Linewidth Control Research Articles

Double-Network Hydrogel 3D BioPrinting Biocompatible with Fibroblast Cells for Tissue Engineering Applications

The present study examines the formulation of a biocompatible hydrogel bioink for 3D bioprinting, integrating poly(ethylene glycol) diacrylate (PEGDA) and sodium alginate (SA) using a double-network approach. These materials were chosen for their synergistic qualities, with PEGDA contributing to mechanical integrity and SA ensuring biocompatibility. Fibroblast cells were included in the bioink and printed with a Reg4Life bioprinter employing micro-extrusion technology. The optimisation of printing parameters included needle size and flow velocities. This led to precise structure development and yielded results with a negligible deviation in printed angles and better control of line widths. The rheological characteristics of the bioink were evaluated, demonstrating appropriate viscosity and shear-thinning behaviour for efficient extrusion. The mechanical characterisation revealed an average compressive modulus of 0.38 MPa, suitable for tissue engineering applications. The printability of the bioink was further confirmed through the evaluations of morphology and diffusion rates, confirming structural integrity. Biocompatibility assessments demonstrated a high cell viability rate of 82.65% following 48 h of incubation, supporting the bioink’s suitability for facilitating cell survival. This study introduced a reliable technique for producing tissue-engineered scaffolds that exhibit outstanding mechanical characteristics and cell viability, highlighting the promise of PEGDA–SA hydrogels in bioprinting applications.

Scalable narrow linewidth high power laser for barium ion optical qubits

The linewidth of a laser plays a pivotal role in ensuring the high fidelity of ion trap quantum processors and optical clocks. As quantum computing endeavors scale up in qubit number, the demand for higher laser power with ultra-narrow linewidth becomes imperative, and leveraging fiber amplifiers emerges as a promising approach to meet these requirements. This study explores the effectiveness of thulium-doped fiber amplifiers (TDFAs) as a viable solution for addressing optical qubit transitions in trapped barium ion qubits. We demonstrate that by performing high-fidelity gates on the qubit while introducing minimal intensity noise, TDFAs do not significantly broaden the linewidth of the seed lasers. We employed a Voigt fitting scheme in conjunction with a delayed self-heterodyne method to accurately measure the linewidth independently, corroborating our findings through quadrupole spectroscopy with trapped barium ions. Our results show linewidth values of 160 ± 15 Hz and 156 ± 16 Hz, respectively, using these two methods, underscoring the reliability of our measurement techniques. The slight variation within the error-bars of the two methods can be attributed to factors such as amplified spontaneous emission in the TDFA or the influence of 1/f noise within the heterodyne setup delay line. These contribute to advancing our understanding of laser linewidth control in the context of ion trap quantum computing as well as stretching the availability of narrow linewidth, high-power tunable lasers beyond the C-band.

Reducing Frequency Scatter in Large Arrays of Superconducting Resonators with Inductor Line Width Control

Reducing Frequency Scatter in Large Arrays of Superconducting Resonators with Inductor Line Width Control

Grating-based microcavity with independent control of resonance energy and linewidth for non-Hermitian polariton system

Exciton–polaritons have become an emerging platform for implementing non-Hermitian physics. The implementation commonly requires control of both the real and imaginary parts of the eigenmodes of the system. We present an experimental method to achieve this purpose using microcavities with sub-wavelength gratings as reflectors. The reflectivity and reflection phase of the grating can be changed by its geometric parameters, and they determine the energy and linewidth of the polariton modes. We demonstrate that this method allows a wide range of possible polariton energy and linewidth, suitable for implementing non-Hermitian polariton systems with coupled modes.

Room-Temperature Observation of Near-Intrinsic Exciton Linewidth in Monolayer WS2.

