Energy scaling and extended tunability of a ring cavity terahertz parametric oscillator based on KTiOPO_4 crystal

A wide terahertz tuning range from 0.96 THz to 7.01 THz has been demonstrated based on ring-cavity THz wave parametric oscillator with a KTiOPO_4（KTP） crystal. The tuning range was observed intermittently from 0.96 THz to 1.87 THz,from 3.04 THz to 3.33 THz, from 4.17 THz to 4.48 THz, from 4.78 THz to 4.97 THz, from 5.125 THz to 5.168 THz, from5.44 THz to 5.97 THz, and from 6.74 THz to 7.01 THz. The dual-Stokes wavelengths resonance phenomena were observed in some certain tuning angle ranges. Through the theoretical analysis of the dispersion curve of the KTP crystal, the intermittent THz wave tuning range and dual-wavelength Stokes waves operation during angle tuning process were explained.The theoretical analysis was in good agreement with the experiment results. The maximum THz output voltage detected by Golay cell was 1.7 V at 5.7 THz under the pump energy of 210 mJ, corresponding to the THz wave output energy of5.47 μJ and conversion efficiency of 2.6 × 10^（-5）.

Tunability of Fano resonance in cylindrical core-shell nanorods

The optical properties of cylindrical core–shell nanorods(CCSNs)are theoretically investigated in this paper.The results show that Fano resonance can be generated in CCSNs,and the wavelength and the intensity at Fano dip can be tuned respectively by adjusting the field coupling of cavity mode inside and near field on gold surface.The high tuning sensitivity which is about 400 nm per refractive-index unit can be obtained,and an easy-to-realize tunable parameter is also proposed.A two-oscillator model is also introduced to describe the generation of Fano resonance in CCSNs,and the results from this model are in good agreement with theoretical results.The CCSNs investigated in this work may have promising applications in optical devices.

Electric-Field Tunability of Dielectric in Polycrystalline Sr1-xMnxTiO3 Thin Films

The electric-field tunability of dielectric constant （ε-E） in Sr1-xMnxTiO3 films （x = 0, 0.005, 0.010, 0.020 and 0.030） prepared by the metal organic decomposition method on Pt/Ti/SiO2/Si substrates is studied in the frequency range from 100Hz to 1MHz with different Mn contents at different temperatures. The frequencyindependent tunability increases strongly with decreasing the temperature from 300 K to 150K. The tunability （-31%） in thin films （x = 0.005） at 150K is obtained and the temperature for the same tunability in ceramics is about 60 K lower than the present one. This tunability is comparable with that in one of ferroelectric Sr1-1.sxBixTiO3 thin films. Similarly, the well-defined P（E） hysteresis 10013 and 2Pr （1.2 μC/cm^2） can be obtained at 300 K in Sr1-xMnxTiO3 films with z = 0.005. Both the existence of electric dipole or poled micro domain introduced by the doped Mn2＋ located in the off-center position at Sr sites and the strain between the thin film and the substrate are the origins of the tunable and polar behavior in Sr1-xMnxTiO3 films.

Ultrahigh frequency tunability of aperture-coupled microstrip antenna via electric-field tunable BST

A composite ceramic with nominal composition of 45.0 wt%（Ba0.5Sr0.5）TiO3–55.0 wt%MgO（acronym is BST–MgO） is sintered for fabricating a frequency reconfigurable aperture-coupled microstrip antenna. The calcined BST–Mg O composite ceramic exhibits good microwave dielectric properties at X-band with appropriate dielectric constant εr around85, lower dielectric loss tan δ about 0.01, and higher permittivity tunability 14.8% at 8.33 k V/cm. An ultrahigh E-field tunability of working frequency up to 11.0%（i.e., from 9.1 GHz to 10.1 GHz with a large frequency shift of 1000 MHz）at a DC bias field from 0 to 8.33 k V/cm and a considerably large center gain over 7.5 d B are obtained in the designed frequency reconfigurable microstrip antenna. These results demonstrate that BST materials are promising for the frequency reconfigurable antenna.

