate that,assisted by computational reconstruction,a synthetic aperture metalens composed of multiple metalenses with relatively small aperture size can achieve an imaging resolution comparable to a conventional lens with an equivalent large aperture.We validate the concept via an outdoor imaging experiment performed with a synthetic aperture metalens-integrated near-infrared camera using natural sunlight for target illumination.

Computational spectropolarimetry with a tunable liquid crystal metasurface

While conventional photodetectors can only measure light intensity,the vectorial light field contains much richer information,including polarization and spectrum,that are essential for numerous applications ranging from imaging to telecommunication.However,the simultaneous measurement of multi-dimensional light field information typically requires the multiplexing of dispersive or polarization-selective elements,leading to excessive system complexity.Here,we demonstrate a near-infrared spectropolarimeter based on an electrically-tunable liquid crystal metasurface.The tunable metasurface,which acts as an encoder of the vectorial light field,is tailored to support high-quality-factor guided-mode resonances with diverse and anisotropic spectral features,thus allowing the full Stokes parameters and the spectrum of the incident light to be computationally reconstructed with high fidelity.The concept of using a tunable metasurface for multi-dimensional light field encoding may open up new horizons for developing vectorial light field sensors with minimized size,weight,cost,and complexity.