This PDF file contains the front matter associated with SPIE Proceedings Volume 12477 including the Title Page, Copyright information, Table of Contents, and Workshop Committee list.

Over the past decade, the benefits of photonics over electronics such as ability to achieve high bandwidth, high interconnectivity, and low latency, together with the high maturity of silicon photonics foundries has spurred robust applications in optical transceivers and in classical and quantum computing. In both application areas, silicon microring resonators (MRRs) using carrier depletion effects in p-n junctions represent the most compact optical switches manufacturable at high volume with 5.2fJ/bit power consumption. Matrix computation approaches as well wavelength-division-multiplexed modulators require several MRRs in series coupled to the silicon waveguide optical bus. Such architectures are potentially limited to ~30 by the limited free-spectral range (FSR) of an individual MRR. However, with ever increasing data volumes, there is a need to process larger matrices and/or modulate more wavelengths in the telecom bands along a single silicon bus channel. Photonic crystal (PC) dielectric structures confine an optical mode to sub-micron mode volumes and have shown the potential to reach 0.1fJ switching energies. Research till date on PC devices have centered on either inline one-dimensional PC nanobeam structures or on two-dimensional PC waveguide coupled microcavity configurations. In this paper, through detailed electrical and optical simulations, we demonstrate the feasibility to achieve compact switches with 1dB insertion loss, 5dB extinction and ~260aJ/bit switching energies in the bus-coupled 1D photonic crystal nanobeam platform. Resonance linewidths <0.1nm and FSR <100nm enable energy efficient computing of larger matrices with ~200 resonators in series separated by ~0.5nm wavelength over the entire C+L bands. Device architectures will be presented.

How are the field profiles of exceptional plane waves, exceptional surface waves, and exceptional compound waves related to those of their unexceptional counterparts? This matter has been investigated in extensive numerical studies which have revealed that the transition from unexceptional to exceptional waves involves only smooth variations in the electric and magnetic field phasors, and in the time-averaged Poynting vector. Therefore, in terms of field profiles, exceptional plane waves, exceptional surface waves, and exceptional compound waves are practically indistinguishable from their unexceptional counterparts that propagate in directions in the immediate neighborhood of the exceptional waves.

Significant developments in material science and nanotechnology have empowered the creation and control of quantum entities in solid-state platforms. This talk focuses on the latest progress in controlling the quantum states of light-matter interactions in two-dimensional widebandgap materials, including hexagonal boron nitride and lead halide perovskite, and their potential applications in integrated quantum photonics.

By changing the doping type, the size of the in-built electric field and the band bending of GaAs photocathode material under different varying doping concentration are simulated to discuss the influence of varying doping concentration on the quantum efficiency of cathode.

Complex-valued refractive indices generally impart unequal optical phase shifts to s and p light polarization components. In a phase-change materials, such as vanadium dioxide (VO2), this effect can be exploited for optical modulation applications in thin films. Adding to this relative phase shift, VO2 exhibits large refractive index changes during the phase transition, which is useful to modulate polarization. In this paper, we review our recent progress on polarization modulation of visible and infrared light interacting with VO2 films. Aspects to be discussed include the best conditions for phase and amplitude modulation, and enhancement by metallic underlayers. Thermal hysteresis of the refractive index and its effect on polarization states during the phase transition will be also discussed.

: We present a unique route to realize a novel class of intrinsically chiral nano-helices that achieves the critical goal of demonstrating high-speed control of opto-chirality over 50,000 cycles via the optically active and tunable Ge₂Sb₂Te₅ nanopatterned medium.

Vanadium dioxide (VO₂) is a very well-known thermochromic material exhibiting a very effective first order semiconductor to metal (SMT) transition at a temperature of around 68°C. In this work we have investigated the thermochromic properties of VO₂ thin films as a function of film thickness. The VO₂ films were deposited by a two-step method on glass substrates. The changes occurring around the SMT have been systematically characterized by structural, optical, electrical, magnetic studies and their hysteresis cycles. The correlation between film thickness and transition temperature has been established for the VO₂ films from the resistance variation during the heating and cooling cycles. The Hall voltage variation as a function of magnetic field has been measured for each of the VO₂ film thicknesses. These Hall voltage measurements have enabled us to calculate the free electron density above and below the transition temperature for each of the VO₂ samples. The free electron density changes conform to the semiconductor to metal transition observed and to the values mentioned in the literature.

