Showing papers on "Electron-beam lithography published in 2019"
20 Sep 2019
TL;DR: In this paper, a chip-integrated lithium niobate microring resonator with a quasi-phase-matched frequency conversion achieved 230,000%/W or 10−6 per single photon.
Abstract: We demonstrate quasi-phase-matched frequency conversion in a chip-integrated lithium niobate microring resonator, whose normalized efficiency reaches 230,000%/W or 10−6 per single photon.
151 citations
01 Jan 2019
TL;DR: In this paper, thermal scanning probe lithography is used to pattern metal electrodes in direct contact with monolayer MoS2, creating field effect transistors that exhibit vanishing Schottky barrier heights, high on/off ratios of 1010, no hysteresis, and subthreshold swings as low as 64
Abstract: Two-dimensional semiconductors, such as molybdenum disulfide (MoS2), exhibit a variety of properties that could be useful in the development of novel electronic devices. However, nanopatterning metal electrodes on such atomic layers, which is typically achieved using electron beam lithography, is currently problematic, leading to non-ohmic contacts and high Schottky barriers. Here, we show that thermal scanning probe lithography can be used to pattern metal electrodes with high reproducibility, sub-10-nm resolution, and high throughput (105 μm2 h−1 per single probe). The approach, which offers simultaneous in situ imaging and patterning, does not require a vacuum, high energy, or charged beams, in contrast to electron beam lithography. Using this technique, we pattern metal electrodes in direct contact with monolayer MoS2 for top-gate and back-gate field-effect transistors. These devices exhibit vanishing Schottky barrier heights (around 0 meV), on/off ratios of 1010, no hysteresis, and subthreshold swings as low as 64 mV per decade without using negative capacitors or hetero-stacks. Thermal scanning probe lithography can be used to pattern metal electrodes in direct contact with monolayer MoS2, creating field-effect transistors that exhibit vanishing Schottky barrier heights, high on/off ratios of 1010, no hysteresis, and subthreshold swings as low as 64 mV per decade.
107 citations
TL;DR: In this paper, a broadband polarization beam splitter (PBS) based on a multimode interference coupler with internal photonic crystal (PC) for the silicon-on-insulator platform is presented.
Abstract: We experimentally demonstrate a compact broadband polarization beam splitter (PBS) based on a multimode interference (MMI) coupler with internal photonic crystal (PC) for the silicon-on-insulator platform. The internal PC structure is optimized to be reflective to the transverse electric polarization and transparent to the transverse magnetic polarization over a broad wavelength range. A detailed study of the device operation, including the photonic band gap and the influence of the internal PC structure on each mode of the MMI coupler, is presented. The designed PBS has been fabricated using electron beam lithography and the feature size used in our design is CMOS compatible. The fabricated device achieves measured extinction ratios higher than 20 dB and insertion losses lower than 2 dB for both polarizations over a 77 nm wavelength range from 1522 to 1599 nm that covers the entire C -band, with a device length of only 71.5 $\mu$ m.
60 citations
TL;DR: This work presents a facile nanocasting technique to fabricate dielectric metasurfaces at low cost and high throughput and will be a promising nanofabrication platform, and thereby facilitate commercialization of dielectrics.
Abstract: This work presents a facile nanocasting technique to fabricate dielectric metasurfaces at low cost and high throughput. A flexible polymer mold is replicated from a master mold, and then the polymer mold is used to shape particle-embedded UV-curable polymer resin. The polymer mold is compatible with flexible and curved substrates. A hard-polydimethylsiloxane improves mechanical stability of the polymer mold providing sub-100 nm patterning resolution. The patterned resin itself can work as a metasurface without secondary operations because dielectric particles sufficiently increase the refractive index of the resin. The absence of the secondary operations allows our method to have higher productivity and cost competitiveness than those of typical nanoimprint lithography. Experimental demonstration verifies the feasibility of our method, and the replicated metasurface exhibits a conversion efficiency of 46% in the visible, which is comparable to metasurfaces based on low-loss dielectrics. Given that conventional dielectric metasurfaces have been fabricated by electron beam lithography at formidable cost due to low throughput, our method will be a promising nanofabrication platform and thereby facilitate commercialization of dielectric metasurfaces.
