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Silicon carbide (SiC) photonic integrated platform has attracted significant research interest for on-chip optical applications, owing to its exceptional optical properties such as a broad transparency window, high refractive index, and strong nonlinearity. Among the various types of SiC, amorphous SiC (a-SiC) has particularly emerged as an accessible choice for forming thin-film SiC-on-insulator (SiCOI) stacks, demonstrating promising capabilities for wafer-scale photonic applications. In this work, we prepare three a-SiCOI samples using the plasma-enhanced chemical vapor deposition, with different refractive indices. We fabricate optical waveguides, conduct four-wave mixing measurements, and characterize the nonlinear refractive index in these samples. Our findings reveal that an increase in the refractive index of a-SiC leads to a corresponding increase in the nonlinear refractive index, which is comparable to that of silicon. Hence, a-SiC offers an approach to develop a SiC platform with a wider bandgap than that of silicon, minimizing two-photon absorption while also providing a higher refractive index and stronger nonlinearity compared to crystalline SiC.
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Polarization manipulation and management are important for 4H-silicon carbide (SiC) integrated photonics, as 4H-SiC has material-based birefringent properties. In this Letter, we propose a low-birefringence polarization beam splitter (PBS) based on asymmetric directional coupler (ADC) mode converters with overall high performances. We numerically and experimentally demonstrate the ADC mode conversion based PBS on a 4H-SiC chip. The experimental results show that the device exhibits high transmittance of -0.6 dB and -1.3 dB for the transverse-electric (TE) and transverse-magnetic (TM) polarized light, respectively, and broad operational bandwidth over 130 nm. The polarization extinction ratio of >25 dB and >17 dB covering the whole C band for the TE and TM polarized light, respectively, and an ultra-large polarization extinction ratio of >32 dB for both polarizations at approximately 1560 nm are achieved.
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Euryale ferox Salisb. (prickly water lily) is the only extent of the genus Euryale that 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 their 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 literature (since 1980), medical classics, database, 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 further research and development of EFS-derived functional products.
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Medicina Tradicional Chinesa , Nymphaeaceae , Nymphaeaceae/química , Antioxidantes/farmacologia , Tocoferóis , Compostos Fitoquímicos/farmacologia , Extratos Vegetais/farmacologia , Extratos Vegetais/químicaRESUMO
The non-Mendelian features of phenotypic variations within monozygotic twins are likely complicated by environmental modifiers of genetic effects that have yet to be elucidated. Here, we performed methylome and genome analyses of blood DNA from psychiatric disorder-discordant monozygotic twins to study how allele-specific methylation (ASM) mediates phenotypic variations. We identified that thousands of genetic variants with ASM imbalances exhibit phenotypic variation-associated switching at regulatory loci. These ASMs have plausible causal associations with psychiatric disorders through effects on interactions between transcription factors, DNA methylations, and other epigenomic markers and then contribute to dysregulated gene expression, which eventually increases disease susceptibility. Moreover, we also experimentally validated the model that the rs4854158 alternative C allele at an ASM switching regulatory locus of EIPR1 encoding endosome-associated recycling protein-interacting protein 1, is associated with demethylation and higher RNA expression and shows lower TF binding affinities in unaffected controls. An epigenetic ASM switching induces C allele hypermethylation and then recruits repressive Polycomb repressive complex 2 (PRC2), reinforces trimethylation of lysine 27 on histone 3 and inhibits its transcriptional activity, thus leading to downregulation of EIPR1 in schizophrenia. Moreover, disruption of rs4854158 induces gain of EIPR1 function and promotes neural development and vesicle trafficking. Our study provides a powerful framework for identifying regulatory risk variants and contributes to our understanding of the interplay between genetic and epigenetic variants in mediating psychiatric disorder susceptibility.
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Metilação de DNA , Proteínas Nucleares/genética , Esquizofrenia , Alelos , Metilação de DNA/genética , Epigênese Genética/genética , Humanos , Regiões Promotoras Genéticas , Esquizofrenia/genética , Gêmeos Monozigóticos/genéticaRESUMO
Schizophrenia is a complex genetic disorder, the non-Mendelian features of which are likely complicated by epigenetic factors yet to be elucidated. Here, we performed RNA sequencing of peripheral blood RNA from monozygotic twins discordant for schizophrenia, and identified a schizophrenia-associated upregulated long noncoding RNA (lncRNA, AC006129.1) that participates in the inflammatory response by enhancing SOCS3 and CASP1 expression in schizophrenia patients and further validated this finding in AC006129.1-overexpressing mice showing schizophrenia-related abnormal behaviors. We find that AC006129.1 binds to the promoter region of the transcriptional repressor Capicua (CIC), facilitates the interactions of DNA methyltransferases with the CIC promoter, and promotes DNA methylation-mediated CIC downregulation, thereby ameliorating CIC-induced SOCS3 and CASP1 repression. Derepression of SOCS3 enhances the anti-inflammatory response by inhibiting JAK/STAT-signaling activation. Our findings reveal an epigenetic mechanism with etiological and therapeutic implications for schizophrenia.
