Nano-optical Components Research Articles

Investigation of an Innovative Roll-to-Plate (R2P) Hot-Embossing Process for Microstructure Arrays of Infrared Glass

The roller-to-plate (R2P) hot-embossing process is an effective, low-cost method for producing high-quality micro-/nano-optical components. In the field of night vision applications, the fabrication of chalcogenide glass microstructures is emerging as a promising alternative to traditional infrared glass. This trend is driven by the potential of chalcogenide glass to surpass conventional materials in terms of performance. However, the development of R2P hot embossing faces challenges, such as the high cost of curved mold manufacturing, the reliance on roll-to-roll processes for nano hot embossing, the limitations of plastic materials, and the unclear viscoelastic properties of infrared glass. In this study, a novel R2P hot-embossing process was developed to fabricate flat chalcogenide glass structures. The key parameters, such as roller temperature, speed, and embossing pressure, were investigated to understand their impact on the glass-filling performance. The deformation mechanism of the glass microstructures was also analyzed. The experimental results show that the R2P hot-embossing method offers excellent reproducibility, achieving a maximum filling rate of 96% and an average roughness deviation of 8.36 nm. The increase in the roller temperature and embossing force increased the filling height of the glass microstructure arrays, while an increase in the roller speed decreased the filling height. Different embossing methods, including variations in speed, temperature, and force, are summarized to analyze the structural changes during embossing. This study provides a foundation and a basis for future research on the roller-to-plate hot embossing process.

Routing the Exciton Emissions of WS2 Monolayer with the High-Order Plasmon Modes of Ag Nanorods.

Locally routing the exciton emissions in two-dimensional (2D) transition-metal dichalcogenides along different directions at the nanophotonic interface is of great interest in exploiting the promising 2D excitonic systems for functional nano-optical components. However, such control has remained elusive. Herein we report on a facile plasmonic approach for electrically controlled spatial modulation of the exciton emissions in a WS2 monolayer. The emission routing is enabled by the resonance coupling between the WS2 excitons and the multipole plasmon modes in individual silver nanorods placed on a WS2 monolayer. Different from prior demonstrations, the routing effect can be modulated by the doping level of the WS2 monolayer, enabling electrical control. Our work takes advantage of the high-quality plasmon modes supported by simple rod-shaped metal nanocrystals for the angularly resolved manipulation of 2D exciton emissions. Active control is achieved, which offers great opportunities for the development of nanoscale light sources and nanophotonic devices.

Multifunctional materials for lean processing of waferscale optics

AbstractThe continuous miniaturization of components and devices along with the increasing need of sustainability in production requires materials which can fulfill the manifold requests concerning their functionality. From an industrial point of view emphasis is on cost reduction either for the materials, the processes, or for both, along with a facilitation of processing and a general reduction of resource consumption in manufacturing. Multifunctional nanoscale materials have been widely investigated due to their tunable material properties and their ability to fulfill the increasingly growing demands in miniaturization, ease of processes, low-cost manufacturing, scalability, reliability, and finally sustainability. A material class which fulfills these requirements and is suited for integrated or waferscale optics are inorganic–organic hybrid polymers such as ORMOCER®s [ORMOCER®is registered by the Fraunhofer Gesellschaft für Angewandte Forschung e.V. and commercialized by microresist technology GmbH under license since 2003]. The combination of chemically designed multifunctional low-cost materials with tunable optical properties is very attractive for (integrated) optical and waferscale applications via a variety of different nano- and microstructuring techniques to fabricate micro- and nano-optical components, typically within less than a handful of process steps. The influence of photoinitiator and cross-linking conditions onto the optical properties of an acrylate-based inorganic–organic hybrid polymer will be discussed, and its suitability for being applied in waferscale optics is demonstrated and discussed for miniaturized multi- and single channel imaging optics.

Visible and Near-IR Nano-Optical Components and Systems in CMOS

Integration of complex optical systems operating in the visible and near-IR range, realized in a CMOS fabrication process with an absolutely ‘no change’ approach, can have a transformative impact in enabling a new class of miniaturized, low-cost, smart optical sensors and imagers for emerging applications. While ‘silicon photonics’ has demonstrated the path towards such advancements in the IR regime, the field of VIS/NIR integrated optics has seen less progress. Therefore, while currently ultra high-density and higher performance image sensors are commonplace in CMOS, all passive optical components (such as lenses, filters, gratings, collimators) that typically constitute a high-performance sensing or imaging system, are typically non-integrated, bulky and expensive, severely limiting their application potential in the space of connected sensors. Here, we present an approach to utilize the embedded copper-based metal interconnect layers in modern CMOS processes with sub-wavelength feature sizes to realize multi-functional nano-optical structures and components. Based on our prior works, we illustrate this electronic-photonic co-design approach exploiting metal/light interactions and integrated electronics in the 400nm-900 nm wavelengths with three design examples. Realized in 65-nm CMOS, these demonstrate for the first time: fully integrated multiplied fluorescence based biosensors with integrated filters, optical spectrometer, and CMOS optical physically unclonable function (PUF). These examples cover a range of optical processing elements in silicon, from deep sub-wavelength nano-optics to diffractive structures. We will demonstrate that when co-designed with embedded photo-detection and signal processing circuitry, this approach can foster millimeter-scale, intelligent optical sensors for a wide range of emerging applications in healthcare, diagnostics, smart sensing, food, air quality, environment monitoring and others.

