A broadband planarized platform for high performance THz quantum cascade photonics

We will present new developments in THz coherent photonics enabled by a recently demonstrated broadband planarized platform based on quantum cascade gain medium. The possibility to integrate onto the same chip active (lasers, detectors, amplifiers) and passive (waveguides, splitters, antennas, chirped mirrors,) photonic elements results extremely attractive, naturally bridging microwaves to THz waves. Such approach allows the adoption of advanced photonics design techniques (inverse design) to tailor facet reflectivities in double metal, subwavelength waveguides. We will present frequency combs exceeding 1 THz bandwidth, operating above liquid nitrogen temperature, with regular far fields and vertical emission. We will as well discuss laser dynamics engineering exploiting extreme field confinement in narrow waveguides, clearly demonstrating FM comb operation in THz QCLs. By exploiting dispersion compensation in planarized double ring cavities we will finally present the achievement of dissipative Kerr solitons with pulses of 10 ps. The application of such waveguides to high-temperature active regions allows the operation of 4 THz QCLs on Peltier cooler with currents below 2.5 A