Proceedings Volume 11201

SPIE Micro + Nano Materials, Devices, and Applications 2019

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Proceedings Volume 11201

SPIE Micro + Nano Materials, Devices, and Applications 2019

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Volume Details

Date Published: 13 January 2020
Contents: 12 Sessions, 59 Papers, 0 Presentations
Conference: ANZCOP 2019
Volume Number: 11201

Table of Contents

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Table of Contents

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  • Front Matter: Volume 11201
  • Special Session on Photonic Crystals and Applications
  • Nonlinear Plasmonics and Photonics
  • Metasurfaces I
  • Metasurfaces II
  • 2D Materials
  • Solar Cell Technologies
  • Direct Laser Writing I
  • Nanotextured Surfaces and Optical Sensors
  • Direct Laser Writing II
  • Biosensing
  • Poster Session
Front Matter: Volume 11201
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Front Matter: Volume 11201
This PDF file contains the front matter associated with SPIE Proceedings Volume 11201, including the title page, copyright information, table of contents, and author and conference committee lists.
Special Session on Photonic Crystals and Applications
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Femtosecond laser 3D nanoprinting for functional devices
Laser nanofabrication is a powerful technique, which could realize 3D programming of materials for the designable fabrication and flexible integration of 3D intelligent devices. No matter hard or soft materials can be manufactured or modified through femtosecond laser. 3D fuchtional devices, including micro-electronics, machines, optics or fluidics are successfully made by this powerful technology. Smart functional devices that could be controllably manipulated to complete predictable actuation have been readily fabricated through laser processing. Recent results on femtosecond laser 3D nanoprinting for functional devices are demonstrated. We believe that in the near future, the femtosecond laser smart processing technology would be widely employed to make smart materials with 3D features, contributing to the development of 3D functional materials, devices, system and robotics.
Graphene on silicon-nitride photodetector
Tania Moein, Darius Gailevicius, Tomas Katkus, et al.
Even though graphene is a gapless material, it demonstrates strong interband absorption from a broad range of wavelengths between VIS and NIR. Recent photocurrent graphene-based detectors demonstrated strong photoresponse signal near the graphene/metal boundaries. To increase the response time of photodetectors, the use of low thermal capacity materials and structures are required. SiN membranes are good candidates due to their high-quality factor (up to 106-107), low mass and excellent optical properties. The motivation for this study was based on a lack of any suitable solution for nano-dimension form factor detector that could be integrated into 3D photonic bandgap structures for real-time internal characterization.
Ablation control by applying magnetic and electric fields
Jovan Maksimovic, Tomas Katkus, Soon Hock Ng, et al.
Laser fabrication with ultra-short laser pulses (sub-1 ps) have the ability for precise energy delivery to target materials for ablation, spallation or polymerisation down to sub-wavelength resolution. We show, that by applying electrical and magnetic fields, the electron-ion ablation plasma can be controlled following the Lorentz force exerted on to the plasma F = eE + e[v ×B], where v is velocity of charge e, E is the applied electrical bias and B is the magnetic flux density. The vectorial nature of the Lorentz force was investigated using the ablation of silicon. The application potential for ablation debris control and mass, charge spectroscopes of ablated materials is discussed.
Nonlinear Plasmonics and Photonics
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Nonlinear plasmonics of NLO polymer/Au nanoparticle hybrid systems
A. Sugita, T. Makiyama, R. Aoshima, et al.
Second harmonic generation (SHG) behaviors will be presented for NLO polymer/Au nanoparticle hybrid structures. The NLO polymer is the material rich in the nonlinear susceptibilities and it is suitable for coating on the metal surfaces. The Au nanoparticles themselves exhibit enhanced SHG effects at localized surface plasmon (LSP) resonances. Our experimental results demonstrated that the Au nanoparticles coated with the NLO polymer emitted more than one magnitude higher SHG signals than the bare Au nanoparticles. The enhanced nonlinearities due to the NLO polymers were explained in terms of not only electromagnetic mechanism but also molecule-to-metal charge transfer mechanism.
Frequency mixing in nonlinear interaction of one-way edge-modes of topological photonic crystals
We investigate topological photonic crystals specially designed such that the frequency band gaps appear around ω0, 2ω0, 3ω0 and, more importantly, each band gap contains exactly one unidirectional edge mode. These one-way edge modes are then utilized to implement key nonlinear frequency mixing processes, such as second- and third-harmonic generation.
Metasurfaces I
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Mid infrared metasurfaces for photo-thermal energy conversion
Mid infrared metasurfaces is one of the key technology for sensors, energy harvesters in renewable society. Especially absorption type of metasurfaces can be applied for mid infrared light source and detectors according to Kirchhoff's law. Here we demonstrate the recent advances of metasurface, fabrication (lithography/lithography free), optical characterization of reflection ,scattering and absorption, photo-thermal energy conversion, and sensing applications in mid infrared wavelength. The experimentally measured optical properties were compared with simulations by finite difference time-domain (FDTD) method and finite element method (FEM).
A simple and robust surface integral method to model light and matter interactions
Qiang Sun, Evert Klaseboer, Alex Yuffa, et al.
We introduce a robust and effective surface integral equation method for modelling light-matter interactions which is simple conceptually and only encompasses the key tasks to obtain the physically important values of the field and its derivative at the surface that are often of interest in micro-photonic applications.
Nonlinear response of surface plasmon polaritons: a systematic comparison with new insights
Gordon Han Ying Li, Alessandro Tuniz, C. Martijn de Sterke
The nonlinear coefficient γ is a key parameter for studying nonlinear pulse propagation, as it relates the power in a waveguide mode to the nonlinear phase shift per unit length. It is well understood in dielectric waveguides, but less so in lossy plasmonic waveguides. A number of methods for calculating γ have been proposed, each producing different expressions. Here, we comprehensively compare these methods for a surface plasmon polariton propagating at a gold-air interface, obtaining new insights into the nonlinear response of lossy waveguides.
