Integrated waveguide frequency-converted laser fabricated by ultrafast laser inscription

Area of Science:

• Optics and Photonics
• Materials Science
• Laser Technology

Background:

• Integrated photonics offers miniaturization and enhanced stability.
• Frequency conversion is crucial for generating various laser wavelengths.
• Combining dissimilar optical materials in a monolithic structure presents fabrication challenges.

Purpose of the Study:

• To fabricate and characterize a monolithic waveguide-based frequency-converted laser source.
• To demonstrate an alignment-free integrated laser by bonding Nd:YAG and periodically poled lithium niobate.
• To investigate the impact of waveguide geometry on second-harmonic generation (SHG) performance.

Main Methods:

• Permanent bonding of Nd:YAG and periodically poled lithium niobate on a fused-silica substrate using ultrafast laser microwelding.
• Fabrication of a continuous double-track waveguide across dissimilar crystals via ultrafast laser inscription.
• Diode-pumping at 808 nm to achieve lasing at 1064 nm and subsequent SHG at 532 nm.

Main Results:

• Successful fabrication of a monolithic, alignment-free frequency-converted laser source.
• Demonstration of diode-pumped lasing at 1064 nm and SHG to 532 nm.
• Analysis of SHG tuning behavior, revealing trade-offs between confinement, efficiency, and mode structure based on track separation.

Conclusions:

• The developed monolithic waveguide laser source provides an integrated and alignment-free solution for frequency conversion.
• Waveguide geometry optimization is critical for balancing optical confinement, conversion efficiency, and mode quality.
• Ultrafast laser processing enables the precise integration of dissimilar optical materials for advanced laser functionalities.