High Modulation Efficiency Research Articles

Causal Language Model Aided Sequential Decoding With Natural Redundancy

A high-performance communication receiver desires a sufficient and accurate recognition of transmitted sources. In this paper, we propose a sequential decoding algorithm for the robust reception of sources with natural redundancy (NR) over the AWGN channel. To fully exploit the abundant NR in the exemplified English text sources, a causal language modeling (CLM) with a powerful Transformer decoder neural network (NN) structure is adopted for modeling the joint probability distribution. For versatility of byte-level tokenization, the UTF-8 encoding scheme is considered for the Wikipedia corpus, namely the English edition of the Wiki-40B dataset. The tree search-based M-algorithm (MA) is integrated with CLM, denoted as CLM-MA algorithm, to synthesize the a priori probability of information sequence and likelihood values of polluted symbols. Both simulation experiments and hardware platform evaluations are conducted to analyze the performance of the CLM-MA algorithm. With an adequately large M value, tremendous performance profit is achievable, especially for high-efficiency modulation levels and extremely noisy conditions. This mechanism of adopting the pre-trained NN model merely desires self-supervised learning architecture and eliminates the requirement of high-cost and accurate labels, which paves a new way for communication receiver design.

Novel warm/cool-tone switchable VO2-based smart window composite films with excellent optical performance

Vanadium dioxide (VO2) is a key material for thermochromic smart windows that can respond to environmental temperature to regulate near-infrared transmittance automatically. To date, VO2-based smart windows have made great progress, but practical applications still remain restricted by two tough challenges, i.e., low solar regulation ability and unpopular color. In view of the above two challenges, in this paper, novel warm/cool-tone switchable VO2-based composite films were designed and prepared. The novel composite films demonstrate outstanding optical properties: ΔTsol = 18.92% and Tlum,l = 48.70%. The high solar modulation efficiency is attributed to the modulation of the thermochromic microcapsules in visible light waveband and VO2 in near-infrared region. Meanwhile changes in color of the composite films at different temperatures were also studied in order to develop high-performance warm/cool-tone switchable thermochromic smart windows. These promising results will benefit to promote the popularization and application of smart windows.

Deep Learning for Waveform Level Receiver Design With Natural Redundancy

High-speed information transmission system demands more powerful communication receivers. In this paper, we integrate deep learning algorithms into constructing waveform level receiver, which is capable of harnessing natural redundancy (NR) in raw message sources. Owing to end-to-end learning paradigm of neural network (NN), the proposed NN receiver can accomplish joint symbol timing synchronization and demodulation based on oversampled waveform sequences directly. The prevalent bidirectional LSTM (BiLSTM) and Transformer structures, suitable for excavating sequential correlation of complex sources and waveform sequences, are considered as the backbone of NN receivers. Under the cases of clean label and noisy label, we conceive two novel training algorithms and interpret their principles in theory. The clean label bits are accessible from original source encoding schemes, while noisy label bits are available from the decision results of canonical receivers with independently noised waveform sequences. When noisy labels possess sufficiently small error rates, optimized NN receiver is competitive with that adopting the accurate labels. As for Markov sources and natural language text sources, simulation results show that the proposed NN receivers’ performances are superior to the classical receivers without a priori knowledge, especially when high spectral efficiency modulation schemes are encountered and random noise is significant.

Over-67-GHz-Bandwidth Membrane InGaAlAs Electro-Absorption Modulator Integrated With DFB Laser on Si Platform

We fabricate a membrane InGaAlAs electro-absorption modulator (EAM) integrated with a distributed feedback (DFB) laser combining direct wafer bonding and epitaxial regrowth of InP-based layers on a silicon-on-insulator wafer. Heterogeneous integration of an InP-based multiple-quantum-well (MQW) layer into the Si photonics simplifies the integration of the O-band EAMs and laser diodes (LDs). EAMs and LDs can be fabricated using the same MQW layer because of the wide operating range and the direct bandgap of the MQWs. A compact and high-speed lumped-electrode EAM can be made because the membrane lateral p-i-n diode structure has low capacitance and a large optical confinement factor. The effective-refractive-index matching between the membrane InP and Si layers enables the DFB laser to be fabricated with a low-loss supermode waveguide whose MQW core was optically coupled to the Si core. The fabricated 100-μm-long membrane EAM has a high modulation efficiency of about 3 dB/V at 1260 nm and E-O bandwidth of over 67 GHz even without a 50-ohm termination. The EAM-integrated DFB laser has a fiber coupled output power of about −2 dBm and clear eye openings with an extinction ratio of 3.8 and 3.2 dB for 100- and 112-Gbit/s non-return-to-zero signals, respectively.