58 citations
TL;DR: A general approach for resist-free direct electron-beam lithography of functional inorganic nanomaterials (DELFIN) which enables all-inorganic NC patterns with feature size down to 30 nm, while preserving the optical and electronic properties of patterned NCs.
Abstract: Direct optical lithography of functional inorganic nanomaterials (DOLFIN) is a photoresist-free method for high-resolution patterning of inorganic nanocrystals (NCs) that has been demonstrated using deep UV (DUV, 254 nm) photons. Here, we expand the versatility of DOLFIN by designing a series of photochemically active NC surface ligands for direct patterning using various photon energies including DUV, near-UV (i-line, 365 nm), blue (h-line, 405 nm), and visible (450 nm) light. We show that the exposure dose for DOLFIN can be ∼30 mJ/cm2, which is small compared to most commercial photopolymer resists. Patterned nanomaterials can serve as highly robust optical diffraction gratings. We also introduce a general approach for resist-free direct electron-beam lithography of functional inorganic nanomaterials (DELFIN) which enables all-inorganic NC patterns with feature size down to 30 nm, while preserving the optical and electronic properties of patterned NCs. The designed ligand chemistries and patterning techniques offer a versatile platform for nano- and micron-scale additive manufacturing, complementing the existing toolbox for device fabrication.
53 citations
TL;DR: The structural, compositional, morphological and optical properties of the high aspect ratio ZnO-CuxO core-shell nanowire arrays were investigated and it was found that these n-p radial heterojunction diodes based on single ZnW nanowires exhibit a change in the current under UV light illumination and therefore behaving as photodetectors.
Abstract: ZnO-CuxO core-shell radial heterojunction nanowire arrays were fabricated by a straightforward approach which combine two simple, cost effective and large-scale preparation methods: (i) thermal oxidation in air of a zinc foil for obtaining ZnO nanowire arrays and (ii) radio frequency magnetron sputtering for covering the surface of the ZnO nanowires with a CuxO thin film. The structural, compositional, morphological and optical properties of the high aspect ratio ZnO-CuxO core-shell nanowire arrays were investigated. Individual ZnO-CuxO core-shell nanowires were contacted with Pt electrodes by means of electron beam lithography technique, diode behaviour being demonstrated. Further it was found that these n-p radial heterojunction diodes based on single ZnO-CuxO nanowires exhibit a change in the current under UV light illumination and therefore behaving as photodetectors.
50 citations
TL;DR: An improved architecture for all-Si based photoelectronic detectors has been developed, consisting of a specially designed metasurface as antennas integrated into a Si nanowire array on insulator by an electron beam lithography based self-alignment process.
Abstract: An improved architecture for all-Si based photoelectronic detectors has been developed, consisting of a specially designed metasurface as the antenna integrated into a Si nanowire array on the insulator by an electron beam lithography based self-alignment process. Simulation using the Finite Difference Time Domain (FDTD) method was carried out to ensure perfect absorption of light by the detector. Optic measurement shows a 90% absorption at 1.05 μm. Photoelectronic characterization demonstrates the responsivity and detectivity as high as 94.5 mA/W and 4.38 × 1011 cm Hz1/2/W, respectively, at 1.15 μm with the bandwidth of 480 nm, which is comparable to that of III-V/II-VI compound detectors. It is understood that the outstanding performances over other reported all-Si based detectors originate from the enhanced quantum efficiency in one-dimensional conduction channels with high density of states, which efficiently accommodate the emitted plasmonic hot electrons for high conduction in the Si nanowires, enabling the near-infrared detection by all-Si based detectors.
45 citations
TL;DR: Scanning-Probe-Assisted Nanowire Circuitry (SPANC) is introduced as a new method to fabricate electrodes for the characterization of electrical transport properties at the nanoscale, allowing robust device fabrication and electrical characterization of several nanoobjects.
Abstract: We introduce scanning-probe-assisted nanowire circuitry (SPANC) as a new method to fabricate electrodes for the characterization of electrical transport properties at the nanoscale. SPANC uses an a...
