Impact of two-photon absorption on self-phase modulation in silicon waveguides

Area of Science:

• Nonlinear optics
• Semiconductor device physics
• Photonics

Background:

• Self-phase modulation (SPM) is a key nonlinear optical phenomenon in waveguides.
• Two-photon absorption (TPA) and free-carrier effects (FCE) can significantly alter SPM in silicon photonics.
• Understanding these effects is crucial for designing high-power optical systems.

Purpose of the Study:

• To investigate the influence of TPA on SPM in silicon waveguides.
• To analyze the impact of free-carrier absorption and dispersion on nonlinear phase shift and spectral broadening.
• To evaluate the role of pulse repetition rate on the SPM process.

Main Methods:

• Development of an analytical solution for low-generated carrier densities.
• Numerical simulations to study FCE under various conditions.
• Analysis of spectral bandwidth and nonlinear phase shift.

Main Results:

• An analytical solution is derived for low carrier densities, aiding spectral bandwidth estimation at low repetition rates.
• Numerical results highlight the significant role of FCE in nonlinear phase shift and spectral broadening.
• The repetition rate of the pulse train is shown to influence the SPM process.

Conclusions:

• TPA and FCE are critical factors modulating SPM in silicon waveguides.
• The study provides tools for estimating spectral broadening and understanding nonlinear effects in pulsed systems.
• Results are relevant for optimizing silicon photonic devices operating at high optical intensities.