Despite the vast promise of abrupt wavefront engineering within subwavelength thickness, most optical metasurfaces are still bound to bulky and rigid substrates. Recently, metasurfaces in suspended membranes (MISMs) have attracted increasing attention due to their unique flexible, conformal properties and their ability to minimize undesired substrate effects. Most importantly, the MISM platform enables metasurface transfer and integration with non-conventional substrates and electronic/photonic devices. By summarizing multiple approaches to create MISMs with a variety of membrane and sacrificial layer materials and configurations, we demonstrate the Omni-Purpose Transfer and Integration of Metasurfaces in Suspended Membranes (OPTIMISM), overcoming the existing limitations on metasurface geometries or materials. It is particularly suitable for metasurface integration on optical fiber tips to form meta-optic probes for broad applications, including biomedical and endoscopic imaging and sensing. Considering the various configurations of membrane dielectric environment in integrated MISM devices, we performed a systematic investigation to demonstrate the strong influence of the surrounding refractive index on ultrathin metasurface design based on both conventional forward design (library search) and inverse design strategy (evolutionary algorithm). Our findings highlight the advantage of the inverse design strategy leveraging meta-atom non-local interactions, and the great potential of the MISM platform for universal and scalable metasurface transfer and integration.

High-speed control of light in 3D space is a rapidly advancing field because it enables unique applications in neurobiology, communications, laser micromachining, and augmented/virtual reality. Several technologies have been demonstrated to advance this field, such as complex spatial light modulators (SLMs) and intricate optical systems that independently control in-plane and out-of-plane beam steering. These systems face significant limitations in speed, data handling, and power dissipation, and their bulky optical components hinder integration into other systems. Here, we present a tip-tilt-curvature micro-electro-mechanical systems (MEMS) scanner that overcomes these limitations by combining rapid lateral beam steering with ultra-fast axial focal tuning in a compact form factor of only a few millimeters. The device achieves lateral scan rates exceeding 10 kHz with axial focus modulation over tens of centimeters at operating frequencies exceeding 100 kHz. In benchmarking our device against other tip-tilt-curvature MEMS scanners, the one presented here demonstrates outstanding performance in combining lateral and axial scanning speeds. This performance, along with its compactness, establishes a new scalable architecture for dynamic three-dimensional control of light with high spatiotemporal resolution.

Abstract Millimeter-scale atomic vapor cells can be accurately and economically batch-fabricated by anodically bonding silicon and glass wafers, enabling the manufacturing of miniature atomic clocks and quantum sensors. However, silicon’s high dielectric constant and conductive losses at millimeter wave frequencies limit its suitability for Rydberg-atom electrometry, which enables highly sensitive electric-field measurements by exploiting the extreme polarizability of Rydberg states in alkali atoms. To address this, we present an all-glass wafer-level microfabrication process that eliminates silicon, creating hermetically sealed vapor cells that are stable over long timelines with embedded cesium dispensers. Femtosecond laser machining precisely defines the cell geometry, and laser-activated alkali loading ensures reliable filling. We demonstrate long-term vacuum stability and robust Rydberg excitation through electromagnetically induced transparency measurements. We then use these cells to measure a 34 GHz millimeter wave field resonant with the $$58{{\rm{D}}}_{5/2}\to 60{{\rm{P}}}_{3/2}$$ 58 D 5 / 2 → 60 P 3 / 2 transition using Autler-Townes splitting and observe the expected linear dependence with field strength. This work demonstrates that the all-glass bonding approach offers a highly durable low-loss cell alternative for miniaturized millimeter wave and microwave quantum sensing, with the potential to flexibly incorporate a range of other dielectric and semiconductor materials and integrate with photonic and electronic technologies.

We present a comprehensive numerical investigation into the radio frequency (RF) field behavior within miniaturized all-glass and hybrid vapor cell geometries designed for Rydberg atom-based electrometry. Using full-vector finite element modeling (FEM), we analyze electromagnetic field enhancement across a wide frequency range (0.05 GHz to 150 GHz) as a function of polarization, incidence angle, and structural configuration. Two primary vapor cell designs are evaluated: translationally invariant "open" cells and periodically structured "supported" cells composed entirely of low-loss glass, as well as hybrid structures incorporating highly doped silicon. Our simulations reveal that the structured all-glass vapor cells exhibit sharp, angle- and polarization-dependent resonant peaks due to guided-mode coupling, resulting in localized RF power enhancements exceeding 8x. In contrast, silicon-based structures demonstrate significant electric field attenuation and suppression of resonant features due to their high dielectric losses. Through k-vector and angle-resolved analyses, we show how cell geometry and material properties critically influence the RF field distribution and coupling efficiency. Our findings open new possibilities for optimizing vapor cell architectures to enhance field sensitivity, directional and polarization selectivity, and integration potential in chip-scale quantum sensing platforms based on Rydberg atoms.