Diode-pumped Kerr-lens mode-locked Ti: sapphire laser with broad wavelength tunability

We report a direct blue-diode-pumped wavelength tunable Kerr-lens mode-locked Ti: sapphire laser.Central wavelength tunability as broad as 89 nm(736-825 nm) is achieved by adjusting the insertion of the prism.Pulses as short as 17 fs are generated at a central wavelength of 736 nm with an average output power of 31 mW.The maximum output power is 46.8 mW at a central wavelength of 797 nm with a pulse duration of 46 fs.

Lithographic printing inspired in-situ transfer of MXene-based films with localized topo-electro tunability for high-performance flexible pressure sensors

MXene-based films have been intensively explored for construction of piezoresistive flexible pressure sensors owing to their excellent mechanical and electrical properties.High pressure sensitivity relies on pre-molding a flexible substrate,or regulating the micromorphology of MXene sheets,to obtain a micro-structured surface.However,the two avenues usually require complicated and time-consuming microfabrication or wet chemical processing,and are limited to non-adjustable topographicelectrical(topo-electro)properties.Herein,we propose a lithographic printing inspired in-situ transfer(LIPIT)strategy to fabricate MXene-ink films(MIFs).In LIPIT,MIFs not only inherit ridge-and-valley microstructure from paper substrate,but also achieve localized topo-electro tunability by programming ink-writing patterns and cycles.The MIF-based flexible pressure sensor with periodical topo-electro gradient exhibits remarkably boosted sensitivity in a wide sensing range(low detection limit of 0.29 Pa and working range of 100 kPa).The MIF sensor demonstrates versatile applicability in both subtle and vigorous pressuresensing fields,ranging from pulse wave extraction and machine learning-assisted surface texture recognition to piano-training glove(PT-glove)for piano learning.The LIPIT is quick,low-cost,and compatible with free ink/substrate combinations,which promises a versatile toolbox for designing functional MXene films with tailored morphological-mechanical-electrical properties for extended application scenarios.

Low cross-talk, deep subwavelength plasmonic metal/insulator/metal waveguide intersections with broadband tunability

We suggest a low cross-talk plasmonic cross-connector based on a metal/insulator/metal cavity and waveguides.We separately investigate the isolated cavity mode, the waveguide mode, and the combination of cavity and waveguide modes using a finite-different time-domain method. Due to resonant tunneling and the cutoff frequency of the odd waveguide mode, our proposed structure achieves a high throughput transmission ratio and eliminates cross-talk. Furthermore, the proposed structure has a broadband tunability of 587 nm, which can be achieved by modulating the cavity air gap thickness. This structure enables the miniaturization of photonic integrated circuits and sensing applications.

Miniature tunable Airy beam optical meta-device

Tunable Airy beams with controllable propagation trajectories have sparked interest in various fields,such as optical manipulation and laser fabrication.Existing research approaches encounter challenges related to insufficient compactness and integration feasibility,or they require enhanced tunability to enable real-time dynamic manipulation of the propagation trajectory.In this work,we present a novel method that utilizes a dual metasurface system to surpass these limitations,significantly enhancing the practical potential of the Airy beam.Our approach involves encoding a cubic phase profile and two off-axis Fresnel lens phase profiles across the two metasurfaces.The validity of the proposed strategy has been confirmed through simulation and experimental results.The proposed meta-device addresses the existing limitations and lays the foundation for broadening the applicability of Airy beams across diverse domains,encompassing light-sheet microscopy,laser fabrication,optical tweezers,etc.

Tunable superconducting resonators via on-chip control of local magnetic field

Superconducting microwave resonators play a pivotal role in superconducting quantum circuits.The ability to finetune their resonant frequencies provides enhanced control and flexibility.Here,we introduce a frequency-tunable superconducting coplanar waveguide resonator.By applying electrical currents through specifically designed ground wires,we achieve the generation and control of a localized magnetic field on the central line of the resonator,enabling continuous tuning of its resonant frequency.We demonstrate a frequency tuning range of 54.85 MHz in a 6.21-GHz resonator.This integrated and tunable resonator holds great potential as a dynamically tunable filter and as a key component of communication buses and memory elements in superconducting quantum computing.

