Browsing by Author "Wu, Chao-Hsin"

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850/940-nm VCSEL for optical communication and 3D sensing
(2018-01-01)
Cheng, Chih-Hsien
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Shen, Chih-Chiang
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Kao, Hsuan-Yun
;
Hsieh, Dan-Hua
;
Wang, Huai-Yung
This paper is going to review the state-of-the-art of the high-speed 850/940-nm vertical cavity surface emitting laser (VCSEL), discussing the structural design, mode control and the related data transmission performance. InGaAs/AlGaAs multiple quantum well (MQW) was used to increase the differential gain and photon density in VCSEL. The multiple oxide layers and oxide-confined aperture were well designed in VCSEL to decrease the parasitic capacitance and generate single mode (SM) VCSEL. The maximal modulation bandwidth of 30 GHz was achieved with well-designed VCSEL structure. At the end of the paper, other applications of the near-infrared VCSELs are discussed.
Characteristics of Blue GaN/InGaN Quantum-Well Light-Emitting Transistor
(2020-01-01)
Lan, Hao-Yu
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Tseng, I-Chen
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Lin, Yung-Hsiang
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Chang, Shu-Wei
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Wu, Chao-Hsin
We demonstrate simultaneous electrical and optical modulations of the first GaN/InGaN quantum-well light-emitting transistor (QW-LET) which contains an In-0.15 Ga0.85N QW in the heavily p-doped In-0.05 Ga0.95N base. Unlike GaAs/InGaAs counterparts, the GaN/InGaN QW- LET has a current gain (up to 5) and optical power which increases linearly with the base current. Its emission spectra are centered at a wavelength of 420 nm and barely shift with the current injection, in contrast to the behavior of typical nitride-based LEDs. The unusual features of this device may be related to the tilted band profile induced by the polarization field in the QW and issue of p-type doping.
Comparison of single-/few-/multi-mode 850 nm VCSELs for optical OFDM transmission
(2017-07-10)
Kao, Hsuan-Yun
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Tsai, Cheng-Ting
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Leong, Shan-Fong
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Peng, Chun-Yen
;
Chi, Yu-Chieh
For high-speed optical OFDM transmission applications, a comprehensive comparison of the homemade multi-/few-/single-transverse mode (MM/FM/SM) vertical cavity surface emitting laser (VCSEL) chips is performed. With microwave probe, the direct encoding of pre-leveled 16-QAM OFDM data and transmission over 100-m-long OM4 multi-mode-fiber (MMF) are demonstrated for intra-datacenter applications. The MM VCSEL chip with the largest emission aperture of 11 mu m reveals the highest differential quantum efficiency which provides the highest optical power of 8.67 mW but exhibits the lowest encodable bandwidth of 21 GHz. In contrast, the SM VCSEL chip fabricated with the smallest emission aperture of only 3 mu m provides the highest 3-dB encoding bandwidth up to 23 GHz at a cost of slight heat accumulation. After optimization, with the trade-off set between the receiving signal-to-noise ratio (SNR) and bandwidth, the FM VCSEL chip guarantees the highest optical OFDM transmission bit rate of 96 Gbit/s under back-to-back case with its strongest throughput. Among three VCSEL chips, the SM VCSEL chip with nearly modal-dispersion free feature is treated as the best candidate for carrying the pre-leveled 16-QAM OFDM data over 100-m OM4-MMF with same material structure but exhibits different oxide-layer confined gain cross-sections with one another at 80-Gbit/s with the smallest receiving power penalty of 1.77 dB. (C) 2017 Optical Society of America
CWDM DFBLD Transmitter Module for 10-km Interdata Center With Single-Channel 50-Gbit/s PAM-4 and 62-Gbit/s QAM-OFDM
(2018-02-01)
Kao, Hsuan-Yun
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Su, Zhe-Xian
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Shih, Hsiang-Shun
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Chi, Yu-Chieh
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Tsai, Cheng-Ting
Single-channel 50-Gbit/s 4-level pulse amplitude modulation (PAM-4) and 62-Gbit/s orthogonal frequency division multiplexed quadrature amplitude modulation (QAM-OFDM) direct encoding of an uncooled coarse wavelength division multiplexer (CWDM) 100-Gbit/s distributed feedback laser diodes (DF-BLD) transmitter module at 1310-nm transmitter interdata center transmission over 10-km single-mode fiber (SMF) are demonstrated. To enable preleveled 16-QAM OFDM and PAM-4 data transmissions at 62 and 50 Gbit/s, the 1310-nm channel of the DFBLD CWDM transmitter provides modulation bandwidth of 15 GHz, side-mode suppression ratio of 48 dB, and relative intensity noise of -126 dBc/Hz. For encoding the PAM-4 data, the 1310nm channel of the CWDM DFBLD 100-Gbit/s transmitter achieves transmission capacities of 58 and 50 Gbit/s after BtB and 10-km SMF transmissions, respectively. Instead of supporting the back-to-back 16-QAM OFDM with the transmission at 62 Gbit/s with forward error correction (FEC) certified BER of 3.3x10(-3), such a CWDM 100-Gbit/s DFBLD transmitter module can still maintain its highest data rate capacity to indicate a receiving power penalty of 0.35 dB even after 10-km SMF propagation. This is mainly attributed to the selected channel wavelength of the narrow-linewidth DFBLD, which suffers from extremely low chromatic dispersion and RF fading effect.
