Non-degenerate two-photon absorption in silicon waveguides: analytical and experimental study

Area of Science:

• Photonics
• Nonlinear Optics
• Materials Science

Background:

• Silicon waveguides are crucial for integrated photonics.
• Nonlinear optical effects like TPA and free-carrier absorption impact signal integrity.
• Understanding and separating these loss mechanisms is vital for device performance.

Purpose of the Study:

• To investigate the nonlinear evolution of optical pulses in silicon waveguides.
• To develop an analytic and numerical framework for analyzing TPA and free-carrier absorption.
• To present a method for experimentally distinguishing these two loss mechanisms.

Main Methods:

• Theoretical analysis using analytic solutions for weak probe waves.
• Numerical simulations for high pump intensities, considering TPA and free carriers.
• Experimental validation in silicon photonic crystal waveguides.

Main Results:

• An analytic solution was derived for non-degenerate two-photon absorption (TPA).
• The interplay between TPA and photo-generated free carriers was studied numerically.
• A method was developed to accurately separate TPA and free-carrier absorption losses from experimental data.

Conclusions:

• The developed approach accurately explains experimental results in silicon waveguides.
• This work provides a powerful tool for characterizing nonlinear losses in photonic devices.
• Accurate loss separation is key for optimizing silicon photonic integrated circuits.