Progress on two-dimensional ferrovalley materials

The electron's charge and spin degrees of freedom are at the core of modern electronic devices. With the in-depth investigation of two-dimensional materials, another degree of freedom, valley, has also attracted tremendous research interest. The intrinsic spontaneous valley polarization in two-dimensional magnetic systems, ferrovalley material, provides convenience for detecting and modulating the valley. In this review, we first introduce the development of valleytronics.Then, the valley polarization forms by the p-, d-, and f-orbit that are discussed. Following, we discuss the investigation progress of modulating the valley polarization of two-dimensional ferrovalley materials by multiple physical fields, such as electric, stacking mode, strain, and interface. Finally, we look forward to the future developments of valleytronics.

The Combined Effect of Spin-Transfer Torque and Voltage-Controlled Strain Gradient on Magnetic Domain-Wall Dynamics:Toward Tunable Spintronic Neuron

Magnetic domain wall(DW), as one of the promising information carriers in spintronic devices, have been widely investigated owing to its nonlinear dynamics and tunable properties. Here, we theoretically and numerically demonstrate the DW dynamics driven by the synergistic interaction between current-induced spin-transfer torque(STT) and voltage-controlled strain gradient(VCSG) in multiferroic heterostructures. Through electromechanical and micromagnetic simulations, we show that a desirable strain gradient can be created and it further modulates the equilibrium position and velocity of the current-driven DW motion. Meanwhile, an analytical Thiele's model is developed to describe the steady motion of DW and the analytical results are quite consistent with the simulation data. Finally, we find that this combination effect can be leveraged to design DW-based biological neurons where the synergistic interaction between STT and VCSG-driven DW motion as integrating and leaking motivates mimicking leaky-integrate-and-fire(LIF) and self-reset function. Importantly, the firing response of the LIF neuron can be efficiently modulated, facilitating the exploration of tunable activation function generators, which can further help improve the computational capability of the neuromorphic system.

Atomically Substitutional Engineering of Transition Metal Dichalcogenide Layers for Enhancing Tailored Properties and Superior Applications

Transition metal dichalcogenides(TMDs)are a promising class of layered materials in the post-graphene era,with extensive research attention due to their diverse alternative elements and fascinating semiconductor behavior.Binary MX2 layers with different metal and/or chalcogen elements have similar structural parameters but varied optoelectronic properties,providing opportunities for atomically substitutional engineering via partial alteration of metal or/and chalcogenide atoms to produce ternary or quaternary TMDs.The resulting multinary TMD layers still maintain structural integrity and homogeneity while achieving tunable(opto)electronic properties across a full range of composition with arbitrary ratios of introduced metal or chalcogen to original counterparts(0–100%).Atomic substitution in TMD layers offers new adjustable degrees of freedom for tailoring crystal phase,band alignment/structure,carrier density,and surface reactive activity,enabling novel and promising applications.This review comprehensively elaborates on atomically substitutional engineering in TMD layers,including theoretical foundations,synthetic strategies,tailored properties,and superior applications.The emerging type of ternary TMDs,Janus TMDs,is presented specifically to highlight their typical compounds,fabrication methods,and potential applications.Finally,opportunities and challenges for further development of multinary TMDs are envisioned to expedite the evolution of this pivotal field.

Non-volatile dynamically switchable color display via chalcogenide stepwise cavity resonators

High-resolution multi-color printing relies upon pixelated optical nanostructures,which is crucial to promote color display by producing nonbleaching colors,yet requires simplicity in fabrication and dynamic switching.Antimony trisulfide(Sb_(2)S_(3))is a newly rising chalcogenide material that possesses prompt and significant transition of its optical characteristics in the visible region between amorphous and crystalline phases,which holds the key to color-varying devices.Herein,we proposed a dynamically switchable color printing method using Sb_(2)S_(3)-based stepwise pixelated Fabry-Pérot(FP)cavities with various cavity lengths.The device was fabricated by employing a direct laser patterning that is a less timeconsuming,more approachable,and low-cost technique.As switching the state of Sb_(2)S_(3) between amorphous and crystalline,the multi-color of stepwise pixelated FP cavities can be actively changed.The color variation is due to the profound change in the refractive index of Sb_(2)S_(3) over the visible spectrum during its phase transition.Moreover,we directly fabricated sub-50 nm nano-grating on ultrathin Sb_(2)S_(3) laminate via microsphere 800-nm femtosecond laser irradiation in far field.The minimum feature size can be further decreased down to~45 nm(λ/17)by varying the thickness of Sb_(2)S_(3) film.Ultrafast switchable Sb_(2)S_(3) photonic devices can take one step toward the next generation of inkless erasable papers or displays and enable information encryption,camouflaging surfaces,anticounterfeiting,etc.Importantly,our work explores the prospects of rapid and rewritable fabrication of periodic structures with nano-scale resolution and can serve as a guideline for further development of chalcogenide-based photonics components.