Design and Optimization of VCSELs for up to 40-Gb/s Error-Free Transmission Through Impurity-Induced Disordering
(2020-03-01)
Peng, Chun-Yen
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Cheng, Hao-Tien
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Kuo, Hao-Chung
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Wu, Chao-Hsin
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光電工程學系
This article describes an optimized design and process for the improvement of the electrical properties of vertical-cavity surface-emitting lasers (VCSELs) via the impurity-induced disordering (IID) technology. Through the IID process, the electrical current path can be tailored to detour around the defect centers introduced by the oxidation process, resulting in a noticeable improvement in the dc and the RF characteristics of the IID VCSEL. The threshold current was reduced from 0.341 to 0.225 mA due to better current injection efficiency in the IID VCSEL. The characteristic temperature of the IID VCSEL increased from 106 to 150 K, and the slope of the I-V characteristics under low-level-injection regime could be improved to a factor of exp. The RF characteristics also echoed the dc characteristics, which the optical bandwidth of the IID VCSEL enhanced from 18.95 to 23.49 GHz, and showed a prominent difference on the factor (similar to 0.26 to similar to 0.22 ns) and the D factor (similar to 7 to similar to 11 GHz/(mA)(1/2)). The IID VCSEL is then employed for a data transmission link, an eye diagram was characterized at up to 44 Gb/s and passed 40-Gb/s error-free testing under on-off-keying (OOK) modulation.
Design, Modeling, and Fabrication of High-Speed VCSEL with Data Rate up to 50 Gb/s
(2019-08-14)
Shen, Chih-Chiang
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Hsu, Tsung-Chi
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Yeh, Yen-Wei
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Kang, Chieh-Yu
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Lu, Yun-Ting
We have studied the characteristics of frequency response at 850-nm GaAs high-speed vertical-cavity surface-emitting lasers (VCSELs) with different kinds of oxide aperture sizes and cavity length using the PICS3D simulation program. Using 5-mu m oxide aperture sizes, the frequency response behavior can be improved from 18.4 GHz and 15.5 GHz to 21.2 GHz and 19 GHz in a maximum of 3 dB at 25 degrees C and 85 degrees C, respectively. Numerical simulation results also suggest that the frequency response performances improved from 21.2 GHz and 19 GHz to 30.5 GHz and 24.5 GHz in a maximum of 3 dB at 25 degrees C and 85 degrees C due to the reduction of cavity length from 3 lambda/2 to lambda/2. Consequently, the high-speed VCSEL devices were fabricated on a modified structure and exhibited 50-Gb/s data rate at 85 degrees C.
Efficient Heat Dissipation of Uncooled 400-Gbps (16x25-Gbps) Optical Transceiver Employing Multimode VCSEL and PD Arrays
(2017-04-18)
Shih, Tien-Tsorng
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Chi, Yu-Chieh
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Wang, Ruei-Nian
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Wu, Chao-Hsin
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Huang, Jian-Jang
An effective heat dissipation of uncooled 400-Gbps (16x25-Gbps) form-factor pluggable (CDFP) optical transceiver module employing chip-on-board multimode 25-Gbps vertical-surface-emitting-laser (VCSEL) and 25-Gbps photodiode (PD) arrays mounted on a brass metal core embedded within a printed circuit board (PCB) is proposed and demonstrated. This new scheme of the hollow PCB filling with thermally-dissipated brass metal core was simulated and used for high temperature and long term stability operation of the proposed 400-Gbps CDFP transceiver. During one-hour testing, a red-shift of central wavelength by 0.4-nm corresponding temperature increment of 6.7 degrees C was observed with the brass core assisted cooler module. Such a temperature change was significantly lower than that of 28.3 degrees C for the optical transceiver driven with conventional circuit board. After 100-m distance transmission over a multimode fiber (OM4), the 400-Gbps CDFP transceiver exhibited dispersion penalty of 2.6-dB, power budget of >= 3-dB, link loss of <= 0.63-dB, mask margin of 20%, and bit error rate (BER) of <10(-12) with maintained stability more than one hour. The developed 400-Gbps CDFP transceiver module employing low-power consumption VCSEL and PD arrays, effective coupling lens arrays, and well thermal-dissipation brass metal core is suitable for use in the low-cost and high-performance data center applications.
