Computational on-chip spectrometers are emerging as a powerful platform for portable spectral analysis, combining photonic integration with advanced signal processing to enable a wide range of in-situ sensing applications. We propose a broadband reconstructive spectrometer based on wave chaos in a stadium microresonator with a nanostructured scattering layer for full-area speckle readout. Wavelength dependent interference within the chaotic microresonator encodes the spectral information into a spatial intensity pattern that can be computationally inverted to reconstruct the input spectra. The optimal fabrication parameters of the SU-8 polymer nanostructured layer yield a surface roughness of 176nm and a root mean square thickness of 2um. We experimentally validate our spectrometer at visible and infrared wavelengths, with resolutions of 43pm at 630nm and 8.2pm at 1550nm. The spectral reconstruction is demonstrated for single and multiple narrowline sources as well as for a broadband ( 1nm) pulsed laser source. The broad experimental validation and compact footprint (0.05mm2) establishes our chaotic microresonator-based speckle spectrometer as a robust and versatile platform for high-resolution, on-chip spectral sensing.

Silicon photonic crystal cavities (PhCC) exhibit high sensitivity to their surrounding environments, making them suitable for a diverse range of sensing applications. These applications include chemical sensing, optomechanical pressure sensing, displacement and radiation pressure measurements, as well as biosensing with potential applications in rapid medical and clinical diagnostics [1]–[3]. The integration of these devices with optical fibre, which offers additional benefits such as flexibility, robustness and immunity to electromagnetic interference [4], enables the development of highly sensitive sensors that can be utilised in challenging environments, such as cryostats or gas chambers.

Photonic crystal cavities (PhCCs) can confine optical fields in ultra-small volumes, enabling efficient light-matter interactions for quantum and non-linear optics, sensing and all-optical signal processing. The inherent nanometric tolerances of micro-fabrication platforms can induce cavity resonant wavelength shifts two-orders of magnitude larger than cavity linewidths, prohibiting fabrication of arrays of nominally identical devices. We address this device variability by fabricating PhCCs as releasable pixels that can be transferred from their native substrate to a receiver where ordered micro-assembly can overcome the inherent fabrication variance. We demonstrate the measurement, binning and transfer of 119 PhCCs in a single session, producing spatially ordered arrays of PhCCs, sorted by resonant wavelength. Furthermore, the rapid in-situ measurement of the devices enables measurements of the PhCCs dynamic response to the print process for the first time, showing plastic and elastic effects in the seconds to hours range.

Recent years have seen a surge in the demand for application-specific neuromorphic hardware, alongside a growing applications space. In the context of optical neural networks, integrated Photonic Extreme Learning Machines (PELMs) offer key advantages for hardware implementation, while meeting requirements for scalability, energy-efficiency and operation bandwidth. PELMs are photonic neural networks with feed-forward connectivity whose operation exploits the intrinsically complex input-to-output information transformation of the network, with training only applied via the readout layer [1]. Chaotic microcavities, i.e. dielectric microcavities with geometries that sustain aperiodic ray trajectories, have been proposed for use as compact physical reservoirs [2], [3]. Previous studies have focussed on numerical modelling of the microcavities, where the wave propagation dynamics can be time-resolved and play the role of a short-term memory. In experimental implementations, the ultrashort time scales involved in the optical path propagation are unpractical to detect and a more efficient mode of operation of such microcavities is as PELMs in classification tasks. Here, we demonstrate fabrication of silicon nitride (SbN4) based chaotic resonators and show application of these as the hidden layer of a PELM for image classification.

The increase in demand for scalable and energy efficient artificial neural networks has put the focus on novel hardware solutions. Integrated photonics offers a compact, parallel and ultra-fast information processing platform, specially suited for extreme learning machine (ELM) architectures. Here we experimentally demonstrate a chip-scale photonic ELM based on wave chaos interference in a stadium microcavity. By encoding the input information in the wavelength of an external single-frequency tunable laser source, we leverage the high sensitivity to wavelength of injection in such photonic resonators. We fabricate the microcavity with direct laser writing of SU-8 polymer on glass. A scattering wall surrounding the stadium operates as readout layer, collecting the light associated with the cavity's leaky modes. We report uncorrelated and aperiodic behavior in the speckles of the scattering barrier from a high resolution scan of the input wavelength. Finally, we characterize the system's performance at classification in four qualitatively different benchmark tasks. As we can control the number of output nodes of our ELM by measuring different parts of the scattering barrier, we demonstrate the capability to optimize our photonic ELM's readout size to the performance required for each task.

