Birefringence phase-matched direct third-harmonic generation in a ridge optical waveguide based on a KTiOPO₄ single...

Area of Science:

• Nonlinear Optics
• Quantum Optics
• Materials Science

Background:

• Third-harmonic generation (THG) is a key nonlinear optical process.
• Efficient THG is crucial for developing advanced photonic devices and quantum technologies.
• Potassium titanyl phosphate (KTiOPO4) is a well-known nonlinear optical crystal.

Purpose of the Study:

• To demonstrate birefringence phase-matched third-harmonic generation in a KTiOPO4 single crystal micrometric ridge waveguide.
• To achieve efficient THG at 1594 nm.
• To explore the potential for future quantum experiments.

Main Methods:

• Fabrication of a KTiOPO4 single crystal micrometric ridge waveguide.
• Experimental setup for third-harmonic generation using pulsed laser excitation at 1594 nm.
• Theoretical modeling to analyze phase-matching conditions and conversion efficiency.

Main Results:

• First demonstration of birefringence phase-matched THG in a KTiOPO4 waveguide.
• Achieved an energy conversion efficiency of 3.4%.
• Observed strong agreement between experimental results and theoretical predictions for phase-matching and efficiency.

Conclusions:

• The developed KTiOPO4 waveguide enables efficient THG.
• The results validate theoretical models for nonlinear optical processes in waveguides.
• This work paves the way for future quantum experiments, particularly those involving triple photon generation.