High Quality Factor Research Articles

Exploring FSO link performance in varied atmospheric conditions to optimize 5G communication with a polarized quasi-diffuse transmitter

Abstract Free space optical (FSO) communication is an innovative technology that holds immense promise for numerous applications thanks to its high data transmission rates, rapid scalability, cost-effectiveness, superior security, and comprehensive capacity access techniques for Gbps data transmission. FSO communication relies on the Earth’s atmosphere as the medium, which introduces atmospheric disturbances that have driven the development of spatial diversity techniques aimed at enhancing the technology’s performance. Our proposed system employs a polarized quasi-diffused system with a fork as a spatial diversity scheme, which eliminates the need for multiple transmitters. We have developed a model that integrates both simulation designs to achieve optimal results. The proposed model has demonstrated excellent performance under various atmospheric turbulences, including rain, fog, and haze, exhibiting a very high maximum quality factor, improved received power, and better bit error rate (BER). Finally, we have obtained, analyzed, and extensively discussed the simulation results to provide a comprehensive understanding of the proposed model’s potential benefits. Our simulations show a maximum quality factor of 23 compared to existing models in much better, a 34 % increase in received power, and a 31 % decrease in BER compared to existing models. These results highlight the potential benefits of the proposed model for FSO communication systems.

Enhancing the quality factor of aerosol jet printed RF spiral inductors through gold electroplating

Aerosol jet printing (AJP) outperforms inkjet printing by significantly reducing printed line width, effectively addressing issues such as bulging and surface irregularities. This technology allows for line widths as narrow as 10–100 μm with high aspect ratios, making it well-suited for radio frequency (RF) applications. Consequently, AJP emerges as a valuable tool for direct printing in RF applications. Among conductive inks, silver nanoparticle (Ag-NP) ink is preferred for its straightforward direct printing process and lower sintering temperature requirements. However, the conductivity of printed Ag NP traces falls markedly below that of bulk silver due to significant porosity, limiting its use in RF applications where a high-quality factor is essential. The quality factor of an inductor, indicative of its efficiency in energy storage and release, inversely correlates with its resistance. Our research combines AJP with selective electroplating to reduce the resistance of printed traces, thereby enhancing the inductor’s quality factor for RF applications. We fabricated spiral inductors on alumina substrates using silver NP ink and subsequently applied selective gold electroplating to these traces. This approach led to a significant increase in the inductors’ quality factor, improving it by a factor of 3–5 in the RF frequency range of 100–700 MHz.

Graphene-integrated microring cavity for electronically controlled molecular fingerprinting

Microring cavities supporting whispering-gallery modes (WGMs) have an exceptionally high quality factor (Q) and a small mode volume, greatly improving the interaction between light and matter, which has attracted great attention in various microscale/nanoscale photonic devices and potential applications. Recently, two-dimensional van der Waals (vdW) materials such as graphene have emerged as a potential platform for next-generation biosensing by enabling the confinement of light fields at the nanoscale. Here, we propose what we believe to be a novel approach to achieve molecular fingerprint retrieval by integrating graphene into a microring cavity and conducting numerical simulations using the finite-difference time-domain (FDTD) method. The hybrid cavity exhibits high-quality WGMs with a high Q factor of up to 800. Moreover, the resonant wavelength can be electronically controlled through modulation of graphene’s Fermi level, enabling coverage of the entire free spectral range at infrared frequencies. By depositing a thin layer of biomolecular material (e.g., CBP) onto the surface of our hybrid cavity, we are able to accurately read out the absorption spectrum at multiple spectral points, thereby achieving broadband fingerprint retrieval for the targeted biomolecule. Our results pave the way for highly sensitive, chip-integrated, miniaturized, and electrically modulated infrared spectroscopy biosensing.

A filtering reconfigurable intelligent surface for interference-free wireless communications

The powerful capability of reconfigurable intelligent surfaces (RISs) in tailoring electromagnetic waves and fields has put them under the spotlight in wireless communications. However, the current designs are criticized due to their poor frequency selectivity, which hinders their applications in real-world scenarios where the spectrum is becoming increasingly congested. Here we propose a filtering RIS to feature sharp frequency-selecting and 2-bit phase-shifting properties. It permits the signals in a narrow bandwidth to transmit but rejects the out-of-band ones; meanwhile, the phase of the transmitted signals can be digitally controlled, enabling flexible manipulations of signal propagations. A prototype is designed, fabricated, and measured, and its high quality factor and phase-shifting characteristics are validated by scattering parameters and beam-steering phenomena. Further, we conduct a wireless communication experiment to illustrate the intriguing functions of the RIS. The filtering behavior enables the RIS to perform wireless signal manipulations with anti-interference ability, thus showing big potential to advance the development of next-generation wireless communications.

