Search

Silicon-based electronic-photonic integrated circuits, which are compatible with state-of-the-art complementary metal-oxide-semiconductor processes, offer promising opportunities for on-chip mid-infrared photonic systems. However, the lack of efficient mid-infrared optical modulators on silicon hinders the utilization of such systems. Here, we demonstrate the Franz-Keldysh effect in GeSn alloys and achieve mid-infrared electro-absorption optical modulation using GeSn heterostructures on silicon. Our experimental and theoretical results verify that the direct bandgap energy of GeSn can be widely tuned by varying the Sn content, thereby realizing wavelength-tunable optical modulation in the mid-infrared range with a figure-of-merit greater than 1.5 and a broadband operating range greater than 140 nm. In contrast to conventional silicon-photonic modulators based on the plasma dispersion effect, our GeSn heterostructure demonstrates practical and effective Franz-Keldysh mid-infrared optical modulation on silicon, helping to unlock the potential of electronic-photonic integrated circuits in a wide range of applications. Silicon-based electronic-photonic integrated circuits are promising for various applications, but their mid-infrared optical modulation is elusive. Here, tunable mid-infrared electro-absorption modulation, with broadband operation range >140 nm, is achieved in GeSn alloys on Si by controlling the Sn content.

Miniaturized flat and ultrathin optical components with spatial and polarization degrees of freedom are important for optical communications. Here, we use nanostructures that act as tiny phase plates on a dielectric metalens to generate a concentric polarization beam with different orientations along the radial direction. The important discoveries are that (1) the circularly polarized light can be converted into linearly polarized states with a different orientation at near field and that (2) this orientation is strongly correlated to the rotation of the nanostructures on the metalens. Stokes parameters are utilized to investigate the comprehensive polarization states embedded in the optical intensity along the propagation direction. The variation of the spatial polarization states transformed by the dielectric metalens can be properly mapped onto the Poincaré sphere. We believe that the variety of spatial polarizations within a miniaturized configuration provides a new degree of freedom for diverse applications in the future.

Recently, autonomous driving has become one of the most popular topics for smart vehicles. However, traditional control strategies are mostly rule-based, which have poor adaptability to the time-varying traffic conditions. Similarly, they have difficulty coping with unexpected situations that may occur any time in the real-world environment. Hence, in this paper, we exploited Deep Reinforcement Learning (DRL) to enhance the quality and safety of autonomous driving control. Based on the road scenes and self-driving simulation modules provided by AirSim, we used the Deep Deterministic Policy Gradient (DDPG) and Recurrent Deterministic Policy Gradient (RDPG) algorithms, combined with the Convolutional Neural Network (CNN), to realize the autonomous driving control of self-driving cars. In particular, by using the real-time images of the road provided by AirSim as the training data, we carefully formulated an appropriate reward-generation method to improve the convergence speed of the adopted DDPG and RDPG models and the control performance of moving driverless cars.

Several tools provide popular solutions for creating innovative Internet of Things (IoT) applications on single Arduino board. However, interactions among multiple Arduino boards need significant effort to be established. This paper proposes Arduino-IoTtalk (ArduTalk), a graphical user interface (GUI)-based platform aims to develop IoT network applications for interaction among multiple Arduino boards. ArduTalk utilizes IoTtalk, an IoT device management platform for quickly establishing connections and meaningful interactions between IoT devices without concerning the lower layer communication protocols. In this paper, the IoTtalk GUI has been significantly enhanced for ArduTalk. By integrating Arduino with the enhanced IoTtalk, ArduTalk allows a user to arbitrarily link and relink sensors to actuators without or with little programming effort, and quickly generate Arduino applications for different purposes. We conduct measurements to investigate the time complexity for data delivery among multiple Arduino boards, and propose a damping mechanism to address the fairness issue caused by the discrepancies between local and remote delays among the Arduino boards.

