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Thin-film lithium niobate on insulator (LNOI) has recently emerged as a promising platform for high-speed optical communication devices. For practical applications, an efficient, polarization-insensitive, misalignment-tolerant and broadband fiber-to-chip optical coupler is necessary. In this paper, we present a fiber-to-chip edge coupler based on trident spot-size convertor (SSC). Experiment shows 1.18/1.10 dB per facet low loss at 1550 nm for TE/TM polarization respectively. A relatively large alignment tolerance (AT) has also been demonstrated. Over a broadband wavelength range from 1490 nm ~ 1640 nm, the edge coupler exhibits a maximum loss of 1.30 dB, a wavelength dependent loss (WDL) of 0.23 dB for TE mode and a polarization dependent loss (PDL) of 0.33 dB when coupled to a single mode fiber (SMF) with a mode field diameter (MFD) of ~6 μm.

We propose the realization of exceptional points (EP) at bound states in the continuum (BIC), with two coupled strips, made of an electron-beam resist and patterned on the thin film photonic integrated platform, which makes possible etchless photonics integrated circuits (PIC). The loss rate of the EP can be significantly decreased through merging the BIC peaks in the dual-BIC scheme. The orthogonality of the eigenvectors is retrieved for evaluating the Hermitian orthogonal eigenvectors and the non-Hermitian EP features. We also find that engineering the dimension of the dual-BIC scheme enables a transition between the coalesced eigenvectors in the EP and the orthogonal eigenvectors in the Hermitian system. This work is of great significance for the exploration on BIC-based directional coupling with ultralow-loss phase matching conditions, special coupling conditions of EPs and BICs with coupled quasi-BIC systems, dynamical EP encircling, and EP topology, in PICs.

The efficacy of acupuncture combined with percutaneous kyphoplasty (PKP) or percutaneous vertebroplasty (PVP) in the treatment of osteoporotic vertebral compression fracture is systematically evaluated. The clinical trials of acupuncture combined with PKP or PVP in the treatment of osteoporotic vertebral compression fracture published before July 2021 are searched in databases of CNKI, WF, VIP, CBM, PubMed, Cochrane Library, and Embase. The information of included studies is extracted, and the quality is assessed by two independent researchers. The meta-analysis is performed by using RevMan 5.3 software. A total of 9 trials are included, involving 851 patients. The experimental results show that the therapeutic effect of acupuncture combined with PKP/PVP in the treatment of osteoporotic vertebral compression fracture (OVCF) is superior to that of PKP/PVP alone, and both the VAS score and ODI score of PKP/PVP combined with ordinary acupuncture or silver needle acupuncture are better than those of the control group one month after the operation. The effect of ordinary acupuncture combined with PKP/PVP on the increase of bone mineral density is better than that of the control group. Acupuncture combined with PKP/PVP in the treatment of osteoporotic vertebral compression fracture has better efficacy than PKP/PVP, and it can effectively relieve patients’ pain, improve bone density, and improve the quality of life.

Euryale ferox, which belongs to the family of Nymphaeaceae, has been widely distributed in China, India, Korea, and Japan. The seeds of E. ferox (EFS) have been categorized as superior food for 2000 years in China, based on its abundant nutrients including polysaccharides, polyphenols, sesquineolignans, tocopherols, cyclic dipeptides, glucosylsterols, cerebrosides, and triterpenoids. These constituents exert multiple pharmacological effects, such as antioxidant, hypoglycemic, cardioprotective, antibacterial, anticancer, antidepression, and hepatoprotective properties. There are very few summarized reports on E. ferox, albeit with its high nutritional value and beneficial activities. Therefore, we collected the reported literatures (since 1980), medical classics, databases, and pharmacopeia of E. ferox, and summarized the botanical classification, traditional uses, phytochemicals, and pharmacological effects of E. ferox, which will provide new insights for the further research and development of EFS-derived functional products.

