Volume Bragg grating with tunable reflectivity and the bandwidth assisted Fabry-Pérot cavity

Area of Science:

• Optical Engineering
• Materials Science
• Sensor Technology

Background:

• Rigid Fabry-Pérot (F-P) cavities are crucial for optical sensing (pressure, vibration, acoustics) in demanding environments due to their reliability.
• Current F-P cavities face precision limitations at high temperatures because of the poor thermal stability of optical dielectric films.
• Volume Bragg gratings (VBGs), created by femtosecond laser modification of glass, offer a promising alternative reflective element.

Purpose of the Study:

• To investigate the suitability of Volume Bragg gratings (VBGs) as reflective components for fully rigid Fabry-Pérot (F-P) cavities.
• To analyze the structural and reflective properties of VBGs for enhanced optical sensing applications.
• To determine the key parameters influencing VBG reflectivity and bandwidth for precise optical measurements.

Main Methods:

• Proposed VBGs as a reflective element within a rigid F-P cavity structure.
• Researched and analyzed the structure and reflection properties of VBGs.
• Investigated the influence of grating period, linewidth, layer count, and refractive index change on VBG performance.

Main Results:

• VBG reflectivity and reflective bandwidth are significantly influenced by variations in grating period, linewidth, number of layers, and refractive index change.
• Identified specific parameters that predominantly control VBG optical characteristics.
• Demonstrated the potential for tailoring VBG properties by adjusting these key parameters.

Conclusions:

• VBGs are a viable and potentially superior alternative to traditional dielectric films for rigid F-P cavities, especially in high-temperature applications.
• Analytical results provide a foundation for selecting optimal VBG parameters based on specific application requirements.
• This research supports the practical preparation and measurement of VBGs for advanced optical sensing.