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DOE OSTI2026

Generalized Theory and Realization of Reconfigurable Bandpass Filtering Equalizers

Here, in this article, a generalized theory of bandpass filtering equalizers is proposed. A filtering equalizer is a device that combines the frequency-selective properties of a filter with the controllable slope of an equalizer into a single component. The equations used to design the function for a desired slope are provided, and the design methodology to determine the necessary filtering polynomials is also shown. The controllable slope of the dual-function component is realized using variable capacitors, which are used to tune both a transmission zero and a matching network to achieve the desired slope. A third-order bandpass filtering equalizer is designed, fabricated, and measured to verify the generalized theory. The component is designed to operate at 1 GHz with a slope that can be reconfigured from 1 to 3 dB along the passband. This proposed filtering equalizer demonstrates the feasibility of a tunable, low-cost, size, weight, and power (C-SWaP) solution to enable increased flatness in the overall system response and thereby decrease the error vector magnitude (EVM) of future radio frequency (RF) systems and a design process that allows for future development of filtering equalizers.

Filter↗

DOE OSTI2021

Ferromagnetic resonances in single-crystal yttrium iron garnet nanofilms fabricated by metal-organic decomposition

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

Wang, Szu-Fan (Paul)↗

DOE OSTI2021

Recent developments on 2D magnetic materials: challenges and opportunities

The emergence of two-dimensional (2D) magnetic materials exhibiting strong magnetization at ultrathin limits above room temperature are promising for miniaturization of devices beyond Moore’s law for future energy efficient nano-electronic devices. Here, the current status, different mechanisms for the existence of magnetism, spin current injection and other magnetic properties of monolayer to few-layers of various 2D magnetic materials are reviewed. Some of the promising applications of these materials are spintronics devices such as spin valves, spin tunnel field-effect transistors, and spin filtering magnetic tunnel junctions. Due to the tunable electronic properties of these 2D materials, it's quite interesting to inject the spin current with suitable ferromagnetic contacts. For instance,black phosphorus is a layered material with a small Schottky barrier height capable of injecting spin current. This review includes many recently explored 2D magnetic materials ranging from exfoliated 2D crystals to CVD grown materials from single to several layers, demonstrating tunable layer dependent magnetic properties. We also explore some of the promising theoretical study based on 2D magnetic compounds such as 2D alkali-based chromium chalcogenides, which shows ferromagnetic as well as semiconducting behavior. The layer-dependent magnetic ordering has been observed in layered compounds like 1T-CrTe 2 , VSe 2 , CrI 3 , and Fe 3 GeTe 2 , which have great potential for the future applications in magnetic based electronic devices. Finally, we emphasize the challenges, opportunities and future directions of the 2D magnetic materials, where new discoveries might have outstanding impact in transformational scientific breakthroughs towards memory, spintronics, optoelectronics and other multifunctional device applications.

36 MATERIALS SCIENCE↗

DOE OSTI2022

Additively manufactured multiplexed inertial coalescence filters

Multiphase flows often pose a significant challenge to the efficient and reliable design of thermofluidic systems. This paper describes multiplexed inertial coalescence filters composed of parallel helical pathways, designed to capture fine droplets (<40 µm) through inertial separation while maintaining a low pressure drop (<400 Pa). Filtration efficiencies for 7 µm and 30 µm droplets were characterized for varying flow conditions, with complete capture observed above a threshold flow rate. Models for filtration efficiency and pressure drop were developed and validated against experimental results to allow system design and optimization, enabled by the tunable additive manufacturing approach used to fabricate the filters. Filter quality factor was computed for varying droplet sizes, showcasing exceptional quality factor when compared to state-of-the-art filters documented in the literature. In conclusion, this multiplexed inertial coalescence filtration approach could find use in dehumidification systems, fog harvesting, chemical reactors, and microgravity droplet capture.

