Three-dimensional on-chip mode converter.

The implementation of transverse mode, polarization, frequency, and other degrees of freedom (d.o.f.s) of photons is an important way to improve the capability of photonic circuits. Here, a three-dimensional (3D) linear polarized (LP) LP11 mode converter was designed and fabricated using a femtosecond laser direct writing (FsLDW) technique. The converter included multi-mode waveguides, symmetric Y splitters, and phase delaying waveguides, which were constructed as different numbers and arrangements of circular cross section waveguides. Finally, the modes (LP11a and LP11b) were generated on-chip with a relatively low insertion loss (IL). The mode converter lays a foundation for on-chip high-order mode generation and conversion between different modes, and will play a significant role in mode coding and decoding of 3D photonic circuits.

Ultralow birefringent glass waveguide fabricated by femtosecond laser direct writing.

Optical waveguides prepared by femtosecond laser direct writing have birefringent properties, which can affect polarization encoding and entanglement on chips. Here, we first propose a shape-stress dual compensation fabrication scheme to decrease birefringence. Ultralow birefringent waveguides (1 × 10-9) were obtained by controlling the cross sectional shape of the main waveguide and adjusting the position of the auxiliary lines. In addition, we prepared polarization-independent directional coupler and demonstrated the evolution of polarization-independent waveguide array with different polarized light. In the future, ultralow birefringent waveguides will be widely applied in polarization encoding and entangled quantum photonic integrated circuits.

40 GHz high-efficiency Michelson interferometer modulator on a silicon-rich nitride and thin-film lithium niobate hybrid platform.

We propose and demonstrate a Michelson interferometer modulator with integrated Bragg reflectors on a silicon-rich nitride-thin-film lithium niobate hybrid platform. High-reflectivity Bragg reflectors are placed at the ends of both arms, which double the electro-optic (E-O) interaction length and reduce the velocity mismatch between the microwave and optical wave. The presented Michelson interferometer modulator achieves a measured half-wave voltage length product as low as 1.06 V cm and high-speed modulation up to 70 Gbps. A 3-dB E-O bandwidth beyond 40 GHz is also achieved, which is, to the best of our knowledge, the highest modulation bandwidth of Michelson interferometer modulators.

On-chip four-mode (de-)multiplexer on thin film lithium niobate-silicon rich nitride hybrid platform.

A four-mode (de-)multiplexer with transverse electric field light (TE0-TE3) is experimentally demonstrated on a thin film lithium niobate-silicon rich nitride hybrid platform. Enabled by cascaded asymmetrical directional couplers, a (de-)multiplexer with low insertion loss (0.38 dB to 1.6 dB) and low cross talk (-18.46dB to -20.43dB) is obtained at 1550 nm. All channels have cross talk <-16dB from 1480 nm to 1580 nm. The transmission of 4×50 Gbps on-off keying signals is experimentally achieved on the proposed (de-)multiplexer. Experimental results show that the proposed (de-)multiplexer is a promising approach to enhance the transmission capacity in thin film lithium niobate based photonics integrated circuits.

Circular cross section waveguides processed by multi-foci-shaped femtosecond pulses.

We developed a simple multi-foci-shaped femtosecond pulsed (MFSFP) method for processing circular cross section waveguides in transparent materials. With this flexible processing method, the focus energy distribution can be designed freely and arbitrarily, and single-mode waveguides with cross section circularity better than 96.0% were achieved. The mode shape difference (1.93%) of circular waveguides is smaller than the difference (7.01%) of normal elliptical waveguides. The coupling abilities of the two kinds of waveguides were investigated with three-dimensional (3D) directional couplers in both experiments and theoretical simulations. The coupling coefficient difference of circular waveguides in vertical and horizontal coupling directions was ∼0.01mm-1, which was smaller than 0.33mm-1 of normal waveguides. The circular symmetric waveguides will play an important role in large-scale high-intensity 3D photonic integrated circuits.

Ultra-compact low-loss variable-ratio 1×2 power splitter with ultra-low phase deviation based on asymmetric ladder-shaped multimode interference coupler.

