An optical phased array (OPA) in silicon nitride (SiN) is conspicuously highlighted as a vital alternative to its counterpart in silicon. However, a limited number of studies have been conducted on this array in terms of wavelength-tuned beam steering. A SiN OPA has been proposed and implemented with a grating antenna that incorporated an array of shallow-etched waveguides, rendering wavelength-tuned beam steering along the longitudinal direction. To accomplish a superior directionality on a wavelength-tuned beam steering, the spectral beam emission characteristics of the antenna have been explored from the viewpoint of a planar structure that entails a buried oxide (BOX), a SiN waveguide core, and an upper cladding. Two OPA devices having substantially different thicknesses of the resonant cavities, established by combining the BOX and SiN core, were considered theoretically and experimentally to scrutinize the spectral emission characteristics of the antenna on beam steering. Both of the fabricated OPA devices steered light by an angle of 7.4° along the longitudinal direction for a wavelength ranging from 1530 to 1630 nm, while they maintained a divergence angle of 0.2°×0.6° in the longitudinal and lateral directions. Meanwhile, the OPA fabricated on a substantially thick BOX layer featured a limited steering performance to attain a stabilized response over a broad spectral region. We examined the influence of the cavity thickness on the spectral response of the antenna in terms of optical thickness. Based on the two antenna characteristics, it was confirmed that the grating antenna emitted the beam with a higher efficiency when the optical thickness of the cavity corresponded to odd integer multiples of the quarter wavelength. This work is a considerable strategy for designing a stabilized SiN OPA over a desired spectral region.

Optical phased array (OPA) devices are being actively investigated to develop compact solid-state beam scanners, which are essential in fields such as LiDAR, free-space optical links, biophotonics, etc. Based on the unique nature of perfluorinated polymers, we propose a polymer waveguide OPA with the advantages of low driving power and high optical throughput. Unlike silicon photonic OPAs, the polymer OPAs enable sustainable phase distribution control during beam scanning, which reduces the burden of beamforming. Moreover, by incorporating a tunable wavelength laser comprising a polymer waveguide Bragg reflector, two-dimensional beam scanning is demonstrated, which facilitates the development of laser-integrated polymeric OPA beam scanners.

ObjectiveRecent genome-wide association studies have identified 33 human genetic loci that influence blood pressure. The 15q24 locus is one such locus that has been confirmed in Asians and Europeans. There are 21 genes in the locus within a 1-Mb boundary, but a functional link of these genes to blood pressure has not been reported. We aimed to identify a causative gene for blood pressure change in the 15q24 locus.Methods and ResultsCSK and ULK3 were selected as candidate genes based on eQTL analysis studies that showed the association between gene transcript levels and the lead SNP (rs1378942). Injection of siRNAs for mouse homologs Csk, Ulk3, and Cyp1a2 (negative control) showed reduced target gene mRNA levels in vivo. However, Csk siRNA only increased blood pressure while Ulk3 and Cyp1a2 siRNA did not change it. Further, blood pressure in Csk+/- heterozygotes was higher than in wild-type, consistent with what we observed in Csk siRNA-injected mice. We confirmed that haploinsufficiency of Csk increased the active form of Src in Csk+/- mice aorta. We also showed that inhibition of Src by PP2, a Src inhibitor decreased high blood pressure in Csk+/- mice and the active Src in Csk+/- mice aorta and in Csk knock-down vascular smooth muscle cells, suggesting blood pressure regulation by Csk through Src.ConclusionsOur study demonstrates that Csk is a causative gene in the 15q24 locus and regulates blood pressure through Src, and these findings provide a novel therapeutic target for the treatment of hypertension.

Wavelength-division multiplexed optical communication systems used in 5G networks require tunable wavelength filters with narrow bandwidth for 100 GHz channel spacing, wide wavelength range to cover 16 channels, and a side mode suppression ratio (SMSR) exceeding 30 dB. To fabricate wavelength filters satisfying these specifications, tunable Bragg grating filters based on polymeric optical waveguides are proposed. The combination of mode-sorting waveguide and tilted Bragg grating enables the extraction of Bragg reflected signals to another path, without using an external circulator. Moreover, the double reflection by the two-stage cascaded structure produces narrower reflection bandwidth, improved SMSR characteristics, and reduced adjacent-channel crosstalk through the suppression of undesired mode coupling. The proposed device exhibits a 20 dB bandwidth of 1.0 nm and SMSR of 35 dB, over the entire wavelength-tuning range.

We have proposed and experimentally realized an ultra-compact and broadband silicon nitride edge-coupler that enables high coupling efficiency. The proposed coupler was realized by concatenating short tapers in four stages, whose angles were designed to minimize the footprint while preserving the coupling efficiency. The constituting taper segments were designed by carefully sectioning a long adiabatic taper while adapting to an appropriate taper angle for each segment. The designed coupler exhibited an extremely short footprint of 76 μm. A coupling efficiency of 92% was experimentally attained at 1550 nm wavelength when coupled to a single-mode fiber having a mode field diameter of ~4 μm. Further, an efficiency of over 90% throughout the C and L bands was observed. A 3-dB bandwidth of 965 nm, spanning λ =1015-1980 nm, was achieved in the simulation. Additionally, the fabricated device exhibited an enhanced cleaving tolerance by virtue of its elongated tip, along with relaxed alignment tolerances ranging up to 3.5 μm. The proposed design was also found to comply with the waveguides having widths between 1 μm and 4 μm without affecting the overall footprint and efficiency. This work is anticipated to provide a promising foundation for the development of compact photonic devices.