38 citations
TL;DR: In this article, the history and progress of ice lithography is reviewed, focusing on its applications in efficient 3D nanofabrication and additive manufacturing or nanoscale 3D printing.
Abstract: Nanotechnology and nanoscience are enabled by nanofabrication. Electron-beam lithography, which makes 2D patterns down to a few nanometers, is one of the fundamental pillars of nanofabrication. Recently, significant progress in 3D electron-beam-based nanofabrication has been made, such as the emerging ice lithography technology, in which ice thin-films are patterned by a focused electron-beam. Here, we review the history and progress of ice lithography, and focus on its applications in efficient 3D nanofabrication and additive manufacturing or nanoscale 3D printing. The finest linewidth made using frozen octane is below 5 nm, and nanostructures can be fabricated in selected areas on non-planar surfaces such as freely suspended nanotubes or nanowires. As developing custom instruments is required to advance this emerging technology, we discuss the evolution of ice lithography instruments and highlight major instrumentation advances. Finally, we present the perspectives of 3D printing of functional materials using organic ices. We believe that we barely scratched the surface of this new and exciting research area, and we hope that this review will stimulate cutting-edge and interdisciplinary research that exploits the undiscovered potentials of ice lithography for 3D photonics, electronics and 3D nanodevices for biology and medicine.
35 citations
34 citations
TL;DR: In this article, the GPW mode excitation in a gap between a monocrystalline silver nanowire and a single nitrogen-vacancy center in a nanodiamond was investigated.
Abstract: Quantum emitters with high emission rates and efficiently coupled to optical waveguides are in demand for various applications in quantum information technologies. Accurate positioning of a quantum emitter within a strongly confined gap-plasmon waveguide (GPW) mode would allow one to significantly enhance the decay rate and efficiency of channeling of emitted photons into the waveguide mode. Here, we present experimental results on the GPW mode excitation in a gap between a monocrystalline silver nanowire and a monocrystalline silver flake by using a single nitrogen-vacancy center in a nanodiamond. The coupled systems containing a nanodiamond and the structure supporting the GPW mode are created by a combination of electron beam lithography and nanomanipulation with an atomic force microscope (AFM). In these systems, we find decay rate enhancements of up to ∼50 and the efficiency of channeling of photons into the GPW mode of up to 82%, resulting in an exceptionally high figure-of-merit of 212 for the emit...
TL;DR: The results indicate that the proposed DMSL can be a significant role in the microfabrication techniques for manufacturing functional microstructures array.
Abstract: A flexible and efficient strategy, digital micromirror devices (DMD) based multistep lithography (DMSL), is proposed to fabricate arrays of user-defined microstructures. Through the combination of dose modulation, flexible pattern generation of DMD, and high-resolution step movement of piezoelectrical stage (PZS), this method enables prototyping a board range of 2D lattices with periodic/nonperiodic spatial distribution and arbitrary shapes and the critical feature size is down to 600 nm. We further explore the use of DMSL to fabricate microlens array by combining with the thermal reflowing process. The square shape and hexagonal shape microlens with customized distribution are realized and characterized. The results indicate that the proposed DMSL can be a significant role in the microfabrication techniques for manufacturing functional microstructures array.
TL;DR: A manufacturing process is demonstrated that enables cost-effective wafer-level fabrication of custom MSFAs in a single lithographic step, maintaining high efficiencies and narrow line widths across the visible to near-infrared bands.
