Browsing by Author "Chen, Jason"

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850 nm Vertical-Cavity Surface-Emitting Laser Arrays With Enhanced High-Speed Transmission Performance Over a Standard Multimode Fiber
(2017-08-01)
Yen, Jia-Liang
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Chen, Xin-Nan
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Chi, Kai-Lun
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Chen, Jason
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Shi, Jin-Wei
The functionality of novel parallel and series highspeed vertical-cavity surface-emitting laser (VCSEL) arrays, which can greatly relax the tradeoff between output power and modulation speed, is demonstrated. Both types of array structure allow improvement in the output power with no degradation in their maximum modulation speed as compared to a single reference unit. The observed invariant electrical-optical bandwidth shown for these array structures is mainly due to the effective reduction of the differential resistance and parasitic capacitance, arising from the Zn-diffusion and oxide-relief apertures fabricated in the VCSEL unit. This in turn minimizes the degradation in the RC-limited bandwidth with the VCSEL arrays. Furthermore, the dense packing of single VCSELs, with Zn-diffusion apertures for optical mode control, minimizes the coupling loss between the output from the array into a standard multimode fiber (MMF). Compared with the single VCSEL unit, the parallel VCSEL array shows a significant enhancement in transmission performance over a standard OM4 MMF, which includes a larger eye margin, a higher signal-to-noise ratio, as well as a higher error-free data rate (48 versus 44 Gbit/sec). The device modeling technique is used to perform device analysis. From the results we can conclude that the improvement with the parallel array is because the value of the internal impedance is closer to the 50-Omega signal source, which minimizes the microwave reflection induced timing jitter in the eye-patterns.
BJT-Type Optical Phase Shifter With Small Power Consumption and Fast Response Time on a Silicon Photonics Foundry Platform
(2020-03-01)
Chao, Rui-Lin
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Ahmad, Zohauddin
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Chen, Jason
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Lai, Yinchieh
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Shi, Jin-Wei
We demonstrate a novel optical phase shifter with a bipolar junction transistor (BJT) type of device structure based on the silicon photonics foundry platform. By operating such a device in saturation mode, we obtain measured output I-EC-V-EC characteristics very similar to those of an ideal diode, which has a nearly zero turn-on voltage and an extremely small differential resistance. The huge amount of injected current under a small voltage swing (0.1 V) in the operation window makes it possible to obtain significant plasma induced change of the refractive index in the optical waveguide with an extremely small driving-voltage. The device has a small foot-print (500 mu m in length), but exhibits small static power consumption for the pi phase-shift (P-pi: 4.1 mW), reasonable propagation loss (0.02 dB/mu m), small driving-voltage (V-pi: 0.12 V), fast switching time (rise/fall <1.6/1 ns), a residue amplitude modulation (RAM) as small as 0.18 dB, and a very-low power consumption (0.45 mW) during dynamic operation.