We propose a novel optical 1×2 power splitter based on an asymmetric ladder-shaped multimode interference (MMI) coupler in silicon-on-insulator (SOI) which has an ultra-compact size of 3.3 µm×2.4 µm. A trapezoid with a small region is removed from the bottom left corner of the MMI coupler to achieve variable splitting ratio. The comparison with the asymmetric rectangular 1×2 splitter is numerically analyzed. By carefully optimizing the width of input taper, the proposed splitter shows a low phase deviation for the two output ports while keeping both of a low-loss performance and feasible splitting ratio. The simulated results show that the splitter can operate with an insertion loss less than 0.67 dB, a large range of splitting ratio from 50:50 to 11:89 and an ultra-low phase deviation less than 2.8° among the C band spectra.

TE/TM-pass polarizers based on lateral leakage in a thin film lithium niobate-silicon nitride hybrid platform.

TE/TM-pass polarizers based on the lithium niobate-silicon nitride hybrid platform are numerically proposed for the first time, to the best of our knowledge. By utilizing the lateral leakage of a shallowly etched rib waveguide, 1-mm-long TE/TM-pass polarizers with high extinction ratios of 28.72/24.03 dB are obtained. Because of the anisotropy of the lithium niobate, the lateral leakage of TE/TM polarization modes can occur along crystallographic z/y directions, respectively. Such TE/TM-pass polarizers can be integrated in the same wafer.

TE/TM-pass polarizers based on lateral leakage in a thin film lithium niobate-silicon nitride hybrid platform: publisher's note.

This publisher's note contains a correction to Opt. Lett.45, 4915 (2020)OPLEDP0146-959210.1364/OL.404197.

Efficient grating couplers on a thin film lithium niobate-silicon rich nitride hybrid platform.

A grating coupler on a thin film x-cut lithium niobate-silicon rich nitride hybrid platform is proposed and demonstrated. An inverse taper is applied to suppress higher-order mode excitation. A coupling efficiency of -5.82dB and 3 dB bandwidth of 57 nm are obtained near the wavelength of 1550 nm between the standard single-mode fiber (SMF-28) and sub-micrometer waveguides.

Diamond optical vortex generator processed by ultraviolet femtosecond laser.

We propose a precise diamond micromachining method based on ultraviolet femtosecond laser direct writing and a mixed acid heating chemical treatment. The chemical composition of the attached clusters generated during laser ablation and their effects on morphologies were investigated in experiments. The averaged roughness of pristine and processed regions reduced to 0.64 nm and 9.4 nm from 20.5 nm and 37.4 nm, respectively. With this method, spiral zone plates (SZPs) were inscribed on a high-pressure high-temperature diamond surface as micro-optical vortex generators. The optical performances of the diamond SZPs were characterized in both experiments and simulations, which were very consistent with each other. This chemical auxiliary processing method will contribute greatly to the wide application of integration and miniaturization of diamond surface optical components.

Passive silicon ring-assisted Mach-Zehnder interleavers operating in the broadband spectral range.

We propose and experimentally demonstrate a passive and compact interleaver on a silicon on insulator (SOI) platform using a ring-assisted asymmetrical Mach-Zehnder interferometer configuration. The wavelength-insensitive couplers, i.e., multimode interference couplers and adiabatic 3-dB couplers, are introduced to eliminate the effect of an unequal splitting ratio and wavelength on crosstalk and the operating spectral range. In addition, there exists an inherent phase shift between the two couplers; the device can be fully passive and works well without additional thermal tuning. In the calculation, the influence of wavelength sensitivity of self-coupling coefficients and couplers on the performance of the interleaver is considered. The experiment shows that, by employing wavelength-insensitive couplers, the operating spectral range of the proposed interleavers was extended to be >140nm for all sorts of channel spacing and channel count. The measured free spectral range is 4.6 nm, and the crosstalk is as low as -46.6dB for the best case.

Ultra-compact low-loss 1 × 4 optical power splitter with splitting ratio of 1∶2∶4∶8 based on two-stage cascaded MMI couplers.