Abstract: Snapshot multispectral image (MSI) sensors have been proposed as a key enabler for a plethora of multispectral imaging applications, from diagnostic medical imaging to remote sensing. With each application requiring a different set, and number, of spectral bands, the absence of a scalable, cost-effective manufacturing solution for custom multispectral filter arrays (MSFAs) has prevented widespread MSI adoption. Despite recent nanophotonic-based efforts, such as plasmonic or high-index metasurface arrays, large-area MSFA manufacturing still consists of many-layer dielectric (Fabry-Perot) stacks, requiring separate complex lithography steps for each spectral band and multiple material compositions for each. It is an expensive, cumbersome, and inflexible undertaking, but yields optimal optical performance. Here, we demonstrate a manufacturing process that enables cost-effective wafer-level fabrication of custom MSFAs in a single lithographic step, maintaining high efficiencies (∼75%) and narrow line widths (∼25 nm) across the visible to near-infrared. By merging grayscale (analog) lithography with metal-insulator-metal (MIM) Fabry-Perot cavities, whereby exposure dose controls cavity thickness, we demonstrate simplified fabrication of MSFAs up to N-wavelength bands. The concept is first proven using low-volume electron beam lithography, followed by the demonstration of large-volume UV mask-based photolithography with MSFAs produced at the wafer level. Our framework provides an attractive alternative to conventional MSFA manufacture and metasurface-based spectral filters by reducing both fabrication complexity and cost of these intricate optical devices, while increasing customizability.
TL;DR: In this article, the authors investigated the coupling of deterministically pre-selected In(Ga)As/GaAs quantum dots (QDs) to low Q circular Bragg grating cavities by employing a combination of state-of-the-art low-temperature in-situ optical lithography and electron-beam lithography.
Abstract: In the present work, we investigate the coupling of deterministically pre-selected In(Ga)As/GaAs quantum dots (QDs) to low Q circular Bragg grating cavities by employing a combination of state-of-the-art low-temperature in-situ optical lithography and electron-beam lithography. The spatial overlap between the cavity mode and quantum emitter is ensured through the accurate determination of the QD position via precise interferometric position readout. Simultaneously, the high precision of the electron-beam lithography is exploited for the cavity fabrication. In order to optimize the spectral overlap, prior to cavity fabrication, finite-difference time-domain simulations are performed to estimate the spectral position of the cavity mode. A Purcell factor of 2 together with an increased count rate is reported for a deterministically positioned cavity where the emission line is detuned by 3.9 nm with respect to the cavity mode. This non-negligible Purcell enhancement for large detunings and, thus, the large range where this can be achieved points towards the possibility of using the cavity for the simultaneous enhancement of spectrally distinct transitions from the same quantum emitter located spatially in the mode maximum. Furthermore, investigations on the bending of the cavity membrane and the effects on the cavity mode and QD emission are presented.In the present work, we investigate the coupling of deterministically pre-selected In(Ga)As/GaAs quantum dots (QDs) to low Q circular Bragg grating cavities by employing a combination of state-of-the-art low-temperature in-situ optical lithography and electron-beam lithography. The spatial overlap between the cavity mode and quantum emitter is ensured through the accurate determination of the QD position via precise interferometric position readout. Simultaneously, the high precision of the electron-beam lithography is exploited for the cavity fabrication. In order to optimize the spectral overlap, prior to cavity fabrication, finite-difference time-domain simulations are performed to estimate the spectral position of the cavity mode. A Purcell factor of 2 together with an increased count rate is reported for a deterministically positioned cavity where the emission line is detuned by 3.9 nm with respect to the cavity mode. This non-negligible Purcell enhancement for large detunings and, thus, the large ra...
TL;DR: Measurements yielding nonconventional, fractional multiples of the typical quantized Hall resistance at ν = 2 (R H ≈ 12906 Ω) that take the form: a b R H .
13 Mar 2019
TL;DR: In this paper, the authors proposed a method for controlling plasmon dephasing time by utilizing plasmanic coupling for stronger near-field enhancement, which can be controlled by the structural design of the stacked nanogap Au structures.
TL;DR: The characterization of the photo-electronic properties as well as the polarimetric detection demonstrate that the fabricated detectors on the silicon substrate possesses great prospects for sensing technology on all-Si.
Abstract: This work developed an all-Si photodetector with a surface plasmonic resonator formed by a sub-wavelength Au grating on the top of a Si-nanowire array and the same one beside the wires. The Au/Si interface with a Schottky barrier allows the photo-electron detection in near-infrared wavelength based on the internal emission of hot electrons generated by the surface plasmons in the cavity. Meanwhile, the Au sub-wavelength grating on the Si nanowire array acts as a polarizer for polarimetric detection. Finite-difference time-domain method was applied in the design of the novel device and state-of-art nanofabrication based on electron beam lithography was carried out. The characterization of the photo-electronic properties as well as the polarimetric detection demonstrate that the fabricated detectors on the silicon substrate possesses great prospects for sensing technology on all-Si.