Cell signaling and regulation of CFTR expression in cystic fibrosis cells in the era of high efficiency modulator therapy

Cystic fibrosis transmembrane conductance regulator (CFTR) is a cAMP- and protein kinase A (PKA)-regulated channel, expressed on the luminal surface of secretory and absorptive epithelial cells. CFTR has a complex, cell-specific regulatory network playing a major role in cAMP- and Ca2+-activated secretion of electrolytes. It secretes intracellular Cl– and bicarbonate and regulates absorption of electrolytes by differentially controlling the activity of the epithelial Na+ channel (ENaC) in colon, airways, and sweat ducts. The CFTR gene expression is regulated by cell-specific, time-dependent mechanisms reviewed elsewhere [1]. This review will focus on the transcriptional, post-transcriptional, and translational regulation of CFTR by cAMP-PKA, non-coding (nc)RNAs, and TGF-β signaling pathways in cystic fibrosis (CF) cells.

Switchable compliant actuator with fast stiffness modulation and energy efficient power transmission

This article presents the design of a switchable compliant actuator (Swi-CA), capable of fast stiffness modulation over a wide range and energy-efficient equilibrium position control. Compliant actuators are designed to have a variable stiffness to generate a restoring force upon displacement. In previous studies, such actuators provided compliance by changing both output stiffness and equilibrium position using a clutch to switch between two modes. We implemented a bifurcation-based switching mechanism to shift between stiffness modulation and equilibrium position control modes via mechanical integration of a variable stiffness spring with a parallel elastic unit without the use of an additional clutch. The distinctive features of the proposed Swi-CA are threefold. First, the central bending of a leaf spring widens the range of modulated stiffness and increases the average stiffness modulation speed. Second, the developed slider-crank mechanism has high power transmission efficiency and fast stiffness modulation. Lastly, an optimized elliptical cam generated negative stiffness during output and enabled switching between the two modes without the use of a controllable clutch. Analytical models and experimental validation of the proposed design clearly demonstrated its advantages for applications requiring fast stiffness modulation and energy-efficient operation, such as some robotics applications.

High-Efficiency Modulation and Harmonic Beam Scanning in Time-Modulated Array

A general high-efficiency time-modulated module and harmonic beam scanning time-modulated array (TMA) are proposed and investigated in this paper. By introducing the periodically controlled phased-shifters, a significant improvement on theoretical overall efficiency and transmitted bandwidth can be realized in harmonic beam scanning. Then equivalent cascade structure of the general modulation module is proposed for RF circuit simplification and practicability in actual applications. Theoretical derivation and simulation results show that increased efficiency, 100% feeding network efficiency and theoretical overall efficiency tending to 100% without consideration of insertion loss, can be achieved with the increase the phase-shifter states when only a single sideband is utilized. Compared to the existing state-of-the-art harmonic beam scanning TMAs, the proposed TMA exhibits a much higher overall efficiency while keeps a similar hardware complexity. Additionally, with acceptable increase of circuit complexity less than existing works, similar level of the wide transmission bandwidth can also be achieved. To experimentally verify the feasibility of the proposed general design, a 4-bit time-modulated module with reconfigurable states and the corresponding 8-element harmonic beam scanning TMA are fabricated and tested. The experiments on signal transmission and harmonic beam scanning demonstrate the effectiveness of power loss reduction and improvement in transmitted bandwidth with the increase of modulation phase states.

Dual-function smart windows with dynamic and fast thermal response for building energy-saving/storage

Thermochromic smart windows are considered an important element for increasing building energy efficiency. However, the phase transition of conventional devices only depends on the surrounding temperature with solar irradiation, which limits their application under different conditions. Here, a thermoelectrochromic dual response device has been designed by combining thermochromic hydroxypropyl cellulose/potassium chloride (HPC/KCl) hydrogel electrolyte and optothermal electrochromic polyaniline (PANI) films. The thermoelectrochromic device (T-ECD) exhibits electrochromic switchable colour tones (light yellow to purple), visible luminous transmittance (15.70–75.53%), and high solar modulation efficiency (60.89%) when this electrochromic switching is combined with thermochromic phenomenon arising from the electrolyte. Further, since PANI is able to store charge reversibly during the electrochromic transition, this device may also be used as a photovoltaic energy storage. Under solar irradiation, the photothermal effect of PANI films can drive the fast phase transition of HPC/KCl hydrogel. The phase transition time of T-ECD is 30 s which is much faster than 3 min of conventional TCD. In addition, a field test further demonstrates that the house model equipped with the T-ECD can reduce the indoor temperature by 13.3 °C compared with that using a traditional glass window. Thus, it is a valuable device to be used in buildings for energy-saving/storage situations. • An innovative T-ECD was designed and shows a wide range of T lum (15.70–75.53%), high ΔT sol (60.89%), low LCST (30 °C). • The T-ECD exhibited photothermal property to drive the fast phase transition (30 s). • Simulating real building-based T-ECD is 13.3 °C lower than that of using a traditional glass window.