As demand surges for miniaturized optical systems capable of three-dimensional imaging, MEMS laser scanners have started gaining momentum. We demonstrate a single, high-speed micromirror scanner capable of changing its focal point within 15µs.

Rydberg-atom electrometry enables highly sensitive electric-field measurements by exploiting the extreme polarizability of Rydberg states in alkali atoms. Millimeter-scale atomic vapor cells can be accurately and economically batch-fabricated by anodically bonding silicon and glass wafers, enabling the large-volume manufacturing of miniature atomic clocks and quantum sensors. However, silicon is not always an ideal constitutive material for electric-field sensing because of its high dielectric constant and conductive losses at millimeter wave frequencies. A broader selection of low-loss all-dielectric alternatives may be beneficial for specific applications. Here, we present an all-glass wafer-level microfabrication process that eliminates silicon, creating hermetically sealed vapor cells that are stable over long timelines with embedded cesium dispensers. Femtosecond laser machining precisely defines the cell geometry, and laser-activated alkali loading ensures reliable filling. We demonstrate long-term vacuum stability and robust Rydberg excitation through electromagnetically induced transparency measurements of several Rydberg states. We then use these cells to measure a 34 GHz millimeter wave field resonant with the 58D_5/2→60P_3/2 transition using Autler-Townes splitting showing expected linear dependence with field strength. This work demonstrates that the all-glass approach offers a highly durable low-loss cell alternative for miniaturized millimeter wave and microwave quantum sensing, with the potential to flexibly incorporate a range of other dielectric and semiconductor materials and integrated photonic and electronic technologies.

Nanomechanical devices made from ultrathin materials are transforming diverse fields, including sensing, signal processing, and quantum technologies. However, as these materials become thinner, their low bending rigidity poses significant fabrication challenges, and achieving nanometer-thick flat cantilevers with consistent and predictable mechanical responses has remained elusive despite decades of research. Here we present nanometer-thick, ultraflat cantilever resonators fabricated using atomic layer deposition. By effectively mitigating the effects of uncontrollable built-in strain and geometric disorder, the ultraflat nanocantilevers exhibit resonance frequencies closely aligned with thin-plate theory predictions and display low sample-to-sample variability. These cantilevers maintain mechanical stability in both vacuum and air environments, even at large length-to-thickness ratios of up to 3,000. The ultraflat nanocantilevers are approaching the thickness limit, beyond which thermal fluctuations at room temperature can spontaneously induce random ripples in otherwise flat films.

Thermally induced ripples are intrinsic features of nanometer-thick films, atomically thin materials, and cell membranes, significantly affecting their elastic properties. Despite decades of theoretical studies on the mechanics of suspended thermalized sheets, controversy still exists over the impact of these ripples, with conflicting predictions about whether elasticity is scale-dependent or scale-independent. Experimental progress has been hindered so far by the inability to have a platform capable of fully isolating and characterizing the effects of ripples. This knowledge gap limits the fundamental understanding of thin materials and their practical applications. Here, we show that thermal-like static ripples shape thin films into a class of metamaterials with scale-dependent, customizable elasticity. Utilizing a scalable semiconductor manufacturing process, we engineered nanometer-thick films with precisely controlled frozen random ripples, resembling snapshots of thermally fluctuating membranes. Resonant frequency measurements of rippled cantilevers reveal that random ripples effectively renormalize and enhance the average bending rigidity and sample-to-sample variations in a scale-dependent manner, consistent with recent theoretical estimations. The predictive power of the theoretical model, combined with the scalability of the fabrication process, was further exploited to create kirigami architectures with tailored bending rigidity and mechanical metamaterials with delayed buckling instability.

Our research unveiled a novel application of torsional MEMS, showcasing their ability to manipulate hard X-ray pulses effectively. This manipulation occurs on a time scale from 300 ps down to an astonishing 50 ps, a range comparable to or even shorter than the pulse length of X-rays from synchrotron sources. This ultra-fast X-ray modulation is achieved by timing nonlinear micro-mechanical resonators with a synchrotron storage ring to diffract X-ray pulses through the narrow Bragg peak of the single-crystalline material. We have achieved an unprecedentedly fast maximum angular velocity exceeding 10 7 degrees/s while maintaining the maximum linear velocity well below sonic speed and material break-down limit. Furthermore, we have demonstrated the potential of highly ultrafast X-ray optics-on-a-chip based on MEMS. These optics can modulate hard X-ray pulses exceeding 350 MHz, a frequency 10 3 times higher than any other mechanical modulator, with a pulse purity >10 6 without compromising the spectral brilliance.

