Second harmonic generation by modal phase matching involving optical and plasmonic modes

Area of Science:

• Nonlinear Optics
• Plasmonics
• Semiconductor Photonics

Background:

• Achieving efficient nonlinear optical processes like second harmonic generation (SHG) is often limited by phase matching conditions.
• Semiconductors like AlGaAs exhibit significant material dispersion, complicating phase matching for SHG.
• Surface plasmonic modes offer high effective indices, potentially aiding phase matching.

Purpose of the Study:

• To demonstrate the feasibility of a modal phase matching scheme using surface plasmonic modes.
• To design a practical device for Type-II second harmonic generation in AlGaAs waveguides.
• To overcome dispersion limitations in semiconductors for efficient nonlinear frequency conversion.

Main Methods:

• Designing AlGaAs-based waveguides for Type-II SHG.
• Utilizing a modal phase matching scheme coupling optical modes with surface plasmonic modes.
• Guiding the generated second harmonic signal within the AlGaAs multilayer to minimize propagation losses.

Main Results:

• Demonstrated the feasibility of modal phase matching between optical and surface plasmonic modes.
• Achieved phase matching in a high-dispersion semiconductor material (AlGaAs).
• Designed a device where one pump mode is plasmonic, and the second harmonic signal propagates in the AlGaAs waveguide, mitigating loss.

Conclusions:

• The proposed modal phase matching scheme is feasible for nonlinear frequency conversion in semiconductors.
• This approach effectively addresses the challenge of large material dispersion in AlGaAs for SHG.
• The device design minimizes propagation losses for the generated second harmonic signal, enhancing overall efficiency.