The homogeneous exciton linewidth, which captures the coherent quantum dynamics of an excitonic state, is a vital parameter in exploring light-matter interactions in 2D transition metal dichalcogenides (TMDs). An efficient control of the exciton linewidth is of great significance, and in particular of its intrinsic linewidth, which determines the minimum timescale for the coherent manipulation of excitons. However, such a control is rarely achieved in TMDs at room temperature (RT). While the intrinsic A exciton linewidth is down to 7 meV in monolayer WS2 , the reported RT linewidth is typically a few tens of meV due to inevitable homogeneous and inhomogeneous broadening effects. Here, it is shown that a 7.18 meV near-intrinsic linewidth can be observed at RT when monolayer WS2 is coupled with a moderate-refractive-index hydrogenated silicon nanosphere in water. By boosting the dynamic competition between exciton and trion decay channels in WS2 through the nanosphere-supported Mie resonances, the coherent linewidth can be tuned from 35 down to 7.18 meV. Such modulation of exciton linewidth and its associated mechanism are robust even in presence of defects, easing the sample quality requirement and providing new opportunities for TMD-based nanophotonics and optoelectronics.

Formation of Functional Silicon Nitride Layers by Selective Plasmochemical Etching

At present, with the development of nanotechnology, plasma-chemical etching remains practically the only tool for transferring an integrated circuit pattern in a masking layer to a substrate material due to the fact that the pattern transfer accuracy is comparable to the size of etching gas ions. Requirements for plasma technology: permissible defects, selectivity (material selectivity), line width control, etching uniformity are becoming more stringent and, as a consequence, more difficult to implement. To increase the rate and selectivity of plasma-chemical etching of silicon nitride films during plasma processing of a gas mixture consisting of both a fluorine-containing gas and oxygen, sulfur hexafluoride with a concentration of 70–91 vol.% was used as a fluorine-containing gas with an oxygen concentration of 9–30 vol.%.

A Systematic Thermal Analysis for Accurately Predicting the Extrusion Printability of Alginate–Gelatin-Based Hydrogel Bioinks

Three-dimensional (3D) bioprinting has significant potential for addressing the global problem of organ shortages. Extrusion printing is a versatile 3D bioprinting technique, but its low accuracy currently limits the solution. This lack of precision is attributed largely to the complex thermal and dynamic properties of bioinks and makes it difficult to provide accurate estimations of the printed results. It is necessary to understand the relationship between printing temperature and materials’ printability to address this issue. This paper proposes a quantitative thermal model incorporating a system’s printing temperatures (syringe, ambient, and bioink) to facilitate accurate estimations of the printing outcomes. A physical model was established to reveal the relationship between temperature, pressure, and velocity in guiding the printing of sodium alginate–gelatin composite hydrogel (a popular bioink) to optimize its extrusion-based printability. The model considered the phenomenon of bioink die swells after extrusion. A series of extrusion experiments confirmed that the proposed model offers enhanced printing outcome estimations compared with conventional models. Two types of nozzles (32- and 23-gauge) were used to print several sets of lines with a linewidth step of 50 μm by regulating the extrudate’s temperature, pressure, and velocity separately. The study confirmed the potential for establishing a reasonable, accurate open-loop linewidth control based on the proposed optimization method to expand the application of extrusion-based bioprinting further.

A Systematic Thermal Analysis for Accurately Predicting the Extrusion Printability of Alginate-Gelatin-Based Hydrogel Bioinks.

Three-dimensional (3D) bioprinting has significant potential for addressing the global problem of organ shortages. Extrusion printing is a versatile 3D bioprinting technique, but its low accuracy currently limits the solution. This lack of precision is attributed largely to the complex thermal and dynamic properties of bioinks and makes it difficult to provide accurate estimations of the printed results. It is necessary to understand the relationship between printing temperature and materials’ printability to address this issue. This paper proposes a quantitative thermal model incorporating a system’s printing temperatures (syringe, ambient, and bioink) to facilitate accurate estimations of the printing outcomes. A physical model was established to reveal the relationship between temperature, pressure, and velocity in guiding the printing of sodium alginate–gelatin composite hydrogel (a popular bioink) to optimize its extrusion-based printability. The model considered the phenomenon of bioink die swells after extrusion. A series of extrusion experiments confirmed that the proposed model offers enhanced printing outcome estimations compared with conventional models. Two types of nozzles (32- and 23-gauge) were used to print several sets of lines with a linewidth step of 50 mm by regulating the extrudate’s temperature, pressure, and velocity separately. The study confirmed the potential for establishing a reasonable, accurate open-loop linewidth control based on the proposed optimization method to expand the application of extrusion-based bioprinting further.