Metasurfaces II
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Plasmonic metasurfaces for optical information processing
L. Wesemann, E. Panchenko, K. Singh, et al.
Optical spatial frequency filtering is a key method for information processing in biological and technical imaging. While conventional approaches rely on bulky components to access and filter the Fourier plane content of a wavefield, nanophotonic approaches for spatial frequency filtering have recently gained attention. Here computational and experimental progress towards the design and demonstration of metasurfaces with spatial frequency filtering capability for optical image processing will be presented. Using the example of a metasurface consisting of radial rod trimers we demonstrate its potential to perform edge enhancement in an amplitude image and conversion of phase gradients in a wavefield into intensity modulations. The presented results indicate a potential avenue for ultra-compact image processing devices with applications in biological live-cell imaging.
Photon-pair generation via bound states in the continuum in nonlinear metasurfaces
Generation of photon pairs in nonlinear materials enables the creation of non-classical entangled photon states. With ultra-thin metasurfaces, composed of optical nano-resonators, one can enable the ultimate in miniaturising nonlinear photon sources along with unprecedented configurability. We present a novel design of a nonlinear metasurface incorporating AlGaAs nanodisks with oligomer-holes, which features symmetry protected bound states in the continuum. It enables enhanced photon-pair generation at non-degenerate photon frequencies via spontaneous parametric down-conversion. This opens the potential for quantum-entanglement between photons at ultra-short time-scales across the visible and infrared regions, leading to new opportunities for quantum spectroscopy, sensing, and imaging.
Nonresonant ENZ metamaterial at visible wavelength for superior refractive index matching sensing
Z. Fusco, M. Taheri, M. Rahmani, et al.
In the compelling race of finding alternative plasmonic material, metallic sodium tungsten bronzes, NaxWO3 with x<0.25, host promising optoelectronic properties emerging from the insulator-metal transition (IMT), such as strong interband transition and intense near-infrared plasmonic absorption. So far, studies have focused on tuning the IR plasmonic properties for the realization of functional devices, ranging from biosensors to smart windows. However, the utilization of the transparency band where the permittivity approaches zero still remains largely unexplored. Here, we show preliminary results which indicates an epsilon-near-zero (ENZ) behavior at optical frequencies of NaxWO3 which arises from the minimization of the total scattering cross-section. Additionally, as a proof of concept, we explore this material for sensing applications and we establish a performant optical sensor with sensitivity of 150 nm/RIU and showing a threefold enhancement with respect to traditional Au nanospheres. The peculiar sensing mechanism is investigated both experimentally and theoretically by means of electrodynamic and first principle calculations. Combined with the high quality of the NaxWO3 single crystals, ENZ properties in the ~400-600 nm region and low losses, these new insights offer great promise for the inexpensive realization of new generations of electro-optical devices with application ranging from ultrasensitive biosensors and light harvesting to exotic cloaking materials.
Dielectric metasurface based advanced image processing
Andrei Komar, Rifat A. Aoni, Lei Xu, et al.
We numerically and experimentally demonstrate an optical image processing technique in the form of edge detection of an object by exploring the angular selectivity of dielectric metasurfaces. By taking the advantages of resonant dielectric metasurfaces with spatial dispersion property, we efficiently filter-out the lower k-vector components of an image and only allow the higher k-vectors resulting in displaying the silhouettes of an object. We have considered dielectric amorphous silicon (a-Si) nanodisk with hexagonal structure interface which provides nearly zero transmission for lower k-vectors and near-unity transmission for higher k-vectors at the operating wavelength of 1550 nm. The proposed metasurface has been fabricated using electron beam lithography followed by a lift-off process. Our results suggest a new way to realize the effective edge detection with dielectric metasurfaces and open new opportunities for ultracompact optical image processing devices, having various applications in microscopy.
2D Materials
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Second harmonic generation from multilayer hexagonal boron nitride
We report second harmonic generation (SHG) from thick hexagonal boron nitride (hBN) flakes with approximately 109 layers. Surprisingly, the resulting signal is stronger when compared to previously reported few-layer experiments that showed the SHG efficiency gradually decreasing with the increasing thickness. This confirms that thick hBN flakes can serve as a platform for nonlinear optics, which is useful because thick flakes are easy to exfoliate while retaining a large flake size. We also show spatial second harmonic maps revealing that SHG remains a useful tool for the characterization of the layer structure even in the case of a large number of layers.
Engineering and application of quantum emitters in hexagonal boron nitride
Layered van der Waals materials are emerging as compelling two-dimensional platforms for nanophotonics, polaritonics, valleytronics and spintronics, and have the potential to transform applications in sensing, imaging and quantum information processing. Amongst these, hexagonal boron nitride (hBN) is known to host ultra-bright, room temperature quantum emitters, whose nature is yet to be fully understood. Here we present a summary of the recent advances in our group on controlling and engineering the quantum emission energies in hBN as well as demonstration of using these emitters for various quantum applications. First, we show a CVD technique to grow hBN hosting high density of emitters with emission energies distributed over 20nm range. This is a milestone on continuing the hBN progress in quantum optics as uncontrollable emission wavelength hinders the potential development of hBN-based devices and applications. In addition, we report our recent understanding of photophysical properties and level structure of hBN emitters. In this regard we show a new modality for super resolution imaging based on quantum emitters in hBN which is expandable to other systems. Our findings expand current understanding of quantum emitters in hBN and demonstrate the potential of hBN for the development of hybrid quantum nanophotonic and optoelectronic devices based on two-dimensional materials.
Tuning the properties of flash-reduced graphene oxide electrodes for supercapacitor applications
Graphene-based porous materials have attracted broad attentions in supercapacitor (SC) applications, due to the high conductivity and large surface area. The most widely used approach to fabricate graphene-based porous electrode materials is the reduction of graphene oxide (GO). The reduction process significantly affects the properties of reduced graphene oxide (RGO), including the conductivity, surface chemistry and the porosity. Therefore, the control the reduction process is of great importance to produce high performance electrode materials. In this paper, we explore the control of the electrical conductivity and surface chemistry of flash reduced GO material, which depends on the reduction degree. The reduction degree is tuned by varying the energy of a camera flash used to reduce the GO. The reduction degree is characterized by X-ray photoelectron spectroscopy (XPS). We find the high reduction degree (low oxygen content) is beneficial to achieve high electrical conductivity, however, the overall specific capacitance becomes lower. As a result, we can see that electrode surface chemistry is more dominant than its electrical conductivity in enhancing SC specific capacitance.