Serrated periodic electrode for high energy efficiency and large bandwidth acousto-optic modulators

In an acousto-optic modulator, the electrode shape plays an important role in performance, since it affects the distribution of the acoustic field. The acousto-optic modulator based on the conventional rectangular electrode has the problems of low energy efficiency and small modulation bandwidth due to an imperfect acoustic field. In this paper, a new serrated periodic electrode has been proposed for using acousto-optic modulator transducers. The proposed electrode has the following advantages. By using serrated periodic electrodes to suppress the sidelobes, the collimation of the acoustic field in the direction perpendicular to the light incidence is improved. This makes the acousto-optic modulator have a stable diffraction efficiency fluctuation and high energy efficiency. In addition, the electrode has a large divergence angle in the direction of light incidence, so a large bandwidth can be obtained. The simulations and experiments demonstrate that the serrated periodic electrode has an increased bandwidth and high energy efficiency.

High optical modulation efficiency in perovskite CsPbI3/Br3 by ionic liquid ionization

An effective method to improve optical properties of perovskite CsPbI3/Br3 is a long-term goal pursued by researchers, such as incorporating, mechanism changing and structure optimizing. However, two significant problems still facing challenges including the complex fabrication process and low modulation efficiency. To contribute these, a method of ionic liquid modulation with respect to the photoluminescence PL intensity and peak position was demonstrated. The micro-structure including the information of crystal and bond in MAPbBr3/I3 soaking in C8H11F3N2O2 and C7H13N2∙ BF4 was supported by x-ray diffraction XRD patterns and Raman spectrum. A cube-like shape and size distribution mostly in 600–950 nm was imaged by scanning electron microscope. Then, compared with CsPbI3 before soaking in Hall measurement, the carrier concentration was improved about 46.1%, the mobility and resistivity were lowered around 39.2% and 40.2%, respectively. The modulation of intensity and peak position were confirmed by PL spectrum at room temperature. The absorption enhancement in excited state absorbs range was proved by transient absorption. Finally, the mechanism for optical modulation in this paper was systematically explained. The research method proposed in this paper can simplify the research process and improve the optical properties of the materials at the same time.

Ultra-short bilayer graphene optical fiber intensity modulator based on silver-semicircular hybrid plasmonic waveguide

The intensity modulator is a key component in optical fiber communication. In this paper, an ultra-short graphene light intensity modulator based on hybrid plasmonic waveguide (HPW) array is proposed. Al2O3 embedded with double-layer graphene at a certain interval is placed on the side polishing surface of the microfiber Mach–Zehnder modulator (MZM), and the silver-semicircular array is placed on the surface of the transition material as hybrid plasmonic waveguide for the first time in all-fiber modulator. Analyzing by building a 3D model in finite difference time domain software, the hybrid surface plasmon polariton (HSPP) between silver-semicircles significantly enhances the subwavelength confinement and the light–graphene interaction. The modulation range of the real part of effective refractive index (Neff) can reach to 0.01984 by adjusting the Fermi level of graphene. Therefore, π phase change can be achieved only in a modulation length of 45 μm, and the insert loss can be controlled below 0.0159 dB/μm through the analysis of the imaginary part of the Neff, which also leads to a low total loss of 0.7155 dB. Owing to the excellent phase modulation efficiency, high extinction ratios of 39.39 dB and 47.77 dB can be reached for port 1 and port 2, respectively. Double-layer graphene forms the flat capacitor, which brings high modulation efficiency while achieving a high modulation bandwidth of 59.945 GHz. The application of HPW in graphene optical fiber modulator greatly improves the working efficiency, reduces the difficulty of integration, overcomes high insert loss, improves the extinction ratio, this modulator can be widely used in the future optical fiber communication system.