Coherently wavelength injection-locking a 600-mu m long cavity colorless laser diode for 16-QAM OFDM at 12 Gbit/s over 25-km SMF
(2013-07-15)
Li, Yi-Cheng
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Chi, Yu-Chieh
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Cheng, Min-Chi
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Lu, I-Cheng
;
Chen, Jason
The coherent injection-locking and directly modulation of a long-cavity colorless laser diode with 1% end-facet reflectance and weak-resonant longitudinal modes is employed as an universal optical transmitter to demonstrated for optical 16-QAM OFDM transmission at 12 Gbit/s over 25 km in a DWDM-PON system. The optimized bias current of 30 mA (similar to 1.5Ith) with corresponding extinction ratio (ER) of 6 dB and the external injection power of -9 dBm is (are) required for such a wavelength-locked universal transmitter to carry the 16-QAM and 122-subcarrier formatted OFDM and data-stream. By increasing external injection-locking from. 9 dBm to 0 dBm, the peak-to-peak chirp of the OFDM data stream reduces from 7.7 to 5.4 GHz. The side mode suppression ratio (SMSR) of up to 50 dB is achieved with wider detuning range between -0.5 nm to 2.0 nm under an injection power of 0 dBm. By modulating such a colorless laser diode with an OFDM data stream of 122 subcarriers at a central carrier frequency of 1.5625 GHz and a total bandwidth of 3 GHz, the transmission data rate of up to 12 Gbit/s in standard single-mode fiber over 25 km is demonstrated to achieve an error vector magnitude (EVM) of 5.435%. Such a universal colorless DWDM-PON transmitter can deliver the optical OFDM data-stream at 12 Gbit/s QAM-OFDM data after 25-km transmission with a receiving power sensitivity of -7 dBm at BER of 3.6x10(-7) when pre-amplifying the OFDM data by 5 dB. (C) 2013 Optical Society of America
Evaluating the performance improvement of differential phase-shift keying signals by amplitude regeneration and phase-noise suppression
(2008-05-15)
Wei, Chia-Chien
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Chen, Jason
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Chen, Yung Jui
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光電工程學系
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Department of Photonics
Theoretical bit error rates of the differential phase-shift keying format with various regeneration schemes is presented. A comparison with ideal regeneration reveals that averaging the phase noise of adjacent bits is found to eliminate most penalties that are induced by phase noise. (C) 2008 Optical Society of America.
Influence of hydrogen plasma treatment on charge storage characteristics in high density tungsten nanocrystal nonvolatile memory
(2011-03-31)
Chen, Shih-Cheng
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Chang, Ting-Chang
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Chen, Wei-Ren
;
Lo, Yuan-Chun
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Wu, Kai-Ting
This study focuses on the influence of a hydrogen plasma treatment on electrical properties of tungsten nanocrystal nonvolatile memory. The X-ray photon emission spectra show that, after the hydrogen plasma treatment, a change in binding energy occurs such that Si(x+) and Si(y+) peaks appear at a position that is shifted about 2.3 and 3.3 eV from Si(o+) in Si 2p spectra. This indicates that Si dangling bonds are passivated to form a Si-H bond structure in the SiO(2). Furthermore, the transmission electron microscopy shows cross-sectional and plane-view for the nanocrystal microstructure after the hydrogen plasma treatment. Electrical measurement analyses show improved data retention because the hydrogen plasma treatment enhances the quality of the oxide surrounding the nanocrystals. The endurance and retention properties of the memory device are improved by about 36% and 30%, respectively. (C) 2011 Elsevier By. All rights reserved.
Interface control of surface photochemical reactivity in ultrathin epitaxial ferroelectric films
(2013-05-06)
Chen, Jason
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Lu, Haidong
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Liu, Heng-Jui
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Chu, Ying-Hao
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Dunn, Steve
Asymmetrical electrical boundary conditions in (001)-oriented Pb(Zr0.2TiO0.8)O-3 (PZT) epitaxial ultrathin ferroelectric films are exploited to control surface photochemical reactivity determined by the sign of the surface polarization charge. It is shown that the preferential orientation of polarization in the as-grown PZT layer can be manipulated by choosing an appropriate type of bottom electrode material. PZT films deposited on the SrRuO3 electrodes exhibit preferential upward polarization (C+) whilst the same films grown on the (La, Sr)CoO3-electrodes are polarized downward (C-). Photochemical activity of the PZT surfaces with different surface polarization charges has been tested by studying deposition of silver nanoparticles from AgNO3 solution under UV irradiation. PZT surfaces with preferential C+ orientation possess a more active surface for metal reduction than their C- counterparts, evidenced by large differences in the concentration of deposited silver nanoparticles. This effect is attributed to band bending at the bottom interface which varies depending on the difference in work functions of PZT and electrode materials. (C) 2013 AIP Publishing LLC.