The transport properties of W-doped thermochromic V_1-xW_xO₂ (x=0 and 0.0074) thin films prepared by pulsed laser deposition were studied to understand the effect of doping on the electrical properties of these films. Temperature dependent magneto-transport measurements (Hall effect) in magnetic fields up to 9 Tesla were performed on thin film vanadium dioxide (VO₂) across the Mott metal-insulator transition (MIT). The Hall carrier density increases by 4 orders of magnitude at MIT. The Hall mobility varies little across the MIT and remains low at ~ 0.05 cm² /V sec. The majority carriers are electrons. Magneto-resistance is small and positive. Comparison of the three Hall parameters including carrier concentration, conductivity and mobility between various doping levels on both metallic and insulating state are reported and a model has been proposed. A correlation between carrier concentration and conductivity of VO₂ films is observed but doesn’t exist between carrier concentration and mobility.

Transition from fourth to fifth generation wireless technologies requires a shift from 2.3 GHz to Ka-band with the promise of revolutionary increases in data handling capacity and transfer rates at greatly reduced latency among other benefits. A key enabling technology is the integration of Ka-band massive multiple input–multiple output (m-MIMO) antenna arrays. m-MIMO array elements simultaneously transmit and receive (STAR) data providing true full duplexing in time and frequency domains. A necessary innovation calls for the integration of device quality Ka-ferrites with wide-bandgap (WBG) semiconductor heterostructures allowing for system on-wafer solutions. Here, we report results of systematic studies of pulsed laser deposited (PLD) barium hexaferrite (BaM) films on industrial compatible WBG semiconductor heterostructures suitable for operation in Ka-band circulators.

Hyperdoped Si materials extend Si response range into near infrared by forming intermediate band in Si band gap. Ti hyperdoped Si (Si:Ti) has been demonstrated to have subbandgap photo response. In this work, we fabricated and characterized Si:Ti photodiodes and optimized the structure. At room temperature, the 3.5×10^-3 EQE has been obtained at telecommunication wavelength 1550nm. And the detectable response extends until 2250nm. The results show the potential of Si:Ti materials being both Si:Ti photovoltaics and commercialized IR detection. To improve the efficiency of Si:Ti photodetectors, the affection of absorption rate, devices structure and the Si:Ti crystal quality is discussed.

In the present work is reported, following a facile process, the synthesis of cobalt ferrite nanoparticles covered with a shell of SiO2, and then, covered with a shell of TiO₂. In the first step, cobalt ferrite nanoparticles were prepared by coprecipitation of Co⁺² and Fe ⁺² ions in basic medium, followed by a simple controlled oxidation process carried out by nitrate ions in basic medium with inert atmosphere at 95°C for 24h. In the second step, SiO₂ particles were deposited by heterogeneous nucleation onto the surface of the ferrite in alcohol medium by alkalinization of tetraethylortosilane solutions, finally, in the third step, the TiO₂ shell film is deposited by using sol-gel technique. Characterization techniques were performed to determine the particle morphology and size distribution (Scanning electron microscopy), crystalline structure (X-ray diffraction). Results showed that cobalt ferrite nanoparticles can be obtained following this synthesis route without using surfactants as size drivers, which is a common reagent in nanoparticle preparation, giving a size distribution of 162 ± 30 nm and a polyhedral geometry. Also, it was observed that SiO₂ is homogeneously distributed onto the surface of the cobalt ferrite, and that TiO₂ shell films covered well, creating a catalyst that also presents magnetic response. This kind of catalyst nanomaterial, presents a magnetic response, and is a stable and environmentally safe, then could be separated easily from the aqueous medium at the end of the purification process by applying an external magnetic field.

Antireflection coatings are vital for reducing loss due to optical reflection in photovoltaic solar cells. A single-layer magnesium fluoride (MgF₂) antireflection coating is usually used in thinfilm CIGS solar cells. According to optics, this coating can be effective only for a narrow spectral regime. Further reduction of reflection loss may require an optimal single-layer or multi-layer coating. Hence, we optimized the refractive indices and thicknesses of single- and double-layer antireflection coatings for CIGS solar cells containing a CIGS absorber layer with: (i) homogeneous bandgap, (ii) linearly graded bandgap, or (iii) nonlinearly graded bandgap. A relative enhancement of up to 1.83% is predicted with an optimal double-layer antireflection coating compared to the efficiency with a single-layer antireflection coating.

