There is provided an external cavity laser, including: a photonic integrated platform including a gain chip providing a gain medium and at least one reflector chip, the photonic integrated platform including first and second functional layers made of different materials; a resonant cavity optically coupled to the gain medium and including a first and a second micro-ring resonators (MRR) in a Vernier configuration, the first MRR and second MRR extending within respective ones of the first and second functional layers made of different materials and having corresponding group indices, the first and second MRRs having different radii selected in view of said corresponding group indices; and a tuning mechanism for tuning a spectral response of at least one of the first and second MRR.

There is provided an external cavity laser, including: a photonic integrated platform including a gain chip providing a gain medium and at least one reflector chip, the photonic integrated platform including first and second functional layers made of different materials; a resonant cavity optically coupled to the gain medium and including a first and a second micro-ring resonators (MRR) in a Vernier configuration, the first MRR and second MRR extending within respective ones of the first and second functional layers made of different materials and having corresponding group indices, the first and second MRRs having different radii selected in view of said corresponding group indices; and a tuning mechanism for tuning a spectral response of at least one of the first and second MRR.