TL;DR: This work produced a pattern with 10 nm critical dimensions, using electron beam lithography, and used it to replicate nanoimprint molds by direct casting of an elastomer onto the patterned resist, and showed that the produced pattern can be faithfully transferred from the mold by thermal nanoim printing.
Abstract: Nanoimprinting with rigid molds offers almost unlimited pattern resolution, but it suffers from high sensitivity to defects, and is limited to pattering flat surfaces. These limitations can be addressed by nanoimprinting with soft molds. However, soft molds have been used so far with UV resists, and could not achieve a resolution and minimal feature size comparable to those of rigid molds. Here, we explore the miniaturization edge of soft nanoimprint molds, and demonstrate their compatibility with thermal imprint resists. To that end, we produced a pattern with 10 nm critical dimensions, using electron beam lithography, and used it to replicate nanoimprint molds by direct casting of an elastomer onto the patterned resist. We showed that the produced pattern can be faithfully transferred from the mold by thermal nanoimprinting. In addition, we showed that similar nanoimprint molds can also be produced by double replication, which includes nanoimprinting of a thermal resist with an ultrahigh resolution rigid mold, and replication of a soft mold from the imprint pattern. We also demonstrated our novel nanoimprinting approach in two unconventional applications: nanopatterning of a thermal resist on a lens surface, and direct nanoimprinting of chalcogenide glass. Our novel nanoimprint approach pushes the envelope of standard nanofabrication, and demonstrates its potential for numerous applications impossible up to now.
TL;DR: Double-nanoholes fabricated by colloidal lithography were used for trapping single colloidal particles and single proteins and this approach is inexpensive and produces high-quality samples.
Abstract: Double-nanoholes fabricated by colloidal lithography were used for trapping single colloidal particles and single proteins. A gap separation of 60 nm between the cusps of the double-nanohole was achieved in a gold film of 70 nm thickness sputter coated onglass. The cusp separation was reduced steadily down to 10 nm by plasma etching the colloidal particles prior to sputter coating. Scanning electron microscopy was used to locate a particular double-nanohole and it was registered for later microscopy experiments. 30 nm polystyrene particles, the rubisco protein and bovine serum albumin were trapped using a laser focused through the aperture. Compared to other methods that require top-down nanofabrication, this approach is inexpensive and produces high-quality samples.
TL;DR: In this paper, both amplitude and phase masks are considered for hexagonal and square arrays of mask openings, respectively, and it is shown how small changes in the mask pitch can dramatically affect the resolution achievable.
Abstract: Displacement Talbot lithography (DTL) is a new technique for patterning large areas with sub-micron periodic features with low cost. It has applications in fields that cannot justify the cost of deep-UV photolithography, such as plasmonics, photonic crystals, and metamaterials and competes with techniques, such as nanoimprint and laser interference lithography. It is based on the interference of coherent light through a periodically patterned photomask. However, the factors affecting the technique’s resolution limit are unknown. Through computer simulations, we show the mask parameter’s impact on the features’ size that can be achieved and describe the separate figures of merit that should be optimized for successful patterning. Both amplitude and phase masks are considered for hexagonal and square arrays of mask openings. For large pitches, amplitude masks are shown to give the best resolution; whereas, for small pitches, phase masks are superior because the required exposure time is shorter. We also show how small changes in the mask pitch can dramatically affect the resolution achievable. As a result, this study provides important information for choosing new masks for DTL for targeted applications.
14 Mar 2019
TL;DR: In this article, cyclic hydrogen and oxygen plasma exposures are utilized to introduce defects and oxidize MoS2 in a controlled manner, which results in the formation of sub-stochiometric MoO3−x, which transforms the semiconducting behavior to metallic conduction.
