Browsing by Author "Xu, Ke"

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56 Gbit/s DMT Signal Generated by an Integrated Silicon Ring Modulator
(2016)
Xu, Ke
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Wong, Chi Yan
;
Zhang, Liang
;
Liu, Lei
;
Liu, Gordon Ning
We demonstrate a 56 Gb/s DMT signal using a compact silicon microring modulator. The measured bit error rate of back to back modulated signal is well below the FEC limit.
A secure WDM ring access network employing silicon micro-ring based remote node
(2014-08-01)
Sung, Jiun-Yu
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Chow, Chi-Wai
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Yeh, Chien-Hung
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Xu, Ke
;
Hsu, Chin-Wei
A secure and scalable wavelength-division-multiplexing (WDM) ring-based access network is proposed and demonstrated using proof-of-concept experiments. In the remote node (RN), wavelength hopping for specific optical networking unit (ONU) is deployed by using silicon micro-ring resonators (SMR). Using silicon-based devices could be cost-effective for the cost-sensitive access network. Hence the optical physical layer security is introduced. The issues of denial of service (DOS) attacks, eavesdropping and masquerading can be made more difficult in the proposed WDM ring-based access network. Besides, the SMRs with different dropped wavelengths can be cascaded, such that the signals pass through the preceding SMRs can be dropped by a succeeding SMR. This can increase the scalability of the RN for supporting more ONUs for future upgrade. Here, error-free 10 Gb/s downlink and 1.25 Gb/s uplink transmission are demonstrated to show the feasibility of the proposed network. (C) 2014 Elsevier Inc. All rights reserved.
AlGaN/GaN high electron mobility transistors with a low sub-threshold swing on free-standing GaN wafer
(2017-09-01)
Liu, Xinke
;
Gu, Hong
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Li, Kuilong
;
Guo, Lunchun
;
Zhu, Deliang
This paper reported AlGaN/GaN high electron mobility transistors (HEMTs) with low sub-threshold swing SS on free-standing GaN wafer. High quality AlGaN/GaN epi-layer has been grown by metal-organic chemical vapor deposition (MOCVD) on free-standing GaN, small full-width hall maximum (FWHM) of 42.9 arcsec for (0002) GaN XRD peaks and ultralow dislocation density (similar to 10(4)-10(5) cm(-2)) were obtained. Due to these extremely high quality material properties, the fabricated AlGaN/GaN HEMTs achieve a low SS (similar to 60 mV/decade), low hysteresis of 54 mV, and high peak electron mobility mu(eff) of similar to 1456 cm(2)V(-1)s(-1). Systematic study of materials properties and device characteristics exhibits that GaN-on-GaN AlGaN/GaNHEMTsare promising candidate for next generation high power device applications. (C) 2017 Author(s).
Amplitude and Phase Modulation of UWB Monocycle Pulses on a Silicon Photonic Chip
(2016-02-01)
Xu, Ke
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Wu, Xinru
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Sung, Jiun-Yu
;
Cheng, Zhenzhou
;
Chow, Chi Wai
We demonstrate both the amplitude and bi-phase modulation of ultrawideband (UWB) monocycle pulses using silicon microring modulator. The integrated silicon ring modulator generates the monocycle pulse train and modulates it simultaneously. By applying different driving voltages, the amplitude and phase-modulated UWB signal with a data rate of 2.5 Gb/s are achieved. The ring modulator can be thermally tuned for a free spectral range with a similar to 50-mW power consumption.
Compatibility of Silicon Mach-Zehnder Modulators for Advanced Modulation Formats
(2013-08-01)
Xu, Ke
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Yang, Ling-Gang
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Sung, Jiun-Yu
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Chen, Yimin M.
;
Cheng, Zhenzhou Z.
Silicon photonics which is compatible with mature complementary metal oxide semiconductor (CMOS) fabrication process has been extensively demonstrated for monolithic integration of photonic and electrical circuits. We show that an integrated silicon Mach-Zehnder modulator (MZM) may be used for advanced modulation formats despite the nonlinear dependence of refractive index change with applied voltage in the free-carrier depletion modulator. We experimentally demonstrated the use of a silicon MZM for direct detection optical orthogonal frequency division multiplexing (DDO-OFDM) modulation with advanced data formats of quadrature phase-shift keying (QPSK), 8 phase-shift keying (8PSK) and 16-quadrature amplitude modulation (16-QAM). The measured bit error rate performance of the back-to-back and 50 km single mode fiber transmission of each format is well below the forward error correction limit.
