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We demonstrate fabrication of nano-patterned thin ALD (Atomic layer deposition) membrane (suspended/transferable) by using a bi-layer resist process where the bottom layer resist acts as a sacrificial layer. This method enables an all dry deterministic transfer of nano-patterned ALD membrane on desired substrate, allowing assembly of multitude of hetero-structures \& functionalities that are not yet accessible. Unlike conventional ways of achieving patterned alumina membrane reported in literature our technique requires significantly less fabrication steps and paves the way for novel ALD membrane-based technology.

Herein, we demonstrate a cavity-enhanced hyperspectral refractometric imaging using an all-dielectric photonic crystal slab (PhCS). Our approach takes advantage of the synergy between two mechanisms, surface-enhanced fluorescence (SEF) and refractometric sensing, both based on high-Q resonances in proximity of bound states in the continuum (BICs). The enhanced local optical field of the first resonance amplifies of 2 orders of magnitude the SEF emission of a probe dye. Simultaneously, hyperspectral refractometric sensing, based on Fano interference between second mode and fluorescence emission, is used for mapping the spatially variant refractive index produced by the specimen on the PhCS. The spectral matching between first resonance and input laser is modulated by the specimen local refractive index, and thanks to the calibrated dependence with the spectral shift of the Fano resonance, the cavity tuning is used to achieve an enhanced correlative refractometric map with a resolution of 10-5 RIU within femtoliter-scale sampling volumes. This is experimentally applied also on live prostate cancer cells grown on the PhCS, reconstructing enhanced surface refractive index images at the single-cell level. This dual mechanism of quasi-BIC spatially variant gain tracked by quasi-BIC refractometric sensing provides a correlative imaging platform that can find application in many fields for monitoring physical and biochemical processes, such as molecular interactions, chemical reactions, or surface cell analysis.

F\"orster Resonant Energy Transfer (FRET)-mediated exciton diffusion through artificial nanoscale building block assemblies could be used as a new optoelectronic design element to transport energy. However, so far nanocrystal (NC) systems supported only diffusion length of 30 nm, which are too small to be useful in devices. Here, we demonstrate a FRET-mediated exciton diffusion length of 200 nm with 0.5 cm2/s diffusivity through an ordered, two-dimensional assembly of cesium lead bromide perovskite nanocrystals (PNC). Exciton diffusion was directly measured via steady-state and time-resolved photoluminescence (PL) microscopy, with physical modeling providing deeper insight into the transport process. This exceptionally efficient exciton transport is facilitated by PNCs high PL quantum yield, large absorption cross-section, and high polarizability, together with minimal energetic and geometric disorder of the assembly. This FRET-mediated exciton diffusion length matches perovskites optical absorption depth, opening the possibility to design new optoelectronic device architectures with improved performances, and providing insight into the high conversion efficiencies of PNC-based optoelectronic devices.

The development of polymeric optical materials with a higher refractive index, transparency in the visible spectrum region and easier processability is increasingly desirable for advanced optical applications such as microlenses, image sensors, and organic light-emitting diodes. Most acrylates have a low refractive index (around 1.50) which does not meet the high performance requirements of advanced optical materials. In this research, three novel acrylates were synthesized via a facile one-step approach and used to fabricate optical transparent polymers. All of the polymers reveal good optical properties including high transparency (≥90%) in the visible spectrum region and high refractive index values (1.6363) at 550 nm. Moreover, nanostructures of these acrylate polymers with various feature sizes including nanogratings and photonic crystals were successfully fabricated using nanoimprint lithography. These results indicate that these acrylates can be used in a wide range of optical and optoelectronic devices where nanopatterned films with high refractive index and transparency are required.

Ultrathin films suspended as freestanding membranes are critical to many microelectronic and materials science applications. However, fabrication methods are currently limited in either their flexibility, due to material selectivity issues during the final membrane release, or their scalability. Here, we demonstrate a novel fabrication process for suspending ultrathin films with thicknesses as low as 4 nm and lateral dimensions up to 20 × 1000 μm from a variety of materials grown by atomic layer deposition. A silicon nitride membrane serves as the support for a sacrificial polymer layer and an ultrathin atomic layer deposition film which, after plasma etching, will form the membrane. The high chemical selectivity between atomic layer deposition-grown transition metal nitrides and oxides and the sacrificial polymer means that ultrathin films of a variety of materials can be released without damage using a single process. Electrically conductive titanium nitride membranes can be produced by this method and are of significant interest for electron microscopy applications. Electron transparency of titanium nitride membranes was found to be ∼14% higher than silicon nitride of the same thickness, and of similar conductivity to graphite, meaning that ultrathin, conductive, and electron transparent membranes can be fabricated at scale. These membranes are ideal supports for electron and photon characterization techniques, as well as microelectromechanical system applications that require a conductive membrane.