We report mid-infrared optical modulation in GeSn photodiodes on silicon. The incorporation of Sn into Ge shrinks the direct bandgap energy, redshifting the absorption edge to longer wavelengths and enabling electro-absorption optical modulation based on Franz-Keldysh effect in the mid-infrared range.

Display Omitted Gd2O3-based flash memories have been fabricated.Ti doping and annealing could enhance good memory performance.Multiple material analyses confirm that annealing eliminated defects.Electrical measurements were used to evaluate memory performance. In this study, the effects of various annealing temperatures on gadolinium oxide (Gd2O3) fabricated with Al2O3 and Ti-doped gadolinium oxide (GdTixOy) fabricated with SiO2 blocking were examined for use in metal/oxide/high-k material/oxide/silicon (MOHOS) memory devices. To investigate the effects of annealing, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM) were used to characterize the trapping layers. Capacitance voltage curves (CV), and P/E (program/erase) cycle experimental details were also applied to analyze the electrical properties of the experimental samples. Study results show that a GdTixOy charge trapping layer annealed at 900?C had a higher window in a current-voltage (CV) hysteresis loop and a higher charge retention capability than under any of the other fabrication conditions. These results were attributed to higher probability of deep-level charge trapping and lower leakage current. A GdTixOy memory device with post-annealing shows promise for future flash memory applications.

LoRa, an emerging wireless technology, is examined for long range communication performance in a large area. Although LoRa shows good performance for long-distance transmission in the countryside, its radio signals can be attenuated and interfered with by buildings, trees and other signal sources. In urban areas, our observation shows that LoRa requires a dense deployment of LoRa gateways to ensure that indoor LoRa devices can transfer data back to remote servers. Mesh networking is a solution for increasing the communication range and packet delivery ratio without the need to install additional LoRa gateways. This study presents our design of a LoRa mesh-networking module for IoT applications (e.g.,collecting data from multiple, widely distributed sensors on a university campus). We deployed 19 LoRa mesh-networking devices distributed in an 800m by 600m area on campus to serve as a gateway and to collect data at one-minute intervals. The results show our LoRa mesh networking module achieved a 88.49% packet delivery ratio (PDR), while the LoRaWAN in star-network topology was only 58.7% under the same conditions.

Optical detection at 2-μm wavelength spectral range has recently attracted increasing attention for many important applications. This can be done using narrow-bandgap III-V or II-VI based semiconductor photodetectors (PDs). Here, we report on group-IV based GeSn/Ge multiple-quantum-well (MQW) photoconductive photodetectors (PDs) for optical detection at the 2μm wavelength band. By introducing Sn into the well, the direct bandgap is reduced, thereby extending the absorption edge into longer wavelengths. The optical responsivity measurements reveal that the detection of the fabricated PDs is extended beyond 2000 nm. These results demonstrate the feasibility of GeSn/Ge MQW PDs for optical detection at the 2μm wavelength band.

We report GeSn p-i-n resonant-cavity-enhanced photodetectors (RCEPDs) grown on silicon-on-insulator substrates. A vertical cavity, composed of a buried oxide as the bottom reflector and a deposited SiO2 layer on the top surface as the top reflector, is created for the GeSn p-i-n structure to enhance the light-matter interaction. The responsivity experiments demonstrate that the photodetection range is extended to 1820 nm, completely covering all the telecommunication bands, because of the introduction of 2.5% Sn in the photon-absorbing layer. In addition, the responsivity is significantly enhanced by the resonant cavity effects, and a responsivity of 0.376 A/W in the telecommunication C-band is achieved that is significantly higher than that of conventional GeSn-based PDs. These results demonstrate the feasibility of CMOS-compatible, high-responsivity GeSn-based PDs for shortwave infrared applications.

