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In this paper, we propose a novel structure of anisotropic graphene-based hyperbolic metamaterial (AGHMM) sandwiched as a defect between two one-dimensional photonic crystals (PCs) in the terahertz (THz) region. The proposed structure is numerically simulated and analyzed using the transfer matrix method, effective medium theory and three-dimensional finite-difference time-domain. The defect layer of AGHMM consists of graphene sheets separated by subwavelength dielectric spacers. According to the presented results, a sharp defect mode originated from the optical Tamm state (OTS) takes place at the interfaces between PCs and AGHMM. The platform is then applied as various THz devices with outstanding characteristics compared with their previous counterparts. The performance of all the proposed devices can be tuned by changing the incident angle and graphene chemical potential. Our designed electro-optical modulator exhibits a high extinction ratio of 24.75 dB. The required switching voltage and insertion loss are as low as 9.94 V and 0.05 dB, respectively. Owing to the anisotropy of graphene, a tunable polarizer over wide incident angles is attained. The highest polarization extinction ratios (PERs) for TE- and TM-pass polarizers are 42.4 dB and 76.8 dB, respectively, which are the highest PER ever reported. By introducing more AGHMM defects, multiband tunable filters with quality factors of as high as 75314 are realized. Finally, a narrowband perfect absorber is proposed so that a high absorption of 99.8% with an ultra-narrow FWHM of 0.00055 THz is achieved. Hence, the proposed structure is a promising platform that could have many potential THz applications., Competing Interests: Declarations. Competing interests: The authors declare no competing interests., (© 2024. The Author(s).)

The brown planthopper (BPH), Nilaparvata lugens (Stål), is a notorious pest affecting Asian rice crops. The evolution of insecticide resistance in BPH has emerged as a significant challenge in effectively managing this pest. This study revealed the resistance status of BPH to nine insecticides in ten provinces and Shanghai City in China from 2020 to 2023. Monitoring results showed that the resistance of BPH to triflumezopyrim, nitenpyram, and dinotefuran increased rapidly. The average resistance ratio of BPH to triflumezopyrim increased from 2.5 to 7.1 fold, nitenpyram from 18.3 to 37.7 fold, and dinotefuran from 119.5 to 268.1 fold. All populations remained extremely high resistance to imidacloprid, thiamethoxam, and buprofezin. Most field populations of BPH maintained moderate resistance to chlorpyrifos and sulfoxaflor, and high resistance to pymetrozine by rice stem dipping method. However, considering the reproduction-inhibiting character of pymetrozine, susceptible to low resistance levels to pymetrozine were monitored by Insecticide Resistance Action Committee (IRAC) NO.005 method. This result indicated that pymetrozine might lose efficacy in the control of application generation, but it could significantly inhibit the reproduction of field populations of BPH. Additionally, we compared the expression levels of 11 nicotinic acetylcholine receptor (nAChR) genes, the targets of nAChR competitive modulators, in four field populations (FY23, YH23, LJ23, LP23) and susceptible strain. The expression level of nAChR α4 was significantly reduced in all field populations, while α1, α2, α6, and α7 were significantly reduced in some field populations. Our findings provide valuable information for resistance management strategies in N. lugens and offer new insights into the resistance mechanisms of nAChR competitive modulators., Competing Interests: Declaration of competing interest The authors declare no competing financial interest., (Copyright © 2024 Elsevier Inc. All rights reserved.)

Efficient fiber-chip coupling interfaces are critically important for integrated photonics. Since surface gratings diffract optical signals vertically out of the chip, these couplers can be placed anywhere in the circuit allowing for wafer-scale testing. While state-of-the-art grating couplers have been developed for silicon-on-insulator (SOI) waveguides, the moderate index contrast of silicon nitride (SiN) presents an outstanding challenge for implementing efficient surface grating couplers on this platform. Due to the reduced grating strength, a longer structure is required to radiate the light from the chip which produces a diffracted field that is too wide to couple into the fiber. In this work, we present a novel grating coupler architecture for silicon nitride photonic integrated circuits that utilizes an amorphous silicon (α-Si) overlay. The high refractive index of the α-Si overlay breaks the coupler's vertical symmetry which increases the directionality. We implement subwavelength metamaterial apodization to optimize the overlap of the diffracted field with the optical fiber Gaussian mode profile. Furthermore, the phase of the diffracted beam is engineered to focalize the field into an SMF-28 optical fiber placed 55 µm above the surface of the chip. The coupler was designed using rigorous three-dimensional (3D) finite-difference time-domain (FDTD) simulations supported by genetic algorithm optimization. Our grating coupler has a footprint of 26.8 × 32.7 µm 2 and operates in the O-band centered at 1.31 μm. It achieves a high directionality of 85% and a field overlap of 90% with a target fiber mode size of 9.2 µm at the focal plane. Our simulations predict a peak coupling efficiency of - 1.3 dB with a 1-dB bandwidth of 31 nm. The α-Si/SiN grating architecture presented in this work enables the development of compact and efficient optical interfaces for SiN integrated photonics circuits with applications including optical communications, sensing, and quantum photonics., (© 2024. The Author(s).)