Optomechanical tension and crumpling of 2D semiconductors
Alexander V. Poshakinskiy, Ivan D. Avdeev, Alexander N. Poddubny
We show that mechanical properties of atomically thin crystals, such as graphene and transition metal dichalcogenides can be efficiently controlled by optical excitation. Illumination by a plane electromagnetic wave with the frequency close to plasmon or exciton resonance affects directly the membrane tension. Depending on the sign of the frequency detuning from the resonance, the membrane is either stretched or crumpled by light. In the latter case, the optomechanical crumpling force competes with the rigidity and the radiation pressure that try to flatten the membrane. When the excitation intensity surpasses the critical value, transition to the crumpled phase occurs.
Electronic and optical properties of Dirac semimetals in InAs/GaInSb superlattice nanostructures
Mikhail Patrashin, Norihiko Sekine, Kouichi Akahane, et al.
In this work we discuss technological aspects of creating a linear energy dispersion spectrum of charge carriers in semiconductor materials and report on the experimental realization of the topological Dirac semimetals (DSM) in nanostructurally engineered zero-gap InAs/GaInSb superlattices (SL) [1]. The SL samples are synthesized by molecular beam epitaxy, which provides monolayer accuracy for growing high-quality single-crystals on large area substrates. The prospects for designing the topological insulator (TI) SLs with the same approach and first results of experimental characterization of the TI candidates are also presented.
Solar Cell Technologies
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Development of plasmonic photocatalysts for inactivation of microorganisms and decomposition of organic compounds
Ewa Kowalska
Plasmonic photocatalysts, composed of titania and nanoparticles (NPs) of noble metals (NMs), were prepared, characterized and tested for decomposition of organic compounds and microorganisms under irradiation with UV and/or vis and in the dark conditions. It was found that modification of titania with NMNPs: (i) enhanced titania activity under UV irradiation (inhibition of charge carriers’ recombination), and (ii) activated titania under vis irradiation (localized surface plasmon absorption). Moreover, the properties of both support (morphology, phase composition, crystallite and particle sizes) and deposited NM (e.g., oxidation state, crystallite size, nanostructure) were crucial for broad response against chemical and microbiological pollutants. Various strategies have been proposed for activity and stability enhancements, e.g., an interface increase between NM and titania and fast “hot” electron transfer via shallow electron traps, which will be discussed in detail during this presentation.
Tuning the florescence color of gradient bandgap perovskite nanoplate by direct laser writing
Lead halide perovskites are widely applied in not only photovoltaics, but also on-chip light source, nanolaser, and photon detection. In order to promote the incorporation of perovskite into integrated devices, microscale color patterning flexibility is a very important step. Femtosecond (fs) laser fabrication has shown significant advantages of high spatial resolution, low surround damage, and high processing efficiency over the other laser fabrication. Compared to the state-of-art techniques, the straightforward fs-direct laser writing (fs-DLW) also has advantages of mask-free, simple one step, and contactless. Here, a specially designed formamidinium lead mixed-halide nanoplatelet (FAPb(BrxI1-x)3 NP) with gradient bandgap is fabricated by chemical vapor deposition method. Then, spatially resolved modulation of the fluorescence by fs-DLW is demonstrated on the as-grown NP. The fluorescence color is modulated from red to green under a controlled laser pulse, due to the replacement of iodide ions by bromide ions. Specifically, the as-grown NP (thickness≈800 nm) is with a gradual bromide-iodide composition along the depth, mainly exhibits an emission of 710-nm from the bottom iodine rich phase. After halide substitution induced by fs-DLW, new fluorescence peaks appear in the wavelength range of 540 to 700 nm, which is controlled by the fs-DLW conditions. The fluorescent color is spatially modulated from red to green, enabling microscale resolved multicolor emission, implying the potential applications in micro-encryption, sensors, multicolor displays, lasers, and light-emitting devices.
Estimation of refractive index profiles of vertically aligned disordered silicon nanowires for photon management applications
We discuss a promising method to assess the refractive index profile of vertically aligned disordered Silicon nanowire arrays. The aberration-free micro-reflectivity set-up equipped with an in-situ optical microscope is designed to measure the reflectivity from 4μm2 area of the nanowires. The spatial- and polarization-dependent reflectivity values along the nanowire length is used to estimate the refractive index profile. The transfer matrix method involving the estimated refractive index profiles is employed to corroborate the measured reflectivity values. The disordered Silicon nanowires with gradient refractive index profile can suppress 96 % reflectivity irrespective of direction, wavelength, and polarization which make them a potential candidate for photon management applications.
Light soak study of perovskite-based materials via scanning imaging spectroscopy
Organic-inorganic halide perovskite has emerged as promising candidate materials for next-generation energy harvesting and light-emitting applications with the advantages of low processing cost, high defects tolerance, and excellent power conversion efficiency. The instability of these perovskite-based materials under illumination, however, remains a major technical barrier for commercialization. Various techniques have been applied to improve the photo-stability of perovskites. Since the dynamic of photo-generated charged carriers and photo-activated mobile ions affect the stable performance of these applications, a comprehensive understanding of how illumination affect perovskites are of vital importance to improve the performance of perovskite-based optoelectronic applications. In this report, the recent progress of the light soak study on three kinds of perovskites is presented, using depth-resolved, temporal-resolved, and detection-wavelength selective spectroscopic imaging techniques. These works clarify different dominate roles in different perovskite structures and demonstrate the advantages of the imaging spectroscopy in studying the carrier dynamics of perovskite-based materials under light soaking, which is of crucial importance for their applications.
Direct Laser Writing I
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Femtosecond laser writing of metallic nanostructures using silver photo-reduction
We report on fabrication of silver nanostructures using femtosecond laser lithography in silver-containing polymers. Various metallic structures were fabricated using tightly focused femtosecond laser beam having circular and linear polarization. Fine gratings consisting of ripple patterns were fabricated using linear polarization, and nanorings having size below the diffraction limit were fabricated using circular polarization. This approach offers a promising route for realization of plasmonic nanostructures on flexible substrates.