Columnar thin films are assemblies of parallel straight columns of nanoscale cross-sectional dimensions grown by physical vapor deposition on appropriate substrates. Sculptured thin films are similar, but the columnar shape is architected for specific objectives. Polarization-universal bandgaps with maximum transmittance under 20% were realized as sculptured thin films of two different types: (i) tightly interlaced matched ambidextrous bilayers (TIMABs) to modify the circular Bragg phenomenon and (ii) equichiral sculptured thin films (ECSTFs) that display the Bragg phenomenon. The serial bideposition technique was employed for architecting the columns. Samples characterized optically as well as with scanning electron microscopy.

In this paper, we design arrays of chiral slab resonators (Fabry-Perot-type (FP)) aligned polygonally and illuminated by a linear, p-polarized plane wave incident normally on the array slabs. Each such slab is analyzed using standard chiral slab resonance analyses developed recently [1]; evaluating the corresponding mode spectra for the right- and left-circular polarization ((RCP and LCP) modes for variable chirality coefficients, considering the slab thickness and substrate placement conditions as a function of the (monochromatic) mode frequency. In the polygonal array configuration, photodetectors (PDs) are added to convert the light into photocurrents (related to optical intensity); the intensities from the PDs are superposed at a single spatial point (chosen to be the centroid of the polygon). Hence, in this approach, a net intensity is generated at the centroid in response to a normally illuminated polygonal array. The array design is numerically analyzed, and the overall frequency and parametric properties evaluated. The spectral and resulting intensity behavior vis-à-vis mode frequencies for M slabs is determined under (1) matched resonator (with identical material parameters including thickness (d) and chirality coefficient (𝜅̃)) illumination with maximal transmission (which gives maximum superposed intensity) given by M times each individual intensity; and (2) unmatched resonators with a spread of d and K, such that the overall superposed array intensity pattern becomes adjustable and controllable, resulting in wideband or narrowband modal responses as desired or attainable by design. Both types of composite behavior for the two types of polygonal arrays are examined in detail and results discussed.

Molybdenum disulfide (MoS₂) gas sensor prototypes report orders of magnitude higher sensitivity towards nitrogen dioxide (NO₂) over ammonia (NH₃). Based on the cluster formation model and density functional theory calculation of charge transfer, NO₂ is found to form a tightly bound cluster of counter charge upon carrier donation. On the other hand, NH₃ forms only a semi-localized cluster of counter charge over wide area MoS₂, which should promote recombination of donated carrier. We report the localization of counter charge cluster as an important factor affecting molecular doping efficiency.

In this work, a novel interface engineering method is proposed to address the relatively large cycle-to-cycle variability of the emerging metal-oxide resistive random access memory (RRAM) device technology. This is achieved by synthesizing the solution-processable graphitic nanosheet (reduced graphene oxide, rGO) with defects of a controllable amount and further integrating it into RRAM as an oxygen exchange layer (OEL). It is demonstrated that rGO-inserted RRAM exhibits reduced cycle-to-cycle variability in the SET switching as compared with one that has a conventional transition metal thin film as OEL. This is best attributed to the fact that our rGO thin film provides nearly the same amount of oxidation-prone atomic sites for each programming cycle. This study is expected to greatly advance the RRAM-based neuromorphic computing by paving a practically viable route to enhance the accuracy of the deep learning model.

Protein nanowires harvested from microbes G. sulfurreducens are a renewable, green electronic material. Electronic devices made from protein nanowires show novel or improved functions in energy harvesting, computing and sensing. First, thin film assembled from protein nanowires is used to construct air generator (air-gen) that can continuously harvest electricity from air humidity, unveiling the potential of continuous and ubiquitous clean energy harvesting. Second, memristors and neuromorphic devices constructed from protein nanowires function at biological amplitude (<100 mV), creating opportunities for ultralow-power electronics and bioelectronic interfaces. Third, electronic sensors made from protein nanowires show enhanced performance for analyte detection. Finally, prototyped microsystems are integrated from above protein nanowire devices to show the potential of fabricating green electronics from biosynthetic nanowire materials.

A variety of materials can be used for the AFMEN including exfoliated graphene, Si (100) treated with solvents, polymer films, and styrene butadiene rubber. This simple one-two stage approach is a tool to pattern almost any semiconductor or dielectric surface at the nanoscale.