3D Printing↗

DOE OSTI2023

High-bandwidth density silicon photonic resonators for energy-efficient optical interconnects

The growth of artificial intelligence applications demands ever larger and more complex deep learning models, dominating today's—and tomorrow's—data center and high-performance computing systems. While traditional electronics are failing to keep pace with application demands, silicon photonic (SiPh) interconnects have emerged as a necessary technology to support these systems. SiPh-driven wavelength-division multiplexing (WDM) offers a particularly promising path toward supporting incredibly high-aggregate link bandwidth in a compact and efficient form factor. One of the basic building blocks of these integrated WDM interconnects is the SiPh resonator. Their inherent wavelength selectivity and compact footprint allow for efficient data transmission multiplexed across dozens of carrier wavelengths. Used as add-drop (AD) filters, SiPh resonators are critical to constructing integrated tunable wavelength-selective optical circuit switches as well as for demultiplexing the different carrier wavelengths toward independent wavelength-insensitive photodiodes in a dense wavelength-division multiplexing receiver. Resonators in the all-pass (AP) configuration are widespread as well, allowing for wavelength-selective modulation to drive aggregate link bandwidths far beyond the individual channel data rate. Unlike SiPh Mach–Zehnder modulators (MZM), resonant modulators can be driven using low, complementary metal-oxide-semiconductor drive voltages, allowing for tight co-integration between photonic integrated circuits, fabricated with larger process node technologies, and electronic integrated circuits, designed to exploit the advantages of the latest node. To push toward practical peta-scale interconnects, a comprehensive review of SiPh resonators is required, addressing bottlenecks and design constraints at both the architecture and device levels. We first describe the predominant integrated link architectures and identify their limits. We then discuss the device-level design considerations that can be made for both AD and AP configuration resonators to overcome the system level limits with novel resonator device designs. Analytical models and numerical simulation of resonators are validated by experimental measurement of devices fabricated in a commercial 300-mm foundry, showing a clear path toward volume manufacturing. The demonstrated resonant modulators and filters support the feasibility of increasing the aggregate bandwidth of resonator-driven SiPh interconnects into the peta-scale regime.

42 ENGINEERING↗

DOE OSTI2022

Narrowband microwave-photonic notch filters using Brillouin-based signal transduction in silicon

Abstract The growing demand for bandwidth makes photonic systems a leading candidate for future telecommunication and radar technologies. Integrated photonic systems offer ultra-wideband performance within a small footprint, which can naturally interface with fiber-optic networks for signal transmission. However, it remains challenging to realize narrowband (∼MHz) filters needed for high-performance communications systems using integrated photonics. In this paper, we demonstrate all-silicon microwave-photonic notch filters with 50× higher spectral resolution than previously realized in silicon photonics. This enhanced performance is achieved by utilizing optomechanical interactions to access long-lived phonons, greatly extending available coherence times in silicon. We use a multi-port Brillouin-based optomechanical system to demonstrate ultra-narrowband (2.7 MHz) notch filters with high rejection (57 dB) and frequency tunability over a wide spectral band (6 GHz) within a microwave-photonic link. We accomplish this with an all-silicon waveguide system, using CMOS-compatible fabrication techniques.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗

DOE OSTI2023

Spectral emission properties of a nitrogen-doped diamond (001) photocathode: Hot electron transport and transverse momentum filtering

The electron emission properties of a single-crystal nitrogen-doped diamond(001) photocathode inserted in a 10 kV DC photoelectron gun are determined using a tunable (235–410 nm) ultraviolet laser radiation source for photoemission from both the back nitrogen-doped substrate face and the front homoepitaxially grown and undoped diamond crystal face. Here, the measured spectral trends of the mean transverse energy and quantum efficiency of the emitted electrons are both anomalous and nonmonotonic, but are shown to be consistent with (i) the known physics of electron photoexcitation from the nitrogen substitution states into the conduction bands of diamond, (ii) the energy position and dispersion characteristics of the conduction bands of diamond in the (001) emission direction, (iii) the effective electron affinity of the crystal faces, (iv) the strong electron-(optical)phonon coupling in diamond, and (v) the associated hot electron transport dynamics under energy equipartition with the optical phonons. Notably, the observed hot electron emission is shown to be restricted parallel to the photocathode surface by the low transverse effective masses of the emitting band states—a transverse momentum filtering effect.