Tightly-focused femtosecond laser interaction with water
Koji Hatanaka
Tightly-focused femtosecond laser pulse (<35fs, 800nm) irradiation up to sub-peta-W/cm2 at the focus onto thin water flow (10-15μm thick) in air results in plasma formation associated with dynamic and macroscopic laser ablation phenomena. Under such experimental conditions, hard X-ray, THz wave, and sound/ultrasound emission were measured with a Geiger counter, time-domain spectroscopy with a ZnTe(110) crystal (1mm-thick) based on electro-optical sampling method, and microphone/transducer, simultaneously. Under the single pulse irradiation, intensities of X-ray, THz wave, and sound show their maxima at the same position of the water flow along the laser irradiation axis (Z-axis), while the width of the intensity profile along the Z-axis is narrower at 44μm in X-ray than that of THz wave at 225μm and sound (10Hz-20kHz) at 400μm when the laser intensity is at 0.4mJ/pulse and focused by an off-axis parabolic mirror (f = 5cm). Under the double pulse irradiation conditions with the time delay between the main pulse (p-pol.) and the prepulse (s-pol.) up to 15ns, those emissions are enhanced, which can be ascribed to time-dependent various phenomena of laser ablation such as pre-plasma formation and transient surface modifications induced by the pre-pulse irradiation.
Response of natural muscovite to a single femtosecond laser pulse
Saurabh Awasthi, Douglas J. Little, Alex Fuerbach, et al.
Muscovite is a naturally occurring crystalline mineral, a mica, with a unique layered structure with planes of low cleavage energy spaced by ~1.3 nm in the crystal structure. It is a dielectric insulator. Freshly cleaved muscovite surfaces are extremely flat, clean and used in many technical applications of the material. Previous laser ablation study of mica using ultraviolet, nanosecond duration pulses, led to a poor finish at the process sites (K. Rubahn et.al., J. Appl. Phys. 86(5), 2847, 1999). Interest in laser processing of the material, other than CO2 laser cutting of mica sheets, was subsequently, and not surprisingly, curtailed. Here-in we report the morphologies of the laser processed site affected by a single, ~150 fs duration, 800nm wavelength, 6 micron spotsize laser pulse focussed on the surface of a mica substrate. A systematic sequence of the morphology as the fluence of the single pulse is increased is obtained. Optical surface profiling and field emission secondary electron microsocopy are used to characterise the site morphology. Time of flight secondary ion mass specroscopy has been used to map the redistribution of key elements at the process site. Muscovite emerges as a fascinating material in its response to a femtosecond laser pulse. Useful marking without creation of debris beyond the footprint of the laser spotsize is achieved at a flunece as low as 2.4 J/cm2. There is evidence of plasticity and cavitation within the sequence of morphologies found.
Direct femtosecond laser writing of low-loss waveguides in chalcogenide glasses for mid-infrared applications
D. Le Coq, J. Carcreff, P. Masselin
Direct femtosecond laser writing technique is now widely used in particular in glass, to produce both passive and active photonic devices. This technique offers a real scientific opportunity to generate three-dimensional optical components. The chalcogenide glasses are of great interest since they possess a transparency window from the visible up to the midinfrared range. Moreover, they also have high optical non-linearity and high photosensitivity that facilitate the inscription of permanent refractive index modification. In this presentation, an original method based on both the filamentation phenomenon and a point-by-point technique will be described. The written waveguide is of multicore type and consists in parallel channels of positive ▵n placed parallel to each other on a hexagonal or a circular mesh. The performances in terms of optical losses at both 1.55 μm and 4.55 μm measured in such photowritten buried infrared waveguide are very competitive. This writing technique is particularly suitable for the design of single mode waveguide for wavelengths ranging from the visible up to the mid-infrared since the geometry of the inscription and the amplitude of the refractive index modification can be easily adapted. This also paves the way for the fabrication of advanced mid-infrared optical components such as Y-splitters.
Nanotextured Surfaces and Optical Sensors
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Hybrid two-dimensional nanostructured hydrogen gas sensors
Two-dimensional (2D) nanostructured materials such as reduced graphene oxide (rGO) are highly promising for hydrogen (H2) sensing due to their narrow bandgap, number of active sites, and high surface area. Detection of hydrogen gas, a renewable and clean source of energy, in the atmosphere is of great importance in maintaining safety at all stages of hydrogen production, storage and use. In this work, a novel conductometric sensor has been developed based on hybrid 2D nanostructured rGO doped with Pd nanoparticles (Pd/rGO) to evaluate its sensing performance towards hydrogen with different concentrations (up to 1%). Various sensing parameters including sensitivity, response/recovery time, stability, and low detection limit have been investigated throughout the experiment. We also evaluate performance of the developed sensors at different operating temperatures (room temperature up to 120°C). Material properties of hybrid Pd/rGO film including surface morphologies, crystallinity, molecular vibration, functional groups, and oxidation states are sufficiently analysed by X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), Energy-dispersive X-ray spectroscopy (EDX), profilometer, X-ray diffraction (XRD), and Raman spectroscopy. Furthermore, fundamental sensing mechanism governing the interactions between Pd/rGO and the hydrogen molecules are studied. It is anticipated that materials and techniques described in this work offers solutions to develop highly sensitive and portable hydrogen sensors with low power consumption and low fabrication and operation cost.
Thermal radiation control structure obtained by anisotropic anode etching of Al
Toshiaki Kondo, Takashi Yanagishita, Hideki Masuda
By anodically etching a (100)-oriented Al foil with an etching mask in hydrochloric acid solution, an ideally ordered array of Al holes was obtained. The Al hole array structure showed wavelength selective thermal radiation property. Wavelength band of the thermal radiation could be tuned by controlling the aperture size of the hole. The aperture size of the Al hole was controlled by optimizing geometrical structures of the etching mask and anode etching conditions.