Designing Multipolar Resonances in Dielectric Metamaterials.

Dielectric resonators form the building blocks of nano-scale optical antennas and metamaterials. Due to their multipolar resonant response and low intrinsic losses they offer design flexibility and high-efficiency performance. These resonators are typically described in terms of a spherical harmonic decomposition with Mie theory. In experimental realizations however, a departure from spherical symmetry and the use of high-index substrates leads to new features appearing in the multipolar response. To clarify this behavior, we present a systematic experimental and numerical characterization of Silicon disk resonators. We demonstrate that for disk resonators on low-index quartz substrates, the electric and magnetic dipole modes are easily identifiable across a wide range of aspect-ratios, but that higher order peaks cannot be unambiguously associated with any specific multipolar mode. On high-index Silicon substrates, even the fundamental dipole modes do not have a clear association. When arranged into arrays, resonances are shifted and pronounced preferential forward and backward scattering conditions appear, which are not as apparent in individual resonators and may be associated with interference between multipolar modes. These findings present new opportunities for engineering the multipolar scattering response of dielectric optical antennas and metamaterials, and provide a strategy for designing nano-optical components with unique functionalities.

Microrobotic Station for Nano-Optical Component Assembly

Compact photonic structures have strategic importance in several fields. In order to fabricate more complex structures with optimized optical function, robotic nano-assembly is a promising solution because it enables to integrate several types of materials from different fabrication processes into the same structure. This paper presents a microrobotic station which is designed for the assembly of nano-optical components. The robotic station has 8-DOF for positioning and 4-DOF microgripper with integrated force sensors to perform dexterous and accurate manipulation of components by considering both position and contact force to achieve precise alignment and parallelism of structures.

Manipulating Bloch surface waves in 2D: a platform concept-based flat lens

At the end of the 1970s, it was confirmed that dielectric multilayers can sustain Bloch surface waves (BSWs). However, BSWs were not widely studied until more recently. Taking advantage of their high-quality factor, sensing applications have focused on BSWs. Thus far, no work has been performed to manipulate and control the natural surface propagations in terms of defined functions with two-dimensional (2D) components, targeting the realization of a 2D system. In this study, we demonstrate that 2D photonic components can be implemented by coating an in-plane shaped ultrathin (∼λ/15) polymer layer on the dielectric multilayer. The presence of the polymer modifies the local effective refractive index, enabling direct manipulation of the BSW. By locally shaping the geometries of the 2D components, the BSW can be deflected, diffracted, focused and coupled with 2D freedom. Enabling BSW manipulation in 2D, the dielectric multilayer can play a new role as a robust platform for 2D optics, which can pave the way for integration in photonic chips. Multiheterodyne near-field measurements are used to study light propagation through micro- and nano-optical components. We demonstrate that a lens-shaped polymer layer can be considered as a 2D component based on the agreement between near-field measurements and theoretical calculations. Both the focal shift and the resolution of a 2D BSW lens are measured for the first time. The proposed platform enables the design of 2D all-optical integrated systems, which have numerous potential applications, including molecular sensing and photonic circuits. Controlling Bloch surface waves in a multilayer dielectric yields a new platform for creating two-dimensional photonic circuitry. Libo Yu and co-workers from the Swiss Federal Institute of Technology in Lausanne used an ultrathin (λ/15) polymer coating to modify the local effective refractive index of a dielectric multilayer stack that guides Bloch surface waves. Careful design of the shape of a polymer layer makes it possible to deflect, diffract and focus the waves within a planar geometry. The researchers used this approach to construct a flat lens capable of operating at a wavelength of 1.5 µm, and used a multiheterodyne scanning near-field optical microscope to observe the near-field behavior of the platform. They say that many other forms of photonic component should be possible.

Moxtek, Inc.

Abstract Moxtek is the leading manufacturer of nano-optical and X-ray components, including high performance X-ray windows for demanding applications. AP3 ultra-thin polymer windows offer the highest transmission of low energy X-rays. Moxtek DuraBeryllium® windows are highly reliable, are resistance to moisture and harsh chemicals, and are available in thicknesses down to 8 μm. Moxtek also provides window solutions for sealed and flow proportional counters. Moxtek X-ray products (X-ray windows, X-ray JFETs, miniature/portable X-ray sources, X-ray detectors) enable compact handheld and benchtop elemental analysis for positive material identification. Moxtek products are used in various EDXRF systems for environmental screening, for hazardous substance analysis, and for sorting and recycling. Moxtek X-ray products are critical for optimal elemental analysis in electron microscopy, especially for low-Z elements. Moxtek strives to deliver products and services that meet or exceed customer requirements for performance, quality, and value.