Silicon nitride (Si 3 N 4 ) is an ideal candidate for the development of low-loss photonic integrated circuits. However, efficient light coupling between standard optical fibers and Si 3 N 4 chips remains a significant challenge. For vertical grating couplers, the lower index contrast yields a weak grating strength, which translates to long diffractive structures, limiting the coupling performance. In response to the rise of hybrid photonic platforms, the adoption of multi-layer grating arrangements has emerged as a promising strategy to enhance the performance of Si 3 N 4 couplers. In this work, we present the design of high-efficiency surface grating couplers for the Si 3 N 4 platform with an amorphous silicon (α-Si) overlay. The surface grating, fully formed in an α-Si waveguide layer, utilizes subwavelength grating (SWG)-engineered metamaterials, enabling simple realization through single-step patterning. This not only provides an extra degree of freedom for controlling the fiber-chip coupling but also facilitates portability to existing foundry fabrication processes. Using rigorous three-dimensional (3D) finite-difference time-domain (FDTD) simulations, a metamaterial-engineered grating coupler is designed with a coupling efficiency of -1.7 dB at an operating wavelength of 1.31 µm, with a 1 dB bandwidth of 31 nm. Our proposed design presents a novel approach to developing high-efficiency fiber-chip interfaces for the silicon nitride integration platform for a wide range of applications, including datacom and quantum photonics.

In this paper, we present a novel, scalable, and reconfigurable optical switch that performs multiple computational logic functions simultaneously. The free-carrier depletion effect is used to perform non-volatile switching operations due to its high speed and low power consumption. We adopt the concept of optical memory using a phase-change material to realize the non-volatile reconfigurability without a constant power supply, in addition to providing a large operating bandwidth required for reconfigurability. The proposed reconfigurable optical logic architecture is realized in a compact microdisk resonator configuration, utilizing both the carrier-depletion-based modulation and phase-change optical memory. This is the first time these two modulation schemes are implemented in the same optical microdisk for the purpose of reconfigurable optical logic., (© 2024. The Author(s).)

Surface grating couplers are an important component for interfacing photonic integrated circuits with optical fibers. However, conventional coupler designs typically provide limited performance due to low directionality and poor fiber-to-grating field overlap. The efficiency can be improved by using non-uniform grating structures at the expense of small critical dimensions complicating the fabrication process. While uniform gratings can alleviate this constraint, they produce an exponentially decaying near-field with the Gaussian fiber mode overlap limited to a theoretical maximum of 80%. In this work, we propose a uniform grating coupler that circumvents this field overlap limitation. This is achieved by leveraging inter-layer mode interference through a virtual directional coupler effect in a hybrid amorphous-silicon (α-Si) on silicon nitride (Si 3 N 4 ) platform. By optimizing the inter-layer gap and grating geometry, a near-Gaussian profile of the out-radiated beam is achieved, resulting in an unprecedented grating-to-fiber overlap of 96%. The full three-dimensional (3D) finite-difference time-domain (FDTD) simulations show a high directionality of 84% and a record coupling loss of -1.27 dB with a 1-dB bandwidth of 20 nm for the uniform grating coupler design. Our device is designed for a wavelength of 950 nm aimed for use in hybrid quantum photonic integrated circuits using III-V quantum dot single photon sources.

We investigate and experimentally demonstrate a cladding modulated Bragg grating superstructure as a dynamically tunable and reconfigurable multi-wavelength notch filter. A non-uniform heater element was implemented to periodically modulate the effective index of the grating. The Bragg grating bandwidth is controlled by judiciously positioning loading segments away from the waveguide core, resulting in a formation of periodically spaced reflection sidebands. The thermal modulation of a periodically configured heater elements modifies the waveguide effective index, where an applied current controls the number and intensity of the secondary peaks. The device was designed to operate in TM polarization near the central wavelength of 1550 nm and was fabricated on a 220-nm silicon-on-insulator platform, using titanium-tungsten heating elements and aluminum interconnects. We experimentally demonstrate that the Bragg grating self-coupling coefficient can be effectively controlled in a range from 7 mm -1 to 110 mm -1 by thermal tuning, with a measured bandgap and sideband separation of 1 nm and 3 nm, respectively. The experimental results are in excellent agreement with simulations.