A platinum modulated tungsten oxide on Ag nanowires network as an indicator for in-situ visualized evaluation of the hydrogen evolution performance

The development of the real-time evaluation for the catalytic hydrogen evolution performance under a simple and convinient condiction is urgently needed, but still a great challenge. Herein, a platinum modulated WOx on Ag nanowires (Pt-WOx@Ag NWs) is developed as an optical-electrochemical catalyst to realize an in-situ intuitive evaluation for the hydrogen evolution performance, in which the color of as-prepared Pt-WOx@Ag NWs catalyst changes from the transparent to the deep blue with the increase of the applied potential. The real-time H2 evolution with an H2 turnover frequency (from 0 to 2.26 s−1 per site), optical transmittance (from 80.3% to 48.7% at the wavelength of 630 nm) and energy consumption (from 0 to 0.74 W h in 1 h) is established. The charge transfer and mass transport are greatly promoted by the three demensional Ag NWs conductive network and abundant active sites, which are provided by the platinum modulated WO3 on the Ag substrate. Density functional theory (DFT) calculations indicate that the modified WOx shows the preferred adsorption affinity toward H2O (ΔGH2O, −0.17 eV), which reach a high coloration efficiency and optical modulation range for the electrochromic reaction. The Pt sites on WOx with a suitable H binding energy (ΔGH∗, 0.38 eV) efficiently promote the H∗ conversion and H2 release of water splitting. This work propose an intelligent hydrogen evolution indicator by real-time color change to boost the high-quality development of green hydrogen energy.

110 GHz, 110 mW hybrid silicon-lithium niobate Mach-Zehnder modulator

High bandwidth, low voltage electro-optic modulators with high optical power handling capability are important for improving the performance of analog optical communications and RF photonic links. Here we designed and fabricated a thin-film lithium niobate (LN) Mach-Zehnder modulator (MZM) which can handle high optical power of 110 mW, while having 3-dB bandwidth greater than 110 GHz at 1550 nm. The design does not require etching of thin-film LN, and uses hybrid optical modes formed by bonding LN to planarized silicon photonic waveguide circuits. A high optical power handling capability in the MZM was achieved by carefully tapering the underlying Si waveguide to reduce the impact of optically-generated carriers, while retaining a high modulation efficiency. The MZM has a V_pi L product of 3.1 V.cm and an on-chip optical insertion loss of 1.8 dB.

Modeling, analysis, and demonstration of a carrier-injection electro-absorption modulator at 2 µm on Ge-on-Si platform.

In this paper, a carrier-injection electro-absorption modulator (EAM) at 2 µm is demonstrated on Ge-on-Si platform. The EAM shows a compact size and high modulation efficiency due to the strong free-carrier electroabsorption (FCEA) effect in Ge. A modulation depth of 40 dB can be obtained under the injection current of only 420 mA. Small-signal frequency response measurement is performed and a small-signal equivalent circuit model is proposed. Based on reflection coefficients and equivalent circuit, the frequency response of carrier-injection EAM is discussed in detail. The 500 Mbps open eye diagram verifies the data-processing capacity of our EAM at 2 µm wavelength for its application in biological, chemical molecular detection, and infrared imaging systems.

Design and simulation of high modulation efficiency, low group velocity dispersion lithium niobate slow-wave electro-optic modulator based on a fishbone-like grating

Thin-film lithium niobate (LN) has emerged as an excellent platform for electro-optic modulators (EOMs) owing to its strong electro-optic (Pockels) effect. However, it remains an open challenge to achieve high modulation efficiency in chip-scale EOMs, primarily due to the limitation of light-matter interaction. Here, we propose an on-chip slow-wave LN EOM with a length of 3.4 mm with high modulation efficiency by using a fishbone-like grating. By assembling the fishbone-like grating, the Pockels effect is significantly enhanced as a result of the compression of the local density of states. Benefiting from this effect, the modulation efficiency of the modulator can be improved to 4.6 times of the original. In addition, a 3 mm matched micro-structure electrode is designed to realize the low group velocity of the microwave modulation signal. The simulation results show that the modulation efficiency of this slow-wave EOM is 1.42 V·cm. The slow-light effect is realized theoretically with a flat optical operating bandwidth of about 21 nm, group velocity dispersion < 2 ps2/mm, and low loss < 0.33 dB. Additionally, a 3 dB modulation bandwidth of 80 GHz is verified by simulation by virtue of the proposed micro-structure electrode.

High brightness and broad modulation bandwidth InGaN-based red micro-LEDs integrated with plasmonic gratings.

We propose red micro-LEDs integrated with plasmonic gratings, which demonstrate high efficiency and broad modulation bandwidth. The Purcell factor and external quantum efficiency (EQE) for an individual device can be improved up to 5.1 and 11%, respectively, due to the strong coupling between surface plasmons and multiple quantum wells. The cross talk effect between adjacent micro-LEDs can be efficiently alleviated as well, thanks to the high-divergence far-field emission pattern. Moreover, the 3-dB modulation bandwidth of the designed red micro-LEDs is predicted to be ∼ 528 MHz. Our results can be used to design high-efficiency and high-speed micro-LEDs for the applications of advanced light display and visible light communication.