Ligand control of low-frequency electron paramagnetic resonance linewidth in Cr(III) complexes.

Understanding how the ligand shell controls low-frequency electron paramagnetic resonance (EPR) spectroscopic properties of metal ions is essential if they are to be used in EPR-based bioimaging schemes. In this work, we probe how specific variations in the ligand structure impact L-band (ca. 1.3 GHz) EPR spectroscopic linewidths in the trichloride salts of five Cr(iii) complexes: [Cr(RR-dphen)3]3+ (RR-dphen = (1R,2R)-(+)-diphenylethylenediamine, 1), [Cr(en)3]3+ (en = ethylenediamine, 2), [Cr(me-en)3]3+ (me-en = 1,2-diaminopropane, 3), [Cr(tn)3]3+ (tn = 1,3-diaminopropane, 4) [Cr(trans-chxn)3]3+ (trans-chxn = trans-(±)-1,2-diaminocyclohexane, 5). Spectral broadening varies in a nonintuitive manner across the series, showing the sharpest peaks for 1 and broadest for 5. Molecular dynamics simulations provide evidence that the broadening is correlated to rigidity in the inner coordination sphere and reflected in ligand-dependent distribution of Cr-N bond distances that can be found in frozen solution.

Modeling and Analysis of the Influence of an Edge Filter on the Combining Efficiency and Beam Quality of a 10-kW-Class Spectral Beam-Combining System

Filter-based spectral beam combining (FSBC) is a promising power-scaling concept for high-power, broad-linewidth fiber lasers, as it relaxes the requirements for linewidth control and also the sizes of the individual beams. As the combining element in the FSBC system, the steep-edge filter plays a major role in achievement of the combining efficiency and the beam quality. In this case, we combine the uncorrelated surface roughness model and the combining efficiency model, and we conduct a comprehensive analysis of the effects of surface roughness, thickness error, and incident angle on the filter’s optical properties and the combining efficiency, in order to determine the optimal configuration for the laser beam-combining system. The simulation results show a good agreement with the measured ones. Meanwhile, through the adoption of the angular spectrum theory, this paper has also conducted a preliminary analysis of the influence of the combining elements on the quality of the combined beam, and some theoretical instructions on the future design of the spectral beam-combining system are provided.

Flexible PET Substrate for High-Definition Printing of Polymer Thick-Film Conductive Pastes

Abstract A major obstacle in screen printing conductive low-temperature curing polymer thick-film (PTF) pastes onto common flexible PET substrate materials is the substantial spread of the pastes beyond the designed line width after printing. Industry observation and controlled testing have shown this spread can be as much as 80% over the circuit design's intended line width. This phenomenon prevents designers from increasing circuit density and/or reducing circuit real estate without incorporating other more involved and higher cost patterning methods. In many cases, flexible circuit fabricators, desiring more accurate high-definition circuit elements, may have to subcontract parts out of house to incorporate alternate patterning methods. This subcontracting, in turn, leads to a loss of control of both cost and lead time. This article will provide results of numerous in-house and field testings, comparing printed line width control, edge definition, and improved conductivity of printed polymer Ag conductors on different flexible PET substrates.

