Efficient third-harmonic generation in partly periodically poled KTiOPO(4) crystal.

Area of Science:

• Nonlinear optics
• Materials science

Background:

• Periodically poled crystals are crucial for nonlinear optical frequency conversion.
• Potassium titanyl phosphate (KTP) is a widely used nonlinear optical material.
• Integrating multiple nonlinear processes in a single crystal can enhance device efficiency and reduce complexity.

Purpose of the Study:

• To design and demonstrate a partly periodically poled KTP crystal capable of simultaneous quasi-phase-matched second-harmonic generation (QPM SHG) and sum-frequency generation (SFG).
• To achieve efficient generation of a third-harmonic beam from a fundamental laser source.
• To investigate the optical properties of periodically poled KTP compared to bulk KTP.

Main Methods:

• Fabrication of a partly periodically poled KTP crystal.
• Experimental setup utilizing picosecond laser pulses at a wavelength of 1.327 microm .
• Measurement of conversion efficiencies for QPM SHG and third-harmonic generation.

Main Results:

• The designed crystal successfully integrated QPM SHG and SFG functionalities.
• Highest achieved conversion efficiencies were 45% for QPM SHG and 3% for third-harmonic generation.
• A slight difference in the refractive index (n(z)) was observed between periodically poled KTP and bulk KTP.

Conclusions:

• Partly periodically poled KTP is a viable material for integrated nonlinear optical frequency conversion.
• The developed crystal architecture enables efficient generation of third-harmonic beams.
• Understanding the refractive index changes in periodically poled KTP is important for optimizing device performance.