Photonic Integrated Fully Tunable Comb Generator Cascading Optical Modulators

We report the first monolithic InP photonic integrated comb generator made by cascading optical modulators. The device is extremely compact and tunable both in repetition frequency and wavelength, making real-world applications possible. A distributed Bragg reflector laser, a Mach-Zehnder intensity modulator, and two phase modulators are monolithically integrated on a 4.5 × 2.5 mm
²
chip that also includes a booster semiconductor optical amplifier at the output. Modulators integrated on the circuit have a 3 dB bandwidth of 7 GHz and can generate up to 28 comb lines within a 5 dB power range when properly electrically driven (here demonstrated in the range 4-5 GHz). Operation up to 10 GHz is also reported.