Background: The brown planthopper (Nilaparvata lugens) is one of the major rice insect pests in Asia. Recently, high levels of insecticide resistance have been frequently reported and cytochrome P450 monooxygenase (P450)-mediated metabolic detoxification is a common resistance mechanism in N. lugens. However, there has been no persuasive genetic method to prove the role of P450s in insecticide resistance in N. lugens., Results: Here, CRISPR/Cas9 system was used to disrupt the P450 gene NlCYP6CS1 to elucidate its role in insecticide resistance in field populations of N. lugens. We successfully constructed a homozygous strain (Nl6CS1-KO) with a 5-bp deletion and 1-bp insertion mutation of NlCYP6CS1. Compared with a background resistant strain (Nl-R), the susceptibility of knockout strain Nl6CS1-KO to imidacloprid, nitenpyram, thiamethoxam, dinotefuran, and pymetrozine was increased by 2.3-, 3.4-, 7.0-, 4.2- and 3.9-fold, respectively, but not significantly changed to triflumezopyrim, chlorpyrifos and buprofezin. Life table analysis demonstrated that the Nl6CS1-KO strain resembled the Nl-R strain in terms of egg and nymph developmental duration and adult lifespan, but differed from the Nl-R strain in the survival rate of eggs and nymphs, reproduction, and body weight., Conclusions: Our study demonstrates the effect of functional deletion of NlCYP6CS1 on multiple insecticide resistance in N. lugens. For the first time, we applied CRISPR/Cas9 system to reveal the mechanism of insecticide resistance in N. lugens, which may shed light on similar studies in other hemipteran insects. © 2023 Society of Chemical Industry., (© 2023 Society of Chemical Industry.)

On the basis of the inhibition effects of pymetrozine on the reproductive behavior of N. lugens, we established a bioassay method to accurately evaluate the toxicity of pymetrozine in N. lugens and clarified the level of pymetrozine resistance of N. lugens in the field. In this study, pymetrozine's effects on the fecundity of N. lugens were evaluated using the topical application method and rice-seedling-dipping method. Moreover, the resistance of N. lugens to pymetrozine in a pymetrozine-resistant strain (Pym-R) and two field populations (YZ21 and QS21) was determined using the rice-seedling-dipping method and fecundity assay methods. The results showed that treatment of N. lugens third-instar nymphs with LC 15 , LC 50 , and LC 85 doses of pymetrozine resulted in a significantly reduced fecundity of N. lugens . In addition, N. lugens adults treated with pymetrozine, using the rice-seedling-dipping and topical application method, also exhibited a significantly inhibited fecundity. Using the rice-stem-dipping method, pymetrozine resistance levels were shown to be high in Pym-R (194.6-fold), YZ21 (205.9-fold), and QS21 (212.8-fold), with LC 50 values of 522.520 mg/L (Pym-R), 552.962 mg/L (YZ21), and 571.315 (QS21) mg/L. However, when using the rice-seedling-dipping or topical application fecundity assay method, Pym-R (EC 50 : 14.370 mg/L, RR = 12.4-fold; ED 50 : 0.560 ng/adult, RR = 10.8-fold), YZ21 (EC 50 : 12.890 mg/L, RR = 11.2-fold; ED 50 : 0.280 ng/adult; RR = 5.4-fold), and QS21 (EC 50 : 13.700 mg/L, RR = 11.9-fold) exhibited moderate or low levels of resistance to pymetrozine. Our studies show that pymetrozine can significantly inhibit the fecundity of N. lugens . The fecundity assay results showed that N. lugens only developed low to moderate levels of resistance to pymetrozine, indicating that pymetrozine can still achieve effective control on the next generation of N. lugens populations.

Metalenses are planar optical components that have demonstrated immense potential for integrated optics. In particular, they are capable of high-efficiency subwavelength focusing without the bulkiness of traditional lenses. Dielectric metalenses operating in the C-band typically employ relatively tall, amorphous silicon structures arranged in a periodic array. Phase control spanning from 0 to 2π is accessed by varying the geometry of these scattering structures. The full 2π phase range is necessary to impose a hyperbolic focusing phase profile, but this is difficult to achieve without custom fabrication practices. In this work, we propose a binary phase Fresnel zone plate metalens designed for the standard 500 nm silicon-on-insulator platform. Our design uses subwavelength gratings with trapezoidal segmentation to form concentric rings. The effective index of the grating is set with the duty cycle using a single full-etch step to form the binary phase profile of the zone plate. The metalens design can be easily tuned to achieve longer focal lengths at different wavelengths. It offers a simple platform for high-throughput wavelength-scale focusing elements in free-space optics, including for microscopy and medical imaging.

Optical antennas are a fundamental element in optical phased arrays (OPA) and free-space optical interconnects. An outstanding challenge in optical antenna design lies in achieving high radiation efficiency, ultra-compact footprint and broad radiation angle simultaneously, as required for dense 2D OPAs with a broad steering range. Here, we demonstrate a fundamentally new concept of a nanophotonic antenna based on near-field phase-engineering. By introducing a specific near-field phase factor in the Fraunhofer transformation, the far-field beam is widened beyond the diffraction limit for a given aperture size. We use transversally interleaved subwavelength grating nanostructures to control the near-field phase. A Bragg reflector is used at the end of the grating to increase both the efficiency and the far-field beam width. The antenna has a compact footprint of 3.1 µm × 1.75 µm and an ultra-broad far-field beam width of 52° and 62° in the longitudinal and transversal direction, respectively, while the radiation efficiency reaches 82% after incorporating a bottom reflector to further improve the directionality. This unprecedented design performance is achieved with a single-etch grating nanostructure in a 300-nm SOI platform., (© 2022. The Author(s).)

