Fig. 1: Two QCLs used for FSO transmission and their characteristics. | Nature Communications

Fig. 1: Two QCLs used for FSO transmission and their characteristics.

From: Unipolar quantum optoelectronics for high speed direct modulation and transmission in 8–14 µm atmospheric window

Fig. 1

a A microscopic photo showing the the wirebonding between the cleavered RF-QCL submount and the PCB to enhance the frequency response. b The measured L-I-V curves of both the Standard-QCL and the RF-QCL at 15 °C in CW mode. Note that these measurements are performed in the system-level setup, and characterized power values are lower than chip-level measurements due to the beam divergence. While the actual output power of the QCL chips are higher, these measured values correspond to the actual power levels the detectors receive in the free-space transmission setup. The measured optical spectra with normalized intensity with respect to the bias current of c the Standard-QCL, and d the RF-QCL. e The characterized modulation bandwidth of the RF-QCL with electrical rectification at different bias current points.

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