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Quantum cascade laser frequency combs are nowadays well-appreciated sources for infrared spectroscopy. Here their applicability for free-space optical communication is demonstrated. The spontaneously-generated intermodal beat note of the frequency comb is used as carrier for transferring the analog signal via frequency modulation. Exploiting the atmospheric transparency window at 4 $\mu$m, an optical communication with a signal-to-noise ratio up to 65 dB is realized, with a modulation bandwidth of 300 kHz. The system tolerates a maximum optical attenuation exceeding 35 dB. The possibility of parallel transmission of an independent digital signal via amplitude modulation at 5 MS/s is also demonstrated., Comment: 17 pages, 13 figures

We present a novel shot-noise-limited balanced-homodyne detector operating in the mid-infrared useful for revealing possible non-classicality in quantum cascade lasers emission. We will give a view to quantum-technologies applications such as free-space quantum communication.

We present the characterization of a novel balanced homodyne detector operating in the mid-infrared. The challenging task of revealing non-classicality in mid-infrared light, e.~g. in quantum cascade lasers emission, requires a high-performance detection system. Through the intensity noise power spectral density analysis of the differential signal coming from the incident radiation, we show that our setup is shot-noise limited. We discuss the experimental results with a view to possible applications to quantum technologies, such as free-space quantum communication., Comment: 15 pages, 6 figures

We are developing an atom-based platform for investigating the non-classical nature of mid infrared light emitted by Quantum Cascade Laser frequency combs, based on four wave mixing 87Rb.