Room-temperature, directly modulated DFB-QCLs and resonant-cavity infrared detectors (RCIDs) for 5 Gb/s OOK free-space, mid-wave infrared atmospheric laser communication

We present results and analysis of 5 Gb/s On-Off-Keyed (OOK) data transmission at ~ 4.6-micron wavelength using, at room temperature, a directly modulated, single-mode DFB-QCL transmitter and a Resonant-Cavity Infrared Detector (RCID) receiver. The DFB-QCL design enables relatively high 165-mW CW output power. We used a 3-mm device with ~ 4-micron aperture for stable single-spatial-mode operation, operating at 65 mW. The RCID detector suppresses background radiation while providing enhanced quantum efficiency, ~ 60%, with low polarization dependence and low dark current at room temperature. The data transmission was achieved with no transmitter pulse shaping, consistent with lower-cost transceiver implementation.