Quantum-Dot Multi-Wavelength Lasers for Millimeter Wave Generation and Transmission

In order to achieve ultrahigh data capacity and to overcome the wireless spectrum crunch, 5G is going to adopt millimeter-wave (mmW) frequencies (30 GHz - 300 GHz). To generate high-quality mm W signals by lasers, it requires optical sources with ultra-narrow optical linewidth and low relative intensity noise (RIN). In this paper, we have developed InAs/InP quantum dot (QD) multi-wavelength lasers (MWLs) around 1550 nm with the frequency spacing from 10 GHz to 1000 GHz. Those QD MWLs have very low RIN, ultra-narrow optical linewidth, small timing jitters, compact size, low power consumption and the ability for hybrid integration with silicon substrates. As an example, we present a buried heterostructure (BH) QD dual-wavelength (DW) DFB laser as an optical beat source for mmW generation. The BH QD DW-DFB laser with the optical linewidth of 16 KHz and the RIN of -158 dB/Hz is capable of generating spectrally pure mm W signals between 46 GHz and 48 GHz. By using it, we have demonstrated a real time 24-Gbit/s (64QAM x 4Gbaud) data bandwidth wireless transmission operating at 47.2-GHz carrier over 25-km SSMF.