Porous biological carbon fiber foam combined by aluminum phosphate for enhancing electric heating and electric thermal storage performance

Electric heating, as a kind of clean heating approach, has aroused worldwide interest due to its exceptional energy conservation, high efficiency, and random switching modulation. However, it is still a great challenge on the practical application of carbon-based electrothermal composites, since the degradation of material long-time operation performances caused by the agglomeration of carbon fillers and the aging of polymer substrates. Herein, we propose a novel porous carbon fiber foam connected by the inorganic compound aluminum phosphate (CKFC), based on the kapok fibers via a vacuum impregnation and carbonization process. The additive agent, including aluminum dihydrogen phosphate and iron(III) chloride hexahydrate, could help to maintain the hollow cylindrical structure, produce more micropores in the carbon fibers, and ensure the fibers are firmly bonded together. The hierarchical carbon fiber structure and strong interfacial interactions endow the CKFC composite with fast heating response speed, high balance temperature under low input voltages (below 36 V), uniform surface temperature distribution, and desirable service stability during the electric heating. Impressively, the further prepared CKFC/paraffin composite exhibits an ultrahigh heat storage efficiency (97.9 %), which could also quickly raise the temperature to 45 °C within safety voltage and delay the heat release. Therefore, we believe that the CKFC/paraffin composite with excellent electric heating and electric thermal storage performances could hold great promise for the practical application in electric indoor heating.

Restoring airway epithelial homeostasis in Cystic Fibrosis

Cystic fibrosis (CF), the most common life-threatening genetic disorder in Caucasians, is caused by recessive mutations in the Cystic Fibrosis Transmembrane Regulator (CFTR) gene encoding a chloride ion channel. Aberrant function of CFTR involves mucus- and sweat-producing epithelia affecting multiple organs, including airways and lungs. This condition facilitates the colonization of fungi, bacteria, or viruses. Recurrent antibiotic administration is commonly used to treat pathogen infections leading to the insurgence of resistant bacteria and to a chronic inflammatory state that jeopardizes airway epithelium repair. The phenotype of patients carrying CFTR mutations does not always present a strict correlation with their genotype, suggesting that the disease may occur because of multiple additive effects. Among them, the frequent microbiota dysbiosis observed in patients affected by CF, might be one cause of the discrepancy observed in their genotype-phenotype correlation. Interestingly, the abnormal polarity of the CF airway epithelium has been observed also under non-infectious and non-inflammatory conditions, suggesting that CFTR dysfunction “per se” perturbs epithelial homeostasis. New pathogen- or host-directed strategies are thus needed to counteract bacterial infections and restore epithelial homeostasis in individuals with CF. In this review, we summarized alternative cutting-edge approaches to high-efficiency modulator therapy that might be promising for these patients.

1.8 m/0.5 s Resolution Coherent Doppler Wind Lidar Using Continuous Phase Modulation

A high-spatial-resolution coherent Doppler wind lidar (CDWL) with high modulation efficiency is reported. The pseudo-random phase coding (PRPC) links the spatial resolution to the modulation rate but suffers from the non-rectangular transition caused by the limited bandwidth. With the help of continuous phase modulation (CPM), the abrupt phase switching between successive bit intervals is avoided, thus significantly reducing the bandwidth requirement. By mapping the binary sequence into different transition states rather than phase levels, a 10-fold modulation efficiency improvement is realized. In experiments, the performance of the proposed lidar is compared with lidars in the PRPC method and conventional non-coding method. Continuous radial wind profile measurement of 800 m is demonstrated with spatial and temporal resolution of 1.8 m and 0.5 s, which is the highest spatial resolution realized by a pulsed CDWL to our best knowledge.

High modulation efficiency and large bandwidth thin-film lithium niobate modulator for visible light.

We experimentally demonstrate an integrated visible light modulator at 532 nm on the thin-film lithium niobate platform. The waveguides on such platform feature a propagation loss of 2.2 dB/mm while a grating for fiber interface has a coupling loss of 5 dB. Our fabricated modulator demonstrates a low voltage-length product of 1.1 V·cm and a large electro-optic bandwidth with a roll-off of -1.59 dB at 25 GHz for a length of 3.3 mm. This device offers a compact and large bandwidth solution to the challenge of integrated visible wavelength modulation in lithium niobate and paves the way for future small-form-factor integrated systems at visible wavelengths.