Background: The brown planthopper, Nilaparvata lugens, is considered the most destructive pest of rice in many Asian countries including China. Use of pymetrozine in insect resistance management (IRM) has been one strategy to control this pest. In this study, we reported the status of pymetrozine resistance in Nilaparvata lugens (Stål) collected from China over the period 2017-2021 and selected a strain of N. lugens resistant to pymetrozine and evaluated the cross-resistance, inheritance and fitness costs of the resistance., Results: Monitoring data (2017-2021) showed that field populations of N. lugens in China developed moderate- to high-level pymetrozine resistance during these 5 years. By continuous selection with pymetrozine in the lab, the pymetrozine selected N. lugens strain (Pym-R 98 ) developed a 225.2-fold resistance compared to a susceptible strain. The Pym-R 98 strain showed high cross-resistance to dinotefuran (66.6-fold) and low cross-resistance to nitenpyram (5.2-fold) and sulfoxaflor (5.8-fold). Inheritance pattern analysis of Pym-R 93 revealed that resistance to pymetrozine was polygenic, autosomal and incompletely dominant. Fitness costs of pymetrozine resistance were present in Pym-R 90 and WA2020 strains with a relative fitness of 0.72 and 0.60, respectively. The developmental duration of Pym-R 90 and WA2020 was significantly longer and hatchability was significantly lower compared to pymetrozine-susceptible strain (Pym-S)., Conclusions: N. lugens has developed high level of resistance to pymetrozine. Pymetrozine-resistance brown planthopper had cross-resistance with some of neonicotinoids such as dinotefuran, nitenpyram and sulfoxaflor. The autosomal, incompletely dominant and polygenic resistance to pymetrozine in N. lugens and the fitness costs associated with this resistance can be exploited in IRM strategies to preserve the lifetime of pymetrozine for control of N. lugens in China. © 2022 Society of Chemical Industry., (© 2022 Society of Chemical Industry.)

Light detection and ranging systems based on optical phased arrays and integrated silicon photonics have sparked a surge of applications over the recent years. This includes applications in sensing, free-space communications, or autonomous vehicles, to name a few. Herein, we report a design of two-dimensional optical phased arrays, which are arranged in a grid of concentric rings. We numerically investigate two designs composed of 110 and 820 elements, respectively. Both single-wavelength (1550 nm) and broadband multi-wavelength (1535 nm to 1565 nm) operations are studied. The proposed phased arrays enable free-space beam steering, offering improved performance with narrow beam divergences of only 0.5° and 0.22° for the 110-element and 820-element arrays, respectively, with a main-to-sidelobe suppression ratio higher than 10 dB. The circular array topology also allows large element spacing far beyond the sub-wavelength-scaled limits that are present in one-dimensional linear or two-dimensional rectangular arrays. Under a single-wavelength operation, a solid-angle steering between 0.21 π sr and 0.51 π sr is obtained for 110- and 820-element arrays, respectively, while the beam steering spans the range of 0.24 π sr and 0.57 π sr for a multi-wavelength operation. This work opens new opportunities for future optical phased arrays in on-chip photonic applications, in which fast, high-resolution, and broadband beam steering is necessary.

On-chip optical phased arrays (OPAs) are the enabling technology for diverse applications, ranging from optical interconnects to metrology and light detection and ranging (LIDAR). To meet the required performance demands, OPAs need to achieve a narrow beam width and wide-angle steering, along with efficient sidelobe suppression. A typical OPA configuration consists of either one-dimensional (1D) linear or two-dimensional (2D) rectangular arrays. However, the presence of grating sidelobes from these array configurations in the far-field pattern limits the aliasing-free beam steering, when the antenna element spacing is larger than half of a wavelength. In this work, we provide numerical analysis for 2D circular OPAs with radially arranged nano-antennas. The circular array geometry is shown to effectively suppress the grating lobes, expand the range for beam steering and obtain narrower beamwidths, while increasing element spacing to about 10 μm. To allow for high coupling efficiency, we propose the use of a central circular grating coupler to feed the designed circular OPA. Leveraging radially positioned nano-antennas and an efficient central grating coupler, our design can yield an aliasing-free azimuthal field of view (FOV) of 360°, while the elevation angle FOV is limited by the far-field beamwidth of the nano-antenna element and its array arrangement. With a main-to-sidelobe contrast ratio of 10 dB, a 110-element OPA offers an elevation FOV of 5° and an angular beamwidth of 1.14°, while an 870-element array provides an elevation FOV up to 20° with an angular beamwidth of 0.35°. Our analysis suggests that the performance of the circular OPAs can be further improved by integrating more elements, achieving larger aliasing-free FOV and narrower beamwidths. Our proposed design paves a new way for the development of on-chip OPAs with large 2D beam steering and high resolutions in communications and LIDAR systems.

