30 years of the quantum cascade laser.

It was January 1994, when the first quantum cascade laser (QCL) displayed laser action in Bell Laboratories. During these 30 years the QCL evolved incessantly, from a lab curiosity to the main on-chip source of coherent radiation in the Mid-IR and THz ranges. The journey has seen an impressive development of the QCL in several fields of laser physics and its applications, with a steady growth of research groups and companies worldwide.

Quantum walk comb in a fast gain laser.

Synthetic lattices in photonics enable the exploration of light states in new dimensions, transcending phenomena common only to physical space. We propose and demonstrate a quantum walk comb in synthetic frequency space formed by externally modulating a ring-shaped semiconductor laser with ultrafast recovery times. The initially ballistic quantum walk does not dissipate into low supermode states of the synthetic lattice; instead, the state stabilizes in a broad frequency comb, unlocking the full potential of the synthetic frequency lattice.

Terahertz optical solitons from dispersion-compensated antenna-coupled planarized ring quantum cascade lasers.

Quantum cascade lasers (QCLs) constitute an intriguing opportunity for the generation of on-chip optical dissipative Kerr solitons (DKSs). Originally demonstrated in passive microresonators, DKSs were recently observed in mid-infrared ring QCL paving the way for their achievement even at longer wavelengths. To this end, we realized defect-free terahertz ring QCLs featuring anomalous dispersion leveraging on a technological platform based on waveguide planarization.

THz optical beat-note detection with a fast superconducting hot electron bolometer operating up to 31 GHz.

We study the performance of a hot-electron bolometer (HEB) operating at THz frequencies based on superconducting niobium nitride films. We report on the voltage response of the detector over a large electrical detection bandwidth carried out with different THz sources. We show that the impulse response of the fully packaged HEB at 7.