A giant enhancement of upconversion luminescence (UCPL) from an all-dielectric metasurface supporting bound states in the continuum (BICs) engineered with lanthanide-doped nanocrystals is herein demonstrated. The strong-coupling mechanism occurring at the edge of the photonic superstructure leads to an UCPL radiance enhancement of ~108.

The ability to correlate optical hyperspectral mapping and high resolution topographic imaging is critically important to gain deep insight into the structure–function relationship of nanomaterial systems. Scanning near-field optical microscopy can achieve this goal, but at the cost of significant effort in probe fabrication and experimental expertise. To overcome these two limitations, we have developed a low-cost and high-throughput nanoimprinting technique to integrate a sharp pyramid structure on the end facet of a single-mode fiber that can be scanned with a simple tuning-fork technique. The nanoimprinted pyramid has two main features: (1) a large taper angle (∼70°), which determines the far-field confinement at the tip, resulting in a spatial resolution of 275 nm, an effective numerical aperture of 1.06, and (2) a sharp apex with a radius of curvature of ∼20 nm, which enables high resolution topographic imaging. Optical performance is demonstrated through evanescent field distribution mapping of a plasmonic nanogroove sample, followed by hyperspectral photoluminescence mapping of nanocrystals using a fiber-in-fiber-out light coupling mode. Through comparative photoluminescence mapping on 2D monolayers, we also show a threefold improvement in spatial resolution over chemically etched fibers. These results show that the bare nanoimprinted near-field probes provide simple access to spectromicroscopy correlated with high resolution topographic mapping and have the potential to advance reproducible fiber-tip-based scanning near-field microscopy.

Pulsed electron beam sources are increasingly in demand, especially as probes for ultrafast science and as patterning tools in lithography applications. Plasmonic nanostructures have been shown to enhance multiphoton photocurrent from metal cathodes by orders of magnitude, but for many applications it is also important to characterize the transverse electron beam properties. Here, we present preliminary work demonstrating a DC photogun setup for characterizing plasmonic photoemitters at Lawrence Berkeley National Laboratory, including measurement of photocurrent and the asymmetric transverse phase space of photoemitted beams from plasmonic nanogroove resonator arrays. This lays the groundwork for future studies of emerging plasmon-enhanced photoemitter designs, such as plasmonic lens nanoemitters.

We describe a technique for measuring the instrument transfer function (ITF) of an interferometric microscope, allowing both characterization and data processing to increase the fidelity and effective resolution of the tool. The technique, based on test samples structured as two-dimensional (2D) binary pseudo-random arrays (BPRAs), employs the unique properties of the BPRA patterns in the spatial frequency domain. The inherent 2D power spectral density of the pattern has a deterministic white-noise-like character that allows direct determination of the ITF with uniform sensitivity over the entire spatial frequency range and field-of-view of an instrument. As such, the BPRA samples satisfy the characteristics of a test standard: functionality, ease of specification and fabrication, reproducibility, and low sensitivity to manufacturing error. We discuss the results of the development and application of highly randomized (HR) BPRA test samples with elementary feature sizes in the range from 80 nm and up to 2.5 μm, optimized for the ITF characterization of interferometric microscopes broadly used for 2D optical surface profiling. The data acquisition and analysis procedures for different applications of the ITF calibration technique developed are also discussed.

The discovery of interaction-driven insulating and superconducting phases in moir\'e van der Waals heterostructures has sparked considerable interest in understanding the novel correlated physics of these systems. While a significant number of studies have focused on twisted bilayer graphene, correlated insulating states and a superconductivity-like transition up to 12 K have been reported in recent transport measurements of twisted double bilayer graphene. Here we present a scanning tunneling microscopy and spectroscopy study of gate-tunable twisted double bilayer graphene devices. We observe splitting of the van Hove singularity peak by ~20 meV at half-filling of the conduction flat band, with a corresponding reduction of the local density of states at the Fermi level. By mapping the tunneling differential conductance we show that this correlated system exhibits energetically split states that are spatially delocalized throughout the different regions in the moir\'e unit cell, inconsistent with order originating solely from onsite Coulomb repulsion within strongly-localized orbitals. We have performed self-consistent Hartree-Fock calculations that suggest exchange-driven spontaneous symmetry breaking in the degenerate conduction flat band is the origin of the observed correlated state. Our results provide new insight into the nature of electron-electron interactions in twisted double bilayer graphene and related moir\'e systems., Comment: 24 pages, 5 figures