36 MATERIALS SCIENCE↗

DOE OSTI2023

Generalized Theory and Realization of Continuously Loss-Programmable Bandpass Filtering Attenuators

With the increased demand for modern wireless systems in various applications, the need for adjustable radio frequency (RF) systems has dramatically increased. These modern systems rely on operating in the microwave frequency spectrum (1 GHz to 1 THz) without interference from other devices while also retaining the ability to detect very low and very high power signals simultaneously. There is also an ever-increasing demand for reducing the cost, size, weight, and power (C-SWaP) of these modern RF systems, driving the demand for more agile filters in the microwave frequency spectrum. In this paper, a generalized theory of bandpass filtering attenuators (filtenuators) is proposed. A filtenuator is a device that combines the frequency- selective characteristics of a filter and the loss-programmable characteristics of an attenuator into a single component. The loss- programmable aspect of the filtenuator is based on the tuning of a π-network of resistances, which are implemented using PIN diodes to control the individual resistance values electronically. A loss-programmable, third-order Chebyshev bandpass filtenuator is designed, fabricated, and measured to verify the generalized theory. The filtenuator is designed to operate at 1 GHz and have a tunable attenuation range of 2-10 dB. This proposed filtenuator demonstrates the feasibility of a tunable, low C-SWaP solution to increase RF system dynamic range and a design process that allows for future development of filtenuators.

42 ENGINEERING↗

DOE OSTI2022

Feasibility of critical infrastructure protection using network functions for programmable and decoupled ICS policy enforcement over WAN

Industrial control systems (ICS) represent a major component of our critical infrastructure. With the increasing need for more control and monitoring of such systems, ICS have seen an increase in connectivity to wide area networks (WAN) exposing aging equipment to rapidly evolving cybersecurity threats. Furthermore, the ICS data requires a reliability measure from the networks for critical functions for infrastructure monitoring and control. Especially when remote plant sites are involved such as pipelines, energy distribution networks, and transportation, WAN transport impairments most often provide a best effort delivery with no strict reliability guarantees. Network functions can provide a vendor agnostic, programmable critical infrastructure protection with a single maintenance, policy determination, and reliability assurance surface. A network function (NF) can be utilized for policy enforcement over the communication between remote entities and the main control office. This paper presents the research on transparent integration with existing ICS without disrupting communications, resulting in minimal downtime while decoupling the fast paced evolution of defensive security measures from the upgrade cycle of expensive long term hardware. We report our measurements on the resource requirements and overhead in the network for successful NF insertion under a wide variety of network impairments (network packet delay, reordering, and loss). Our paired NF implementation provides a policy enforcement platform extensible to cover myriad cybersecurity-related communication goals, including packet signing for verification, encryption for data privacy, packet filtering and data diode operation (i.e. protecting against eavesdropping, packet injection, and denial-of-service). Furthermore, bundling communication specifications into packet flows allows for tunability in applying policies as coarse- or fine-grained as the needs of the operator. We report on network function resource requirements in the form of required queue depth and network utilization overhead to inform the decision making against hardware cost constraints.

42 ENGINEERING↗

DOE OSTI2024

Birefringent Color Filter by Layered Metal‐Organic Chalcogenides: In‐Plane Anisotropy and Odd/Even Effect

Anisotropic 2D materials are gaining interest recently as building blocks for angular‐dependent optical/electrical devices. However, the fundamental understanding of their structure‐property‐relationship is limited, which hinders further modulation of their unique characteristics via structure tailoring. Here the in‐plane structural anisotropy and the tunable optical/electrical properties of a series of radiation‐sensitive (X‐ray, e‐beam) metal‐organic chalcogenide (MOC) single crystals are comprehensively revealed with ligands of variable length/parity. Their monoclinic crystallography is determined at atomic resolution by a simple method that couples X‐ray/electron diffraction with first‐principles calculations. The in‐plane inorganic backbone of the MOCs exhibits a strong lattice anisotropy with odd/even alternations, which originates from that of the out‐of‐plane organic motifs via organic/inorganic accommodation. Such structural anisotropy is implied mechanically by the preferred orientation of crystal cleavage. It triggers a maximum ≈8 × distinction of in‐plane electrical conductivity of the semiconducting MOCs, plus a distinct birefringence (maximum Δn ≈ 0.03) with a dispersive orientation of dielectric axes, which rotate up to 25.7° from UV to visible‐light regime, inspiring an emerging pathway for color filtering via single crystal rotation. Such in‐plane optical characteristics also exhibit odd/even alternation and can be flexibly tuned by the designable out‐of‐plane ligands.