Microstructure and bidirectional dielectric tunability behaviour of Nd^(3+)-doped KSr_(2)Nb_(5)O_(15) lead-free ceramics

The luminescence modulation behaviour under the in-situ electric field of rare-earth doped KSr_(2)Nb_(5)O_(15) ceramics opened a new door for the development of dielectric materials.Where the understanding the effect of rare-earth doping on the electric properties of host,especially at the similar doping concentration with luminescence researches(low concentrations)is very important for the exploration of mechanism of electric-luminescent coupling effect.In this work,Nd^(3+)-doped KSr_(2)Nb_(5)O_(15)(KSN-xNd)ceramics were synthesized,and the electric properties were investigated systematically.Our results suggest that the Nd^(3+) doping slightly increased the phase transition temperatures and improved the piezoelectric response of KSr_(2)Nb_(5)O_(15).Most importantly,a bidirectional dielectric tunability is revealed in KSr_(2)Nb_(5)O_(15).The dielectric permittivity can be adjusted by the DC electric bias,with tunability ranging from12.3% to 21.9%.The related mechanism and relationship between the bidirectional dielectric tunability and ferroelectricity are revealed by temperature-dependent dielectric and ferroelectric characterization.The researches of electric properties and bidirectional dielectric tunability of KSN-based ceramics paved the way to further exploration of electric-luminescent coupling mechanism.

High OSNR and simple configuration dual-wavelength fiber laser with wide tunability in S＋C＋L band

A simple configuration dual-wavelength fiber laser,by combining the first-order Brillouin laser and the residual pump laser,is proposed and experimentally demonstrated.A 1 km long single-mode fiber is used as the stimulated Brillouin scattering gain medium pumped by a narrow linewidth tunable laser source（TLS）.Through simply adjusting the TLS output power,power-equalized dual-wavelength lasing can be achieved with a high optical signal to noise ratio（OSNR） of 〉80 d B.With the good tunability of the TLS,the dual-wavelength fiber laser has a tunable range of -130 nm,and simultaneously the beat frequency of the two lasing wavelengths can be tuned from 10.1875 to 11.0815 GHz with the tunable range of 0.8940 GHz.The high stability of the dualwavelength operation is experimentally verified by the measured beat frequency fluctuation of ≤6 MHz in 1 h and power fluctuation of ≤0.03 d B in 2 h.The temporal characteristics of the fiber laser are also investigated experimentally.The fiber laser will find good applications in fiber sensing and microwave photonics areas.

Radio-frequency arbitrary waveform generation based on dispersion compensated tunable optoelectronic oscillator with ultra-wide tunability

Photonic generation of radio-frequency（RF） arbitrary microwave waveform with ultra-wide frequency tunable range based on a dispersion compensated optoelectronic oscillator（OEO） is proposed and experimentally demonstrated. Dispersion compensation scheme and specially designed fiber Bragg grating（FBG）-based Fabry-Perot（F-P） filters are employed in the OEO loop to realize a frequency tunable range of 3.5-45.4 GHz. An optimization process provided by the combination of an erbium-doped fiber amplifier（EDFA）and FBG is employed to improve the signal-to-noise ratio（SNR） of final RF signals. The generation of linearfrequency and phase-coded microwave waveforms, with a tunable carrier frequency ranging from 4 to 45 GHz and tuned chirping bandwidths or code rates, is experimentally demonstrated.

