Integrated Optical Waveguide Electric Field Sensors Based on Bismuth Germanate

Area of Science:

• Materials Science
• Optoelectronics
• Laser Physics

Background:

• Bismuth germanate (Bi4Ge3O12, BGO) is a crucial optical sensing material for electric field measurements due to its high electro-optic coefficient.
• Precise electric field sensing necessitates the fabrication of optical waveguides on BGO, a process challenging for conventional methods.

Purpose of the Study:

• To investigate femtosecond laser writing as a novel technique for fabricating optical waveguides on BGO crystals.
• To characterize the light-guiding properties and refractive index modulation of laser-written waveguides for optical electric field sensors.

Main Methods:

• Femtosecond laser writing was employed to fabricate cladding-type waveguides on BGO.
• Experimental analysis involved optimizing laser parameters (200 kHz, 10.15 mW) and characterizing waveguide performance.
• Near-field optical intensity distribution and refractive index variations were simulated and reconstructed.

Main Results:

• A cladding-type waveguide with excellent light-guiding characteristics was successfully fabricated using femtosecond laser writing.
• Simulations confirmed that refractive index modulation ensures single-mode transmission and effective light confinement.
• The fabricated waveguide exhibited a low loss of approximately 1.2 dB/cm, validated by in situ refractive index characterization.

Conclusions:

• Femtosecond laser writing is a feasible and effective method for fabricating optical waveguides on BGO with reduced refractive index.
• The developed waveguide fabrication process provides a strong foundation for advancing BGO-based optical electric field sensors.
• Integration of antenna electrode design and performance analysis further supports practical sensor applications.