Integrated optical antennas are key components for on-chip light detection and ranging technology (LIDAR). In order to achieve a highly collimated far field with reduced beam divergence, antenna lengths on the order of several millimeters are required. In the high-index contrast silicon photonics platform, achieving such long antennas typically demands weakly modulated gratings with lithographic minimum feature sizes below 10 nm. Here, we experimentally demonstrate a new, to the best of our knowledge, strategy to make long antennas in silicon waveguides using a metamaterial subwavelength grating (SWG) waveguide core loaded with a lateral periodic array of radiative elements. The mode field confinement is controlled by the SWG duty cycle, and the delocalized propagating mode overlaps with the periodic perturbations. With this arrangement, weak antenna radiation strength can be achieved while maintaining a minimum feature size as large as 80 nm. Using this strategy, we experimentally demonstrate a 2-millimeter-long, single-etched subwavelength-engineered optical antenna on a conventional 220 nm SOI platform, presenting a measured far-field beam divergence of 0.1° and a wavelength scanning sensitivity of 0.13°/nm.

Spectral filters are important building blocks for many applications in integrated photonics, including datacom and telecom, optical signal processing and astrophotonics. Sidewall-corrugated waveguide grating is typically the preferred option to implement spectral filters in integrated photonic devices. However, in the high-index contrast silicon-on-insulator (SOI) platform, designs with corrugation sizes of only a few tens of nanometers are often required, which hinders their fabrication. In this work, we propose a novel geometry to design complex Bragg filters with an arbitrary spectral response in silicon waveguides with laterally coupled Bragg loading segments. The waveguide core is designed to operate with a delocalized mode field, which helps reduce sensitivity to fabrication errors and increase accuracy on synthesized coupling coefficients and the corresponding spectral shape control. We present an efficient design strategy, based on the layer-peeling and layer-adding algorithms, that allows to readily synthesize an arbitrary target spectrum for our cladding-modulated Bragg gratings. The proposed filter concept and design methodology are validated by designing and experimentally demonstrating a complex spectral filter in an SOI platform, with 20 non-uniformly spaced spectral notches with a 3-dB linewidth as small as 210 pm.

We present a compact silicon-based surface grating antenna design with a high diffraction efficiency of 89% (-0.5 dB) and directionality of 0.94. The antenna is designed with subwavelength-based L-shaped radiating elements in a 300-nm silicon core, maintaining high efficiency with a compact footprint of 7.6 µm × 4.5 µm. The reflectivity remains below -10 dB over the S, C and L optical communication bands. A broad 1-dB bandwidth of 230 nm in diffraction efficiency is achieved with a central wavelength of 1550 nm.

We experimentally demonstrate, to the best of our knowledge, the first microdisk-based silicon-photonic mode-division (de)multiplexer circuit, which is compatible with wavelength-division multiplexing for high aggregate bandwidth on-chip optical communications. This circuit uses waveguide-wrapped microdisk resonators, featuring low levels of intermodal crosstalk and insertion loss within an ultracompact footprint. In addition, the proposed device presents an increased free spectral range, allowing for 530 combined data channels. Furthermore, the microdisk structure naturally supports vertically oriented depletion-type pn junctions, which have been shown to reach subfemtojoule-per-bit modulation efficiencies. The high modulation efficiency, compactness, and wide free spectral range of waveguide-wrapped microdisk resonators present the potential for higher bandwidth and lower energy consumption in next-generation data processing and communication applications.

Optical antennas are key components in optical phased arrays for light detection and ranging technology requiring long sensing range and high scanning resolution. To achieve a narrow beam width in the far-field region, antenna lengths of several millimeters or more are required. To date, such long antennas have been impossible to achieve in silicon waveguides because currently demonstrated technologies do not allow accurate control of grating strength. Here, we report on a new type of surface-emitting silicon waveguide with a dramatically increased antenna length of L =3.65 m m . This is achieved by using a subwavelength metamaterial waveguide core evanescently coupled with radiative segments laterally separated from the core. This results in a far-field diffracted beam width of 0.025°, which is a record small beam divergence for a silicon photonics surface-emitting device. We also demonstrate that by using a design with L -shaped surface-emitting segments, the radiation efficiency of the antenna can be substantially increased compared to a conventional design, with an efficiency of 72% at the wavelength of 1550 nm.

