High-Quality Fiber Bragg Gratings Inscribed by Femtosecond Laser Point-by-Point Technology.

Area of Science:

• Optics and Photonics
• Materials Science

Background:

• Fiber Bragg gratings (FBGs) are crucial components in optical fiber technologies.
• Traditional FBG fabrication methods have limitations in precision and flexibility.

Purpose of the Study:

• To investigate femtosecond laser point-by-point (PbP) technology for FBG inscription.
• To optimize FBG parameters for enhanced spectral characteristics and performance.
• To explore the application of PbP FBG technology in WDM systems and Fabry-Perot cavities.

Main Methods:

• Femtosecond (fs) laser point-by-point (PbP) inscription of FBGs.
• Systematic investigation of focusing geometry, grating order, laser energy, and grating length.
• Optimization of parameters for high reflectivity and low insertion loss.
• Fabrication of various Bragg wavelengths and wavelength-division-multiplexed (WDM) FBG arrays.
• Realization of a Fabry-Perot cavity and birefringence reduction using slit beam shaping.

Main Results:

• Achieved high-quality first-order PbP FBG with reflectivity > 99.9% and insertion loss of 0.03 dB.
• Successfully inscribed FBGs with Bragg wavelengths from 856 to 1902.6 nm.
• Rapidly constructed 10-FBG wavelength-division-multiplexed (WDM) FBG arrays.
• Reduced birefringence in a Fabry-Perot cavity from 3.04 × 10−5 to 1.77 × 10−6.

Conclusions:

• Femtosecond laser PbP technology enables high-performance FBG fabrication.
• The flexibility of PbP technology allows for diverse FBG designs and applications.
• These high-quality FBGs show significant potential for improving optical fiber sensors, lasers, and communication devices.