Super-resolved critical dimensions in far-field I-line photolithography

Background: Resolution enhancement combined with multiple patterning enables photolithography to write patterns with both feature size and spacing below the diffraction limit. Continued resolution enhancement at i-line will enable an older generation of lithographic tools to reach resolutions typically achieved using deep UV (DUV). Aim: A demonstration and deterministic model of large critical dimension enhancement at i-line. In addition to enhanced resolution, the technique must also achieve high repeatability and low line edge roughness (LER), while using commercial resists. Approach: Overexposing photoresist with high-contrast interference nulls leads to subwavelength critical dimensions. Starting with a theoretical analysis of the technique, we consider limits imposed by optics, linewidth scaling rates, and LER. This analysis shows that low LER and deterministic linewidth control are both readily achievable. Results: We demonstrate large area, i-line patterning of features with 50-nm linewidth, without the aid of subsequent trim or etch and with LER of 5 nm. Linewidth is shown to scale with dose as predicted from the optical model, independent of photoresist. Conclusions: These dimensions are similar to what may be achieved using scanning near-field, DUV, or e-beam lithography, yet achieved with far-field near UV exposures over a large area. Deterministic linewidth control and low LER make this process viable for fabrication at length scales well below those typically achieved with i-line tools.

Flexible PET Substrate for High Definition Printing of Polymer Thick Film Conductive Pastes

Abstract A major obstacle in screen printing conductive low temperature curing polymer thick film (PTF) pastes onto common flexible PET substrate materials is the substantial spread of the pastes beyond the designed line width after printing. Industry observation and controlled testing have shown this spread can be as much as 80% over the circuit design's intended line width. This phenomenon prevents designers from increasing circuit density and/or reducing circuit real estate without incorporating other, more involved and higher cost patterning methods. In many cases, flexible circuit fabricators, desiring more accurate high definition circuit elements, may have to subcontract parts out of house in order to incorporate alternate patterning methods. In-turn this subcontracting leads to a loss of control of both cost and lead time. This paper will provide results of numerous in-house and field testing, comparing printed line width control, edge definition, and improved conductivity of printed polymer Ag conductors on different flexible PET substrates.

Impact of Shell Growth on Recombination Dynamics and Exciton-Phonon Interaction in CdSe-CdS Core-Shell Nanoplatelets.

We investigate the impact of shell growth on the carrier dynamics and exciton-phonon coupling in CdSe-CdS core-shell nanoplatelets with varying shell thickness. We observe that the recombination dynamics can be prolonged by more than one order of magnitude, and analyze the results in a global rate model as well as with simulations including strain and excitonic effects. We reveal that type I band alignment in the hetero platelets is maintained at least up to three monolayers of CdS, resulting in approximately constant radiative rates. Hence, observed changes of decay dynamics are not the result of an increasingly different electron and hole exciton wave function delocalization as often assumed, but an increasingly better passivation of nonradiative surface defects by the shell. Based on a global analysis of time-resolved and time-integrated data, we recover and model the temperature dependent quantum yield of these nanostructures and show that CdS shell growth leads to a strong enhancement of the photoluminescence quantum yield. Our results explain, for example, the very high lasing gain observed in CdSe-CdS nanoplatelets due to the type I band alignment that also makes them interesting as solar energy concentrators. Further, we reveal that the exciton-LO-phonon coupling is strongly tunable by the CdS shell thickness, enabling emission line width and coherence length control.

Voltage tunable microwave multiband filters through meta-interferometer.

First it has been observed that microwave interferometer with embedded metastructure, meta-surface or meta-atom as voltage-controlled original beam-splitter can show new functionalities, such as specific selective control of line width and intensity, as well line shape and position in multiband spectral filtering. We realize and investigate modified meta-interferometer on basis of rectangular waveguide tee with varactor-loaded conductive resonance elements as a beam splitter at 3 – 6 GHz. It is achieved tunable considerable narrowing and 0.15 – 0.2 GHz shifting of band; switching between stop-band (-25 dB) and pass-band (-2;-5 dB), as well widening and intensification of each filtering band by turns in dependence on resonance element properties and bias voltage 0 – 10 V. The results open up a new approach to implement switchable and tunable multiband microwave filters.