Abstract: Tailoring the electrical transport properties of two-dimensional transition metal dichalcogenides can enable the formation of atomically thin circuits. In this work, cyclic hydrogen and oxygen plasma exposures are utilized to introduce defects and oxidize MoS2 in a controlled manner. This results in the formation of sub-stochiometric MoO3−x, which transforms the semiconducting behavior to metallic conduction. To demonstrate functionality, single flakes of MoS2 were lithographically oxidized using electron beam lithography and subsequent plasma exposures. This enabled the formation of atomically thin inverters from a single flake of MoS2, which represents an advancement toward atomically thin circuitry.
TL;DR: In this paper, the authors showed that UV absorption in single-layer graphene can be enhanced by converting it to a nanomembrane-like structure, or nanomesh.
TL;DR: In this article, a successful realization of photonic systems with characteristics of the Morpho butterfly coloration is reported using two-photon polymerization, where submicron structure features have been fabricated through the interference of the incident beam and the reflected beam in a thin polymer film.
Abstract: A successful realization of photonic systems with characteristics of the Morpho butterfly coloration is reported using two-photon polymerization. Submicron structure features have been fabricated through the interference of the incident beam and the reflected beam in a thin polymer film. Furthermore, the influence of the lateral microstructure organization on the color formation has been studied in detail. The design of the polymerized structures was validated by scanning electron microscopy. The optical properties were analyzed using an angle-resolved spectrometer. Tunable angle-independence, based on reflection intensity modulation, has been investigated by using photonic structures with less degree of symmetry. Finally, these findings were used to demonstrate the high potential of two-photon polymerization in the field of biomimetic research and for technical application, e.g. for sensing and anti-counterfeiting.
TL;DR: An improved approach to integrate various color filters on a chip-scale by using stepwise metal-insulator-metal FP cavities that can realize large-scale filter arrays with simple processing and may facilitate the use of structural color filters in displays and sensing.
Abstract: We demonstrate an improved approach to integrate various color filters on a chip-scale by using stepwise metal-insulator-metal FP cavities. The cavity is composed of a thick silver mirror, an SU8 gap layer of controlled thickness, and a thin nickel layer. Reflective colors from red to blue can be generated from these filters through a simple UV lithography process. The filters were also fabricated on a flexible substrate which could be incorporated into wearable devices. This method can realize large-scale filter arrays with simple processing and may facilitate the use of structural color filters in displays and sensing.
TL;DR: Thin film stacks consisting of multiple repeats M of synthetic antiferromagnetic (SAF) units with perpendicular magnetic anisotropy were explored as potential starting materials to fabricate free-standing micro/nanodisks, which represent a promising candidate system for theranostic applications.
Abstract: Thin film stacks consisting of multiple repeats M of synthetic antiferromagnetic (SAF) [Co/Pd]N/Ru/[Co/Pd]N units with perpendicular magnetic anisotropy were explored as potential starting materials to fabricate free-standing micro/nanodisks, which represent a promising candidate system for theranostic applications. The films were directly grown on a sacrificial resist layer spin-coated on SiOx/Si(100) substrates, required for the preparation of free-standing disks after its dissolution. Furthermore, the film stack was sandwiched between two Au layers to allow further bio-functionalization. For M ≤ 5, the samples fulfill all the key criteria mandatory for biomedical applications, i.e., zero remanence, zero field susceptibility at small fields and sharp switching to saturation, together with the ability to vary the total magnetic moment at saturation by changing the number of repetitions of the multi-stack. Moreover, the samples show strong perpendicular magnetic anisotropy, which is required for applications relying on the transduction of a mechanical force through the micro/nano-disks under a magnetic field, such as the mechanical cell disruption, which is nowadays considered a promising alternative to the more investigated magnetic hyperthermia approach for cancer treatment. In a further step, SAF microdisks were prepared from the continuous multi-stacks by combining electron beam lithography and Ar ion milling, revealing similar magnetic properties as compared to the continuous films.
15 May 2019
TL;DR: In this paper, an active plasmonic tuning of polymer gels with a low deviation was proposed to tune the gap distances of nanopatterns on silicon substrates by electron beam lithography.