In the last two decades, bulk, homoepitaxial, and heteroepitaxial growth of silicon carbide (SiC) has witnessed many advances, giving rise to electronic devices widely used in high-power and high-frequency applications. Recent research has revealed that SiC also exhibits unique optical properties that can be utilized for novel photonic devices. SiC is a transparent material from the UV to the infrared, possess nonlinear optical properties from the visible to the mid-infrared and it is a meta-material in the mid-infrared range. SiC fluorescence due to color centers can be associated with single photon emitters and can be used as spin qubits for quantum computation and communication networks and quantum sensing. This unique combination of excellent electronic, photonic and spintronic properties has prompted research to develop novel devices and sensors in the quantum technology domain. In this perspective, we highlight progress, current trends and prospects of SiC science and technology underpinning the development of classical and quantum photonic devices. Specifically, we lay out the main steps recently undertaken to achieve high quality photonic components, and outline some of the current challenges SiC faces to establish its relevance as a viable photonic technology. We will also focus on its unique potential to bridge the gap between classical and quantum photonics, and to technologically advance quantum sensing applications. We will finally provide an outlook on possible alternative applications where photonics, electronics, and spintronics could merge.

International audience; Herein, the grown-into-glass (GIG) CsPbBr 3 :Ln 3+ (Ln = La, Lu) nanocrystals (NCs) are designed and fabrictaed using an in situ nanocrystallization method. It is shown that a substitution of Pb 2+ sites with Ln 3+ ions leads to a blueshift of emission position induced by an increase of the bandgap of CsPbBr 3. Additionally, the GIG-samples are revealed to feature excellent photoluminescent (PL) properties after being immersed respectively in water for 300 days at room temperature, boiling water for 12 h, and corrosive environments for 24 h, as well as recoverable PL intensity either after several cycles of heat-cooling experiments or after being continuously exposed to a 405 nm laser irradiation. Besides, a spontaneous enhancement of 20-25% of emission intensity during the 1-2.5 hours' stage of a 405 nm laser irradiation, attributed to the radiative recombination of charge carriers that can be de-trapped from trapping levels upon the laser light irradiation and that then spontaneously reinforces the emission intensity, is observed in the GIG-CsPbBr 3 :Ln 3+ NCs. Finally, a white light-emitting prototype, with a CIE chromaticity coordinate at (0.4110, 0.3706), a color rendering index of 89 and a correlated color temperature of 3363 K is realized by combining the GIG-CsPbBr 3 NCs, YAG:Ce and CaWO4:Eu phosphors.

Schizophrenia is a polygenetic disease, the heterogeneity of which is likely complicated by epigenetic modifications yet to be elucidated. Here, we performed transcriptomic analysis of peripheral blood RNA from monozygotic twins discordant for schizophrenia and identified a schizophrenia-associated down-regulated microRNA, miR-501-3p. We showed that the loss of miR-501-3p in germline knockout (KO) male mice resulted in dendritic structure defects, glutamatergic transmission enhancement, and sociability, memory, and sensorimotor gating disruptions, which were attenuated when miR-501 expression was conditionally restored in the nervous system. Combining the results of proteomic analyses with the known genes linked to schizophrenia revealed that metabotropic glutamate receptor 5 (mGluR5) was one of the miR-501-3p targets and was elevated in vivo upon loss of miR-501. Treatment with the mGluR5 negative allosteric modulator 3-2((-methyl-4-thiazolyl) ethynyl) pyridine or the N -methyl- d -aspartate receptor antagonist 2-amino-5-phosphonopentanoic acid ameliorated the deficits observed in Mir501 -KO mice. The epigenetic and pathophysiological mechanism that links miR-501-3p to the modulation of glutamatergic transmission provides etiological implications for schizophrenia.

Silicon carbide (SiC), containing various intrinsic color centers, is a highly promising optical materials for making monolithic quantum integrated photonic circuits, by combining the single-photon sources with the integrated photonic components in SiC integrated platforms. In this work, we, for the first time, propose compact, efficient and broadband polarization-independent 12 and 22 multimode interference based beam splitters and Mach-Zehnder interferometers (MZI) in SiC integrated platforms for single-photon manipulation. We experimentally demonstrate that these devices exhibit excellent performances. The 12 beam splitter has low average loss of 100 nm. The 22 beam splitter has low loss of 70 nm. The MZI exhibits high transmission efficiency, with a high classical visibility of 98.3% and 97.6% and a high quantum visibility of 99.0% and 98.7%, for the TE and TM polarized light and photons, respectively.