64‐2: Fabrication of Auxiliary Electrodes using Ag Inkjet Printing for OLED Lighting

This study introduces the novel fabrication of auxiliary electrodes using silver (Ag) inkjet printing for OLED lighting. Generally, inkjet printing has limits to feature size and resolution due to nozzle size, jetting volume and ink spread. To fabricate narrow auxiliary electrodes, this study introduces a unique line width control method using a hydrophilic track formed by spreading barriers. The grid‐like auxiliary electrodes were fabricated by directly‐patterning of Ag conductive line and insulator. The most densely fabricated grid electrode has the line width of 18 µm, the space distance of 0.15 mm. For the feasibility test of the developed grid‐like auxiliary electrode, we fabricated OLED lighting using ITO electrode substrates printed with the grid‐like auxiliary electrode.

Organic Damascene Process for 1.5-<inline-formula> <tex-math notation="LaTeX">$\mu$ </tex-math> </inline-formula>m Panel-Scale Redistribution Layer Technology Using 5-<inline-formula> <tex-math notation="LaTeX">$\mu$ </tex-math> </inline-formula>m-Thick Dry Film Photosensitive Dielectrics

This paper presents a novel organic embedded trace damascene redistribution layer (RDL) process for panel-scale 2.5-D interposers and high-density fan-out package (HDFO) substrates. A minimum feature size of 1.5- $\mu \text{m}$ line and space using ultrathin polymer dielectrics on glass, silicon, and as well as on organic laminate was demonstrated. This is the first demonstration of a complete set of materials and processes that can be applied to large glass or organic panels, to bridge the interconnect gap between current semiadditive process (SAP) RDL and wafer back-end-of-line (BEOL) RDL. The ultra-fine pitch multilayer RDL structures demonstrated in this paper achieve an optimum balance of high IO density, high electrical performance, and low process costs. IO density in terms of IOs per mm per layer, as defined by Intel, refers to the number of traces routed per millimeter of die edge on one RDL layer of an interposer or package substrate. The current SAP technology can achieve an IO density of about 40 IOs/mm/layer on 510 mm $\times \,\, 510$ mm organic laminate panels. The challenges of fabricating copper metal traces below 5 $\mu \text{m}$ width and 5 $\mu \text{m}$ space using conventional SAP are discussed. On the other hand, wafer-based BEOL damascene RDL technology can scale to IO densities of greater than 200 IOs/mm/layer, but at relatively higher costs on 300-mm-diameter round wafers. An additional challenge for silicon interposers is low die-to-die interconnect data rate of single copper trace due to the high resistance of BEOL RDL structure. A combination of larger cross-sectional area with high aspect ratio (AR) is preferred for low-resistance, high-bandwidth escape routing traces. In this paper, the materials and process flow of embedded trace damascene RDL technology featuring trenches of 1.5 $\mu \text{m}$ width and 1.5 $\mu \text{m}$ space with AR of 2–4 will be described. A new 5- $\mu \text{m}$ -thick dry film photosensitive polymer dielectric IF4605 was used for the trench layer as well as the via layer. A large panel-scalable Surface Planar DFS8910 tool was used to achieve a highly planar metal–polymer RDL surface, at potentially lower costs than chemical-mechanical polishing that has been used in prior work. The processes discussed in this paper will enable routing of fine copper traces on panel-based interposers and HDFOs at higher throughput and potentially lower costs than BEOL processes. A two-metal layer, 20- $\mu \text{m}$ IO pitch silicon-like RDL test vehicle was fabricated with 2.5- $\mu \text{m}$ -wide and 2.5- $\mu \text{m}$ -space embedded traces and integrated with 2- $\mu \text{m}$ -diameter microvias using IF4605 on glass. There was no pad in the integration. This pad-less structure can be used for achieving theoretically maximum interconnect density. The process flow emulates the salient features of damascene processes used for BEOL RDL on semiconductor wafers, but simplifies them using dry film polymer materials and panel processes. Hence, it is referred to as organic embedded trace damascene or simplified as an organic damascene process (ODP) in this paper. The novel ODP interconnect addresses the current limitations of both SAP and BEOL processes. The key highlights of this new ODP technology are: 1) IO densities of 200 IO/mm/layer or more; 2) via-to-via pitch of $20~\mu \text{m}$ or less; 3) high AR of routing traces in the range of 2–4; 4) precise RDL linewidth control; 5) double-sided process with glass core; and 6) reduced number of process steps and panel-scalability leading to lower fabrication costs.

