Monolithically Integrated Optical Frequency Comb Generator Based on Mutually Injection Locked Gain Switched Lasers

The authors demonstrate and characterise a monolithically integrated optical frequency comb (OFC) source, based on mutually injection-locked gain-switched lasers (MIL-GSL). The photonic integrated circuit (PIC) consists of two single mode slave lasers and a wavelength tunable single mode master laser. The working principle of this PIC relies on the simultaneous injection-locking of the two gain switched slave lasers, with partially overlapping spectra, with a common master laser. This results in the generation of a MIL-GSL expanded comb, exhibiting a spectral width of 256.25 GHz, low phase and amplitude noise, excellent phase correlation between the comb lines, and flexibility in terms of comb line separation. The PIC-based implementation offers additional advantage of lower complexity, small footprint, and reduced energy consumption.