Utility pattern mining has received extensive attentions in recent years due to the wide and novel applications in various fields like e-commerce, Web mining, finance, biomedicine, etc. However, there exists not yet a toolbox for utility pattern mining so far. In this work, we address this issue by proposing a first-of-its-kind toolbox named UP-Miner (Utility Pattern Miner) that provides various functions for utility pattern mining. The main merits of UP-Miner lie in three aspects: First, it offers implementations of thirteen state-of-the-art algorithms for efficiently mining different types of utility patterns, such as high utility itemsets, high utility episodes and utility-based sequential patterns, as well as four functionalities for processing utility-based databases. Second, it is a cross-platform system implemented in Java with a user-friendly graphical interface. Third, the toolbox and relevant materials, including source codes, benchmark datasets and data generators, are made public on Web (http://bigdatalab.cs.nctu.edu.tw/software.htm) for benefiting the research community.

It is reported that field emission can effectively enhanced for aligned carbon nanotubes (CNTs) as field emitters when the ratio of distance between neighboring nano-tubes to the height of each individual CNT is about 2. In this paper, we proposed pillar array design of CNTs to fulfill the optimum R/H ratio (the ratio between inter-pillar distance R and pillar height H) with high density of aligned CNTs by changing H while maintaining R at 100μm, respectively. From the obtained experimental results, ultra-low turn-on field at 0.81V/μm and the ultra-high field emission current density (1A/cm2 at 2.8 V/μm) were achieved at the optimum R/H ratio of 2 with the inter-pillar distance of 100μm.

In this paper, Fe/Ti and Co/Ti bi-layered catalysts were used to study the growth and field emission characteristics of carbon nanotubes(CNTs). Nanoparticles of Co/Ti bi-layered catalyst are uniform in size and smaller than those from Fe/Ti bi-layered catalyst. Well graphite structure of CNTs grown by Fe/Ti and Co/Ti bi-layered catalysts were confirmed by TEM and Raman analyses. Besides, CNTs grown by Co/Ti catalyst show better field emission image uniformity and stability than that by Fe/Ti catalyst. Besides, the turn-on fields of CNTs Grown by Fe/Ti and Co/Ti bi-layered catalysts were about the same (1.6 V/μm for Co case and 1.9V/μm for Fe case). The field emission current density at 6.667V/μm achieved 678.2A/cm2 and 730.7 mA/cm2 for Fe/Ti and Co/Ti bi-layered catalysts, respectively.

Effect of carbon nanotube pillar arrays' edge effect on field emission characteristics is first studied. The ratio of field emission current density at 5.733V/µm is about 55∶ 6.5∶ 1 which is nearly proportional to the edge ratio (50∶5∶1) for small, middle, and large sizes of CNTs' arrays. Besides, ultra low turn-on field (∼1.4 V/µm), well emission image uniformity and stability of about ±6.52 % at 650V were also achieved.

In order to improve the thermostability of the Penicillium expansum Lipase (PEL), the lipase encoding genes was mutated by site-directed mutagenesis. A recombinant vector pAO815-ep8-K55R which contain double mutant genes was constructed by overlap extension PCR using the cDNA of a random-mutant lipase ep8 (a single site mutant) as the template and two special primers were used to generate another mutation site K55R. The recombinant vector was transformed into Pichia pastoris GS115 by electroporation and the recombinant mutant GS-pAO815-ep8- K55R can secret double-mutant lipase PEL-ep8-K55R-GS into the medium when it was induced by Methanol. The yield of the double-mutant lipase is 508 u/mL, which is 81% that of the wild type lipase PEL-GS (627 u/mL) and 55% that of random-mutant PEL-ep8-GS (924 u/mL). The specific activity of double-mutant lipase is 2309.1 u/mg, which is similar to random-mutant lipase PEL-ep8-GS and the wild type lipase PEL-GS. The optimum temperature of the double-mutant lipase is same with the wild type lipase PEL-GS and random-mutant lipase PEL-ep8-GS. While the Tm of the double-mutant lipase is 41.0 degrees C, 2.3 degrees C higher than the wild type lipase PEL-GS and 0.8% higher than the random-mutant lipase PEL-ep8-GS, indicating that the double-mutant lipase PEL-ep8-K55R-GS has higher thermostability.