In this letter, a capacitor-splitting switching algorithm for successive approximation register (SAR) analog-to-digital converters is proposed. To achieve low power, the hybrid switching scheme is involved. The monotonic switching technique is used during the last bit cycle; for other bit cycles except the first one, the switching is based on MSB and the former determined bit. Besides, the common-mode voltage remains constant during the entire bit cycles except the last one. In addition, the proposed capacitor-splitting switching process is easily performed, relaxing the design complexity of the SAR control logic. As a result, the proposed switching scheme is a better trade-off among energy-efficiency, common-mode voltage variation, and logic complexity.

We investigate single-cycle terahertz (THz) field-induced nonlinear absorption in doped silicon carbide. We find that the nonlinear response is ultrafast, and we observe up to 20% reduction of transmission of single THz pulses at peak field strengths of 280 kV/cm. We model the field and temperature dependence of the nonlinear response by a finite-difference time-domain simulation that incorporates the temporally nonlocal nonlinear conductivity of the silicon carbide. Nonlinear two-dimensional THz spectroscopy reveals that the nonlinear absorption has an ultrafast subpicosecond recovery time, with contributions from both sum-frequency generation and four-wave mixing, in the form of a photon-echo signal. The ultrafast nonlinearity with its equally fast recovery time makes silicon carbide an interesting candidate material for extremely fast nonlinear THz modulators.

The polarization beam splitter is a key component for polarization manipulation in photonic integrated circuits, but it is challenging to design for low-refractive-index optical materials, due to the low birefringence of the waveguides. We propose what we believe is a novel compact vertical-dual-slot waveguide-based coupling scheme for silicon carbide, enabling efficient low-birefringence polarization splitting by extensively modulating the transverse-magnetic mode distribution. We numerically and experimentally demonstrate the device in the 4H-silicon-carbide-on-insulator integrated platform, with a small footprint of 2 . 2 μm × 15 μm . The device, easy to fabricate via a single lithography process as other components on the chip, exhibits low insertion loss of < 0.71 dB and < 0.51 dB for the transverse-electric and transverse-magnetic polarized light, respectively, and polarization extinction ratio of > 13 dB , over 80 nm wavelength range.

4H-silicon carbide (SiC) integrated platforms have shown great potential in quantum and nonlinear photonics. However, the thermal properties of 4H-SiC waveguides are still unknown, even though thermo-optic effects can play an important role in fundamental measurements and practical applications. Herein, the thermo-optic effects in a 4H-SiC microring resonator are comprehensively studied, by means of both temperature tuning and self-heating. The thermo-optic coefficient and the ratio between the thermal absorption and the thermal diffusion of 4H-SiC are quantitatively measured to be4.21×10−5 K−14.21×10−5 K−1and14.9 K W−114.9 K W−1, respectively. Considering the acquired thermal properties, Kerr-nonlinearity-based dual-pump optical parametric oscillation (OPO) is experimentally achieved, and thus, it is demonstrated that broadband solitons can feasibly be generated through thermal tuning of 4H-SiC-on-insulator (SiCOI) microring resonators.

A comprehensive study of surface passivation effect on porous fluorescent silicon carbide (SiC) was carried out to elucidate the luminescence properties by temperature dependent photoluminescence (PL) measurement. The porous structures were prepared using an anodic oxidation etching method and passivated by atomic layer deposited (ALD) Al2O3 films. An impressive enhancement of PL intensity was observed in porous SiC with ALD Al2O3, especially at low temperatures. At temperatures below 150 K, two prominent PL emission peaks located at 517 nm and 650 nm were observed. The broad emission peak at 517 nm was attributed to originate from the surface states in the porous structures, which was supported by X-ray photoelectron spectra characterization. The emission peak at 650 nm is due to donor-acceptor-pairs (DAP) recombination via nitrogen donors and boron-related double D-centers in fluorescent SiC substrates. The results of the present work suggest that the ALD Al2O3 films can effectively suppress the non-radiative recombination for the porous structures on fluorescent SiC. In addition, we provide the evidence based on the low-temperature time-resolved PL that the mechanism behind the PL emission in porous structures is mainly related to the transitions via surface states.