We propose a U-shaped pn junction in a silicon-on-insulator microdisk resonator to effectively double the junction-mode overlap in the state-of-the-art, vertical pn junction microdisk electro-optical (EO) modulators. The U-shaped pn junction promotes the maximum overlap between the junction depletion zone and the whispering gallery optical mode in the microdisk. By fully depleting the p region of the npn-sequenced U-junction, the capacitance is reduced below 3 fF, which significantly improves the speed and power performance. In this work, we implement the high-efficiency, depleted U-junction design to maximize the operating bandwidth of EO modulators, EO logic elements, EO 2 × 2 switches for wavelength-division cross-connects, 2 × 2 reconfigurable optical add-drop multiplexers, optical-to-electrical-to-optical (OEO) repeaters-with-gain, OEO wavelength converters, and 2 × 2 optical-optical logic gates. These devices all operate in the 7.6-to-50 GHz bandwidth range with ultralow energy consumption between 0.4 and 9.8 fJ/bit. By using CMOS-compatible materials and fabrication-feasible design dimensions, our proposed high-performance devices offer a promising potential in next-generation, high-volume electro-optical communications and computing circuits.

To review and analyze the clinical outcomes of thermal therapy (≤1.4°C increase in core body temperature) in patients with heart failure (HF). A systematic review and meta-analysis regarding the effects of thermal therapy on HF was done by searching PubMed, Ovid Medline, Ovid Embase, Scopus, and internal databases up to date (2019). Improvement in the New York Heart Association (NYHA) class: Ten studies with 310 patients showed significant improvement in NYHA class. Only 7 among 40 patients remained in Class IV and 99 patients in Class III from 155 patients. Increased patients in lower classes indicate that more patients showed improvement. Sixteen studies on 506 patients showed an overall improvement of 4.4% of left ventricular ejection fraction (LVEF). Four studies reported improved endothelial dysfunction by 1.7% increase in flow-mediated dilation (FMD) on 130 patients. Reduction in blood pressure: Thermal therapy reduced both systolic blood pressure (SBP) and diastolic blood pressure by 3.1% and 5.31%, respectively, in 431 patients of 15 studies. Decrease in cardiothoracic ratio (CTR): Eight studies reported an average of 5.55% reduction of CTR in a total of 347 patients. Improvement in oxidative stress markers: Plasma brain natriuretic peptide (BNP) levels significantly decreased (mean difference of 14.8 pg/dL) in 303 patients of 9 studies. Improvement of quality of life: Among 65 patients, thermal therapy reduced cardiac death and rehospitalization by 31.3%. A slight increase in core body temperature is a promising, noninvasive, effective, and complementary therapy for patients with HF. Further clinical studies are recommended., (© 2020 International Center for Artificial Organs and Transplantation and Wiley Periodicals, Inc.)

In this work we investigate the implementation of ultra-wideband polarization rotator in the mid-infrared spectral region. A new design method of the rotation section is proposed, yielding a polarization rotator with an extinction ratio of at least 15 dB in a wavelength range of 2 µm. For a spectral range wider than 3.8 µm, an extinction ratio of at least 10 dB is achieved for this design. The device is 1660 µm long and the associated insertion loss is below 1.2 dB on the full operational wavelength range. The influence of geometrical parameters with respect to the design method to obtain such a broadband behavior is discussed. Finally, to increase the tolerance to fabrication errors, a tapered rotator design is proposed. Such a device can support up to ± 100 nm fabrication errors and still guarantees remarkable broadband behavior. To the best of our knowledge, this is the first time an integrated polarization rotator is designed to operate for the wavelength range of 4 to 9 µm with a bandwidth exceeding 2 µm.

We present a CMOS-compatible optoelectronic directed logic architecture that achieves high computational throughput (number of operations per second per unit area) by its ultracompact form factor. High speed-to-power performance is also achieved, by the low capacitance and high junction-to-mode overlap of low-radii SOI vertical pn junction microdisk switches. By using wavelength-division multiplexing and two electrical control signals per disk, each switch performs (N)OR, (N)AND, and X(N)OR operations simultaneously. Connecting multiple switches together, we demonstrate higher-order scalability in five fundamental N-bit logic circuits: AND/OR gates, adders, comparators, encoders, and decoders. To the best of our knowledge, these circuits achieve the lowest footprint of silicon-based multigigabit-per-second optical logic devices in literature.

We experimentally demonstrate a compact, low-cross talk and fabrication-tolerant two-mode (de)multiplexer on the silicon-on-insulator platform. The device consists of a silicon wire waveguide coupled to a taper-etched waveguide. The partially etched taper structure is used to relax fabrication tolerance and thus to ensure high mode-conversion efficiency. The device is 68 μm in length, with a TE0-to-TE1 mode conversion loss of better than -0.8  dB demonstrated over the C-band wavelengths. In addition, the device demonstrates a low TE0-to-TE0 through waveguide insertion loss of better than -1.3  dB with modal cross talk lower than -26  dB, over a 65 nm wavelength range. Finally, we have experimentally demonstrated that the device is tolerant of fabrication errors of up to 20 nm. Better than -6  dB TE0-TE1 conversion loss with a cross talk lower than -23  dB over a 55 nm bandwidth has been obtained with a fabrication tolerance as large as 40 nm.