Magnetoelectric effect in a Metglas–langatate ring heterostructure for current sensing

The magnetoelectric (ME) effect was observed and investigated in a planar ring-type heterostructure containing mechanically coupled rings of magnetostrictive amorphous alloy Metglas and a piezoelectric single crystal langatate. The structure was excited by a circumferential ac magnetic field in the presence of a circumferential dc bias magnetic field. Due to the absence of demagnetization and the high acoustic quality factor of the langatate, a high ME field conversion coefficient of α E ≈ 53 V (Oe cm)−1 was obtained at the frequency 221 kHz of the fundamental radial acoustic resonance mode. The structure can be used as a non-contact ac or dc current sensor. The sensitivity of the structure to the ac current was 1.6 V A−1, whereas for the dc current it reached 4.2 V A−1.

High Performance Electrically‐Injected InGaN Microdisk Lasers through Simultaneous Enhancement of Optical Confinement and Overlap Factor

AbstractDespite the considerable research interest in InGaN‐based microdisk lasers, owing to their unique circular geometry distinct from vertical cavity surface‐emitting lasers (VCSEL) or edge‐emitting lasers, commercial products remain scant due to deficient performance under electrical injection. This study proposes an innovative method integrating a thin‐film configuration with a metallic undercut, significantly augmenting optical confinement, overlap factor, and thus lasing performance. This approach results in a diminished lasing threshold from 1500 to 670 Wcm−2 and a record high quality (Q) factor of 10100 under electrical injection. Strain relaxation in the metallic undercut, identified via scanning near‐field optical microscopy (SNOM), beneficially mitigates the Quantum Confined Stark Effect (QCSE), boosting the internal quantum efficiency of the laser. Furthermore, a beneficial blue‐shift in the emission spectrum aligns with the lasing peak, strengthening the Q factor. A tactfully implemented recessed top contact enables electrical injection lasing without optical performance compromise. The study provides invaluable insights for future microdisk laser technology advancements, potentially leading to specialized functionalities, including quantum optics, thereby opening new avenues for research and applications in this field.

Terahertz biosensor for amino acids upon all-dielectric metasurfaces with high-quality factor

Terahertz biosensor for amino acids upon all-dielectric metasurfaces with high-quality factor

Interface state-based bound states in continuum and below-continuum-resonance modes with high-Q factors in the rotational periodic system

Abstract In thispaper, we have introduced a new approach to calculate the orbital angular momentum (OAM) of bound states in the continuum (BICs) and below-continuum-resonance (BCR) modes in the rotational periodic system nested inside and outside by transforming the Bloch wave number from the translational periodic system. We extensively classify and study these BICs and BCR modes, which exhibit high-quality (high-Q) factors, in different regions relative to the interface of system. These BICs and BCR modes with high-Q factor have been studied in detail based on the distinctive structural parameters and scattering theory. Outcomes of this research break the periodic limitation of interface state-based BICs, and realize more and higher symmetry interface state-based BICs and BCR modes. Moreover, we can control the region that light captured by adjusting the frequency, and show that Q factor of BICs is more closely related to the ordinal number of rings and rotational symmetry number of the system.

Chiral photothermoelectric effect driven by high-Q quasi-bound states in the continuum

Bound states in continuum (BIC) have been proposed as a means to efficiently improve light-matter interactions in metasurfaces. While breaking the mirror symmetry of structure and developing BIC into a reachable and observable quasi-BIC, it is usually accompanied by the chiral phenomenon with high quality (Q) factor. Here, we report a spin-sensitive photodetector in the infrared (NIR) region comprising a silicon metasurface with chiral quasi-BIC, a silver layer, and a thermoelectric layer. A chiral quasi-BIC supported by a silicon metasurface can be realized under normal incidence. Based on finite element method simulations, a silicon metasurface with a silver layer shows a high Q-factor of 958.6 with a giant absorption circular dichroism of 0.83. Subsequently, we study the thermal performance of the chiral absorbers by using the heat transfer module of COMSOL. Combined with the thermoelectric material bismuth telluride, we calculate the differential photothermoelectric effects of the system under circular-polarized light irradiation. When the incident flux is 100 W cm−2, the output voltage under right-circular-polarization (left-circular-polarization) light reaches 0.59 mV (0.08 mV), which can be used for polarization detection. Therefore, our designed structure incorporating thermoelectricity broadens the applications of chiral BIC in sensors and detectors.

