Xuelin Yang

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By employing a single AlGaN layer with low Al composition, high quality and uniformity AlGaN/GaN heterostructures have been successfully grown on Si substrates by metal-organic chemical vapor deposition (MOCVD). The heterostructures exhibit a high electron mobility of 2150 cm(2)/Vs with an electron density of 9.3 × 10(12) cm(-2). The sheet resistance is 313(More)
Fifteen dihydroartemisinin derivatives containing a substituted chalcone linked by either ether or ester were synthesized and investigated for their cytotoxicity in human leukemia HL-60 and mouse lymphoma P388 cells. These derivatives have greater antiproliferative and cytotoxic effects in both cell lines than dihydroartemisinin. Dihydroartemisinin(More)
Dirac-like surface states on surfaces of topological insulators have a chiral spin structure with spin locked to momentum, which is interesting in physics and may also have important applications in spintronics. In this work, by measuring the tunable helicity-dependent photocurrent (HDP), we present an identification of the HDP from the Dirac-like surface(More)
This paper reviews some of the most recent methods for increasing the speed of operation of all-optical switches based on semiconductor optical amplifiers (SOAs). We concentrate on two approaches; namely, methods to utilise the high-frequency tail of the nonlinear optical response of SOAs, and ways to reduce their gain recovery time.
We propose a symmetric 40-Gb/s aggregate rate time and wavelength division multiplexed passive optical network (TWDM-PON) system with the capability of simultaneous downstream differential phase shift keying (DPSK) signal demodulation and upstream signal chirp management based on delay interferometer (DI). With the bi-pass characteristic of DI, we(More)
We propose and analyze a novel physical layer security scheme with the capability of resisting the chosen plaintext attacks in OFDM data transmission. The proposed security scheme consists of a multiple-fold data encryption based on hyper digital chaos, which provides a huge key space. The first chaotic encryption is applied in the chaotic OFDM subcarrier(More)
We present two types of 42.6 Gbit/s all-optical non-return-zero (NRZ) to return-zero (RZ) format converters using semiconductor optical amplifiers (SOAs). The converters are based on cross-phase modulation (XPM) and cross-polarisation modulation (XPolM) in SOAs. Both format converters produce a correctly-coded, polarity- preserved RZ signal at the output(More)
Cloud radio access networks (C-RANs) feature central pooling baseband processing units (BBUs) and lowcost remote radio headends (RRHs) with fiber-connected fronthauls between them, and they are promising for 4G. Researchers are redesigning the C-RAN with different split approaches to relax the fronthaul capacity for 5G with massive antennas, which is termed(More)
We propose a symmetric 40-Gb/s time and wavelength division multiplexed passive optical network (TWDM-PON) system with directly modulated laser (DML) as both downstream and upstream transmitters. A single bi-pass delay interferometer (DI), deployed in the optical line terminal (OLT), is used to mitigate multiple channels' signal distortions induced by laser(More)
We report an all-optical flip-flop that is based on two coupled actively mode-locked fiber ring lasers. The lasers are coupled so that when one of the lasers lases, it quenches lasing in the other laser. The state of the flip-flop is determined by the wavelength of the laser that is currently lasing. The concept of the flip-flop is explained and(More)