We report an adhesive bonding approach using hydrogen silsesquioxane (HSQ) for silicon carbide (SiC) samples. A hybrid light-emitting diode (LED) was successfully fabricated through bonding a near-ultraviolet (NUV) LED grown on a commercial 4H-SiC substrate to a free-standing boron-nitrogen co-doped fluorescent-SiC epi-layer. The bonding quality and the electrical performance of the hybrid LED device were characterized. Neither voids nor defects were observed which indicates a good bonding quality of the proposed HSQ approach. A strong warm white emission was successfully obtained from the hybrid LED through an electric current injection of 30 mA. Funding Agencies|Innovation Fund Denmark [4106-00018B]

Silicon carbide (SiC) has large refractive index, wide bandgap, and strong material-based second- and third-order nonlinearities. Thus, in recent years, SiC has attracted considerable interests in quantum and nonlinear integrated photonics [1] – [3] with potential applications within broadband nonlinear light sources, including photon-pair sources, supercontinuum generation, and frequency combs. Optical parametric oscillation (OPO) is regarded as a promising way to produce new frequencies and an important tool in generation of coherent light sources, such as frequency combs. In this work, we experimentally demonstrate a Kerr-nonlinearity based dual continuous-wave(CW) pumped OPO in a 4H-SiC-on-insulator (4H-SiCOI) microring resonator.

Contribution to conference. Abstract from the 47thMicro and Nano Engineering Conference 2021, Turin,20/09/2021-23/09/2021.

This study investigated the fabrication of porous fluorescent SiC using a constant voltage-controlled anodic oxidation process. The application of a high, constant voltage resulted in a spatial distinction between the porous structures formed inside the fluorescent SiC substrates, due to the different etching rates at the terrace and the large step bunches. Large, dendritic porous structures were formed as the etching process continued and the porous layer thickened. Under the conditions of low hydrofluoric acid (HF) concentration, the uniformity of the dendritic porous structures through the entire porous layer was considerably improved compared with the conditions of high HF concentration. The resulting large uniform structure offered a sizable surface area, and promoted the penetration of atomic layer-deposited (ALD) Al2O3 films (ALD&ndash, Al2O3). The emission intensity in the porous fluorescent SiC was confirmed via photoluminescence (PL) measurements to be significantly improved by a factor of 128 after ALD passivation. With surface passivation, there was a clear blueshift in the emission wavelength, owing to the effective suppression of the non-radiative recombination rate in the porous structures. Furthermore, the spatial uniformity of emitted light was examined via PL mapping using three different excitation lasers, which resulted in the observation of uniform and distinctive emissions in the fluorescent SiC bulk and porous areas.

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We propose a silicon strip waveguide structure with alumina thin-film coating in-between the core and the cladding for group-velocity dispersion tailoring. By carefully designing the core dimension and the coating thickness, a spectrally-flattened near-zero anomalous group-velocity dispersion within the telecom spectral range is obtained, which is predicted to significantly broaden the bandwidth of four-wave mixing. We validate this by characterizing the wavelength conversion in a waveguide sample by atomic layer deposition technology, which to our best knowledge is the first experimental demonstration of the proposed structure. Due to the alumina thin-film coating, the wavelength conversion bandwidth reaches $58\sim\mathrm{nm}$, an increase by a factor of 1.3 compared to the corresponding structure without coating. This method can also be applied to other material platforms and applications requiring accurate group-velocity dispersion control.

AbstarctWe report for the first time a NUV light to white light conversion in a N-B co-doped 6H-SiC (fluorescent SiC) layer containing a hybrid structure. The surface of fluorescent SiC sample contains porous structures fabricated by anodic oxidation method. After passivation by 20 nm thick Al2O3, the photoluminescence intensity from the porous layer was significant enhanced by a factor of more than 12. Using a porous layer of moderate thickness (~10 µm), high-quality white light emission was realized by combining the independent emissions of blue-green emission from the porous layer and yellow emission from the bulk fluorescent SiC layer. A high color rendering index of 81.1 has been achieved. Photoluminescence spectra in porous layers fabricated in both commercial n-type and lab grown N-B co-doped 6H-SiC show two emission peaks centered approximately at 460 nm and 530 nm. Such blue-green emission phenomenon can be attributed to neutral oxygen vacancies and interface C-related surface defects generated dring anodic oxidation process. Porous fluorescent SiC can offer a great flexibility in color rendering by changing the thickness of porous layer and bulk fluorescent layer. Such a novel approach opens a new perspective for the development of high performance and rare-earth element free white light emitting materials.