GaN Schottky Barrier Diodes on Free-Standing GaN Wafer
(2017-01-01)
Liu, Xinke
;
Gu, Hong
;
Li, Kuilong
;
Wang, Jianfeng
;
Wang, Lei
In this paper, vertical GaN Schottky barrier diodes (SBDs) have been demonstrated on the freestanding (FS) GaN wafer. Room temperature photoluminescence shows no emission of yellow luminescence, due to the eliminating the point defects (O-N, V-Ga). The average full width half maximum (FWHM) value of.-scans for (0001) and (10-12) planes is 53 and 103 arcsec, respectively, as measured by high resolution X-ray diffraction; the average dislocation density at the top surface measured by cathodoluminescence is similar to 7.7 x 10(5) cm(-2). The vertical GaN SBDs fabricated on this FS-GaN wafer achieve a breakdown voltage of 1200 V, an on-state resistance R-on of 7 m Omega.cm(2), and a current on/off ratio I-on/I-off of similar to 2.3 x 10(10), which leads to a power device figure-of-merit V-BR(2)/R-on of 2.1 x 10(8) V-2 Omega(-1) cm(-2). TCAD simulation was employed to study the device breakdown mechanism, and shows the breakdown mechanism is due to the impact ionization at the edge of the Schottky gate. (c) 2017 The Electrochemical Society. All rights reserved.
Methods for Power/Throughput/Area Optimization of H.264/AVC Decoding
(2010-07-01)
Xu, Ke
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Liu, Tsu-Ming
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Guo, Jiun-In
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Choy, Chiu-Sing
;
交大名義發表
This paper presents methods for efficient optimization of ASIC implementation for H.264/AVC video decoding. A systematic approach in optimization is presented in a top-down flow. Tradeoffs among Power, Throughput, and Area (PTA) at both system level and block level are studied and balanced. The system architecture is first evaluated. We then focus on the pipeline organization, parallelism, and memory architecture optimization. Different pipeline granularities are compared and their pros-and-cons are evaluated. Various parallel scenarios, especially 1 x 4-column and 4 x 1-row, are analyzed and compared. Then the detailed designs of various building blocks, such as inverse transform, inter prediction, and deblocking filter, are evaluated and their intrinsic characteristics are exploited to facilitate PTA optimization. Finally, we provide the design guidelines for ASIC implementation based on the analysis and our design experiences of five dedicated decoder chips.
Optical Nyquist filters based on silicon coupled resonator optical waveguides
(2014-10-15)
Xu, Ke
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Sung, Jiun-Yu
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Wong, Chi Yan
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Cheng, Zhenzhou
;
Chow, Chi Wai
We propose an integrated optical Nyquist filter based on silicon coupled resonator optical waveguides (CROW). The designed filter can shape the 28 Gbaud QPSK spectrum to a spectrum having 0.2 roll-off raised cosine shape with G-dB bandwidth equals to the baud rate. The impact of the fabrication tolerance induced coupling coefficients error on the figure of merits of the filter is considered. The filter overall performance is investigated in a Nyquist-WDM system and compared with a 4th order super Gaussian filter. (C) 2014 Elsevier B.V. All rights reserved.
Scalable Ultra-Wideband Pulse Generation Based on Silicon Photonic Integrated Circuits
(2017-11-01)
Wu, Xinru
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Xu, Ke
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Zhou, Wen
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Chow, Chi Wai
;
Tsang, Hon Ki
We demonstrate a scalable ultra-wideband (UWB) pulse generator using silicon photonic integrated circuits. A delay-and-superimpose principle for higher order UWB Guassian pulse generation is realized by monolithically integrating a pair of tunable microring resonators, a delayline waveguide, tap couplers, and an on-chip photodiode. The two microrings function as discrimination filters and generate the asymmetric monocycle pulses. For a proof-of-concept demonstration, the doublet pulses with a 10-dB fractional bandwidth of 100% and the triplet pulses with a 10-dB fractional bandwidth of 132% are generated by superposition of the two asymmetric pulses with a proper delay between them. The proposed scheme and the photonic chip can be scaled to generate more kinds of power-efficient pulses.
Vertical GaN-on-GaN PIN diodes fabricated on free-standing GaN wafer using an ammonothermal method
(2019-10-05)
Chen, Sung-Wen Huang
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Wang, Hao-Yu
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Hu, Cong
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Chen, Yong
;
Wang, Hao
We report vertical GaN-on-GaN PIN diodes with a record high figure-of-merit (V-BR(2)/R-on) of 29.7 GW/cm(2) on free-standing GaN wafer using a complementary metal-oxide-semiconductor (CMOS) compatible contact materials. Due to the low substrate resistivity, low contact resistance, and high quality of GaN drift layer, a low on-state resistance R(on )of 0.31 m Omega cm(2) is obtained. With integrating of the metal filed plate structure in the vertical device, the peak electrical field along the GaN mesa edge can be significantly reduced, thus leading to a high breakdown voltage V-BR of 3.04 kV. The vertical GaN-on-GaN PIN diodes in this work show turn-on voltage V-on of similar to 3.4 V, on/off current ratio of similar to 1.3 x 10(7), and ideal factor n of similar to 2.2. According to the reverse switching measurement, the reverse recovery time T-rr. (reverse recovery charge Q(rr)) is 22.8 ns (4.8 nC) and 24.0 ns (5.4 nC), respectively, under a testing temperature of 300 K and 500 K. (C) 2019 Elsevier B.V. All rights reserved.