Spectral complexity is a useful resource in physical device identification, disorder-enhanced spectroscopy, and machine learning, but is often achieved in chip-scale devices at the expense of propagation loss, scalability, or reconfigurability. In this work, we demonstrate that device specific spectral complexity can be achieved using completely standardized photonic building blocks. Using a waveguide Mach-Zehnder interferometer internally loaded with two sets of non-concentric dual ring resonators, we demonstrate the generation of unclonable keys for one-time pad encryption which can be reconfigured on the fly by applying small voltages to on-chip thermo-optic elements. With this method, we access a keyspace larger than 12 Tb for a single device with simple, single-mode waveguide input and output coupling. Using two devices at either end of a communication channel, we show that an eavesdropper tapping the channel fibre link would be unable to recover the same spectrum measured at either end of the link, providing physical encryption for key distribution. Furthermore, being purely classical, this form of secure communications does not require quantum photonic sources or detectors, and can therefore be easily integrated into pre-existing telecommunication architectures.

Planar 45o turning mirrors with metal coating embedded in SU8 polymer waveguides enable waveguide to vertical mode coupling across a broad range of wavelengths from the visible to IR. The fabrication of these 2.5D structures is achieved using relatively simple grayscale lithography in thin film resists, compatible with standard planar lithography methods. Mirror losses of <1 dB are measured from 516 -1630 nm, and direct coupling to single mode fibre is achieved.

Transfer printing integration of planar membrane devices on photonic and electronic circuits is becoming a well established technology. Typical systems incorporate a single planar layer printed into full contact with the host substrate. In this work we present an advanced transfer print system that enables printing of optical devices in non-planar geometries and allows in-situ optical monitoring of devices. We show micro-resonators with air-clad whispering gallery modes coupled to on-chip waveguides, inverted device printing and three dimensionally assembled micro-cavities incorporating semiconductor micro-lenses and nanowire lasers. We demonstrate printing onto non-standard substrates including optical chip facets and single-mode fibre ends. The optical fibre printing was carried out with alignment assistance from in-situ optical coupling through the transfer printing system in real-time allowing active alignment of the system.

Silicon nitride (Si3N4) is an excellent material platform for visible wavelength photonic integrated circuits, in particular, as a host for the heterogeneous/hybrid integration of complementary materials. In this work, we characterise the performance of the Si3N4 from LIGENTEC as a base for hybrid integration.

We present a high performance silicon nitride photonic integrated circuit platform operating at visible wavelengths, accessible through the commercial foundry, LIGENTEC. Propagation losses were measured across the visible spectrum from 450 nm to 850 nm. For wavelengths above 630 nm, losses were <1 dB/cm in TE and <0.5 dB/cm in TM. Additionally, sets of single mode waveguide-coupled ring resonators across three separate chips were tested and analysed. A peak intrinsic Q factor of 3.69 × 106 was measured for a single resonance at ∼635.3 nm, with an average value of 2.28 × 106 recorded over 10 peaks in a 3 nm tuning range. Analyses of the loss and coupling, as functions of bus-ring coupling gap and waveguide width, are also presented. High confinement, low loss devices realised on the chip-scale in a wide-bandgap material like silicon nitride are increasingly important for the next generation of integrated optical devices operating at visible wavelengths.

The Pulsar Science Collaboratory (PSC) is a research project engaging high school students, teachers, and undergraduates in searching for pulsars in data collected using radio telescopes. The goals are to stimulate student interest in science, technology, engineering, and mathematics careers; prepare teachers to implement authentic research with students by training them within a professional scientific community; promote student use of information technologies; and assist the research community through pulsar discoveries. The learning is facilitated through online training, in-person workshops and camps, discussion forums, participation in capstone events, conferences, and so on. The PSC is powered by HUBzero, a platform for building science gateways, and combines analytical tools, community management, course components, and collaborations in one ecosystem. The participants gain access to radio astronomy data after successful completion of training workshops and passing a certification test. PSC students make authentic research contributions to the scientific community, pulsar astrophysics, and radio astronomy.

