Backward optical parametric efficiency in quasi-phase-matched GaN waveguide presenting stitching faults.

Area of Science:

• Nonlinear optics
• Materials science
• Waveguide optics

Background:

• Optical parametric oscillators (OPOs) are crucial for generating tunable coherent light.
• Fabricating uniform quasi-phase-matched waveguides with nanoscale precision is challenging.
• Fragmented waveguides with stitching errors are typically considered detrimental to device performance.

Purpose of the Study:

• To investigate the performance of a backward mirrorless optical parametric oscillator in a fragmented Gallium Nitride (GaN) waveguide.
• To understand the impact of stitching errors on the coherence and efficiency of backward wave generation.
• To explore the potential of GaN epitaxy for achieving nanoscale poled periodicities.

Main Methods:

• Modeling a backward mirrorless optical parametric oscillator.
• Simulating a fragmented GaN waveguide with periodically poled elements and connection sections (stitching errors).
• Analyzing the phase locking dynamics between forward and backward propagating waves.

Main Results:

• The generated coherent phase of the backscattered wave effectively locks the phases of forward propagating waves.
• The dynamics of the fragmented waveguide are unexpectedly as efficient as a uniform quasi-phase-matched waveguide.
• Optimal coherence transfer to the backward wave requires perfect group-velocity matching and nanoscale poled periodicity.

Conclusions:

• Fragmented GaN waveguides can achieve efficient backward wave generation despite stitching errors.
• The phase-locking mechanism in these fragmented structures compensates for imperfections.
• Gallium Nitride (GaN) epitaxy is a viable method for fabricating the required nanoscale periodicities for advanced optical devices.