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Metilação de DNA , RNA Longo não Codificante , Esquizofrenia , Proteína 3 Supressora da Sinalização de Citocinas , Animais , Regulação para Baixo , Humanos , Inflamação , Camundongos , RNA Longo não Codificante/genética , Esquizofrenia/genética , Proteína 3 Supressora da Sinalização de Citocinas/genética , Proteína 3 Supressora da Sinalização de Citocinas/metabolismoRESUMO
Waveguide taper, a key component in the photonic integrated circuit (PIC), enables on-chip mode conversion, but large-footprint tapers are detrimental to the PIC, which desires compact and efficient devices. Polarization sensitivity also limits the tapers in the applications involving orthogonal modes. In this work, we design an efficient polarization-insensitive ultra-short MMI-based waveguide taper, through the mode spreading principle and the self-image principle. The proposed taper is 26.3 µm long, one order of magnitude shorter than the standard linear taper. We fabricate the taper, and experimentally demonstrate that it exhibits a high transmission efficiency of â¼70% and a wide 1 dB bandwidth of >54nm, for both TE and TM polarizations.
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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.
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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.
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This paper presents a method to identify the axial location of targets in an optical scanning holography (OSH) system. By combining time reversal (TR) technique with the multiple signal classification (MUSIC) method in OSH, axial location can be detected with high resolution. Both simulation and experimental work have been carried out to verify the feasibility of the proposed work.
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In this Letter, we propose a new method for auto-focusing and reconstruction without defocus noise in optical scanning holography. By using a connected domain (CD) to calculate the area of different domains, which are labeled by a connected component, the focus distance can be found via the smallest area of each CD. Meanwhile, the sectional images without defocus noise can also be reconstructed based on the labeled domains. The effectiveness of this method has been verified with a simulation and experiments.
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We derive from Maxwell's equations full-vectorial nonlinear propagation equations of four-wave mixing valid in straight semiconductor-on-insulator waveguides. Special attention is given to the resulting effective mode area, which takes a convenient form known from studies in photonic crystal fibers, but has not been introduced in the context of integrated waveguides. We show that the difference between our full-vectorial effective mode area and the scalar equivalent often referred to in the literature may lead to mistakes when evaluating the nonlinear refractive index and optimizing designs of new waveguides. We verify the results of our derivation by comparing it to experimental measurements in a silicon-on-insulator waveguide, taking tolerances on fabrication parameters into account.
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We report the design and fabrication of a compact multi-core fiber fan-in/fan-out using a grating coupler array on the SOI platform. The grating couplers are fully-etched, enabling the whole circuit to be fabricated in a single lithography and etching step. Thanks to the apodized design for the grating couplers and the introduction of an aluminum reflective mirror, a highest coupling efficiency of -3.8 dB with 3 dB coupling bandwidth of 48 nm and 1.5 dB bandwidth covering the whole C band, together with crosstalk lower than -32 dB are demonstrated.
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Random phase masks can transform the defocus noise into a speckle-like pattern in optical scanning holography (OSH). In this Letter, we presented a speckle reduction based on combined frame difference and connected component method in a random phase-coded OSH system. The image quality of the reconstructed sections is improved with better visibility.
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We propose and demonstrate all-optical mode-selective wavelength conversion in a silicon waveguide. The mode-selective wavelength conversion relies on strong four-wave mixing when pump and signal light are on the same spatial mode, while weak four-wave mixing is obtained between different modes due to phase mismatch. A two-mode division multiplexing circuit with tapered directional coupler based (de)multiplexers and a multimode waveguide is designed and fabricated for this application. Experimental results show clear eye-diagrams and moderate power penalties for the wavelength conversion of both modes.
