IMPROVING THE MODULATION BANDWIDTH OF LED-VLC BY QDs

Release time:2016-10-10 Source:Wang Group

Recently, the latest research article Improving the Modulation Bandwidth of LED by CdSe/ZnS Quantum Dots for Visible Light Communication by Xiao Xiangtian and Tang Haodong, undergraduates from the Department of Electrical and Electronic Engineering, SUSTech was published on Optics Express (Impact Factor 3.148, JCR Q1), an international academic journal from Optical Society of America (OSA). 

 

Visible light communication (VLC) is an advanced and high-efficiency wireless communication technology. As one of the most important light sources in VLC, conventional white light emitting diode (WLED) based on Y3Al5O12:Ce3+ (YAG:Ce) phosphor limits the system transmitting rate severely due to its narrow modulation bandwidth. Considering the short fluorescent lifetime of quantum dots (QDs), QD-LEDs with wide modulation bandwidths were designed here to improve the transmitting rate of VLC. CdSe/ZnS core/shell QDs and related luminescent microspheres (LMS) were implemented as light conversion materials for the QD-LEDs. Compared with conventional phosphor WLED, the proposed QD-LED and QD-WLED reached maximum improvement on modulation bandwidth at 74.19% and 67.75% respectively. Furthermore, mathematical modeling of smearing was analyzed to establish the relationship between fluorescent lifetime and modulation bandwidth. Our findings will provide an effective solution of white LEDs for high speed VLC.

 

Visible light communication (VLC) technology based on white LED (WLED) light source, which features high transmitting rate, enhanced security and fusion lighting, has gradually become an important development orientation concerning wireless communication. It has a promising prospect in areas such as smart city, “integration of three networks” (telecommunication network, computer network and cable television network) and national defense communication. However, as a significant signal source of VLC, the conventional WLED (generated by excitation of yellow fluorescent powder by blue LED) has long fluorescent lifetime and a narrow modulation bandwidth. As a consequence, these have become the bottleneck of raising the VLC transmitting rate. This study puts forward the new method of improving the VLC transmitting rate with wide modulation bandwidth quantum dots WLED (QD-WLEDs), and develops QLMS for WLED. The study takes the advantage of short fluorescent lifetime and wide modulation bandwidth of QLMS, to widen the bandwidth by 67.75% compared with the conventional WLED bandwidth. Meanwhile, the study makes a modeling analysis regarding the internal relations between modulation bandwidth and fluorescent lifetime.

 

This project was undertaken by Xiao Xiangtian, Tang Haodong and Zhang Tianqi, undergraduates from the Department of Electrical and Electronic Engineering, SUSTech, among which Zhang Tianqi was the second author of the article. All of them have keen interests in VLC, an inter-discipline of photo-electricity and communication, and have devoted themselves to their work launched by the research group since the summer vacation of their sophomore year. Assistant Professor Wang Kai and Associate Professor Wang Rui were corresponding authors who jointly guided the research. They encouraged students to bring into full play their innovative thoughts and cultivated their competence of self-study.

 

Details could be found: 

Campus news： http://www.sustc.edu.cn/en/news_events_1_6/1498

Article link： https://www.osapublishing.org/oe/abstract.cfm?uri=oe-24-19-21577