An ultra-compact low-loss 1×4 optical power splitter with a splitting ratio of 1∶2∶4∶8 is proposed and demonstrated on a 220-nm-thick silicon-on-insulator (SOI) platform at the C band. The splitter is based on two stages of a cascaded 1×3 multimode interference (MMI) coupler and a 4×4 MMI coupler. The footprint of the device is 124.0 µm×6.4 µm, which is more compact than the traditional scheme of four-stage cascaded 1×2 MMI couplers. Phase shifters based on taper waveguides are incorporated in the device as the connection of two MMI couplers. The fabricated device exhibits a 3 dB power difference with a deviation of less than 0.88 dB from 1530 nm to 1570 nm. The average power difference is 3.14 dB at the center of the C band with an insertion loss of 1.84 dB.

Polarization beam splitter based on a silicon nitride-silica-silicon horizontal slot waveguide.

A novel compact polarization beam splitter (PBS) based on a silicon nitride-silica-silicon horizontal slot waveguide is numerically proposed, to the best of our knowledge. In the slot waveguide, the transverse electric (TE) mode propagates through the silicon layer, while the transverse magnetic (TM) mode is confined in the slot region. By utilizing an asymmetric directional coupler (DC) and bent directional coupler (bent DC) consisting of a slot waveguide and a thin silicon waveguide, PBSs with 14.6 µm (DC) and 5.2 µm (bent DC) coupling regions are obtained. Without cascading other structures, the DC PBS shows a low insertion loss (IL) of 0.4 (0.2) dB and high extinction ratio (ER) of 31.56 (24.61) dB for a TE (TM) port around 1.55 µm, while the IL and ER of the bent DC PBS are 0.4 (0.15) dB and 35.83 (21.74) dB, respectively. The proposed PBSs also have a good fabrication tolerance and broad bandwidth (>40 nm) for an ER of >20 dB.

Huangqi Decoction Ameliorates Streptozotocin-Induced Rat Diabetic Nephropathy through Antioxidant and Regulation of the TGF-ß/MAPK/PPAR-γ Signaling.

BACKGROUND/AIMS: Huangqi Decoction (HQD) has been traditionally used to treat diabetes mellitus in China. The present study was carried out to assess the protective effect of HQD on diabetic nephropathy (DN) using the streptozotocin-induced (STZ) diabetic rats. METHODS: Diabetes was induced by a single intraperitoneal injection of STZ (60 mg/kg) in male Wistar rats. 40 diabetic rats were divided into 5 groups: vehicle-treated (DN group), 0.45, 0.15, 0.05 g/kg HQD-treated diabetic group (HQD group) and 1 mg/kg rosiglitazone-treated diabetic group (RGZ group). 16 normal rats were randomly divided into 2 groups: vehicle-treated normal control group (NC) and 0.45 g/kg HQD-treated normal control group (NC+0.45 g/kg HQD). At the end of 8-week experiment, we measured changes of renal pathological morphology, function, antioxidant enzyme levels and the activation of TGF-ß/PPAR-γ/MAPK signaling pathway. RESULTS: After HQD treatment, renal function, including blood urea nitrogen (BUN), 24-h albuminuria and blood glucose level were improved significantly; meanwhile, impaired kidney redox balance was diminished in diabetic rats. The activation of TGF-ß, phospho-JNK, phospho-p44/42, p47 and p42 phox was blocked and the decrease in PPAR-γ in diabetic rats was attenuated by treatment with HQD in a dose-dependent manner. CONCLUSION: These results suggest that HQD shows therapeutic efficacy in DN characterized by renal dysfunction and pathological changes through hypoglycemic and antioxidant effects.

Human adipose-derived stem cells modified by HIF-1α accelerate the recovery of cisplatin-induced acute renal injury in vitro.