A novel hyperspectral sensing imaging taking advantage of engineered all-dielectric metasurfaces supporting bound states in the continuum here is discussed. This approach combines surface-enhanced fluorescence and res- onant shift both based on high-Q resonances in proximity of bound states in the continuum. The amplification of the optical field on resonance allows increasing the fluorescence emission of a dye as a function of the spatial- variant dielectric environment in the near-field of the structure. We first demonstrate the fluorescence emission amplification by resonant pump matching in microscopy configuration. Then, we take advantage of Fano reso- nances in the fluorescence emission to map the spatially variant environment of biological cells. To demonstrate the real implementation of the proposed BIC-enhanced imaging as a platform for biosensing, hyperspectral maps of prostate cancer cells are experimentally reconstructed.

Optically transparent polymers with a high refractive index can find a broad range of applications in optoelectronics. The majority of available polymers present lower refractive index values ranging from 1.50 to 1.60. Here, we demonstrate the development of organic polymers with a high refractive index (up to 1.90) for thin-film applications. The synthesized polymers show high transparency in the visible wavelength and are entirely nanoparticle free. They are among the organic polymers with the highest refractive index ever reported. The developed polymers can be nanopatterned via nanoimprint lithography, a powerful method to fabricate nanostructures following a simple and scalable process.

The theory behind the electrical switching of antiferromagnets is premised on the existence of a well defined broken symmetry state that can be rotated to encode information. A spin glass is in many ways the antithesis of this state, characterized by an ergodic landscape of nearly degenerate magnetic configurations, choosing to freeze into a distribution of these in a manner that is seemingly bereft of information. In this study, we show that the coexistence of spin glass and antiferromagnetic order allows a novel mechanism to facilitate the switching of the antiferromagnet Fe$_{1/3+\delta}$NbS$_2$, which is rooted in the electrically-stimulated collective winding of the spin glass. The local texture of the spin glass opens an anisotropic channel of interaction that can be used to rotate the equilibrium orientation of the antiferromagnetic state. The use of a spin glass' collective dynamics to electrically manipulate antiferromagnetic spin textures has never been applied before, opening the field of antiferromagnetic spintronics to many more material platforms with complex magnetic textures., Comment: 7 pages, 4 Figures, supplement available on reasonable request

Large-area and transparent all-dielectric metasurfaces sustaining photonic bound states in the continuum (BICs) provide a set of fundamental advantages for ultrasensitive biosensing. BICs bridge the gap of large effective mode volume with large experimental quality factor. Relying on the transduction mechanism of reactive sensing principle, herein, we first numerically study the potential of subwavelength confinement driven by topological decoupling from free space radiation for BIC-based biosensing. Then, we experimentally combine this capability with minimal and low-cost optical setup, applying the devised quasi-BIC resonator for PNA/DNA selective biosensing with real-time monitoring of the binding event. A sensitivity of 20 molecules per micron squared is achieved, i.e. ≃0.01 pg. Further enhancement can easily be envisaged, pointing out the possibility of single-molecule regime. This work aims at a precise and ultrasensitive approach for developing low-cost point-of-care tools suitable for routine disease prescreening analyses in laboratory, also adaptable to industrial production control.

Neural probes are in vivo brain-invasive devices that record and manipulate neural circuits using electricity, light, or drugs. The capability to shine distinct wavelengths and control their respective output locations for activation or deactivation of specific groups of neurons is desirable but remains unachieved. Here, we discuss our probe’s capability to deliver two independently controllable wavelengths (450 and 655 nm) in the location(s) of interest using nanophotonic directional couplers and ring resonators. These nanophotonics are scalable to dozens of outputs without significantly increasing the device’s lateral dimensions. Furthermore, they are entirely passive and thus do not require electrical input that results in heat generation. Besides, we integrate a high number of electrodes for a simultaneous neural activity readout. Thus, we overcome the challenges associated with multicolor illumination for neural devices by exploiting the capability of miniaturizable, passive probes to deliver two different frequencies in several areas of interest. These devices open the path towards investigating the in vivo electrical signal propagation under the individual or simultaneous activation or inhibition of distinct brain regions.