Technology for chip based optical gyroscope
Muhammad Hassan Iqbal, Choon Kong Lai, Steve Madden
Low cost and highly reliable integrated optical gyroscopes with a resolution of ≤ 10 °/h can potentially replace the bulk optical angular velocity sensors which are currently being used in medium/high performance applications. i.e. missiles and telescopes. Therefore, research aiming to fabricate chip-based optical gyroscopes are attracting attention and integrated optics is an approach that would provide a product with moderate performance.
Revisiting high order anapole mode in single dielectric nanostructure with high refractive index
We investigate the high order anapole mode in single dielectric nanostructure with high refractive index from eigenmode perspective. We find that the anapole mode in both cylinder and sphere can only occur in the following two situations:(1) If only one mode is involved, the combined phase of intrinsic and extrinsic phase should be equal to 2π at certain frequency that is close to the resonance. (2) If two leaky modes are involved, the combined phase for each mode must be 2π at same frequency which is located between two resonances.
Optical metagrating for one-shot polarization measurements
Shaun Lung, Nicolas R. H. Pedersen, Kai Wang, et al.
We formulate a new conceptual approach for one-shot full Stokes polarization measurement with a single meta- grating, and develop novel design through advanced computational optimization of individual nano-resonator properties delivering robust operation even under strong fabrication inaccuracy. We fabricated the metasurface from amorphous silicon nanostructures deposited on glass, and experimentally confirmed accurate optical polarization reconstruction. We anticipate that our new concept will facilitate diverse applications such as optimal polarization state imaging tailored for computer vision or quantum state characterization.
Direct Laser Writing II
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Laser writing of color centers in silicon carbide
S. Castelletto, T. Katkus, S. Juodkazis
In this paper, we describe direct laser writing employed in 4H-SiC to create a controlled array or patterns of luminescent emission in the red and near infrared region (from 900nm to 1200nm) under green, red and infrared lasers excitations, respectively. The observed emissions are mainly attributed to vacancies related color centers in 4H-SiC.
The double-edged sword of femtosecond laser-induced periodic surface structures for sub-diffraction and high-efficient nanotexturing
Laser-induced periodic surface structures (LIPSS) have gained lots of attention for the rich physics and potentials in subdiffraction nanostructuring. Herein, we report new aspects of LIPSS to uniformly extend the periodicity to macro, or conversely suppress the periodicity to obtain freeform nanostructures. We have focused on the electron excitation, effective surface permittivity modifications, and plasmonic standing wave ablation for the structure origination and evolution. A plasmonic nanoimprinting model in long range and a nanohole-based light field enhancement in the nearfield are proposed, which are in good accord with the experiments. The nanotextured surface is obtained in a large area by light tailoring method with a cylindrical lens focusing and scanning. Besides, a critical power control method to confine the light field in nanoregion are conducted to obtain the freeform nanostructures, which have potential applications in birefringent optics and nanoscience.
Femtosecond laser fabrication of hybrid optical element in glass: volume grating embedded inside refractive lens
Femtosecond laser direct writing in glass is used to fabricate micro-optical elements with hybrid optical functions. Formation of hybrid refractive-diffractive elements by femtosecond laser direct writing in glass was demonstrated. By fabricating a diffraction grating inside a refractive lens, an element with two functions of light focusing and diffraction was fabricated. Hybrid optical element of volume grating embedded inside refractive lens element with a diffraction efficiency of 89% (at 633 nm wavelength) is achieved.
Evolution of femtosecond laser-induced periodic structures: from nanoholes to regular structures
Femtosecond laser-induced periodic surface structures have opened broad prospects in the aspect of high-efficient and low-cost nanotextured patterning, yet defined great challenges on how to keep the periodicity in a macro area. Herein, we report a transition from non-periodicity to periodicity as the scan strategies changing. By suppressing the transition from the initial structures to the nanogratings with long-range order, arbitrary high-resolution direct writing patterns have been obtained in a large area. We attribute this phenomenon to the dynamic evolution of the near-field energy deposition around the pre-existing structures. This approach paves another way to high-precision laser processing.
Biosensing
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Towards an active micropump-mixer for rapid anti-platelet drug screening in whole blood
This work reports on development and characterization of an on-chip microfluidic handling system for application in preclinical anti-platelet drug screening. A reciprocating elastomeric micropump/mixer design is presented for use with whole human blood, utilizing flexible structural and actuation properties to manage hemodynamics for an on-chip platelet thrombosis assay on fibrillar collagen. The hemocompatibility of the design is assessed across a range of operational configurations, demonstrating equivalent or superior performance to common microcapillary systems at a range of physiologically relevant shear conditions. Surprisingly efficient mixing phenomena are briefly investigated, validated using dyes within the molecular weight range of common antiplatelet therapies. Finally, a proof-of-concept preclinical application is explored, demonstrating that this prototype can act as a real-time assay of anti-platelet drug pharmacokinetics, compared to an equivalent microcapillary system.
An optical fiber microprobe for surface-enhanced Raman scattering sensing with enhanced signal-to-background ratio
Md Abdullah Al Mamun, Tomas Katkus, Saulius Juodkazis, et al.
Surface-enhanced Raman scattering (SERS) is a highly sensitive and versatile analytical technique that can be implemented on an optical fiber platform for use in challenging environments. This work has sought to address a major factor limiting the use of optical fibers for SERS analytical applications, namely the silica Raman background generated inside the fiber can make it difficult to detect the target analyte. Two different approaches were investigated to address this problem. Firstly, double clad fiber (DCF) was found to increase the collection of Raman scattered signal from the analyte, giving up to twelve-fold improvement in the signal-to-background ratio (SBR). Secondly, a prototype microfilter was manufactured by femtosecond laser machining and attached directly to the DCF tip. Its performance in rejecting background signal was then evaluated. When taking the lengths of the optical fibers into account, the filtered DCF microprobe delivers 7.0 SBR.cm, while the bare DCF probe provided 3.0 SBR.cm. Therefore, the microfilter assembly more than doubled the performance of the SERS probe and, with further optimization in future, it shows great promise for ultra-compact SERS and Raman optical fiber probes.