Human adipose-derived stem cells (hASCs) improve renal function in acute kidney injury. Hypoxia-inducible factor-1α (HIF-1α) was transfected into hASCs. hASCs modified by lentivirus-mediated empty-vector and HIF-1α maintained their stem cell characteristics. The expression of the renal-protective gene, heme oxygenase-1 and vascular endothelial growth factor were significantly increased in hASCs modified by HIF-1α, compared to hASCs modified by empty-vector. Cellular ultra-structure and TUNEL staining revealed that hASCs modified by HIF-1α promoted the recovery of apoptotic morphology in cisplatin-treated human kidney-2 cells (HK-2 cells) when compared to hASCs modified by empty-vector. Additionally, hASCs modified by empty-vector inhibited caspase-3 expression and up-regulated Bcl-2 expression in cisplatin-treated HK-2 cells, an effect even more pronounced with hASCs modified by HIF-1α. Thus, HIF-1α gene-modified ASCs could be an effective way to enhance the renal-protective effect.

An Efficient Multiscale Spatial Rearrangement MLP Architecture for Image Restoration.

The effective use of long-range information can yield improved network performance, which is very important for image restoration. Although local window-based models have linear complexity and can be feasibly applied to process high-resolution images, a single-scale window has a limited receptive field and is less efficient for encoding long-range context information. To address this issue, this paper presents a single-stage multiscale spatial rearrangement multilayer perceptron (MSSR-MLP) architecture that can obtain information at different scales within a local window. Specifically, we propose a simple and efficient spatial rearrangement module (SRM) that moves information outside the local window to the inside of the local window so that long-range dependencies can be modeled using only a window-based fully connected (FC) layer. The SRM can extend the local receptive field of a window-based FC layer without introducing additional parameters and FLOPs. Utilizing several spatial rearrangement modules with different step sizes, we design an efficient multiscale spatial rearrangement MLP architecture for image restoration. This design aggregates multiscale information to achieve improved restoration quality while maintaining a low computational cost. Extensive experiments conducted on several image restoration tasks demonstrate the efficiency and effectiveness of our method. For example, it requires only ~4.3% of the FLOPs needed by SwinIR for Gaussian gray image denoising, ~13.9% of the FLOPs needed by C2 PNet for single-image dehazing and ~18.9% of the FLOPs needed by MAXIM for single-image motion deblurring but achieves better performance on each of these restoration tasks.

Quercetin Regulates Lipid Metabolism and Fat Accumulation by Regulating Inflammatory Responses and Glycometabolism Pathways: A Review.

Fat synthesis and lipolysis are natural processes in growth and have a close association with health. Fat provides energy, maintains physiological function, and so on, and thus plays a significant role in the body. However, excessive/abnormal fat accumulation leads to obesity and lipid metabolism disorder, which can have a detrimental impact on growth and even harm one's health. Aside from genetic effects, there are a range of factors related to obesity, such as excessive nutrient intake, inflammation, glycometabolism disease, and so on. These factors could serve as potential targets for anti-obesity therapy. Quercetin is a flavonol that has received a lot of attention recently because of its role in anti-obesity. It was thought to have the ability to regulate lipid metabolism and have a positive effect on anti-obesity, but the processes are still unknown. Recent studies have shown the role of quercetin in lipid metabolism might be related to its effects on inflammatory responses and glycometabolism. The references were chosen for this review with no date restrictions applied based on the topics they addressed, and the databases PubMed and Web of Sicence was used to conduct the references research, using the following search terms: "quercetin", "obesity", "inflammation", "glycometabolism", "insulin sensitivity", etc. This review summarizes the potential mechanisms of quercetin in alleviating lipid metabolism through anti-inflammatory and hypoglycemic signaling pathways, and describes the possible signaling pathways in the interaction of inflammation and glycometabolism, with the goal of providing references for future research and application of quercetin in the regulation of lipid metabolism.

A Time Mode Pulse Interleaver in a Silicon-on-Insulator Platform for Optical Analog-to-Digital Converters.