Abstract: Active plasmonic tuning is an attractive but challenging research subject, leading to various promising applications. As one of the approaches, nanostructures are placed in or on soft matter, such as elastomers and gels, and their gap distances are tuned by the mechanical extension or volume change of the supporting matrices. As hydrogels possess various types of stimuli-responsiveness with large volume change and biocompatibility, they are good candidates as supporting materials for active nanostructure tuning. However, it remains unclear how accurately we can control their nanogap distance changes using polymer gels with a low deviation due to major difficulties in the precise observation of nanostructures on the gels. Here, we prepared gold arrays with sub-100 nm dots on silicon substrates by electron beam lithography and transferred them onto the hydrogel surface. Then, their nanopattern was actively tuned by the changes in gel size in water and their structural changes were confirmed by optical microscopy, microspectroscopy, and atomic force microscopy (AFM). Further, we successfully prepared ionic liquid (IL) gels with various degrees of swelling via solvent exchange. Scanning electron microscopy (SEM) observation of the IL gels provided clear pictures at nanoscale resolution. Finally, we calculated the plasmonic spectra using a finite difference time domain (FDTD) simulation based on the SEM images and compared them with the measured spectra. The results in this study totally support the notion that active changes in plasmonic nanodot patterns via volume changes in the hydrogel are quite homogenous on a several nanometer scale, making them ideal for precise active surface plasmon tuning.
TL;DR: Direct electron beam lithography of QDs has emerged as a straightforward patterning process that does not require ligand exchange and results in structures that retain bright PL, and this method can be applied to nanophotonics by measuring the complex refractive index of the QD materials to model the absorption and scattering cross sections of QD structures of various sizes and shapes.
Abstract: The small size of colloidal nanocrystal quantum dots (QDs) leads to a variety of unique optical properties that are well-suited to nanophotonics, including bright, tunable photoluminescence (PL). H...
TL;DR: Coupling using a cleaved bow-tie fiber and a lensed fiber is demonstrated, and the grating coupling efficiencies are determined in both cases over a broad operating wavelength range.
Abstract: Long-range surface plasmon polariton waveguides consisting of Au stripes integrated with input and output grating couplers embedded in thick Cytop claddings are proposed and demonstrated experimentally. Under the right conditions, grating couplers enable broadside (top) coupling with good efficiency while producing a low level of background light. The scheme does not require high-quality input and output edge facets, and it simplifies optical alignments. We demonstrate coupling using a cleaved bow-tie fiber and a lensed fiber, and we determine the grating coupling efficiencies in both cases over a broad operating wavelength range. The lensed fiber produces a better overlap with the long-range surface plasmon mode of interest and thus results in a better coupling efficiency with essentially no background light as observed on an infrared camera. The measurements are compared with theoretical results obtained using a realistic model of the structures, including out-of-plane curvature in the grating profile resulting from our fabrication process. The coupling scheme along with the surface plasmon waveguides hold strong potential for biosensing applications.
TL;DR: The design, simulation, fabrication, and test of an L-band SAW resonator based on 128° Y-X LiNbO3 substrate, which exhibits a Rayleigh wave resonance peaks at 1.55 GHz and a well linear dependence of temperature/strain on frequency-shift.
Abstract: High frequency surface acoustic wave (SAW) technology offers many opportunities for aerospace applications in passive wireless sensing and communication. This paper presents the design, simulation, fabrication, and test of an L-band SAW resonator based on 128° Y-X LiNbO3 substrate. The design parameters of SAW resonator were optimized by the finite element (FEM) method and the coupling-of-mode (COM) theory. Electron-beam lithography (EBL) technology was used to fabricate the submicron-scale of interdigital transducers (IDTs) and grating reflectors. The effects of some key EBL processes (e.g., the use of electron beam resist, the choice of metal deposition methods, the charge-accumulation effect, and the proximity-effect) on the fabrication precision of SAW devices were discussed. Experimentally, the LiNbO3-based SAW resonators fabricated using improved EBL technology exhibits a Rayleigh wave resonance peaks at 1.55 GHz with return loss about −12 dB, and quality factor Q is 517. Based on this SAW resonator, the temperature and strain sensing tests were performed, respectively. The experimental results exhibit a well linear dependence of temperature/strain on frequency-shift, with a temperature sensitivity of 125.4 kHz/°C and a strain sensitivity of −831 Hz/μe, respectively.