Evaluation and Selection of Materials for Particulate Matter MEMS Sensors by Using Hybrid MCDM Methods
(2018-10-01)
Huang, Chi-Yo
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Chung, Pei-Han
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Shyu, Joseph Z.
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Ho, Yao-Hua
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Wu, Chao-Hsin
Air pollution poses serious problems as global industrialization continues to thrive. Since air pollution has grave impacts on human health, industry experts are starting to fathom how to integrate particulate matter (PM) sensors into portable devices; however, traditional micro-electro-mechanical systems (MEMS) gas sensors are too large. To overcome this challenge, experts from industry and academia have recently begun to investigate replacing the traditional etching techniques used on MEMS with semiconductor-based manufacturing processes and materials, such as gallium nitride (GaN), gallium arsenide (GaAs), and silicon. However, studies showing how to systematically evaluate and select suitable materials are rare in the literature. Therefore, this study aims to propose an analytic framework based on multiple criteria decision making (MCDM) to evaluate and select the most suitable materials for fabricating PM sensors. An empirical study based on recent research was conducted to demonstrate the feasibility of our analytic framework. The results provide an invaluable future reference for research institutes and providers.
Few-Mode 850-nm VCSEL Chip with Direct 16-QAM OFDM Encoding at 80-Gbit/s for 100-m OM4 MMF Link
(2017-01-01)
Kao, Hsuan-Yun
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Tsai, Cheng-Ting
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Pong, Chun-Yen
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Liang, Shan-Fong
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Weng, Zu-Kai
Chip-level direct 16-QAM OFDM encoding of a few-transverse-mode 850-nm Zn-diffused VCSEL is employed to transmit 80-Gbit/s data covering 20-GHz analog bandwidth over 100-m-long OM4 MMF with corresponding BER of 3.3x10(-3).
Few-mode VCSEL chip for 100-Gb/s transmission over 100 m multimode fiber
(2017-10-01)
Kao, Hsuan-Yun
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Chi, Yu-Chieh
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Tsai, Cheng-Ting
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Leong, Shan-Fong
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Peng, Chun-Yen
A few-mode (FM) vertical cavity surface emitting laser (VCSEL) chip with heavily zinc-diffused contact layer and oxide-confined cross-section is demonstrated for carrying pre-leveled 16-quadrature amplitude modulation orthogonal frequency division multiplexing (QAM-OFDM) data in OM4 multi-mode fiber (MMF) over 100 m for intra-data-center applications. The FM VCSEL chip, which has an oxide-confined emission aperture of 5 mu m, demonstrates high external quantum efficiency, provides an optical power of 2.2 mW at 38 times threshold condition, and exhibits 3 dB direct-modulation bandwidth beyond 22 GHz at a cost of slight heat accumulation. At a DC bias point of 5 mA (22.6I(th)) the FM VCSEL chip, with sufficiently normalized modulation output, supports Baud and data rates of 25 and 100 Gb/s, respectively, with forward error correction (FEC) certifying receiving quality after back-to-back transmission. After passing through 100 m OM4 MMF with a receiving power penalty of 4 dB, the FM VCSEL chip demonstrates FEC-certified transmission of the pre-leveled 16-QAM OFDM data at 92 Gb/s. (C) 2017 Chinese Laser Press
Long-Term Thermal Stability of Single-Mode VCSEL Under 96-Gbit/s OFDM Transmission
(2019-11-01)
Kao, Hsuan-Yun
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Tsai, Cheng-Ting
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Chi, Yu-Chieh
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Peng, Chun-Yen
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Leong, Shan-Fong
Thermal-dependent transmission performance and long-term stability of a single-transverse-mode (SM) vertical-cavity surface-emitting laser (VCSEL) with directly pre-leveled 16quadrature amplitude modulation orthogonal frequency-division multiplexing (16-QAM OFDM) data over 100 m 0M4 multi-mode-fiber (MMF) are demonstrated. Although narrowing the oxide-confined aperture to 3 mu m enables the SM VCSEL with low threshold current of 0.21 mA and high modulation bandwidth of 21.4 GHz, this technology also enlarges the insulating oxide area to accumulate the heat for raising core temperature. This induces a harsh environment as the core temperature persistently increases without dissipation even under the water-cooling control at 20 degrees C. As a result, the SM VCSEL can only guarantee a stable operation for 1.5 h under the encoding of QAM-OFDM data for transmission. After optimization, the SM VCSEL successfully supports a back-to-back transmission capacity as high as 96 Gbit/s. With the assistance of OFDM pre-leveling technique, the 96-Gbit/s QAM-OFDM data transmission is qualified over 100 m OM4 MMF with a receiving power penalty as low as 13 dB.