Chemical bond features and microwave dielectric properties of olivine-type LiMSiO4 (M = Ho, In) ceramics

Orthorhombic olivine-structured LiMSiO4 (M = Ho, In) ceramics were synthesised using the solid-state reaction. Promising microwave dielectric properties of εr = 10.04, τf = 23.3 ppm/°C and a high-quality factor (Q × f) of 11,415 GHz for LiHoSiO4 were obtained at 1050 °C, and εr = 7.78, τf = −46.8 ppm/°C and Q × f = 23,390 GHz for LiInSiO4 were achieved at 1140 °C. According to the bond valence result, Ho3+ presented a slightly compressed state but Li+ and Si4+ exhibited a strong rattling state in LiHoSiO4, which led to higher εr than the εtheo. The integrated effect of rattling cations (Li+ and In3+) and a compressed cation (Si4+) in LiInSiO4 resulted in a small positive deviation Δεr. The larger packing fraction of LiInSiO4 contributed to a higher Q × f than LiHoSiO4. The Si–O bond in both ceramics played a leading role in influencing the Q × f according to the Phillips−Van Vechten−Levine chemical bond theory.

High-Q silicon microring resonator with ultrathin sub-wavelength thicknesses for sensitive gas sensing

Microring resonators, due to their ability to enable robust strong light–matter interactions within their structures, have garnered substantial interest for their utility in sensing applications, particularly in the realm of gas detection. However, there is an inherent trade-off between a microring resonator's quality factor and confinement factor in the air, making it difficult to balance them. Here, we demonstrate a novel solution with a suspended nanomembrane silicon (SNS) microring resonator. This resonator has ultrathin sub-wavelength thicknesses (0.02–0.03λ), which breaks the trade-off, offering not only a high intrinsic quality factor of 6 × 105 but also an extraordinarily large confinement factor of ∼80% in the air at mid-infrared wavelengths. As a proof-of-concept demonstration, we applied the SNS microring resonator for CO2 gas sensing, exhibiting a sensitivity over 10 times higher than conventional silicon resonators and a large dynamic sensing range spanning from 0% to 100% with a high resolution of better than 4% and chemical specificity. By virtue of its excellent properties, the SNS microring resonator has the potential to open new possibilities for the development of unprecedented nanophotonic integrated circuits, with a broad range of applications in on-chip sensing scenarios.

All Dielectric High Q-Factor Metasurface Refractive Index Sensor Based on Dual Fano Resonances in THz Region

All Dielectric High Q-Factor Metasurface Refractive Index Sensor Based on Dual Fano Resonances in THz Region

Multiple toroidal dipole Fano resonances from quasi-bound states in the continuum in an all-dielectric metasurface

In this paper, a highly sensitive sensor consisting of a silicon nanorod and symmetric rings (SNSR) is presented. Theoretically, three Fano resonances with high Q-factors are excited in the near-infrared range by breaking the symmetry structure based on quasi-bound states in the continuum (Q-BICs). The electromagnetic near-field analysis confirms that the resonances are mainly controlled by toroidal dipole (TD) resonance. The structure is optimized by adjusting different geometrical parameters, and the maximum Q-factor of the Fano resonances can reach 7427. To evaluate the sensing performance of the structure, the sensitivity and the figure of merit (FOM) are calculated by adjusting the environmental refractive index: the maximum sensitivity of 474 nm/RIU and the maximum FOM of 3306 RIU-1. The SNSR can be fabricated by semiconductor-compatible processes, which is experimentally evaluated for changes in transmission spectra at different solution concentrations. The results show that the sensitivity and the Q-factor of the designed metasurface can reach 295 nm/RIU and 850, while the FOM can reach 235 RIU-1. Therefore, the metasurface of SNSR is characterized by high sensitivity and multi-wavelength sensing, which are current research hotspots in the field of optics and can be applied to biomedical sensing and multi-target detection.