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Modelos Químicos , Espalhamento de Radiação , Silício/química , Ressonância de Plasmônio de Superfície/instrumentação , Ressonância de Plasmônio de Superfície/métodos , Simulação por Computador , Desenho Assistido por Computador , Desenho de Equipamento , Análise de Falha de Equipamento , LuzRESUMO
Polarization insensitive wavelength conversion of a 40 Gb/s non-return-to-zero (NRZ) differential phase-shift keying (DPSK) data signal is demonstrated using four-wave mixing (FWM) in a silicon nanowire circuit. Polarization independence is achieved using a diversity circuit based on polarization rotators and splitters, which is fabricated by a simple process on the silicon-on-insulator (SOI) platform. Error-free performance is achieved with only 0.5 dB of power penalty compared to the wavelength conversion of a signal with well optimized input polarization. Additionally, data transmission over 161 km standard single-mode fiber (SSMF) is demonstrated at 40 Gb/s using optical phase conjugation (OPC) in the proposed circuit.
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Ultra-wide band signal generation using a silicon microring resonator tuned to an NRZ-DPSK modulated optical carrier is proposed and demonstrated. The scheme is shown to enable the generation of UWB signals with switchable polarity and tunable bandwidth by simply tuning the coupling regions of the microring resonator. Monocycle pulses with both negative and positive polarities are successfully synthesized experimentally.
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We design and fabricate an ultrahigh coupling efficiency (CE) fully etched apodized grating coupler on the silicon-on-insulator (SOI) platform using subwavelength photonic crystals and bonded aluminum mirror. Fabrication error sensitivity and coupling angle dependence are experimentally investigated. A record ultrahigh CE of -0.58 dB with a 3 dB bandwidth of 71 nm and low back reflection are demonstrated.
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Implementing stimulated Raman scattering in a low-loss microresonator could lead to Raman lasing. Here, we report the demonstration of an efficient Raman laser with >50% power efficiency in an integrated silicon carbide platform for the first time. By fine-tuning the free spectral range (FSR) of 43 µm-radius silicon carbide microresonators, the Stokes resonance corresponding to the dominant Raman shift of 777 cm-1 (23.3 THz) is aligned to the center of the Raman gain spectrum, resulting in a low power threshold of 2.5 mW. The peak Raman gain coefficient is estimated to be (0.75 ± 0.15) cm/GW in the 1550 nm band, with an approximate full width at half-maximum of (120 ± 30) GHz. In addition, the microresonator is designed to exhibit normal dispersion at the pump wavelength near 1550 nm while possessing anomalous dispersion at the first Stokes near 1760 nm. At high enough input powers, a Kerr microcomb is generated by the Stokes signal acting as the secondary pump, which then mixes with the pump laser through four-wave mixing to attain a wider spectral coverage. Furthermore, cascaded Raman lasing and the occurrence of multiple Raman shifts, including 204 cm-1 (6.1 THz) and 266 cm-1 (8.0 THz) transitions, are also observed. Finally, we show that the Stokes Raman could also help broaden the spectrum in a Kerr microcomb which has anomalous dispersion at the pump wavelength. Our example of a 100 GHz-FSR microcomb has a wavelength span from 1200 to 1900 nm with 300 mW on-chip power.
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We demonstrate a novel polarization diversity differential phase-shift keying (DPSK) demodulator on the SOI platform, which is fabricated in a single lithography and etching step. The polarization diversity DPSK demodulator is based on a novel polarization splitter and rotator, which consists of a tapered waveguide followed by a 2 × 2 multimode interferometer. A lowest insertion loss of 0.5 dB with low polarization dependent loss of 1.6 dB and low polarization dependent extinction ratio smaller than 3 dB are measured for the polarization diversity circuit. Clear eye-diagrams and a finite power penalty of only 3 dB when the input state of polarization is scrambled are obtained for 40 Gbit/s non return-to-zero DPSK (NRZ-DPSK) demodulation.
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Interferometria/instrumentação , Refratometria/instrumentação , Silício/química , Ressonância de Plasmônio de Superfície/instrumentação , Telecomunicações/instrumentação , Condutividade Elétrica , Desenho de Equipamento , Análise de Falha de EquipamentoRESUMO
An all-optical AND logic gate in a single silicon microring resonator is experimentally demonstrated at 10 Gb/s with 50% RZ-OOK signals. By setting the wavelengths of two intensity-modulated input pumps on the resonances of the microring resonator, field-enhanced four-wave mixing with a total input power of only 8.5 dBm takes place in the ring, resulting in the generation of an idler whose intensity follows the logic operation between the pumps. Clear and open eye diagrams with a bit-error- ratio below 10(-9) are achieved.