Silver Nanowires Terminated by Metallic Nanoparticles as Effective Plasmonic Antennas

Metallic nanowires constitute a distinctive class of nanostructures that are able to guide surface plasmons in subwavelength dimensions. The effective use of light in- and out-coupling in low dimensional systems, such as excitation of surface plasmon polaritons along metallic nanowires, has been proposed to reduce physical dimensions of opto-electronic and nano-optical components and for high-resolution microscopy applications. Our investigation of light in- and out-coupling on silver nanowire systems by scanning optical coupling microscopy (SOCM) performed in combination with atomic force microscopy (AFM) revealed that the maximum coupling was obtained when the exciting laser light is projected at the end of the nanowire with a positioning accuracy of approximately 100 nm. Furthermore, it was found that a nanoparticle positioned at the end of a nanowire imparts an enhanced (by almost the factor of 4) plasmon in- and out-coupling light efficiency as compared to a free nanowire under the same excitation conditions. These findings are supported by theoretical simulations, which in addition provide a correlation between the nanoparticle size and the out-coupling light efficiency. Our investigations demonstrate that a combination of SOCM and AFM methods provide reliable qualitative and quantitative evaluation of plasmon in- and out-coupling characteristics on metallic nanowire systems.

PFPE-based materials for the fabrication of micro- and nano-optical components

Preliminary results of an exploration of the use of a specially prepared UV-curable tetrafunctional urethane methacrylate perfluoropolyether (PFPE) for polymer molding are presented in this work. Different PFPE-based elastomeric micro and nanostructures were generated either by UV-lithography from integrated microlenses or replica molding of different optical components, such as diffraction gratings, waveguides and photonic crystals. Fast replication without applying pressure or thermal treatments, demonstrated the efficiency of this polymer to reproduce micro and over 100nm features with large aspect ratios, whereas in the case of smaller features the fabrication is still facing distortion and resolution problems, possibly due to a higher than expected viscosity of the prepolymer.

Ultra-wideband optical leaky-wave slot antennas

We propose and investigate an ultra-wideband leaky-wave antenna that operates at optical frequencies for the purpose of efficient energy coupling between localized nanoscale optical circuits and the far-field. The antenna consists of an optically narrow aluminum slot on a silicon substrate. We analyze its far-field radiation pattern in the spectral region centered around 1550 nm with a 50% bandwidth ranging from 2000 nm to 1200 nm. This plasmonic leaky-wave slot produces a maximum far-field radiation angle at 32° and a 3 dB beamwidth of 24° at its center wavelength. The radiation pattern is preserved within the 50% bandwidth suffering only insignificant changes in both the radiation angle and the beamwidth. This wide-band performance is quite unique when compared to other optical antenna designs. Furthermore, the antenna effective length for radiating 90% and 99.9% of the input power is only 0.5λ(0) and 1.5λ(0) respectively at 1550 nm. The versatility and simplicity of the proposed design along with its small footprint makes it extremely attractive for integration with nano-optical components using existing technologies.

High Q optomechanical resonators in silicon nitride nanophotonic circuits

We demonstrate integrated photonic circuits made from stoichiometric silicon nitride for effective integration of high Q micromechanical resonators and nano-optical components. Using silicon bulk micromachining techniques we fabricate free-standing highly tensile nanostrings exceeding 400 μm in length. The nanostrings are actuated using gradient optical force and their mechanical motion is readout with a sensitive interferometric scheme. A mechanical Q of 340 000 is obtained in vacuum. This fully integrated optomechanical circuit presents a promising scheme for on-chip high Q mechanical sensing applications.

Simulation method improves accuracy for optical metrology and nanooptics design

With advances in nanotechnology growing at a fast pace, reliable simulations of nanooptical devices are crucial for research and development. Designing and optimizing the functionality of nanooptical components is typically assisted by computer simulations in combination with optical inspection as a critical step in product development and quality control. Dimensional metrology, for example, relies essentially on a numerical comparison of measurements with simulations. In addition, the latter are used in most scientific nanooptics publications to support theoretical and experimental results. The evolution of electric and magnetic fields in any welldefined nanostructure is described by Maxwell’s equations. All information about the classical properties of light is contained in the electromagnetic fields, which is used to solve these differential equations. A variety of methods exist to perform rigorous simulations of Maxwell’s equations. These include finite-element, finite-difference time-domain, Fouriermodal, and boundary-element approaches. However, especially