Free-Space Communications Enabled by Quantum Cascade Lasers

摘要

Future generations of wireless communication systems are expected to supportorders of magnitude faster data transfer with much lower latency than thecurrently deployed solutions. Development of wireless transceivers of higherbandwidth, low energy consumption, and small footprint becomes challengingwith radio frequency (RF) electronic technologies. Photonics-assisted technologiesshow many advantages in generating signals of ultrabroad bandwidth at highcarrier frequencies in the millimeter-wave, terahertz, and IR bands. Among thesefrequency options, the mid-IR band has recently attracted great interest for futurewireless communication due to its intrinsic merits of low propagation loss andhigh tolerance of atmospheric perturbations. A promising source for mid-IR freespacecommunications is the semiconductor quantum cascade laser (QCL), whichcan be directly modulated at a high speed and facilitates monolithic integration forcompact transceivers. Herein, the research and development of QCL-based freespacecommunications are reviewed and a recent experimental study of multigigabittransmission with a directly modulated mid-IR QCL and a commercialoff-the-shelf IR photodetector is reported on. Up to 4 Gb s~(-1) transmission of twoadvanced modulation formats, namely, four-level pulse amplitude modulation(PAM-4) and discrete multitone (DMT) modulation, is demonstrated.