Electro-optic guided-to-radiation mode conversion in annealed proton-exchanged PPLN waveguides

Area of Science:

• Photonics and Optical Engineering
• Materials Science
• Integrated Optics

Background:

• Periodically poled lithium niobate (PPLN) is crucial for nonlinear optical devices.
• Efficient mode conversion is essential for advanced photonic integrated circuits.
• Annealed proton-exchange (APE) waveguides offer enhanced optical properties.

Purpose of the Study:

• To design and demonstrate electro-optically active TM-guided to TE-radiation mode converters.
• To achieve high conversion efficiency in the telecom S-C-L bands.
• To improve upon existing guided-to-radiation (GTR) mode converter performance.

Main Methods:

• Fabrication of APE PPLN channel waveguides.
• Experimental characterization of mode conversion efficiency under an applied electro-optic (EO) field.
• Utilizing periodic poling for quasi-phase-matching.

Main Results:

• Maximum mode conversion efficiency exceeding 95%/cm at 1520 nm.
• Achieved with a 24-μm-period APE PPLN waveguide and an EO field of ~6.3 V/μm.
• Efficiency is >4.6 times higher than in single-domain LiNbO3 waveguides.
• Observed a conversion bandwidth of approximately 250 nm.

Conclusions:

• The developed EO GTR mode converter demonstrates record efficiency for LiNbO3 on-axis waveguides.
• The device operates effectively within the telecom S-C-L bands.
• This technology holds promise for next-generation photonic devices and optical signal processing.