Nonvolatile memory effect of tungsten nanocrystals under oxygen plasma treatments
(2010-10-01)
Chen, Shih-Cheng
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Chang, Ting-Chang
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Chen, Wei-Ren
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Lo, Yuan-Chun
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Wu, Kai-Ting
In this work, an oxygen plasma treatment was used to improve the memory effect of nonvolatile W nanocrystal memory, including memory window, retention and endurance. To investigate the role of the oxygen plasma treatment in charge storage characteristics, the X-ray photon-emission spectra (XPS) were performed to analyze the variation of chemical composition for W nanocrystal embedded oxide both with and without the oxygen plasma treatment. In addition, the transmission electron microscopy (TEM) analyses were also used to identify the microstructure in the thin film and the size and density of W nanocrystals. The device with the oxygen plasma treatment shows a significant improvement of charge storage effect, because the oxygen plasma treatment enhanced the quality of silicon oxide surrounding the W nanocrystals. Therefore, the data retention and endurance characteristics were also improved by the passivation. (C) 2010 Elsevier B.V. All rights reserved.
Nonvolatile memory effect of tungsten nanocrystals under oxygen plasma treatments
(2010-10-01)
Chen, Shih-Cheng
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Chang, Ting-Chang
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Chen, Wei-Ren
;
Lo, Yuan-Chun
;
Wu, Kai-Ting
In this work, an oxygen plasma treatment was used to improve the memory effect of nonvolatile W nanocrystal memory, including memory window, retention and endurance. To investigate the role of the oxygen plasma treatment in charge storage characteristics, the X-ray photon-emission spectra (XPS) were performed to analyze the variation of chemical composition for W nanocrystal embedded oxide both with and without the oxygen plasma treatment. In addition, the transmission electron microscopy (TEM) analyses were also used to identify the microstructure in the thin film and the size and density of W nanocrystals. The device with the oxygen plasma treatment shows a significant improvement of charge storage effect, because the oxygen plasma treatment enhanced the quality of silicon oxide surrounding the W nanocrystals. Therefore, the data retention and endurance characteristics were also improved by the passivation. (C) 2010 Elsevier B.V. All rights reserved.
Oxide-Relief and Zn-Diffusion 850-nm Vertical-Cavity Surface-Emitting Lasers With Extremely Low Energy-to-Data-Rate Ratios for 40 Gbit/s Operations
(2013-03-01)
Shi, Jin-Wei
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Yan, Jhih-Cheng
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Wun, Jhih-Min
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Chen, Jason
;
Yang, Ying-Jay
We demonstrate novel structures of a vertical-cavity surface-emitting laser (VCSEL) for high-speed (similar to 40 Gbit/s) operation with ultralow power consumption performance. Downscaling the size of oxide aperture of VCSELs is one of the most effective ways to reduce the power consumption during high-speed operation. However, such miniaturized oxide apertures (similar to 2 mu m diameter) in VCSELs will result in a large differential resistance, optical single-mode output, and a small maximum output power (< 1 mW). These characteristics seriously limit the maximum electrical-to-optical (E-O) bandwidth and device reliability. By the use of the oxide-relief and Zn-diffusion techniques in our demonstrated 850-nm VCSELs, we can not only release the burden imposed on downscaling the current-confined aperture for high speed with low-power consumption performance, but can also manipulate the number of optical modes inside the cavity to maximize the E-O bandwidth and product of bit-rate transmission distance in an OM4 fiber. State-of-the-art dynamic performances at both room temperature and 85 degrees C operations can be achieved by the use of our device. These include extremely high D-factors (similar to 13.5 GHz/mA(1/2)), as well as record-low energy-to-data ratios (EDR: 140 fJ/bit) at 34 Gbit/s operation, and error-free transmission over a 0.8-km OM4 multimode fiber with a record-low energy-to-data distance ratio (EDDR: 175.5 fJ/bit. km) at 25 Gbit/s.