Ultrasensitive biosensing based on plasmonic nanostructures
P. Venugopalan, N. S. Susan Mousavi, A. Dabirian, et al.
Hafnium-doped zinc oxide (HZO) has been recently demonstrated to be implemented as a transparent conducting oxide (TCO) material in photovoltaic applications but its plasmonic properties are left untouched. In this work, we systematically investigate the plasmonic properties of gold nanoparticle (Au NP) arrays on thin HZO film, for different ratios of Hf dopants to Zinc oxide (ZnO) film. A localized surface plasmon resonant (LSPR) mode and two Bragg modes (due to the coupling of plasmon modes inside the film to array periodicity) are observed in the proposed structure. Resonant excitation of these modes produces large field enhancement at the surface of the NPs as well as Au NP/HZO film interface and was observed with FDTD simulations. The optimized plasmonic structure will be fabricated on quartz crystal microbalance (QCM) using laser interference lithography, based on the plasmonic resonant position and the SERS (surface enhanced Raman scattering) intensity, and it will be integrated to a microfluidic device in the configuration of the lab-on-a-chip concept for biosensing applications.
Poster Session
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Curcumin-nanodiamond-silk wound dressings for sensing infection
The presence of an infection in a wound site is typically diagnosed based on the external appearance, such as redness, swelling, odour, and/or loss of function. However, this can lead to inaccurate and untimely diagnoses, since an infection might be present without obvious symptoms. This would commonly require removal of any dressing that might be present, which can cause further pain to the patient. Therefore, there is a need for more precise methods of detecting infections, with minimal effects to the patient. Comparison of temperature differences between infected tissue and healthy tissue shows an increase ranging from 3-4 °C, while normal skin has a temperature gradient of ±1 °C. Hence, monitoring temperature of wounds can be used to detect the presence of an infection. Nanodiamonds (NDs) containing negatively charged nitrogen-vacancy (NV-) centres are capable of monitoring changes in temperature with minimal influence by environmental factors such as pH, ion concentration or molecular interaction. This study looks at encapsulating these NDs into silk fibres for use as a wound dressing that can monitor temperature changes in the wound, without requiring the removal of the dressing. To further enhance the wound healing and anti-bacterial properties, curcumin was also incorporated into the silk fibres. Curcumin is one of the active ingredients in turmeric and is known to significantly enhance wound healing through its anti-inflammatory and antibacterial properties. This study used this curcumin-nanodiamond-silk hybrid wound dressing to investigate the healing capabilities and temperature sensing properties for use as a wound dressing.
Nonlinear imaging through magnetic dipole quasi-BIC ultra-thin resonators
We propose an ultra-thin silicon metasurface supporting a high-quality leaky mode which is formed by partially breaking a bound-state-in-the-continuum (BIC) generated by the collective magnetic dipole (MD) resonance excited in the subdiffractive periodic systems. Such a quasi-BIC MD state leads to a robust near-field enhancement and a significant boost of the nonlinear process, resulting in measured 500-fold enhancement of third-harmonic emission in comparison to the conventional silicon disk metasurface. We further experimentally demonstrate the highly-efficient nonlinear image tuning via polarisation and wavelength control, opening the way for various applications in high-performance nonlinear metadevices including tunable laser, tunable displays, nonlinear imaging.
Solid-state light-emitting devices using novel green luminescent material of semiconductive nanoporous ZnMnO
Sejoon Lee, Youngmin Lee, Deuk Young Kim, et al.
The novel green luminescent material of the semiconductive nanoporous ZnMnO thin film was fabricated by grain boundary engineering and thermal stress engineering via the thermal nucleation of the sputter-grown ZnMnO layers. Nanoporous ZnMnO exhibited the strong green luminescence characteristics, attributing to the photon confinement at the localized green-emission band formed near the edge area of ZnMnO nanopores. Using semiconductive nanoporous ZnMnO, two different types of high-performance solid-state lighting devices (i.e., field emission device and light-emitting diode) were demonstrated as tangible applications of semiconductive nanoporous ZnMnO.
Antireflective surfaces for astro-photonic applications
Daniel Smith, Nguyen Hoai An Le, Soon Hock Ng, et al.
Antireflection patterns for optical elements used in astro-photonic applications require optimisation for different wavelengths, a defined angular selectivity and have to be made on large curved surfaces. Sputtered film of tens-of-nm of gold was annealed at 500°C for 1 hour to form a pattern of nano-islands used as a mask for plasma etching. Separation between islands depended on the annealing time and an initial film thickness and provides a method to control a characteristic length between etched nano-pillars. Fabricated surfaces were characterised by transmission and reflection spectroscopy.
Enhancement of photocurrent in InGaN/pseudo-AlIGaN multi quantum wells by surface acoustic wave
In this work, we have investigated the variation of internal electric field of 4-period In0.16Ga0.84N/pseudo-AlInGaN multiquantum wells (MQWs) embedded in p-i-n structure by surface acoustic waves (SAWs). The pseudo-AlInGaN barriers consist of two In0.16Ga0.84N(11 Å) sandwiched by three Al0.064Ga0.936N (15 Å). The equivalent indium and aluminum compositions in pseudo-AlInGaN barrier are 0.043 and 0.052, respectively, which can be calculated by volume ratio. For reference purpose, In0.16Ga0.84N/GaN MQWs was also used. To generate surface acoustic wave, interdigital patterns with 1 μm finger width were fabricated by e-beam lithography. The piezoelectric fields for GaN barrier and pseudo- Al0.043In0.052Ga0.905N barrier samples are found to be 1.5 MV/cm, 0.33 MV/cm from bias-PL. From μ-PL measurement for pseudo-Al0.043In0.052Ga0.905N barrier sample, we observed lowest luminescence intensity at 100 MHz and 13 dBm in radio frequency (RF) generator, which means that electron-hole recombination can be suppressed by SAWs. The Photocurrent measurement for pseudo-Al0.043In0.052Ga0.905N barrier sample was observed increasing around 2 orders of magnitude at 100 MHz when compare to GaN barrier sample. Based on our results, the reduced piezoelectric field added to SAWs can be provided one of the solutions for enhancing photocurrent in III-nitride photovoltaic devices by extract carriers from quantum wells easily and enhancing traveling length of carriers.
