Ion-exchanged waveguides in periodically poled Rb-doped KTiOPO₄ for efficient second harmonic generation

Area of Science:

• Nonlinear Optics
• Materials Science
• Integrated Photonics

Background:

• Periodically poled materials are crucial for nonlinear optical frequency conversion.
• Developing stable, efficient channel waveguides in such materials remains a challenge.
• Rubidium-doped Potassium Titanyl Phosphate (RKTP) offers potential for enhanced nonlinear properties.

Purpose of the Study:

• To develop and characterize an ion-exchange process for creating channel waveguides in periodically poled Rb-doped KTiOPO4 (RKTP).
• To investigate the domain stability of RKTP during the ion-exchange process.
• To demonstrate the performance of these waveguides in second harmonic generation.

Main Methods:

• An optimized ion-exchange process was applied to RKTP crystals.
• Domain stability was assessed by examining domain gratings post-ion exchange.
• Second harmonic generation (SHG) efficiency was measured by coupling 940.2 nm fundamental light into fabricated waveguides.

Main Results:

• The ion-exchange process was successfully implemented in RKTP, yielding high-efficiency, low-loss channel waveguides.
• Domain gratings with uncharged walls exhibited excellent stability, with no deterioration observed.
• A normalized conversion efficiency of 115%/Wcm² was achieved, generating 3.1 mW of blue light.

Conclusions:

• Ion-exchanged waveguides in RKTP are stable and efficient for nonlinear optical applications.
• These waveguides facilitate stable high-power operation and the generation of entangled photons.
• RKTP waveguides open avenues for exploring novel nonlinear optical phenomena in integrated formats.