There are few materials that are broadly used for fabricating optical metasurfaces for visible light applications. Gallium phosphide (GaP) is a material that, due to its optical properties, has the potential to become a primary choice but due to the difficulties in fabrication, GaP thin films deposited on transparent substrates have never been exploited. In this article we report the design, fabrication, and characterization of three different amorphous GaP metasurfaces obtained through sputtering. Although the material properties can be further optimized, our results show the potential of this material for visible applications making it a viable alternative in the material selection for optical metasurfaces.

Plasmon-enhanced fluorescence is demonstrated in the vicinity of metal surfaces due to strong local field enhancement. Meanwhile, fluorescence quenching is observed as the spacing between fluorophore molecules and the adjacent metal is reduced below a threshold of a few nanometers. Here, we introduce a technology, placing the fluorophore molecules in plasmonic hotspots between pairs of collapsible nanofingers with tunable gap sizes at sub-nanometer precision. Optimal gap sizes with maximum plasmon enhanced fluorescence are experimentally identified for different dielectric spacer materials. The ultrastrong local field enhancement enables simultaneous detection and characterization of sharp Raman fingerprints in the fluorescence spectra. This platform thus enables in situ monitoring of competing excitation enhancement and emission quenching processes. We systematically investigate the mechanisms behind fluorescence quenching. A quantum mechanical model is developed which explains the experimental data and will guide the future design of plasmon enhanced spectroscopy applications.

Plasmonic nanostructures serve as optical antennas for concentrating the energy of incoming light in localized hotspots close to their surface. By positioning nanoemitters in the antenna hotspots, energy transfer is enabled, leading to novel hybrid antenna-emitter-systems, where the antenna can be used to manipulate the optical properties of the nano-objects. The challenge remains how to precisely position emitters within the hotspots. We report a self-aligned process based on dry laser ablation of a calixarene that enables the attachment of molecules within the electromagnetic hotspots at the tips of gold nanocones. Within the laser focus, the ablation threshold is exceeded in nanoscale volumes, leading to selective access of the hotspot areas. A first indication of the site-selective functionalization process is given by attaching fluorescently labelled proteins to the nanocones. In a second example, Raman-active molecules are selectively attached only to nanocones that were previously exposed in the laser focus, which is verified by surface enhanced Raman spectroscopy. Enabling selective functionalization is an important prerequisite e.g. for preparing single photon sources for quantum optical technologies, or multiplexed Raman sensing platforms.

Recently, a technique for calibrating the modulation transfer function (MTF) of a broad variety of metrology instrumentation has been demonstrated. This technique is based on test samples structured as one-dimensional binary pseudo-random (BPR) sequences and two-dimensional BPR arrays (BPRAs). The inherent power spectral density of BPR gratings (sequences) and arrays has a deterministic white-noise-like character that allows direct determination of the MTF with uniform sensitivity over the entire spatial frequency range and field-of-view of an instrument. As such, the BPR samples satisfy the characteristics of a test standard: functionality, ease of specification and fabrication, reproducibility, and low sensitivity to manufacturing error. Here we discuss our recent developments directed to the optimization of the sample design, fabrication, application, and data processing procedures, suitable for thorough characterization of large aperture optical interferometers. Compared with the previous coded-aperture based design, the improved, ‘highly randomized’ BPRA pattern of the new test standard provides better accuracy and reliability of instrument MTF and aberration characterization, and enables operation optimization of large aperture optical interferometers. We describe the pattern generation algorithm and tests to verify the compliance to desired BPRA topography. The data acquisition and analysis procedures for different applications of the technique are also discussed.

The combination of electrophysiology and optogenetics enables the exploration of how the brain operates down to a single neuron and its network activity. Neural probes are in vivo invasive devices that integrate sensors and stimulation sites to record and manipulate neuronal activity with high spatiotemporal resolution. State-of-the-art probes are limited by tradeoffs involving their lateral dimension, number of sensors, and ability to access independent stimulation sites. Here, we realize a highly scalable probe that features three-dimensional integration of small-footprint arrays of sensors and nanophotonic circuits to scale the density of sensors per cross-section by one order of magnitude with respect to state-of-the-art devices. For the first time, we overcome the spatial limit of the nanophotonic circuit by coupling only one waveguide to numerous optical ring resonators as passive nanophotonic switches. With this strategy, we achieve accurate on-demand light localization while avoiding spatially demanding bundles of waveguides and demonstrate the feasibility with a proof-of-concept device and its scalability towards high-resolution and low-damage neural optoelectrodes.