Black metals
Stefan Lundgaard, Soon Hock Ng, Michael Mazilu, et al.
Novel optical absorbers are made using titanium metal and silicon dioxide thin films in specific layer thicknesses that create a low fractional reflectance and transmittance material. The absorbers have high absorption fraction measured from 200 - 1400 nm at normal incidence and specific reflectance band peaks. Layer thicknesses affect the wavelength at which light is reflected or absorbed and opens up tuneability for specific wavelengths within the visible spectrum depending on applications such as for solar cells and light modulation.
Scalable and consistent fabrication of plasmonic colors via nanoimprint lithography
M. Faris Shanin Shahidan, Jingchao Song, Timothy D. James, et al.
We utilised thermal and UV-assisted Nanoimprint Lithography (NIL) i.e. thermal and UV-assisted to produce plasmonic coloration, and compare their ability for scalable fabrication. Several designs are presented and we show the generated colors are dependent on their geometry and the direction of polarisation of incident illumination. Finally, we demonstrated UV-NIL for consistent production of large-area (0.6×0.4 cm2) plasmonic color with extended color gamut.
Large-area mask patterning for solar cell applications
Jingwen Hu, Jovan Maksimovic, Soon Hock Ng, et al.
Light harvesting using photonic crystal (PhC) surface patterns provides an opportunity to surpass the ray-optics defined light trapping and to approach thermodynamic ShockleyQueisser limit of solar cell efficiency, which for a single junction Si solar cell is ~ 32%. For an industry amenable nano-patterning of Si solar cells, we used laser direct write and stepper lithography based approaches for defining a large area (1 cm2) light trapping PhC patterns on silicon. Nanoholes of ~ 500 nm in diameter were fabricated by direct laser writing in a thin layer of chromium to act as a mask for subsequent reactive plasma etching to fabricate the nanostructures forming a PhC surface over a square centimeter. Surface area fabrication throughput was improved by more than order of magnitude as compared with electron beam lithography required to achieve sub-1 μm resolution.
Design and optimization of broadband and transparent SERS based on transformation optics
Mohammadrahim Kazemzadeh, Neil Broderick, Weiliang Xu, et al.
In this work, a novel transparent surface-enhanced Raman scattering (SERS) for the application of probe sensing is presented. This SERS is made by a two-dimensional array of noble metal which contains nano bowls with scattered nanospheres on its surface. Using the theory of transformation optics, we show that the curvature of nano bowls amplify the electric field around the nanospheres. This amplification is broadband due to the inherent nature of space transformation which does not rely on frequency. Comparisons with conventional flat SERS are done to demonstrate the advantages of the present design. We show that the curvature of these nano bowls increases the volume of the hotspot by one order of magnitude. This significantly reduces the response time of the SERS. Also, it is shown that this curvature amplifies the electric field in hotspot more than hundreds of times greater than SERS without using those nano bowls. The calculated amplification of the Raman signal is more than one billion times so this surface is a promising candidate for single molecule detection. The optimization and simulations are done using the Finite Element numerical algorithm.
Ultraviolet light emitting diode lamp for color perception research
Charitha Weerasuriya, William Woods, Soon Hock Ng, et al.
Color influences human decision making process, affects mood. It is important to investigate human color judgment of objects under different illumination. By controlling of a red (R), green (G), Blue (B) and Amber (A) colored lamp a MagnetoEncephaloGraphy (MEG) brain scanner was tested for its performance. We developed a software to generate all the colors in the visual spectrum, predefined white light combinations and saturation of an illuminated objects by using RGBA colors. The lamp was controlled from outside of the shielded MEG room while the LED lamp was located inside of electromagnetically shielded room. The USB was used as for LED-lamp control. To check the feasibility of using LED lamp with MEG brain scanner and showed feasibility to use the LED-lamp, color control software and MEG scanner together for human and color related research.
Formation of micro-groove on diamond by femtosecond laser micromachining
Laser processing of diamond have attracted attention. Ultrashort laser pulses can be used for micro-structuring on diamond and in bulk diamond. In this paper, we report on laser parameters for surface structuring of diamond by using femtosecond laser pluses at a repetition rate of 1 kHz. By changing scanning speed and energy, different types of grooves were inscribed. The morphology and depth of grooves were investigated.
Silicon nitride based fluidically tuned photonic crystal for bio-sensing application
Manoranjan Kumar, Shwetha M., Poojith T., et al.
In this work, silicon nitride (Si3N4) based fluidically tuned photonic crystal for a biosensing application is presented. The optical structure is designed on Si3N4 on insulator. The Si3N4 on insulator substrate is found to be one of the most promising materials for the design of bio- sensor at short wavelength. At short wavelength Si3N4 material is found to be most promising material for optical integrated circuits. The structure of the sensor consists of Silicon nitride input and output waveguides separated by a fluidically tuned photonic crystal. Fluidically tuned photonic crystal acts as a sensing region. The sensitivity is based on refractive index of fluidically tuned photonic crystal. The proposed sensor is designed to operate in the visible wavelength range of 660nm. Fluidically tuned photonic crystal consists of rectangular photonic crystal array. The holes of photonic crystal are approximately 160nm in diameter and height is 200nm. Organic light emitting diode is used as an optical source. OLED is coupled to input waveguide. The PDMS microfluidic channel is moulded on the rectangular photonic crystal structure. The structure is modelled and analysis is carried out by using Lumerical mode solution and Lumerical Finite Difference Time Domain (FDTD) simulation tools. Such devices if fabricated can be employed for early detection of various diseases related to pathological parameters.
Strong Kerr nonlinearity in BiOBr nanoflakes
We experimentally characterize the third-order optical Kerr nonlinearity of BiOBr nanoflakes via Z-Scan technique. Strong nonlinear absorption as well as high Kerr nonlinearity (n2) are observed at both 800 nm and 1550 nm, with a large nonlinear absorption coefficient on the order of 10-7 m/W and a high Kerr coefficient on the order of 10-14 m2/W being measured.
Deep-subwavelength metamaterial resonators operating at dual frequency regions
Shridhar Manjunath, Mingkai Liu, Vidur Raj, et al.