In lieu of continuous time active feedback control in complex systems, nonlinear dynamics offers a means to generate desired long-term responses using short-time control signals. This type of control has been proposed for use in resonators that exhibit a plethora of complex dynamic behaviors resulting from energy exchange between modes. However, the dynamic response and, ultimately, the ability to control the response of these systems remains poorly understood. Here, we show that a micromechanical resonator can generate diverse, robust dynamical responses that occur on a timescale five orders of magnitude larger than the external harmonic driving and these responses can be selected by inserting small pulses at specific branching points. We develop a theoretical model and experimentally show the ability to control these response patterns. Hence, these mechanical resonators may represent a simple physical platform for the development of springboard concepts for nonlinear, flexible, yet robust dynamics found in other areas of physics, chemistry, and biology.

Metasurfaces offer a versatile platform for engineering the wavefront of light using nanostructures with subwavelength dimensions and hold great promise for dramatically miniaturizing conventional optical elements due to their small footprint and broad functionality. However, metasurfaces so far have been mainly demonstrated on bulky and planar substrates that are often orders of magnitude thicker than the metasurface itself. Conventional substrates not only nullify the reduced footprint advantage of metasurfaces, but also limit their application scenarios. The bulk substrate also determines the metasurface dielectric environment, with potentially undesired optical effects that undermine the optical performance. Here we develop a universal polymer-assisted transfer technique to tackle this challenge by decoupling the substrate employed on the fabrication of metasurfaces from that used for the target application. As an example, Huygens' metasurfaces with 120 nm thickness in the visible range (532 nm) are demonstrated to be transferred onto a 100 nm thick freestanding SiN x membrane while maintaining excellent structural integrity and optical performance of diffraction-limited focusing. This transfer method not only enables the thinnest dielectric metalens to the best of our knowledge, but also opens up new opportunities in integrating cascaded and multilayer metasurfaces, as well as the heterogeneous integration with nonconventional substrates and various electronic/photonic devices.

When two eigenmodes are at internal resonance, i.e. they have commensurate eigenfrequencies, their coupling strength can be significantly enhanced.Rich nonlinear dynamics have been shown at internal resonance.In this work, we present a novel nonmonotonic energy dissipation rate of microelectromechanical systems (MEMs) at internal resonance.We demonstrate that the MEMS can selectively dissipate via two largely distinctive pathways, solely depending on the choice of their relative initial phase.Remarkably, these novel and complicated behaviors can be understood by an intuitive parametric-oscillator-like model.Our work illuminates a path to dissipation engineering, frequency stabilization, and sensitivity enhancement.

Synchrotrons are powerful and productive in revealing the spatiotemporal complexities in matter. However, X-ray pulses produced by the synchrotrons are predetermined in specific patterns and widths, limiting their operational flexibility and temporal resolution. Here, we introduce the on-chip picosecond synchrotron pulse shaper that shapes the sub-nm-wavelength hard X-ray pulses at individual beamlines, flexibly and efficiently beyond the synchrotron pulse limit. The pulse shaper is developed using the widely available silicon-on-insulator technology, oscillates in torsional motion at the same frequency or at harmonics of the storage ring, and manipulates X-ray pulses through the narrow Bragg peak of the crystalline silicon. Stable pulse manipulation is achieved by synchronizing the shaper timing to the X-ray timing using electrostatic closed-loop control. Tunable shaping windows down to 40 $ps$ are demonstrated, allowing X-ray pulse picking, streaking, and slicing in the majority of worldwide synchrotrons. The compact, on-chip shaper offers a simple but versatile approach to boost synchrotron operating flexibility and to investigate structural dynamics from condensed matter to biological systems beyond the current synchrotron-source limit.

Command shaping is a driving technique for handling the large settling time of the high-Q-MEMS actuators. The strong nonlinearity due to the electrostatic actuation limits the linear operation range in cantilevered or torsional micro-mirrors where command shaping techniques can be applied for positioning. Experimental and simulation results of this research demonstrate the effectiveness of using electrostatic levitation to overcome the actuation nonlinearities and a significant increase in the operation range. The motivation for this research is that applying the nonlinear command shaping causes complexity in command manipulation and requires an accurate knowledge of the nonlinear terms involved in the system model. The large linear operation range generated by the levitating force allows using the practical simple command shaping methods for open-loop control.

