Subharmonic comb spacing in a gain switched PIC

Area of Science:

• Photonics
• Integrated Optics
• Nonlinear Optics

Background:

• Optical frequency combs are crucial for precision measurement and spectroscopy.
• Photonic integrated circuits (PICs) offer miniaturization and scalability for optical systems.
• Gain-switched lasers are used for generating pulsed light sources.

Purpose of the Study:

• To demonstrate subharmonic spectral regimes in a gain-switched PIC.
• To achieve tunable frequency division using a PIC.
• To explore dense optical comb generation on chip.

Main Methods:

• Utilizing a three-sectioned, symmetrically coupled InP-based PIC.
• Employing gain switching with varying modulation frequencies.
• Analyzing spectral dynamics using a delay-differential rate equation (DDE) model.

Main Results:

• Generation of optical frequency combs with subharmonic spacings (1/2, 1/3, 1/4 of modulation frequency).
• Observation of period doubling and bifurcations leading to subharmonic generation.
• Identification of stable subharmonic operation regions within parameter space.

Conclusions:

• Symmetrically coupled gain-switched lasers in PICs enable tunable frequency division.
• PICs provide a compact platform for dense optical comb generation.
• Phase noise is critical for accurately modeling the device's spectral dynamics.