Optimizing the quality factor of InP nanobeam cavities using atomic layer deposition

Photonic crystal nanobeam cavities are valued for their small mode volume, CMOS compatibility, and high coupling efficiency-crucial features for various low-power photonic applications and quantum information processing. However, despite their potential, nanobeam cavities often suffer from low quality factors due to fabrication imperfections that create surface states and optical absorption. In this work, we demonstrate InP nanobeam cavities with up to 140% higher quality factors by applying a coating of Al2O3 via atomic layer deposition to terminate dangling bonds and reduce surface absorption. Additionally, changing the deposition thickness allows precise tuning of the cavity mode wavelength without compromising the quality factor. This Al2O3 atomic layer deposition approach holds great promise for optimizing nanobeam cavities that are well-suited for integration with a wide range of photonic applications.

Frequency tunable magnetostatic wave filters with zero static power magnetic biasing circuitry

A single tunable filter simplifies complexity, reduces insertion loss, and minimizes size compared to frequency switchable filter banks commonly used for radio frequency (RF) band selection. Magnetostatic wave (MSW) filters stand out for their wide, continuous frequency tuning and high-quality factor. However, MSW filters employing electromagnets for tuning consume excessive power and space, unsuitable for consumer wireless applications. Here, we demonstrate miniature and high selectivity MSW tunable filters with zero static power consumption, occupying less than 2 cc. The center frequency is continuously tunable from 3.4 GHz to 11.1 GHz via current pulses of sub-millisecond duration applied to a small and nonvolatile magnetic bias assembly. This assembly is limited in the area over which it can achieve a large and uniform magnetic field, necessitating filters realized from small resonant cavities micromachined in thin films of Yttrium Iron Garnet. Filter insertion loss of 3.2 dB to 5.1 dB and out-of-band third order input intercept point greater than 41 dBm are achieved. The filter’s broad frequency range, compact size, low insertion loss, high out-of-band linearity, and zero static power consumption are essential for protecting RF transceivers from interference, thus facilitating their use in mobile applications like IoT and 6 G networks.

Combining Solution-Blowing and Melt-Blowing Techniques to Produce an Efficient Non-Woven Filter

New substances and particles appearing in the environment following technological development pose new challenges for separation methods. Moreover, the growing amount of waste also forces us to look for environmentally friendly solutions. One way to create filtration structures with the desired properties is to combine known techniques, thanks to which the advantages of one technique complement the deficiencies and disadvantages of another. Combining the melt-blowing and solution-blowing processes seems to be promising. Fibres created from melt-blowing will provide mechanical strength, while solution-blowing will allow the introduction of nanofibres into the structure with unique filtration and functional properties. Both methods enable working with biodegradable polymers, so the resulting filter can also be environmentally friendly after operation. Our research aimed to check whether combining two fibre production techniques (melt-blown and solution-blowing) is possible and how the joining method will affect the final product. We created a multilayer structure by placing a layer of solution-blowing nanofibres between melt-blown layers, and a mixed structure by simultaneous melt-blowing and solution-blowing. The created multilayer structure was characterised by high filtration efficiency and high-pressure drop. In contrast, the mixed structure achieved a high-quality factor and high mass of deposited droplets per 1 J of energy used for work.

Demonstration of high-impedance superconducting NbRe Dayem bridges

Here, we demonstrate superconducting Dayem-bridge weak-links made of different stoichiometric compositions of NbRe. Our devices possess a relatively high critical temperature, normal-state resistance, and kinetic inductance. In particular, the high kinetic inductance makes this material a good alternative to more conventional niobium-based superconductors (e.g., NbN or NbTiN) for the realization of superinductors and high-quality factor resonators, whereas the high normal-state resistance yields a large output voltage in superconducting switches and logic elements realized upon this compound. Moreover, out-of-plane critical magnetic fields exceeding 2 T ensure that possible applications requiring high magnetic fields can also be envisaged. Altogether, these features make this material appealing for a number of applications in the framework of quantum technologies.