Luminescence Enhancement and Enlarged Dirac Point Shift of MoS2/Graphene Hetero-Structure Photodetectors With Postgrowth Annealing Treatment
(2017-01-02)
Wu, Chong-Rong
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Liao, Kun-Cheng
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Wu, Chao-Hsin
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Lin, Shih-Yen
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影像與生醫光電研究所
Enhanced photoluminescence intensities are observed for the MoS2 film prepared by chemical vapor deposition (CVD) with an additional 850 degrees C postgrowth annealing procedure under sulfur-rich environment. The enlarged Dirac point shift of the MoS2/graphene hetero-structure photodetectors with the postgrowth annealing procedure suggests that more photoexcited electrons will transport to the graphene and effectively higher n-type doped the channel. The direct 2-D crystal hetero-structure growth by using CVD has avoided the complicated procedure of sequential attachment of different 2-D crystals, which is advantageous for the practical application of 2-D crystal heterostructures.
Modal Linewidth Dependent Transmission Performance of 850-nm VCSELs With Encoding PAM-4 Over 100-m MMF
(2017-10-01)
Kao, Hsuan-Yun
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Chi, Yu-Chieh
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Peng, Chun-Yen
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Leong, Shan-Fong
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Chang, Chun-Kai
By changing the transverse-mode spectral linewidth of vertical cavity surface emitting lasers (VCSELs) at 850 nm, the directly encoded four-level pulse amplitude modulation data transmission performance over 100-m-long OM4 multimode fiber (MMF) are demonstrated and compared. The multi-mode VCSEL chip with the largest aperture of 11 mu m reveals the widest spectral linewidth and the highest optical power, but provides the smallest modulation bandwidth to support only 44-and 28-Gb/s data rates for back-to-back (BtB) and 100-m OM4 MMF transmission cases, respectively. By shrinking the aperture size to reduce transverse-mode number, the few-mode VCSEL with the strongest throughput power enables a BtB transmission capacity as high as 52 Gb/s. However, its modal dispersion induced after OM4 MMF transmission inevitably degrade the data rate to 32 Gb/s. In contrast, the single-mode VCSEL with the smallest aperture of 3 mu m reveals the highest modulation bandwidth and negligible modal dispersion to show competitive BtB transmission capacity with that of the few-mode VCSEL. In particular, the single-mode VCSEL successfully achieves a data rate of 34 Gb/s with a power penalty as low as 1.4 dB, after 100-m OM4 MMF transmission.
Multilayer MoS2 prepared by one-time and repeated chemical vapor depositions: anomalous Raman shifts and transistors with high ON/OFF ratio
(2015-11-04)
Wu, Chong-Rong
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Chang, Xiang-Rui
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Chang, Shu-Wei
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Chang, Chung-En
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Wu, Chao-Hsin
We show that multilayer molybdenum disulfide (MoS2) grown with the chemical vapor deposition (CVD) may exhibit quite distinct behaviors of Raman shifts from those of exfoliated ones. The anomalous Raman shifts depend on CVD growth modes and are attributed to the modified dielectric screening and interlayer coupling of MoS2 in various growth conditions. With repeated CVD growths, we demonstrated the precise control over the layer number of MoS2. A decently large drain current, high ON/OFF ratio of 10(5), and enhanced field-effect mobility can be achieved in transistors fabricated on the six-layer MoS2.
Pre-leveled 16-QAM OFDM Modulation of an 850-nm VCSEL for 56-Gbit/s Transmission
(2016)
Tsai, Cheng-Ting
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Pong, Chun-Yen
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Wu, Yun-Chen
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Leong, Shan-Fong
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Chi, Yu-Chieh
An 850-nm VCSEL carried 16-QAM OFDM transmission at 56 Gbit/s is demonstrated by using the pre-leveling technology, which reveals an optimized signal-to-noise ratio, error vector magnitude and bit-error-rate of 16. 4 dB, 15.1 % and 1.2 x10(-3), respectively.
