Optical and Communication Performance Investigation of UV and DUV Light-Stimulated Quantum Dots

To investigate optical and communication performances of quantum dots (QDs) under ultraviolet (UV) and solar-blind deep-ultraviolet (DUV) environments, we manufacture green-, orange-, and red-emissive thin films as light converters by using II-VI family CdSe-based QDs; and prepare 385- and 375-nm UV lights, as well as 280-nm DUV light as excitation sources in an optical wireless communication (OWC) system. With a 1.5-m distance and 385-nm UV excitation, the highest data rate of the orange QDs reaches 77 Mb/s below the forward-error-correction (FEC) limit (
$3.8\times 10^{-3} $
), using on-off keying (OOK) modulation and post-equalization. This value slightly decreases to 72 Mb/s with 375-nm UV excitation and further decreases to 48 and 42 Mb/s when replaced with green and red QDs, respectively. High quantum yield and absorbance of the orange QDs become the main reasons for achieving the highest data rate among others. Equalization shows apparent benefit in reducing the bit error rate (BER) when the emitting optical power of QDs is sufficient. Without equalization, only 62, 45, and 40 Mb/s can be achieved under the same condition, whereas the BER increases drastically when using 280-nm DUV light due to a decrease in optical emission. Optical performances of QDs, such as quantum yield, absorbance, and fluorescent lifetime, are evaluated to analyze their influences on the communication performance of QD-based OWC systems, such as frequency response, data rate, BER, and eye diagram. These comprehensive studies provide effective guidelines for designing diversified OWC systems.