Strong Wavelength Detuning of 850 nm Vertical-Cavity Surface-Emitting Lasers for High-Speed (>40 Gbit/s) and Low-Energy Consumption Operation
(2015-11-01)
Chi, Kai-Lun
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Yen, Jia-Liang
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Wun, Jhih-Min
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Jiang, Jia-Wei
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Lu, I-Cheng
The strong (>20 nm) wavelength detuning technique has been demonstrated to enhance the modulation speed and high-temperature characteristics (at 85 degrees C), as well as lower the required driving current density performance of oxide-relief 850-nm vertical-cavity surface-emitting lasers (VCSELs) for >40 Gbit/s operation. By increasing the wavelength detuning from 15 to 20 nm, a significant improvement in the electrical-to-optical (E-O) bandwidth (20 to 27 GHz) of the VCSEL can be observed. This detuning design (similar to 20 nm) is incorporated along with a Zn-diffusion structure into our oxide-relief VCSEL with a miniaturized oxide-relief aperture (similar to 3 mu m). Highly single-mode, high-speed (26 GHz) operation, and moderate differential resistance (100 Omega) values can be simultaneously achieved. In addition, it is found that devices with a further larger detuning wavelength (>20 nm) and enlarged oxide-relief apertures (similar to 8 mu m) can sustain the same maximum E-O bandwidth (26 GHz) as that of a miniaturized (similar to 3 mu m) VCSEL, resulting in the lower driving current density (8 versus 18.8 kA/cm(2)) required for high-speed performance. Excellent transmission performance, which includes an extremely low energy-to-data rate ratio (EDR: 228 fJ/bit; over 100 m OM4 fiber) and record-low driving-current density (8 kA/cm(2); 3.5 mA) has been successfully achieved for 41 Gbit/s error-free transmission for these VCSELs.
Tungsten nanocrystal memory devices improved by supercritical fluid treatment
(2007-12-03)
Chen, C. H.
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Chang, T. C.
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Liao, I. H.
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Xi, P. B.
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Tsai, C. T.
A supercritical CO(2) (SCCO(2)) fluid technique is proposed to improve electrical characteristics for W nanocrystal nonvolatile memory devices, since the thickness and quality of tunnel oxide are critical issues for the fabrication of nonvolatile memory devices. After SCCO(2) treatments, C-V curves are restored to normal, as well as the leakage current of W nanocrystal memory devices are reduced significantly. It reveals that W nanocrystal memory devices could be formed with shorter oxidation time, moreover, dangling bonds and trapping states initially created within an incomplete oxidized film will be efficiently repaired after SCCO(2) treatment. (c) 2007 American Institute of Physics.
Tungsten oxide/tungsten nanocrystals for nonvolatile memory devices
(2008-01-07)
Chen, C. H.
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Chang, T. C.
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Liao, I. H.
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Xi, P. B.
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Hsieh, Joe
In this work, the fabrication of WO(3)/W nanocrystals for nonvolatile memory devices has been achieved via rapid thermal oxidation of tungsten silicide. Amorphous Si and WSi(x) (x=2.7) layers were deposited onto the tunneling oxide and sequentially oxidized to form well-shaped WO(3)/W nanocrystals. The mean size of WO(3)/W nanocrystals is similar to 8.4 nm, while density is similar to 1.57x10(11) cm(-2). Moreover, the nonvolatile memory device for WO(3)/W nanocrystals exhibits similar to 0.53 V threshold voltage shift under 1 V/(-5 V) operation. The sample without capping a-Si layer was also fabricated for comparison. By material analyses, reasonable formation mechanisms are proposed in this letter. (C) 2008 American Institute of Physics.
W-Band Wireless Data Transmission by the Integration of a Near-Ballistic Unitraveling-Carrier Photodiode With a Horn Antenna Fed by a Quasi-Yagi Radiator
(2009-11-01)
Kuo, F. -M.
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Shi, J. -W.
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Wang, Shao-Ning
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Chen, Nan-Wei
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Shih, Po-Tsung
We demonstrate a novel W-band photonic transmitter mixer, which is composed of a planar quasi-Yagi radiator for feeding a WR-10 waveguide-based horn antenna and a near-ballistic unitraveling-carrier photodiode. The module demonstrates reasonable coupling loss in terms of the millimeter-wave (MMW) power launched from the integrated radiator into the WR-10 waveguide. With the bias-modulation technique and an optical MMW source, we can successfully achieve a wireless data transmission of 2.5-Gb/s quadrature phase shift keying at a carrier wave frequency of 102.5 GHz with a transmission distance of over 2.3 m.