birefringence↗

DOE OSTI2023

A versatile high-average-power ultrafast infrared driver tailored for high-harmonic generation and vibrational spectroscopy

We report on an ultrafast infrared optical parametric chirped-pulse amplifier (OPCPA), pumped by a 200-W thin-disk Yb-based regenerative amplifier at a repetition rate of 100 kHz. The OPCPA is tunable in the spectral range 1.4–3.9 μm, generating up to 23 W of < 100-fs signal and 13 W of < 200-fs idler pulses for infrared spectroscopy, with additional spectral filtering capabilities for Raman spectroscopy. The OPCPA can also yield 19 W of 49-fs 1.75- μm signal or 5 W of 62-fs 2.8- μm idler pulses with active carrier-to-envelope-phase (CEP) stabilisation for high-harmonic generation (HHG). We illustrate the versatility of the laser design, catering to various experimental requirements for probing ultrafast science.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗

DOE OSTI2020

High permeability sub-nanometre sieve composite MoS 2 membranes

Two-dimensional membranes have gained enormous interest due to their potential to deliver precision filtration of species with performance that can challenge current desalination membrane platforms. Molybdenum disulfide (MoS 2 ) laminar membranes have recently demonstrated superior stability in aqueous environment to their extensively-studied analogs graphene-based membranes; however, challenges such as low ion rejection for high salinity water, low water flux, and low stability over time delay their potential adoption as a viable technology. Here, we report composite laminate multilayer MoS 2 membranes with stacked heterodimensional one- to two-layer-thick porous nanosheets and nanodisks. These membranes have a multimodal porous network structure with tunable surface charge, pore size, and interlayer spacing. In forward osmosis, our membranes reject more than 99% of salts at high salinities and, in reverse osmosis, small-molecule organic dyes and salts are efficiently filtered. Finally, our membranes stably operate for over a month, implying their potential for use in commercial water purification applications.

36 MATERIALS SCIENCE↗

DOE OSTI2020

Experimental parameters, combined dynamics, and nonlinearity of a magnonic-opto-electronic oscillator (MOEO)

We report the construction and characterization of a comprehensive magnonic-opto-electronic oscillator (MOEO) system based on 1550-nm photonics and yttrium iron garnet (YIG) magnonics. The system exhibits a rich and synergistic parameter space because of the ability to control individual photonic, electronic, and magnonic components. Taking advantage of the spin wave dispersion of YIG, the frequency self-generation as well as the related nonlinear processes becomes sensitive to the external magnetic field. Besides being known as a band-pass filter and a delay element, the YIG delay line possesses spin wave modes that can be controlled to mix with the optoelectronic modes to generate higher-order harmonic beating modes. With the high sensitivity and external tunability, the MOEO system may find usefulness in sensing applications in magnetism and spintronics beyond optoelectronics and photonics.

47 OTHER INSTRUMENTATION↗

DOE OSTI2020

III/V silicon hybrid laser based on a resonant Bragg structure

We demonstrate a laser tunable in intensity with gigahertz tuning speed based on a III/V reflective semiconductor optical amplifier (RSOA) coupled to a silicon photonic chip. The silicon chip contains a Bragg-based Fabry–Perot resonator to form a passive bandpass filter within its stopband to enable single-mode operation of the laser. We observe a side mode suppression ratio of 43 dB, linewidth of 790 kHz, and an optical output power of 1.65 mW around 1530 nm. We also investigate using a micro-ball lens as an alternative coupling method between the RSOA and the silicon chip.

Davis, Jordan A. (ORCID:0000000343483295)↗

DOE OSTI2022

Portable diagnostic package for Thomson scattering and optical emission spectroscopy on Princeton field-reversed configuration 2 (PFRC 2)

