Self-organized spatiotemporal quasi-phase-matching in microresonators

Area of Science:

• Nonlinear Optics
• Photonics
• Materials Science

Background:

• Quasi-phase-matching (QPM) is crucial for nonlinear optical processes like second-harmonic generation (SHG), compensating for phase velocity mismatches.
• Traditional QPM relies on periodic modulation of the nonlinear medium, but spatiotemporal extensions can induce frequency shifts.

Purpose of the Study:

• To demonstrate a self-organized spatiotemporal QPM grating in silicon nitride microresonators.
• To investigate the induction of frequency shifts in generated light via all-optical poling.

Main Methods:

• Utilizing all-optical poling in silicon nitride microresonators to create a concurrent spatial and temporal modulation of the nonlinear response.
• Leveraging the coherent photogalvanic effect to self-organize a traveling space-charge grating.

Main Results:

• Observation of a naturally emerging spatiotemporal QPM grating.
• Generation of a quasi-phase-matched and Doppler-shifted second harmonic.
• Demonstration of momentum and energy conservation being affected by the photoinduced grating.

Conclusions:

• The study successfully demonstrates photoinduced spatiotemporal QPM in silicon nitride microresonators.
• This work expands the understanding and application of phase-matching conditions in nonlinear photonics.
• The findings open new avenues for controlling light-matter interactions in integrated photonic devices.