Rainbow light trapping in plasmonic devices allows for field enhancement of multiple wavelengths within a single device. However, many of these devices lack precise control over spatial and spectral enhancement profiles and cannot provide extremely high localised field strengths. Here we present a versatile, analytical design paradigm for rainbow trapping in nanogroove arrays by utilising both the groove-width and groove-length as tuning parameters. We couple this design technique with fabrication through multilayer thin-film deposition and focused ion beam milling, which enables the realisation of unprecedented feature sizes down to 5 nm and corresponding extreme normalised local field enhancements up to 103. We demonstrate rainbow trapping within the devices through hyperspectral microscopy and show agreement between the experimental results and simulation. The combination of expeditious design and precise fabrication underpins the implementation of these nanogroove arrays for manifold applications in sensing and nanoscale optics., Plasmonics: Trapping a rainbow with nanogrooves A new approach facilitates the fast and versatile design and easy fabrication of nanogroove arrays that can trap the full spectrum of visible light, with potential applications in sensing and nanoscale optics. Katelyn Dixon of the University of Toronto and colleagues conducted mathematical analyses followed by software simulations to determine the wavelengths of visible light that elicit ‘resonance’ within a single metal-insulator-metal nanogroove depending on its width and length. When designed within an array, each nanogroove will have a specific optical response depending on the wavelength of light that causes it to resonate. The team used a unique technique to fabricate devices made of arrays of nanogrooves with different lengths and widths. The narrowest reached five nanometres; ten times smaller than previously designed grooves. The rainbow-trapping arrays overcome limitations in previous designs.

Nanoscale electron pulses are increasingly in demand, including as probes of nanoscale ultrafast dynamics and for emerging light source and lithography applications. Using electromagnetic simulations, we show that gold plasmonic lenses as multiphoton photoemitters provide unique advantages, including emission from an atomically at surface, nanoscale pulse diameter regardless of laser spot size, and femtosecond-scale response time. We then present fabrication of prototypes with sub-nm roughness via e-beam lithography, as well as electro-optical characterization using cathodoluminescence spectromicroscopy. Finally, we introduce a DC photogun at LBNL built for testing ultrafast photoemitters. We discuss measurement considerations for ultrafast nanoemitters and predict that we can extract tens of pA photocurrent from a single plasmonic lens using a Ti:Sa oscillator. Altogether, this lays the groundwork to develop and test a broad class of plasmon-enhanced ultrafast nanoemitters.

We show the capability of plasmonic lenses for next-generation ultrafast electron sources. Using electromagnetic simulations, we design structures capable of femtosecond, nanoscale electron pulses. Plasmonic properties of template-stripped gold prototypes are characterized using cathodoluminescence spectromicroscopy.

Plasmonic substrates play a crucial role in the confinement and manipulation of localized electromagnetic fields at the nanoscale. The large electromagnetic field enhancement at metal/dielectric interfaces is widely exploited in surface-enhanced fluorescence (SEF) and surface-enhanced Raman scattering (SERS) spectroscopies. Despite the advantage of near-field enhancement, unfortunately, in metals, the large absorption at optical frequencies induces local heating of the analyte fluid with possible damage of the biological material. In addition, in SEF plasmonic substrates, spacer layers are necessary to minimize undesired fluorescence quenching due to nonradiative decay, which strongly depends on the distance between molecules and metallic substrates. Therefore, the possibility of managing surface electromagnetic states mimicking surface-plasmon resonances in terms of spatial localization, high-field intensity, and dispersion characteristics, while avoiding metallic losses is of great interest. However, dielectric nanoantennas can currently provide limited possibilities in the visible range of optical frequencies. We present the realization of all-dielectric metasurfaces made of nanostructured transparent silicon nitride supporting bound states in the continuum (BICs). We show that this special kind of Fano resonances can be effectively used in standard microscopy for practical applications. We achieved concurrent enhancements of ~103 fold of fluorescence emission and Raman scattering far-field intensities of molecules dispersed on these metasurfaces. In addition, we demonstrate that the gain of conventional SERS signals can be increased by more than one order of magnitude by resonant matching of the localized surface plasmon resonance with the BIC field. Our results can find significant applications for enhanced sensing, Raman imaging, and nonlinear processes.