Nano-scale materials are known to offer significant advantages in surface activity and quantum effects, but their integration into thin-films for interactive devices is often limited by the surface area of the film, and the tendency of nanocomponents to proliferate into the environment. Many natural living systems address these challenges through elegant hierachical surface architectures such as microvilli and dendrites, where a larger substrate is covalently anchored to progressively smaller functional entities. This three-dimensional surface design offers exceptionally high levels of solid-fluid interaction in very compact space for important functions such as electrical/thermal transport, bio-scaffolding, adsorption and catalysis. However, this architecture has been traditionally avoided in engineered devices due to the complexities of creating strong primary bonds between components having different size, shape and compositions to form a durable integrated solid. In recent years, advances in surface engineering and nanoscale processing have made fabrication of these types of surface coatings possible in our laboratory, which provide several advantages over conventional films. This talk will present processing-structure-property relationships of some of these materials with special emphasis on three selected applications: micro fluidic devices, solid state heat exchangers for power electronics, and pollutant degradation membranes.

Films of Ge_1-xSn_x have been grown on Ge, Si, and Al₂O₃ substrates by remote plasmaenhanced chemical vapor deposition with Sn concentrations greater than 10% and thicknesses greater than 1 μm. Characterization data of the structural, optical, and electrical properties of these alloys are presented. Device characteristics from planar photoconductor and vertical p-n devices grown directly on Si substrates show promise for future MWIR sensing applications.

When designing static filters such as edge, line, bandpass etc.. the conventional approach relies on exploiting the resonances and bandgaps (stop-bands) that occur inside a multilayer thin film structure. When designing for tunability, a different approach is needed, arising primarily from the fact that the refractive index changes that occur in a phase change material (PCM) are generally complex-valued. In this paper, we will review the principles and strategies for designing tunable optical filters.

Combining multilayer metallo-dielectric metamaterials with tunable liquid crystals and electro-optical materials provides a unique approach to develop multifunctional devices for spectral filtering and custom control over light propagation.

The ink formulation process of stable black phosphorus (BP) inks for aerosol jet printing (AJP) is presented. Formulating BP stable photonic inks involves tailoring the flake size and ink solvents to AJP. Single crystal BP inks were used to print both backgated FET devices with a resistivity as low as 105Ω-cm and the resulting thin films showed photoluminescence emission in the NIR regime paving the way to printed optoelectronic devices.

In this work we build upon a previously published technique for printing dielectric ramps and printed RF interconnects across leveled surfaces to gain a better understanding of the effects that the dielectric material itself has on the conductivity of the printed conductive ink. The use of printed dielectric ramps, referred to as fillets, to assist in additively manufactured RF circuits and interconnects can be found throughout literature. One of the most widely used materials for these ramps, the UV-curable adhesive NEA-121, was found to exhibit physical changes when exposed to high curing temperatures and to have a significant effect on the conductivity of a wide variety of commercially available conductive ink materials; in some cases causing a 2x drop in conductivity compared with the expected conductivity reported by the manufacturer. We report on the conductivity effects from printing on the NEA-121 dielectric surface for three commercially available Ag inks for an RF circuit application and report the manufacturing techniques necessary to optimize both the dielectric ramp and the conductive ink performance.

Piezoresistive strain sensors, commonly known as resistance strain gauge, have many important applications. In this work, an alternative method to fabricate piezoresistive strain sensors directly on the structure of interest is demonstrated using a particle-free silver ink as the sensing material. The sensing material is first printed as a rectangular film on the structure of interest and a conductive serpentine pattern is generated by selective laser sintering. Only the material exposed to the focused laser is sintered and becomes conductive. The rest is washed-off by 1-dodecene solvent, leaving only the serpentine pattern, which serves as the piezoresistive strain sensor. This alternative method eliminates the need for a carrier or backing substrate and thus improves the mechanical coupling between the sensing material and the structure of interest. It also removes reinforcement effect due to the stiffness of the carrier substrate. Results from electrical characterization revealed that laser sintering power is a crucial parameter that influences fundamental properties of the sensing material such as electrical conductivity and work function. In addition, it was observed that there exists an optimum laser sintering power that results in a maximum gauge factor (GF). For strain sensors, the GF is the most important parameter because it is the measure of sensor sensitivity. When the particle-free silver ink was printed as a serpentine pattern followed by thermal sintering on a hot plate, a lower GF was measured. This shows that the alternative method to fabricate piezoresistive strain sensors is more attractive than printing the serpentine pattern then thermally sintering it.

The lack of drinkable water in rural areas or in places affected by natural disasters, motivated us to develop an efficient way to obtain drinking water. In this work we will present the development of an autonomous and portable water purification plant, based on a supported TiO₂ film reactor, to promote the photocatalytic disinfection of bacteria in water. It is concluded that the supported TiO₂ film onto a polyethylene based reactor shows good photocatalytic disinfect water under laboratory conditions and land field experiments. At the laboratory, up to 6 orders of magnitude of E-coli were reduced in less than 30 min, whereas under real conditions, water contaminated with 3480 CFU/100 mL of wild bacteria colonies, the disinfection was reached in less than 15 min. This System could be used in places in which safe drinking water is not available, like in rural areas, or under situations in which access to water through centralized public services are temporarily suspended, as for example after a natural disaster.