Silver (Ag) nanoparticles (NPs) were deposited on the surface of bulk Nitrogen-Boron co-doped 6H silicon carbide (SiC), and the Ag NPs were observed to induce localized surface plasmons (LSP) resonances on the SiC substrate, which was expected to improve the internal quantum efficiency (IQE) of the emissions of the donor-acceptor pairs of the SiC substrate. Room-temperature measurements of photoluminescence (PL), transmittance and time-resolved photoluminescence (TRPL) were applied to characterize the LSP resonances. Through the finite-difference time-domain (FDTD) simulation of the LSP resonance of an Ag nanoparticle on the SiC substrate, it is predicted that when the diameter of the cross section on the xy plane of the Ag nanoparticle is greater than 225 nm, the LSP starts to enhance the PL intensity. With implementation of a 3rd order exponential decay fitting model to the TRPL results, it is found that the average minority carrier lifetime of the SiC substrate decreased.

In this paper, an efficient domain decomposition (DD) technique is originally introduced into the unconditionally stable Crank–Nicolson finite-difference time-domain (CN-FDTD) method for analyzing the extraordinary optical transmission (EOT) phenomenon of periodic metallic gratings. Being caused by the evanescent waves propagating along the metal-dielectric interface in the visible and near infrared regions, the dispersion of the considered metal in this case is expressed by the Drude model and solved with a generalized auxiliary differential equation (ADE) technique. The periodic boundary condition is applied to the two-dimensional periodic metallic grating structures due to their periodicity. Then, the standard unsplit-field perfectly matched layer is derived as the absorbing boundary condition for CN-FDTD based on the ADE concept. In DD structures, the whole computational domain is divided into several subdomains to reduce the matrix size and save calculating time. Furthermore, the reverse Cuthill–Mckee scheme for the lower–upper decomposition is applied to the subdomain matrices individually to improve the efficiency of DD-CN-FDTD. Finally, two numerical examples are calculated and the physical mechanism of the EOT phenomenon is investigated. The results from the proposed method demonstrate its accuracy and efficiency for the nanostructures.

In this paper, the Newmark-Beta algorithm is introduced into the finite-difference time-domain (FDTD) method in dispersion media, resulting in an unconditionally stable method for periodic metallic grating analysis. The proposed method eliminates the Courant-Friedrich-Levy constraint and improves the simulation efficiency for multiscale problems. The dispersion of the metal, which is caused by the evanescent waves propagating along the interface between the metal and dielectric materials in the visible and near-infrared regions, is solved with a generalized auxiliary differential equation (ADE) technique. The extraordinary optical transmission through a periodic metallic grating with different number and different size of the perpendicular bump is also investigated. Compared with the traditional ADE-FDTD method and ADE alternating-direction-implicit FDTD method, the results from the proposed method show its accuracy and efficiency.

We demonstrate enhanced four-wave mixing (FWM) in high-quality factor, high-confinement 4H-SiC microring resonators via continuous-wave FWM. With the large power buildup effect of the microring resonator, −21.7 dBFWM conversion efficiency is achieved with 79 mW pump power. Thanks to the strong light confinement in SiC-on-insulator (SiCOI) waveguides with submicrometer cross-sectional dimensions, a high nonlinear parameter wγ of 7.4±0.9 W−1 m−1 is obtained, from which the nonlinear refractive index (n2) of 4H-SiC is estimated to be (6.0±0.6)×10−19 m2/W at the telecom wavelengths. Besides, we are able to engineer the dispersion of a SiCOI waveguide to achieve 3 dB FWM conversion bandwidth of more than 130 nm. This work represents a step toward enabling all-optical signal processing functionalities using highly nonlinear SiCOI waveguides.

