Reduction of the Radiation Dose by Decreasing the Tube Current without Degradation of Low-Contrast Detectability on Abdominal Multi-Detector Row CT: A Phantom-Based Study

As use of the lowest acceptable radiation dose during routine diagnostic imaging is important, we determined the optimal tube current without degradation of low-contrast detectability on abdominal multi-detector row CT (MDCT). CT scanning was performed with a Catphan®?500 phantom. The optimal tube current was 300 mA on 64-MDCT and 160 mA on 8-MDCT, with a fixed voltage of 120 kV. Reduction of the radiation dose in abdominal CT scanning by lowering the tube current proved to be feasible.

On-chip generation of Bessel–Gaussian beam via concentrically distributed grating arrays for long-range sensing

Bessel beam featured with self-healing is essential to the optical sensing applications in the obstacle scattering environment.Integrated on-chip generation of the Bessel beam outperforms the conventional structure by small size,robustness,and alignment-free scheme.However,the maximum propagation distance(Z_(max))provided by the existing approaches cannot support long-range sensing,and thus,it restricts its potential applications.In this work,we propose an integrated silicon photonic chip with unique structures featured with concentrically distributed grating arrays to generate the Bessel-Gaussian beam with a long propagation distance.The spot with the Bessel function profile is measured at 10.24m without optical lenses,and the photonic chip’s operation wavelength can be continuously performed from 1500 to 1630 nm.To demonstrate the functionality of the generated Bessel-Gaussian beam,we also experimentally measure the rotation speeds of a spinning object via the rotational Doppler Effect and the distance through the phase laser ranging principle.The maximum error of the rotation speed in this experiment is measured to be 0.05%,indicating the minimum error in the current reports.By the compact size,low cost,and mass production potential of the integrated process,our approach is promising to readily enable the Bessel-Gaussian beam in widespread optical communication and micro-manipulation applications.

Silicon photonic platforms for mid-infrared applications [Invited]

Silicon photonic integrated circuits for telecommunication and data centers have been well studied in the past decade, and now most related efforts have been progressing toward commercialization. Scaling up the silicon-oninsulator(SOI)-based device dimensions in order to extend the operation wavelength to the short mid-infrared(MIR) range(2–4 μm) is attracting research interest, owing to the host of potential applications in lab-on-chip sensors, free space communications, and much more. Other material systems and technology platforms, including silicon-on-silicon nitride, germanium-on-silicon, germanium-on-SOI, germanium-on-silicon nitride, sapphireon-silicon, Si Ge alloy-on-silicon, and aluminum nitride-on-insulator are explored as well in order to realize low-loss waveguide devices for different MIR wavelengths. In this paper, we will comprehensively review silicon photonics for MIR applications, with regard to the state-of-the-art achievements from various device demonstrations in different material platforms by various groups. We will then introduce in detail of our institute's research and development efforts on the MIR photonic platforms as one case study. Meanwhile, we will discuss the integration schemes along with remaining challenges in devices(e.g., light source) and integration. A few application-oriented examples will be examined to illustrate the issues needing a critical solution toward the final production path(e.g., gas sensors). Finally, we will provide our assessment of the outlook of potential futureresearch topics and engineering challenges along with opportunities.

Wide-steering-angle high-resolution optical phased array

Optical phased array(OPA)technology is considered a promising solution for solid-state beam steering to supersede the traditional mechanical beam steering.As a key component of the LIDAR system for long-range detection,OPAs featuring a wide steering angle and high resolution without beam aliasing are highly desired.However,a wide steering range requires a waveguide pitch less than half of the wavelength,which is easily subjected to cross talk.Besides,high resolution requires a large aperture,and it is normally achieved by a high count number of waveguides,which complicates the control system.To solve the mentioned issues,we design two high-performance 128-channel OPAs fabricated on a multilayered SiN-on-SOI platform.Attributed to the nonuniform antenna pitch,only 128 waveguides are used to achieve a 4 mm wide aperture.Besides,by virtue of innovative dual-level silicon nitride(Si_(3)N_(4))waveguide grating antennas,the fishbone antenna OPA achieves a 100°×19.4°field of view(FOV)with divergence of 0.021°×0.029°,and the chain antenna OPA realizes a 140°×19.23°FOV with divergence of 0.021°×0.1°.To our best knowledge,140°is the widest lateral steering range in two-dimensional OPA,and 0.029°is the smallest longitudinal divergence.Finally,we embed the OPA into a frequency-modulated continuous-wave system to achieve 100 m distance measurement.The reflected signal from 100 m distance is well detected with 26 dBm input transmitter power,which proves that OPA serves as a promising candidate for transceiving optical signal in a LIDAR system.

Experimental observations of boundary conditions of continuous-time quantum walks

The continuous-time quantum walk (CTQW) is the quantum analogue of the continuous-time classical walk and is widely used in universal quantiim computations. Here, taking the advantages of the waveguide arrays, we implement large-scale CTQWs on chips. We couple the single-photon source into the middle port of the waveguide arrays and measure the emergent photon number distributions by utilizing the fiber coupling platform. Subsequently, we simulate the photon number distributions of the waveguide arrays by considering the boundary conditions. The boundary conditions are quite necessary in solving the problems of quantum mazes.

Three-terminal germanium-on-silicon avalanche photodiode with extended p-charge layer for dark current reduction

Germanium-on-silicon(Ge-on-Si) avalanche photodiodes(APDs) are widely used in near-infrared detection, laser ranging, free space communication, quantum communication, and other fields. However, the existence of lattice defects at the Ge/Si interface causes a high dark current in the Ge-on-Si APD, degrading the device sensitivity and also increasing energy consumption in integrated circuits. In this work, we propose a novel surface illuminated Ge-on-Si APD architecture with three terminals. Besides two electrodes on Si substrates, a third electrode is designed for Ge to regulate the control current and bandwidth, achieving multiple outputs of a single device and reducing the dark current of the device. When the voltage on Ge is -27.5 V, the proposed device achieves a dark current of 100 n A, responsivity of 9.97 A/W at -40 d Bm input laser power at 1550 nm, and optimal bandwidth of 142 MHz. The low dark current and improved responsivity can meet the requirements of autonomous driving and other applications demanding weak light detection.

Multivalent Display of Lipophilic DNA Binders for Dual-Selective Anti-Mycobacterium Peptidomimetics with Binary Mechanism of Action

We made oligoamidine-based peptidomimetics highly specific for mycobacteria eradication by introducing and arraying lipophilic DNA binding motifs on macromolecular backbones.The short poly(amidino-phenylindole)(PAPI)structures feature an alternating amphiphilic structure with cationic,lipophilic DNA-binding moieties,enabling fast and selective eradication of mycobacteria through binary,membrane-and DNA-selective mechanisms of action.More importantly,PAPIs address the primary treatment challenge by combating mycobacteria in eukaryotic cells and working as a sensitizer for conventional antibiotics,in bothways promoting more thorough removal of pathogens and reducing the mycobacteria’s resistance generation rate during treatment.Structural optimizationwas achieved to counter specific pathogens,including Mycobacterium tuberculosis,in the Mycobacterium genus.One of the hit peptidomimetics was evaluated in a zebrafish-based aquatic infection model using Mycobacterium fortuitum and a mice tail infection model using Mycobacterium marinum,both revealing excellent in vivo performance.