Optimization of Phase Modulation Formats for Suppression of Stimulated Brillouin Scattering in Optical Fibers

We theoretically investigate nonlinear optimization of periodic phase modulation for suppression of stimulated Brillouin scattering (SBS) in single-mode optical fibers. We use nonlinear multiparameter Pareto optimization to find modulations that represent the best tradeoff between SBS and optical linewidth, as measured by its rms value. The optimization uses a temporal-amplitude-domain finite-difference Brillouin solver with noise initiation to find the best phase modulation patterns in the presence of coherent so-called cross-interactions. These can be important in short fibers, when the period is large enough to make the frequency-domain separation of the modulated signal comparable to, or smaller than, the Brillouin gain linewidth. We calculate the SBS threshold for the optimized modulation patterns and find that smaller spectral line spacing improves the SBS threshold for the same linewidth. By contrast, whereas the maximum modulation depth and modulation frequency influence the range of accessible linewidths, they do not significantly alter the threshold for a given linewidth. We investigate the dependence on fiber length and find that while shorter fibers have a higher threshold, the increase is smaller than the often-assumed inverse dependence on length. Furthermore, we find that optimized formats are superior in terms of SBS threshold as well as in terms of linewidth control, compared to random modulation.

The implications of grading on the emission line width of core–shell nanocrystals

An excitonic coupling with phonons leads to broadening of the emission line. The narrow excitonic emission line width observed in CdZnS/ZnS alloy core graded shell nanocrystals (NCs) with varying compositions is studied using temperature-dependent photoluminescence measurements. Contrary to the consensus that a narrow emission line width is observable with a reduction in size (due to the increased exciton–acoustic phonon coupling coefficient σ), an increased value is noted with reduced size. Based on a theoretical approach to graded core–shell NCs, the relationship between the electron–hole wave function overlap and exciton lifetime is invoked to understand this anomaly. Smaller alloy core–shell NCs (CdZnS/ZnS-I) have a longer lifetime than larger NCs (CdZnS/ZnS-II), indicating reduced electron–hole wave function overlap for CdZnS/ZnS-I NCs and hence a larger ‘effective size’ of NCs, even though the actual size is smaller. The experimental findings demonstrate that graded core–shell NCs reveal an additional functionality, facilitating control of the emission line width of NCs via minimal interaction with the solid state environment.

Control of Ferromagnetic Resonance Frequency and Frequency Linewidth by Electrical Fields in FeCo/[Pb(Mg1/3Nb2/3)O3]0.68-[PbTiO3]0.32(011) Heterostructures

We report our detailed investigation of the electrical tuning of the ferromagnetic resonance frequency and frequency linewidth in multiferroic heterostructures consisting of FeCo thin films grown onto [Pb(Mg1/3Nb2/3) O3]0.68-[PbTiO3]0.32 (PMN–PT) substrates with NiFe underlayers. Our study shows that the electrical tuning range of both ferromagnetic resonance frequency and frequency linewidth in this FeCo/PMN-PT heterostructure can be very large. Specifically, the resonance frequency can be tuned from 1.8 GHz to 10.3 GHz, and the frequency linewidth can be changed from 1.6 GHz to 7.3 GHz. The electrical tuning of these microwave properties is discussed in conjunction with the result from the static magnetic characterization and is explained based on the strain-driven magnetoelectric heterostructured effect.