850/940-nm VCSEL for optical communication and 3D sensing
As the main transmitter for the intra-data-center link, the 850-nm vertical cavity surface emitting laser (VCSEL) array module is standardized toward 100/200/400 Gbps or beyond, which effectively increases the cloud transmission rate in data centers to meet the urgent demand on huge amount of audio/video/data exchange and streaming nowadays. It has been scheduled to apply the 400-Gbps VCSEL optical transceiver module for the cloud data center application in 2020. On the other hand, the 940-nm VCSEL array has also emerged for comprehensive contour mapping or range sensing applications built-in with portable and handheld devices, such as the face recognition in mobile phone and tablet, and the distance and geomorphological sensing in Lidar for unmanned vehicles.
To catch up the pace of enlarged modulation bandwidth, Ingham et al. employed the oxide-confined VCSEL with 20-GHz bandwidth to demonstrate the 32-Gbps PAM-4 data transmission with pre-distortion in 2011. Szczerba et al. used the directly PAM-4 modulated 850-nm VCSEL to transmit 60-Gbps data over 2-m MMF and 50-Gbps data over 50-m MMF in 2015. Castro et al. employed a pre-distorted PAM-4 data format to perform 50-Gbit/s transmission over 200-m wideband MMF. In addition, the Finisar Co. has already reported the 4-channel VCSEL chip for 45-Gbps PAM-4 over 300-m-long OM4 MMF with a BER lower than the KP4 criterion of 2×10-4. In 2017, Kao et al. employed the pre-emphasized PAM-4 data at >50-Gbps to encode the SM VCSEL for the OM4 MMF link over 300 m. Even with a finite bandwidth of 18.9 GHz, the 64-Gbps BtB and 100-m MMF transmissions and the 48-Gbps transmission in the MMF with length of 200-300 m can be enabled. In 2015, Lu et al. further used the discrete multi-tone (DMT) data format to modulate SM VCSEL with 12-GHz bandwidth to perform a 50-Gbps link. In 2016, Puerta et al. further demonstrate the ODFM encoded VCSEL at 107.5 Gbps over 10-m MMF. In addition, Tsai et al. employed MM VCSEL with 14-GHz bandwidth to perform QAM-OFDM in MMF, and Kao et al. compared VCSELs with different transverse mode numbers to transmit 16-QAM-OFDM data over 100-m OM4 MMF. The SM VCSEL exhibits modal-dispersion-free transmission to demonstrate the best transmission performance. On the other hand, the 940-nm VCSEL array has also emerged to facilitate the optical radar applications. Koyama et al. used the VCSEL to demonstrate the highly distinguished beam steering device in 2013. In 2018, Warren et al. designed the 150-element VCSEL array chips as the optical radar light source to achieve the divergent angle below 15o and the peak power up to 400 W. RPMC Lasers Inc. further developed the 940-nm VCSEL chip module with its peak power of 50 W for the 3D sensing and optical radar application. Therefore, the high-power VCSEL array has become a key device on the light source of the 3D sensing or optical radar.
Prof. Gong-Ru Lin’s group in Taiwan University advances the researches in visible lighting communications, millimeter-wave radio over fiber access, colorless LD based DWDM-PON, waveguide all-optical data conversion, and passively mode-locked fiber laser self-started by nano-materials. Remarkable results include the 18-Gbps QAM-ODFM encoded blue LD for free-space and under-water communications, the blue/violet LD color-converted white-lighting communication over 10 Gbps, the dual-mode colorless laser diode enabled 28/39/60-GHz millimeter-wave radio over fiber at 60 Gbps, the <300-fs saturable absorption induced mode-locking in fiber lasers, the Si quantum dots light emitting diode, and the free-carrier absorption and nonlinear Kerr switching induced all-optical switching logics. Prof. Lin has some leading results pioneered research peers, in which two works on the blue LD enabled free-space/under-water data transmission were selected as highly cited papers in the Web of Science, and was awarded the TOP100 paper in Scientific Reports. Prof. Lin is currently the director of the Institute of Optics and electronics, Taiwan University, and the OSA Fellow.
Semiconductor Laser Technology Laboratory (SC Lab.) was supervised by distinguished Prof. Han-Chung Kuo. Our research majored in semiconductor laser diodes, light emitting diodes, III-V semiconductor material, and devices. The world first GaN-based vertical cavity surface emitting diodes (VCSELs) were demonstrated by Semiconductor Laser Technology Laboratory in 2008 and first continued-wave GaN-based VCSELs operated at room temperature at 2010. Semiconductor Laser Technology Laboratory has focused on the improvement of the droop effect of light emitting diodes and investigated the high efficiency and high power light emitting diodes. The related research results have been reported by a lot of international technology news such as SPIE News report, Semiconductor Today, Compound semiconductor, CLEO Post deadline, Laser Focus World and IOP Nanotechnology. Semiconductor Laser Technology Laboratory keep working on solid-state lighting and compound semiconductor for a long time, and always dedicated to core problems of it. Prof. Kuo is a professor of "the Yangtze River Scholar Award Program", the OSA Fellow and the IEEE Fellow.
The Integrated Opto-Electronic Device (IOED) group of Taiwan University, led by Dr. Chao-Hsin (Wayne) Wu, is the world-leading group in the design and fabrication of high-speed optoelectronic and microelectronic devices. Dr. Wu, the principle investigator of the IOED group, received his PhD from University of Illinois at Urbana-Champaign. He is currently the associate professor of Department of Electrical Engineering, Graduate Institute of Photonics and Optoelectronics, and Graduate Institute of Electronics Engineering. In Illinois, he pioneered the development of light-emitting transistors and transistor lasers with Prof. Milton Feng and Prof. Nick Holonyak, Jr. His current research at Taiwan University includes high speed VCSELs for optical interconnects, GaN-on-Si power and rf electronics, 2D material field-effect transistors, Si photonics, light-emitting transistors and transistor lasers for optical logic gates, GaN LED for visible light communications. He has published more than 40 journal papers and 60 conference papers. Dr. Wu is a member of IEEE, SPIE, and OSA. He received the Nick and Katherine Holonyak, Jr. Award in 2010 from UIUC. He was entitled Irving T. Ho Outstanding Young Scholar and received the Academic Contribution Award from EECS College of Taiwan University in 2017.
Cheng C H, Shen C C, Kao H Y, Hsieh D H, Wang H Y et al. 850/940-nm VCSEL for optical communication and 3D sensing. Opto-Electronic Advances 1, 180005 (2018).