Abstract
AbstractFree space optics data transmission with bitrate in excess of 10 Gbit s−1 is demonstrated at 9 µm wavelength by using a unipolar quantum optoelectronic system at room temperature, composed of a quantum cascade laser, a modulator, and a quantum cascade detector. The large frequency bandwidth of the system is set by the detector and the modulator that are both high frequency devices, while the laser emits in continuous wave. The amplitude modulator relies on the Stark shift of an absorbing optical transition in and out of the laser frequency. This device is designed to avoid charge displacement, and therefore it is characterized by an intrinsically large bandwidth and very low electrical power consumption. This demonstration of high‐bitrate data transmission sets unipolar quantum devices as the most performing platform for the development of optoelectronic systems operating at very high frequency in the mid‐infrared for several applications, such as digital communications and high‐resolution spectroscopy.
Highlights
Unipolar quantum optoelectronics (UQOs) comprises an ensemble of semiconductor devices operating at room temperature in the mid-infrared ( 4 – 16 μm) with bandwidths of tens of GHz
Highly sensitive and ultrafast optoelectronic systems are required for free-space communications,[2,3,4,5] light detection and ranging (LIDAR),[6] high resolution spectroscopy,[7] and in observational astronomy.[8,9]
We present the realisation of an UQO system for data transmission in the 8 to 14 μm atmospheric window comprising a continuous wave quantum cascade (QC) laser, an external modulator, and a QC detector (Figure 1)
Summary
Unipolar quantum optoelectronics (UQOs) comprises an ensemble of semiconductor devices operating at room temperature in the mid-infrared ( 4 – 16 μm) with bandwidths of tens of GHz. In contrast to previous studies based on directly modulating a QC laser current,[2,10,11,12] data-bits are written onto the laser emission in our system using a high frequency external modulator that operates by shifting the absorption of an optical transition in and out of the laser frequency This device is designed to avoid charge displacement or electron depletion,[13] and it is characterized by an intrinsically large bandwidth and very low electrical power consumption in comparison with direct current modulation of the laser.[10,14,15] This modulation scheme is a step forward to increase the bitrate for free-space communication with enhanced privacy in the midinfrared.[16] Using the set-up illustrated, we have demonstrated a data rate transmission of 10 Gigabits per second on a single channel, with bit error rate of the order of 10-3, compatible with common protocols for data transmission. Given that a BER ≤ 4 x 10-3 can be corrected using error correction codes without excessive overhead,[2,26] we achieved an error-free transmission up to 10 Gbit ·s-1 which is far beyond the state-of-the-art at this wavelength in free-space using either external[27] or direct[2] modulation, without any post processing nor equalization
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