Quantum Cascade Laser Applications in Free-Space Optical Communication
Summary
Quantum cascade lasers (QCLs) have emerged as pivotal sources for free-space optical communication (FSO) in the mid-infrared spectral region. Owing to their intrinsically narrow linewidth, high output power and suitability for direct high-speed modulation, QCLs offer a pathway to robust wireless links that exploit atmospheric transmission windows between 3 µm and 12 µm. The reduced scattering and lower absorption of mid-infrared beams under fog, haze and turbulence endows such links with enhanced resilience compared with near-infrared and visible alternatives. Recent advances integrate QCLs with monolithic detectors or passive quantum cascade devices, delivering compact, energy-efficient transceivers capable of multilevel modulation schemes. System-level digital signal processing and advanced waveform design have been employed to mitigate distortion and optimise spectral efficiency. Applications span terrestrial fixed-wireless access, mobile backhaul and short-range space communications, where high bit-rates, low latency and small form factors are paramount. Continued progress in device engineering, thermal management and atmospheric modelling is driving mid-IR FSO closer to commercial deployment.
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Quantum Cascade Laser Applications in Free-Space Optical Communication publication trend
The graph below shows the total number of articles in quantum cascade laser applications in free-space optical communication across all publications each year (not limited to Nature Index journals).
Technical terms
Quantum cascade laser (QCL): A semiconductor laser that emits in the mid-infrared via intersubband transitions, capable of high-speed direct modulation.
Free-space optical communication (FSO): Wireless data transmission using light propagating through the atmosphere or vacuum without guiding fibres.
Mid-infrared atmospheric window: Spectral regions (approximately 3–5 µm and 8–12 µm) where atmospheric absorption and scattering are minimal.
Pulse amplitude modulation (PAM): A multilevel encoding scheme in which data are represented by discrete amplitude levels of the optical carrier.
Quantum cascade detector (QCD): An unipolar photodetector exploiting intersubband transitions, often integrated monolithically with QCLs for compact transceiver design.
Bit error rate (BER): The ratio of incorrectly received bits to the total number of transmitted bits, used to assess link reliability.
Digital signal processing (DSP): Algorithms applied to received signals for equalisation, error correction and spectral shaping to improve transmission performance.
References
- High Spectral Efficiency Long-Wave Infrared Free-Space Optical Transmission With Multilevel Signals. Journal of Lightwave Technology (2023).
- High-capacity free-space optical link in the midinfrared thermal atmospheric windows using unipolar quantum devices. Advanced Photonics (2022).
- High-Speed 9.6-m Long-Wave Infrared Free-Space Transmission With a Directly-Modulated QCL and a Fully-Passive QCD. Journal of Lightwave Technology (2022).
- Free‐Space Communications Enabled by Quantum Cascade Lasers. physica status solidi (a) – applications and materials science (2020).
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