Author(s): Caldas, L; Andaloro, A; Calafiore, G; Munechika, K; Taube, B; Oliveira, M; Cabrini, S | Abstract: Fog harvesting stands out as a simple and inexpensive form to produce drinkable water from alternative sources, when compared to other available techniques. This paper presents results from a set of experiments performed on radiative condensers, deemed as a promising system to be integrated in building envelopes, following a literature review on fog condensers presented in a previous work. An analysis of condensation potential obtained using high emissivity substrates and titanium dioxide nanocoatings is presented, as well as the influence of sample position and orientation, and impact of climatic variables. Finally, the role of nanotechnology in overcoming limitations of radiative systems is discussed as a means to increase harvesting efficiency with functionalized, engineered nano-patterns on collector surface. Based on biomimicry principles, nanocoatings including nanoscale 3D optimal geometries are discussed, and the use of nanoimprint technology (NIL) is proposed to massively produce nano-patterned panels with biomimetic fog capturing features.

A novel optical polymer with a high refractive index (n = 1.707 at 590 nm) was developed consisting of episulfide and thiol bifunctional monomers. The episulfide derivative of 9,9-bis(4-glycidyloxyphenyl)fluorene, synthesized by the reaction of an epoxide and inorganic thiocyanate, reacts by a ring-opening polymerization with 4,4-thiodibenzenethiol to produce the optical polymer with high transparency over the visible region of the spectrum and thermally stable up to 290 °C. The developed episulfide-thiol optical polymer can be thermally nanoimprinted at 160 °C with nanoscale size resolution. Different nanostructures including sub-micron and nanoscale size gratings, two-dimensional photonic crystals, and plano-convex semispherical microlenses were successfully nanoimprinted with excellent pattern fidelity and low defectivity. These results exhibit the episulfide-thiol optical polymer as a potential candidate for applications in optical and optoelectronic devices.

Neural optoelectrodes can read and manipulate large numbers of neurons in vivo. However, state-of-the-art devices rely on either standard microfabrication materials (i.e., silicon and silicon nitride), which result in high scalability and throughput but cause severe brain damage due to implant stiffness, or polymeric devices, which are more compliant but whose scalability and implantation in the brain are challenging. Here, we merge the gap between silicon-based fabrication scalability and low (polymeric-like) stiffness by fabricating a nitride and oxide-based optoelectrode with a high density of sensing microelectrodes, passive photonic circuits, and a very small tip thickness (5 μm). We achieve this by removing all the silicon supporting material underneath the probe’s tip—while leaving only the nitride and glass optical ultrathin layers—through a single isotropic etch step. Our optoelectrode integrates 64 electrodes and multiple passive optical outputs, resulting in a cross-sectional area coefficient (the cross section divided by the number of sensors and light emitters) of 3.1—smaller than other optoelectrodes. It also combines a low bending stiffness (∼4.4 × 10−11 N m2), comparable or approaching several state-of-the-art polymeric optoelectrodes. We tested several mechanical insertions of our devices in vivo in rats and demonstrated that we can pierce the pia without using additional temporary supports.

Tunable microwave and millimeter wave oscillators and bandpass filters with ultra-low phase noise play a critical role in electronic devices, including wireless communication, microelectronics, and quantum computing. Magnetic materials, such as yttrium iron garnet (YIG), possess ultra-low phase noise and a ferromagnetic resonance tunable up to tens of gigahertz. Here, we report structural and magnetic properties of single-crystal 60 and 130 nm-thick YIG films prepared by metal-organic decomposition epitaxy. These films, consisting of multiple homoepitaxially grown monolayers, are atomically flat and possess magnetic properties similar to those grown with liquid-phase epitaxy, pulsed laser deposition, and sputtering. Our approach does not involve expensive high-vacuum deposition systems and is a true low-cost alternative to current commercial techniques that have the potential to transform the industry.