An Advanced Research Projects Agency-Energy funded diagnostic system has been deployed to the Princeton field-reversed configuration 2 (PFRC-2) device, located at Princeton Plasma Physics Laboratory. The Portable Diagnostic Package (PDP), designed at Oak Ridge National Laboratory, allows for the measurement of Thomson Scattering (TS) for electron density and temperature and Optical Emission Spectroscopy (OES) for ion temperature, impurity density, and ion velocity. A tunable spectrometer on the PDP with three gratings provides the flexibility to measure low (1 eV) and high (1000 eV) electron temperature ranges from TS. Additionally, using a second spectrometer, the OES diagnostic can survey light emission from various ion excitation levels for wide wavelength ranges. The electron density (<2 × 10 19 m –3 ) of plasmas generated in PFRC-2 has been below the PDP TS discrimination threshold, which has made TS signal detection challenging against a high-background of laser stray light. The laser stray light was iteratively reduced by making modifications to the entrance and exit geometry on PFRC-2. Rayleigh scattering experiments on PFRC have yielded the TS discrimination sensitivity to be >1 × 10 20 m –3 for the PDP. A recently implemented narrow-band notch spectral filter that masks the second harmonic 532 nm Nd:YAG laser wavelength has increased the system’s TS light discrimination sensitivity 65 times compared to the instance when the notch filter was not implemented. The hardware implementation including design changes to the flight tubes and Brewster windows will be discussed, along with results from Rayleigh and rotational Raman scattering sensitivity analyses, which were used to establish a quantitative figure of merit on the system performance. Further, the Raman scattering calibration with the notch filter has improved the PDP electron density threshold to 1 ± 0.5 × 10 18 m –3 .

47 OTHER INSTRUMENTATION↗

DOE OSTI2020

Widely tunable, heterogeneously integrated quantum-dot O-band lasers on silicon

Heterogeneously integrated lasers in the O-band are a key component in realizing low-power optical interconnects for data centers and high-performance computing. Quantum-dot-based materials have been particularly appealing for light generation due to their ultralow lasing thresholds, small linewidth enhancement factor, and low sensitivity to reflections. Here, we present widely tunable quantum-dot lasers heterogeneously integrated on silicon-on-insulator substrate. The tuning mechanism is based on Vernier dual-ring geometry, and a 47 nm tuning range with 52 dB side-mode suppression ratio is observed. These parameters show an increase to 52 nm and 58 dB, respectively, when an additional wavelength filter in the form of a Mach–Zehnder interferometer is added to the cavity. The Lorentzian linewidth of the lasers is measured as low as 5.3 kHz.

Malik, Aditya (ORCID:0000000334487577)↗

DOE OSTI2021

Bound States in the Continuum on a Silicon Chip with Dynamic Tuning

Expanding bound states in the continuum (BIC) beyond photonic crystal systems may enable broader applications benefiting from the unique properties of BIC states. We use photonic integrated circuit to realize a Fabry-Pérot BIC on a silicon chip. The devices consist of cascaded ring resonators with tunable resonance frequencies and phase delays. As a result, the BIC state is dynamically tuned with electrical I/O. We analyze the mechanism of the formation of BIC states in this waveguide system and point out the fundamental differences between the BIC states and electromagnetically induced transparency states in integrated photonics. The high transmission protected by the BIC state enables versatile optical filters, which are capable of independent control over switching, peak position, and quality factor. We also demonstrate the scalability of this platform. As a result, this integrated silicon photonic platform brings opportunities for practical BIC applications.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗

DOE OSTI2024

In situ oxidation of reduced graphene oxide membranes by peracetic acid for dye desalination

Graphene oxide (GO) membranes with tunable interlayer spacings are of interest for dye removal from salty textile wastewater, and the membranes are often reduced to improve their stability, which inevitably lowers water permeance. Herein, we demonstrate that reduced GO (rGO) membranes can be facilely modified using peracetic acid (PAA) in situ to dramatically enhance water permeance while retaining dye rejection. Specifically, PAA-modified membranes (PrGO) are synthesized by vacuum-filtering hydrazine-reduced rGO nanosheets onto Nylon substrate and then exposing them to PAA solutions. The effects of the rGO layer thickness, PAA content, and PAA exposure time on the membrane chemistry, nanostructures, and salt/dye separation properties are thoroughly examined. For example, the PAA oxidation of a 100 nm-thick rGO membrane for 10 min increases water permeance by 180 %, from 35 to 93 Liter m −2 h −1 bar −1 , and decreases Na 2 SO 4 rejection from 10 % to 3.3 % while retaining the rejection of Congo red at ≈99.7 %. The PrGO membranes exhibit stable water permeance and >99 % dye rejection in multi-cycle tests in a crossflow system, surpassing state-of-the-art GO membranes and showcasing their potential for practical applications.

Dye desalination↗