Optical scanning is a prevalent technique for optical neural interfaces where light delivery with high spatial and temporal precision is desired. However, due to the sequential nature of point-scanning techniques, the settling time of optical modulators is a major bottleneck for throughput and limits random-access targeting capabilities. While fast lateral scanners exist, commercially available varifocal elements are constrained to >3ms settling times, limiting the speed of the overall system to hundreds of Hz. Faster focusing methods exist but cannot combine fast operation and dwelling capability with electrical and optical efficiency. Here, we present a varifocal mirror comprised of an array of piston-motion MEMS micromirrors and a custom driver ASIC, offering fast operation with dwelling capability while maintaining high diffraction efficiency. The ASIC features a reconfigurable nonlinear DAC to simultaneously compensate for the built-in nonlinearity of electrostatic actuators and the global process variations in MEMS mirrors. Experimental results demonstrate a wide continuous sweeping range that spans 22 distinctly resolvable depth planes with refresh rates greater than 12 kHz.

Metasurfaces infiltrated with liquid crystals have become a particularly promising means of tuning their optical properties, due to liquid crystals' large and broadband optical anisotropy. In order to fully explore the parameter space of broadband all-dielectric liquid crystal tunable metasurfaces in the visible, we undertake a comprehensive study based on TiO2 nanoresonator superarrays, sweeping geometric parameters (i.e. disc radius and disc-to-disc gap). We demonstrate both electrical and thermal switching, and visualize the resonance change caused by either the orientation or phase change of liquid crystal, which provides a practical library for the rational design of liquid crystal tunable metasurfaces.

In article number 2005275, Horacio D. Espinosa, Daniel Lopez, and co-workers demonstrate the engineering of nanoscale kirigami structures exhibiting a range of buckling-induced controllable 3D configurations. By combining nanomanufacturing, in situ microscopy experimentation, and computational modeling, symmetric and asymmetric 3D configurations relevant to numerous applications are demonstrated, including kirigami-based soft nanogrippers (robotics), light modulation, deformable electronics, and tunable metamaterials.

Microelectromechanical systems (MEMS) are miniature devices integrated into a vast range of industrial and consumer applications. Optical MEMS are developed for dynamic spatiotemporal control in lightwave manipulation and communication as modulators, switches, multiplexers, spectrometer, etc. However, they have not been shown to function similarly in sub-nm wavelength regimes, namely, with hard x-rays, as high-brilliance pulsed x-rays have proven powerful for addressing challenges in time-domain science, from energy conversion to neurobiological control. While desirable temporal properties of x-ray pulses can be enhanced by optics, conventional x-ray optics are inherently massive in size, hence, never dynamic. We demonstrate highly ultrafast x-ray optics-on-a-chip based on MEMS capable of modulating hard x-ray pulses exceeding 350 MHz, 10 3 × higher than any other mechanical modulator, with a pulse purity >10 6 without compromising the spectral brilliance. Moreover, the timing characteristics of the devices can be tuned on-the-fly to deliver optimal pulse properties to create a host of dynamic x-ray instruments and applications, impossible with traditional optics of 10 9 × bulkier and more massive. The advent of the ultrafast optics-on-a-chip heralds a new paradigm of x-ray photonics, time-domain science, and accelerator diagnostics, especially at not only the future-generation light sources that offer coherent and high-frequency pulses but also lab-based facilities that normally do not offer timing structures.

Optogenetics is a technique that involves the use of light to excite or inhibit neurons that have been genetically modified to express light-sensitive ion channels (opsins). Implanted LEDs or optical fibers are the most common approaches in optogenetic stimulation systems, but their broad illumination and lack of beam steering capability make them insufficient for probing individual neurons. When a 3D scanning optical system is used to control the position of a laser spot, single-cell precision can be achieved in a volume of tissue containing millions of cells. Due to the sub-ms response time of modern opsins and a demand for high throughput neural stimulation [1], a random-access scanning system requires a kHz refresh rate, and the capability to dwell on a target depth for an arbitrary length of time. Existing lateral (XY) scanning tools are fast, however state-of-the-art axial (Z) scanning technologies such as electrically tunable lenses (ETLs) [2] and liquid crystal (LC) lenses [3] are limited to < 3ms settling times. Alternative axial scanning tools either lack dwelling capability [4] or have impractical actuator drive requirements [5].

The adoption of metasurfaces has led to revolutionary advances in holography due to improved compactness, integrability, and performance. Switchable meta-holograms projecting different replay field images in a controllable manner are highly desirable. Still, existing technologies generally rely on the use of polarized light and additional optics to facilitate switching. Consequently, the potential benefits afforded through the use of metasurfaces are limited both by the system complexity and a fixed relationship between the optical input and output. In this manuscript, we demonstrate polarization-insensitive metasurfaces encoding arbitrary and independent holograms, which can be switched between by changing the refractive index of the infiltration medium while maintaining identical illumination conditions. By sidestepping the requirements for high-performance light sources, switching optics, or delicate alignment, this approach points toward ultracompact and cost-effective switchable meta-holograms for various practical applications, such as holographic image projection, eye-perceptible sensors, optical information storage, processing, and security.