Fiber-chip edge couplers are extensively used in integrated optics for coupling of light between planar waveguide circuits and optical fibers. In this work, we report on a new fiber-chip edge coupler concept with large mode size for silicon photonic wire waveguides. The coupler allows direct coupling with conventional cleaved optical fibers with large mode size while circumventing the need for lensed fibers. The coupler is designed for 220 nm silicon-on-insulator (SOI) platform. It exhibits an overall coupling efficiency exceeding 90%, as independently confirmed by 3D Finite-Difference Time-Domain (FDTD) and fully vectorial 3D Eigenmode Expansion (EME) calculations. We present two specific coupler designs, namely for a high numerical aperture single mode optical fiber with 6 µm mode field diameter (MFD) and a standard SMF-28 fiber with 10.4 µm MFD. An important advantage of our coupler concept is the ability to expand the mode at the chip edge without leading to high substrate leakage losses through buried oxide (BOX), which in our design is set to 3 µm. This remarkable feature is achieved by implementing in the SiO 2 upper cladding thin high-index Si 3 N 4 layers. The Si 3 N 4 layers increase the effective refractive index of the upper cladding near the facet. The index is controlled along the taper by subwavelength refractive index engineering to facilitate adiabatic mode transformation to the silicon wire waveguide while the Si-wire waveguide is inversely tapered along the coupler. The mode overlap optimization at the chip facet is carried out with a full vectorial mode solver. The mode transformation along the coupler is studied using 3D-FDTD simulations and with fully-vectorial 3D-EME calculations. The couplers are optimized for operating with transverse electric (TE) polarization and the operating wavelength is centered at 1.55 µm.

We propose a novel method to implement a compact and fabrication-tolerant polarization splitter and rotator (PSR) on the silicon-on-insulator platform. The PSR consists of a silicon wire waveguide coupled to a subwavelength grating (SWG) waveguide in an asymmetrical directional coupler. The SWG effect allows an additional degree of design freedom to engineer the equivalent material refractive index. This is advantageously used to effectively compensate for fabrication inaccuracies in PSRs. Our simulation results show that the PSR has a low TM-to-TE polarization conversion loss of -0.13  dB (a conversion efficiency of 97%) at the wavelength of 1550 nm, and better than -0.4 dB conversion loss over the entire C-band wavelength range. Compared to the PSRs made of conventional wire waveguides, the use of SWG index engineering improves the waveguide width fabrication tolerance substantially, from ±3  nm to ±40  nm. A compact device size with a coupling length of 25 μm is achieved.

We propose a fabrication tolerant polarization splitter and rotator (PSR) on the silicon-on-insulator platform based on the mode-coupling mechanism. The PSR consists of a silicon wire waveguide coupled to a taper-etched waveguide. Compared to previously reported PSRs based on directional couplers which are sensitive to fabrication variations, the partially etched taper structure can compensate for fabrication inaccuracies. In addition, the taper-etched geometry breaks both the horizontal and vertical symmetries of the waveguide, introducing an additional degree of design freedom to accommodate different upper cladding layers. The proposed PSR can be readily integrated in a planar waveguide circuit using e.g. SiO(2) cladding, making it compatible with typical metal back-end-of-line processes. Our simulation results show that the PSR has a low TM-to-TE polarization conversion loss of -0.09 dB in the C-band (or a conversion efficiency of 98%). A low TE-to-TE through insertion loss (-0.07 dB) and a very low polarization crosstalk (-30 dB) over a wide wavelength range exceeding 160 nm with a large fabrication tolerance (>50 nm) are numerically demonstrated.

Mode-division multiplexing (MDM) is an emerging multiple-input multiple-output method, utilizing multimode waveguides to increase channel numbers. In the past, silicon-on-insulator (SOI) devices have been primarily focused on single-mode waveguides. We present the design and fabrication of a two-mode SOI ring resonator for MDM systems. By optimizing the device parameters, we have ensured that each mode is treated equally within the ring. Using adiabatic Bezier curves in the ring bends, our ring demonstrated a signal-to-crosstalk ratio above 18 dB for both modes at the through and drop ports. We conclude that the ring resonator has the potential for filtering and switching for MDM systems on SOI.

We theoretically investigate for the first time an all-optical switch using a silicon-based ring-assisted Mach-Zehnder interferometer (RAMZI), where the switch mechanism relies on Raman-induced loss. Compared to the conventional standalone microring resonator (MRR) switches, the RAMZI structure improves the fabrication tolerances by removing the critical coupling requirement for the MRR without compensating the switch performance. Moreover, the RAMZI structure provides an improved switching speed (5× faster) by shortening the photon lifetime of the MRR. Finally, the inverse Raman scattering of silicon guarantees a single wavelength selectivity for the switch.

We use the LOCal oxidation of silicon (LOCOS) method as a fabrication technique to define submicrometer photonic waveguides. We attempted fabricating the wire waveguides with two different masking processes, one with a stack of pad oxide and silicon nitride layers, and the other with a single silicon nitride layer. The smallest waveguide we achieved had a cross-section profile of 280 nm×650 nm. The propagation loss of the waveguides was measured by the cut-back method, and the bending loss was measured by employing the serpentine pattern. The minimum propagation loss achieved was 8.78 dB/cm and the bending loss was 0.0089 dB/90° bend for a 5 μm bending radius.