Pulse compression irrespective of fiber dispersion using chirp of transistor lasers
(2019-04-15)
Tung, Chien-Ting
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Chang, Chi-Hsiang
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Chang, Shu-Wei
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Wu, Chao-Hsin
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光電工程學系
The voltage modulation of transistor lasers (TLs) through Franze-Keldysh absorption can impose an unconventional chirp on optical signals. In this Letter, we model this chirp effect and demonstrate how the output Gaussian pulse is reshaped through optical fibers. It is shown that pre-chirped pulses of TLs may be compressed in fibers with both normal and anomalous dispersions. (C) 2019 Optical Society of America
RIN Suppressed Multimode 850-nm VCSEL for 56-Gbps 16-QAM OFDM and 22-Gbps PAM-4 Transmission
(2016)
Tsai, Cheng-Ting
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Chang, Shuo
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Pong, Chun-Yen
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Liang, Shan-Fong
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Chi, Yu-Chieh
A multimode 850-nm VCSEL with its relative-intensive-noise suppressed to -145 dBc/Hz is employed for directly encoded 56-Gbps 16-QAM OFDM and 22-Gbps PAM-4 transmissions with corresponding BERs of 3.2x10(-3) and 1.9x10(-10), respectively.
Simulation Model of Oxide-Aperture Strain Quantum Well VCSEL
(2019-01-01)
Shih, Hsiang-Yun
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Cho, Yu-Yun
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Hsu, Shun-Chieh
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Huang, Yu-Ming
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Wang, Shou-Wei
An oxide aperture strained quantum well VCSEL model was built based on measured results. The indium composition of MQW was changed to maximize the frequency response. The simulation result shows that the bandwidth can be improved and reach 30.88GHz.
Single-mode VCSEL for pre-emphasis PAM-4 transmission up to 64 Gbit/s over 100-300 m in OM4 MMF
(2018-07-01)
Kao, Hsuan-Yun
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Tsai, Cheng-Ting
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Leong, Shan-Fong
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Peng, Chun-Yen
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Chi, Yu-Chieh
A 850 nm single-mode vertical cavity surface emitting laser (VCSEL)-based data transmission is demonstrated, enabling four-level pulse amplitude modulation (PAM-4) at 64 Gbit/s over 100-300 m in an OM4 multi-mode fiber (MMF). By optimizing the bias of the single-mode VCSEL with a differential resistance of 159 Omega, the related electrical return loss of -5.7 dB is determined to provide an analog modulation bandwidth of 18.9 GHz. After pre-emphasizing the waveform of the PAM-4 format, the PAM-4 data stream can be successfully delivered by the single-mode VCSEL at 64 Gbit/s under back-to-back and 100 m long OM4 MMF conditions. Lengthening the transmission distance worsens the signal-to-noise ratio (SNR) of PAM-4 data to the FEC criterion, as the waveform pre-emphasis of the PAM-4 data stream inevitably induces spectral power compensation from low to high frequencies. Therefore, increasing the OM4 MMF distance from 200 to 300 m significantly reduces the peak-to-peak amplitude of data to suppress the SNR and reduce the transmission capacity from 52 to 48 Gbit/s. (C) 2018 Chinese Laser Press
The role of optoelectronic feedback on Franz-Keldysh voltage modulation of transistor lasers
(2016-01-01)
Chang, Chi-Hsiang
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Chang, Shu-Wei
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Wu, Chao-Hsin
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光電工程學系
;
Department of Photonics
Possessing both the high-speed characteristics of heterojunction bipolar transistors (HBTs) and enhanced radiative recombination of quantum wells (QWs), the light-emitting transistor (LET) which operates in the regime of spontaneous emissions has achieved up to 4.3 GHz modulation bandwidth. A 40 Gbit/s transmission rate can be even achieved using transistor laser (TL). The transistor laser provides not only the current modulation but also direct voltage-controlled modulation scheme of optical signals via Franz-Keldysh (FK) photon-assisted tunneling effect. In this work, the effect of FK absorption on the voltage modulation of TLs is investigated. In order to analyze the dynamics and optical responses of voltage modulation in TLs, the conventional rate equations relevant to diode lasers (DLs) are first modified to include the FK effect intuitively. The theoretical results of direct-current (DC) and small-signal alternating-current (AC) characteristics of optical responses are both investigated. While the DC characteristics look physical, the intrinsic optical response of TLs under the FK voltage modulation shows an AC enhancement with a 20 dB peak, which however is not observed in experiment. A complete model composed of the intrinsic optical transfer function and an electrical transfer function fed back by optical responses is proposed to explain the behaviors of voltage modulation in TLs. The abnormal AC peak disappears through this optoelectronic feedback. With the electrical response along with FK-included photoncarrier rate equations taken into account, the complete voltage-controlled optical modulation response of TLs is demonstrated.