We experimentally demonstrate a photon-pair source, based on continuous-wave pumped spontaneous four-wave mixing in a silicon microring resonator, which efficiently generates photon pairs with high coincidence counts, high brightness, and high coincidence-to-accidental ratio at multiple resonance wavelengths matching a standard International Telecommunication Union (ITU) frequency grid. The signal-idler joint spectral intensity is measured with a very high resolution of 2pm over multiple wavelengths by an optical spectrum analyzer through probe-swept stimulated four-wave mixing, allowing an accurate quantification of the spectral correlation. Strong spectral correlation and uniform degree of quantum correlation are observed from the source, and the measured amount of spectral modes agrees well with that obtained by unheralded second-order correlation measurements.

Silicon carbide (SiC) exhibits promising material properties for nonlinear integrated optics. We report on a SiC-on-insulator platform based on crystalline 4H-SiC and demonstrate high-confinement SiC microring resonators with sub-micron waveguide cross-sectional dimensions. The Q factor of SiC microring resonators in such a sub-micron waveguide dimension is improved by a factor of six after surface roughness reduction by applying a wet oxidation process. We achieve a high Q factor (73,000) for such devices and show engineerable dispersion from normal to anomalous dispersion by controlling the waveguide cross-sectional dimension, which paves the way toward nonlinear applications in SiC microring resonators.

The excitation-dependent photoluminescence quantum yield (PL-QY) of strong n-type nitrogen-boron codoped 6H fluorescent silicon carbide (f-SiC) at room temperature is experimentally determined for the first time. The PL-QY measurements are realized by an integrating sphere system based on a classical two-measurement approach. In particular, in accordance to the difference between our in-lab setup and the standard setup of the two-measurement approach, we have technically modified the experimental design, the data processing algorithm, and the estimation of relative uncertainty. The measured highest PL-QY of f-SiC samples is found to reach above 30%. We compare the PL-QYs at a certain excitation power of all f-SiC samples by considering their intrinsic defect densities. Finally, the evolution of the excitation power-dependent PL-QY of f-SiC is attributed to both band-to-band and impurity-assisted Auger recombination.

A new boron-induced deeper acceptor level (D*-center) different from the D-center in nitrogen-boron co-doped 6H fluorescent silicon carbide (f-SiC) is revealed by measuring the temperature-dependent photoluminescence (PL). The D*-center is correlated to the dominate donor-acceptor-pair (DAP) recombination at low temperature ranges in f-SiC with a PL peak around 1.90 eV. A hole-trap with an energy level that lies between the D*-center and the D-center is predicted to exist in the f-SiC samples. A two-step thermal ionization involving the hole-trap is proposed to explain the evolution of both D*-center and D-center related temperature-dependent DAP recombination.

We generate correlated photon pairs in an all-pass silicon microring resonator using continuous-wave pumped spontaneous four-wave mixing and we characterize in detail the optical bistability in the non-classical single-photon regime. Special attention is given to the resonance-locked method by balancing the pump-induced heating and the active off-chip cooling, leading to stable operation of the photon-pair source. The maximal coincidence rate of 20.53 ± 0.34 Hz, maximal coincidence-to-accidental ratio of 654 ± 125, and minimal zero-delayed heralded second-order correlation of 0.14 ± 0.09 are achieved. The wavelengths of photon pairs remain unchanged at different pump power, indicating that our source is more compatible with the common communication systems than those using conventional on-resonance strategies, that tunes the pump wavelength. This work not only experimentally validates the nonclassical bistability behaviors, but also puts forward a simple method of pump-resonance matching for high-quality performance.

An intense and broadband photoluminescence emission is demonstrated in a bio-compatible film produced by thermal annealing of poly(acrylic acid) (PAA). The annealing process enhances the emission intensity from weakly emitting sub-luminophores of C–O and C=O functional groups by a factor of more than two orders of magnitude. The emission property can be sensitively tuned by the annealing temperature, duration, the PAA solution preparation conditions such as solvent type and solvent:PAA ratio. The strong luminescence is attributed to the formation of rigid molecular structure due to aggregation and crosslinking. FTIR measurements show that the aggregation and crosslinking processes subdue nonradiative recombination pathways.