Keggin-type aluminum polycations are an important class of compounds from metal-oxo family that includes polyoxometalates and other nanocomplexes. Investigation of the Al3+ based polycation system is of particular importance given the environmental relevance within acid mine drainage and application in wastewater treatment. Within streams impacted with acid mine drainage, different toxic metal species, including chromium, can incorporate into these soluble polycations and impact the transport of contaminants. Currently, there is a limited understanding about chemical interaction of chromium with Keggin-type aluminum polycations; therefore, the work herein describes the synthesis and characterization Cr3+ substitution within Keggin-based polyaluminum species. The polyaluminum cations crystallized as [Al25.7Cr6.3O8(OH)60(H2O)28(SO4)2](SO4)8 (H2O)29 from a partially hydrolyzed Al3+ solution and structural elucidation obtained by single crystal X-ray diffraction revealed the presence of Cr3+ within the octahedral sites of the Keggin species. Inductively coupled plasma mass spectroscopy confirmed the presence of Cr3+ in the structure with Al3+/Cr3+ similar to refined crystal structure. Additional physicochemical characterization, including vibrational spectroscopy, thermogravimetry and powder X-ray diffraction were performed on the isolated crystals and confirm the structural model of the solid phase.

Coagulation processes within water treatment plays an important role in contaminant removal and aluminum-oxo Keggin polycations are proved to be an effective coagulating agents. Previous work demonstrated that heteroatom substitution within the Keggin-type polycation ε-Al13 to form ε-GaAl12 and ε-GeAl12 can enhance removal of bacteria, DOC, and turbidity from wastewater. Additional hydrolysis of the ε-Al13 species to form larger Al30 species has also been shown to improve coagulation, but this aspect has not been evaluated for the ε-GaAl12 and ε-GeAl12 systems. In the current study, hydrolysis of ε-Al13, ε-GaAl12 and ε-GeAl12 was promoted through hydrothermal aging to evaluate the overall solution stability/behavior and water treatment efficiency. Turbidity measurement of aged solution indicated that Ga substituted aluminum-oxo Keggin polycations remain stable in solution and DLS studies demonstrated greater diversity in particle sizes within the system. Additional thermogravimetric analyses of metal hydroxide precipitates formed from the aging studies indicate that the GaAl12 system behaves more like an amorphous Al(OH)3 phase, which has higher solubility than other aluminum hydroxide phases. Hydrothermal aging did not significantly change %DOC removal as all solution showed high efficiency for removal across a range of pH values. GaAl12 solutions demonstrated good turbidity removal efficiency in all pH range, with enhanced performance at pH 5. The study suggests that larger, relatively stable oligomers do exist within the aged GaAl12 solutions that may contribute to enhanced contaminant removal in a similar manner to what is observed within the PACl-Al30 coagulant.

The heterogeneous integration of lithium niobate photonic waveguide devices onto a silicon nitride waveguide platform via a transfer-printing approach has been demonstrated for the first time. A fabrication process was developed to make free-standing lithium niobate membrane devices compatible with back-end integration onto photonic integrated circuits. Micro-ring resonators in membrane format were lithographically defined by using laser direct writing and plasma dry etching. The lithium niobate micro-ring resonators were then transferred from their host substrate and released onto a silicon nitride waveguide chip. An all-pass ring resonator transmission spectrum was obtained in the 1.5 μm to 1.6 μm wavelength range, with a measured loaded Q-factor larger than 32000.

There has been an increasing interest in and growing need for high performance computing (HPC), popularly known as supercomputing, in domains such as textual analytics, business domains analytics, forecasting and natural language processing (NLP), in addition to the relatively mature supercomputing domains of quantum physics and biology. HPC has been widely used in computer science (CS) and other traditionally computation intensive disciplines, but has remained largely siloed away from the vast array of social, behavioral, business and economics disciplines. However, with ubiquitous big data, there is a compelling need to make HPC technologically and economically accessible, easy to use, and operationally democratized. Therefore, this research focuses on making two key contributions, the first is the articulation of strategies based on availability, accessibility and usability for the demystification and democratization of HPC, based on an analytical review of Caliburn, a notable supercomputer at its inception. The second contribution is a set of principles for HPC adoption based on an experiential narrative of HPC usage for textual analytics and NLP of social media data from a first-time user perspective. Both, the HPC usage process and the output of the early stage analytics are summarized. This research study synthesizes expert input on HPC democratization strategies, and chronicles the challenges and opportunities from a multidisciplinary perspective, of a case of rapid adoption of supercomputing for textual analytics and NLP. Deductive logic is used to identify strategies which can lead to efficacious engagement, adoption, production and sustained usage for research, teaching, application and innovation by researchers, faculty, professionals and students across a broad range of disciplines.