In this paper, athermal silicon waveguides using bridged subwavelength grating (BSWG) structures are proposed and investigated. The realization of temperature-independent BSWG waveguides for both polarizations is demonstrated numerically and experimentally. SU-8 polymer is used as the cladding material to compensate for the positive thermo-optic (TO) coefficient (dn/dT) of silicon. We investigate the dependence of the effective TO coefficient of BSWG waveguides on both the bridge width and grating duty cycle. The BSWG waveguides have a width of 490 nm, a height of 260 nm, and a grating pitch of 250 nm. Athermal behavior is achieved for both the transverse-magnetic (TM) and the transverse-electric (TE) polarized light for a variety of bridge width and duty cycle combinations. Furthermore, the BSWGs can be designed to be athermal for both TE and TM polarization simultaneously.

We demonstrate, by experiment and numerical calculations, temperature-independent subwavelength grating waveguides with a periodic composite core composed of alternating regions of silicon and SU-8 polymer. The polymer has a negative thermo-optic (TO) material coefficient that cancels the large positive TO effect of the silicon. Measurements and Bloch mode calculations were carried out over a range of silicon-polymer duty ratios. The lowest measured TO coefficient at a wavelength of 1550 nm is 1.8×10(-6) K(-1); 2 orders of magnitude smaller than a conventional silicon photonic wire waveguide. Calculations predict the possibility of complete cancellation of the silicon waveguide temperature dependence., (© 2011 Optical Society of America)

We report the design criteria and performance of Si ring resonators for passive athermal applications in wavelength division multiplexing (WDM). The waveguide design rules address i) positive-negative thermo-optic (TO) composite structures, ii) resonant wavelength dependent geometry to achieve constant confinement factor (Gamma), and iii) observation of small residual second order effects. We develop exact design requirements for a temperature dependent resonant wavelength shift (TDWS) of 0 pm/K and present prototype TDWS performance of 0.5 pm/K. We evaluate the materials selection tradeoffs between high-index contrast (HIC) and low-index contrast (LIC) systems and show, remarkably, that FSR and footprint become comparable under the constraint of athermal design.

We demonstrate a form of scanning microscopy using a short-focal-length Fresnel zone plate and a low-NA relay telescope. Owing to a focal length of only 5 microm, the zone plate produces large wavefront tilt and consequently severe vignetting for off-axis illumination. By scanning an optically trapped fluorescent sphere, we measure the vignetted collection region of the zone-plate imaging system. The fluorescence collection efficiency is sharply peaked and has a lateral width of 550 nm, which agrees with numerical simulations.

We present the implementation of a novel wavelength independent polarization splitter on a silicon-on-insulator platform. The waveguide splitter is based on a zero-order arrayed waveguide grating (AWG) configuration. The splitting function is realized by employing cladding stress-induced birefringence. The device demonstrated a TE to TM splitting ratio better than -15 dB over a 20 nm tuning range centered around lambda=1550 nm and better than -10 dB over our entire accessible wavelength range from lambda=1465 nm to 1580 nm. The highest splitting extinction ratio achieved was -20 dB. To our knowledge, this is the first reported passive broadband polarization splitter based on AWG.

We propose and demonstrate the use of the cladding stress-induced photoelastic effect to eliminate modal birefringence in silicon-on-insulator (SOI) ridge waveguides. Birefringence-free operation was achieved for waveguides with otherwise large birefringence by use of properly chosen thickness and stress of the upper cladding layer. With the stress levels typically found in cladding materials such as SiO2, the birefringence modification range can be as large as 10(-3). In arrayed waveguide grating demultiplexers that were fabricated in a SOI platform, we demonstrated the reduction of the birefringence from 1.2 x 10(-3) (without the upper cladding) to 4.5 x 10(-5) when a 0.8-microm oxide upper cladding with a stress of -320 MPa (compressive) was used. Because the index changes induced by the stress are orders of magnitude smaller than the waveguide core-cladding index contrast, the associated mode mismatch loss is negligible.

The thermostability of glucose oxidase (beta-D-glucose: oxygen 1-oxidoreductase, EC 1.1.3.4) at 60 degrees C has been studied as a function of its concentration in various media (pure water and pure deuterium oxide). In deuterium oxide, glucose oxidase is more stable than in water, and two kinds of stabilizing effect have been observed: the medium-organization effect and the enzyme-concentration effect. This effect has been related to the glucose oxidase subunit structure. This enzyme contains four forms of subunit: monomer, dimer, trimer, and tetramer, which are all composed of the identical monomer. The monomers of glucose oxidase subunits are linked by the non-covalent bond. Only dimer and trimer possess the enzymatic activity. During glucose oxidase denaturing, monomers assemble into dimer, trimer, or tetramer. This redistribution behavior depends on the enzyme concentration and the nature of the medium.