Fano resonance refers to an interference between localized and continuum states that was firstly reported for atomic physics and solid-state quantum devices. In recent years, Fano interference gained more and more attention for its importance in metamaterials, nanoscale photonic devices, plasmonic nanoclusters and surface-enhanced Raman scattering (SERS). Despite such interest in nano-optics, no experimental evidence of Fano interference was reported up to now for purely nanomechanical resonators, even if classical mechanical analogies were referred from a theoretical point of view. Here we demonstrate for the first time that harmonic nanomechanical resonators with relatively high quality factors, such as cantilevers vibrating in vacuum, can show characteristic Fano asymmetric curves when coupled in arrays. The reported findings open new perspectives in fundamental aspects of classical nanomechanical resonators and pave the way to a new generation of chemical and biological nanoresonator sensors with higher parallelization capability.

The effect of the nanoscale array geometry on the interaction between optically generated surface acoustic waves (SAWs) and nanomagnet dynamics is investigated using Time-Resolved Magneto-Optical Kerr Effect Microscopy (TR-MOKE). It is demonstrated that altering the nanomagnet geometry from a periodic to a randomized aperiodic pattern effectively removes the magneto-elastic effect of SAWs on the magnetization dynamics. The efficiency of this method depends on the extent of any residual spatial correlations and is quantified by spatial Fourier analysis of the two structures. Randomization allows observation and extraction of intrinsic magnetic parameters such as spin wave frequencies and damping to be resolvable using all-optical methods, enabling the conclusion that the fabrication process does not affect the damping.

We use the term “single-digit nanofabrication” (SDN) to describe the structuring and characterization of materials whose key features are defined and resolved on a scale of 10 nm or less. Achieving single-digit nano resolution in synthesis and fabrication is a central challenge for the development of next-generation functional nanoscale and mesoscale materials Single digit nanostructured materials have special properties with regard to the control and flow of energy. Energy can take, for example, electronic, magnetic, thermal or photonic forms. We will focus on how material components can be structured with high accuracy and precision in classical lithographic processes 2D and how we can achieve new or improved properties in 3D fabrication. One of the field that requires such precision, resolution and control of materials is nanophotonics. Nanophotonics covers light interactions with dielectric materials and plasmonic effects in metallic structures. In addition, we have emerging efforts in exciton transport in organized nanomaterials. PLASMONIC LIMITS Gap Plasmonic antennas are of great interest due to their ability to concentrate light into small volumes. Smaller the volume higher is the enhancement until the gap is so closed that other effect start to became more important. Theoretical studies, considering quantum mechanical effects, have predicted the optimal spatial gap between adjacent nanoparticles to be in the subnanometer regime in order to achieve the strongest possible field enhancement. We developed a technology [1] to fabricate gap plasmonic structures with subnanometer resolution, high reliability, and high throughput using collapsible nanofingers. The systematic investigation of the effects of gap size are consistent with previous findings as well as with a straightforward theoretical model that is presented here. LARGE AREA METASURFACES Metasurfaces have facilitated the replacement of conventional optical elements with ultrathin and planar photonic structures. Previous designs of metasurfaces were limited to small deflection angles and small ranges of the angle of incidence. We have created two types of Si-based metasurfaces, [2] working both in transmission and reflection modes, to steer visible light to a large deflection angle. These structures exhibit high diffraction efficiencies over a broad range of angles of incidence. We have demonstrated metasurfaces based on conventional thin film silicon processes that are suitable for the largescale fabrication of high-performance devices. EXCITONIC PROPERTIES OF DIRECTED ASSEMBLY PEROVSKITE NANOCRYSTALS Colloidal nanomaterials display a broad range of unique chemical and physical properties that make them prime candidates as nanoscale building blocks for the development of future technologies. Towards this goal, one of the main challenges resides in developing methods to manipulate these materials with a level of precision comparable with their small size. We studied the effects of topography and surface chemistry on the assembly behavior of perovskite nanocrystals PNC [3] with outstanding optical properties and great potential for applications in optoelectronics and photonics. Arranging PNCs in 1D-like features allows careful studies of the collective mechanisms of exciton diffusion and recombination in PNCs assemblies, which in turn determine the optoelectronic behavior of the system and offer fundamental guidance in engineering new optoelectronic devices made of PNCs. Work was supported by the Office of Science,Office of Basic Energy Sciences, of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231. [1] Boxiang Song et al “Probing Gap Plasmons Down to Subnanometer Scales Using Collapsible Nanofingers”; ACS Nano, June 2017 [2] Dianmin Lin et al ”Optical metasurfaces for high angle steering at visible wavelengths”; Scientific Reports 7, Article number: 2286 (2017) [3]L. Protesescu et al. Nano Letters 15 (2015) 3692-3696