We propose and demonstrate a novel on-chip optical sampling pulse interleaver based on time mode interleaving. The designed pulse interleaver was fabricated on a 220 nm silicon-on-insulator (SOI) platform, utilizing only one S-shaped delay waveguide. Interleaving is achieved by the relative time delay between different optical modes in the waveguide, eliminating the need for any active tuning. The total length of the delay waveguide is 5620.5 µm, which is reduced by a factor of 46.3% compared with previously reported time-wavelength interleaver schemes. The experimental results indicate that the device can convert an optical pulse into a 40 GHz pulse sequence composed of four pulses with a root mean square (RMS) timing error of 0.9 ps, making it well suited for generating high-frequency sampling pulses for optical analog-to-digital converters.

Mercury bioaccumulation in thresher sharks from the eastern tropical Pacific: Influences of body size, maturation stage, and feeding habitat.

Sharks, as top order predators, provide a guidance on how contaminants such as mercury bioaccumulate in marine environments. This study assessed the bioaccumulation of mercury (total mercury, THg) in the muscle, liver, red blood cells (RBC), and plasma of pelagic and bigeye thresher sharks (Alopias pelagicus and A. superciliosus) from eastern tropical Pacific. Additionally, the concentration of methylmercury (MeHg) in muscle was also determined to assess risks for human consumption. For both species, muscle THg concentrations (4.05 ± 2.15 and 4.12 ± 1.84 µg g-1 dry weight for pelagic and bigeye thresher shark) were higher than that in other tissues. THg concentrations for all tissues were significantly correlated with precaudal length, with higher accumulation rates after maturity in pelagic than bigeye thresher sharks, suggesting an associated dietary shift at maturation. Correlations among tissues in both species suggested similar transportation and distribution patterns in internal tissues. The δ13C values in muscle, RBC and plasma suggested that habitat shifts influenced Hg accumulation, whereas trophic position, estimated by δ15N values, had limited effects on patterns of Hg bioaccumulation. Diet shifts towards prey more cephalopods that content higher Hg than small fishes (large fishes: 1.77 µg g-1; cephalopods: 0.66 µg g-1 and small fishes 0.48 µg g-1, dry weight) increased Hg accumulation rates in adult pelagic thresher sharks. Concentrations of MeHg in the muscle of both thresher shark (3.42 ± 1.68 µg g-1 in A. pelagicus and 3.78 ± 2.13 µg g-1 in A. superciliosus) exceeded the recommended levels for human consumption. This research provides insight into the factors influencing mercury bioaccumulation in thresher sharks, which are essential for the management and conservation of these species.

Lipid-extracted muscle and liver tissues: Can they reveal mercury exposure of pelagic sharks?

Pelagic sharks are apex predators in oceanic ecosystems and tend to accumulate high amounts of mercury (Hg). The conventional method for assessing Hg exposure in sharks involves analyzing tissue samples without any chemical treatment. However, a substantial number of chemically treated tissue samples are still being preserved in laboratories or museums. It is critical to maximize the utilization of existing samples to reduce the need for additional sampling of pelagic sharks, especially endangered species. Lipid extraction is a widely employed pretreatment process for carbon isotope analysis in shark trophic ecology, while its impact on Hg quantification remains uncertain. Here, we evaluated the feasibility of using lipid-free muscle and liver tissues for investigation of Hg exposure in four endangered pelagic sharks inhabiting the eastern Pacific, including bigeye thresher (Alopias superciliosus), pelagic thresher (A. pelagicus), blue shark (Prionace glauca) and silky shark (Carcharhinus falciformis). Results showed that total Hg concentrations (THg) differed between untreated (THgbulk) and lipid-free (THglipid-free) samples for each tissue type of each species. In addition, dichloromethane-methanol extractions significantly altered the amount of Hg. This may result from the removal of lipoprotein compounds that vary between tissues and species. The THgbulk can be calculated by THglipid-free using the following formulas, THgbulk = 1.14 × THglipid-free + 0.30 and THgbulk = 0.33 × THglipid-free + 0.18, for muscle and liver tissues, respectively. These findings emphasize the applications of lipid-free tissues in THg analysis. This study may have important implications for improving evaluation of Hg exposure in endangered pelagic sharks.