Intensity Correlations in Quantum Cascade Laser Harmonic Frequency Combs

A novel study on harmonic frequency combs emitted by quantum cascade lasers (QCLs) is presented here, demonstrating the presence of intensity correlations between twin modes characterizing emission spectra. These originate from a four-wave mixing process driven active medium's third-order nonlinearity. The such essential for engineering new generation semiconductor devices with potential becoming integrated emitters light properties, as squeezing and entanglement. Starting experimental results, limits state-of-the-art technology are discussed well possible methodologies that could lead to detection nonclassical phenomena, or alternatively improve design QCLs, in compelling perspective generating mid-infrared light.