Keggin‐type polyaluminum cations belong to a unique class of compounds with their large positive charge, hydroxo bridges, and divergent isomerization/oligomerization. Previous reports indicated that oligomerization of this species can only occur through one isomer (δ), but herein we report the isolation of largest Keggin‐type cluster that occurs through self‐condensation of four ϵ‐isomers ϵ‐GeAl 12 8+ to form [Ge 4 O 16 Al 48 (OH) 108 (H 2 O) 24 ] 20+ cluster ( Ge 4 Al 48 ). The cluster was crystallized and structurally characterized by single‐crystal X‐ray diffraction (SCXRD) and the elemental composition was confirmed by ICP‐MS and SEM‐EDS. Additional dynamic light scattering experiments confirms the presence of the Ge 4 Al 48 in thermally aged solutions. DFT calculations reveal that a single atom Ge substitution in tetrahedral site of ϵ‐isomer is the key for the formation of Ge 4 Al 48 because it activates deprotonation at key surface sites that control the self‐condensation process.

The Tapis framework, an NSF-funded project, is an open-source, scalable API platform that enables researchers to perform distributed computational experiments securely and achieve faster scientific results with increased reproducibility. Tapis Streams API focuses on supporting scientific use cases that require working with real-time sensor data. The Streams Service, built on the top of the CHORDS time-series data service, allows storing, processing, annotating, querying, and archiving time-series data. This paper focuses on the new Tapis Streams API functionality that enables researchers to design and execute real-time data-driven event workflow for their research. We describe the architecture and design choices towards achieving this new capability with Streams API. Specifically, we demonstrate the integration of Streams API with Kapacitor, a native data processing engine for time-series database InfluxDB, and Abaco, an NSF Funded project, web service, and distributed computing platform providing function-as-a-Service (FaaS). The Streams API, which includes a wrapper interface for the Kapacitor alerting system, can define and enable alerts. Finally, simulation results from the water-quality use case depict that Streams API’s new capabilities can support real-time streaming data event-driven workflows.

Hybrid integration of photonic membrane and nanowire devices from multiple material platforms is demonstrated using high-accuracy transfer printing. The deterministic assembly technique enables serially printed devices with separations as low as 100 nm.

The future for science gateways warrants exploration as we consider the possibilities that extend well beyond ’science’ and high-performance computing into new interfaces, applications and user communities. In this paper, we look retrospectively at the successes of representative gateways thus far. This serves to highlight existing gaps gateways need to overcome in areas such as accessibility, usability and interoperability, and in the need for broader outreach by drawing insights from technology adoption research. We explore two particularly promising opportunities for gateways - computational social sciences and virtual reality – and make the case for the gateway community to be more intentional in engaging with users to encourage adoption and implementation, especially in the area of educational usage. We conclude with a call for focused attention on legal hurdles in order to realize the full future potential of science gateways. This paper serves as a roadmap for a vision of science gateways in the next ten years.

Keggin-type polyaluminum cations belong to a unique class of polyoxometalates (POMs) with their large positive charge, hydroxo bridges, and divergent isomerization/oligomerization. Previously reported oligomerizations of the polyaluminum cations were driven solely by the δ-Keggin isomer, which created Al26, Al30, and Al32 dimeric species. We herein report the isolation of largest ever Keggin-type structure for this system through a unique mode of self-condensation among four ε-GeAl128+ to form [NaGe4O16Al48(OH)108(H2O)24]21+(Ge4Al48). Elemental analysis confirms the Ge4+ substitution, and dynamic light scattering experiments indicated that these larger species exist in the thermally aged solutions. DFT calculations have revealed that a single atom Ge substitution in tetrahedral site of ε-Al137+ is the key for the formation this cluster because it activates the deprotonation at certain octahedral sites to assist self-condensation in a specific mode.