Multiband highly sensitive metamaterial-based THz absorber for edible oil adulteration sensing

A terahertz (THz) wave technology is very appealing for applications in detection in biomedicine, biological spectroscopy, material characterization, detection, imaging, sensing, and other convenient applications. Metamaterials (MMs) are artificial structures that have structures in a regular periodic arrangement and don’t exist in nature. By utilizing a proposed terahertz metamaterial absorber, a broad spectrum of adulterated lubricants can be detected. It is an efficient detection process that enables the development of a THz detection approach by making use of the metamaterial as a sensor. The proposed terahertz absorber is analyzed and optimized using the CST Microwave Studio 2019 software. The article proposed a multiband THz metamaterial absorber with a unit size of 70 µm. According to the demonstrated results, we can achieve five narrow absorption peaks with perfect absorption within the frequency range between (0.2–4.2) Terahertz. Also, the result shows that, the average absorbance of 99.07% at the resonance frequencies of 0.56, 1.42, 2.676, 3.14, and 3.89 THz. The E (electric) and H (magnetic)-field distributions on the resonator at different resonance frequencies were also analyzed as well as. The recommended metamaterial absorber has a good sensing capability at different resonant frequencies, with refractive index sensitivities of 80 GHz/RIU, 240 GHz/RIU, 480 GHz/RIU, 480 GHz/RIU, and 520 GHz/RIU obtained by modifying the refractive index of the sample holder or the analytic layer, respectively. As a result, the proposed detector has a high refractive index sensitivity, high Q-factor, and high FOM, making it suitable for detecting oil adulteration.

Novel multi-hierarchical nanofiber aerogel for high efficient filtration of high-temperature flue gas

Fibrous air filtration materials are highly effective at capturing particulate matter (PM) from emissions. Yet, many commercially available filters are difficult to achieve high filtration efficiency for PM while maintaining low filtration resistance. Furthermore, the elevated temperatures (ranging from 100.0 to 250.0 °C) commonly associated with pollution sources necessitate stringent thermal resistance requirements for filtration materials. Here, a new strategy for the preparation of aerogels for high-temperature gas filtration is reported. Firstly, a unique “grooved and secondary pore” structure polyaryl thioether sulfone (GPASS) nanofibers are initially fabricated using a combination of “wet” electrostatic spinning and aqueous etching. And then, the oxidized GPPASS aerogel (O-GPPASS) can be obtained through simple acid and freeze-dried treatment. It is found that the as-prepared aerogel exhibits high filtration efficiency of 99.7 % for PM0.3, accompanied by low pressure drop of 17.2 Pa, and high quality factor (QF) of 0.362 Pa−1. Remarkably, after enduring high-temperature conditions of 330.0 °C for 4.0 h, the O-GPPASS aerogel still maintains an impressive filtration performance, with a 99.6 % efficiency and a pressure drop of 17.6 Pa for PM0.3 particles. It will well meet the needs of filter materials used in high temperature environments. This innovation is poised to supersede traditional high-temperature air filtration materials, paving the way for sustainable advancements in industrial applications.

High Q Ultra‐Low Threshold Lasing in Conjugated Polymer Blend Microspheres Promoted by FRET

AbstractConjugated polymer (CP) based microspheres of very high definition and outstanding photonic and luminescent properties are prepared by a technique based on slow solvent‐controlled diffusion into micelles formed by the surfactant cetyl(trimethyl)ammonium bromide (CTAB). Poly[(9,9‐di‐n‐octylfluorenyl‐2,7‐diyl)‐alt‐(benzo[2,1,3]thiadiazol‐4,8‐diyl)] (F8BT) and mixtures of F8BT with poly[2‐methoxy‐5‐(2’‐ethylhexyloxy)‐1,4‐phenylene vinylene (MEH‐PPV) are used for this purpose. Microspheres with diameters between 1 and 10 µm are obtained and structural characterization by AFM and SEM demonstrate good sphericity and low surface roughness. Correspondingly, spontaneous emission of the spheres exhibits Mie resonances of high quality factor (Q > 1800), appropriately reproduced employing standard Mie theory. Upon pumping the microspheres with a pulsed Nd:YAG laser operating at 355 nm lasing at low threshold fluences (≈ 4 µJ cm−2) is obtained with instrumentally limited linewidths corresponding to Q > 18000. Lasing in microspheres composed of blends of both CPs coupled by Förster resonant energy transfer (FRET), on the other hand, is observed at extremely low threshold fluences down to ≈ 0.5 µJ cm−2. Spherical structures based on appropriate blends of CPs are therefore promising candidates in the search for low‐threshold organic microlasers excited by light‐emitting diodes or diode lasers or for ultrasensitive optical sensing.