Excitation of coherent high-frequency magnons (quanta of spin waves) is critical to the development of high-speed magnonic devices. Here we computationally demonstrate the excitation of coherent terahertz (THz) magnons in ferromagnetic and antiferromagnetic thin films by a photoinduced picosecond acoustic pulse. Analytical calculations are performed to reveal the magnon excitation mechanism. Through spin pumping and spin-charge conversion, these magnons can inject THz charge current into an adjacent heavy-metal film which in turn emits electromagnetic (EM) waves. Based on dynamical phase-field simulations, we show that the emitted EM wave retains the spectral information of all the magnon modes, providing a basis for detection via THz emission spectroscopy.

We report ultrafast all-optical manipulation of magnetization in ferromagnetic Co/Pt thin films, which are covered by an Au capping layer or Au nanoparticles. In the first configuration, we observe robust all-optical helicity-dependent switching of magnetization under different conditions. In the second configuration, the strong plasmonic resonance of Au nanoparticles results in an 18.5% decrease in the minimum laser power required to manipulate the magnetization.

Investigation into the interface formed between Sb₂Te₃/Ni₈₀Fe₂₀ heterostructures – this is studied using temperature dependent magnetometry, scanning transmission electron microscopy, ferromagnetic resonance, and theoretical support.

Barium strontium titanate (BST-Ba_0.5Sr_0.5TiO₃) thin films are deposited over RT/Duroid substrate at a temperature of 250°C and are then crystallized by laser annealing. The laser annealed films are XRD crystalline. The microwave dielectric properties are measured by fabricating circular patch capacitor (CPC) using these dielectric films and a maximum tunability of 34% is obtained. Thus, integrated monolithic varactors on a polymer composite substrate exploiting the electric fielddependent dielectric constant exhibited by crystalline ferroelectric thin films are demonstrated.

Magnetoelectric (ME) multiferroics (MFs) materials, which exhibit electric order and some magnetic order, are of great interest for memory, energy harvesting, and sensing applications. Such ME MFs can be :(i) single-phase MFs and (ii) biphasic MFs. In this work, structural, ferroelectric, magnetic and ME properties of thin films of both type of ME MFs were studied. Facile and cost-effective solution-methods were used to fabricate thin films and nanocomposites of ME MF materials. The single-phase DyCrO₃ and GdFe_0.5Cr_0.5O₃ thin films showed magnetically induced dielectric behavior and independent magnetic/electric orders, respectively. In biphasic nanocomposites, concentration and connectivity of two phases play an important role in defining the ME coupling that is mediated through mechanical strain at the interfaces between the two phases. The ME switching and coupling behavior in the nanocomposite PbZr_0.52Ti_0.48O₃:CoFe₂O₄ thin films will be presented in detail.

Coherent interaction between a single magnon mode and multiple phonon modes is demonstrated on hybrid magnonic device made of ferrimagnetic thin films. Thanks to the high crystalline quality of the thin film, both magnon and phonon modes have very low losses that are comparable to their coupling strengths. This ensures excellent coherence in their interaction, allowing the observation of coherent phenomena such as pulse echo.

The coexistence of electric polarization and magnetization in multiferroic materials provides great opportunities for realizing magnetoelectric coupling, including electric field control of magnetism, or vice versa, through a strain mediated magnetoelectric coupling in layered magnetic/ferroelectric multiferroic heterostructures. Strong magnetoelectric coupling has been the enabling factor for different multiferroic devices, which, however, has been elusive, particularly at RF/microwave frequencies. In this presentation, I will cover the most recent progress on new integrated RF magnetoelectric materials and devices. Specifically, we will introduce magnetoelectric multiferroic materials and their applications in different devices, including voltage tunable RF magnetic components, ultracompact magnetoelectric mechanical antennas immune from ground plane effect with < λ₀/100 in size, self-biased operation, excellent impedance matching and ground plane immunity, etc. These magnetoelectric antennas are also smart antennas with picoTesla magnetic field sensitivity, and with orders of magnitude improved figure of merit for wireless power, transfer compared to state-of-the-art technologies. These novel magnetoelectric materials and antennas show great promise for applications in compact, lightweight and power-efficient sensors, antennas and tunable components for radars, communication systems, biomedical devices, IoT, etc.