Metamaterials are engineered structures designed to interact with electromagnetic radiation. The common understanding in the scientific community is that, a typical metamaterial operates within a particular frequency range that is determined by the metamaterials’ dimensions. In this paper, for the first time to the best of our knowledge, we demonstrate that a metamaterial can be functional in more than one frequency region. We propose an advanced design that can interact with both THz and near-infrared (NIR) frequencies concurrently. Moreover, our novel metamaterial can work independently of the input polarisation in both wavelength regions. We designed and fabricated meander line resonators with 300 nm linewidth distributed over 16.26 μm area and experimentally demonstrate a structure that can simultaneously interact with NIR and THz frequencies with a high miniaturisation factor. This dual-band photonic metamaterials can be used as an advanced device in applications such as sensing, imaging, filtering, modulation, and absorption.
Infrared imaging in nonlinear GaAs metasurfaces
Dielectric metasurfaces have recently shown to be an excellent candidate for efficient frequency mixing at the nanoscale due to the excitation of Mie resonances. Among various dielectric materials, GaAs-based nanostructures have been reported to have high-efficiency of second-order nonlinear processes due to their high quadratic nonlinear susceptibility. Efficient frequency up-conversion can thereby be realised in GaAs-based metasurfaces through the process of sum-frequency generation (SFG), thereby opening new opportunities for nonlinear imaging and infrared vision not possible before. Here we demonstrate for the first time, infrared imaging based on nonlinear mixing of an infrared image with a pump beam in a GaAs resonant metasurface. The nonlinear mixing process generates visible images (Fig. 1a), which can be time resolved with femtosecond resolution and can be observed on a conventional CMOS sensor. Our results open new opportunities for the development of compact night-vision devices operating at room temperature and have multiple applications in defense and life sciences.
Silicon-based metasurfaces for vortex beam generation
Raghu Dharmavarapu, Soon Hock Ng, Shanti Bhattacharya, et al.
Silicon metasurfaces were fabricated on fused silica substrates by using sputtering, electron beam lithography and reactive ion etching. A chromium etch mask was used to protect the silicon during plasma etching. We designed a hologram with phase range of 0 - 1.17π to generate a higher order Bessel beam. The device produced the expected beam profile and the presence of charge 3 was confirmed using a interference test. Tests on spiral plate devices were less successful owing to the thickness non-uniformity in the sputtered Si film.
Optical frequency comb by giant nonlinear capillary waves
Nonlinear optical processes are essential for modern photonics and they are possible mostly when light is produced by a high-power laser. However, nonlinear effects of non-optical origin, such as those observed in acoustical and mechanical systems, are many orders of magnitude stronger than optical nonlinearities, and therefore they can be induced with energy that is much lower than that of a laser pulse. Here, we experimentally confirm our theoretical prediction of the possibility to convert giant acoustic and capillary wave nonlinearities into optical signals, thereby effectively reproducing the result of a conventional nonlinear-optical interaction. We excite highly nonlinear capillary Faraday waves on the surface of a thin layer of ethanol and we reflect a beam of low-power, incoherent light from these waves to produce an optical frequency comb. Our results can be used in many areas of photonics, including new classes of biomedical sensors that do not rely on high laser powers.
Measuring absorption coefficient of excised animal skin exposed to THz radiation
By employing a FTIR spectrometer aligned for THz beam in the Australian Synchrotron, we measured absorption coefficients of different toad skin patches. Skin samples were precisely excised from cane toad and prepared for experiments in dried and fresh states. The transmission and attenuated total reflection modes were designated to measure absorption coefficients through mathematical relations between transmittance and absorption. The transmission study shows that in the frequency range of 0.8 to around 3 THz the dark part of toad skin demonstrates higher absorption than the pale part in both dried and fresh states while it is reversed at higher frequencies. Both dark and pale skin patches perform much less absorption than distilled water. ATR data corroborates the same result in the frequency range of 0.75 to 0.95 THz.
Non-linear absorption coefficient measurement of thin films by Z-scan in near- and mid-infrared range
Stuart J. Flanders, James W. M. Chon
Research into multi-photon absorption of plasmonic metal and dielectric nanoparticles have gained a lot of interest recently because information on the multi-photon absorption coefficient is necessary for modeling and designing these nanoparticles for application in biolabelling and deep tissue imaging. Here we present Z-scan measurement results on gold thin films by using femtosecond pulsed laser at wavelengths in near and mid infra-red range (1 μm – 2 μm).
Uptake study of gold nanoparticles into cancer cells using high-order image correlation spectroscopy
D. Katoozi, A. H. A. Clayton, D. J. Moss, et al.
Gold nanoparticles (AuNPs), due to unique optical properties and has become excellent tools for cancer diagnosis and therapy. Various techniques are used to get information about AuNPs cellar uptake and aggregation, however; these methods are not suitable for live cell imaging. Here we used non-destructive characterisation method namely High order Image Correlation Spectroscopy (HICS) combined with Dark Field Microscopy (DFM) is used to get information about cellular uptake and aggregation of 80 nm gold nanosphere (AuNSs) inside HeLa cell. Results confirm the accuracy and simple nature of the proposed method for future live-cell imaging.
Towards a deep submicron CMOS image sensor on a standard FDSOI process
Paul Beckett, Ranjith Rajasekharan Unnithan
Lab-on-chip is a very promising point-of-care technology, where the specimen is placed directly on a CMOS chip for imaging without the use of any labels or chemicals and with no intervening optical components. However, lab-on-chip technologies developed so far have been limited by the existing pixel size of CMOS image sensors. To be able to accurately resolve small biological samples, the sensor pixel size must be less than the size of the object under examination. For example, bacteria range from 500nm to 5μm and viruses from 30nm to 300nm and thus require image sensors with nanoscale dimensions. However, reducing the size of an image sensor is challenging. Light sensitivity greatly reduces at and below the optical diffraction limit due to increasingly poorer coupling. In addition, CMOS image sensors typically use a refractive microlens that will not scale due to diffraction limits below around 1.4 μm. Further, conventional colour filters are made of absorptive dyes or pigments that do not work at nanometer thicknesses.