On-chip multi-wavelength lasers for programmable THz frequency comb generation

Frequency combs in the THz range (0.1 to 10 THz) are useful for applications such as spectroscopy of biomolecules, remote sensing, and broadband wireless communications. THz wireless communications, in particular, is becoming a highly-relevant research field, driven by the need for ever more bandwidth. Naturally, pushing the carrier frequencies toward the THz range would unlock unprecedented data rates. The THz range, however, lacks efficient, coherent, and compact sources, which is known as the "THz gap". In this sense, photonic techniques have emerged as a potential solution to unlock the THz regime. Photonic THz sources typically rely on heterodyning of independent optical modes, resulting in THz signals with low coherence and poor scalability. In this project, I propose a photonic-based approach to allow for tunable and coherent THz comb generation. The technique is based on a feedback-controlled multi-wavelength laser (MWL) under optical frequency comb injection. The output of the MWL consists of two correlated frequency combs separated by a THz-range frequency. By controlling the feedback phase and amplitude, such THz frequency can be adjusted, leading to programmable THz comb generation after heterodyning. This solution will present critical advantages beyond the state of the art when it comes to spectral coverage, tunability, and coherence of the generated THz signal. In addition, it will provide a generic approach to embrace the various THz applications.