Time-reversed and reciprocal second-harmonic generation with pump depletion.

Area of Science:

• Photonics
• Nonlinear Optics
• Materials Science

Background:

• Nonlinear photonic crystals enable unique light-matter interactions.
• Time-reversed phenomena offer novel applications in optics and information processing.

Purpose of the Study:

• To theoretically investigate time-reversed second-harmonic generation (TR-SHG) in 1D nonlinear photonic crystals.
• To develop criteria for controlling energy flow and achieving TR-SHG.
• To propose structures for realizing nonlinear time reversal effects.

Main Methods:

• Theoretical analysis of second-harmonic generation without the undepleted pump approximation.
• Deduction of an energy flow criterion.
• Design of two distinct 1D nonlinear photonic crystal structures based on symmetry.

Main Results:

• A simple criterion for determining energy flow in TR-SHG was established.
• Two structures with different symmetries were proposed to achieve nonlinear time reversal.
• A completely reciprocal nonlinear response was observed.
• A multi-section-cascaded structure was designed for localized TR-SHG.

Conclusions:

• Nonlinear time reversal is achievable in 1D nonlinear photonic crystals.
• The proposed structures and criterion offer precise control over TR-SHG.
• The findings pave the way for advanced optical devices with time-reversal capabilities.