Dispersion-Controlled Quantum-Walk Comb Generation in Metasurface THz QC-VECSELs

We report RF-injection-locked quantum-cascade vertical-external-cavity surface-emitting lasers (QC-VECSELs) operating in the THz regime. By injecting RF signals at the cavity round-trip frequency as well as at harmonic and sub-harmonic orders, the device produce stable, evenly spaced multimode emission with bandwidths exceeding 300 GHz. Owing to the fast saturable gain of QC active region and the absence of spatial hole burning in the external-cavity geometry, the platform enables the realization of Quantum-Walk (QW) combs using strong RF modulation. Distinct on- and off-resonance behaviors are observed, demonstrating QC-VECSELs as a versatile and tunable source for broadband THz frequency-comb generation.