Wavelength-tunable organic semiconductor lasers based on elastic distributed feedback gratings

Wavelength-tunable organic semiconductor lasers based on mechanically stretchable polydimethylsiloxane (PDMS) gratings were developed. The intrinsic stretchability of PDMS was explored to modulate the period of the distributed feedback gratings for fine tuning the lasing wavelength. Notably, elastic lasers based on three typical light-emitting molecules show com-parable lasing threshold values analogous to rigid devices and a continuous wavelength tunability of about 10 nm by mechanic-al stretching. In addition, the stretchability provides a simple solution for dynamically tuning the lasing wavelength in a spec-tral range that is challenging to achieve for inorganic counterparts. Our work has provided a simple and efficient method of fab-ricating tunable organic lasers that depend on stretchable distributed feedback gratings, demonstrating a significant step in the advancement of flexible organic optoelectronic devices.

CNTFET Based Fully Differential First Order All Pass Filter

A novel,carbon nanotubefield effect transistor(CNTFET)based fully differentialfirst order all passfilter(FDFAPF)circuit configuration is presented.The FDFAPF uses CNTFET based negative transconductors(NTs)and positive transconductors(PTs)in its realization.The proposed circuit topology employs two PTs,two NTs,two resistors and one capacitor.All the passive components of the realized topology are grounded.Active only fully differentialfirst order all passfilter(AO-FDFAPF)topology is also derived from the proposed FDFAPF.The electronic tunability of the AO-FDFAPF is obtained by controlling the employed CNTFET based varactor.A tunabilty of pole frequency in the range of 10.5 to 26 GHz is obtained.Both the circuits are potential candidates for high frequency fully differential analog signal processing applications.As compared to prior state-of-the-art works,both the realized topologies have achieved highest pole frequency and lowest power dissipation.Moreover,they utilize compact circuit structures and suitable for low voltage applications.Moreover,both topologies work equally well in the deep submicron.The proposedfilters are analyzed and verified through HPSPICE simulations by utilizing Stanford CNTFET model at 16 nm technology node.It is observed that the proposed circuit simulation outcomes verify the theory.

Engineering HOF‑Based Mixed‑Matrix Membranes for Efficient CO_(2) Separation

Hydrogen-bonded organic frameworks(HOFs)have emerged as a new class of crystalline porous materials,and their application in membrane technology needs to be explored.Herein,for the first time,we demonstrated the utilization of HOF-based mixed-matrix membrane for CO_(2) separation.HOF-21,a unique metallo-hydrogen-bonded organic framework material,was designed and processed into nanofillers via amine modulator,uniformly dispersing with Pebax polymer.Featured with the mix-bonded framework,HOF-21 possessed moderate pore size of 0.35 nm and displayed excellent stability under humid feed gas.The chemical functions of multiple binding sites and continuous hydrogen-bonded network jointly facilitated the mass transport of CO_(2).The resulting HOF-21 mixed-matrix membrane exhibited a permeability above 750 Barrer,a selectivity of~40 for CO_(2)/CH_(4) and~60 for CO_(2)/N_(2),surpassing the 2008 Robeson upper bound.This work enlarges the family of mixed-matrix membranes and lays the foundation for HOF membrane development.

Fibrous MXene Aerogels with Tunable Pore of Contaminated Seawater

The seawater desalination based on solardriven interfacial evaporation has emerged as a promising technique to alleviate the global crisis on freshwater shortage.However,achieving high desalination performance on actual,oil-contaminated seawater remains a critical challenge,because the transport channels and evaporation interfaces of the current solar evaporators are easily blocked by the oil slicks,resulting in undermined evaporation rate and conversion efficiency.Herein,we propose a facile strategy for fabricating a modularized solar evaporator based on flexible MXene aerogels with arbitrarily tunable,highly ordered cellular/lamellar pore structures for high-efficiency oil interception and desalination.The core design is the creation of 1D fibrous MXenes with sufficiently large aspect ratios,whose superior flexibility and plentiful link forms lay the basis for controllable 3D assembly into more complicated pore structures.The cellular pore structure is responsible for effective contaminants rejection due to the multi-sieving effect achieved by the omnipresent,isotropic wall apertures together with underwater superhydrophobicity,while the lamellar pore structure is favorable for rapid evaporation due to the presence of continuous,large-area evaporation channels.The modularized solar evaporator delivers the best evaporation rate(1.48 kg m-2h-1)and conversion efficiency(92.08%)among all MXene-based desalination materials on oil-contaminated seawater.